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diff --git a/doc/html/NON-AUTOTOOLS-BUILD.txt b/doc/html/NON-AUTOTOOLS-BUILD.txt new file mode 100644 index 0000000..3910059 --- /dev/null +++ b/doc/html/NON-AUTOTOOLS-BUILD.txt @@ -0,0 +1,772 @@ +Building PCRE without using autotools +------------------------------------- + +NOTE: This document relates to PCRE releases that use the original API, with +library names libpcre, libpcre16, and libpcre32. January 2015 saw the first +release of a new API, known as PCRE2, with release numbers starting at 10.00 +and library names libpcre2-8, libpcre2-16, and libpcre2-32. The old libraries +(now called PCRE1) are still being maintained for bug fixes, but there will be +no new development. New projects are advised to use the new PCRE2 libraries. + + +This document contains the following sections: + + General + Generic instructions for the PCRE C library + The C++ wrapper functions + Building for virtual Pascal + Stack size in Windows environments + Linking programs in Windows environments + Calling conventions in Windows environments + Comments about Win32 builds + Building PCRE on Windows with CMake + Use of relative paths with CMake on Windows + Testing with RunTest.bat + Building under Windows CE with Visual Studio 200x + Building under Windows with BCC5.5 + Building using Borland C++ Builder 2007 (CB2007) and higher + Building PCRE on OpenVMS + Building PCRE on Stratus OpenVOS + Building PCRE on native z/OS and z/VM + + +GENERAL + +I (Philip Hazel) have no experience of Windows or VMS sytems and how their +libraries work. The items in the PCRE distribution and Makefile that relate to +anything other than Linux systems are untested by me. + +There are some other comments and files (including some documentation in CHM +format) in the Contrib directory on the FTP site: + + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib + +The basic PCRE library consists entirely of code written in Standard C, and so +should compile successfully on any system that has a Standard C compiler and +library. The C++ wrapper functions are a separate issue (see below). + +The PCRE distribution includes a "configure" file for use by the configure/make +(autotools) build system, as found in many Unix-like environments. The README +file contains information about the options for "configure". + +There is also support for CMake, which some users prefer, especially in Windows +environments, though it can also be run in Unix-like environments. See the +section entitled "Building PCRE on Windows with CMake" below. + +Versions of config.h and pcre.h are distributed in the PCRE tarballs under the +names config.h.generic and pcre.h.generic. These are provided for those who +build PCRE without using "configure" or CMake. If you use "configure" or CMake, +the .generic versions are not used. + + +GENERIC INSTRUCTIONS FOR THE PCRE C LIBRARY + +The following are generic instructions for building the PCRE C library "by +hand". If you are going to use CMake, this section does not apply to you; you +can skip ahead to the CMake section. + + (1) Copy or rename the file config.h.generic as config.h, and edit the macro + settings that it contains to whatever is appropriate for your environment. + + In particular, you can alter the definition of the NEWLINE macro to + specify what character(s) you want to be interpreted as line terminators. + In an EBCDIC environment, you MUST change NEWLINE, because its default + value is 10, an ASCII LF. The usual EBCDIC newline character is 21 (0x15, + NL), though in some cases it may be 37 (0x25). + + When you compile any of the PCRE modules, you must specify -DHAVE_CONFIG_H + to your compiler so that config.h is included in the sources. + + An alternative approach is not to edit config.h, but to use -D on the + compiler command line to make any changes that you need to the + configuration options. In this case -DHAVE_CONFIG_H must not be set. + + NOTE: There have been occasions when the way in which certain parameters + in config.h are used has changed between releases. (In the configure/make + world, this is handled automatically.) When upgrading to a new release, + you are strongly advised to review config.h.generic before re-using what + you had previously. + + (2) Copy or rename the file pcre.h.generic as pcre.h. + + (3) EITHER: + Copy or rename file pcre_chartables.c.dist as pcre_chartables.c. + + OR: + Compile dftables.c as a stand-alone program (using -DHAVE_CONFIG_H if + you have set up config.h), and then run it with the single argument + "pcre_chartables.c". This generates a set of standard character tables + and writes them to that file. The tables are generated using the default + C locale for your system. If you want to use a locale that is specified + by LC_xxx environment variables, add the -L option to the dftables + command. You must use this method if you are building on a system that + uses EBCDIC code. + + The tables in pcre_chartables.c are defaults. The caller of PCRE can + specify alternative tables at run time. + + (4) Ensure that you have the following header files: + + pcre_internal.h + ucp.h + + (5) For an 8-bit library, compile the following source files, setting + -DHAVE_CONFIG_H as a compiler option if you have set up config.h with your + configuration, or else use other -D settings to change the configuration + as required. + + pcre_byte_order.c + pcre_chartables.c + pcre_compile.c + pcre_config.c + pcre_dfa_exec.c + pcre_exec.c + pcre_fullinfo.c + pcre_get.c + pcre_globals.c + pcre_jit_compile.c + pcre_maketables.c + pcre_newline.c + pcre_ord2utf8.c + pcre_refcount.c + pcre_string_utils.c + pcre_study.c + pcre_tables.c + pcre_ucd.c + pcre_valid_utf8.c + pcre_version.c + pcre_xclass.c + + Make sure that you include -I. in the compiler command (or equivalent for + an unusual compiler) so that all included PCRE header files are first + sought in the current directory. Otherwise you run the risk of picking up + a previously-installed file from somewhere else. + + Note that you must still compile pcre_jit_compile.c, even if you have not + defined SUPPORT_JIT in config.h, because when JIT support is not + configured, dummy functions are compiled. When JIT support IS configured, + pcre_jit_compile.c #includes sources from the sljit subdirectory, where + there should be 16 files, all of whose names begin with "sljit". + + (6) Now link all the compiled code into an object library in whichever form + your system keeps such libraries. This is the basic PCRE C 8-bit library. + If your system has static and shared libraries, you may have to do this + once for each type. + + (7) If you want to build a 16-bit library (as well as, or instead of the 8-bit + or 32-bit libraries) repeat steps 5-6 with the following files: + + pcre16_byte_order.c + pcre16_chartables.c + pcre16_compile.c + pcre16_config.c + pcre16_dfa_exec.c + pcre16_exec.c + pcre16_fullinfo.c + pcre16_get.c + pcre16_globals.c + pcre16_jit_compile.c + pcre16_maketables.c + pcre16_newline.c + pcre16_ord2utf16.c + pcre16_refcount.c + pcre16_string_utils.c + pcre16_study.c + pcre16_tables.c + pcre16_ucd.c + pcre16_utf16_utils.c + pcre16_valid_utf16.c + pcre16_version.c + pcre16_xclass.c + + (8) If you want to build a 32-bit library (as well as, or instead of the 8-bit + or 16-bit libraries) repeat steps 5-6 with the following files: + + pcre32_byte_order.c + pcre32_chartables.c + pcre32_compile.c + pcre32_config.c + pcre32_dfa_exec.c + pcre32_exec.c + pcre32_fullinfo.c + pcre32_get.c + pcre32_globals.c + pcre32_jit_compile.c + pcre32_maketables.c + pcre32_newline.c + pcre32_ord2utf32.c + pcre32_refcount.c + pcre32_string_utils.c + pcre32_study.c + pcre32_tables.c + pcre32_ucd.c + pcre32_utf32_utils.c + pcre32_valid_utf32.c + pcre32_version.c + pcre32_xclass.c + + (9) If you want to build the POSIX wrapper functions (which apply only to the + 8-bit library), ensure that you have the pcreposix.h file and then compile + pcreposix.c (remembering -DHAVE_CONFIG_H if necessary). Link the result + (on its own) as the pcreposix library. + +(10) The pcretest program can be linked with any combination of the 8-bit, + 16-bit and 32-bit libraries (depending on what you selected in config.h). + Compile pcretest.c and pcre_printint.c (again, don't forget + -DHAVE_CONFIG_H) and link them together with the appropriate library/ies. + If you compiled an 8-bit library, pcretest also needs the pcreposix + wrapper library unless you compiled it with -DNOPOSIX. + +(11) Run pcretest on the testinput files in the testdata directory, and check + that the output matches the corresponding testoutput files. There are + comments about what each test does in the section entitled "Testing PCRE" + in the README file. If you compiled more than one of the 8-bit, 16-bit and + 32-bit libraries, you need to run pcretest with the -16 option to do + 16-bit tests and with the -32 option to do 32-bit tests. + + Some tests are relevant only when certain build-time options are selected. + For example, test 4 is for UTF-8/UTF-16/UTF-32 support, and will not run + if you have built PCRE without it. See the comments at the start of each + testinput file. If you have a suitable Unix-like shell, the RunTest script + will run the appropriate tests for you. The command "RunTest list" will + output a list of all the tests. + + Note that the supplied files are in Unix format, with just LF characters + as line terminators. You may need to edit them to change this if your + system uses a different convention. If you are using Windows, you probably + should use the wintestinput3 file instead of testinput3 (and the + corresponding output file). This is a locale test; wintestinput3 sets the + locale to "french" rather than "fr_FR", and there some minor output + differences. + +(12) If you have built PCRE with SUPPORT_JIT, the JIT features will be tested + by the testdata files. However, you might also like to build and run + the freestanding JIT test program, pcre_jit_test.c. + +(13) If you want to use the pcregrep command, compile and link pcregrep.c; it + uses only the basic 8-bit PCRE library (it does not need the pcreposix + library). + + +THE C++ WRAPPER FUNCTIONS + +The PCRE distribution also contains some C++ wrapper functions and tests, +applicable to the 8-bit library, which were contributed by Google Inc. On a +system that can use "configure" and "make", the functions are automatically +built into a library called pcrecpp. It should be straightforward to compile +the .cc files manually on other systems. The files called xxx_unittest.cc are +test programs for each of the corresponding xxx.cc files. + + +BUILDING FOR VIRTUAL PASCAL + +A script for building PCRE using Borland's C++ compiler for use with VPASCAL +was contributed by Alexander Tokarev. Stefan Weber updated the script and added +additional files. The following files in the distribution are for building PCRE +for use with VP/Borland: makevp_c.txt, makevp_l.txt, makevp.bat, pcregexp.pas. + + +STACK SIZE IN WINDOWS ENVIRONMENTS + +The default processor stack size of 1Mb in some Windows environments is too +small for matching patterns that need much recursion. In particular, test 2 may +fail because of this. Normally, running out of stack causes a crash, but there +have been cases where the test program has just died silently. See your linker +documentation for how to increase stack size if you experience problems. The +Linux default of 8Mb is a reasonable choice for the stack, though even that can +be too small for some pattern/subject combinations. + +PCRE has a compile configuration option to disable the use of stack for +recursion so that heap is used instead. However, pattern matching is +significantly slower when this is done. There is more about stack usage in the +"pcrestack" documentation. + + +LINKING PROGRAMS IN WINDOWS ENVIRONMENTS + +If you want to statically link a program against a PCRE library in the form of +a non-dll .a file, you must define PCRE_STATIC before including pcre.h or +pcrecpp.h, otherwise the pcre_malloc() and pcre_free() exported functions will +be declared __declspec(dllimport), with unwanted results. + + +CALLING CONVENTIONS IN WINDOWS ENVIRONMENTS + +It is possible to compile programs to use different calling conventions using +MSVC. Search the web for "calling conventions" for more information. To make it +easier to change the calling convention for the exported functions in the +PCRE library, the macro PCRE_CALL_CONVENTION is present in all the external +definitions. It can be set externally when compiling (e.g. in CFLAGS). If it is +not set, it defaults to empty; the default calling convention is then used +(which is what is wanted most of the time). + + +COMMENTS ABOUT WIN32 BUILDS (see also "BUILDING PCRE ON WINDOWS WITH CMAKE") + +There are two ways of building PCRE using the "configure, make, make install" +paradigm on Windows systems: using MinGW or using Cygwin. These are not at all +the same thing; they are completely different from each other. There is also +support for building using CMake, which some users find a more straightforward +way of building PCRE under Windows. + +The MinGW home page (http://www.mingw.org/) says this: + + MinGW: A collection of freely available and freely distributable Windows + specific header files and import libraries combined with GNU toolsets that + allow one to produce native Windows programs that do not rely on any + 3rd-party C runtime DLLs. + +The Cygwin home page (http://www.cygwin.com/) says this: + + Cygwin is a Linux-like environment for Windows. It consists of two parts: + + . A DLL (cygwin1.dll) which acts as a Linux API emulation layer providing + substantial Linux API functionality + + . A collection of tools which provide Linux look and feel. + + The Cygwin DLL currently works with all recent, commercially released x86 32 + bit and 64 bit versions of Windows, with the exception of Windows CE. + +On both MinGW and Cygwin, PCRE should build correctly using: + + ./configure && make && make install + +This should create two libraries called libpcre and libpcreposix, and, if you +have enabled building the C++ wrapper, a third one called libpcrecpp. These are +independent libraries: when you link with libpcreposix or libpcrecpp you must +also link with libpcre, which contains the basic functions. (Some earlier +releases of PCRE included the basic libpcre functions in libpcreposix. This no +longer happens.) + +A user submitted a special-purpose patch that makes it easy to create +"pcre.dll" under mingw32 using the "msys" environment. It provides "pcre.dll" +as a special target. If you use this target, no other files are built, and in +particular, the pcretest and pcregrep programs are not built. An example of how +this might be used is: + + ./configure --enable-utf --disable-cpp CFLAGS="-03 -s"; make pcre.dll + +Using Cygwin's compiler generates libraries and executables that depend on +cygwin1.dll. If a library that is generated this way is distributed, +cygwin1.dll has to be distributed as well. Since cygwin1.dll is under the GPL +licence, this forces not only PCRE to be under the GPL, but also the entire +application. A distributor who wants to keep their own code proprietary must +purchase an appropriate Cygwin licence. + +MinGW has no such restrictions. The MinGW compiler generates a library or +executable that can run standalone on Windows without any third party dll or +licensing issues. + +But there is more complication: + +If a Cygwin user uses the -mno-cygwin Cygwin gcc flag, what that really does is +to tell Cygwin's gcc to use the MinGW gcc. Cygwin's gcc is only acting as a +front end to MinGW's gcc (if you install Cygwin's gcc, you get both Cygwin's +gcc and MinGW's gcc). So, a user can: + +. Build native binaries by using MinGW or by getting Cygwin and using + -mno-cygwin. + +. Build binaries that depend on cygwin1.dll by using Cygwin with the normal + compiler flags. + +The test files that are supplied with PCRE are in UNIX format, with LF +characters as line terminators. Unless your PCRE library uses a default newline +option that includes LF as a valid newline, it may be necessary to change the +line terminators in the test files to get some of the tests to work. + + +BUILDING PCRE ON WINDOWS WITH CMAKE + +CMake is an alternative configuration facility that can be used instead of +"configure". CMake creates project files (make files, solution files, etc.) +tailored to numerous development environments, including Visual Studio, +Borland, Msys, MinGW, NMake, and Unix. If possible, use short paths with no +spaces in the names for your CMake installation and your PCRE source and build +directories. + +The following instructions were contributed by a PCRE user. If they are not +followed exactly, errors may occur. In the event that errors do occur, it is +recommended that you delete the CMake cache before attempting to repeat the +CMake build process. In the CMake GUI, the cache can be deleted by selecting +"File > Delete Cache". + +1. Install the latest CMake version available from http://www.cmake.org/, and + ensure that cmake\bin is on your path. + +2. Unzip (retaining folder structure) the PCRE source tree into a source + directory such as C:\pcre. You should ensure your local date and time + is not earlier than the file dates in your source dir if the release is + very new. + +3. Create a new, empty build directory, preferably a subdirectory of the + source dir. For example, C:\pcre\pcre-xx\build. + +4. Run cmake-gui from the Shell envirornment of your build tool, for example, + Msys for Msys/MinGW or Visual Studio Command Prompt for VC/VC++. Do not try + to start Cmake from the Windows Start menu, as this can lead to errors. + +5. Enter C:\pcre\pcre-xx and C:\pcre\pcre-xx\build for the source and build + directories, respectively. + +6. Hit the "Configure" button. + +7. Select the particular IDE / build tool that you are using (Visual + Studio, MSYS makefiles, MinGW makefiles, etc.) + +8. The GUI will then list several configuration options. This is where + you can enable UTF-8 support or other PCRE optional features. + +9. Hit "Configure" again. The adjacent "Generate" button should now be + active. + +10. Hit "Generate". + +11. The build directory should now contain a usable build system, be it a + solution file for Visual Studio, makefiles for MinGW, etc. Exit from + cmake-gui and use the generated build system with your compiler or IDE. + E.g., for MinGW you can run "make", or for Visual Studio, open the PCRE + solution, select the desired configuration (Debug, or Release, etc.) and + build the ALL_BUILD project. + +12. If during configuration with cmake-gui you've elected to build the test + programs, you can execute them by building the test project. E.g., for + MinGW: "make test"; for Visual Studio build the RUN_TESTS project. The + most recent build configuration is targeted by the tests. A summary of + test results is presented. Complete test output is subsequently + available for review in Testing\Temporary under your build dir. + + +USE OF RELATIVE PATHS WITH CMAKE ON WINDOWS + +A PCRE user comments as follows: I thought that others may want to know the +current state of CMAKE_USE_RELATIVE_PATHS support on Windows. Here it is: + +-- AdditionalIncludeDirectories is only partially modified (only the + first path - see below) +-- Only some of the contained file paths are modified - shown below for + pcre.vcproj +-- It properly modifies + +I am sure CMake people can fix that if they want to. Until then one will +need to replace existing absolute paths in project files with relative +paths manually (e.g. from VS) - relative to project file location. I did +just that before being told to try CMAKE_USE_RELATIVE_PATHS. Not a big +deal. + +AdditionalIncludeDirectories="E:\builds\pcre\build;E:\builds\pcre\pcre-7.5;" +AdditionalIncludeDirectories=".;E:\builds\pcre\pcre-7.5;" + +RelativePath="pcre.h" +RelativePath="pcre_chartables.c" +RelativePath="pcre_chartables.c.rule" + + +TESTING WITH RUNTEST.BAT + +If configured with CMake, building the test project ("make test" or building +ALL_TESTS in Visual Studio) creates (and runs) pcre_test.bat (and depending +on your configuration options, possibly other test programs) in the build +directory. Pcre_test.bat runs RunTest.Bat with correct source and exe paths. + +For manual testing with RunTest.bat, provided the build dir is a subdirectory +of the source directory: Open command shell window. Chdir to the location +of your pcretest.exe and pcregrep.exe programs. Call RunTest.bat with +"..\RunTest.Bat" or "..\..\RunTest.bat" as appropriate. + +To run only a particular test with RunTest.Bat provide a test number argument. + +Otherwise: + +1. Copy RunTest.bat into the directory where pcretest.exe and pcregrep.exe + have been created. + +2. Edit RunTest.bat to indentify the full or relative location of + the pcre source (wherein which the testdata folder resides), e.g.: + + set srcdir=C:\pcre\pcre-8.20 + +3. In a Windows command environment, chdir to the location of your bat and + exe programs. + +4. Run RunTest.bat. Test outputs will automatically be compared to expected + results, and discrepancies will be identified in the console output. + +To independently test the just-in-time compiler, run pcre_jit_test.exe. +To test pcrecpp, run pcrecpp_unittest.exe, pcre_stringpiece_unittest.exe and +pcre_scanner_unittest.exe. + + +BUILDING UNDER WINDOWS CE WITH VISUAL STUDIO 200x + +Vincent Richomme sent a zip archive of files to help with this process. They +can be found in the file "pcre-vsbuild.zip" in the Contrib directory of the FTP +site. + + +BUILDING UNDER WINDOWS WITH BCC5.5 + +Michael Roy sent these comments about building PCRE under Windows with BCC5.5: + +Some of the core BCC libraries have a version of PCRE from 1998 built in, which +can lead to pcre_exec() giving an erroneous PCRE_ERROR_NULL from a version +mismatch. I'm including an easy workaround below, if you'd like to include it +in the non-unix instructions: + +When linking a project with BCC5.5, pcre.lib must be included before any of the +libraries cw32.lib, cw32i.lib, cw32mt.lib, and cw32mti.lib on the command line. + + +BUILDING USING BORLAND C++ BUILDER 2007 (CB2007) AND HIGHER + +A PCRE user sent these comments about this environment (see also the comment +from another user that follows them): + +The XE versions of C++ Builder come with a RegularExpressionsCore class which +contain a version of TPerlRegEx. However, direct use of the C PCRE library may +be desirable. + +The default makevp.bat, however, supplied with PCRE builds a version of PCRE +that is not usable with any version of C++ Builder because the compiler ships +with an embedded version of PCRE, version 2.01 from 1998! [See also the note +about BCC5.5 above.] If you want to use PCRE you'll need to rename the +functions (pcre_compile to pcre_compile_bcc, etc) or do as I have done and just +use the 16 bit versions. I'm using std::wstring everywhere anyway. Since the +embedded version of PCRE does not have the 16 bit function names, there is no +conflict. + +Building PCRE using a C++ Builder static library project file (recommended): + +1. Rename or remove pcre.h, pcreposi.h, and pcreposix.h from your C++ Builder +original include path. + +2. Download PCRE from pcre.org and extract to a directory. + +3. Rename pcre_chartables.c.dist to pcre_chartables.c, pcre.h.generic to +pcre.h, and config.h.generic to config.h. + +4. Edit pcre.h and pcre_config.c so that they include config.h. + +5. Edit config.h like so: + +Comment out the following lines: +#define PACKAGE "pcre" +#define PACKAGE_BUGREPORT "" +#define PACKAGE_NAME "PCRE" +#define PACKAGE_STRING "PCRE 8.32" +#define PACKAGE_TARNAME "pcre" +#define PACKAGE_URL "" +#define PACKAGE_VERSION "8.32" + +Add the following lines: +#ifndef SUPPORT_UTF +#define SUPPORT_UTF 100 // any value is fine +#endif + +#ifndef SUPPORT_UCP +#define SUPPORT_UCP 101 // any value is fine +#endif + +#ifndef SUPPORT_UCP +#define SUPPORT_PCRE16 102 // any value is fine +#endif + +#ifndef SUPPORT_UTF8 +#define SUPPORT_UTF8 103 // any value is fine +#endif + +6. Build a C++ Builder project using the IDE. Go to File / New / Other and +choose Static Library. You can name it pcre.cbproj or whatever. Now set your +paths by going to Project / Options. Set the Include path. Do this from the +"Base" option to apply to both Release and Debug builds. Now add the following +files to the project: + +pcre.h +pcre16_byte_order.c +pcre16_chartables.c +pcre16_compile.c +pcre16_config.c +pcre16_dfa_exec.c +pcre16_exec.c +pcre16_fullinfo.c +pcre16_get.c +pcre16_globals.c +pcre16_maketables.c +pcre16_newline.c +pcre16_ord2utf16.c +pcre16_printint.c +pcre16_refcount.c +pcre16_string_utils.c +pcre16_study.c +pcre16_tables.c +pcre16_ucd.c +pcre16_utf16_utils.c +pcre16_valid_utf16.c +pcre16_version.c +pcre16_xclass.c + +//Optional +pcre_version.c + +7. After compiling the .lib file, copy the .lib and header files to a project +you want to use PCRE with. Enjoy. + +Optional ... Building PCRE using the makevp.bat file: + +1. Edit makevp_c.txt and makevp_l.txt and change all the names to the 16 bit +versions. + +2. Edit makevp.bat and set the path to C++ Builder. Run makevp.bat. + +Another PCRE user added this comment: + +Another approach I successfully used for some years with BCB 5 and 6 was to +make sure that include and library paths of PCRE are configured before the +default paths of the IDE in the dialogs where one can manage those paths. +Afterwards one can open the project files using a text editor and manually add +the self created library for pcre itself, pcrecpp doesn't ship with the IDE, in +the library nodes where the IDE manages its own libraries to link against in +front of the IDE-own libraries. This way one can use the default PCRE function +names without getting access violations on runtime. + + <ALLLIB value="libpcre.lib $(LIBFILES) $(LIBRARIES) import32.lib cp32mt.lib"/> + + +BUILDING PCRE ON OPENVMS + +Stephen Hoffman sent the following, in December 2012: + +"Here <http://labs.hoffmanlabs.com/node/1847> is a very short write-up on the +OpenVMS port and here + +<http://labs.hoffmanlabs.com/labsnotes/pcre-vms-8_32.zip> + +is a zip with the OpenVMS files, and with one modified testing-related PCRE +file." This is a port of PCRE 8.32. + +Earlier, Dan Mooney sent the following comments about building PCRE on OpenVMS. +They relate to an older version of PCRE that used fewer source files, so the +exact commands will need changing. See the current list of source files above. + +"It was quite easy to compile and link the library. I don't have a formal +make file but the attached file [reproduced below] contains the OpenVMS DCL +commands I used to build the library. I had to add #define +POSIX_MALLOC_THRESHOLD 10 to pcre.h since it was not defined anywhere. + +The library was built on: +O/S: HP OpenVMS v7.3-1 +Compiler: Compaq C v6.5-001-48BCD +Linker: vA13-01 + +The test results did not match 100% due to the issues you mention in your +documentation regarding isprint(), iscntrl(), isgraph() and ispunct(). I +modified some of the character tables temporarily and was able to get the +results to match. Tests using the fr locale did not match since I don't have +that locale loaded. The study size was always reported to be 3 less than the +value in the standard test output files." + +========================= +$! This DCL procedure builds PCRE on OpenVMS +$! +$! I followed the instructions in the non-unix-use file in the distribution. +$! +$ COMPILE == "CC/LIST/NOMEMBER_ALIGNMENT/PREFIX_LIBRARY_ENTRIES=ALL_ENTRIES +$ COMPILE DFTABLES.C +$ LINK/EXE=DFTABLES.EXE DFTABLES.OBJ +$ RUN DFTABLES.EXE/OUTPUT=CHARTABLES.C +$ COMPILE MAKETABLES.C +$ COMPILE GET.C +$ COMPILE STUDY.C +$! I had to set POSIX_MALLOC_THRESHOLD to 10 in PCRE.H since the symbol +$! did not seem to be defined anywhere. +$! I edited pcre.h and added #DEFINE SUPPORT_UTF8 to enable UTF8 support. +$ COMPILE PCRE.C +$ LIB/CREATE PCRE MAKETABLES.OBJ, GET.OBJ, STUDY.OBJ, PCRE.OBJ +$! I had to set POSIX_MALLOC_THRESHOLD to 10 in PCRE.H since the symbol +$! did not seem to be defined anywhere. +$ COMPILE PCREPOSIX.C +$ LIB/CREATE PCREPOSIX PCREPOSIX.OBJ +$ COMPILE PCRETEST.C +$ LINK/EXE=PCRETEST.EXE PCRETEST.OBJ, PCRE/LIB, PCREPOSIX/LIB +$! C programs that want access to command line arguments must be +$! defined as a symbol +$ PCRETEST :== "$ SYS$ROADSUSERS:[DMOONEY.REGEXP]PCRETEST.EXE" +$! Arguments must be enclosed in quotes. +$ PCRETEST "-C" +$! Test results: +$! +$! The test results did not match 100%. The functions isprint(), iscntrl(), +$! isgraph() and ispunct() on OpenVMS must not produce the same results +$! as the system that built the test output files provided with the +$! distribution. +$! +$! The study size did not match and was always 3 less on OpenVMS. +$! +$! Locale could not be set to fr +$! +========================= + + +BUILDING PCRE ON STRATUS OPENVOS + +These notes on the port of PCRE to VOS (lightly edited) were supplied by +Ashutosh Warikoo, whose email address has the local part awarikoo and the +domain nse.co.in. The port was for version 7.9 in August 2009. + +1. Building PCRE + +I built pcre on OpenVOS Release 17.0.1at using GNU Tools 3.4a without any +problems. I used the following packages to build PCRE: + + ftp://ftp.stratus.com/pub/vos/posix/ga/posix.save.evf.gz + +Please read and follow the instructions that come with these packages. To start +the build of pcre, from the root of the package type: + + ./build.sh + +2. Installing PCRE + +Once you have successfully built PCRE, login to the SysAdmin group, switch to +the root user, and type + + [ !create_dir (master_disk)>usr --if needed ] + [ !create_dir (master_disk)>usr>local --if needed ] + !gmake install + +This installs PCRE and its man pages into /usr/local. You can add +(master_disk)>usr>local>bin to your command search paths, or if you are in +BASH, add /usr/local/bin to the PATH environment variable. + +4. Restrictions + +This port requires readline library optionally. However during the build I +faced some yet unexplored errors while linking with readline. As it was an +optional component I chose to disable it. + +5. Known Problems + +I ran the test suite, but you will have to be your own judge of whether this +command, and this port, suits your purposes. If you find any problems that +appear to be related to the port itself, please let me know. Please see the +build.log file in the root of the package also. + + +BUILDING PCRE ON NATIVE Z/OS AND Z/VM + +z/OS and z/VM are operating systems for mainframe computers, produced by IBM. +The character code used is EBCDIC, not ASCII or Unicode. In z/OS, UNIX APIs and +applications can be supported through UNIX System Services, and in such an +environment PCRE can be built in the same way as in other systems. However, in +native z/OS (without UNIX System Services) and in z/VM, special ports are +required. For details, please see this web site: + + http://www.zaconsultants.net + +You may download PCRE from WWW.CBTTAPE.ORG, file 882.  Everything, source and +executable, is in EBCDIC and native z/OS file formats and this is the +recommended download site. + +========================== +Last Updated: 25 June 2015 diff --git a/doc/html/README.txt b/doc/html/README.txt new file mode 100644 index 0000000..4887ebf --- /dev/null +++ b/doc/html/README.txt @@ -0,0 +1,1002 @@ +README file for PCRE (Perl-compatible regular expression library) +----------------------------------------------------------------- + +NOTE: This set of files relates to PCRE releases that use the original API, +with library names libpcre, libpcre16, and libpcre32. January 2015 saw the +first release of a new API, known as PCRE2, with release numbers starting at +10.00 and library names libpcre2-8, libpcre2-16, and libpcre2-32. The old +libraries (now called PCRE1) are still being maintained for bug fixes, but +there will be no new development. New projects are advised to use the new PCRE2 +libraries. + + +The latest release of PCRE1 is always available in three alternative formats +from: + + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.bz2 + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.zip + +There is a mailing list for discussion about the development of PCRE at +pcre-dev@exim.org. You can access the archives and subscribe or manage your +subscription here: + + https://lists.exim.org/mailman/listinfo/pcre-dev + +Please read the NEWS file if you are upgrading from a previous release. +The contents of this README file are: + + The PCRE APIs + Documentation for PCRE + Contributions by users of PCRE + Building PCRE on non-Unix-like systems + Building PCRE without using autotools + Building PCRE using autotools + Retrieving configuration information + Shared libraries + Cross-compiling using autotools + Using HP's ANSI C++ compiler (aCC) + Compiling in Tru64 using native compilers + Using Sun's compilers for Solaris + Using PCRE from MySQL + Making new tarballs + Testing PCRE + Character tables + File manifest + + +The PCRE APIs +------------- + +PCRE is written in C, and it has its own API. There are three sets of +functions, one for the 8-bit library, which processes strings of bytes, one for +the 16-bit library, which processes strings of 16-bit values, and one for the +32-bit library, which processes strings of 32-bit values. The distribution also +includes a set of C++ wrapper functions (see the pcrecpp man page for details), +courtesy of Google Inc., which can be used to call the 8-bit PCRE library from +C++. Other C++ wrappers have been created from time to time. See, for example: +https://github.com/YasserAsmi/regexp, which aims to be simple and similar in +style to the C API. + +The distribution also contains a set of C wrapper functions (again, just for +the 8-bit library) that are based on the POSIX regular expression API (see the +pcreposix man page). These end up in the library called libpcreposix. Note that +this just provides a POSIX calling interface to PCRE; the regular expressions +themselves still follow Perl syntax and semantics. The POSIX API is restricted, +and does not give full access to all of PCRE's facilities. + +The header file for the POSIX-style functions is called pcreposix.h. The +official POSIX name is regex.h, but I did not want to risk possible problems +with existing files of that name by distributing it that way. To use PCRE with +an existing program that uses the POSIX API, pcreposix.h will have to be +renamed or pointed at by a link. + +If you are using the POSIX interface to PCRE and there is already a POSIX regex +library installed on your system, as well as worrying about the regex.h header +file (as mentioned above), you must also take care when linking programs to +ensure that they link with PCRE's libpcreposix library. Otherwise they may pick +up the POSIX functions of the same name from the other library. + +One way of avoiding this confusion is to compile PCRE with the addition of +-Dregcomp=PCREregcomp (and similarly for the other POSIX functions) to the +compiler flags (CFLAGS if you are using "configure" -- see below). This has the +effect of renaming the functions so that the names no longer clash. Of course, +you have to do the same thing for your applications, or write them using the +new names. + + +Documentation for PCRE +---------------------- + +If you install PCRE in the normal way on a Unix-like system, you will end up +with a set of man pages whose names all start with "pcre". The one that is just +called "pcre" lists all the others. In addition to these man pages, the PCRE +documentation is supplied in two other forms: + + 1. There are files called doc/pcre.txt, doc/pcregrep.txt, and + doc/pcretest.txt in the source distribution. The first of these is a + concatenation of the text forms of all the section 3 man pages except + the listing of pcredemo.c and those that summarize individual functions. + The other two are the text forms of the section 1 man pages for the + pcregrep and pcretest commands. These text forms are provided for ease of + scanning with text editors or similar tools. They are installed in + <prefix>/share/doc/pcre, where <prefix> is the installation prefix + (defaulting to /usr/local). + + 2. A set of files containing all the documentation in HTML form, hyperlinked + in various ways, and rooted in a file called index.html, is distributed in + doc/html and installed in <prefix>/share/doc/pcre/html. + +Users of PCRE have contributed files containing the documentation for various +releases in CHM format. These can be found in the Contrib directory of the FTP +site (see next section). + + +Contributions by users of PCRE +------------------------------ + +You can find contributions from PCRE users in the directory + + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib + +There is a README file giving brief descriptions of what they are. Some are +complete in themselves; others are pointers to URLs containing relevant files. +Some of this material is likely to be well out-of-date. Several of the earlier +contributions provided support for compiling PCRE on various flavours of +Windows (I myself do not use Windows). Nowadays there is more Windows support +in the standard distribution, so these contibutions have been archived. + +A PCRE user maintains downloadable Windows binaries of the pcregrep and +pcretest programs here: + + http://www.rexegg.com/pcregrep-pcretest.html + + +Building PCRE on non-Unix-like systems +-------------------------------------- + +For a non-Unix-like system, please read the comments in the file +NON-AUTOTOOLS-BUILD, though if your system supports the use of "configure" and +"make" you may be able to build PCRE using autotools in the same way as for +many Unix-like systems. + +PCRE can also be configured using the GUI facility provided by CMake's +cmake-gui command. This creates Makefiles, solution files, etc. The file +NON-AUTOTOOLS-BUILD has information about CMake. + +PCRE has been compiled on many different operating systems. It should be +straightforward to build PCRE on any system that has a Standard C compiler and +library, because it uses only Standard C functions. + + +Building PCRE without using autotools +------------------------------------- + +The use of autotools (in particular, libtool) is problematic in some +environments, even some that are Unix or Unix-like. See the NON-AUTOTOOLS-BUILD +file for ways of building PCRE without using autotools. + + +Building PCRE using autotools +----------------------------- + +If you are using HP's ANSI C++ compiler (aCC), please see the special note +in the section entitled "Using HP's ANSI C++ compiler (aCC)" below. + +The following instructions assume the use of the widely used "configure; make; +make install" (autotools) process. + +To build PCRE on system that supports autotools, first run the "configure" +command from the PCRE distribution directory, with your current directory set +to the directory where you want the files to be created. This command is a +standard GNU "autoconf" configuration script, for which generic instructions +are supplied in the file INSTALL. + +Most commonly, people build PCRE within its own distribution directory, and in +this case, on many systems, just running "./configure" is sufficient. However, +the usual methods of changing standard defaults are available. For example: + +CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local + +This command specifies that the C compiler should be run with the flags '-O2 +-Wall' instead of the default, and that "make install" should install PCRE +under /opt/local instead of the default /usr/local. + +If you want to build in a different directory, just run "configure" with that +directory as current. For example, suppose you have unpacked the PCRE source +into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx: + +cd /build/pcre/pcre-xxx +/source/pcre/pcre-xxx/configure + +PCRE is written in C and is normally compiled as a C library. However, it is +possible to build it as a C++ library, though the provided building apparatus +does not have any features to support this. + +There are some optional features that can be included or omitted from the PCRE +library. They are also documented in the pcrebuild man page. + +. By default, both shared and static libraries are built. You can change this + by adding one of these options to the "configure" command: + + --disable-shared + --disable-static + + (See also "Shared libraries on Unix-like systems" below.) + +. By default, only the 8-bit library is built. If you add --enable-pcre16 to + the "configure" command, the 16-bit library is also built. If you add + --enable-pcre32 to the "configure" command, the 32-bit library is also built. + If you want only the 16-bit or 32-bit library, use --disable-pcre8 to disable + building the 8-bit library. + +. If you are building the 8-bit library and want to suppress the building of + the C++ wrapper library, you can add --disable-cpp to the "configure" + command. Otherwise, when "configure" is run without --disable-pcre8, it will + try to find a C++ compiler and C++ header files, and if it succeeds, it will + try to build the C++ wrapper. + +. If you want to include support for just-in-time compiling, which can give + large performance improvements on certain platforms, add --enable-jit to the + "configure" command. This support is available only for certain hardware + architectures. If you try to enable it on an unsupported architecture, there + will be a compile time error. + +. When JIT support is enabled, pcregrep automatically makes use of it, unless + you add --disable-pcregrep-jit to the "configure" command. + +. If you want to make use of the support for UTF-8 Unicode character strings in + the 8-bit library, or UTF-16 Unicode character strings in the 16-bit library, + or UTF-32 Unicode character strings in the 32-bit library, you must add + --enable-utf to the "configure" command. Without it, the code for handling + UTF-8, UTF-16 and UTF-8 is not included in the relevant library. Even + when --enable-utf is included, the use of a UTF encoding still has to be + enabled by an option at run time. When PCRE is compiled with this option, its + input can only either be ASCII or UTF-8/16/32, even when running on EBCDIC + platforms. It is not possible to use both --enable-utf and --enable-ebcdic at + the same time. + +. There are no separate options for enabling UTF-8, UTF-16 and UTF-32 + independently because that would allow ridiculous settings such as requesting + UTF-16 support while building only the 8-bit library. However, the option + --enable-utf8 is retained for backwards compatibility with earlier releases + that did not support 16-bit or 32-bit character strings. It is synonymous with + --enable-utf. It is not possible to configure one library with UTF support + and the other without in the same configuration. + +. If, in addition to support for UTF-8/16/32 character strings, you want to + include support for the \P, \p, and \X sequences that recognize Unicode + character properties, you must add --enable-unicode-properties to the + "configure" command. This adds about 30K to the size of the library (in the + form of a property table); only the basic two-letter properties such as Lu + are supported. + +. You can build PCRE to recognize either CR or LF or the sequence CRLF or any + of the preceding, or any of the Unicode newline sequences as indicating the + end of a line. Whatever you specify at build time is the default; the caller + of PCRE can change the selection at run time. The default newline indicator + is a single LF character (the Unix standard). You can specify the default + newline indicator by adding --enable-newline-is-cr or --enable-newline-is-lf + or --enable-newline-is-crlf or --enable-newline-is-anycrlf or + --enable-newline-is-any to the "configure" command, respectively. + + If you specify --enable-newline-is-cr or --enable-newline-is-crlf, some of + the standard tests will fail, because the lines in the test files end with + LF. Even if the files are edited to change the line endings, there are likely + to be some failures. With --enable-newline-is-anycrlf or + --enable-newline-is-any, many tests should succeed, but there may be some + failures. + +. By default, the sequence \R in a pattern matches any Unicode line ending + sequence. This is independent of the option specifying what PCRE considers to + be the end of a line (see above). However, the caller of PCRE can restrict \R + to match only CR, LF, or CRLF. You can make this the default by adding + --enable-bsr-anycrlf to the "configure" command (bsr = "backslash R"). + +. When called via the POSIX interface, PCRE uses malloc() to get additional + storage for processing capturing parentheses if there are more than 10 of + them in a pattern. You can increase this threshold by setting, for example, + + --with-posix-malloc-threshold=20 + + on the "configure" command. + +. PCRE has a counter that limits the depth of nesting of parentheses in a + pattern. This limits the amount of system stack that a pattern uses when it + is compiled. The default is 250, but you can change it by setting, for + example, + + --with-parens-nest-limit=500 + +. PCRE has a counter that can be set to limit the amount of resources it uses + when matching a pattern. If the limit is exceeded during a match, the match + fails. The default is ten million. You can change the default by setting, for + example, + + --with-match-limit=500000 + + on the "configure" command. This is just the default; individual calls to + pcre_exec() can supply their own value. There is more discussion on the + pcreapi man page. + +. There is a separate counter that limits the depth of recursive function calls + during a matching process. This also has a default of ten million, which is + essentially "unlimited". You can change the default by setting, for example, + + --with-match-limit-recursion=500000 + + Recursive function calls use up the runtime stack; running out of stack can + cause programs to crash in strange ways. There is a discussion about stack + sizes in the pcrestack man page. + +. The default maximum compiled pattern size is around 64K. You can increase + this by adding --with-link-size=3 to the "configure" command. In the 8-bit + library, PCRE then uses three bytes instead of two for offsets to different + parts of the compiled pattern. In the 16-bit library, --with-link-size=3 is + the same as --with-link-size=4, which (in both libraries) uses four-byte + offsets. Increasing the internal link size reduces performance. In the 32-bit + library, the only supported link size is 4. + +. You can build PCRE so that its internal match() function that is called from + pcre_exec() does not call itself recursively. Instead, it uses memory blocks + obtained from the heap via the special functions pcre_stack_malloc() and + pcre_stack_free() to save data that would otherwise be saved on the stack. To + build PCRE like this, use + + --disable-stack-for-recursion + + on the "configure" command. PCRE runs more slowly in this mode, but it may be + necessary in environments with limited stack sizes. This applies only to the + normal execution of the pcre_exec() function; if JIT support is being + successfully used, it is not relevant. Equally, it does not apply to + pcre_dfa_exec(), which does not use deeply nested recursion. There is a + discussion about stack sizes in the pcrestack man page. + +. For speed, PCRE uses four tables for manipulating and identifying characters + whose code point values are less than 256. By default, it uses a set of + tables for ASCII encoding that is part of the distribution. If you specify + + --enable-rebuild-chartables + + a program called dftables is compiled and run in the default C locale when + you obey "make". It builds a source file called pcre_chartables.c. If you do + not specify this option, pcre_chartables.c is created as a copy of + pcre_chartables.c.dist. See "Character tables" below for further information. + +. It is possible to compile PCRE for use on systems that use EBCDIC as their + character code (as opposed to ASCII/Unicode) by specifying + + --enable-ebcdic + + This automatically implies --enable-rebuild-chartables (see above). However, + when PCRE is built this way, it always operates in EBCDIC. It cannot support + both EBCDIC and UTF-8/16/32. There is a second option, --enable-ebcdic-nl25, + which specifies that the code value for the EBCDIC NL character is 0x25 + instead of the default 0x15. + +. In environments where valgrind is installed, if you specify + + --enable-valgrind + + PCRE will use valgrind annotations to mark certain memory regions as + unaddressable. This allows it to detect invalid memory accesses, and is + mostly useful for debugging PCRE itself. + +. In environments where the gcc compiler is used and lcov version 1.6 or above + is installed, if you specify + + --enable-coverage + + the build process implements a code coverage report for the test suite. The + report is generated by running "make coverage". If ccache is installed on + your system, it must be disabled when building PCRE for coverage reporting. + You can do this by setting the environment variable CCACHE_DISABLE=1 before + running "make" to build PCRE. There is more information about coverage + reporting in the "pcrebuild" documentation. + +. The pcregrep program currently supports only 8-bit data files, and so + requires the 8-bit PCRE library. It is possible to compile pcregrep to use + libz and/or libbz2, in order to read .gz and .bz2 files (respectively), by + specifying one or both of + + --enable-pcregrep-libz + --enable-pcregrep-libbz2 + + Of course, the relevant libraries must be installed on your system. + +. The default size (in bytes) of the internal buffer used by pcregrep can be + set by, for example: + + --with-pcregrep-bufsize=51200 + + The value must be a plain integer. The default is 20480. + +. It is possible to compile pcretest so that it links with the libreadline + or libedit libraries, by specifying, respectively, + + --enable-pcretest-libreadline or --enable-pcretest-libedit + + If this is done, when pcretest's input is from a terminal, it reads it using + the readline() function. This provides line-editing and history facilities. + Note that libreadline is GPL-licenced, so if you distribute a binary of + pcretest linked in this way, there may be licensing issues. These can be + avoided by linking with libedit (which has a BSD licence) instead. + + Enabling libreadline causes the -lreadline option to be added to the pcretest + build. In many operating environments with a sytem-installed readline + library this is sufficient. However, in some environments (e.g. if an + unmodified distribution version of readline is in use), it may be necessary + to specify something like LIBS="-lncurses" as well. This is because, to quote + the readline INSTALL, "Readline uses the termcap functions, but does not link + with the termcap or curses library itself, allowing applications which link + with readline the to choose an appropriate library." If you get error + messages about missing functions tgetstr, tgetent, tputs, tgetflag, or tgoto, + this is the problem, and linking with the ncurses library should fix it. + +The "configure" script builds the following files for the basic C library: + +. Makefile the makefile that builds the library +. config.h build-time configuration options for the library +. pcre.h the public PCRE header file +. pcre-config script that shows the building settings such as CFLAGS + that were set for "configure" +. libpcre.pc ) data for the pkg-config command +. libpcre16.pc ) +. libpcre32.pc ) +. libpcreposix.pc ) +. libtool script that builds shared and/or static libraries + +Versions of config.h and pcre.h are distributed in the PCRE tarballs under the +names config.h.generic and pcre.h.generic. These are provided for those who +have to built PCRE without using "configure" or CMake. If you use "configure" +or CMake, the .generic versions are not used. + +When building the 8-bit library, if a C++ compiler is found, the following +files are also built: + +. libpcrecpp.pc data for the pkg-config command +. pcrecpparg.h header file for calling PCRE via the C++ wrapper +. pcre_stringpiece.h header for the C++ "stringpiece" functions + +The "configure" script also creates config.status, which is an executable +script that can be run to recreate the configuration, and config.log, which +contains compiler output from tests that "configure" runs. + +Once "configure" has run, you can run "make". This builds the the libraries +libpcre, libpcre16 and/or libpcre32, and a test program called pcretest. If you +enabled JIT support with --enable-jit, a test program called pcre_jit_test is +built as well. + +If the 8-bit library is built, libpcreposix and the pcregrep command are also +built, and if a C++ compiler was found on your system, and you did not disable +it with --disable-cpp, "make" builds the C++ wrapper library, which is called +libpcrecpp, as well as some test programs called pcrecpp_unittest, +pcre_scanner_unittest, and pcre_stringpiece_unittest. + +The command "make check" runs all the appropriate tests. Details of the PCRE +tests are given below in a separate section of this document. + +You can use "make install" to install PCRE into live directories on your +system. The following are installed (file names are all relative to the +<prefix> that is set when "configure" is run): + + Commands (bin): + pcretest + pcregrep (if 8-bit support is enabled) + pcre-config + + Libraries (lib): + libpcre16 (if 16-bit support is enabled) + libpcre32 (if 32-bit support is enabled) + libpcre (if 8-bit support is enabled) + libpcreposix (if 8-bit support is enabled) + libpcrecpp (if 8-bit and C++ support is enabled) + + Configuration information (lib/pkgconfig): + libpcre16.pc + libpcre32.pc + libpcre.pc + libpcreposix.pc + libpcrecpp.pc (if C++ support is enabled) + + Header files (include): + pcre.h + pcreposix.h + pcre_scanner.h ) + pcre_stringpiece.h ) if C++ support is enabled + pcrecpp.h ) + pcrecpparg.h ) + + Man pages (share/man/man{1,3}): + pcregrep.1 + pcretest.1 + pcre-config.1 + pcre.3 + pcre*.3 (lots more pages, all starting "pcre") + + HTML documentation (share/doc/pcre/html): + index.html + *.html (lots more pages, hyperlinked from index.html) + + Text file documentation (share/doc/pcre): + AUTHORS + COPYING + ChangeLog + LICENCE + NEWS + README + pcre.txt (a concatenation of the man(3) pages) + pcretest.txt the pcretest man page + pcregrep.txt the pcregrep man page + pcre-config.txt the pcre-config man page + +If you want to remove PCRE from your system, you can run "make uninstall". +This removes all the files that "make install" installed. However, it does not +remove any directories, because these are often shared with other programs. + + +Retrieving configuration information +------------------------------------ + +Running "make install" installs the command pcre-config, which can be used to +recall information about the PCRE configuration and installation. For example: + + pcre-config --version + +prints the version number, and + + pcre-config --libs + +outputs information about where the library is installed. This command can be +included in makefiles for programs that use PCRE, saving the programmer from +having to remember too many details. + +The pkg-config command is another system for saving and retrieving information +about installed libraries. Instead of separate commands for each library, a +single command is used. For example: + + pkg-config --cflags pcre + +The data is held in *.pc files that are installed in a directory called +<prefix>/lib/pkgconfig. + + +Shared libraries +---------------- + +The default distribution builds PCRE as shared libraries and static libraries, +as long as the operating system supports shared libraries. Shared library +support relies on the "libtool" script which is built as part of the +"configure" process. + +The libtool script is used to compile and link both shared and static +libraries. They are placed in a subdirectory called .libs when they are newly +built. The programs pcretest and pcregrep are built to use these uninstalled +libraries (by means of wrapper scripts in the case of shared libraries). When +you use "make install" to install shared libraries, pcregrep and pcretest are +automatically re-built to use the newly installed shared libraries before being +installed themselves. However, the versions left in the build directory still +use the uninstalled libraries. + +To build PCRE using static libraries only you must use --disable-shared when +configuring it. For example: + +./configure --prefix=/usr/gnu --disable-shared + +Then run "make" in the usual way. Similarly, you can use --disable-static to +build only shared libraries. + + +Cross-compiling using autotools +------------------------------- + +You can specify CC and CFLAGS in the normal way to the "configure" command, in +order to cross-compile PCRE for some other host. However, you should NOT +specify --enable-rebuild-chartables, because if you do, the dftables.c source +file is compiled and run on the local host, in order to generate the inbuilt +character tables (the pcre_chartables.c file). This will probably not work, +because dftables.c needs to be compiled with the local compiler, not the cross +compiler. + +When --enable-rebuild-chartables is not specified, pcre_chartables.c is created +by making a copy of pcre_chartables.c.dist, which is a default set of tables +that assumes ASCII code. Cross-compiling with the default tables should not be +a problem. + +If you need to modify the character tables when cross-compiling, you should +move pcre_chartables.c.dist out of the way, then compile dftables.c by hand and +run it on the local host to make a new version of pcre_chartables.c.dist. +Then when you cross-compile PCRE this new version of the tables will be used. + + +Using HP's ANSI C++ compiler (aCC) +---------------------------------- + +Unless C++ support is disabled by specifying the "--disable-cpp" option of the +"configure" script, you must include the "-AA" option in the CXXFLAGS +environment variable in order for the C++ components to compile correctly. + +Also, note that the aCC compiler on PA-RISC platforms may have a defect whereby +needed libraries fail to get included when specifying the "-AA" compiler +option. If you experience unresolved symbols when linking the C++ programs, +use the workaround of specifying the following environment variable prior to +running the "configure" script: + + CXXLDFLAGS="-lstd_v2 -lCsup_v2" + + +Compiling in Tru64 using native compilers +----------------------------------------- + +The following error may occur when compiling with native compilers in the Tru64 +operating system: + + CXX libpcrecpp_la-pcrecpp.lo +cxx: Error: /usr/lib/cmplrs/cxx/V7.1-006/include/cxx/iosfwd, line 58: #error + directive: "cannot include iosfwd -- define __USE_STD_IOSTREAM to + override default - see section 7.1.2 of the C++ Using Guide" +#error "cannot include iosfwd -- define __USE_STD_IOSTREAM to override default +- see section 7.1.2 of the C++ Using Guide" + +This may be followed by other errors, complaining that 'namespace "std" has no +member'. The solution to this is to add the line + +#define __USE_STD_IOSTREAM 1 + +to the config.h file. + + +Using Sun's compilers for Solaris +--------------------------------- + +A user reports that the following configurations work on Solaris 9 sparcv9 and +Solaris 9 x86 (32-bit): + + Solaris 9 sparcv9: ./configure --disable-cpp CC=/bin/cc CFLAGS="-m64 -g" + Solaris 9 x86: ./configure --disable-cpp CC=/bin/cc CFLAGS="-g" + + +Using PCRE from MySQL +--------------------- + +On systems where both PCRE and MySQL are installed, it is possible to make use +of PCRE from within MySQL, as an alternative to the built-in pattern matching. +There is a web page that tells you how to do this: + + http://www.mysqludf.org/lib_mysqludf_preg/index.php + + +Making new tarballs +------------------- + +The command "make dist" creates three PCRE tarballs, in tar.gz, tar.bz2, and +zip formats. The command "make distcheck" does the same, but then does a trial +build of the new distribution to ensure that it works. + +If you have modified any of the man page sources in the doc directory, you +should first run the PrepareRelease script before making a distribution. This +script creates the .txt and HTML forms of the documentation from the man pages. + + +Testing PCRE +------------ + +To test the basic PCRE library on a Unix-like system, run the RunTest script. +There is another script called RunGrepTest that tests the options of the +pcregrep command. If the C++ wrapper library is built, three test programs +called pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest +are also built. When JIT support is enabled, another test program called +pcre_jit_test is built. + +Both the scripts and all the program tests are run if you obey "make check" or +"make test". For other environments, see the instructions in +NON-AUTOTOOLS-BUILD. + +The RunTest script runs the pcretest test program (which is documented in its +own man page) on each of the relevant testinput files in the testdata +directory, and compares the output with the contents of the corresponding +testoutput files. RunTest uses a file called testtry to hold the main output +from pcretest. Other files whose names begin with "test" are used as working +files in some tests. + +Some tests are relevant only when certain build-time options were selected. For +example, the tests for UTF-8/16/32 support are run only if --enable-utf was +used. RunTest outputs a comment when it skips a test. + +Many of the tests that are not skipped are run up to three times. The second +run forces pcre_study() to be called for all patterns except for a few in some +tests that are marked "never study" (see the pcretest program for how this is +done). If JIT support is available, the non-DFA tests are run a third time, +this time with a forced pcre_study() with the PCRE_STUDY_JIT_COMPILE option. +This testing can be suppressed by putting "nojit" on the RunTest command line. + +The entire set of tests is run once for each of the 8-bit, 16-bit and 32-bit +libraries that are enabled. If you want to run just one set of tests, call +RunTest with either the -8, -16 or -32 option. + +If valgrind is installed, you can run the tests under it by putting "valgrind" +on the RunTest command line. To run pcretest on just one or more specific test +files, give their numbers as arguments to RunTest, for example: + + RunTest 2 7 11 + +You can also specify ranges of tests such as 3-6 or 3- (meaning 3 to the +end), or a number preceded by ~ to exclude a test. For example: + + Runtest 3-15 ~10 + +This runs tests 3 to 15, excluding test 10, and just ~13 runs all the tests +except test 13. Whatever order the arguments are in, the tests are always run +in numerical order. + +You can also call RunTest with the single argument "list" to cause it to output +a list of tests. + +The first test file can be fed directly into the perltest.pl script to check +that Perl gives the same results. The only difference you should see is in the +first few lines, where the Perl version is given instead of the PCRE version. + +The second set of tests check pcre_fullinfo(), pcre_study(), +pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error +detection, and run-time flags that are specific to PCRE, as well as the POSIX +wrapper API. It also uses the debugging flags to check some of the internals of +pcre_compile(). + +If you build PCRE with a locale setting that is not the standard C locale, the +character tables may be different (see next paragraph). In some cases, this may +cause failures in the second set of tests. For example, in a locale where the +isprint() function yields TRUE for characters in the range 128-255, the use of +[:isascii:] inside a character class defines a different set of characters, and +this shows up in this test as a difference in the compiled code, which is being +listed for checking. Where the comparison test output contains [\x00-\x7f] the +test will contain [\x00-\xff], and similarly in some other cases. This is not a +bug in PCRE. + +The third set of tests checks pcre_maketables(), the facility for building a +set of character tables for a specific locale and using them instead of the +default tables. The tests make use of the "fr_FR" (French) locale. Before +running the test, the script checks for the presence of this locale by running +the "locale" command. If that command fails, or if it doesn't include "fr_FR" +in the list of available locales, the third test cannot be run, and a comment +is output to say why. If running this test produces instances of the error + + ** Failed to set locale "fr_FR" + +in the comparison output, it means that locale is not available on your system, +despite being listed by "locale". This does not mean that PCRE is broken. + +[If you are trying to run this test on Windows, you may be able to get it to +work by changing "fr_FR" to "french" everywhere it occurs. Alternatively, use +RunTest.bat. The version of RunTest.bat included with PCRE 7.4 and above uses +Windows versions of test 2. More info on using RunTest.bat is included in the +document entitled NON-UNIX-USE.] + +The fourth and fifth tests check the UTF-8/16/32 support and error handling and +internal UTF features of PCRE that are not relevant to Perl, respectively. The +sixth and seventh tests do the same for Unicode character properties support. + +The eighth, ninth, and tenth tests check the pcre_dfa_exec() alternative +matching function, in non-UTF-8/16/32 mode, UTF-8/16/32 mode, and UTF-8/16/32 +mode with Unicode property support, respectively. + +The eleventh test checks some internal offsets and code size features; it is +run only when the default "link size" of 2 is set (in other cases the sizes +change) and when Unicode property support is enabled. + +The twelfth test is run only when JIT support is available, and the thirteenth +test is run only when JIT support is not available. They test some JIT-specific +features such as information output from pcretest about JIT compilation. + +The fourteenth, fifteenth, and sixteenth tests are run only in 8-bit mode, and +the seventeenth, eighteenth, and nineteenth tests are run only in 16/32-bit +mode. These are tests that generate different output in the two modes. They are +for general cases, UTF-8/16/32 support, and Unicode property support, +respectively. + +The twentieth test is run only in 16/32-bit mode. It tests some specific +16/32-bit features of the DFA matching engine. + +The twenty-first and twenty-second tests are run only in 16/32-bit mode, when +the link size is set to 2 for the 16-bit library. They test reloading +pre-compiled patterns. + +The twenty-third and twenty-fourth tests are run only in 16-bit mode. They are +for general cases, and UTF-16 support, respectively. + +The twenty-fifth and twenty-sixth tests are run only in 32-bit mode. They are +for general cases, and UTF-32 support, respectively. + + +Character tables +---------------- + +For speed, PCRE uses four tables for manipulating and identifying characters +whose code point values are less than 256. The final argument of the +pcre_compile() function is a pointer to a block of memory containing the +concatenated tables. A call to pcre_maketables() can be used to generate a set +of tables in the current locale. If the final argument for pcre_compile() is +passed as NULL, a set of default tables that is built into the binary is used. + +The source file called pcre_chartables.c contains the default set of tables. By +default, this is created as a copy of pcre_chartables.c.dist, which contains +tables for ASCII coding. However, if --enable-rebuild-chartables is specified +for ./configure, a different version of pcre_chartables.c is built by the +program dftables (compiled from dftables.c), which uses the ANSI C character +handling functions such as isalnum(), isalpha(), isupper(), islower(), etc. to +build the table sources. This means that the default C locale which is set for +your system will control the contents of these default tables. You can change +the default tables by editing pcre_chartables.c and then re-building PCRE. If +you do this, you should take care to ensure that the file does not get +automatically re-generated. The best way to do this is to move +pcre_chartables.c.dist out of the way and replace it with your customized +tables. + +When the dftables program is run as a result of --enable-rebuild-chartables, +it uses the default C locale that is set on your system. It does not pay +attention to the LC_xxx environment variables. In other words, it uses the +system's default locale rather than whatever the compiling user happens to have +set. If you really do want to build a source set of character tables in a +locale that is specified by the LC_xxx variables, you can run the dftables +program by hand with the -L option. For example: + + ./dftables -L pcre_chartables.c.special + +The first two 256-byte tables provide lower casing and case flipping functions, +respectively. The next table consists of three 32-byte bit maps which identify +digits, "word" characters, and white space, respectively. These are used when +building 32-byte bit maps that represent character classes for code points less +than 256. + +The final 256-byte table has bits indicating various character types, as +follows: + + 1 white space character + 2 letter + 4 decimal digit + 8 hexadecimal digit + 16 alphanumeric or '_' + 128 regular expression metacharacter or binary zero + +You should not alter the set of characters that contain the 128 bit, as that +will cause PCRE to malfunction. + + +File manifest +------------- + +The distribution should contain the files listed below. Where a file name is +given as pcre[16|32]_xxx it means that there are three files, one with the name +pcre_xxx, one with the name pcre16_xx, and a third with the name pcre32_xxx. + +(A) Source files of the PCRE library functions and their headers: + + dftables.c auxiliary program for building pcre_chartables.c + when --enable-rebuild-chartables is specified + + pcre_chartables.c.dist a default set of character tables that assume ASCII + coding; used, unless --enable-rebuild-chartables is + specified, by copying to pcre[16]_chartables.c + + pcreposix.c ) + pcre[16|32]_byte_order.c ) + pcre[16|32]_compile.c ) + pcre[16|32]_config.c ) + pcre[16|32]_dfa_exec.c ) + pcre[16|32]_exec.c ) + pcre[16|32]_fullinfo.c ) + pcre[16|32]_get.c ) sources for the functions in the library, + pcre[16|32]_globals.c ) and some internal functions that they use + pcre[16|32]_jit_compile.c ) + pcre[16|32]_maketables.c ) + pcre[16|32]_newline.c ) + pcre[16|32]_refcount.c ) + pcre[16|32]_string_utils.c ) + pcre[16|32]_study.c ) + pcre[16|32]_tables.c ) + pcre[16|32]_ucd.c ) + pcre[16|32]_version.c ) + pcre[16|32]_xclass.c ) + pcre_ord2utf8.c ) + pcre_valid_utf8.c ) + pcre16_ord2utf16.c ) + pcre16_utf16_utils.c ) + pcre16_valid_utf16.c ) + pcre32_utf32_utils.c ) + pcre32_valid_utf32.c ) + + pcre[16|32]_printint.c ) debugging function that is used by pcretest, + ) and can also be #included in pcre_compile() + + pcre.h.in template for pcre.h when built by "configure" + pcreposix.h header for the external POSIX wrapper API + pcre_internal.h header for internal use + sljit/* 16 files that make up the JIT compiler + ucp.h header for Unicode property handling + + config.h.in template for config.h, which is built by "configure" + + pcrecpp.h public header file for the C++ wrapper + pcrecpparg.h.in template for another C++ header file + pcre_scanner.h public header file for C++ scanner functions + pcrecpp.cc ) + pcre_scanner.cc ) source for the C++ wrapper library + + pcre_stringpiece.h.in template for pcre_stringpiece.h, the header for the + C++ stringpiece functions + pcre_stringpiece.cc source for the C++ stringpiece functions + +(B) Source files for programs that use PCRE: + + pcredemo.c simple demonstration of coding calls to PCRE + pcregrep.c source of a grep utility that uses PCRE + pcretest.c comprehensive test program + +(C) Auxiliary files: + + 132html script to turn "man" pages into HTML + AUTHORS information about the author of PCRE + ChangeLog log of changes to the code + CleanTxt script to clean nroff output for txt man pages + Detrail script to remove trailing spaces + HACKING some notes about the internals of PCRE + INSTALL generic installation instructions + LICENCE conditions for the use of PCRE + COPYING the same, using GNU's standard name + Makefile.in ) template for Unix Makefile, which is built by + ) "configure" + Makefile.am ) the automake input that was used to create + ) Makefile.in + NEWS important changes in this release + NON-UNIX-USE the previous name for NON-AUTOTOOLS-BUILD + NON-AUTOTOOLS-BUILD notes on building PCRE without using autotools + PrepareRelease script to make preparations for "make dist" + README this file + RunTest a Unix shell script for running tests + RunGrepTest a Unix shell script for pcregrep tests + aclocal.m4 m4 macros (generated by "aclocal") + config.guess ) files used by libtool, + config.sub ) used only when building a shared library + configure a configuring shell script (built by autoconf) + configure.ac ) the autoconf input that was used to build + ) "configure" and config.h + depcomp ) script to find program dependencies, generated by + ) automake + doc/*.3 man page sources for PCRE + doc/*.1 man page sources for pcregrep and pcretest + doc/index.html.src the base HTML page + doc/html/* HTML documentation + doc/pcre.txt plain text version of the man pages + doc/pcretest.txt plain text documentation of test program + doc/perltest.txt plain text documentation of Perl test program + install-sh a shell script for installing files + libpcre16.pc.in template for libpcre16.pc for pkg-config + libpcre32.pc.in template for libpcre32.pc for pkg-config + libpcre.pc.in template for libpcre.pc for pkg-config + libpcreposix.pc.in template for libpcreposix.pc for pkg-config + libpcrecpp.pc.in template for libpcrecpp.pc for pkg-config + ltmain.sh file used to build a libtool script + missing ) common stub for a few missing GNU programs while + ) installing, generated by automake + mkinstalldirs script for making install directories + perltest.pl Perl test program + pcre-config.in source of script which retains PCRE information + pcre_jit_test.c test program for the JIT compiler + pcrecpp_unittest.cc ) + pcre_scanner_unittest.cc ) test programs for the C++ wrapper + pcre_stringpiece_unittest.cc ) + testdata/testinput* test data for main library tests + testdata/testoutput* expected test results + testdata/grep* input and output for pcregrep tests + testdata/* other supporting test files + +(D) Auxiliary files for cmake support + + cmake/COPYING-CMAKE-SCRIPTS + cmake/FindPackageHandleStandardArgs.cmake + cmake/FindEditline.cmake + cmake/FindReadline.cmake + CMakeLists.txt + config-cmake.h.in + +(E) Auxiliary files for VPASCAL + + makevp.bat + makevp_c.txt + makevp_l.txt + pcregexp.pas + +(F) Auxiliary files for building PCRE "by hand" + + pcre.h.generic ) a version of the public PCRE header file + ) for use in non-"configure" environments + config.h.generic ) a version of config.h for use in non-"configure" + ) environments + +(F) Miscellaneous + + RunTest.bat a script for running tests under Windows + +Philip Hazel +Email local part: ph10 +Email domain: cam.ac.uk +Last updated: 10 February 2015 diff --git a/doc/html/index.html b/doc/html/index.html new file mode 100644 index 0000000..352c55d --- /dev/null +++ b/doc/html/index.html @@ -0,0 +1,185 @@ +<html> +<!-- This is a manually maintained file that is the root of the HTML version of + the PCRE documentation. When the HTML documents are built from the man + page versions, the entire doc/html directory is emptied, this file is then + copied into doc/html/index.html, and the remaining files therein are + created by the 132html script. +--> +<head> +<title>PCRE specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>Perl-compatible Regular Expressions (PCRE)</h1> +<p> +The HTML documentation for PCRE consists of a number of pages that are listed +below in alphabetical order. If you are new to PCRE, please read the first one +first. +</p> + +<table> +<tr><td><a href="pcre.html">pcre</a></td> + <td> Introductory page</td></tr> + +<tr><td><a href="pcre-config.html">pcre-config</a></td> + <td> Information about the installation configuration</td></tr> + +<tr><td><a href="pcre16.html">pcre16</a></td> + <td> Discussion of the 16-bit PCRE library</td></tr> + +<tr><td><a href="pcre32.html">pcre32</a></td> + <td> Discussion of the 32-bit PCRE library</td></tr> + +<tr><td><a href="pcreapi.html">pcreapi</a></td> + <td> PCRE's native API</td></tr> + +<tr><td><a href="pcrebuild.html">pcrebuild</a></td> + <td> Building PCRE</td></tr> + +<tr><td><a href="pcrecallout.html">pcrecallout</a></td> + <td> The <i>callout</i> facility</td></tr> + +<tr><td><a href="pcrecompat.html">pcrecompat</a></td> + <td> Compability with Perl</td></tr> + +<tr><td><a href="pcrecpp.html">pcrecpp</a></td> + <td> The C++ wrapper for the PCRE library</td></tr> + +<tr><td><a href="pcredemo.html">pcredemo</a></td> + <td> A demonstration C program that uses the PCRE library</td></tr> + +<tr><td><a href="pcregrep.html">pcregrep</a></td> + <td> The <b>pcregrep</b> command</td></tr> + +<tr><td><a href="pcrejit.html">pcrejit</a></td> + <td> Discussion of the just-in-time optimization support</td></tr> + +<tr><td><a href="pcrelimits.html">pcrelimits</a></td> + <td> Details of size and other limits</td></tr> + +<tr><td><a href="pcrematching.html">pcrematching</a></td> + <td> Discussion of the two matching algorithms</td></tr> + +<tr><td><a href="pcrepartial.html">pcrepartial</a></td> + <td> Using PCRE for partial matching</td></tr> + +<tr><td><a href="pcrepattern.html">pcrepattern</a></td> + <td> Specification of the regular expressions supported by PCRE</td></tr> + +<tr><td><a href="pcreperform.html">pcreperform</a></td> + <td> Some comments on performance</td></tr> + +<tr><td><a href="pcreposix.html">pcreposix</a></td> + <td> The POSIX API to the PCRE 8-bit library</td></tr> + +<tr><td><a href="pcreprecompile.html">pcreprecompile</a></td> + <td> How to save and re-use compiled patterns</td></tr> + +<tr><td><a href="pcresample.html">pcresample</a></td> + <td> Discussion of the pcredemo program</td></tr> + +<tr><td><a href="pcrestack.html">pcrestack</a></td> + <td> Discussion of PCRE's stack usage</td></tr> + +<tr><td><a href="pcresyntax.html">pcresyntax</a></td> + <td> Syntax quick-reference summary</td></tr> + +<tr><td><a href="pcretest.html">pcretest</a></td> + <td> The <b>pcretest</b> command for testing PCRE</td></tr> + +<tr><td><a href="pcreunicode.html">pcreunicode</a></td> + <td> Discussion of Unicode and UTF-8/UTF-16/UTF-32 support</td></tr> +</table> + +<p> +There are also individual pages that summarize the interface for each function +in the library. There is a single page for each triple of 8-bit/16-bit/32-bit +functions. +</p> + +<table> + +<tr><td><a href="pcre_assign_jit_stack.html">pcre_assign_jit_stack</a></td> + <td> Assign stack for JIT matching</td></tr> + +<tr><td><a href="pcre_compile.html">pcre_compile</a></td> + <td> Compile a regular expression</td></tr> + +<tr><td><a href="pcre_compile2.html">pcre_compile2</a></td> + <td> Compile a regular expression (alternate interface)</td></tr> + +<tr><td><a href="pcre_config.html">pcre_config</a></td> + <td> Show build-time configuration options</td></tr> + +<tr><td><a href="pcre_copy_named_substring.html">pcre_copy_named_substring</a></td> + <td> Extract named substring into given buffer</td></tr> + +<tr><td><a href="pcre_copy_substring.html">pcre_copy_substring</a></td> + <td> Extract numbered substring into given buffer</td></tr> + +<tr><td><a href="pcre_dfa_exec.html">pcre_dfa_exec</a></td> + <td> Match a compiled pattern to a subject string + (DFA algorithm; <i>not</i> Perl compatible)</td></tr> + +<tr><td><a href="pcre_exec.html">pcre_exec</a></td> + <td> Match a compiled pattern to a subject string + (Perl compatible)</td></tr> + +<tr><td><a href="pcre_free_study.html">pcre_free_study</a></td> + <td> Free study data</td></tr> + +<tr><td><a href="pcre_free_substring.html">pcre_free_substring</a></td> + <td> Free extracted substring</td></tr> + +<tr><td><a href="pcre_free_substring_list.html">pcre_free_substring_list</a></td> + <td> Free list of extracted substrings</td></tr> + +<tr><td><a href="pcre_fullinfo.html">pcre_fullinfo</a></td> + <td> Extract information about a pattern</td></tr> + +<tr><td><a href="pcre_get_named_substring.html">pcre_get_named_substring</a></td> + <td> Extract named substring into new memory</td></tr> + +<tr><td><a href="pcre_get_stringnumber.html">pcre_get_stringnumber</a></td> + <td> Convert captured string name to number</td></tr> + +<tr><td><a href="pcre_get_stringtable_entries.html">pcre_get_stringtable_entries</a></td> + <td> Find table entries for given string name</td></tr> + +<tr><td><a href="pcre_get_substring.html">pcre_get_substring</a></td> + <td> Extract numbered substring into new memory</td></tr> + +<tr><td><a href="pcre_get_substring_list.html">pcre_get_substring_list</a></td> + <td> Extract all substrings into new memory</td></tr> + +<tr><td><a href="pcre_jit_exec.html">pcre_jit_exec</a></td> + <td> Fast path interface to JIT matching</td></tr> + +<tr><td><a href="pcre_jit_stack_alloc.html">pcre_jit_stack_alloc</a></td> + <td> Create a stack for JIT matching</td></tr> + +<tr><td><a href="pcre_jit_stack_free.html">pcre_jit_stack_free</a></td> + <td> Free a JIT matching stack</td></tr> + +<tr><td><a href="pcre_maketables.html">pcre_maketables</a></td> + <td> Build character tables in current locale</td></tr> + +<tr><td><a href="pcre_pattern_to_host_byte_order.html">pcre_pattern_to_host_byte_order</a></td> + <td> Convert compiled pattern to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_refcount.html">pcre_refcount</a></td> + <td> Maintain reference count in compiled pattern</td></tr> + +<tr><td><a href="pcre_study.html">pcre_study</a></td> + <td> Study a compiled pattern</td></tr> + +<tr><td><a href="pcre_utf16_to_host_byte_order.html">pcre_utf16_to_host_byte_order</a></td> + <td> Convert UTF-16 string to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_utf32_to_host_byte_order.html">pcre_utf32_to_host_byte_order</a></td> + <td> Convert UTF-32 string to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_version.html">pcre_version</a></td> + <td> Return PCRE version and release date</td></tr> +</table> + +</html> diff --git a/doc/html/pcre-config.html b/doc/html/pcre-config.html new file mode 100644 index 0000000..56a8060 --- /dev/null +++ b/doc/html/pcre-config.html @@ -0,0 +1,109 @@ +<html> +<head> +<title>pcre-config specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre-config man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">OPTIONS</a> +<li><a name="TOC4" href="#SEC4">SEE ALSO</a> +<li><a name="TOC5" href="#SEC5">AUTHOR</a> +<li><a name="TOC6" href="#SEC6">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>pcre-config [--prefix] [--exec-prefix] [--version] [--libs]</b> +<b> [--libs16] [--libs32] [--libs-cpp] [--libs-posix]</b> +<b> [--cflags] [--cflags-posix]</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +<b>pcre-config</b> returns the configuration of the installed PCRE +libraries and the options required to compile a program to use them. Some of +the options apply only to the 8-bit, or 16-bit, or 32-bit libraries, +respectively, and are +not available if only one of those libraries has been built. If an unavailable +option is encountered, the "usage" information is output. +</P> +<br><a name="SEC3" href="#TOC1">OPTIONS</a><br> +<P> +<b>--prefix</b> +Writes the directory prefix used in the PCRE installation for architecture +independent files (<i>/usr</i> on many systems, <i>/usr/local</i> on some +systems) to the standard output. +</P> +<P> +<b>--exec-prefix</b> +Writes the directory prefix used in the PCRE installation for architecture +dependent files (normally the same as <b>--prefix</b>) to the standard output. +</P> +<P> +<b>--version</b> +Writes the version number of the installed PCRE libraries to the standard +output. +</P> +<P> +<b>--libs</b> +Writes to the standard output the command line options required to link +with the 8-bit PCRE library (<b>-lpcre</b> on many systems). +</P> +<P> +<b>--libs16</b> +Writes to the standard output the command line options required to link +with the 16-bit PCRE library (<b>-lpcre16</b> on many systems). +</P> +<P> +<b>--libs32</b> +Writes to the standard output the command line options required to link +with the 32-bit PCRE library (<b>-lpcre32</b> on many systems). +</P> +<P> +<b>--libs-cpp</b> +Writes to the standard output the command line options required to link with +PCRE's C++ wrapper library (<b>-lpcrecpp</b> <b>-lpcre</b> on many +systems). +</P> +<P> +<b>--libs-posix</b> +Writes to the standard output the command line options required to link with +PCRE's POSIX API wrapper library (<b>-lpcreposix</b> <b>-lpcre</b> on many +systems). +</P> +<P> +<b>--cflags</b> +Writes to the standard output the command line options required to compile +files that use PCRE (this may include some <b>-I</b> options, but is blank on +many systems). +</P> +<P> +<b>--cflags-posix</b> +Writes to the standard output the command line options required to compile +files that use PCRE's POSIX API wrapper library (this may include some <b>-I</b> +options, but is blank on many systems). +</P> +<br><a name="SEC4" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcre(3)</b> +</P> +<br><a name="SEC5" href="#TOC1">AUTHOR</a><br> +<P> +This manual page was originally written by Mark Baker for the Debian GNU/Linux +system. It has been subsequently revised as a generic PCRE man page. +</P> +<br><a name="SEC6" href="#TOC1">REVISION</a><br> +<P> +Last updated: 24 June 2012 +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre.html b/doc/html/pcre.html new file mode 100644 index 0000000..c87b106 --- /dev/null +++ b/doc/html/pcre.html @@ -0,0 +1,224 @@ +<html> +<head> +<title>pcre specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PLEASE TAKE NOTE</a> +<li><a name="TOC2" href="#SEC2">INTRODUCTION</a> +<li><a name="TOC3" href="#SEC3">SECURITY CONSIDERATIONS</a> +<li><a name="TOC4" href="#SEC4">USER DOCUMENTATION</a> +<li><a name="TOC5" href="#SEC5">AUTHOR</a> +<li><a name="TOC6" href="#SEC6">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PLEASE TAKE NOTE</a><br> +<P> +This document relates to PCRE releases that use the original API, +with library names libpcre, libpcre16, and libpcre32. January 2015 saw the +first release of a new API, known as PCRE2, with release numbers starting at +10.00 and library names libpcre2-8, libpcre2-16, and libpcre2-32. The old +libraries (now called PCRE1) are still being maintained for bug fixes, but +there will be no new development. New projects are advised to use the new PCRE2 +libraries. +</P> +<br><a name="SEC2" href="#TOC1">INTRODUCTION</a><br> +<P> +The PCRE library is a set of functions that implement regular expression +pattern matching using the same syntax and semantics as Perl, with just a few +differences. Some features that appeared in Python and PCRE before they +appeared in Perl are also available using the Python syntax, there is some +support for one or two .NET and Oniguruma syntax items, and there is an option +for requesting some minor changes that give better JavaScript compatibility. +</P> +<P> +Starting with release 8.30, it is possible to compile two separate PCRE +libraries: the original, which supports 8-bit character strings (including +UTF-8 strings), and a second library that supports 16-bit character strings +(including UTF-16 strings). The build process allows either one or both to be +built. The majority of the work to make this possible was done by Zoltan +Herczeg. +</P> +<P> +Starting with release 8.32 it is possible to compile a third separate PCRE +library that supports 32-bit character strings (including UTF-32 strings). The +build process allows any combination of the 8-, 16- and 32-bit libraries. The +work to make this possible was done by Christian Persch. +</P> +<P> +The three libraries contain identical sets of functions, except that the names +in the 16-bit library start with <b>pcre16_</b> instead of <b>pcre_</b>, and the +names in the 32-bit library start with <b>pcre32_</b> instead of <b>pcre_</b>. To +avoid over-complication and reduce the documentation maintenance load, most of +the documentation describes the 8-bit library, with the differences for the +16-bit and 32-bit libraries described separately in the +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +pages. References to functions or structures of the form <i>pcre[16|32]_xxx</i> +should be read as meaning "<i>pcre_xxx</i> when using the 8-bit library, +<i>pcre16_xxx</i> when using the 16-bit library, or <i>pcre32_xxx</i> when using +the 32-bit library". +</P> +<P> +The current implementation of PCRE corresponds approximately with Perl 5.12, +including support for UTF-8/16/32 encoded strings and Unicode general category +properties. However, UTF-8/16/32 and Unicode support has to be explicitly +enabled; it is not the default. The Unicode tables correspond to Unicode +release 6.3.0. +</P> +<P> +In addition to the Perl-compatible matching function, PCRE contains an +alternative function that matches the same compiled patterns in a different +way. In certain circumstances, the alternative function has some advantages. +For a discussion of the two matching algorithms, see the +<a href="pcrematching.html"><b>pcrematching</b></a> +page. +</P> +<P> +PCRE is written in C and released as a C library. A number of people have +written wrappers and interfaces of various kinds. In particular, Google Inc. +have provided a comprehensive C++ wrapper for the 8-bit library. This is now +included as part of the PCRE distribution. The +<a href="pcrecpp.html"><b>pcrecpp</b></a> +page has details of this interface. Other people's contributions can be found +in the <i>Contrib</i> directory at the primary FTP site, which is: +<a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre</a> +</P> +<P> +Details of exactly which Perl regular expression features are and are not +supported by PCRE are given in separate documents. See the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +and +<a href="pcrecompat.html"><b>pcrecompat</b></a> +pages. There is a syntax summary in the +<a href="pcresyntax.html"><b>pcresyntax</b></a> +page. +</P> +<P> +Some features of PCRE can be included, excluded, or changed when the library is +built. The +<a href="pcre_config.html"><b>pcre_config()</b></a> +function makes it possible for a client to discover which features are +available. The features themselves are described in the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +page. Documentation about building PCRE for various operating systems can be +found in the +<a href="README.txt"><b>README</b></a> +and +<a href="NON-AUTOTOOLS-BUILD.txt"><b>NON-AUTOTOOLS_BUILD</b></a> +files in the source distribution. +</P> +<P> +The libraries contains a number of undocumented internal functions and data +tables that are used by more than one of the exported external functions, but +which are not intended for use by external callers. Their names all begin with +"_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name +clashes. In some environments, it is possible to control which external symbols +are exported when a shared library is built, and in these cases the +undocumented symbols are not exported. +</P> +<br><a name="SEC3" href="#TOC1">SECURITY CONSIDERATIONS</a><br> +<P> +If you are using PCRE in a non-UTF application that permits users to supply +arbitrary patterns for compilation, you should be aware of a feature that +allows users to turn on UTF support from within a pattern, provided that PCRE +was built with UTF support. For example, an 8-bit pattern that begins with +"(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and +subjects as strings of UTF-8 characters instead of individual 8-bit characters. +This causes both the pattern and any data against which it is matched to be +checked for UTF-8 validity. If the data string is very long, such a check might +use sufficiently many resources as to cause your application to lose +performance. +</P> +<P> +One way of guarding against this possibility is to use the +<b>pcre_fullinfo()</b> function to check the compiled pattern's options for UTF. +Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at +compile time. This causes an compile time error if a pattern contains a +UTF-setting sequence. +</P> +<P> +If your application is one that supports UTF, be aware that validity checking +can take time. If the same data string is to be matched many times, you can use +the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to +save redundant checks. +</P> +<P> +Another way that performance can be hit is by running a pattern that has a very +large search tree against a string that will never match. Nested unlimited +repeats in a pattern are a common example. PCRE provides some protection +against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. +</P> +<br><a name="SEC4" href="#TOC1">USER DOCUMENTATION</a><br> +<P> +The user documentation for PCRE comprises a number of different sections. In +the "man" format, each of these is a separate "man page". In the HTML format, +each is a separate page, linked from the index page. In the plain text format, +the descriptions of the <b>pcregrep</b> and <b>pcretest</b> programs are in files +called <b>pcregrep.txt</b> and <b>pcretest.txt</b>, respectively. The remaining +sections, except for the <b>pcredemo</b> section (which is a program listing), +are concatenated in <b>pcre.txt</b>, for ease of searching. The sections are as +follows: +<pre> + pcre this document + pcre-config show PCRE installation configuration information + pcre16 details of the 16-bit library + pcre32 details of the 32-bit library + pcreapi details of PCRE's native C API + pcrebuild building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcrecpp details of the C++ wrapper for the 8-bit library + pcredemo a demonstration C program that uses PCRE + pcregrep description of the <b>pcregrep</b> command (8-bit only) + pcrejit discussion of the just-in-time optimization support + pcrelimits details of size and other limits + pcrematching discussion of the two matching algorithms + pcrepartial details of the partial matching facility + pcrepattern syntax and semantics of supported regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible C API for the 8-bit library + pcreprecompile details of saving and re-using precompiled patterns + pcresample discussion of the pcredemo program + pcrestack discussion of stack usage + pcresyntax quick syntax reference + pcretest description of the <b>pcretest</b> testing command + pcreunicode discussion of Unicode and UTF-8/16/32 support +</pre> +In the "man" and HTML formats, there is also a short page for each C library +function, listing its arguments and results. +</P> +<br><a name="SEC5" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<P> +Putting an actual email address here seems to have been a spam magnet, so I've +taken it away. If you want to email me, use my two initials, followed by the +two digits 10, at the domain cam.ac.uk. +</P> +<br><a name="SEC6" href="#TOC1">REVISION</a><br> +<P> +Last updated: 10 February 2015 +<br> +Copyright © 1997-2015 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre16.html b/doc/html/pcre16.html new file mode 100644 index 0000000..f00859f --- /dev/null +++ b/doc/html/pcre16.html @@ -0,0 +1,384 @@ +<html> +<head> +<title>pcre16 specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre16 man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE 16-BIT API BASIC FUNCTIONS</a> +<li><a name="TOC2" href="#SEC2">PCRE 16-BIT API STRING EXTRACTION FUNCTIONS</a> +<li><a name="TOC3" href="#SEC3">PCRE 16-BIT API AUXILIARY FUNCTIONS</a> +<li><a name="TOC4" href="#SEC4">PCRE 16-BIT API INDIRECTED FUNCTIONS</a> +<li><a name="TOC5" href="#SEC5">PCRE 16-BIT API 16-BIT-ONLY FUNCTION</a> +<li><a name="TOC6" href="#SEC6">THE PCRE 16-BIT LIBRARY</a> +<li><a name="TOC7" href="#SEC7">THE HEADER FILE</a> +<li><a name="TOC8" href="#SEC8">THE LIBRARY NAME</a> +<li><a name="TOC9" href="#SEC9">STRING TYPES</a> +<li><a name="TOC10" href="#SEC10">STRUCTURE TYPES</a> +<li><a name="TOC11" href="#SEC11">16-BIT FUNCTIONS</a> +<li><a name="TOC12" href="#SEC12">SUBJECT STRING OFFSETS</a> +<li><a name="TOC13" href="#SEC13">NAMED SUBPATTERNS</a> +<li><a name="TOC14" href="#SEC14">OPTION NAMES</a> +<li><a name="TOC15" href="#SEC15">CHARACTER CODES</a> +<li><a name="TOC16" href="#SEC16">ERROR NAMES</a> +<li><a name="TOC17" href="#SEC17">ERROR TEXTS</a> +<li><a name="TOC18" href="#SEC18">CALLOUTS</a> +<li><a name="TOC19" href="#SEC19">TESTING</a> +<li><a name="TOC20" href="#SEC20">NOT SUPPORTED IN 16-BIT MODE</a> +<li><a name="TOC21" href="#SEC21">AUTHOR</a> +<li><a name="TOC22" href="#SEC22">REVISION</a> +</ul> +<P> +<b>#include <pcre.h></b> +</P> +<br><a name="SEC1" href="#TOC1">PCRE 16-BIT API BASIC FUNCTIONS</a><br> +<P> +<b>pcre16 *pcre16_compile(PCRE_SPTR16 <i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre16 *pcre16_compile2(PCRE_SPTR16 <i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre16_extra *pcre16_study(const pcre16 *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>void pcre16_free_study(pcre16_extra *<i>extra</i>);</b> +<br> +<br> +<b>int pcre16_exec(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<b>int pcre16_dfa_exec(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +</P> +<br><a name="SEC2" href="#TOC1">PCRE 16-BIT API STRING EXTRACTION FUNCTIONS</a><br> +<P> +<b>int pcre16_copy_named_substring(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR16 <i>stringname</i>,</b> +<b> PCRE_UCHAR16 *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre16_copy_substring(PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, PCRE_UCHAR16 *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre16_get_named_substring(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR16 <i>stringname</i>,</b> +<b> PCRE_SPTR16 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre16_get_stringnumber(const pcre16 *<i>code</i>,</b> +<b>" PCRE_SPTR16 <i>name</i>);</b> +<br> +<br> +<b>int pcre16_get_stringtable_entries(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>name</i>, PCRE_UCHAR16 **<i>first</i>, PCRE_UCHAR16 **<i>last</i>);</b> +<br> +<br> +<b>int pcre16_get_substring(PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> PCRE_SPTR16 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre16_get_substring_list(PCRE_SPTR16 <i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, PCRE_SPTR16 **<i>listptr</i>);</b> +<br> +<br> +<b>void pcre16_free_substring(PCRE_SPTR16 <i>stringptr</i>);</b> +<br> +<br> +<b>void pcre16_free_substring_list(PCRE_SPTR16 *<i>stringptr</i>);</b> +</P> +<br><a name="SEC3" href="#TOC1">PCRE 16-BIT API AUXILIARY FUNCTIONS</a><br> +<P> +<b>pcre16_jit_stack *pcre16_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b> +<br> +<br> +<b>void pcre16_jit_stack_free(pcre16_jit_stack *<i>stack</i>);</b> +<br> +<br> +<b>void pcre16_assign_jit_stack(pcre16_extra *<i>extra</i>,</b> +<b> pcre16_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>const unsigned char *pcre16_maketables(void);</b> +<br> +<br> +<b>int pcre16_fullinfo(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>int pcre16_refcount(pcre16 *<i>code</i>, int <i>adjust</i>);</b> +<br> +<br> +<b>int pcre16_config(int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>const char *pcre16_version(void);</b> +<br> +<br> +<b>int pcre16_pattern_to_host_byte_order(pcre16 *<i>code</i>,</b> +<b> pcre16_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +</P> +<br><a name="SEC4" href="#TOC1">PCRE 16-BIT API INDIRECTED FUNCTIONS</a><br> +<P> +<b>void *(*pcre16_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre16_free)(void *);</b> +<br> +<br> +<b>void *(*pcre16_stack_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre16_stack_free)(void *);</b> +<br> +<br> +<b>int (*pcre16_callout)(pcre16_callout_block *);</b> +</P> +<br><a name="SEC5" href="#TOC1">PCRE 16-BIT API 16-BIT-ONLY FUNCTION</a><br> +<P> +<b>int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *<i>output</i>,</b> +<b> PCRE_SPTR16 <i>input</i>, int <i>length</i>, int *<i>byte_order</i>,</b> +<b> int <i>keep_boms</i>);</b> +</P> +<br><a name="SEC6" href="#TOC1">THE PCRE 16-BIT LIBRARY</a><br> +<P> +Starting with release 8.30, it is possible to compile a PCRE library that +supports 16-bit character strings, including UTF-16 strings, as well as or +instead of the original 8-bit library. The majority of the work to make this +possible was done by Zoltan Herczeg. The two libraries contain identical sets +of functions, used in exactly the same way. Only the names of the functions and +the data types of their arguments and results are different. To avoid +over-complication and reduce the documentation maintenance load, most of the +PCRE documentation describes the 8-bit library, with only occasional references +to the 16-bit library. This page describes what is different when you use the +16-bit library. +</P> +<P> +WARNING: A single application can be linked with both libraries, but you must +take care when processing any particular pattern to use functions from just one +library. For example, if you want to study a pattern that was compiled with +<b>pcre16_compile()</b>, you must do so with <b>pcre16_study()</b>, not +<b>pcre_study()</b>, and you must free the study data with +<b>pcre16_free_study()</b>. +</P> +<br><a name="SEC7" href="#TOC1">THE HEADER FILE</a><br> +<P> +There is only one header file, <b>pcre.h</b>. It contains prototypes for all the +functions in all libraries, as well as definitions of flags, structures, error +codes, etc. +</P> +<br><a name="SEC8" href="#TOC1">THE LIBRARY NAME</a><br> +<P> +In Unix-like systems, the 16-bit library is called <b>libpcre16</b>, and can +normally be accesss by adding <b>-lpcre16</b> to the command for linking an +application that uses PCRE. +</P> +<br><a name="SEC9" href="#TOC1">STRING TYPES</a><br> +<P> +In the 8-bit library, strings are passed to PCRE library functions as vectors +of bytes with the C type "char *". In the 16-bit library, strings are passed as +vectors of unsigned 16-bit quantities. The macro PCRE_UCHAR16 specifies an +appropriate data type, and PCRE_SPTR16 is defined as "const PCRE_UCHAR16 *". In +very many environments, "short int" is a 16-bit data type. When PCRE is built, +it defines PCRE_UCHAR16 as "unsigned short int", but checks that it really is a +16-bit data type. If it is not, the build fails with an error message telling +the maintainer to modify the definition appropriately. +</P> +<br><a name="SEC10" href="#TOC1">STRUCTURE TYPES</a><br> +<P> +The types of the opaque structures that are used for compiled 16-bit patterns +and JIT stacks are <b>pcre16</b> and <b>pcre16_jit_stack</b> respectively. The +type of the user-accessible structure that is returned by <b>pcre16_study()</b> +is <b>pcre16_extra</b>, and the type of the structure that is used for passing +data to a callout function is <b>pcre16_callout_block</b>. These structures +contain the same fields, with the same names, as their 8-bit counterparts. The +only difference is that pointers to character strings are 16-bit instead of +8-bit types. +</P> +<br><a name="SEC11" href="#TOC1">16-BIT FUNCTIONS</a><br> +<P> +For every function in the 8-bit library there is a corresponding function in +the 16-bit library with a name that starts with <b>pcre16_</b> instead of +<b>pcre_</b>. The prototypes are listed above. In addition, there is one extra +function, <b>pcre16_utf16_to_host_byte_order()</b>. This is a utility function +that converts a UTF-16 character string to host byte order if necessary. The +other 16-bit functions expect the strings they are passed to be in host byte +order. +</P> +<P> +The <i>input</i> and <i>output</i> arguments of +<b>pcre16_utf16_to_host_byte_order()</b> may point to the same address, that is, +conversion in place is supported. The output buffer must be at least as long as +the input. +</P> +<P> +The <i>length</i> argument specifies the number of 16-bit data units in the +input string; a negative value specifies a zero-terminated string. +</P> +<P> +If <i>byte_order</i> is NULL, it is assumed that the string starts off in host +byte order. This may be changed by byte-order marks (BOMs) anywhere in the +string (commonly as the first character). +</P> +<P> +If <i>byte_order</i> is not NULL, a non-zero value of the integer to which it +points means that the input starts off in host byte order, otherwise the +opposite order is assumed. Again, BOMs in the string can change this. The final +byte order is passed back at the end of processing. +</P> +<P> +If <i>keep_boms</i> is not zero, byte-order mark characters (0xfeff) are copied +into the output string. Otherwise they are discarded. +</P> +<P> +The result of the function is the number of 16-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +</P> +<br><a name="SEC12" href="#TOC1">SUBJECT STRING OFFSETS</a><br> +<P> +The lengths and starting offsets of subject strings must be specified in 16-bit +data units, and the offsets within subject strings that are returned by the +matching functions are in also 16-bit units rather than bytes. +</P> +<br><a name="SEC13" href="#TOC1">NAMED SUBPATTERNS</a><br> +<P> +The name-to-number translation table that is maintained for named subpatterns +uses 16-bit characters. The <b>pcre16_get_stringtable_entries()</b> function +returns the length of each entry in the table as the number of 16-bit data +units. +</P> +<br><a name="SEC14" href="#TOC1">OPTION NAMES</a><br> +<P> +There are two new general option names, PCRE_UTF16 and PCRE_NO_UTF16_CHECK, +which correspond to PCRE_UTF8 and PCRE_NO_UTF8_CHECK in the 8-bit library. In +fact, these new options define the same bits in the options word. There is a +discussion about the +<a href="pcreunicode.html#utf16strings">validity of UTF-16 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. +</P> +<P> +For the <b>pcre16_config()</b> function there is an option PCRE_CONFIG_UTF16 +that returns 1 if UTF-16 support is configured, otherwise 0. If this option is +given to <b>pcre_config()</b> or <b>pcre32_config()</b>, or if the +PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 option is given to <b>pcre16_config()</b>, +the result is the PCRE_ERROR_BADOPTION error. +</P> +<br><a name="SEC15" href="#TOC1">CHARACTER CODES</a><br> +<P> +In 16-bit mode, when PCRE_UTF16 is not set, character values are treated in the +same way as in 8-bit, non UTF-8 mode, except, of course, that they can range +from 0 to 0xffff instead of 0 to 0xff. Character types for characters less than +0xff can therefore be influenced by the locale in the same way as before. +Characters greater than 0xff have only one case, and no "type" (such as letter +or digit). +</P> +<P> +In UTF-16 mode, the character code is Unicode, in the range 0 to 0x10ffff, with +the exception of values in the range 0xd800 to 0xdfff because those are +"surrogate" values that are used in pairs to encode values greater than 0xffff. +</P> +<P> +A UTF-16 string can indicate its endianness by special code knows as a +byte-order mark (BOM). The PCRE functions do not handle this, expecting strings +to be in host byte order. A utility function called +<b>pcre16_utf16_to_host_byte_order()</b> is provided to help with this (see +above). +</P> +<br><a name="SEC16" href="#TOC1">ERROR NAMES</a><br> +<P> +The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 correspond to +their 8-bit counterparts. The error PCRE_ERROR_BADMODE is given when a compiled +pattern is passed to a function that processes patterns in the other +mode, for example, if a pattern compiled with <b>pcre_compile()</b> is passed to +<b>pcre16_exec()</b>. +</P> +<P> +There are new error codes whose names begin with PCRE_UTF16_ERR for invalid +UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for UTF-8 strings that +are described in the section entitled +<a href="pcreapi.html#badutf8reasons">"Reason codes for invalid UTF-8 strings"</a> +in the main +<a href="pcreapi.html"><b>pcreapi</b></a> +page. The UTF-16 errors are: +<pre> + PCRE_UTF16_ERR1 Missing low surrogate at end of string + PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate + PCRE_UTF16_ERR3 Isolated low surrogate + PCRE_UTF16_ERR4 Non-character +</PRE> +</P> +<br><a name="SEC17" href="#TOC1">ERROR TEXTS</a><br> +<P> +If there is an error while compiling a pattern, the error text that is passed +back by <b>pcre16_compile()</b> or <b>pcre16_compile2()</b> is still an 8-bit +character string, zero-terminated. +</P> +<br><a name="SEC18" href="#TOC1">CALLOUTS</a><br> +<P> +The <i>subject</i> and <i>mark</i> fields in the callout block that is passed to +a callout function point to 16-bit vectors. +</P> +<br><a name="SEC19" href="#TOC1">TESTING</a><br> +<P> +The <b>pcretest</b> program continues to operate with 8-bit input and output +files, but it can be used for testing the 16-bit library. If it is run with the +command line option <b>-16</b>, patterns and subject strings are converted from +8-bit to 16-bit before being passed to PCRE, and the 16-bit library functions +are used instead of the 8-bit ones. Returned 16-bit strings are converted to +8-bit for output. If both the 8-bit and the 32-bit libraries were not compiled, +<b>pcretest</b> defaults to 16-bit and the <b>-16</b> option is ignored. +</P> +<P> +When PCRE is being built, the <b>RunTest</b> script that is called by "make +check" uses the <b>pcretest</b> <b>-C</b> option to discover which of the 8-bit, +16-bit and 32-bit libraries has been built, and runs the tests appropriately. +</P> +<br><a name="SEC20" href="#TOC1">NOT SUPPORTED IN 16-BIT MODE</a><br> +<P> +Not all the features of the 8-bit library are available with the 16-bit +library. The C++ and POSIX wrapper functions support only the 8-bit library, +and the <b>pcregrep</b> program is at present 8-bit only. +</P> +<br><a name="SEC21" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC22" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 May 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre32.html b/doc/html/pcre32.html new file mode 100644 index 0000000..f96876e --- /dev/null +++ b/doc/html/pcre32.html @@ -0,0 +1,382 @@ +<html> +<head> +<title>pcre32 specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre32 man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE 32-BIT API BASIC FUNCTIONS</a> +<li><a name="TOC2" href="#SEC2">PCRE 32-BIT API STRING EXTRACTION FUNCTIONS</a> +<li><a name="TOC3" href="#SEC3">PCRE 32-BIT API AUXILIARY FUNCTIONS</a> +<li><a name="TOC4" href="#SEC4">PCRE 32-BIT API INDIRECTED FUNCTIONS</a> +<li><a name="TOC5" href="#SEC5">PCRE 32-BIT API 32-BIT-ONLY FUNCTION</a> +<li><a name="TOC6" href="#SEC6">THE PCRE 32-BIT LIBRARY</a> +<li><a name="TOC7" href="#SEC7">THE HEADER FILE</a> +<li><a name="TOC8" href="#SEC8">THE LIBRARY NAME</a> +<li><a name="TOC9" href="#SEC9">STRING TYPES</a> +<li><a name="TOC10" href="#SEC10">STRUCTURE TYPES</a> +<li><a name="TOC11" href="#SEC11">32-BIT FUNCTIONS</a> +<li><a name="TOC12" href="#SEC12">SUBJECT STRING OFFSETS</a> +<li><a name="TOC13" href="#SEC13">NAMED SUBPATTERNS</a> +<li><a name="TOC14" href="#SEC14">OPTION NAMES</a> +<li><a name="TOC15" href="#SEC15">CHARACTER CODES</a> +<li><a name="TOC16" href="#SEC16">ERROR NAMES</a> +<li><a name="TOC17" href="#SEC17">ERROR TEXTS</a> +<li><a name="TOC18" href="#SEC18">CALLOUTS</a> +<li><a name="TOC19" href="#SEC19">TESTING</a> +<li><a name="TOC20" href="#SEC20">NOT SUPPORTED IN 32-BIT MODE</a> +<li><a name="TOC21" href="#SEC21">AUTHOR</a> +<li><a name="TOC22" href="#SEC22">REVISION</a> +</ul> +<P> +<b>#include <pcre.h></b> +</P> +<br><a name="SEC1" href="#TOC1">PCRE 32-BIT API BASIC FUNCTIONS</a><br> +<P> +<b>pcre32 *pcre32_compile(PCRE_SPTR32 <i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre32 *pcre32_compile2(PCRE_SPTR32 <i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre32_extra *pcre32_study(const pcre32 *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>void pcre32_free_study(pcre32_extra *<i>extra</i>);</b> +<br> +<br> +<b>int pcre32_exec(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<b>int pcre32_dfa_exec(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +</P> +<br><a name="SEC2" href="#TOC1">PCRE 32-BIT API STRING EXTRACTION FUNCTIONS</a><br> +<P> +<b>int pcre32_copy_named_substring(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR32 <i>stringname</i>,</b> +<b> PCRE_UCHAR32 *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre32_copy_substring(PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, PCRE_UCHAR32 *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre32_get_named_substring(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR32 <i>stringname</i>,</b> +<b> PCRE_SPTR32 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre32_get_stringnumber(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>name</i>);</b> +<br> +<br> +<b>int pcre32_get_stringtable_entries(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>name</i>, PCRE_UCHAR32 **<i>first</i>, PCRE_UCHAR32 **<i>last</i>);</b> +<br> +<br> +<b>int pcre32_get_substring(PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> PCRE_SPTR32 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre32_get_substring_list(PCRE_SPTR32 <i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, PCRE_SPTR32 **<i>listptr</i>);</b> +<br> +<br> +<b>void pcre32_free_substring(PCRE_SPTR32 <i>stringptr</i>);</b> +<br> +<br> +<b>void pcre32_free_substring_list(PCRE_SPTR32 *<i>stringptr</i>);</b> +</P> +<br><a name="SEC3" href="#TOC1">PCRE 32-BIT API AUXILIARY FUNCTIONS</a><br> +<P> +<b>pcre32_jit_stack *pcre32_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b> +<br> +<br> +<b>void pcre32_jit_stack_free(pcre32_jit_stack *<i>stack</i>);</b> +<br> +<br> +<b>void pcre32_assign_jit_stack(pcre32_extra *<i>extra</i>,</b> +<b> pcre32_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>const unsigned char *pcre32_maketables(void);</b> +<br> +<br> +<b>int pcre32_fullinfo(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>int pcre32_refcount(pcre32 *<i>code</i>, int <i>adjust</i>);</b> +<br> +<br> +<b>int pcre32_config(int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>const char *pcre32_version(void);</b> +<br> +<br> +<b>int pcre32_pattern_to_host_byte_order(pcre32 *<i>code</i>,</b> +<b> pcre32_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +</P> +<br><a name="SEC4" href="#TOC1">PCRE 32-BIT API INDIRECTED FUNCTIONS</a><br> +<P> +<b>void *(*pcre32_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre32_free)(void *);</b> +<br> +<br> +<b>void *(*pcre32_stack_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre32_stack_free)(void *);</b> +<br> +<br> +<b>int (*pcre32_callout)(pcre32_callout_block *);</b> +</P> +<br><a name="SEC5" href="#TOC1">PCRE 32-BIT API 32-BIT-ONLY FUNCTION</a><br> +<P> +<b>int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *<i>output</i>,</b> +<b> PCRE_SPTR32 <i>input</i>, int <i>length</i>, int *<i>byte_order</i>,</b> +<b> int <i>keep_boms</i>);</b> +</P> +<br><a name="SEC6" href="#TOC1">THE PCRE 32-BIT LIBRARY</a><br> +<P> +Starting with release 8.32, it is possible to compile a PCRE library that +supports 32-bit character strings, including UTF-32 strings, as well as or +instead of the original 8-bit library. This work was done by Christian Persch, +based on the work done by Zoltan Herczeg for the 16-bit library. All three +libraries contain identical sets of functions, used in exactly the same way. +Only the names of the functions and the data types of their arguments and +results are different. To avoid over-complication and reduce the documentation +maintenance load, most of the PCRE documentation describes the 8-bit library, +with only occasional references to the 16-bit and 32-bit libraries. This page +describes what is different when you use the 32-bit library. +</P> +<P> +WARNING: A single application can be linked with all or any of the three +libraries, but you must take care when processing any particular pattern +to use functions from just one library. For example, if you want to study +a pattern that was compiled with <b>pcre32_compile()</b>, you must do so +with <b>pcre32_study()</b>, not <b>pcre_study()</b>, and you must free the +study data with <b>pcre32_free_study()</b>. +</P> +<br><a name="SEC7" href="#TOC1">THE HEADER FILE</a><br> +<P> +There is only one header file, <b>pcre.h</b>. It contains prototypes for all the +functions in all libraries, as well as definitions of flags, structures, error +codes, etc. +</P> +<br><a name="SEC8" href="#TOC1">THE LIBRARY NAME</a><br> +<P> +In Unix-like systems, the 32-bit library is called <b>libpcre32</b>, and can +normally be accesss by adding <b>-lpcre32</b> to the command for linking an +application that uses PCRE. +</P> +<br><a name="SEC9" href="#TOC1">STRING TYPES</a><br> +<P> +In the 8-bit library, strings are passed to PCRE library functions as vectors +of bytes with the C type "char *". In the 32-bit library, strings are passed as +vectors of unsigned 32-bit quantities. The macro PCRE_UCHAR32 specifies an +appropriate data type, and PCRE_SPTR32 is defined as "const PCRE_UCHAR32 *". In +very many environments, "unsigned int" is a 32-bit data type. When PCRE is +built, it defines PCRE_UCHAR32 as "unsigned int", but checks that it really is +a 32-bit data type. If it is not, the build fails with an error message telling +the maintainer to modify the definition appropriately. +</P> +<br><a name="SEC10" href="#TOC1">STRUCTURE TYPES</a><br> +<P> +The types of the opaque structures that are used for compiled 32-bit patterns +and JIT stacks are <b>pcre32</b> and <b>pcre32_jit_stack</b> respectively. The +type of the user-accessible structure that is returned by <b>pcre32_study()</b> +is <b>pcre32_extra</b>, and the type of the structure that is used for passing +data to a callout function is <b>pcre32_callout_block</b>. These structures +contain the same fields, with the same names, as their 8-bit counterparts. The +only difference is that pointers to character strings are 32-bit instead of +8-bit types. +</P> +<br><a name="SEC11" href="#TOC1">32-BIT FUNCTIONS</a><br> +<P> +For every function in the 8-bit library there is a corresponding function in +the 32-bit library with a name that starts with <b>pcre32_</b> instead of +<b>pcre_</b>. The prototypes are listed above. In addition, there is one extra +function, <b>pcre32_utf32_to_host_byte_order()</b>. This is a utility function +that converts a UTF-32 character string to host byte order if necessary. The +other 32-bit functions expect the strings they are passed to be in host byte +order. +</P> +<P> +The <i>input</i> and <i>output</i> arguments of +<b>pcre32_utf32_to_host_byte_order()</b> may point to the same address, that is, +conversion in place is supported. The output buffer must be at least as long as +the input. +</P> +<P> +The <i>length</i> argument specifies the number of 32-bit data units in the +input string; a negative value specifies a zero-terminated string. +</P> +<P> +If <i>byte_order</i> is NULL, it is assumed that the string starts off in host +byte order. This may be changed by byte-order marks (BOMs) anywhere in the +string (commonly as the first character). +</P> +<P> +If <i>byte_order</i> is not NULL, a non-zero value of the integer to which it +points means that the input starts off in host byte order, otherwise the +opposite order is assumed. Again, BOMs in the string can change this. The final +byte order is passed back at the end of processing. +</P> +<P> +If <i>keep_boms</i> is not zero, byte-order mark characters (0xfeff) are copied +into the output string. Otherwise they are discarded. +</P> +<P> +The result of the function is the number of 32-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +</P> +<br><a name="SEC12" href="#TOC1">SUBJECT STRING OFFSETS</a><br> +<P> +The lengths and starting offsets of subject strings must be specified in 32-bit +data units, and the offsets within subject strings that are returned by the +matching functions are in also 32-bit units rather than bytes. +</P> +<br><a name="SEC13" href="#TOC1">NAMED SUBPATTERNS</a><br> +<P> +The name-to-number translation table that is maintained for named subpatterns +uses 32-bit characters. The <b>pcre32_get_stringtable_entries()</b> function +returns the length of each entry in the table as the number of 32-bit data +units. +</P> +<br><a name="SEC14" href="#TOC1">OPTION NAMES</a><br> +<P> +There are two new general option names, PCRE_UTF32 and PCRE_NO_UTF32_CHECK, +which correspond to PCRE_UTF8 and PCRE_NO_UTF8_CHECK in the 8-bit library. In +fact, these new options define the same bits in the options word. There is a +discussion about the +<a href="pcreunicode.html#utf32strings">validity of UTF-32 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. +</P> +<P> +For the <b>pcre32_config()</b> function there is an option PCRE_CONFIG_UTF32 +that returns 1 if UTF-32 support is configured, otherwise 0. If this option is +given to <b>pcre_config()</b> or <b>pcre16_config()</b>, or if the +PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 option is given to <b>pcre32_config()</b>, +the result is the PCRE_ERROR_BADOPTION error. +</P> +<br><a name="SEC15" href="#TOC1">CHARACTER CODES</a><br> +<P> +In 32-bit mode, when PCRE_UTF32 is not set, character values are treated in the +same way as in 8-bit, non UTF-8 mode, except, of course, that they can range +from 0 to 0x7fffffff instead of 0 to 0xff. Character types for characters less +than 0xff can therefore be influenced by the locale in the same way as before. +Characters greater than 0xff have only one case, and no "type" (such as letter +or digit). +</P> +<P> +In UTF-32 mode, the character code is Unicode, in the range 0 to 0x10ffff, with +the exception of values in the range 0xd800 to 0xdfff because those are +"surrogate" values that are ill-formed in UTF-32. +</P> +<P> +A UTF-32 string can indicate its endianness by special code knows as a +byte-order mark (BOM). The PCRE functions do not handle this, expecting strings +to be in host byte order. A utility function called +<b>pcre32_utf32_to_host_byte_order()</b> is provided to help with this (see +above). +</P> +<br><a name="SEC16" href="#TOC1">ERROR NAMES</a><br> +<P> +The error PCRE_ERROR_BADUTF32 corresponds to its 8-bit counterpart. +The error PCRE_ERROR_BADMODE is given when a compiled +pattern is passed to a function that processes patterns in the other +mode, for example, if a pattern compiled with <b>pcre_compile()</b> is passed to +<b>pcre32_exec()</b>. +</P> +<P> +There are new error codes whose names begin with PCRE_UTF32_ERR for invalid +UTF-32 strings, corresponding to the PCRE_UTF8_ERR codes for UTF-8 strings that +are described in the section entitled +<a href="pcreapi.html#badutf8reasons">"Reason codes for invalid UTF-8 strings"</a> +in the main +<a href="pcreapi.html"><b>pcreapi</b></a> +page. The UTF-32 errors are: +<pre> + PCRE_UTF32_ERR1 Surrogate character (range from 0xd800 to 0xdfff) + PCRE_UTF32_ERR2 Non-character + PCRE_UTF32_ERR3 Character > 0x10ffff +</PRE> +</P> +<br><a name="SEC17" href="#TOC1">ERROR TEXTS</a><br> +<P> +If there is an error while compiling a pattern, the error text that is passed +back by <b>pcre32_compile()</b> or <b>pcre32_compile2()</b> is still an 8-bit +character string, zero-terminated. +</P> +<br><a name="SEC18" href="#TOC1">CALLOUTS</a><br> +<P> +The <i>subject</i> and <i>mark</i> fields in the callout block that is passed to +a callout function point to 32-bit vectors. +</P> +<br><a name="SEC19" href="#TOC1">TESTING</a><br> +<P> +The <b>pcretest</b> program continues to operate with 8-bit input and output +files, but it can be used for testing the 32-bit library. If it is run with the +command line option <b>-32</b>, patterns and subject strings are converted from +8-bit to 32-bit before being passed to PCRE, and the 32-bit library functions +are used instead of the 8-bit ones. Returned 32-bit strings are converted to +8-bit for output. If both the 8-bit and the 16-bit libraries were not compiled, +<b>pcretest</b> defaults to 32-bit and the <b>-32</b> option is ignored. +</P> +<P> +When PCRE is being built, the <b>RunTest</b> script that is called by "make +check" uses the <b>pcretest</b> <b>-C</b> option to discover which of the 8-bit, +16-bit and 32-bit libraries has been built, and runs the tests appropriately. +</P> +<br><a name="SEC20" href="#TOC1">NOT SUPPORTED IN 32-BIT MODE</a><br> +<P> +Not all the features of the 8-bit library are available with the 32-bit +library. The C++ and POSIX wrapper functions support only the 8-bit library, +and the <b>pcregrep</b> program is at present 8-bit only. +</P> +<br><a name="SEC21" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC22" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 May 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_assign_jit_stack.html b/doc/html/pcre_assign_jit_stack.html new file mode 100644 index 0000000..b2eef70 --- /dev/null +++ b/doc/html/pcre_assign_jit_stack.html @@ -0,0 +1,76 @@ +<html> +<head> +<title>pcre_assign_jit_stack specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_assign_jit_stack man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b> +<b> pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>void pcre16_assign_jit_stack(pcre16_extra *<i>extra</i>,</b> +<b> pcre16_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>void pcre32_assign_jit_stack(pcre32_extra *<i>extra</i>,</b> +<b> pcre32_jit_callback <i>callback</i>, void *<i>data</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function provides control over the memory used as a stack at run-time by a +call to <b>pcre[16|32]_exec()</b> with a pattern that has been successfully +compiled with JIT optimization. The arguments are: +<pre> + extra the data pointer returned by <b>pcre[16|32]_study()</b> + callback a callback function + data a JIT stack or a value to be passed to the callback + function +</PRE> +</P> +<P> +If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block on +the machine stack is used. +</P> +<P> +If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must +be a valid JIT stack, the result of calling <b>pcre[16|32]_jit_stack_alloc()</b>. +</P> +<P> +If <i>callback</i> not NULL, it is called with <i>data</i> as an argument at +the start of matching, in order to set up a JIT stack. If the result is NULL, +the internal 32K stack is used; otherwise the return value must be a valid JIT +stack, the result of calling <b>pcre[16|32]_jit_stack_alloc()</b>. +</P> +<P> +You may safely assign the same JIT stack to multiple patterns, as long as they +are all matched in the same thread. In a multithread application, each thread +must use its own JIT stack. For more details, see the +<a href="pcrejit.html"><b>pcrejit</b></a> +page. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_compile.html b/doc/html/pcre_compile.html new file mode 100644 index 0000000..95b4bec --- /dev/null +++ b/doc/html/pcre_compile.html @@ -0,0 +1,111 @@ +<html> +<head> +<title>pcre_compile specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_compile man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre16 *pcre16_compile(PCRE_SPTR16 <i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre32 *pcre32_compile(PCRE_SPTR32 <i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function compiles a regular expression into an internal form. It is the +same as <b>pcre[16|32]_compile2()</b>, except for the absence of the +<i>errorcodeptr</i> argument. Its arguments are: +<pre> + <i>pattern</i> A zero-terminated string containing the + regular expression to be compiled + <i>options</i> Zero or more option bits + <i>errptr</i> Where to put an error message + <i>erroffset</i> Offset in pattern where error was found + <i>tableptr</i> Pointer to character tables, or NULL to + use the built-in default +</pre> +The option bits are: +<pre> + PCRE_ANCHORED Force pattern anchoring + PCRE_AUTO_CALLOUT Compile automatic callouts + PCRE_BSR_ANYCRLF \R matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \R matches all Unicode line endings + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_DUPNAMES Allow duplicate names for subpatterns + PCRE_EXTENDED Ignore white space and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_FIRSTLINE Force matching to be before newline + PCRE_JAVASCRIPT_COMPAT JavaScript compatibility + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NEVER_UTF Lock out UTF, e.g. via (*UTF) + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, and CRLF as newline + sequences + PCRE_NEWLINE_CR Set CR as the newline sequence + PCRE_NEWLINE_CRLF Set CRLF as the newline sequence + PCRE_NEWLINE_LF Set LF as the newline sequence + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_NO_AUTO_POSSESS Disable auto-possessification + PCRE_NO_START_OPTIMIZE Disable match-time start optimizations + PCRE_NO_UTF16_CHECK Do not check the pattern for UTF-16 + validity (only relevant if + PCRE_UTF16 is set) + PCRE_NO_UTF32_CHECK Do not check the pattern for UTF-32 + validity (only relevant if + PCRE_UTF32 is set) + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) + PCRE_UCP Use Unicode properties for \d, \w, etc. + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF16 Run in <b>pcre16_compile()</b> UTF-16 mode + PCRE_UTF32 Run in <b>pcre32_compile()</b> UTF-32 mode + PCRE_UTF8 Run in <b>pcre_compile()</b> UTF-8 mode +</pre> +PCRE must be built with UTF support in order to use PCRE_UTF8/16/32 and +PCRE_NO_UTF8/16/32_CHECK, and with UCP support if PCRE_UCP is used. +</P> +<P> +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. Note that +compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_compile2.html b/doc/html/pcre_compile2.html new file mode 100644 index 0000000..9cd56a2 --- /dev/null +++ b/doc/html/pcre_compile2.html @@ -0,0 +1,115 @@ +<html> +<head> +<title>pcre_compile2 specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_compile2 man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre16 *pcre16_compile2(PCRE_SPTR16 <i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre32 *pcre32_compile2(PCRE_SPTR32 <i>pattern</i>, int <i>options</i>,</b> +<b>" int *<i>errorcodeptr</i>,£</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function compiles a regular expression into an internal form. It is the +same as <b>pcre[16|32]_compile()</b>, except for the addition of the +<i>errorcodeptr</i> argument. The arguments are: +<pre> + <i>pattern</i> A zero-terminated string containing the + regular expression to be compiled + <i>options</i> Zero or more option bits + <i>errorcodeptr</i> Where to put an error code + <i>errptr</i> Where to put an error message + <i>erroffset</i> Offset in pattern where error was found + <i>tableptr</i> Pointer to character tables, or NULL to + use the built-in default +</pre> +The option bits are: +<pre> + PCRE_ANCHORED Force pattern anchoring + PCRE_AUTO_CALLOUT Compile automatic callouts + PCRE_BSR_ANYCRLF \R matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \R matches all Unicode line endings + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_DUPNAMES Allow duplicate names for subpatterns + PCRE_EXTENDED Ignore white space and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_FIRSTLINE Force matching to be before newline + PCRE_JAVASCRIPT_COMPAT JavaScript compatibility + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NEVER_UTF Lock out UTF, e.g. via (*UTF) + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, and CRLF as newline + sequences + PCRE_NEWLINE_CR Set CR as the newline sequence + PCRE_NEWLINE_CRLF Set CRLF as the newline sequence + PCRE_NEWLINE_LF Set LF as the newline sequence + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_NO_AUTO_POSSESS Disable auto-possessification + PCRE_NO_START_OPTIMIZE Disable match-time start optimizations + PCRE_NO_UTF16_CHECK Do not check the pattern for UTF-16 + validity (only relevant if + PCRE_UTF16 is set) + PCRE_NO_UTF32_CHECK Do not check the pattern for UTF-32 + validity (only relevant if + PCRE_UTF32 is set) + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) + PCRE_UCP Use Unicode properties for \d, \w, etc. + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF16 Run <b>pcre16_compile()</b> in UTF-16 mode + PCRE_UTF32 Run <b>pcre32_compile()</b> in UTF-32 mode + PCRE_UTF8 Run <b>pcre_compile()</b> in UTF-8 mode +</pre> +PCRE must be built with UTF support in order to use PCRE_UTF8/16/32 and +PCRE_NO_UTF8/16/32_CHECK, and with UCP support if PCRE_UCP is used. +</P> +<P> +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. Note that +compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_config.html b/doc/html/pcre_config.html new file mode 100644 index 0000000..72fb9ca --- /dev/null +++ b/doc/html/pcre_config.html @@ -0,0 +1,94 @@ +<html> +<head> +<title>pcre_config specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_config man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +<b>int pcre16_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +<b>int pcre32_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function makes it possible for a client program to find out which optional +features are available in the version of the PCRE library it is using. The +arguments are as follows: +<pre> + <i>what</i> A code specifying what information is required + <i>where</i> Points to where to put the data +</pre> +The <i>where</i> argument must point to an integer variable, except for +PCRE_CONFIG_MATCH_LIMIT, PCRE_CONFIG_MATCH_LIMIT_RECURSION, and +PCRE_CONFIG_PARENS_LIMIT, when it must point to an unsigned long integer, +and for PCRE_CONFIG_JITTARGET, when it must point to a const char*. +The available codes are: +<pre> + PCRE_CONFIG_JIT Availability of just-in-time compiler + support (1=yes 0=no) + PCRE_CONFIG_JITTARGET String containing information about the + target architecture for the JIT compiler, + or NULL if there is no JIT support + PCRE_CONFIG_LINK_SIZE Internal link size: 2, 3, or 4 + PCRE_CONFIG_PARENS_LIMIT Parentheses nesting limit + PCRE_CONFIG_MATCH_LIMIT Internal resource limit + PCRE_CONFIG_MATCH_LIMIT_RECURSION + Internal recursion depth limit + PCRE_CONFIG_NEWLINE Value of the default newline sequence: + 13 (0x000d) for CR + 10 (0x000a) for LF + 3338 (0x0d0a) for CRLF + -2 for ANYCRLF + -1 for ANY + PCRE_CONFIG_BSR Indicates what \R matches by default: + 0 all Unicode line endings + 1 CR, LF, or CRLF only + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + Threshold of return slots, above which + <b>malloc()</b> is used by the POSIX API + PCRE_CONFIG_STACKRECURSE Recursion implementation (1=stack 0=heap) + PCRE_CONFIG_UTF16 Availability of UTF-16 support (1=yes + 0=no); option for <b>pcre16_config()</b> + PCRE_CONFIG_UTF32 Availability of UTF-32 support (1=yes + 0=no); option for <b>pcre32_config()</b> + PCRE_CONFIG_UTF8 Availability of UTF-8 support (1=yes 0=no); + option for <b>pcre_config()</b> + PCRE_CONFIG_UNICODE_PROPERTIES + Availability of Unicode property support + (1=yes 0=no) +</pre> +The function yields 0 on success or PCRE_ERROR_BADOPTION otherwise. That error +is also given if PCRE_CONFIG_UTF16 or PCRE_CONFIG_UTF32 is passed to +<b>pcre_config()</b>, if PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 is passed to +<b>pcre16_config()</b>, or if PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 is passed to +<b>pcre32_config()</b>. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_copy_named_substring.html b/doc/html/pcre_copy_named_substring.html new file mode 100644 index 0000000..77b4804 --- /dev/null +++ b/doc/html/pcre_copy_named_substring.html @@ -0,0 +1,65 @@ +<html> +<head> +<title>pcre_copy_named_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_copy_named_substring man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> char *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre16_copy_named_substring(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR16 <i>stringname</i>,</b> +<b> PCRE_UCHAR16 *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre32_copy_named_substring(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR32 <i>stringname</i>,</b> +<b> PCRE_UCHAR32 *<i>buffer</i>, int <i>buffersize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring, identified +by name, into a given buffer. The arguments are: +<pre> + <i>code</i> Pattern that was successfully matched + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre[16|32]_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre[16|32]_exec()</b> + <i>stringname</i> Name of the required substring + <i>buffer</i> Buffer to receive the string + <i>buffersize</i> Size of buffer +</pre> +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string name is invalid. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_copy_substring.html b/doc/html/pcre_copy_substring.html new file mode 100644 index 0000000..ecaebe8 --- /dev/null +++ b/doc/html/pcre_copy_substring.html @@ -0,0 +1,61 @@ +<html> +<head> +<title>pcre_copy_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_copy_substring man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre16_copy_substring(PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, PCRE_UCHAR16 *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre32_copy_substring(PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, PCRE_UCHAR32 *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring into a given +buffer. The arguments are: +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre[16|32]_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre[16|32]_exec()</b> + <i>stringnumber</i> Number of the required substring + <i>buffer</i> Buffer to receive the string + <i>buffersize</i> Size of buffer +</pre> +The yield is the length of the string, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string number is invalid. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_dfa_exec.html b/doc/html/pcre_dfa_exec.html new file mode 100644 index 0000000..5fff6a7 --- /dev/null +++ b/doc/html/pcre_dfa_exec.html @@ -0,0 +1,129 @@ +<html> +<head> +<title>pcre_dfa_exec specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_dfa_exec man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +<br> +<br> +<b>int pcre16_dfa_exec(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +<br> +<br> +<b>int pcre32_dfa_exec(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function matches a compiled regular expression against a given subject +string, using an alternative matching algorithm that scans the subject string +just once (<i>not</i> Perl-compatible). Note that the main, Perl-compatible, +matching function is <b>pcre[16|32]_exec()</b>. The arguments for this function +are: +<pre> + <i>code</i> Points to the compiled pattern + <i>extra</i> Points to an associated <b>pcre[16|32]_extra</b> structure, + or is NULL + <i>subject</i> Points to the subject string + <i>length</i> Length of the subject string + <i>startoffset</i> Offset in the subject at which to start matching + <i>options</i> Option bits + <i>ovector</i> Points to a vector of ints for result offsets + <i>ovecsize</i> Number of elements in the vector + <i>workspace</i> Points to a vector of ints used as working space + <i>wscount</i> Number of elements in the vector +</pre> +The units for <i>length</i> and <i>startoffset</i> are bytes for +<b>pcre_exec()</b>, 16-bit data items for <b>pcre16_exec()</b>, and 32-bit items +for <b>pcre32_exec()</b>. The options are: +<pre> + PCRE_ANCHORED Match only at the first position + PCRE_BSR_ANYCRLF \R matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \R matches all Unicode line endings + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, & CRLF as newline sequences + PCRE_NEWLINE_CR Recognize CR as the only newline sequence + PCRE_NEWLINE_CRLF Recognize CRLF as the only newline sequence + PCRE_NEWLINE_LF Recognize LF as the only newline sequence + PCRE_NOTBOL Subject is not the beginning of a line + PCRE_NOTEOL Subject is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_START_OPTIMIZE Do not do "start-match" optimizations + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + even if there is a full match as well + PCRE_DFA_SHORTEST Return only the shortest match + PCRE_DFA_RESTART Restart after a partial match +</pre> +There are restrictions on what may appear in a pattern when using this matching +function. Details are given in the +<a href="pcrematching.html"><b>pcrematching</b></a> +documentation. For details of partial matching, see the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +page. +</P> +<P> +A <b>pcre[16|32]_extra</b> structure contains the following fields: +<pre> + <i>flags</i> Bits indicating which fields are set + <i>study_data</i> Opaque data from <b>pcre[16|32]_study()</b> + <i>match_limit</i> Limit on internal resource use + <i>match_limit_recursion</i> Limit on internal recursion depth + <i>callout_data</i> Opaque data passed back to callouts + <i>tables</i> Points to character tables or is NULL + <i>mark</i> For passing back a *MARK pointer + <i>executable_jit</i> Opaque data from JIT compilation +</pre> +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. For this +matching function, the <i>match_limit</i> and <i>match_limit_recursion</i> fields +are not used, and must not be set. The PCRE_EXTRA_EXECUTABLE_JIT flag and +the corresponding variable are ignored. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_exec.html b/doc/html/pcre_exec.html new file mode 100644 index 0000000..18e1a13 --- /dev/null +++ b/doc/html/pcre_exec.html @@ -0,0 +1,111 @@ +<html> +<head> +<title>pcre_exec specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_exec man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<b>int pcre16_exec(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<b>int pcre32_exec(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function matches a compiled regular expression against a given subject +string, using a matching algorithm that is similar to Perl's. It returns +offsets to captured substrings. Its arguments are: +<pre> + <i>code</i> Points to the compiled pattern + <i>extra</i> Points to an associated <b>pcre[16|32]_extra</b> structure, + or is NULL + <i>subject</i> Points to the subject string + <i>length</i> Length of the subject string + <i>startoffset</i> Offset in the subject at which to start matching + <i>options</i> Option bits + <i>ovector</i> Points to a vector of ints for result offsets + <i>ovecsize</i> Number of elements in the vector (a multiple of 3) +</pre> +The units for <i>length</i> and <i>startoffset</i> are bytes for +<b>pcre_exec()</b>, 16-bit data items for <b>pcre16_exec()</b>, and 32-bit items +for <b>pcre32_exec()</b>. The options are: +<pre> + PCRE_ANCHORED Match only at the first position + PCRE_BSR_ANYCRLF \R matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \R matches all Unicode line endings + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, & CRLF as newline sequences + PCRE_NEWLINE_CR Recognize CR as the only newline sequence + PCRE_NEWLINE_CRLF Recognize CRLF as the only newline sequence + PCRE_NEWLINE_LF Recognize LF as the only newline sequence + PCRE_NOTBOL Subject string is not the beginning of a line + PCRE_NOTEOL Subject string is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_START_OPTIMIZE Do not do "start-match" optimizations + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + if that is found before a full match +</pre> +For details of partial matching, see the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +page. A <b>pcre_extra</b> structure contains the following fields: +<pre> + <i>flags</i> Bits indicating which fields are set + <i>study_data</i> Opaque data from <b>pcre[16|32]_study()</b> + <i>match_limit</i> Limit on internal resource use + <i>match_limit_recursion</i> Limit on internal recursion depth + <i>callout_data</i> Opaque data passed back to callouts + <i>tables</i> Points to character tables or is NULL + <i>mark</i> For passing back a *MARK pointer + <i>executable_jit</i> Opaque data from JIT compilation +</pre> +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_free_study.html b/doc/html/pcre_free_study.html new file mode 100644 index 0000000..7f9e10e --- /dev/null +++ b/doc/html/pcre_free_study.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_free_study specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_free_study man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_free_study(pcre_extra *<i>extra</i>);</b> +</P> +<P> +<b>void pcre16_free_study(pcre16_extra *<i>extra</i>);</b> +</P> +<P> +<b>void pcre32_free_study(pcre32_extra *<i>extra</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function is used to free the memory used for the data generated by a call +to <b>pcre[16|32]_study()</b> when it is no longer needed. The argument must be the +result of such a call. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_free_substring.html b/doc/html/pcre_free_substring.html new file mode 100644 index 0000000..1fe6610 --- /dev/null +++ b/doc/html/pcre_free_substring.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_free_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_free_substring man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_free_substring(const char *<i>stringptr</i>);</b> +</P> +<P> +<b>void pcre16_free_substring(PCRE_SPTR16 <i>stringptr</i>);</b> +</P> +<P> +<b>void pcre32_free_substring(PCRE_SPTR32 <i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for freeing the store obtained by a previous +call to <b>pcre[16|32]_get_substring()</b> or <b>pcre[16|32]_get_named_substring()</b>. +Its only argument is a pointer to the string. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_free_substring_list.html b/doc/html/pcre_free_substring_list.html new file mode 100644 index 0000000..c086178 --- /dev/null +++ b/doc/html/pcre_free_substring_list.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_free_substring_list specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_free_substring_list man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b> +</P> +<P> +<b>void pcre16_free_substring_list(PCRE_SPTR16 *<i>stringptr</i>);</b> +</P> +<P> +<b>void pcre32_free_substring_list(PCRE_SPTR32 *<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for freeing the store obtained by a previous +call to <b>pcre[16|32]_get_substring_list()</b>. Its only argument is a pointer to +the list of string pointers. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_fullinfo.html b/doc/html/pcre_fullinfo.html new file mode 100644 index 0000000..2b7c72b --- /dev/null +++ b/doc/html/pcre_fullinfo.html @@ -0,0 +1,118 @@ +<html> +<head> +<title>pcre_fullinfo specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_fullinfo man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>int pcre16_fullinfo(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>int pcre32_fullinfo(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function returns information about a compiled pattern. Its arguments are: +<pre> + <i>code</i> Compiled regular expression + <i>extra</i> Result of <b>pcre[16|32]_study()</b> or NULL + <i>what</i> What information is required + <i>where</i> Where to put the information +</pre> +The following information is available: +<pre> + PCRE_INFO_BACKREFMAX Number of highest back reference + PCRE_INFO_CAPTURECOUNT Number of capturing subpatterns + PCRE_INFO_DEFAULT_TABLES Pointer to default tables + PCRE_INFO_FIRSTBYTE Fixed first data unit for a match, or + -1 for start of string + or after newline, or + -2 otherwise + PCRE_INFO_FIRSTTABLE Table of first data units (after studying) + PCRE_INFO_HASCRORLF Return 1 if explicit CR or LF matches exist + PCRE_INFO_JCHANGED Return 1 if (?J) or (?-J) was used + PCRE_INFO_JIT Return 1 after successful JIT compilation + PCRE_INFO_JITSIZE Size of JIT compiled code + PCRE_INFO_LASTLITERAL Literal last data unit required + PCRE_INFO_MINLENGTH Lower bound length of matching strings + PCRE_INFO_MATCHEMPTY Return 1 if the pattern can match an empty string, + 0 otherwise + PCRE_INFO_MATCHLIMIT Match limit if set, otherwise PCRE_RROR_UNSET + PCRE_INFO_MAXLOOKBEHIND Length (in characters) of the longest lookbehind assertion + PCRE_INFO_NAMECOUNT Number of named subpatterns + PCRE_INFO_NAMEENTRYSIZE Size of name table entry + PCRE_INFO_NAMETABLE Pointer to name table + PCRE_INFO_OKPARTIAL Return 1 if partial matching can be tried + (always returns 1 after release 8.00) + PCRE_INFO_OPTIONS Option bits used for compilation + PCRE_INFO_SIZE Size of compiled pattern + PCRE_INFO_STUDYSIZE Size of study data + PCRE_INFO_FIRSTCHARACTER Fixed first data unit for a match + PCRE_INFO_FIRSTCHARACTERFLAGS Returns + 1 if there is a first data character set, which can + then be retrieved using PCRE_INFO_FIRSTCHARACTER, + 2 if the first character is at the start of the data + string or after a newline, and + 0 otherwise + PCRE_INFO_RECURSIONLIMIT Recursion limit if set, otherwise PCRE_ERROR_UNSET + PCRE_INFO_REQUIREDCHAR Literal last data unit required + PCRE_INFO_REQUIREDCHARFLAGS Returns 1 if the last data character is set (which can then + be retrieved using PCRE_INFO_REQUIREDCHAR); 0 otherwise +</pre> +The <i>where</i> argument must point to an integer variable, except for the +following <i>what</i> values: +<pre> + PCRE_INFO_DEFAULT_TABLES const uint8_t * + PCRE_INFO_FIRSTCHARACTER uint32_t + PCRE_INFO_FIRSTTABLE const uint8_t * + PCRE_INFO_JITSIZE size_t + PCRE_INFO_MATCHLIMIT uint32_t + PCRE_INFO_NAMETABLE PCRE_SPTR16 (16-bit library) + PCRE_INFO_NAMETABLE PCRE_SPTR32 (32-bit library) + PCRE_INFO_NAMETABLE const unsigned char * (8-bit library) + PCRE_INFO_OPTIONS unsigned long int + PCRE_INFO_SIZE size_t + PCRE_INFO_STUDYSIZE size_t + PCRE_INFO_RECURSIONLIMIT uint32_t + PCRE_INFO_REQUIREDCHAR uint32_t +</pre> +The yield of the function is zero on success or: +<pre> + PCRE_ERROR_NULL the argument <i>code</i> was NULL + the argument <i>where</i> was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid + PCRE_ERROR_UNSET the option was not set +</PRE> +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_get_named_substring.html b/doc/html/pcre_get_named_substring.html new file mode 100644 index 0000000..72924d9 --- /dev/null +++ b/doc/html/pcre_get_named_substring.html @@ -0,0 +1,68 @@ +<html> +<head> +<title>pcre_get_named_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_get_named_substring man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre16_get_named_substring(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR16 <i>stringname</i>,</b> +<b> PCRE_SPTR16 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre32_get_named_substring(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, PCRE_SPTR32 <i>stringname</i>,</b> +<b> PCRE_SPTR32 *<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring by name. The +arguments are: +<pre> + <i>code</i> Compiled pattern + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre[16|32]_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre[16|32]_exec()</b> + <i>stringname</i> Name of the required substring + <i>stringptr</i> Where to put the string pointer +</pre> +The memory in which the substring is placed is obtained by calling +<b>pcre[16|32]_malloc()</b>. The convenience function +<b>pcre[16|32]_free_substring()</b> can be used to free it when it is no longer +needed. The yield of the function is the length of the extracted substring, +PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or +PCRE_ERROR_NOSUBSTRING if the string name is invalid. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_get_stringnumber.html b/doc/html/pcre_get_stringnumber.html new file mode 100644 index 0000000..7324d78 --- /dev/null +++ b/doc/html/pcre_get_stringnumber.html @@ -0,0 +1,57 @@ +<html> +<head> +<title>pcre_get_stringnumber specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_get_stringnumber man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>);</b> +<br> +<br> +<b>int pcre16_get_stringnumber(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>name</i>);</b> +<br> +<br> +<b>int pcre32_get_stringnumber(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>name</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This convenience function finds the number of a named substring capturing +parenthesis in a compiled pattern. Its arguments are: +<pre> + <i>code</i> Compiled regular expression + <i>name</i> Name whose number is required +</pre> +The yield of the function is the number of the parenthesis if the name is +found, or PCRE_ERROR_NOSUBSTRING otherwise. When duplicate names are allowed +(PCRE_DUPNAMES is set), it is not defined which of the numbers is returned by +<b>pcre[16|32]_get_stringnumber()</b>. You can obtain the complete list by calling +<b>pcre[16|32]_get_stringtable_entries()</b>. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_get_stringtable_entries.html b/doc/html/pcre_get_stringtable_entries.html new file mode 100644 index 0000000..7990679 --- /dev/null +++ b/doc/html/pcre_get_stringtable_entries.html @@ -0,0 +1,60 @@ +<html> +<head> +<title>pcre_get_stringtable_entries specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_get_stringtable_entries man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b> +<br> +<br> +<b>int pcre16_get_stringtable_entries(const pcre16 *<i>code</i>,</b> +<b> PCRE_SPTR16 <i>name</i>, PCRE_UCHAR16 **<i>first</i>, PCRE_UCHAR16 **<i>last</i>);</b> +<br> +<br> +<b>int pcre32_get_stringtable_entries(const pcre32 *<i>code</i>,</b> +<b> PCRE_SPTR32 <i>name</i>, PCRE_UCHAR32 **<i>first</i>, PCRE_UCHAR32 **<i>last</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This convenience function finds, for a compiled pattern, the first and last +entries for a given name in the table that translates capturing parenthesis +names into numbers. When names are required to be unique (PCRE_DUPNAMES is +<i>not</i> set), it is usually easier to use <b>pcre[16|32]_get_stringnumber()</b> +instead. +<pre> + <i>code</i> Compiled regular expression + <i>name</i> Name whose entries required + <i>first</i> Where to return a pointer to the first entry + <i>last</i> Where to return a pointer to the last entry +</pre> +The yield of the function is the length of each entry, or +PCRE_ERROR_NOSUBSTRING if none are found. +</P> +<P> +There is a complete description of the PCRE native API, including the format of +the table entries, in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page, and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_get_substring.html b/doc/html/pcre_get_substring.html new file mode 100644 index 0000000..1a8e4f5 --- /dev/null +++ b/doc/html/pcre_get_substring.html @@ -0,0 +1,64 @@ +<html> +<head> +<title>pcre_get_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_get_substring man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre16_get_substring(PCRE_SPTR16 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> PCRE_SPTR16 *<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre32_get_substring(PCRE_SPTR32 <i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> PCRE_SPTR32 *<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring. The +arguments are: +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre[16|32]_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre[16|32]_exec()</b> + <i>stringnumber</i> Number of the required substring + <i>stringptr</i> Where to put the string pointer +</pre> +The memory in which the substring is placed is obtained by calling +<b>pcre[16|32]_malloc()</b>. The convenience function +<b>pcre[16|32]_free_substring()</b> can be used to free it when it is no longer +needed. The yield of the function is the length of the substring, +PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or +PCRE_ERROR_NOSUBSTRING if the string number is invalid. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_get_substring_list.html b/doc/html/pcre_get_substring_list.html new file mode 100644 index 0000000..7e8c6bc --- /dev/null +++ b/doc/html/pcre_get_substring_list.html @@ -0,0 +1,61 @@ +<html> +<head> +<title>pcre_get_substring_list specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_get_substring_list man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +<br> +<br> +<b>int pcre16_get_substring_list(PCRE_SPTR16 <i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, PCRE_SPTR16 **<i>listptr</i>);</b> +<br> +<br> +<b>int pcre32_get_substring_list(PCRE_SPTR32 <i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, PCRE_SPTR32 **<i>listptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a list of all the captured +substrings. The arguments are: +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre[16|32]_exec</b> used + <i>stringcount</i> Value returned by <b>pcre[16|32]_exec</b> + <i>listptr</i> Where to put a pointer to the list +</pre> +The memory in which the substrings and the list are placed is obtained by +calling <b>pcre[16|32]_malloc()</b>. The convenience function +<b>pcre[16|32]_free_substring_list()</b> can be used to free it when it is no +longer needed. A pointer to a list of pointers is put in the variable whose +address is in <i>listptr</i>. The list is terminated by a NULL pointer. The +yield of the function is zero on success or PCRE_ERROR_NOMEMORY if sufficient +memory could not be obtained. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_jit_exec.html b/doc/html/pcre_jit_exec.html new file mode 100644 index 0000000..4ebb0cb --- /dev/null +++ b/doc/html/pcre_jit_exec.html @@ -0,0 +1,108 @@ +<html> +<head> +<title>pcre_jit_exec specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_jit_exec man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_jit_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> pcre_jit_stack *<i>jstack</i>);</b> +<br> +<br> +<b>int pcre16_jit_exec(const pcre16 *<i>code</i>, const pcre16_extra *<i>extra</i>,</b> +<b> PCRE_SPTR16 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> pcre_jit_stack *<i>jstack</i>);</b> +<br> +<br> +<b>int pcre32_jit_exec(const pcre32 *<i>code</i>, const pcre32_extra *<i>extra</i>,</b> +<b> PCRE_SPTR32 <i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> pcre_jit_stack *<i>jstack</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function matches a compiled regular expression that has been successfully +studied with one of the JIT options against a given subject string, using a +matching algorithm that is similar to Perl's. It is a "fast path" interface to +JIT, and it bypasses some of the sanity checks that <b>pcre_exec()</b> applies. +It returns offsets to captured substrings. Its arguments are: +<pre> + <i>code</i> Points to the compiled pattern + <i>extra</i> Points to an associated <b>pcre[16|32]_extra</b> structure, + or is NULL + <i>subject</i> Points to the subject string + <i>length</i> Length of the subject string, in bytes + <i>startoffset</i> Offset in bytes in the subject at which to + start matching + <i>options</i> Option bits + <i>ovector</i> Points to a vector of ints for result offsets + <i>ovecsize</i> Number of elements in the vector (a multiple of 3) + <i>jstack</i> Pointer to a JIT stack +</pre> +The allowed options are: +<pre> + PCRE_NOTBOL Subject string is not the beginning of a line + PCRE_NOTEOL Subject string is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + if that is found before a full match +</pre> +However, the PCRE_NO_UTF[8|16|32]_CHECK options have no effect, as this check +is never applied. For details of partial matching, see the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +page. A <b>pcre_extra</b> structure contains the following fields: +<pre> + <i>flags</i> Bits indicating which fields are set + <i>study_data</i> Opaque data from <b>pcre[16|32]_study()</b> + <i>match_limit</i> Limit on internal resource use + <i>match_limit_recursion</i> Limit on internal recursion depth + <i>callout_data</i> Opaque data passed back to callouts + <i>tables</i> Points to character tables or is NULL + <i>mark</i> For passing back a *MARK pointer + <i>executable_jit</i> Opaque data from JIT compilation +</pre> +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the JIT API in the +<a href="pcrejit.html"><b>pcrejit</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_jit_stack_alloc.html b/doc/html/pcre_jit_stack_alloc.html new file mode 100644 index 0000000..23ba450 --- /dev/null +++ b/doc/html/pcre_jit_stack_alloc.html @@ -0,0 +1,55 @@ +<html> +<head> +<title>pcre_jit_stack_alloc specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_jit_stack_alloc man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>,</b> +<b> int <i>maxsize</i>);</b> +<br> +<br> +<b>pcre16_jit_stack *pcre16_jit_stack_alloc(int <i>startsize</i>,</b> +<b> int <i>maxsize</i>);</b> +<br> +<br> +<b>pcre32_jit_stack *pcre32_jit_stack_alloc(int <i>startsize</i>,</b> +<b> int <i>maxsize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function is used to create a stack for use by the code compiled by the JIT +optimization of <b>pcre[16|32]_study()</b>. The arguments are a starting size for +the stack, and a maximum size to which it is allowed to grow. The result can be +passed to the JIT run-time code by <b>pcre[16|32]_assign_jit_stack()</b>, or that +function can set up a callback for obtaining a stack. A maximum stack size of +512K to 1M should be more than enough for any pattern. For more details, see +the +<a href="pcrejit.html"><b>pcrejit</b></a> +page. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_jit_stack_free.html b/doc/html/pcre_jit_stack_free.html new file mode 100644 index 0000000..8bd06e4 --- /dev/null +++ b/doc/html/pcre_jit_stack_free.html @@ -0,0 +1,48 @@ +<html> +<head> +<title>pcre_jit_stack_free specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_jit_stack_free man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b> +</P> +<P> +<b>void pcre16_jit_stack_free(pcre16_jit_stack *<i>stack</i>);</b> +</P> +<P> +<b>void pcre32_jit_stack_free(pcre32_jit_stack *<i>stack</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function is used to free a JIT stack that was created by +<b>pcre[16|32]_jit_stack_alloc()</b> when it is no longer needed. For more details, +see the +<a href="pcrejit.html"><b>pcrejit</b></a> +page. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_maketables.html b/doc/html/pcre_maketables.html new file mode 100644 index 0000000..3a7b5eb --- /dev/null +++ b/doc/html/pcre_maketables.html @@ -0,0 +1,48 @@ +<html> +<head> +<title>pcre_maketables specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_maketables man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>const unsigned char *pcre_maketables(void);</b> +</P> +<P> +<b>const unsigned char *pcre16_maketables(void);</b> +</P> +<P> +<b>const unsigned char *pcre32_maketables(void);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function builds a set of character tables for character values less than +256. These can be passed to <b>pcre[16|32]_compile()</b> to override PCRE's +internal, built-in tables (which were made by <b>pcre[16|32]_maketables()</b> when +PCRE was compiled). You might want to do this if you are using a non-standard +locale. The function yields a pointer to the tables. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_pattern_to_host_byte_order.html b/doc/html/pcre_pattern_to_host_byte_order.html new file mode 100644 index 0000000..1b1c803 --- /dev/null +++ b/doc/html/pcre_pattern_to_host_byte_order.html @@ -0,0 +1,58 @@ +<html> +<head> +<title>pcre_pattern_to_host_byte_order specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_pattern_to_host_byte_order man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_pattern_to_host_byte_order(pcre *<i>code</i>,</b> +<b> pcre_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +<br> +<br> +<b>int pcre16_pattern_to_host_byte_order(pcre16 *<i>code</i>,</b> +<b> pcre16_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +<br> +<br> +<b>int pcre32_pattern_to_host_byte_order(pcre32 *<i>code</i>,</b> +<b> pcre32_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function ensures that the bytes in 2-byte and 4-byte values in a compiled +pattern are in the correct order for the current host. It is useful when a +pattern that has been compiled on one host is transferred to another that might +have different endianness. The arguments are: +<pre> + <i>code</i> A compiled regular expression + <i>extra</i> Points to an associated <b>pcre[16|32]_extra</b> structure, + or is NULL + <i>tables</i> Pointer to character tables, or NULL to + set the built-in default +</pre> +The result is 0 for success, a negative PCRE_ERROR_xxx value otherwise. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_refcount.html b/doc/html/pcre_refcount.html new file mode 100644 index 0000000..bfb92e6 --- /dev/null +++ b/doc/html/pcre_refcount.html @@ -0,0 +1,51 @@ +<html> +<head> +<title>pcre_refcount specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_refcount man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b> +</P> +<P> +<b>int pcre16_refcount(pcre16 *<i>code</i>, int <i>adjust</i>);</b> +</P> +<P> +<b>int pcre32_refcount(pcre32 *<i>code</i>, int <i>adjust</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function is used to maintain a reference count inside a data block that +contains a compiled pattern. Its arguments are: +<pre> + <i>code</i> Compiled regular expression + <i>adjust</i> Adjustment to reference value +</pre> +The yield of the function is the adjusted reference value, which is constrained +to lie between 0 and 65535. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_study.html b/doc/html/pcre_study.html new file mode 100644 index 0000000..af82f11 --- /dev/null +++ b/doc/html/pcre_study.html @@ -0,0 +1,68 @@ +<html> +<head> +<title>pcre_study specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_study man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>pcre16_extra *pcre16_study(const pcre16 *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>pcre32_extra *pcre32_study(const pcre32 *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function studies a compiled pattern, to see if additional information can +be extracted that might speed up matching. Its arguments are: +<pre> + <i>code</i> A compiled regular expression + <i>options</i> Options for <b>pcre[16|32]_study()</b> + <i>errptr</i> Where to put an error message +</pre> +If the function succeeds, it returns a value that can be passed to +<b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> via their <i>extra</i> +arguments. +</P> +<P> +If the function returns NULL, either it could not find any additional +information, or there was an error. You can tell the difference by looking at +the error value. It is NULL in first case. +</P> +<P> +The only option is PCRE_STUDY_JIT_COMPILE. It requests just-in-time compilation +if possible. If PCRE has been compiled without JIT support, this option is +ignored. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +page for further details. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_utf16_to_host_byte_order.html b/doc/html/pcre_utf16_to_host_byte_order.html new file mode 100644 index 0000000..18e7788 --- /dev/null +++ b/doc/html/pcre_utf16_to_host_byte_order.html @@ -0,0 +1,57 @@ +<html> +<head> +<title>pcre_utf16_to_host_byte_order specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_utf16_to_host_byte_order man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *<i>output</i>,</b> +<b> PCRE_SPTR16 <i>input</i>, int <i>length</i>, int *<i>host_byte_order</i>,</b> +<b> int <i>keep_boms</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function, which exists only in the 16-bit library, converts a UTF-16 +string to the correct order for the current host, taking account of any byte +order marks (BOMs) within the string. Its arguments are: +<pre> + <i>output</i> pointer to output buffer, may be the same as <i>input</i> + <i>input</i> pointer to input buffer + <i>length</i> number of 16-bit units in the input, or negative for + a zero-terminated string + <i>host_byte_order</i> a NULL value or a non-zero value pointed to means + start in host byte order + <i>keep_boms</i> if non-zero, BOMs are copied to the output string +</pre> +The result of the function is the number of 16-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +</P> +<P> +If <i>host_byte_order</i> is not NULL, it is set to indicate the byte order that +is current at the end of the string. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_utf32_to_host_byte_order.html b/doc/html/pcre_utf32_to_host_byte_order.html new file mode 100644 index 0000000..772ae40 --- /dev/null +++ b/doc/html/pcre_utf32_to_host_byte_order.html @@ -0,0 +1,57 @@ +<html> +<head> +<title>pcre_utf32_to_host_byte_order specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_utf32_to_host_byte_order man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *<i>output</i>,</b> +<b> PCRE_SPTR32 <i>input</i>, int <i>length</i>, int *<i>host_byte_order</i>,</b> +<b> int <i>keep_boms</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function, which exists only in the 32-bit library, converts a UTF-32 +string to the correct order for the current host, taking account of any byte +order marks (BOMs) within the string. Its arguments are: +<pre> + <i>output</i> pointer to output buffer, may be the same as <i>input</i> + <i>input</i> pointer to input buffer + <i>length</i> number of 32-bit units in the input, or negative for + a zero-terminated string + <i>host_byte_order</i> a NULL value or a non-zero value pointed to means + start in host byte order + <i>keep_boms</i> if non-zero, BOMs are copied to the output string +</pre> +The result of the function is the number of 32-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +</P> +<P> +If <i>host_byte_order</i> is not NULL, it is set to indicate the byte order that +is current at the end of the string. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcre_version.html b/doc/html/pcre_version.html new file mode 100644 index 0000000..d33e718 --- /dev/null +++ b/doc/html/pcre_version.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_version specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcre_version man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>const char *pcre_version(void);</b> +</P> +<P> +<b>const char *pcre16_version(void);</b> +</P> +<P> +<b>const char *pcre32_version(void);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function (even in the 16-bit and 32-bit libraries) returns a +zero-terminated, 8-bit character string that gives the version number of the +PCRE library and the date of its release. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcreapi.html b/doc/html/pcreapi.html new file mode 100644 index 0000000..b401ecc --- /dev/null +++ b/doc/html/pcreapi.html @@ -0,0 +1,2922 @@ +<html> +<head> +<title>pcreapi specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreapi man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE NATIVE API BASIC FUNCTIONS</a> +<li><a name="TOC2" href="#SEC2">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a> +<li><a name="TOC3" href="#SEC3">PCRE NATIVE API AUXILIARY FUNCTIONS</a> +<li><a name="TOC4" href="#SEC4">PCRE NATIVE API INDIRECTED FUNCTIONS</a> +<li><a name="TOC5" href="#SEC5">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a> +<li><a name="TOC6" href="#SEC6">PCRE API OVERVIEW</a> +<li><a name="TOC7" href="#SEC7">NEWLINES</a> +<li><a name="TOC8" href="#SEC8">MULTITHREADING</a> +<li><a name="TOC9" href="#SEC9">SAVING PRECOMPILED PATTERNS FOR LATER USE</a> +<li><a name="TOC10" href="#SEC10">CHECKING BUILD-TIME OPTIONS</a> +<li><a name="TOC11" href="#SEC11">COMPILING A PATTERN</a> +<li><a name="TOC12" href="#SEC12">COMPILATION ERROR CODES</a> +<li><a name="TOC13" href="#SEC13">STUDYING A PATTERN</a> +<li><a name="TOC14" href="#SEC14">LOCALE SUPPORT</a> +<li><a name="TOC15" href="#SEC15">INFORMATION ABOUT A PATTERN</a> +<li><a name="TOC16" href="#SEC16">REFERENCE COUNTS</a> +<li><a name="TOC17" href="#SEC17">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a> +<li><a name="TOC18" href="#SEC18">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> +<li><a name="TOC19" href="#SEC19">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> +<li><a name="TOC20" href="#SEC20">DUPLICATE SUBPATTERN NAMES</a> +<li><a name="TOC21" href="#SEC21">FINDING ALL POSSIBLE MATCHES</a> +<li><a name="TOC22" href="#SEC22">OBTAINING AN ESTIMATE OF STACK USAGE</a> +<li><a name="TOC23" href="#SEC23">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a> +<li><a name="TOC24" href="#SEC24">SEE ALSO</a> +<li><a name="TOC25" href="#SEC25">AUTHOR</a> +<li><a name="TOC26" href="#SEC26">REVISION</a> +</ul> +<P> +<b>#include <pcre.h></b> +</P> +<br><a name="SEC1" href="#TOC1">PCRE NATIVE API BASIC FUNCTIONS</a><br> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +<br> +<br> +<b>void pcre_free_study(pcre_extra *<i>extra</i>);</b> +<br> +<br> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +<br> +<br> +<b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +</P> +<br><a name="SEC2" href="#TOC1">PCRE NATIVE API STRING EXTRACTION FUNCTIONS</a><br> +<P> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> char *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>);</b> +<br> +<br> +<b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b> +<br> +<br> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +<br> +<br> +<b>void pcre_free_substring(const char *<i>stringptr</i>);</b> +<br> +<br> +<b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b> +</P> +<br><a name="SEC3" href="#TOC1">PCRE NATIVE API AUXILIARY FUNCTIONS</a><br> +<P> +<b>int pcre_jit_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> pcre_jit_stack *<i>jstack</i>);</b> +<br> +<br> +<b>pcre_jit_stack *pcre_jit_stack_alloc(int <i>startsize</i>, int <i>maxsize</i>);</b> +<br> +<br> +<b>void pcre_jit_stack_free(pcre_jit_stack *<i>stack</i>);</b> +<br> +<br> +<b>void pcre_assign_jit_stack(pcre_extra *<i>extra</i>,</b> +<b> pcre_jit_callback <i>callback</i>, void *<i>data</i>);</b> +<br> +<br> +<b>const unsigned char *pcre_maketables(void);</b> +<br> +<br> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b> +<br> +<br> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +<br> +<br> +<b>const char *pcre_version(void);</b> +<br> +<br> +<b>int pcre_pattern_to_host_byte_order(pcre *<i>code</i>,</b> +<b> pcre_extra *<i>extra</i>, const unsigned char *<i>tables</i>);</b> +</P> +<br><a name="SEC4" href="#TOC1">PCRE NATIVE API INDIRECTED FUNCTIONS</a><br> +<P> +<b>void *(*pcre_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre_free)(void *);</b> +<br> +<br> +<b>void *(*pcre_stack_malloc)(size_t);</b> +<br> +<br> +<b>void (*pcre_stack_free)(void *);</b> +<br> +<br> +<b>int (*pcre_callout)(pcre_callout_block *);</b> +<br> +<br> +<b>int (*pcre_stack_guard)(void);</b> +</P> +<br><a name="SEC5" href="#TOC1">PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> +<P> +As well as support for 8-bit character strings, PCRE also supports 16-bit +strings (from release 8.30) and 32-bit strings (from release 8.32), by means of +two additional libraries. They can be built as well as, or instead of, the +8-bit library. To avoid too much complication, this document describes the +8-bit versions of the functions, with only occasional references to the 16-bit +and 32-bit libraries. +</P> +<P> +The 16-bit and 32-bit functions operate in the same way as their 8-bit +counterparts; they just use different data types for their arguments and +results, and their names start with <b>pcre16_</b> or <b>pcre32_</b> instead of +<b>pcre_</b>. For every option that has UTF8 in its name (for example, +PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced +by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the +16-bit and 32-bit option names define the same bit values. +</P> +<P> +References to bytes and UTF-8 in this document should be read as references to +16-bit data units and UTF-16 when using the 16-bit library, or 32-bit data +units and UTF-32 when using the 32-bit library, unless specified otherwise. +More details of the specific differences for the 16-bit and 32-bit libraries +are given in the +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +pages. +</P> +<br><a name="SEC6" href="#TOC1">PCRE API OVERVIEW</a><br> +<P> +PCRE has its own native API, which is described in this document. There are +also some wrapper functions (for the 8-bit library only) that correspond to the +POSIX regular expression API, but they do not give access to all the +functionality. They are described in the +<a href="pcreposix.html"><b>pcreposix</b></a> +documentation. Both of these APIs define a set of C function calls. A C++ +wrapper (again for the 8-bit library only) is also distributed with PCRE. It is +documented in the +<a href="pcrecpp.html"><b>pcrecpp</b></a> +page. +</P> +<P> +The native API C function prototypes are defined in the header file +<b>pcre.h</b>, and on Unix-like systems the (8-bit) library itself is called +<b>libpcre</b>. It can normally be accessed by adding <b>-lpcre</b> to the +command for linking an application that uses PCRE. The header file defines the +macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers +for the library. Applications can use these to include support for different +releases of PCRE. +</P> +<P> +In a Windows environment, if you want to statically link an application program +against a non-dll <b>pcre.a</b> file, you must define PCRE_STATIC before +including <b>pcre.h</b> or <b>pcrecpp.h</b>, because otherwise the +<b>pcre_malloc()</b> and <b>pcre_free()</b> exported functions will be declared +<b>__declspec(dllimport)</b>, with unwanted results. +</P> +<P> +The functions <b>pcre_compile()</b>, <b>pcre_compile2()</b>, <b>pcre_study()</b>, +and <b>pcre_exec()</b> are used for compiling and matching regular expressions +in a Perl-compatible manner. A sample program that demonstrates the simplest +way of using them is provided in the file called <i>pcredemo.c</i> in the PCRE +source distribution. A listing of this program is given in the +<a href="pcredemo.html"><b>pcredemo</b></a> +documentation, and the +<a href="pcresample.html"><b>pcresample</b></a> +documentation describes how to compile and run it. +</P> +<P> +Just-in-time compiler support is an optional feature of PCRE that can be built +in appropriate hardware environments. It greatly speeds up the matching +performance of many patterns. Simple programs can easily request that it be +used if available, by setting an option that is ignored when it is not +relevant. More complicated programs might need to make use of the functions +<b>pcre_jit_stack_alloc()</b>, <b>pcre_jit_stack_free()</b>, and +<b>pcre_assign_jit_stack()</b> in order to control the JIT code's memory usage. +</P> +<P> +From release 8.32 there is also a direct interface for JIT execution, which +gives improved performance. The JIT-specific functions are discussed in the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation. +</P> +<P> +A second matching function, <b>pcre_dfa_exec()</b>, which is not +Perl-compatible, is also provided. This uses a different algorithm for the +matching. The alternative algorithm finds all possible matches (at a given +point in the subject), and scans the subject just once (unless there are +lookbehind assertions). However, this algorithm does not return captured +substrings. A description of the two matching algorithms and their advantages +and disadvantages is given in the +<a href="pcrematching.html"><b>pcrematching</b></a> +documentation. +</P> +<P> +In addition to the main compiling and matching functions, there are convenience +functions for extracting captured substrings from a subject string that is +matched by <b>pcre_exec()</b>. They are: +<pre> + <b>pcre_copy_substring()</b> + <b>pcre_copy_named_substring()</b> + <b>pcre_get_substring()</b> + <b>pcre_get_named_substring()</b> + <b>pcre_get_substring_list()</b> + <b>pcre_get_stringnumber()</b> + <b>pcre_get_stringtable_entries()</b> +</pre> +<b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also +provided, to free the memory used for extracted strings. +</P> +<P> +The function <b>pcre_maketables()</b> is used to build a set of character tables +in the current locale for passing to <b>pcre_compile()</b>, <b>pcre_exec()</b>, +or <b>pcre_dfa_exec()</b>. This is an optional facility that is provided for +specialist use. Most commonly, no special tables are passed, in which case +internal tables that are generated when PCRE is built are used. +</P> +<P> +The function <b>pcre_fullinfo()</b> is used to find out information about a +compiled pattern. The function <b>pcre_version()</b> returns a pointer to a +string containing the version of PCRE and its date of release. +</P> +<P> +The function <b>pcre_refcount()</b> maintains a reference count in a data block +containing a compiled pattern. This is provided for the benefit of +object-oriented applications. +</P> +<P> +The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain +the entry points of the standard <b>malloc()</b> and <b>free()</b> functions, +respectively. PCRE calls the memory management functions via these variables, +so a calling program can replace them if it wishes to intercept the calls. This +should be done before calling any PCRE functions. +</P> +<P> +The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also +indirections to memory management functions. These special functions are used +only when PCRE is compiled to use the heap for remembering data, instead of +recursive function calls, when running the <b>pcre_exec()</b> function. See the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation for details of how to do this. It is a non-standard way of +building PCRE, for use in environments that have limited stacks. Because of the +greater use of memory management, it runs more slowly. Separate functions are +provided so that special-purpose external code can be used for this case. When +used, these functions are always called in a stack-like manner (last obtained, +first freed), and always for memory blocks of the same size. There is a +discussion about PCRE's stack usage in the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation. +</P> +<P> +The global variable <b>pcre_callout</b> initially contains NULL. It can be set +by the caller to a "callout" function, which PCRE will then call at specified +points during a matching operation. Details are given in the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +The global variable <b>pcre_stack_guard</b> initially contains NULL. It can be +set by the caller to a function that is called by PCRE whenever it starts +to compile a parenthesized part of a pattern. When parentheses are nested, PCRE +uses recursive function calls, which use up the system stack. This function is +provided so that applications with restricted stacks can force a compilation +error if the stack runs out. The function should return zero if all is well, or +non-zero to force an error. +<a name="newlines"></a></P> +<br><a name="SEC7" href="#TOC1">NEWLINES</a><br> +<P> +PCRE supports five different conventions for indicating line breaks in +strings: a single CR (carriage return) character, a single LF (linefeed) +character, the two-character sequence CRLF, any of the three preceding, or any +Unicode newline sequence. The Unicode newline sequences are the three just +mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, +U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). +</P> +<P> +Each of the first three conventions is used by at least one operating system as +its standard newline sequence. When PCRE is built, a default can be specified. +The default default is LF, which is the Unix standard. When PCRE is run, the +default can be overridden, either when a pattern is compiled, or when it is +matched. +</P> +<P> +At compile time, the newline convention can be specified by the <i>options</i> +argument of <b>pcre_compile()</b>, or it can be specified by special text at the +start of the pattern itself; this overrides any other settings. See the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page for details of the special character sequences. +</P> +<P> +In the PCRE documentation the word "newline" is used to mean "the character or +pair of characters that indicate a line break". The choice of newline +convention affects the handling of the dot, circumflex, and dollar +metacharacters, the handling of #-comments in /x mode, and, when CRLF is a +recognized line ending sequence, the match position advancement for a +non-anchored pattern. There is more detail about this in the +<a href="#execoptions">section on <b>pcre_exec()</b> options</a> +below. +</P> +<P> +The choice of newline convention does not affect the interpretation of +the \n or \r escape sequences, nor does it affect what \R matches, which is +controlled in a similar way, but by separate options. +</P> +<br><a name="SEC8" href="#TOC1">MULTITHREADING</a><br> +<P> +The PCRE functions can be used in multi-threading applications, with the +proviso that the memory management functions pointed to by <b>pcre_malloc</b>, +<b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the +callout and stack-checking functions pointed to by <b>pcre_callout</b> and +<b>pcre_stack_guard</b>, are shared by all threads. +</P> +<P> +The compiled form of a regular expression is not altered during matching, so +the same compiled pattern can safely be used by several threads at once. +</P> +<P> +If the just-in-time optimization feature is being used, it needs separate +memory stack areas for each thread. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +</P> +<br><a name="SEC9" href="#TOC1">SAVING PRECOMPILED PATTERNS FOR LATER USE</a><br> +<P> +The compiled form of a regular expression can be saved and re-used at a later +time, possibly by a different program, and even on a host other than the one on +which it was compiled. Details are given in the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation, which includes a description of the +<b>pcre_pattern_to_host_byte_order()</b> function. However, compiling a regular +expression with one version of PCRE for use with a different version is not +guaranteed to work and may cause crashes. +</P> +<br><a name="SEC10" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +The function <b>pcre_config()</b> makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation has more details about these optional features. +</P> +<P> +The first argument for <b>pcre_config()</b> is an integer, specifying which +information is required; the second argument is a pointer to a variable into +which the information is placed. The returned value is zero on success, or the +negative error code PCRE_ERROR_BADOPTION if the value in the first argument is +not recognized. The following information is available: +<pre> + PCRE_CONFIG_UTF8 +</pre> +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. This value should normally be given to the 8-bit +version of this function, <b>pcre_config()</b>. If it is given to the 16-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + PCRE_CONFIG_UTF16 +</pre> +The output is an integer that is set to one if UTF-16 support is available; +otherwise it is set to zero. This value should normally be given to the 16-bit +version of this function, <b>pcre16_config()</b>. If it is given to the 8-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + PCRE_CONFIG_UTF32 +</pre> +The output is an integer that is set to one if UTF-32 support is available; +otherwise it is set to zero. This value should normally be given to the 32-bit +version of this function, <b>pcre32_config()</b>. If it is given to the 8-bit +or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION. +<pre> + PCRE_CONFIG_UNICODE_PROPERTIES +</pre> +The output is an integer that is set to one if support for Unicode character +properties is available; otherwise it is set to zero. +<pre> + PCRE_CONFIG_JIT +</pre> +The output is an integer that is set to one if support for just-in-time +compiling is available; otherwise it is set to zero. +<pre> + PCRE_CONFIG_JITTARGET +</pre> +The output is a pointer to a zero-terminated "const char *" string. If JIT +support is available, the string contains the name of the architecture for +which the JIT compiler is configured, for example "x86 32bit (little endian + +unaligned)". If JIT support is not available, the result is NULL. +<pre> + PCRE_CONFIG_NEWLINE +</pre> +The output is an integer whose value specifies the default character sequence +that is recognized as meaning "newline". The values that are supported in +ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for +ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the +same values. However, the value for LF is normally 21, though some EBCDIC +environments use 37. The corresponding values for CRLF are 3349 and 3365. The +default should normally correspond to the standard sequence for your operating +system. +<pre> + PCRE_CONFIG_BSR +</pre> +The output is an integer whose value indicates what character sequences the \R +escape sequence matches by default. A value of 0 means that \R matches any +Unicode line ending sequence; a value of 1 means that \R matches only CR, LF, +or CRLF. The default can be overridden when a pattern is compiled or matched. +<pre> + PCRE_CONFIG_LINK_SIZE +</pre> +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. For the 8-bit library, the value can +be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still +a number of bytes. For the 32-bit library, the value is either 2 or 4 and is +still a number of bytes. The default value of 2 is sufficient for all but the +most massive patterns, since it allows the compiled pattern to be up to 64K in +size. Larger values allow larger regular expressions to be compiled, at the +expense of slower matching. +<pre> + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD +</pre> +The output is an integer that contains the threshold above which the POSIX +interface uses <b>malloc()</b> for output vectors. Further details are given in +the +<a href="pcreposix.html"><b>pcreposix</b></a> +documentation. +<pre> + PCRE_CONFIG_PARENS_LIMIT +</pre> +The output is a long integer that gives the maximum depth of nesting of +parentheses (of any kind) in a pattern. This limit is imposed to cap the amount +of system stack used when a pattern is compiled. It is specified when PCRE is +built; the default is 250. This limit does not take into account the stack that +may already be used by the calling application. For finer control over +compilation stack usage, you can set a pointer to an external checking function +in <b>pcre_stack_guard</b>. +<pre> + PCRE_CONFIG_MATCH_LIMIT +</pre> +The output is a long integer that gives the default limit for the number of +internal matching function calls in a <b>pcre_exec()</b> execution. Further +details are given with <b>pcre_exec()</b> below. +<pre> + PCRE_CONFIG_MATCH_LIMIT_RECURSION +</pre> +The output is a long integer that gives the default limit for the depth of +recursion when calling the internal matching function in a <b>pcre_exec()</b> +execution. Further details are given with <b>pcre_exec()</b> below. +<pre> + PCRE_CONFIG_STACKRECURSE +</pre> +The output is an integer that is set to one if internal recursion when running +<b>pcre_exec()</b> is implemented by recursive function calls that use the stack +to remember their state. This is the usual way that PCRE is compiled. The +output is zero if PCRE was compiled to use blocks of data on the heap instead +of recursive function calls. In this case, <b>pcre_stack_malloc</b> and +<b>pcre_stack_free</b> are called to manage memory blocks on the heap, thus +avoiding the use of the stack. +</P> +<br><a name="SEC11" href="#TOC1">COMPILING A PATTERN</a><br> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +<br> +<br> +<b>pcre *pcre_compile2(const char *<i>pattern</i>, int <i>options</i>,</b> +<b> int *<i>errorcodeptr</i>,</b> +<b> const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b> const unsigned char *<i>tableptr</i>);</b> +</P> +<P> +Either of the functions <b>pcre_compile()</b> or <b>pcre_compile2()</b> can be +called to compile a pattern into an internal form. The only difference between +the two interfaces is that <b>pcre_compile2()</b> has an additional argument, +<i>errorcodeptr</i>, via which a numerical error code can be returned. To avoid +too much repetition, we refer just to <b>pcre_compile()</b> below, but the +information applies equally to <b>pcre_compile2()</b>. +</P> +<P> +The pattern is a C string terminated by a binary zero, and is passed in the +<i>pattern</i> argument. A pointer to a single block of memory that is obtained +via <b>pcre_malloc</b> is returned. This contains the compiled code and related +data. The <b>pcre</b> type is defined for the returned block; this is a typedef +for a structure whose contents are not externally defined. It is up to the +caller to free the memory (via <b>pcre_free</b>) when it is no longer required. +</P> +<P> +Although the compiled code of a PCRE regex is relocatable, that is, it does not +depend on memory location, the complete <b>pcre</b> data block is not +fully relocatable, because it may contain a copy of the <i>tableptr</i> +argument, which is an address (see below). +</P> +<P> +The <i>options</i> argument contains various bit settings that affect the +compilation. It should be zero if no options are required. The available +options are described below. Some of them (in particular, those that are +compatible with Perl, but some others as well) can also be set and unset from +within the pattern (see the detailed description in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation). For those options that can be different in different parts of +the pattern, the contents of the <i>options</i> argument specifies their +settings at the start of compilation and execution. The PCRE_ANCHORED, +PCRE_BSR_<i>xxx</i>, PCRE_NEWLINE_<i>xxx</i>, PCRE_NO_UTF8_CHECK, and +PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at +compile time. +</P> +<P> +If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately. +Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns +NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual +error message. This is a static string that is part of the library. You must +not try to free it. Normally, the offset from the start of the pattern to the +data unit that was being processed when the error was discovered is placed in +the variable pointed to by <i>erroffset</i>, which must not be NULL (if it is, +an immediate error is given). However, for an invalid UTF-8 or UTF-16 string, +the offset is that of the first data unit of the failing character. +</P> +<P> +Some errors are not detected until the whole pattern has been scanned; in these +cases, the offset passed back is the length of the pattern. Note that the +offset is in data units, not characters, even in a UTF mode. It may sometimes +point into the middle of a UTF-8 or UTF-16 character. +</P> +<P> +If <b>pcre_compile2()</b> is used instead of <b>pcre_compile()</b>, and the +<i>errorcodeptr</i> argument is not NULL, a non-zero error code number is +returned via this argument in the event of an error. This is in addition to the +textual error message. Error codes and messages are listed below. +</P> +<P> +If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of +character tables that are built when PCRE is compiled, using the default C +locale. Otherwise, <i>tableptr</i> must be an address that is the result of a +call to <b>pcre_maketables()</b>. This value is stored with the compiled +pattern, and used again by <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> when the +pattern is matched. For more discussion, see the section on locale support +below. +</P> +<P> +This code fragment shows a typical straightforward call to <b>pcre_compile()</b>: +<pre> + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ +</pre> +The following names for option bits are defined in the <b>pcre.h</b> header +file: +<pre> + PCRE_ANCHORED +</pre> +If this bit is set, the pattern is forced to be "anchored", that is, it is +constrained to match only at the first matching point in the string that is +being searched (the "subject string"). This effect can also be achieved by +appropriate constructs in the pattern itself, which is the only way to do it in +Perl. +<pre> + PCRE_AUTO_CALLOUT +</pre> +If this bit is set, <b>pcre_compile()</b> automatically inserts callout items, +all with number 255, before each pattern item. For discussion of the callout +facility, see the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +<pre> + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE +</pre> +These options (which are mutually exclusive) control what the \R escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. The default is specified when PCRE is +built. It can be overridden from within the pattern, or by setting an option +when a compiled pattern is matched. +<pre> + PCRE_CASELESS +</pre> +If this bit is set, letters in the pattern match both upper and lower case +letters. It is equivalent to Perl's /i option, and it can be changed within a +pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the +concept of case for characters whose values are less than 128, so caseless +matching is always possible. For characters with higher values, the concept of +case is supported if PCRE is compiled with Unicode property support, but not +otherwise. If you want to use caseless matching for characters 128 and above, +you must ensure that PCRE is compiled with Unicode property support as well as +with UTF-8 support. +<pre> + PCRE_DOLLAR_ENDONLY +</pre> +If this bit is set, a dollar metacharacter in the pattern matches only at the +end of the subject string. Without this option, a dollar also matches +immediately before a newline at the end of the string (but not before any other +newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set. +There is no equivalent to this option in Perl, and no way to set it within a +pattern. +<pre> + PCRE_DOTALL +</pre> +If this bit is set, a dot metacharacter in the pattern matches a character of +any value, including one that indicates a newline. However, it only ever +matches one character, even if newlines are coded as CRLF. Without this option, +a dot does not match when the current position is at a newline. This option is +equivalent to Perl's /s option, and it can be changed within a pattern by a +(?s) option setting. A negative class such as [^a] always matches newline +characters, independent of the setting of this option. +<pre> + PCRE_DUPNAMES +</pre> +If this bit is set, names used to identify capturing subpatterns need not be +unique. This can be helpful for certain types of pattern when it is known that +only one instance of the named subpattern can ever be matched. There are more +details of named subpatterns below; see also the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +<pre> + PCRE_EXTENDED +</pre> +If this bit is set, most white space characters in the pattern are totally +ignored except when escaped or inside a character class. However, white space +is not allowed within sequences such as (?> that introduce various +parenthesized subpatterns, nor within a numerical quantifier such as {1,3}. +However, ignorable white space is permitted between an item and a following +quantifier and between a quantifier and a following + that indicates +possessiveness. +</P> +<P> +White space did not used to include the VT character (code 11), because Perl +did not treat this character as white space. However, Perl changed at release +5.18, so PCRE followed at release 8.34, and VT is now treated as white space. +</P> +<P> +PCRE_EXTENDED also causes characters between an unescaped # outside a character +class and the next newline, inclusive, to be ignored. PCRE_EXTENDED is +equivalent to Perl's /x option, and it can be changed within a pattern by a +(?x) option setting. +</P> +<P> +Which characters are interpreted as newlines is controlled by the options +passed to <b>pcre_compile()</b> or by a special sequence at the start of the +pattern, as described in the section entitled +<a href="pcrepattern.html#newlines">"Newline conventions"</a> +in the <b>pcrepattern</b> documentation. Note that the end of this type of +comment is a literal newline sequence in the pattern; escape sequences that +happen to represent a newline do not count. +</P> +<P> +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. White space characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( that introduces a conditional subpattern. +<pre> + PCRE_EXTRA +</pre> +This option was invented in order to turn on additional functionality of PCRE +that is incompatible with Perl, but it is currently of very little use. When +set, any backslash in a pattern that is followed by a letter that has no +special meaning causes an error, thus reserving these combinations for future +expansion. By default, as in Perl, a backslash followed by a letter with no +special meaning is treated as a literal. (Perl can, however, be persuaded to +give an error for this, by running it with the -w option.) There are at present +no other features controlled by this option. It can also be set by a (?X) +option setting within a pattern. +<pre> + PCRE_FIRSTLINE +</pre> +If this option is set, an unanchored pattern is required to match before or at +the first newline in the subject string, though the matched text may continue +over the newline. +<pre> + PCRE_JAVASCRIPT_COMPAT +</pre> +If this option is set, PCRE's behaviour is changed in some ways so that it is +compatible with JavaScript rather than Perl. The changes are as follows: +</P> +<P> +(1) A lone closing square bracket in a pattern causes a compile-time error, +because this is illegal in JavaScript (by default it is treated as a data +character). Thus, the pattern AB]CD becomes illegal when this option is set. +</P> +<P> +(2) At run time, a back reference to an unset subpattern group matches an empty +string (by default this causes the current matching alternative to fail). A +pattern such as (\1)(a) succeeds when this option is set (assuming it can find +an "a" in the subject), whereas it fails by default, for Perl compatibility. +</P> +<P> +(3) \U matches an upper case "U" character; by default \U causes a compile +time error (Perl uses \U to upper case subsequent characters). +</P> +<P> +(4) \u matches a lower case "u" character unless it is followed by four +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, \u causes a compile time error (Perl uses it to upper +case the following character). +</P> +<P> +(5) \x matches a lower case "x" character unless it is followed by two +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, as in Perl, a hexadecimal number is always expected after +\x, but it may have zero, one, or two digits (so, for example, \xz matches a +binary zero character followed by z). +<pre> + PCRE_MULTILINE +</pre> +By default, for the purposes of matching "start of line" and "end of line", +PCRE treats the subject string as consisting of a single line of characters, +even if it actually contains newlines. The "start of line" metacharacter (^) +matches only at the start of the string, and the "end of line" metacharacter +($) matches only at the end of the string, or before a terminating newline +(except when PCRE_DOLLAR_ENDONLY is set). Note, however, that unless +PCRE_DOTALL is set, the "any character" metacharacter (.) does not match at a +newline. This behaviour (for ^, $, and dot) is the same as Perl. +</P> +<P> +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before internal newlines in the +subject string, respectively, as well as at the very start and end. This is +equivalent to Perl's /m option, and it can be changed within a pattern by a +(?m) option setting. If there are no newlines in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. +<pre> + PCRE_NEVER_UTF +</pre> +This option locks out interpretation of the pattern as UTF-8 (or UTF-16 or +UTF-32 in the 16-bit and 32-bit libraries). In particular, it prevents the +creator of the pattern from switching to UTF interpretation by starting the +pattern with (*UTF). This may be useful in applications that process patterns +from external sources. The combination of PCRE_UTF8 and PCRE_NEVER_UTF also +causes an error. +<pre> + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +</pre> +These options override the default newline definition that was chosen when PCRE +was built. Setting the first or the second specifies that a newline is +indicated by a single character (CR or LF, respectively). Setting +PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character +CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three +preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies +that any Unicode newline sequence should be recognized. +</P> +<P> +In an ASCII/Unicode environment, the Unicode newline sequences are the three +just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form +feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). For the 8-bit library, the last two are +recognized only in UTF-8 mode. +</P> +<P> +When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for +CR is 0x0d, the same as ASCII. However, the character code for LF is normally +0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is +not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all +less than 256. For more details, see the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation. +</P> +<P> +The newline setting in the options word uses three bits that are treated +as a number, giving eight possibilities. Currently only six are used (default +plus the five values above). This means that if you set more than one newline +option, the combination may or may not be sensible. For example, +PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but +other combinations may yield unused numbers and cause an error. +</P> +<P> +The only time that a line break in a pattern is specially recognized when +compiling is when PCRE_EXTENDED is set. CR and LF are white space characters, +and so are ignored in this mode. Also, an unescaped # outside a character class +indicates a comment that lasts until after the next line break sequence. In +other circumstances, line break sequences in patterns are treated as literal +data. +</P> +<P> +The newline option that is set at compile time becomes the default that is used +for <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, but it can be overridden. +<pre> + PCRE_NO_AUTO_CAPTURE +</pre> +If this option is set, it disables the use of numbered capturing parentheses in +the pattern. Any opening parenthesis that is not followed by ? behaves as if it +were followed by ?: but named parentheses can still be used for capturing (and +they acquire numbers in the usual way). There is no equivalent of this option +in Perl. +<pre> + PCRE_NO_AUTO_POSSESS +</pre> +If this option is set, it disables "auto-possessification". This is an +optimization that, for example, turns a+b into a++b in order to avoid +backtracks into a+ that can never be successful. However, if callouts are in +use, auto-possessification means that some of them are never taken. You can set +this option if you want the matching functions to do a full unoptimized search +and run all the callouts, but it is mainly provided for testing purposes. +<pre> + PCRE_NO_START_OPTIMIZE +</pre> +This is an option that acts at matching time; that is, it is really an option +for <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. If it is set at compile time, +it is remembered with the compiled pattern and assumed at matching time. This +is necessary if you want to use JIT execution, because the JIT compiler needs +to know whether or not this option is set. For details see the discussion of +PCRE_NO_START_OPTIMIZE +<a href="#execoptions">below.</a> +<pre> + PCRE_UCP +</pre> +This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, +\w, and some of the POSIX character classes. By default, only ASCII characters +are recognized, but if PCRE_UCP is set, Unicode properties are used instead to +classify characters. More details are given in the section on +<a href="pcre.html#genericchartypes">generic character types</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page. If you set PCRE_UCP, matching one of the items it affects takes much +longer. The option is available only if PCRE has been compiled with Unicode +property support. +<pre> + PCRE_UNGREEDY +</pre> +This option inverts the "greediness" of the quantifiers so that they are not +greedy by default, but become greedy if followed by "?". It is not compatible +with Perl. It can also be set by a (?U) option setting within the pattern. +<pre> + PCRE_UTF8 +</pre> +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte strings. However, it is available +only when PCRE is built to include UTF support. If not, the use of this option +provokes an error. Details of how this option changes the behaviour of PCRE are +given in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. +<pre> + PCRE_NO_UTF8_CHECK +</pre> +When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is +automatically checked. There is a discussion about the +<a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. If an invalid UTF-8 sequence is found, <b>pcre_compile()</b> returns an +error. If you already know that your pattern is valid, and you want to skip +this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option. +When it is set, the effect of passing an invalid UTF-8 string as a pattern is +undefined. It may cause your program to crash or loop. Note that this option +can also be passed to <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>, to suppress +the validity checking of subject strings only. If the same string is being +matched many times, the option can be safely set for the second and subsequent +matchings to improve performance. +</P> +<br><a name="SEC12" href="#TOC1">COMPILATION ERROR CODES</a><br> +<P> +The following table lists the error codes than may be returned by +<b>pcre_compile2()</b>, along with the error messages that may be returned by +both compiling functions. Note that error messages are always 8-bit ASCII +strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes +have fallen out of use. To avoid confusion, they have not been re-used. +<pre> + 0 no error + 1 \ at end of pattern + 2 \c at end of pattern + 3 unrecognized character follows \ + 4 numbers out of order in {} quantifier + 5 number too big in {} quantifier + 6 missing terminating ] for character class + 7 invalid escape sequence in character class + 8 range out of order in character class + 9 nothing to repeat + 10 [this code is not in use] + 11 internal error: unexpected repeat + 12 unrecognized character after (? or (?- + 13 POSIX named classes are supported only within a class + 14 missing ) + 15 reference to non-existent subpattern + 16 erroffset passed as NULL + 17 unknown option bit(s) set + 18 missing ) after comment + 19 [this code is not in use] + 20 regular expression is too large + 21 failed to get memory + 22 unmatched parentheses + 23 internal error: code overflow + 24 unrecognized character after (?< + 25 lookbehind assertion is not fixed length + 26 malformed number or name after (?( + 27 conditional group contains more than two branches + 28 assertion expected after (?( + 29 (?R or (?[+-]digits must be followed by ) + 30 unknown POSIX class name + 31 POSIX collating elements are not supported + 32 this version of PCRE is compiled without UTF support + 33 [this code is not in use] + 34 character value in \x{} or \o{} is too large + 35 invalid condition (?(0) + 36 \C not allowed in lookbehind assertion + 37 PCRE does not support \L, \l, \N{name}, \U, or \u + 38 number after (?C is > 255 + 39 closing ) for (?C expected + 40 recursive call could loop indefinitely + 41 unrecognized character after (?P + 42 syntax error in subpattern name (missing terminator) + 43 two named subpatterns have the same name + 44 invalid UTF-8 string (specifically UTF-8) + 45 support for \P, \p, and \X has not been compiled + 46 malformed \P or \p sequence + 47 unknown property name after \P or \p + 48 subpattern name is too long (maximum 32 characters) + 49 too many named subpatterns (maximum 10000) + 50 [this code is not in use] + 51 octal value is greater than \377 in 8-bit non-UTF-8 mode + 52 internal error: overran compiling workspace + 53 internal error: previously-checked referenced subpattern + not found + 54 DEFINE group contains more than one branch + 55 repeating a DEFINE group is not allowed + 56 inconsistent NEWLINE options + 57 \g is not followed by a braced, angle-bracketed, or quoted + name/number or by a plain number + 58 a numbered reference must not be zero + 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT) + 60 (*VERB) not recognized or malformed + 61 number is too big + 62 subpattern name expected + 63 digit expected after (?+ + 64 ] is an invalid data character in JavaScript compatibility mode + 65 different names for subpatterns of the same number are + not allowed + 66 (*MARK) must have an argument + 67 this version of PCRE is not compiled with Unicode property + support + 68 \c must be followed by an ASCII character + 69 \k is not followed by a braced, angle-bracketed, or quoted name + 70 internal error: unknown opcode in find_fixedlength() + 71 \N is not supported in a class + 72 too many forward references + 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff) + 74 invalid UTF-16 string (specifically UTF-16) + 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN) + 76 character value in \u.... sequence is too large + 77 invalid UTF-32 string (specifically UTF-32) + 78 setting UTF is disabled by the application + 79 non-hex character in \x{} (closing brace missing?) + 80 non-octal character in \o{} (closing brace missing?) + 81 missing opening brace after \o + 82 parentheses are too deeply nested + 83 invalid range in character class + 84 group name must start with a non-digit + 85 parentheses are too deeply nested (stack check) +</pre> +The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may +be used if the limits were changed when PCRE was built. +<a name="studyingapattern"></a></P> +<br><a name="SEC13" href="#TOC1">STUDYING A PATTERN</a><br> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b> const char **<i>errptr</i>);</b> +</P> +<P> +If a compiled pattern is going to be used several times, it is worth spending +more time analyzing it in order to speed up the time taken for matching. The +function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first +argument. If studying the pattern produces additional information that will +help speed up matching, <b>pcre_study()</b> returns a pointer to a +<b>pcre_extra</b> block, in which the <i>study_data</i> field points to the +results of the study. +</P> +<P> +The returned value from <b>pcre_study()</b> can be passed directly to +<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. However, a <b>pcre_extra</b> block +also contains other fields that can be set by the caller before the block is +passed; these are described +<a href="#extradata">below</a> +in the section on matching a pattern. +</P> +<P> +If studying the pattern does not produce any useful information, +<b>pcre_study()</b> returns NULL by default. In that circumstance, if the +calling program wants to pass any of the other fields to <b>pcre_exec()</b> or +<b>pcre_dfa_exec()</b>, it must set up its own <b>pcre_extra</b> block. However, +if <b>pcre_study()</b> is called with the PCRE_STUDY_EXTRA_NEEDED option, it +returns a <b>pcre_extra</b> block even if studying did not find any additional +information. It may still return NULL, however, if an error occurs in +<b>pcre_study()</b>. +</P> +<P> +The second argument of <b>pcre_study()</b> contains option bits. There are three +further options in addition to PCRE_STUDY_EXTRA_NEEDED: +<pre> + PCRE_STUDY_JIT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE +</pre> +If any of these are set, and the just-in-time compiler is available, the +pattern is further compiled into machine code that executes much faster than +the <b>pcre_exec()</b> interpretive matching function. If the just-in-time +compiler is not available, these options are ignored. All undefined bits in the +<i>options</i> argument must be zero. +</P> +<P> +JIT compilation is a heavyweight optimization. It can take some time for +patterns to be analyzed, and for one-off matches and simple patterns the +benefit of faster execution might be offset by a much slower study time. +Not all patterns can be optimized by the JIT compiler. For those that cannot be +handled, matching automatically falls back to the <b>pcre_exec()</b> +interpreter. For more details, see the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation. +</P> +<P> +The third argument for <b>pcre_study()</b> is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it is set to point to a textual error message. This is a +static string that is part of the library. You must not try to free it. You +should test the error pointer for NULL after calling <b>pcre_study()</b>, to be +sure that it has run successfully. +</P> +<P> +When you are finished with a pattern, you can free the memory used for the +study data by calling <b>pcre_free_study()</b>. This function was added to the +API for release 8.20. For earlier versions, the memory could be freed with +<b>pcre_free()</b>, just like the pattern itself. This will still work in cases +where JIT optimization is not used, but it is advisable to change to the new +function when convenient. +</P> +<P> +This is a typical way in which <b>pcre_study</b>() is used (except that in a +real application there should be tests for errors): +<pre> + int rc; + pcre *re; + pcre_extra *sd; + re = pcre_compile("pattern", 0, &error, &erroroffset, NULL); + sd = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options */ + &error); /* set to NULL or points to a message */ + rc = pcre_exec( /* see below for details of pcre_exec() options */ + re, sd, "subject", 7, 0, 0, ovector, 30); + ... + pcre_free_study(sd); + pcre_free(re); +</pre> +Studying a pattern does two things: first, a lower bound for the length of +subject string that is needed to match the pattern is computed. This does not +mean that there are any strings of that length that match, but it does +guarantee that no shorter strings match. The value is used to avoid wasting +time by trying to match strings that are shorter than the lower bound. You can +find out the value in a calling program via the <b>pcre_fullinfo()</b> function. +</P> +<P> +Studying a pattern is also useful for non-anchored patterns that do not have a +single fixed starting character. A bitmap of possible starting bytes is +created. This speeds up finding a position in the subject at which to start +matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256. +In 32-bit mode, the bitmap is used for 32-bit values less than 256.) +</P> +<P> +These two optimizations apply to both <b>pcre_exec()</b> and +<b>pcre_dfa_exec()</b>, and the information is also used by the JIT compiler. +The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option. +You might want to do this if your pattern contains callouts or (*MARK) and you +want to make use of these facilities in cases where matching fails. +</P> +<P> +PCRE_NO_START_OPTIMIZE can be specified at either compile time or execution +time. However, if PCRE_NO_START_OPTIMIZE is passed to <b>pcre_exec()</b>, (that +is, after any JIT compilation has happened) JIT execution is disabled. For JIT +execution to work with PCRE_NO_START_OPTIMIZE, the option must be set at +compile time. +</P> +<P> +There is a longer discussion of PCRE_NO_START_OPTIMIZE +<a href="#execoptions">below.</a> +<a name="localesupport"></a></P> +<br><a name="SEC14" href="#TOC1">LOCALE SUPPORT</a><br> +<P> +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables, indexed by character +code point. When running in UTF-8 mode, or in the 16- or 32-bit libraries, this +applies only to characters with code points less than 256. By default, +higher-valued code points never match escapes such as \w or \d. However, if +PCRE is built with Unicode property support, all characters can be tested with +\p and \P, or, alternatively, the PCRE_UCP option can be set when a pattern +is compiled; this causes \w and friends to use Unicode property support +instead of the built-in tables. +</P> +<P> +The use of locales with Unicode is discouraged. If you are handling characters +with code points greater than 128, you should either use Unicode support, or +use locales, but not try to mix the two. +</P> +<P> +PCRE contains an internal set of tables that are used when the final argument +of <b>pcre_compile()</b> is NULL. These are sufficient for many applications. +Normally, the internal tables recognize only ASCII characters. However, when +PCRE is built, it is possible to cause the internal tables to be rebuilt in the +default "C" locale of the local system, which may cause them to be different. +</P> +<P> +The internal tables can always be overridden by tables supplied by the +application that calls PCRE. These may be created in a different locale from +the default. As more and more applications change to using Unicode, the need +for this locale support is expected to die away. +</P> +<P> +External tables are built by calling the <b>pcre_maketables()</b> function, +which has no arguments, in the relevant locale. The result can then be passed +to <b>pcre_compile()</b> as often as necessary. For example, to build and use +tables that are appropriate for the French locale (where accented characters +with values greater than 128 are treated as letters), the following code could +be used: +<pre> + setlocale(LC_CTYPE, "fr_FR"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); +</pre> +The locale name "fr_FR" is used on Linux and other Unix-like systems; if you +are using Windows, the name for the French locale is "french". +</P> +<P> +When <b>pcre_maketables()</b> runs, the tables are built in memory that is +obtained via <b>pcre_malloc</b>. It is the caller's responsibility to ensure +that the memory containing the tables remains available for as long as it is +needed. +</P> +<P> +The pointer that is passed to <b>pcre_compile()</b> is saved with the compiled +pattern, and the same tables are used via this pointer by <b>pcre_study()</b> +and also by <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b>. Thus, for any single +pattern, compilation, studying and matching all happen in the same locale, but +different patterns can be processed in different locales. +</P> +<P> +It is possible to pass a table pointer or NULL (indicating the use of the +internal tables) to <b>pcre_exec()</b> or <b>pcre_dfa_exec()</b> (see the +discussion below in the section on matching a pattern). This facility is +provided for use with pre-compiled patterns that have been saved and reloaded. +Character tables are not saved with patterns, so if a non-standard table was +used at compile time, it must be provided again when the reloaded pattern is +matched. Attempting to use this facility to match a pattern in a different +locale from the one in which it was compiled is likely to lead to anomalous +(usually incorrect) results. +<a name="infoaboutpattern"></a></P> +<br><a name="SEC15" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br> +<P> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +The <b>pcre_fullinfo()</b> function returns information about a compiled +pattern. It replaces the <b>pcre_info()</b> function, which was removed from the +library at version 8.30, after more than 10 years of obsolescence. +</P> +<P> +The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled +pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if +the pattern was not studied. The third argument specifies which piece of +information is required, and the fourth argument is a pointer to a variable +to receive the data. The yield of the function is zero for success, or one of +the following negative numbers: +<pre> + PCRE_ERROR_NULL the argument <i>code</i> was NULL + the argument <i>where</i> was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADENDIANNESS the pattern was compiled with different + endianness + PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid + PCRE_ERROR_UNSET the requested field is not set +</pre> +The "magic number" is placed at the start of each compiled pattern as an simple +check against passing an arbitrary memory pointer. The endianness error can +occur if a compiled pattern is saved and reloaded on a different host. Here is +a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the compiled +pattern: +<pre> + int rc; + size_t length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + sd, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ +</pre> +The possible values for the third argument are defined in <b>pcre.h</b>, and are +as follows: +<pre> + PCRE_INFO_BACKREFMAX +</pre> +Return the number of the highest back reference in the pattern. The fourth +argument should point to an <b>int</b> variable. Zero is returned if there are +no back references. +<pre> + PCRE_INFO_CAPTURECOUNT +</pre> +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an <b>int</b> variable. +<pre> + PCRE_INFO_DEFAULT_TABLES +</pre> +Return a pointer to the internal default character tables within PCRE. The +fourth argument should point to an <b>unsigned char *</b> variable. This +information call is provided for internal use by the <b>pcre_study()</b> +function. External callers can cause PCRE to use its internal tables by passing +a NULL table pointer. +<pre> + PCRE_INFO_FIRSTBYTE (deprecated) +</pre> +Return information about the first data unit of any matched string, for a +non-anchored pattern. The name of this option refers to the 8-bit library, +where data units are bytes. The fourth argument should point to an <b>int</b> +variable. Negative values are used for special cases. However, this means that +when the 32-bit library is in non-UTF-32 mode, the full 32-bit range of +characters cannot be returned. For this reason, this value is deprecated; use +PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER instead. +</P> +<P> +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), its value is returned. In the 8-bit library, the +value is always less than 256. In the 16-bit library the value can be up to +0xffff. In the 32-bit library the value can be up to 0x10ffff. +</P> +<P> +If there is no fixed first value, and if either +<br> +<br> +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +<br> +<br> +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +<br> +<br> +-1 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise -2 is +returned. For anchored patterns, -2 is returned. +<pre> + PCRE_INFO_FIRSTCHARACTER +</pre> +Return the value of the first data unit (non-UTF character) of any matched +string in the situation where PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; +otherwise return 0. The fourth argument should point to an <b>uint_t</b> +variable. +</P> +<P> +In the 8-bit library, the value is always less than 256. In the 16-bit library +the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value +can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode. +<pre> + PCRE_INFO_FIRSTCHARACTERFLAGS +</pre> +Return information about the first data unit of any matched string, for a +non-anchored pattern. The fourth argument should point to an <b>int</b> +variable. +</P> +<P> +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), 1 is returned, and the character value can be +retrieved using PCRE_INFO_FIRSTCHARACTER. If there is no fixed first value, and +if either +<br> +<br> +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +<br> +<br> +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +<br> +<br> +2 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise 0 is +returned. For anchored patterns, 0 is returned. +<pre> + PCRE_INFO_FIRSTTABLE +</pre> +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of values for the first data unit in any matching +string, a pointer to the table is returned. Otherwise NULL is returned. The +fourth argument should point to an <b>unsigned char *</b> variable. +<pre> + PCRE_INFO_HASCRORLF +</pre> +Return 1 if the pattern contains any explicit matches for CR or LF characters, +otherwise 0. The fourth argument should point to an <b>int</b> variable. An +explicit match is either a literal CR or LF character, or \r or \n. +<pre> + PCRE_INFO_JCHANGED +</pre> +Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise +0. The fourth argument should point to an <b>int</b> variable. (?J) and +(?-J) set and unset the local PCRE_DUPNAMES option, respectively. +<pre> + PCRE_INFO_JIT +</pre> +Return 1 if the pattern was studied with one of the JIT options, and +just-in-time compiling was successful. The fourth argument should point to an +<b>int</b> variable. A return value of 0 means that JIT support is not available +in this version of PCRE, or that the pattern was not studied with a JIT option, +or that the JIT compiler could not handle this particular pattern. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for details of what can and cannot be handled. +<pre> + PCRE_INFO_JITSIZE +</pre> +If the pattern was successfully studied with a JIT option, return the size of +the JIT compiled code, otherwise return zero. The fourth argument should point +to a <b>size_t</b> variable. +<pre> + PCRE_INFO_LASTLITERAL +</pre> +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an <b>int</b> variable. If there is no such +value, -1 is returned. For anchored patterns, a last literal value is recorded +only if it follows something of variable length. For example, for the pattern +/^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value +is -1. +</P> +<P> +Since for the 32-bit library using the non-UTF-32 mode, this function is unable +to return the full 32-bit range of characters, this value is deprecated; +instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should +be used. +<pre> + PCRE_INFO_MATCH_EMPTY +</pre> +Return 1 if the pattern can match an empty string, otherwise 0. The fourth +argument should point to an <b>int</b> variable. +<pre> + PCRE_INFO_MATCHLIMIT +</pre> +If the pattern set a match limit by including an item of the form +(*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth argument +should point to an unsigned 32-bit integer. If no such value has been set, the +call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET. +<pre> + PCRE_INFO_MAXLOOKBEHIND +</pre> +Return the number of characters (NB not data units) in the longest lookbehind +assertion in the pattern. This information is useful when doing multi-segment +matching using the partial matching facilities. Note that the simple assertions +\b and \B require a one-character lookbehind. \A also registers a +one-character lookbehind, though it does not actually inspect the previous +character. This is to ensure that at least one character from the old segment +is retained when a new segment is processed. Otherwise, if there are no +lookbehinds in the pattern, \A might match incorrectly at the start of a new +segment. +<pre> + PCRE_INFO_MINLENGTH +</pre> +If the pattern was studied and a minimum length for matching subject strings +was computed, its value is returned. Otherwise the returned value is -1. The +value is a number of characters, which in UTF mode may be different from the +number of data units. The fourth argument should point to an <b>int</b> +variable. A non-negative value is a lower bound to the length of any matching +string. There may not be any strings of that length that do actually match, but +every string that does match is at least that long. +<pre> + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE +</pre> +PCRE supports the use of named as well as numbered capturing parentheses. The +names are just an additional way of identifying the parentheses, which still +acquire numbers. Several convenience functions such as +<b>pcre_get_named_substring()</b> are provided for extracting captured +substrings by name. It is also possible to extract the data directly, by first +converting the name to a number in order to access the correct pointers in the +output vector (described with <b>pcre_exec()</b> below). To do the conversion, +you need to use the name-to-number map, which is described by these three +values. +</P> +<P> +The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an <b>int</b> value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table. This is a pointer to <b>char</b> in the 8-bit library, where +the first two bytes of each entry are the number of the capturing parenthesis, +most significant byte first. In the 16-bit library, the pointer points to +16-bit data units, the first of which contains the parenthesis number. In the +32-bit library, the pointer points to 32-bit data units, the first of which +contains the parenthesis number. The rest of the entry is the corresponding +name, zero terminated. +</P> +<P> +The names are in alphabetical order. If (?| is used to create multiple groups +with the same number, as described in the +<a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page, the groups may be given the same name, but there is only one entry in the +table. Different names for groups of the same number are not permitted. +Duplicate names for subpatterns with different numbers are permitted, +but only if PCRE_DUPNAMES is set. They appear in the table in the order in +which they were found in the pattern. In the absence of (?| this is the order +of increasing number; when (?| is used this is not necessarily the case because +later subpatterns may have lower numbers. +</P> +<P> +As a simple example of the name/number table, consider the following pattern +after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white +space - including newlines - is ignored): +<pre> + (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) +</pre> +There are four named subpatterns, so the table has four entries, and each entry +in the table is eight bytes long. The table is as follows, with non-printing +bytes shows in hexadecimal, and undefined bytes shown as ??: +<pre> + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? +</pre> +When writing code to extract data from named subpatterns using the +name-to-number map, remember that the length of the entries is likely to be +different for each compiled pattern. +<pre> + PCRE_INFO_OKPARTIAL +</pre> +Return 1 if the pattern can be used for partial matching with +<b>pcre_exec()</b>, otherwise 0. The fourth argument should point to an +<b>int</b> variable. From release 8.00, this always returns 1, because the +restrictions that previously applied to partial matching have been lifted. The +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation gives details of partial matching. +<pre> + PCRE_INFO_OPTIONS +</pre> +Return a copy of the options with which the pattern was compiled. The fourth +argument should point to an <b>unsigned long int</b> variable. These option bits +are those specified in the call to <b>pcre_compile()</b>, modified by any +top-level option settings at the start of the pattern itself. In other words, +they are the options that will be in force when matching starts. For example, +if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the +result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED. +</P> +<P> +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: +<pre> + ^ unless PCRE_MULTILINE is set + \A always + \G always + .* if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears +</pre> +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +<b>pcre_fullinfo()</b>. +<pre> + PCRE_INFO_RECURSIONLIMIT +</pre> +If the pattern set a recursion limit by including an item of the form +(*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth +argument should point to an unsigned 32-bit integer. If no such value has been +set, the call to <b>pcre_fullinfo()</b> returns the error PCRE_ERROR_UNSET. +<pre> + PCRE_INFO_SIZE +</pre> +Return the size of the compiled pattern in bytes (for all three libraries). The +fourth argument should point to a <b>size_t</b> variable. This value does not +include the size of the <b>pcre</b> structure that is returned by +<b>pcre_compile()</b>. The value that is passed as the argument to +<b>pcre_malloc()</b> when <b>pcre_compile()</b> is getting memory in which to +place the compiled data is the value returned by this option plus the size of +the <b>pcre</b> structure. Studying a compiled pattern, with or without JIT, +does not alter the value returned by this option. +<pre> + PCRE_INFO_STUDYSIZE +</pre> +Return the size in bytes (for all three libraries) of the data block pointed to +by the <i>study_data</i> field in a <b>pcre_extra</b> block. If <b>pcre_extra</b> +is NULL, or there is no study data, zero is returned. The fourth argument +should point to a <b>size_t</b> variable. The <i>study_data</i> field is set by +<b>pcre_study()</b> to record information that will speed up matching (see the +section entitled +<a href="#studyingapattern">"Studying a pattern"</a> +above). The format of the <i>study_data</i> block is private, but its length +is made available via this option so that it can be saved and restored (see the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation for details). +<pre> + PCRE_INFO_REQUIREDCHARFLAGS +</pre> +Returns 1 if there is a rightmost literal data unit that must exist in any +matched string, other than at its start. The fourth argument should point to +an <b>int</b> variable. If there is no such value, 0 is returned. If returning +1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR. +</P> +<P> +For anchored patterns, a last literal value is recorded only if it follows +something of variable length. For example, for the pattern /^a\d+z\d+/ the +returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for +/^a\dz\d/ the returned value is 0. +<pre> + PCRE_INFO_REQUIREDCHAR +</pre> +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an <b>uint32_t</b> variable. If there is no such +value, 0 is returned. +</P> +<br><a name="SEC16" href="#TOC1">REFERENCE COUNTS</a><br> +<P> +<b>int pcre_refcount(pcre *<i>code</i>, int <i>adjust</i>);</b> +</P> +<P> +The <b>pcre_refcount()</b> function is used to maintain a reference count in the +data block that contains a compiled pattern. It is provided for the benefit of +applications that operate in an object-oriented manner, where different parts +of the application may be using the same compiled pattern, but you want to free +the block when they are all done. +</P> +<P> +When a pattern is compiled, the reference count field is initialized to zero. +It is changed only by calling this function, whose action is to add the +<i>adjust</i> value (which may be positive or negative) to it. The yield of the +function is the new value. However, the value of the count is constrained to +lie between 0 and 65535, inclusive. If the new value is outside these limits, +it is forced to the appropriate limit value. +</P> +<P> +Except when it is zero, the reference count is not correctly preserved if a +pattern is compiled on one host and then transferred to a host whose byte-order +is different. (This seems a highly unlikely scenario.) +</P> +<br><a name="SEC17" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> +<P> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<P> +The function <b>pcre_exec()</b> is called to match a subject string against a +compiled pattern, which is passed in the <i>code</i> argument. If the +pattern was studied, the result of the study should be passed in the +<i>extra</i> argument. You can call <b>pcre_exec()</b> with the same <i>code</i> +and <i>extra</i> arguments as many times as you like, in order to match +different subject strings with the same pattern. +</P> +<P> +This function is the main matching facility of the library, and it operates in +a Perl-like manner. For specialist use there is also an alternative matching +function, which is described +<a href="#dfamatch">below</a> +in the section about the <b>pcre_dfa_exec()</b> function. +</P> +<P> +In most applications, the pattern will have been compiled (and optionally +studied) in the same process that calls <b>pcre_exec()</b>. However, it is +possible to save compiled patterns and study data, and then use them later +in different processes, possibly even on different hosts. For a discussion +about this, see the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation. +</P> +<P> +Here is an example of a simple call to <b>pcre_exec()</b>: +<pre> + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 30); /* number of elements (NOT size in bytes) */ +<a name="extradata"></a></PRE> +</P> +<br><b> +Extra data for <b>pcre_exec()</b> +</b><br> +<P> +If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b> +data block. The <b>pcre_study()</b> function returns such a block (when it +doesn't return NULL), but you can also create one for yourself, and pass +additional information in it. The <b>pcre_extra</b> block contains the following +fields (not necessarily in this order): +<pre> + unsigned long int <i>flags</i>; + void *<i>study_data</i>; + void *<i>executable_jit</i>; + unsigned long int <i>match_limit</i>; + unsigned long int <i>match_limit_recursion</i>; + void *<i>callout_data</i>; + const unsigned char *<i>tables</i>; + unsigned char **<i>mark</i>; +</pre> +In the 16-bit version of this structure, the <i>mark</i> field has type +"PCRE_UCHAR16 **". +<br> +<br> +In the 32-bit version of this structure, the <i>mark</i> field has type +"PCRE_UCHAR32 **". +</P> +<P> +The <i>flags</i> field is used to specify which of the other fields are set. The +flag bits are: +<pre> + PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_EXECUTABLE_JIT + PCRE_EXTRA_MARK + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_MATCH_LIMIT_RECURSION + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_TABLES +</pre> +Other flag bits should be set to zero. The <i>study_data</i> field and sometimes +the <i>executable_jit</i> field are set in the <b>pcre_extra</b> block that is +returned by <b>pcre_study()</b>, together with the appropriate flag bits. You +should not set these yourself, but you may add to the block by setting other +fields and their corresponding flag bits. +</P> +<P> +The <i>match_limit</i> field provides a means of preventing PCRE from using up a +vast amount of resources when running patterns that are not going to match, +but which have a very large number of possibilities in their search trees. The +classic example is a pattern that uses nested unlimited repeats. +</P> +<P> +Internally, <b>pcre_exec()</b> uses a function called <b>match()</b>, which it +calls repeatedly (sometimes recursively). The limit set by <i>match_limit</i> is +imposed on the number of times this function is called during a match, which +has the effect of limiting the amount of backtracking that can take place. For +patterns that are not anchored, the count restarts from zero for each position +in the subject string. +</P> +<P> +When <b>pcre_exec()</b> is called with a pattern that was successfully studied +with a JIT option, the way that the matching is executed is entirely different. +However, there is still the possibility of runaway matching that goes on for a +very long time, and so the <i>match_limit</i> value is also used in this case +(but in a different way) to limit how long the matching can continue. +</P> +<P> +The default value for the limit can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +override the default by suppling <b>pcre_exec()</b> with a <b>pcre_extra</b> +block in which <i>match_limit</i> is set, and PCRE_EXTRA_MATCH_LIMIT is set in +the <i>flags</i> field. If the limit is exceeded, <b>pcre_exec()</b> returns +PCRE_ERROR_MATCHLIMIT. +</P> +<P> +A value for the match limit may also be supplied by an item at the start of a +pattern of the form +<pre> + (*LIMIT_MATCH=d) +</pre> +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit +is set, less than the default. +</P> +<P> +The <i>match_limit_recursion</i> field is similar to <i>match_limit</i>, but +instead of limiting the total number of times that <b>match()</b> is called, it +limits the depth of recursion. The recursion depth is a smaller number than the +total number of calls, because not all calls to <b>match()</b> are recursive. +This limit is of use only if it is set smaller than <i>match_limit</i>. +</P> +<P> +Limiting the recursion depth limits the amount of machine stack that can be +used, or, when PCRE has been compiled to use memory on the heap instead of the +stack, the amount of heap memory that can be used. This limit is not relevant, +and is ignored, when matching is done using JIT compiled code. +</P> +<P> +The default value for <i>match_limit_recursion</i> can be set when PCRE is +built; the default default is the same value as the default for +<i>match_limit</i>. You can override the default by suppling <b>pcre_exec()</b> +with a <b>pcre_extra</b> block in which <i>match_limit_recursion</i> is set, and +PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the <i>flags</i> field. If the limit +is exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_RECURSIONLIMIT. +</P> +<P> +A value for the recursion limit may also be supplied by an item at the start of +a pattern of the form +<pre> + (*LIMIT_RECURSION=d) +</pre> +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of <b>pcre_exec()</b> or, if no such limit +is set, less than the default. +</P> +<P> +The <i>callout_data</i> field is used in conjunction with the "callout" feature, +and is described in the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +The <i>tables</i> field is provided for use with patterns that have been +pre-compiled using custom character tables, saved to disc or elsewhere, and +then reloaded, because the tables that were used to compile a pattern are not +saved with it. See the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation for a discussion of saving compiled patterns for later use. If +NULL is passed using this mechanism, it forces PCRE's internal tables to be +used. +</P> +<P> +<b>Warning:</b> The tables that <b>pcre_exec()</b> uses must be the same as those +that were used when the pattern was compiled. If this is not the case, the +behaviour of <b>pcre_exec()</b> is undefined. Therefore, when a pattern is +compiled and matched in the same process, this field should never be set. In +this (the most common) case, the correct table pointer is automatically passed +with the compiled pattern from <b>pcre_compile()</b> to <b>pcre_exec()</b>. +</P> +<P> +If PCRE_EXTRA_MARK is set in the <i>flags</i> field, the <i>mark</i> field must +be set to point to a suitable variable. If the pattern contains any +backtracking control verbs such as (*MARK:NAME), and the execution ends up with +a name to pass back, a pointer to the name string (zero terminated) is placed +in the variable pointed to by the <i>mark</i> field. The names are within the +compiled pattern; if you wish to retain such a name you must copy it before +freeing the memory of a compiled pattern. If there is no name to pass back, the +variable pointed to by the <i>mark</i> field is set to NULL. For details of the +backtracking control verbs, see the section entitled +<a href="pcrepattern#backtrackcontrol">"Backtracking control"</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +<a name="execoptions"></a></P> +<br><b> +Option bits for <b>pcre_exec()</b> +</b><br> +<P> +The unused bits of the <i>options</i> argument for <b>pcre_exec()</b> must be +zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and +PCRE_PARTIAL_SOFT. +</P> +<P> +If the pattern was successfully studied with one of the just-in-time (JIT) +compile options, the only supported options for JIT execution are +PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, +PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an +unsupported option is used, JIT execution is disabled and the normal +interpretive code in <b>pcre_exec()</b> is run. +<pre> + PCRE_ANCHORED +</pre> +The PCRE_ANCHORED option limits <b>pcre_exec()</b> to matching at the first +matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out +to be anchored by virtue of its contents, it cannot be made unachored at +matching time. +<pre> + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE +</pre> +These options (which are mutually exclusive) control what the \R escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. These options override the choice that was +made or defaulted when the pattern was compiled. +<pre> + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +</pre> +These options override the newline definition that was chosen or defaulted when +the pattern was compiled. For details, see the description of +<b>pcre_compile()</b> above. During matching, the newline choice affects the +behaviour of the dot, circumflex, and dollar metacharacters. It may also alter +the way the match position is advanced after a match failure for an unanchored +pattern. +</P> +<P> +When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a +match attempt for an unanchored pattern fails when the current position is at a +CRLF sequence, and the pattern contains no explicit matches for CR or LF +characters, the match position is advanced by two characters instead of one, in +other words, to after the CRLF. +</P> +<P> +The above rule is a compromise that makes the most common cases work as +expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not +set), it does not match the string "\r\nA" because, after failing at the +start, it skips both the CR and the LF before retrying. However, the pattern +[\r\n]A does match that string, because it contains an explicit CR or LF +reference, and so advances only by one character after the first failure. +</P> +<P> +An explicit match for CR of LF is either a literal appearance of one of those +characters, or one of the \r or \n escape sequences. Implicit matches such as +[^X] do not count, nor does \s (which includes CR and LF in the characters +that it matches). +</P> +<P> +Notwithstanding the above, anomalous effects may still occur when CRLF is a +valid newline sequence and explicit \r or \n escapes appear in the pattern. +<pre> + PCRE_NOTBOL +</pre> +This option specifies that first character of the subject string is not the +beginning of a line, so the circumflex metacharacter should not match before +it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex +never to match. This option affects only the behaviour of the circumflex +metacharacter. It does not affect \A. +<pre> + PCRE_NOTEOL +</pre> +This option specifies that the end of the subject string is not the end of a +line, so the dollar metacharacter should not match it nor (except in multiline +mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at +compile time) causes dollar never to match. This option affects only the +behaviour of the dollar metacharacter. It does not affect \Z or \z. +<pre> + PCRE_NOTEMPTY +</pre> +An empty string is not considered to be a valid match if this option is set. If +there are alternatives in the pattern, they are tried. If all the alternatives +match the empty string, the entire match fails. For example, if the pattern +<pre> + a?b? +</pre> +is applied to a string not beginning with "a" or "b", it matches an empty +string at the start of the subject. With PCRE_NOTEMPTY set, this match is not +valid, so PCRE searches further into the string for occurrences of "a" or "b". +<pre> + PCRE_NOTEMPTY_ATSTART +</pre> +This is like PCRE_NOTEMPTY, except that an empty string match that is not at +the start of the subject is permitted. If the pattern is anchored, such a match +can occur only if the pattern contains \K. +</P> +<P> +Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it +does make a special case of a pattern match of the empty string within its +<b>split()</b> function, and when using the /g modifier. It is possible to +emulate Perl's behaviour after matching a null string by first trying the match +again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then +if that fails, by advancing the starting offset (see below) and trying an +ordinary match again. There is some code that demonstrates how to do this in +the +<a href="pcredemo.html"><b>pcredemo</b></a> +sample program. In the most general case, you have to check to see if the +newline convention recognizes CRLF as a newline, and if so, and the current +character is CR followed by LF, advance the starting offset by two characters +instead of one. +<pre> + PCRE_NO_START_OPTIMIZE +</pre> +There are a number of optimizations that <b>pcre_exec()</b> uses at the start of +a match, in order to speed up the process. For example, if it is known that an +unanchored match must start with a specific character, it searches the subject +for that character, and fails immediately if it cannot find it, without +actually running the main matching function. This means that a special item +such as (*COMMIT) at the start of a pattern is not considered until after a +suitable starting point for the match has been found. Also, when callouts or +(*MARK) items are in use, these "start-up" optimizations can cause them to be +skipped if the pattern is never actually used. The start-up optimizations are +in effect a pre-scan of the subject that takes place before the pattern is run. +</P> +<P> +The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly +causing performance to suffer, but ensuring that in cases where the result is +"no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK) +are considered at every possible starting position in the subject string. If +PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching +time. The use of PCRE_NO_START_OPTIMIZE at matching time (that is, passing it +to <b>pcre_exec()</b>) disables JIT execution; in this situation, matching is +always done using interpretively. +</P> +<P> +Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation. +Consider the pattern +<pre> + (*COMMIT)ABC +</pre> +When this is compiled, PCRE records the fact that a match must start with the +character "A". Suppose the subject string is "DEFABC". The start-up +optimization scans along the subject, finds "A" and runs the first match +attempt from there. The (*COMMIT) item means that the pattern must match the +current starting position, which in this case, it does. However, if the same +match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the +subject string does not happen. The first match attempt is run starting from +"D" and when this fails, (*COMMIT) prevents any further matches being tried, so +the overall result is "no match". If the pattern is studied, more start-up +optimizations may be used. For example, a minimum length for the subject may be +recorded. Consider the pattern +<pre> + (*MARK:A)(X|Y) +</pre> +The minimum length for a match is one character. If the subject is "ABC", there +will be attempts to match "ABC", "BC", "C", and then finally an empty string. +If the pattern is studied, the final attempt does not take place, because PCRE +knows that the subject is too short, and so the (*MARK) is never encountered. +In this case, studying the pattern does not affect the overall match result, +which is still "no match", but it does affect the auxiliary information that is +returned. +<pre> + PCRE_NO_UTF8_CHECK +</pre> +When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8 +string is automatically checked when <b>pcre_exec()</b> is subsequently called. +The entire string is checked before any other processing takes place. The value +of <i>startoffset</i> is also checked to ensure that it points to the start of a +UTF-8 character. There is a discussion about the +<a href="pcreunicode.html#utf8strings">validity of UTF-8 strings</a> +in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. If an invalid sequence of bytes is found, <b>pcre_exec()</b> returns the +error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a +truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both +cases, information about the precise nature of the error may also be returned +(see the descriptions of these errors in the section entitled \fIError return +values from\fP <b>pcre_exec()</b> +<a href="#errorlist">below).</a> +If <i>startoffset</i> contains a value that does not point to the start of a +UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is +returned. +</P> +<P> +If you already know that your subject is valid, and you want to skip these +checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when +calling <b>pcre_exec()</b>. You might want to do this for the second and +subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find +all the matches in a single subject string. However, you should be sure that +the value of <i>startoffset</i> points to the start of a character (or the end +of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an +invalid string as a subject or an invalid value of <i>startoffset</i> is +undefined. Your program may crash or loop. +<pre> + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +</pre> +These options turn on the partial matching feature. For backwards +compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match +occurs if the end of the subject string is reached successfully, but there are +not enough subject characters to complete the match. If this happens when +PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by +testing any remaining alternatives. Only if no complete match can be found is +PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words, +PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match, +but only if no complete match can be found. +</P> +<P> +If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a +partial match is found, <b>pcre_exec()</b> immediately returns +PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words, +when PCRE_PARTIAL_HARD is set, a partial match is considered to be more +important that an alternative complete match. +</P> +<P> +In both cases, the portion of the string that was inspected when the partial +match was found is set as the first matching string. There is a more detailed +discussion of partial and multi-segment matching, with examples, in the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation. +</P> +<br><b> +The string to be matched by <b>pcre_exec()</b> +</b><br> +<P> +The subject string is passed to <b>pcre_exec()</b> as a pointer in +<i>subject</i>, a length in <i>length</i>, and a starting offset in +<i>startoffset</i>. The units for <i>length</i> and <i>startoffset</i> are bytes +for the 8-bit library, 16-bit data items for the 16-bit library, and 32-bit +data items for the 32-bit library. +</P> +<P> +If <i>startoffset</i> is negative or greater than the length of the subject, +<b>pcre_exec()</b> returns PCRE_ERROR_BADOFFSET. When the starting offset is +zero, the search for a match starts at the beginning of the subject, and this +is by far the most common case. In UTF-8 or UTF-16 mode, the offset must point +to the start of a character, or the end of the subject (in UTF-32 mode, one +data unit equals one character, so all offsets are valid). Unlike the pattern +string, the subject may contain binary zeroes. +</P> +<P> +A non-zero starting offset is useful when searching for another match in the +same subject by calling <b>pcre_exec()</b> again after a previous success. +Setting <i>startoffset</i> differs from just passing over a shortened string and +setting PCRE_NOTBOL in the case of a pattern that begins with any kind of +lookbehind. For example, consider the pattern +<pre> + \Biss\B +</pre> +which finds occurrences of "iss" in the middle of words. (\B matches only if +the current position in the subject is not a word boundary.) When applied to +the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first +occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the +subject, namely "issipi", it does not match, because \B is always false at the +start of the subject, which is deemed to be a word boundary. However, if +<b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i> +set to 4, it finds the second occurrence of "iss" because it is able to look +behind the starting point to discover that it is preceded by a letter. +</P> +<P> +Finding all the matches in a subject is tricky when the pattern can match an +empty string. It is possible to emulate Perl's /g behaviour by first trying the +match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and +PCRE_ANCHORED options, and then if that fails, advancing the starting offset +and trying an ordinary match again. There is some code that demonstrates how to +do this in the +<a href="pcredemo.html"><b>pcredemo</b></a> +sample program. In the most general case, you have to check to see if the +newline convention recognizes CRLF as a newline, and if so, and the current +character is CR followed by LF, advance the starting offset by two characters +instead of one. +</P> +<P> +If a non-zero starting offset is passed when the pattern is anchored, one +attempt to match at the given offset is made. This can only succeed if the +pattern does not require the match to be at the start of the subject. +</P> +<br><b> +How <b>pcre_exec()</b> returns captured substrings +</b><br> +<P> +In general, a pattern matches a certain portion of the subject, and in +addition, further substrings from the subject may be picked out by parts of the +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. +</P> +<P> +Captured substrings are returned to the caller via a vector of integers whose +address is passed in <i>ovector</i>. The number of elements in the vector is +passed in <i>ovecsize</i>, which must be a non-negative number. <b>Note</b>: this +argument is NOT the size of <i>ovector</i> in bytes. +</P> +<P> +The first two-thirds of the vector is used to pass back captured substrings, +each substring using a pair of integers. The remaining third of the vector is +used as workspace by <b>pcre_exec()</b> while matching capturing subpatterns, +and is not available for passing back information. The number passed in +<i>ovecsize</i> should always be a multiple of three. If it is not, it is +rounded down. +</P> +<P> +When a match is successful, information about captured substrings is returned +in pairs of integers, starting at the beginning of <i>ovector</i>, and +continuing up to two-thirds of its length at the most. The first element of +each pair is set to the offset of the first character in a substring, and the +second is set to the offset of the first character after the end of a +substring. These values are always data unit offsets, even in UTF mode. They +are byte offsets in the 8-bit library, 16-bit data item offsets in the 16-bit +library, and 32-bit data item offsets in the 32-bit library. <b>Note</b>: they +are not character counts. +</P> +<P> +The first pair of integers, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the +portion of the subject string matched by the entire pattern. The next pair is +used for the first capturing subpattern, and so on. The value returned by +<b>pcre_exec()</b> is one more than the highest numbered pair that has been set. +For example, if two substrings have been captured, the returned value is 3. If +there are no capturing subpatterns, the return value from a successful match is +1, indicating that just the first pair of offsets has been set. +</P> +<P> +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that is returned. +</P> +<P> +If the vector is too small to hold all the captured substring offsets, it is +used as far as possible (up to two-thirds of its length), and the function +returns a value of zero. If neither the actual string matched nor any captured +substrings are of interest, <b>pcre_exec()</b> may be called with <i>ovector</i> +passed as NULL and <i>ovecsize</i> as zero. However, if the pattern contains +back references and the <i>ovector</i> is not big enough to remember the related +substrings, PCRE has to get additional memory for use during matching. Thus it +is usually advisable to supply an <i>ovector</i> of reasonable size. +</P> +<P> +There are some cases where zero is returned (indicating vector overflow) when +in fact the vector is exactly the right size for the final match. For example, +consider the pattern +<pre> + (a)(?:(b)c|bd) +</pre> +If a vector of 6 elements (allowing for only 1 captured substring) is given +with subject string "abd", <b>pcre_exec()</b> will try to set the second +captured string, thereby recording a vector overflow, before failing to match +"c" and backing up to try the second alternative. The zero return, however, +does correctly indicate that the maximum number of slots (namely 2) have been +filled. In similar cases where there is temporary overflow, but the final +number of used slots is actually less than the maximum, a non-zero value is +returned. +</P> +<P> +The <b>pcre_fullinfo()</b> function can be used to find out how many capturing +subpatterns there are in a compiled pattern. The smallest size for +<i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to +the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3. +</P> +<P> +It is possible for capturing subpattern number <i>n+1</i> to match some part of +the subject when subpattern <i>n</i> has not been used at all. For example, if +the string "abc" is matched against the pattern (a|(z))(bc) the return from the +function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this +happens, both values in the offset pairs corresponding to unused subpatterns +are set to -1. +</P> +<P> +Offset values that correspond to unused subpatterns at the end of the +expression are also set to -1. For example, if the string "abc" is matched +against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The +return from the function is 2, because the highest used capturing subpattern +number is 1, and the offsets for for the second and third capturing subpatterns +(assuming the vector is large enough, of course) are set to -1. +</P> +<P> +<b>Note</b>: Elements in the first two-thirds of <i>ovector</i> that do not +correspond to capturing parentheses in the pattern are never changed. That is, +if a pattern contains <i>n</i> capturing parentheses, no more than +<i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by <b>pcre_exec()</b>. The other +elements (in the first two-thirds) retain whatever values they previously had. +</P> +<P> +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described below. +<a name="errorlist"></a></P> +<br><b> +Error return values from <b>pcre_exec()</b> +</b><br> +<P> +If <b>pcre_exec()</b> fails, it returns a negative number. The following are +defined in the header file: +<pre> + PCRE_ERROR_NOMATCH (-1) +</pre> +The subject string did not match the pattern. +<pre> + PCRE_ERROR_NULL (-2) +</pre> +Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was +NULL and <i>ovecsize</i> was not zero. +<pre> + PCRE_ERROR_BADOPTION (-3) +</pre> +An unrecognized bit was set in the <i>options</i> argument. +<pre> + PCRE_ERROR_BADMAGIC (-4) +</pre> +PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch +the case when it is passed a junk pointer and to detect when a pattern that was +compiled in an environment of one endianness is run in an environment with the +other endianness. This is the error that PCRE gives when the magic number is +not present. +<pre> + PCRE_ERROR_UNKNOWN_OPCODE (-5) +</pre> +While running the pattern match, an unknown item was encountered in the +compiled pattern. This error could be caused by a bug in PCRE or by overwriting +of the compiled pattern. +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +If a pattern contains back references, but the <i>ovector</i> that is passed to +<b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE +gets a block of memory at the start of matching to use for this purpose. If the +call via <b>pcre_malloc()</b> fails, this error is given. The memory is +automatically freed at the end of matching. +</P> +<P> +This error is also given if <b>pcre_stack_malloc()</b> fails in +<b>pcre_exec()</b>. This can happen only when PCRE has been compiled with +<b>--disable-stack-for-recursion</b>. +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</pre> +This error is used by the <b>pcre_copy_substring()</b>, +<b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see +below). It is never returned by <b>pcre_exec()</b>. +<pre> + PCRE_ERROR_MATCHLIMIT (-8) +</pre> +The backtracking limit, as specified by the <i>match_limit</i> field in a +<b>pcre_extra</b> structure (or defaulted) was reached. See the description +above. +<pre> + PCRE_ERROR_CALLOUT (-9) +</pre> +This error is never generated by <b>pcre_exec()</b> itself. It is provided for +use by callout functions that want to yield a distinctive error code. See the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation for details. +<pre> + PCRE_ERROR_BADUTF8 (-10) +</pre> +A string that contains an invalid UTF-8 byte sequence was passed as a subject, +and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector +(<i>ovecsize</i>) is at least 2, the byte offset to the start of the the invalid +UTF-8 character is placed in the first element, and a reason code is placed in +the second element. The reason codes are listed in the +<a href="#badutf8reasons">following section.</a> +For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a +truncated UTF-8 character at the end of the subject (reason codes 1 to 5), +PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. +<pre> + PCRE_ERROR_BADUTF8_OFFSET (-11) +</pre> +The UTF-8 byte sequence that was passed as a subject was checked and found to +be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of +<i>startoffset</i> did not point to the beginning of a UTF-8 character or the +end of the subject. +<pre> + PCRE_ERROR_PARTIAL (-12) +</pre> +The subject string did not match, but it did match partially. See the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation for details of partial matching. +<pre> + PCRE_ERROR_BADPARTIAL (-13) +</pre> +This code is no longer in use. It was formerly returned when the PCRE_PARTIAL +option was used with a compiled pattern containing items that were not +supported for partial matching. From release 8.00 onwards, there are no +restrictions on partial matching. +<pre> + PCRE_ERROR_INTERNAL (-14) +</pre> +An unexpected internal error has occurred. This error could be caused by a bug +in PCRE or by overwriting of the compiled pattern. +<pre> + PCRE_ERROR_BADCOUNT (-15) +</pre> +This error is given if the value of the <i>ovecsize</i> argument is negative. +<pre> + PCRE_ERROR_RECURSIONLIMIT (-21) +</pre> +The internal recursion limit, as specified by the <i>match_limit_recursion</i> +field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the +description above. +<pre> + PCRE_ERROR_BADNEWLINE (-23) +</pre> +An invalid combination of PCRE_NEWLINE_<i>xxx</i> options was given. +<pre> + PCRE_ERROR_BADOFFSET (-24) +</pre> +The value of <i>startoffset</i> was negative or greater than the length of the +subject, that is, the value in <i>length</i>. +<pre> + PCRE_ERROR_SHORTUTF8 (-25) +</pre> +This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string +ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set. +Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in +fact sufficient to detect this case, but this special error code for +PCRE_PARTIAL_HARD precedes the implementation of returned information; it is +retained for backwards compatibility. +<pre> + PCRE_ERROR_RECURSELOOP (-26) +</pre> +This error is returned when <b>pcre_exec()</b> detects a recursion loop within +the pattern. Specifically, it means that either the whole pattern or a +subpattern has been called recursively for the second time at the same position +in the subject string. Some simple patterns that might do this are detected and +faulted at compile time, but more complicated cases, in particular mutual +recursions between two different subpatterns, cannot be detected until run +time. +<pre> + PCRE_ERROR_JIT_STACKLIMIT (-27) +</pre> +This error is returned when a pattern that was successfully studied using a +JIT compile option is being matched, but the memory available for the +just-in-time processing stack is not large enough. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +<pre> + PCRE_ERROR_BADMODE (-28) +</pre> +This error is given if a pattern that was compiled by the 8-bit library is +passed to a 16-bit or 32-bit library function, or vice versa. +<pre> + PCRE_ERROR_BADENDIANNESS (-29) +</pre> +This error is given if a pattern that was compiled and saved is reloaded on a +host with different endianness. The utility function +<b>pcre_pattern_to_host_byte_order()</b> can be used to convert such a pattern +so that it runs on the new host. +<pre> + PCRE_ERROR_JIT_BADOPTION +</pre> +This error is returned when a pattern that was successfully studied using a JIT +compile option is being matched, but the matching mode (partial or complete +match) does not correspond to any JIT compilation mode. When the JIT fast path +function is used, this error may be also given for invalid options. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for more details. +<pre> + PCRE_ERROR_BADLENGTH (-32) +</pre> +This error is given if <b>pcre_exec()</b> is called with a negative value for +the <i>length</i> argument. +</P> +<P> +Error numbers -16 to -20, -22, and 30 are not used by <b>pcre_exec()</b>. +<a name="badutf8reasons"></a></P> +<br><b> +Reason codes for invalid UTF-8 strings +</b><br> +<P> +This section applies only to the 8-bit library. The corresponding information +for the 16-bit and 32-bit libraries is given in the +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +pages. +</P> +<P> +When <b>pcre_exec()</b> returns either PCRE_ERROR_BADUTF8 or +PCRE_ERROR_SHORTUTF8, and the size of the output vector (<i>ovecsize</i>) is at +least 2, the offset of the start of the invalid UTF-8 character is placed in +the first output vector element (<i>ovector[0]</i>) and a reason code is placed +in the second element (<i>ovector[1]</i>). The reason codes are given names in +the <b>pcre.h</b> header file: +<pre> + PCRE_UTF8_ERR1 + PCRE_UTF8_ERR2 + PCRE_UTF8_ERR3 + PCRE_UTF8_ERR4 + PCRE_UTF8_ERR5 +</pre> +The string ends with a truncated UTF-8 character; the code specifies how many +bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be +no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279) +allows for up to 6 bytes, and this is checked first; hence the possibility of +4 or 5 missing bytes. +<pre> + PCRE_UTF8_ERR6 + PCRE_UTF8_ERR7 + PCRE_UTF8_ERR8 + PCRE_UTF8_ERR9 + PCRE_UTF8_ERR10 +</pre> +The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the +character do not have the binary value 0b10 (that is, either the most +significant bit is 0, or the next bit is 1). +<pre> + PCRE_UTF8_ERR11 + PCRE_UTF8_ERR12 +</pre> +A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long; +these code points are excluded by RFC 3629. +<pre> + PCRE_UTF8_ERR13 +</pre> +A 4-byte character has a value greater than 0x10fff; these code points are +excluded by RFC 3629. +<pre> + PCRE_UTF8_ERR14 +</pre> +A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of +code points are reserved by RFC 3629 for use with UTF-16, and so are excluded +from UTF-8. +<pre> + PCRE_UTF8_ERR15 + PCRE_UTF8_ERR16 + PCRE_UTF8_ERR17 + PCRE_UTF8_ERR18 + PCRE_UTF8_ERR19 +</pre> +A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a +value that can be represented by fewer bytes, which is invalid. For example, +the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just +one byte. +<pre> + PCRE_UTF8_ERR20 +</pre> +The two most significant bits of the first byte of a character have the binary +value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a +byte can only validly occur as the second or subsequent byte of a multi-byte +character. +<pre> + PCRE_UTF8_ERR21 +</pre> +The first byte of a character has the value 0xfe or 0xff. These values can +never occur in a valid UTF-8 string. +<pre> + PCRE_UTF8_ERR22 +</pre> +This error code was formerly used when the presence of a so-called +"non-character" caused an error. Unicode corrigendum #9 makes it clear that +such characters should not cause a string to be rejected, and so this code is +no longer in use and is never returned. +</P> +<br><a name="SEC18" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> +<P> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b> int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b> const char **<i>stringptr</i>);</b> +<br> +<br> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b> int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +</P> +<P> +Captured substrings can be accessed directly by using the offsets returned by +<b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions +<b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and +<b>pcre_get_substring_list()</b> are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. +</P> +<P> +A substring that contains a binary zero is correctly extracted and has a +further zero added on the end, but the result is not, of course, a C string. +However, you can process such a string by referring to the length that is +returned by <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b>. +Unfortunately, the interface to <b>pcre_get_substring_list()</b> is not adequate +for handling strings containing binary zeros, because the end of the final +string is not independently indicated. +</P> +<P> +The first three arguments are the same for all three of these functions: +<i>subject</i> is the subject string that has just been successfully matched, +<i>ovector</i> is a pointer to the vector of integer offsets that was passed to +<b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were +captured by the match, including the substring that matched the entire regular +expression. This is the value returned by <b>pcre_exec()</b> if it is greater +than zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of +space in <i>ovector</i>, the value passed as <i>stringcount</i> should be the +number of elements in the vector divided by three. +</P> +<P> +The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b> +extract a single substring, whose number is given as <i>stringnumber</i>. A +value of zero extracts the substring that matched the entire pattern, whereas +higher values extract the captured substrings. For <b>pcre_copy_substring()</b>, +the string is placed in <i>buffer</i>, whose length is given by +<i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is +obtained via <b>pcre_malloc</b>, and its address is returned via +<i>stringptr</i>. The yield of the function is the length of the string, not +including the terminating zero, or one of these error codes: +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get +memory failed for <b>pcre_get_substring()</b>. +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</pre> +There is no substring whose number is <i>stringnumber</i>. +</P> +<P> +The <b>pcre_get_substring_list()</b> function extracts all available substrings +and builds a list of pointers to them. All this is done in a single block of +memory that is obtained via <b>pcre_malloc</b>. The address of the memory block +is returned via <i>listptr</i>, which is also the start of the list of string +pointers. The end of the list is marked by a NULL pointer. The yield of the +function is zero if all went well, or the error code +<pre> + PCRE_ERROR_NOMEMORY (-6) +</pre> +if the attempt to get the memory block failed. +</P> +<P> +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number <i>n+1</i> matches some part of the +subject, but subpattern <i>n</i> has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in <i>ovector</i>, which is negative for unset +substrings. +</P> +<P> +The two convenience functions <b>pcre_free_substring()</b> and +<b>pcre_free_substring_list()</b> can be used to free the memory returned by +a previous call of <b>pcre_get_substring()</b> or +<b>pcre_get_substring_list()</b>, respectively. They do nothing more than call +the function pointed to by <b>pcre_free</b>, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language that cannot use +<b>pcre_free</b> directly; it is for these cases that the functions are +provided. +</P> +<br><a name="SEC19" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> +<P> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>);</b> +<br> +<br> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> char *<i>buffer</i>, int <i>buffersize</i>);</b> +<br> +<br> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b> const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b> int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b> const char **<i>stringptr</i>);</b> +</P> +<P> +To extract a substring by name, you first have to find associated number. +For example, for this pattern +<pre> + (a+)b(?<xxx>\d+)... +</pre> +the number of the subpattern called "xxx" is 2. If the name is known to be +unique (PCRE_DUPNAMES was not set), you can find the number from the name by +calling <b>pcre_get_stringnumber()</b>. The first argument is the compiled +pattern, and the second is the name. The yield of the function is the +subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of +that name. +</P> +<P> +Given the number, you can extract the substring directly, or use one of the +functions described in the previous section. For convenience, there are also +two functions that do the whole job. +</P> +<P> +Most of the arguments of <b>pcre_copy_named_substring()</b> and +<b>pcre_get_named_substring()</b> are the same as those for the similarly named +functions that extract by number. As these are described in the previous +section, they are not re-described here. There are just two differences: +</P> +<P> +First, instead of a substring number, a substring name is given. Second, there +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. +</P> +<P> +These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they +then call <b>pcre_copy_substring()</b> or <b>pcre_get_substring()</b>, as +appropriate. <b>NOTE:</b> If PCRE_DUPNAMES is set and there are duplicate names, +the behaviour may not be what you want (see the next section). +</P> +<P> +<b>Warning:</b> If the pattern uses the (?| feature to set up multiple +subpatterns with the same number, as described in the +<a href="pcrepattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page, you cannot use names to distinguish the different subpatterns, because +names are not included in the compiled code. The matching process uses only +numbers. For this reason, the use of different names for subpatterns of the +same number causes an error at compile time. +</P> +<br><a name="SEC20" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br> +<P> +<b>int pcre_get_stringtable_entries(const pcre *<i>code</i>,</b> +<b> const char *<i>name</i>, char **<i>first</i>, char **<i>last</i>);</b> +</P> +<P> +When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns +are not required to be unique. (Duplicate names are always allowed for +subpatterns with the same number, created by using the (?| feature. Indeed, if +such subpatterns are named, they are required to use the same names.) +</P> +<P> +Normally, patterns with duplicate names are such that in any one match, only +one of the named subpatterns participates. An example is shown in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +</P> +<P> +When duplicates are present, <b>pcre_copy_named_substring()</b> and +<b>pcre_get_named_substring()</b> return the first substring corresponding to +the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is +returned; no data is returned. The <b>pcre_get_stringnumber()</b> function +returns one of the numbers that are associated with the name, but it is not +defined which it is. +</P> +<P> +If you want to get full details of all captured substrings for a given name, +you must use the <b>pcre_get_stringtable_entries()</b> function. The first +argument is the compiled pattern, and the second is the name. The third and +fourth are pointers to variables which are updated by the function. After it +has run, they point to the first and last entries in the name-to-number table +for the given name. The function itself returns the length of each entry, or +PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is +described above in the section entitled <i>Information about a pattern</i> +<a href="#infoaboutpattern">above.</a> +Given all the relevant entries for the name, you can extract each of their +numbers, and hence the captured data, if any. +</P> +<br><a name="SEC21" href="#TOC1">FINDING ALL POSSIBLE MATCHES</a><br> +<P> +The traditional matching function uses a similar algorithm to Perl, which stops +when it finds the first match, starting at a given point in the subject. If you +want to find all possible matches, or the longest possible match, consider +using the alternative matching function (see below) instead. If you cannot use +the alternative function, but still need to find all possible matches, you +can kludge it up by making use of the callout facility, which is described in +the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +What you have to do is to insert a callout right at the end of the pattern. +When your callout function is called, extract and save the current matched +substring. Then return 1, which forces <b>pcre_exec()</b> to backtrack and try +other alternatives. Ultimately, when it runs out of matches, <b>pcre_exec()</b> +will yield PCRE_ERROR_NOMATCH. +</P> +<br><a name="SEC22" href="#TOC1">OBTAINING AN ESTIMATE OF STACK USAGE</a><br> +<P> +Matching certain patterns using <b>pcre_exec()</b> can use a lot of process +stack, which in certain environments can be rather limited in size. Some users +find it helpful to have an estimate of the amount of stack that is used by +<b>pcre_exec()</b>, to help them set recursion limits, as described in the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation. The estimate that is output by <b>pcretest</b> when called with +the <b>-m</b> and <b>-C</b> options is obtained by calling <b>pcre_exec</b> with +the values NULL, NULL, NULL, -999, and -999 for its first five arguments. +</P> +<P> +Normally, if its first argument is NULL, <b>pcre_exec()</b> immediately returns +the negative error code PCRE_ERROR_NULL, but with this special combination of +arguments, it returns instead a negative number whose absolute value is the +approximate stack frame size in bytes. (A negative number is used so that it is +clear that no match has happened.) The value is approximate because in some +cases, recursive calls to <b>pcre_exec()</b> occur when there are one or two +additional variables on the stack. +</P> +<P> +If PCRE has been compiled to use the heap instead of the stack for recursion, +the value returned is the size of each block that is obtained from the heap. +<a name="dfamatch"></a></P> +<br><a name="SEC23" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> +<P> +<b>int pcre_dfa_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b> const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b> int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>,</b> +<b> int *<i>workspace</i>, int <i>wscount</i>);</b> +</P> +<P> +The function <b>pcre_dfa_exec()</b> is called to match a subject string against +a compiled pattern, using a matching algorithm that scans the subject string +just once, and does not backtrack. This has different characteristics to the +normal algorithm, and is not compatible with Perl. Some of the features of PCRE +patterns are not supported. Nevertheless, there are times when this kind of +matching can be useful. For a discussion of the two matching algorithms, and a +list of features that <b>pcre_dfa_exec()</b> does not support, see the +<a href="pcrematching.html"><b>pcrematching</b></a> +documentation. +</P> +<P> +The arguments for the <b>pcre_dfa_exec()</b> function are the same as for +<b>pcre_exec()</b>, plus two extras. The <i>ovector</i> argument is used in a +different way, and this is described below. The other common arguments are used +in the same way as for <b>pcre_exec()</b>, so their description is not repeated +here. +</P> +<P> +The two additional arguments provide workspace for the function. The workspace +vector should contain at least 20 elements. It is used for keeping track of +multiple paths through the pattern tree. More workspace will be needed for +patterns and subjects where there are a lot of potential matches. +</P> +<P> +Here is an example of a simple call to <b>pcre_dfa_exec()</b>: +<pre> + int rc; + int ovector[10]; + int wspace[20]; + rc = pcre_dfa_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 10, /* number of elements (NOT size in bytes) */ + wspace, /* working space vector */ + 20); /* number of elements (NOT size in bytes) */ +</PRE> +</P> +<br><b> +Option bits for <b>pcre_dfa_exec()</b> +</b><br> +<P> +The unused bits of the <i>options</i> argument for <b>pcre_dfa_exec()</b> must be +zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_<i>xxx</i>, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, +PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. +All but the last four of these are exactly the same as for <b>pcre_exec()</b>, +so their description is not repeated here. +<pre> + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +</pre> +These have the same general effect as they do for <b>pcre_exec()</b>, but the +details are slightly different. When PCRE_PARTIAL_HARD is set for +<b>pcre_dfa_exec()</b>, it returns PCRE_ERROR_PARTIAL if the end of the subject +is reached and there is still at least one matching possibility that requires +additional characters. This happens even if some complete matches have also +been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH +is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached, +there have been no complete matches, but there is still at least one matching +possibility. The portion of the string that was inspected when the longest +partial match was found is set as the first matching string in both cases. +There is a more detailed discussion of partial and multi-segment matching, with +examples, in the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation. +<pre> + PCRE_DFA_SHORTEST +</pre> +Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as +soon as it has found one match. Because of the way the alternative algorithm +works, this is necessarily the shortest possible match at the first possible +matching point in the subject string. +<pre> + PCRE_DFA_RESTART +</pre> +When <b>pcre_dfa_exec()</b> returns a partial match, it is possible to call it +again, with additional subject characters, and have it continue with the same +match. The PCRE_DFA_RESTART option requests this action; when it is set, the +<i>workspace</i> and <i>wscount</i> options must reference the same vector as +before because data about the match so far is left in them after a partial +match. There is more discussion of this facility in the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation. +</P> +<br><b> +Successful returns from <b>pcre_dfa_exec()</b> +</b><br> +<P> +When <b>pcre_dfa_exec()</b> succeeds, it may have matched more than one +substring in the subject. Note, however, that all the matches from one run of +the function start at the same point in the subject. The shorter matches are +all initial substrings of the longer matches. For example, if the pattern +<pre> + <.*> +</pre> +is matched against the string +<pre> + This is <something> <something else> <something further> no more +</pre> +the three matched strings are +<pre> + <something> + <something> <something else> + <something> <something else> <something further> +</pre> +On success, the yield of the function is a number greater than zero, which is +the number of matched substrings. The substrings themselves are returned in +<i>ovector</i>. Each string uses two elements; the first is the offset to the +start, and the second is the offset to the end. In fact, all the strings have +the same start offset. (Space could have been saved by giving this only once, +but it was decided to retain some compatibility with the way <b>pcre_exec()</b> +returns data, even though the meaning of the strings is different.) +</P> +<P> +The strings are returned in reverse order of length; that is, the longest +matching string is given first. If there were too many matches to fit into +<i>ovector</i>, the yield of the function is zero, and the vector is filled with +the longest matches. Unlike <b>pcre_exec()</b>, <b>pcre_dfa_exec()</b> can use +the entire <i>ovector</i> for returning matched strings. +</P> +<P> +NOTE: PCRE's "auto-possessification" optimization usually applies to character +repeats at the end of a pattern (as well as internally). For example, the +pattern "a\d+" is compiled as if it were "a\d++" because there is no point +even considering the possibility of backtracking into the repeated digits. For +DFA matching, this means that only one possible match is found. If you really +do want multiple matches in such cases, either use an ungreedy repeat +("a\d+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. +</P> +<br><b> +Error returns from <b>pcre_dfa_exec()</b> +</b><br> +<P> +The <b>pcre_dfa_exec()</b> function returns a negative number when it fails. +Many of the errors are the same as for <b>pcre_exec()</b>, and these are +described +<a href="#errorlist">above.</a> +There are in addition the following errors that are specific to +<b>pcre_dfa_exec()</b>: +<pre> + PCRE_ERROR_DFA_UITEM (-16) +</pre> +This return is given if <b>pcre_dfa_exec()</b> encounters an item in the pattern +that it does not support, for instance, the use of \C or a back reference. +<pre> + PCRE_ERROR_DFA_UCOND (-17) +</pre> +This return is given if <b>pcre_dfa_exec()</b> encounters a condition item that +uses a back reference for the condition, or a test for recursion in a specific +group. These are not supported. +<pre> + PCRE_ERROR_DFA_UMLIMIT (-18) +</pre> +This return is given if <b>pcre_dfa_exec()</b> is called with an <i>extra</i> +block that contains a setting of the <i>match_limit</i> or +<i>match_limit_recursion</i> fields. This is not supported (these fields are +meaningless for DFA matching). +<pre> + PCRE_ERROR_DFA_WSSIZE (-19) +</pre> +This return is given if <b>pcre_dfa_exec()</b> runs out of space in the +<i>workspace</i> vector. +<pre> + PCRE_ERROR_DFA_RECURSE (-20) +</pre> +When a recursive subpattern is processed, the matching function calls itself +recursively, using private vectors for <i>ovector</i> and <i>workspace</i>. This +error is given if the output vector is not large enough. This should be +extremely rare, as a vector of size 1000 is used. +<pre> + PCRE_ERROR_DFA_BADRESTART (-30) +</pre> +When <b>pcre_dfa_exec()</b> is called with the <b>PCRE_DFA_RESTART</b> option, +some plausibility checks are made on the contents of the workspace, which +should contain data about the previous partial match. If any of these checks +fail, this error is given. +</P> +<br><a name="SEC24" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcre16</b>(3), <b>pcre32</b>(3), <b>pcrebuild</b>(3), <b>pcrecallout</b>(3), +<b>pcrecpp(3)</b>(3), <b>pcrematching</b>(3), <b>pcrepartial</b>(3), +<b>pcreposix</b>(3), <b>pcreprecompile</b>(3), <b>pcresample</b>(3), +<b>pcrestack</b>(3). +</P> +<br><a name="SEC25" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC26" href="#TOC1">REVISION</a><br> +<P> +Last updated: 09 February 2014 +<br> +Copyright © 1997-2014 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrebuild.html b/doc/html/pcrebuild.html new file mode 100644 index 0000000..03c8cbe --- /dev/null +++ b/doc/html/pcrebuild.html @@ -0,0 +1,534 @@ +<html> +<head> +<title>pcrebuild specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrebuild man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">BUILDING PCRE</a> +<li><a name="TOC2" href="#SEC2">PCRE BUILD-TIME OPTIONS</a> +<li><a name="TOC3" href="#SEC3">BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES</a> +<li><a name="TOC4" href="#SEC4">BUILDING SHARED AND STATIC LIBRARIES</a> +<li><a name="TOC5" href="#SEC5">C++ SUPPORT</a> +<li><a name="TOC6" href="#SEC6">UTF-8, UTF-16 AND UTF-32 SUPPORT</a> +<li><a name="TOC7" href="#SEC7">UNICODE CHARACTER PROPERTY SUPPORT</a> +<li><a name="TOC8" href="#SEC8">JUST-IN-TIME COMPILER SUPPORT</a> +<li><a name="TOC9" href="#SEC9">CODE VALUE OF NEWLINE</a> +<li><a name="TOC10" href="#SEC10">WHAT \R MATCHES</a> +<li><a name="TOC11" href="#SEC11">POSIX MALLOC USAGE</a> +<li><a name="TOC12" href="#SEC12">HANDLING VERY LARGE PATTERNS</a> +<li><a name="TOC13" href="#SEC13">AVOIDING EXCESSIVE STACK USAGE</a> +<li><a name="TOC14" href="#SEC14">LIMITING PCRE RESOURCE USAGE</a> +<li><a name="TOC15" href="#SEC15">CREATING CHARACTER TABLES AT BUILD TIME</a> +<li><a name="TOC16" href="#SEC16">USING EBCDIC CODE</a> +<li><a name="TOC17" href="#SEC17">PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT</a> +<li><a name="TOC18" href="#SEC18">PCREGREP BUFFER SIZE</a> +<li><a name="TOC19" href="#SEC19">PCRETEST OPTION FOR LIBREADLINE SUPPORT</a> +<li><a name="TOC20" href="#SEC20">DEBUGGING WITH VALGRIND SUPPORT</a> +<li><a name="TOC21" href="#SEC21">CODE COVERAGE REPORTING</a> +<li><a name="TOC22" href="#SEC22">SEE ALSO</a> +<li><a name="TOC23" href="#SEC23">AUTHOR</a> +<li><a name="TOC24" href="#SEC24">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">BUILDING PCRE</a><br> +<P> +PCRE is distributed with a <b>configure</b> script that can be used to build the +library in Unix-like environments using the applications known as Autotools. +Also in the distribution are files to support building using <b>CMake</b> +instead of <b>configure</b>. The text file +<a href="README.txt"><b>README</b></a> +contains general information about building with Autotools (some of which is +repeated below), and also has some comments about building on various operating +systems. There is a lot more information about building PCRE without using +Autotools (including information about using <b>CMake</b> and building "by +hand") in the text file called +<a href="NON-AUTOTOOLS-BUILD.txt"><b>NON-AUTOTOOLS-BUILD</b>.</a> +You should consult this file as well as the +<a href="README.txt"><b>README</b></a> +file if you are building in a non-Unix-like environment. +</P> +<br><a name="SEC2" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br> +<P> +The rest of this document describes the optional features of PCRE that can be +selected when the library is compiled. It assumes use of the <b>configure</b> +script, where the optional features are selected or deselected by providing +options to <b>configure</b> before running the <b>make</b> command. However, the +same options can be selected in both Unix-like and non-Unix-like environments +using the GUI facility of <b>cmake-gui</b> if you are using <b>CMake</b> instead +of <b>configure</b> to build PCRE. +</P> +<P> +If you are not using Autotools or <b>CMake</b>, option selection can be done by +editing the <b>config.h</b> file, or by passing parameter settings to the +compiler, as described in +<a href="NON-AUTOTOOLS-BUILD.txt"><b>NON-AUTOTOOLS-BUILD</b>.</a> +</P> +<P> +The complete list of options for <b>configure</b> (which includes the standard +ones such as the selection of the installation directory) can be obtained by +running +<pre> + ./configure --help +</pre> +The following sections include descriptions of options whose names begin with +--enable or --disable. These settings specify changes to the defaults for the +<b>configure</b> command. Because of the way that <b>configure</b> works, +--enable and --disable always come in pairs, so the complementary option always +exists as well, but as it specifies the default, it is not described. +</P> +<br><a name="SEC3" href="#TOC1">BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES</a><br> +<P> +By default, a library called <b>libpcre</b> is built, containing functions that +take string arguments contained in vectors of bytes, either as single-byte +characters, or interpreted as UTF-8 strings. You can also build a separate +library, called <b>libpcre16</b>, in which strings are contained in vectors of +16-bit data units and interpreted either as single-unit characters or UTF-16 +strings, by adding +<pre> + --enable-pcre16 +</pre> +to the <b>configure</b> command. You can also build yet another separate +library, called <b>libpcre32</b>, in which strings are contained in vectors of +32-bit data units and interpreted either as single-unit characters or UTF-32 +strings, by adding +<pre> + --enable-pcre32 +</pre> +to the <b>configure</b> command. If you do not want the 8-bit library, add +<pre> + --disable-pcre8 +</pre> +as well. At least one of the three libraries must be built. Note that the C++ +and POSIX wrappers are for the 8-bit library only, and that <b>pcregrep</b> is +an 8-bit program. None of these are built if you select only the 16-bit or +32-bit libraries. +</P> +<br><a name="SEC4" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br> +<P> +The Autotools PCRE building process uses <b>libtool</b> to build both shared and +static libraries by default. You can suppress one of these by adding one of +<pre> + --disable-shared + --disable-static +</pre> +to the <b>configure</b> command, as required. +</P> +<br><a name="SEC5" href="#TOC1">C++ SUPPORT</a><br> +<P> +By default, if the 8-bit library is being built, the <b>configure</b> script +will search for a C++ compiler and C++ header files. If it finds them, it +automatically builds the C++ wrapper library (which supports only 8-bit +strings). You can disable this by adding +<pre> + --disable-cpp +</pre> +to the <b>configure</b> command. +</P> +<br><a name="SEC6" href="#TOC1">UTF-8, UTF-16 AND UTF-32 SUPPORT</a><br> +<P> +To build PCRE with support for UTF Unicode character strings, add +<pre> + --enable-utf +</pre> +to the <b>configure</b> command. This setting applies to all three libraries, +adding support for UTF-8 to the 8-bit library, support for UTF-16 to the 16-bit +library, and support for UTF-32 to the to the 32-bit library. There are no +separate options for enabling UTF-8, UTF-16 and UTF-32 independently because +that would allow ridiculous settings such as requesting UTF-16 support while +building only the 8-bit library. It is not possible to build one library with +UTF support and another without in the same configuration. (For backwards +compatibility, --enable-utf8 is a synonym of --enable-utf.) +</P> +<P> +Of itself, this setting does not make PCRE treat strings as UTF-8, UTF-16 or +UTF-32. As well as compiling PCRE with this option, you also have have to set +the PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as appropriate) when you call +one of the pattern compiling functions. +</P> +<P> +If you set --enable-utf when compiling in an EBCDIC environment, PCRE expects +its input to be either ASCII or UTF-8 (depending on the run-time option). It is +not possible to support both EBCDIC and UTF-8 codes in the same version of the +library. Consequently, --enable-utf and --enable-ebcdic are mutually +exclusive. +</P> +<br><a name="SEC7" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br> +<P> +UTF support allows the libraries to process character codepoints up to 0x10ffff +in the strings that they handle. On its own, however, it does not provide any +facilities for accessing the properties of such characters. If you want to be +able to use the pattern escapes \P, \p, and \X, which refer to Unicode +character properties, you must add +<pre> + --enable-unicode-properties +</pre> +to the <b>configure</b> command. This implies UTF support, even if you have +not explicitly requested it. +</P> +<P> +Including Unicode property support adds around 30K of tables to the PCRE +library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are +supported. Details are given in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +</P> +<br><a name="SEC8" href="#TOC1">JUST-IN-TIME COMPILER SUPPORT</a><br> +<P> +Just-in-time compiler support is included in the build by specifying +<pre> + --enable-jit +</pre> +This support is available only for certain hardware architectures. If this +option is set for an unsupported architecture, a compile time error occurs. +See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for a discussion of JIT usage. When JIT support is enabled, +pcregrep automatically makes use of it, unless you add +<pre> + --disable-pcregrep-jit +</pre> +to the "configure" command. +</P> +<br><a name="SEC9" href="#TOC1">CODE VALUE OF NEWLINE</a><br> +<P> +By default, PCRE interprets the linefeed (LF) character as indicating the end +of a line. This is the normal newline character on Unix-like systems. You can +compile PCRE to use carriage return (CR) instead, by adding +<pre> + --enable-newline-is-cr +</pre> +to the <b>configure</b> command. There is also a --enable-newline-is-lf option, +which explicitly specifies linefeed as the newline character. +<br> +<br> +Alternatively, you can specify that line endings are to be indicated by the two +character sequence CRLF. If you want this, add +<pre> + --enable-newline-is-crlf +</pre> +to the <b>configure</b> command. There is a fourth option, specified by +<pre> + --enable-newline-is-anycrlf +</pre> +which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as +indicating a line ending. Finally, a fifth option, specified by +<pre> + --enable-newline-is-any +</pre> +causes PCRE to recognize any Unicode newline sequence. +</P> +<P> +Whatever line ending convention is selected when PCRE is built can be +overridden when the library functions are called. At build time it is +conventional to use the standard for your operating system. +</P> +<br><a name="SEC10" href="#TOC1">WHAT \R MATCHES</a><br> +<P> +By default, the sequence \R in a pattern matches any Unicode newline sequence, +whatever has been selected as the line ending sequence. If you specify +<pre> + --enable-bsr-anycrlf +</pre> +the default is changed so that \R matches only CR, LF, or CRLF. Whatever is +selected when PCRE is built can be overridden when the library functions are +called. +</P> +<br><a name="SEC11" href="#TOC1">POSIX MALLOC USAGE</a><br> +<P> +When the 8-bit library is called through the POSIX interface (see the +<a href="pcreposix.html"><b>pcreposix</b></a> +documentation), additional working storage is required for holding the pointers +to capturing substrings, because PCRE requires three integers per substring, +whereas the POSIX interface provides only two. If the number of expected +substrings is small, the wrapper function uses space on the stack, because this +is faster than using <b>malloc()</b> for each call. The default threshold above +which the stack is no longer used is 10; it can be changed by adding a setting +such as +<pre> + --with-posix-malloc-threshold=20 +</pre> +to the <b>configure</b> command. +</P> +<br><a name="SEC12" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br> +<P> +Within a compiled pattern, offset values are used to point from one part to +another (for example, from an opening parenthesis to an alternation +metacharacter). By default, in the 8-bit and 16-bit libraries, two-byte values +are used for these offsets, leading to a maximum size for a compiled pattern of +around 64K. This is sufficient to handle all but the most gigantic patterns. +Nevertheless, some people do want to process truly enormous patterns, so it is +possible to compile PCRE to use three-byte or four-byte offsets by adding a +setting such as +<pre> + --with-link-size=3 +</pre> +to the <b>configure</b> command. The value given must be 2, 3, or 4. For the +16-bit library, a value of 3 is rounded up to 4. In these libraries, using +longer offsets slows down the operation of PCRE because it has to load +additional data when handling them. For the 32-bit library the value is always +4 and cannot be overridden; the value of --with-link-size is ignored. +</P> +<br><a name="SEC13" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br> +<P> +When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking +by making recursive calls to an internal function called <b>match()</b>. In +environments where the size of the stack is limited, this can severely limit +PCRE's operation. (The Unix environment does not usually suffer from this +problem, but it may sometimes be necessary to increase the maximum stack size. +There is a discussion in the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation.) An alternative approach to recursion that uses memory from the +heap to remember data, instead of using recursive function calls, has been +implemented to work round the problem of limited stack size. If you want to +build a version of PCRE that works this way, add +<pre> + --disable-stack-for-recursion +</pre> +to the <b>configure</b> command. With this configuration, PCRE will use the +<b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory +management functions. By default these point to <b>malloc()</b> and +<b>free()</b>, but you can replace the pointers so that your own functions are +used instead. +</P> +<P> +Separate functions are provided rather than using <b>pcre_malloc</b> and +<b>pcre_free</b> because the usage is very predictable: the block sizes +requested are always the same, and the blocks are always freed in reverse +order. A calling program might be able to implement optimized functions that +perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more +slowly when built in this way. This option affects only the <b>pcre_exec()</b> +function; it is not relevant for <b>pcre_dfa_exec()</b>. +</P> +<br><a name="SEC14" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br> +<P> +Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly +(sometimes recursively) when matching a pattern with the <b>pcre_exec()</b> +function. By controlling the maximum number of times this function may be +called during a single matching operation, a limit can be placed on the +resources used by a single call to <b>pcre_exec()</b>. The limit can be changed +at run time, as described in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. The default is 10 million, but this can be changed by adding a +setting such as +<pre> + --with-match-limit=500000 +</pre> +to the <b>configure</b> command. This setting has no effect on the +<b>pcre_dfa_exec()</b> matching function. +</P> +<P> +In some environments it is desirable to limit the depth of recursive calls of +<b>match()</b> more strictly than the total number of calls, in order to +restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion +is specified) that is used. A second limit controls this; it defaults to the +value that is set for --with-match-limit, which imposes no additional +constraints. However, you can set a lower limit by adding, for example, +<pre> + --with-match-limit-recursion=10000 +</pre> +to the <b>configure</b> command. This value can also be overridden at run time. +</P> +<br><a name="SEC15" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br> +<P> +PCRE uses fixed tables for processing characters whose code values are less +than 256. By default, PCRE is built with a set of tables that are distributed +in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes +only. If you add +<pre> + --enable-rebuild-chartables +</pre> +to the <b>configure</b> command, the distributed tables are no longer used. +Instead, a program called <b>dftables</b> is compiled and run. This outputs the +source for new set of tables, created in the default locale of your C run-time +system. (This method of replacing the tables does not work if you are cross +compiling, because <b>dftables</b> is run on the local host. If you need to +create alternative tables when cross compiling, you will have to do so "by +hand".) +</P> +<br><a name="SEC16" href="#TOC1">USING EBCDIC CODE</a><br> +<P> +PCRE assumes by default that it will run in an environment where the character +code is ASCII (or Unicode, which is a superset of ASCII). This is the case for +most computer operating systems. PCRE can, however, be compiled to run in an +EBCDIC environment by adding +<pre> + --enable-ebcdic +</pre> +to the <b>configure</b> command. This setting implies +--enable-rebuild-chartables. You should only use it if you know that you are in +an EBCDIC environment (for example, an IBM mainframe operating system). The +--enable-ebcdic option is incompatible with --enable-utf. +</P> +<P> +The EBCDIC character that corresponds to an ASCII LF is assumed to have the +value 0x15 by default. However, in some EBCDIC environments, 0x25 is used. In +such an environment you should use +<pre> + --enable-ebcdic-nl25 +</pre> +as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR has the +same value as in ASCII, namely, 0x0d. Whichever of 0x15 and 0x25 is <i>not</i> +chosen as LF is made to correspond to the Unicode NEL character (which, in +Unicode, is 0x85). +</P> +<P> +The options that select newline behaviour, such as --enable-newline-is-cr, +and equivalent run-time options, refer to these character values in an EBCDIC +environment. +</P> +<br><a name="SEC17" href="#TOC1">PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT</a><br> +<P> +By default, <b>pcregrep</b> reads all files as plain text. You can build it so +that it recognizes files whose names end in <b>.gz</b> or <b>.bz2</b>, and reads +them with <b>libz</b> or <b>libbz2</b>, respectively, by adding one or both of +<pre> + --enable-pcregrep-libz + --enable-pcregrep-libbz2 +</pre> +to the <b>configure</b> command. These options naturally require that the +relevant libraries are installed on your system. Configuration will fail if +they are not. +</P> +<br><a name="SEC18" href="#TOC1">PCREGREP BUFFER SIZE</a><br> +<P> +<b>pcregrep</b> uses an internal buffer to hold a "window" on the file it is +scanning, in order to be able to output "before" and "after" lines when it +finds a match. The size of the buffer is controlled by a parameter whose +default value is 20K. The buffer itself is three times this size, but because +of the way it is used for holding "before" lines, the longest line that is +guaranteed to be processable is the parameter size. You can change the default +parameter value by adding, for example, +<pre> + --with-pcregrep-bufsize=50K +</pre> +to the <b>configure</b> command. The caller of \fPpcregrep\fP can, however, +override this value by specifying a run-time option. +</P> +<br><a name="SEC19" href="#TOC1">PCRETEST OPTION FOR LIBREADLINE SUPPORT</a><br> +<P> +If you add +<pre> + --enable-pcretest-libreadline +</pre> +to the <b>configure</b> command, <b>pcretest</b> is linked with the +<b>libreadline</b> library, and when its input is from a terminal, it reads it +using the <b>readline()</b> function. This provides line-editing and history +facilities. Note that <b>libreadline</b> is GPL-licensed, so if you distribute a +binary of <b>pcretest</b> linked in this way, there may be licensing issues. +</P> +<P> +Setting this option causes the <b>-lreadline</b> option to be added to the +<b>pcretest</b> build. In many operating environments with a sytem-installed +<b>libreadline</b> this is sufficient. However, in some environments (e.g. +if an unmodified distribution version of readline is in use), some extra +configuration may be necessary. The INSTALL file for <b>libreadline</b> says +this: +<pre> + "Readline uses the termcap functions, but does not link with the + termcap or curses library itself, allowing applications which link + with readline the to choose an appropriate library." +</pre> +If your environment has not been set up so that an appropriate library is +automatically included, you may need to add something like +<pre> + LIBS="-ncurses" +</pre> +immediately before the <b>configure</b> command. +</P> +<br><a name="SEC20" href="#TOC1">DEBUGGING WITH VALGRIND SUPPORT</a><br> +<P> +By adding the +<pre> + --enable-valgrind +</pre> +option to to the <b>configure</b> command, PCRE will use valgrind annotations +to mark certain memory regions as unaddressable. This allows it to detect +invalid memory accesses, and is mostly useful for debugging PCRE itself. +</P> +<br><a name="SEC21" href="#TOC1">CODE COVERAGE REPORTING</a><br> +<P> +If your C compiler is gcc, you can build a version of PCRE that can generate a +code coverage report for its test suite. To enable this, you must install +<b>lcov</b> version 1.6 or above. Then specify +<pre> + --enable-coverage +</pre> +to the <b>configure</b> command and build PCRE in the usual way. +</P> +<P> +Note that using <b>ccache</b> (a caching C compiler) is incompatible with code +coverage reporting. If you have configured <b>ccache</b> to run automatically +on your system, you must set the environment variable +<pre> + CCACHE_DISABLE=1 +</pre> +before running <b>make</b> to build PCRE, so that <b>ccache</b> is not used. +</P> +<P> +When --enable-coverage is used, the following addition targets are added to the +<i>Makefile</i>: +<pre> + make coverage +</pre> +This creates a fresh coverage report for the PCRE test suite. It is equivalent +to running "make coverage-reset", "make coverage-baseline", "make check", and +then "make coverage-report". +<pre> + make coverage-reset +</pre> +This zeroes the coverage counters, but does nothing else. +<pre> + make coverage-baseline +</pre> +This captures baseline coverage information. +<pre> + make coverage-report +</pre> +This creates the coverage report. +<pre> + make coverage-clean-report +</pre> +This removes the generated coverage report without cleaning the coverage data +itself. +<pre> + make coverage-clean-data +</pre> +This removes the captured coverage data without removing the coverage files +created at compile time (*.gcno). +<pre> + make coverage-clean +</pre> +This cleans all coverage data including the generated coverage report. For more +information about code coverage, see the <b>gcov</b> and <b>lcov</b> +documentation. +</P> +<br><a name="SEC22" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcreapi</b>(3), <b>pcre16</b>, <b>pcre32</b>, <b>pcre_config</b>(3). +</P> +<br><a name="SEC23" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC24" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 May 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrecallout.html b/doc/html/pcrecallout.html new file mode 100644 index 0000000..53a937f --- /dev/null +++ b/doc/html/pcrecallout.html @@ -0,0 +1,286 @@ +<html> +<head> +<title>pcrecallout specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrecallout man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">MISSING CALLOUTS</a> +<li><a name="TOC4" href="#SEC4">THE CALLOUT INTERFACE</a> +<li><a name="TOC5" href="#SEC5">RETURN VALUES</a> +<li><a name="TOC6" href="#SEC6">AUTHOR</a> +<li><a name="TOC7" href="#SEC7">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int (*pcre_callout)(pcre_callout_block *);</b> +</P> +<P> +<b>int (*pcre16_callout)(pcre16_callout_block *);</b> +</P> +<P> +<b>int (*pcre32_callout)(pcre32_callout_block *);</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +PCRE provides a feature called "callout", which is a means of temporarily +passing control to the caller of PCRE in the middle of pattern matching. The +caller of PCRE provides an external function by putting its entry point in the +global variable <i>pcre_callout</i> (<i>pcre16_callout</i> for the 16-bit +library, <i>pcre32_callout</i> for the 32-bit library). By default, this +variable contains NULL, which disables all calling out. +</P> +<P> +Within a regular expression, (?C) indicates the points at which the external +function is to be called. Different callout points can be identified by putting +a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +<pre> + (?C1)abc(?C2)def +</pre> +If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, PCRE +automatically inserts callouts, all with number 255, before each item in the +pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern +<pre> + A(\d{2}|--) +</pre> +it is processed as if it were +<br> +<br> +(?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255) +<br> +<br> +Notice that there is a callout before and after each parenthesis and +alternation bar. If the pattern contains a conditional group whose condition is +an assertion, an automatic callout is inserted immediately before the +condition. Such a callout may also be inserted explicitly, for example: +<pre> + (?(?C9)(?=a)ab|de) +</pre> +This applies only to assertion conditions (because they are themselves +independent groups). +</P> +<P> +Automatic callouts can be used for tracking the progress of pattern matching. +The +<a href="pcretest.html"><b>pcretest</b></a> +program has a pattern qualifier (/C) that sets automatic callouts; when it is +used, the output indicates how the pattern is being matched. This is useful +information when you are trying to optimize the performance of a particular +pattern. +</P> +<br><a name="SEC3" href="#TOC1">MISSING CALLOUTS</a><br> +<P> +You should be aware that, because of optimizations in the way PCRE compiles and +matches patterns, callouts sometimes do not happen exactly as you might expect. +</P> +<P> +At compile time, PCRE "auto-possessifies" repeated items when it knows that +what follows cannot be part of the repeat. For example, a+[bc] is compiled as +if it were a++[bc]. The <b>pcretest</b> output when this pattern is anchored and +then applied with automatic callouts to the string "aaaa" is: +<pre> + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + No match +</pre> +This indicates that when matching [bc] fails, there is no backtracking into a+ +and therefore the callouts that would be taken for the backtracks do not occur. +You can disable the auto-possessify feature by passing PCRE_NO_AUTO_POSSESS +to <b>pcre_compile()</b>, or starting the pattern with (*NO_AUTO_POSSESS). If +this is done in <b>pcretest</b> (using the /O qualifier), the output changes to +this: +<pre> + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^^ [bc] + No match +</pre> +This time, when matching [bc] fails, the matcher backtracks into a+ and tries +again, repeatedly, until a+ itself fails. +</P> +<P> +Other optimizations that provide fast "no match" results also affect callouts. +For example, if the pattern is +<pre> + ab(?C4)cd +</pre> +PCRE knows that any matching string must contain the letter "d". If the subject +string is "abyz", the lack of "d" means that matching doesn't ever start, and +the callout is never reached. However, with "abyd", though the result is still +no match, the callout is obeyed. +</P> +<P> +If the pattern is studied, PCRE knows the minimum length of a matching string, +and will immediately give a "no match" return without actually running a match +if the subject is not long enough, or, for unanchored patterns, if it has +been scanned far enough. +</P> +<P> +You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE +option to the matching function, or by starting the pattern with +(*NO_START_OPT). This slows down the matching process, but does ensure that +callouts such as the example above are obeyed. +</P> +<br><a name="SEC4" href="#TOC1">THE CALLOUT INTERFACE</a><br> +<P> +During matching, when PCRE reaches a callout point, the external function +defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called (if it is +set). This applies to both normal and DFA matching. The only argument to the +callout function is a pointer to a <b>pcre_callout</b> or +<b>pcre[16|32]_callout</b> block. These structures contains the following +fields: +<pre> + int <i>version</i>; + int <i>callout_number</i>; + int *<i>offset_vector</i>; + const char *<i>subject</i>; (8-bit version) + PCRE_SPTR16 <i>subject</i>; (16-bit version) + PCRE_SPTR32 <i>subject</i>; (32-bit version) + int <i>subject_length</i>; + int <i>start_match</i>; + int <i>current_position</i>; + int <i>capture_top</i>; + int <i>capture_last</i>; + void *<i>callout_data</i>; + int <i>pattern_position</i>; + int <i>next_item_length</i>; + const unsigned char *<i>mark</i>; (8-bit version) + const PCRE_UCHAR16 *<i>mark</i>; (16-bit version) + const PCRE_UCHAR32 *<i>mark</i>; (32-bit version) +</pre> +The <i>version</i> field is an integer containing the version number of the +block format. The initial version was 0; the current version is 2. The version +number will change again in future if additional fields are added, but the +intention is never to remove any of the existing fields. +</P> +<P> +The <i>callout_number</i> field contains the number of the callout, as compiled +into the pattern (that is, the number after ?C for manual callouts, and 255 for +automatically generated callouts). +</P> +<P> +The <i>offset_vector</i> field is a pointer to the vector of offsets that was +passed by the caller to the matching function. When <b>pcre_exec()</b> or +<b>pcre[16|32]_exec()</b> is used, the contents can be inspected, in order to +extract substrings that have been matched so far, in the same way as for +extracting substrings after a match has completed. For the DFA matching +functions, this field is not useful. +</P> +<P> +The <i>subject</i> and <i>subject_length</i> fields contain copies of the values +that were passed to the matching function. +</P> +<P> +The <i>start_match</i> field normally contains the offset within the subject at +which the current match attempt started. However, if the escape sequence \K +has been encountered, this value is changed to reflect the modified starting +point. If the pattern is not anchored, the callout function may be called +several times from the same point in the pattern for different starting points +in the subject. +</P> +<P> +The <i>current_position</i> field contains the offset within the subject of the +current match pointer. +</P> +<P> +When the <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> is used, the +<i>capture_top</i> field contains one more than the number of the highest +numbered captured substring so far. If no substrings have been captured, the +value of <i>capture_top</i> is one. This is always the case when the DFA +functions are used, because they do not support captured substrings. +</P> +<P> +The <i>capture_last</i> field contains the number of the most recently captured +substring. However, when a recursion exits, the value reverts to what it was +outside the recursion, as do the values of all captured substrings. If no +substrings have been captured, the value of <i>capture_last</i> is -1. This is +always the case for the DFA matching functions. +</P> +<P> +The <i>callout_data</i> field contains a value that is passed to a matching +function specifically so that it can be passed back in callouts. It is passed +in the <i>callout_data</i> field of a <b>pcre_extra</b> or <b>pcre[16|32]_extra</b> +data structure. If no such data was passed, the value of <i>callout_data</i> in +a callout block is NULL. There is a description of the <b>pcre_extra</b> +structure in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<P> +The <i>pattern_position</i> field is present from version 1 of the callout +structure. It contains the offset to the next item to be matched in the pattern +string. +</P> +<P> +The <i>next_item_length</i> field is present from version 1 of the callout +structure. It contains the length of the next item to be matched in the pattern +string. When the callout immediately precedes an alternation bar, a closing +parenthesis, or the end of the pattern, the length is zero. When the callout +precedes an opening parenthesis, the length is that of the entire subpattern. +</P> +<P> +The <i>pattern_position</i> and <i>next_item_length</i> fields are intended to +help in distinguishing between different automatic callouts, which all have the +same callout number. However, they are set for all callouts. +</P> +<P> +The <i>mark</i> field is present from version 2 of the callout structure. In +callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a +pointer to the zero-terminated name of the most recently passed (*MARK), +(*PRUNE), or (*THEN) item in the match, or NULL if no such items have been +passed. Instances of (*PRUNE) or (*THEN) without a name do not obliterate a +previous (*MARK). In callouts from the DFA matching functions this field always +contains NULL. +</P> +<br><a name="SEC5" href="#TOC1">RETURN VALUES</a><br> +<P> +The external callout function returns an integer to PCRE. If the value is zero, +matching proceeds as normal. If the value is greater than zero, matching fails +at the current point, but the testing of other matching possibilities goes +ahead, just as if a lookahead assertion had failed. If the value is less than +zero, the match is abandoned, the matching function returns the negative value. +</P> +<P> +Negative values should normally be chosen from the set of PCRE_ERROR_xxx +values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure. +The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; +it will never be used by PCRE itself. +</P> +<br><a name="SEC6" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC7" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 November 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrecompat.html b/doc/html/pcrecompat.html new file mode 100644 index 0000000..3e62266 --- /dev/null +++ b/doc/html/pcrecompat.html @@ -0,0 +1,235 @@ +<html> +<head> +<title>pcrecompat specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrecompat man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +DIFFERENCES BETWEEN PCRE AND PERL +</b><br> +<P> +This document describes the differences in the ways that PCRE and Perl handle +regular expressions. The differences described here are with respect to Perl +versions 5.10 and above. +</P> +<P> +1. PCRE has only a subset of Perl's Unicode support. Details of what it does +have are given in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. +</P> +<P> +2. PCRE allows repeat quantifiers only on parenthesized assertions, but they do +not mean what you might think. For example, (?!a){3} does not assert that the +next three characters are not "a". It just asserts that the next character is +not "a" three times (in principle: PCRE optimizes this to run the assertion +just once). Perl allows repeat quantifiers on other assertions such as \b, but +these do not seem to have any use. +</P> +<P> +3. Capturing subpatterns that occur inside negative lookahead assertions are +counted, but their entries in the offsets vector are never set. Perl sometimes +(but not always) sets its numerical variables from inside negative assertions. +</P> +<P> +4. Though binary zero characters are supported in the subject string, they are +not allowed in a pattern string because it is passed as a normal C string, +terminated by zero. The escape sequence \0 can be used in the pattern to +represent a binary zero. +</P> +<P> +5. The following Perl escape sequences are not supported: \l, \u, \L, +\U, and \N when followed by a character name or Unicode value. (\N on its +own, matching a non-newline character, is supported.) In fact these are +implemented by Perl's general string-handling and are not part of its pattern +matching engine. If any of these are encountered by PCRE, an error is +generated by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set, +\U and \u are interpreted as JavaScript interprets them. +</P> +<P> +6. The Perl escape sequences \p, \P, and \X are supported only if PCRE is +built with Unicode character property support. The properties that can be +tested with \p and \P are limited to the general category properties such as +Lu and Nd, script names such as Greek or Han, and the derived properties Any +and L&. PCRE does support the Cs (surrogate) property, which Perl does not; the +Perl documentation says "Because Perl hides the need for the user to understand +the internal representation of Unicode characters, there is no need to +implement the somewhat messy concept of surrogates." +</P> +<P> +7. PCRE does support the \Q...\E escape for quoting substrings. Characters in +between are treated as literals. This is slightly different from Perl in that $ +and @ are also handled as literals inside the quotes. In Perl, they cause +variable interpolation (but of course PCRE does not have variables). Note the +following examples: +<pre> + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz +</pre> +The \Q...\E sequence is recognized both inside and outside character classes. +</P> +<P> +8. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) +constructions. However, there is support for recursive patterns. This is not +available in Perl 5.8, but it is in Perl 5.10. Also, the PCRE "callout" +feature allows an external function to be called during pattern matching. See +the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation for details. +</P> +<P> +9. Subpatterns that are called as subroutines (whether or not recursively) are +always treated as atomic groups in PCRE. This is like Python, but unlike Perl. +Captured values that are set outside a subroutine call can be reference from +inside in PCRE, but not in Perl. There is a discussion that explains these +differences in more detail in the +<a href="pcrepattern.html#recursiondifference">section on recursion differences from Perl</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +page. +</P> +<P> +10. If any of the backtracking control verbs are used in a subpattern that is +called as a subroutine (whether or not recursively), their effect is confined +to that subpattern; it does not extend to the surrounding pattern. This is not +always the case in Perl. In particular, if (*THEN) is present in a group that +is called as a subroutine, its action is limited to that group, even if the +group does not contain any | characters. Note that such subpatterns are +processed as anchored at the point where they are tested. +</P> +<P> +11. If a pattern contains more than one backtracking control verb, the first +one that is backtracked onto acts. For example, in the pattern +A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure in C +triggers (*PRUNE). Perl's behaviour is more complex; in many cases it is the +same as PCRE, but there are examples where it differs. +</P> +<P> +12. Most backtracking verbs in assertions have their normal actions. They are +not confined to the assertion. +</P> +<P> +13. There are some differences that are concerned with the settings of captured +strings when part of a pattern is repeated. For example, matching "aba" against +the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". +</P> +<P> +14. PCRE's handling of duplicate subpattern numbers and duplicate subpattern +names is not as general as Perl's. This is a consequence of the fact the PCRE +works internally just with numbers, using an external table to translate +between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B), +where the two capturing parentheses have the same number but different names, +is not supported, and causes an error at compile time. If it were allowed, it +would not be possible to distinguish which parentheses matched, because both +names map to capturing subpattern number 1. To avoid this confusing situation, +an error is given at compile time. +</P> +<P> +15. Perl recognizes comments in some places that PCRE does not, for example, +between the ( and ? at the start of a subpattern. If the /x modifier is set, +Perl allows white space between ( and ? (though current Perls warn that this is +deprecated) but PCRE never does, even if the PCRE_EXTENDED option is set. +</P> +<P> +16. Perl, when in warning mode, gives warnings for character classes such as +[A-\d] or [a-[:digit:]]. It then treats the hyphens as literals. PCRE has no +warning features, so it gives an error in these cases because they are almost +certainly user mistakes. +</P> +<P> +17. In PCRE, the upper/lower case character properties Lu and Ll are not +affected when case-independent matching is specified. For example, \p{Lu} +always matches an upper case letter. I think Perl has changed in this respect; +in the release at the time of writing (5.16), \p{Lu} and \p{Ll} match all +letters, regardless of case, when case independence is specified. +</P> +<P> +18. PCRE provides some extensions to the Perl regular expression facilities. +Perl 5.10 includes new features that are not in earlier versions of Perl, some +of which (such as named parentheses) have been in PCRE for some time. This list +is with respect to Perl 5.10: +<br> +<br> +(a) Although lookbehind assertions in PCRE must match fixed length strings, +each alternative branch of a lookbehind assertion can match a different length +of string. Perl requires them all to have the same length. +<br> +<br> +(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ +meta-character matches only at the very end of the string. +<br> +<br> +(c) If PCRE_EXTRA is set, a backslash followed by a letter with no special +meaning is faulted. Otherwise, like Perl, the backslash is quietly ignored. +(Perl can be made to issue a warning.) +<br> +<br> +(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is +inverted, that is, by default they are not greedy, but if followed by a +question mark they are. +<br> +<br> +(e) PCRE_ANCHORED can be used at matching time to force a pattern to be tried +only at the first matching position in the subject string. +<br> +<br> +(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, and +PCRE_NO_AUTO_CAPTURE options for <b>pcre_exec()</b> have no Perl equivalents. +<br> +<br> +(g) The \R escape sequence can be restricted to match only CR, LF, or CRLF +by the PCRE_BSR_ANYCRLF option. +<br> +<br> +(h) The callout facility is PCRE-specific. +<br> +<br> +(i) The partial matching facility is PCRE-specific. +<br> +<br> +(j) Patterns compiled by PCRE can be saved and re-used at a later time, even on +different hosts that have the other endianness. However, this does not apply to +optimized data created by the just-in-time compiler. +<br> +<br> +(k) The alternative matching functions (<b>pcre_dfa_exec()</b>, +<b>pcre16_dfa_exec()</b> and <b>pcre32_dfa_exec()</b>,) match in a different way +and are not Perl-compatible. +<br> +<br> +(l) PCRE recognizes some special sequences such as (*CR) at the start of +a pattern that set overall options that cannot be changed within the pattern. +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 10 November 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrecpp.html b/doc/html/pcrecpp.html new file mode 100644 index 0000000..b7eac3a --- /dev/null +++ b/doc/html/pcrecpp.html @@ -0,0 +1,368 @@ +<html> +<head> +<title>pcrecpp specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrecpp man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS OF C++ WRAPPER</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">MATCHING INTERFACE</a> +<li><a name="TOC4" href="#SEC4">QUOTING METACHARACTERS</a> +<li><a name="TOC5" href="#SEC5">PARTIAL MATCHES</a> +<li><a name="TOC6" href="#SEC6">UTF-8 AND THE MATCHING INTERFACE</a> +<li><a name="TOC7" href="#SEC7">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a> +<li><a name="TOC8" href="#SEC8">SCANNING TEXT INCREMENTALLY</a> +<li><a name="TOC9" href="#SEC9">PARSING HEX/OCTAL/C-RADIX NUMBERS</a> +<li><a name="TOC10" href="#SEC10">REPLACING PARTS OF STRINGS</a> +<li><a name="TOC11" href="#SEC11">AUTHOR</a> +<li><a name="TOC12" href="#SEC12">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS OF C++ WRAPPER</a><br> +<P> +<b>#include <pcrecpp.h></b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +The C++ wrapper for PCRE was provided by Google Inc. Some additional +functionality was added by Giuseppe Maxia. This brief man page was constructed +from the notes in the <i>pcrecpp.h</i> file, which should be consulted for +further details. Note that the C++ wrapper supports only the original 8-bit +PCRE library. There is no 16-bit or 32-bit support at present. +</P> +<br><a name="SEC3" href="#TOC1">MATCHING INTERFACE</a><br> +<P> +The "FullMatch" operation checks that supplied text matches a supplied pattern +exactly. If pointer arguments are supplied, it copies matched sub-strings that +match sub-patterns into them. +<pre> + Example: successful match + pcrecpp::RE re("h.*o"); + re.FullMatch("hello"); + + Example: unsuccessful match (requires full match): + pcrecpp::RE re("e"); + !re.FullMatch("hello"); + + Example: creating a temporary RE object: + pcrecpp::RE("h.*o").FullMatch("hello"); +</pre> +You can pass in a "const char*" or a "string" for "text". The examples below +tend to use a const char*. You can, as in the different examples above, store +the RE object explicitly in a variable or use a temporary RE object. The +examples below use one mode or the other arbitrarily. Either could correctly be +used for any of these examples. +</P> +<P> +You must supply extra pointer arguments to extract matched subpieces. +<pre> + Example: extracts "ruby" into "s" and 1234 into "i" + int i; + string s; + pcrecpp::RE re("(\\w+):(\\d+)"); + re.FullMatch("ruby:1234", &s, &i); + + Example: does not try to extract any extra sub-patterns + re.FullMatch("ruby:1234", &s); + + Example: does not try to extract into NULL + re.FullMatch("ruby:1234", NULL, &i); + + Example: integer overflow causes failure + !re.FullMatch("ruby:1234567891234", NULL, &i); + + Example: fails because there aren't enough sub-patterns: + !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s); + + Example: fails because string cannot be stored in integer + !pcrecpp::RE("(.*)").FullMatch("ruby", &i); +</pre> +The provided pointer arguments can be pointers to any scalar numeric +type, or one of: +<pre> + string (matched piece is copied to string) + StringPiece (StringPiece is mutated to point to matched piece) + T (where "bool T::ParseFrom(const char*, int)" exists) + NULL (the corresponding matched sub-pattern is not copied) +</pre> +The function returns true iff all of the following conditions are satisfied: +<pre> + a. "text" matches "pattern" exactly; + + b. The number of matched sub-patterns is >= number of supplied + pointers; + + c. The "i"th argument has a suitable type for holding the + string captured as the "i"th sub-pattern. If you pass in + void * NULL for the "i"th argument, or a non-void * NULL + of the correct type, or pass fewer arguments than the + number of sub-patterns, "i"th captured sub-pattern is + ignored. +</pre> +CAVEAT: An optional sub-pattern that does not exist in the matched +string is assigned the empty string. Therefore, the following will +return false (because the empty string is not a valid number): +<pre> + int number; + pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number); +</pre> +The matching interface supports at most 16 arguments per call. +If you need more, consider using the more general interface +<b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for +<b>DoMatch</b>. +</P> +<P> +NOTE: Do not use <b>no_arg</b>, which is used internally to mark the end of a +list of optional arguments, as a placeholder for missing arguments, as this can +lead to segfaults. +</P> +<br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br> +<P> +You can use the "QuoteMeta" operation to insert backslashes before all +potentially meaningful characters in a string. The returned string, used as a +regular expression, will exactly match the original string. +<pre> + Example: + string quoted = RE::QuoteMeta(unquoted); +</pre> +Note that it's legal to escape a character even if it has no special meaning in +a regular expression -- so this function does that. (This also makes it +identical to the perl function of the same name; see "perldoc -f quotemeta".) +For example, "1.5-2.0?" becomes "1\.5\-2\.0\?". +</P> +<br><a name="SEC5" href="#TOC1">PARTIAL MATCHES</a><br> +<P> +You can use the "PartialMatch" operation when you want the pattern +to match any substring of the text. +<pre> + Example: simple search for a string: + pcrecpp::RE("ell").PartialMatch("hello"); + + Example: find first number in a string: + int number; + pcrecpp::RE re("(\\d+)"); + re.PartialMatch("x*100 + 20", &number); + assert(number == 100); +</PRE> +</P> +<br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br> +<P> +By default, pattern and text are plain text, one byte per character. The UTF8 +flag, passed to the constructor, causes both pattern and string to be treated +as UTF-8 text, still a byte stream but potentially multiple bytes per +character. In practice, the text is likelier to be UTF-8 than the pattern, but +the match returned may depend on the UTF8 flag, so always use it when matching +UTF8 text. For example, "." will match one byte normally but with UTF8 set may +match up to three bytes of a multi-byte character. +<pre> + Example: + pcrecpp::RE_Options options; + options.set_utf8(); + pcrecpp::RE re(utf8_pattern, options); + re.FullMatch(utf8_string); + + Example: using the convenience function UTF8(): + pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8()); + re.FullMatch(utf8_string); +</pre> +NOTE: The UTF8 flag is ignored if pcre was not configured with the +<pre> + --enable-utf8 flag. +</PRE> +</P> +<br><a name="SEC7" href="#TOC1">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a><br> +<P> +PCRE defines some modifiers to change the behavior of the regular expression +engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to +pass such modifiers to a RE class. Currently, the following modifiers are +supported: +<pre> + modifier description Perl corresponding + + PCRE_CASELESS case insensitive match /i + PCRE_MULTILINE multiple lines match /m + PCRE_DOTALL dot matches newlines /s + PCRE_DOLLAR_ENDONLY $ matches only at end N/A + PCRE_EXTRA strict escape parsing N/A + PCRE_EXTENDED ignore white spaces /x + PCRE_UTF8 handles UTF8 chars built-in + PCRE_UNGREEDY reverses * and *? N/A + PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*) +</pre> +(*) Both Perl and PCRE allow non capturing parentheses by means of the +"?:" modifier within the pattern itself. e.g. (?:ab|cd) does not +capture, while (ab|cd) does. +</P> +<P> +For a full account on how each modifier works, please check the +PCRE API reference page. +</P> +<P> +For each modifier, there are two member functions whose name is made +out of the modifier in lowercase, without the "PCRE_" prefix. For +instance, PCRE_CASELESS is handled by +<pre> + bool caseless() +</pre> +which returns true if the modifier is set, and +<pre> + RE_Options & set_caseless(bool) +</pre> +which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be +accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member +functions. Setting <i>match_limit</i> to a non-zero value will limit the +execution of pcre to keep it from doing bad things like blowing the stack or +taking an eternity to return a result. A value of 5000 is good enough to stop +stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables +match limiting. Alternatively, you can call <b>match_limit_recursion()</b> +which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE +recurses. <b>match_limit()</b> limits the number of matches PCRE does; +<b>match_limit_recursion()</b> limits the depth of internal recursion, and +therefore the amount of stack that is used. +</P> +<P> +Normally, to pass one or more modifiers to a RE class, you declare +a <i>RE_Options</i> object, set the appropriate options, and pass this +object to a RE constructor. Example: +<pre> + RE_Options opt; + opt.set_caseless(true); + if (RE("HELLO", opt).PartialMatch("hello world")) ... +</pre> +RE_options has two constructors. The default constructor takes no arguments and +creates a set of flags that are off by default. The optional parameter +<i>option_flags</i> is to facilitate transfer of legacy code from C programs. +This lets you do +<pre> + RE(pattern, + RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str); +</pre> +However, new code is better off doing +<pre> + RE(pattern, + RE_Options().set_caseless(true).set_multiline(true)) + .PartialMatch(str); +</pre> +If you are going to pass one of the most used modifiers, there are some +convenience functions that return a RE_Options class with the +appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>, +<b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>. +</P> +<P> +If you need to set several options at once, and you don't want to go through +the pains of declaring a RE_Options object and setting several options, there +is a parallel method that give you such ability on the fly. You can concatenate +several <b>set_xxxxx()</b> member functions, since each of them returns a +reference to its class object. For example, to pass PCRE_CASELESS, +PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write: +<pre> + RE(" ^ xyz \\s+ .* blah$", + RE_Options() + .set_caseless(true) + .set_extended(true) + .set_multiline(true)).PartialMatch(sometext); + +</PRE> +</P> +<br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br> +<P> +The "Consume" operation may be useful if you want to repeatedly +match regular expressions at the front of a string and skip over +them as they match. This requires use of the "StringPiece" type, +which represents a sub-range of a real string. Like RE, StringPiece +is defined in the pcrecpp namespace. +<pre> + Example: read lines of the form "var = value" from a string. + string contents = ...; // Fill string somehow + pcrecpp::StringPiece input(contents); // Wrap in a StringPiece + + string var; + int value; + pcrecpp::RE re("(\\w+) = (\\d+)\n"); + while (re.Consume(&input, &var, &value)) { + ...; + } +</pre> +Each successful call to "Consume" will set "var/value", and also +advance "input" so it points past the matched text. +</P> +<P> +The "FindAndConsume" operation is similar to "Consume" but does not +anchor your match at the beginning of the string. For example, you +could extract all words from a string by repeatedly calling +<pre> + pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word) +</PRE> +</P> +<br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br> +<P> +By default, if you pass a pointer to a numeric value, the +corresponding text is interpreted as a base-10 number. You can +instead wrap the pointer with a call to one of the operators Hex(), +Octal(), or CRadix() to interpret the text in another base. The +CRadix operator interprets C-style "0" (base-8) and "0x" (base-16) +prefixes, but defaults to base-10. +<pre> + Example: + int a, b, c, d; + pcrecpp::RE re("(.*) (.*) (.*) (.*)"); + re.FullMatch("100 40 0100 0x40", + pcrecpp::Octal(&a), pcrecpp::Hex(&b), + pcrecpp::CRadix(&c), pcrecpp::CRadix(&d)); +</pre> +will leave 64 in a, b, c, and d. +</P> +<br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br> +<P> +You can replace the first match of "pattern" in "str" with "rewrite". +Within "rewrite", backslash-escaped digits (\1 to \9) can be +used to insert text matching corresponding parenthesized group +from the pattern. \0 in "rewrite" refers to the entire matching +text. For example: +<pre> + string s = "yabba dabba doo"; + pcrecpp::RE("b+").Replace("d", &s); +</pre> +will leave "s" containing "yada dabba doo". The result is true if the pattern +matches and a replacement occurs, false otherwise. +</P> +<P> +<b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all +occurrences of the pattern in the string with the rewrite. Replacements are +not subject to re-matching. For example: +<pre> + string s = "yabba dabba doo"; + pcrecpp::RE("b+").GlobalReplace("d", &s); +</pre> +will leave "s" containing "yada dada doo". It returns the number of +replacements made. +</P> +<P> +<b>Extract</b> is like <b>Replace</b>, except that if the pattern matches, +"rewrite" is copied into "out" (an additional argument) with substitutions. +The non-matching portions of "text" are ignored. Returns true iff a match +occurred and the extraction happened successfully; if no match occurs, the +string is left unaffected. +</P> +<br><a name="SEC11" href="#TOC1">AUTHOR</a><br> +<P> +The C++ wrapper was contributed by Google Inc. +<br> +Copyright © 2007 Google Inc. +<br> +</P> +<br><a name="SEC12" href="#TOC1">REVISION</a><br> +<P> +Last updated: 08 January 2012 +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcredemo.html b/doc/html/pcredemo.html new file mode 100644 index 0000000..894a930 --- /dev/null +++ b/doc/html/pcredemo.html @@ -0,0 +1,426 @@ +<html> +<head> +<title>pcredemo specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcredemo man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +</ul> +<PRE> +/************************************************* +* PCRE DEMONSTRATION PROGRAM * +*************************************************/ + +/* This is a demonstration program to illustrate the most straightforward ways +of calling the PCRE regular expression library from a C program. See the +pcresample documentation for a short discussion ("man pcresample" if you have +the PCRE man pages installed). + +In Unix-like environments, if PCRE is installed in your standard system +libraries, you should be able to compile this program using this command: + +gcc -Wall pcredemo.c -lpcre -o pcredemo + +If PCRE is not installed in a standard place, it is likely to be installed with +support for the pkg-config mechanism. If you have pkg-config, you can compile +this program using this command: + +gcc -Wall pcredemo.c `pkg-config --cflags --libs libpcre` -o pcredemo + +If you do not have pkg-config, you may have to use this: + +gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \ + -R/usr/local/lib -lpcre -o pcredemo + +Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and +library files for PCRE are installed on your system. Only some operating +systems (e.g. Solaris) use the -R option. + +Building under Windows: + +If you want to statically link this program against a non-dll .a file, you must +define PCRE_STATIC before including pcre.h, otherwise the pcre_malloc() and +pcre_free() exported functions will be declared __declspec(dllimport), with +unwanted results. So in this environment, uncomment the following line. */ + +/* #define PCRE_STATIC */ + +#include <stdio.h> +#include <string.h> +#include <pcre.h> + +#define OVECCOUNT 30 /* should be a multiple of 3 */ + + +int main(int argc, char **argv) +{ +pcre *re; +const char *error; +char *pattern; +char *subject; +unsigned char *name_table; +unsigned int option_bits; +int erroffset; +int find_all; +int crlf_is_newline; +int namecount; +int name_entry_size; +int ovector[OVECCOUNT]; +int subject_length; +int rc, i; +int utf8; + + +/************************************************************************** +* First, sort out the command line. There is only one possible option at * +* the moment, "-g" to request repeated matching to find all occurrences, * +* like Perl's /g option. We set the variable find_all to a non-zero value * +* if the -g option is present. Apart from that, there must be exactly two * +* arguments. * +**************************************************************************/ + +find_all = 0; +for (i = 1; i < argc; i++) + { + if (strcmp(argv[i], "-g") == 0) find_all = 1; + else break; + } + +/* After the options, we require exactly two arguments, which are the pattern, +and the subject string. */ + +if (argc - i != 2) + { + printf("Two arguments required: a regex and a subject string\n"); + return 1; + } + +pattern = argv[i]; +subject = argv[i+1]; +subject_length = (int)strlen(subject); + + +/************************************************************************* +* Now we are going to compile the regular expression pattern, and handle * +* and errors that are detected. * +*************************************************************************/ + +re = pcre_compile( + pattern, /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ + +/* Compilation failed: print the error message and exit */ + +if (re == NULL) + { + printf("PCRE compilation failed at offset %d: %s\n", erroffset, error); + return 1; + } + + +/************************************************************************* +* If the compilation succeeded, we call PCRE again, in order to do a * +* pattern match against the subject string. This does just ONE match. If * +* further matching is needed, it will be done below. * +*************************************************************************/ + +rc = pcre_exec( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + subject, /* the subject string */ + subject_length, /* the length of the subject */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* output vector for substring information */ + OVECCOUNT); /* number of elements in the output vector */ + +/* Matching failed: handle error cases */ + +if (rc < 0) + { + switch(rc) + { + case PCRE_ERROR_NOMATCH: printf("No match\n"); break; + /* + Handle other special cases if you like + */ + default: printf("Matching error %d\n", rc); break; + } + pcre_free(re); /* Release memory used for the compiled pattern */ + return 1; + } + +/* Match succeded */ + +printf("\nMatch succeeded at offset %d\n", ovector[0]); + + +/************************************************************************* +* We have found the first match within the subject string. If the output * +* vector wasn't big enough, say so. Then output any substrings that were * +* captured. * +*************************************************************************/ + +/* The output vector wasn't big enough */ + +if (rc == 0) + { + rc = OVECCOUNT/3; + printf("ovector only has room for %d captured substrings\n", rc - 1); + } + +/* Show substrings stored in the output vector by number. Obviously, in a real +application you might want to do things other than print them. */ + +for (i = 0; i < rc; i++) + { + char *substring_start = subject + ovector[2*i]; + int substring_length = ovector[2*i+1] - ovector[2*i]; + printf("%2d: %.*s\n", i, substring_length, substring_start); + } + + +/************************************************************************** +* That concludes the basic part of this demonstration program. We have * +* compiled a pattern, and performed a single match. The code that follows * +* shows first how to access named substrings, and then how to code for * +* repeated matches on the same subject. * +**************************************************************************/ + +/* See if there are any named substrings, and if so, show them by name. First +we have to extract the count of named parentheses from the pattern. */ + +(void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMECOUNT, /* number of named substrings */ + &namecount); /* where to put the answer */ + +if (namecount <= 0) printf("No named substrings\n"); else + { + unsigned char *tabptr; + printf("Named substrings\n"); + + /* Before we can access the substrings, we must extract the table for + translating names to numbers, and the size of each entry in the table. */ + + (void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMETABLE, /* address of the table */ + &name_table); /* where to put the answer */ + + (void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMEENTRYSIZE, /* size of each entry in the table */ + &name_entry_size); /* where to put the answer */ + + /* Now we can scan the table and, for each entry, print the number, the name, + and the substring itself. */ + + tabptr = name_table; + for (i = 0; i < namecount; i++) + { + int n = (tabptr[0] << 8) | tabptr[1]; + printf("(%d) %*s: %.*s\n", n, name_entry_size - 3, tabptr + 2, + ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]); + tabptr += name_entry_size; + } + } + + +/************************************************************************* +* If the "-g" option was given on the command line, we want to continue * +* to search for additional matches in the subject string, in a similar * +* way to the /g option in Perl. This turns out to be trickier than you * +* might think because of the possibility of matching an empty string. * +* What happens is as follows: * +* * +* If the previous match was NOT for an empty string, we can just start * +* the next match at the end of the previous one. * +* * +* If the previous match WAS for an empty string, we can't do that, as it * +* would lead to an infinite loop. Instead, a special call of pcre_exec() * +* is made with the PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED flags set. * +* The first of these tells PCRE that an empty string at the start of the * +* subject is not a valid match; other possibilities must be tried. The * +* second flag restricts PCRE to one match attempt at the initial string * +* position. If this match succeeds, an alternative to the empty string * +* match has been found, and we can print it and proceed round the loop, * +* advancing by the length of whatever was found. If this match does not * +* succeed, we still stay in the loop, advancing by just one character. * +* In UTF-8 mode, which can be set by (*UTF8) in the pattern, this may be * +* more than one byte. * +* * +* However, there is a complication concerned with newlines. When the * +* newline convention is such that CRLF is a valid newline, we must * +* advance by two characters rather than one. The newline convention can * +* be set in the regex by (*CR), etc.; if not, we must find the default. * +*************************************************************************/ + +if (!find_all) /* Check for -g */ + { + pcre_free(re); /* Release the memory used for the compiled pattern */ + return 0; /* Finish unless -g was given */ + } + +/* Before running the loop, check for UTF-8 and whether CRLF is a valid newline +sequence. First, find the options with which the regex was compiled; extract +the UTF-8 state, and mask off all but the newline options. */ + +(void)pcre_fullinfo(re, NULL, PCRE_INFO_OPTIONS, &option_bits); +utf8 = option_bits & PCRE_UTF8; +option_bits &= PCRE_NEWLINE_CR|PCRE_NEWLINE_LF|PCRE_NEWLINE_CRLF| + PCRE_NEWLINE_ANY|PCRE_NEWLINE_ANYCRLF; + +/* If no newline options were set, find the default newline convention from the +build configuration. */ + +if (option_bits == 0) + { + int d; + (void)pcre_config(PCRE_CONFIG_NEWLINE, &d); + /* Note that these values are always the ASCII ones, even in + EBCDIC environments. CR = 13, NL = 10. */ + option_bits = (d == 13)? PCRE_NEWLINE_CR : + (d == 10)? PCRE_NEWLINE_LF : + (d == (13<<8 | 10))? PCRE_NEWLINE_CRLF : + (d == -2)? PCRE_NEWLINE_ANYCRLF : + (d == -1)? PCRE_NEWLINE_ANY : 0; + } + +/* See if CRLF is a valid newline sequence. */ + +crlf_is_newline = + option_bits == PCRE_NEWLINE_ANY || + option_bits == PCRE_NEWLINE_CRLF || + option_bits == PCRE_NEWLINE_ANYCRLF; + +/* Loop for second and subsequent matches */ + +for (;;) + { + int options = 0; /* Normally no options */ + int start_offset = ovector[1]; /* Start at end of previous match */ + + /* If the previous match was for an empty string, we are finished if we are + at the end of the subject. Otherwise, arrange to run another match at the + same point to see if a non-empty match can be found. */ + + if (ovector[0] == ovector[1]) + { + if (ovector[0] == subject_length) break; + options = PCRE_NOTEMPTY_ATSTART | PCRE_ANCHORED; + } + + /* Run the next matching operation */ + + rc = pcre_exec( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + subject, /* the subject string */ + subject_length, /* the length of the subject */ + start_offset, /* starting offset in the subject */ + options, /* options */ + ovector, /* output vector for substring information */ + OVECCOUNT); /* number of elements in the output vector */ + + /* This time, a result of NOMATCH isn't an error. If the value in "options" + is zero, it just means we have found all possible matches, so the loop ends. + Otherwise, it means we have failed to find a non-empty-string match at a + point where there was a previous empty-string match. In this case, we do what + Perl does: advance the matching position by one character, and continue. We + do this by setting the "end of previous match" offset, because that is picked + up at the top of the loop as the point at which to start again. + + There are two complications: (a) When CRLF is a valid newline sequence, and + the current position is just before it, advance by an extra byte. (b) + Otherwise we must ensure that we skip an entire UTF-8 character if we are in + UTF-8 mode. */ + + if (rc == PCRE_ERROR_NOMATCH) + { + if (options == 0) break; /* All matches found */ + ovector[1] = start_offset + 1; /* Advance one byte */ + if (crlf_is_newline && /* If CRLF is newline & */ + start_offset < subject_length - 1 && /* we are at CRLF, */ + subject[start_offset] == '\r' && + subject[start_offset + 1] == '\n') + ovector[1] += 1; /* Advance by one more. */ + else if (utf8) /* Otherwise, ensure we */ + { /* advance a whole UTF-8 */ + while (ovector[1] < subject_length) /* character. */ + { + if ((subject[ovector[1]] & 0xc0) != 0x80) break; + ovector[1] += 1; + } + } + continue; /* Go round the loop again */ + } + + /* Other matching errors are not recoverable. */ + + if (rc < 0) + { + printf("Matching error %d\n", rc); + pcre_free(re); /* Release memory used for the compiled pattern */ + return 1; + } + + /* Match succeded */ + + printf("\nMatch succeeded again at offset %d\n", ovector[0]); + + /* The match succeeded, but the output vector wasn't big enough. */ + + if (rc == 0) + { + rc = OVECCOUNT/3; + printf("ovector only has room for %d captured substrings\n", rc - 1); + } + + /* As before, show substrings stored in the output vector by number, and then + also any named substrings. */ + + for (i = 0; i < rc; i++) + { + char *substring_start = subject + ovector[2*i]; + int substring_length = ovector[2*i+1] - ovector[2*i]; + printf("%2d: %.*s\n", i, substring_length, substring_start); + } + + if (namecount <= 0) printf("No named substrings\n"); else + { + unsigned char *tabptr = name_table; + printf("Named substrings\n"); + for (i = 0; i < namecount; i++) + { + int n = (tabptr[0] << 8) | tabptr[1]; + printf("(%d) %*s: %.*s\n", n, name_entry_size - 3, tabptr + 2, + ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]); + tabptr += name_entry_size; + } + } + } /* End of loop to find second and subsequent matches */ + +printf("\n"); +pcre_free(re); /* Release memory used for the compiled pattern */ +return 0; +} + +/* End of pcredemo.c */ +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcregrep.html b/doc/html/pcregrep.html new file mode 100644 index 0000000..dacbb49 --- /dev/null +++ b/doc/html/pcregrep.html @@ -0,0 +1,759 @@ +<html> +<head> +<title>pcregrep specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcregrep man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">SUPPORT FOR COMPRESSED FILES</a> +<li><a name="TOC4" href="#SEC4">BINARY FILES</a> +<li><a name="TOC5" href="#SEC5">OPTIONS</a> +<li><a name="TOC6" href="#SEC6">ENVIRONMENT VARIABLES</a> +<li><a name="TOC7" href="#SEC7">NEWLINES</a> +<li><a name="TOC8" href="#SEC8">OPTIONS COMPATIBILITY</a> +<li><a name="TOC9" href="#SEC9">OPTIONS WITH DATA</a> +<li><a name="TOC10" href="#SEC10">MATCHING ERRORS</a> +<li><a name="TOC11" href="#SEC11">DIAGNOSTICS</a> +<li><a name="TOC12" href="#SEC12">SEE ALSO</a> +<li><a name="TOC13" href="#SEC13">AUTHOR</a> +<li><a name="TOC14" href="#SEC14">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>pcregrep [options] [long options] [pattern] [path1 path2 ...]</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +<b>pcregrep</b> searches files for character patterns, in the same way as other +grep commands do, but it uses the PCRE regular expression library to support +patterns that are compatible with the regular expressions of Perl 5. See +<a href="pcresyntax.html"><b>pcresyntax</b>(3)</a> +for a quick-reference summary of pattern syntax, or +<a href="pcrepattern.html"><b>pcrepattern</b>(3)</a> +for a full description of the syntax and semantics of the regular expressions +that PCRE supports. +</P> +<P> +Patterns, whether supplied on the command line or in a separate file, are given +without delimiters. For example: +<pre> + pcregrep Thursday /etc/motd +</pre> +If you attempt to use delimiters (for example, by surrounding a pattern with +slashes, as is common in Perl scripts), they are interpreted as part of the +pattern. Quotes can of course be used to delimit patterns on the command line +because they are interpreted by the shell, and indeed quotes are required if a +pattern contains white space or shell metacharacters. +</P> +<P> +The first argument that follows any option settings is treated as the single +pattern to be matched when neither <b>-e</b> nor <b>-f</b> is present. +Conversely, when one or both of these options are used to specify patterns, all +arguments are treated as path names. At least one of <b>-e</b>, <b>-f</b>, or an +argument pattern must be provided. +</P> +<P> +If no files are specified, <b>pcregrep</b> reads the standard input. The +standard input can also be referenced by a name consisting of a single hyphen. +For example: +<pre> + pcregrep some-pattern /file1 - /file3 +</pre> +By default, each line that matches a pattern is copied to the standard +output, and if there is more than one file, the file name is output at the +start of each line, followed by a colon. However, there are options that can +change how <b>pcregrep</b> behaves. In particular, the <b>-M</b> option makes it +possible to search for patterns that span line boundaries. What defines a line +boundary is controlled by the <b>-N</b> (<b>--newline</b>) option. +</P> +<P> +The amount of memory used for buffering files that are being scanned is +controlled by a parameter that can be set by the <b>--buffer-size</b> option. +The default value for this parameter is specified when <b>pcregrep</b> is built, +with the default default being 20K. A block of memory three times this size is +used (to allow for buffering "before" and "after" lines). An error occurs if a +line overflows the buffer. +</P> +<P> +Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the greater. +BUFSIZ is defined in <b><stdio.h></b>. When there is more than one pattern +(specified by the use of <b>-e</b> and/or <b>-f</b>), each pattern is applied to +each line in the order in which they are defined, except that all the <b>-e</b> +patterns are tried before the <b>-f</b> patterns. +</P> +<P> +By default, as soon as one pattern matches a line, no further patterns are +considered. However, if <b>--colour</b> (or <b>--color</b>) is used to colour the +matching substrings, or if <b>--only-matching</b>, <b>--file-offsets</b>, or +<b>--line-offsets</b> is used to output only the part of the line that matched +(either shown literally, or as an offset), scanning resumes immediately +following the match, so that further matches on the same line can be found. If +there are multiple patterns, they are all tried on the remainder of the line, +but patterns that follow the one that matched are not tried on the earlier part +of the line. +</P> +<P> +This behaviour means that the order in which multiple patterns are specified +can affect the output when one of the above options is used. This is no longer +the same behaviour as GNU grep, which now manages to display earlier matches +for later patterns (as long as there is no overlap). +</P> +<P> +Patterns that can match an empty string are accepted, but empty string +matches are never recognized. An example is the pattern "(super)?(man)?", in +which all components are optional. This pattern finds all occurrences of both +"super" and "man"; the output differs from matching with "super|man" when only +the matching substrings are being shown. +</P> +<P> +If the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variable is set, +<b>pcregrep</b> uses the value to set a locale when calling the PCRE library. +The <b>--locale</b> option can be used to override this. +</P> +<br><a name="SEC3" href="#TOC1">SUPPORT FOR COMPRESSED FILES</a><br> +<P> +It is possible to compile <b>pcregrep</b> so that it uses <b>libz</b> or +<b>libbz2</b> to read files whose names end in <b>.gz</b> or <b>.bz2</b>, +respectively. You can find out whether your binary has support for one or both +of these file types by running it with the <b>--help</b> option. If the +appropriate support is not present, files are treated as plain text. The +standard input is always so treated. +</P> +<br><a name="SEC4" href="#TOC1">BINARY FILES</a><br> +<P> +By default, a file that contains a binary zero byte within the first 1024 bytes +is identified as a binary file, and is processed specially. (GNU grep also +identifies binary files in this manner.) See the <b>--binary-files</b> option +for a means of changing the way binary files are handled. +</P> +<br><a name="SEC5" href="#TOC1">OPTIONS</a><br> +<P> +The order in which some of the options appear can affect the output. For +example, both the <b>-h</b> and <b>-l</b> options affect the printing of file +names. Whichever comes later in the command line will be the one that takes +effect. Similarly, except where noted below, if an option is given twice, the +later setting is used. Numerical values for options may be followed by K or M, +to signify multiplication by 1024 or 1024*1024 respectively. +</P> +<P> +<b>--</b> +This terminates the list of options. It is useful if the next item on the +command line starts with a hyphen but is not an option. This allows for the +processing of patterns and filenames that start with hyphens. +</P> +<P> +<b>-A</b> <i>number</i>, <b>--after-context=</b><i>number</i> +Output <i>number</i> lines of context after each matching line. If filenames +and/or line numbers are being output, a hyphen separator is used instead of a +colon for the context lines. A line containing "--" is output between each +group of lines, unless they are in fact contiguous in the input file. The value +of <i>number</i> is expected to be relatively small. However, <b>pcregrep</b> +guarantees to have up to 8K of following text available for context output. +</P> +<P> +<b>-a</b>, <b>--text</b> +Treat binary files as text. This is equivalent to +<b>--binary-files</b>=<i>text</i>. +</P> +<P> +<b>-B</b> <i>number</i>, <b>--before-context=</b><i>number</i> +Output <i>number</i> lines of context before each matching line. If filenames +and/or line numbers are being output, a hyphen separator is used instead of a +colon for the context lines. A line containing "--" is output between each +group of lines, unless they are in fact contiguous in the input file. The value +of <i>number</i> is expected to be relatively small. However, <b>pcregrep</b> +guarantees to have up to 8K of preceding text available for context output. +</P> +<P> +<b>--binary-files=</b><i>word</i> +Specify how binary files are to be processed. If the word is "binary" (the +default), pattern matching is performed on binary files, but the only output is +"Binary file <name> matches" when a match succeeds. If the word is "text", +which is equivalent to the <b>-a</b> or <b>--text</b> option, binary files are +processed in the same way as any other file. In this case, when a match +succeeds, the output may be binary garbage, which can have nasty effects if +sent to a terminal. If the word is "without-match", which is equivalent to the +<b>-I</b> option, binary files are not processed at all; they are assumed not to +be of interest. +</P> +<P> +<b>--buffer-size=</b><i>number</i> +Set the parameter that controls how much memory is used for buffering files +that are being scanned. +</P> +<P> +<b>-C</b> <i>number</i>, <b>--context=</b><i>number</i> +Output <i>number</i> lines of context both before and after each matching line. +This is equivalent to setting both <b>-A</b> and <b>-B</b> to the same value. +</P> +<P> +<b>-c</b>, <b>--count</b> +Do not output individual lines from the files that are being scanned; instead +output the number of lines that would otherwise have been shown. If no lines +are selected, the number zero is output. If several files are are being +scanned, a count is output for each of them. However, if the +<b>--files-with-matches</b> option is also used, only those files whose counts +are greater than zero are listed. When <b>-c</b> is used, the <b>-A</b>, +<b>-B</b>, and <b>-C</b> options are ignored. +</P> +<P> +<b>--colour</b>, <b>--color</b> +If this option is given without any data, it is equivalent to "--colour=auto". +If data is required, it must be given in the same shell item, separated by an +equals sign. +</P> +<P> +<b>--colour=</b><i>value</i>, <b>--color=</b><i>value</i> +This option specifies under what circumstances the parts of a line that matched +a pattern should be coloured in the output. By default, the output is not +coloured. The value (which is optional, see above) may be "never", "always", or +"auto". In the latter case, colouring happens only if the standard output is +connected to a terminal. More resources are used when colouring is enabled, +because <b>pcregrep</b> has to search for all possible matches in a line, not +just one, in order to colour them all. +<br> +<br> +The colour that is used can be specified by setting the environment variable +PCREGREP_COLOUR or PCREGREP_COLOR. The value of this variable should be a +string of two numbers, separated by a semicolon. They are copied directly into +the control string for setting colour on a terminal, so it is your +responsibility to ensure that they make sense. If neither of the environment +variables is set, the default is "1;31", which gives red. +</P> +<P> +<b>-D</b> <i>action</i>, <b>--devices=</b><i>action</i> +If an input path is not a regular file or a directory, "action" specifies how +it is to be processed. Valid values are "read" (the default) or "skip" +(silently skip the path). +</P> +<P> +<b>-d</b> <i>action</i>, <b>--directories=</b><i>action</i> +If an input path is a directory, "action" specifies how it is to be processed. +Valid values are "read" (the default in non-Windows environments, for +compatibility with GNU grep), "recurse" (equivalent to the <b>-r</b> option), or +"skip" (silently skip the path, the default in Windows environments). In the +"read" case, directories are read as if they were ordinary files. In some +operating systems the effect of reading a directory like this is an immediate +end-of-file; in others it may provoke an error. +</P> +<P> +<b>-e</b> <i>pattern</i>, <b>--regex=</b><i>pattern</i>, <b>--regexp=</b><i>pattern</i> +Specify a pattern to be matched. This option can be used multiple times in +order to specify several patterns. It can also be used as a way of specifying a +single pattern that starts with a hyphen. When <b>-e</b> is used, no argument +pattern is taken from the command line; all arguments are treated as file +names. There is no limit to the number of patterns. They are applied to each +line in the order in which they are defined until one matches. +<br> +<br> +If <b>-f</b> is used with <b>-e</b>, the command line patterns are matched first, +followed by the patterns from the file(s), independent of the order in which +these options are specified. Note that multiple use of <b>-e</b> is not the same +as a single pattern with alternatives. For example, X|Y finds the first +character in a line that is X or Y, whereas if the two patterns are given +separately, with X first, <b>pcregrep</b> finds X if it is present, even if it +follows Y in the line. It finds Y only if there is no X in the line. This +matters only if you are using <b>-o</b> or <b>--colo(u)r</b> to show the part(s) +of the line that matched. +</P> +<P> +<b>--exclude</b>=<i>pattern</i> +Files (but not directories) whose names match the pattern are skipped without +being processed. This applies to all files, whether listed on the command line, +obtained from <b>--file-list</b>, or by scanning a directory. The pattern is a +PCRE regular expression, and is matched against the final component of the file +name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not +apply to this pattern. The option may be given any number of times in order to +specify multiple patterns. If a file name matches both an <b>--include</b> +and an <b>--exclude</b> pattern, it is excluded. There is no short form for this +option. +</P> +<P> +<b>--exclude-from=</b><i>filename</i> +Treat each non-empty line of the file as the data for an <b>--exclude</b> +option. What constitutes a newline when reading the file is the operating +system's default. The <b>--newline</b> option has no effect on this option. This +option may be given more than once in order to specify a number of files to +read. +</P> +<P> +<b>--exclude-dir</b>=<i>pattern</i> +Directories whose names match the pattern are skipped without being processed, +whatever the setting of the <b>--recursive</b> option. This applies to all +directories, whether listed on the command line, obtained from +<b>--file-list</b>, or by scanning a parent directory. The pattern is a PCRE +regular expression, and is matched against the final component of the directory +name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not +apply to this pattern. The option may be given any number of times in order to +specify more than one pattern. If a directory matches both <b>--include-dir</b> +and <b>--exclude-dir</b>, it is excluded. There is no short form for this +option. +</P> +<P> +<b>-F</b>, <b>--fixed-strings</b> +Interpret each data-matching pattern as a list of fixed strings, separated by +newlines, instead of as a regular expression. What constitutes a newline for +this purpose is controlled by the <b>--newline</b> option. The <b>-w</b> (match +as a word) and <b>-x</b> (match whole line) options can be used with <b>-F</b>. +They apply to each of the fixed strings. A line is selected if any of the fixed +strings are found in it (subject to <b>-w</b> or <b>-x</b>, if present). This +option applies only to the patterns that are matched against the contents of +files; it does not apply to patterns specified by any of the <b>--include</b> or +<b>--exclude</b> options. +</P> +<P> +<b>-f</b> <i>filename</i>, <b>--file=</b><i>filename</i> +Read patterns from the file, one per line, and match them against +each line of input. What constitutes a newline when reading the file is the +operating system's default. The <b>--newline</b> option has no effect on this +option. Trailing white space is removed from each line, and blank lines are +ignored. An empty file contains no patterns and therefore matches nothing. See +also the comments about multiple patterns versus a single pattern with +alternatives in the description of <b>-e</b> above. +<br> +<br> +If this option is given more than once, all the specified files are +read. A data line is output if any of the patterns match it. A filename can +be given as "-" to refer to the standard input. When <b>-f</b> is used, patterns +specified on the command line using <b>-e</b> may also be present; they are +tested before the file's patterns. However, no other pattern is taken from the +command line; all arguments are treated as the names of paths to be searched. +</P> +<P> +<b>--file-list</b>=<i>filename</i> +Read a list of files and/or directories that are to be scanned from the given +file, one per line. Trailing white space is removed from each line, and blank +lines are ignored. These paths are processed before any that are listed on the +command line. The filename can be given as "-" to refer to the standard input. +If <b>--file</b> and <b>--file-list</b> are both specified as "-", patterns are +read first. This is useful only when the standard input is a terminal, from +which further lines (the list of files) can be read after an end-of-file +indication. If this option is given more than once, all the specified files are +read. +</P> +<P> +<b>--file-offsets</b> +Instead of showing lines or parts of lines that match, show each match as an +offset from the start of the file and a length, separated by a comma. In this +mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b> +options are ignored. If there is more than one match in a line, each of them is +shown separately. This option is mutually exclusive with <b>--line-offsets</b> +and <b>--only-matching</b>. +</P> +<P> +<b>-H</b>, <b>--with-filename</b> +Force the inclusion of the filename at the start of output lines when searching +a single file. By default, the filename is not shown in this case. For matching +lines, the filename is followed by a colon; for context lines, a hyphen +separator is used. If a line number is also being output, it follows the file +name. +</P> +<P> +<b>-h</b>, <b>--no-filename</b> +Suppress the output filenames when searching multiple files. By default, +filenames are shown when multiple files are searched. For matching lines, the +filename is followed by a colon; for context lines, a hyphen separator is used. +If a line number is also being output, it follows the file name. +</P> +<P> +<b>--help</b> +Output a help message, giving brief details of the command options and file +type support, and then exit. Anything else on the command line is +ignored. +</P> +<P> +<b>-I</b> +Treat binary files as never matching. This is equivalent to +<b>--binary-files</b>=<i>without-match</i>. +</P> +<P> +<b>-i</b>, <b>--ignore-case</b> +Ignore upper/lower case distinctions during comparisons. +</P> +<P> +<b>--include</b>=<i>pattern</i> +If any <b>--include</b> patterns are specified, the only files that are +processed are those that match one of the patterns (and do not match an +<b>--exclude</b> pattern). This option does not affect directories, but it +applies to all files, whether listed on the command line, obtained from +<b>--file-list</b>, or by scanning a directory. The pattern is a PCRE regular +expression, and is matched against the final component of the file name, not +the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not apply to +this pattern. The option may be given any number of times. If a file name +matches both an <b>--include</b> and an <b>--exclude</b> pattern, it is excluded. +There is no short form for this option. +</P> +<P> +<b>--include-from=</b><i>filename</i> +Treat each non-empty line of the file as the data for an <b>--include</b> +option. What constitutes a newline for this purpose is the operating system's +default. The <b>--newline</b> option has no effect on this option. This option +may be given any number of times; all the files are read. +</P> +<P> +<b>--include-dir</b>=<i>pattern</i> +If any <b>--include-dir</b> patterns are specified, the only directories that +are processed are those that match one of the patterns (and do not match an +<b>--exclude-dir</b> pattern). This applies to all directories, whether listed +on the command line, obtained from <b>--file-list</b>, or by scanning a parent +directory. The pattern is a PCRE regular expression, and is matched against the +final component of the directory name, not the entire path. The <b>-F</b>, +<b>-w</b>, and <b>-x</b> options do not apply to this pattern. The option may be +given any number of times. If a directory matches both <b>--include-dir</b> and +<b>--exclude-dir</b>, it is excluded. There is no short form for this option. +</P> +<P> +<b>-L</b>, <b>--files-without-match</b> +Instead of outputting lines from the files, just output the names of the files +that do not contain any lines that would have been output. Each file name is +output once, on a separate line. +</P> +<P> +<b>-l</b>, <b>--files-with-matches</b> +Instead of outputting lines from the files, just output the names of the files +containing lines that would have been output. Each file name is output +once, on a separate line. Searching normally stops as soon as a matching line +is found in a file. However, if the <b>-c</b> (count) option is also used, +matching continues in order to obtain the correct count, and those files that +have at least one match are listed along with their counts. Using this option +with <b>-c</b> is a way of suppressing the listing of files with no matches. +</P> +<P> +<b>--label</b>=<i>name</i> +This option supplies a name to be used for the standard input when file names +are being output. If not supplied, "(standard input)" is used. There is no +short form for this option. +</P> +<P> +<b>--line-buffered</b> +When this option is given, input is read and processed line by line, and the +output is flushed after each write. By default, input is read in large chunks, +unless <b>pcregrep</b> can determine that it is reading from a terminal (which +is currently possible only in Unix-like environments). Output to terminal is +normally automatically flushed by the operating system. This option can be +useful when the input or output is attached to a pipe and you do not want +<b>pcregrep</b> to buffer up large amounts of data. However, its use will affect +performance, and the <b>-M</b> (multiline) option ceases to work. +</P> +<P> +<b>--line-offsets</b> +Instead of showing lines or parts of lines that match, show each match as a +line number, the offset from the start of the line, and a length. The line +number is terminated by a colon (as usual; see the <b>-n</b> option), and the +offset and length are separated by a comma. In this mode, no context is shown. +That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b> options are ignored. If there is +more than one match in a line, each of them is shown separately. This option is +mutually exclusive with <b>--file-offsets</b> and <b>--only-matching</b>. +</P> +<P> +<b>--locale</b>=<i>locale-name</i> +This option specifies a locale to be used for pattern matching. It overrides +the value in the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variables. If no +locale is specified, the PCRE library's default (usually the "C" locale) is +used. There is no short form for this option. +</P> +<P> +<b>--match-limit</b>=<i>number</i> +Processing some regular expression patterns can require a very large amount of +memory, leading in some cases to a program crash if not enough is available. +Other patterns may take a very long time to search for all possible matching +strings. The <b>pcre_exec()</b> function that is called by <b>pcregrep</b> to do +the matching has two parameters that can limit the resources that it uses. +<br> +<br> +The <b>--match-limit</b> option provides a means of limiting resource usage +when processing patterns that are not going to match, but which have a very +large number of possibilities in their search trees. The classic example is a +pattern that uses nested unlimited repeats. Internally, PCRE uses a function +called <b>match()</b> which it calls repeatedly (sometimes recursively). The +limit set by <b>--match-limit</b> is imposed on the number of times this +function is called during a match, which has the effect of limiting the amount +of backtracking that can take place. +<br> +<br> +The <b>--recursion-limit</b> option is similar to <b>--match-limit</b>, but +instead of limiting the total number of times that <b>match()</b> is called, it +limits the depth of recursive calls, which in turn limits the amount of memory +that can be used. The recursion depth is a smaller number than the total number +of calls, because not all calls to <b>match()</b> are recursive. This limit is +of use only if it is set smaller than <b>--match-limit</b>. +<br> +<br> +There are no short forms for these options. The default settings are specified +when the PCRE library is compiled, with the default default being 10 million. +</P> +<P> +<b>-M</b>, <b>--multiline</b> +Allow patterns to match more than one line. When this option is given, patterns +may usefully contain literal newline characters and internal occurrences of ^ +and $ characters. The output for a successful match may consist of more than +one line, the last of which is the one in which the match ended. If the matched +string ends with a newline sequence the output ends at the end of that line. +<br> +<br> +When this option is set, the PCRE library is called in "multiline" mode. +There is a limit to the number of lines that can be matched, imposed by the way +that <b>pcregrep</b> buffers the input file as it scans it. However, +<b>pcregrep</b> ensures that at least 8K characters or the rest of the document +(whichever is the shorter) are available for forward matching, and similarly +the previous 8K characters (or all the previous characters, if fewer than 8K) +are guaranteed to be available for lookbehind assertions. This option does not +work when input is read line by line (see \fP--line-buffered\fP.) +</P> +<P> +<b>-N</b> <i>newline-type</i>, <b>--newline</b>=<i>newline-type</i> +The PCRE library supports five different conventions for indicating +the ends of lines. They are the single-character sequences CR (carriage return) +and LF (linefeed), the two-character sequence CRLF, an "anycrlf" convention, +which recognizes any of the preceding three types, and an "any" convention, in +which any Unicode line ending sequence is assumed to end a line. The Unicode +sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF +(form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and +PS (paragraph separator, U+2029). +<br> +<br> +When the PCRE library is built, a default line-ending sequence is specified. +This is normally the standard sequence for the operating system. Unless +otherwise specified by this option, <b>pcregrep</b> uses the library's default. +The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This +makes it possible to use <b>pcregrep</b> to scan files that have come from other +environments without having to modify their line endings. If the data that is +being scanned does not agree with the convention set by this option, +<b>pcregrep</b> may behave in strange ways. Note that this option does not +apply to files specified by the <b>-f</b>, <b>--exclude-from</b>, or +<b>--include-from</b> options, which are expected to use the operating system's +standard newline sequence. +</P> +<P> +<b>-n</b>, <b>--line-number</b> +Precede each output line by its line number in the file, followed by a colon +for matching lines or a hyphen for context lines. If the filename is also being +output, it precedes the line number. This option is forced if +<b>--line-offsets</b> is used. +</P> +<P> +<b>--no-jit</b> +If the PCRE library is built with support for just-in-time compiling (which +speeds up matching), <b>pcregrep</b> automatically makes use of this, unless it +was explicitly disabled at build time. This option can be used to disable the +use of JIT at run time. It is provided for testing and working round problems. +It should never be needed in normal use. +</P> +<P> +<b>-o</b>, <b>--only-matching</b> +Show only the part of the line that matched a pattern instead of the whole +line. In this mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and +<b>-C</b> options are ignored. If there is more than one match in a line, each +of them is shown separately. If <b>-o</b> is combined with <b>-v</b> (invert the +sense of the match to find non-matching lines), no output is generated, but the +return code is set appropriately. If the matched portion of the line is empty, +nothing is output unless the file name or line number are being printed, in +which case they are shown on an otherwise empty line. This option is mutually +exclusive with <b>--file-offsets</b> and <b>--line-offsets</b>. +</P> +<P> +<b>-o</b><i>number</i>, <b>--only-matching</b>=<i>number</i> +Show only the part of the line that matched the capturing parentheses of the +given number. Up to 32 capturing parentheses are supported, and -o0 is +equivalent to <b>-o</b> without a number. Because these options can be given +without an argument (see above), if an argument is present, it must be given in +the same shell item, for example, -o3 or --only-matching=2. The comments given +for the non-argument case above also apply to this case. If the specified +capturing parentheses do not exist in the pattern, or were not set in the +match, nothing is output unless the file name or line number are being printed. +<br> +<br> +If this option is given multiple times, multiple substrings are output, in the +order the options are given. For example, -o3 -o1 -o3 causes the substrings +matched by capturing parentheses 3 and 1 and then 3 again to be output. By +default, there is no separator (but see the next option). +</P> +<P> +<b>--om-separator</b>=<i>text</i> +Specify a separating string for multiple occurrences of <b>-o</b>. The default +is an empty string. Separating strings are never coloured. +</P> +<P> +<b>-q</b>, <b>--quiet</b> +Work quietly, that is, display nothing except error messages. The exit +status indicates whether or not any matches were found. +</P> +<P> +<b>-r</b>, <b>--recursive</b> +If any given path is a directory, recursively scan the files it contains, +taking note of any <b>--include</b> and <b>--exclude</b> settings. By default, a +directory is read as a normal file; in some operating systems this gives an +immediate end-of-file. This option is a shorthand for setting the <b>-d</b> +option to "recurse". +</P> +<P> +<b>--recursion-limit</b>=<i>number</i> +See <b>--match-limit</b> above. +</P> +<P> +<b>-s</b>, <b>--no-messages</b> +Suppress error messages about non-existent or unreadable files. Such files are +quietly skipped. However, the return code is still 2, even if matches were +found in other files. +</P> +<P> +<b>-u</b>, <b>--utf-8</b> +Operate in UTF-8 mode. This option is available only if PCRE has been compiled +with UTF-8 support. All patterns (including those for any <b>--exclude</b> and +<b>--include</b> options) and all subject lines that are scanned must be valid +strings of UTF-8 characters. +</P> +<P> +<b>-V</b>, <b>--version</b> +Write the version numbers of <b>pcregrep</b> and the PCRE library to the +standard output and then exit. Anything else on the command line is +ignored. +</P> +<P> +<b>-v</b>, <b>--invert-match</b> +Invert the sense of the match, so that lines which do <i>not</i> match any of +the patterns are the ones that are found. +</P> +<P> +<b>-w</b>, <b>--word-regex</b>, <b>--word-regexp</b> +Force the patterns to match only whole words. This is equivalent to having \b +at the start and end of the pattern. This option applies only to the patterns +that are matched against the contents of files; it does not apply to patterns +specified by any of the <b>--include</b> or <b>--exclude</b> options. +</P> +<P> +<b>-x</b>, <b>--line-regex</b>, <b>--line-regexp</b> +Force the patterns to be anchored (each must start matching at the beginning of +a line) and in addition, require them to match entire lines. This is equivalent +to having ^ and $ characters at the start and end of each alternative branch in +every pattern. This option applies only to the patterns that are matched +against the contents of files; it does not apply to patterns specified by any +of the <b>--include</b> or <b>--exclude</b> options. +</P> +<br><a name="SEC6" href="#TOC1">ENVIRONMENT VARIABLES</a><br> +<P> +The environment variables <b>LC_ALL</b> and <b>LC_CTYPE</b> are examined, in that +order, for a locale. The first one that is set is used. This can be overridden +by the <b>--locale</b> option. If no locale is set, the PCRE library's default +(usually the "C" locale) is used. +</P> +<br><a name="SEC7" href="#TOC1">NEWLINES</a><br> +<P> +The <b>-N</b> (<b>--newline</b>) option allows <b>pcregrep</b> to scan files with +different newline conventions from the default. Any parts of the input files +that are written to the standard output are copied identically, with whatever +newline sequences they have in the input. However, the setting of this option +does not affect the interpretation of files specified by the <b>-f</b>, +<b>--exclude-from</b>, or <b>--include-from</b> options, which are assumed to use +the operating system's standard newline sequence, nor does it affect the way in +which <b>pcregrep</b> writes informational messages to the standard error and +output streams. For these it uses the string "\n" to indicate newlines, +relying on the C I/O library to convert this to an appropriate sequence. +</P> +<br><a name="SEC8" href="#TOC1">OPTIONS COMPATIBILITY</a><br> +<P> +Many of the short and long forms of <b>pcregrep</b>'s options are the same +as in the GNU <b>grep</b> program. Any long option of the form +<b>--xxx-regexp</b> (GNU terminology) is also available as <b>--xxx-regex</b> +(PCRE terminology). However, the <b>--file-list</b>, <b>--file-offsets</b>, +<b>--include-dir</b>, <b>--line-offsets</b>, <b>--locale</b>, <b>--match-limit</b>, +<b>-M</b>, <b>--multiline</b>, <b>-N</b>, <b>--newline</b>, <b>--om-separator</b>, +<b>--recursion-limit</b>, <b>-u</b>, and <b>--utf-8</b> options are specific to +<b>pcregrep</b>, as is the use of the <b>--only-matching</b> option with a +capturing parentheses number. +</P> +<P> +Although most of the common options work the same way, a few are different in +<b>pcregrep</b>. For example, the <b>--include</b> option's argument is a glob +for GNU <b>grep</b>, but a regular expression for <b>pcregrep</b>. If both the +<b>-c</b> and <b>-l</b> options are given, GNU grep lists only file names, +without counts, but <b>pcregrep</b> gives the counts. +</P> +<br><a name="SEC9" href="#TOC1">OPTIONS WITH DATA</a><br> +<P> +There are four different ways in which an option with data can be specified. +If a short form option is used, the data may follow immediately, or (with one +exception) in the next command line item. For example: +<pre> + -f/some/file + -f /some/file +</pre> +The exception is the <b>-o</b> option, which may appear with or without data. +Because of this, if data is present, it must follow immediately in the same +item, for example -o3. +</P> +<P> +If a long form option is used, the data may appear in the same command line +item, separated by an equals character, or (with two exceptions) it may appear +in the next command line item. For example: +<pre> + --file=/some/file + --file /some/file +</pre> +Note, however, that if you want to supply a file name beginning with ~ as data +in a shell command, and have the shell expand ~ to a home directory, you must +separate the file name from the option, because the shell does not treat ~ +specially unless it is at the start of an item. +</P> +<P> +The exceptions to the above are the <b>--colour</b> (or <b>--color</b>) and +<b>--only-matching</b> options, for which the data is optional. If one of these +options does have data, it must be given in the first form, using an equals +character. Otherwise <b>pcregrep</b> will assume that it has no data. +</P> +<br><a name="SEC10" href="#TOC1">MATCHING ERRORS</a><br> +<P> +It is possible to supply a regular expression that takes a very long time to +fail to match certain lines. Such patterns normally involve nested indefinite +repeats, for example: (a+)*\d when matched against a line of a's with no final +digit. The PCRE matching function has a resource limit that causes it to abort +in these circumstances. If this happens, <b>pcregrep</b> outputs an error +message and the line that caused the problem to the standard error stream. If +there are more than 20 such errors, <b>pcregrep</b> gives up. +</P> +<P> +The <b>--match-limit</b> option of <b>pcregrep</b> can be used to set the overall +resource limit; there is a second option called <b>--recursion-limit</b> that +sets a limit on the amount of memory (usually stack) that is used (see the +discussion of these options above). +</P> +<br><a name="SEC11" href="#TOC1">DIAGNOSTICS</a><br> +<P> +Exit status is 0 if any matches were found, 1 if no matches were found, and 2 +for syntax errors, overlong lines, non-existent or inaccessible files (even if +matches were found in other files) or too many matching errors. Using the +<b>-s</b> option to suppress error messages about inaccessible files does not +affect the return code. +</P> +<br><a name="SEC12" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcrepattern</b>(3), <b>pcresyntax</b>(3), <b>pcretest</b>(1). +</P> +<br><a name="SEC13" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC14" href="#TOC1">REVISION</a><br> +<P> +Last updated: 03 April 2014 +<br> +Copyright © 1997-2014 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrejit.html b/doc/html/pcrejit.html new file mode 100644 index 0000000..210f1da --- /dev/null +++ b/doc/html/pcrejit.html @@ -0,0 +1,452 @@ +<html> +<head> +<title>pcrejit specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrejit man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a> +<li><a name="TOC2" href="#SEC2">8-BIT, 16-BIT AND 32-BIT SUPPORT</a> +<li><a name="TOC3" href="#SEC3">AVAILABILITY OF JIT SUPPORT</a> +<li><a name="TOC4" href="#SEC4">SIMPLE USE OF JIT</a> +<li><a name="TOC5" href="#SEC5">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a> +<li><a name="TOC6" href="#SEC6">RETURN VALUES FROM JIT EXECUTION</a> +<li><a name="TOC7" href="#SEC7">SAVING AND RESTORING COMPILED PATTERNS</a> +<li><a name="TOC8" href="#SEC8">CONTROLLING THE JIT STACK</a> +<li><a name="TOC9" href="#SEC9">JIT STACK FAQ</a> +<li><a name="TOC10" href="#SEC10">EXAMPLE CODE</a> +<li><a name="TOC11" href="#SEC11">JIT FAST PATH API</a> +<li><a name="TOC12" href="#SEC12">SEE ALSO</a> +<li><a name="TOC13" href="#SEC13">AUTHOR</a> +<li><a name="TOC14" href="#SEC14">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a><br> +<P> +Just-in-time compiling is a heavyweight optimization that can greatly speed up +pattern matching. However, it comes at the cost of extra processing before the +match is performed. Therefore, it is of most benefit when the same pattern is +going to be matched many times. This does not necessarily mean many calls of a +matching function; if the pattern is not anchored, matching attempts may take +place many times at various positions in the subject, even for a single call. +Therefore, if the subject string is very long, it may still pay to use JIT for +one-off matches. +</P> +<P> +JIT support applies only to the traditional Perl-compatible matching function. +It does not apply when the DFA matching function is being used. The code for +this support was written by Zoltan Herczeg. +</P> +<br><a name="SEC2" href="#TOC1">8-BIT, 16-BIT AND 32-BIT SUPPORT</a><br> +<P> +JIT support is available for all of the 8-bit, 16-bit and 32-bit PCRE +libraries. To keep this documentation simple, only the 8-bit interface is +described in what follows. If you are using the 16-bit library, substitute the +16-bit functions and 16-bit structures (for example, <i>pcre16_jit_stack</i> +instead of <i>pcre_jit_stack</i>). If you are using the 32-bit library, +substitute the 32-bit functions and 32-bit structures (for example, +<i>pcre32_jit_stack</i> instead of <i>pcre_jit_stack</i>). +</P> +<br><a name="SEC3" href="#TOC1">AVAILABILITY OF JIT SUPPORT</a><br> +<P> +JIT support is an optional feature of PCRE. The "configure" option --enable-jit +(or equivalent CMake option) must be set when PCRE is built if you want to use +JIT. The support is limited to the following hardware platforms: +<pre> + ARM v5, v7, and Thumb2 + Intel x86 32-bit and 64-bit + MIPS 32-bit + Power PC 32-bit and 64-bit + SPARC 32-bit (experimental) +</pre> +If --enable-jit is set on an unsupported platform, compilation fails. +</P> +<P> +A program that is linked with PCRE 8.20 or later can tell if JIT support is +available by calling <b>pcre_config()</b> with the PCRE_CONFIG_JIT option. The +result is 1 when JIT is available, and 0 otherwise. However, a simple program +does not need to check this in order to use JIT. The normal API is implemented +in a way that falls back to the interpretive code if JIT is not available. For +programs that need the best possible performance, there is also a "fast path" +API that is JIT-specific. +</P> +<P> +If your program may sometimes be linked with versions of PCRE that are older +than 8.20, but you want to use JIT when it is available, you can test +the values of PCRE_MAJOR and PCRE_MINOR, or the existence of a JIT macro such +as PCRE_CONFIG_JIT, for compile-time control of your code. +</P> +<br><a name="SEC4" href="#TOC1">SIMPLE USE OF JIT</a><br> +<P> +You have to do two things to make use of the JIT support in the simplest way: +<pre> + (1) Call <b>pcre_study()</b> with the PCRE_STUDY_JIT_COMPILE option for + each compiled pattern, and pass the resulting <b>pcre_extra</b> block to + <b>pcre_exec()</b>. + + (2) Use <b>pcre_free_study()</b> to free the <b>pcre_extra</b> block when it is + no longer needed, instead of just freeing it yourself. This ensures that + any JIT data is also freed. +</pre> +For a program that may be linked with pre-8.20 versions of PCRE, you can insert +<pre> + #ifndef PCRE_STUDY_JIT_COMPILE + #define PCRE_STUDY_JIT_COMPILE 0 + #endif +</pre> +so that no option is passed to <b>pcre_study()</b>, and then use something like +this to free the study data: +<pre> + #ifdef PCRE_CONFIG_JIT + pcre_free_study(study_ptr); + #else + pcre_free(study_ptr); + #endif +</pre> +PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for complete +matches. If you want to run partial matches using the PCRE_PARTIAL_HARD or +PCRE_PARTIAL_SOFT options of <b>pcre_exec()</b>, you should set one or both of +the following options in addition to, or instead of, PCRE_STUDY_JIT_COMPILE +when you call <b>pcre_study()</b>: +<pre> + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE +</pre> +The JIT compiler generates different optimized code for each of the three +modes (normal, soft partial, hard partial). When <b>pcre_exec()</b> is called, +the appropriate code is run if it is available. Otherwise, the pattern is +matched using interpretive code. +</P> +<P> +In some circumstances you may need to call additional functions. These are +described in the section entitled +<a href="#stackcontrol">"Controlling the JIT stack"</a> +below. +</P> +<P> +If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are ignored, and +no JIT data is created. Otherwise, the compiled pattern is passed to the JIT +compiler, which turns it into machine code that executes much faster than the +normal interpretive code. When <b>pcre_exec()</b> is passed a <b>pcre_extra</b> +block containing a pointer to JIT code of the appropriate mode (normal or +hard/soft partial), it obeys that code instead of running the interpreter. The +result is identical, but the compiled JIT code runs much faster. +</P> +<P> +There are some <b>pcre_exec()</b> options that are not supported for JIT +execution. There are also some pattern items that JIT cannot handle. Details +are given below. In both cases, execution automatically falls back to the +interpretive code. If you want to know whether JIT was actually used for a +particular match, you should arrange for a JIT callback function to be set up +as described in the section entitled +<a href="#stackcontrol">"Controlling the JIT stack"</a> +below, even if you do not need to supply a non-default JIT stack. Such a +callback function is called whenever JIT code is about to be obeyed. If the +execution options are not right for JIT execution, the callback function is not +obeyed. +</P> +<P> +If the JIT compiler finds an unsupported item, no JIT data is generated. You +can find out if JIT execution is available after studying a pattern by calling +<b>pcre_fullinfo()</b> with the PCRE_INFO_JIT option. A result of 1 means that +JIT compilation was successful. A result of 0 means that JIT support is not +available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE etc., or +the JIT compiler was not able to handle the pattern. +</P> +<P> +Once a pattern has been studied, with or without JIT, it can be used as many +times as you like for matching different subject strings. +</P> +<br><a name="SEC5" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br> +<P> +The only <b>pcre_exec()</b> options that are supported for JIT execution are +PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NO_UTF32_CHECK, PCRE_NOTBOL, +PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and +PCRE_PARTIAL_SOFT. +</P> +<P> +The only unsupported pattern items are \C (match a single data unit) when +running in a UTF mode, and a callout immediately before an assertion condition +in a conditional group. +</P> +<br><a name="SEC6" href="#TOC1">RETURN VALUES FROM JIT EXECUTION</a><br> +<P> +When a pattern is matched using JIT execution, the return values are the same +as those given by the interpretive <b>pcre_exec()</b> code, with the addition of +one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means that the memory used +for the JIT stack was insufficient. See +<a href="#stackcontrol">"Controlling the JIT stack"</a> +below for a discussion of JIT stack usage. For compatibility with the +interpretive <b>pcre_exec()</b> code, no more than two-thirds of the +<i>ovector</i> argument is used for passing back captured substrings. +</P> +<P> +The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if searching a +very large pattern tree goes on for too long, as it is in the same circumstance +when JIT is not used, but the details of exactly what is counted are not the +same. The PCRE_ERROR_RECURSIONLIMIT error code is never returned by JIT +execution. +</P> +<br><a name="SEC7" href="#TOC1">SAVING AND RESTORING COMPILED PATTERNS</a><br> +<P> +The code that is generated by the JIT compiler is architecture-specific, and is +also position dependent. For those reasons it cannot be saved (in a file or +database) and restored later like the bytecode and other data of a compiled +pattern. Saving and restoring compiled patterns is not something many people +do. More detail about this facility is given in the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation. It should be possible to run <b>pcre_study()</b> on a saved and +restored pattern, and thereby recreate the JIT data, but because JIT +compilation uses significant resources, it is probably not worth doing this; +you might as well recompile the original pattern. +<a name="stackcontrol"></a></P> +<br><a name="SEC8" href="#TOC1">CONTROLLING THE JIT STACK</a><br> +<P> +When the compiled JIT code runs, it needs a block of memory to use as a stack. +By default, it uses 32K on the machine stack. However, some large or +complicated patterns need more than this. The error PCRE_ERROR_JIT_STACKLIMIT +is given when there is not enough stack. Three functions are provided for +managing blocks of memory for use as JIT stacks. There is further discussion +about the use of JIT stacks in the section entitled +<a href="#stackcontrol">"JIT stack FAQ"</a> +below. +</P> +<P> +The <b>pcre_jit_stack_alloc()</b> function creates a JIT stack. Its arguments +are a starting size and a maximum size, and it returns a pointer to an opaque +structure of type <b>pcre_jit_stack</b>, or NULL if there is an error. The +<b>pcre_jit_stack_free()</b> function can be used to free a stack that is no +longer needed. (For the technically minded: the address space is allocated by +mmap or VirtualAlloc.) +</P> +<P> +JIT uses far less memory for recursion than the interpretive code, +and a maximum stack size of 512K to 1M should be more than enough for any +pattern. +</P> +<P> +The <b>pcre_assign_jit_stack()</b> function specifies which stack JIT code +should use. Its arguments are as follows: +<pre> + pcre_extra *extra + pcre_jit_callback callback + void *data +</pre> +The <i>extra</i> argument must be the result of studying a pattern with +PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the other +two options: +<pre> + (1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block + on the machine stack is used. + + (2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be + a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>. + + (3) If <i>callback</i> is not NULL, it must point to a function that is + called with <i>data</i> as an argument at the start of matching, in + order to set up a JIT stack. If the return from the callback + function is NULL, the internal 32K stack is used; otherwise the + return value must be a valid JIT stack, the result of calling + <b>pcre_jit_stack_alloc()</b>. +</pre> +A callback function is obeyed whenever JIT code is about to be run; it is not +obeyed when <b>pcre_exec()</b> is called with options that are incompatible for +JIT execution. A callback function can therefore be used to determine whether a +match operation was executed by JIT or by the interpreter. +</P> +<P> +You may safely use the same JIT stack for more than one pattern (either by +assigning directly or by callback), as long as the patterns are all matched +sequentially in the same thread. In a multithread application, if you do not +specify a JIT stack, or if you assign or pass back NULL from a callback, that +is thread-safe, because each thread has its own machine stack. However, if you +assign or pass back a non-NULL JIT stack, this must be a different stack for +each thread so that the application is thread-safe. +</P> +<P> +Strictly speaking, even more is allowed. You can assign the same non-NULL stack +to any number of patterns as long as they are not used for matching by multiple +threads at the same time. For example, you can assign the same stack to all +compiled patterns, and use a global mutex in the callback to wait until the +stack is available for use. However, this is an inefficient solution, and not +recommended. +</P> +<P> +This is a suggestion for how a multithreaded program that needs to set up +non-default JIT stacks might operate: +<pre> + During thread initalization + thread_local_var = pcre_jit_stack_alloc(...) + + During thread exit + pcre_jit_stack_free(thread_local_var) + + Use a one-line callback function + return thread_local_var +</pre> +All the functions described in this section do nothing if JIT is not available, +and <b>pcre_assign_jit_stack()</b> does nothing unless the <b>extra</b> argument +is non-NULL and points to a <b>pcre_extra</b> block that is the result of a +successful study with PCRE_STUDY_JIT_COMPILE etc. +<a name="stackfaq"></a></P> +<br><a name="SEC9" href="#TOC1">JIT STACK FAQ</a><br> +<P> +(1) Why do we need JIT stacks? +<br> +<br> +PCRE (and JIT) is a recursive, depth-first engine, so it needs a stack where +the local data of the current node is pushed before checking its child nodes. +Allocating real machine stack on some platforms is difficult. For example, the +stack chain needs to be updated every time if we extend the stack on PowerPC. +Although it is possible, its updating time overhead decreases performance. So +we do the recursion in memory. +</P> +<P> +(2) Why don't we simply allocate blocks of memory with <b>malloc()</b>? +<br> +<br> +Modern operating systems have a nice feature: they can reserve an address space +instead of allocating memory. We can safely allocate memory pages inside this +address space, so the stack could grow without moving memory data (this is +important because of pointers). Thus we can allocate 1M address space, and use +only a single memory page (usually 4K) if that is enough. However, we can still +grow up to 1M anytime if needed. +</P> +<P> +(3) Who "owns" a JIT stack? +<br> +<br> +The owner of the stack is the user program, not the JIT studied pattern or +anything else. The user program must ensure that if a stack is used by +<b>pcre_exec()</b>, (that is, it is assigned to the pattern currently running), +that stack must not be used by any other threads (to avoid overwriting the same +memory area). The best practice for multithreaded programs is to allocate a +stack for each thread, and return this stack through the JIT callback function. +</P> +<P> +(4) When should a JIT stack be freed? +<br> +<br> +You can free a JIT stack at any time, as long as it will not be used by +<b>pcre_exec()</b> again. When you assign the stack to a pattern, only a pointer +is set. There is no reference counting or any other magic. You can free the +patterns and stacks in any order, anytime. Just <i>do not</i> call +<b>pcre_exec()</b> with a pattern pointing to an already freed stack, as that +will cause SEGFAULT. (Also, do not free a stack currently used by +<b>pcre_exec()</b> in another thread). You can also replace the stack for a +pattern at any time. You can even free the previous stack before assigning a +replacement. +</P> +<P> +(5) Should I allocate/free a stack every time before/after calling +<b>pcre_exec()</b>? +<br> +<br> +No, because this is too costly in terms of resources. However, you could +implement some clever idea which release the stack if it is not used in let's +say two minutes. The JIT callback can help to achieve this without keeping a +list of the currently JIT studied patterns. +</P> +<P> +(6) OK, the stack is for long term memory allocation. But what happens if a +pattern causes stack overflow with a stack of 1M? Is that 1M kept until the +stack is freed? +<br> +<br> +Especially on embedded sytems, it might be a good idea to release memory +sometimes without freeing the stack. There is no API for this at the moment. +Probably a function call which returns with the currently allocated memory for +any stack and another which allows releasing memory (shrinking the stack) would +be a good idea if someone needs this. +</P> +<P> +(7) This is too much of a headache. Isn't there any better solution for JIT +stack handling? +<br> +<br> +No, thanks to Windows. If POSIX threads were used everywhere, we could throw +out this complicated API. +</P> +<br><a name="SEC10" href="#TOC1">EXAMPLE CODE</a><br> +<P> +This is a single-threaded example that specifies a JIT stack without using a +callback. +<pre> + int rc; + int ovector[30]; + pcre *re; + pcre_extra *extra; + pcre_jit_stack *jit_stack; + + re = pcre_compile(pattern, 0, &error, &erroffset, NULL); + /* Check for errors */ + extra = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &error); + jit_stack = pcre_jit_stack_alloc(32*1024, 512*1024); + /* Check for error (NULL) */ + pcre_assign_jit_stack(extra, NULL, jit_stack); + rc = pcre_exec(re, extra, subject, length, 0, 0, ovector, 30); + /* Check results */ + pcre_free(re); + pcre_free_study(extra); + pcre_jit_stack_free(jit_stack); + +</PRE> +</P> +<br><a name="SEC11" href="#TOC1">JIT FAST PATH API</a><br> +<P> +Because the API described above falls back to interpreted execution when JIT is +not available, it is convenient for programs that are written for general use +in many environments. However, calling JIT via <b>pcre_exec()</b> does have a +performance impact. Programs that are written for use where JIT is known to be +available, and which need the best possible performance, can instead use a +"fast path" API to call JIT execution directly instead of calling +<b>pcre_exec()</b> (obviously only for patterns that have been successfully +studied by JIT). +</P> +<P> +The fast path function is called <b>pcre_jit_exec()</b>, and it takes exactly +the same arguments as <b>pcre_exec()</b>, plus one additional argument that +must point to a JIT stack. The JIT stack arrangements described above do not +apply. The return values are the same as for <b>pcre_exec()</b>. +</P> +<P> +When you call <b>pcre_exec()</b>, as well as testing for invalid options, a +number of other sanity checks are performed on the arguments. For example, if +the subject pointer is NULL, or its length is negative, an immediate error is +given. Also, unless PCRE_NO_UTF[8|16|32] is set, a UTF subject string is tested +for validity. In the interests of speed, these checks do not happen on the JIT +fast path, and if invalid data is passed, the result is undefined. +</P> +<P> +Bypassing the sanity checks and the <b>pcre_exec()</b> wrapping can give +speedups of more than 10%. +</P> +<br><a name="SEC12" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcreapi</b>(3) +</P> +<br><a name="SEC13" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel (FAQ by Zoltan Herczeg) +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC14" href="#TOC1">REVISION</a><br> +<P> +Last updated: 17 March 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrelimits.html b/doc/html/pcrelimits.html new file mode 100644 index 0000000..ee5ebf0 --- /dev/null +++ b/doc/html/pcrelimits.html @@ -0,0 +1,90 @@ +<html> +<head> +<title>pcrelimits specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrelimits man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +SIZE AND OTHER LIMITATIONS +</b><br> +<P> +There are some size limitations in PCRE but it is hoped that they will never in +practice be relevant. +</P> +<P> +The maximum length of a compiled pattern is approximately 64K data units (bytes +for the 8-bit library, 16-bit units for the 16-bit library, and 32-bit units for +the 32-bit library) if PCRE is compiled with the default internal linkage size, +which is 2 bytes for the 8-bit and 16-bit libraries, and 4 bytes for the 32-bit +library. If you want to process regular expressions that are truly enormous, +you can compile PCRE with an internal linkage size of 3 or 4 (when building the +16-bit or 32-bit library, 3 is rounded up to 4). See the <b>README</b> file in +the source distribution and the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation for details. In these cases the limit is substantially larger. +However, the speed of execution is slower. +</P> +<P> +All values in repeating quantifiers must be less than 65536. +</P> +<P> +There is no limit to the number of parenthesized subpatterns, but there can be +no more than 65535 capturing subpatterns. There is, however, a limit to the +depth of nesting of parenthesized subpatterns of all kinds. This is imposed in +order to limit the amount of system stack used at compile time. The limit can +be specified when PCRE is built; the default is 250. +</P> +<P> +There is a limit to the number of forward references to subsequent subpatterns +of around 200,000. Repeated forward references with fixed upper limits, for +example, (?2){0,100} when subpattern number 2 is to the right, are included in +the count. There is no limit to the number of backward references. +</P> +<P> +The maximum length of name for a named subpattern is 32 characters, and the +maximum number of named subpatterns is 10000. +</P> +<P> +The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb +is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries. +</P> +<P> +The maximum length of a subject string is the largest positive number that an +integer variable can hold. However, when using the traditional matching +function, PCRE uses recursion to handle subpatterns and indefinite repetition. +This means that the available stack space may limit the size of a subject +string that can be processed by certain patterns. For a discussion of stack +issues, see the +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation. +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 05 November 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrematching.html b/doc/html/pcrematching.html new file mode 100644 index 0000000..a1af39b --- /dev/null +++ b/doc/html/pcrematching.html @@ -0,0 +1,242 @@ +<html> +<head> +<title>pcrematching specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrematching man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE MATCHING ALGORITHMS</a> +<li><a name="TOC2" href="#SEC2">REGULAR EXPRESSIONS AS TREES</a> +<li><a name="TOC3" href="#SEC3">THE STANDARD MATCHING ALGORITHM</a> +<li><a name="TOC4" href="#SEC4">THE ALTERNATIVE MATCHING ALGORITHM</a> +<li><a name="TOC5" href="#SEC5">ADVANTAGES OF THE ALTERNATIVE ALGORITHM</a> +<li><a name="TOC6" href="#SEC6">DISADVANTAGES OF THE ALTERNATIVE ALGORITHM</a> +<li><a name="TOC7" href="#SEC7">AUTHOR</a> +<li><a name="TOC8" href="#SEC8">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE MATCHING ALGORITHMS</a><br> +<P> +This document describes the two different algorithms that are available in PCRE +for matching a compiled regular expression against a given subject string. The +"standard" algorithm is the one provided by the <b>pcre_exec()</b>, +<b>pcre16_exec()</b> and <b>pcre32_exec()</b> functions. These work in the same +as as Perl's matching function, and provide a Perl-compatible matching operation. +The just-in-time (JIT) optimization that is described in the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation is compatible with these functions. +</P> +<P> +An alternative algorithm is provided by the <b>pcre_dfa_exec()</b>, +<b>pcre16_dfa_exec()</b> and <b>pcre32_dfa_exec()</b> functions; they operate in +a different way, and are not Perl-compatible. This alternative has advantages +and disadvantages compared with the standard algorithm, and these are described +below. +</P> +<P> +When there is only one possible way in which a given subject string can match a +pattern, the two algorithms give the same answer. A difference arises, however, +when there are multiple possibilities. For example, if the pattern +<pre> + ^<.*> +</pre> +is matched against the string +<pre> + <something> <something else> <something further> +</pre> +there are three possible answers. The standard algorithm finds only one of +them, whereas the alternative algorithm finds all three. +</P> +<br><a name="SEC2" href="#TOC1">REGULAR EXPRESSIONS AS TREES</a><br> +<P> +The set of strings that are matched by a regular expression can be represented +as a tree structure. An unlimited repetition in the pattern makes the tree of +infinite size, but it is still a tree. Matching the pattern to a given subject +string (from a given starting point) can be thought of as a search of the tree. +There are two ways to search a tree: depth-first and breadth-first, and these +correspond to the two matching algorithms provided by PCRE. +</P> +<br><a name="SEC3" href="#TOC1">THE STANDARD MATCHING ALGORITHM</a><br> +<P> +In the terminology of Jeffrey Friedl's book "Mastering Regular +Expressions", the standard algorithm is an "NFA algorithm". It conducts a +depth-first search of the pattern tree. That is, it proceeds along a single +path through the tree, checking that the subject matches what is required. When +there is a mismatch, the algorithm tries any alternatives at the current point, +and if they all fail, it backs up to the previous branch point in the tree, and +tries the next alternative branch at that level. This often involves backing up +(moving to the left) in the subject string as well. The order in which +repetition branches are tried is controlled by the greedy or ungreedy nature of +the quantifier. +</P> +<P> +If a leaf node is reached, a matching string has been found, and at that point +the algorithm stops. Thus, if there is more than one possible match, this +algorithm returns the first one that it finds. Whether this is the shortest, +the longest, or some intermediate length depends on the way the greedy and +ungreedy repetition quantifiers are specified in the pattern. +</P> +<P> +Because it ends up with a single path through the tree, it is relatively +straightforward for this algorithm to keep track of the substrings that are +matched by portions of the pattern in parentheses. This provides support for +capturing parentheses and back references. +</P> +<br><a name="SEC4" href="#TOC1">THE ALTERNATIVE MATCHING ALGORITHM</a><br> +<P> +This algorithm conducts a breadth-first search of the tree. Starting from the +first matching point in the subject, it scans the subject string from left to +right, once, character by character, and as it does this, it remembers all the +paths through the tree that represent valid matches. In Friedl's terminology, +this is a kind of "DFA algorithm", though it is not implemented as a +traditional finite state machine (it keeps multiple states active +simultaneously). +</P> +<P> +Although the general principle of this matching algorithm is that it scans the +subject string only once, without backtracking, there is one exception: when a +lookaround assertion is encountered, the characters following or preceding the +current point have to be independently inspected. +</P> +<P> +The scan continues until either the end of the subject is reached, or there are +no more unterminated paths. At this point, terminated paths represent the +different matching possibilities (if there are none, the match has failed). +Thus, if there is more than one possible match, this algorithm finds all of +them, and in particular, it finds the longest. The matches are returned in +decreasing order of length. There is an option to stop the algorithm after the +first match (which is necessarily the shortest) is found. +</P> +<P> +Note that all the matches that are found start at the same point in the +subject. If the pattern +<pre> + cat(er(pillar)?)? +</pre> +is matched against the string "the caterpillar catchment", the result will be +the three strings "caterpillar", "cater", and "cat" that start at the fifth +character of the subject. The algorithm does not automatically move on to find +matches that start at later positions. +</P> +<P> +PCRE's "auto-possessification" optimization usually applies to character +repeats at the end of a pattern (as well as internally). For example, the +pattern "a\d+" is compiled as if it were "a\d++" because there is no point +even considering the possibility of backtracking into the repeated digits. For +DFA matching, this means that only one possible match is found. If you really +do want multiple matches in such cases, either use an ungreedy repeat +("a\d+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. +</P> +<P> +There are a number of features of PCRE regular expressions that are not +supported by the alternative matching algorithm. They are as follows: +</P> +<P> +1. Because the algorithm finds all possible matches, the greedy or ungreedy +nature of repetition quantifiers is not relevant. Greedy and ungreedy +quantifiers are treated in exactly the same way. However, possessive +quantifiers can make a difference when what follows could also match what is +quantified, for example in a pattern like this: +<pre> + ^a++\w! +</pre> +This pattern matches "aaab!" but not "aaa!", which would be matched by a +non-possessive quantifier. Similarly, if an atomic group is present, it is +matched as if it were a standalone pattern at the current point, and the +longest match is then "locked in" for the rest of the overall pattern. +</P> +<P> +2. When dealing with multiple paths through the tree simultaneously, it is not +straightforward to keep track of captured substrings for the different matching +possibilities, and PCRE's implementation of this algorithm does not attempt to +do this. This means that no captured substrings are available. +</P> +<P> +3. Because no substrings are captured, back references within the pattern are +not supported, and cause errors if encountered. +</P> +<P> +4. For the same reason, conditional expressions that use a backreference as the +condition or test for a specific group recursion are not supported. +</P> +<P> +5. Because many paths through the tree may be active, the \K escape sequence, +which resets the start of the match when encountered (but may be on some paths +and not on others), is not supported. It causes an error if encountered. +</P> +<P> +6. Callouts are supported, but the value of the <i>capture_top</i> field is +always 1, and the value of the <i>capture_last</i> field is always -1. +</P> +<P> +7. The \C escape sequence, which (in the standard algorithm) always matches a +single data unit, even in UTF-8, UTF-16 or UTF-32 modes, is not supported in +these modes, because the alternative algorithm moves through the subject string +one character (not data unit) at a time, for all active paths through the tree. +</P> +<P> +8. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not +supported. (*FAIL) is supported, and behaves like a failing negative assertion. +</P> +<br><a name="SEC5" href="#TOC1">ADVANTAGES OF THE ALTERNATIVE ALGORITHM</a><br> +<P> +Using the alternative matching algorithm provides the following advantages: +</P> +<P> +1. All possible matches (at a single point in the subject) are automatically +found, and in particular, the longest match is found. To find more than one +match using the standard algorithm, you have to do kludgy things with +callouts. +</P> +<P> +2. Because the alternative algorithm scans the subject string just once, and +never needs to backtrack (except for lookbehinds), it is possible to pass very +long subject strings to the matching function in several pieces, checking for +partial matching each time. Although it is possible to do multi-segment +matching using the standard algorithm by retaining partially matched +substrings, it is more complicated. The +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation gives details of partial matching and discusses multi-segment +matching. +</P> +<br><a name="SEC6" href="#TOC1">DISADVANTAGES OF THE ALTERNATIVE ALGORITHM</a><br> +<P> +The alternative algorithm suffers from a number of disadvantages: +</P> +<P> +1. It is substantially slower than the standard algorithm. This is partly +because it has to search for all possible matches, but is also because it is +less susceptible to optimization. +</P> +<P> +2. Capturing parentheses and back references are not supported. +</P> +<P> +3. Although atomic groups are supported, their use does not provide the +performance advantage that it does for the standard algorithm. +</P> +<br><a name="SEC7" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC8" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 November 2013 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrepartial.html b/doc/html/pcrepartial.html new file mode 100644 index 0000000..4faeafc --- /dev/null +++ b/doc/html/pcrepartial.html @@ -0,0 +1,509 @@ +<html> +<head> +<title>pcrepartial specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrepartial man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PARTIAL MATCHING IN PCRE</a> +<li><a name="TOC2" href="#SEC2">PARTIAL MATCHING USING pcre_exec() OR pcre[16|32]_exec()</a> +<li><a name="TOC3" href="#SEC3">PARTIAL MATCHING USING pcre_dfa_exec() OR pcre[16|32]_dfa_exec()</a> +<li><a name="TOC4" href="#SEC4">PARTIAL MATCHING AND WORD BOUNDARIES</a> +<li><a name="TOC5" href="#SEC5">FORMERLY RESTRICTED PATTERNS</a> +<li><a name="TOC6" href="#SEC6">EXAMPLE OF PARTIAL MATCHING USING PCRETEST</a> +<li><a name="TOC7" href="#SEC7">MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec()</a> +<li><a name="TOC8" href="#SEC8">MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre[16|32]_exec()</a> +<li><a name="TOC9" href="#SEC9">ISSUES WITH MULTI-SEGMENT MATCHING</a> +<li><a name="TOC10" href="#SEC10">AUTHOR</a> +<li><a name="TOC11" href="#SEC11">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PARTIAL MATCHING IN PCRE</a><br> +<P> +In normal use of PCRE, if the subject string that is passed to a matching +function matches as far as it goes, but is too short to match the entire +pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances where it might +be helpful to distinguish this case from other cases in which there is no +match. +</P> +<P> +Consider, for example, an application where a human is required to type in data +for a field with specific formatting requirements. An example might be a date +in the form <i>ddmmmyy</i>, defined by this pattern: +<pre> + ^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$ +</pre> +If the application sees the user's keystrokes one by one, and can check that +what has been typed so far is potentially valid, it is able to raise an error +as soon as a mistake is made, by beeping and not reflecting the character that +has been typed, for example. This immediate feedback is likely to be a better +user interface than a check that is delayed until the entire string has been +entered. Partial matching can also be useful when the subject string is very +long and is not all available at once. +</P> +<P> +PCRE supports partial matching by means of the PCRE_PARTIAL_SOFT and +PCRE_PARTIAL_HARD options, which can be set when calling any of the matching +functions. For backwards compatibility, PCRE_PARTIAL is a synonym for +PCRE_PARTIAL_SOFT. The essential difference between the two options is whether +or not a partial match is preferred to an alternative complete match, though +the details differ between the two types of matching function. If both options +are set, PCRE_PARTIAL_HARD takes precedence. +</P> +<P> +If you want to use partial matching with just-in-time optimized code, you must +call <b>pcre_study()</b>, <b>pcre16_study()</b> or <b>pcre32_study()</b> with one +or both of these options: +<pre> + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE +</pre> +PCRE_STUDY_JIT_COMPILE should also be set if you are going to run non-partial +matches on the same pattern. If the appropriate JIT study mode has not been set +for a match, the interpretive matching code is used. +</P> +<P> +Setting a partial matching option disables two of PCRE's standard +optimizations. PCRE remembers the last literal data unit in a pattern, and +abandons matching immediately if it is not present in the subject string. This +optimization cannot be used for a subject string that might match only +partially. If the pattern was studied, PCRE knows the minimum length of a +matching string, and does not bother to run the matching function on shorter +strings. This optimization is also disabled for partial matching. +</P> +<br><a name="SEC2" href="#TOC1">PARTIAL MATCHING USING pcre_exec() OR pcre[16|32]_exec()</a><br> +<P> +A partial match occurs during a call to <b>pcre_exec()</b> or +<b>pcre[16|32]_exec()</b> when the end of the subject string is reached +successfully, but matching cannot continue because more characters are needed. +However, at least one character in the subject must have been inspected. This +character need not form part of the final matched string; lookbehind assertions +and the \K escape sequence provide ways of inspecting characters before the +start of a matched substring. The requirement for inspecting at least one +character exists because an empty string can always be matched; without such a +restriction there would always be a partial match of an empty string at the end +of the subject. +</P> +<P> +If there are at least two slots in the offsets vector when a partial match is +returned, the first slot is set to the offset of the earliest character that +was inspected. For convenience, the second offset points to the end of the +subject so that a substring can easily be identified. If there are at least +three slots in the offsets vector, the third slot is set to the offset of the +character where matching started. +</P> +<P> +For the majority of patterns, the contents of the first and third slots will be +the same. However, for patterns that contain lookbehind assertions, or begin +with \b or \B, characters before the one where matching started may have been +inspected while carrying out the match. For example, consider this pattern: +<pre> + /(?<=abc)123/ +</pre> +This pattern matches "123", but only if it is preceded by "abc". If the subject +string is "xyzabc12", the first two offsets after a partial match are for the +substring "abc12", because all these characters were inspected. However, the +third offset is set to 6, because that is the offset where matching began. +</P> +<P> +What happens when a partial match is identified depends on which of the two +partial matching options are set. +</P> +<br><b> +PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre[16|32]_exec() +</b><br> +<P> +If PCRE_PARTIAL_SOFT is set when <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> +identifies a partial match, the partial match is remembered, but matching +continues as normal, and other alternatives in the pattern are tried. If no +complete match can be found, PCRE_ERROR_PARTIAL is returned instead of +PCRE_ERROR_NOMATCH. +</P> +<P> +This option is "soft" because it prefers a complete match over a partial match. +All the various matching items in a pattern behave as if the subject string is +potentially complete. For example, \z, \Z, and $ match at the end of the +subject, as normal, and for \b and \B the end of the subject is treated as a +non-alphanumeric. +</P> +<P> +If there is more than one partial match, the first one that was found provides +the data that is returned. Consider this pattern: +<pre> + /123\w+X|dogY/ +</pre> +If this is matched against the subject string "abc123dog", both +alternatives fail to match, but the end of the subject is reached during +matching, so PCRE_ERROR_PARTIAL is returned. The offsets are set to 3 and 9, +identifying "123dog" as the first partial match that was found. (In this +example, there are two partial matches, because "dog" on its own partially +matches the second alternative.) +</P> +<br><b> +PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre[16|32]_exec() +</b><br> +<P> +If PCRE_PARTIAL_HARD is set for <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b>, +PCRE_ERROR_PARTIAL is returned as soon as a partial match is found, without +continuing to search for possible complete matches. This option is "hard" +because it prefers an earlier partial match over a later complete match. For +this reason, the assumption is made that the end of the supplied subject string +may not be the true end of the available data, and so, if \z, \Z, \b, \B, +or $ are encountered at the end of the subject, the result is +PCRE_ERROR_PARTIAL, provided that at least one character in the subject has +been inspected. +</P> +<P> +Setting PCRE_PARTIAL_HARD also affects the way UTF-8 and UTF-16 +subject strings are checked for validity. Normally, an invalid sequence +causes the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the +special case of a truncated character at the end of the subject, +PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when +PCRE_PARTIAL_HARD is set. +</P> +<br><b> +Comparing hard and soft partial matching +</b><br> +<P> +The difference between the two partial matching options can be illustrated by a +pattern such as: +<pre> + /dog(sbody)?/ +</pre> +This matches either "dog" or "dogsbody", greedily (that is, it prefers the +longer string if possible). If it is matched against the string "dog" with +PCRE_PARTIAL_SOFT, it yields a complete match for "dog". However, if +PCRE_PARTIAL_HARD is set, the result is PCRE_ERROR_PARTIAL. On the other hand, +if the pattern is made ungreedy the result is different: +<pre> + /dog(sbody)??/ +</pre> +In this case the result is always a complete match because that is found first, +and matching never continues after finding a complete match. It might be easier +to follow this explanation by thinking of the two patterns like this: +<pre> + /dog(sbody)?/ is the same as /dogsbody|dog/ + /dog(sbody)??/ is the same as /dog|dogsbody/ +</pre> +The second pattern will never match "dogsbody", because it will always find the +shorter match first. +</P> +<br><a name="SEC3" href="#TOC1">PARTIAL MATCHING USING pcre_dfa_exec() OR pcre[16|32]_dfa_exec()</a><br> +<P> +The DFA functions move along the subject string character by character, without +backtracking, searching for all possible matches simultaneously. If the end of +the subject is reached before the end of the pattern, there is the possibility +of a partial match, again provided that at least one character has been +inspected. +</P> +<P> +When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if there +have been no complete matches. Otherwise, the complete matches are returned. +However, if PCRE_PARTIAL_HARD is set, a partial match takes precedence over any +complete matches. The portion of the string that was inspected when the longest +partial match was found is set as the first matching string, provided there are +at least two slots in the offsets vector. +</P> +<P> +Because the DFA functions always search for all possible matches, and there is +no difference between greedy and ungreedy repetition, their behaviour is +different from the standard functions when PCRE_PARTIAL_HARD is set. Consider +the string "dog" matched against the ungreedy pattern shown above: +<pre> + /dog(sbody)??/ +</pre> +Whereas the standard functions stop as soon as they find the complete match for +"dog", the DFA functions also find the partial match for "dogsbody", and so +return that when PCRE_PARTIAL_HARD is set. +</P> +<br><a name="SEC4" href="#TOC1">PARTIAL MATCHING AND WORD BOUNDARIES</a><br> +<P> +If a pattern ends with one of sequences \b or \B, which test for word +boundaries, partial matching with PCRE_PARTIAL_SOFT can give counter-intuitive +results. Consider this pattern: +<pre> + /\bcat\b/ +</pre> +This matches "cat", provided there is a word boundary at either end. If the +subject string is "the cat", the comparison of the final "t" with a following +character cannot take place, so a partial match is found. However, normal +matching carries on, and \b matches at the end of the subject when the last +character is a letter, so a complete match is found. The result, therefore, is +<i>not</i> PCRE_ERROR_PARTIAL. Using PCRE_PARTIAL_HARD in this case does yield +PCRE_ERROR_PARTIAL, because then the partial match takes precedence. +</P> +<br><a name="SEC5" href="#TOC1">FORMERLY RESTRICTED PATTERNS</a><br> +<P> +For releases of PCRE prior to 8.00, because of the way certain internal +optimizations were implemented in the <b>pcre_exec()</b> function, the +PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be used with +all patterns. From release 8.00 onwards, the restrictions no longer apply, and +partial matching with can be requested for any pattern. +</P> +<P> +Items that were formerly restricted were repeated single characters and +repeated metasequences. If PCRE_PARTIAL was set for a pattern that did not +conform to the restrictions, <b>pcre_exec()</b> returned the error code +PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The +PCRE_INFO_OKPARTIAL call to <b>pcre_fullinfo()</b> to find out if a compiled +pattern can be used for partial matching now always returns 1. +</P> +<br><a name="SEC6" href="#TOC1">EXAMPLE OF PARTIAL MATCHING USING PCRETEST</a><br> +<P> +If the escape sequence \P is present in a <b>pcretest</b> data line, the +PCRE_PARTIAL_SOFT option is used for the match. Here is a run of <b>pcretest</b> +that uses the date example quoted above: +<pre> + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 25jun04\P + 0: 25jun04 + 1: jun + data> 25dec3\P + Partial match: 23dec3 + data> 3ju\P + Partial match: 3ju + data> 3juj\P + No match + data> j\P + No match +</pre> +The first data string is matched completely, so <b>pcretest</b> shows the +matched substrings. The remaining four strings do not match the complete +pattern, but the first two are partial matches. Similar output is obtained +if DFA matching is used. +</P> +<P> +If the escape sequence \P is present more than once in a <b>pcretest</b> data +line, the PCRE_PARTIAL_HARD option is set for the match. +</P> +<br><a name="SEC7" href="#TOC1">MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec()</a><br> +<P> +When a partial match has been found using a DFA matching function, it is +possible to continue the match by providing additional subject data and calling +the function again with the same compiled regular expression, this time setting +the PCRE_DFA_RESTART option. You must pass the same working space as before, +because this is where details of the previous partial match are stored. Here is +an example using <b>pcretest</b>, using the \R escape sequence to set the +PCRE_DFA_RESTART option (\D specifies the use of the DFA matching function): +<pre> + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 23ja\P\D + Partial match: 23ja + data> n05\R\D + 0: n05 +</pre> +The first call has "23ja" as the subject, and requests partial matching; the +second call has "n05" as the subject for the continued (restarted) match. +Notice that when the match is complete, only the last part is shown; PCRE does +not retain the previously partially-matched string. It is up to the calling +program to do that if it needs to. +</P> +<P> +That means that, for an unanchored pattern, if a continued match fails, it is +not possible to try again at a new starting point. All this facility is capable +of doing is continuing with the previous match attempt. In the previous +example, if the second set of data is "ug23" the result is no match, even +though there would be a match for "aug23" if the entire string were given at +once. Depending on the application, this may or may not be what you want. +The only way to allow for starting again at the next character is to retain the +matched part of the subject and try a new complete match. +</P> +<P> +You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with +PCRE_DFA_RESTART to continue partial matching over multiple segments. This +facility can be used to pass very long subject strings to the DFA matching +functions. +</P> +<br><a name="SEC8" href="#TOC1">MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre[16|32]_exec()</a><br> +<P> +From release 8.00, the standard matching functions can also be used to do +multi-segment matching. Unlike the DFA functions, it is not possible to +restart the previous match with a new segment of data. Instead, new data must +be added to the previous subject string, and the entire match re-run, starting +from the point where the partial match occurred. Earlier data can be discarded. +</P> +<P> +It is best to use PCRE_PARTIAL_HARD in this situation, because it does not +treat the end of a segment as the end of the subject when matching \z, \Z, +\b, \B, and $. Consider an unanchored pattern that matches dates: +<pre> + re> /\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d/ + data> The date is 23ja\P\P + Partial match: 23ja +</pre> +At this stage, an application could discard the text preceding "23ja", add on +text from the next segment, and call the matching function again. Unlike the +DFA matching functions, the entire matching string must always be available, +and the complete matching process occurs for each call, so more memory and more +processing time is needed. +</P> +<P> +<b>Note:</b> If the pattern contains lookbehind assertions, or \K, or starts +with \b or \B, the string that is returned for a partial match includes +characters that precede the start of what would be returned for a complete +match, because it contains all the characters that were inspected during the +partial match. +</P> +<br><a name="SEC9" href="#TOC1">ISSUES WITH MULTI-SEGMENT MATCHING</a><br> +<P> +Certain types of pattern may give problems with multi-segment matching, +whichever matching function is used. +</P> +<P> +1. If the pattern contains a test for the beginning of a line, you need to pass +the PCRE_NOTBOL option when the subject string for any call does start at the +beginning of a line. There is also a PCRE_NOTEOL option, but in practice when +doing multi-segment matching you should be using PCRE_PARTIAL_HARD, which +includes the effect of PCRE_NOTEOL. +</P> +<P> +2. Lookbehind assertions that have already been obeyed are catered for in the +offsets that are returned for a partial match. However a lookbehind assertion +later in the pattern could require even earlier characters to be inspected. You +can handle this case by using the PCRE_INFO_MAXLOOKBEHIND option of the +<b>pcre_fullinfo()</b> or <b>pcre[16|32]_fullinfo()</b> functions to obtain the +length of the longest lookbehind in the pattern. This length is given in +characters, not bytes. If you always retain at least that many characters +before the partially matched string, all should be well. (Of course, near the +start of the subject, fewer characters may be present; in that case all +characters should be retained.) +</P> +<P> +From release 8.33, there is a more accurate way of deciding which characters to +retain. Instead of subtracting the length of the longest lookbehind from the +earliest inspected character (<i>offsets[0]</i>), the match start position +(<i>offsets[2]</i>) should be used, and the next match attempt started at the +<i>offsets[2]</i> character by setting the <i>startoffset</i> argument of +<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. +</P> +<P> +For example, if the pattern "(?<=123)abc" is partially +matched against the string "xx123a", the three offset values returned are 2, 6, +and 5. This indicates that the matching process that gave a partial match +started at offset 5, but the characters "123a" were all inspected. The maximum +lookbehind for that pattern is 3, so taking that away from 5 shows that we need +only keep "123a", and the next match attempt can be started at offset 3 (that +is, at "a") when further characters have been added. When the match start is +not the earliest inspected character, <b>pcretest</b> shows it explicitly: +<pre> + re> "(?<=123)abc" + data> xx123a\P\P + Partial match at offset 5: 123a +</PRE> +</P> +<P> +3. Because a partial match must always contain at least one character, what +might be considered a partial match of an empty string actually gives a "no +match" result. For example: +<pre> + re> /c(?<=abc)x/ + data> ab\P + No match +</pre> +If the next segment begins "cx", a match should be found, but this will only +happen if characters from the previous segment are retained. For this reason, a +"no match" result should be interpreted as "partial match of an empty string" +when the pattern contains lookbehinds. +</P> +<P> +4. Matching a subject string that is split into multiple segments may not +always produce exactly the same result as matching over one single long string, +especially when PCRE_PARTIAL_SOFT is used. The section "Partial Matching and +Word Boundaries" above describes an issue that arises if the pattern ends with +\b or \B. Another kind of difference may occur when there are multiple +matching possibilities, because (for PCRE_PARTIAL_SOFT) a partial match result +is given only when there are no completed matches. This means that as soon as +the shortest match has been found, continuation to a new subject segment is no +longer possible. Consider again this <b>pcretest</b> example: +<pre> + re> /dog(sbody)?/ + data> dogsb\P + 0: dog + data> do\P\D + Partial match: do + data> gsb\R\P\D + 0: g + data> dogsbody\D + 0: dogsbody + 1: dog +</pre> +The first data line passes the string "dogsb" to a standard matching function, +setting the PCRE_PARTIAL_SOFT option. Although the string is a partial match +for "dogsbody", the result is not PCRE_ERROR_PARTIAL, because the shorter +string "dog" is a complete match. Similarly, when the subject is presented to +a DFA matching function in several parts ("do" and "gsb" being the first two) +the match stops when "dog" has been found, and it is not possible to continue. +On the other hand, if "dogsbody" is presented as a single string, a DFA +matching function finds both matches. +</P> +<P> +Because of these problems, it is best to use PCRE_PARTIAL_HARD when matching +multi-segment data. The example above then behaves differently: +<pre> + re> /dog(sbody)?/ + data> dogsb\P\P + Partial match: dogsb + data> do\P\D + Partial match: do + data> gsb\R\P\P\D + Partial match: gsb +</pre> +5. Patterns that contain alternatives at the top level which do not all start +with the same pattern item may not work as expected when PCRE_DFA_RESTART is +used. For example, consider this pattern: +<pre> + 1234|3789 +</pre> +If the first part of the subject is "ABC123", a partial match of the first +alternative is found at offset 3. There is no partial match for the second +alternative, because such a match does not start at the same point in the +subject string. Attempting to continue with the string "7890" does not yield a +match because only those alternatives that match at one point in the subject +are remembered. The problem arises because the start of the second alternative +matches within the first alternative. There is no problem with anchored +patterns or patterns such as: +<pre> + 1234|ABCD +</pre> +where no string can be a partial match for both alternatives. This is not a +problem if a standard matching function is used, because the entire match has +to be rerun each time: +<pre> + re> /1234|3789/ + data> ABC123\P\P + Partial match: 123 + data> 1237890 + 0: 3789 +</pre> +Of course, instead of using PCRE_DFA_RESTART, the same technique of re-running +the entire match can also be used with the DFA matching functions. Another +possibility is to work with two buffers. If a partial match at offset <i>n</i> +in the first buffer is followed by "no match" when PCRE_DFA_RESTART is used on +the second buffer, you can then try a new match starting at offset <i>n+1</i> in +the first buffer. +</P> +<br><a name="SEC10" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC11" href="#TOC1">REVISION</a><br> +<P> +Last updated: 02 July 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrepattern.html b/doc/html/pcrepattern.html new file mode 100644 index 0000000..55034a7 --- /dev/null +++ b/doc/html/pcrepattern.html @@ -0,0 +1,3273 @@ +<html> +<head> +<title>pcrepattern specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrepattern man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE REGULAR EXPRESSION DETAILS</a> +<li><a name="TOC2" href="#SEC2">SPECIAL START-OF-PATTERN ITEMS</a> +<li><a name="TOC3" href="#SEC3">EBCDIC CHARACTER CODES</a> +<li><a name="TOC4" href="#SEC4">CHARACTERS AND METACHARACTERS</a> +<li><a name="TOC5" href="#SEC5">BACKSLASH</a> +<li><a name="TOC6" href="#SEC6">CIRCUMFLEX AND DOLLAR</a> +<li><a name="TOC7" href="#SEC7">FULL STOP (PERIOD, DOT) AND \N</a> +<li><a name="TOC8" href="#SEC8">MATCHING A SINGLE DATA UNIT</a> +<li><a name="TOC9" href="#SEC9">SQUARE BRACKETS AND CHARACTER CLASSES</a> +<li><a name="TOC10" href="#SEC10">POSIX CHARACTER CLASSES</a> +<li><a name="TOC11" href="#SEC11">COMPATIBILITY FEATURE FOR WORD BOUNDARIES</a> +<li><a name="TOC12" href="#SEC12">VERTICAL BAR</a> +<li><a name="TOC13" href="#SEC13">INTERNAL OPTION SETTING</a> +<li><a name="TOC14" href="#SEC14">SUBPATTERNS</a> +<li><a name="TOC15" href="#SEC15">DUPLICATE SUBPATTERN NUMBERS</a> +<li><a name="TOC16" href="#SEC16">NAMED SUBPATTERNS</a> +<li><a name="TOC17" href="#SEC17">REPETITION</a> +<li><a name="TOC18" href="#SEC18">ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS</a> +<li><a name="TOC19" href="#SEC19">BACK REFERENCES</a> +<li><a name="TOC20" href="#SEC20">ASSERTIONS</a> +<li><a name="TOC21" href="#SEC21">CONDITIONAL SUBPATTERNS</a> +<li><a name="TOC22" href="#SEC22">COMMENTS</a> +<li><a name="TOC23" href="#SEC23">RECURSIVE PATTERNS</a> +<li><a name="TOC24" href="#SEC24">SUBPATTERNS AS SUBROUTINES</a> +<li><a name="TOC25" href="#SEC25">ONIGURUMA SUBROUTINE SYNTAX</a> +<li><a name="TOC26" href="#SEC26">CALLOUTS</a> +<li><a name="TOC27" href="#SEC27">BACKTRACKING CONTROL</a> +<li><a name="TOC28" href="#SEC28">SEE ALSO</a> +<li><a name="TOC29" href="#SEC29">AUTHOR</a> +<li><a name="TOC30" href="#SEC30">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION DETAILS</a><br> +<P> +The syntax and semantics of the regular expressions that are supported by PCRE +are described in detail below. There is a quick-reference syntax summary in the +<a href="pcresyntax.html"><b>pcresyntax</b></a> +page. PCRE tries to match Perl syntax and semantics as closely as it can. PCRE +also supports some alternative regular expression syntax (which does not +conflict with the Perl syntax) in order to provide some compatibility with +regular expressions in Python, .NET, and Oniguruma. +</P> +<P> +Perl's regular expressions are described in its own documentation, and +regular expressions in general are covered in a number of books, some of which +have copious examples. Jeffrey Friedl's "Mastering Regular Expressions", +published by O'Reilly, covers regular expressions in great detail. This +description of PCRE's regular expressions is intended as reference material. +</P> +<P> +This document discusses the patterns that are supported by PCRE when one its +main matching functions, <b>pcre_exec()</b> (8-bit) or <b>pcre[16|32]_exec()</b> +(16- or 32-bit), is used. PCRE also has alternative matching functions, +<b>pcre_dfa_exec()</b> and <b>pcre[16|32_dfa_exec()</b>, which match using a +different algorithm that is not Perl-compatible. Some of the features discussed +below are not available when DFA matching is used. The advantages and +disadvantages of the alternative functions, and how they differ from the normal +functions, are discussed in the +<a href="pcrematching.html"><b>pcrematching</b></a> +page. +</P> +<br><a name="SEC2" href="#TOC1">SPECIAL START-OF-PATTERN ITEMS</a><br> +<P> +A number of options that can be passed to <b>pcre_compile()</b> can also be set +by special items at the start of a pattern. These are not Perl-compatible, but +are provided to make these options accessible to pattern writers who are not +able to change the program that processes the pattern. Any number of these +items may appear, but they must all be together right at the start of the +pattern string, and the letters must be in upper case. +</P> +<br><b> +UTF support +</b><br> +<P> +The original operation of PCRE was on strings of one-byte characters. However, +there is now also support for UTF-8 strings in the original library, an +extra library that supports 16-bit and UTF-16 character strings, and a +third library that supports 32-bit and UTF-32 character strings. To use these +features, PCRE must be built to include appropriate support. When using UTF +strings you must either call the compiling function with the PCRE_UTF8, +PCRE_UTF16, or PCRE_UTF32 option, or the pattern must start with one of +these special sequences: +<pre> + (*UTF8) + (*UTF16) + (*UTF32) + (*UTF) +</pre> +(*UTF) is a generic sequence that can be used with any of the libraries. +Starting a pattern with such a sequence is equivalent to setting the relevant +option. How setting a UTF mode affects pattern matching is mentioned in several +places below. There is also a summary of features in the +<a href="pcreunicode.html"><b>pcreunicode</b></a> +page. +</P> +<P> +Some applications that allow their users to supply patterns may wish to +restrict them to non-UTF data for security reasons. If the PCRE_NEVER_UTF +option is set at compile time, (*UTF) etc. are not allowed, and their +appearance causes an error. +</P> +<br><b> +Unicode property support +</b><br> +<P> +Another special sequence that may appear at the start of a pattern is (*UCP). +This has the same effect as setting the PCRE_UCP option: it causes sequences +such as \d and \w to use Unicode properties to determine character types, +instead of recognizing only characters with codes less than 128 via a lookup +table. +</P> +<br><b> +Disabling auto-possessification +</b><br> +<P> +If a pattern starts with (*NO_AUTO_POSSESS), it has the same effect as setting +the PCRE_NO_AUTO_POSSESS option at compile time. This stops PCRE from making +quantifiers possessive when what follows cannot match the repeated item. For +example, by default a+b is treated as a++b. For more details, see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<br><b> +Disabling start-up optimizations +</b><br> +<P> +If a pattern starts with (*NO_START_OPT), it has the same effect as setting the +PCRE_NO_START_OPTIMIZE option either at compile or matching time. This disables +several optimizations for quickly reaching "no match" results. For more +details, see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +<a name="newlines"></a></P> +<br><b> +Newline conventions +</b><br> +<P> +PCRE supports five different conventions for indicating line breaks in +strings: a single CR (carriage return) character, a single LF (linefeed) +character, the two-character sequence CRLF, any of the three preceding, or any +Unicode newline sequence. The +<a href="pcreapi.html"><b>pcreapi</b></a> +page has +<a href="pcreapi.html#newlines">further discussion</a> +about newlines, and shows how to set the newline convention in the +<i>options</i> arguments for the compiling and matching functions. +</P> +<P> +It is also possible to specify a newline convention by starting a pattern +string with one of the following five sequences: +<pre> + (*CR) carriage return + (*LF) linefeed + (*CRLF) carriage return, followed by linefeed + (*ANYCRLF) any of the three above + (*ANY) all Unicode newline sequences +</pre> +These override the default and the options given to the compiling function. For +example, on a Unix system where LF is the default newline sequence, the pattern +<pre> + (*CR)a.b +</pre> +changes the convention to CR. That pattern matches "a\nb" because LF is no +longer a newline. If more than one of these settings is present, the last one +is used. +</P> +<P> +The newline convention affects where the circumflex and dollar assertions are +true. It also affects the interpretation of the dot metacharacter when +PCRE_DOTALL is not set, and the behaviour of \N. However, it does not affect +what the \R escape sequence matches. By default, this is any Unicode newline +sequence, for Perl compatibility. However, this can be changed; see the +description of \R in the section entitled +<a href="#newlineseq">"Newline sequences"</a> +below. A change of \R setting can be combined with a change of newline +convention. +</P> +<br><b> +Setting match and recursion limits +</b><br> +<P> +The caller of <b>pcre_exec()</b> can set a limit on the number of times the +internal <b>match()</b> function is called and on the maximum depth of +recursive calls. These facilities are provided to catch runaway matches that +are provoked by patterns with huge matching trees (a typical example is a +pattern with nested unlimited repeats) and to avoid running out of system stack +by too much recursion. When one of these limits is reached, <b>pcre_exec()</b> +gives an error return. The limits can also be set by items at the start of the +pattern of the form +<pre> + (*LIMIT_MATCH=d) + (*LIMIT_RECURSION=d) +</pre> +where d is any number of decimal digits. However, the value of the setting must +be less than the value set (or defaulted) by the caller of <b>pcre_exec()</b> +for it to have any effect. In other words, the pattern writer can lower the +limits set by the programmer, but not raise them. If there is more than one +setting of one of these limits, the lower value is used. +</P> +<br><a name="SEC3" href="#TOC1">EBCDIC CHARACTER CODES</a><br> +<P> +PCRE can be compiled to run in an environment that uses EBCDIC as its character +code rather than ASCII or Unicode (typically a mainframe system). In the +sections below, character code values are ASCII or Unicode; in an EBCDIC +environment these characters may have different code values, and there are no +code points greater than 255. +</P> +<br><a name="SEC4" href="#TOC1">CHARACTERS AND METACHARACTERS</a><br> +<P> +A regular expression is a pattern that is matched against a subject string from +left to right. Most characters stand for themselves in a pattern, and match the +corresponding characters in the subject. As a trivial example, the pattern +<pre> + The quick brown fox +</pre> +matches a portion of a subject string that is identical to itself. When +caseless matching is specified (the PCRE_CASELESS option), letters are matched +independently of case. In a UTF mode, PCRE always understands the concept of +case for characters whose values are less than 128, so caseless matching is +always possible. For characters with higher values, the concept of case is +supported if PCRE is compiled with Unicode property support, but not otherwise. +If you want to use caseless matching for characters 128 and above, you must +ensure that PCRE is compiled with Unicode property support as well as with +UTF support. +</P> +<P> +The power of regular expressions comes from the ability to include alternatives +and repetitions in the pattern. These are encoded in the pattern by the use of +<i>metacharacters</i>, which do not stand for themselves but instead are +interpreted in some special way. +</P> +<P> +There are two different sets of metacharacters: those that are recognized +anywhere in the pattern except within square brackets, and those that are +recognized within square brackets. Outside square brackets, the metacharacters +are as follows: +<pre> + \ general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier +</pre> +Part of a pattern that is in square brackets is called a "character class". In +a character class the only metacharacters are: +<pre> + \ general escape character + ^ negate the class, but only if the first character + - indicates character range + [ POSIX character class (only if followed by POSIX syntax) + ] terminates the character class +</pre> +The following sections describe the use of each of the metacharacters. +</P> +<br><a name="SEC5" href="#TOC1">BACKSLASH</a><br> +<P> +The backslash character has several uses. Firstly, if it is followed by a +character that is not a number or a letter, it takes away any special meaning +that character may have. This use of backslash as an escape character applies +both inside and outside character classes. +</P> +<P> +For example, if you want to match a * character, you write \* in the pattern. +This escaping action applies whether or not the following character would +otherwise be interpreted as a metacharacter, so it is always safe to precede a +non-alphanumeric with backslash to specify that it stands for itself. In +particular, if you want to match a backslash, you write \\. +</P> +<P> +In a UTF mode, only ASCII numbers and letters have any special meaning after a +backslash. All other characters (in particular, those whose codepoints are +greater than 127) are treated as literals. +</P> +<P> +If a pattern is compiled with the PCRE_EXTENDED option, most white space in the +pattern (other than in a character class), and characters between a # outside a +character class and the next newline, inclusive, are ignored. An escaping +backslash can be used to include a white space or # character as part of the +pattern. +</P> +<P> +If you want to remove the special meaning from a sequence of characters, you +can do so by putting them between \Q and \E. This is different from Perl in +that $ and @ are handled as literals in \Q...\E sequences in PCRE, whereas in +Perl, $ and @ cause variable interpolation. Note the following examples: +<pre> + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz +</pre> +The \Q...\E sequence is recognized both inside and outside character classes. +An isolated \E that is not preceded by \Q is ignored. If \Q is not followed +by \E later in the pattern, the literal interpretation continues to the end of +the pattern (that is, \E is assumed at the end). If the isolated \Q is inside +a character class, this causes an error, because the character class is not +terminated. +<a name="digitsafterbackslash"></a></P> +<br><b> +Non-printing characters +</b><br> +<P> +A second use of backslash provides a way of encoding non-printing characters +in patterns in a visible manner. There is no restriction on the appearance of +non-printing characters, apart from the binary zero that terminates a pattern, +but when a pattern is being prepared by text editing, it is often easier to use +one of the following escape sequences than the binary character it represents. +In an ASCII or Unicode environment, these escapes are as follows: +<pre> + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any ASCII character + \e escape (hex 1B) + \f form feed (hex 0C) + \n linefeed (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \0dd character with octal code 0dd + \ddd character with octal code ddd, or back reference + \o{ddd..} character with octal code ddd.. + \xhh character with hex code hh + \x{hhh..} character with hex code hhh.. (non-JavaScript mode) + \uhhhh character with hex code hhhh (JavaScript mode only) +</pre> +The precise effect of \cx on ASCII characters is as follows: if x is a lower +case letter, it is converted to upper case. Then bit 6 of the character (hex +40) is inverted. Thus \cA to \cZ become hex 01 to hex 1A (A is 41, Z is 5A), +but \c{ becomes hex 3B ({ is 7B), and \c; becomes hex 7B (; is 3B). If the +data item (byte or 16-bit value) following \c has a value greater than 127, a +compile-time error occurs. This locks out non-ASCII characters in all modes. +</P> +<P> +When PCRE is compiled in EBCDIC mode, \a, \e, \f, \n, \r, and \t +generate the appropriate EBCDIC code values. The \c escape is processed +as specified for Perl in the <b>perlebcdic</b> document. The only characters +that are allowed after \c are A-Z, a-z, or one of @, [, \, ], ^, _, or ?. Any +other character provokes a compile-time error. The sequence \@ encodes +character code 0; the letters (in either case) encode characters 1-26 (hex 01 +to hex 1A); [, \, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and +\? becomes either 255 (hex FF) or 95 (hex 5F). +</P> +<P> +Thus, apart from \?, these escapes generate the same character code values as +they do in an ASCII environment, though the meanings of the values mostly +differ. For example, \G always generates code value 7, which is BEL in ASCII +but DEL in EBCDIC. +</P> +<P> +The sequence \? generates DEL (127, hex 7F) in an ASCII environment, but +because 127 is not a control character in EBCDIC, Perl makes it generate the +APC character. Unfortunately, there are several variants of EBCDIC. In most of +them the APC character has the value 255 (hex FF), but in the one Perl calls +POSIX-BC its value is 95 (hex 5F). If certain other characters have POSIX-BC +values, PCRE makes \? generate 95; otherwise it generates 255. +</P> +<P> +After \0 up to two further octal digits are read. If there are fewer than two +digits, just those that are present are used. Thus the sequence \0\x\015 +specifies two binary zeros followed by a CR character (code value 13). Make +sure you supply two digits after the initial zero if the pattern character that +follows is itself an octal digit. +</P> +<P> +The escape \o must be followed by a sequence of octal digits, enclosed in +braces. An error occurs if this is not the case. This escape is a recent +addition to Perl; it provides way of specifying character code points as octal +numbers greater than 0777, and it also allows octal numbers and back references +to be unambiguously specified. +</P> +<P> +For greater clarity and unambiguity, it is best to avoid following \ by a +digit greater than zero. Instead, use \o{} or \x{} to specify character +numbers, and \g{} to specify back references. The following paragraphs +describe the old, ambiguous syntax. +</P> +<P> +The handling of a backslash followed by a digit other than 0 is complicated, +and Perl has changed in recent releases, causing PCRE also to change. Outside a +character class, PCRE reads the digit and any following digits as a decimal +number. If the number is less than 8, or if there have been at least that many +previous capturing left parentheses in the expression, the entire sequence is +taken as a <i>back reference</i>. A description of how this works is given +<a href="#backreferences">later,</a> +following the discussion of +<a href="#subpattern">parenthesized subpatterns.</a> +</P> +<P> +Inside a character class, or if the decimal number following \ is greater than +7 and there have not been that many capturing subpatterns, PCRE handles \8 and +\9 as the literal characters "8" and "9", and otherwise re-reads up to three +octal digits following the backslash, using them to generate a data character. +Any subsequent digits stand for themselves. For example: +<pre> + \040 is another way of writing an ASCII space + \40 is the same, provided there are fewer than 40 previous capturing subpatterns + \7 is always a back reference + \11 might be a back reference, or another way of writing a tab + \011 is always a tab + \0113 is a tab followed by the character "3" + \113 might be a back reference, otherwise the character with octal code 113 + \377 might be a back reference, otherwise the value 255 (decimal) + \81 is either a back reference, or the two characters "8" and "1" +</pre> +Note that octal values of 100 or greater that are specified using this syntax +must not be introduced by a leading zero, because no more than three octal +digits are ever read. +</P> +<P> +By default, after \x that is not followed by {, from zero to two hexadecimal +digits are read (letters can be in upper or lower case). Any number of +hexadecimal digits may appear between \x{ and }. If a character other than +a hexadecimal digit appears between \x{ and }, or if there is no terminating +}, an error occurs. +</P> +<P> +If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \x is +as just described only when it is followed by two hexadecimal digits. +Otherwise, it matches a literal "x" character. In JavaScript mode, support for +code points greater than 256 is provided by \u, which must be followed by +four hexadecimal digits; otherwise it matches a literal "u" character. +</P> +<P> +Characters whose value is less than 256 can be defined by either of the two +syntaxes for \x (or by \u in JavaScript mode). There is no difference in the +way they are handled. For example, \xdc is exactly the same as \x{dc} (or +\u00dc in JavaScript mode). +</P> +<br><b> +Constraints on character values +</b><br> +<P> +Characters that are specified using octal or hexadecimal numbers are +limited to certain values, as follows: +<pre> + 8-bit non-UTF mode less than 0x100 + 8-bit UTF-8 mode less than 0x10ffff and a valid codepoint + 16-bit non-UTF mode less than 0x10000 + 16-bit UTF-16 mode less than 0x10ffff and a valid codepoint + 32-bit non-UTF mode less than 0x100000000 + 32-bit UTF-32 mode less than 0x10ffff and a valid codepoint +</pre> +Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called +"surrogate" codepoints), and 0xffef. +</P> +<br><b> +Escape sequences in character classes +</b><br> +<P> +All the sequences that define a single character value can be used both inside +and outside character classes. In addition, inside a character class, \b is +interpreted as the backspace character (hex 08). +</P> +<P> +\N is not allowed in a character class. \B, \R, and \X are not special +inside a character class. Like other unrecognized escape sequences, they are +treated as the literal characters "B", "R", and "X" by default, but cause an +error if the PCRE_EXTRA option is set. Outside a character class, these +sequences have different meanings. +</P> +<br><b> +Unsupported escape sequences +</b><br> +<P> +In Perl, the sequences \l, \L, \u, and \U are recognized by its string +handler and used to modify the case of following characters. By default, PCRE +does not support these escape sequences. However, if the PCRE_JAVASCRIPT_COMPAT +option is set, \U matches a "U" character, and \u can be used to define a +character by code point, as described in the previous section. +</P> +<br><b> +Absolute and relative back references +</b><br> +<P> +The sequence \g followed by an unsigned or a negative number, optionally +enclosed in braces, is an absolute or relative back reference. A named back +reference can be coded as \g{name}. Back references are discussed +<a href="#backreferences">later,</a> +following the discussion of +<a href="#subpattern">parenthesized subpatterns.</a> +</P> +<br><b> +Absolute and relative subroutine calls +</b><br> +<P> +For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or +a number enclosed either in angle brackets or single quotes, is an alternative +syntax for referencing a subpattern as a "subroutine". Details are discussed +<a href="#onigurumasubroutines">later.</a> +Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are <i>not</i> +synonymous. The former is a back reference; the latter is a +<a href="#subpatternsassubroutines">subroutine</a> +call. +<a name="genericchartypes"></a></P> +<br><b> +Generic character types +</b><br> +<P> +Another use of backslash is for specifying generic character types: +<pre> + \d any decimal digit + \D any character that is not a decimal digit + \h any horizontal white space character + \H any character that is not a horizontal white space character + \s any white space character + \S any character that is not a white space character + \v any vertical white space character + \V any character that is not a vertical white space character + \w any "word" character + \W any "non-word" character +</pre> +There is also the single sequence \N, which matches a non-newline character. +This is the same as +<a href="#fullstopdot">the "." metacharacter</a> +when PCRE_DOTALL is not set. Perl also uses \N to match characters by name; +PCRE does not support this. +</P> +<P> +Each pair of lower and upper case escape sequences partitions the complete set +of characters into two disjoint sets. Any given character matches one, and only +one, of each pair. The sequences can appear both inside and outside character +classes. They each match one character of the appropriate type. If the current +matching point is at the end of the subject string, all of them fail, because +there is no character to match. +</P> +<P> +For compatibility with Perl, \s did not used to match the VT character (code +11), which made it different from the the POSIX "space" class. However, Perl +added VT at release 5.18, and PCRE followed suit at release 8.34. The default +\s characters are now HT (9), LF (10), VT (11), FF (12), CR (13), and space +(32), which are defined as white space in the "C" locale. This list may vary if +locale-specific matching is taking place. For example, in some locales the +"non-breaking space" character (\xA0) is recognized as white space, and in +others the VT character is not. +</P> +<P> +A "word" character is an underscore or any character that is a letter or digit. +By default, the definition of letters and digits is controlled by PCRE's +low-valued character tables, and may vary if locale-specific matching is taking +place (see +<a href="pcreapi.html#localesupport">"Locale support"</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page). For example, in a French locale such as "fr_FR" in Unix-like systems, +or "french" in Windows, some character codes greater than 127 are used for +accented letters, and these are then matched by \w. The use of locales with +Unicode is discouraged. +</P> +<P> +By default, characters whose code points are greater than 127 never match \d, +\s, or \w, and always match \D, \S, and \W, although this may vary for +characters in the range 128-255 when locale-specific matching is happening. +These escape sequences retain their original meanings from before Unicode +support was available, mainly for efficiency reasons. If PCRE is compiled with +Unicode property support, and the PCRE_UCP option is set, the behaviour is +changed so that Unicode properties are used to determine character types, as +follows: +<pre> + \d any character that matches \p{Nd} (decimal digit) + \s any character that matches \p{Z} or \h or \v + \w any character that matches \p{L} or \p{N}, plus underscore +</pre> +The upper case escapes match the inverse sets of characters. Note that \d +matches only decimal digits, whereas \w matches any Unicode digit, as well as +any Unicode letter, and underscore. Note also that PCRE_UCP affects \b, and +\B because they are defined in terms of \w and \W. Matching these sequences +is noticeably slower when PCRE_UCP is set. +</P> +<P> +The sequences \h, \H, \v, and \V are features that were added to Perl at +release 5.10. In contrast to the other sequences, which match only ASCII +characters by default, these always match certain high-valued code points, +whether or not PCRE_UCP is set. The horizontal space characters are: +<pre> + U+0009 Horizontal tab (HT) + U+0020 Space + U+00A0 Non-break space + U+1680 Ogham space mark + U+180E Mongolian vowel separator + U+2000 En quad + U+2001 Em quad + U+2002 En space + U+2003 Em space + U+2004 Three-per-em space + U+2005 Four-per-em space + U+2006 Six-per-em space + U+2007 Figure space + U+2008 Punctuation space + U+2009 Thin space + U+200A Hair space + U+202F Narrow no-break space + U+205F Medium mathematical space + U+3000 Ideographic space +</pre> +The vertical space characters are: +<pre> + U+000A Linefeed (LF) + U+000B Vertical tab (VT) + U+000C Form feed (FF) + U+000D Carriage return (CR) + U+0085 Next line (NEL) + U+2028 Line separator + U+2029 Paragraph separator +</pre> +In 8-bit, non-UTF-8 mode, only the characters with codepoints less than 256 are +relevant. +<a name="newlineseq"></a></P> +<br><b> +Newline sequences +</b><br> +<P> +Outside a character class, by default, the escape sequence \R matches any +Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent to the +following: +<pre> + (?>\r\n|\n|\x0b|\f|\r|\x85) +</pre> +This is an example of an "atomic group", details of which are given +<a href="#atomicgroup">below.</a> +This particular group matches either the two-character sequence CR followed by +LF, or one of the single characters LF (linefeed, U+000A), VT (vertical tab, +U+000B), FF (form feed, U+000C), CR (carriage return, U+000D), or NEL (next +line, U+0085). The two-character sequence is treated as a single unit that +cannot be split. +</P> +<P> +In other modes, two additional characters whose codepoints are greater than 255 +are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029). +Unicode character property support is not needed for these characters to be +recognized. +</P> +<P> +It is possible to restrict \R to match only CR, LF, or CRLF (instead of the +complete set of Unicode line endings) by setting the option PCRE_BSR_ANYCRLF +either at compile time or when the pattern is matched. (BSR is an abbrevation +for "backslash R".) This can be made the default when PCRE is built; if this is +the case, the other behaviour can be requested via the PCRE_BSR_UNICODE option. +It is also possible to specify these settings by starting a pattern string with +one of the following sequences: +<pre> + (*BSR_ANYCRLF) CR, LF, or CRLF only + (*BSR_UNICODE) any Unicode newline sequence +</pre> +These override the default and the options given to the compiling function, but +they can themselves be overridden by options given to a matching function. Note +that these special settings, which are not Perl-compatible, are recognized only +at the very start of a pattern, and that they must be in upper case. If more +than one of them is present, the last one is used. They can be combined with a +change of newline convention; for example, a pattern can start with: +<pre> + (*ANY)(*BSR_ANYCRLF) +</pre> +They can also be combined with the (*UTF8), (*UTF16), (*UTF32), (*UTF) or +(*UCP) special sequences. Inside a character class, \R is treated as an +unrecognized escape sequence, and so matches the letter "R" by default, but +causes an error if PCRE_EXTRA is set. +<a name="uniextseq"></a></P> +<br><b> +Unicode character properties +</b><br> +<P> +When PCRE is built with Unicode character property support, three additional +escape sequences that match characters with specific properties are available. +When in 8-bit non-UTF-8 mode, these sequences are of course limited to testing +characters whose codepoints are less than 256, but they do work in this mode. +The extra escape sequences are: +<pre> + \p{<i>xx</i>} a character with the <i>xx</i> property + \P{<i>xx</i>} a character without the <i>xx</i> property + \X a Unicode extended grapheme cluster +</pre> +The property names represented by <i>xx</i> above are limited to the Unicode +script names, the general category properties, "Any", which matches any +character (including newline), and some special PCRE properties (described +in the +<a href="#extraprops">next section).</a> +Other Perl properties such as "InMusicalSymbols" are not currently supported by +PCRE. Note that \P{Any} does not match any characters, so always causes a +match failure. +</P> +<P> +Sets of Unicode characters are defined as belonging to certain scripts. A +character from one of these sets can be matched using a script name. For +example: +<pre> + \p{Greek} + \P{Han} +</pre> +Those that are not part of an identified script are lumped together as +"Common". The current list of scripts is: +</P> +<P> +Arabic, +Armenian, +Avestan, +Balinese, +Bamum, +Bassa_Vah, +Batak, +Bengali, +Bopomofo, +Brahmi, +Braille, +Buginese, +Buhid, +Canadian_Aboriginal, +Carian, +Caucasian_Albanian, +Chakma, +Cham, +Cherokee, +Common, +Coptic, +Cuneiform, +Cypriot, +Cyrillic, +Deseret, +Devanagari, +Duployan, +Egyptian_Hieroglyphs, +Elbasan, +Ethiopic, +Georgian, +Glagolitic, +Gothic, +Grantha, +Greek, +Gujarati, +Gurmukhi, +Han, +Hangul, +Hanunoo, +Hebrew, +Hiragana, +Imperial_Aramaic, +Inherited, +Inscriptional_Pahlavi, +Inscriptional_Parthian, +Javanese, +Kaithi, +Kannada, +Katakana, +Kayah_Li, +Kharoshthi, +Khmer, +Khojki, +Khudawadi, +Lao, +Latin, +Lepcha, +Limbu, +Linear_A, +Linear_B, +Lisu, +Lycian, +Lydian, +Mahajani, +Malayalam, +Mandaic, +Manichaean, +Meetei_Mayek, +Mende_Kikakui, +Meroitic_Cursive, +Meroitic_Hieroglyphs, +Miao, +Modi, +Mongolian, +Mro, +Myanmar, +Nabataean, +New_Tai_Lue, +Nko, +Ogham, +Ol_Chiki, +Old_Italic, +Old_North_Arabian, +Old_Permic, +Old_Persian, +Old_South_Arabian, +Old_Turkic, +Oriya, +Osmanya, +Pahawh_Hmong, +Palmyrene, +Pau_Cin_Hau, +Phags_Pa, +Phoenician, +Psalter_Pahlavi, +Rejang, +Runic, +Samaritan, +Saurashtra, +Sharada, +Shavian, +Siddham, +Sinhala, +Sora_Sompeng, +Sundanese, +Syloti_Nagri, +Syriac, +Tagalog, +Tagbanwa, +Tai_Le, +Tai_Tham, +Tai_Viet, +Takri, +Tamil, +Telugu, +Thaana, +Thai, +Tibetan, +Tifinagh, +Tirhuta, +Ugaritic, +Vai, +Warang_Citi, +Yi. +</P> +<P> +Each character has exactly one Unicode general category property, specified by +a two-letter abbreviation. For compatibility with Perl, negation can be +specified by including a circumflex between the opening brace and the property +name. For example, \p{^Lu} is the same as \P{Lu}. +</P> +<P> +If only one letter is specified with \p or \P, it includes all the general +category properties that start with that letter. In this case, in the absence +of negation, the curly brackets in the escape sequence are optional; these two +examples have the same effect: +<pre> + \p{L} + \pL +</pre> +The following general category property codes are supported: +<pre> + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate + + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter + + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark + + N Number + Nd Decimal number + Nl Letter number + No Other number + + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation + + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol + + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator +</pre> +The special property L& is also supported: it matches a character that has +the Lu, Ll, or Lt property, in other words, a letter that is not classified as +a modifier or "other". +</P> +<P> +The Cs (Surrogate) property applies only to characters in the range U+D800 to +U+DFFF. Such characters are not valid in Unicode strings and so +cannot be tested by PCRE, unless UTF validity checking has been turned off +(see the discussion of PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK and +PCRE_NO_UTF32_CHECK in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page). Perl does not support the Cs property. +</P> +<P> +The long synonyms for property names that Perl supports (such as \p{Letter}) +are not supported by PCRE, nor is it permitted to prefix any of these +properties with "Is". +</P> +<P> +No character that is in the Unicode table has the Cn (unassigned) property. +Instead, this property is assumed for any code point that is not in the +Unicode table. +</P> +<P> +Specifying caseless matching does not affect these escape sequences. For +example, \p{Lu} always matches only upper case letters. This is different from +the behaviour of current versions of Perl. +</P> +<P> +Matching characters by Unicode property is not fast, because PCRE has to do a +multistage table lookup in order to find a character's property. That is why +the traditional escape sequences such as \d and \w do not use Unicode +properties in PCRE by default, though you can make them do so by setting the +PCRE_UCP option or by starting the pattern with (*UCP). +</P> +<br><b> +Extended grapheme clusters +</b><br> +<P> +The \X escape matches any number of Unicode characters that form an "extended +grapheme cluster", and treats the sequence as an atomic group +<a href="#atomicgroup">(see below).</a> +Up to and including release 8.31, PCRE matched an earlier, simpler definition +that was equivalent to +<pre> + (?>\PM\pM*) +</pre> +That is, it matched a character without the "mark" property, followed by zero +or more characters with the "mark" property. Characters with the "mark" +property are typically non-spacing accents that affect the preceding character. +</P> +<P> +This simple definition was extended in Unicode to include more complicated +kinds of composite character by giving each character a grapheme breaking +property, and creating rules that use these properties to define the boundaries +of extended grapheme clusters. In releases of PCRE later than 8.31, \X matches +one of these clusters. +</P> +<P> +\X always matches at least one character. Then it decides whether to add +additional characters according to the following rules for ending a cluster: +</P> +<P> +1. End at the end of the subject string. +</P> +<P> +2. Do not end between CR and LF; otherwise end after any control character. +</P> +<P> +3. Do not break Hangul (a Korean script) syllable sequences. Hangul characters +are of five types: L, V, T, LV, and LVT. An L character may be followed by an +L, V, LV, or LVT character; an LV or V character may be followed by a V or T +character; an LVT or T character may be follwed only by a T character. +</P> +<P> +4. Do not end before extending characters or spacing marks. Characters with +the "mark" property always have the "extend" grapheme breaking property. +</P> +<P> +5. Do not end after prepend characters. +</P> +<P> +6. Otherwise, end the cluster. +<a name="extraprops"></a></P> +<br><b> +PCRE's additional properties +</b><br> +<P> +As well as the standard Unicode properties described above, PCRE supports four +more that make it possible to convert traditional escape sequences such as \w +and \s to use Unicode properties. PCRE uses these non-standard, non-Perl +properties internally when PCRE_UCP is set. However, they may also be used +explicitly. These properties are: +<pre> + Xan Any alphanumeric character + Xps Any POSIX space character + Xsp Any Perl space character + Xwd Any Perl "word" character +</pre> +Xan matches characters that have either the L (letter) or the N (number) +property. Xps matches the characters tab, linefeed, vertical tab, form feed, or +carriage return, and any other character that has the Z (separator) property. +Xsp is the same as Xps; it used to exclude vertical tab, for Perl +compatibility, but Perl changed, and so PCRE followed at release 8.34. Xwd +matches the same characters as Xan, plus underscore. +</P> +<P> +There is another non-standard property, Xuc, which matches any character that +can be represented by a Universal Character Name in C++ and other programming +languages. These are the characters $, @, ` (grave accent), and all characters +with Unicode code points greater than or equal to U+00A0, except for the +surrogates U+D800 to U+DFFF. Note that most base (ASCII) characters are +excluded. (Universal Character Names are of the form \uHHHH or \UHHHHHHHH +where H is a hexadecimal digit. Note that the Xuc property does not match these +sequences but the characters that they represent.) +<a name="resetmatchstart"></a></P> +<br><b> +Resetting the match start +</b><br> +<P> +The escape sequence \K causes any previously matched characters not to be +included in the final matched sequence. For example, the pattern: +<pre> + foo\Kbar +</pre> +matches "foobar", but reports that it has matched "bar". This feature is +similar to a lookbehind assertion +<a href="#lookbehind">(described below).</a> +However, in this case, the part of the subject before the real match does not +have to be of fixed length, as lookbehind assertions do. The use of \K does +not interfere with the setting of +<a href="#subpattern">captured substrings.</a> +For example, when the pattern +<pre> + (foo)\Kbar +</pre> +matches "foobar", the first substring is still set to "foo". +</P> +<P> +Perl documents that the use of \K within assertions is "not well defined". In +PCRE, \K is acted upon when it occurs inside positive assertions, but is +ignored in negative assertions. Note that when a pattern such as (?=ab\K) +matches, the reported start of the match can be greater than the end of the +match. +<a name="smallassertions"></a></P> +<br><b> +Simple assertions +</b><br> +<P> +The final use of backslash is for certain simple assertions. An assertion +specifies a condition that has to be met at a particular point in a match, +without consuming any characters from the subject string. The use of +subpatterns for more complicated assertions is described +<a href="#bigassertions">below.</a> +The backslashed assertions are: +<pre> + \b matches at a word boundary + \B matches when not at a word boundary + \A matches at the start of the subject + \Z matches at the end of the subject + also matches before a newline at the end of the subject + \z matches only at the end of the subject + \G matches at the first matching position in the subject +</pre> +Inside a character class, \b has a different meaning; it matches the backspace +character. If any other of these assertions appears in a character class, by +default it matches the corresponding literal character (for example, \B +matches the letter B). However, if the PCRE_EXTRA option is set, an "invalid +escape sequence" error is generated instead. +</P> +<P> +A word boundary is a position in the subject string where the current character +and the previous character do not both match \w or \W (i.e. one matches +\w and the other matches \W), or the start or end of the string if the +first or last character matches \w, respectively. In a UTF mode, the meanings +of \w and \W can be changed by setting the PCRE_UCP option. When this is +done, it also affects \b and \B. Neither PCRE nor Perl has a separate "start +of word" or "end of word" metasequence. However, whatever follows \b normally +determines which it is. For example, the fragment \ba matches "a" at the start +of a word. +</P> +<P> +The \A, \Z, and \z assertions differ from the traditional circumflex and +dollar (described in the next section) in that they only ever match at the very +start and end of the subject string, whatever options are set. Thus, they are +independent of multiline mode. These three assertions are not affected by the +PCRE_NOTBOL or PCRE_NOTEOL options, which affect only the behaviour of the +circumflex and dollar metacharacters. However, if the <i>startoffset</i> +argument of <b>pcre_exec()</b> is non-zero, indicating that matching is to start +at a point other than the beginning of the subject, \A can never match. The +difference between \Z and \z is that \Z matches before a newline at the end +of the string as well as at the very end, whereas \z matches only at the end. +</P> +<P> +The \G assertion is true only when the current matching position is at the +start point of the match, as specified by the <i>startoffset</i> argument of +<b>pcre_exec()</b>. It differs from \A when the value of <i>startoffset</i> is +non-zero. By calling <b>pcre_exec()</b> multiple times with appropriate +arguments, you can mimic Perl's /g option, and it is in this kind of +implementation where \G can be useful. +</P> +<P> +Note, however, that PCRE's interpretation of \G, as the start of the current +match, is subtly different from Perl's, which defines it as the end of the +previous match. In Perl, these can be different when the previously matched +string was empty. Because PCRE does just one match at a time, it cannot +reproduce this behaviour. +</P> +<P> +If all the alternatives of a pattern begin with \G, the expression is anchored +to the starting match position, and the "anchored" flag is set in the compiled +regular expression. +</P> +<br><a name="SEC6" href="#TOC1">CIRCUMFLEX AND DOLLAR</a><br> +<P> +The circumflex and dollar metacharacters are zero-width assertions. That is, +they test for a particular condition being true without consuming any +characters from the subject string. +</P> +<P> +Outside a character class, in the default matching mode, the circumflex +character is an assertion that is true only if the current matching point is at +the start of the subject string. If the <i>startoffset</i> argument of +<b>pcre_exec()</b> is non-zero, circumflex can never match if the PCRE_MULTILINE +option is unset. Inside a character class, circumflex has an entirely different +meaning +<a href="#characterclass">(see below).</a> +</P> +<P> +Circumflex need not be the first character of the pattern if a number of +alternatives are involved, but it should be the first thing in each alternative +in which it appears if the pattern is ever to match that branch. If all +possible alternatives start with a circumflex, that is, if the pattern is +constrained to match only at the start of the subject, it is said to be an +"anchored" pattern. (There are also other constructs that can cause a pattern +to be anchored.) +</P> +<P> +The dollar character is an assertion that is true only if the current matching +point is at the end of the subject string, or immediately before a newline at +the end of the string (by default). Note, however, that it does not actually +match the newline. Dollar need not be the last character of the pattern if a +number of alternatives are involved, but it should be the last item in any +branch in which it appears. Dollar has no special meaning in a character class. +</P> +<P> +The meaning of dollar can be changed so that it matches only at the very end of +the string, by setting the PCRE_DOLLAR_ENDONLY option at compile time. This +does not affect the \Z assertion. +</P> +<P> +The meanings of the circumflex and dollar characters are changed if the +PCRE_MULTILINE option is set. When this is the case, a circumflex matches +immediately after internal newlines as well as at the start of the subject +string. It does not match after a newline that ends the string. A dollar +matches before any newlines in the string, as well as at the very end, when +PCRE_MULTILINE is set. When newline is specified as the two-character +sequence CRLF, isolated CR and LF characters do not indicate newlines. +</P> +<P> +For example, the pattern /^abc$/ matches the subject string "def\nabc" (where +\n represents a newline) in multiline mode, but not otherwise. Consequently, +patterns that are anchored in single line mode because all branches start with +^ are not anchored in multiline mode, and a match for circumflex is possible +when the <i>startoffset</i> argument of <b>pcre_exec()</b> is non-zero. The +PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set. +</P> +<P> +Note that the sequences \A, \Z, and \z can be used to match the start and +end of the subject in both modes, and if all branches of a pattern start with +\A it is always anchored, whether or not PCRE_MULTILINE is set. +<a name="fullstopdot"></a></P> +<br><a name="SEC7" href="#TOC1">FULL STOP (PERIOD, DOT) AND \N</a><br> +<P> +Outside a character class, a dot in the pattern matches any one character in +the subject string except (by default) a character that signifies the end of a +line. +</P> +<P> +When a line ending is defined as a single character, dot never matches that +character; when the two-character sequence CRLF is used, dot does not match CR +if it is immediately followed by LF, but otherwise it matches all characters +(including isolated CRs and LFs). When any Unicode line endings are being +recognized, dot does not match CR or LF or any of the other line ending +characters. +</P> +<P> +The behaviour of dot with regard to newlines can be changed. If the PCRE_DOTALL +option is set, a dot matches any one character, without exception. If the +two-character sequence CRLF is present in the subject string, it takes two dots +to match it. +</P> +<P> +The handling of dot is entirely independent of the handling of circumflex and +dollar, the only relationship being that they both involve newlines. Dot has no +special meaning in a character class. +</P> +<P> +The escape sequence \N behaves like a dot, except that it is not affected by +the PCRE_DOTALL option. In other words, it matches any character except one +that signifies the end of a line. Perl also uses \N to match characters by +name; PCRE does not support this. +</P> +<br><a name="SEC8" href="#TOC1">MATCHING A SINGLE DATA UNIT</a><br> +<P> +Outside a character class, the escape sequence \C matches any one data unit, +whether or not a UTF mode is set. In the 8-bit library, one data unit is one +byte; in the 16-bit library it is a 16-bit unit; in the 32-bit library it is +a 32-bit unit. Unlike a dot, \C always +matches line-ending characters. The feature is provided in Perl in order to +match individual bytes in UTF-8 mode, but it is unclear how it can usefully be +used. Because \C breaks up characters into individual data units, matching one +unit with \C in a UTF mode means that the rest of the string may start with a +malformed UTF character. This has undefined results, because PCRE assumes that +it is dealing with valid UTF strings (and by default it checks this at the +start of processing unless the PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK or +PCRE_NO_UTF32_CHECK option is used). +</P> +<P> +PCRE does not allow \C to appear in lookbehind assertions +<a href="#lookbehind">(described below)</a> +in a UTF mode, because this would make it impossible to calculate the length of +the lookbehind. +</P> +<P> +In general, the \C escape sequence is best avoided. However, one +way of using it that avoids the problem of malformed UTF characters is to use a +lookahead to check the length of the next character, as in this pattern, which +could be used with a UTF-8 string (ignore white space and line breaks): +<pre> + (?| (?=[\x00-\x7f])(\C) | + (?=[\x80-\x{7ff}])(\C)(\C) | + (?=[\x{800}-\x{ffff}])(\C)(\C)(\C) | + (?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C)) +</pre> +A group that starts with (?| resets the capturing parentheses numbers in each +alternative (see +<a href="#dupsubpatternnumber">"Duplicate Subpattern Numbers"</a> +below). The assertions at the start of each branch check the next UTF-8 +character for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The +character's individual bytes are then captured by the appropriate number of +groups. +<a name="characterclass"></a></P> +<br><a name="SEC9" href="#TOC1">SQUARE BRACKETS AND CHARACTER CLASSES</a><br> +<P> +An opening square bracket introduces a character class, terminated by a closing +square bracket. A closing square bracket on its own is not special by default. +However, if the PCRE_JAVASCRIPT_COMPAT option is set, a lone closing square +bracket causes a compile-time error. If a closing square bracket is required as +a member of the class, it should be the first data character in the class +(after an initial circumflex, if present) or escaped with a backslash. +</P> +<P> +A character class matches a single character in the subject. In a UTF mode, the +character may be more than one data unit long. A matched character must be in +the set of characters defined by the class, unless the first character in the +class definition is a circumflex, in which case the subject character must not +be in the set defined by the class. If a circumflex is actually required as a +member of the class, ensure it is not the first character, or escape it with a +backslash. +</P> +<P> +For example, the character class [aeiou] matches any lower case vowel, while +[^aeiou] matches any character that is not a lower case vowel. Note that a +circumflex is just a convenient notation for specifying the characters that +are in the class by enumerating those that are not. A class that starts with a +circumflex is not an assertion; it still consumes a character from the subject +string, and therefore it fails if the current pointer is at the end of the +string. +</P> +<P> +In UTF-8 (UTF-16, UTF-32) mode, characters with values greater than 255 (0xffff) +can be included in a class as a literal string of data units, or by using the +\x{ escaping mechanism. +</P> +<P> +When caseless matching is set, any letters in a class represent both their +upper case and lower case versions, so for example, a caseless [aeiou] matches +"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a +caseful version would. In a UTF mode, PCRE always understands the concept of +case for characters whose values are less than 128, so caseless matching is +always possible. For characters with higher values, the concept of case is +supported if PCRE is compiled with Unicode property support, but not otherwise. +If you want to use caseless matching in a UTF mode for characters 128 and +above, you must ensure that PCRE is compiled with Unicode property support as +well as with UTF support. +</P> +<P> +Characters that might indicate line breaks are never treated in any special way +when matching character classes, whatever line-ending sequence is in use, and +whatever setting of the PCRE_DOTALL and PCRE_MULTILINE options is used. A class +such as [^a] always matches one of these characters. +</P> +<P> +The minus (hyphen) character can be used to specify a range of characters in a +character class. For example, [d-m] matches any letter between d and m, +inclusive. If a minus character is required in a class, it must be escaped with +a backslash or appear in a position where it cannot be interpreted as +indicating a range, typically as the first or last character in the class, or +immediately after a range. For example, [b-d-z] matches letters in the range b +to d, a hyphen character, or z. +</P> +<P> +It is not possible to have the literal character "]" as the end character of a +range. A pattern such as [W-]46] is interpreted as a class of two characters +("W" and "-") followed by a literal string "46]", so it would match "W46]" or +"-46]". However, if the "]" is escaped with a backslash it is interpreted as +the end of range, so [W-\]46] is interpreted as a class containing a range +followed by two other characters. The octal or hexadecimal representation of +"]" can also be used to end a range. +</P> +<P> +An error is generated if a POSIX character class (see below) or an escape +sequence other than one that defines a single character appears at a point +where a range ending character is expected. For example, [z-\xff] is valid, +but [A-\d] and [A-[:digit:]] are not. +</P> +<P> +Ranges operate in the collating sequence of character values. They can also be +used for characters specified numerically, for example [\000-\037]. Ranges +can include any characters that are valid for the current mode. +</P> +<P> +If a range that includes letters is used when caseless matching is set, it +matches the letters in either case. For example, [W-c] is equivalent to +[][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if character +tables for a French locale are in use, [\xc8-\xcb] matches accented E +characters in both cases. In UTF modes, PCRE supports the concept of case for +characters with values greater than 128 only when it is compiled with Unicode +property support. +</P> +<P> +The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, +\V, \w, and \W may appear in a character class, and add the characters that +they match to the class. For example, [\dABCDEF] matches any hexadecimal +digit. In UTF modes, the PCRE_UCP option affects the meanings of \d, \s, \w +and their upper case partners, just as it does when they appear outside a +character class, as described in the section entitled +<a href="#genericchartypes">"Generic character types"</a> +above. The escape sequence \b has a different meaning inside a character +class; it matches the backspace character. The sequences \B, \N, \R, and \X +are not special inside a character class. Like any other unrecognized escape +sequences, they are treated as the literal characters "B", "N", "R", and "X" by +default, but cause an error if the PCRE_EXTRA option is set. +</P> +<P> +A circumflex can conveniently be used with the upper case character types to +specify a more restricted set of characters than the matching lower case type. +For example, the class [^\W_] matches any letter or digit, but not underscore, +whereas [\w] includes underscore. A positive character class should be read as +"something OR something OR ..." and a negative class as "NOT something AND NOT +something AND NOT ...". +</P> +<P> +The only metacharacters that are recognized in character classes are backslash, +hyphen (only where it can be interpreted as specifying a range), circumflex +(only at the start), opening square bracket (only when it can be interpreted as +introducing a POSIX class name, or for a special compatibility feature - see +the next two sections), and the terminating closing square bracket. However, +escaping other non-alphanumeric characters does no harm. +</P> +<br><a name="SEC10" href="#TOC1">POSIX CHARACTER CLASSES</a><br> +<P> +Perl supports the POSIX notation for character classes. This uses names +enclosed by [: and :] within the enclosing square brackets. PCRE also supports +this notation. For example, +<pre> + [01[:alpha:]%] +</pre> +matches "0", "1", any alphabetic character, or "%". The supported class names +are: +<pre> + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \d) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits and space + space white space (the same as \s from PCRE 8.34) + upper upper case letters + word "word" characters (same as \w) + xdigit hexadecimal digits +</pre> +The default "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), +and space (32). If locale-specific matching is taking place, the list of space +characters may be different; there may be fewer or more of them. "Space" used +to be different to \s, which did not include VT, for Perl compatibility. +However, Perl changed at release 5.18, and PCRE followed at release 8.34. +"Space" and \s now match the same set of characters. +</P> +<P> +The name "word" is a Perl extension, and "blank" is a GNU extension from Perl +5.8. Another Perl extension is negation, which is indicated by a ^ character +after the colon. For example, +<pre> + [12[:^digit:]] +</pre> +matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX +syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not +supported, and an error is given if they are encountered. +</P> +<P> +By default, characters with values greater than 128 do not match any of the +POSIX character classes. However, if the PCRE_UCP option is passed to +<b>pcre_compile()</b>, some of the classes are changed so that Unicode character +properties are used. This is achieved by replacing certain POSIX classes by +other sequences, as follows: +<pre> + [:alnum:] becomes \p{Xan} + [:alpha:] becomes \p{L} + [:blank:] becomes \h + [:digit:] becomes \p{Nd} + [:lower:] becomes \p{Ll} + [:space:] becomes \p{Xps} + [:upper:] becomes \p{Lu} + [:word:] becomes \p{Xwd} +</pre> +Negated versions, such as [:^alpha:] use \P instead of \p. Three other POSIX +classes are handled specially in UCP mode: +</P> +<P> +[:graph:] +This matches characters that have glyphs that mark the page when printed. In +Unicode property terms, it matches all characters with the L, M, N, P, S, or Cf +properties, except for: +<pre> + U+061C Arabic Letter Mark + U+180E Mongolian Vowel Separator + U+2066 - U+2069 Various "isolate"s + +</PRE> +</P> +<P> +[:print:] +This matches the same characters as [:graph:] plus space characters that are +not controls, that is, characters with the Zs property. +</P> +<P> +[:punct:] +This matches all characters that have the Unicode P (punctuation) property, +plus those characters whose code points are less than 128 that have the S +(Symbol) property. +</P> +<P> +The other POSIX classes are unchanged, and match only characters with code +points less than 128. +</P> +<br><a name="SEC11" href="#TOC1">COMPATIBILITY FEATURE FOR WORD BOUNDARIES</a><br> +<P> +In the POSIX.2 compliant library that was included in 4.4BSD Unix, the ugly +syntax [[:<:]] and [[:>:]] is used for matching "start of word" and "end of +word". PCRE treats these items as follows: +<pre> + [[:<:]] is converted to \b(?=\w) + [[:>:]] is converted to \b(?<=\w) +</pre> +Only these exact character sequences are recognized. A sequence such as +[a[:<:]b] provokes error for an unrecognized POSIX class name. This support is +not compatible with Perl. It is provided to help migrations from other +environments, and is best not used in any new patterns. Note that \b matches +at the start and the end of a word (see +<a href="#smallassertions">"Simple assertions"</a> +above), and in a Perl-style pattern the preceding or following character +normally shows which is wanted, without the need for the assertions that are +used above in order to give exactly the POSIX behaviour. +</P> +<br><a name="SEC12" href="#TOC1">VERTICAL BAR</a><br> +<P> +Vertical bar characters are used to separate alternative patterns. For example, +the pattern +<pre> + gilbert|sullivan +</pre> +matches either "gilbert" or "sullivan". Any number of alternatives may appear, +and an empty alternative is permitted (matching the empty string). The matching +process tries each alternative in turn, from left to right, and the first one +that succeeds is used. If the alternatives are within a subpattern +<a href="#subpattern">(defined below),</a> +"succeeds" means matching the rest of the main pattern as well as the +alternative in the subpattern. +</P> +<br><a name="SEC13" href="#TOC1">INTERNAL OPTION SETTING</a><br> +<P> +The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and +PCRE_EXTENDED options (which are Perl-compatible) can be changed from within +the pattern by a sequence of Perl option letters enclosed between "(?" and ")". +The option letters are +<pre> + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED +</pre> +For example, (?im) sets caseless, multiline matching. It is also possible to +unset these options by preceding the letter with a hyphen, and a combined +setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and +PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also +permitted. If a letter appears both before and after the hyphen, the option is +unset. +</P> +<P> +The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA can be +changed in the same way as the Perl-compatible options by using the characters +J, U and X respectively. +</P> +<P> +When one of these option changes occurs at top level (that is, not inside +subpattern parentheses), the change applies to the remainder of the pattern +that follows. If the change is placed right at the start of a pattern, PCRE +extracts it into the global options (and it will therefore show up in data +extracted by the <b>pcre_fullinfo()</b> function). +</P> +<P> +An option change within a subpattern (see below for a description of +subpatterns) affects only that part of the subpattern that follows it, so +<pre> + (a(?i)b)c +</pre> +matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). +By this means, options can be made to have different settings in different +parts of the pattern. Any changes made in one alternative do carry on +into subsequent branches within the same subpattern. For example, +<pre> + (a(?i)b|c) +</pre> +matches "ab", "aB", "c", and "C", even though when matching "C" the first +branch is abandoned before the option setting. This is because the effects of +option settings happen at compile time. There would be some very weird +behaviour otherwise. +</P> +<P> +<b>Note:</b> There are other PCRE-specific options that can be set by the +application when the compiling or matching functions are called. In some cases +the pattern can contain special leading sequences such as (*CRLF) to override +what the application has set or what has been defaulted. Details are given in +the section entitled +<a href="#newlineseq">"Newline sequences"</a> +above. There are also the (*UTF8), (*UTF16),(*UTF32), and (*UCP) leading +sequences that can be used to set UTF and Unicode property modes; they are +equivalent to setting the PCRE_UTF8, PCRE_UTF16, PCRE_UTF32 and the PCRE_UCP +options, respectively. The (*UTF) sequence is a generic version that can be +used with any of the libraries. However, the application can set the +PCRE_NEVER_UTF option, which locks out the use of the (*UTF) sequences. +<a name="subpattern"></a></P> +<br><a name="SEC14" href="#TOC1">SUBPATTERNS</a><br> +<P> +Subpatterns are delimited by parentheses (round brackets), which can be nested. +Turning part of a pattern into a subpattern does two things: +<br> +<br> +1. It localizes a set of alternatives. For example, the pattern +<pre> + cat(aract|erpillar|) +</pre> +matches "cataract", "caterpillar", or "cat". Without the parentheses, it would +match "cataract", "erpillar" or an empty string. +<br> +<br> +2. It sets up the subpattern as a capturing subpattern. This means that, when +the whole pattern matches, that portion of the subject string that matched the +subpattern is passed back to the caller via the <i>ovector</i> argument of the +matching function. (This applies only to the traditional matching functions; +the DFA matching functions do not support capturing.) +</P> +<P> +Opening parentheses are counted from left to right (starting from 1) to obtain +numbers for the capturing subpatterns. For example, if the string "the red +king" is matched against the pattern +<pre> + the ((red|white) (king|queen)) +</pre> +the captured substrings are "red king", "red", and "king", and are numbered 1, +2, and 3, respectively. +</P> +<P> +The fact that plain parentheses fulfil two functions is not always helpful. +There are often times when a grouping subpattern is required without a +capturing requirement. If an opening parenthesis is followed by a question mark +and a colon, the subpattern does not do any capturing, and is not counted when +computing the number of any subsequent capturing subpatterns. For example, if +the string "the white queen" is matched against the pattern +<pre> + the ((?:red|white) (king|queen)) +</pre> +the captured substrings are "white queen" and "queen", and are numbered 1 and +2. The maximum number of capturing subpatterns is 65535. +</P> +<P> +As a convenient shorthand, if any option settings are required at the start of +a non-capturing subpattern, the option letters may appear between the "?" and +the ":". Thus the two patterns +<pre> + (?i:saturday|sunday) + (?:(?i)saturday|sunday) +</pre> +match exactly the same set of strings. Because alternative branches are tried +from left to right, and options are not reset until the end of the subpattern +is reached, an option setting in one branch does affect subsequent branches, so +the above patterns match "SUNDAY" as well as "Saturday". +<a name="dupsubpatternnumber"></a></P> +<br><a name="SEC15" href="#TOC1">DUPLICATE SUBPATTERN NUMBERS</a><br> +<P> +Perl 5.10 introduced a feature whereby each alternative in a subpattern uses +the same numbers for its capturing parentheses. Such a subpattern starts with +(?| and is itself a non-capturing subpattern. For example, consider this +pattern: +<pre> + (?|(Sat)ur|(Sun))day +</pre> +Because the two alternatives are inside a (?| group, both sets of capturing +parentheses are numbered one. Thus, when the pattern matches, you can look +at captured substring number one, whichever alternative matched. This construct +is useful when you want to capture part, but not all, of one of a number of +alternatives. Inside a (?| group, parentheses are numbered as usual, but the +number is reset at the start of each branch. The numbers of any capturing +parentheses that follow the subpattern start after the highest number used in +any branch. The following example is taken from the Perl documentation. The +numbers underneath show in which buffer the captured content will be stored. +<pre> + # before ---------------branch-reset----------- after + / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x + # 1 2 2 3 2 3 4 +</pre> +A back reference to a numbered subpattern uses the most recent value that is +set for that number by any subpattern. The following pattern matches "abcabc" +or "defdef": +<pre> + /(?|(abc)|(def))\1/ +</pre> +In contrast, a subroutine call to a numbered subpattern always refers to the +first one in the pattern with the given number. The following pattern matches +"abcabc" or "defabc": +<pre> + /(?|(abc)|(def))(?1)/ +</pre> +If a +<a href="#conditions">condition test</a> +for a subpattern's having matched refers to a non-unique number, the test is +true if any of the subpatterns of that number have matched. +</P> +<P> +An alternative approach to using this "branch reset" feature is to use +duplicate named subpatterns, as described in the next section. +</P> +<br><a name="SEC16" href="#TOC1">NAMED SUBPATTERNS</a><br> +<P> +Identifying capturing parentheses by number is simple, but it can be very hard +to keep track of the numbers in complicated regular expressions. Furthermore, +if an expression is modified, the numbers may change. To help with this +difficulty, PCRE supports the naming of subpatterns. This feature was not +added to Perl until release 5.10. Python had the feature earlier, and PCRE +introduced it at release 4.0, using the Python syntax. PCRE now supports both +the Perl and the Python syntax. Perl allows identically numbered subpatterns to +have different names, but PCRE does not. +</P> +<P> +In PCRE, a subpattern can be named in one of three ways: (?<name>...) or +(?'name'...) as in Perl, or (?P<name>...) as in Python. References to capturing +parentheses from other parts of the pattern, such as +<a href="#backreferences">back references,</a> +<a href="#recursion">recursion,</a> +and +<a href="#conditions">conditions,</a> +can be made by name as well as by number. +</P> +<P> +Names consist of up to 32 alphanumeric characters and underscores, but must +start with a non-digit. Named capturing parentheses are still allocated numbers +as well as names, exactly as if the names were not present. The PCRE API +provides function calls for extracting the name-to-number translation table +from a compiled pattern. There is also a convenience function for extracting a +captured substring by name. +</P> +<P> +By default, a name must be unique within a pattern, but it is possible to relax +this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate +names are also always permitted for subpatterns with the same number, set up as +described in the previous section.) Duplicate names can be useful for patterns +where only one instance of the named parentheses can match. Suppose you want to +match the name of a weekday, either as a 3-letter abbreviation or as the full +name, and in both cases you want to extract the abbreviation. This pattern +(ignoring the line breaks) does the job: +<pre> + (?<DN>Mon|Fri|Sun)(?:day)?| + (?<DN>Tue)(?:sday)?| + (?<DN>Wed)(?:nesday)?| + (?<DN>Thu)(?:rsday)?| + (?<DN>Sat)(?:urday)? +</pre> +There are five capturing substrings, but only one is ever set after a match. +(An alternative way of solving this problem is to use a "branch reset" +subpattern, as described in the previous section.) +</P> +<P> +The convenience function for extracting the data by name returns the substring +for the first (and in this example, the only) subpattern of that name that +matched. This saves searching to find which numbered subpattern it was. +</P> +<P> +If you make a back reference to a non-unique named subpattern from elsewhere in +the pattern, the subpatterns to which the name refers are checked in the order +in which they appear in the overall pattern. The first one that is set is used +for the reference. For example, this pattern matches both "foofoo" and +"barbar" but not "foobar" or "barfoo": +<pre> + (?:(?<n>foo)|(?<n>bar))\k<n> + +</PRE> +</P> +<P> +If you make a subroutine call to a non-unique named subpattern, the one that +corresponds to the first occurrence of the name is used. In the absence of +duplicate numbers (see the previous section) this is the one with the lowest +number. +</P> +<P> +If you use a named reference in a condition +test (see the +<a href="#conditions">section about conditions</a> +below), either to check whether a subpattern has matched, or to check for +recursion, all subpatterns with the same name are tested. If the condition is +true for any one of them, the overall condition is true. This is the same +behaviour as testing by number. For further details of the interfaces for +handling named subpatterns, see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<P> +<b>Warning:</b> You cannot use different names to distinguish between two +subpatterns with the same number because PCRE uses only the numbers when +matching. For this reason, an error is given at compile time if different names +are given to subpatterns with the same number. However, you can always give the +same name to subpatterns with the same number, even when PCRE_DUPNAMES is not +set. +</P> +<br><a name="SEC17" href="#TOC1">REPETITION</a><br> +<P> +Repetition is specified by quantifiers, which can follow any of the following +items: +<pre> + a literal data character + the dot metacharacter + the \C escape sequence + the \X escape sequence + the \R escape sequence + an escape such as \d or \pL that matches a single character + a character class + a back reference (see next section) + a parenthesized subpattern (including assertions) + a subroutine call to a subpattern (recursive or otherwise) +</pre> +The general repetition quantifier specifies a minimum and maximum number of +permitted matches, by giving the two numbers in curly brackets (braces), +separated by a comma. The numbers must be less than 65536, and the first must +be less than or equal to the second. For example: +<pre> + z{2,4} +</pre> +matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special +character. If the second number is omitted, but the comma is present, there is +no upper limit; if the second number and the comma are both omitted, the +quantifier specifies an exact number of required matches. Thus +<pre> + [aeiou]{3,} +</pre> +matches at least 3 successive vowels, but may match many more, while +<pre> + \d{8} +</pre> +matches exactly 8 digits. An opening curly bracket that appears in a position +where a quantifier is not allowed, or one that does not match the syntax of a +quantifier, is taken as a literal character. For example, {,6} is not a +quantifier, but a literal string of four characters. +</P> +<P> +In UTF modes, quantifiers apply to characters rather than to individual data +units. Thus, for example, \x{100}{2} matches two characters, each of +which is represented by a two-byte sequence in a UTF-8 string. Similarly, +\X{3} matches three Unicode extended grapheme clusters, each of which may be +several data units long (and they may be of different lengths). +</P> +<P> +The quantifier {0} is permitted, causing the expression to behave as if the +previous item and the quantifier were not present. This may be useful for +subpatterns that are referenced as +<a href="#subpatternsassubroutines">subroutines</a> +from elsewhere in the pattern (but see also the section entitled +<a href="#subdefine">"Defining subpatterns for use by reference only"</a> +below). Items other than subpatterns that have a {0} quantifier are omitted +from the compiled pattern. +</P> +<P> +For convenience, the three most common quantifiers have single-character +abbreviations: +<pre> + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} +</pre> +It is possible to construct infinite loops by following a subpattern that can +match no characters with a quantifier that has no upper limit, for example: +<pre> + (a?)* +</pre> +Earlier versions of Perl and PCRE used to give an error at compile time for +such patterns. However, because there are cases where this can be useful, such +patterns are now accepted, but if any repetition of the subpattern does in fact +match no characters, the loop is forcibly broken. +</P> +<P> +By default, the quantifiers are "greedy", that is, they match as much as +possible (up to the maximum number of permitted times), without causing the +rest of the pattern to fail. The classic example of where this gives problems +is in trying to match comments in C programs. These appear between /* and */ +and within the comment, individual * and / characters may appear. An attempt to +match C comments by applying the pattern +<pre> + /\*.*\*/ +</pre> +to the string +<pre> + /* first comment */ not comment /* second comment */ +</pre> +fails, because it matches the entire string owing to the greediness of the .* +item. +</P> +<P> +However, if a quantifier is followed by a question mark, it ceases to be +greedy, and instead matches the minimum number of times possible, so the +pattern +<pre> + /\*.*?\*/ +</pre> +does the right thing with the C comments. The meaning of the various +quantifiers is not otherwise changed, just the preferred number of matches. +Do not confuse this use of question mark with its use as a quantifier in its +own right. Because it has two uses, it can sometimes appear doubled, as in +<pre> + \d??\d +</pre> +which matches one digit by preference, but can match two if that is the only +way the rest of the pattern matches. +</P> +<P> +If the PCRE_UNGREEDY option is set (an option that is not available in Perl), +the quantifiers are not greedy by default, but individual ones can be made +greedy by following them with a question mark. In other words, it inverts the +default behaviour. +</P> +<P> +When a parenthesized subpattern is quantified with a minimum repeat count that +is greater than 1 or with a limited maximum, more memory is required for the +compiled pattern, in proportion to the size of the minimum or maximum. +</P> +<P> +If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent +to Perl's /s) is set, thus allowing the dot to match newlines, the pattern is +implicitly anchored, because whatever follows will be tried against every +character position in the subject string, so there is no point in retrying the +overall match at any position after the first. PCRE normally treats such a +pattern as though it were preceded by \A. +</P> +<P> +In cases where it is known that the subject string contains no newlines, it is +worth setting PCRE_DOTALL in order to obtain this optimization, or +alternatively using ^ to indicate anchoring explicitly. +</P> +<P> +However, there are some cases where the optimization cannot be used. When .* +is inside capturing parentheses that are the subject of a back reference +elsewhere in the pattern, a match at the start may fail where a later one +succeeds. Consider, for example: +<pre> + (.*)abc\1 +</pre> +If the subject is "xyz123abc123" the match point is the fourth character. For +this reason, such a pattern is not implicitly anchored. +</P> +<P> +Another case where implicit anchoring is not applied is when the leading .* is +inside an atomic group. Once again, a match at the start may fail where a later +one succeeds. Consider this pattern: +<pre> + (?>.*?a)b +</pre> +It matches "ab" in the subject "aab". The use of the backtracking control verbs +(*PRUNE) and (*SKIP) also disable this optimization. +</P> +<P> +When a capturing subpattern is repeated, the value captured is the substring +that matched the final iteration. For example, after +<pre> + (tweedle[dume]{3}\s*)+ +</pre> +has matched "tweedledum tweedledee" the value of the captured substring is +"tweedledee". However, if there are nested capturing subpatterns, the +corresponding captured values may have been set in previous iterations. For +example, after +<pre> + /(a|(b))+/ +</pre> +matches "aba" the value of the second captured substring is "b". +<a name="atomicgroup"></a></P> +<br><a name="SEC18" href="#TOC1">ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS</a><br> +<P> +With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") +repetition, failure of what follows normally causes the repeated item to be +re-evaluated to see if a different number of repeats allows the rest of the +pattern to match. Sometimes it is useful to prevent this, either to change the +nature of the match, or to cause it fail earlier than it otherwise might, when +the author of the pattern knows there is no point in carrying on. +</P> +<P> +Consider, for example, the pattern \d+foo when applied to the subject line +<pre> + 123456bar +</pre> +After matching all 6 digits and then failing to match "foo", the normal +action of the matcher is to try again with only 5 digits matching the \d+ +item, and then with 4, and so on, before ultimately failing. "Atomic grouping" +(a term taken from Jeffrey Friedl's book) provides the means for specifying +that once a subpattern has matched, it is not to be re-evaluated in this way. +</P> +<P> +If we use atomic grouping for the previous example, the matcher gives up +immediately on failing to match "foo" the first time. The notation is a kind of +special parenthesis, starting with (?> as in this example: +<pre> + (?>\d+)foo +</pre> +This kind of parenthesis "locks up" the part of the pattern it contains once +it has matched, and a failure further into the pattern is prevented from +backtracking into it. Backtracking past it to previous items, however, works as +normal. +</P> +<P> +An alternative description is that a subpattern of this type matches the string +of characters that an identical standalone pattern would match, if anchored at +the current point in the subject string. +</P> +<P> +Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as +the above example can be thought of as a maximizing repeat that must swallow +everything it can. So, while both \d+ and \d+? are prepared to adjust the +number of digits they match in order to make the rest of the pattern match, +(?>\d+) can only match an entire sequence of digits. +</P> +<P> +Atomic groups in general can of course contain arbitrarily complicated +subpatterns, and can be nested. However, when the subpattern for an atomic +group is just a single repeated item, as in the example above, a simpler +notation, called a "possessive quantifier" can be used. This consists of an +additional + character following a quantifier. Using this notation, the +previous example can be rewritten as +<pre> + \d++foo +</pre> +Note that a possessive quantifier can be used with an entire group, for +example: +<pre> + (abc|xyz){2,3}+ +</pre> +Possessive quantifiers are always greedy; the setting of the PCRE_UNGREEDY +option is ignored. They are a convenient notation for the simpler forms of +atomic group. However, there is no difference in the meaning of a possessive +quantifier and the equivalent atomic group, though there may be a performance +difference; possessive quantifiers should be slightly faster. +</P> +<P> +The possessive quantifier syntax is an extension to the Perl 5.8 syntax. +Jeffrey Friedl originated the idea (and the name) in the first edition of his +book. Mike McCloskey liked it, so implemented it when he built Sun's Java +package, and PCRE copied it from there. It ultimately found its way into Perl +at release 5.10. +</P> +<P> +PCRE has an optimization that automatically "possessifies" certain simple +pattern constructs. For example, the sequence A+B is treated as A++B because +there is no point in backtracking into a sequence of A's when B must follow. +</P> +<P> +When a pattern contains an unlimited repeat inside a subpattern that can itself +be repeated an unlimited number of times, the use of an atomic group is the +only way to avoid some failing matches taking a very long time indeed. The +pattern +<pre> + (\D+|<\d+>)*[!?] +</pre> +matches an unlimited number of substrings that either consist of non-digits, or +digits enclosed in <>, followed by either ! or ?. When it matches, it runs +quickly. However, if it is applied to +<pre> + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +</pre> +it takes a long time before reporting failure. This is because the string can +be divided between the internal \D+ repeat and the external * repeat in a +large number of ways, and all have to be tried. (The example uses [!?] rather +than a single character at the end, because both PCRE and Perl have an +optimization that allows for fast failure when a single character is used. They +remember the last single character that is required for a match, and fail early +if it is not present in the string.) If the pattern is changed so that it uses +an atomic group, like this: +<pre> + ((?>\D+)|<\d+>)*[!?] +</pre> +sequences of non-digits cannot be broken, and failure happens quickly. +<a name="backreferences"></a></P> +<br><a name="SEC19" href="#TOC1">BACK REFERENCES</a><br> +<P> +Outside a character class, a backslash followed by a digit greater than 0 (and +possibly further digits) is a back reference to a capturing subpattern earlier +(that is, to its left) in the pattern, provided there have been that many +previous capturing left parentheses. +</P> +<P> +However, if the decimal number following the backslash is less than 10, it is +always taken as a back reference, and causes an error only if there are not +that many capturing left parentheses in the entire pattern. In other words, the +parentheses that are referenced need not be to the left of the reference for +numbers less than 10. A "forward back reference" of this type can make sense +when a repetition is involved and the subpattern to the right has participated +in an earlier iteration. +</P> +<P> +It is not possible to have a numerical "forward back reference" to a subpattern +whose number is 10 or more using this syntax because a sequence such as \50 is +interpreted as a character defined in octal. See the subsection entitled +"Non-printing characters" +<a href="#digitsafterbackslash">above</a> +for further details of the handling of digits following a backslash. There is +no such problem when named parentheses are used. A back reference to any +subpattern is possible using named parentheses (see below). +</P> +<P> +Another way of avoiding the ambiguity inherent in the use of digits following a +backslash is to use the \g escape sequence. This escape must be followed by an +unsigned number or a negative number, optionally enclosed in braces. These +examples are all identical: +<pre> + (ring), \1 + (ring), \g1 + (ring), \g{1} +</pre> +An unsigned number specifies an absolute reference without the ambiguity that +is present in the older syntax. It is also useful when literal digits follow +the reference. A negative number is a relative reference. Consider this +example: +<pre> + (abc(def)ghi)\g{-1} +</pre> +The sequence \g{-1} is a reference to the most recently started capturing +subpattern before \g, that is, is it equivalent to \2 in this example. +Similarly, \g{-2} would be equivalent to \1. The use of relative references +can be helpful in long patterns, and also in patterns that are created by +joining together fragments that contain references within themselves. +</P> +<P> +A back reference matches whatever actually matched the capturing subpattern in +the current subject string, rather than anything matching the subpattern +itself (see +<a href="#subpatternsassubroutines">"Subpatterns as subroutines"</a> +below for a way of doing that). So the pattern +<pre> + (sens|respons)e and \1ibility +</pre> +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If caseful matching is in force at the time of the +back reference, the case of letters is relevant. For example, +<pre> + ((?i)rah)\s+\1 +</pre> +matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original +capturing subpattern is matched caselessly. +</P> +<P> +There are several different ways of writing back references to named +subpatterns. The .NET syntax \k{name} and the Perl syntax \k<name> or +\k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's unified +back reference syntax, in which \g can be used for both numeric and named +references, is also supported. We could rewrite the above example in any of +the following ways: +<pre> + (?<p1>(?i)rah)\s+\k<p1> + (?'p1'(?i)rah)\s+\k{p1} + (?P<p1>(?i)rah)\s+(?P=p1) + (?<p1>(?i)rah)\s+\g{p1} +</pre> +A subpattern that is referenced by name may appear in the pattern before or +after the reference. +</P> +<P> +There may be more than one back reference to the same subpattern. If a +subpattern has not actually been used in a particular match, any back +references to it always fail by default. For example, the pattern +<pre> + (a|(bc))\2 +</pre> +always fails if it starts to match "a" rather than "bc". However, if the +PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back reference to an +unset value matches an empty string. +</P> +<P> +Because there may be many capturing parentheses in a pattern, all digits +following a backslash are taken as part of a potential back reference number. +If the pattern continues with a digit character, some delimiter must be used to +terminate the back reference. If the PCRE_EXTENDED option is set, this can be +white space. Otherwise, the \g{ syntax or an empty comment (see +<a href="#comments">"Comments"</a> +below) can be used. +</P> +<br><b> +Recursive back references +</b><br> +<P> +A back reference that occurs inside the parentheses to which it refers fails +when the subpattern is first used, so, for example, (a\1) never matches. +However, such references can be useful inside repeated subpatterns. For +example, the pattern +<pre> + (a|b\1)+ +</pre> +matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of +the subpattern, the back reference matches the character string corresponding +to the previous iteration. In order for this to work, the pattern must be such +that the first iteration does not need to match the back reference. This can be +done using alternation, as in the example above, or by a quantifier with a +minimum of zero. +</P> +<P> +Back references of this type cause the group that they reference to be treated +as an +<a href="#atomicgroup">atomic group.</a> +Once the whole group has been matched, a subsequent matching failure cannot +cause backtracking into the middle of the group. +<a name="bigassertions"></a></P> +<br><a name="SEC20" href="#TOC1">ASSERTIONS</a><br> +<P> +An assertion is a test on the characters following or preceding the current +matching point that does not actually consume any characters. The simple +assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described +<a href="#smallassertions">above.</a> +</P> +<P> +More complicated assertions are coded as subpatterns. There are two kinds: +those that look ahead of the current position in the subject string, and those +that look behind it. An assertion subpattern is matched in the normal way, +except that it does not cause the current matching position to be changed. +</P> +<P> +Assertion subpatterns are not capturing subpatterns. If such an assertion +contains capturing subpatterns within it, these are counted for the purposes of +numbering the capturing subpatterns in the whole pattern. However, substring +capturing is carried out only for positive assertions. (Perl sometimes, but not +always, does do capturing in negative assertions.) +</P> +<P> +For compatibility with Perl, assertion subpatterns may be repeated; though +it makes no sense to assert the same thing several times, the side effect of +capturing parentheses may occasionally be useful. In practice, there only three +cases: +<br> +<br> +(1) If the quantifier is {0}, the assertion is never obeyed during matching. +However, it may contain internal capturing parenthesized groups that are called +from elsewhere via the +<a href="#subpatternsassubroutines">subroutine mechanism.</a> +<br> +<br> +(2) If quantifier is {0,n} where n is greater than zero, it is treated as if it +were {0,1}. At run time, the rest of the pattern match is tried with and +without the assertion, the order depending on the greediness of the quantifier. +<br> +<br> +(3) If the minimum repetition is greater than zero, the quantifier is ignored. +The assertion is obeyed just once when encountered during matching. +</P> +<br><b> +Lookahead assertions +</b><br> +<P> +Lookahead assertions start with (?= for positive assertions and (?! for +negative assertions. For example, +<pre> + \w+(?=;) +</pre> +matches a word followed by a semicolon, but does not include the semicolon in +the match, and +<pre> + foo(?!bar) +</pre> +matches any occurrence of "foo" that is not followed by "bar". Note that the +apparently similar pattern +<pre> + (?!foo)bar +</pre> +does not find an occurrence of "bar" that is preceded by something other than +"foo"; it finds any occurrence of "bar" whatsoever, because the assertion +(?!foo) is always true when the next three characters are "bar". A +lookbehind assertion is needed to achieve the other effect. +</P> +<P> +If you want to force a matching failure at some point in a pattern, the most +convenient way to do it is with (?!) because an empty string always matches, so +an assertion that requires there not to be an empty string must always fail. +The backtracking control verb (*FAIL) or (*F) is a synonym for (?!). +<a name="lookbehind"></a></P> +<br><b> +Lookbehind assertions +</b><br> +<P> +Lookbehind assertions start with (?<= for positive assertions and (?<! for +negative assertions. For example, +<pre> + (?<!foo)bar +</pre> +does find an occurrence of "bar" that is not preceded by "foo". The contents of +a lookbehind assertion are restricted such that all the strings it matches must +have a fixed length. However, if there are several top-level alternatives, they +do not all have to have the same fixed length. Thus +<pre> + (?<=bullock|donkey) +</pre> +is permitted, but +<pre> + (?<!dogs?|cats?) +</pre> +causes an error at compile time. Branches that match different length strings +are permitted only at the top level of a lookbehind assertion. This is an +extension compared with Perl, which requires all branches to match the same +length of string. An assertion such as +<pre> + (?<=ab(c|de)) +</pre> +is not permitted, because its single top-level branch can match two different +lengths, but it is acceptable to PCRE if rewritten to use two top-level +branches: +<pre> + (?<=abc|abde) +</pre> +In some cases, the escape sequence \K +<a href="#resetmatchstart">(see above)</a> +can be used instead of a lookbehind assertion to get round the fixed-length +restriction. +</P> +<P> +The implementation of lookbehind assertions is, for each alternative, to +temporarily move the current position back by the fixed length and then try to +match. If there are insufficient characters before the current position, the +assertion fails. +</P> +<P> +In a UTF mode, PCRE does not allow the \C escape (which matches a single data +unit even in a UTF mode) to appear in lookbehind assertions, because it makes +it impossible to calculate the length of the lookbehind. The \X and \R +escapes, which can match different numbers of data units, are also not +permitted. +</P> +<P> +<a href="#subpatternsassubroutines">"Subroutine"</a> +calls (see below) such as (?2) or (?&X) are permitted in lookbehinds, as long +as the subpattern matches a fixed-length string. +<a href="#recursion">Recursion,</a> +however, is not supported. +</P> +<P> +Possessive quantifiers can be used in conjunction with lookbehind assertions to +specify efficient matching of fixed-length strings at the end of subject +strings. Consider a simple pattern such as +<pre> + abcd$ +</pre> +when applied to a long string that does not match. Because matching proceeds +from left to right, PCRE will look for each "a" in the subject and then see if +what follows matches the rest of the pattern. If the pattern is specified as +<pre> + ^.*abcd$ +</pre> +the initial .* matches the entire string at first, but when this fails (because +there is no following "a"), it backtracks to match all but the last character, +then all but the last two characters, and so on. Once again the search for "a" +covers the entire string, from right to left, so we are no better off. However, +if the pattern is written as +<pre> + ^.*+(?<=abcd) +</pre> +there can be no backtracking for the .*+ item; it can match only the entire +string. The subsequent lookbehind assertion does a single test on the last four +characters. If it fails, the match fails immediately. For long strings, this +approach makes a significant difference to the processing time. +</P> +<br><b> +Using multiple assertions +</b><br> +<P> +Several assertions (of any sort) may occur in succession. For example, +<pre> + (?<=\d{3})(?<!999)foo +</pre> +matches "foo" preceded by three digits that are not "999". Notice that each of +the assertions is applied independently at the same point in the subject +string. First there is a check that the previous three characters are all +digits, and then there is a check that the same three characters are not "999". +This pattern does <i>not</i> match "foo" preceded by six characters, the first +of which are digits and the last three of which are not "999". For example, it +doesn't match "123abcfoo". A pattern to do that is +<pre> + (?<=\d{3}...)(?<!999)foo +</pre> +This time the first assertion looks at the preceding six characters, checking +that the first three are digits, and then the second assertion checks that the +preceding three characters are not "999". +</P> +<P> +Assertions can be nested in any combination. For example, +<pre> + (?<=(?<!foo)bar)baz +</pre> +matches an occurrence of "baz" that is preceded by "bar" which in turn is not +preceded by "foo", while +<pre> + (?<=\d{3}(?!999)...)foo +</pre> +is another pattern that matches "foo" preceded by three digits and any three +characters that are not "999". +<a name="conditions"></a></P> +<br><a name="SEC21" href="#TOC1">CONDITIONAL SUBPATTERNS</a><br> +<P> +It is possible to cause the matching process to obey a subpattern +conditionally or to choose between two alternative subpatterns, depending on +the result of an assertion, or whether a specific capturing subpattern has +already been matched. The two possible forms of conditional subpattern are: +<pre> + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) +</pre> +If the condition is satisfied, the yes-pattern is used; otherwise the +no-pattern (if present) is used. If there are more than two alternatives in the +subpattern, a compile-time error occurs. Each of the two alternatives may +itself contain nested subpatterns of any form, including conditional +subpatterns; the restriction to two alternatives applies only at the level of +the condition. This pattern fragment is an example where the alternatives are +complex: +<pre> + (?(1) (A|B|C) | (D | (?(2)E|F) | E) ) + +</PRE> +</P> +<P> +There are four kinds of condition: references to subpatterns, references to +recursion, a pseudo-condition called DEFINE, and assertions. +</P> +<br><b> +Checking for a used subpattern by number +</b><br> +<P> +If the text between the parentheses consists of a sequence of digits, the +condition is true if a capturing subpattern of that number has previously +matched. If there is more than one capturing subpattern with the same number +(see the earlier +<a href="#recursion">section about duplicate subpattern numbers),</a> +the condition is true if any of them have matched. An alternative notation is +to precede the digits with a plus or minus sign. In this case, the subpattern +number is relative rather than absolute. The most recently opened parentheses +can be referenced by (?(-1), the next most recent by (?(-2), and so on. Inside +loops it can also make sense to refer to subsequent groups. The next +parentheses to be opened can be referenced as (?(+1), and so on. (The value +zero in any of these forms is not used; it provokes a compile-time error.) +</P> +<P> +Consider the following pattern, which contains non-significant white space to +make it more readable (assume the PCRE_EXTENDED option) and to divide it into +three parts for ease of discussion: +<pre> + ( \( )? [^()]+ (?(1) \) ) +</pre> +The first part matches an optional opening parenthesis, and if that +character is present, sets it as the first captured substring. The second part +matches one or more characters that are not parentheses. The third part is a +conditional subpattern that tests whether or not the first set of parentheses +matched. If they did, that is, if subject started with an opening parenthesis, +the condition is true, and so the yes-pattern is executed and a closing +parenthesis is required. Otherwise, since no-pattern is not present, the +subpattern matches nothing. In other words, this pattern matches a sequence of +non-parentheses, optionally enclosed in parentheses. +</P> +<P> +If you were embedding this pattern in a larger one, you could use a relative +reference: +<pre> + ...other stuff... ( \( )? [^()]+ (?(-1) \) ) ... +</pre> +This makes the fragment independent of the parentheses in the larger pattern. +</P> +<br><b> +Checking for a used subpattern by name +</b><br> +<P> +Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used +subpattern by name. For compatibility with earlier versions of PCRE, which had +this facility before Perl, the syntax (?(name)...) is also recognized. +</P> +<P> +Rewriting the above example to use a named subpattern gives this: +<pre> + (?<OPEN> \( )? [^()]+ (?(<OPEN>) \) ) +</pre> +If the name used in a condition of this kind is a duplicate, the test is +applied to all subpatterns of the same name, and is true if any one of them has +matched. +</P> +<br><b> +Checking for pattern recursion +</b><br> +<P> +If the condition is the string (R), and there is no subpattern with the name R, +the condition is true if a recursive call to the whole pattern or any +subpattern has been made. If digits or a name preceded by ampersand follow the +letter R, for example: +<pre> + (?(R3)...) or (?(R&name)...) +</pre> +the condition is true if the most recent recursion is into a subpattern whose +number or name is given. This condition does not check the entire recursion +stack. If the name used in a condition of this kind is a duplicate, the test is +applied to all subpatterns of the same name, and is true if any one of them is +the most recent recursion. +</P> +<P> +At "top level", all these recursion test conditions are false. +<a href="#recursion">The syntax for recursive patterns</a> +is described below. +<a name="subdefine"></a></P> +<br><b> +Defining subpatterns for use by reference only +</b><br> +<P> +If the condition is the string (DEFINE), and there is no subpattern with the +name DEFINE, the condition is always false. In this case, there may be only one +alternative in the subpattern. It is always skipped if control reaches this +point in the pattern; the idea of DEFINE is that it can be used to define +subroutines that can be referenced from elsewhere. (The use of +<a href="#subpatternsassubroutines">subroutines</a> +is described below.) For example, a pattern to match an IPv4 address such as +"192.168.23.245" could be written like this (ignore white space and line +breaks): +<pre> + (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) + \b (?&byte) (\.(?&byte)){3} \b +</pre> +The first part of the pattern is a DEFINE group inside which a another group +named "byte" is defined. This matches an individual component of an IPv4 +address (a number less than 256). When matching takes place, this part of the +pattern is skipped because DEFINE acts like a false condition. The rest of the +pattern uses references to the named group to match the four dot-separated +components of an IPv4 address, insisting on a word boundary at each end. +</P> +<br><b> +Assertion conditions +</b><br> +<P> +If the condition is not in any of the above formats, it must be an assertion. +This may be a positive or negative lookahead or lookbehind assertion. Consider +this pattern, again containing non-significant white space, and with the two +alternatives on the second line: +<pre> + (?(?=[^a-z]*[a-z]) + \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) +</pre> +The condition is a positive lookahead assertion that matches an optional +sequence of non-letters followed by a letter. In other words, it tests for the +presence of at least one letter in the subject. If a letter is found, the +subject is matched against the first alternative; otherwise it is matched +against the second. This pattern matches strings in one of the two forms +dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. +<a name="comments"></a></P> +<br><a name="SEC22" href="#TOC1">COMMENTS</a><br> +<P> +There are two ways of including comments in patterns that are processed by +PCRE. In both cases, the start of the comment must not be in a character class, +nor in the middle of any other sequence of related characters such as (?: or a +subpattern name or number. The characters that make up a comment play no part +in the pattern matching. +</P> +<P> +The sequence (?# marks the start of a comment that continues up to the next +closing parenthesis. Nested parentheses are not permitted. If the PCRE_EXTENDED +option is set, an unescaped # character also introduces a comment, which in +this case continues to immediately after the next newline character or +character sequence in the pattern. Which characters are interpreted as newlines +is controlled by the options passed to a compiling function or by a special +sequence at the start of the pattern, as described in the section entitled +<a href="#newlines">"Newline conventions"</a> +above. Note that the end of this type of comment is a literal newline sequence +in the pattern; escape sequences that happen to represent a newline do not +count. For example, consider this pattern when PCRE_EXTENDED is set, and the +default newline convention is in force: +<pre> + abc #comment \n still comment +</pre> +On encountering the # character, <b>pcre_compile()</b> skips along, looking for +a newline in the pattern. The sequence \n is still literal at this stage, so +it does not terminate the comment. Only an actual character with the code value +0x0a (the default newline) does so. +<a name="recursion"></a></P> +<br><a name="SEC23" href="#TOC1">RECURSIVE PATTERNS</a><br> +<P> +Consider the problem of matching a string in parentheses, allowing for +unlimited nested parentheses. Without the use of recursion, the best that can +be done is to use a pattern that matches up to some fixed depth of nesting. It +is not possible to handle an arbitrary nesting depth. +</P> +<P> +For some time, Perl has provided a facility that allows regular expressions to +recurse (amongst other things). It does this by interpolating Perl code in the +expression at run time, and the code can refer to the expression itself. A Perl +pattern using code interpolation to solve the parentheses problem can be +created like this: +<pre> + $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; +</pre> +The (?p{...}) item interpolates Perl code at run time, and in this case refers +recursively to the pattern in which it appears. +</P> +<P> +Obviously, PCRE cannot support the interpolation of Perl code. Instead, it +supports special syntax for recursion of the entire pattern, and also for +individual subpattern recursion. After its introduction in PCRE and Python, +this kind of recursion was subsequently introduced into Perl at release 5.10. +</P> +<P> +A special item that consists of (? followed by a number greater than zero and a +closing parenthesis is a recursive subroutine call of the subpattern of the +given number, provided that it occurs inside that subpattern. (If not, it is a +<a href="#subpatternsassubroutines">non-recursive subroutine</a> +call, which is described in the next section.) The special item (?R) or (?0) is +a recursive call of the entire regular expression. +</P> +<P> +This PCRE pattern solves the nested parentheses problem (assume the +PCRE_EXTENDED option is set so that white space is ignored): +<pre> + \( ( [^()]++ | (?R) )* \) +</pre> +First it matches an opening parenthesis. Then it matches any number of +substrings which can either be a sequence of non-parentheses, or a recursive +match of the pattern itself (that is, a correctly parenthesized substring). +Finally there is a closing parenthesis. Note the use of a possessive quantifier +to avoid backtracking into sequences of non-parentheses. +</P> +<P> +If this were part of a larger pattern, you would not want to recurse the entire +pattern, so instead you could use this: +<pre> + ( \( ( [^()]++ | (?1) )* \) ) +</pre> +We have put the pattern into parentheses, and caused the recursion to refer to +them instead of the whole pattern. +</P> +<P> +In a larger pattern, keeping track of parenthesis numbers can be tricky. This +is made easier by the use of relative references. Instead of (?1) in the +pattern above you can write (?-2) to refer to the second most recently opened +parentheses preceding the recursion. In other words, a negative number counts +capturing parentheses leftwards from the point at which it is encountered. +</P> +<P> +It is also possible to refer to subsequently opened parentheses, by writing +references such as (?+2). However, these cannot be recursive because the +reference is not inside the parentheses that are referenced. They are always +<a href="#subpatternsassubroutines">non-recursive subroutine</a> +calls, as described in the next section. +</P> +<P> +An alternative approach is to use named parentheses instead. The Perl syntax +for this is (?&name); PCRE's earlier syntax (?P>name) is also supported. We +could rewrite the above example as follows: +<pre> + (?<pn> \( ( [^()]++ | (?&pn) )* \) ) +</pre> +If there is more than one subpattern with the same name, the earliest one is +used. +</P> +<P> +This particular example pattern that we have been looking at contains nested +unlimited repeats, and so the use of a possessive quantifier for matching +strings of non-parentheses is important when applying the pattern to strings +that do not match. For example, when this pattern is applied to +<pre> + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() +</pre> +it yields "no match" quickly. However, if a possessive quantifier is not used, +the match runs for a very long time indeed because there are so many different +ways the + and * repeats can carve up the subject, and all have to be tested +before failure can be reported. +</P> +<P> +At the end of a match, the values of capturing parentheses are those from +the outermost level. If you want to obtain intermediate values, a callout +function can be used (see below and the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation). If the pattern above is matched against +<pre> + (ab(cd)ef) +</pre> +the value for the inner capturing parentheses (numbered 2) is "ef", which is +the last value taken on at the top level. If a capturing subpattern is not +matched at the top level, its final captured value is unset, even if it was +(temporarily) set at a deeper level during the matching process. +</P> +<P> +If there are more than 15 capturing parentheses in a pattern, PCRE has to +obtain extra memory to store data during a recursion, which it does by using +<b>pcre_malloc</b>, freeing it via <b>pcre_free</b> afterwards. If no memory can +be obtained, the match fails with the PCRE_ERROR_NOMEMORY error. +</P> +<P> +Do not confuse the (?R) item with the condition (R), which tests for recursion. +Consider this pattern, which matches text in angle brackets, allowing for +arbitrary nesting. Only digits are allowed in nested brackets (that is, when +recursing), whereas any characters are permitted at the outer level. +<pre> + < (?: (?(R) \d++ | [^<>]*+) | (?R)) * > +</pre> +In this pattern, (?(R) is the start of a conditional subpattern, with two +different alternatives for the recursive and non-recursive cases. The (?R) item +is the actual recursive call. +<a name="recursiondifference"></a></P> +<br><b> +Differences in recursion processing between PCRE and Perl +</b><br> +<P> +Recursion processing in PCRE differs from Perl in two important ways. In PCRE +(like Python, but unlike Perl), a recursive subpattern call is always treated +as an atomic group. That is, once it has matched some of the subject string, it +is never re-entered, even if it contains untried alternatives and there is a +subsequent matching failure. This can be illustrated by the following pattern, +which purports to match a palindromic string that contains an odd number of +characters (for example, "a", "aba", "abcba", "abcdcba"): +<pre> + ^(.|(.)(?1)\2)$ +</pre> +The idea is that it either matches a single character, or two identical +characters surrounding a sub-palindrome. In Perl, this pattern works; in PCRE +it does not if the pattern is longer than three characters. Consider the +subject string "abcba": +</P> +<P> +At the top level, the first character is matched, but as it is not at the end +of the string, the first alternative fails; the second alternative is taken +and the recursion kicks in. The recursive call to subpattern 1 successfully +matches the next character ("b"). (Note that the beginning and end of line +tests are not part of the recursion). +</P> +<P> +Back at the top level, the next character ("c") is compared with what +subpattern 2 matched, which was "a". This fails. Because the recursion is +treated as an atomic group, there are now no backtracking points, and so the +entire match fails. (Perl is able, at this point, to re-enter the recursion and +try the second alternative.) However, if the pattern is written with the +alternatives in the other order, things are different: +<pre> + ^((.)(?1)\2|.)$ +</pre> +This time, the recursing alternative is tried first, and continues to recurse +until it runs out of characters, at which point the recursion fails. But this +time we do have another alternative to try at the higher level. That is the big +difference: in the previous case the remaining alternative is at a deeper +recursion level, which PCRE cannot use. +</P> +<P> +To change the pattern so that it matches all palindromic strings, not just +those with an odd number of characters, it is tempting to change the pattern to +this: +<pre> + ^((.)(?1)\2|.?)$ +</pre> +Again, this works in Perl, but not in PCRE, and for the same reason. When a +deeper recursion has matched a single character, it cannot be entered again in +order to match an empty string. The solution is to separate the two cases, and +write out the odd and even cases as alternatives at the higher level: +<pre> + ^(?:((.)(?1)\2|)|((.)(?3)\4|.)) +</pre> +If you want to match typical palindromic phrases, the pattern has to ignore all +non-word characters, which can be done like this: +<pre> + ^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$ +</pre> +If run with the PCRE_CASELESS option, this pattern matches phrases such as "A +man, a plan, a canal: Panama!" and it works well in both PCRE and Perl. Note +the use of the possessive quantifier *+ to avoid backtracking into sequences of +non-word characters. Without this, PCRE takes a great deal longer (ten times or +more) to match typical phrases, and Perl takes so long that you think it has +gone into a loop. +</P> +<P> +<b>WARNING</b>: The palindrome-matching patterns above work only if the subject +string does not start with a palindrome that is shorter than the entire string. +For example, although "abcba" is correctly matched, if the subject is "ababa", +PCRE finds the palindrome "aba" at the start, then fails at top level because +the end of the string does not follow. Once again, it cannot jump back into the +recursion to try other alternatives, so the entire match fails. +</P> +<P> +The second way in which PCRE and Perl differ in their recursion processing is +in the handling of captured values. In Perl, when a subpattern is called +recursively or as a subpattern (see the next section), it has no access to any +values that were captured outside the recursion, whereas in PCRE these values +can be referenced. Consider this pattern: +<pre> + ^(.)(\1|a(?2)) +</pre> +In PCRE, this pattern matches "bab". The first capturing parentheses match "b", +then in the second group, when the back reference \1 fails to match "b", the +second alternative matches "a" and then recurses. In the recursion, \1 does +now match "b" and so the whole match succeeds. In Perl, the pattern fails to +match because inside the recursive call \1 cannot access the externally set +value. +<a name="subpatternsassubroutines"></a></P> +<br><a name="SEC24" href="#TOC1">SUBPATTERNS AS SUBROUTINES</a><br> +<P> +If the syntax for a recursive subpattern call (either by number or by +name) is used outside the parentheses to which it refers, it operates like a +subroutine in a programming language. The called subpattern may be defined +before or after the reference. A numbered reference can be absolute or +relative, as in these examples: +<pre> + (...(absolute)...)...(?2)... + (...(relative)...)...(?-1)... + (...(?+1)...(relative)... +</pre> +An earlier example pointed out that the pattern +<pre> + (sens|respons)e and \1ibility +</pre> +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If instead the pattern +<pre> + (sens|respons)e and (?1)ibility +</pre> +is used, it does match "sense and responsibility" as well as the other two +strings. Another example is given in the discussion of DEFINE above. +</P> +<P> +All subroutine calls, whether recursive or not, are always treated as atomic +groups. That is, once a subroutine has matched some of the subject string, it +is never re-entered, even if it contains untried alternatives and there is a +subsequent matching failure. Any capturing parentheses that are set during the +subroutine call revert to their previous values afterwards. +</P> +<P> +Processing options such as case-independence are fixed when a subpattern is +defined, so if it is used as a subroutine, such options cannot be changed for +different calls. For example, consider this pattern: +<pre> + (abc)(?i:(?-1)) +</pre> +It matches "abcabc". It does not match "abcABC" because the change of +processing option does not affect the called subpattern. +<a name="onigurumasubroutines"></a></P> +<br><a name="SEC25" href="#TOC1">ONIGURUMA SUBROUTINE SYNTAX</a><br> +<P> +For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or +a number enclosed either in angle brackets or single quotes, is an alternative +syntax for referencing a subpattern as a subroutine, possibly recursively. Here +are two of the examples used above, rewritten using this syntax: +<pre> + (?<pn> \( ( (?>[^()]+) | \g<pn> )* \) ) + (sens|respons)e and \g'1'ibility +</pre> +PCRE supports an extension to Oniguruma: if a number is preceded by a +plus or a minus sign it is taken as a relative reference. For example: +<pre> + (abc)(?i:\g<-1>) +</pre> +Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are <i>not</i> +synonymous. The former is a back reference; the latter is a subroutine call. +</P> +<br><a name="SEC26" href="#TOC1">CALLOUTS</a><br> +<P> +Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl +code to be obeyed in the middle of matching a regular expression. This makes it +possible, amongst other things, to extract different substrings that match the +same pair of parentheses when there is a repetition. +</P> +<P> +PCRE provides a similar feature, but of course it cannot obey arbitrary Perl +code. The feature is called "callout". The caller of PCRE provides an external +function by putting its entry point in the global variable <i>pcre_callout</i> +(8-bit library) or <i>pcre[16|32]_callout</i> (16-bit or 32-bit library). +By default, this variable contains NULL, which disables all calling out. +</P> +<P> +Within a regular expression, (?C) indicates the points at which the external +function is to be called. If you want to identify different callout points, you +can put a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +<pre> + (?C1)abc(?C2)def +</pre> +If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, callouts are +automatically installed before each item in the pattern. They are all numbered +255. If there is a conditional group in the pattern whose condition is an +assertion, an additional callout is inserted just before the condition. An +explicit callout may also be set at this position, as in this example: +<pre> + (?(?C9)(?=a)abc|def) +</pre> +Note that this applies only to assertion conditions, not to other types of +condition. +</P> +<P> +During matching, when PCRE reaches a callout point, the external function is +called. It is provided with the number of the callout, the position in the +pattern, and, optionally, one item of data originally supplied by the caller of +the matching function. The callout function may cause matching to proceed, to +backtrack, or to fail altogether. +</P> +<P> +By default, PCRE implements a number of optimizations at compile time and +matching time, and one side-effect is that sometimes callouts are skipped. If +you need all possible callouts to happen, you need to set options that disable +the relevant optimizations. More details, and a complete description of the +interface to the callout function, are given in the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +<a name="backtrackcontrol"></a></P> +<br><a name="SEC27" href="#TOC1">BACKTRACKING CONTROL</a><br> +<P> +Perl 5.10 introduced a number of "Special Backtracking Control Verbs", which +are still described in the Perl documentation as "experimental and subject to +change or removal in a future version of Perl". It goes on to say: "Their usage +in production code should be noted to avoid problems during upgrades." The same +remarks apply to the PCRE features described in this section. +</P> +<P> +The new verbs make use of what was previously invalid syntax: an opening +parenthesis followed by an asterisk. They are generally of the form +(*VERB) or (*VERB:NAME). Some may take either form, possibly behaving +differently depending on whether or not a name is present. A name is any +sequence of characters that does not include a closing parenthesis. The maximum +length of name is 255 in the 8-bit library and 65535 in the 16-bit and 32-bit +libraries. If the name is empty, that is, if the closing parenthesis +immediately follows the colon, the effect is as if the colon were not there. +Any number of these verbs may occur in a pattern. +</P> +<P> +Since these verbs are specifically related to backtracking, most of them can be +used only when the pattern is to be matched using one of the traditional +matching functions, because these use a backtracking algorithm. With the +exception of (*FAIL), which behaves like a failing negative assertion, the +backtracking control verbs cause an error if encountered by a DFA matching +function. +</P> +<P> +The behaviour of these verbs in +<a href="#btrepeat">repeated groups,</a> +<a href="#btassert">assertions,</a> +and in +<a href="#btsub">subpatterns called as subroutines</a> +(whether or not recursively) is documented below. +<a name="nooptimize"></a></P> +<br><b> +Optimizations that affect backtracking verbs +</b><br> +<P> +PCRE contains some optimizations that are used to speed up matching by running +some checks at the start of each match attempt. For example, it may know the +minimum length of matching subject, or that a particular character must be +present. When one of these optimizations bypasses the running of a match, any +included backtracking verbs will not, of course, be processed. You can suppress +the start-of-match optimizations by setting the PCRE_NO_START_OPTIMIZE option +when calling <b>pcre_compile()</b> or <b>pcre_exec()</b>, or by starting the +pattern with (*NO_START_OPT). There is more discussion of this option in the +section entitled +<a href="pcreapi.html#execoptions">"Option bits for <b>pcre_exec()</b>"</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<P> +Experiments with Perl suggest that it too has similar optimizations, sometimes +leading to anomalous results. +</P> +<br><b> +Verbs that act immediately +</b><br> +<P> +The following verbs act as soon as they are encountered. They may not be +followed by a name. +<pre> + (*ACCEPT) +</pre> +This verb causes the match to end successfully, skipping the remainder of the +pattern. However, when it is inside a subpattern that is called as a +subroutine, only that subpattern is ended successfully. Matching then continues +at the outer level. If (*ACCEPT) in triggered in a positive assertion, the +assertion succeeds; in a negative assertion, the assertion fails. +</P> +<P> +If (*ACCEPT) is inside capturing parentheses, the data so far is captured. For +example: +<pre> + A((?:A|B(*ACCEPT)|C)D) +</pre> +This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is captured by +the outer parentheses. +<pre> + (*FAIL) or (*F) +</pre> +This verb causes a matching failure, forcing backtracking to occur. It is +equivalent to (?!) but easier to read. The Perl documentation notes that it is +probably useful only when combined with (?{}) or (??{}). Those are, of course, +Perl features that are not present in PCRE. The nearest equivalent is the +callout feature, as for example in this pattern: +<pre> + a+(?C)(*FAIL) +</pre> +A match with the string "aaaa" always fails, but the callout is taken before +each backtrack happens (in this example, 10 times). +</P> +<br><b> +Recording which path was taken +</b><br> +<P> +There is one verb whose main purpose is to track how a match was arrived at, +though it also has a secondary use in conjunction with advancing the match +starting point (see (*SKIP) below). +<pre> + (*MARK:NAME) or (*:NAME) +</pre> +A name is always required with this verb. There may be as many instances of +(*MARK) as you like in a pattern, and their names do not have to be unique. +</P> +<P> +When a match succeeds, the name of the last-encountered (*MARK:NAME), +(*PRUNE:NAME), or (*THEN:NAME) on the matching path is passed back to the +caller as described in the section entitled +<a href="pcreapi.html#extradata">"Extra data for <b>pcre_exec()</b>"</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. Here is an example of <b>pcretest</b> output, where the /K +modifier requests the retrieval and outputting of (*MARK) data: +<pre> + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XY + 0: XY + MK: A + XZ + 0: XZ + MK: B +</pre> +The (*MARK) name is tagged with "MK:" in this output, and in this example it +indicates which of the two alternatives matched. This is a more efficient way +of obtaining this information than putting each alternative in its own +capturing parentheses. +</P> +<P> +If a verb with a name is encountered in a positive assertion that is true, the +name is recorded and passed back if it is the last-encountered. This does not +happen for negative assertions or failing positive assertions. +</P> +<P> +After a partial match or a failed match, the last encountered name in the +entire match process is returned. For example: +<pre> + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XP + No match, mark = B +</pre> +Note that in this unanchored example the mark is retained from the match +attempt that started at the letter "X" in the subject. Subsequent match +attempts starting at "P" and then with an empty string do not get as far as the +(*MARK) item, but nevertheless do not reset it. +</P> +<P> +If you are interested in (*MARK) values after failed matches, you should +probably set the PCRE_NO_START_OPTIMIZE option +<a href="#nooptimize">(see above)</a> +to ensure that the match is always attempted. +</P> +<br><b> +Verbs that act after backtracking +</b><br> +<P> +The following verbs do nothing when they are encountered. Matching continues +with what follows, but if there is no subsequent match, causing a backtrack to +the verb, a failure is forced. That is, backtracking cannot pass to the left of +the verb. However, when one of these verbs appears inside an atomic group or an +assertion that is true, its effect is confined to that group, because once the +group has been matched, there is never any backtracking into it. In this +situation, backtracking can "jump back" to the left of the entire atomic group +or assertion. (Remember also, as stated above, that this localization also +applies in subroutine calls.) +</P> +<P> +These verbs differ in exactly what kind of failure occurs when backtracking +reaches them. The behaviour described below is what happens when the verb is +not in a subroutine or an assertion. Subsequent sections cover these special +cases. +<pre> + (*COMMIT) +</pre> +This verb, which may not be followed by a name, causes the whole match to fail +outright if there is a later matching failure that causes backtracking to reach +it. Even if the pattern is unanchored, no further attempts to find a match by +advancing the starting point take place. If (*COMMIT) is the only backtracking +verb that is encountered, once it has been passed <b>pcre_exec()</b> is +committed to finding a match at the current starting point, or not at all. For +example: +<pre> + a+(*COMMIT)b +</pre> +This matches "xxaab" but not "aacaab". It can be thought of as a kind of +dynamic anchor, or "I've started, so I must finish." The name of the most +recently passed (*MARK) in the path is passed back when (*COMMIT) forces a +match failure. +</P> +<P> +If there is more than one backtracking verb in a pattern, a different one that +follows (*COMMIT) may be triggered first, so merely passing (*COMMIT) during a +match does not always guarantee that a match must be at this starting point. +</P> +<P> +Note that (*COMMIT) at the start of a pattern is not the same as an anchor, +unless PCRE's start-of-match optimizations are turned off, as shown in this +output from <b>pcretest</b>: +<pre> + re> /(*COMMIT)abc/ + data> xyzabc + 0: abc + data> xyzabc\Y + No match +</pre> +For this pattern, PCRE knows that any match must start with "a", so the +optimization skips along the subject to "a" before applying the pattern to the +first set of data. The match attempt then succeeds. In the second set of data, +the escape sequence \Y is interpreted by the <b>pcretest</b> program. It causes +the PCRE_NO_START_OPTIMIZE option to be set when <b>pcre_exec()</b> is called. +This disables the optimization that skips along to the first character. The +pattern is now applied starting at "x", and so the (*COMMIT) causes the match +to fail without trying any other starting points. +<pre> + (*PRUNE) or (*PRUNE:NAME) +</pre> +This verb causes the match to fail at the current starting position in the +subject if there is a later matching failure that causes backtracking to reach +it. If the pattern is unanchored, the normal "bumpalong" advance to the next +starting character then happens. Backtracking can occur as usual to the left of +(*PRUNE), before it is reached, or when matching to the right of (*PRUNE), but +if there is no match to the right, backtracking cannot cross (*PRUNE). In +simple cases, the use of (*PRUNE) is just an alternative to an atomic group or +possessive quantifier, but there are some uses of (*PRUNE) that cannot be +expressed in any other way. In an anchored pattern (*PRUNE) has the same effect +as (*COMMIT). +</P> +<P> +The behaviour of (*PRUNE:NAME) is the not the same as (*MARK:NAME)(*PRUNE). +It is like (*MARK:NAME) in that the name is remembered for passing back to the +caller. However, (*SKIP:NAME) searches only for names set with (*MARK). +<pre> + (*SKIP) +</pre> +This verb, when given without a name, is like (*PRUNE), except that if the +pattern is unanchored, the "bumpalong" advance is not to the next character, +but to the position in the subject where (*SKIP) was encountered. (*SKIP) +signifies that whatever text was matched leading up to it cannot be part of a +successful match. Consider: +<pre> + a+(*SKIP)b +</pre> +If the subject is "aaaac...", after the first match attempt fails (starting at +the first character in the string), the starting point skips on to start the +next attempt at "c". Note that a possessive quantifer does not have the same +effect as this example; although it would suppress backtracking during the +first match attempt, the second attempt would start at the second character +instead of skipping on to "c". +<pre> + (*SKIP:NAME) +</pre> +When (*SKIP) has an associated name, its behaviour is modified. When it is +triggered, the previous path through the pattern is searched for the most +recent (*MARK) that has the same name. If one is found, the "bumpalong" advance +is to the subject position that corresponds to that (*MARK) instead of to where +(*SKIP) was encountered. If no (*MARK) with a matching name is found, the +(*SKIP) is ignored. +</P> +<P> +Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It ignores +names that are set by (*PRUNE:NAME) or (*THEN:NAME). +<pre> + (*THEN) or (*THEN:NAME) +</pre> +This verb causes a skip to the next innermost alternative when backtracking +reaches it. That is, it cancels any further backtracking within the current +alternative. Its name comes from the observation that it can be used for a +pattern-based if-then-else block: +<pre> + ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ... +</pre> +If the COND1 pattern matches, FOO is tried (and possibly further items after +the end of the group if FOO succeeds); on failure, the matcher skips to the +second alternative and tries COND2, without backtracking into COND1. If that +succeeds and BAR fails, COND3 is tried. If subsequently BAZ fails, there are no +more alternatives, so there is a backtrack to whatever came before the entire +group. If (*THEN) is not inside an alternation, it acts like (*PRUNE). +</P> +<P> +The behaviour of (*THEN:NAME) is the not the same as (*MARK:NAME)(*THEN). +It is like (*MARK:NAME) in that the name is remembered for passing back to the +caller. However, (*SKIP:NAME) searches only for names set with (*MARK). +</P> +<P> +A subpattern that does not contain a | character is just a part of the +enclosing alternative; it is not a nested alternation with only one +alternative. The effect of (*THEN) extends beyond such a subpattern to the +enclosing alternative. Consider this pattern, where A, B, etc. are complex +pattern fragments that do not contain any | characters at this level: +<pre> + A (B(*THEN)C) | D +</pre> +If A and B are matched, but there is a failure in C, matching does not +backtrack into A; instead it moves to the next alternative, that is, D. +However, if the subpattern containing (*THEN) is given an alternative, it +behaves differently: +<pre> + A (B(*THEN)C | (*FAIL)) | D +</pre> +The effect of (*THEN) is now confined to the inner subpattern. After a failure +in C, matching moves to (*FAIL), which causes the whole subpattern to fail +because there are no more alternatives to try. In this case, matching does now +backtrack into A. +</P> +<P> +Note that a conditional subpattern is not considered as having two +alternatives, because only one is ever used. In other words, the | character in +a conditional subpattern has a different meaning. Ignoring white space, +consider: +<pre> + ^.*? (?(?=a) a | b(*THEN)c ) +</pre> +If the subject is "ba", this pattern does not match. Because .*? is ungreedy, +it initially matches zero characters. The condition (?=a) then fails, the +character "b" is matched, but "c" is not. At this point, matching does not +backtrack to .*? as might perhaps be expected from the presence of the | +character. The conditional subpattern is part of the single alternative that +comprises the whole pattern, and so the match fails. (If there was a backtrack +into .*?, allowing it to match "b", the match would succeed.) +</P> +<P> +The verbs just described provide four different "strengths" of control when +subsequent matching fails. (*THEN) is the weakest, carrying on the match at the +next alternative. (*PRUNE) comes next, failing the match at the current +starting position, but allowing an advance to the next character (for an +unanchored pattern). (*SKIP) is similar, except that the advance may be more +than one character. (*COMMIT) is the strongest, causing the entire match to +fail. +</P> +<br><b> +More than one backtracking verb +</b><br> +<P> +If more than one backtracking verb is present in a pattern, the one that is +backtracked onto first acts. For example, consider this pattern, where A, B, +etc. are complex pattern fragments: +<pre> + (A(*COMMIT)B(*THEN)C|ABD) +</pre> +If A matches but B fails, the backtrack to (*COMMIT) causes the entire match to +fail. However, if A and B match, but C fails, the backtrack to (*THEN) causes +the next alternative (ABD) to be tried. This behaviour is consistent, but is +not always the same as Perl's. It means that if two or more backtracking verbs +appear in succession, all the the last of them has no effect. Consider this +example: +<pre> + ...(*COMMIT)(*PRUNE)... +</pre> +If there is a matching failure to the right, backtracking onto (*PRUNE) causes +it to be triggered, and its action is taken. There can never be a backtrack +onto (*COMMIT). +<a name="btrepeat"></a></P> +<br><b> +Backtracking verbs in repeated groups +</b><br> +<P> +PCRE differs from Perl in its handling of backtracking verbs in repeated +groups. For example, consider: +<pre> + /(a(*COMMIT)b)+ac/ +</pre> +If the subject is "abac", Perl matches, but PCRE fails because the (*COMMIT) in +the second repeat of the group acts. +<a name="btassert"></a></P> +<br><b> +Backtracking verbs in assertions +</b><br> +<P> +(*FAIL) in an assertion has its normal effect: it forces an immediate backtrack. +</P> +<P> +(*ACCEPT) in a positive assertion causes the assertion to succeed without any +further processing. In a negative assertion, (*ACCEPT) causes the assertion to +fail without any further processing. +</P> +<P> +The other backtracking verbs are not treated specially if they appear in a +positive assertion. In particular, (*THEN) skips to the next alternative in the +innermost enclosing group that has alternations, whether or not this is within +the assertion. +</P> +<P> +Negative assertions are, however, different, in order to ensure that changing a +positive assertion into a negative assertion changes its result. Backtracking +into (*COMMIT), (*SKIP), or (*PRUNE) causes a negative assertion to be true, +without considering any further alternative branches in the assertion. +Backtracking into (*THEN) causes it to skip to the next enclosing alternative +within the assertion (the normal behaviour), but if the assertion does not have +such an alternative, (*THEN) behaves like (*PRUNE). +<a name="btsub"></a></P> +<br><b> +Backtracking verbs in subroutines +</b><br> +<P> +These behaviours occur whether or not the subpattern is called recursively. +Perl's treatment of subroutines is different in some cases. +</P> +<P> +(*FAIL) in a subpattern called as a subroutine has its normal effect: it forces +an immediate backtrack. +</P> +<P> +(*ACCEPT) in a subpattern called as a subroutine causes the subroutine match to +succeed without any further processing. Matching then continues after the +subroutine call. +</P> +<P> +(*COMMIT), (*SKIP), and (*PRUNE) in a subpattern called as a subroutine cause +the subroutine match to fail. +</P> +<P> +(*THEN) skips to the next alternative in the innermost enclosing group within +the subpattern that has alternatives. If there is no such group within the +subpattern, (*THEN) causes the subroutine match to fail. +</P> +<br><a name="SEC28" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcreapi</b>(3), <b>pcrecallout</b>(3), <b>pcrematching</b>(3), +<b>pcresyntax</b>(3), <b>pcre</b>(3), <b>pcre16(3)</b>, <b>pcre32(3)</b>. +</P> +<br><a name="SEC29" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC30" href="#TOC1">REVISION</a><br> +<P> +Last updated: 14 June 2015 +<br> +Copyright © 1997-2015 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcreperform.html b/doc/html/pcreperform.html new file mode 100644 index 0000000..dda207f --- /dev/null +++ b/doc/html/pcreperform.html @@ -0,0 +1,195 @@ +<html> +<head> +<title>pcreperform specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreperform man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +PCRE PERFORMANCE +</b><br> +<P> +Two aspects of performance are discussed below: memory usage and processing +time. The way you express your pattern as a regular expression can affect both +of them. +</P> +<br><b> +COMPILED PATTERN MEMORY USAGE +</b><br> +<P> +Patterns are compiled by PCRE into a reasonably efficient interpretive code, so +that most simple patterns do not use much memory. However, there is one case +where the memory usage of a compiled pattern can be unexpectedly large. If a +parenthesized subpattern has a quantifier with a minimum greater than 1 and/or +a limited maximum, the whole subpattern is repeated in the compiled code. For +example, the pattern +<pre> + (abc|def){2,4} +</pre> +is compiled as if it were +<pre> + (abc|def)(abc|def)((abc|def)(abc|def)?)? +</pre> +(Technical aside: It is done this way so that backtrack points within each of +the repetitions can be independently maintained.) +</P> +<P> +For regular expressions whose quantifiers use only small numbers, this is not +usually a problem. However, if the numbers are large, and particularly if such +repetitions are nested, the memory usage can become an embarrassment. For +example, the very simple pattern +<pre> + ((ab){1,1000}c){1,3} +</pre> +uses 51K bytes when compiled using the 8-bit library. When PCRE is compiled +with its default internal pointer size of two bytes, the size limit on a +compiled pattern is 64K data units, and this is reached with the above pattern +if the outer repetition is increased from 3 to 4. PCRE can be compiled to use +larger internal pointers and thus handle larger compiled patterns, but it is +better to try to rewrite your pattern to use less memory if you can. +</P> +<P> +One way of reducing the memory usage for such patterns is to make use of PCRE's +<a href="pcrepattern.html#subpatternsassubroutines">"subroutine"</a> +facility. Re-writing the above pattern as +<pre> + ((ab)(?2){0,999}c)(?1){0,2} +</pre> +reduces the memory requirements to 18K, and indeed it remains under 20K even +with the outer repetition increased to 100. However, this pattern is not +exactly equivalent, because the "subroutine" calls are treated as +<a href="pcrepattern.html#atomicgroup">atomic groups</a> +into which there can be no backtracking if there is a subsequent matching +failure. Therefore, PCRE cannot do this kind of rewriting automatically. +Furthermore, there is a noticeable loss of speed when executing the modified +pattern. Nevertheless, if the atomic grouping is not a problem and the loss of +speed is acceptable, this kind of rewriting will allow you to process patterns +that PCRE cannot otherwise handle. +</P> +<br><b> +STACK USAGE AT RUN TIME +</b><br> +<P> +When <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> is used for matching, certain +kinds of pattern can cause it to use large amounts of the process stack. In +some environments the default process stack is quite small, and if it runs out +the result is often SIGSEGV. This issue is probably the most frequently raised +problem with PCRE. Rewriting your pattern can often help. The +<a href="pcrestack.html"><b>pcrestack</b></a> +documentation discusses this issue in detail. +</P> +<br><b> +PROCESSING TIME +</b><br> +<P> +Certain items in regular expression patterns are processed more efficiently +than others. It is more efficient to use a character class like [aeiou] than a +set of single-character alternatives such as (a|e|i|o|u). In general, the +simplest construction that provides the required behaviour is usually the most +efficient. Jeffrey Friedl's book contains a lot of useful general discussion +about optimizing regular expressions for efficient performance. This document +contains a few observations about PCRE. +</P> +<P> +Using Unicode character properties (the \p, \P, and \X escapes) is slow, +because PCRE has to use a multi-stage table lookup whenever it needs a +character's property. If you can find an alternative pattern that does not use +character properties, it will probably be faster. +</P> +<P> +By default, the escape sequences \b, \d, \s, and \w, and the POSIX +character classes such as [:alpha:] do not use Unicode properties, partly for +backwards compatibility, and partly for performance reasons. However, you can +set PCRE_UCP if you want Unicode character properties to be used. This can +double the matching time for items such as \d, when matched with +a traditional matching function; the performance loss is less with +a DFA matching function, and in both cases there is not much difference for +\b. +</P> +<P> +When a pattern begins with .* not in parentheses, or in parentheses that are +not the subject of a backreference, and the PCRE_DOTALL option is set, the +pattern is implicitly anchored by PCRE, since it can match only at the start of +a subject string. However, if PCRE_DOTALL is not set, PCRE cannot make this +optimization, because the . metacharacter does not then match a newline, and if +the subject string contains newlines, the pattern may match from the character +immediately following one of them instead of from the very start. For example, +the pattern +<pre> + .*second +</pre> +matches the subject "first\nand second" (where \n stands for a newline +character), with the match starting at the seventh character. In order to do +this, PCRE has to retry the match starting after every newline in the subject. +</P> +<P> +If you are using such a pattern with subject strings that do not contain +newlines, the best performance is obtained by setting PCRE_DOTALL, or starting +the pattern with ^.* or ^.*? to indicate explicit anchoring. That saves PCRE +from having to scan along the subject looking for a newline to restart at. +</P> +<P> +Beware of patterns that contain nested indefinite repeats. These can take a +long time to run when applied to a string that does not match. Consider the +pattern fragment +<pre> + ^(a+)* +</pre> +This can match "aaaa" in 16 different ways, and this number increases very +rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 +times, and for each of those cases other than 0 or 4, the + repeats can match +different numbers of times.) When the remainder of the pattern is such that the +entire match is going to fail, PCRE has in principle to try every possible +variation, and this can take an extremely long time, even for relatively short +strings. +</P> +<P> +An optimization catches some of the more simple cases such as +<pre> + (a+)*b +</pre> +where a literal character follows. Before embarking on the standard matching +procedure, PCRE checks that there is a "b" later in the subject string, and if +there is not, it fails the match immediately. However, when there is no +following literal this optimization cannot be used. You can see the difference +by comparing the behaviour of +<pre> + (a+)*\d +</pre> +with the pattern above. The former gives a failure almost instantly when +applied to a whole line of "a" characters, whereas the latter takes an +appreciable time with strings longer than about 20 characters. +</P> +<P> +In many cases, the solution to this kind of performance issue is to use an +atomic group or a possessive quantifier. +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 25 August 2012 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcreposix.html b/doc/html/pcreposix.html new file mode 100644 index 0000000..18924cf --- /dev/null +++ b/doc/html/pcreposix.html @@ -0,0 +1,290 @@ +<html> +<head> +<title>pcreposix specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreposix man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">COMPILING A PATTERN</a> +<li><a name="TOC4" href="#SEC4">MATCHING NEWLINE CHARACTERS</a> +<li><a name="TOC5" href="#SEC5">MATCHING A PATTERN</a> +<li><a name="TOC6" href="#SEC6">ERROR MESSAGES</a> +<li><a name="TOC7" href="#SEC7">MEMORY USAGE</a> +<li><a name="TOC8" href="#SEC8">AUTHOR</a> +<li><a name="TOC9" href="#SEC9">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>#include <pcreposix.h></b> +</P> +<P> +<b>int regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b> +<b> int <i>cflags</i>);</b> +<br> +<br> +<b>int regexec(regex_t *<i>preg</i>, const char *<i>string</i>,</b> +<b> size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b> +<b> size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b> +<b> char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b> +<br> +<br> +<b>void regfree(regex_t *<i>preg</i>);</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +This set of functions provides a POSIX-style API for the PCRE regular +expression 8-bit library. See the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation for a description of PCRE's native API, which contains much +additional functionality. There is no POSIX-style wrapper for PCRE's 16-bit +and 32-bit library. +</P> +<P> +The functions described here are just wrapper functions that ultimately call +the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b> +header file, and on Unix systems the library itself is called +<b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the +command for linking an application that uses them. Because the POSIX functions +call the native ones, it is also necessary to add <b>-lpcre</b>. +</P> +<P> +I have implemented only those POSIX option bits that can be reasonably mapped +to PCRE native options. In addition, the option REG_EXTENDED is defined with +the value zero. This has no effect, but since programs that are written to the +POSIX interface often use it, this makes it easier to slot in PCRE as a +replacement library. Other POSIX options are not even defined. +</P> +<P> +There are also some other options that are not defined by POSIX. These have +been added at the request of users who want to make use of certain +PCRE-specific features via the POSIX calling interface. +</P> +<P> +When PCRE is called via these functions, it is only the API that is POSIX-like +in style. The syntax and semantics of the regular expressions themselves are +still those of Perl, subject to the setting of various PCRE options, as +described below. "POSIX-like in style" means that the API approximates to the +POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding +domains it is probably even less compatible. +</P> +<P> +The header for these functions is supplied as <b>pcreposix.h</b> to avoid any +potential clash with other POSIX libraries. It can, of course, be renamed or +aliased as <b>regex.h</b>, which is the "correct" name. It provides two +structure types, <i>regex_t</i> for compiled internal forms, and +<i>regmatch_t</i> for returning captured substrings. It also defines some +constants whose names start with "REG_"; these are used for setting options and +identifying error codes. +</P> +<br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br> +<P> +The function <b>regcomp()</b> is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer +to a <b>regex_t</b> structure that is used as a base for storing information +about the compiled regular expression. +</P> +<P> +The argument <i>cflags</i> is either zero, or contains one or more of the bits +defined by the following macros: +<pre> + REG_DOTALL +</pre> +The PCRE_DOTALL option is set when the regular expression is passed for +compilation to the native function. Note that REG_DOTALL is not part of the +POSIX standard. +<pre> + REG_ICASE +</pre> +The PCRE_CASELESS option is set when the regular expression is passed for +compilation to the native function. +<pre> + REG_NEWLINE +</pre> +The PCRE_MULTILINE option is set when the regular expression is passed for +compilation to the native function. Note that this does <i>not</i> mimic the +defined POSIX behaviour for REG_NEWLINE (see the following section). +<pre> + REG_NOSUB +</pre> +The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed +for compilation to the native function. In addition, when a pattern that is +compiled with this flag is passed to <b>regexec()</b> for matching, the +<i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings +are returned. +<pre> + REG_UCP +</pre> +The PCRE_UCP option is set when the regular expression is passed for +compilation to the native function. This causes PCRE to use Unicode properties +when matchine \d, \w, etc., instead of just recognizing ASCII values. Note +that REG_UTF8 is not part of the POSIX standard. +<pre> + REG_UNGREEDY +</pre> +The PCRE_UNGREEDY option is set when the regular expression is passed for +compilation to the native function. Note that REG_UNGREEDY is not part of the +POSIX standard. +<pre> + REG_UTF8 +</pre> +The PCRE_UTF8 option is set when the regular expression is passed for +compilation to the native function. This causes the pattern itself and all data +strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 +is not part of the POSIX standard. +</P> +<P> +In the absence of these flags, no options are passed to the native function. +This means the the regex is compiled with PCRE default semantics. In +particular, the way it handles newline characters in the subject string is the +Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only +<i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way +newlines are matched by . (they are not) or by a negative class such as [^a] +(they are). +</P> +<P> +The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The +<i>preg</i> structure is filled in on success, and one member of the structure +is public: <i>re_nsub</i> contains the number of capturing subpatterns in +the regular expression. Various error codes are defined in the header file. +</P> +<P> +NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to +use the contents of the <i>preg</i> structure. If, for example, you pass it to +<b>regexec()</b>, the result is undefined and your program is likely to crash. +</P> +<br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br> +<P> +This area is not simple, because POSIX and Perl take different views of things. +It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never +intended to be a POSIX engine. The following table lists the different +possibilities for matching newline characters in PCRE: +<pre> + Default Change with + + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \n at end yes PCRE_DOLLARENDONLY + $ matches \n in middle no PCRE_MULTILINE + ^ matches \n in middle no PCRE_MULTILINE +</pre> +This is the equivalent table for POSIX: +<pre> + Default Change with + + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \n at end no REG_NEWLINE + $ matches \n in middle no REG_NEWLINE + ^ matches \n in middle no REG_NEWLINE +</pre> +PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop +newline from matching [^a]. +</P> +<P> +The default POSIX newline handling can be obtained by setting PCRE_DOTALL and +PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the +REG_NEWLINE action. +</P> +<br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br> +<P> +The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i> +against a given <i>string</i>, which is by default terminated by a zero byte +(but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can +be: +<pre> + REG_NOTBOL +</pre> +The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. +<pre> + REG_NOTEMPTY +</pre> +The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching +function. Note that REG_NOTEMPTY is not part of the POSIX standard. However, +setting this option can give more POSIX-like behaviour in some situations. +<pre> + REG_NOTEOL +</pre> +The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. +<pre> + REG_STARTEND +</pre> +The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and +to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i> +(there need not actually be a NUL at that location), regardless of the value of +<i>nmatch</i>. This is a BSD extension, compatible with but not specified by +IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software +intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does +not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not +how it is matched. +</P> +<P> +If the pattern was compiled with the REG_NOSUB flag, no data about any matched +strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of +<b>regexec()</b> are ignored. +</P> +<P> +If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL, +no data about any matched strings is returned. +</P> +<P> +Otherwise,the portion of the string that was matched, and also any captured +substrings, are returned via the <i>pmatch</i> argument, which points to an +array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the +members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first +character of each substring and the offset to the first character after the end +of each substring, respectively. The 0th element of the vector relates to the +entire portion of <i>string</i> that was matched; subsequent elements relate to +the capturing subpatterns of the regular expression. Unused entries in the +array have both structure members set to -1. +</P> +<P> +A successful match yields a zero return; various error codes are defined in the +header file, of which REG_NOMATCH is the "expected" failure code. +</P> +<br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br> +<P> +The <b>regerror()</b> function maps a non-zero errorcode from either +<b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not +NULL, the error should have arisen from the use of that structure. A message +terminated by a binary zero is placed in <i>errbuf</i>. The length of the +message, including the zero, is limited to <i>errbuf_size</i>. The yield of the +function is the size of buffer needed to hold the whole message. +</P> +<br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br> +<P> +Compiling a regular expression causes memory to be allocated and associated +with the <i>preg</i> structure. The function <b>regfree()</b> frees all such +memory, after which <i>preg</i> may no longer be used as a compiled expression. +</P> +<br><a name="SEC8" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC9" href="#TOC1">REVISION</a><br> +<P> +Last updated: 09 January 2012 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcreprecompile.html b/doc/html/pcreprecompile.html new file mode 100644 index 0000000..decb1d6 --- /dev/null +++ b/doc/html/pcreprecompile.html @@ -0,0 +1,163 @@ +<html> +<head> +<title>pcreprecompile specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreprecompile man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SAVING AND RE-USING PRECOMPILED PCRE PATTERNS</a> +<li><a name="TOC2" href="#SEC2">SAVING A COMPILED PATTERN</a> +<li><a name="TOC3" href="#SEC3">RE-USING A PRECOMPILED PATTERN</a> +<li><a name="TOC4" href="#SEC4">COMPATIBILITY WITH DIFFERENT PCRE RELEASES</a> +<li><a name="TOC5" href="#SEC5">AUTHOR</a> +<li><a name="TOC6" href="#SEC6">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SAVING AND RE-USING PRECOMPILED PCRE PATTERNS</a><br> +<P> +If you are running an application that uses a large number of regular +expression patterns, it may be useful to store them in a precompiled form +instead of having to compile them every time the application is run. +If you are not using any private character tables (see the +<a href="pcre_maketables.html"><b>pcre_maketables()</b></a> +documentation), this is relatively straightforward. If you are using private +tables, it is a little bit more complicated. However, if you are using the +just-in-time optimization feature, it is not possible to save and reload the +JIT data. +</P> +<P> +If you save compiled patterns to a file, you can copy them to a different host +and run them there. If the two hosts have different endianness (byte order), +you should run the <b>pcre[16|32]_pattern_to_host_byte_order()</b> function on the +new host before trying to match the pattern. The matching functions return +PCRE_ERROR_BADENDIANNESS if they detect a pattern with the wrong endianness. +</P> +<P> +Compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes, and saving and +restoring a compiled pattern loses any JIT optimization data. +</P> +<br><a name="SEC2" href="#TOC1">SAVING A COMPILED PATTERN</a><br> +<P> +The value returned by <b>pcre[16|32]_compile()</b> points to a single block of +memory that holds the compiled pattern and associated data. You can find the +length of this block in bytes by calling <b>pcre[16|32]_fullinfo()</b> with an +argument of PCRE_INFO_SIZE. You can then save the data in any appropriate +manner. Here is sample code for the 8-bit library that compiles a pattern and +writes it to a file. It assumes that the variable <i>fd</i> refers to a file +that is open for output: +<pre> + int erroroffset, rc, size; + char *error; + pcre *re; + + re = pcre_compile("my pattern", 0, &error, &erroroffset, NULL); + if (re == NULL) { ... handle errors ... } + rc = pcre_fullinfo(re, NULL, PCRE_INFO_SIZE, &size); + if (rc < 0) { ... handle errors ... } + rc = fwrite(re, 1, size, fd); + if (rc != size) { ... handle errors ... } +</pre> +In this example, the bytes that comprise the compiled pattern are copied +exactly. Note that this is binary data that may contain any of the 256 possible +byte values. On systems that make a distinction between binary and non-binary +data, be sure that the file is opened for binary output. +</P> +<P> +If you want to write more than one pattern to a file, you will have to devise a +way of separating them. For binary data, preceding each pattern with its length +is probably the most straightforward approach. Another possibility is to write +out the data in hexadecimal instead of binary, one pattern to a line. +</P> +<P> +Saving compiled patterns in a file is only one possible way of storing them for +later use. They could equally well be saved in a database, or in the memory of +some daemon process that passes them via sockets to the processes that want +them. +</P> +<P> +If the pattern has been studied, it is also possible to save the normal study +data in a similar way to the compiled pattern itself. However, if the +PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is created cannot +be saved because it is too dependent on the current environment. When studying +generates additional information, <b>pcre[16|32]_study()</b> returns a pointer to a +<b>pcre[16|32]_extra</b> data block. Its format is defined in the +<a href="pcreapi.html#extradata">section on matching a pattern</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. The <i>study_data</i> field points to the binary study data, and +this is what you must save (not the <b>pcre[16|32]_extra</b> block itself). The +length of the study data can be obtained by calling <b>pcre[16|32]_fullinfo()</b> +with an argument of PCRE_INFO_STUDYSIZE. Remember to check that +<b>pcre[16|32]_study()</b> did return a non-NULL value before trying to save the +study data. +</P> +<br><a name="SEC3" href="#TOC1">RE-USING A PRECOMPILED PATTERN</a><br> +<P> +Re-using a precompiled pattern is straightforward. Having reloaded it into main +memory, called <b>pcre[16|32]_pattern_to_host_byte_order()</b> if necessary, you +pass its pointer to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> in +the usual way. +</P> +<P> +However, if you passed a pointer to custom character tables when the pattern +was compiled (the <i>tableptr</i> argument of <b>pcre[16|32]_compile()</b>), you +must now pass a similar pointer to <b>pcre[16|32]_exec()</b> or +<b>pcre[16|32]_dfa_exec()</b>, because the value saved with the compiled pattern +will obviously be nonsense. A field in a <b>pcre[16|32]_extra()</b> block is used +to pass this data, as described in the +<a href="pcreapi.html#extradata">section on matching a pattern</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<P> +<b>Warning:</b> The tables that <b>pcre_exec()</b> and <b>pcre_dfa_exec()</b> use +must be the same as those that were used when the pattern was compiled. If this +is not the case, the behaviour is undefined. +</P> +<P> +If you did not provide custom character tables when the pattern was compiled, +the pointer in the compiled pattern is NULL, which causes the matching +functions to use PCRE's internal tables. Thus, you do not need to take any +special action at run time in this case. +</P> +<P> +If you saved study data with the compiled pattern, you need to create your own +<b>pcre[16|32]_extra</b> data block and set the <i>study_data</i> field to point +to the reloaded study data. You must also set the PCRE_EXTRA_STUDY_DATA bit in +the <i>flags</i> field to indicate that study data is present. Then pass the +<b>pcre[16|32]_extra</b> block to the matching function in the usual way. If the +pattern was studied for just-in-time optimization, that data cannot be saved, +and so is lost by a save/restore cycle. +</P> +<br><a name="SEC4" href="#TOC1">COMPATIBILITY WITH DIFFERENT PCRE RELEASES</a><br> +<P> +In general, it is safest to recompile all saved patterns when you update to a +new PCRE release, though not all updates actually require this. +</P> +<br><a name="SEC5" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC6" href="#TOC1">REVISION</a><br> +<P> +Last updated: 12 November 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcresample.html b/doc/html/pcresample.html new file mode 100644 index 0000000..aca9184 --- /dev/null +++ b/doc/html/pcresample.html @@ -0,0 +1,110 @@ +<html> +<head> +<title>pcresample specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcresample man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +PCRE SAMPLE PROGRAM +</b><br> +<P> +A simple, complete demonstration program, to get you started with using PCRE, +is supplied in the file <i>pcredemo.c</i> in the PCRE distribution. A listing of +this program is given in the +<a href="pcredemo.html"><b>pcredemo</b></a> +documentation. If you do not have a copy of the PCRE distribution, you can save +this listing to re-create <i>pcredemo.c</i>. +</P> +<P> +The demonstration program, which uses the original PCRE 8-bit library, compiles +the regular expression that is its first argument, and matches it against the +subject string in its second argument. No PCRE options are set, and default +character tables are used. If matching succeeds, the program outputs the +portion of the subject that matched, together with the contents of any captured +substrings. +</P> +<P> +If the -g option is given on the command line, the program then goes on to +check for further matches of the same regular expression in the same subject +string. The logic is a little bit tricky because of the possibility of matching +an empty string. Comments in the code explain what is going on. +</P> +<P> +If PCRE is installed in the standard include and library directories for your +operating system, you should be able to compile the demonstration program using +this command: +<pre> + gcc -o pcredemo pcredemo.c -lpcre +</pre> +If PCRE is installed elsewhere, you may need to add additional options to the +command line. For example, on a Unix-like system that has PCRE installed in +<i>/usr/local</i>, you can compile the demonstration program using a command +like this: +<pre> + gcc -o pcredemo -I/usr/local/include pcredemo.c -L/usr/local/lib -lpcre +</pre> +In a Windows environment, if you want to statically link the program against a +non-dll <b>pcre.a</b> file, you must uncomment the line that defines PCRE_STATIC +before including <b>pcre.h</b>, because otherwise the <b>pcre_malloc()</b> and +<b>pcre_free()</b> exported functions will be declared +<b>__declspec(dllimport)</b>, with unwanted results. +</P> +<P> +Once you have compiled and linked the demonstration program, you can run simple +tests like this: +<pre> + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' +</pre> +Note that there is a much more comprehensive test program, called +<a href="pcretest.html"><b>pcretest</b>,</a> +which supports many more facilities for testing regular expressions and both +PCRE libraries. The +<a href="pcredemo.html"><b>pcredemo</b></a> +program is provided as a simple coding example. +</P> +<P> +If you try to run +<a href="pcredemo.html"><b>pcredemo</b></a> +when PCRE is not installed in the standard library directory, you may get an +error like this on some operating systems (e.g. Solaris): +<pre> + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory +</pre> +This is caused by the way shared library support works on those systems. You +need to add +<pre> + -R/usr/local/lib +</pre> +(for example) to the compile command to get round this problem. +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 10 January 2012 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcrestack.html b/doc/html/pcrestack.html new file mode 100644 index 0000000..af6406d --- /dev/null +++ b/doc/html/pcrestack.html @@ -0,0 +1,225 @@ +<html> +<head> +<title>pcrestack specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcrestack man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +PCRE DISCUSSION OF STACK USAGE +</b><br> +<P> +When you call <b>pcre[16|32]_exec()</b>, it makes use of an internal function +called <b>match()</b>. This calls itself recursively at branch points in the +pattern, in order to remember the state of the match so that it can back up and +try a different alternative if the first one fails. As matching proceeds deeper +and deeper into the tree of possibilities, the recursion depth increases. The +<b>match()</b> function is also called in other circumstances, for example, +whenever a parenthesized sub-pattern is entered, and in certain cases of +repetition. +</P> +<P> +Not all calls of <b>match()</b> increase the recursion depth; for an item such +as a* it may be called several times at the same level, after matching +different numbers of a's. Furthermore, in a number of cases where the result of +the recursive call would immediately be passed back as the result of the +current call (a "tail recursion"), the function is just restarted instead. +</P> +<P> +The above comments apply when <b>pcre[16|32]_exec()</b> is run in its normal +interpretive manner. If the pattern was studied with the +PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling was successful, and +the options passed to <b>pcre[16|32]_exec()</b> were not incompatible, the matching +process uses the JIT-compiled code instead of the <b>match()</b> function. In +this case, the memory requirements are handled entirely differently. See the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation for details. +</P> +<P> +The <b>pcre[16|32]_dfa_exec()</b> function operates in an entirely different way, +and uses recursion only when there is a regular expression recursion or +subroutine call in the pattern. This includes the processing of assertion and +"once-only" subpatterns, which are handled like subroutine calls. Normally, +these are never very deep, and the limit on the complexity of +<b>pcre[16|32]_dfa_exec()</b> is controlled by the amount of workspace it is given. +However, it is possible to write patterns with runaway infinite recursions; +such patterns will cause <b>pcre[16|32]_dfa_exec()</b> to run out of stack. At +present, there is no protection against this. +</P> +<P> +The comments that follow do NOT apply to <b>pcre[16|32]_dfa_exec()</b>; they are +relevant only for <b>pcre[16|32]_exec()</b> without the JIT optimization. +</P> +<br><b> +Reducing <b>pcre[16|32]_exec()</b>'s stack usage +</b><br> +<P> +Each time that <b>match()</b> is actually called recursively, it uses memory +from the process stack. For certain kinds of pattern and data, very large +amounts of stack may be needed, despite the recognition of "tail recursion". +You can often reduce the amount of recursion, and therefore the amount of stack +used, by modifying the pattern that is being matched. Consider, for example, +this pattern: +<pre> + ([^<]|<(?!inet))+ +</pre> +It matches from wherever it starts until it encounters "<inet" or the end of +the data, and is the kind of pattern that might be used when processing an XML +file. Each iteration of the outer parentheses matches either one character that +is not "<" or a "<" that is not followed by "inet". However, each time a +parenthesis is processed, a recursion occurs, so this formulation uses a stack +frame for each matched character. For a long string, a lot of stack is +required. Consider now this rewritten pattern, which matches exactly the same +strings: +<pre> + ([^<]++|<(?!inet))+ +</pre> +This uses very much less stack, because runs of characters that do not contain +"<" are "swallowed" in one item inside the parentheses. Recursion happens only +when a "<" character that is not followed by "inet" is encountered (and we +assume this is relatively rare). A possessive quantifier is used to stop any +backtracking into the runs of non-"<" characters, but that is not related to +stack usage. +</P> +<P> +This example shows that one way of avoiding stack problems when matching long +subject strings is to write repeated parenthesized subpatterns to match more +than one character whenever possible. +</P> +<br><b> +Compiling PCRE to use heap instead of stack for <b>pcre[16|32]_exec()</b> +</b><br> +<P> +In environments where stack memory is constrained, you might want to compile +PCRE to use heap memory instead of stack for remembering back-up points when +<b>pcre[16|32]_exec()</b> is running. This makes it run a lot more slowly, however. +Details of how to do this are given in the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation. When built in this way, instead of using the stack, PCRE obtains +and frees memory by calling the functions that are pointed to by the +<b>pcre[16|32]_stack_malloc</b> and <b>pcre[16|32]_stack_free</b> variables. By +default, these point to <b>malloc()</b> and <b>free()</b>, but you can replace +the pointers to cause PCRE to use your own functions. Since the block sizes are +always the same, and are always freed in reverse order, it may be possible to +implement customized memory handlers that are more efficient than the standard +functions. +</P> +<br><b> +Limiting <b>pcre[16|32]_exec()</b>'s stack usage +</b><br> +<P> +You can set limits on the number of times that <b>match()</b> is called, both in +total and recursively. If a limit is exceeded, <b>pcre[16|32]_exec()</b> returns an +error code. Setting suitable limits should prevent it from running out of +stack. The default values of the limits are very large, and unlikely ever to +operate. They can be changed when PCRE is built, and they can also be set when +<b>pcre[16|32]_exec()</b> is called. For details of these interfaces, see the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation and the +<a href="pcreapi.html#extradata">section on extra data for <b>pcre[16|32]_exec()</b></a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<P> +As a very rough rule of thumb, you should reckon on about 500 bytes per +recursion. Thus, if you want to limit your stack usage to 8Mb, you should set +the limit at 16000 recursions. A 64Mb stack, on the other hand, can support +around 128000 recursions. +</P> +<P> +In Unix-like environments, the <b>pcretest</b> test program has a command line +option (<b>-S</b>) that can be used to increase the size of its stack. As long +as the stack is large enough, another option (<b>-M</b>) can be used to find the +smallest limits that allow a particular pattern to match a given subject +string. This is done by calling <b>pcre[16|32]_exec()</b> repeatedly with different +limits. +</P> +<br><b> +Obtaining an estimate of stack usage +</b><br> +<P> +The actual amount of stack used per recursion can vary quite a lot, depending +on the compiler that was used to build PCRE and the optimization or debugging +options that were set for it. The rule of thumb value of 500 bytes mentioned +above may be larger or smaller than what is actually needed. A better +approximation can be obtained by running this command: +<pre> + pcretest -m -C +</pre> +The <b>-C</b> option causes <b>pcretest</b> to output information about the +options with which PCRE was compiled. When <b>-m</b> is also given (before +<b>-C</b>), information about stack use is given in a line like this: +<pre> + Match recursion uses stack: approximate frame size = 640 bytes +</pre> +The value is approximate because some recursions need a bit more (up to perhaps +16 more bytes). +</P> +<P> +If the above command is given when PCRE is compiled to use the heap instead of +the stack for recursion, the value that is output is the size of each block +that is obtained from the heap. +</P> +<br><b> +Changing stack size in Unix-like systems +</b><br> +<P> +In Unix-like environments, there is not often a problem with the stack unless +very long strings are involved, though the default limit on stack size varies +from system to system. Values from 8Mb to 64Mb are common. You can find your +default limit by running the command: +<pre> + ulimit -s +</pre> +Unfortunately, the effect of running out of stack is often SIGSEGV, though +sometimes a more explicit error message is given. You can normally increase the +limit on stack size by code such as this: +<pre> + struct rlimit rlim; + getrlimit(RLIMIT_STACK, &rlim); + rlim.rlim_cur = 100*1024*1024; + setrlimit(RLIMIT_STACK, &rlim); +</pre> +This reads the current limits (soft and hard) using <b>getrlimit()</b>, then +attempts to increase the soft limit to 100Mb using <b>setrlimit()</b>. You must +do this before calling <b>pcre[16|32]_exec()</b>. +</P> +<br><b> +Changing stack size in Mac OS X +</b><br> +<P> +Using <b>setrlimit()</b>, as described above, should also work on Mac OS X. It +is also possible to set a stack size when linking a program. There is a +discussion about stack sizes in Mac OS X at this web site: +<a href="http://developer.apple.com/qa/qa2005/qa1419.html">http://developer.apple.com/qa/qa2005/qa1419.html.</a> +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 24 June 2012 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcresyntax.html b/doc/html/pcresyntax.html new file mode 100644 index 0000000..5896b9e --- /dev/null +++ b/doc/html/pcresyntax.html @@ -0,0 +1,561 @@ +<html> +<head> +<title>pcresyntax specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcresyntax man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a> +<li><a name="TOC2" href="#SEC2">QUOTING</a> +<li><a name="TOC3" href="#SEC3">CHARACTERS</a> +<li><a name="TOC4" href="#SEC4">CHARACTER TYPES</a> +<li><a name="TOC5" href="#SEC5">GENERAL CATEGORY PROPERTIES FOR \p and \P</a> +<li><a name="TOC6" href="#SEC6">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a> +<li><a name="TOC7" href="#SEC7">SCRIPT NAMES FOR \p AND \P</a> +<li><a name="TOC8" href="#SEC8">CHARACTER CLASSES</a> +<li><a name="TOC9" href="#SEC9">QUANTIFIERS</a> +<li><a name="TOC10" href="#SEC10">ANCHORS AND SIMPLE ASSERTIONS</a> +<li><a name="TOC11" href="#SEC11">MATCH POINT RESET</a> +<li><a name="TOC12" href="#SEC12">ALTERNATION</a> +<li><a name="TOC13" href="#SEC13">CAPTURING</a> +<li><a name="TOC14" href="#SEC14">ATOMIC GROUPS</a> +<li><a name="TOC15" href="#SEC15">COMMENT</a> +<li><a name="TOC16" href="#SEC16">OPTION SETTING</a> +<li><a name="TOC17" href="#SEC17">NEWLINE CONVENTION</a> +<li><a name="TOC18" href="#SEC18">WHAT \R MATCHES</a> +<li><a name="TOC19" href="#SEC19">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a> +<li><a name="TOC20" href="#SEC20">BACKREFERENCES</a> +<li><a name="TOC21" href="#SEC21">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a> +<li><a name="TOC22" href="#SEC22">CONDITIONAL PATTERNS</a> +<li><a name="TOC23" href="#SEC23">BACKTRACKING CONTROL</a> +<li><a name="TOC24" href="#SEC24">CALLOUTS</a> +<li><a name="TOC25" href="#SEC25">SEE ALSO</a> +<li><a name="TOC26" href="#SEC26">AUTHOR</a> +<li><a name="TOC27" href="#SEC27">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a><br> +<P> +The full syntax and semantics of the regular expressions that are supported by +PCRE are described in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. This document contains a quick-reference summary of the syntax. +</P> +<br><a name="SEC2" href="#TOC1">QUOTING</a><br> +<P> +<pre> + \x where x is non-alphanumeric is a literal x + \Q...\E treat enclosed characters as literal +</PRE> +</P> +<br><a name="SEC3" href="#TOC1">CHARACTERS</a><br> +<P> +<pre> + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any ASCII character + \e escape (hex 1B) + \f form feed (hex 0C) + \n newline (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \0dd character with octal code 0dd + \ddd character with octal code ddd, or backreference + \o{ddd..} character with octal code ddd.. + \xhh character with hex code hh + \x{hhh..} character with hex code hhh.. +</pre> +Note that \0dd is always an octal code, and that \8 and \9 are the literal +characters "8" and "9". +</P> +<br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br> +<P> +<pre> + . any character except newline; + in dotall mode, any character whatsoever + \C one data unit, even in UTF mode (best avoided) + \d a decimal digit + \D a character that is not a decimal digit + \h a horizontal white space character + \H a character that is not a horizontal white space character + \N a character that is not a newline + \p{<i>xx</i>} a character with the <i>xx</i> property + \P{<i>xx</i>} a character without the <i>xx</i> property + \R a newline sequence + \s a white space character + \S a character that is not a white space character + \v a vertical white space character + \V a character that is not a vertical white space character + \w a "word" character + \W a "non-word" character + \X a Unicode extended grapheme cluster +</pre> +By default, \d, \s, and \w match only ASCII characters, even in UTF-8 mode +or in the 16- bit and 32-bit libraries. However, if locale-specific matching is +happening, \s and \w may also match characters with code points in the range +128-255. If the PCRE_UCP option is set, the behaviour of these escape sequences +is changed to use Unicode properties and they match many more characters. +</P> +<br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a><br> +<P> +<pre> + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate + + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter + L& Ll, Lu, or Lt + + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark + + N Number + Nd Decimal number + Nl Letter number + No Other number + + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation + + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol + + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator +</PRE> +</P> +<br><a name="SEC6" href="#TOC1">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br> +<P> +<pre> + Xan Alphanumeric: union of properties L and N + Xps POSIX space: property Z or tab, NL, VT, FF, CR + Xsp Perl space: property Z or tab, NL, VT, FF, CR + Xuc Univerally-named character: one that can be + represented by a Universal Character Name + Xwd Perl word: property Xan or underscore +</pre> +Perl and POSIX space are now the same. Perl added VT to its space character set +at release 5.18 and PCRE changed at release 8.34. +</P> +<br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br> +<P> +Arabic, +Armenian, +Avestan, +Balinese, +Bamum, +Bassa_Vah, +Batak, +Bengali, +Bopomofo, +Brahmi, +Braille, +Buginese, +Buhid, +Canadian_Aboriginal, +Carian, +Caucasian_Albanian, +Chakma, +Cham, +Cherokee, +Common, +Coptic, +Cuneiform, +Cypriot, +Cyrillic, +Deseret, +Devanagari, +Duployan, +Egyptian_Hieroglyphs, +Elbasan, +Ethiopic, +Georgian, +Glagolitic, +Gothic, +Grantha, +Greek, +Gujarati, +Gurmukhi, +Han, +Hangul, +Hanunoo, +Hebrew, +Hiragana, +Imperial_Aramaic, +Inherited, +Inscriptional_Pahlavi, +Inscriptional_Parthian, +Javanese, +Kaithi, +Kannada, +Katakana, +Kayah_Li, +Kharoshthi, +Khmer, +Khojki, +Khudawadi, +Lao, +Latin, +Lepcha, +Limbu, +Linear_A, +Linear_B, +Lisu, +Lycian, +Lydian, +Mahajani, +Malayalam, +Mandaic, +Manichaean, +Meetei_Mayek, +Mende_Kikakui, +Meroitic_Cursive, +Meroitic_Hieroglyphs, +Miao, +Modi, +Mongolian, +Mro, +Myanmar, +Nabataean, +New_Tai_Lue, +Nko, +Ogham, +Ol_Chiki, +Old_Italic, +Old_North_Arabian, +Old_Permic, +Old_Persian, +Old_South_Arabian, +Old_Turkic, +Oriya, +Osmanya, +Pahawh_Hmong, +Palmyrene, +Pau_Cin_Hau, +Phags_Pa, +Phoenician, +Psalter_Pahlavi, +Rejang, +Runic, +Samaritan, +Saurashtra, +Sharada, +Shavian, +Siddham, +Sinhala, +Sora_Sompeng, +Sundanese, +Syloti_Nagri, +Syriac, +Tagalog, +Tagbanwa, +Tai_Le, +Tai_Tham, +Tai_Viet, +Takri, +Tamil, +Telugu, +Thaana, +Thai, +Tibetan, +Tifinagh, +Tirhuta, +Ugaritic, +Vai, +Warang_Citi, +Yi. +</P> +<br><a name="SEC8" href="#TOC1">CHARACTER CLASSES</a><br> +<P> +<pre> + [...] positive character class + [^...] negative character class + [x-y] range (can be used for hex characters) + [[:xxx:]] positive POSIX named set + [[:^xxx:]] negative POSIX named set + + alnum alphanumeric + alpha alphabetic + ascii 0-127 + blank space or tab + cntrl control character + digit decimal digit + graph printing, excluding space + lower lower case letter + print printing, including space + punct printing, excluding alphanumeric + space white space + upper upper case letter + word same as \w + xdigit hexadecimal digit +</pre> +In PCRE, POSIX character set names recognize only ASCII characters by default, +but some of them use Unicode properties if PCRE_UCP is set. You can use +\Q...\E inside a character class. +</P> +<br><a name="SEC9" href="#TOC1">QUANTIFIERS</a><br> +<P> +<pre> + ? 0 or 1, greedy + ?+ 0 or 1, possessive + ?? 0 or 1, lazy + * 0 or more, greedy + *+ 0 or more, possessive + *? 0 or more, lazy + + 1 or more, greedy + ++ 1 or more, possessive + +? 1 or more, lazy + {n} exactly n + {n,m} at least n, no more than m, greedy + {n,m}+ at least n, no more than m, possessive + {n,m}? at least n, no more than m, lazy + {n,} n or more, greedy + {n,}+ n or more, possessive + {n,}? n or more, lazy +</PRE> +</P> +<br><a name="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br> +<P> +<pre> + \b word boundary + \B not a word boundary + ^ start of subject + also after internal newline in multiline mode + \A start of subject + $ end of subject + also before newline at end of subject + also before internal newline in multiline mode + \Z end of subject + also before newline at end of subject + \z end of subject + \G first matching position in subject +</PRE> +</P> +<br><a name="SEC11" href="#TOC1">MATCH POINT RESET</a><br> +<P> +<pre> + \K reset start of match +</pre> +\K is honoured in positive assertions, but ignored in negative ones. +</P> +<br><a name="SEC12" href="#TOC1">ALTERNATION</a><br> +<P> +<pre> + expr|expr|expr... +</PRE> +</P> +<br><a name="SEC13" href="#TOC1">CAPTURING</a><br> +<P> +<pre> + (...) capturing group + (?<name>...) named capturing group (Perl) + (?'name'...) named capturing group (Perl) + (?P<name>...) named capturing group (Python) + (?:...) non-capturing group + (?|...) non-capturing group; reset group numbers for + capturing groups in each alternative +</PRE> +</P> +<br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br> +<P> +<pre> + (?>...) atomic, non-capturing group +</PRE> +</P> +<br><a name="SEC15" href="#TOC1">COMMENT</a><br> +<P> +<pre> + (?#....) comment (not nestable) +</PRE> +</P> +<br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br> +<P> +<pre> + (?i) caseless + (?J) allow duplicate names + (?m) multiline + (?s) single line (dotall) + (?U) default ungreedy (lazy) + (?x) extended (ignore white space) + (?-...) unset option(s) +</pre> +The following are recognized only at the very start of a pattern or after one +of the newline or \R options with similar syntax. More than one of them may +appear. +<pre> + (*LIMIT_MATCH=d) set the match limit to d (decimal number) + (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number) + (*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS) + (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE) + (*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8) + (*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16) + (*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32) + (*UTF) set appropriate UTF mode for the library in use + (*UCP) set PCRE_UCP (use Unicode properties for \d etc) +</pre> +Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the +limits set by the caller of pcre_exec(), not increase them. +</P> +<br><a name="SEC17" href="#TOC1">NEWLINE CONVENTION</a><br> +<P> +These are recognized only at the very start of the pattern or after option +settings with a similar syntax. +<pre> + (*CR) carriage return only + (*LF) linefeed only + (*CRLF) carriage return followed by linefeed + (*ANYCRLF) all three of the above + (*ANY) any Unicode newline sequence +</PRE> +</P> +<br><a name="SEC18" href="#TOC1">WHAT \R MATCHES</a><br> +<P> +These are recognized only at the very start of the pattern or after option +setting with a similar syntax. +<pre> + (*BSR_ANYCRLF) CR, LF, or CRLF + (*BSR_UNICODE) any Unicode newline sequence +</PRE> +</P> +<br><a name="SEC19" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br> +<P> +<pre> + (?=...) positive look ahead + (?!...) negative look ahead + (?<=...) positive look behind + (?<!...) negative look behind +</pre> +Each top-level branch of a look behind must be of a fixed length. +</P> +<br><a name="SEC20" href="#TOC1">BACKREFERENCES</a><br> +<P> +<pre> + \n reference by number (can be ambiguous) + \gn reference by number + \g{n} reference by number + \g{-n} relative reference by number + \k<name> reference by name (Perl) + \k'name' reference by name (Perl) + \g{name} reference by name (Perl) + \k{name} reference by name (.NET) + (?P=name) reference by name (Python) +</PRE> +</P> +<br><a name="SEC21" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br> +<P> +<pre> + (?R) recurse whole pattern + (?n) call subpattern by absolute number + (?+n) call subpattern by relative number + (?-n) call subpattern by relative number + (?&name) call subpattern by name (Perl) + (?P>name) call subpattern by name (Python) + \g<name> call subpattern by name (Oniguruma) + \g'name' call subpattern by name (Oniguruma) + \g<n> call subpattern by absolute number (Oniguruma) + \g'n' call subpattern by absolute number (Oniguruma) + \g<+n> call subpattern by relative number (PCRE extension) + \g'+n' call subpattern by relative number (PCRE extension) + \g<-n> call subpattern by relative number (PCRE extension) + \g'-n' call subpattern by relative number (PCRE extension) +</PRE> +</P> +<br><a name="SEC22" href="#TOC1">CONDITIONAL PATTERNS</a><br> +<P> +<pre> + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) + + (?(n)... absolute reference condition + (?(+n)... relative reference condition + (?(-n)... relative reference condition + (?(<name>)... named reference condition (Perl) + (?('name')... named reference condition (Perl) + (?(name)... named reference condition (PCRE) + (?(R)... overall recursion condition + (?(Rn)... specific group recursion condition + (?(R&name)... specific recursion condition + (?(DEFINE)... define subpattern for reference + (?(assert)... assertion condition +</PRE> +</P> +<br><a name="SEC23" href="#TOC1">BACKTRACKING CONTROL</a><br> +<P> +The following act immediately they are reached: +<pre> + (*ACCEPT) force successful match + (*FAIL) force backtrack; synonym (*F) + (*MARK:NAME) set name to be passed back; synonym (*:NAME) +</pre> +The following act only when a subsequent match failure causes a backtrack to +reach them. They all force a match failure, but they differ in what happens +afterwards. Those that advance the start-of-match point do so only if the +pattern is not anchored. +<pre> + (*COMMIT) overall failure, no advance of starting point + (*PRUNE) advance to next starting character + (*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE) + (*SKIP) advance to current matching position + (*SKIP:NAME) advance to position corresponding to an earlier + (*MARK:NAME); if not found, the (*SKIP) is ignored + (*THEN) local failure, backtrack to next alternation + (*THEN:NAME) equivalent to (*MARK:NAME)(*THEN) +</PRE> +</P> +<br><a name="SEC24" href="#TOC1">CALLOUTS</a><br> +<P> +<pre> + (?C) callout + (?Cn) callout with data n +</PRE> +</P> +<br><a name="SEC25" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcrepattern</b>(3), <b>pcreapi</b>(3), <b>pcrecallout</b>(3), +<b>pcrematching</b>(3), <b>pcre</b>(3). +</P> +<br><a name="SEC26" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC27" href="#TOC1">REVISION</a><br> +<P> +Last updated: 08 January 2014 +<br> +Copyright © 1997-2014 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcretest.html b/doc/html/pcretest.html new file mode 100644 index 0000000..839fabf --- /dev/null +++ b/doc/html/pcretest.html @@ -0,0 +1,1158 @@ +<html> +<head> +<title>pcretest specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcretest man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">INPUT DATA FORMAT</a> +<li><a name="TOC3" href="#SEC3">PCRE's 8-BIT, 16-BIT AND 32-BIT LIBRARIES</a> +<li><a name="TOC4" href="#SEC4">COMMAND LINE OPTIONS</a> +<li><a name="TOC5" href="#SEC5">DESCRIPTION</a> +<li><a name="TOC6" href="#SEC6">PATTERN MODIFIERS</a> +<li><a name="TOC7" href="#SEC7">DATA LINES</a> +<li><a name="TOC8" href="#SEC8">THE ALTERNATIVE MATCHING FUNCTION</a> +<li><a name="TOC9" href="#SEC9">DEFAULT OUTPUT FROM PCRETEST</a> +<li><a name="TOC10" href="#SEC10">OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION</a> +<li><a name="TOC11" href="#SEC11">RESTARTING AFTER A PARTIAL MATCH</a> +<li><a name="TOC12" href="#SEC12">CALLOUTS</a> +<li><a name="TOC13" href="#SEC13">NON-PRINTING CHARACTERS</a> +<li><a name="TOC14" href="#SEC14">SAVING AND RELOADING COMPILED PATTERNS</a> +<li><a name="TOC15" href="#SEC15">SEE ALSO</a> +<li><a name="TOC16" href="#SEC16">AUTHOR</a> +<li><a name="TOC17" href="#SEC17">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>pcretest [options] [input file [output file]]</b> +<br> +<br> +<b>pcretest</b> was written as a test program for the PCRE regular expression +library itself, but it can also be used for experimenting with regular +expressions. This document describes the features of the test program; for +details of the regular expressions themselves, see the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. For details of the PCRE library function calls and their +options, see the +<a href="pcreapi.html"><b>pcreapi</b></a> +, +<a href="pcre16.html"><b>pcre16</b></a> +and +<a href="pcre32.html"><b>pcre32</b></a> +documentation. +</P> +<P> +The input for <b>pcretest</b> is a sequence of regular expression patterns and +strings to be matched, as described below. The output shows the result of each +match. Options on the command line and the patterns control PCRE options and +exactly what is output. +</P> +<P> +As PCRE has evolved, it has acquired many different features, and as a result, +<b>pcretest</b> now has rather a lot of obscure options for testing every +possible feature. Some of these options are specifically designed for use in +conjunction with the test script and data files that are distributed as part of +PCRE, and are unlikely to be of use otherwise. They are all documented here, +but without much justification. +</P> +<br><a name="SEC2" href="#TOC1">INPUT DATA FORMAT</a><br> +<P> +Input to <b>pcretest</b> is processed line by line, either by calling the C +library's <b>fgets()</b> function, or via the <b>libreadline</b> library (see +below). In Unix-like environments, <b>fgets()</b> treats any bytes other than +newline as data characters. However, in some Windows environments character 26 +(hex 1A) causes an immediate end of file, and no further data is read. For +maximum portability, therefore, it is safest to use only ASCII characters in +<b>pcretest</b> input files. +</P> +<br><a name="SEC3" href="#TOC1">PCRE's 8-BIT, 16-BIT AND 32-BIT LIBRARIES</a><br> +<P> +From release 8.30, two separate PCRE libraries can be built. The original one +supports 8-bit character strings, whereas the newer 16-bit library supports +character strings encoded in 16-bit units. From release 8.32, a third library +can be built, supporting character strings encoded in 32-bit units. The +<b>pcretest</b> program can be used to test all three libraries. However, it is +itself still an 8-bit program, reading 8-bit input and writing 8-bit output. +When testing the 16-bit or 32-bit library, the patterns and data strings are +converted to 16- or 32-bit format before being passed to the PCRE library +functions. Results are converted to 8-bit for output. +</P> +<P> +References to functions and structures of the form <b>pcre[16|32]_xx</b> below +mean "<b>pcre_xx</b> when using the 8-bit library, <b>pcre16_xx</b> when using +the 16-bit library, or <b>pcre32_xx</b> when using the 32-bit library". +</P> +<br><a name="SEC4" href="#TOC1">COMMAND LINE OPTIONS</a><br> +<P> +<b>-8</b> +If both the 8-bit library has been built, this option causes the 8-bit library +to be used (which is the default); if the 8-bit library has not been built, +this option causes an error. +</P> +<P> +<b>-16</b> +If both the 8-bit or the 32-bit, and the 16-bit libraries have been built, this +option causes the 16-bit library to be used. If only the 16-bit library has been +built, this is the default (so has no effect). If only the 8-bit or the 32-bit +library has been built, this option causes an error. +</P> +<P> +<b>-32</b> +If both the 8-bit or the 16-bit, and the 32-bit libraries have been built, this +option causes the 32-bit library to be used. If only the 32-bit library has been +built, this is the default (so has no effect). If only the 8-bit or the 16-bit +library has been built, this option causes an error. +</P> +<P> +<b>-b</b> +Behave as if each pattern has the <b>/B</b> (show byte code) modifier; the +internal form is output after compilation. +</P> +<P> +<b>-C</b> +Output the version number of the PCRE library, and all available information +about the optional features that are included, and then exit with zero exit +code. All other options are ignored. +</P> +<P> +<b>-C</b> <i>option</i> +Output information about a specific build-time option, then exit. This +functionality is intended for use in scripts such as <b>RunTest</b>. The +following options output the value and set the exit code as indicated: +<pre> + ebcdic-nl the code for LF (= NL) in an EBCDIC environment: + 0x15 or 0x25 + 0 if used in an ASCII environment + exit code is always 0 + linksize the configured internal link size (2, 3, or 4) + exit code is set to the link size + newline the default newline setting: + CR, LF, CRLF, ANYCRLF, or ANY + exit code is always 0 + bsr the default setting for what \R matches: + ANYCRLF or ANY + exit code is always 0 +</pre> +The following options output 1 for true or 0 for false, and set the exit code +to the same value: +<pre> + ebcdic compiled for an EBCDIC environment + jit just-in-time support is available + pcre16 the 16-bit library was built + pcre32 the 32-bit library was built + pcre8 the 8-bit library was built + ucp Unicode property support is available + utf UTF-8 and/or UTF-16 and/or UTF-32 support + is available +</pre> +If an unknown option is given, an error message is output; the exit code is 0. +</P> +<P> +<b>-d</b> +Behave as if each pattern has the <b>/D</b> (debug) modifier; the internal +form and information about the compiled pattern is output after compilation; +<b>-d</b> is equivalent to <b>-b -i</b>. +</P> +<P> +<b>-dfa</b> +Behave as if each data line contains the \D escape sequence; this causes the +alternative matching function, <b>pcre[16|32]_dfa_exec()</b>, to be used instead +of the standard <b>pcre[16|32]_exec()</b> function (more detail is given below). +</P> +<P> +<b>-help</b> +Output a brief summary these options and then exit. +</P> +<P> +<b>-i</b> +Behave as if each pattern has the <b>/I</b> modifier; information about the +compiled pattern is given after compilation. +</P> +<P> +<b>-M</b> +Behave as if each data line contains the \M escape sequence; this causes +PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by +calling <b>pcre[16|32]_exec()</b> repeatedly with different limits. +</P> +<P> +<b>-m</b> +Output the size of each compiled pattern after it has been compiled. This is +equivalent to adding <b>/M</b> to each regular expression. The size is given in +bytes for both libraries. +</P> +<P> +<b>-O</b> +Behave as if each pattern has the <b>/O</b> modifier, that is disable +auto-possessification for all patterns. +</P> +<P> +<b>-o</b> <i>osize</i> +Set the number of elements in the output vector that is used when calling +<b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> to be <i>osize</i>. The +default value is 45, which is enough for 14 capturing subexpressions for +<b>pcre[16|32]_exec()</b> or 22 different matches for +<b>pcre[16|32]_dfa_exec()</b>. +The vector size can be changed for individual matching calls by including \O +in the data line (see below). +</P> +<P> +<b>-p</b> +Behave as if each pattern has the <b>/P</b> modifier; the POSIX wrapper API is +used to call PCRE. None of the other options has any effect when <b>-p</b> is +set. This option can be used only with the 8-bit library. +</P> +<P> +<b>-q</b> +Do not output the version number of <b>pcretest</b> at the start of execution. +</P> +<P> +<b>-S</b> <i>size</i> +On Unix-like systems, set the size of the run-time stack to <i>size</i> +megabytes. +</P> +<P> +<b>-s</b> or <b>-s+</b> +Behave as if each pattern has the <b>/S</b> modifier; in other words, force each +pattern to be studied. If <b>-s+</b> is used, all the JIT compile options are +passed to <b>pcre[16|32]_study()</b>, causing just-in-time optimization to be set +up if it is available, for both full and partial matching. Specific JIT compile +options can be selected by following <b>-s+</b> with a digit in the range 1 to +7, which selects the JIT compile modes as follows: +<pre> + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) +</pre> +If <b>-s++</b> is used instead of <b>-s+</b> (with or without a following digit), +the text "(JIT)" is added to the first output line after a match or no match +when JIT-compiled code was actually used. +<br> +<br> +Note that there are pattern options that can override <b>-s</b>, either +specifying no studying at all, or suppressing JIT compilation. +<br> +<br> +If the <b>/I</b> or <b>/D</b> option is present on a pattern (requesting output +about the compiled pattern), information about the result of studying is not +included when studying is caused only by <b>-s</b> and neither <b>-i</b> nor +<b>-d</b> is present on the command line. This behaviour means that the output +from tests that are run with and without <b>-s</b> should be identical, except +when options that output information about the actual running of a match are +set. +<br> +<br> +The <b>-M</b>, <b>-t</b>, and <b>-tm</b> options, which give information about +resources used, are likely to produce different output with and without +<b>-s</b>. Output may also differ if the <b>/C</b> option is present on an +individual pattern. This uses callouts to trace the the matching process, and +this may be different between studied and non-studied patterns. If the pattern +contains (*MARK) items there may also be differences, for the same reason. The +<b>-s</b> command line option can be overridden for specific patterns that +should never be studied (see the <b>/S</b> pattern modifier below). +</P> +<P> +<b>-t</b> +Run each compile, study, and match many times with a timer, and output the +resulting times per compile, study, or match (in milliseconds). Do not set +<b>-m</b> with <b>-t</b>, because you will then get the size output a zillion +times, and the timing will be distorted. You can control the number of +iterations that are used for timing by following <b>-t</b> with a number (as a +separate item on the command line). For example, "-t 1000" iterates 1000 times. +The default is to iterate 500000 times. +</P> +<P> +<b>-tm</b> +This is like <b>-t</b> except that it times only the matching phase, not the +compile or study phases. +</P> +<P> +<b>-T</b> <b>-TM</b> +These behave like <b>-t</b> and <b>-tm</b>, but in addition, at the end of a run, +the total times for all compiles, studies, and matches are output. +</P> +<br><a name="SEC5" href="#TOC1">DESCRIPTION</a><br> +<P> +If <b>pcretest</b> is given two filename arguments, it reads from the first and +writes to the second. If it is given only one filename argument, it reads from +that file and writes to stdout. Otherwise, it reads from stdin and writes to +stdout, and prompts for each line of input, using "re>" to prompt for regular +expressions, and "data>" to prompt for data lines. +</P> +<P> +When <b>pcretest</b> is built, a configuration option can specify that it should +be linked with the <b>libreadline</b> library. When this is done, if the input +is from a terminal, it is read using the <b>readline()</b> function. This +provides line-editing and history facilities. The output from the <b>-help</b> +option states whether or not <b>readline()</b> will be used. +</P> +<P> +The program handles any number of sets of input on a single input file. Each +set starts with a regular expression, and continues with any number of data +lines to be matched against that pattern. +</P> +<P> +Each data line is matched separately and independently. If you want to do +multi-line matches, you have to use the \n escape sequence (or \r or \r\n, +etc., depending on the newline setting) in a single line of input to encode the +newline sequences. There is no limit on the length of data lines; the input +buffer is automatically extended if it is too small. +</P> +<P> +An empty line signals the end of the data lines, at which point a new regular +expression is read. The regular expressions are given enclosed in any +non-alphanumeric delimiters other than backslash, for example: +<pre> + /(a|bc)x+yz/ +</pre> +White space before the initial delimiter is ignored. A regular expression may +be continued over several input lines, in which case the newline characters are +included within it. It is possible to include the delimiter within the pattern +by escaping it, for example +<pre> + /abc\/def/ +</pre> +If you do so, the escape and the delimiter form part of the pattern, but since +delimiters are always non-alphanumeric, this does not affect its interpretation. +If the terminating delimiter is immediately followed by a backslash, for +example, +<pre> + /abc/\ +</pre> +then a backslash is added to the end of the pattern. This is done to provide a +way of testing the error condition that arises if a pattern finishes with a +backslash, because +<pre> + /abc\/ +</pre> +is interpreted as the first line of a pattern that starts with "abc/", causing +pcretest to read the next line as a continuation of the regular expression. +</P> +<br><a name="SEC6" href="#TOC1">PATTERN MODIFIERS</a><br> +<P> +A pattern may be followed by any number of modifiers, which are mostly single +characters, though some of these can be qualified by further characters. +Following Perl usage, these are referred to below as, for example, "the +<b>/i</b> modifier", even though the delimiter of the pattern need not always be +a slash, and no slash is used when writing modifiers. White space may appear +between the final pattern delimiter and the first modifier, and between the +modifiers themselves. For reference, here is a complete list of modifiers. They +fall into several groups that are described in detail in the following +sections. +<pre> + <b>/8</b> set UTF mode + <b>/9</b> set PCRE_NEVER_UTF (locks out UTF mode) + <b>/?</b> disable UTF validity check + <b>/+</b> show remainder of subject after match + <b>/=</b> show all captures (not just those that are set) + + <b>/A</b> set PCRE_ANCHORED + <b>/B</b> show compiled code + <b>/C</b> set PCRE_AUTO_CALLOUT + <b>/D</b> same as <b>/B</b> plus <b>/I</b> + <b>/E</b> set PCRE_DOLLAR_ENDONLY + <b>/F</b> flip byte order in compiled pattern + <b>/f</b> set PCRE_FIRSTLINE + <b>/G</b> find all matches (shorten string) + <b>/g</b> find all matches (use startoffset) + <b>/I</b> show information about pattern + <b>/i</b> set PCRE_CASELESS + <b>/J</b> set PCRE_DUPNAMES + <b>/K</b> show backtracking control names + <b>/L</b> set locale + <b>/M</b> show compiled memory size + <b>/m</b> set PCRE_MULTILINE + <b>/N</b> set PCRE_NO_AUTO_CAPTURE + <b>/O</b> set PCRE_NO_AUTO_POSSESS + <b>/P</b> use the POSIX wrapper + <b>/Q</b> test external stack check function + <b>/S</b> study the pattern after compilation + <b>/s</b> set PCRE_DOTALL + <b>/T</b> select character tables + <b>/U</b> set PCRE_UNGREEDY + <b>/W</b> set PCRE_UCP + <b>/X</b> set PCRE_EXTRA + <b>/x</b> set PCRE_EXTENDED + <b>/Y</b> set PCRE_NO_START_OPTIMIZE + <b>/Z</b> don't show lengths in <b>/B</b> output + + <b>/<any></b> set PCRE_NEWLINE_ANY + <b>/<anycrlf></b> set PCRE_NEWLINE_ANYCRLF + <b>/<cr></b> set PCRE_NEWLINE_CR + <b>/<crlf></b> set PCRE_NEWLINE_CRLF + <b>/<lf></b> set PCRE_NEWLINE_LF + <b>/<bsr_anycrlf></b> set PCRE_BSR_ANYCRLF + <b>/<bsr_unicode></b> set PCRE_BSR_UNICODE + <b>/<JS></b> set PCRE_JAVASCRIPT_COMPAT + +</PRE> +</P> +<br><b> +Perl-compatible modifiers +</b><br> +<P> +The <b>/i</b>, <b>/m</b>, <b>/s</b>, and <b>/x</b> modifiers set the PCRE_CASELESS, +PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when +<b>pcre[16|32]_compile()</b> is called. These four modifier letters have the same +effect as they do in Perl. For example: +<pre> + /caseless/i + +</PRE> +</P> +<br><b> +Modifiers for other PCRE options +</b><br> +<P> +The following table shows additional modifiers for setting PCRE compile-time +options that do not correspond to anything in Perl: +<pre> + <b>/8</b> PCRE_UTF8 ) when using the 8-bit + <b>/?</b> PCRE_NO_UTF8_CHECK ) library + + <b>/8</b> PCRE_UTF16 ) when using the 16-bit + <b>/?</b> PCRE_NO_UTF16_CHECK ) library + + <b>/8</b> PCRE_UTF32 ) when using the 32-bit + <b>/?</b> PCRE_NO_UTF32_CHECK ) library + + <b>/9</b> PCRE_NEVER_UTF + <b>/A</b> PCRE_ANCHORED + <b>/C</b> PCRE_AUTO_CALLOUT + <b>/E</b> PCRE_DOLLAR_ENDONLY + <b>/f</b> PCRE_FIRSTLINE + <b>/J</b> PCRE_DUPNAMES + <b>/N</b> PCRE_NO_AUTO_CAPTURE + <b>/O</b> PCRE_NO_AUTO_POSSESS + <b>/U</b> PCRE_UNGREEDY + <b>/W</b> PCRE_UCP + <b>/X</b> PCRE_EXTRA + <b>/Y</b> PCRE_NO_START_OPTIMIZE + <b>/<any></b> PCRE_NEWLINE_ANY + <b>/<anycrlf></b> PCRE_NEWLINE_ANYCRLF + <b>/<cr></b> PCRE_NEWLINE_CR + <b>/<crlf></b> PCRE_NEWLINE_CRLF + <b>/<lf></b> PCRE_NEWLINE_LF + <b>/<bsr_anycrlf></b> PCRE_BSR_ANYCRLF + <b>/<bsr_unicode></b> PCRE_BSR_UNICODE + <b>/<JS></b> PCRE_JAVASCRIPT_COMPAT +</pre> +The modifiers that are enclosed in angle brackets are literal strings as shown, +including the angle brackets, but the letters within can be in either case. +This example sets multiline matching with CRLF as the line ending sequence: +<pre> + /^abc/m<CRLF> +</pre> +As well as turning on the PCRE_UTF8/16/32 option, the <b>/8</b> modifier causes +all non-printing characters in output strings to be printed using the +\x{hh...} notation. Otherwise, those less than 0x100 are output in hex without +the curly brackets. +</P> +<P> +Full details of the PCRE options are given in the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<br><b> +Finding all matches in a string +</b><br> +<P> +Searching for all possible matches within each subject string can be requested +by the <b>/g</b> or <b>/G</b> modifier. After finding a match, PCRE is called +again to search the remainder of the subject string. The difference between +<b>/g</b> and <b>/G</b> is that the former uses the <i>startoffset</i> argument to +<b>pcre[16|32]_exec()</b> to start searching at a new point within the entire +string (which is in effect what Perl does), whereas the latter passes over a +shortened substring. This makes a difference to the matching process if the +pattern begins with a lookbehind assertion (including \b or \B). +</P> +<P> +If any call to <b>pcre[16|32]_exec()</b> in a <b>/g</b> or <b>/G</b> sequence matches +an empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and +PCRE_ANCHORED flags set in order to search for another, non-empty, match at the +same point. If this second match fails, the start offset is advanced, and the +normal match is retried. This imitates the way Perl handles such cases when +using the <b>/g</b> modifier or the <b>split()</b> function. Normally, the start +offset is advanced by one character, but if the newline convention recognizes +CRLF as a newline, and the current character is CR followed by LF, an advance +of two is used. +</P> +<br><b> +Other modifiers +</b><br> +<P> +There are yet more modifiers for controlling the way <b>pcretest</b> +operates. +</P> +<P> +The <b>/+</b> modifier requests that as well as outputting the substring that +matched the entire pattern, <b>pcretest</b> should in addition output the +remainder of the subject string. This is useful for tests where the subject +contains multiple copies of the same substring. If the <b>+</b> modifier appears +twice, the same action is taken for captured substrings. In each case the +remainder is output on the following line with a plus character following the +capture number. Note that this modifier must not immediately follow the /S +modifier because /S+ and /S++ have other meanings. +</P> +<P> +The <b>/=</b> modifier requests that the values of all potential captured +parentheses be output after a match. By default, only those up to the highest +one actually used in the match are output (corresponding to the return code +from <b>pcre[16|32]_exec()</b>). Values in the offsets vector corresponding to +higher numbers should be set to -1, and these are output as "<unset>". This +modifier gives a way of checking that this is happening. +</P> +<P> +The <b>/B</b> modifier is a debugging feature. It requests that <b>pcretest</b> +output a representation of the compiled code after compilation. Normally this +information contains length and offset values; however, if <b>/Z</b> is also +present, this data is replaced by spaces. This is a special feature for use in +the automatic test scripts; it ensures that the same output is generated for +different internal link sizes. +</P> +<P> +The <b>/D</b> modifier is a PCRE debugging feature, and is equivalent to +<b>/BI</b>, that is, both the <b>/B</b> and the <b>/I</b> modifiers. +</P> +<P> +The <b>/F</b> modifier causes <b>pcretest</b> to flip the byte order of the +2-byte and 4-byte fields in the compiled pattern. This facility is for testing +the feature in PCRE that allows it to execute patterns that were compiled on a +host with a different endianness. This feature is not available when the POSIX +interface to PCRE is being used, that is, when the <b>/P</b> pattern modifier is +specified. See also the section about saving and reloading compiled patterns +below. +</P> +<P> +The <b>/I</b> modifier requests that <b>pcretest</b> output information about the +compiled pattern (whether it is anchored, has a fixed first character, and +so on). It does this by calling <b>pcre[16|32]_fullinfo()</b> after compiling a +pattern. If the pattern is studied, the results of that are also output. In +this output, the word "char" means a non-UTF character, that is, the value of a +single data item (8-bit, 16-bit, or 32-bit, depending on the library that is +being tested). +</P> +<P> +The <b>/K</b> modifier requests <b>pcretest</b> to show names from backtracking +control verbs that are returned from calls to <b>pcre[16|32]_exec()</b>. It causes +<b>pcretest</b> to create a <b>pcre[16|32]_extra</b> block if one has not already +been created by a call to <b>pcre[16|32]_study()</b>, and to set the +PCRE_EXTRA_MARK flag and the <b>mark</b> field within it, every time that +<b>pcre[16|32]_exec()</b> is called. If the variable that the <b>mark</b> field +points to is non-NULL for a match, non-match, or partial match, <b>pcretest</b> +prints the string to which it points. For a match, this is shown on a line by +itself, tagged with "MK:". For a non-match it is added to the message. +</P> +<P> +The <b>/L</b> modifier must be followed directly by the name of a locale, for +example, +<pre> + /pattern/Lfr_FR +</pre> +For this reason, it must be the last modifier. The given locale is set, +<b>pcre[16|32]_maketables()</b> is called to build a set of character tables for +the locale, and this is then passed to <b>pcre[16|32]_compile()</b> when compiling +the regular expression. Without an <b>/L</b> (or <b>/T</b>) modifier, NULL is +passed as the tables pointer; that is, <b>/L</b> applies only to the expression +on which it appears. +</P> +<P> +The <b>/M</b> modifier causes the size in bytes of the memory block used to hold +the compiled pattern to be output. This does not include the size of the +<b>pcre[16|32]</b> block; it is just the actual compiled data. If the pattern is +successfully studied with the PCRE_STUDY_JIT_COMPILE option, the size of the +JIT compiled code is also output. +</P> +<P> +The <b>/Q</b> modifier is used to test the use of <b>pcre_stack_guard</b>. It +must be followed by '0' or '1', specifying the return code to be given from an +external function that is passed to PCRE and used for stack checking during +compilation (see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation for details). +</P> +<P> +The <b>/S</b> modifier causes <b>pcre[16|32]_study()</b> to be called after the +expression has been compiled, and the results used when the expression is +matched. There are a number of qualifying characters that may follow <b>/S</b>. +They may appear in any order. +</P> +<P> +If <b>/S</b> is followed by an exclamation mark, <b>pcre[16|32]_study()</b> is +called with the PCRE_STUDY_EXTRA_NEEDED option, causing it always to return a +<b>pcre_extra</b> block, even when studying discovers no useful information. +</P> +<P> +If <b>/S</b> is followed by a second S character, it suppresses studying, even +if it was requested externally by the <b>-s</b> command line option. This makes +it possible to specify that certain patterns are always studied, and others are +never studied, independently of <b>-s</b>. This feature is used in the test +files in a few cases where the output is different when the pattern is studied. +</P> +<P> +If the <b>/S</b> modifier is followed by a + character, the call to +<b>pcre[16|32]_study()</b> is made with all the JIT study options, requesting +just-in-time optimization support if it is available, for both normal and +partial matching. If you want to restrict the JIT compiling modes, you can +follow <b>/S+</b> with a digit in the range 1 to 7: +<pre> + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) +</pre> +If <b>/S++</b> is used instead of <b>/S+</b> (with or without a following digit), +the text "(JIT)" is added to the first output line after a match or no match +when JIT-compiled code was actually used. +</P> +<P> +Note that there is also an independent <b>/+</b> modifier; it must not be given +immediately after <b>/S</b> or <b>/S+</b> because this will be misinterpreted. +</P> +<P> +If JIT studying is successful, the compiled JIT code will automatically be used +when <b>pcre[16|32]_exec()</b> is run, except when incompatible run-time options +are specified. For more details, see the +<a href="pcrejit.html"><b>pcrejit</b></a> +documentation. See also the <b>\J</b> escape sequence below for a way of +setting the size of the JIT stack. +</P> +<P> +Finally, if <b>/S</b> is followed by a minus character, JIT compilation is +suppressed, even if it was requested externally by the <b>-s</b> command line +option. This makes it possible to specify that JIT is never to be used for +certain patterns. +</P> +<P> +The <b>/T</b> modifier must be followed by a single digit. It causes a specific +set of built-in character tables to be passed to <b>pcre[16|32]_compile()</b>. It +is used in the standard PCRE tests to check behaviour with different character +tables. The digit specifies the tables as follows: +<pre> + 0 the default ASCII tables, as distributed in + pcre_chartables.c.dist + 1 a set of tables defining ISO 8859 characters +</pre> +In table 1, some characters whose codes are greater than 128 are identified as +letters, digits, spaces, etc. +</P> +<br><b> +Using the POSIX wrapper API +</b><br> +<P> +The <b>/P</b> modifier causes <b>pcretest</b> to call PCRE via the POSIX wrapper +API rather than its native API. This supports only the 8-bit library. When +<b>/P</b> is set, the following modifiers set options for the <b>regcomp()</b> +function: +<pre> + /i REG_ICASE + /m REG_NEWLINE + /N REG_NOSUB + /s REG_DOTALL ) + /U REG_UNGREEDY ) These options are not part of + /W REG_UCP ) the POSIX standard + /8 REG_UTF8 ) +</pre> +The <b>/+</b> modifier works as described above. All other modifiers are +ignored. +</P> +<br><b> +Locking out certain modifiers +</b><br> +<P> +PCRE can be compiled with or without support for certain features such as +UTF-8/16/32 or Unicode properties. Accordingly, the standard tests are split up +into a number of different files that are selected for running depending on +which features are available. When updating the tests, it is all too easy to +put a new test into the wrong file by mistake; for example, to put a test that +requires UTF support into a file that is used when it is not available. To help +detect such mistakes as early as possible, there is a facility for locking out +specific modifiers. If an input line for <b>pcretest</b> starts with the string +"< forbid " the following sequence of characters is taken as a list of +forbidden modifiers. For example, in the test files that must not use UTF or +Unicode property support, this line appears: +<pre> + < forbid 8W +</pre> +This locks out the /8 and /W modifiers. An immediate error is given if they are +subsequently encountered. If the character string contains < but not >, all the +multi-character modifiers that begin with < are locked out. Otherwise, such +modifiers must be explicitly listed, for example: +<pre> + < forbid <JS><cr> +</pre> +There must be a single space between < and "forbid" for this feature to be +recognised. If there is not, the line is interpreted either as a request to +re-load a pre-compiled pattern (see "SAVING AND RELOADING COMPILED PATTERNS" +below) or, if there is a another < character, as a pattern that uses < as its +delimiter. +</P> +<br><a name="SEC7" href="#TOC1">DATA LINES</a><br> +<P> +Before each data line is passed to <b>pcre[16|32]_exec()</b>, leading and trailing +white space is removed, and it is then scanned for \ escapes. Some of these +are pretty esoteric features, intended for checking out some of the more +complicated features of PCRE. If you are just testing "ordinary" regular +expressions, you probably don't need any of these. The following escapes are +recognized: +<pre> + \a alarm (BEL, \x07) + \b backspace (\x08) + \e escape (\x27) + \f form feed (\x0c) + \n newline (\x0a) + \qdd set the PCRE_MATCH_LIMIT limit to dd (any number of digits) + \r carriage return (\x0d) + \t tab (\x09) + \v vertical tab (\x0b) + \nnn octal character (up to 3 octal digits); always + a byte unless > 255 in UTF-8 or 16-bit or 32-bit mode + \o{dd...} octal character (any number of octal digits} + \xhh hexadecimal byte (up to 2 hex digits) + \x{hh...} hexadecimal character (any number of hex digits) + \A pass the PCRE_ANCHORED option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \B pass the PCRE_NOTBOL option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \Cdd call pcre[16|32]_copy_substring() for substring dd after a successful match (number less than 32) + \Cname call pcre[16|32]_copy_named_substring() for substring "name" after a successful match (name termin- + ated by next non alphanumeric character) + \C+ show the current captured substrings at callout time + \C- do not supply a callout function + \C!n return 1 instead of 0 when callout number n is reached + \C!n!m return 1 instead of 0 when callout number n is reached for the nth time + \C*n pass the number n (may be negative) as callout data; this is used as the callout return value + \D use the <b>pcre[16|32]_dfa_exec()</b> match function + \F only shortest match for <b>pcre[16|32]_dfa_exec()</b> + \Gdd call pcre[16|32]_get_substring() for substring dd after a successful match (number less than 32) + \Gname call pcre[16|32]_get_named_substring() for substring "name" after a successful match (name termin- + ated by next non-alphanumeric character) + \Jdd set up a JIT stack of dd kilobytes maximum (any number of digits) + \L call pcre[16|32]_get_substringlist() after a successful match + \M discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings + \N pass the PCRE_NOTEMPTY option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b>; if used twice, pass the + PCRE_NOTEMPTY_ATSTART option + \Odd set the size of the output vector passed to <b>pcre[16|32]_exec()</b> to dd (any number of digits) + \P pass the PCRE_PARTIAL_SOFT option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b>; if used twice, pass the + PCRE_PARTIAL_HARD option + \Qdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd (any number of digits) + \R pass the PCRE_DFA_RESTART option to <b>pcre[16|32]_dfa_exec()</b> + \S output details of memory get/free calls during matching + \Y pass the PCRE_NO_START_OPTIMIZE option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \Z pass the PCRE_NOTEOL option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \? pass the PCRE_NO_UTF[8|16|32]_CHECK option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \>dd start the match at offset dd (optional "-"; then any number of digits); this sets the <i>startoffset</i> + argument for <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \<cr> pass the PCRE_NEWLINE_CR option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \<lf> pass the PCRE_NEWLINE_LF option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \<crlf> pass the PCRE_NEWLINE_CRLF option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> + \<any> pass the PCRE_NEWLINE_ANY option to <b>pcre[16|32]_exec()</b> or <b>pcre[16|32]_dfa_exec()</b> +</pre> +The use of \x{hh...} is not dependent on the use of the <b>/8</b> modifier on +the pattern. It is recognized always. There may be any number of hexadecimal +digits inside the braces; invalid values provoke error messages. +</P> +<P> +Note that \xhh specifies one byte rather than one character in UTF-8 mode; +this makes it possible to construct invalid UTF-8 sequences for testing +purposes. On the other hand, \x{hh} is interpreted as a UTF-8 character in +UTF-8 mode, generating more than one byte if the value is greater than 127. +When testing the 8-bit library not in UTF-8 mode, \x{hh} generates one byte +for values less than 256, and causes an error for greater values. +</P> +<P> +In UTF-16 mode, all 4-digit \x{hhhh} values are accepted. This makes it +possible to construct invalid UTF-16 sequences for testing purposes. +</P> +<P> +In UTF-32 mode, all 4- to 8-digit \x{...} values are accepted. This makes it +possible to construct invalid UTF-32 sequences for testing purposes. +</P> +<P> +The escapes that specify line ending sequences are literal strings, exactly as +shown. No more than one newline setting should be present in any data line. +</P> +<P> +A backslash followed by anything else just escapes the anything else. If +the very last character is a backslash, it is ignored. This gives a way of +passing an empty line as data, since a real empty line terminates the data +input. +</P> +<P> +The <b>\J</b> escape provides a way of setting the maximum stack size that is +used by the just-in-time optimization code. It is ignored if JIT optimization +is not being used. Providing a stack that is larger than the default 32K is +necessary only for very complicated patterns. +</P> +<P> +If \M is present, <b>pcretest</b> calls <b>pcre[16|32]_exec()</b> several times, +with different values in the <i>match_limit</i> and <i>match_limit_recursion</i> +fields of the <b>pcre[16|32]_extra</b> data structure, until it finds the minimum +numbers for each parameter that allow <b>pcre[16|32]_exec()</b> to complete without +error. Because this is testing a specific feature of the normal interpretive +<b>pcre[16|32]_exec()</b> execution, the use of any JIT optimization that might +have been set up by the <b>/S+</b> qualifier of <b>-s+</b> option is disabled. +</P> +<P> +The <i>match_limit</i> number is a measure of the amount of backtracking +that takes place, and checking it out can be instructive. For most simple +matches, the number is quite small, but for patterns with very large numbers of +matching possibilities, it can become large very quickly with increasing length +of subject string. The <i>match_limit_recursion</i> number is a measure of how +much stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is +needed to complete the match attempt. +</P> +<P> +When \O is used, the value specified may be higher or lower than the size set +by the <b>-O</b> command line option (or defaulted to 45); \O applies only to +the call of <b>pcre[16|32]_exec()</b> for the line in which it appears. +</P> +<P> +If the <b>/P</b> modifier was present on the pattern, causing the POSIX wrapper +API to be used, the only option-setting sequences that have any effect are \B, +\N, and \Z, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively, +to be passed to <b>regexec()</b>. +</P> +<br><a name="SEC8" href="#TOC1">THE ALTERNATIVE MATCHING FUNCTION</a><br> +<P> +By default, <b>pcretest</b> uses the standard PCRE matching function, +<b>pcre[16|32]_exec()</b> to match each data line. PCRE also supports an +alternative matching function, <b>pcre[16|32]_dfa_test()</b>, which operates in a +different way, and has some restrictions. The differences between the two +functions are described in the +<a href="pcrematching.html"><b>pcrematching</b></a> +documentation. +</P> +<P> +If a data line contains the \D escape sequence, or if the command line +contains the <b>-dfa</b> option, the alternative matching function is used. +This function finds all possible matches at a given point. If, however, the \F +escape sequence is present in the data line, it stops after the first match is +found. This is always the shortest possible match. +</P> +<br><a name="SEC9" href="#TOC1">DEFAULT OUTPUT FROM PCRETEST</a><br> +<P> +This section describes the output when the normal matching function, +<b>pcre[16|32]_exec()</b>, is being used. +</P> +<P> +When a match succeeds, <b>pcretest</b> outputs the list of captured substrings +that <b>pcre[16|32]_exec()</b> returns, starting with number 0 for the string that +matched the whole pattern. Otherwise, it outputs "No match" when the return is +PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching +substring when <b>pcre[16|32]_exec()</b> returns PCRE_ERROR_PARTIAL. (Note that +this is the entire substring that was inspected during the partial match; it +may include characters before the actual match start if a lookbehind assertion, +\K, \b, or \B was involved.) For any other return, <b>pcretest</b> outputs +the PCRE negative error number and a short descriptive phrase. If the error is +a failed UTF string check, the offset of the start of the failing character and +the reason code are also output, provided that the size of the output vector is +at least two. Here is an example of an interactive <b>pcretest</b> run. +<pre> + $ pcretest + PCRE version 8.13 2011-04-30 + + re> /^abc(\d+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match +</pre> +Unset capturing substrings that are not followed by one that is set are not +returned by <b>pcre[16|32]_exec()</b>, and are not shown by <b>pcretest</b>. In the +following example, there are two capturing substrings, but when the first data +line is matched, the second, unset substring is not shown. An "internal" unset +substring is shown as "<unset>", as for the second data line. +<pre> + re> /(a)|(b)/ + data> a + 0: a + 1: a + data> b + 0: b + 1: <unset> + 2: b +</pre> +If the strings contain any non-printing characters, they are output as \xhh +escapes if the value is less than 256 and UTF mode is not set. Otherwise they +are output as \x{hh...} escapes. See below for the definition of non-printing +characters. If the pattern has the <b>/+</b> modifier, the output for substring +0 is followed by the the rest of the subject string, identified by "0+" like +this: +<pre> + re> /cat/+ + data> cataract + 0: cat + 0+ aract +</pre> +If the pattern has the <b>/g</b> or <b>/G</b> modifier, the results of successive +matching attempts are output in sequence, like this: +<pre> + re> /\Bi(\w\w)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp +</pre> +"No match" is output only if the first match attempt fails. Here is an example +of a failure message (the offset 4 that is specified by \>4 is past the end of +the subject string): +<pre> + re> /xyz/ + data> xyz\>4 + Error -24 (bad offset value) +</PRE> +</P> +<P> +If any of the sequences <b>\C</b>, <b>\G</b>, or <b>\L</b> are present in a +data line that is successfully matched, the substrings extracted by the +convenience functions are output with C, G, or L after the string number +instead of a colon. This is in addition to the normal full list. The string +length (that is, the return from the extraction function) is given in +parentheses after each string for <b>\C</b> and <b>\G</b>. +</P> +<P> +Note that whereas patterns can be continued over several lines (a plain ">" +prompt is used for continuations), data lines may not. However newlines can be +included in data by means of the \n escape (or \r, \r\n, etc., depending on +the newline sequence setting). +</P> +<br><a name="SEC10" href="#TOC1">OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION</a><br> +<P> +When the alternative matching function, <b>pcre[16|32]_dfa_exec()</b>, is used (by +means of the \D escape sequence or the <b>-dfa</b> command line option), the +output consists of a list of all the matches that start at the first point in +the subject where there is at least one match. For example: +<pre> + re> /(tang|tangerine|tan)/ + data> yellow tangerine\D + 0: tangerine + 1: tang + 2: tan +</pre> +(Using the normal matching function on this data finds only "tang".) The +longest matching string is always given first (and numbered zero). After a +PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the +partially matching substring. (Note that this is the entire substring that was +inspected during the partial match; it may include characters before the actual +match start if a lookbehind assertion, \K, \b, or \B was involved.) +</P> +<P> +If <b>/g</b> is present on the pattern, the search for further matches resumes +at the end of the longest match. For example: +<pre> + re> /(tang|tangerine|tan)/g + data> yellow tangerine and tangy sultana\D + 0: tangerine + 1: tang + 2: tan + 0: tang + 1: tan + 0: tan +</pre> +Since the matching function does not support substring capture, the escape +sequences that are concerned with captured substrings are not relevant. +</P> +<br><a name="SEC11" href="#TOC1">RESTARTING AFTER A PARTIAL MATCH</a><br> +<P> +When the alternative matching function has given the PCRE_ERROR_PARTIAL return, +indicating that the subject partially matched the pattern, you can restart the +match with additional subject data by means of the \R escape sequence. For +example: +<pre> + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 23ja\P\D + Partial match: 23ja + data> n05\R\D + 0: n05 +</pre> +For further information about partial matching, see the +<a href="pcrepartial.html"><b>pcrepartial</b></a> +documentation. +</P> +<br><a name="SEC12" href="#TOC1">CALLOUTS</a><br> +<P> +If the pattern contains any callout requests, <b>pcretest</b>'s callout function +is called during matching. This works with both matching functions. By default, +the called function displays the callout number, the start and current +positions in the text at the callout time, and the next pattern item to be +tested. For example: +<pre> + --->pqrabcdef + 0 ^ ^ \d +</pre> +This output indicates that callout number 0 occurred for a match attempt +starting at the fourth character of the subject string, when the pointer was at +the seventh character of the data, and when the next pattern item was \d. Just +one circumflex is output if the start and current positions are the same. +</P> +<P> +Callouts numbered 255 are assumed to be automatic callouts, inserted as a +result of the <b>/C</b> pattern modifier. In this case, instead of showing the +callout number, the offset in the pattern, preceded by a plus, is output. For +example: +<pre> + re> /\d?[A-E]\*/C + data> E* + --->E* + +0 ^ \d? + +3 ^ [A-E] + +8 ^^ \* + +10 ^ ^ + 0: E* +</pre> +If a pattern contains (*MARK) items, an additional line is output whenever +a change of latest mark is passed to the callout function. For example: +<pre> + re> /a(*MARK:X)bc/C + data> abc + --->abc + +0 ^ a + +1 ^^ (*MARK:X) + +10 ^^ b + Latest Mark: X + +11 ^ ^ c + +12 ^ ^ + 0: abc +</pre> +The mark changes between matching "a" and "b", but stays the same for the rest +of the match, so nothing more is output. If, as a result of backtracking, the +mark reverts to being unset, the text "<unset>" is output. +</P> +<P> +The callout function in <b>pcretest</b> returns zero (carry on matching) by +default, but you can use a \C item in a data line (as described above) to +change this and other parameters of the callout. +</P> +<P> +Inserting callouts can be helpful when using <b>pcretest</b> to check +complicated regular expressions. For further information about callouts, see +the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<br><a name="SEC13" href="#TOC1">NON-PRINTING CHARACTERS</a><br> +<P> +When <b>pcretest</b> is outputting text in the compiled version of a pattern, +bytes other than 32-126 are always treated as non-printing characters are are +therefore shown as hex escapes. +</P> +<P> +When <b>pcretest</b> is outputting text that is a matched part of a subject +string, it behaves in the same way, unless a different locale has been set for +the pattern (using the <b>/L</b> modifier). In this case, the <b>isprint()</b> +function to distinguish printing and non-printing characters. +</P> +<br><a name="SEC14" href="#TOC1">SAVING AND RELOADING COMPILED PATTERNS</a><br> +<P> +The facilities described in this section are not available when the POSIX +interface to PCRE is being used, that is, when the <b>/P</b> pattern modifier is +specified. +</P> +<P> +When the POSIX interface is not in use, you can cause <b>pcretest</b> to write a +compiled pattern to a file, by following the modifiers with > and a file name. +For example: +<pre> + /pattern/im >/some/file +</pre> +See the +<a href="pcreprecompile.html"><b>pcreprecompile</b></a> +documentation for a discussion about saving and re-using compiled patterns. +Note that if the pattern was successfully studied with JIT optimization, the +JIT data cannot be saved. +</P> +<P> +The data that is written is binary. The first eight bytes are the length of the +compiled pattern data followed by the length of the optional study data, each +written as four bytes in big-endian order (most significant byte first). If +there is no study data (either the pattern was not studied, or studying did not +return any data), the second length is zero. The lengths are followed by an +exact copy of the compiled pattern. If there is additional study data, this +(excluding any JIT data) follows immediately after the compiled pattern. After +writing the file, <b>pcretest</b> expects to read a new pattern. +</P> +<P> +A saved pattern can be reloaded into <b>pcretest</b> by specifying < and a file +name instead of a pattern. There must be no space between < and the file name, +which must not contain a < character, as otherwise <b>pcretest</b> will +interpret the line as a pattern delimited by < characters. For example: +<pre> + re> </some/file + Compiled pattern loaded from /some/file + No study data +</pre> +If the pattern was previously studied with the JIT optimization, the JIT +information cannot be saved and restored, and so is lost. When the pattern has +been loaded, <b>pcretest</b> proceeds to read data lines in the usual way. +</P> +<P> +You can copy a file written by <b>pcretest</b> to a different host and reload it +there, even if the new host has opposite endianness to the one on which the +pattern was compiled. For example, you can compile on an i86 machine and run on +a SPARC machine. When a pattern is reloaded on a host with different +endianness, the confirmation message is changed to: +<pre> + Compiled pattern (byte-inverted) loaded from /some/file +</pre> +The test suite contains some saved pre-compiled patterns with different +endianness. These are reloaded using "<!" instead of just "<". This suppresses +the "(byte-inverted)" text so that the output is the same on all hosts. It also +forces debugging output once the pattern has been reloaded. +</P> +<P> +File names for saving and reloading can be absolute or relative, but note that +the shell facility of expanding a file name that starts with a tilde (~) is not +available. +</P> +<P> +The ability to save and reload files in <b>pcretest</b> is intended for testing +and experimentation. It is not intended for production use because only a +single pattern can be written to a file. Furthermore, there is no facility for +supplying custom character tables for use with a reloaded pattern. If the +original pattern was compiled with custom tables, an attempt to match a subject +string using a reloaded pattern is likely to cause <b>pcretest</b> to crash. +Finally, if you attempt to load a file that is not in the correct format, the +result is undefined. +</P> +<br><a name="SEC15" href="#TOC1">SEE ALSO</a><br> +<P> +<b>pcre</b>(3), <b>pcre16</b>(3), <b>pcre32</b>(3), <b>pcreapi</b>(3), +<b>pcrecallout</b>(3), +<b>pcrejit</b>, <b>pcrematching</b>(3), <b>pcrepartial</b>(d), +<b>pcrepattern</b>(3), <b>pcreprecompile</b>(3). +</P> +<br><a name="SEC16" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC17" href="#TOC1">REVISION</a><br> +<P> +Last updated: 09 February 2014 +<br> +Copyright © 1997-2014 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/html/pcreunicode.html b/doc/html/pcreunicode.html new file mode 100644 index 0000000..ab36bc6 --- /dev/null +++ b/doc/html/pcreunicode.html @@ -0,0 +1,262 @@ +<html> +<head> +<title>pcreunicode specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreunicode man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was generated automatically +from the original man page. If there is any nonsense in it, please consult the +man page, in case the conversion went wrong. +<br> +<br><b> +UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT +</b><br> +<P> +As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and +UTF-32 (from release 8.32), by means of two additional libraries. They can be +built as well as, or instead of, the 8-bit library. +</P> +<br><b> +UTF-8 SUPPORT +</b><br> +<P> +In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF +support, and, in addition, you must call +<a href="pcre_compile.html"><b>pcre_compile()</b></a> +with the PCRE_UTF8 option flag, or the pattern must start with the sequence +(*UTF8) or (*UTF). When either of these is the case, both the pattern and any +subject strings that are matched against it are treated as UTF-8 strings +instead of strings of individual 1-byte characters. +</P> +<br><b> +UTF-16 AND UTF-32 SUPPORT +</b><br> +<P> +In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit or +32-bit library with UTF support, and, in addition, you must call +<a href="pcre16_compile.html"><b>pcre16_compile()</b></a> +or +<a href="pcre32_compile.html"><b>pcre32_compile()</b></a> +with the PCRE_UTF16 or PCRE_UTF32 option flag, as appropriate. Alternatively, +the pattern must start with the sequence (*UTF16), (*UTF32), as appropriate, or +(*UTF), which can be used with either library. When UTF mode is set, both the +pattern and any subject strings that are matched against it are treated as +UTF-16 or UTF-32 strings instead of strings of individual 16-bit or 32-bit +characters. +</P> +<br><b> +UTF SUPPORT OVERHEAD +</b><br> +<P> +If you compile PCRE with UTF support, but do not use it at run time, the +library will be a bit bigger, but the additional run time overhead is limited +to testing the PCRE_UTF[8|16|32] flag occasionally, so should not be very big. +</P> +<br><b> +UNICODE PROPERTY SUPPORT +</b><br> +<P> +If PCRE is built with Unicode character property support (which implies UTF +support), the escape sequences \p{..}, \P{..}, and \X can be used. +The available properties that can be tested are limited to the general +category properties such as Lu for an upper case letter or Nd for a decimal +number, the Unicode script names such as Arabic or Han, and the derived +properties Any and L&. Full lists is given in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +and +<a href="pcresyntax.html"><b>pcresyntax</b></a> +documentation. Only the short names for properties are supported. For example, +\p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported. +Furthermore, in Perl, many properties may optionally be prefixed by "Is", for +compatibility with Perl 5.6. PCRE does not support this. +<a name="utf8strings"></a></P> +<br><b> +Validity of UTF-8 strings +</b><br> +<P> +When you set the PCRE_UTF8 flag, the byte strings passed as patterns and +subjects are (by default) checked for validity on entry to the relevant +functions. The entire string is checked before any other processing takes +place. From release 7.3 of PCRE, the check is according the rules of RFC 3629, +which are themselves derived from the Unicode specification. Earlier releases +of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit +values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0 +to U+10FFFF, excluding the surrogate area. (From release 8.33 the so-called +"non-character" code points are no longer excluded because Unicode corrigendum +#9 makes it clear that they should not be.) +</P> +<P> +Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16, +where they are used in pairs to encode codepoints with values greater than +0xFFFF. The code points that are encoded by UTF-16 pairs are available +independently in the UTF-8 and UTF-32 encodings. (In other words, the whole +surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8 and +UTF-32.) +</P> +<P> +If an invalid UTF-8 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first byte +of the failing character. The run-time functions <b>pcre_exec()</b> and +<b>pcre_dfa_exec()</b> also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +</P> +<P> +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance, for +example in the case of a long subject string that is being scanned repeatedly. +If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE +assumes that the pattern or subject it is given (respectively) contains only +valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 string. +</P> +<P> +Note that passing PCRE_NO_UTF8_CHECK to <b>pcre_compile()</b> just disables the +check for the pattern; it does not also apply to subject strings. If you want +to disable the check for a subject string you must pass this option to +<b>pcre_exec()</b> or <b>pcre_dfa_exec()</b>. +</P> +<P> +If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the result +is undefined and your program may crash. +<a name="utf16strings"></a></P> +<br><b> +Validity of UTF-16 strings +</b><br> +<P> +When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are +passed as patterns and subjects are (by default) checked for validity on entry +to the relevant functions. Values other than those in the surrogate range +U+D800 to U+DFFF are independent code points. Values in the surrogate range +must be used in pairs in the correct manner. +</P> +<P> +If an invalid UTF-16 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first data +unit of the failing character. The run-time functions <b>pcre16_exec()</b> and +<b>pcre16_dfa_exec()</b> also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +</P> +<P> +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance. If you set +the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that +the pattern or subject it is given (respectively) contains only valid UTF-16 +sequences. In this case, it does not diagnose an invalid UTF-16 string. +However, if an invalid string is passed, the result is undefined. +<a name="utf32strings"></a></P> +<br><b> +Validity of UTF-32 strings +</b><br> +<P> +When you set the PCRE_UTF32 flag, the strings of 32-bit data units that are +passed as patterns and subjects are (by default) checked for validity on entry +to the relevant functions. This check allows only values in the range U+0 +to U+10FFFF, excluding the surrogate area U+D800 to U+DFFF. +</P> +<P> +If an invalid UTF-32 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first data +unit of the failing character. The run-time functions <b>pcre32_exec()</b> and +<b>pcre32_dfa_exec()</b> also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +</P> +<P> +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance. If you set +the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that +the pattern or subject it is given (respectively) contains only valid UTF-32 +sequences. In this case, it does not diagnose an invalid UTF-32 string. +However, if an invalid string is passed, the result is undefined. +</P> +<br><b> +General comments about UTF modes +</b><br> +<P> +1. Codepoints less than 256 can be specified in patterns by either braced or +unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger +values have to use braced sequences. +</P> +<P> +2. Octal numbers up to \777 are recognized, and in UTF-8 mode they match +two-byte characters for values greater than \177. +</P> +<P> +3. Repeat quantifiers apply to complete UTF characters, not to individual +data units, for example: \x{100}{3}. +</P> +<P> +4. The dot metacharacter matches one UTF character instead of a single data +unit. +</P> +<P> +5. The escape sequence \C can be used to match a single byte in UTF-8 mode, or +a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in +UTF-32 mode, but its use can lead to some strange effects because it breaks up +multi-unit characters (see the description of \C in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation). The use of \C is not supported in the alternative matching +function <b>pcre[16|32]_dfa_exec()</b>, nor is it supported in UTF mode by the +JIT optimization of <b>pcre[16|32]_exec()</b>. If JIT optimization is requested +for a UTF pattern that contains \C, it will not succeed, and so the matching +will be carried out by the normal interpretive function. +</P> +<P> +6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly +test characters of any code value, but, by default, the characters that PCRE +recognizes as digits, spaces, or word characters remain the same set as in +non-UTF mode, all with values less than 256. This remains true even when PCRE +is built to include Unicode property support, because to do otherwise would +slow down PCRE in many common cases. Note in particular that this applies to +\b and \B, because they are defined in terms of \w and \W. If you really +want to test for a wider sense of, say, "digit", you can use explicit Unicode +property tests such as \p{Nd}. Alternatively, if you set the PCRE_UCP option, +the way that the character escapes work is changed so that Unicode properties +are used to determine which characters match. There are more details in the +section on +<a href="pcrepattern.html#genericchartypes">generic character types</a> +in the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. +</P> +<P> +7. Similarly, characters that match the POSIX named character classes are all +low-valued characters, unless the PCRE_UCP option is set. +</P> +<P> +8. However, the horizontal and vertical white space matching escapes (\h, \H, +\v, and \V) do match all the appropriate Unicode characters, whether or not +PCRE_UCP is set. +</P> +<P> +9. Case-insensitive matching applies only to characters whose values are less +than 128, unless PCRE is built with Unicode property support. A few Unicode +characters such as Greek sigma have more than two codepoints that are +case-equivalent. Up to and including PCRE release 8.31, only one-to-one case +mappings were supported, but later releases (with Unicode property support) do +treat as case-equivalent all versions of characters such as Greek sigma. +</P> +<br><b> +AUTHOR +</b><br> +<P> +Philip Hazel +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><b> +REVISION +</b><br> +<P> +Last updated: 27 February 2013 +<br> +Copyright © 1997-2013 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> diff --git a/doc/index.html.src b/doc/index.html.src new file mode 100644 index 0000000..887f4d7 --- /dev/null +++ b/doc/index.html.src @@ -0,0 +1,185 @@ +<html> +<!-- This is a manually maintained file that is the root of the HTML version of + the PCRE documentation. When the HTML documents are built from the man + page versions, the entire doc/html directory is emptied, this file is then + copied into doc/html/index.html, and the remaining files therein are + created by the 132html script. +--> +<head> +<title>PCRE specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>Perl-compatible Regular Expressions (PCRE)</h1> +<p> +The HTML documentation for PCRE consists of a number of pages that are listed +below in alphabetical order. If you are new to PCRE, please read the first one +first. +</p> + +<table> +<tr><td><a href="pcre.html">pcre</a></td> + <td> Introductory page</td></tr> + +<tr><td><a href="pcre-config.html">pcre-config</a></td> + <td> Information about the installation configuration</td></tr> + +<tr><td><a href="pcre16.html">pcre16</a></td> + <td> Discussion of the 16-bit PCRE library</td></tr> + +<tr><td><a href="pcre32.html">pcre32</a></td> + <td> Discussion of the 32-bit PCRE library</td></tr> + +<tr><td><a href="pcreapi.html">pcreapi</a></td> + <td> PCRE's native API</td></tr> + +<tr><td><a href="pcrebuild.html">pcrebuild</a></td> + <td> Building PCRE</td></tr> + +<tr><td><a href="pcrecallout.html">pcrecallout</a></td> + <td> The <i>callout</i> facility</td></tr> + +<tr><td><a href="pcrecompat.html">pcrecompat</a></td> + <td> Compability with Perl</td></tr> + +<tr><td><a href="pcrecpp.html">pcrecpp</a></td> + <td> The C++ wrapper for the PCRE library</td></tr> + +<tr><td><a href="pcredemo.html">pcredemo</a></td> + <td> A demonstration C program that uses the PCRE library</td></tr> + +<tr><td><a href="pcregrep.html">pcregrep</a></td> + <td> The <b>pcregrep</b> command</td></tr> + +<tr><td><a href="pcrejit.html">pcrejit</a></td> + <td> Discussion of the just-in-time optimization support</td></tr> + +<tr><td><a href="pcrelimits.html">pcrelimits</a></td> + <td> Details of size and other limits</td></tr> + +<tr><td><a href="pcrematching.html">pcrematching</a></td> + <td> Discussion of the two matching algorithms</td></tr> + +<tr><td><a href="pcrepartial.html">pcrepartial</a></td> + <td> Using PCRE for partial matching</td></tr> + +<tr><td><a href="pcrepattern.html">pcrepattern</a></td> + <td> Specification of the regular expressions supported by PCRE</td></tr> + +<tr><td><a href="pcreperform.html">pcreperform</a></td> + <td> Some comments on performance</td></tr> + +<tr><td><a href="pcreposix.html">pcreposix</a></td> + <td> The POSIX API to the PCRE 8-bit library</td></tr> + +<tr><td><a href="pcreprecompile.html">pcreprecompile</a></td> + <td> How to save and re-use compiled patterns</td></tr> + +<tr><td><a href="pcresample.html">pcresample</a></td> + <td> Discussion of the pcredemo program</td></tr> + +<tr><td><a href="pcrestack.html">pcrestack</a></td> + <td> Discussion of PCRE's stack usage</td></tr> + +<tr><td><a href="pcresyntax.html">pcresyntax</a></td> + <td> Syntax quick-reference summary</td></tr> + +<tr><td><a href="pcretest.html">pcretest</a></td> + <td> The <b>pcretest</b> command for testing PCRE</td></tr> + +<tr><td><a href="pcreunicode.html">pcreunicode</a></td> + <td> Discussion of Unicode and UTF-8/UTF-16/UTF-32 support</td></tr> +</table> + +<p> +There are also individual pages that summarize the interface for each function +in the library. There is a single page for each triple of 8-bit/16-bit/32-bit +functions. +</p> + +<table> + +<tr><td><a href="pcre_assign_jit_stack.html">pcre_assign_jit_stack</a></td> + <td> Assign stack for JIT matching</td></tr> + +<tr><td><a href="pcre_compile.html">pcre_compile</a></td> + <td> Compile a regular expression</td></tr> + +<tr><td><a href="pcre_compile2.html">pcre_compile2</a></td> + <td> Compile a regular expression (alternate interface)</td></tr> + +<tr><td><a href="pcre_config.html">pcre_config</a></td> + <td> Show build-time configuration options</td></tr> + +<tr><td><a href="pcre_copy_named_substring.html">pcre_copy_named_substring</a></td> + <td> Extract named substring into given buffer</td></tr> + +<tr><td><a href="pcre_copy_substring.html">pcre_copy_substring</a></td> + <td> Extract numbered substring into given buffer</td></tr> + +<tr><td><a href="pcre_dfa_exec.html">pcre_dfa_exec</a></td> + <td> Match a compiled pattern to a subject string + (DFA algorithm; <i>not</i> Perl compatible)</td></tr> + +<tr><td><a href="pcre_exec.html">pcre_exec</a></td> + <td> Match a compiled pattern to a subject string + (Perl compatible)</td></tr> + +<tr><td><a href="pcre_free_study.html">pcre_free_study</a></td> + <td> Free study data</td></tr> + +<tr><td><a href="pcre_free_substring.html">pcre_free_substring</a></td> + <td> Free extracted substring</td></tr> + +<tr><td><a href="pcre_free_substring_list.html">pcre_free_substring_list</a></td> + <td> Free list of extracted substrings</td></tr> + +<tr><td><a href="pcre_fullinfo.html">pcre_fullinfo</a></td> + <td> Extract information about a pattern</td></tr> + +<tr><td><a href="pcre_get_named_substring.html">pcre_get_named_substring</a></td> + <td> Extract named substring into new memory</td></tr> + +<tr><td><a href="pcre_get_stringnumber.html">pcre_get_stringnumber</a></td> + <td> Convert captured string name to number</td></tr> + +<tr><td><a href="pcre_get_stringtable_entries.html">pcre_get_stringtable_entries</a></td> + <td> Find table entries for given string name</td></tr> + +<tr><td><a href="pcre_get_substring.html">pcre_get_substring</a></td> + <td> Extract numbered substring into new memory</td></tr> + +<tr><td><a href="pcre_get_substring_list.html">pcre_get_substring_list</a></td> + <td> Extract all substrings into new memory</td></tr> + +<tr><td><a href="pcre_jit_exec.html">pcre_jit_exec</a></td> + <td> Fast path interface to JIT matching</td></tr> + +<tr><td><a href="pcre_jit_stack_alloc.html">pcre_jit_stack_alloc</a></td> + <td> Create a stack for JIT matching</td></tr> + +<tr><td><a href="pcre_jit_stack_free.html">pcre_jit_stack_free</a></td> + <td> Free a JIT matching stack</td></tr> + +<tr><td><a href="pcre_maketables.html">pcre_maketables</a></td> + <td> Build character tables in current locale</td></tr> + +<tr><td><a href="pcre_pattern_to_host_byte_order.html">pcre_pattern_to_host_byte_order</a></td> + <td> Convert compiled pattern to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_refcount.html">pcre_refcount</a></td> + <td> Maintain reference count in compiled pattern</td></tr> + +<tr><td><a href="pcre_study.html">pcre_study</a></td> + <td> Study a compiled pattern</td></tr> + +<tr><td><a href="pcre_utf16_to_host_byte_order.html">pcre_utf16_to_host_byte_order</a></td> + <td> Convert UTF-16 string to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_utf32_to_host_byte_order.html">pcre_utf32_to_host_byte_order</a></td> + <td> Convert UTF-32 string to host byte order if necessary</td></tr> + +<tr><td><a href="pcre_version.html">pcre_version</a></td> + <td> Return PCRE version and release date</td></tr> +</table> + +</html> diff --git a/doc/pcre-config.1 b/doc/pcre-config.1 new file mode 100644 index 0000000..52eb4fb --- /dev/null +++ b/doc/pcre-config.1 @@ -0,0 +1,92 @@ +.TH PCRE-CONFIG 1 "01 January 2012" "PCRE 8.30" +.SH NAME +pcre-config - program to return PCRE configuration +.SH SYNOPSIS +.rs +.sp +.nf +.B pcre-config [--prefix] [--exec-prefix] [--version] [--libs] +.B " [--libs16] [--libs32] [--libs-cpp] [--libs-posix]" +.B " [--cflags] [--cflags-posix]" +.fi +. +. +.SH DESCRIPTION +.rs +.sp +\fBpcre-config\fP returns the configuration of the installed PCRE +libraries and the options required to compile a program to use them. Some of +the options apply only to the 8-bit, or 16-bit, or 32-bit libraries, +respectively, and are +not available if only one of those libraries has been built. If an unavailable +option is encountered, the "usage" information is output. +. +. +.SH OPTIONS +.rs +.TP 10 +\fB--prefix\fP +Writes the directory prefix used in the PCRE installation for architecture +independent files (\fI/usr\fP on many systems, \fI/usr/local\fP on some +systems) to the standard output. +.TP 10 +\fB--exec-prefix\fP +Writes the directory prefix used in the PCRE installation for architecture +dependent files (normally the same as \fB--prefix\fP) to the standard output. +.TP 10 +\fB--version\fP +Writes the version number of the installed PCRE libraries to the standard +output. +.TP 10 +\fB--libs\fP +Writes to the standard output the command line options required to link +with the 8-bit PCRE library (\fB-lpcre\fP on many systems). +.TP 10 +\fB--libs16\fP +Writes to the standard output the command line options required to link +with the 16-bit PCRE library (\fB-lpcre16\fP on many systems). +.TP 10 +\fB--libs32\fP +Writes to the standard output the command line options required to link +with the 32-bit PCRE library (\fB-lpcre32\fP on many systems). +.TP 10 +\fB--libs-cpp\fP +Writes to the standard output the command line options required to link with +PCRE's C++ wrapper library (\fB-lpcrecpp\fP \fB-lpcre\fP on many +systems). +.TP 10 +\fB--libs-posix\fP +Writes to the standard output the command line options required to link with +PCRE's POSIX API wrapper library (\fB-lpcreposix\fP \fB-lpcre\fP on many +systems). +.TP 10 +\fB--cflags\fP +Writes to the standard output the command line options required to compile +files that use PCRE (this may include some \fB-I\fP options, but is blank on +many systems). +.TP 10 +\fB--cflags-posix\fP +Writes to the standard output the command line options required to compile +files that use PCRE's POSIX API wrapper library (this may include some \fB-I\fP +options, but is blank on many systems). +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcre(3)\fP +. +. +.SH AUTHOR +.rs +.sp +This manual page was originally written by Mark Baker for the Debian GNU/Linux +system. It has been subsequently revised as a generic PCRE man page. +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 24 June 2012 +.fi diff --git a/doc/pcre-config.txt b/doc/pcre-config.txt new file mode 100644 index 0000000..8503ab0 --- /dev/null +++ b/doc/pcre-config.txt @@ -0,0 +1,86 @@ +PCRE-CONFIG(1) General Commands Manual PCRE-CONFIG(1) + + + +NAME + pcre-config - program to return PCRE configuration + +SYNOPSIS + + pcre-config [--prefix] [--exec-prefix] [--version] [--libs] + [--libs16] [--libs32] [--libs-cpp] [--libs-posix] + [--cflags] [--cflags-posix] + + +DESCRIPTION + + pcre-config returns the configuration of the installed PCRE libraries + and the options required to compile a program to use them. Some of the + options apply only to the 8-bit, or 16-bit, or 32-bit libraries, + respectively, and are not available if only one of those libraries has + been built. If an unavailable option is encountered, the "usage" infor- + mation is output. + + +OPTIONS + + --prefix Writes the directory prefix used in the PCRE installation for + architecture independent files (/usr on many systems, + /usr/local on some systems) to the standard output. + + --exec-prefix + Writes the directory prefix used in the PCRE installation for + architecture dependent files (normally the same as --prefix) + to the standard output. + + --version Writes the version number of the installed PCRE libraries to + the standard output. + + --libs Writes to the standard output the command line options + required to link with the 8-bit PCRE library (-lpcre on many + systems). + + --libs16 Writes to the standard output the command line options + required to link with the 16-bit PCRE library (-lpcre16 on + many systems). + + --libs32 Writes to the standard output the command line options + required to link with the 32-bit PCRE library (-lpcre32 on + many systems). + + --libs-cpp + Writes to the standard output the command line options + required to link with PCRE's C++ wrapper library (-lpcrecpp + -lpcre on many systems). + + --libs-posix + Writes to the standard output the command line options + required to link with PCRE's POSIX API wrapper library + (-lpcreposix -lpcre on many systems). + + --cflags Writes to the standard output the command line options + required to compile files that use PCRE (this may include + some -I options, but is blank on many systems). + + --cflags-posix + Writes to the standard output the command line options + required to compile files that use PCRE's POSIX API wrapper + library (this may include some -I options, but is blank on + many systems). + + +SEE ALSO + + pcre(3) + + +AUTHOR + + This manual page was originally written by Mark Baker for the Debian + GNU/Linux system. It has been subsequently revised as a generic PCRE + man page. + + +REVISION + + Last updated: 24 June 2012 diff --git a/doc/pcre.3 b/doc/pcre.3 new file mode 100644 index 0000000..0f2837e --- /dev/null +++ b/doc/pcre.3 @@ -0,0 +1,230 @@ +.TH PCRE 3 "10 February 2015" "PCRE 8.37" +.SH NAME +PCRE - Perl-compatible regular expressions (original API) +.SH "PLEASE TAKE NOTE" +.rs +.sp +This document relates to PCRE releases that use the original API, +with library names libpcre, libpcre16, and libpcre32. January 2015 saw the +first release of a new API, known as PCRE2, with release numbers starting at +10.00 and library names libpcre2-8, libpcre2-16, and libpcre2-32. The old +libraries (now called PCRE1) are still being maintained for bug fixes, but +there will be no new development. New projects are advised to use the new PCRE2 +libraries. +. +. +.SH INTRODUCTION +.rs +.sp +The PCRE library is a set of functions that implement regular expression +pattern matching using the same syntax and semantics as Perl, with just a few +differences. Some features that appeared in Python and PCRE before they +appeared in Perl are also available using the Python syntax, there is some +support for one or two .NET and Oniguruma syntax items, and there is an option +for requesting some minor changes that give better JavaScript compatibility. +.P +Starting with release 8.30, it is possible to compile two separate PCRE +libraries: the original, which supports 8-bit character strings (including +UTF-8 strings), and a second library that supports 16-bit character strings +(including UTF-16 strings). The build process allows either one or both to be +built. The majority of the work to make this possible was done by Zoltan +Herczeg. +.P +Starting with release 8.32 it is possible to compile a third separate PCRE +library that supports 32-bit character strings (including UTF-32 strings). The +build process allows any combination of the 8-, 16- and 32-bit libraries. The +work to make this possible was done by Christian Persch. +.P +The three libraries contain identical sets of functions, except that the names +in the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP, and the +names in the 32-bit library start with \fBpcre32_\fP instead of \fBpcre_\fP. To +avoid over-complication and reduce the documentation maintenance load, most of +the documentation describes the 8-bit library, with the differences for the +16-bit and 32-bit libraries described separately in the +.\" HREF +\fBpcre16\fP +and +.\" HREF +\fBpcre32\fP +.\" +pages. References to functions or structures of the form \fIpcre[16|32]_xxx\fP +should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library, +\fIpcre16_xxx\fP when using the 16-bit library, or \fIpcre32_xxx\fP when using +the 32-bit library". +.P +The current implementation of PCRE corresponds approximately with Perl 5.12, +including support for UTF-8/16/32 encoded strings and Unicode general category +properties. However, UTF-8/16/32 and Unicode support has to be explicitly +enabled; it is not the default. The Unicode tables correspond to Unicode +release 6.3.0. +.P +In addition to the Perl-compatible matching function, PCRE contains an +alternative function that matches the same compiled patterns in a different +way. In certain circumstances, the alternative function has some advantages. +For a discussion of the two matching algorithms, see the +.\" HREF +\fBpcrematching\fP +.\" +page. +.P +PCRE is written in C and released as a C library. A number of people have +written wrappers and interfaces of various kinds. In particular, Google Inc. +have provided a comprehensive C++ wrapper for the 8-bit library. This is now +included as part of the PCRE distribution. The +.\" HREF +\fBpcrecpp\fP +.\" +page has details of this interface. Other people's contributions can be found +in the \fIContrib\fP directory at the primary FTP site, which is: +.sp +.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre"> +.\" </a> +ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre +.\" +.P +Details of exactly which Perl regular expression features are and are not +supported by PCRE are given in separate documents. See the +.\" HREF +\fBpcrepattern\fP +.\" +and +.\" HREF +\fBpcrecompat\fP +.\" +pages. There is a syntax summary in the +.\" HREF +\fBpcresyntax\fP +.\" +page. +.P +Some features of PCRE can be included, excluded, or changed when the library is +built. The +.\" HREF +\fBpcre_config()\fP +.\" +function makes it possible for a client to discover which features are +available. The features themselves are described in the +.\" HREF +\fBpcrebuild\fP +.\" +page. Documentation about building PCRE for various operating systems can be +found in the +.\" HTML <a href="README.txt"> +.\" </a> +\fBREADME\fP +.\" +and +.\" HTML <a href="NON-AUTOTOOLS-BUILD.txt"> +.\" </a> +\fBNON-AUTOTOOLS_BUILD\fP +.\" +files in the source distribution. +.P +The libraries contains a number of undocumented internal functions and data +tables that are used by more than one of the exported external functions, but +which are not intended for use by external callers. Their names all begin with +"_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name +clashes. In some environments, it is possible to control which external symbols +are exported when a shared library is built, and in these cases the +undocumented symbols are not exported. +. +. +.SH "SECURITY CONSIDERATIONS" +.rs +.sp +If you are using PCRE in a non-UTF application that permits users to supply +arbitrary patterns for compilation, you should be aware of a feature that +allows users to turn on UTF support from within a pattern, provided that PCRE +was built with UTF support. For example, an 8-bit pattern that begins with +"(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and +subjects as strings of UTF-8 characters instead of individual 8-bit characters. +This causes both the pattern and any data against which it is matched to be +checked for UTF-8 validity. If the data string is very long, such a check might +use sufficiently many resources as to cause your application to lose +performance. +.P +One way of guarding against this possibility is to use the +\fBpcre_fullinfo()\fP function to check the compiled pattern's options for UTF. +Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at +compile time. This causes an compile time error if a pattern contains a +UTF-setting sequence. +.P +If your application is one that supports UTF, be aware that validity checking +can take time. If the same data string is to be matched many times, you can use +the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to +save redundant checks. +.P +Another way that performance can be hit is by running a pattern that has a very +large search tree against a string that will never match. Nested unlimited +repeats in a pattern are a common example. PCRE provides some protection +against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the +.\" HREF +\fBpcreapi\fP +.\" +page. +. +. +.SH "USER DOCUMENTATION" +.rs +.sp +The user documentation for PCRE comprises a number of different sections. In +the "man" format, each of these is a separate "man page". In the HTML format, +each is a separate page, linked from the index page. In the plain text format, +the descriptions of the \fBpcregrep\fP and \fBpcretest\fP programs are in files +called \fBpcregrep.txt\fP and \fBpcretest.txt\fP, respectively. The remaining +sections, except for the \fBpcredemo\fP section (which is a program listing), +are concatenated in \fBpcre.txt\fP, for ease of searching. The sections are as +follows: +.sp + pcre this document + pcre-config show PCRE installation configuration information + pcre16 details of the 16-bit library + pcre32 details of the 32-bit library + pcreapi details of PCRE's native C API + pcrebuild building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcrecpp details of the C++ wrapper for the 8-bit library + pcredemo a demonstration C program that uses PCRE + pcregrep description of the \fBpcregrep\fP command (8-bit only) + pcrejit discussion of the just-in-time optimization support + pcrelimits details of size and other limits + pcrematching discussion of the two matching algorithms + pcrepartial details of the partial matching facility +.\" JOIN + pcrepattern syntax and semantics of supported + regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible C API for the 8-bit library + pcreprecompile details of saving and re-using precompiled patterns + pcresample discussion of the pcredemo program + pcrestack discussion of stack usage + pcresyntax quick syntax reference + pcretest description of the \fBpcretest\fP testing command + pcreunicode discussion of Unicode and UTF-8/16/32 support +.sp +In the "man" and HTML formats, there is also a short page for each C library +function, listing its arguments and results. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +.P +Putting an actual email address here seems to have been a spam magnet, so I've +taken it away. If you want to email me, use my two initials, followed by the +two digits 10, at the domain cam.ac.uk. +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 10 February 2015 +Copyright (c) 1997-2015 University of Cambridge. +.fi diff --git a/doc/pcre.txt b/doc/pcre.txt new file mode 100644 index 0000000..76a47c7 --- /dev/null +++ b/doc/pcre.txt @@ -0,0 +1,10455 @@ +----------------------------------------------------------------------------- +This file contains a concatenation of the PCRE man pages, converted to plain +text format for ease of searching with a text editor, or for use on systems +that do not have a man page processor. The small individual files that give +synopses of each function in the library have not been included. Neither has +the pcredemo program. There are separate text files for the pcregrep and +pcretest commands. +----------------------------------------------------------------------------- + + +PCRE(3) Library Functions Manual PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions (original API) + +PLEASE TAKE NOTE + + This document relates to PCRE releases that use the original API, with + library names libpcre, libpcre16, and libpcre32. January 2015 saw the + first release of a new API, known as PCRE2, with release numbers start- + ing at 10.00 and library names libpcre2-8, libpcre2-16, and + libpcre2-32. The old libraries (now called PCRE1) are still being main- + tained for bug fixes, but there will be no new development. New + projects are advised to use the new PCRE2 libraries. + + +INTRODUCTION + + The PCRE library is a set of functions that implement regular expres- + sion pattern matching using the same syntax and semantics as Perl, with + just a few differences. Some features that appeared in Python and PCRE + before they appeared in Perl are also available using the Python syn- + tax, there is some support for one or two .NET and Oniguruma syntax + items, and there is an option for requesting some minor changes that + give better JavaScript compatibility. + + Starting with release 8.30, it is possible to compile two separate PCRE + libraries: the original, which supports 8-bit character strings + (including UTF-8 strings), and a second library that supports 16-bit + character strings (including UTF-16 strings). The build process allows + either one or both to be built. The majority of the work to make this + possible was done by Zoltan Herczeg. + + Starting with release 8.32 it is possible to compile a third separate + PCRE library that supports 32-bit character strings (including UTF-32 + strings). The build process allows any combination of the 8-, 16- and + 32-bit libraries. The work to make this possible was done by Christian + Persch. + + The three libraries contain identical sets of functions, except that + the names in the 16-bit library start with pcre16_ instead of pcre_, + and the names in the 32-bit library start with pcre32_ instead of + pcre_. To avoid over-complication and reduce the documentation mainte- + nance load, most of the documentation describes the 8-bit library, with + the differences for the 16-bit and 32-bit libraries described sepa- + rately in the pcre16 and pcre32 pages. References to functions or + structures of the form pcre[16|32]_xxx should be read as meaning + "pcre_xxx when using the 8-bit library, pcre16_xxx when using the + 16-bit library, or pcre32_xxx when using the 32-bit library". + + The current implementation of PCRE corresponds approximately with Perl + 5.12, including support for UTF-8/16/32 encoded strings and Unicode + general category properties. However, UTF-8/16/32 and Unicode support + has to be explicitly enabled; it is not the default. The Unicode tables + correspond to Unicode release 6.3.0. + + In addition to the Perl-compatible matching function, PCRE contains an + alternative function that matches the same compiled patterns in a dif- + ferent way. In certain circumstances, the alternative function has some + advantages. For a discussion of the two matching algorithms, see the + pcrematching page. + + PCRE is written in C and released as a C library. A number of people + have written wrappers and interfaces of various kinds. In particular, + Google Inc. have provided a comprehensive C++ wrapper for the 8-bit + library. This is now included as part of the PCRE distribution. The + pcrecpp page has details of this interface. Other people's contribu- + tions can be found in the Contrib directory at the primary FTP site, + which is: + + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre + + Details of exactly which Perl regular expression features are and are + not supported by PCRE are given in separate documents. See the pcrepat- + tern and pcrecompat pages. There is a syntax summary in the pcresyntax + page. + + Some features of PCRE can be included, excluded, or changed when the + library is built. The pcre_config() function makes it possible for a + client to discover which features are available. The features them- + selves are described in the pcrebuild page. Documentation about build- + ing PCRE for various operating systems can be found in the README and + NON-AUTOTOOLS_BUILD files in the source distribution. + + The libraries contains a number of undocumented internal functions and + data tables that are used by more than one of the exported external + functions, but which are not intended for use by external callers. + Their names all begin with "_pcre_" or "_pcre16_" or "_pcre32_", which + hopefully will not provoke any name clashes. In some environments, it + is possible to control which external symbols are exported when a + shared library is built, and in these cases the undocumented symbols + are not exported. + + +SECURITY CONSIDERATIONS + + If you are using PCRE in a non-UTF application that permits users to + supply arbitrary patterns for compilation, you should be aware of a + feature that allows users to turn on UTF support from within a pattern, + provided that PCRE was built with UTF support. For example, an 8-bit + pattern that begins with "(*UTF8)" or "(*UTF)" turns on UTF-8 mode, + which interprets patterns and subjects as strings of UTF-8 characters + instead of individual 8-bit characters. This causes both the pattern + and any data against which it is matched to be checked for UTF-8 valid- + ity. If the data string is very long, such a check might use suffi- + ciently many resources as to cause your application to lose perfor- + mance. + + One way of guarding against this possibility is to use the + pcre_fullinfo() function to check the compiled pattern's options for + UTF. Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF + option at compile time. This causes an compile time error if a pattern + contains a UTF-setting sequence. + + If your application is one that supports UTF, be aware that validity + checking can take time. If the same data string is to be matched many + times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second + and subsequent matches to save redundant checks. + + Another way that performance can be hit is by running a pattern that + has a very large search tree against a string that will never match. + Nested unlimited repeats in a pattern are a common example. PCRE pro- + vides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT fea- + ture in the pcreapi page. + + +USER DOCUMENTATION + + The user documentation for PCRE comprises a number of different sec- + tions. In the "man" format, each of these is a separate "man page". In + the HTML format, each is a separate page, linked from the index page. + In the plain text format, the descriptions of the pcregrep and pcretest + programs are in files called pcregrep.txt and pcretest.txt, respec- + tively. The remaining sections, except for the pcredemo section (which + is a program listing), are concatenated in pcre.txt, for ease of + searching. The sections are as follows: + + pcre this document + pcre-config show PCRE installation configuration information + pcre16 details of the 16-bit library + pcre32 details of the 32-bit library + pcreapi details of PCRE's native C API + pcrebuild building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcrecpp details of the C++ wrapper for the 8-bit library + pcredemo a demonstration C program that uses PCRE + pcregrep description of the pcregrep command (8-bit only) + pcrejit discussion of the just-in-time optimization support + pcrelimits details of size and other limits + pcrematching discussion of the two matching algorithms + pcrepartial details of the partial matching facility + pcrepattern syntax and semantics of supported + regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible C API for the 8-bit library + pcreprecompile details of saving and re-using precompiled patterns + pcresample discussion of the pcredemo program + pcrestack discussion of stack usage + pcresyntax quick syntax reference + pcretest description of the pcretest testing command + pcreunicode discussion of Unicode and UTF-8/16/32 support + + In the "man" and HTML formats, there is also a short page for each C + library function, listing its arguments and results. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + Putting an actual email address here seems to have been a spam magnet, + so I've taken it away. If you want to email me, use my two initials, + followed by the two digits 10, at the domain cam.ac.uk. + + +REVISION + + Last updated: 10 February 2015 + Copyright (c) 1997-2015 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRE(3) Library Functions Manual PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + + #include <pcre.h> + + +PCRE 16-BIT API BASIC FUNCTIONS + + pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options, + int *errorcodeptr, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre16_extra *pcre16_study(const pcre16 *code, int options, + const char **errptr); + + void pcre16_free_study(pcre16_extra *extra); + + int pcre16_exec(const pcre16 *code, const pcre16_extra *extra, + PCRE_SPTR16 subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra, + PCRE_SPTR16 subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + int *workspace, int wscount); + + +PCRE 16-BIT API STRING EXTRACTION FUNCTIONS + + int pcre16_copy_named_substring(const pcre16 *code, + PCRE_SPTR16 subject, int *ovector, + int stringcount, PCRE_SPTR16 stringname, + PCRE_UCHAR16 *buffer, int buffersize); + + int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector, + int stringcount, int stringnumber, PCRE_UCHAR16 *buffer, + int buffersize); + + int pcre16_get_named_substring(const pcre16 *code, + PCRE_SPTR16 subject, int *ovector, + int stringcount, PCRE_SPTR16 stringname, + PCRE_SPTR16 *stringptr); + + int pcre16_get_stringnumber(const pcre16 *code, + PCRE_SPTR16 name); + + int pcre16_get_stringtable_entries(const pcre16 *code, + PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last); + + int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector, + int stringcount, int stringnumber, + PCRE_SPTR16 *stringptr); + + int pcre16_get_substring_list(PCRE_SPTR16 subject, + int *ovector, int stringcount, PCRE_SPTR16 **listptr); + + void pcre16_free_substring(PCRE_SPTR16 stringptr); + + void pcre16_free_substring_list(PCRE_SPTR16 *stringptr); + + +PCRE 16-BIT API AUXILIARY FUNCTIONS + + pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize); + + void pcre16_jit_stack_free(pcre16_jit_stack *stack); + + void pcre16_assign_jit_stack(pcre16_extra *extra, + pcre16_jit_callback callback, void *data); + + const unsigned char *pcre16_maketables(void); + + int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra, + int what, void *where); + + int pcre16_refcount(pcre16 *code, int adjust); + + int pcre16_config(int what, void *where); + + const char *pcre16_version(void); + + int pcre16_pattern_to_host_byte_order(pcre16 *code, + pcre16_extra *extra, const unsigned char *tables); + + +PCRE 16-BIT API INDIRECTED FUNCTIONS + + void *(*pcre16_malloc)(size_t); + + void (*pcre16_free)(void *); + + void *(*pcre16_stack_malloc)(size_t); + + void (*pcre16_stack_free)(void *); + + int (*pcre16_callout)(pcre16_callout_block *); + + +PCRE 16-BIT API 16-BIT-ONLY FUNCTION + + int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output, + PCRE_SPTR16 input, int length, int *byte_order, + int keep_boms); + + +THE PCRE 16-BIT LIBRARY + + Starting with release 8.30, it is possible to compile a PCRE library + that supports 16-bit character strings, including UTF-16 strings, as + well as or instead of the original 8-bit library. The majority of the + work to make this possible was done by Zoltan Herczeg. The two + libraries contain identical sets of functions, used in exactly the same + way. Only the names of the functions and the data types of their argu- + ments and results are different. To avoid over-complication and reduce + the documentation maintenance load, most of the PCRE documentation + describes the 8-bit library, with only occasional references to the + 16-bit library. This page describes what is different when you use the + 16-bit library. + + WARNING: A single application can be linked with both libraries, but + you must take care when processing any particular pattern to use func- + tions from just one library. For example, if you want to study a pat- + tern that was compiled with pcre16_compile(), you must do so with + pcre16_study(), not pcre_study(), and you must free the study data with + pcre16_free_study(). + + +THE HEADER FILE + + There is only one header file, pcre.h. It contains prototypes for all + the functions in all libraries, as well as definitions of flags, struc- + tures, error codes, etc. + + +THE LIBRARY NAME + + In Unix-like systems, the 16-bit library is called libpcre16, and can + normally be accesss by adding -lpcre16 to the command for linking an + application that uses PCRE. + + +STRING TYPES + + In the 8-bit library, strings are passed to PCRE library functions as + vectors of bytes with the C type "char *". In the 16-bit library, + strings are passed as vectors of unsigned 16-bit quantities. The macro + PCRE_UCHAR16 specifies an appropriate data type, and PCRE_SPTR16 is + defined as "const PCRE_UCHAR16 *". In very many environments, "short + int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16 + as "unsigned short int", but checks that it really is a 16-bit data + type. If it is not, the build fails with an error message telling the + maintainer to modify the definition appropriately. + + +STRUCTURE TYPES + + The types of the opaque structures that are used for compiled 16-bit + patterns and JIT stacks are pcre16 and pcre16_jit_stack respectively. + The type of the user-accessible structure that is returned by + pcre16_study() is pcre16_extra, and the type of the structure that is + used for passing data to a callout function is pcre16_callout_block. + These structures contain the same fields, with the same names, as their + 8-bit counterparts. The only difference is that pointers to character + strings are 16-bit instead of 8-bit types. + + +16-BIT FUNCTIONS + + For every function in the 8-bit library there is a corresponding func- + tion in the 16-bit library with a name that starts with pcre16_ instead + of pcre_. The prototypes are listed above. In addition, there is one + extra function, pcre16_utf16_to_host_byte_order(). This is a utility + function that converts a UTF-16 character string to host byte order if + necessary. The other 16-bit functions expect the strings they are + passed to be in host byte order. + + The input and output arguments of pcre16_utf16_to_host_byte_order() may + point to the same address, that is, conversion in place is supported. + The output buffer must be at least as long as the input. + + The length argument specifies the number of 16-bit data units in the + input string; a negative value specifies a zero-terminated string. + + If byte_order is NULL, it is assumed that the string starts off in host + byte order. This may be changed by byte-order marks (BOMs) anywhere in + the string (commonly as the first character). + + If byte_order is not NULL, a non-zero value of the integer to which it + points means that the input starts off in host byte order, otherwise + the opposite order is assumed. Again, BOMs in the string can change + this. The final byte order is passed back at the end of processing. + + If keep_boms is not zero, byte-order mark characters (0xfeff) are + copied into the output string. Otherwise they are discarded. + + The result of the function is the number of 16-bit units placed into + the output buffer, including the zero terminator if the string was + zero-terminated. + + +SUBJECT STRING OFFSETS + + The lengths and starting offsets of subject strings must be specified + in 16-bit data units, and the offsets within subject strings that are + returned by the matching functions are in also 16-bit units rather than + bytes. + + +NAMED SUBPATTERNS + + The name-to-number translation table that is maintained for named sub- + patterns uses 16-bit characters. The pcre16_get_stringtable_entries() + function returns the length of each entry in the table as the number of + 16-bit data units. + + +OPTION NAMES + + There are two new general option names, PCRE_UTF16 and + PCRE_NO_UTF16_CHECK, which correspond to PCRE_UTF8 and + PCRE_NO_UTF8_CHECK in the 8-bit library. In fact, these new options + define the same bits in the options word. There is a discussion about + the validity of UTF-16 strings in the pcreunicode page. + + For the pcre16_config() function there is an option PCRE_CONFIG_UTF16 + that returns 1 if UTF-16 support is configured, otherwise 0. If this + option is given to pcre_config() or pcre32_config(), or if the + PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 option is given to pcre16_con- + fig(), the result is the PCRE_ERROR_BADOPTION error. + + +CHARACTER CODES + + In 16-bit mode, when PCRE_UTF16 is not set, character values are + treated in the same way as in 8-bit, non UTF-8 mode, except, of course, + that they can range from 0 to 0xffff instead of 0 to 0xff. Character + types for characters less than 0xff can therefore be influenced by the + locale in the same way as before. Characters greater than 0xff have + only one case, and no "type" (such as letter or digit). + + In UTF-16 mode, the character code is Unicode, in the range 0 to + 0x10ffff, with the exception of values in the range 0xd800 to 0xdfff + because those are "surrogate" values that are used in pairs to encode + values greater than 0xffff. + + A UTF-16 string can indicate its endianness by special code knows as a + byte-order mark (BOM). The PCRE functions do not handle this, expecting + strings to be in host byte order. A utility function called + pcre16_utf16_to_host_byte_order() is provided to help with this (see + above). + + +ERROR NAMES + + The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 corre- + spond to their 8-bit counterparts. The error PCRE_ERROR_BADMODE is + given when a compiled pattern is passed to a function that processes + patterns in the other mode, for example, if a pattern compiled with + pcre_compile() is passed to pcre16_exec(). + + There are new error codes whose names begin with PCRE_UTF16_ERR for + invalid UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for + UTF-8 strings that are described in the section entitled "Reason codes + for invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors + are: + + PCRE_UTF16_ERR1 Missing low surrogate at end of string + PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate + PCRE_UTF16_ERR3 Isolated low surrogate + PCRE_UTF16_ERR4 Non-character + + +ERROR TEXTS + + If there is an error while compiling a pattern, the error text that is + passed back by pcre16_compile() or pcre16_compile2() is still an 8-bit + character string, zero-terminated. + + +CALLOUTS + + The subject and mark fields in the callout block that is passed to a + callout function point to 16-bit vectors. + + +TESTING + + The pcretest program continues to operate with 8-bit input and output + files, but it can be used for testing the 16-bit library. If it is run + with the command line option -16, patterns and subject strings are con- + verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit + library functions are used instead of the 8-bit ones. Returned 16-bit + strings are converted to 8-bit for output. If both the 8-bit and the + 32-bit libraries were not compiled, pcretest defaults to 16-bit and the + -16 option is ignored. + + When PCRE is being built, the RunTest script that is called by "make + check" uses the pcretest -C option to discover which of the 8-bit, + 16-bit and 32-bit libraries has been built, and runs the tests appro- + priately. + + +NOT SUPPORTED IN 16-BIT MODE + + Not all the features of the 8-bit library are available with the 16-bit + library. The C++ and POSIX wrapper functions support only the 8-bit + library, and the pcregrep program is at present 8-bit only. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRE(3) Library Functions Manual PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + + #include <pcre.h> + + +PCRE 32-BIT API BASIC FUNCTIONS + + pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options, + int *errorcodeptr, + const unsigned char *tableptr); + + pcre32_extra *pcre32_study(const pcre32 *code, int options, + const char **errptr); + + void pcre32_free_study(pcre32_extra *extra); + + int pcre32_exec(const pcre32 *code, const pcre32_extra *extra, + PCRE_SPTR32 subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + int pcre32_dfa_exec(const pcre32 *code, const pcre32_extra *extra, + PCRE_SPTR32 subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + int *workspace, int wscount); + + +PCRE 32-BIT API STRING EXTRACTION FUNCTIONS + + int pcre32_copy_named_substring(const pcre32 *code, + PCRE_SPTR32 subject, int *ovector, + int stringcount, PCRE_SPTR32 stringname, + PCRE_UCHAR32 *buffer, int buffersize); + + int pcre32_copy_substring(PCRE_SPTR32 subject, int *ovector, + int stringcount, int stringnumber, PCRE_UCHAR32 *buffer, + int buffersize); + + int pcre32_get_named_substring(const pcre32 *code, + PCRE_SPTR32 subject, int *ovector, + int stringcount, PCRE_SPTR32 stringname, + PCRE_SPTR32 *stringptr); + + int pcre32_get_stringnumber(const pcre32 *code, + PCRE_SPTR32 name); + + int pcre32_get_stringtable_entries(const pcre32 *code, + PCRE_SPTR32 name, PCRE_UCHAR32 **first, PCRE_UCHAR32 **last); + + int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector, + int stringcount, int stringnumber, + PCRE_SPTR32 *stringptr); + + int pcre32_get_substring_list(PCRE_SPTR32 subject, + int *ovector, int stringcount, PCRE_SPTR32 **listptr); + + void pcre32_free_substring(PCRE_SPTR32 stringptr); + + void pcre32_free_substring_list(PCRE_SPTR32 *stringptr); + + +PCRE 32-BIT API AUXILIARY FUNCTIONS + + pcre32_jit_stack *pcre32_jit_stack_alloc(int startsize, int maxsize); + + void pcre32_jit_stack_free(pcre32_jit_stack *stack); + + void pcre32_assign_jit_stack(pcre32_extra *extra, + pcre32_jit_callback callback, void *data); + + const unsigned char *pcre32_maketables(void); + + int pcre32_fullinfo(const pcre32 *code, const pcre32_extra *extra, + int what, void *where); + + int pcre32_refcount(pcre32 *code, int adjust); + + int pcre32_config(int what, void *where); + + const char *pcre32_version(void); + + int pcre32_pattern_to_host_byte_order(pcre32 *code, + pcre32_extra *extra, const unsigned char *tables); + + +PCRE 32-BIT API INDIRECTED FUNCTIONS + + void *(*pcre32_malloc)(size_t); + + void (*pcre32_free)(void *); + + void *(*pcre32_stack_malloc)(size_t); + + void (*pcre32_stack_free)(void *); + + int (*pcre32_callout)(pcre32_callout_block *); + + +PCRE 32-BIT API 32-BIT-ONLY FUNCTION + + int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *output, + PCRE_SPTR32 input, int length, int *byte_order, + int keep_boms); + + +THE PCRE 32-BIT LIBRARY + + Starting with release 8.32, it is possible to compile a PCRE library + that supports 32-bit character strings, including UTF-32 strings, as + well as or instead of the original 8-bit library. This work was done by + Christian Persch, based on the work done by Zoltan Herczeg for the + 16-bit library. All three libraries contain identical sets of func- + tions, used in exactly the same way. Only the names of the functions + and the data types of their arguments and results are different. To + avoid over-complication and reduce the documentation maintenance load, + most of the PCRE documentation describes the 8-bit library, with only + occasional references to the 16-bit and 32-bit libraries. This page + describes what is different when you use the 32-bit library. + + WARNING: A single application can be linked with all or any of the + three libraries, but you must take care when processing any particular + pattern to use functions from just one library. For example, if you + want to study a pattern that was compiled with pcre32_compile(), you + must do so with pcre32_study(), not pcre_study(), and you must free the + study data with pcre32_free_study(). + + +THE HEADER FILE + + There is only one header file, pcre.h. It contains prototypes for all + the functions in all libraries, as well as definitions of flags, struc- + tures, error codes, etc. + + +THE LIBRARY NAME + + In Unix-like systems, the 32-bit library is called libpcre32, and can + normally be accesss by adding -lpcre32 to the command for linking an + application that uses PCRE. + + +STRING TYPES + + In the 8-bit library, strings are passed to PCRE library functions as + vectors of bytes with the C type "char *". In the 32-bit library, + strings are passed as vectors of unsigned 32-bit quantities. The macro + PCRE_UCHAR32 specifies an appropriate data type, and PCRE_SPTR32 is + defined as "const PCRE_UCHAR32 *". In very many environments, "unsigned + int" is a 32-bit data type. When PCRE is built, it defines PCRE_UCHAR32 + as "unsigned int", but checks that it really is a 32-bit data type. If + it is not, the build fails with an error message telling the maintainer + to modify the definition appropriately. + + +STRUCTURE TYPES + + The types of the opaque structures that are used for compiled 32-bit + patterns and JIT stacks are pcre32 and pcre32_jit_stack respectively. + The type of the user-accessible structure that is returned by + pcre32_study() is pcre32_extra, and the type of the structure that is + used for passing data to a callout function is pcre32_callout_block. + These structures contain the same fields, with the same names, as their + 8-bit counterparts. The only difference is that pointers to character + strings are 32-bit instead of 8-bit types. + + +32-BIT FUNCTIONS + + For every function in the 8-bit library there is a corresponding func- + tion in the 32-bit library with a name that starts with pcre32_ instead + of pcre_. The prototypes are listed above. In addition, there is one + extra function, pcre32_utf32_to_host_byte_order(). This is a utility + function that converts a UTF-32 character string to host byte order if + necessary. The other 32-bit functions expect the strings they are + passed to be in host byte order. + + The input and output arguments of pcre32_utf32_to_host_byte_order() may + point to the same address, that is, conversion in place is supported. + The output buffer must be at least as long as the input. + + The length argument specifies the number of 32-bit data units in the + input string; a negative value specifies a zero-terminated string. + + If byte_order is NULL, it is assumed that the string starts off in host + byte order. This may be changed by byte-order marks (BOMs) anywhere in + the string (commonly as the first character). + + If byte_order is not NULL, a non-zero value of the integer to which it + points means that the input starts off in host byte order, otherwise + the opposite order is assumed. Again, BOMs in the string can change + this. The final byte order is passed back at the end of processing. + + If keep_boms is not zero, byte-order mark characters (0xfeff) are + copied into the output string. Otherwise they are discarded. + + The result of the function is the number of 32-bit units placed into + the output buffer, including the zero terminator if the string was + zero-terminated. + + +SUBJECT STRING OFFSETS + + The lengths and starting offsets of subject strings must be specified + in 32-bit data units, and the offsets within subject strings that are + returned by the matching functions are in also 32-bit units rather than + bytes. + + +NAMED SUBPATTERNS + + The name-to-number translation table that is maintained for named sub- + patterns uses 32-bit characters. The pcre32_get_stringtable_entries() + function returns the length of each entry in the table as the number of + 32-bit data units. + + +OPTION NAMES + + There are two new general option names, PCRE_UTF32 and + PCRE_NO_UTF32_CHECK, which correspond to PCRE_UTF8 and + PCRE_NO_UTF8_CHECK in the 8-bit library. In fact, these new options + define the same bits in the options word. There is a discussion about + the validity of UTF-32 strings in the pcreunicode page. + + For the pcre32_config() function there is an option PCRE_CONFIG_UTF32 + that returns 1 if UTF-32 support is configured, otherwise 0. If this + option is given to pcre_config() or pcre16_config(), or if the + PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 option is given to pcre32_con- + fig(), the result is the PCRE_ERROR_BADOPTION error. + + +CHARACTER CODES + + In 32-bit mode, when PCRE_UTF32 is not set, character values are + treated in the same way as in 8-bit, non UTF-8 mode, except, of course, + that they can range from 0 to 0x7fffffff instead of 0 to 0xff. Charac- + ter types for characters less than 0xff can therefore be influenced by + the locale in the same way as before. Characters greater than 0xff + have only one case, and no "type" (such as letter or digit). + + In UTF-32 mode, the character code is Unicode, in the range 0 to + 0x10ffff, with the exception of values in the range 0xd800 to 0xdfff + because those are "surrogate" values that are ill-formed in UTF-32. + + A UTF-32 string can indicate its endianness by special code knows as a + byte-order mark (BOM). The PCRE functions do not handle this, expecting + strings to be in host byte order. A utility function called + pcre32_utf32_to_host_byte_order() is provided to help with this (see + above). + + +ERROR NAMES + + The error PCRE_ERROR_BADUTF32 corresponds to its 8-bit counterpart. + The error PCRE_ERROR_BADMODE is given when a compiled pattern is passed + to a function that processes patterns in the other mode, for example, + if a pattern compiled with pcre_compile() is passed to pcre32_exec(). + + There are new error codes whose names begin with PCRE_UTF32_ERR for + invalid UTF-32 strings, corresponding to the PCRE_UTF8_ERR codes for + UTF-8 strings that are described in the section entitled "Reason codes + for invalid UTF-8 strings" in the main pcreapi page. The UTF-32 errors + are: + + PCRE_UTF32_ERR1 Surrogate character (range from 0xd800 to 0xdfff) + PCRE_UTF32_ERR2 Non-character + PCRE_UTF32_ERR3 Character > 0x10ffff + + +ERROR TEXTS + + If there is an error while compiling a pattern, the error text that is + passed back by pcre32_compile() or pcre32_compile2() is still an 8-bit + character string, zero-terminated. + + +CALLOUTS + + The subject and mark fields in the callout block that is passed to a + callout function point to 32-bit vectors. + + +TESTING + + The pcretest program continues to operate with 8-bit input and output + files, but it can be used for testing the 32-bit library. If it is run + with the command line option -32, patterns and subject strings are con- + verted from 8-bit to 32-bit before being passed to PCRE, and the 32-bit + library functions are used instead of the 8-bit ones. Returned 32-bit + strings are converted to 8-bit for output. If both the 8-bit and the + 16-bit libraries were not compiled, pcretest defaults to 32-bit and the + -32 option is ignored. + + When PCRE is being built, the RunTest script that is called by "make + check" uses the pcretest -C option to discover which of the 8-bit, + 16-bit and 32-bit libraries has been built, and runs the tests appro- + priately. + + +NOT SUPPORTED IN 32-BIT MODE + + Not all the features of the 8-bit library are available with the 32-bit + library. The C++ and POSIX wrapper functions support only the 8-bit + library, and the pcregrep program is at present 8-bit only. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREBUILD(3) Library Functions Manual PCREBUILD(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +BUILDING PCRE + + PCRE is distributed with a configure script that can be used to build + the library in Unix-like environments using the applications known as + Autotools. Also in the distribution are files to support building + using CMake instead of configure. The text file README contains general + information about building with Autotools (some of which is repeated + below), and also has some comments about building on various operating + systems. There is a lot more information about building PCRE without + using Autotools (including information about using CMake and building + "by hand") in the text file called NON-AUTOTOOLS-BUILD. You should + consult this file as well as the README file if you are building in a + non-Unix-like environment. + + +PCRE BUILD-TIME OPTIONS + + The rest of this document describes the optional features of PCRE that + can be selected when the library is compiled. It assumes use of the + configure script, where the optional features are selected or dese- + lected by providing options to configure before running the make com- + mand. However, the same options can be selected in both Unix-like and + non-Unix-like environments using the GUI facility of cmake-gui if you + are using CMake instead of configure to build PCRE. + + If you are not using Autotools or CMake, option selection can be done + by editing the config.h file, or by passing parameter settings to the + compiler, as described in NON-AUTOTOOLS-BUILD. + + The complete list of options for configure (which includes the standard + ones such as the selection of the installation directory) can be + obtained by running + + ./configure --help + + The following sections include descriptions of options whose names + begin with --enable or --disable. These settings specify changes to the + defaults for the configure command. Because of the way that configure + works, --enable and --disable always come in pairs, so the complemen- + tary option always exists as well, but as it specifies the default, it + is not described. + + +BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES + + By default, a library called libpcre is built, containing functions + that take string arguments contained in vectors of bytes, either as + single-byte characters, or interpreted as UTF-8 strings. You can also + build a separate library, called libpcre16, in which strings are con- + tained in vectors of 16-bit data units and interpreted either as sin- + gle-unit characters or UTF-16 strings, by adding + + --enable-pcre16 + + to the configure command. You can also build yet another separate + library, called libpcre32, in which strings are contained in vectors of + 32-bit data units and interpreted either as single-unit characters or + UTF-32 strings, by adding + + --enable-pcre32 + + to the configure command. If you do not want the 8-bit library, add + + --disable-pcre8 + + as well. At least one of the three libraries must be built. Note that + the C++ and POSIX wrappers are for the 8-bit library only, and that + pcregrep is an 8-bit program. None of these are built if you select + only the 16-bit or 32-bit libraries. + + +BUILDING SHARED AND STATIC LIBRARIES + + The Autotools PCRE building process uses libtool to build both shared + and static libraries by default. You can suppress one of these by + adding one of + + --disable-shared + --disable-static + + to the configure command, as required. + + +C++ SUPPORT + + By default, if the 8-bit library is being built, the configure script + will search for a C++ compiler and C++ header files. If it finds them, + it automatically builds the C++ wrapper library (which supports only + 8-bit strings). You can disable this by adding + + --disable-cpp + + to the configure command. + + +UTF-8, UTF-16 AND UTF-32 SUPPORT + + To build PCRE with support for UTF Unicode character strings, add + + --enable-utf + + to the configure command. This setting applies to all three libraries, + adding support for UTF-8 to the 8-bit library, support for UTF-16 to + the 16-bit library, and support for UTF-32 to the to the 32-bit + library. There are no separate options for enabling UTF-8, UTF-16 and + UTF-32 independently because that would allow ridiculous settings such + as requesting UTF-16 support while building only the 8-bit library. It + is not possible to build one library with UTF support and another with- + out in the same configuration. (For backwards compatibility, --enable- + utf8 is a synonym of --enable-utf.) + + Of itself, this setting does not make PCRE treat strings as UTF-8, + UTF-16 or UTF-32. As well as compiling PCRE with this option, you also + have have to set the PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as + appropriate) when you call one of the pattern compiling functions. + + If you set --enable-utf when compiling in an EBCDIC environment, PCRE + expects its input to be either ASCII or UTF-8 (depending on the run- + time option). It is not possible to support both EBCDIC and UTF-8 codes + in the same version of the library. Consequently, --enable-utf and + --enable-ebcdic are mutually exclusive. + + +UNICODE CHARACTER PROPERTY SUPPORT + + UTF support allows the libraries to process character codepoints up to + 0x10ffff in the strings that they handle. On its own, however, it does + not provide any facilities for accessing the properties of such charac- + ters. If you want to be able to use the pattern escapes \P, \p, and \X, + which refer to Unicode character properties, you must add + + --enable-unicode-properties + + to the configure command. This implies UTF support, even if you have + not explicitly requested it. + + Including Unicode property support adds around 30K of tables to the + PCRE library. Only the general category properties such as Lu and Nd + are supported. Details are given in the pcrepattern documentation. + + +JUST-IN-TIME COMPILER SUPPORT + + Just-in-time compiler support is included in the build by specifying + + --enable-jit + + This support is available only for certain hardware architectures. If + this option is set for an unsupported architecture, a compile time + error occurs. See the pcrejit documentation for a discussion of JIT + usage. When JIT support is enabled, pcregrep automatically makes use of + it, unless you add + + --disable-pcregrep-jit + + to the "configure" command. + + +CODE VALUE OF NEWLINE + + By default, PCRE interprets the linefeed (LF) character as indicating + the end of a line. This is the normal newline character on Unix-like + systems. You can compile PCRE to use carriage return (CR) instead, by + adding + + --enable-newline-is-cr + + to the configure command. There is also a --enable-newline-is-lf + option, which explicitly specifies linefeed as the newline character. + + Alternatively, you can specify that line endings are to be indicated by + the two character sequence CRLF. If you want this, add + + --enable-newline-is-crlf + + to the configure command. There is a fourth option, specified by + + --enable-newline-is-anycrlf + + which causes PCRE to recognize any of the three sequences CR, LF, or + CRLF as indicating a line ending. Finally, a fifth option, specified by + + --enable-newline-is-any + + causes PCRE to recognize any Unicode newline sequence. + + Whatever line ending convention is selected when PCRE is built can be + overridden when the library functions are called. At build time it is + conventional to use the standard for your operating system. + + +WHAT \R MATCHES + + By default, the sequence \R in a pattern matches any Unicode newline + sequence, whatever has been selected as the line ending sequence. If + you specify + + --enable-bsr-anycrlf + + the default is changed so that \R matches only CR, LF, or CRLF. What- + ever is selected when PCRE is built can be overridden when the library + functions are called. + + +POSIX MALLOC USAGE + + When the 8-bit library is called through the POSIX interface (see the + pcreposix documentation), additional working storage is required for + holding the pointers to capturing substrings, because PCRE requires + three integers per substring, whereas the POSIX interface provides only + two. If the number of expected substrings is small, the wrapper func- + tion uses space on the stack, because this is faster than using mal- + loc() for each call. The default threshold above which the stack is no + longer used is 10; it can be changed by adding a setting such as + + --with-posix-malloc-threshold=20 + + to the configure command. + + +HANDLING VERY LARGE PATTERNS + + Within a compiled pattern, offset values are used to point from one + part to another (for example, from an opening parenthesis to an alter- + nation metacharacter). By default, in the 8-bit and 16-bit libraries, + two-byte values are used for these offsets, leading to a maximum size + for a compiled pattern of around 64K. This is sufficient to handle all + but the most gigantic patterns. Nevertheless, some people do want to + process truly enormous patterns, so it is possible to compile PCRE to + use three-byte or four-byte offsets by adding a setting such as + + --with-link-size=3 + + to the configure command. The value given must be 2, 3, or 4. For the + 16-bit library, a value of 3 is rounded up to 4. In these libraries, + using longer offsets slows down the operation of PCRE because it has to + load additional data when handling them. For the 32-bit library the + value is always 4 and cannot be overridden; the value of --with-link- + size is ignored. + + +AVOIDING EXCESSIVE STACK USAGE + + When matching with the pcre_exec() function, PCRE implements backtrack- + ing by making recursive calls to an internal function called match(). + In environments where the size of the stack is limited, this can se- + verely limit PCRE's operation. (The Unix environment does not usually + suffer from this problem, but it may sometimes be necessary to increase + the maximum stack size. There is a discussion in the pcrestack docu- + mentation.) An alternative approach to recursion that uses memory from + the heap to remember data, instead of using recursive function calls, + has been implemented to work round the problem of limited stack size. + If you want to build a version of PCRE that works this way, add + + --disable-stack-for-recursion + + to the configure command. With this configuration, PCRE will use the + pcre_stack_malloc and pcre_stack_free variables to call memory manage- + ment functions. By default these point to malloc() and free(), but you + can replace the pointers so that your own functions are used instead. + + Separate functions are provided rather than using pcre_malloc and + pcre_free because the usage is very predictable: the block sizes + requested are always the same, and the blocks are always freed in + reverse order. A calling program might be able to implement optimized + functions that perform better than malloc() and free(). PCRE runs + noticeably more slowly when built in this way. This option affects only + the pcre_exec() function; it is not relevant for pcre_dfa_exec(). + + +LIMITING PCRE RESOURCE USAGE + + Internally, PCRE has a function called match(), which it calls repeat- + edly (sometimes recursively) when matching a pattern with the + pcre_exec() function. By controlling the maximum number of times this + function may be called during a single matching operation, a limit can + be placed on the resources used by a single call to pcre_exec(). The + limit can be changed at run time, as described in the pcreapi documen- + tation. The default is 10 million, but this can be changed by adding a + setting such as + + --with-match-limit=500000 + + to the configure command. This setting has no effect on the + pcre_dfa_exec() matching function. + + In some environments it is desirable to limit the depth of recursive + calls of match() more strictly than the total number of calls, in order + to restrict the maximum amount of stack (or heap, if --disable-stack- + for-recursion is specified) that is used. A second limit controls this; + it defaults to the value that is set for --with-match-limit, which + imposes no additional constraints. However, you can set a lower limit + by adding, for example, + + --with-match-limit-recursion=10000 + + to the configure command. This value can also be overridden at run + time. + + +CREATING CHARACTER TABLES AT BUILD TIME + + PCRE uses fixed tables for processing characters whose code values are + less than 256. By default, PCRE is built with a set of tables that are + distributed in the file pcre_chartables.c.dist. These tables are for + ASCII codes only. If you add + + --enable-rebuild-chartables + + to the configure command, the distributed tables are no longer used. + Instead, a program called dftables is compiled and run. This outputs + the source for new set of tables, created in the default locale of your + C run-time system. (This method of replacing the tables does not work + if you are cross compiling, because dftables is run on the local host. + If you need to create alternative tables when cross compiling, you will + have to do so "by hand".) + + +USING EBCDIC CODE + + PCRE assumes by default that it will run in an environment where the + character code is ASCII (or Unicode, which is a superset of ASCII). + This is the case for most computer operating systems. PCRE can, how- + ever, be compiled to run in an EBCDIC environment by adding + + --enable-ebcdic + + to the configure command. This setting implies --enable-rebuild-charta- + bles. You should only use it if you know that you are in an EBCDIC + environment (for example, an IBM mainframe operating system). The + --enable-ebcdic option is incompatible with --enable-utf. + + The EBCDIC character that corresponds to an ASCII LF is assumed to have + the value 0x15 by default. However, in some EBCDIC environments, 0x25 + is used. In such an environment you should use + + --enable-ebcdic-nl25 + + as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR + has the same value as in ASCII, namely, 0x0d. Whichever of 0x15 and + 0x25 is not chosen as LF is made to correspond to the Unicode NEL char- + acter (which, in Unicode, is 0x85). + + The options that select newline behaviour, such as --enable-newline-is- + cr, and equivalent run-time options, refer to these character values in + an EBCDIC environment. + + +PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT + + By default, pcregrep reads all files as plain text. You can build it so + that it recognizes files whose names end in .gz or .bz2, and reads them + with libz or libbz2, respectively, by adding one or both of + + --enable-pcregrep-libz + --enable-pcregrep-libbz2 + + to the configure command. These options naturally require that the rel- + evant libraries are installed on your system. Configuration will fail + if they are not. + + +PCREGREP BUFFER SIZE + + pcregrep uses an internal buffer to hold a "window" on the file it is + scanning, in order to be able to output "before" and "after" lines when + it finds a match. The size of the buffer is controlled by a parameter + whose default value is 20K. The buffer itself is three times this size, + but because of the way it is used for holding "before" lines, the long- + est line that is guaranteed to be processable is the parameter size. + You can change the default parameter value by adding, for example, + + --with-pcregrep-bufsize=50K + + to the configure command. The caller of pcregrep can, however, override + this value by specifying a run-time option. + + +PCRETEST OPTION FOR LIBREADLINE SUPPORT + + If you add + + --enable-pcretest-libreadline + + to the configure command, pcretest is linked with the libreadline + library, and when its input is from a terminal, it reads it using the + readline() function. This provides line-editing and history facilities. + Note that libreadline is GPL-licensed, so if you distribute a binary of + pcretest linked in this way, there may be licensing issues. + + Setting this option causes the -lreadline option to be added to the + pcretest build. In many operating environments with a sytem-installed + libreadline this is sufficient. However, in some environments (e.g. if + an unmodified distribution version of readline is in use), some extra + configuration may be necessary. The INSTALL file for libreadline says + this: + + "Readline uses the termcap functions, but does not link with the + termcap or curses library itself, allowing applications which link + with readline the to choose an appropriate library." + + If your environment has not been set up so that an appropriate library + is automatically included, you may need to add something like + + LIBS="-ncurses" + + immediately before the configure command. + + +DEBUGGING WITH VALGRIND SUPPORT + + By adding the + + --enable-valgrind + + option to to the configure command, PCRE will use valgrind annotations + to mark certain memory regions as unaddressable. This allows it to + detect invalid memory accesses, and is mostly useful for debugging PCRE + itself. + + +CODE COVERAGE REPORTING + + If your C compiler is gcc, you can build a version of PCRE that can + generate a code coverage report for its test suite. To enable this, you + must install lcov version 1.6 or above. Then specify + + --enable-coverage + + to the configure command and build PCRE in the usual way. + + Note that using ccache (a caching C compiler) is incompatible with code + coverage reporting. If you have configured ccache to run automatically + on your system, you must set the environment variable + + CCACHE_DISABLE=1 + + before running make to build PCRE, so that ccache is not used. + + When --enable-coverage is used, the following addition targets are + added to the Makefile: + + make coverage + + This creates a fresh coverage report for the PCRE test suite. It is + equivalent to running "make coverage-reset", "make coverage-baseline", + "make check", and then "make coverage-report". + + make coverage-reset + + This zeroes the coverage counters, but does nothing else. + + make coverage-baseline + + This captures baseline coverage information. + + make coverage-report + + This creates the coverage report. + + make coverage-clean-report + + This removes the generated coverage report without cleaning the cover- + age data itself. + + make coverage-clean-data + + This removes the captured coverage data without removing the coverage + files created at compile time (*.gcno). + + make coverage-clean + + This cleans all coverage data including the generated coverage report. + For more information about code coverage, see the gcov and lcov docu- + mentation. + + +SEE ALSO + + pcreapi(3), pcre16, pcre32, pcre_config(3). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 May 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREMATCHING(3) Library Functions Manual PCREMATCHING(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE MATCHING ALGORITHMS + + This document describes the two different algorithms that are available + in PCRE for matching a compiled regular expression against a given sub- + ject string. The "standard" algorithm is the one provided by the + pcre_exec(), pcre16_exec() and pcre32_exec() functions. These work in + the same as as Perl's matching function, and provide a Perl-compatible + matching operation. The just-in-time (JIT) optimization that is + described in the pcrejit documentation is compatible with these func- + tions. + + An alternative algorithm is provided by the pcre_dfa_exec(), + pcre16_dfa_exec() and pcre32_dfa_exec() functions; they operate in a + different way, and are not Perl-compatible. This alternative has advan- + tages and disadvantages compared with the standard algorithm, and these + are described below. + + When there is only one possible way in which a given subject string can + match a pattern, the two algorithms give the same answer. A difference + arises, however, when there are multiple possibilities. For example, if + the pattern + + ^<.*> + + is matched against the string + + <something> <something else> <something further> + + there are three possible answers. The standard algorithm finds only one + of them, whereas the alternative algorithm finds all three. + + +REGULAR EXPRESSIONS AS TREES + + The set of strings that are matched by a regular expression can be rep- + resented as a tree structure. An unlimited repetition in the pattern + makes the tree of infinite size, but it is still a tree. Matching the + pattern to a given subject string (from a given starting point) can be + thought of as a search of the tree. There are two ways to search a + tree: depth-first and breadth-first, and these correspond to the two + matching algorithms provided by PCRE. + + +THE STANDARD MATCHING ALGORITHM + + In the terminology of Jeffrey Friedl's book "Mastering Regular Expres- + sions", the standard algorithm is an "NFA algorithm". It conducts a + depth-first search of the pattern tree. That is, it proceeds along a + single path through the tree, checking that the subject matches what is + required. When there is a mismatch, the algorithm tries any alterna- + tives at the current point, and if they all fail, it backs up to the + previous branch point in the tree, and tries the next alternative + branch at that level. This often involves backing up (moving to the + left) in the subject string as well. The order in which repetition + branches are tried is controlled by the greedy or ungreedy nature of + the quantifier. + + If a leaf node is reached, a matching string has been found, and at + that point the algorithm stops. Thus, if there is more than one possi- + ble match, this algorithm returns the first one that it finds. Whether + this is the shortest, the longest, or some intermediate length depends + on the way the greedy and ungreedy repetition quantifiers are specified + in the pattern. + + Because it ends up with a single path through the tree, it is rela- + tively straightforward for this algorithm to keep track of the sub- + strings that are matched by portions of the pattern in parentheses. + This provides support for capturing parentheses and back references. + + +THE ALTERNATIVE MATCHING ALGORITHM + + This algorithm conducts a breadth-first search of the tree. Starting + from the first matching point in the subject, it scans the subject + string from left to right, once, character by character, and as it does + this, it remembers all the paths through the tree that represent valid + matches. In Friedl's terminology, this is a kind of "DFA algorithm", + though it is not implemented as a traditional finite state machine (it + keeps multiple states active simultaneously). + + Although the general principle of this matching algorithm is that it + scans the subject string only once, without backtracking, there is one + exception: when a lookaround assertion is encountered, the characters + following or preceding the current point have to be independently + inspected. + + The scan continues until either the end of the subject is reached, or + there are no more unterminated paths. At this point, terminated paths + represent the different matching possibilities (if there are none, the + match has failed). Thus, if there is more than one possible match, + this algorithm finds all of them, and in particular, it finds the long- + est. The matches are returned in decreasing order of length. There is + an option to stop the algorithm after the first match (which is neces- + sarily the shortest) is found. + + Note that all the matches that are found start at the same point in the + subject. If the pattern + + cat(er(pillar)?)? + + is matched against the string "the caterpillar catchment", the result + will be the three strings "caterpillar", "cater", and "cat" that start + at the fifth character of the subject. The algorithm does not automati- + cally move on to find matches that start at later positions. + + PCRE's "auto-possessification" optimization usually applies to charac- + ter repeats at the end of a pattern (as well as internally). For exam- + ple, the pattern "a\d+" is compiled as if it were "a\d++" because there + is no point even considering the possibility of backtracking into the + repeated digits. For DFA matching, this means that only one possible + match is found. If you really do want multiple matches in such cases, + either use an ungreedy repeat ("a\d+?") or set the PCRE_NO_AUTO_POSSESS + option when compiling. + + There are a number of features of PCRE regular expressions that are not + supported by the alternative matching algorithm. They are as follows: + + 1. Because the algorithm finds all possible matches, the greedy or + ungreedy nature of repetition quantifiers is not relevant. Greedy and + ungreedy quantifiers are treated in exactly the same way. However, pos- + sessive quantifiers can make a difference when what follows could also + match what is quantified, for example in a pattern like this: + + ^a++\w! + + This pattern matches "aaab!" but not "aaa!", which would be matched by + a non-possessive quantifier. Similarly, if an atomic group is present, + it is matched as if it were a standalone pattern at the current point, + and the longest match is then "locked in" for the rest of the overall + pattern. + + 2. When dealing with multiple paths through the tree simultaneously, it + is not straightforward to keep track of captured substrings for the + different matching possibilities, and PCRE's implementation of this + algorithm does not attempt to do this. This means that no captured sub- + strings are available. + + 3. Because no substrings are captured, back references within the pat- + tern are not supported, and cause errors if encountered. + + 4. For the same reason, conditional expressions that use a backrefer- + ence as the condition or test for a specific group recursion are not + supported. + + 5. Because many paths through the tree may be active, the \K escape + sequence, which resets the start of the match when encountered (but may + be on some paths and not on others), is not supported. It causes an + error if encountered. + + 6. Callouts are supported, but the value of the capture_top field is + always 1, and the value of the capture_last field is always -1. + + 7. The \C escape sequence, which (in the standard algorithm) always + matches a single data unit, even in UTF-8, UTF-16 or UTF-32 modes, is + not supported in these modes, because the alternative algorithm moves + through the subject string one character (not data unit) at a time, for + all active paths through the tree. + + 8. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) + are not supported. (*FAIL) is supported, and behaves like a failing + negative assertion. + + +ADVANTAGES OF THE ALTERNATIVE ALGORITHM + + Using the alternative matching algorithm provides the following advan- + tages: + + 1. All possible matches (at a single point in the subject) are automat- + ically found, and in particular, the longest match is found. To find + more than one match using the standard algorithm, you have to do kludgy + things with callouts. + + 2. Because the alternative algorithm scans the subject string just + once, and never needs to backtrack (except for lookbehinds), it is pos- + sible to pass very long subject strings to the matching function in + several pieces, checking for partial matching each time. Although it is + possible to do multi-segment matching using the standard algorithm by + retaining partially matched substrings, it is more complicated. The + pcrepartial documentation gives details of partial matching and dis- + cusses multi-segment matching. + + +DISADVANTAGES OF THE ALTERNATIVE ALGORITHM + + The alternative algorithm suffers from a number of disadvantages: + + 1. It is substantially slower than the standard algorithm. This is + partly because it has to search for all possible matches, but is also + because it is less susceptible to optimization. + + 2. Capturing parentheses and back references are not supported. + + 3. Although atomic groups are supported, their use does not provide the + performance advantage that it does for the standard algorithm. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 November 2013 + Copyright (c) 1997-2012 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREAPI(3) Library Functions Manual PCREAPI(3) + + + +NAME + PCRE - Perl-compatible regular expressions + + #include <pcre.h> + + +PCRE NATIVE API BASIC FUNCTIONS + + pcre *pcre_compile(const char *pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre *pcre_compile2(const char *pattern, int options, + int *errorcodeptr, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre_extra *pcre_study(const pcre *code, int options, + const char **errptr); + + void pcre_free_study(pcre_extra *extra); + + int pcre_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + int pcre_dfa_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + int *workspace, int wscount); + + +PCRE NATIVE API STRING EXTRACTION FUNCTIONS + + int pcre_copy_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + char *buffer, int buffersize); + + int pcre_copy_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, char *buffer, + int buffersize); + + int pcre_get_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + const char **stringptr); + + int pcre_get_stringnumber(const pcre *code, + const char *name); + + int pcre_get_stringtable_entries(const pcre *code, + const char *name, char **first, char **last); + + int pcre_get_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, + const char **stringptr); + + int pcre_get_substring_list(const char *subject, + int *ovector, int stringcount, const char ***listptr); + + void pcre_free_substring(const char *stringptr); + + void pcre_free_substring_list(const char **stringptr); + + +PCRE NATIVE API AUXILIARY FUNCTIONS + + int pcre_jit_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + pcre_jit_stack *jstack); + + pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize); + + void pcre_jit_stack_free(pcre_jit_stack *stack); + + void pcre_assign_jit_stack(pcre_extra *extra, + pcre_jit_callback callback, void *data); + + const unsigned char *pcre_maketables(void); + + int pcre_fullinfo(const pcre *code, const pcre_extra *extra, + int what, void *where); + + int pcre_refcount(pcre *code, int adjust); + + int pcre_config(int what, void *where); + + const char *pcre_version(void); + + int pcre_pattern_to_host_byte_order(pcre *code, + pcre_extra *extra, const unsigned char *tables); + + +PCRE NATIVE API INDIRECTED FUNCTIONS + + void *(*pcre_malloc)(size_t); + + void (*pcre_free)(void *); + + void *(*pcre_stack_malloc)(size_t); + + void (*pcre_stack_free)(void *); + + int (*pcre_callout)(pcre_callout_block *); + + int (*pcre_stack_guard)(void); + + +PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES + + As well as support for 8-bit character strings, PCRE also supports + 16-bit strings (from release 8.30) and 32-bit strings (from release + 8.32), by means of two additional libraries. They can be built as well + as, or instead of, the 8-bit library. To avoid too much complication, + this document describes the 8-bit versions of the functions, with only + occasional references to the 16-bit and 32-bit libraries. + + The 16-bit and 32-bit functions operate in the same way as their 8-bit + counterparts; they just use different data types for their arguments + and results, and their names start with pcre16_ or pcre32_ instead of + pcre_. For every option that has UTF8 in its name (for example, + PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 + replaced by UTF16 or UTF32, respectively. This facility is in fact just + cosmetic; the 16-bit and 32-bit option names define the same bit val- + ues. + + References to bytes and UTF-8 in this document should be read as refer- + ences to 16-bit data units and UTF-16 when using the 16-bit library, or + 32-bit data units and UTF-32 when using the 32-bit library, unless + specified otherwise. More details of the specific differences for the + 16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages. + + +PCRE API OVERVIEW + + PCRE has its own native API, which is described in this document. There + are also some wrapper functions (for the 8-bit library only) that cor- + respond to the POSIX regular expression API, but they do not give + access to all the functionality. They are described in the pcreposix + documentation. Both of these APIs define a set of C function calls. A + C++ wrapper (again for the 8-bit library only) is also distributed with + PCRE. It is documented in the pcrecpp page. + + The native API C function prototypes are defined in the header file + pcre.h, and on Unix-like systems the (8-bit) library itself is called + libpcre. It can normally be accessed by adding -lpcre to the command + for linking an application that uses PCRE. The header file defines the + macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release + numbers for the library. Applications can use these to include support + for different releases of PCRE. + + In a Windows environment, if you want to statically link an application + program against a non-dll pcre.a file, you must define PCRE_STATIC + before including pcre.h or pcrecpp.h, because otherwise the pcre_mal- + loc() and pcre_free() exported functions will be declared + __declspec(dllimport), with unwanted results. + + The functions pcre_compile(), pcre_compile2(), pcre_study(), and + pcre_exec() are used for compiling and matching regular expressions in + a Perl-compatible manner. A sample program that demonstrates the sim- + plest way of using them is provided in the file called pcredemo.c in + the PCRE source distribution. A listing of this program is given in the + pcredemo documentation, and the pcresample documentation describes how + to compile and run it. + + Just-in-time compiler support is an optional feature of PCRE that can + be built in appropriate hardware environments. It greatly speeds up the + matching performance of many patterns. Simple programs can easily + request that it be used if available, by setting an option that is + ignored when it is not relevant. More complicated programs might need + to make use of the functions pcre_jit_stack_alloc(), + pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to control + the JIT code's memory usage. + + From release 8.32 there is also a direct interface for JIT execution, + which gives improved performance. The JIT-specific functions are dis- + cussed in the pcrejit documentation. + + A second matching function, pcre_dfa_exec(), which is not Perl-compati- + ble, is also provided. This uses a different algorithm for the match- + ing. The alternative algorithm finds all possible matches (at a given + point in the subject), and scans the subject just once (unless there + are lookbehind assertions). However, this algorithm does not return + captured substrings. A description of the two matching algorithms and + their advantages and disadvantages is given in the pcrematching docu- + mentation. + + In addition to the main compiling and matching functions, there are + convenience functions for extracting captured substrings from a subject + string that is matched by pcre_exec(). They are: + + pcre_copy_substring() + pcre_copy_named_substring() + pcre_get_substring() + pcre_get_named_substring() + pcre_get_substring_list() + pcre_get_stringnumber() + pcre_get_stringtable_entries() + + pcre_free_substring() and pcre_free_substring_list() are also provided, + to free the memory used for extracted strings. + + The function pcre_maketables() is used to build a set of character + tables in the current locale for passing to pcre_compile(), + pcre_exec(), or pcre_dfa_exec(). This is an optional facility that is + provided for specialist use. Most commonly, no special tables are + passed, in which case internal tables that are generated when PCRE is + built are used. + + The function pcre_fullinfo() is used to find out information about a + compiled pattern. The function pcre_version() returns a pointer to a + string containing the version of PCRE and its date of release. + + The function pcre_refcount() maintains a reference count in a data + block containing a compiled pattern. This is provided for the benefit + of object-oriented applications. + + The global variables pcre_malloc and pcre_free initially contain the + entry points of the standard malloc() and free() functions, respec- + tively. PCRE calls the memory management functions via these variables, + so a calling program can replace them if it wishes to intercept the + calls. This should be done before calling any PCRE functions. + + The global variables pcre_stack_malloc and pcre_stack_free are also + indirections to memory management functions. These special functions + are used only when PCRE is compiled to use the heap for remembering + data, instead of recursive function calls, when running the pcre_exec() + function. See the pcrebuild documentation for details of how to do + this. It is a non-standard way of building PCRE, for use in environ- + ments that have limited stacks. Because of the greater use of memory + management, it runs more slowly. Separate functions are provided so + that special-purpose external code can be used for this case. When + used, these functions are always called in a stack-like manner (last + obtained, first freed), and always for memory blocks of the same size. + There is a discussion about PCRE's stack usage in the pcrestack docu- + mentation. + + The global variable pcre_callout initially contains NULL. It can be set + by the caller to a "callout" function, which PCRE will then call at + specified points during a matching operation. Details are given in the + pcrecallout documentation. + + The global variable pcre_stack_guard initially contains NULL. It can be + set by the caller to a function that is called by PCRE whenever it + starts to compile a parenthesized part of a pattern. When parentheses + are nested, PCRE uses recursive function calls, which use up the system + stack. This function is provided so that applications with restricted + stacks can force a compilation error if the stack runs out. The func- + tion should return zero if all is well, or non-zero to force an error. + + +NEWLINES + + PCRE supports five different conventions for indicating line breaks in + strings: a single CR (carriage return) character, a single LF (line- + feed) character, the two-character sequence CRLF, any of the three pre- + ceding, or any Unicode newline sequence. The Unicode newline sequences + are the three just mentioned, plus the single characters VT (vertical + tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line + separator, U+2028), and PS (paragraph separator, U+2029). + + Each of the first three conventions is used by at least one operating + system as its standard newline sequence. When PCRE is built, a default + can be specified. The default default is LF, which is the Unix stan- + dard. When PCRE is run, the default can be overridden, either when a + pattern is compiled, or when it is matched. + + At compile time, the newline convention can be specified by the options + argument of pcre_compile(), or it can be specified by special text at + the start of the pattern itself; this overrides any other settings. See + the pcrepattern page for details of the special character sequences. + + In the PCRE documentation the word "newline" is used to mean "the char- + acter or pair of characters that indicate a line break". The choice of + newline convention affects the handling of the dot, circumflex, and + dollar metacharacters, the handling of #-comments in /x mode, and, when + CRLF is a recognized line ending sequence, the match position advance- + ment for a non-anchored pattern. There is more detail about this in the + section on pcre_exec() options below. + + The choice of newline convention does not affect the interpretation of + the \n or \r escape sequences, nor does it affect what \R matches, + which is controlled in a similar way, but by separate options. + + +MULTITHREADING + + The PCRE functions can be used in multi-threading applications, with + the proviso that the memory management functions pointed to by + pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the + callout and stack-checking functions pointed to by pcre_callout and + pcre_stack_guard, are shared by all threads. + + The compiled form of a regular expression is not altered during match- + ing, so the same compiled pattern can safely be used by several threads + at once. + + If the just-in-time optimization feature is being used, it needs sepa- + rate memory stack areas for each thread. See the pcrejit documentation + for more details. + + +SAVING PRECOMPILED PATTERNS FOR LATER USE + + The compiled form of a regular expression can be saved and re-used at a + later time, possibly by a different program, and even on a host other + than the one on which it was compiled. Details are given in the + pcreprecompile documentation, which includes a description of the + pcre_pattern_to_host_byte_order() function. However, compiling a regu- + lar expression with one version of PCRE for use with a different ver- + sion is not guaranteed to work and may cause crashes. + + +CHECKING BUILD-TIME OPTIONS + + int pcre_config(int what, void *where); + + The function pcre_config() makes it possible for a PCRE client to dis- + cover which optional features have been compiled into the PCRE library. + The pcrebuild documentation has more details about these optional fea- + tures. + + The first argument for pcre_config() is an integer, specifying which + information is required; the second argument is a pointer to a variable + into which the information is placed. The returned value is zero on + success, or the negative error code PCRE_ERROR_BADOPTION if the value + in the first argument is not recognized. The following information is + available: + + PCRE_CONFIG_UTF8 + + The output is an integer that is set to one if UTF-8 support is avail- + able; otherwise it is set to zero. This value should normally be given + to the 8-bit version of this function, pcre_config(). If it is given to + the 16-bit or 32-bit version of this function, the result is + PCRE_ERROR_BADOPTION. + + PCRE_CONFIG_UTF16 + + The output is an integer that is set to one if UTF-16 support is avail- + able; otherwise it is set to zero. This value should normally be given + to the 16-bit version of this function, pcre16_config(). If it is given + to the 8-bit or 32-bit version of this function, the result is + PCRE_ERROR_BADOPTION. + + PCRE_CONFIG_UTF32 + + The output is an integer that is set to one if UTF-32 support is avail- + able; otherwise it is set to zero. This value should normally be given + to the 32-bit version of this function, pcre32_config(). If it is given + to the 8-bit or 16-bit version of this function, the result is + PCRE_ERROR_BADOPTION. + + PCRE_CONFIG_UNICODE_PROPERTIES + + The output is an integer that is set to one if support for Unicode + character properties is available; otherwise it is set to zero. + + PCRE_CONFIG_JIT + + The output is an integer that is set to one if support for just-in-time + compiling is available; otherwise it is set to zero. + + PCRE_CONFIG_JITTARGET + + The output is a pointer to a zero-terminated "const char *" string. If + JIT support is available, the string contains the name of the architec- + ture for which the JIT compiler is configured, for example "x86 32bit + (little endian + unaligned)". If JIT support is not available, the + result is NULL. + + PCRE_CONFIG_NEWLINE + + The output is an integer whose value specifies the default character + sequence that is recognized as meaning "newline". The values that are + supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 + for CRLF, -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, + ANYCRLF, and ANY yield the same values. However, the value for LF is + normally 21, though some EBCDIC environments use 37. The corresponding + values for CRLF are 3349 and 3365. The default should normally corre- + spond to the standard sequence for your operating system. + + PCRE_CONFIG_BSR + + The output is an integer whose value indicates what character sequences + the \R escape sequence matches by default. A value of 0 means that \R + matches any Unicode line ending sequence; a value of 1 means that \R + matches only CR, LF, or CRLF. The default can be overridden when a pat- + tern is compiled or matched. + + PCRE_CONFIG_LINK_SIZE + + The output is an integer that contains the number of bytes used for + internal linkage in compiled regular expressions. For the 8-bit + library, the value can be 2, 3, or 4. For the 16-bit library, the value + is either 2 or 4 and is still a number of bytes. For the 32-bit + library, the value is either 2 or 4 and is still a number of bytes. The + default value of 2 is sufficient for all but the most massive patterns, + since it allows the compiled pattern to be up to 64K in size. Larger + values allow larger regular expressions to be compiled, at the expense + of slower matching. + + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + + The output is an integer that contains the threshold above which the + POSIX interface uses malloc() for output vectors. Further details are + given in the pcreposix documentation. + + PCRE_CONFIG_PARENS_LIMIT + + The output is a long integer that gives the maximum depth of nesting of + parentheses (of any kind) in a pattern. This limit is imposed to cap + the amount of system stack used when a pattern is compiled. It is spec- + ified when PCRE is built; the default is 250. This limit does not take + into account the stack that may already be used by the calling applica- + tion. For finer control over compilation stack usage, you can set a + pointer to an external checking function in pcre_stack_guard. + + PCRE_CONFIG_MATCH_LIMIT + + The output is a long integer that gives the default limit for the num- + ber of internal matching function calls in a pcre_exec() execution. + Further details are given with pcre_exec() below. + + PCRE_CONFIG_MATCH_LIMIT_RECURSION + + The output is a long integer that gives the default limit for the depth + of recursion when calling the internal matching function in a + pcre_exec() execution. Further details are given with pcre_exec() + below. + + PCRE_CONFIG_STACKRECURSE + + The output is an integer that is set to one if internal recursion when + running pcre_exec() is implemented by recursive function calls that use + the stack to remember their state. This is the usual way that PCRE is + compiled. The output is zero if PCRE was compiled to use blocks of data + on the heap instead of recursive function calls. In this case, + pcre_stack_malloc and pcre_stack_free are called to manage memory + blocks on the heap, thus avoiding the use of the stack. + + +COMPILING A PATTERN + + pcre *pcre_compile(const char *pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre *pcre_compile2(const char *pattern, int options, + int *errorcodeptr, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + Either of the functions pcre_compile() or pcre_compile2() can be called + to compile a pattern into an internal form. The only difference between + the two interfaces is that pcre_compile2() has an additional argument, + errorcodeptr, via which a numerical error code can be returned. To + avoid too much repetition, we refer just to pcre_compile() below, but + the information applies equally to pcre_compile2(). + + The pattern is a C string terminated by a binary zero, and is passed in + the pattern argument. A pointer to a single block of memory that is + obtained via pcre_malloc is returned. This contains the compiled code + and related data. The pcre type is defined for the returned block; this + is a typedef for a structure whose contents are not externally defined. + It is up to the caller to free the memory (via pcre_free) when it is no + longer required. + + Although the compiled code of a PCRE regex is relocatable, that is, it + does not depend on memory location, the complete pcre data block is not + fully relocatable, because it may contain a copy of the tableptr argu- + ment, which is an address (see below). + + The options argument contains various bit settings that affect the com- + pilation. It should be zero if no options are required. The available + options are described below. Some of them (in particular, those that + are compatible with Perl, but some others as well) can also be set and + unset from within the pattern (see the detailed description in the + pcrepattern documentation). For those options that can be different in + different parts of the pattern, the contents of the options argument + specifies their settings at the start of compilation and execution. The + PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and + PCRE_NO_START_OPTIMIZE options can be set at the time of matching as + well as at compile time. + + If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise, + if compilation of a pattern fails, pcre_compile() returns NULL, and + sets the variable pointed to by errptr to point to a textual error mes- + sage. This is a static string that is part of the library. You must not + try to free it. Normally, the offset from the start of the pattern to + the data unit that was being processed when the error was discovered is + placed in the variable pointed to by erroffset, which must not be NULL + (if it is, an immediate error is given). However, for an invalid UTF-8 + or UTF-16 string, the offset is that of the first data unit of the + failing character. + + Some errors are not detected until the whole pattern has been scanned; + in these cases, the offset passed back is the length of the pattern. + Note that the offset is in data units, not characters, even in a UTF + mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char- + acter. + + If pcre_compile2() is used instead of pcre_compile(), and the error- + codeptr argument is not NULL, a non-zero error code number is returned + via this argument in the event of an error. This is in addition to the + textual error message. Error codes and messages are listed below. + + If the final argument, tableptr, is NULL, PCRE uses a default set of + character tables that are built when PCRE is compiled, using the + default C locale. Otherwise, tableptr must be an address that is the + result of a call to pcre_maketables(). This value is stored with the + compiled pattern, and used again by pcre_exec() and pcre_dfa_exec() + when the pattern is matched. For more discussion, see the section on + locale support below. + + This code fragment shows a typical straightforward call to pcre_com- + pile(): + + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ + + The following names for option bits are defined in the pcre.h header + file: + + PCRE_ANCHORED + + If this bit is set, the pattern is forced to be "anchored", that is, it + is constrained to match only at the first matching point in the string + that is being searched (the "subject string"). This effect can also be + achieved by appropriate constructs in the pattern itself, which is the + only way to do it in Perl. + + PCRE_AUTO_CALLOUT + + If this bit is set, pcre_compile() automatically inserts callout items, + all with number 255, before each pattern item. For discussion of the + callout facility, see the pcrecallout documentation. + + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE + + These options (which are mutually exclusive) control what the \R escape + sequence matches. The choice is either to match only CR, LF, or CRLF, + or to match any Unicode newline sequence. The default is specified when + PCRE is built. It can be overridden from within the pattern, or by set- + ting an option when a compiled pattern is matched. + + PCRE_CASELESS + + If this bit is set, letters in the pattern match both upper and lower + case letters. It is equivalent to Perl's /i option, and it can be + changed within a pattern by a (?i) option setting. In UTF-8 mode, PCRE + always understands the concept of case for characters whose values are + less than 128, so caseless matching is always possible. For characters + with higher values, the concept of case is supported if PCRE is com- + piled with Unicode property support, but not otherwise. If you want to + use caseless matching for characters 128 and above, you must ensure + that PCRE is compiled with Unicode property support as well as with + UTF-8 support. + + PCRE_DOLLAR_ENDONLY + + If this bit is set, a dollar metacharacter in the pattern matches only + at the end of the subject string. Without this option, a dollar also + matches immediately before a newline at the end of the string (but not + before any other newlines). The PCRE_DOLLAR_ENDONLY option is ignored + if PCRE_MULTILINE is set. There is no equivalent to this option in + Perl, and no way to set it within a pattern. + + PCRE_DOTALL + + If this bit is set, a dot metacharacter in the pattern matches a char- + acter of any value, including one that indicates a newline. However, it + only ever matches one character, even if newlines are coded as CRLF. + Without this option, a dot does not match when the current position is + at a newline. This option is equivalent to Perl's /s option, and it can + be changed within a pattern by a (?s) option setting. A negative class + such as [^a] always matches newline characters, independent of the set- + ting of this option. + + PCRE_DUPNAMES + + If this bit is set, names used to identify capturing subpatterns need + not be unique. This can be helpful for certain types of pattern when it + is known that only one instance of the named subpattern can ever be + matched. There are more details of named subpatterns below; see also + the pcrepattern documentation. + + PCRE_EXTENDED + + If this bit is set, most white space characters in the pattern are + totally ignored except when escaped or inside a character class. How- + ever, white space is not allowed within sequences such as (?> that + introduce various parenthesized subpatterns, nor within a numerical + quantifier such as {1,3}. However, ignorable white space is permitted + between an item and a following quantifier and between a quantifier and + a following + that indicates possessiveness. + + White space did not used to include the VT character (code 11), because + Perl did not treat this character as white space. However, Perl changed + at release 5.18, so PCRE followed at release 8.34, and VT is now + treated as white space. + + PCRE_EXTENDED also causes characters between an unescaped # outside a + character class and the next newline, inclusive, to be ignored. + PCRE_EXTENDED is equivalent to Perl's /x option, and it can be changed + within a pattern by a (?x) option setting. + + Which characters are interpreted as newlines is controlled by the + options passed to pcre_compile() or by a special sequence at the start + of the pattern, as described in the section entitled "Newline conven- + tions" in the pcrepattern documentation. Note that the end of this type + of comment is a literal newline sequence in the pattern; escape + sequences that happen to represent a newline do not count. + + This option makes it possible to include comments inside complicated + patterns. Note, however, that this applies only to data characters. + White space characters may never appear within special character + sequences in a pattern, for example within the sequence (?( that intro- + duces a conditional subpattern. + + PCRE_EXTRA + + This option was invented in order to turn on additional functionality + of PCRE that is incompatible with Perl, but it is currently of very + little use. When set, any backslash in a pattern that is followed by a + letter that has no special meaning causes an error, thus reserving + these combinations for future expansion. By default, as in Perl, a + backslash followed by a letter with no special meaning is treated as a + literal. (Perl can, however, be persuaded to give an error for this, by + running it with the -w option.) There are at present no other features + controlled by this option. It can also be set by a (?X) option setting + within a pattern. + + PCRE_FIRSTLINE + + If this option is set, an unanchored pattern is required to match + before or at the first newline in the subject string, though the + matched text may continue over the newline. + + PCRE_JAVASCRIPT_COMPAT + + If this option is set, PCRE's behaviour is changed in some ways so that + it is compatible with JavaScript rather than Perl. The changes are as + follows: + + (1) A lone closing square bracket in a pattern causes a compile-time + error, because this is illegal in JavaScript (by default it is treated + as a data character). Thus, the pattern AB]CD becomes illegal when this + option is set. + + (2) At run time, a back reference to an unset subpattern group matches + an empty string (by default this causes the current matching alterna- + tive to fail). A pattern such as (\1)(a) succeeds when this option is + set (assuming it can find an "a" in the subject), whereas it fails by + default, for Perl compatibility. + + (3) \U matches an upper case "U" character; by default \U causes a com- + pile time error (Perl uses \U to upper case subsequent characters). + + (4) \u matches a lower case "u" character unless it is followed by four + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, \u causes a compile time error (Perl + uses it to upper case the following character). + + (5) \x matches a lower case "x" character unless it is followed by two + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, as in Perl, a hexadecimal number is + always expected after \x, but it may have zero, one, or two digits (so, + for example, \xz matches a binary zero character followed by z). + + PCRE_MULTILINE + + By default, for the purposes of matching "start of line" and "end of + line", PCRE treats the subject string as consisting of a single line of + characters, even if it actually contains newlines. The "start of line" + metacharacter (^) matches only at the start of the string, and the "end + of line" metacharacter ($) matches only at the end of the string, or + before a terminating newline (except when PCRE_DOLLAR_ENDONLY is set). + Note, however, that unless PCRE_DOTALL is set, the "any character" + metacharacter (.) does not match at a newline. This behaviour (for ^, + $, and dot) is the same as Perl. + + When PCRE_MULTILINE it is set, the "start of line" and "end of line" + constructs match immediately following or immediately before internal + newlines in the subject string, respectively, as well as at the very + start and end. This is equivalent to Perl's /m option, and it can be + changed within a pattern by a (?m) option setting. If there are no new- + lines in a subject string, or no occurrences of ^ or $ in a pattern, + setting PCRE_MULTILINE has no effect. + + PCRE_NEVER_UTF + + This option locks out interpretation of the pattern as UTF-8 (or UTF-16 + or UTF-32 in the 16-bit and 32-bit libraries). In particular, it pre- + vents the creator of the pattern from switching to UTF interpretation + by starting the pattern with (*UTF). This may be useful in applications + that process patterns from external sources. The combination of + PCRE_UTF8 and PCRE_NEVER_UTF also causes an error. + + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY + + These options override the default newline definition that was chosen + when PCRE was built. Setting the first or the second specifies that a + newline is indicated by a single character (CR or LF, respectively). + Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by the + two-character CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies + that any of the three preceding sequences should be recognized. Setting + PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should be + recognized. + + In an ASCII/Unicode environment, the Unicode newline sequences are the + three just mentioned, plus the single characters VT (vertical tab, + U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep- + arator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit + library, the last two are recognized only in UTF-8 mode. + + When PCRE is compiled to run in an EBCDIC (mainframe) environment, the + code for CR is 0x0d, the same as ASCII. However, the character code for + LF is normally 0x15, though in some EBCDIC environments 0x25 is used. + Whichever of these is not LF is made to correspond to Unicode's NEL + character. EBCDIC codes are all less than 256. For more details, see + the pcrebuild documentation. + + The newline setting in the options word uses three bits that are + treated as a number, giving eight possibilities. Currently only six are + used (default plus the five values above). This means that if you set + more than one newline option, the combination may or may not be sensi- + ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to + PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers and + cause an error. + + The only time that a line break in a pattern is specially recognized + when compiling is when PCRE_EXTENDED is set. CR and LF are white space + characters, and so are ignored in this mode. Also, an unescaped # out- + side a character class indicates a comment that lasts until after the + next line break sequence. In other circumstances, line break sequences + in patterns are treated as literal data. + + The newline option that is set at compile time becomes the default that + is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden. + + PCRE_NO_AUTO_CAPTURE + + If this option is set, it disables the use of numbered capturing paren- + theses in the pattern. Any opening parenthesis that is not followed by + ? behaves as if it were followed by ?: but named parentheses can still + be used for capturing (and they acquire numbers in the usual way). + There is no equivalent of this option in Perl. + + PCRE_NO_AUTO_POSSESS + + If this option is set, it disables "auto-possessification". This is an + optimization that, for example, turns a+b into a++b in order to avoid + backtracks into a+ that can never be successful. However, if callouts + are in use, auto-possessification means that some of them are never + taken. You can set this option if you want the matching functions to do + a full unoptimized search and run all the callouts, but it is mainly + provided for testing purposes. + + PCRE_NO_START_OPTIMIZE + + This is an option that acts at matching time; that is, it is really an + option for pcre_exec() or pcre_dfa_exec(). If it is set at compile + time, it is remembered with the compiled pattern and assumed at match- + ing time. This is necessary if you want to use JIT execution, because + the JIT compiler needs to know whether or not this option is set. For + details see the discussion of PCRE_NO_START_OPTIMIZE below. + + PCRE_UCP + + This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, + \w, and some of the POSIX character classes. By default, only ASCII + characters are recognized, but if PCRE_UCP is set, Unicode properties + are used instead to classify characters. More details are given in the + section on generic character types in the pcrepattern page. If you set + PCRE_UCP, matching one of the items it affects takes much longer. The + option is available only if PCRE has been compiled with Unicode prop- + erty support. + + PCRE_UNGREEDY + + This option inverts the "greediness" of the quantifiers so that they + are not greedy by default, but become greedy if followed by "?". It is + not compatible with Perl. It can also be set by a (?U) option setting + within the pattern. + + PCRE_UTF8 + + This option causes PCRE to regard both the pattern and the subject as + strings of UTF-8 characters instead of single-byte strings. However, it + is available only when PCRE is built to include UTF support. If not, + the use of this option provokes an error. Details of how this option + changes the behaviour of PCRE are given in the pcreunicode page. + + PCRE_NO_UTF8_CHECK + + When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is + automatically checked. There is a discussion about the validity of + UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence is + found, pcre_compile() returns an error. If you already know that your + pattern is valid, and you want to skip this check for performance rea- + sons, you can set the PCRE_NO_UTF8_CHECK option. When it is set, the + effect of passing an invalid UTF-8 string as a pattern is undefined. It + may cause your program to crash or loop. Note that this option can also + be passed to pcre_exec() and pcre_dfa_exec(), to suppress the validity + checking of subject strings only. If the same string is being matched + many times, the option can be safely set for the second and subsequent + matchings to improve performance. + + +COMPILATION ERROR CODES + + The following table lists the error codes than may be returned by + pcre_compile2(), along with the error messages that may be returned by + both compiling functions. Note that error messages are always 8-bit + ASCII strings, even in 16-bit or 32-bit mode. As PCRE has developed, + some error codes have fallen out of use. To avoid confusion, they have + not been re-used. + + 0 no error + 1 \ at end of pattern + 2 \c at end of pattern + 3 unrecognized character follows \ + 4 numbers out of order in {} quantifier + 5 number too big in {} quantifier + 6 missing terminating ] for character class + 7 invalid escape sequence in character class + 8 range out of order in character class + 9 nothing to repeat + 10 [this code is not in use] + 11 internal error: unexpected repeat + 12 unrecognized character after (? or (?- + 13 POSIX named classes are supported only within a class + 14 missing ) + 15 reference to non-existent subpattern + 16 erroffset passed as NULL + 17 unknown option bit(s) set + 18 missing ) after comment + 19 [this code is not in use] + 20 regular expression is too large + 21 failed to get memory + 22 unmatched parentheses + 23 internal error: code overflow + 24 unrecognized character after (?< + 25 lookbehind assertion is not fixed length + 26 malformed number or name after (?( + 27 conditional group contains more than two branches + 28 assertion expected after (?( + 29 (?R or (?[+-]digits must be followed by ) + 30 unknown POSIX class name + 31 POSIX collating elements are not supported + 32 this version of PCRE is compiled without UTF support + 33 [this code is not in use] + 34 character value in \x{} or \o{} is too large + 35 invalid condition (?(0) + 36 \C not allowed in lookbehind assertion + 37 PCRE does not support \L, \l, \N{name}, \U, or \u + 38 number after (?C is > 255 + 39 closing ) for (?C expected + 40 recursive call could loop indefinitely + 41 unrecognized character after (?P + 42 syntax error in subpattern name (missing terminator) + 43 two named subpatterns have the same name + 44 invalid UTF-8 string (specifically UTF-8) + 45 support for \P, \p, and \X has not been compiled + 46 malformed \P or \p sequence + 47 unknown property name after \P or \p + 48 subpattern name is too long (maximum 32 characters) + 49 too many named subpatterns (maximum 10000) + 50 [this code is not in use] + 51 octal value is greater than \377 in 8-bit non-UTF-8 mode + 52 internal error: overran compiling workspace + 53 internal error: previously-checked referenced subpattern + not found + 54 DEFINE group contains more than one branch + 55 repeating a DEFINE group is not allowed + 56 inconsistent NEWLINE options + 57 \g is not followed by a braced, angle-bracketed, or quoted + name/number or by a plain number + 58 a numbered reference must not be zero + 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT) + 60 (*VERB) not recognized or malformed + 61 number is too big + 62 subpattern name expected + 63 digit expected after (?+ + 64 ] is an invalid data character in JavaScript compatibility mode + 65 different names for subpatterns of the same number are + not allowed + 66 (*MARK) must have an argument + 67 this version of PCRE is not compiled with Unicode property + support + 68 \c must be followed by an ASCII character + 69 \k is not followed by a braced, angle-bracketed, or quoted name + 70 internal error: unknown opcode in find_fixedlength() + 71 \N is not supported in a class + 72 too many forward references + 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff) + 74 invalid UTF-16 string (specifically UTF-16) + 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN) + 76 character value in \u.... sequence is too large + 77 invalid UTF-32 string (specifically UTF-32) + 78 setting UTF is disabled by the application + 79 non-hex character in \x{} (closing brace missing?) + 80 non-octal character in \o{} (closing brace missing?) + 81 missing opening brace after \o + 82 parentheses are too deeply nested + 83 invalid range in character class + 84 group name must start with a non-digit + 85 parentheses are too deeply nested (stack check) + + The numbers 32 and 10000 in errors 48 and 49 are defaults; different + values may be used if the limits were changed when PCRE was built. + + +STUDYING A PATTERN + + pcre_extra *pcre_study(const pcre *code, int options, + const char **errptr); + + If a compiled pattern is going to be used several times, it is worth + spending more time analyzing it in order to speed up the time taken for + matching. The function pcre_study() takes a pointer to a compiled pat- + tern as its first argument. If studying the pattern produces additional + information that will help speed up matching, pcre_study() returns a + pointer to a pcre_extra block, in which the study_data field points to + the results of the study. + + The returned value from pcre_study() can be passed directly to + pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block also con- + tains other fields that can be set by the caller before the block is + passed; these are described below in the section on matching a pattern. + + If studying the pattern does not produce any useful information, + pcre_study() returns NULL by default. In that circumstance, if the + calling program wants to pass any of the other fields to pcre_exec() or + pcre_dfa_exec(), it must set up its own pcre_extra block. However, if + pcre_study() is called with the PCRE_STUDY_EXTRA_NEEDED option, it + returns a pcre_extra block even if studying did not find any additional + information. It may still return NULL, however, if an error occurs in + pcre_study(). + + The second argument of pcre_study() contains option bits. There are + three further options in addition to PCRE_STUDY_EXTRA_NEEDED: + + PCRE_STUDY_JIT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + + If any of these are set, and the just-in-time compiler is available, + the pattern is further compiled into machine code that executes much + faster than the pcre_exec() interpretive matching function. If the + just-in-time compiler is not available, these options are ignored. All + undefined bits in the options argument must be zero. + + JIT compilation is a heavyweight optimization. It can take some time + for patterns to be analyzed, and for one-off matches and simple pat- + terns the benefit of faster execution might be offset by a much slower + study time. Not all patterns can be optimized by the JIT compiler. For + those that cannot be handled, matching automatically falls back to the + pcre_exec() interpreter. For more details, see the pcrejit documenta- + tion. + + The third argument for pcre_study() is a pointer for an error message. + If studying succeeds (even if no data is returned), the variable it + points to is set to NULL. Otherwise it is set to point to a textual + error message. This is a static string that is part of the library. You + must not try to free it. You should test the error pointer for NULL + after calling pcre_study(), to be sure that it has run successfully. + + When you are finished with a pattern, you can free the memory used for + the study data by calling pcre_free_study(). This function was added to + the API for release 8.20. For earlier versions, the memory could be + freed with pcre_free(), just like the pattern itself. This will still + work in cases where JIT optimization is not used, but it is advisable + to change to the new function when convenient. + + This is a typical way in which pcre_study() is used (except that in a + real application there should be tests for errors): + + int rc; + pcre *re; + pcre_extra *sd; + re = pcre_compile("pattern", 0, &error, &erroroffset, NULL); + sd = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options */ + &error); /* set to NULL or points to a message */ + rc = pcre_exec( /* see below for details of pcre_exec() options */ + re, sd, "subject", 7, 0, 0, ovector, 30); + ... + pcre_free_study(sd); + pcre_free(re); + + Studying a pattern does two things: first, a lower bound for the length + of subject string that is needed to match the pattern is computed. This + does not mean that there are any strings of that length that match, but + it does guarantee that no shorter strings match. The value is used to + avoid wasting time by trying to match strings that are shorter than the + lower bound. You can find out the value in a calling program via the + pcre_fullinfo() function. + + Studying a pattern is also useful for non-anchored patterns that do not + have a single fixed starting character. A bitmap of possible starting + bytes is created. This speeds up finding a position in the subject at + which to start matching. (In 16-bit mode, the bitmap is used for 16-bit + values less than 256. In 32-bit mode, the bitmap is used for 32-bit + values less than 256.) + + These two optimizations apply to both pcre_exec() and pcre_dfa_exec(), + and the information is also used by the JIT compiler. The optimiza- + tions can be disabled by setting the PCRE_NO_START_OPTIMIZE option. + You might want to do this if your pattern contains callouts or (*MARK) + and you want to make use of these facilities in cases where matching + fails. + + PCRE_NO_START_OPTIMIZE can be specified at either compile time or exe- + cution time. However, if PCRE_NO_START_OPTIMIZE is passed to + pcre_exec(), (that is, after any JIT compilation has happened) JIT exe- + cution is disabled. For JIT execution to work with PCRE_NO_START_OPTI- + MIZE, the option must be set at compile time. + + There is a longer discussion of PCRE_NO_START_OPTIMIZE below. + + +LOCALE SUPPORT + + PCRE handles caseless matching, and determines whether characters are + letters, digits, or whatever, by reference to a set of tables, indexed + by character code point. When running in UTF-8 mode, or in the 16- or + 32-bit libraries, this applies only to characters with code points less + than 256. By default, higher-valued code points never match escapes + such as \w or \d. However, if PCRE is built with Unicode property sup- + port, all characters can be tested with \p and \P, or, alternatively, + the PCRE_UCP option can be set when a pattern is compiled; this causes + \w and friends to use Unicode property support instead of the built-in + tables. + + The use of locales with Unicode is discouraged. If you are handling + characters with code points greater than 128, you should either use + Unicode support, or use locales, but not try to mix the two. + + PCRE contains an internal set of tables that are used when the final + argument of pcre_compile() is NULL. These are sufficient for many + applications. Normally, the internal tables recognize only ASCII char- + acters. However, when PCRE is built, it is possible to cause the inter- + nal tables to be rebuilt in the default "C" locale of the local system, + which may cause them to be different. + + The internal tables can always be overridden by tables supplied by the + application that calls PCRE. These may be created in a different locale + from the default. As more and more applications change to using Uni- + code, the need for this locale support is expected to die away. + + External tables are built by calling the pcre_maketables() function, + which has no arguments, in the relevant locale. The result can then be + passed to pcre_compile() as often as necessary. For example, to build + and use tables that are appropriate for the French locale (where + accented characters with values greater than 128 are treated as let- + ters), the following code could be used: + + setlocale(LC_CTYPE, "fr_FR"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); + + The locale name "fr_FR" is used on Linux and other Unix-like systems; + if you are using Windows, the name for the French locale is "french". + + When pcre_maketables() runs, the tables are built in memory that is + obtained via pcre_malloc. It is the caller's responsibility to ensure + that the memory containing the tables remains available for as long as + it is needed. + + The pointer that is passed to pcre_compile() is saved with the compiled + pattern, and the same tables are used via this pointer by pcre_study() + and also by pcre_exec() and pcre_dfa_exec(). Thus, for any single pat- + tern, compilation, studying and matching all happen in the same locale, + but different patterns can be processed in different locales. + + It is possible to pass a table pointer or NULL (indicating the use of + the internal tables) to pcre_exec() or pcre_dfa_exec() (see the discus- + sion below in the section on matching a pattern). This facility is pro- + vided for use with pre-compiled patterns that have been saved and + reloaded. Character tables are not saved with patterns, so if a non- + standard table was used at compile time, it must be provided again when + the reloaded pattern is matched. Attempting to use this facility to + match a pattern in a different locale from the one in which it was com- + piled is likely to lead to anomalous (usually incorrect) results. + + +INFORMATION ABOUT A PATTERN + + int pcre_fullinfo(const pcre *code, const pcre_extra *extra, + int what, void *where); + + The pcre_fullinfo() function returns information about a compiled pat- + tern. It replaces the pcre_info() function, which was removed from the + library at version 8.30, after more than 10 years of obsolescence. + + The first argument for pcre_fullinfo() is a pointer to the compiled + pattern. The second argument is the result of pcre_study(), or NULL if + the pattern was not studied. The third argument specifies which piece + of information is required, and the fourth argument is a pointer to a + variable to receive the data. The yield of the function is zero for + success, or one of the following negative numbers: + + PCRE_ERROR_NULL the argument code was NULL + the argument where was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADENDIANNESS the pattern was compiled with different + endianness + PCRE_ERROR_BADOPTION the value of what was invalid + PCRE_ERROR_UNSET the requested field is not set + + The "magic number" is placed at the start of each compiled pattern as + an simple check against passing an arbitrary memory pointer. The endi- + anness error can occur if a compiled pattern is saved and reloaded on a + different host. Here is a typical call of pcre_fullinfo(), to obtain + the length of the compiled pattern: + + int rc; + size_t length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + sd, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ + + The possible values for the third argument are defined in pcre.h, and + are as follows: + + PCRE_INFO_BACKREFMAX + + Return the number of the highest back reference in the pattern. The + fourth argument should point to an int variable. Zero is returned if + there are no back references. + + PCRE_INFO_CAPTURECOUNT + + Return the number of capturing subpatterns in the pattern. The fourth + argument should point to an int variable. + + PCRE_INFO_DEFAULT_TABLES + + Return a pointer to the internal default character tables within PCRE. + The fourth argument should point to an unsigned char * variable. This + information call is provided for internal use by the pcre_study() func- + tion. External callers can cause PCRE to use its internal tables by + passing a NULL table pointer. + + PCRE_INFO_FIRSTBYTE (deprecated) + + Return information about the first data unit of any matched string, for + a non-anchored pattern. The name of this option refers to the 8-bit + library, where data units are bytes. The fourth argument should point + to an int variable. Negative values are used for special cases. How- + ever, this means that when the 32-bit library is in non-UTF-32 mode, + the full 32-bit range of characters cannot be returned. For this rea- + son, this value is deprecated; use PCRE_INFO_FIRSTCHARACTERFLAGS and + PCRE_INFO_FIRSTCHARACTER instead. + + If there is a fixed first value, for example, the letter "c" from a + pattern such as (cat|cow|coyote), its value is returned. In the 8-bit + library, the value is always less than 256. In the 16-bit library the + value can be up to 0xffff. In the 32-bit library the value can be up to + 0x10ffff. + + If there is no fixed first value, and if either + + (a) the pattern was compiled with the PCRE_MULTILINE option, and every + branch starts with "^", or + + (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not + set (if it were set, the pattern would be anchored), + + -1 is returned, indicating that the pattern matches only at the start + of a subject string or after any newline within the string. Otherwise + -2 is returned. For anchored patterns, -2 is returned. + + PCRE_INFO_FIRSTCHARACTER + + Return the value of the first data unit (non-UTF character) of any + matched string in the situation where PCRE_INFO_FIRSTCHARACTERFLAGS + returns 1; otherwise return 0. The fourth argument should point to an + uint_t variable. + + In the 8-bit library, the value is always less than 256. In the 16-bit + library the value can be up to 0xffff. In the 32-bit library in UTF-32 + mode the value can be up to 0x10ffff, and up to 0xffffffff when not + using UTF-32 mode. + + PCRE_INFO_FIRSTCHARACTERFLAGS + + Return information about the first data unit of any matched string, for + a non-anchored pattern. The fourth argument should point to an int + variable. + + If there is a fixed first value, for example, the letter "c" from a + pattern such as (cat|cow|coyote), 1 is returned, and the character + value can be retrieved using PCRE_INFO_FIRSTCHARACTER. If there is no + fixed first value, and if either + + (a) the pattern was compiled with the PCRE_MULTILINE option, and every + branch starts with "^", or + + (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not + set (if it were set, the pattern would be anchored), + + 2 is returned, indicating that the pattern matches only at the start of + a subject string or after any newline within the string. Otherwise 0 is + returned. For anchored patterns, 0 is returned. + + PCRE_INFO_FIRSTTABLE + + If the pattern was studied, and this resulted in the construction of a + 256-bit table indicating a fixed set of values for the first data unit + in any matching string, a pointer to the table is returned. Otherwise + NULL is returned. The fourth argument should point to an unsigned char + * variable. + + PCRE_INFO_HASCRORLF + + Return 1 if the pattern contains any explicit matches for CR or LF + characters, otherwise 0. The fourth argument should point to an int + variable. An explicit match is either a literal CR or LF character, or + \r or \n. + + PCRE_INFO_JCHANGED + + Return 1 if the (?J) or (?-J) option setting is used in the pattern, + otherwise 0. The fourth argument should point to an int variable. (?J) + and (?-J) set and unset the local PCRE_DUPNAMES option, respectively. + + PCRE_INFO_JIT + + Return 1 if the pattern was studied with one of the JIT options, and + just-in-time compiling was successful. The fourth argument should point + to an int variable. A return value of 0 means that JIT support is not + available in this version of PCRE, or that the pattern was not studied + with a JIT option, or that the JIT compiler could not handle this par- + ticular pattern. See the pcrejit documentation for details of what can + and cannot be handled. + + PCRE_INFO_JITSIZE + + If the pattern was successfully studied with a JIT option, return the + size of the JIT compiled code, otherwise return zero. The fourth argu- + ment should point to a size_t variable. + + PCRE_INFO_LASTLITERAL + + Return the value of the rightmost literal data unit that must exist in + any matched string, other than at its start, if such a value has been + recorded. The fourth argument should point to an int variable. If there + is no such value, -1 is returned. For anchored patterns, a last literal + value is recorded only if it follows something of variable length. For + example, for the pattern /^a\d+z\d+/ the returned value is "z", but for + /^a\dz\d/ the returned value is -1. + + Since for the 32-bit library using the non-UTF-32 mode, this function + is unable to return the full 32-bit range of characters, this value is + deprecated; instead the PCRE_INFO_REQUIREDCHARFLAGS and + PCRE_INFO_REQUIREDCHAR values should be used. + + PCRE_INFO_MATCH_EMPTY + + Return 1 if the pattern can match an empty string, otherwise 0. The + fourth argument should point to an int variable. + + PCRE_INFO_MATCHLIMIT + + If the pattern set a match limit by including an item of the form + (*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth + argument should point to an unsigned 32-bit integer. If no such value + has been set, the call to pcre_fullinfo() returns the error + PCRE_ERROR_UNSET. + + PCRE_INFO_MAXLOOKBEHIND + + Return the number of characters (NB not data units) in the longest + lookbehind assertion in the pattern. This information is useful when + doing multi-segment matching using the partial matching facilities. + Note that the simple assertions \b and \B require a one-character look- + behind. \A also registers a one-character lookbehind, though it does + not actually inspect the previous character. This is to ensure that at + least one character from the old segment is retained when a new segment + is processed. Otherwise, if there are no lookbehinds in the pattern, \A + might match incorrectly at the start of a new segment. + + PCRE_INFO_MINLENGTH + + If the pattern was studied and a minimum length for matching subject + strings was computed, its value is returned. Otherwise the returned + value is -1. The value is a number of characters, which in UTF mode may + be different from the number of data units. The fourth argument should + point to an int variable. A non-negative value is a lower bound to the + length of any matching string. There may not be any strings of that + length that do actually match, but every string that does match is at + least that long. + + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE + + PCRE supports the use of named as well as numbered capturing parenthe- + ses. The names are just an additional way of identifying the parenthe- + ses, which still acquire numbers. Several convenience functions such as + pcre_get_named_substring() are provided for extracting captured sub- + strings by name. It is also possible to extract the data directly, by + first converting the name to a number in order to access the correct + pointers in the output vector (described with pcre_exec() below). To do + the conversion, you need to use the name-to-number map, which is + described by these three values. + + The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT + gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size + of each entry; both of these return an int value. The entry size + depends on the length of the longest name. PCRE_INFO_NAMETABLE returns + a pointer to the first entry of the table. This is a pointer to char in + the 8-bit library, where the first two bytes of each entry are the num- + ber of the capturing parenthesis, most significant byte first. In the + 16-bit library, the pointer points to 16-bit data units, the first of + which contains the parenthesis number. In the 32-bit library, the + pointer points to 32-bit data units, the first of which contains the + parenthesis number. The rest of the entry is the corresponding name, + zero terminated. + + The names are in alphabetical order. If (?| is used to create multiple + groups with the same number, as described in the section on duplicate + subpattern numbers in the pcrepattern page, the groups may be given the + same name, but there is only one entry in the table. Different names + for groups of the same number are not permitted. Duplicate names for + subpatterns with different numbers are permitted, but only if PCRE_DUP- + NAMES is set. They appear in the table in the order in which they were + found in the pattern. In the absence of (?| this is the order of + increasing number; when (?| is used this is not necessarily the case + because later subpatterns may have lower numbers. + + As a simple example of the name/number table, consider the following + pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is + set, so white space - including newlines - is ignored): + + (?<date> (?<year>(\d\d)?\d\d) - + (?<month>\d\d) - (?<day>\d\d) ) + + There are four named subpatterns, so the table has four entries, and + each entry in the table is eight bytes long. The table is as follows, + with non-printing bytes shows in hexadecimal, and undefined bytes shown + as ??: + + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? + + When writing code to extract data from named subpatterns using the + name-to-number map, remember that the length of the entries is likely + to be different for each compiled pattern. + + PCRE_INFO_OKPARTIAL + + Return 1 if the pattern can be used for partial matching with + pcre_exec(), otherwise 0. The fourth argument should point to an int + variable. From release 8.00, this always returns 1, because the + restrictions that previously applied to partial matching have been + lifted. The pcrepartial documentation gives details of partial match- + ing. + + PCRE_INFO_OPTIONS + + Return a copy of the options with which the pattern was compiled. The + fourth argument should point to an unsigned long int variable. These + option bits are those specified in the call to pcre_compile(), modified + by any top-level option settings at the start of the pattern itself. In + other words, they are the options that will be in force when matching + starts. For example, if the pattern /(?im)abc(?-i)d/ is compiled with + the PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE, + and PCRE_EXTENDED. + + A pattern is automatically anchored by PCRE if all of its top-level + alternatives begin with one of the following: + + ^ unless PCRE_MULTILINE is set + \A always + \G always + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears + + For such patterns, the PCRE_ANCHORED bit is set in the options returned + by pcre_fullinfo(). + + PCRE_INFO_RECURSIONLIMIT + + If the pattern set a recursion limit by including an item of the form + (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth + argument should point to an unsigned 32-bit integer. If no such value + has been set, the call to pcre_fullinfo() returns the error + PCRE_ERROR_UNSET. + + PCRE_INFO_SIZE + + Return the size of the compiled pattern in bytes (for all three + libraries). The fourth argument should point to a size_t variable. This + value does not include the size of the pcre structure that is returned + by pcre_compile(). The value that is passed as the argument to + pcre_malloc() when pcre_compile() is getting memory in which to place + the compiled data is the value returned by this option plus the size of + the pcre structure. Studying a compiled pattern, with or without JIT, + does not alter the value returned by this option. + + PCRE_INFO_STUDYSIZE + + Return the size in bytes (for all three libraries) of the data block + pointed to by the study_data field in a pcre_extra block. If pcre_extra + is NULL, or there is no study data, zero is returned. The fourth argu- + ment should point to a size_t variable. The study_data field is set by + pcre_study() to record information that will speed up matching (see the + section entitled "Studying a pattern" above). The format of the + study_data block is private, but its length is made available via this + option so that it can be saved and restored (see the pcreprecompile + documentation for details). + + PCRE_INFO_REQUIREDCHARFLAGS + + Returns 1 if there is a rightmost literal data unit that must exist in + any matched string, other than at its start. The fourth argument should + point to an int variable. If there is no such value, 0 is returned. If + returning 1, the character value itself can be retrieved using + PCRE_INFO_REQUIREDCHAR. + + For anchored patterns, a last literal value is recorded only if it fol- + lows something of variable length. For example, for the pattern + /^a\d+z\d+/ the returned value 1 (with "z" returned from + PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0. + + PCRE_INFO_REQUIREDCHAR + + Return the value of the rightmost literal data unit that must exist in + any matched string, other than at its start, if such a value has been + recorded. The fourth argument should point to an uint32_t variable. If + there is no such value, 0 is returned. + + +REFERENCE COUNTS + + int pcre_refcount(pcre *code, int adjust); + + The pcre_refcount() function is used to maintain a reference count in + the data block that contains a compiled pattern. It is provided for the + benefit of applications that operate in an object-oriented manner, + where different parts of the application may be using the same compiled + pattern, but you want to free the block when they are all done. + + When a pattern is compiled, the reference count field is initialized to + zero. It is changed only by calling this function, whose action is to + add the adjust value (which may be positive or negative) to it. The + yield of the function is the new value. However, the value of the count + is constrained to lie between 0 and 65535, inclusive. If the new value + is outside these limits, it is forced to the appropriate limit value. + + Except when it is zero, the reference count is not correctly preserved + if a pattern is compiled on one host and then transferred to a host + whose byte-order is different. (This seems a highly unlikely scenario.) + + +MATCHING A PATTERN: THE TRADITIONAL FUNCTION + + int pcre_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + The function pcre_exec() is called to match a subject string against a + compiled pattern, which is passed in the code argument. If the pattern + was studied, the result of the study should be passed in the extra + argument. You can call pcre_exec() with the same code and extra argu- + ments as many times as you like, in order to match different subject + strings with the same pattern. + + This function is the main matching facility of the library, and it + operates in a Perl-like manner. For specialist use there is also an + alternative matching function, which is described below in the section + about the pcre_dfa_exec() function. + + In most applications, the pattern will have been compiled (and option- + ally studied) in the same process that calls pcre_exec(). However, it + is possible to save compiled patterns and study data, and then use them + later in different processes, possibly even on different hosts. For a + discussion about this, see the pcreprecompile documentation. + + Here is an example of a simple call to pcre_exec(): + + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 30); /* number of elements (NOT size in bytes) */ + + Extra data for pcre_exec() + + If the extra argument is not NULL, it must point to a pcre_extra data + block. The pcre_study() function returns such a block (when it doesn't + return NULL), but you can also create one for yourself, and pass addi- + tional information in it. The pcre_extra block contains the following + fields (not necessarily in this order): + + unsigned long int flags; + void *study_data; + void *executable_jit; + unsigned long int match_limit; + unsigned long int match_limit_recursion; + void *callout_data; + const unsigned char *tables; + unsigned char **mark; + + In the 16-bit version of this structure, the mark field has type + "PCRE_UCHAR16 **". + + In the 32-bit version of this structure, the mark field has type + "PCRE_UCHAR32 **". + + The flags field is used to specify which of the other fields are set. + The flag bits are: + + PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_EXECUTABLE_JIT + PCRE_EXTRA_MARK + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_MATCH_LIMIT_RECURSION + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_TABLES + + Other flag bits should be set to zero. The study_data field and some- + times the executable_jit field are set in the pcre_extra block that is + returned by pcre_study(), together with the appropriate flag bits. You + should not set these yourself, but you may add to the block by setting + other fields and their corresponding flag bits. + + The match_limit field provides a means of preventing PCRE from using up + a vast amount of resources when running patterns that are not going to + match, but which have a very large number of possibilities in their + search trees. The classic example is a pattern that uses nested unlim- + ited repeats. + + Internally, pcre_exec() uses a function called match(), which it calls + repeatedly (sometimes recursively). The limit set by match_limit is + imposed on the number of times this function is called during a match, + which has the effect of limiting the amount of backtracking that can + take place. For patterns that are not anchored, the count restarts from + zero for each position in the subject string. + + When pcre_exec() is called with a pattern that was successfully studied + with a JIT option, the way that the matching is executed is entirely + different. However, there is still the possibility of runaway matching + that goes on for a very long time, and so the match_limit value is also + used in this case (but in a different way) to limit how long the match- + ing can continue. + + The default value for the limit can be set when PCRE is built; the + default default is 10 million, which handles all but the most extreme + cases. You can override the default by suppling pcre_exec() with a + pcre_extra block in which match_limit is set, and + PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is + exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT. + + A value for the match limit may also be supplied by an item at the + start of a pattern of the form + + (*LIMIT_MATCH=d) + + where d is a decimal number. However, such a setting is ignored unless + d is less than the limit set by the caller of pcre_exec() or, if no + such limit is set, less than the default. + + The match_limit_recursion field is similar to match_limit, but instead + of limiting the total number of times that match() is called, it limits + the depth of recursion. The recursion depth is a smaller number than + the total number of calls, because not all calls to match() are recur- + sive. This limit is of use only if it is set smaller than match_limit. + + Limiting the recursion depth limits the amount of machine stack that + can be used, or, when PCRE has been compiled to use memory on the heap + instead of the stack, the amount of heap memory that can be used. This + limit is not relevant, and is ignored, when matching is done using JIT + compiled code. + + The default value for match_limit_recursion can be set when PCRE is + built; the default default is the same value as the default for + match_limit. You can override the default by suppling pcre_exec() with + a pcre_extra block in which match_limit_recursion is set, and + PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the flags field. If the + limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT. + + A value for the recursion limit may also be supplied by an item at the + start of a pattern of the form + + (*LIMIT_RECURSION=d) + + where d is a decimal number. However, such a setting is ignored unless + d is less than the limit set by the caller of pcre_exec() or, if no + such limit is set, less than the default. + + The callout_data field is used in conjunction with the "callout" fea- + ture, and is described in the pcrecallout documentation. + + The tables field is provided for use with patterns that have been pre- + compiled using custom character tables, saved to disc or elsewhere, and + then reloaded, because the tables that were used to compile a pattern + are not saved with it. See the pcreprecompile documentation for a dis- + cussion of saving compiled patterns for later use. If NULL is passed + using this mechanism, it forces PCRE's internal tables to be used. + + Warning: The tables that pcre_exec() uses must be the same as those + that were used when the pattern was compiled. If this is not the case, + the behaviour of pcre_exec() is undefined. Therefore, when a pattern is + compiled and matched in the same process, this field should never be + set. In this (the most common) case, the correct table pointer is auto- + matically passed with the compiled pattern from pcre_compile() to + pcre_exec(). + + If PCRE_EXTRA_MARK is set in the flags field, the mark field must be + set to point to a suitable variable. If the pattern contains any back- + tracking control verbs such as (*MARK:NAME), and the execution ends up + with a name to pass back, a pointer to the name string (zero termi- + nated) is placed in the variable pointed to by the mark field. The + names are within the compiled pattern; if you wish to retain such a + name you must copy it before freeing the memory of a compiled pattern. + If there is no name to pass back, the variable pointed to by the mark + field is set to NULL. For details of the backtracking control verbs, + see the section entitled "Backtracking control" in the pcrepattern doc- + umentation. + + Option bits for pcre_exec() + + The unused bits of the options argument for pcre_exec() must be zero. + The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx, + PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, + PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and + PCRE_PARTIAL_SOFT. + + If the pattern was successfully studied with one of the just-in-time + (JIT) compile options, the only supported options for JIT execution are + PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, + PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an + unsupported option is used, JIT execution is disabled and the normal + interpretive code in pcre_exec() is run. + + PCRE_ANCHORED + + The PCRE_ANCHORED option limits pcre_exec() to matching at the first + matching position. If a pattern was compiled with PCRE_ANCHORED, or + turned out to be anchored by virtue of its contents, it cannot be made + unachored at matching time. + + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE + + These options (which are mutually exclusive) control what the \R escape + sequence matches. The choice is either to match only CR, LF, or CRLF, + or to match any Unicode newline sequence. These options override the + choice that was made or defaulted when the pattern was compiled. + + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY + + These options override the newline definition that was chosen or + defaulted when the pattern was compiled. For details, see the descrip- + tion of pcre_compile() above. During matching, the newline choice + affects the behaviour of the dot, circumflex, and dollar metacharac- + ters. It may also alter the way the match position is advanced after a + match failure for an unanchored pattern. + + When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is + set, and a match attempt for an unanchored pattern fails when the cur- + rent position is at a CRLF sequence, and the pattern contains no + explicit matches for CR or LF characters, the match position is + advanced by two characters instead of one, in other words, to after the + CRLF. + + The above rule is a compromise that makes the most common cases work as + expected. For example, if the pattern is .+A (and the PCRE_DOTALL + option is not set), it does not match the string "\r\nA" because, after + failing at the start, it skips both the CR and the LF before retrying. + However, the pattern [\r\n]A does match that string, because it con- + tains an explicit CR or LF reference, and so advances only by one char- + acter after the first failure. + + An explicit match for CR of LF is either a literal appearance of one of + those characters, or one of the \r or \n escape sequences. Implicit + matches such as [^X] do not count, nor does \s (which includes CR and + LF in the characters that it matches). + + Notwithstanding the above, anomalous effects may still occur when CRLF + is a valid newline sequence and explicit \r or \n escapes appear in the + pattern. + + PCRE_NOTBOL + + This option specifies that first character of the subject string is not + the beginning of a line, so the circumflex metacharacter should not + match before it. Setting this without PCRE_MULTILINE (at compile time) + causes circumflex never to match. This option affects only the behav- + iour of the circumflex metacharacter. It does not affect \A. + + PCRE_NOTEOL + + This option specifies that the end of the subject string is not the end + of a line, so the dollar metacharacter should not match it nor (except + in multiline mode) a newline immediately before it. Setting this with- + out PCRE_MULTILINE (at compile time) causes dollar never to match. This + option affects only the behaviour of the dollar metacharacter. It does + not affect \Z or \z. + + PCRE_NOTEMPTY + + An empty string is not considered to be a valid match if this option is + set. If there are alternatives in the pattern, they are tried. If all + the alternatives match the empty string, the entire match fails. For + example, if the pattern + + a?b? + + is applied to a string not beginning with "a" or "b", it matches an + empty string at the start of the subject. With PCRE_NOTEMPTY set, this + match is not valid, so PCRE searches further into the string for occur- + rences of "a" or "b". + + PCRE_NOTEMPTY_ATSTART + + This is like PCRE_NOTEMPTY, except that an empty string match that is + not at the start of the subject is permitted. If the pattern is + anchored, such a match can occur only if the pattern contains \K. + + Perl has no direct equivalent of PCRE_NOTEMPTY or + PCRE_NOTEMPTY_ATSTART, but it does make a special case of a pattern + match of the empty string within its split() function, and when using + the /g modifier. It is possible to emulate Perl's behaviour after + matching a null string by first trying the match again at the same off- + set with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then if that + fails, by advancing the starting offset (see below) and trying an ordi- + nary match again. There is some code that demonstrates how to do this + in the pcredemo sample program. In the most general case, you have to + check to see if the newline convention recognizes CRLF as a newline, + and if so, and the current character is CR followed by LF, advance the + starting offset by two characters instead of one. + + PCRE_NO_START_OPTIMIZE + + There are a number of optimizations that pcre_exec() uses at the start + of a match, in order to speed up the process. For example, if it is + known that an unanchored match must start with a specific character, it + searches the subject for that character, and fails immediately if it + cannot find it, without actually running the main matching function. + This means that a special item such as (*COMMIT) at the start of a pat- + tern is not considered until after a suitable starting point for the + match has been found. Also, when callouts or (*MARK) items are in use, + these "start-up" optimizations can cause them to be skipped if the pat- + tern is never actually used. The start-up optimizations are in effect a + pre-scan of the subject that takes place before the pattern is run. + + The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, + possibly causing performance to suffer, but ensuring that in cases + where the result is "no match", the callouts do occur, and that items + such as (*COMMIT) and (*MARK) are considered at every possible starting + position in the subject string. If PCRE_NO_START_OPTIMIZE is set at + compile time, it cannot be unset at matching time. The use of + PCRE_NO_START_OPTIMIZE at matching time (that is, passing it to + pcre_exec()) disables JIT execution; in this situation, matching is + always done using interpretively. + + Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching + operation. Consider the pattern + + (*COMMIT)ABC + + When this is compiled, PCRE records the fact that a match must start + with the character "A". Suppose the subject string is "DEFABC". The + start-up optimization scans along the subject, finds "A" and runs the + first match attempt from there. The (*COMMIT) item means that the pat- + tern must match the current starting position, which in this case, it + does. However, if the same match is run with PCRE_NO_START_OPTIMIZE + set, the initial scan along the subject string does not happen. The + first match attempt is run starting from "D" and when this fails, + (*COMMIT) prevents any further matches being tried, so the overall + result is "no match". If the pattern is studied, more start-up opti- + mizations may be used. For example, a minimum length for the subject + may be recorded. Consider the pattern + + (*MARK:A)(X|Y) + + The minimum length for a match is one character. If the subject is + "ABC", there will be attempts to match "ABC", "BC", "C", and then + finally an empty string. If the pattern is studied, the final attempt + does not take place, because PCRE knows that the subject is too short, + and so the (*MARK) is never encountered. In this case, studying the + pattern does not affect the overall match result, which is still "no + match", but it does affect the auxiliary information that is returned. + + PCRE_NO_UTF8_CHECK + + When PCRE_UTF8 is set at compile time, the validity of the subject as a + UTF-8 string is automatically checked when pcre_exec() is subsequently + called. The entire string is checked before any other processing takes + place. The value of startoffset is also checked to ensure that it + points to the start of a UTF-8 character. There is a discussion about + the validity of UTF-8 strings in the pcreunicode page. If an invalid + sequence of bytes is found, pcre_exec() returns the error + PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a + truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In + both cases, information about the precise nature of the error may also + be returned (see the descriptions of these errors in the section enti- + tled Error return values from pcre_exec() below). If startoffset con- + tains a value that does not point to the start of a UTF-8 character (or + to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned. + + If you already know that your subject is valid, and you want to skip + these checks for performance reasons, you can set the + PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to + do this for the second and subsequent calls to pcre_exec() if you are + making repeated calls to find all the matches in a single subject + string. However, you should be sure that the value of startoffset + points to the start of a character (or the end of the subject). When + PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a + subject or an invalid value of startoffset is undefined. Your program + may crash or loop. + + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT + + These options turn on the partial matching feature. For backwards com- + patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial + match occurs if the end of the subject string is reached successfully, + but there are not enough subject characters to complete the match. If + this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, + matching continues by testing any remaining alternatives. Only if no + complete match can be found is PCRE_ERROR_PARTIAL returned instead of + PCRE_ERROR_NOMATCH. In other words, PCRE_PARTIAL_SOFT says that the + caller is prepared to handle a partial match, but only if no complete + match can be found. + + If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this + case, if a partial match is found, pcre_exec() immediately returns + PCRE_ERROR_PARTIAL, without considering any other alternatives. In + other words, when PCRE_PARTIAL_HARD is set, a partial match is consid- + ered to be more important that an alternative complete match. + + In both cases, the portion of the string that was inspected when the + partial match was found is set as the first matching string. There is a + more detailed discussion of partial and multi-segment matching, with + examples, in the pcrepartial documentation. + + The string to be matched by pcre_exec() + + The subject string is passed to pcre_exec() as a pointer in subject, a + length in length, and a starting offset in startoffset. The units for + length and startoffset are bytes for the 8-bit library, 16-bit data + items for the 16-bit library, and 32-bit data items for the 32-bit + library. + + If startoffset is negative or greater than the length of the subject, + pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting offset is + zero, the search for a match starts at the beginning of the subject, + and this is by far the most common case. In UTF-8 or UTF-16 mode, the + offset must point to the start of a character, or the end of the sub- + ject (in UTF-32 mode, one data unit equals one character, so all off- + sets are valid). Unlike the pattern string, the subject may contain + binary zeroes. + + A non-zero starting offset is useful when searching for another match + in the same subject by calling pcre_exec() again after a previous suc- + cess. Setting startoffset differs from just passing over a shortened + string and setting PCRE_NOTBOL in the case of a pattern that begins + with any kind of lookbehind. For example, consider the pattern + + \Biss\B + + which finds occurrences of "iss" in the middle of words. (\B matches + only if the current position in the subject is not a word boundary.) + When applied to the string "Mississipi" the first call to pcre_exec() + finds the first occurrence. If pcre_exec() is called again with just + the remainder of the subject, namely "issipi", it does not match, + because \B is always false at the start of the subject, which is deemed + to be a word boundary. However, if pcre_exec() is passed the entire + string again, but with startoffset set to 4, it finds the second occur- + rence of "iss" because it is able to look behind the starting point to + discover that it is preceded by a letter. + + Finding all the matches in a subject is tricky when the pattern can + match an empty string. It is possible to emulate Perl's /g behaviour by + first trying the match again at the same offset, with the + PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED options, and then if that + fails, advancing the starting offset and trying an ordinary match + again. There is some code that demonstrates how to do this in the pcre- + demo sample program. In the most general case, you have to check to see + if the newline convention recognizes CRLF as a newline, and if so, and + the current character is CR followed by LF, advance the starting offset + by two characters instead of one. + + If a non-zero starting offset is passed when the pattern is anchored, + one attempt to match at the given offset is made. This can only succeed + if the pattern does not require the match to be at the start of the + subject. + + How pcre_exec() returns captured substrings + + In general, a pattern matches a certain portion of the subject, and in + addition, further substrings from the subject may be picked out by + parts of the pattern. Following the usage in Jeffrey Friedl's book, + this is called "capturing" in what follows, and the phrase "capturing + subpattern" is used for a fragment of a pattern that picks out a sub- + string. PCRE supports several other kinds of parenthesized subpattern + that do not cause substrings to be captured. + + Captured substrings are returned to the caller via a vector of integers + whose address is passed in ovector. The number of elements in the vec- + tor is passed in ovecsize, which must be a non-negative number. Note: + this argument is NOT the size of ovector in bytes. + + The first two-thirds of the vector is used to pass back captured sub- + strings, each substring using a pair of integers. The remaining third + of the vector is used as workspace by pcre_exec() while matching cap- + turing subpatterns, and is not available for passing back information. + The number passed in ovecsize should always be a multiple of three. If + it is not, it is rounded down. + + When a match is successful, information about captured substrings is + returned in pairs of integers, starting at the beginning of ovector, + and continuing up to two-thirds of its length at the most. The first + element of each pair is set to the offset of the first character in a + substring, and the second is set to the offset of the first character + after the end of a substring. These values are always data unit off- + sets, even in UTF mode. They are byte offsets in the 8-bit library, + 16-bit data item offsets in the 16-bit library, and 32-bit data item + offsets in the 32-bit library. Note: they are not character counts. + + The first pair of integers, ovector[0] and ovector[1], identify the + portion of the subject string matched by the entire pattern. The next + pair is used for the first capturing subpattern, and so on. The value + returned by pcre_exec() is one more than the highest numbered pair that + has been set. For example, if two substrings have been captured, the + returned value is 3. If there are no capturing subpatterns, the return + value from a successful match is 1, indicating that just the first pair + of offsets has been set. + + If a capturing subpattern is matched repeatedly, it is the last portion + of the string that it matched that is returned. + + If the vector is too small to hold all the captured substring offsets, + it is used as far as possible (up to two-thirds of its length), and the + function returns a value of zero. If neither the actual string matched + nor any captured substrings are of interest, pcre_exec() may be called + with ovector passed as NULL and ovecsize as zero. However, if the pat- + tern contains back references and the ovector is not big enough to + remember the related substrings, PCRE has to get additional memory for + use during matching. Thus it is usually advisable to supply an ovector + of reasonable size. + + There are some cases where zero is returned (indicating vector over- + flow) when in fact the vector is exactly the right size for the final + match. For example, consider the pattern + + (a)(?:(b)c|bd) + + If a vector of 6 elements (allowing for only 1 captured substring) is + given with subject string "abd", pcre_exec() will try to set the second + captured string, thereby recording a vector overflow, before failing to + match "c" and backing up to try the second alternative. The zero + return, however, does correctly indicate that the maximum number of + slots (namely 2) have been filled. In similar cases where there is tem- + porary overflow, but the final number of used slots is actually less + than the maximum, a non-zero value is returned. + + The pcre_fullinfo() function can be used to find out how many capturing + subpatterns there are in a compiled pattern. The smallest size for + ovector that will allow for n captured substrings, in addition to the + offsets of the substring matched by the whole pattern, is (n+1)*3. + + It is possible for capturing subpattern number n+1 to match some part + of the subject when subpattern n has not been used at all. For example, + if the string "abc" is matched against the pattern (a|(z))(bc) the + return from the function is 4, and subpatterns 1 and 3 are matched, but + 2 is not. When this happens, both values in the offset pairs corre- + sponding to unused subpatterns are set to -1. + + Offset values that correspond to unused subpatterns at the end of the + expression are also set to -1. For example, if the string "abc" is + matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not + matched. The return from the function is 2, because the highest used + capturing subpattern number is 1, and the offsets for for the second + and third capturing subpatterns (assuming the vector is large enough, + of course) are set to -1. + + Note: Elements in the first two-thirds of ovector that do not corre- + spond to capturing parentheses in the pattern are never changed. That + is, if a pattern contains n capturing parentheses, no more than ovec- + tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements (in + the first two-thirds) retain whatever values they previously had. + + Some convenience functions are provided for extracting the captured + substrings as separate strings. These are described below. + + Error return values from pcre_exec() + + If pcre_exec() fails, it returns a negative number. The following are + defined in the header file: + + PCRE_ERROR_NOMATCH (-1) + + The subject string did not match the pattern. + + PCRE_ERROR_NULL (-2) + + Either code or subject was passed as NULL, or ovector was NULL and + ovecsize was not zero. + + PCRE_ERROR_BADOPTION (-3) + + An unrecognized bit was set in the options argument. + + PCRE_ERROR_BADMAGIC (-4) + + PCRE stores a 4-byte "magic number" at the start of the compiled code, + to catch the case when it is passed a junk pointer and to detect when a + pattern that was compiled in an environment of one endianness is run in + an environment with the other endianness. This is the error that PCRE + gives when the magic number is not present. + + PCRE_ERROR_UNKNOWN_OPCODE (-5) + + While running the pattern match, an unknown item was encountered in the + compiled pattern. This error could be caused by a bug in PCRE or by + overwriting of the compiled pattern. + + PCRE_ERROR_NOMEMORY (-6) + + If a pattern contains back references, but the ovector that is passed + to pcre_exec() is not big enough to remember the referenced substrings, + PCRE gets a block of memory at the start of matching to use for this + purpose. If the call via pcre_malloc() fails, this error is given. The + memory is automatically freed at the end of matching. + + This error is also given if pcre_stack_malloc() fails in pcre_exec(). + This can happen only when PCRE has been compiled with --disable-stack- + for-recursion. + + PCRE_ERROR_NOSUBSTRING (-7) + + This error is used by the pcre_copy_substring(), pcre_get_substring(), + and pcre_get_substring_list() functions (see below). It is never + returned by pcre_exec(). + + PCRE_ERROR_MATCHLIMIT (-8) + + The backtracking limit, as specified by the match_limit field in a + pcre_extra structure (or defaulted) was reached. See the description + above. + + PCRE_ERROR_CALLOUT (-9) + + This error is never generated by pcre_exec() itself. It is provided for + use by callout functions that want to yield a distinctive error code. + See the pcrecallout documentation for details. + + PCRE_ERROR_BADUTF8 (-10) + + A string that contains an invalid UTF-8 byte sequence was passed as a + subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size of + the output vector (ovecsize) is at least 2, the byte offset to the + start of the the invalid UTF-8 character is placed in the first ele- + ment, and a reason code is placed in the second element. The reason + codes are listed in the following section. For backward compatibility, + if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char- + acter at the end of the subject (reason codes 1 to 5), + PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. + + PCRE_ERROR_BADUTF8_OFFSET (-11) + + The UTF-8 byte sequence that was passed as a subject was checked and + found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the + value of startoffset did not point to the beginning of a UTF-8 charac- + ter or the end of the subject. + + PCRE_ERROR_PARTIAL (-12) + + The subject string did not match, but it did match partially. See the + pcrepartial documentation for details of partial matching. + + PCRE_ERROR_BADPARTIAL (-13) + + This code is no longer in use. It was formerly returned when the + PCRE_PARTIAL option was used with a compiled pattern containing items + that were not supported for partial matching. From release 8.00 + onwards, there are no restrictions on partial matching. + + PCRE_ERROR_INTERNAL (-14) + + An unexpected internal error has occurred. This error could be caused + by a bug in PCRE or by overwriting of the compiled pattern. + + PCRE_ERROR_BADCOUNT (-15) + + This error is given if the value of the ovecsize argument is negative. + + PCRE_ERROR_RECURSIONLIMIT (-21) + + The internal recursion limit, as specified by the match_limit_recursion + field in a pcre_extra structure (or defaulted) was reached. See the + description above. + + PCRE_ERROR_BADNEWLINE (-23) + + An invalid combination of PCRE_NEWLINE_xxx options was given. + + PCRE_ERROR_BADOFFSET (-24) + + The value of startoffset was negative or greater than the length of the + subject, that is, the value in length. + + PCRE_ERROR_SHORTUTF8 (-25) + + This error is returned instead of PCRE_ERROR_BADUTF8 when the subject + string ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD + option is set. Information about the failure is returned as for + PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this case, but + this special error code for PCRE_PARTIAL_HARD precedes the implementa- + tion of returned information; it is retained for backwards compatibil- + ity. + + PCRE_ERROR_RECURSELOOP (-26) + + This error is returned when pcre_exec() detects a recursion loop within + the pattern. Specifically, it means that either the whole pattern or a + subpattern has been called recursively for the second time at the same + position in the subject string. Some simple patterns that might do this + are detected and faulted at compile time, but more complicated cases, + in particular mutual recursions between two different subpatterns, can- + not be detected until run time. + + PCRE_ERROR_JIT_STACKLIMIT (-27) + + This error is returned when a pattern that was successfully studied + using a JIT compile option is being matched, but the memory available + for the just-in-time processing stack is not large enough. See the + pcrejit documentation for more details. + + PCRE_ERROR_BADMODE (-28) + + This error is given if a pattern that was compiled by the 8-bit library + is passed to a 16-bit or 32-bit library function, or vice versa. + + PCRE_ERROR_BADENDIANNESS (-29) + + This error is given if a pattern that was compiled and saved is + reloaded on a host with different endianness. The utility function + pcre_pattern_to_host_byte_order() can be used to convert such a pattern + so that it runs on the new host. + + PCRE_ERROR_JIT_BADOPTION + + This error is returned when a pattern that was successfully studied + using a JIT compile option is being matched, but the matching mode + (partial or complete match) does not correspond to any JIT compilation + mode. When the JIT fast path function is used, this error may be also + given for invalid options. See the pcrejit documentation for more + details. + + PCRE_ERROR_BADLENGTH (-32) + + This error is given if pcre_exec() is called with a negative value for + the length argument. + + Error numbers -16 to -20, -22, and 30 are not used by pcre_exec(). + + Reason codes for invalid UTF-8 strings + + This section applies only to the 8-bit library. The corresponding + information for the 16-bit and 32-bit libraries is given in the pcre16 + and pcre32 pages. + + When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT- + UTF8, and the size of the output vector (ovecsize) is at least 2, the + offset of the start of the invalid UTF-8 character is placed in the + first output vector element (ovector[0]) and a reason code is placed in + the second element (ovector[1]). The reason codes are given names in + the pcre.h header file: + + PCRE_UTF8_ERR1 + PCRE_UTF8_ERR2 + PCRE_UTF8_ERR3 + PCRE_UTF8_ERR4 + PCRE_UTF8_ERR5 + + The string ends with a truncated UTF-8 character; the code specifies + how many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 + characters to be no longer than 4 bytes, the encoding scheme (origi- + nally defined by RFC 2279) allows for up to 6 bytes, and this is + checked first; hence the possibility of 4 or 5 missing bytes. + + PCRE_UTF8_ERR6 + PCRE_UTF8_ERR7 + PCRE_UTF8_ERR8 + PCRE_UTF8_ERR9 + PCRE_UTF8_ERR10 + + The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of + the character do not have the binary value 0b10 (that is, either the + most significant bit is 0, or the next bit is 1). + + PCRE_UTF8_ERR11 + PCRE_UTF8_ERR12 + + A character that is valid by the RFC 2279 rules is either 5 or 6 bytes + long; these code points are excluded by RFC 3629. + + PCRE_UTF8_ERR13 + + A 4-byte character has a value greater than 0x10fff; these code points + are excluded by RFC 3629. + + PCRE_UTF8_ERR14 + + A 3-byte character has a value in the range 0xd800 to 0xdfff; this + range of code points are reserved by RFC 3629 for use with UTF-16, and + so are excluded from UTF-8. + + PCRE_UTF8_ERR15 + PCRE_UTF8_ERR16 + PCRE_UTF8_ERR17 + PCRE_UTF8_ERR18 + PCRE_UTF8_ERR19 + + A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes + for a value that can be represented by fewer bytes, which is invalid. + For example, the two bytes 0xc0, 0xae give the value 0x2e, whose cor- + rect coding uses just one byte. + + PCRE_UTF8_ERR20 + + The two most significant bits of the first byte of a character have the + binary value 0b10 (that is, the most significant bit is 1 and the sec- + ond is 0). Such a byte can only validly occur as the second or subse- + quent byte of a multi-byte character. + + PCRE_UTF8_ERR21 + + The first byte of a character has the value 0xfe or 0xff. These values + can never occur in a valid UTF-8 string. + + PCRE_UTF8_ERR22 + + This error code was formerly used when the presence of a so-called + "non-character" caused an error. Unicode corrigendum #9 makes it clear + that such characters should not cause a string to be rejected, and so + this code is no longer in use and is never returned. + + +EXTRACTING CAPTURED SUBSTRINGS BY NUMBER + + int pcre_copy_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, char *buffer, + int buffersize); + + int pcre_get_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, + const char **stringptr); + + int pcre_get_substring_list(const char *subject, + int *ovector, int stringcount, const char ***listptr); + + Captured substrings can be accessed directly by using the offsets + returned by pcre_exec() in ovector. For convenience, the functions + pcre_copy_substring(), pcre_get_substring(), and pcre_get_sub- + string_list() are provided for extracting captured substrings as new, + separate, zero-terminated strings. These functions identify substrings + by number. The next section describes functions for extracting named + substrings. + + A substring that contains a binary zero is correctly extracted and has + a further zero added on the end, but the result is not, of course, a C + string. However, you can process such a string by referring to the + length that is returned by pcre_copy_substring() and pcre_get_sub- + string(). Unfortunately, the interface to pcre_get_substring_list() is + not adequate for handling strings containing binary zeros, because the + end of the final string is not independently indicated. + + The first three arguments are the same for all three of these func- + tions: subject is the subject string that has just been successfully + matched, ovector is a pointer to the vector of integer offsets that was + passed to pcre_exec(), and stringcount is the number of substrings that + were captured by the match, including the substring that matched the + entire regular expression. This is the value returned by pcre_exec() if + it is greater than zero. If pcre_exec() returned zero, indicating that + it ran out of space in ovector, the value passed as stringcount should + be the number of elements in the vector divided by three. + + The functions pcre_copy_substring() and pcre_get_substring() extract a + single substring, whose number is given as stringnumber. A value of + zero extracts the substring that matched the entire pattern, whereas + higher values extract the captured substrings. For pcre_copy_sub- + string(), the string is placed in buffer, whose length is given by + buffersize, while for pcre_get_substring() a new block of memory is + obtained via pcre_malloc, and its address is returned via stringptr. + The yield of the function is the length of the string, not including + the terminating zero, or one of these error codes: + + PCRE_ERROR_NOMEMORY (-6) + + The buffer was too small for pcre_copy_substring(), or the attempt to + get memory failed for pcre_get_substring(). + + PCRE_ERROR_NOSUBSTRING (-7) + + There is no substring whose number is stringnumber. + + The pcre_get_substring_list() function extracts all available sub- + strings and builds a list of pointers to them. All this is done in a + single block of memory that is obtained via pcre_malloc. The address of + the memory block is returned via listptr, which is also the start of + the list of string pointers. The end of the list is marked by a NULL + pointer. The yield of the function is zero if all went well, or the + error code + + PCRE_ERROR_NOMEMORY (-6) + + if the attempt to get the memory block failed. + + When any of these functions encounter a substring that is unset, which + can happen when capturing subpattern number n+1 matches some part of + the subject, but subpattern n has not been used at all, they return an + empty string. This can be distinguished from a genuine zero-length sub- + string by inspecting the appropriate offset in ovector, which is nega- + tive for unset substrings. + + The two convenience functions pcre_free_substring() and pcre_free_sub- + string_list() can be used to free the memory returned by a previous + call of pcre_get_substring() or pcre_get_substring_list(), respec- + tively. They do nothing more than call the function pointed to by + pcre_free, which of course could be called directly from a C program. + However, PCRE is used in some situations where it is linked via a spe- + cial interface to another programming language that cannot use + pcre_free directly; it is for these cases that the functions are pro- + vided. + + +EXTRACTING CAPTURED SUBSTRINGS BY NAME + + int pcre_get_stringnumber(const pcre *code, + const char *name); + + int pcre_copy_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + char *buffer, int buffersize); + + int pcre_get_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + const char **stringptr); + + To extract a substring by name, you first have to find associated num- + ber. For example, for this pattern + + (a+)b(?<xxx>\d+)... + + the number of the subpattern called "xxx" is 2. If the name is known to + be unique (PCRE_DUPNAMES was not set), you can find the number from the + name by calling pcre_get_stringnumber(). The first argument is the com- + piled pattern, and the second is the name. The yield of the function is + the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no + subpattern of that name. + + Given the number, you can extract the substring directly, or use one of + the functions described in the previous section. For convenience, there + are also two functions that do the whole job. + + Most of the arguments of pcre_copy_named_substring() and + pcre_get_named_substring() are the same as those for the similarly + named functions that extract by number. As these are described in the + previous section, they are not re-described here. There are just two + differences: + + First, instead of a substring number, a substring name is given. Sec- + ond, there is an extra argument, given at the start, which is a pointer + to the compiled pattern. This is needed in order to gain access to the + name-to-number translation table. + + These functions call pcre_get_stringnumber(), and if it succeeds, they + then call pcre_copy_substring() or pcre_get_substring(), as appropri- + ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, the + behaviour may not be what you want (see the next section). + + Warning: If the pattern uses the (?| feature to set up multiple subpat- + terns with the same number, as described in the section on duplicate + subpattern numbers in the pcrepattern page, you cannot use names to + distinguish the different subpatterns, because names are not included + in the compiled code. The matching process uses only numbers. For this + reason, the use of different names for subpatterns of the same number + causes an error at compile time. + + +DUPLICATE SUBPATTERN NAMES + + int pcre_get_stringtable_entries(const pcre *code, + const char *name, char **first, char **last); + + When a pattern is compiled with the PCRE_DUPNAMES option, names for + subpatterns are not required to be unique. (Duplicate names are always + allowed for subpatterns with the same number, created by using the (?| + feature. Indeed, if such subpatterns are named, they are required to + use the same names.) + + Normally, patterns with duplicate names are such that in any one match, + only one of the named subpatterns participates. An example is shown in + the pcrepattern documentation. + + When duplicates are present, pcre_copy_named_substring() and + pcre_get_named_substring() return the first substring corresponding to + the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING + (-7) is returned; no data is returned. The pcre_get_stringnumber() + function returns one of the numbers that are associated with the name, + but it is not defined which it is. + + If you want to get full details of all captured substrings for a given + name, you must use the pcre_get_stringtable_entries() function. The + first argument is the compiled pattern, and the second is the name. The + third and fourth are pointers to variables which are updated by the + function. After it has run, they point to the first and last entries in + the name-to-number table for the given name. The function itself + returns the length of each entry, or PCRE_ERROR_NOSUBSTRING (-7) if + there are none. The format of the table is described above in the sec- + tion entitled Information about a pattern above. Given all the rele- + vant entries for the name, you can extract each of their numbers, and + hence the captured data, if any. + + +FINDING ALL POSSIBLE MATCHES + + The traditional matching function uses a similar algorithm to Perl, + which stops when it finds the first match, starting at a given point in + the subject. If you want to find all possible matches, or the longest + possible match, consider using the alternative matching function (see + below) instead. If you cannot use the alternative function, but still + need to find all possible matches, you can kludge it up by making use + of the callout facility, which is described in the pcrecallout documen- + tation. + + What you have to do is to insert a callout right at the end of the pat- + tern. When your callout function is called, extract and save the cur- + rent matched substring. Then return 1, which forces pcre_exec() to + backtrack and try other alternatives. Ultimately, when it runs out of + matches, pcre_exec() will yield PCRE_ERROR_NOMATCH. + + +OBTAINING AN ESTIMATE OF STACK USAGE + + Matching certain patterns using pcre_exec() can use a lot of process + stack, which in certain environments can be rather limited in size. + Some users find it helpful to have an estimate of the amount of stack + that is used by pcre_exec(), to help them set recursion limits, as + described in the pcrestack documentation. The estimate that is output + by pcretest when called with the -m and -C options is obtained by call- + ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for its + first five arguments. + + Normally, if its first argument is NULL, pcre_exec() immediately + returns the negative error code PCRE_ERROR_NULL, but with this special + combination of arguments, it returns instead a negative number whose + absolute value is the approximate stack frame size in bytes. (A nega- + tive number is used so that it is clear that no match has happened.) + The value is approximate because in some cases, recursive calls to + pcre_exec() occur when there are one or two additional variables on the + stack. + + If PCRE has been compiled to use the heap instead of the stack for + recursion, the value returned is the size of each block that is + obtained from the heap. + + +MATCHING A PATTERN: THE ALTERNATIVE FUNCTION + + int pcre_dfa_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize, + int *workspace, int wscount); + + The function pcre_dfa_exec() is called to match a subject string + against a compiled pattern, using a matching algorithm that scans the + subject string just once, and does not backtrack. This has different + characteristics to the normal algorithm, and is not compatible with + Perl. Some of the features of PCRE patterns are not supported. Never- + theless, there are times when this kind of matching can be useful. For + a discussion of the two matching algorithms, and a list of features + that pcre_dfa_exec() does not support, see the pcrematching documenta- + tion. + + The arguments for the pcre_dfa_exec() function are the same as for + pcre_exec(), plus two extras. The ovector argument is used in a differ- + ent way, and this is described below. The other common arguments are + used in the same way as for pcre_exec(), so their description is not + repeated here. + + The two additional arguments provide workspace for the function. The + workspace vector should contain at least 20 elements. It is used for + keeping track of multiple paths through the pattern tree. More + workspace will be needed for patterns and subjects where there are a + lot of potential matches. + + Here is an example of a simple call to pcre_dfa_exec(): + + int rc; + int ovector[10]; + int wspace[20]; + rc = pcre_dfa_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 10, /* number of elements (NOT size in bytes) */ + wspace, /* working space vector */ + 20); /* number of elements (NOT size in bytes) */ + + Option bits for pcre_dfa_exec() + + The unused bits of the options argument for pcre_dfa_exec() must be + zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEW- + LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, + PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, + PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR- + TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last + four of these are exactly the same as for pcre_exec(), so their + description is not repeated here. + + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT + + These have the same general effect as they do for pcre_exec(), but the + details are slightly different. When PCRE_PARTIAL_HARD is set for + pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of the sub- + ject is reached and there is still at least one matching possibility + that requires additional characters. This happens even if some complete + matches have also been found. When PCRE_PARTIAL_SOFT is set, the return + code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end + of the subject is reached, there have been no complete matches, but + there is still at least one matching possibility. The portion of the + string that was inspected when the longest partial match was found is + set as the first matching string in both cases. There is a more + detailed discussion of partial and multi-segment matching, with exam- + ples, in the pcrepartial documentation. + + PCRE_DFA_SHORTEST + + Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to + stop as soon as it has found one match. Because of the way the alterna- + tive algorithm works, this is necessarily the shortest possible match + at the first possible matching point in the subject string. + + PCRE_DFA_RESTART + + When pcre_dfa_exec() returns a partial match, it is possible to call it + again, with additional subject characters, and have it continue with + the same match. The PCRE_DFA_RESTART option requests this action; when + it is set, the workspace and wscount options must reference the same + vector as before because data about the match so far is left in them + after a partial match. There is more discussion of this facility in the + pcrepartial documentation. + + Successful returns from pcre_dfa_exec() + + When pcre_dfa_exec() succeeds, it may have matched more than one sub- + string in the subject. Note, however, that all the matches from one run + of the function start at the same point in the subject. The shorter + matches are all initial substrings of the longer matches. For example, + if the pattern + + <.*> + + is matched against the string + + This is <something> <something else> <something further> no more + + the three matched strings are + + <something> + <something> <something else> + <something> <something else> <something further> + + On success, the yield of the function is a number greater than zero, + which is the number of matched substrings. The substrings themselves + are returned in ovector. Each string uses two elements; the first is + the offset to the start, and the second is the offset to the end. In + fact, all the strings have the same start offset. (Space could have + been saved by giving this only once, but it was decided to retain some + compatibility with the way pcre_exec() returns data, even though the + meaning of the strings is different.) + + The strings are returned in reverse order of length; that is, the long- + est matching string is given first. If there were too many matches to + fit into ovector, the yield of the function is zero, and the vector is + filled with the longest matches. Unlike pcre_exec(), pcre_dfa_exec() + can use the entire ovector for returning matched strings. + + NOTE: PCRE's "auto-possessification" optimization usually applies to + character repeats at the end of a pattern (as well as internally). For + example, the pattern "a\d+" is compiled as if it were "a\d++" because + there is no point even considering the possibility of backtracking into + the repeated digits. For DFA matching, this means that only one possi- + ble match is found. If you really do want multiple matches in such + cases, either use an ungreedy repeat ("a\d+?") or set the + PCRE_NO_AUTO_POSSESS option when compiling. + + Error returns from pcre_dfa_exec() + + The pcre_dfa_exec() function returns a negative number when it fails. + Many of the errors are the same as for pcre_exec(), and these are + described above. There are in addition the following errors that are + specific to pcre_dfa_exec(): + + PCRE_ERROR_DFA_UITEM (-16) + + This return is given if pcre_dfa_exec() encounters an item in the pat- + tern that it does not support, for instance, the use of \C or a back + reference. + + PCRE_ERROR_DFA_UCOND (-17) + + This return is given if pcre_dfa_exec() encounters a condition item + that uses a back reference for the condition, or a test for recursion + in a specific group. These are not supported. + + PCRE_ERROR_DFA_UMLIMIT (-18) + + This return is given if pcre_dfa_exec() is called with an extra block + that contains a setting of the match_limit or match_limit_recursion + fields. This is not supported (these fields are meaningless for DFA + matching). + + PCRE_ERROR_DFA_WSSIZE (-19) + + This return is given if pcre_dfa_exec() runs out of space in the + workspace vector. + + PCRE_ERROR_DFA_RECURSE (-20) + + When a recursive subpattern is processed, the matching function calls + itself recursively, using private vectors for ovector and workspace. + This error is given if the output vector is not large enough. This + should be extremely rare, as a vector of size 1000 is used. + + PCRE_ERROR_DFA_BADRESTART (-30) + + When pcre_dfa_exec() is called with the PCRE_DFA_RESTART option, some + plausibility checks are made on the contents of the workspace, which + should contain data about the previous partial match. If any of these + checks fail, this error is given. + + +SEE ALSO + + pcre16(3), pcre32(3), pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), + pcrematching(3), pcrepartial(3), pcreposix(3), pcreprecompile(3), pcre- + sample(3), pcrestack(3). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 09 February 2014 + Copyright (c) 1997-2014 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRECALLOUT(3) Library Functions Manual PCRECALLOUT(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +SYNOPSIS + + #include <pcre.h> + + int (*pcre_callout)(pcre_callout_block *); + + int (*pcre16_callout)(pcre16_callout_block *); + + int (*pcre32_callout)(pcre32_callout_block *); + + +DESCRIPTION + + PCRE provides a feature called "callout", which is a means of temporar- + ily passing control to the caller of PCRE in the middle of pattern + matching. The caller of PCRE provides an external function by putting + its entry point in the global variable pcre_callout (pcre16_callout for + the 16-bit library, pcre32_callout for the 32-bit library). By default, + this variable contains NULL, which disables all calling out. + + Within a regular expression, (?C) indicates the points at which the + external function is to be called. Different callout points can be + identified by putting a number less than 256 after the letter C. The + default value is zero. For example, this pattern has two callout + points: + + (?C1)abc(?C2)def + + If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, + PCRE automatically inserts callouts, all with number 255, before each + item in the pattern. For example, if PCRE_AUTO_CALLOUT is used with the + pattern + + A(\d{2}|--) + + it is processed as if it were + + (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255) + + Notice that there is a callout before and after each parenthesis and + alternation bar. If the pattern contains a conditional group whose con- + dition is an assertion, an automatic callout is inserted immediately + before the condition. Such a callout may also be inserted explicitly, + for example: + + (?(?C9)(?=a)ab|de) + + This applies only to assertion conditions (because they are themselves + independent groups). + + Automatic callouts can be used for tracking the progress of pattern + matching. The pcretest program has a pattern qualifier (/C) that sets + automatic callouts; when it is used, the output indicates how the pat- + tern is being matched. This is useful information when you are trying + to optimize the performance of a particular pattern. + + +MISSING CALLOUTS + + You should be aware that, because of optimizations in the way PCRE com- + piles and matches patterns, callouts sometimes do not happen exactly as + you might expect. + + At compile time, PCRE "auto-possessifies" repeated items when it knows + that what follows cannot be part of the repeat. For example, a+[bc] is + compiled as if it were a++[bc]. The pcretest output when this pattern + is anchored and then applied with automatic callouts to the string + "aaaa" is: + + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + No match + + This indicates that when matching [bc] fails, there is no backtracking + into a+ and therefore the callouts that would be taken for the back- + tracks do not occur. You can disable the auto-possessify feature by + passing PCRE_NO_AUTO_POSSESS to pcre_compile(), or starting the pattern + with (*NO_AUTO_POSSESS). If this is done in pcretest (using the /O + qualifier), the output changes to this: + + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^^ [bc] + No match + + This time, when matching [bc] fails, the matcher backtracks into a+ and + tries again, repeatedly, until a+ itself fails. + + Other optimizations that provide fast "no match" results also affect + callouts. For example, if the pattern is + + ab(?C4)cd + + PCRE knows that any matching string must contain the letter "d". If the + subject string is "abyz", the lack of "d" means that matching doesn't + ever start, and the callout is never reached. However, with "abyd", + though the result is still no match, the callout is obeyed. + + If the pattern is studied, PCRE knows the minimum length of a matching + string, and will immediately give a "no match" return without actually + running a match if the subject is not long enough, or, for unanchored + patterns, if it has been scanned far enough. + + You can disable these optimizations by passing the PCRE_NO_START_OPTI- + MIZE option to the matching function, or by starting the pattern with + (*NO_START_OPT). This slows down the matching process, but does ensure + that callouts such as the example above are obeyed. + + +THE CALLOUT INTERFACE + + During matching, when PCRE reaches a callout point, the external func- + tion defined by pcre_callout or pcre[16|32]_callout is called (if it is + set). This applies to both normal and DFA matching. The only argument + to the callout function is a pointer to a pcre_callout or + pcre[16|32]_callout block. These structures contains the following + fields: + + int version; + int callout_number; + int *offset_vector; + const char *subject; (8-bit version) + PCRE_SPTR16 subject; (16-bit version) + PCRE_SPTR32 subject; (32-bit version) + int subject_length; + int start_match; + int current_position; + int capture_top; + int capture_last; + void *callout_data; + int pattern_position; + int next_item_length; + const unsigned char *mark; (8-bit version) + const PCRE_UCHAR16 *mark; (16-bit version) + const PCRE_UCHAR32 *mark; (32-bit version) + + The version field is an integer containing the version number of the + block format. The initial version was 0; the current version is 2. The + version number will change again in future if additional fields are + added, but the intention is never to remove any of the existing fields. + + The callout_number field contains the number of the callout, as com- + piled into the pattern (that is, the number after ?C for manual call- + outs, and 255 for automatically generated callouts). + + The offset_vector field is a pointer to the vector of offsets that was + passed by the caller to the matching function. When pcre_exec() or + pcre[16|32]_exec() is used, the contents can be inspected, in order to + extract substrings that have been matched so far, in the same way as + for extracting substrings after a match has completed. For the DFA + matching functions, this field is not useful. + + The subject and subject_length fields contain copies of the values that + were passed to the matching function. + + The start_match field normally contains the offset within the subject + at which the current match attempt started. However, if the escape + sequence \K has been encountered, this value is changed to reflect the + modified starting point. If the pattern is not anchored, the callout + function may be called several times from the same point in the pattern + for different starting points in the subject. + + The current_position field contains the offset within the subject of + the current match pointer. + + When the pcre_exec() or pcre[16|32]_exec() is used, the capture_top + field contains one more than the number of the highest numbered cap- + tured substring so far. If no substrings have been captured, the value + of capture_top is one. This is always the case when the DFA functions + are used, because they do not support captured substrings. + + The capture_last field contains the number of the most recently cap- + tured substring. However, when a recursion exits, the value reverts to + what it was outside the recursion, as do the values of all captured + substrings. If no substrings have been captured, the value of cap- + ture_last is -1. This is always the case for the DFA matching func- + tions. + + The callout_data field contains a value that is passed to a matching + function specifically so that it can be passed back in callouts. It is + passed in the callout_data field of a pcre_extra or pcre[16|32]_extra + data structure. If no such data was passed, the value of callout_data + in a callout block is NULL. There is a description of the pcre_extra + structure in the pcreapi documentation. + + The pattern_position field is present from version 1 of the callout + structure. It contains the offset to the next item to be matched in the + pattern string. + + The next_item_length field is present from version 1 of the callout + structure. It contains the length of the next item to be matched in the + pattern string. When the callout immediately precedes an alternation + bar, a closing parenthesis, or the end of the pattern, the length is + zero. When the callout precedes an opening parenthesis, the length is + that of the entire subpattern. + + The pattern_position and next_item_length fields are intended to help + in distinguishing between different automatic callouts, which all have + the same callout number. However, they are set for all callouts. + + The mark field is present from version 2 of the callout structure. In + callouts from pcre_exec() or pcre[16|32]_exec() it contains a pointer + to the zero-terminated name of the most recently passed (*MARK), + (*PRUNE), or (*THEN) item in the match, or NULL if no such items have + been passed. Instances of (*PRUNE) or (*THEN) without a name do not + obliterate a previous (*MARK). In callouts from the DFA matching func- + tions this field always contains NULL. + + +RETURN VALUES + + The external callout function returns an integer to PCRE. If the value + is zero, matching proceeds as normal. If the value is greater than + zero, matching fails at the current point, but the testing of other + matching possibilities goes ahead, just as if a lookahead assertion had + failed. If the value is less than zero, the match is abandoned, the + matching function returns the negative value. + + Negative values should normally be chosen from the set of + PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan- + dard "no match" failure. The error number PCRE_ERROR_CALLOUT is + reserved for use by callout functions; it will never be used by PCRE + itself. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRECOMPAT(3) Library Functions Manual PCRECOMPAT(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +DIFFERENCES BETWEEN PCRE AND PERL + + This document describes the differences in the ways that PCRE and Perl + handle regular expressions. The differences described here are with + respect to Perl versions 5.10 and above. + + 1. PCRE has only a subset of Perl's Unicode support. Details of what it + does have are given in the pcreunicode page. + + 2. PCRE allows repeat quantifiers only on parenthesized assertions, but + they do not mean what you might think. For example, (?!a){3} does not + assert that the next three characters are not "a". It just asserts that + the next character is not "a" three times (in principle: PCRE optimizes + this to run the assertion just once). Perl allows repeat quantifiers on + other assertions such as \b, but these do not seem to have any use. + + 3. Capturing subpatterns that occur inside negative lookahead asser- + tions are counted, but their entries in the offsets vector are never + set. Perl sometimes (but not always) sets its numerical variables from + inside negative assertions. + + 4. Though binary zero characters are supported in the subject string, + they are not allowed in a pattern string because it is passed as a nor- + mal C string, terminated by zero. The escape sequence \0 can be used in + the pattern to represent a binary zero. + + 5. The following Perl escape sequences are not supported: \l, \u, \L, + \U, and \N when followed by a character name or Unicode value. (\N on + its own, matching a non-newline character, is supported.) In fact these + are implemented by Perl's general string-handling and are not part of + its pattern matching engine. If any of these are encountered by PCRE, + an error is generated by default. However, if the PCRE_JAVASCRIPT_COM- + PAT option is set, \U and \u are interpreted as JavaScript interprets + them. + + 6. The Perl escape sequences \p, \P, and \X are supported only if PCRE + is built with Unicode character property support. The properties that + can be tested with \p and \P are limited to the general category prop- + erties such as Lu and Nd, script names such as Greek or Han, and the + derived properties Any and L&. PCRE does support the Cs (surrogate) + property, which Perl does not; the Perl documentation says "Because + Perl hides the need for the user to understand the internal representa- + tion of Unicode characters, there is no need to implement the somewhat + messy concept of surrogates." + + 7. PCRE does support the \Q...\E escape for quoting substrings. Charac- + ters in between are treated as literals. This is slightly different + from Perl in that $ and @ are also handled as literals inside the + quotes. In Perl, they cause variable interpolation (but of course PCRE + does not have variables). Note the following examples: + + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz + + The \Q...\E sequence is recognized both inside and outside character + classes. + + 8. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) + constructions. However, there is support for recursive patterns. This + is not available in Perl 5.8, but it is in Perl 5.10. Also, the PCRE + "callout" feature allows an external function to be called during pat- + tern matching. See the pcrecallout documentation for details. + + 9. Subpatterns that are called as subroutines (whether or not recur- + sively) are always treated as atomic groups in PCRE. This is like + Python, but unlike Perl. Captured values that are set outside a sub- + routine call can be reference from inside in PCRE, but not in Perl. + There is a discussion that explains these differences in more detail in + the section on recursion differences from Perl in the pcrepattern page. + + 10. If any of the backtracking control verbs are used in a subpattern + that is called as a subroutine (whether or not recursively), their + effect is confined to that subpattern; it does not extend to the sur- + rounding pattern. This is not always the case in Perl. In particular, + if (*THEN) is present in a group that is called as a subroutine, its + action is limited to that group, even if the group does not contain any + | characters. Note that such subpatterns are processed as anchored at + the point where they are tested. + + 11. If a pattern contains more than one backtracking control verb, the + first one that is backtracked onto acts. For example, in the pattern + A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure + in C triggers (*PRUNE). Perl's behaviour is more complex; in many cases + it is the same as PCRE, but there are examples where it differs. + + 12. Most backtracking verbs in assertions have their normal actions. + They are not confined to the assertion. + + 13. There are some differences that are concerned with the settings of + captured strings when part of a pattern is repeated. For example, + matching "aba" against the pattern /^(a(b)?)+$/ in Perl leaves $2 + unset, but in PCRE it is set to "b". + + 14. PCRE's handling of duplicate subpattern numbers and duplicate sub- + pattern names is not as general as Perl's. This is a consequence of the + fact the PCRE works internally just with numbers, using an external ta- + ble to translate between numbers and names. In particular, a pattern + such as (?|(?<a>A)|(?<b)B), where the two capturing parentheses have + the same number but different names, is not supported, and causes an + error at compile time. If it were allowed, it would not be possible to + distinguish which parentheses matched, because both names map to cap- + turing subpattern number 1. To avoid this confusing situation, an error + is given at compile time. + + 15. Perl recognizes comments in some places that PCRE does not, for + example, between the ( and ? at the start of a subpattern. If the /x + modifier is set, Perl allows white space between ( and ? (though cur- + rent Perls warn that this is deprecated) but PCRE never does, even if + the PCRE_EXTENDED option is set. + + 16. Perl, when in warning mode, gives warnings for character classes + such as [A-\d] or [a-[:digit:]]. It then treats the hyphens as liter- + als. PCRE has no warning features, so it gives an error in these cases + because they are almost certainly user mistakes. + + 17. In PCRE, the upper/lower case character properties Lu and Ll are + not affected when case-independent matching is specified. For example, + \p{Lu} always matches an upper case letter. I think Perl has changed in + this respect; in the release at the time of writing (5.16), \p{Lu} and + \p{Ll} match all letters, regardless of case, when case independence is + specified. + + 18. PCRE provides some extensions to the Perl regular expression facil- + ities. Perl 5.10 includes new features that are not in earlier ver- + sions of Perl, some of which (such as named parentheses) have been in + PCRE for some time. This list is with respect to Perl 5.10: + + (a) Although lookbehind assertions in PCRE must match fixed length + strings, each alternative branch of a lookbehind assertion can match a + different length of string. Perl requires them all to have the same + length. + + (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ + meta-character matches only at the very end of the string. + + (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe- + cial meaning is faulted. Otherwise, like Perl, the backslash is quietly + ignored. (Perl can be made to issue a warning.) + + (d) If PCRE_UNGREEDY is set, the greediness of the repetition quanti- + fiers is inverted, that is, by default they are not greedy, but if fol- + lowed by a question mark they are. + + (e) PCRE_ANCHORED can be used at matching time to force a pattern to be + tried only at the first matching position in the subject string. + + (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, + and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no Perl equiva- + lents. + + (g) The \R escape sequence can be restricted to match only CR, LF, or + CRLF by the PCRE_BSR_ANYCRLF option. + + (h) The callout facility is PCRE-specific. + + (i) The partial matching facility is PCRE-specific. + + (j) Patterns compiled by PCRE can be saved and re-used at a later time, + even on different hosts that have the other endianness. However, this + does not apply to optimized data created by the just-in-time compiler. + + (k) The alternative matching functions (pcre_dfa_exec(), + pcre16_dfa_exec() and pcre32_dfa_exec(),) match in a different way and + are not Perl-compatible. + + (l) PCRE recognizes some special sequences such as (*CR) at the start + of a pattern that set overall options that cannot be changed within the + pattern. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 10 November 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREPATTERN(3) Library Functions Manual PCREPATTERN(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE REGULAR EXPRESSION DETAILS + + The syntax and semantics of the regular expressions that are supported + by PCRE are described in detail below. There is a quick-reference syn- + tax summary in the pcresyntax page. PCRE tries to match Perl syntax and + semantics as closely as it can. PCRE also supports some alternative + regular expression syntax (which does not conflict with the Perl syn- + tax) in order to provide some compatibility with regular expressions in + Python, .NET, and Oniguruma. + + Perl's regular expressions are described in its own documentation, and + regular expressions in general are covered in a number of books, some + of which have copious examples. Jeffrey Friedl's "Mastering Regular + Expressions", published by O'Reilly, covers regular expressions in + great detail. This description of PCRE's regular expressions is + intended as reference material. + + This document discusses the patterns that are supported by PCRE when + one its main matching functions, pcre_exec() (8-bit) or + pcre[16|32]_exec() (16- or 32-bit), is used. PCRE also has alternative + matching functions, pcre_dfa_exec() and pcre[16|32_dfa_exec(), which + match using a different algorithm that is not Perl-compatible. Some of + the features discussed below are not available when DFA matching is + used. The advantages and disadvantages of the alternative functions, + and how they differ from the normal functions, are discussed in the + pcrematching page. + + +SPECIAL START-OF-PATTERN ITEMS + + A number of options that can be passed to pcre_compile() can also be + set by special items at the start of a pattern. These are not Perl-com- + patible, but are provided to make these options accessible to pattern + writers who are not able to change the program that processes the pat- + tern. Any number of these items may appear, but they must all be + together right at the start of the pattern string, and the letters must + be in upper case. + + UTF support + + The original operation of PCRE was on strings of one-byte characters. + However, there is now also support for UTF-8 strings in the original + library, an extra library that supports 16-bit and UTF-16 character + strings, and a third library that supports 32-bit and UTF-32 character + strings. To use these features, PCRE must be built to include appropri- + ate support. When using UTF strings you must either call the compiling + function with the PCRE_UTF8, PCRE_UTF16, or PCRE_UTF32 option, or the + pattern must start with one of these special sequences: + + (*UTF8) + (*UTF16) + (*UTF32) + (*UTF) + + (*UTF) is a generic sequence that can be used with any of the + libraries. Starting a pattern with such a sequence is equivalent to + setting the relevant option. How setting a UTF mode affects pattern + matching is mentioned in several places below. There is also a summary + of features in the pcreunicode page. + + Some applications that allow their users to supply patterns may wish to + restrict them to non-UTF data for security reasons. If the + PCRE_NEVER_UTF option is set at compile time, (*UTF) etc. are not + allowed, and their appearance causes an error. + + Unicode property support + + Another special sequence that may appear at the start of a pattern is + (*UCP). This has the same effect as setting the PCRE_UCP option: it + causes sequences such as \d and \w to use Unicode properties to deter- + mine character types, instead of recognizing only characters with codes + less than 128 via a lookup table. + + Disabling auto-possessification + + If a pattern starts with (*NO_AUTO_POSSESS), it has the same effect as + setting the PCRE_NO_AUTO_POSSESS option at compile time. This stops + PCRE from making quantifiers possessive when what follows cannot match + the repeated item. For example, by default a+b is treated as a++b. For + more details, see the pcreapi documentation. + + Disabling start-up optimizations + + If a pattern starts with (*NO_START_OPT), it has the same effect as + setting the PCRE_NO_START_OPTIMIZE option either at compile or matching + time. This disables several optimizations for quickly reaching "no + match" results. For more details, see the pcreapi documentation. + + Newline conventions + + PCRE supports five different conventions for indicating line breaks in + strings: a single CR (carriage return) character, a single LF (line- + feed) character, the two-character sequence CRLF, any of the three pre- + ceding, or any Unicode newline sequence. The pcreapi page has further + discussion about newlines, and shows how to set the newline convention + in the options arguments for the compiling and matching functions. + + It is also possible to specify a newline convention by starting a pat- + tern string with one of the following five sequences: + + (*CR) carriage return + (*LF) linefeed + (*CRLF) carriage return, followed by linefeed + (*ANYCRLF) any of the three above + (*ANY) all Unicode newline sequences + + These override the default and the options given to the compiling func- + tion. For example, on a Unix system where LF is the default newline + sequence, the pattern + + (*CR)a.b + + changes the convention to CR. That pattern matches "a\nb" because LF is + no longer a newline. If more than one of these settings is present, the + last one is used. + + The newline convention affects where the circumflex and dollar asser- + tions are true. It also affects the interpretation of the dot metachar- + acter when PCRE_DOTALL is not set, and the behaviour of \N. However, it + does not affect what the \R escape sequence matches. By default, this + is any Unicode newline sequence, for Perl compatibility. However, this + can be changed; see the description of \R in the section entitled "New- + line sequences" below. A change of \R setting can be combined with a + change of newline convention. + + Setting match and recursion limits + + The caller of pcre_exec() can set a limit on the number of times the + internal match() function is called and on the maximum depth of recur- + sive calls. These facilities are provided to catch runaway matches that + are provoked by patterns with huge matching trees (a typical example is + a pattern with nested unlimited repeats) and to avoid running out of + system stack by too much recursion. When one of these limits is + reached, pcre_exec() gives an error return. The limits can also be set + by items at the start of the pattern of the form + + (*LIMIT_MATCH=d) + (*LIMIT_RECURSION=d) + + where d is any number of decimal digits. However, the value of the set- + ting must be less than the value set (or defaulted) by the caller of + pcre_exec() for it to have any effect. In other words, the pattern + writer can lower the limits set by the programmer, but not raise them. + If there is more than one setting of one of these limits, the lower + value is used. + + +EBCDIC CHARACTER CODES + + PCRE can be compiled to run in an environment that uses EBCDIC as its + character code rather than ASCII or Unicode (typically a mainframe sys- + tem). In the sections below, character code values are ASCII or Uni- + code; in an EBCDIC environment these characters may have different code + values, and there are no code points greater than 255. + + +CHARACTERS AND METACHARACTERS + + A regular expression is a pattern that is matched against a subject + string from left to right. Most characters stand for themselves in a + pattern, and match the corresponding characters in the subject. As a + trivial example, the pattern + + The quick brown fox + + matches a portion of a subject string that is identical to itself. When + caseless matching is specified (the PCRE_CASELESS option), letters are + matched independently of case. In a UTF mode, PCRE always understands + the concept of case for characters whose values are less than 128, so + caseless matching is always possible. For characters with higher val- + ues, the concept of case is supported if PCRE is compiled with Unicode + property support, but not otherwise. If you want to use caseless + matching for characters 128 and above, you must ensure that PCRE is + compiled with Unicode property support as well as with UTF support. + + The power of regular expressions comes from the ability to include + alternatives and repetitions in the pattern. These are encoded in the + pattern by the use of metacharacters, which do not stand for themselves + but instead are interpreted in some special way. + + There are two different sets of metacharacters: those that are recog- + nized anywhere in the pattern except within square brackets, and those + that are recognized within square brackets. Outside square brackets, + the metacharacters are as follows: + + \ general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier + + Part of a pattern that is in square brackets is called a "character + class". In a character class the only metacharacters are: + + \ general escape character + ^ negate the class, but only if the first character + - indicates character range + [ POSIX character class (only if followed by POSIX + syntax) + ] terminates the character class + + The following sections describe the use of each of the metacharacters. + + +BACKSLASH + + The backslash character has several uses. Firstly, if it is followed by + a character that is not a number or a letter, it takes away any special + meaning that character may have. This use of backslash as an escape + character applies both inside and outside character classes. + + For example, if you want to match a * character, you write \* in the + pattern. This escaping action applies whether or not the following + character would otherwise be interpreted as a metacharacter, so it is + always safe to precede a non-alphanumeric with backslash to specify + that it stands for itself. In particular, if you want to match a back- + slash, you write \\. + + In a UTF mode, only ASCII numbers and letters have any special meaning + after a backslash. All other characters (in particular, those whose + codepoints are greater than 127) are treated as literals. + + If a pattern is compiled with the PCRE_EXTENDED option, most white + space in the pattern (other than in a character class), and characters + between a # outside a character class and the next newline, inclusive, + are ignored. An escaping backslash can be used to include a white space + or # character as part of the pattern. + + If you want to remove the special meaning from a sequence of charac- + ters, you can do so by putting them between \Q and \E. This is differ- + ent from Perl in that $ and @ are handled as literals in \Q...\E + sequences in PCRE, whereas in Perl, $ and @ cause variable interpola- + tion. Note the following examples: + + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz + + The \Q...\E sequence is recognized both inside and outside character + classes. An isolated \E that is not preceded by \Q is ignored. If \Q + is not followed by \E later in the pattern, the literal interpretation + continues to the end of the pattern (that is, \E is assumed at the + end). If the isolated \Q is inside a character class, this causes an + error, because the character class is not terminated. + + Non-printing characters + + A second use of backslash provides a way of encoding non-printing char- + acters in patterns in a visible manner. There is no restriction on the + appearance of non-printing characters, apart from the binary zero that + terminates a pattern, but when a pattern is being prepared by text + editing, it is often easier to use one of the following escape + sequences than the binary character it represents. In an ASCII or Uni- + code environment, these escapes are as follows: + + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any ASCII character + \e escape (hex 1B) + \f form feed (hex 0C) + \n linefeed (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \0dd character with octal code 0dd + \ddd character with octal code ddd, or back reference + \o{ddd..} character with octal code ddd.. + \xhh character with hex code hh + \x{hhh..} character with hex code hhh.. (non-JavaScript mode) + \uhhhh character with hex code hhhh (JavaScript mode only) + + The precise effect of \cx on ASCII characters is as follows: if x is a + lower case letter, it is converted to upper case. Then bit 6 of the + character (hex 40) is inverted. Thus \cA to \cZ become hex 01 to hex 1A + (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and \c; becomes + hex 7B (; is 3B). If the data item (byte or 16-bit value) following \c + has a value greater than 127, a compile-time error occurs. This locks + out non-ASCII characters in all modes. + + When PCRE is compiled in EBCDIC mode, \a, \e, \f, \n, \r, and \t gener- + ate the appropriate EBCDIC code values. The \c escape is processed as + specified for Perl in the perlebcdic document. The only characters that + are allowed after \c are A-Z, a-z, or one of @, [, \, ], ^, _, or ?. + Any other character provokes a compile-time error. The sequence \@ + encodes character code 0; the letters (in either case) encode charac- + ters 1-26 (hex 01 to hex 1A); [, \, ], ^, and _ encode characters 27-31 + (hex 1B to hex 1F), and \? becomes either 255 (hex FF) or 95 (hex 5F). + + Thus, apart from \?, these escapes generate the same character code + values as they do in an ASCII environment, though the meanings of the + values mostly differ. For example, \G always generates code value 7, + which is BEL in ASCII but DEL in EBCDIC. + + The sequence \? generates DEL (127, hex 7F) in an ASCII environment, + but because 127 is not a control character in EBCDIC, Perl makes it + generate the APC character. Unfortunately, there are several variants + of EBCDIC. In most of them the APC character has the value 255 (hex + FF), but in the one Perl calls POSIX-BC its value is 95 (hex 5F). If + certain other characters have POSIX-BC values, PCRE makes \? generate + 95; otherwise it generates 255. + + After \0 up to two further octal digits are read. If there are fewer + than two digits, just those that are present are used. Thus the + sequence \0\x\015 specifies two binary zeros followed by a CR character + (code value 13). Make sure you supply two digits after the initial zero + if the pattern character that follows is itself an octal digit. + + The escape \o must be followed by a sequence of octal digits, enclosed + in braces. An error occurs if this is not the case. This escape is a + recent addition to Perl; it provides way of specifying character code + points as octal numbers greater than 0777, and it also allows octal + numbers and back references to be unambiguously specified. + + For greater clarity and unambiguity, it is best to avoid following \ by + a digit greater than zero. Instead, use \o{} or \x{} to specify charac- + ter numbers, and \g{} to specify back references. The following para- + graphs describe the old, ambiguous syntax. + + The handling of a backslash followed by a digit other than 0 is compli- + cated, and Perl has changed in recent releases, causing PCRE also to + change. Outside a character class, PCRE reads the digit and any follow- + ing digits as a decimal number. If the number is less than 8, or if + there have been at least that many previous capturing left parentheses + in the expression, the entire sequence is taken as a back reference. A + description of how this works is given later, following the discussion + of parenthesized subpatterns. + + Inside a character class, or if the decimal number following \ is + greater than 7 and there have not been that many capturing subpatterns, + PCRE handles \8 and \9 as the literal characters "8" and "9", and oth- + erwise re-reads up to three octal digits following the backslash, using + them to generate a data character. Any subsequent digits stand for + themselves. For example: + + \040 is another way of writing an ASCII space + \40 is the same, provided there are fewer than 40 + previous capturing subpatterns + \7 is always a back reference + \11 might be a back reference, or another way of + writing a tab + \011 is always a tab + \0113 is a tab followed by the character "3" + \113 might be a back reference, otherwise the + character with octal code 113 + \377 might be a back reference, otherwise + the value 255 (decimal) + \81 is either a back reference, or the two + characters "8" and "1" + + Note that octal values of 100 or greater that are specified using this + syntax must not be introduced by a leading zero, because no more than + three octal digits are ever read. + + By default, after \x that is not followed by {, from zero to two hexa- + decimal digits are read (letters can be in upper or lower case). Any + number of hexadecimal digits may appear between \x{ and }. If a charac- + ter other than a hexadecimal digit appears between \x{ and }, or if + there is no terminating }, an error occurs. + + If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \x + is as just described only when it is followed by two hexadecimal dig- + its. Otherwise, it matches a literal "x" character. In JavaScript + mode, support for code points greater than 256 is provided by \u, which + must be followed by four hexadecimal digits; otherwise it matches a + literal "u" character. + + Characters whose value is less than 256 can be defined by either of the + two syntaxes for \x (or by \u in JavaScript mode). There is no differ- + ence in the way they are handled. For example, \xdc is exactly the same + as \x{dc} (or \u00dc in JavaScript mode). + + Constraints on character values + + Characters that are specified using octal or hexadecimal numbers are + limited to certain values, as follows: + + 8-bit non-UTF mode less than 0x100 + 8-bit UTF-8 mode less than 0x10ffff and a valid codepoint + 16-bit non-UTF mode less than 0x10000 + 16-bit UTF-16 mode less than 0x10ffff and a valid codepoint + 32-bit non-UTF mode less than 0x100000000 + 32-bit UTF-32 mode less than 0x10ffff and a valid codepoint + + Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so- + called "surrogate" codepoints), and 0xffef. + + Escape sequences in character classes + + All the sequences that define a single character value can be used both + inside and outside character classes. In addition, inside a character + class, \b is interpreted as the backspace character (hex 08). + + \N is not allowed in a character class. \B, \R, and \X are not special + inside a character class. Like other unrecognized escape sequences, + they are treated as the literal characters "B", "R", and "X" by + default, but cause an error if the PCRE_EXTRA option is set. Outside a + character class, these sequences have different meanings. + + Unsupported escape sequences + + In Perl, the sequences \l, \L, \u, and \U are recognized by its string + handler and used to modify the case of following characters. By + default, PCRE does not support these escape sequences. However, if the + PCRE_JAVASCRIPT_COMPAT option is set, \U matches a "U" character, and + \u can be used to define a character by code point, as described in the + previous section. + + Absolute and relative back references + + The sequence \g followed by an unsigned or a negative number, option- + ally enclosed in braces, is an absolute or relative back reference. A + named back reference can be coded as \g{name}. Back references are dis- + cussed later, following the discussion of parenthesized subpatterns. + + Absolute and relative subroutine calls + + For compatibility with Oniguruma, the non-Perl syntax \g followed by a + name or a number enclosed either in angle brackets or single quotes, is + an alternative syntax for referencing a subpattern as a "subroutine". + Details are discussed later. Note that \g{...} (Perl syntax) and + \g<...> (Oniguruma syntax) are not synonymous. The former is a back + reference; the latter is a subroutine call. + + Generic character types + + Another use of backslash is for specifying generic character types: + + \d any decimal digit + \D any character that is not a decimal digit + \h any horizontal white space character + \H any character that is not a horizontal white space character + \s any white space character + \S any character that is not a white space character + \v any vertical white space character + \V any character that is not a vertical white space character + \w any "word" character + \W any "non-word" character + + There is also the single sequence \N, which matches a non-newline char- + acter. This is the same as the "." metacharacter when PCRE_DOTALL is + not set. Perl also uses \N to match characters by name; PCRE does not + support this. + + Each pair of lower and upper case escape sequences partitions the com- + plete set of characters into two disjoint sets. Any given character + matches one, and only one, of each pair. The sequences can appear both + inside and outside character classes. They each match one character of + the appropriate type. If the current matching point is at the end of + the subject string, all of them fail, because there is no character to + match. + + For compatibility with Perl, \s did not used to match the VT character + (code 11), which made it different from the the POSIX "space" class. + However, Perl added VT at release 5.18, and PCRE followed suit at + release 8.34. The default \s characters are now HT (9), LF (10), VT + (11), FF (12), CR (13), and space (32), which are defined as white + space in the "C" locale. This list may vary if locale-specific matching + is taking place. For example, in some locales the "non-breaking space" + character (\xA0) is recognized as white space, and in others the VT + character is not. + + A "word" character is an underscore or any character that is a letter + or digit. By default, the definition of letters and digits is con- + trolled by PCRE's low-valued character tables, and may vary if locale- + specific matching is taking place (see "Locale support" in the pcreapi + page). For example, in a French locale such as "fr_FR" in Unix-like + systems, or "french" in Windows, some character codes greater than 127 + are used for accented letters, and these are then matched by \w. The + use of locales with Unicode is discouraged. + + By default, characters whose code points are greater than 127 never + match \d, \s, or \w, and always match \D, \S, and \W, although this may + vary for characters in the range 128-255 when locale-specific matching + is happening. These escape sequences retain their original meanings + from before Unicode support was available, mainly for efficiency rea- + sons. If PCRE is compiled with Unicode property support, and the + PCRE_UCP option is set, the behaviour is changed so that Unicode prop- + erties are used to determine character types, as follows: + + \d any character that matches \p{Nd} (decimal digit) + \s any character that matches \p{Z} or \h or \v + \w any character that matches \p{L} or \p{N}, plus underscore + + The upper case escapes match the inverse sets of characters. Note that + \d matches only decimal digits, whereas \w matches any Unicode digit, + as well as any Unicode letter, and underscore. Note also that PCRE_UCP + affects \b, and \B because they are defined in terms of \w and \W. + Matching these sequences is noticeably slower when PCRE_UCP is set. + + The sequences \h, \H, \v, and \V are features that were added to Perl + at release 5.10. In contrast to the other sequences, which match only + ASCII characters by default, these always match certain high-valued + code points, whether or not PCRE_UCP is set. The horizontal space char- + acters are: + + U+0009 Horizontal tab (HT) + U+0020 Space + U+00A0 Non-break space + U+1680 Ogham space mark + U+180E Mongolian vowel separator + U+2000 En quad + U+2001 Em quad + U+2002 En space + U+2003 Em space + U+2004 Three-per-em space + U+2005 Four-per-em space + U+2006 Six-per-em space + U+2007 Figure space + U+2008 Punctuation space + U+2009 Thin space + U+200A Hair space + U+202F Narrow no-break space + U+205F Medium mathematical space + U+3000 Ideographic space + + The vertical space characters are: + + U+000A Linefeed (LF) + U+000B Vertical tab (VT) + U+000C Form feed (FF) + U+000D Carriage return (CR) + U+0085 Next line (NEL) + U+2028 Line separator + U+2029 Paragraph separator + + In 8-bit, non-UTF-8 mode, only the characters with codepoints less than + 256 are relevant. + + Newline sequences + + Outside a character class, by default, the escape sequence \R matches + any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent + to the following: + + (?>\r\n|\n|\x0b|\f|\r|\x85) + + This is an example of an "atomic group", details of which are given + below. This particular group matches either the two-character sequence + CR followed by LF, or one of the single characters LF (linefeed, + U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car- + riage return, U+000D), or NEL (next line, U+0085). The two-character + sequence is treated as a single unit that cannot be split. + + In other modes, two additional characters whose codepoints are greater + than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa- + rator, U+2029). Unicode character property support is not needed for + these characters to be recognized. + + It is possible to restrict \R to match only CR, LF, or CRLF (instead of + the complete set of Unicode line endings) by setting the option + PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched. + (BSR is an abbrevation for "backslash R".) This can be made the default + when PCRE is built; if this is the case, the other behaviour can be + requested via the PCRE_BSR_UNICODE option. It is also possible to + specify these settings by starting a pattern string with one of the + following sequences: + + (*BSR_ANYCRLF) CR, LF, or CRLF only + (*BSR_UNICODE) any Unicode newline sequence + + These override the default and the options given to the compiling func- + tion, but they can themselves be overridden by options given to a + matching function. Note that these special settings, which are not + Perl-compatible, are recognized only at the very start of a pattern, + and that they must be in upper case. If more than one of them is + present, the last one is used. They can be combined with a change of + newline convention; for example, a pattern can start with: + + (*ANY)(*BSR_ANYCRLF) + + They can also be combined with the (*UTF8), (*UTF16), (*UTF32), (*UTF) + or (*UCP) special sequences. Inside a character class, \R is treated as + an unrecognized escape sequence, and so matches the letter "R" by + default, but causes an error if PCRE_EXTRA is set. + + Unicode character properties + + When PCRE is built with Unicode character property support, three addi- + tional escape sequences that match characters with specific properties + are available. When in 8-bit non-UTF-8 mode, these sequences are of + course limited to testing characters whose codepoints are less than + 256, but they do work in this mode. The extra escape sequences are: + + \p{xx} a character with the xx property + \P{xx} a character without the xx property + \X a Unicode extended grapheme cluster + + The property names represented by xx above are limited to the Unicode + script names, the general category properties, "Any", which matches any + character (including newline), and some special PCRE properties + (described in the next section). Other Perl properties such as "InMu- + sicalSymbols" are not currently supported by PCRE. Note that \P{Any} + does not match any characters, so always causes a match failure. + + Sets of Unicode characters are defined as belonging to certain scripts. + A character from one of these sets can be matched using a script name. + For example: + + \p{Greek} + \P{Han} + + Those that are not part of an identified script are lumped together as + "Common". The current list of scripts is: + + Arabic, Armenian, Avestan, Balinese, Bamum, Bassa_Vah, Batak, Bengali, + Bopomofo, Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Car- + ian, Caucasian_Albanian, Chakma, Cham, Cherokee, Common, Coptic, Cunei- + form, Cypriot, Cyrillic, Deseret, Devanagari, Duployan, Egyptian_Hiero- + glyphs, Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, + Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, + Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- + tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, + Kharoshthi, Khmer, Khojki, Khudawadi, Lao, Latin, Lepcha, Limbu, Lin- + ear_A, Linear_B, Lisu, Lycian, Lydian, Mahajani, Malayalam, Mandaic, + Manichaean, Meetei_Mayek, Mende_Kikakui, Meroitic_Cursive, + Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Myanmar, Nabataean, + New_Tai_Lue, Nko, Ogham, Ol_Chiki, Old_Italic, Old_North_Arabian, + Old_Permic, Old_Persian, Old_South_Arabian, Old_Turkic, Oriya, Osmanya, + Pahawh_Hmong, Palmyrene, Pau_Cin_Hau, Phags_Pa, Phoenician, + Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha- + vian, Siddham, Sinhala, Sora_Sompeng, Sundanese, Syloti_Nagri, Syriac, + Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, Takri, Tamil, Telugu, + Thaana, Thai, Tibetan, Tifinagh, Tirhuta, Ugaritic, Vai, Warang_Citi, + Yi. + + Each character has exactly one Unicode general category property, spec- + ified by a two-letter abbreviation. For compatibility with Perl, nega- + tion can be specified by including a circumflex between the opening + brace and the property name. For example, \p{^Lu} is the same as + \P{Lu}. + + If only one letter is specified with \p or \P, it includes all the gen- + eral category properties that start with that letter. In this case, in + the absence of negation, the curly brackets in the escape sequence are + optional; these two examples have the same effect: + + \p{L} + \pL + + The following general category property codes are supported: + + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate + + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter + + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark + + N Number + Nd Decimal number + Nl Letter number + No Other number + + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation + + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol + + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator + + The special property L& is also supported: it matches a character that + has the Lu, Ll, or Lt property, in other words, a letter that is not + classified as a modifier or "other". + + The Cs (Surrogate) property applies only to characters in the range + U+D800 to U+DFFF. Such characters are not valid in Unicode strings and + so cannot be tested by PCRE, unless UTF validity checking has been + turned off (see the discussion of PCRE_NO_UTF8_CHECK, + PCRE_NO_UTF16_CHECK and PCRE_NO_UTF32_CHECK in the pcreapi page). Perl + does not support the Cs property. + + The long synonyms for property names that Perl supports (such as + \p{Letter}) are not supported by PCRE, nor is it permitted to prefix + any of these properties with "Is". + + No character that is in the Unicode table has the Cn (unassigned) prop- + erty. Instead, this property is assumed for any code point that is not + in the Unicode table. + + Specifying caseless matching does not affect these escape sequences. + For example, \p{Lu} always matches only upper case letters. This is + different from the behaviour of current versions of Perl. + + Matching characters by Unicode property is not fast, because PCRE has + to do a multistage table lookup in order to find a character's prop- + erty. That is why the traditional escape sequences such as \d and \w do + not use Unicode properties in PCRE by default, though you can make them + do so by setting the PCRE_UCP option or by starting the pattern with + (*UCP). + + Extended grapheme clusters + + The \X escape matches any number of Unicode characters that form an + "extended grapheme cluster", and treats the sequence as an atomic group + (see below). Up to and including release 8.31, PCRE matched an ear- + lier, simpler definition that was equivalent to + + (?>\PM\pM*) + + That is, it matched a character without the "mark" property, followed + by zero or more characters with the "mark" property. Characters with + the "mark" property are typically non-spacing accents that affect the + preceding character. + + This simple definition was extended in Unicode to include more compli- + cated kinds of composite character by giving each character a grapheme + breaking property, and creating rules that use these properties to + define the boundaries of extended grapheme clusters. In releases of + PCRE later than 8.31, \X matches one of these clusters. + + \X always matches at least one character. Then it decides whether to + add additional characters according to the following rules for ending a + cluster: + + 1. End at the end of the subject string. + + 2. Do not end between CR and LF; otherwise end after any control char- + acter. + + 3. Do not break Hangul (a Korean script) syllable sequences. Hangul + characters are of five types: L, V, T, LV, and LVT. An L character may + be followed by an L, V, LV, or LVT character; an LV or V character may + be followed by a V or T character; an LVT or T character may be follwed + only by a T character. + + 4. Do not end before extending characters or spacing marks. Characters + with the "mark" property always have the "extend" grapheme breaking + property. + + 5. Do not end after prepend characters. + + 6. Otherwise, end the cluster. + + PCRE's additional properties + + As well as the standard Unicode properties described above, PCRE sup- + ports four more that make it possible to convert traditional escape + sequences such as \w and \s to use Unicode properties. PCRE uses these + non-standard, non-Perl properties internally when PCRE_UCP is set. How- + ever, they may also be used explicitly. These properties are: + + Xan Any alphanumeric character + Xps Any POSIX space character + Xsp Any Perl space character + Xwd Any Perl "word" character + + Xan matches characters that have either the L (letter) or the N (num- + ber) property. Xps matches the characters tab, linefeed, vertical tab, + form feed, or carriage return, and any other character that has the Z + (separator) property. Xsp is the same as Xps; it used to exclude ver- + tical tab, for Perl compatibility, but Perl changed, and so PCRE fol- + lowed at release 8.34. Xwd matches the same characters as Xan, plus + underscore. + + There is another non-standard property, Xuc, which matches any charac- + ter that can be represented by a Universal Character Name in C++ and + other programming languages. These are the characters $, @, ` (grave + accent), and all characters with Unicode code points greater than or + equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that + most base (ASCII) characters are excluded. (Universal Character Names + are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit. + Note that the Xuc property does not match these sequences but the char- + acters that they represent.) + + Resetting the match start + + The escape sequence \K causes any previously matched characters not to + be included in the final matched sequence. For example, the pattern: + + foo\Kbar + + matches "foobar", but reports that it has matched "bar". This feature + is similar to a lookbehind assertion (described below). However, in + this case, the part of the subject before the real match does not have + to be of fixed length, as lookbehind assertions do. The use of \K does + not interfere with the setting of captured substrings. For example, + when the pattern + + (foo)\Kbar + + matches "foobar", the first substring is still set to "foo". + + Perl documents that the use of \K within assertions is "not well + defined". In PCRE, \K is acted upon when it occurs inside positive + assertions, but is ignored in negative assertions. Note that when a + pattern such as (?=ab\K) matches, the reported start of the match can + be greater than the end of the match. + + Simple assertions + + The final use of backslash is for certain simple assertions. An asser- + tion specifies a condition that has to be met at a particular point in + a match, without consuming any characters from the subject string. The + use of subpatterns for more complicated assertions is described below. + The backslashed assertions are: + + \b matches at a word boundary + \B matches when not at a word boundary + \A matches at the start of the subject + \Z matches at the end of the subject + also matches before a newline at the end of the subject + \z matches only at the end of the subject + \G matches at the first matching position in the subject + + Inside a character class, \b has a different meaning; it matches the + backspace character. If any other of these assertions appears in a + character class, by default it matches the corresponding literal char- + acter (for example, \B matches the letter B). However, if the + PCRE_EXTRA option is set, an "invalid escape sequence" error is gener- + ated instead. + + A word boundary is a position in the subject string where the current + character and the previous character do not both match \w or \W (i.e. + one matches \w and the other matches \W), or the start or end of the + string if the first or last character matches \w, respectively. In a + UTF mode, the meanings of \w and \W can be changed by setting the + PCRE_UCP option. When this is done, it also affects \b and \B. Neither + PCRE nor Perl has a separate "start of word" or "end of word" metase- + quence. However, whatever follows \b normally determines which it is. + For example, the fragment \ba matches "a" at the start of a word. + + The \A, \Z, and \z assertions differ from the traditional circumflex + and dollar (described in the next section) in that they only ever match + at the very start and end of the subject string, whatever options are + set. Thus, they are independent of multiline mode. These three asser- + tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which + affect only the behaviour of the circumflex and dollar metacharacters. + However, if the startoffset argument of pcre_exec() is non-zero, indi- + cating that matching is to start at a point other than the beginning of + the subject, \A can never match. The difference between \Z and \z is + that \Z matches before a newline at the end of the string as well as at + the very end, whereas \z matches only at the end. + + The \G assertion is true only when the current matching position is at + the start point of the match, as specified by the startoffset argument + of pcre_exec(). It differs from \A when the value of startoffset is + non-zero. By calling pcre_exec() multiple times with appropriate argu- + ments, you can mimic Perl's /g option, and it is in this kind of imple- + mentation where \G can be useful. + + Note, however, that PCRE's interpretation of \G, as the start of the + current match, is subtly different from Perl's, which defines it as the + end of the previous match. In Perl, these can be different when the + previously matched string was empty. Because PCRE does just one match + at a time, it cannot reproduce this behaviour. + + If all the alternatives of a pattern begin with \G, the expression is + anchored to the starting match position, and the "anchored" flag is set + in the compiled regular expression. + + +CIRCUMFLEX AND DOLLAR + + The circumflex and dollar metacharacters are zero-width assertions. + That is, they test for a particular condition being true without con- + suming any characters from the subject string. + + Outside a character class, in the default matching mode, the circumflex + character is an assertion that is true only if the current matching + point is at the start of the subject string. If the startoffset argu- + ment of pcre_exec() is non-zero, circumflex can never match if the + PCRE_MULTILINE option is unset. Inside a character class, circumflex + has an entirely different meaning (see below). + + Circumflex need not be the first character of the pattern if a number + of alternatives are involved, but it should be the first thing in each + alternative in which it appears if the pattern is ever to match that + branch. If all possible alternatives start with a circumflex, that is, + if the pattern is constrained to match only at the start of the sub- + ject, it is said to be an "anchored" pattern. (There are also other + constructs that can cause a pattern to be anchored.) + + The dollar character is an assertion that is true only if the current + matching point is at the end of the subject string, or immediately + before a newline at the end of the string (by default). Note, however, + that it does not actually match the newline. Dollar need not be the + last character of the pattern if a number of alternatives are involved, + but it should be the last item in any branch in which it appears. Dol- + lar has no special meaning in a character class. + + The meaning of dollar can be changed so that it matches only at the + very end of the string, by setting the PCRE_DOLLAR_ENDONLY option at + compile time. This does not affect the \Z assertion. + + The meanings of the circumflex and dollar characters are changed if the + PCRE_MULTILINE option is set. When this is the case, a circumflex + matches immediately after internal newlines as well as at the start of + the subject string. It does not match after a newline that ends the + string. A dollar matches before any newlines in the string, as well as + at the very end, when PCRE_MULTILINE is set. When newline is specified + as the two-character sequence CRLF, isolated CR and LF characters do + not indicate newlines. + + For example, the pattern /^abc$/ matches the subject string "def\nabc" + (where \n represents a newline) in multiline mode, but not otherwise. + Consequently, patterns that are anchored in single line mode because + all branches start with ^ are not anchored in multiline mode, and a + match for circumflex is possible when the startoffset argument of + pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if + PCRE_MULTILINE is set. + + Note that the sequences \A, \Z, and \z can be used to match the start + and end of the subject in both modes, and if all branches of a pattern + start with \A it is always anchored, whether or not PCRE_MULTILINE is + set. + + +FULL STOP (PERIOD, DOT) AND \N + + Outside a character class, a dot in the pattern matches any one charac- + ter in the subject string except (by default) a character that signi- + fies the end of a line. + + When a line ending is defined as a single character, dot never matches + that character; when the two-character sequence CRLF is used, dot does + not match CR if it is immediately followed by LF, but otherwise it + matches all characters (including isolated CRs and LFs). When any Uni- + code line endings are being recognized, dot does not match CR or LF or + any of the other line ending characters. + + The behaviour of dot with regard to newlines can be changed. If the + PCRE_DOTALL option is set, a dot matches any one character, without + exception. If the two-character sequence CRLF is present in the subject + string, it takes two dots to match it. + + The handling of dot is entirely independent of the handling of circum- + flex and dollar, the only relationship being that they both involve + newlines. Dot has no special meaning in a character class. + + The escape sequence \N behaves like a dot, except that it is not + affected by the PCRE_DOTALL option. In other words, it matches any + character except one that signifies the end of a line. Perl also uses + \N to match characters by name; PCRE does not support this. + + +MATCHING A SINGLE DATA UNIT + + Outside a character class, the escape sequence \C matches any one data + unit, whether or not a UTF mode is set. In the 8-bit library, one data + unit is one byte; in the 16-bit library it is a 16-bit unit; in the + 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches + line-ending characters. The feature is provided in Perl in order to + match individual bytes in UTF-8 mode, but it is unclear how it can use- + fully be used. Because \C breaks up characters into individual data + units, matching one unit with \C in a UTF mode means that the rest of + the string may start with a malformed UTF character. This has undefined + results, because PCRE assumes that it is dealing with valid UTF strings + (and by default it checks this at the start of processing unless the + PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK or PCRE_NO_UTF32_CHECK option + is used). + + PCRE does not allow \C to appear in lookbehind assertions (described + below) in a UTF mode, because this would make it impossible to calcu- + late the length of the lookbehind. + + In general, the \C escape sequence is best avoided. However, one way of + using it that avoids the problem of malformed UTF characters is to use + a lookahead to check the length of the next character, as in this pat- + tern, which could be used with a UTF-8 string (ignore white space and + line breaks): + + (?| (?=[\x00-\x7f])(\C) | + (?=[\x80-\x{7ff}])(\C)(\C) | + (?=[\x{800}-\x{ffff}])(\C)(\C)(\C) | + (?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C)) + + A group that starts with (?| resets the capturing parentheses numbers + in each alternative (see "Duplicate Subpattern Numbers" below). The + assertions at the start of each branch check the next UTF-8 character + for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The + character's individual bytes are then captured by the appropriate num- + ber of groups. + + +SQUARE BRACKETS AND CHARACTER CLASSES + + An opening square bracket introduces a character class, terminated by a + closing square bracket. A closing square bracket on its own is not spe- + cial by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set, + a lone closing square bracket causes a compile-time error. If a closing + square bracket is required as a member of the class, it should be the + first data character in the class (after an initial circumflex, if + present) or escaped with a backslash. + + A character class matches a single character in the subject. In a UTF + mode, the character may be more than one data unit long. A matched + character must be in the set of characters defined by the class, unless + the first character in the class definition is a circumflex, in which + case the subject character must not be in the set defined by the class. + If a circumflex is actually required as a member of the class, ensure + it is not the first character, or escape it with a backslash. + + For example, the character class [aeiou] matches any lower case vowel, + while [^aeiou] matches any character that is not a lower case vowel. + Note that a circumflex is just a convenient notation for specifying the + characters that are in the class by enumerating those that are not. A + class that starts with a circumflex is not an assertion; it still con- + sumes a character from the subject string, and therefore it fails if + the current pointer is at the end of the string. + + In UTF-8 (UTF-16, UTF-32) mode, characters with values greater than 255 + (0xffff) can be included in a class as a literal string of data units, + or by using the \x{ escaping mechanism. + + When caseless matching is set, any letters in a class represent both + their upper case and lower case versions, so for example, a caseless + [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not + match "A", whereas a caseful version would. In a UTF mode, PCRE always + understands the concept of case for characters whose values are less + than 128, so caseless matching is always possible. For characters with + higher values, the concept of case is supported if PCRE is compiled + with Unicode property support, but not otherwise. If you want to use + caseless matching in a UTF mode for characters 128 and above, you must + ensure that PCRE is compiled with Unicode property support as well as + with UTF support. + + Characters that might indicate line breaks are never treated in any + special way when matching character classes, whatever line-ending + sequence is in use, and whatever setting of the PCRE_DOTALL and + PCRE_MULTILINE options is used. A class such as [^a] always matches one + of these characters. + + The minus (hyphen) character can be used to specify a range of charac- + ters in a character class. For example, [d-m] matches any letter + between d and m, inclusive. If a minus character is required in a + class, it must be escaped with a backslash or appear in a position + where it cannot be interpreted as indicating a range, typically as the + first or last character in the class, or immediately after a range. For + example, [b-d-z] matches letters in the range b to d, a hyphen charac- + ter, or z. + + It is not possible to have the literal character "]" as the end charac- + ter of a range. A pattern such as [W-]46] is interpreted as a class of + two characters ("W" and "-") followed by a literal string "46]", so it + would match "W46]" or "-46]". However, if the "]" is escaped with a + backslash it is interpreted as the end of range, so [W-\]46] is inter- + preted as a class containing a range followed by two other characters. + The octal or hexadecimal representation of "]" can also be used to end + a range. + + An error is generated if a POSIX character class (see below) or an + escape sequence other than one that defines a single character appears + at a point where a range ending character is expected. For example, + [z-\xff] is valid, but [A-\d] and [A-[:digit:]] are not. + + Ranges operate in the collating sequence of character values. They can + also be used for characters specified numerically, for example + [\000-\037]. Ranges can include any characters that are valid for the + current mode. + + If a range that includes letters is used when caseless matching is set, + it matches the letters in either case. For example, [W-c] is equivalent + to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if + character tables for a French locale are in use, [\xc8-\xcb] matches + accented E characters in both cases. In UTF modes, PCRE supports the + concept of case for characters with values greater than 128 only when + it is compiled with Unicode property support. + + The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, + \w, and \W may appear in a character class, and add the characters that + they match to the class. For example, [\dABCDEF] matches any hexadeci- + mal digit. In UTF modes, the PCRE_UCP option affects the meanings of + \d, \s, \w and their upper case partners, just as it does when they + appear outside a character class, as described in the section entitled + "Generic character types" above. The escape sequence \b has a different + meaning inside a character class; it matches the backspace character. + The sequences \B, \N, \R, and \X are not special inside a character + class. Like any other unrecognized escape sequences, they are treated + as the literal characters "B", "N", "R", and "X" by default, but cause + an error if the PCRE_EXTRA option is set. + + A circumflex can conveniently be used with the upper case character + types to specify a more restricted set of characters than the matching + lower case type. For example, the class [^\W_] matches any letter or + digit, but not underscore, whereas [\w] includes underscore. A positive + character class should be read as "something OR something OR ..." and a + negative class as "NOT something AND NOT something AND NOT ...". + + The only metacharacters that are recognized in character classes are + backslash, hyphen (only where it can be interpreted as specifying a + range), circumflex (only at the start), opening square bracket (only + when it can be interpreted as introducing a POSIX class name, or for a + special compatibility feature - see the next two sections), and the + terminating closing square bracket. However, escaping other non- + alphanumeric characters does no harm. + + +POSIX CHARACTER CLASSES + + Perl supports the POSIX notation for character classes. This uses names + enclosed by [: and :] within the enclosing square brackets. PCRE also + supports this notation. For example, + + [01[:alpha:]%] + + matches "0", "1", any alphabetic character, or "%". The supported class + names are: + + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \d) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits and space + space white space (the same as \s from PCRE 8.34) + upper upper case letters + word "word" characters (same as \w) + xdigit hexadecimal digits + + The default "space" characters are HT (9), LF (10), VT (11), FF (12), + CR (13), and space (32). If locale-specific matching is taking place, + the list of space characters may be different; there may be fewer or + more of them. "Space" used to be different to \s, which did not include + VT, for Perl compatibility. However, Perl changed at release 5.18, and + PCRE followed at release 8.34. "Space" and \s now match the same set + of characters. + + The name "word" is a Perl extension, and "blank" is a GNU extension + from Perl 5.8. Another Perl extension is negation, which is indicated + by a ^ character after the colon. For example, + + [12[:^digit:]] + + matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the + POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but + these are not supported, and an error is given if they are encountered. + + By default, characters with values greater than 128 do not match any of + the POSIX character classes. However, if the PCRE_UCP option is passed + to pcre_compile(), some of the classes are changed so that Unicode + character properties are used. This is achieved by replacing certain + POSIX classes by other sequences, as follows: + + [:alnum:] becomes \p{Xan} + [:alpha:] becomes \p{L} + [:blank:] becomes \h + [:digit:] becomes \p{Nd} + [:lower:] becomes \p{Ll} + [:space:] becomes \p{Xps} + [:upper:] becomes \p{Lu} + [:word:] becomes \p{Xwd} + + Negated versions, such as [:^alpha:] use \P instead of \p. Three other + POSIX classes are handled specially in UCP mode: + + [:graph:] This matches characters that have glyphs that mark the page + when printed. In Unicode property terms, it matches all char- + acters with the L, M, N, P, S, or Cf properties, except for: + + U+061C Arabic Letter Mark + U+180E Mongolian Vowel Separator + U+2066 - U+2069 Various "isolate"s + + + [:print:] This matches the same characters as [:graph:] plus space + characters that are not controls, that is, characters with + the Zs property. + + [:punct:] This matches all characters that have the Unicode P (punctua- + tion) property, plus those characters whose code points are + less than 128 that have the S (Symbol) property. + + The other POSIX classes are unchanged, and match only characters with + code points less than 128. + + +COMPATIBILITY FEATURE FOR WORD BOUNDARIES + + In the POSIX.2 compliant library that was included in 4.4BSD Unix, the + ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word" + and "end of word". PCRE treats these items as follows: + + [[:<:]] is converted to \b(?=\w) + [[:>:]] is converted to \b(?<=\w) + + Only these exact character sequences are recognized. A sequence such as + [a[:<:]b] provokes error for an unrecognized POSIX class name. This + support is not compatible with Perl. It is provided to help migrations + from other environments, and is best not used in any new patterns. Note + that \b matches at the start and the end of a word (see "Simple asser- + tions" above), and in a Perl-style pattern the preceding or following + character normally shows which is wanted, without the need for the + assertions that are used above in order to give exactly the POSIX be- + haviour. + + +VERTICAL BAR + + Vertical bar characters are used to separate alternative patterns. For + example, the pattern + + gilbert|sullivan + + matches either "gilbert" or "sullivan". Any number of alternatives may + appear, and an empty alternative is permitted (matching the empty + string). The matching process tries each alternative in turn, from left + to right, and the first one that succeeds is used. If the alternatives + are within a subpattern (defined below), "succeeds" means matching the + rest of the main pattern as well as the alternative in the subpattern. + + +INTERNAL OPTION SETTING + + The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and + PCRE_EXTENDED options (which are Perl-compatible) can be changed from + within the pattern by a sequence of Perl option letters enclosed + between "(?" and ")". The option letters are + + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED + + For example, (?im) sets caseless, multiline matching. It is also possi- + ble to unset these options by preceding the letter with a hyphen, and a + combined setting and unsetting such as (?im-sx), which sets PCRE_CASE- + LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, + is also permitted. If a letter appears both before and after the + hyphen, the option is unset. + + The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA + can be changed in the same way as the Perl-compatible options by using + the characters J, U and X respectively. + + When one of these option changes occurs at top level (that is, not + inside subpattern parentheses), the change applies to the remainder of + the pattern that follows. If the change is placed right at the start of + a pattern, PCRE extracts it into the global options (and it will there- + fore show up in data extracted by the pcre_fullinfo() function). + + An option change within a subpattern (see below for a description of + subpatterns) affects only that part of the subpattern that follows it, + so + + (a(?i)b)c + + matches abc and aBc and no other strings (assuming PCRE_CASELESS is not + used). By this means, options can be made to have different settings + in different parts of the pattern. Any changes made in one alternative + do carry on into subsequent branches within the same subpattern. For + example, + + (a(?i)b|c) + + matches "ab", "aB", "c", and "C", even though when matching "C" the + first branch is abandoned before the option setting. This is because + the effects of option settings happen at compile time. There would be + some very weird behaviour otherwise. + + Note: There are other PCRE-specific options that can be set by the + application when the compiling or matching functions are called. In + some cases the pattern can contain special leading sequences such as + (*CRLF) to override what the application has set or what has been + defaulted. Details are given in the section entitled "Newline + sequences" above. There are also the (*UTF8), (*UTF16),(*UTF32), and + (*UCP) leading sequences that can be used to set UTF and Unicode prop- + erty modes; they are equivalent to setting the PCRE_UTF8, PCRE_UTF16, + PCRE_UTF32 and the PCRE_UCP options, respectively. The (*UTF) sequence + is a generic version that can be used with any of the libraries. How- + ever, the application can set the PCRE_NEVER_UTF option, which locks + out the use of the (*UTF) sequences. + + +SUBPATTERNS + + Subpatterns are delimited by parentheses (round brackets), which can be + nested. Turning part of a pattern into a subpattern does two things: + + 1. It localizes a set of alternatives. For example, the pattern + + cat(aract|erpillar|) + + matches "cataract", "caterpillar", or "cat". Without the parentheses, + it would match "cataract", "erpillar" or an empty string. + + 2. It sets up the subpattern as a capturing subpattern. This means + that, when the whole pattern matches, that portion of the subject + string that matched the subpattern is passed back to the caller via the + ovector argument of the matching function. (This applies only to the + traditional matching functions; the DFA matching functions do not sup- + port capturing.) + + Opening parentheses are counted from left to right (starting from 1) to + obtain numbers for the capturing subpatterns. For example, if the + string "the red king" is matched against the pattern + + the ((red|white) (king|queen)) + + the captured substrings are "red king", "red", and "king", and are num- + bered 1, 2, and 3, respectively. + + The fact that plain parentheses fulfil two functions is not always + helpful. There are often times when a grouping subpattern is required + without a capturing requirement. If an opening parenthesis is followed + by a question mark and a colon, the subpattern does not do any captur- + ing, and is not counted when computing the number of any subsequent + capturing subpatterns. For example, if the string "the white queen" is + matched against the pattern + + the ((?:red|white) (king|queen)) + + the captured substrings are "white queen" and "queen", and are numbered + 1 and 2. The maximum number of capturing subpatterns is 65535. + + As a convenient shorthand, if any option settings are required at the + start of a non-capturing subpattern, the option letters may appear + between the "?" and the ":". Thus the two patterns + + (?i:saturday|sunday) + (?:(?i)saturday|sunday) + + match exactly the same set of strings. Because alternative branches are + tried from left to right, and options are not reset until the end of + the subpattern is reached, an option setting in one branch does affect + subsequent branches, so the above patterns match "SUNDAY" as well as + "Saturday". + + +DUPLICATE SUBPATTERN NUMBERS + + Perl 5.10 introduced a feature whereby each alternative in a subpattern + uses the same numbers for its capturing parentheses. Such a subpattern + starts with (?| and is itself a non-capturing subpattern. For example, + consider this pattern: + + (?|(Sat)ur|(Sun))day + + Because the two alternatives are inside a (?| group, both sets of cap- + turing parentheses are numbered one. Thus, when the pattern matches, + you can look at captured substring number one, whichever alternative + matched. This construct is useful when you want to capture part, but + not all, of one of a number of alternatives. Inside a (?| group, paren- + theses are numbered as usual, but the number is reset at the start of + each branch. The numbers of any capturing parentheses that follow the + subpattern start after the highest number used in any branch. The fol- + lowing example is taken from the Perl documentation. The numbers under- + neath show in which buffer the captured content will be stored. + + # before ---------------branch-reset----------- after + / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x + # 1 2 2 3 2 3 4 + + A back reference to a numbered subpattern uses the most recent value + that is set for that number by any subpattern. The following pattern + matches "abcabc" or "defdef": + + /(?|(abc)|(def))\1/ + + In contrast, a subroutine call to a numbered subpattern always refers + to the first one in the pattern with the given number. The following + pattern matches "abcabc" or "defabc": + + /(?|(abc)|(def))(?1)/ + + If a condition test for a subpattern's having matched refers to a non- + unique number, the test is true if any of the subpatterns of that num- + ber have matched. + + An alternative approach to using this "branch reset" feature is to use + duplicate named subpatterns, as described in the next section. + + +NAMED SUBPATTERNS + + Identifying capturing parentheses by number is simple, but it can be + very hard to keep track of the numbers in complicated regular expres- + sions. Furthermore, if an expression is modified, the numbers may + change. To help with this difficulty, PCRE supports the naming of sub- + patterns. This feature was not added to Perl until release 5.10. Python + had the feature earlier, and PCRE introduced it at release 4.0, using + the Python syntax. PCRE now supports both the Perl and the Python syn- + tax. Perl allows identically numbered subpatterns to have different + names, but PCRE does not. + + In PCRE, a subpattern can be named in one of three ways: (?<name>...) + or (?'name'...) as in Perl, or (?P<name>...) as in Python. References + to capturing parentheses from other parts of the pattern, such as back + references, recursion, and conditions, can be made by name as well as + by number. + + Names consist of up to 32 alphanumeric characters and underscores, but + must start with a non-digit. Named capturing parentheses are still + allocated numbers as well as names, exactly as if the names were not + present. The PCRE API provides function calls for extracting the name- + to-number translation table from a compiled pattern. There is also a + convenience function for extracting a captured substring by name. + + By default, a name must be unique within a pattern, but it is possible + to relax this constraint by setting the PCRE_DUPNAMES option at compile + time. (Duplicate names are also always permitted for subpatterns with + the same number, set up as described in the previous section.) Dupli- + cate names can be useful for patterns where only one instance of the + named parentheses can match. Suppose you want to match the name of a + weekday, either as a 3-letter abbreviation or as the full name, and in + both cases you want to extract the abbreviation. This pattern (ignoring + the line breaks) does the job: + + (?<DN>Mon|Fri|Sun)(?:day)?| + (?<DN>Tue)(?:sday)?| + (?<DN>Wed)(?:nesday)?| + (?<DN>Thu)(?:rsday)?| + (?<DN>Sat)(?:urday)? + + There are five capturing substrings, but only one is ever set after a + match. (An alternative way of solving this problem is to use a "branch + reset" subpattern, as described in the previous section.) + + The convenience function for extracting the data by name returns the + substring for the first (and in this example, the only) subpattern of + that name that matched. This saves searching to find which numbered + subpattern it was. + + If you make a back reference to a non-unique named subpattern from + elsewhere in the pattern, the subpatterns to which the name refers are + checked in the order in which they appear in the overall pattern. The + first one that is set is used for the reference. For example, this pat- + tern matches both "foofoo" and "barbar" but not "foobar" or "barfoo": + + (?:(?<n>foo)|(?<n>bar))\k<n> + + + If you make a subroutine call to a non-unique named subpattern, the one + that corresponds to the first occurrence of the name is used. In the + absence of duplicate numbers (see the previous section) this is the one + with the lowest number. + + If you use a named reference in a condition test (see the section about + conditions below), either to check whether a subpattern has matched, or + to check for recursion, all subpatterns with the same name are tested. + If the condition is true for any one of them, the overall condition is + true. This is the same behaviour as testing by number. For further + details of the interfaces for handling named subpatterns, see the + pcreapi documentation. + + Warning: You cannot use different names to distinguish between two sub- + patterns with the same number because PCRE uses only the numbers when + matching. For this reason, an error is given at compile time if differ- + ent names are given to subpatterns with the same number. However, you + can always give the same name to subpatterns with the same number, even + when PCRE_DUPNAMES is not set. + + +REPETITION + + Repetition is specified by quantifiers, which can follow any of the + following items: + + a literal data character + the dot metacharacter + the \C escape sequence + the \X escape sequence + the \R escape sequence + an escape such as \d or \pL that matches a single character + a character class + a back reference (see next section) + a parenthesized subpattern (including assertions) + a subroutine call to a subpattern (recursive or otherwise) + + The general repetition quantifier specifies a minimum and maximum num- + ber of permitted matches, by giving the two numbers in curly brackets + (braces), separated by a comma. The numbers must be less than 65536, + and the first must be less than or equal to the second. For example: + + z{2,4} + + matches "zz", "zzz", or "zzzz". A closing brace on its own is not a + special character. If the second number is omitted, but the comma is + present, there is no upper limit; if the second number and the comma + are both omitted, the quantifier specifies an exact number of required + matches. Thus + + [aeiou]{3,} + + matches at least 3 successive vowels, but may match many more, while + + \d{8} + + matches exactly 8 digits. An opening curly bracket that appears in a + position where a quantifier is not allowed, or one that does not match + the syntax of a quantifier, is taken as a literal character. For exam- + ple, {,6} is not a quantifier, but a literal string of four characters. + + In UTF modes, quantifiers apply to characters rather than to individual + data units. Thus, for example, \x{100}{2} matches two characters, each + of which is represented by a two-byte sequence in a UTF-8 string. Simi- + larly, \X{3} matches three Unicode extended grapheme clusters, each of + which may be several data units long (and they may be of different + lengths). + + The quantifier {0} is permitted, causing the expression to behave as if + the previous item and the quantifier were not present. This may be use- + ful for subpatterns that are referenced as subroutines from elsewhere + in the pattern (but see also the section entitled "Defining subpatterns + for use by reference only" below). Items other than subpatterns that + have a {0} quantifier are omitted from the compiled pattern. + + For convenience, the three most common quantifiers have single-charac- + ter abbreviations: + + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} + + It is possible to construct infinite loops by following a subpattern + that can match no characters with a quantifier that has no upper limit, + for example: + + (a?)* + + Earlier versions of Perl and PCRE used to give an error at compile time + for such patterns. However, because there are cases where this can be + useful, such patterns are now accepted, but if any repetition of the + subpattern does in fact match no characters, the loop is forcibly bro- + ken. + + By default, the quantifiers are "greedy", that is, they match as much + as possible (up to the maximum number of permitted times), without + causing the rest of the pattern to fail. The classic example of where + this gives problems is in trying to match comments in C programs. These + appear between /* and */ and within the comment, individual * and / + characters may appear. An attempt to match C comments by applying the + pattern + + /\*.*\*/ + + to the string + + /* first comment */ not comment /* second comment */ + + fails, because it matches the entire string owing to the greediness of + the .* item. + + However, if a quantifier is followed by a question mark, it ceases to + be greedy, and instead matches the minimum number of times possible, so + the pattern + + /\*.*?\*/ + + does the right thing with the C comments. The meaning of the various + quantifiers is not otherwise changed, just the preferred number of + matches. Do not confuse this use of question mark with its use as a + quantifier in its own right. Because it has two uses, it can sometimes + appear doubled, as in + + \d??\d + + which matches one digit by preference, but can match two if that is the + only way the rest of the pattern matches. + + If the PCRE_UNGREEDY option is set (an option that is not available in + Perl), the quantifiers are not greedy by default, but individual ones + can be made greedy by following them with a question mark. In other + words, it inverts the default behaviour. + + When a parenthesized subpattern is quantified with a minimum repeat + count that is greater than 1 or with a limited maximum, more memory is + required for the compiled pattern, in proportion to the size of the + minimum or maximum. + + If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv- + alent to Perl's /s) is set, thus allowing the dot to match newlines, + the pattern is implicitly anchored, because whatever follows will be + tried against every character position in the subject string, so there + is no point in retrying the overall match at any position after the + first. PCRE normally treats such a pattern as though it were preceded + by \A. + + In cases where it is known that the subject string contains no new- + lines, it is worth setting PCRE_DOTALL in order to obtain this opti- + mization, or alternatively using ^ to indicate anchoring explicitly. + + However, there are some cases where the optimization cannot be used. + When .* is inside capturing parentheses that are the subject of a back + reference elsewhere in the pattern, a match at the start may fail where + a later one succeeds. Consider, for example: + + (.*)abc\1 + + If the subject is "xyz123abc123" the match point is the fourth charac- + ter. For this reason, such a pattern is not implicitly anchored. + + Another case where implicit anchoring is not applied is when the lead- + ing .* is inside an atomic group. Once again, a match at the start may + fail where a later one succeeds. Consider this pattern: + + (?>.*?a)b + + It matches "ab" in the subject "aab". The use of the backtracking con- + trol verbs (*PRUNE) and (*SKIP) also disable this optimization. + + When a capturing subpattern is repeated, the value captured is the sub- + string that matched the final iteration. For example, after + + (tweedle[dume]{3}\s*)+ + + has matched "tweedledum tweedledee" the value of the captured substring + is "tweedledee". However, if there are nested capturing subpatterns, + the corresponding captured values may have been set in previous itera- + tions. For example, after + + /(a|(b))+/ + + matches "aba" the value of the second captured substring is "b". + + +ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS + + With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") + repetition, failure of what follows normally causes the repeated item + to be re-evaluated to see if a different number of repeats allows the + rest of the pattern to match. Sometimes it is useful to prevent this, + either to change the nature of the match, or to cause it fail earlier + than it otherwise might, when the author of the pattern knows there is + no point in carrying on. + + Consider, for example, the pattern \d+foo when applied to the subject + line + + 123456bar + + After matching all 6 digits and then failing to match "foo", the normal + action of the matcher is to try again with only 5 digits matching the + \d+ item, and then with 4, and so on, before ultimately failing. + "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides + the means for specifying that once a subpattern has matched, it is not + to be re-evaluated in this way. + + If we use atomic grouping for the previous example, the matcher gives + up immediately on failing to match "foo" the first time. The notation + is a kind of special parenthesis, starting with (?> as in this example: + + (?>\d+)foo + + This kind of parenthesis "locks up" the part of the pattern it con- + tains once it has matched, and a failure further into the pattern is + prevented from backtracking into it. Backtracking past it to previous + items, however, works as normal. + + An alternative description is that a subpattern of this type matches + the string of characters that an identical standalone pattern would + match, if anchored at the current point in the subject string. + + Atomic grouping subpatterns are not capturing subpatterns. Simple cases + such as the above example can be thought of as a maximizing repeat that + must swallow everything it can. So, while both \d+ and \d+? are pre- + pared to adjust the number of digits they match in order to make the + rest of the pattern match, (?>\d+) can only match an entire sequence of + digits. + + Atomic groups in general can of course contain arbitrarily complicated + subpatterns, and can be nested. However, when the subpattern for an + atomic group is just a single repeated item, as in the example above, a + simpler notation, called a "possessive quantifier" can be used. This + consists of an additional + character following a quantifier. Using + this notation, the previous example can be rewritten as + + \d++foo + + Note that a possessive quantifier can be used with an entire group, for + example: + + (abc|xyz){2,3}+ + + Possessive quantifiers are always greedy; the setting of the + PCRE_UNGREEDY option is ignored. They are a convenient notation for the + simpler forms of atomic group. However, there is no difference in the + meaning of a possessive quantifier and the equivalent atomic group, + though there may be a performance difference; possessive quantifiers + should be slightly faster. + + The possessive quantifier syntax is an extension to the Perl 5.8 syn- + tax. Jeffrey Friedl originated the idea (and the name) in the first + edition of his book. Mike McCloskey liked it, so implemented it when he + built Sun's Java package, and PCRE copied it from there. It ultimately + found its way into Perl at release 5.10. + + PCRE has an optimization that automatically "possessifies" certain sim- + ple pattern constructs. For example, the sequence A+B is treated as + A++B because there is no point in backtracking into a sequence of A's + when B must follow. + + When a pattern contains an unlimited repeat inside a subpattern that + can itself be repeated an unlimited number of times, the use of an + atomic group is the only way to avoid some failing matches taking a + very long time indeed. The pattern + + (\D+|<\d+>)*[!?] + + matches an unlimited number of substrings that either consist of non- + digits, or digits enclosed in <>, followed by either ! or ?. When it + matches, it runs quickly. However, if it is applied to + + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + + it takes a long time before reporting failure. This is because the + string can be divided between the internal \D+ repeat and the external + * repeat in a large number of ways, and all have to be tried. (The + example uses [!?] rather than a single character at the end, because + both PCRE and Perl have an optimization that allows for fast failure + when a single character is used. They remember the last single charac- + ter that is required for a match, and fail early if it is not present + in the string.) If the pattern is changed so that it uses an atomic + group, like this: + + ((?>\D+)|<\d+>)*[!?] + + sequences of non-digits cannot be broken, and failure happens quickly. + + +BACK REFERENCES + + Outside a character class, a backslash followed by a digit greater than + 0 (and possibly further digits) is a back reference to a capturing sub- + pattern earlier (that is, to its left) in the pattern, provided there + have been that many previous capturing left parentheses. + + However, if the decimal number following the backslash is less than 10, + it is always taken as a back reference, and causes an error only if + there are not that many capturing left parentheses in the entire pat- + tern. In other words, the parentheses that are referenced need not be + to the left of the reference for numbers less than 10. A "forward back + reference" of this type can make sense when a repetition is involved + and the subpattern to the right has participated in an earlier itera- + tion. + + It is not possible to have a numerical "forward back reference" to a + subpattern whose number is 10 or more using this syntax because a + sequence such as \50 is interpreted as a character defined in octal. + See the subsection entitled "Non-printing characters" above for further + details of the handling of digits following a backslash. There is no + such problem when named parentheses are used. A back reference to any + subpattern is possible using named parentheses (see below). + + Another way of avoiding the ambiguity inherent in the use of digits + following a backslash is to use the \g escape sequence. This escape + must be followed by an unsigned number or a negative number, optionally + enclosed in braces. These examples are all identical: + + (ring), \1 + (ring), \g1 + (ring), \g{1} + + An unsigned number specifies an absolute reference without the ambigu- + ity that is present in the older syntax. It is also useful when literal + digits follow the reference. A negative number is a relative reference. + Consider this example: + + (abc(def)ghi)\g{-1} + + The sequence \g{-1} is a reference to the most recently started captur- + ing subpattern before \g, that is, is it equivalent to \2 in this exam- + ple. Similarly, \g{-2} would be equivalent to \1. The use of relative + references can be helpful in long patterns, and also in patterns that + are created by joining together fragments that contain references + within themselves. + + A back reference matches whatever actually matched the capturing sub- + pattern in the current subject string, rather than anything matching + the subpattern itself (see "Subpatterns as subroutines" below for a way + of doing that). So the pattern + + (sens|respons)e and \1ibility + + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If caseful matching is in force at the + time of the back reference, the case of letters is relevant. For exam- + ple, + + ((?i)rah)\s+\1 + + matches "rah rah" and "RAH RAH", but not "RAH rah", even though the + original capturing subpattern is matched caselessly. + + There are several different ways of writing back references to named + subpatterns. The .NET syntax \k{name} and the Perl syntax \k<name> or + \k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's + unified back reference syntax, in which \g can be used for both numeric + and named references, is also supported. We could rewrite the above + example in any of the following ways: + + (?<p1>(?i)rah)\s+\k<p1> + (?'p1'(?i)rah)\s+\k{p1} + (?P<p1>(?i)rah)\s+(?P=p1) + (?<p1>(?i)rah)\s+\g{p1} + + A subpattern that is referenced by name may appear in the pattern + before or after the reference. + + There may be more than one back reference to the same subpattern. If a + subpattern has not actually been used in a particular match, any back + references to it always fail by default. For example, the pattern + + (a|(bc))\2 + + always fails if it starts to match "a" rather than "bc". However, if + the PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back refer- + ence to an unset value matches an empty string. + + Because there may be many capturing parentheses in a pattern, all dig- + its following a backslash are taken as part of a potential back refer- + ence number. If the pattern continues with a digit character, some + delimiter must be used to terminate the back reference. If the + PCRE_EXTENDED option is set, this can be white space. Otherwise, the + \g{ syntax or an empty comment (see "Comments" below) can be used. + + Recursive back references + + A back reference that occurs inside the parentheses to which it refers + fails when the subpattern is first used, so, for example, (a\1) never + matches. However, such references can be useful inside repeated sub- + patterns. For example, the pattern + + (a|b\1)+ + + matches any number of "a"s and also "aba", "ababbaa" etc. At each iter- + ation of the subpattern, the back reference matches the character + string corresponding to the previous iteration. In order for this to + work, the pattern must be such that the first iteration does not need + to match the back reference. This can be done using alternation, as in + the example above, or by a quantifier with a minimum of zero. + + Back references of this type cause the group that they reference to be + treated as an atomic group. Once the whole group has been matched, a + subsequent matching failure cannot cause backtracking into the middle + of the group. + + +ASSERTIONS + + An assertion is a test on the characters following or preceding the + current matching point that does not actually consume any characters. + The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are + described above. + + More complicated assertions are coded as subpatterns. There are two + kinds: those that look ahead of the current position in the subject + string, and those that look behind it. An assertion subpattern is + matched in the normal way, except that it does not cause the current + matching position to be changed. + + Assertion subpatterns are not capturing subpatterns. If such an asser- + tion contains capturing subpatterns within it, these are counted for + the purposes of numbering the capturing subpatterns in the whole pat- + tern. However, substring capturing is carried out only for positive + assertions. (Perl sometimes, but not always, does do capturing in nega- + tive assertions.) + + For compatibility with Perl, assertion subpatterns may be repeated; + though it makes no sense to assert the same thing several times, the + side effect of capturing parentheses may occasionally be useful. In + practice, there only three cases: + + (1) If the quantifier is {0}, the assertion is never obeyed during + matching. However, it may contain internal capturing parenthesized + groups that are called from elsewhere via the subroutine mechanism. + + (2) If quantifier is {0,n} where n is greater than zero, it is treated + as if it were {0,1}. At run time, the rest of the pattern match is + tried with and without the assertion, the order depending on the greed- + iness of the quantifier. + + (3) If the minimum repetition is greater than zero, the quantifier is + ignored. The assertion is obeyed just once when encountered during + matching. + + Lookahead assertions + + Lookahead assertions start with (?= for positive assertions and (?! for + negative assertions. For example, + + \w+(?=;) + + matches a word followed by a semicolon, but does not include the semi- + colon in the match, and + + foo(?!bar) + + matches any occurrence of "foo" that is not followed by "bar". Note + that the apparently similar pattern + + (?!foo)bar + + does not find an occurrence of "bar" that is preceded by something + other than "foo"; it finds any occurrence of "bar" whatsoever, because + the assertion (?!foo) is always true when the next three characters are + "bar". A lookbehind assertion is needed to achieve the other effect. + + If you want to force a matching failure at some point in a pattern, the + most convenient way to do it is with (?!) because an empty string + always matches, so an assertion that requires there not to be an empty + string must always fail. The backtracking control verb (*FAIL) or (*F) + is a synonym for (?!). + + Lookbehind assertions + + Lookbehind assertions start with (?<= for positive assertions and (?<! + for negative assertions. For example, + + (?<!foo)bar + + does find an occurrence of "bar" that is not preceded by "foo". The + contents of a lookbehind assertion are restricted such that all the + strings it matches must have a fixed length. However, if there are sev- + eral top-level alternatives, they do not all have to have the same + fixed length. Thus + + (?<=bullock|donkey) + + is permitted, but + + (?<!dogs?|cats?) + + causes an error at compile time. Branches that match different length + strings are permitted only at the top level of a lookbehind assertion. + This is an extension compared with Perl, which requires all branches to + match the same length of string. An assertion such as + + (?<=ab(c|de)) + + is not permitted, because its single top-level branch can match two + different lengths, but it is acceptable to PCRE if rewritten to use two + top-level branches: + + (?<=abc|abde) + + In some cases, the escape sequence \K (see above) can be used instead + of a lookbehind assertion to get round the fixed-length restriction. + + The implementation of lookbehind assertions is, for each alternative, + to temporarily move the current position back by the fixed length and + then try to match. If there are insufficient characters before the cur- + rent position, the assertion fails. + + In a UTF mode, PCRE does not allow the \C escape (which matches a sin- + gle data unit even in a UTF mode) to appear in lookbehind assertions, + because it makes it impossible to calculate the length of the lookbe- + hind. The \X and \R escapes, which can match different numbers of data + units, are also not permitted. + + "Subroutine" calls (see below) such as (?2) or (?&X) are permitted in + lookbehinds, as long as the subpattern matches a fixed-length string. + Recursion, however, is not supported. + + Possessive quantifiers can be used in conjunction with lookbehind + assertions to specify efficient matching of fixed-length strings at the + end of subject strings. Consider a simple pattern such as + + abcd$ + + when applied to a long string that does not match. Because matching + proceeds from left to right, PCRE will look for each "a" in the subject + and then see if what follows matches the rest of the pattern. If the + pattern is specified as + + ^.*abcd$ + + the initial .* matches the entire string at first, but when this fails + (because there is no following "a"), it backtracks to match all but the + last character, then all but the last two characters, and so on. Once + again the search for "a" covers the entire string, from right to left, + so we are no better off. However, if the pattern is written as + + ^.*+(?<=abcd) + + there can be no backtracking for the .*+ item; it can match only the + entire string. The subsequent lookbehind assertion does a single test + on the last four characters. If it fails, the match fails immediately. + For long strings, this approach makes a significant difference to the + processing time. + + Using multiple assertions + + Several assertions (of any sort) may occur in succession. For example, + + (?<=\d{3})(?<!999)foo + + matches "foo" preceded by three digits that are not "999". Notice that + each of the assertions is applied independently at the same point in + the subject string. First there is a check that the previous three + characters are all digits, and then there is a check that the same + three characters are not "999". This pattern does not match "foo" pre- + ceded by six characters, the first of which are digits and the last + three of which are not "999". For example, it doesn't match "123abc- + foo". A pattern to do that is + + (?<=\d{3}...)(?<!999)foo + + This time the first assertion looks at the preceding six characters, + checking that the first three are digits, and then the second assertion + checks that the preceding three characters are not "999". + + Assertions can be nested in any combination. For example, + + (?<=(?<!foo)bar)baz + + matches an occurrence of "baz" that is preceded by "bar" which in turn + is not preceded by "foo", while + + (?<=\d{3}(?!999)...)foo + + is another pattern that matches "foo" preceded by three digits and any + three characters that are not "999". + + +CONDITIONAL SUBPATTERNS + + It is possible to cause the matching process to obey a subpattern con- + ditionally or to choose between two alternative subpatterns, depending + on the result of an assertion, or whether a specific capturing subpat- + tern has already been matched. The two possible forms of conditional + subpattern are: + + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) + + If the condition is satisfied, the yes-pattern is used; otherwise the + no-pattern (if present) is used. If there are more than two alterna- + tives in the subpattern, a compile-time error occurs. Each of the two + alternatives may itself contain nested subpatterns of any form, includ- + ing conditional subpatterns; the restriction to two alternatives + applies only at the level of the condition. This pattern fragment is an + example where the alternatives are complex: + + (?(1) (A|B|C) | (D | (?(2)E|F) | E) ) + + + There are four kinds of condition: references to subpatterns, refer- + ences to recursion, a pseudo-condition called DEFINE, and assertions. + + Checking for a used subpattern by number + + If the text between the parentheses consists of a sequence of digits, + the condition is true if a capturing subpattern of that number has pre- + viously matched. If there is more than one capturing subpattern with + the same number (see the earlier section about duplicate subpattern + numbers), the condition is true if any of them have matched. An alter- + native notation is to precede the digits with a plus or minus sign. In + this case, the subpattern number is relative rather than absolute. The + most recently opened parentheses can be referenced by (?(-1), the next + most recent by (?(-2), and so on. Inside loops it can also make sense + to refer to subsequent groups. The next parentheses to be opened can be + referenced as (?(+1), and so on. (The value zero in any of these forms + is not used; it provokes a compile-time error.) + + Consider the following pattern, which contains non-significant white + space to make it more readable (assume the PCRE_EXTENDED option) and to + divide it into three parts for ease of discussion: + + ( \( )? [^()]+ (?(1) \) ) + + The first part matches an optional opening parenthesis, and if that + character is present, sets it as the first captured substring. The sec- + ond part matches one or more characters that are not parentheses. The + third part is a conditional subpattern that tests whether or not the + first set of parentheses matched. If they did, that is, if subject + started with an opening parenthesis, the condition is true, and so the + yes-pattern is executed and a closing parenthesis is required. Other- + wise, since no-pattern is not present, the subpattern matches nothing. + In other words, this pattern matches a sequence of non-parentheses, + optionally enclosed in parentheses. + + If you were embedding this pattern in a larger one, you could use a + relative reference: + + ...other stuff... ( \( )? [^()]+ (?(-1) \) ) ... + + This makes the fragment independent of the parentheses in the larger + pattern. + + Checking for a used subpattern by name + + Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a + used subpattern by name. For compatibility with earlier versions of + PCRE, which had this facility before Perl, the syntax (?(name)...) is + also recognized. + + Rewriting the above example to use a named subpattern gives this: + + (?<OPEN> \( )? [^()]+ (?(<OPEN>) \) ) + + If the name used in a condition of this kind is a duplicate, the test + is applied to all subpatterns of the same name, and is true if any one + of them has matched. + + Checking for pattern recursion + + If the condition is the string (R), and there is no subpattern with the + name R, the condition is true if a recursive call to the whole pattern + or any subpattern has been made. If digits or a name preceded by amper- + sand follow the letter R, for example: + + (?(R3)...) or (?(R&name)...) + + the condition is true if the most recent recursion is into a subpattern + whose number or name is given. This condition does not check the entire + recursion stack. If the name used in a condition of this kind is a + duplicate, the test is applied to all subpatterns of the same name, and + is true if any one of them is the most recent recursion. + + At "top level", all these recursion test conditions are false. The + syntax for recursive patterns is described below. + + Defining subpatterns for use by reference only + + If the condition is the string (DEFINE), and there is no subpattern + with the name DEFINE, the condition is always false. In this case, + there may be only one alternative in the subpattern. It is always + skipped if control reaches this point in the pattern; the idea of + DEFINE is that it can be used to define subroutines that can be refer- + enced from elsewhere. (The use of subroutines is described below.) For + example, a pattern to match an IPv4 address such as "192.168.23.245" + could be written like this (ignore white space and line breaks): + + (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) + \b (?&byte) (\.(?&byte)){3} \b + + The first part of the pattern is a DEFINE group inside which a another + group named "byte" is defined. This matches an individual component of + an IPv4 address (a number less than 256). When matching takes place, + this part of the pattern is skipped because DEFINE acts like a false + condition. The rest of the pattern uses references to the named group + to match the four dot-separated components of an IPv4 address, insist- + ing on a word boundary at each end. + + Assertion conditions + + If the condition is not in any of the above formats, it must be an + assertion. This may be a positive or negative lookahead or lookbehind + assertion. Consider this pattern, again containing non-significant + white space, and with the two alternatives on the second line: + + (?(?=[^a-z]*[a-z]) + \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) + + The condition is a positive lookahead assertion that matches an + optional sequence of non-letters followed by a letter. In other words, + it tests for the presence of at least one letter in the subject. If a + letter is found, the subject is matched against the first alternative; + otherwise it is matched against the second. This pattern matches + strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are + letters and dd are digits. + + +COMMENTS + + There are two ways of including comments in patterns that are processed + by PCRE. In both cases, the start of the comment must not be in a char- + acter class, nor in the middle of any other sequence of related charac- + ters such as (?: or a subpattern name or number. The characters that + make up a comment play no part in the pattern matching. + + The sequence (?# marks the start of a comment that continues up to the + next closing parenthesis. Nested parentheses are not permitted. If the + PCRE_EXTENDED option is set, an unescaped # character also introduces a + comment, which in this case continues to immediately after the next + newline character or character sequence in the pattern. Which charac- + ters are interpreted as newlines is controlled by the options passed to + a compiling function or by a special sequence at the start of the pat- + tern, as described in the section entitled "Newline conventions" above. + Note that the end of this type of comment is a literal newline sequence + in the pattern; escape sequences that happen to represent a newline do + not count. For example, consider this pattern when PCRE_EXTENDED is + set, and the default newline convention is in force: + + abc #comment \n still comment + + On encountering the # character, pcre_compile() skips along, looking + for a newline in the pattern. The sequence \n is still literal at this + stage, so it does not terminate the comment. Only an actual character + with the code value 0x0a (the default newline) does so. + + +RECURSIVE PATTERNS + + Consider the problem of matching a string in parentheses, allowing for + unlimited nested parentheses. Without the use of recursion, the best + that can be done is to use a pattern that matches up to some fixed + depth of nesting. It is not possible to handle an arbitrary nesting + depth. + + For some time, Perl has provided a facility that allows regular expres- + sions to recurse (amongst other things). It does this by interpolating + Perl code in the expression at run time, and the code can refer to the + expression itself. A Perl pattern using code interpolation to solve the + parentheses problem can be created like this: + + $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; + + The (?p{...}) item interpolates Perl code at run time, and in this case + refers recursively to the pattern in which it appears. + + Obviously, PCRE cannot support the interpolation of Perl code. Instead, + it supports special syntax for recursion of the entire pattern, and + also for individual subpattern recursion. After its introduction in + PCRE and Python, this kind of recursion was subsequently introduced + into Perl at release 5.10. + + A special item that consists of (? followed by a number greater than + zero and a closing parenthesis is a recursive subroutine call of the + subpattern of the given number, provided that it occurs inside that + subpattern. (If not, it is a non-recursive subroutine call, which is + described in the next section.) The special item (?R) or (?0) is a + recursive call of the entire regular expression. + + This PCRE pattern solves the nested parentheses problem (assume the + PCRE_EXTENDED option is set so that white space is ignored): + + \( ( [^()]++ | (?R) )* \) + + First it matches an opening parenthesis. Then it matches any number of + substrings which can either be a sequence of non-parentheses, or a + recursive match of the pattern itself (that is, a correctly parenthe- + sized substring). Finally there is a closing parenthesis. Note the use + of a possessive quantifier to avoid backtracking into sequences of non- + parentheses. + + If this were part of a larger pattern, you would not want to recurse + the entire pattern, so instead you could use this: + + ( \( ( [^()]++ | (?1) )* \) ) + + We have put the pattern into parentheses, and caused the recursion to + refer to them instead of the whole pattern. + + In a larger pattern, keeping track of parenthesis numbers can be + tricky. This is made easier by the use of relative references. Instead + of (?1) in the pattern above you can write (?-2) to refer to the second + most recently opened parentheses preceding the recursion. In other + words, a negative number counts capturing parentheses leftwards from + the point at which it is encountered. + + It is also possible to refer to subsequently opened parentheses, by + writing references such as (?+2). However, these cannot be recursive + because the reference is not inside the parentheses that are refer- + enced. They are always non-recursive subroutine calls, as described in + the next section. + + An alternative approach is to use named parentheses instead. The Perl + syntax for this is (?&name); PCRE's earlier syntax (?P>name) is also + supported. We could rewrite the above example as follows: + + (?<pn> \( ( [^()]++ | (?&pn) )* \) ) + + If there is more than one subpattern with the same name, the earliest + one is used. + + This particular example pattern that we have been looking at contains + nested unlimited repeats, and so the use of a possessive quantifier for + matching strings of non-parentheses is important when applying the pat- + tern to strings that do not match. For example, when this pattern is + applied to + + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() + + it yields "no match" quickly. However, if a possessive quantifier is + not used, the match runs for a very long time indeed because there are + so many different ways the + and * repeats can carve up the subject, + and all have to be tested before failure can be reported. + + At the end of a match, the values of capturing parentheses are those + from the outermost level. If you want to obtain intermediate values, a + callout function can be used (see below and the pcrecallout documenta- + tion). If the pattern above is matched against + + (ab(cd)ef) + + the value for the inner capturing parentheses (numbered 2) is "ef", + which is the last value taken on at the top level. If a capturing sub- + pattern is not matched at the top level, its final captured value is + unset, even if it was (temporarily) set at a deeper level during the + matching process. + + If there are more than 15 capturing parentheses in a pattern, PCRE has + to obtain extra memory to store data during a recursion, which it does + by using pcre_malloc, freeing it via pcre_free afterwards. If no memory + can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error. + + Do not confuse the (?R) item with the condition (R), which tests for + recursion. Consider this pattern, which matches text in angle brack- + ets, allowing for arbitrary nesting. Only digits are allowed in nested + brackets (that is, when recursing), whereas any characters are permit- + ted at the outer level. + + < (?: (?(R) \d++ | [^<>]*+) | (?R)) * > + + In this pattern, (?(R) is the start of a conditional subpattern, with + two different alternatives for the recursive and non-recursive cases. + The (?R) item is the actual recursive call. + + Differences in recursion processing between PCRE and Perl + + Recursion processing in PCRE differs from Perl in two important ways. + In PCRE (like Python, but unlike Perl), a recursive subpattern call is + always treated as an atomic group. That is, once it has matched some of + the subject string, it is never re-entered, even if it contains untried + alternatives and there is a subsequent matching failure. This can be + illustrated by the following pattern, which purports to match a palin- + dromic string that contains an odd number of characters (for example, + "a", "aba", "abcba", "abcdcba"): + + ^(.|(.)(?1)\2)$ + + The idea is that it either matches a single character, or two identical + characters surrounding a sub-palindrome. In Perl, this pattern works; + in PCRE it does not if the pattern is longer than three characters. + Consider the subject string "abcba": + + At the top level, the first character is matched, but as it is not at + the end of the string, the first alternative fails; the second alterna- + tive is taken and the recursion kicks in. The recursive call to subpat- + tern 1 successfully matches the next character ("b"). (Note that the + beginning and end of line tests are not part of the recursion). + + Back at the top level, the next character ("c") is compared with what + subpattern 2 matched, which was "a". This fails. Because the recursion + is treated as an atomic group, there are now no backtracking points, + and so the entire match fails. (Perl is able, at this point, to re- + enter the recursion and try the second alternative.) However, if the + pattern is written with the alternatives in the other order, things are + different: + + ^((.)(?1)\2|.)$ + + This time, the recursing alternative is tried first, and continues to + recurse until it runs out of characters, at which point the recursion + fails. But this time we do have another alternative to try at the + higher level. That is the big difference: in the previous case the + remaining alternative is at a deeper recursion level, which PCRE cannot + use. + + To change the pattern so that it matches all palindromic strings, not + just those with an odd number of characters, it is tempting to change + the pattern to this: + + ^((.)(?1)\2|.?)$ + + Again, this works in Perl, but not in PCRE, and for the same reason. + When a deeper recursion has matched a single character, it cannot be + entered again in order to match an empty string. The solution is to + separate the two cases, and write out the odd and even cases as alter- + natives at the higher level: + + ^(?:((.)(?1)\2|)|((.)(?3)\4|.)) + + If you want to match typical palindromic phrases, the pattern has to + ignore all non-word characters, which can be done like this: + + ^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$ + + If run with the PCRE_CASELESS option, this pattern matches phrases such + as "A man, a plan, a canal: Panama!" and it works well in both PCRE and + Perl. Note the use of the possessive quantifier *+ to avoid backtrack- + ing into sequences of non-word characters. Without this, PCRE takes a + great deal longer (ten times or more) to match typical phrases, and + Perl takes so long that you think it has gone into a loop. + + WARNING: The palindrome-matching patterns above work only if the sub- + ject string does not start with a palindrome that is shorter than the + entire string. For example, although "abcba" is correctly matched, if + the subject is "ababa", PCRE finds the palindrome "aba" at the start, + then fails at top level because the end of the string does not follow. + Once again, it cannot jump back into the recursion to try other alter- + natives, so the entire match fails. + + The second way in which PCRE and Perl differ in their recursion pro- + cessing is in the handling of captured values. In Perl, when a subpat- + tern is called recursively or as a subpattern (see the next section), + it has no access to any values that were captured outside the recur- + sion, whereas in PCRE these values can be referenced. Consider this + pattern: + + ^(.)(\1|a(?2)) + + In PCRE, this pattern matches "bab". The first capturing parentheses + match "b", then in the second group, when the back reference \1 fails + to match "b", the second alternative matches "a" and then recurses. In + the recursion, \1 does now match "b" and so the whole match succeeds. + In Perl, the pattern fails to match because inside the recursive call + \1 cannot access the externally set value. + + +SUBPATTERNS AS SUBROUTINES + + If the syntax for a recursive subpattern call (either by number or by + name) is used outside the parentheses to which it refers, it operates + like a subroutine in a programming language. The called subpattern may + be defined before or after the reference. A numbered reference can be + absolute or relative, as in these examples: + + (...(absolute)...)...(?2)... + (...(relative)...)...(?-1)... + (...(?+1)...(relative)... + + An earlier example pointed out that the pattern + + (sens|respons)e and \1ibility + + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If instead the pattern + + (sens|respons)e and (?1)ibility + + is used, it does match "sense and responsibility" as well as the other + two strings. Another example is given in the discussion of DEFINE + above. + + All subroutine calls, whether recursive or not, are always treated as + atomic groups. That is, once a subroutine has matched some of the sub- + ject string, it is never re-entered, even if it contains untried alter- + natives and there is a subsequent matching failure. Any capturing + parentheses that are set during the subroutine call revert to their + previous values afterwards. + + Processing options such as case-independence are fixed when a subpat- + tern is defined, so if it is used as a subroutine, such options cannot + be changed for different calls. For example, consider this pattern: + + (abc)(?i:(?-1)) + + It matches "abcabc". It does not match "abcABC" because the change of + processing option does not affect the called subpattern. + + +ONIGURUMA SUBROUTINE SYNTAX + + For compatibility with Oniguruma, the non-Perl syntax \g followed by a + name or a number enclosed either in angle brackets or single quotes, is + an alternative syntax for referencing a subpattern as a subroutine, + possibly recursively. Here are two of the examples used above, rewrit- + ten using this syntax: + + (?<pn> \( ( (?>[^()]+) | \g<pn> )* \) ) + (sens|respons)e and \g'1'ibility + + PCRE supports an extension to Oniguruma: if a number is preceded by a + plus or a minus sign it is taken as a relative reference. For example: + + (abc)(?i:\g<-1>) + + Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not + synonymous. The former is a back reference; the latter is a subroutine + call. + + +CALLOUTS + + Perl has a feature whereby using the sequence (?{...}) causes arbitrary + Perl code to be obeyed in the middle of matching a regular expression. + This makes it possible, amongst other things, to extract different sub- + strings that match the same pair of parentheses when there is a repeti- + tion. + + PCRE provides a similar feature, but of course it cannot obey arbitrary + Perl code. The feature is called "callout". The caller of PCRE provides + an external function by putting its entry point in the global variable + pcre_callout (8-bit library) or pcre[16|32]_callout (16-bit or 32-bit + library). By default, this variable contains NULL, which disables all + calling out. + + Within a regular expression, (?C) indicates the points at which the + external function is to be called. If you want to identify different + callout points, you can put a number less than 256 after the letter C. + The default value is zero. For example, this pattern has two callout + points: + + (?C1)abc(?C2)def + + If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, call- + outs are automatically installed before each item in the pattern. They + are all numbered 255. If there is a conditional group in the pattern + whose condition is an assertion, an additional callout is inserted just + before the condition. An explicit callout may also be set at this posi- + tion, as in this example: + + (?(?C9)(?=a)abc|def) + + Note that this applies only to assertion conditions, not to other types + of condition. + + During matching, when PCRE reaches a callout point, the external func- + tion is called. It is provided with the number of the callout, the + position in the pattern, and, optionally, one item of data originally + supplied by the caller of the matching function. The callout function + may cause matching to proceed, to backtrack, or to fail altogether. + + By default, PCRE implements a number of optimizations at compile time + and matching time, and one side-effect is that sometimes callouts are + skipped. If you need all possible callouts to happen, you need to set + options that disable the relevant optimizations. More details, and a + complete description of the interface to the callout function, are + given in the pcrecallout documentation. + + +BACKTRACKING CONTROL + + Perl 5.10 introduced a number of "Special Backtracking Control Verbs", + which are still described in the Perl documentation as "experimental + and subject to change or removal in a future version of Perl". It goes + on to say: "Their usage in production code should be noted to avoid + problems during upgrades." The same remarks apply to the PCRE features + described in this section. + + The new verbs make use of what was previously invalid syntax: an open- + ing parenthesis followed by an asterisk. They are generally of the form + (*VERB) or (*VERB:NAME). Some may take either form, possibly behaving + differently depending on whether or not a name is present. A name is + any sequence of characters that does not include a closing parenthesis. + The maximum length of name is 255 in the 8-bit library and 65535 in the + 16-bit and 32-bit libraries. If the name is empty, that is, if the + closing parenthesis immediately follows the colon, the effect is as if + the colon were not there. Any number of these verbs may occur in a + pattern. + + Since these verbs are specifically related to backtracking, most of + them can be used only when the pattern is to be matched using one of + the traditional matching functions, because these use a backtracking + algorithm. With the exception of (*FAIL), which behaves like a failing + negative assertion, the backtracking control verbs cause an error if + encountered by a DFA matching function. + + The behaviour of these verbs in repeated groups, assertions, and in + subpatterns called as subroutines (whether or not recursively) is docu- + mented below. + + Optimizations that affect backtracking verbs + + PCRE contains some optimizations that are used to speed up matching by + running some checks at the start of each match attempt. For example, it + may know the minimum length of matching subject, or that a particular + character must be present. When one of these optimizations bypasses the + running of a match, any included backtracking verbs will not, of + course, be processed. You can suppress the start-of-match optimizations + by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_com- + pile() or pcre_exec(), or by starting the pattern with (*NO_START_OPT). + There is more discussion of this option in the section entitled "Option + bits for pcre_exec()" in the pcreapi documentation. + + Experiments with Perl suggest that it too has similar optimizations, + sometimes leading to anomalous results. + + Verbs that act immediately + + The following verbs act as soon as they are encountered. They may not + be followed by a name. + + (*ACCEPT) + + This verb causes the match to end successfully, skipping the remainder + of the pattern. However, when it is inside a subpattern that is called + as a subroutine, only that subpattern is ended successfully. Matching + then continues at the outer level. If (*ACCEPT) in triggered in a posi- + tive assertion, the assertion succeeds; in a negative assertion, the + assertion fails. + + If (*ACCEPT) is inside capturing parentheses, the data so far is cap- + tured. For example: + + A((?:A|B(*ACCEPT)|C)D) + + This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap- + tured by the outer parentheses. + + (*FAIL) or (*F) + + This verb causes a matching failure, forcing backtracking to occur. It + is equivalent to (?!) but easier to read. The Perl documentation notes + that it is probably useful only when combined with (?{}) or (??{}). + Those are, of course, Perl features that are not present in PCRE. The + nearest equivalent is the callout feature, as for example in this pat- + tern: + + a+(?C)(*FAIL) + + A match with the string "aaaa" always fails, but the callout is taken + before each backtrack happens (in this example, 10 times). + + Recording which path was taken + + There is one verb whose main purpose is to track how a match was + arrived at, though it also has a secondary use in conjunction with + advancing the match starting point (see (*SKIP) below). + + (*MARK:NAME) or (*:NAME) + + A name is always required with this verb. There may be as many + instances of (*MARK) as you like in a pattern, and their names do not + have to be unique. + + When a match succeeds, the name of the last-encountered (*MARK:NAME), + (*PRUNE:NAME), or (*THEN:NAME) on the matching path is passed back to + the caller as described in the section entitled "Extra data for + pcre_exec()" in the pcreapi documentation. Here is an example of + pcretest output, where the /K modifier requests the retrieval and out- + putting of (*MARK) data: + + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XY + 0: XY + MK: A + XZ + 0: XZ + MK: B + + The (*MARK) name is tagged with "MK:" in this output, and in this exam- + ple it indicates which of the two alternatives matched. This is a more + efficient way of obtaining this information than putting each alterna- + tive in its own capturing parentheses. + + If a verb with a name is encountered in a positive assertion that is + true, the name is recorded and passed back if it is the last-encoun- + tered. This does not happen for negative assertions or failing positive + assertions. + + After a partial match or a failed match, the last encountered name in + the entire match process is returned. For example: + + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XP + No match, mark = B + + Note that in this unanchored example the mark is retained from the + match attempt that started at the letter "X" in the subject. Subsequent + match attempts starting at "P" and then with an empty string do not get + as far as the (*MARK) item, but nevertheless do not reset it. + + If you are interested in (*MARK) values after failed matches, you + should probably set the PCRE_NO_START_OPTIMIZE option (see above) to + ensure that the match is always attempted. + + Verbs that act after backtracking + + The following verbs do nothing when they are encountered. Matching con- + tinues with what follows, but if there is no subsequent match, causing + a backtrack to the verb, a failure is forced. That is, backtracking + cannot pass to the left of the verb. However, when one of these verbs + appears inside an atomic group or an assertion that is true, its effect + is confined to that group, because once the group has been matched, + there is never any backtracking into it. In this situation, backtrack- + ing can "jump back" to the left of the entire atomic group or asser- + tion. (Remember also, as stated above, that this localization also + applies in subroutine calls.) + + These verbs differ in exactly what kind of failure occurs when back- + tracking reaches them. The behaviour described below is what happens + when the verb is not in a subroutine or an assertion. Subsequent sec- + tions cover these special cases. + + (*COMMIT) + + This verb, which may not be followed by a name, causes the whole match + to fail outright if there is a later matching failure that causes back- + tracking to reach it. Even if the pattern is unanchored, no further + attempts to find a match by advancing the starting point take place. If + (*COMMIT) is the only backtracking verb that is encountered, once it + has been passed pcre_exec() is committed to finding a match at the cur- + rent starting point, or not at all. For example: + + a+(*COMMIT)b + + This matches "xxaab" but not "aacaab". It can be thought of as a kind + of dynamic anchor, or "I've started, so I must finish." The name of the + most recently passed (*MARK) in the path is passed back when (*COMMIT) + forces a match failure. + + If there is more than one backtracking verb in a pattern, a different + one that follows (*COMMIT) may be triggered first, so merely passing + (*COMMIT) during a match does not always guarantee that a match must be + at this starting point. + + Note that (*COMMIT) at the start of a pattern is not the same as an + anchor, unless PCRE's start-of-match optimizations are turned off, as + shown in this output from pcretest: + + re> /(*COMMIT)abc/ + data> xyzabc + 0: abc + data> xyzabc\Y + No match + + For this pattern, PCRE knows that any match must start with "a", so the + optimization skips along the subject to "a" before applying the pattern + to the first set of data. The match attempt then succeeds. In the sec- + ond set of data, the escape sequence \Y is interpreted by the pcretest + program. It causes the PCRE_NO_START_OPTIMIZE option to be set when + pcre_exec() is called. This disables the optimization that skips along + to the first character. The pattern is now applied starting at "x", and + so the (*COMMIT) causes the match to fail without trying any other + starting points. + + (*PRUNE) or (*PRUNE:NAME) + + This verb causes the match to fail at the current starting position in + the subject if there is a later matching failure that causes backtrack- + ing to reach it. If the pattern is unanchored, the normal "bumpalong" + advance to the next starting character then happens. Backtracking can + occur as usual to the left of (*PRUNE), before it is reached, or when + matching to the right of (*PRUNE), but if there is no match to the + right, backtracking cannot cross (*PRUNE). In simple cases, the use of + (*PRUNE) is just an alternative to an atomic group or possessive quan- + tifier, but there are some uses of (*PRUNE) that cannot be expressed in + any other way. In an anchored pattern (*PRUNE) has the same effect as + (*COMMIT). + + The behaviour of (*PRUNE:NAME) is the not the same as + (*MARK:NAME)(*PRUNE). It is like (*MARK:NAME) in that the name is + remembered for passing back to the caller. However, (*SKIP:NAME) + searches only for names set with (*MARK). + + (*SKIP) + + This verb, when given without a name, is like (*PRUNE), except that if + the pattern is unanchored, the "bumpalong" advance is not to the next + character, but to the position in the subject where (*SKIP) was encoun- + tered. (*SKIP) signifies that whatever text was matched leading up to + it cannot be part of a successful match. Consider: + + a+(*SKIP)b + + If the subject is "aaaac...", after the first match attempt fails + (starting at the first character in the string), the starting point + skips on to start the next attempt at "c". Note that a possessive quan- + tifer does not have the same effect as this example; although it would + suppress backtracking during the first match attempt, the second + attempt would start at the second character instead of skipping on to + "c". + + (*SKIP:NAME) + + When (*SKIP) has an associated name, its behaviour is modified. When it + is triggered, the previous path through the pattern is searched for the + most recent (*MARK) that has the same name. If one is found, the + "bumpalong" advance is to the subject position that corresponds to that + (*MARK) instead of to where (*SKIP) was encountered. If no (*MARK) with + a matching name is found, the (*SKIP) is ignored. + + Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It + ignores names that are set by (*PRUNE:NAME) or (*THEN:NAME). + + (*THEN) or (*THEN:NAME) + + This verb causes a skip to the next innermost alternative when back- + tracking reaches it. That is, it cancels any further backtracking + within the current alternative. Its name comes from the observation + that it can be used for a pattern-based if-then-else block: + + ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ... + + If the COND1 pattern matches, FOO is tried (and possibly further items + after the end of the group if FOO succeeds); on failure, the matcher + skips to the second alternative and tries COND2, without backtracking + into COND1. If that succeeds and BAR fails, COND3 is tried. If subse- + quently BAZ fails, there are no more alternatives, so there is a back- + track to whatever came before the entire group. If (*THEN) is not + inside an alternation, it acts like (*PRUNE). + + The behaviour of (*THEN:NAME) is the not the same as + (*MARK:NAME)(*THEN). It is like (*MARK:NAME) in that the name is + remembered for passing back to the caller. However, (*SKIP:NAME) + searches only for names set with (*MARK). + + A subpattern that does not contain a | character is just a part of the + enclosing alternative; it is not a nested alternation with only one + alternative. The effect of (*THEN) extends beyond such a subpattern to + the enclosing alternative. Consider this pattern, where A, B, etc. are + complex pattern fragments that do not contain any | characters at this + level: + + A (B(*THEN)C) | D + + If A and B are matched, but there is a failure in C, matching does not + backtrack into A; instead it moves to the next alternative, that is, D. + However, if the subpattern containing (*THEN) is given an alternative, + it behaves differently: + + A (B(*THEN)C | (*FAIL)) | D + + The effect of (*THEN) is now confined to the inner subpattern. After a + failure in C, matching moves to (*FAIL), which causes the whole subpat- + tern to fail because there are no more alternatives to try. In this + case, matching does now backtrack into A. + + Note that a conditional subpattern is not considered as having two + alternatives, because only one is ever used. In other words, the | + character in a conditional subpattern has a different meaning. Ignoring + white space, consider: + + ^.*? (?(?=a) a | b(*THEN)c ) + + If the subject is "ba", this pattern does not match. Because .*? is + ungreedy, it initially matches zero characters. The condition (?=a) + then fails, the character "b" is matched, but "c" is not. At this + point, matching does not backtrack to .*? as might perhaps be expected + from the presence of the | character. The conditional subpattern is + part of the single alternative that comprises the whole pattern, and so + the match fails. (If there was a backtrack into .*?, allowing it to + match "b", the match would succeed.) + + The verbs just described provide four different "strengths" of control + when subsequent matching fails. (*THEN) is the weakest, carrying on the + match at the next alternative. (*PRUNE) comes next, failing the match + at the current starting position, but allowing an advance to the next + character (for an unanchored pattern). (*SKIP) is similar, except that + the advance may be more than one character. (*COMMIT) is the strongest, + causing the entire match to fail. + + More than one backtracking verb + + If more than one backtracking verb is present in a pattern, the one + that is backtracked onto first acts. For example, consider this pat- + tern, where A, B, etc. are complex pattern fragments: + + (A(*COMMIT)B(*THEN)C|ABD) + + If A matches but B fails, the backtrack to (*COMMIT) causes the entire + match to fail. However, if A and B match, but C fails, the backtrack to + (*THEN) causes the next alternative (ABD) to be tried. This behaviour + is consistent, but is not always the same as Perl's. It means that if + two or more backtracking verbs appear in succession, all the the last + of them has no effect. Consider this example: + + ...(*COMMIT)(*PRUNE)... + + If there is a matching failure to the right, backtracking onto (*PRUNE) + causes it to be triggered, and its action is taken. There can never be + a backtrack onto (*COMMIT). + + Backtracking verbs in repeated groups + + PCRE differs from Perl in its handling of backtracking verbs in + repeated groups. For example, consider: + + /(a(*COMMIT)b)+ac/ + + If the subject is "abac", Perl matches, but PCRE fails because the + (*COMMIT) in the second repeat of the group acts. + + Backtracking verbs in assertions + + (*FAIL) in an assertion has its normal effect: it forces an immediate + backtrack. + + (*ACCEPT) in a positive assertion causes the assertion to succeed with- + out any further processing. In a negative assertion, (*ACCEPT) causes + the assertion to fail without any further processing. + + The other backtracking verbs are not treated specially if they appear + in a positive assertion. In particular, (*THEN) skips to the next + alternative in the innermost enclosing group that has alternations, + whether or not this is within the assertion. + + Negative assertions are, however, different, in order to ensure that + changing a positive assertion into a negative assertion changes its + result. Backtracking into (*COMMIT), (*SKIP), or (*PRUNE) causes a neg- + ative assertion to be true, without considering any further alternative + branches in the assertion. Backtracking into (*THEN) causes it to skip + to the next enclosing alternative within the assertion (the normal be- + haviour), but if the assertion does not have such an alternative, + (*THEN) behaves like (*PRUNE). + + Backtracking verbs in subroutines + + These behaviours occur whether or not the subpattern is called recur- + sively. Perl's treatment of subroutines is different in some cases. + + (*FAIL) in a subpattern called as a subroutine has its normal effect: + it forces an immediate backtrack. + + (*ACCEPT) in a subpattern called as a subroutine causes the subroutine + match to succeed without any further processing. Matching then contin- + ues after the subroutine call. + + (*COMMIT), (*SKIP), and (*PRUNE) in a subpattern called as a subroutine + cause the subroutine match to fail. + + (*THEN) skips to the next alternative in the innermost enclosing group + within the subpattern that has alternatives. If there is no such group + within the subpattern, (*THEN) causes the subroutine match to fail. + + +SEE ALSO + + pcreapi(3), pcrecallout(3), pcrematching(3), pcresyntax(3), pcre(3), + pcre16(3), pcre32(3). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 14 June 2015 + Copyright (c) 1997-2015 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRESYNTAX(3) Library Functions Manual PCRESYNTAX(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE REGULAR EXPRESSION SYNTAX SUMMARY + + The full syntax and semantics of the regular expressions that are sup- + ported by PCRE are described in the pcrepattern documentation. This + document contains a quick-reference summary of the syntax. + + +QUOTING + + \x where x is non-alphanumeric is a literal x + \Q...\E treat enclosed characters as literal + + +CHARACTERS + + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any ASCII character + \e escape (hex 1B) + \f form feed (hex 0C) + \n newline (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \0dd character with octal code 0dd + \ddd character with octal code ddd, or backreference + \o{ddd..} character with octal code ddd.. + \xhh character with hex code hh + \x{hhh..} character with hex code hhh.. + + Note that \0dd is always an octal code, and that \8 and \9 are the lit- + eral characters "8" and "9". + + +CHARACTER TYPES + + . any character except newline; + in dotall mode, any character whatsoever + \C one data unit, even in UTF mode (best avoided) + \d a decimal digit + \D a character that is not a decimal digit + \h a horizontal white space character + \H a character that is not a horizontal white space character + \N a character that is not a newline + \p{xx} a character with the xx property + \P{xx} a character without the xx property + \R a newline sequence + \s a white space character + \S a character that is not a white space character + \v a vertical white space character + \V a character that is not a vertical white space character + \w a "word" character + \W a "non-word" character + \X a Unicode extended grapheme cluster + + By default, \d, \s, and \w match only ASCII characters, even in UTF-8 + mode or in the 16- bit and 32-bit libraries. However, if locale-spe- + cific matching is happening, \s and \w may also match characters with + code points in the range 128-255. If the PCRE_UCP option is set, the + behaviour of these escape sequences is changed to use Unicode proper- + ties and they match many more characters. + + +GENERAL CATEGORY PROPERTIES FOR \p and \P + + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate + + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter + L& Ll, Lu, or Lt + + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark + + N Number + Nd Decimal number + Nl Letter number + No Other number + + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation + + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol + + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator + + +PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P + + Xan Alphanumeric: union of properties L and N + Xps POSIX space: property Z or tab, NL, VT, FF, CR + Xsp Perl space: property Z or tab, NL, VT, FF, CR + Xuc Univerally-named character: one that can be + represented by a Universal Character Name + Xwd Perl word: property Xan or underscore + + Perl and POSIX space are now the same. Perl added VT to its space char- + acter set at release 5.18 and PCRE changed at release 8.34. + + +SCRIPT NAMES FOR \p AND \P + + Arabic, Armenian, Avestan, Balinese, Bamum, Bassa_Vah, Batak, Bengali, + Bopomofo, Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Car- + ian, Caucasian_Albanian, Chakma, Cham, Cherokee, Common, Coptic, Cunei- + form, Cypriot, Cyrillic, Deseret, Devanagari, Duployan, Egyptian_Hiero- + glyphs, Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, + Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, + Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscrip- + tional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, + Kharoshthi, Khmer, Khojki, Khudawadi, Lao, Latin, Lepcha, Limbu, Lin- + ear_A, Linear_B, Lisu, Lycian, Lydian, Mahajani, Malayalam, Mandaic, + Manichaean, Meetei_Mayek, Mende_Kikakui, Meroitic_Cursive, + Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Myanmar, Nabataean, + New_Tai_Lue, Nko, Ogham, Ol_Chiki, Old_Italic, Old_North_Arabian, + Old_Permic, Old_Persian, Old_South_Arabian, Old_Turkic, Oriya, Osmanya, + Pahawh_Hmong, Palmyrene, Pau_Cin_Hau, Phags_Pa, Phoenician, + Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha- + vian, Siddham, Sinhala, Sora_Sompeng, Sundanese, Syloti_Nagri, Syriac, + Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, Takri, Tamil, Telugu, + Thaana, Thai, Tibetan, Tifinagh, Tirhuta, Ugaritic, Vai, Warang_Citi, + Yi. + + +CHARACTER CLASSES + + [...] positive character class + [^...] negative character class + [x-y] range (can be used for hex characters) + [[:xxx:]] positive POSIX named set + [[:^xxx:]] negative POSIX named set + + alnum alphanumeric + alpha alphabetic + ascii 0-127 + blank space or tab + cntrl control character + digit decimal digit + graph printing, excluding space + lower lower case letter + print printing, including space + punct printing, excluding alphanumeric + space white space + upper upper case letter + word same as \w + xdigit hexadecimal digit + + In PCRE, POSIX character set names recognize only ASCII characters by + default, but some of them use Unicode properties if PCRE_UCP is set. + You can use \Q...\E inside a character class. + + +QUANTIFIERS + + ? 0 or 1, greedy + ?+ 0 or 1, possessive + ?? 0 or 1, lazy + * 0 or more, greedy + *+ 0 or more, possessive + *? 0 or more, lazy + + 1 or more, greedy + ++ 1 or more, possessive + +? 1 or more, lazy + {n} exactly n + {n,m} at least n, no more than m, greedy + {n,m}+ at least n, no more than m, possessive + {n,m}? at least n, no more than m, lazy + {n,} n or more, greedy + {n,}+ n or more, possessive + {n,}? n or more, lazy + + +ANCHORS AND SIMPLE ASSERTIONS + + \b word boundary + \B not a word boundary + ^ start of subject + also after internal newline in multiline mode + \A start of subject + $ end of subject + also before newline at end of subject + also before internal newline in multiline mode + \Z end of subject + also before newline at end of subject + \z end of subject + \G first matching position in subject + + +MATCH POINT RESET + + \K reset start of match + + \K is honoured in positive assertions, but ignored in negative ones. + + +ALTERNATION + + expr|expr|expr... + + +CAPTURING + + (...) capturing group + (?<name>...) named capturing group (Perl) + (?'name'...) named capturing group (Perl) + (?P<name>...) named capturing group (Python) + (?:...) non-capturing group + (?|...) non-capturing group; reset group numbers for + capturing groups in each alternative + + +ATOMIC GROUPS + + (?>...) atomic, non-capturing group + + +COMMENT + + (?#....) comment (not nestable) + + +OPTION SETTING + + (?i) caseless + (?J) allow duplicate names + (?m) multiline + (?s) single line (dotall) + (?U) default ungreedy (lazy) + (?x) extended (ignore white space) + (?-...) unset option(s) + + The following are recognized only at the very start of a pattern or + after one of the newline or \R options with similar syntax. More than + one of them may appear. + + (*LIMIT_MATCH=d) set the match limit to d (decimal number) + (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number) + (*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS) + (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE) + (*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8) + (*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16) + (*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32) + (*UTF) set appropriate UTF mode for the library in use + (*UCP) set PCRE_UCP (use Unicode properties for \d etc) + + Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of + the limits set by the caller of pcre_exec(), not increase them. + + +NEWLINE CONVENTION + + These are recognized only at the very start of the pattern or after + option settings with a similar syntax. + + (*CR) carriage return only + (*LF) linefeed only + (*CRLF) carriage return followed by linefeed + (*ANYCRLF) all three of the above + (*ANY) any Unicode newline sequence + + +WHAT \R MATCHES + + These are recognized only at the very start of the pattern or after + option setting with a similar syntax. + + (*BSR_ANYCRLF) CR, LF, or CRLF + (*BSR_UNICODE) any Unicode newline sequence + + +LOOKAHEAD AND LOOKBEHIND ASSERTIONS + + (?=...) positive look ahead + (?!...) negative look ahead + (?<=...) positive look behind + (?<!...) negative look behind + + Each top-level branch of a look behind must be of a fixed length. + + +BACKREFERENCES + + \n reference by number (can be ambiguous) + \gn reference by number + \g{n} reference by number + \g{-n} relative reference by number + \k<name> reference by name (Perl) + \k'name' reference by name (Perl) + \g{name} reference by name (Perl) + \k{name} reference by name (.NET) + (?P=name) reference by name (Python) + + +SUBROUTINE REFERENCES (POSSIBLY RECURSIVE) + + (?R) recurse whole pattern + (?n) call subpattern by absolute number + (?+n) call subpattern by relative number + (?-n) call subpattern by relative number + (?&name) call subpattern by name (Perl) + (?P>name) call subpattern by name (Python) + \g<name> call subpattern by name (Oniguruma) + \g'name' call subpattern by name (Oniguruma) + \g<n> call subpattern by absolute number (Oniguruma) + \g'n' call subpattern by absolute number (Oniguruma) + \g<+n> call subpattern by relative number (PCRE extension) + \g'+n' call subpattern by relative number (PCRE extension) + \g<-n> call subpattern by relative number (PCRE extension) + \g'-n' call subpattern by relative number (PCRE extension) + + +CONDITIONAL PATTERNS + + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) + + (?(n)... absolute reference condition + (?(+n)... relative reference condition + (?(-n)... relative reference condition + (?(<name>)... named reference condition (Perl) + (?('name')... named reference condition (Perl) + (?(name)... named reference condition (PCRE) + (?(R)... overall recursion condition + (?(Rn)... specific group recursion condition + (?(R&name)... specific recursion condition + (?(DEFINE)... define subpattern for reference + (?(assert)... assertion condition + + +BACKTRACKING CONTROL + + The following act immediately they are reached: + + (*ACCEPT) force successful match + (*FAIL) force backtrack; synonym (*F) + (*MARK:NAME) set name to be passed back; synonym (*:NAME) + + The following act only when a subsequent match failure causes a back- + track to reach them. They all force a match failure, but they differ in + what happens afterwards. Those that advance the start-of-match point do + so only if the pattern is not anchored. + + (*COMMIT) overall failure, no advance of starting point + (*PRUNE) advance to next starting character + (*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE) + (*SKIP) advance to current matching position + (*SKIP:NAME) advance to position corresponding to an earlier + (*MARK:NAME); if not found, the (*SKIP) is ignored + (*THEN) local failure, backtrack to next alternation + (*THEN:NAME) equivalent to (*MARK:NAME)(*THEN) + + +CALLOUTS + + (?C) callout + (?Cn) callout with data n + + +SEE ALSO + + pcrepattern(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 08 January 2014 + Copyright (c) 1997-2014 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREUNICODE(3) Library Functions Manual PCREUNICODE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT + + As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) + and UTF-32 (from release 8.32), by means of two additional libraries. + They can be built as well as, or instead of, the 8-bit library. + + +UTF-8 SUPPORT + + In order process UTF-8 strings, you must build PCRE's 8-bit library + with UTF support, and, in addition, you must call pcre_compile() with + the PCRE_UTF8 option flag, or the pattern must start with the sequence + (*UTF8) or (*UTF). When either of these is the case, both the pattern + and any subject strings that are matched against it are treated as + UTF-8 strings instead of strings of individual 1-byte characters. + + +UTF-16 AND UTF-32 SUPPORT + + In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit + or 32-bit library with UTF support, and, in addition, you must call + pcre16_compile() or pcre32_compile() with the PCRE_UTF16 or PCRE_UTF32 + option flag, as appropriate. Alternatively, the pattern must start with + the sequence (*UTF16), (*UTF32), as appropriate, or (*UTF), which can + be used with either library. When UTF mode is set, both the pattern and + any subject strings that are matched against it are treated as UTF-16 + or UTF-32 strings instead of strings of individual 16-bit or 32-bit + characters. + + +UTF SUPPORT OVERHEAD + + If you compile PCRE with UTF support, but do not use it at run time, + the library will be a bit bigger, but the additional run time overhead + is limited to testing the PCRE_UTF[8|16|32] flag occasionally, so + should not be very big. + + +UNICODE PROPERTY SUPPORT + + If PCRE is built with Unicode character property support (which implies + UTF support), the escape sequences \p{..}, \P{..}, and \X can be used. + The available properties that can be tested are limited to the general + category properties such as Lu for an upper case letter or Nd for a + decimal number, the Unicode script names such as Arabic or Han, and the + derived properties Any and L&. Full lists is given in the pcrepattern + and pcresyntax documentation. Only the short names for properties are + supported. For example, \p{L} matches a letter. Its Perl synonym, + \p{Letter}, is not supported. Furthermore, in Perl, many properties + may optionally be prefixed by "Is", for compatibility with Perl 5.6. + PCRE does not support this. + + Validity of UTF-8 strings + + When you set the PCRE_UTF8 flag, the byte strings passed as patterns + and subjects are (by default) checked for validity on entry to the rel- + evant functions. The entire string is checked before any other process- + ing takes place. From release 7.3 of PCRE, the check is according the + rules of RFC 3629, which are themselves derived from the Unicode speci- + fication. Earlier releases of PCRE followed the rules of RFC 2279, + which allows the full range of 31-bit values (0 to 0x7FFFFFFF). The + current check allows only values in the range U+0 to U+10FFFF, exclud- + ing the surrogate area. (From release 8.33 the so-called "non-charac- + ter" code points are no longer excluded because Unicode corrigendum #9 + makes it clear that they should not be.) + + Characters in the "Surrogate Area" of Unicode are reserved for use by + UTF-16, where they are used in pairs to encode codepoints with values + greater than 0xFFFF. The code points that are encoded by UTF-16 pairs + are available independently in the UTF-8 and UTF-32 encodings. (In + other words, the whole surrogate thing is a fudge for UTF-16 which + unfortunately messes up UTF-8 and UTF-32.) + + If an invalid UTF-8 string is passed to PCRE, an error return is given. + At compile time, the only additional information is the offset to the + first byte of the failing character. The run-time functions pcre_exec() + and pcre_dfa_exec() also pass back this information, as well as a more + detailed reason code if the caller has provided memory in which to do + this. + + In some situations, you may already know that your strings are valid, + and therefore want to skip these checks in order to improve perfor- + mance, for example in the case of a long subject string that is being + scanned repeatedly. If you set the PCRE_NO_UTF8_CHECK flag at compile + time or at run time, PCRE assumes that the pattern or subject it is + given (respectively) contains only valid UTF-8 codes. In this case, it + does not diagnose an invalid UTF-8 string. + + Note that passing PCRE_NO_UTF8_CHECK to pcre_compile() just disables + the check for the pattern; it does not also apply to subject strings. + If you want to disable the check for a subject string you must pass + this option to pcre_exec() or pcre_dfa_exec(). + + If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the + result is undefined and your program may crash. + + Validity of UTF-16 strings + + When you set the PCRE_UTF16 flag, the strings of 16-bit data units that + are passed as patterns and subjects are (by default) checked for valid- + ity on entry to the relevant functions. Values other than those in the + surrogate range U+D800 to U+DFFF are independent code points. Values in + the surrogate range must be used in pairs in the correct manner. + + If an invalid UTF-16 string is passed to PCRE, an error return is + given. At compile time, the only additional information is the offset + to the first data unit of the failing character. The run-time functions + pcre16_exec() and pcre16_dfa_exec() also pass back this information, as + well as a more detailed reason code if the caller has provided memory + in which to do this. + + In some situations, you may already know that your strings are valid, + and therefore want to skip these checks in order to improve perfor- + mance. If you set the PCRE_NO_UTF16_CHECK flag at compile time or at + run time, PCRE assumes that the pattern or subject it is given (respec- + tively) contains only valid UTF-16 sequences. In this case, it does not + diagnose an invalid UTF-16 string. However, if an invalid string is + passed, the result is undefined. + + Validity of UTF-32 strings + + When you set the PCRE_UTF32 flag, the strings of 32-bit data units that + are passed as patterns and subjects are (by default) checked for valid- + ity on entry to the relevant functions. This check allows only values + in the range U+0 to U+10FFFF, excluding the surrogate area U+D800 to + U+DFFF. + + If an invalid UTF-32 string is passed to PCRE, an error return is + given. At compile time, the only additional information is the offset + to the first data unit of the failing character. The run-time functions + pcre32_exec() and pcre32_dfa_exec() also pass back this information, as + well as a more detailed reason code if the caller has provided memory + in which to do this. + + In some situations, you may already know that your strings are valid, + and therefore want to skip these checks in order to improve perfor- + mance. If you set the PCRE_NO_UTF32_CHECK flag at compile time or at + run time, PCRE assumes that the pattern or subject it is given (respec- + tively) contains only valid UTF-32 sequences. In this case, it does not + diagnose an invalid UTF-32 string. However, if an invalid string is + passed, the result is undefined. + + General comments about UTF modes + + 1. Codepoints less than 256 can be specified in patterns by either + braced or unbraced hexadecimal escape sequences (for example, \x{b3} or + \xb3). Larger values have to use braced sequences. + + 2. Octal numbers up to \777 are recognized, and in UTF-8 mode they + match two-byte characters for values greater than \177. + + 3. Repeat quantifiers apply to complete UTF characters, not to individ- + ual data units, for example: \x{100}{3}. + + 4. The dot metacharacter matches one UTF character instead of a single + data unit. + + 5. The escape sequence \C can be used to match a single byte in UTF-8 + mode, or a single 16-bit data unit in UTF-16 mode, or a single 32-bit + data unit in UTF-32 mode, but its use can lead to some strange effects + because it breaks up multi-unit characters (see the description of \C + in the pcrepattern documentation). The use of \C is not supported in + the alternative matching function pcre[16|32]_dfa_exec(), nor is it + supported in UTF mode by the JIT optimization of pcre[16|32]_exec(). If + JIT optimization is requested for a UTF pattern that contains \C, it + will not succeed, and so the matching will be carried out by the normal + interpretive function. + + 6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly + test characters of any code value, but, by default, the characters that + PCRE recognizes as digits, spaces, or word characters remain the same + set as in non-UTF mode, all with values less than 256. This remains + true even when PCRE is built to include Unicode property support, + because to do otherwise would slow down PCRE in many common cases. Note + in particular that this applies to \b and \B, because they are defined + in terms of \w and \W. If you really want to test for a wider sense of, + say, "digit", you can use explicit Unicode property tests such as + \p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that the + character escapes work is changed so that Unicode properties are used + to determine which characters match. There are more details in the sec- + tion on generic character types in the pcrepattern documentation. + + 7. Similarly, characters that match the POSIX named character classes + are all low-valued characters, unless the PCRE_UCP option is set. + + 8. However, the horizontal and vertical white space matching escapes + (\h, \H, \v, and \V) do match all the appropriate Unicode characters, + whether or not PCRE_UCP is set. + + 9. Case-insensitive matching applies only to characters whose values + are less than 128, unless PCRE is built with Unicode property support. + A few Unicode characters such as Greek sigma have more than two code- + points that are case-equivalent. Up to and including PCRE release 8.31, + only one-to-one case mappings were supported, but later releases (with + Unicode property support) do treat as case-equivalent all versions of + characters such as Greek sigma. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 27 February 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREJIT(3) Library Functions Manual PCREJIT(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE JUST-IN-TIME COMPILER SUPPORT + + Just-in-time compiling is a heavyweight optimization that can greatly + speed up pattern matching. However, it comes at the cost of extra pro- + cessing before the match is performed. Therefore, it is of most benefit + when the same pattern is going to be matched many times. This does not + necessarily mean many calls of a matching function; if the pattern is + not anchored, matching attempts may take place many times at various + positions in the subject, even for a single call. Therefore, if the + subject string is very long, it may still pay to use JIT for one-off + matches. + + JIT support applies only to the traditional Perl-compatible matching + function. It does not apply when the DFA matching function is being + used. The code for this support was written by Zoltan Herczeg. + + +8-BIT, 16-BIT AND 32-BIT SUPPORT + + JIT support is available for all of the 8-bit, 16-bit and 32-bit PCRE + libraries. To keep this documentation simple, only the 8-bit interface + is described in what follows. If you are using the 16-bit library, sub- + stitute the 16-bit functions and 16-bit structures (for example, + pcre16_jit_stack instead of pcre_jit_stack). If you are using the + 32-bit library, substitute the 32-bit functions and 32-bit structures + (for example, pcre32_jit_stack instead of pcre_jit_stack). + + +AVAILABILITY OF JIT SUPPORT + + JIT support is an optional feature of PCRE. The "configure" option + --enable-jit (or equivalent CMake option) must be set when PCRE is + built if you want to use JIT. The support is limited to the following + hardware platforms: + + ARM v5, v7, and Thumb2 + Intel x86 32-bit and 64-bit + MIPS 32-bit + Power PC 32-bit and 64-bit + SPARC 32-bit (experimental) + + If --enable-jit is set on an unsupported platform, compilation fails. + + A program that is linked with PCRE 8.20 or later can tell if JIT sup- + port is available by calling pcre_config() with the PCRE_CONFIG_JIT + option. The result is 1 when JIT is available, and 0 otherwise. How- + ever, a simple program does not need to check this in order to use JIT. + The normal API is implemented in a way that falls back to the interpre- + tive code if JIT is not available. For programs that need the best pos- + sible performance, there is also a "fast path" API that is JIT-spe- + cific. + + If your program may sometimes be linked with versions of PCRE that are + older than 8.20, but you want to use JIT when it is available, you can + test the values of PCRE_MAJOR and PCRE_MINOR, or the existence of a JIT + macro such as PCRE_CONFIG_JIT, for compile-time control of your code. + + +SIMPLE USE OF JIT + + You have to do two things to make use of the JIT support in the sim- + plest way: + + (1) Call pcre_study() with the PCRE_STUDY_JIT_COMPILE option for + each compiled pattern, and pass the resulting pcre_extra block to + pcre_exec(). + + (2) Use pcre_free_study() to free the pcre_extra block when it is + no longer needed, instead of just freeing it yourself. This + ensures that + any JIT data is also freed. + + For a program that may be linked with pre-8.20 versions of PCRE, you + can insert + + #ifndef PCRE_STUDY_JIT_COMPILE + #define PCRE_STUDY_JIT_COMPILE 0 + #endif + + so that no option is passed to pcre_study(), and then use something + like this to free the study data: + + #ifdef PCRE_CONFIG_JIT + pcre_free_study(study_ptr); + #else + pcre_free(study_ptr); + #endif + + PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for + complete matches. If you want to run partial matches using the + PCRE_PARTIAL_HARD or PCRE_PARTIAL_SOFT options of pcre_exec(), you + should set one or both of the following options in addition to, or + instead of, PCRE_STUDY_JIT_COMPILE when you call pcre_study(): + + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + + The JIT compiler generates different optimized code for each of the + three modes (normal, soft partial, hard partial). When pcre_exec() is + called, the appropriate code is run if it is available. Otherwise, the + pattern is matched using interpretive code. + + In some circumstances you may need to call additional functions. These + are described in the section entitled "Controlling the JIT stack" + below. + + If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are + ignored, and no JIT data is created. Otherwise, the compiled pattern is + passed to the JIT compiler, which turns it into machine code that exe- + cutes much faster than the normal interpretive code. When pcre_exec() + is passed a pcre_extra block containing a pointer to JIT code of the + appropriate mode (normal or hard/soft partial), it obeys that code + instead of running the interpreter. The result is identical, but the + compiled JIT code runs much faster. + + There are some pcre_exec() options that are not supported for JIT exe- + cution. There are also some pattern items that JIT cannot handle. + Details are given below. In both cases, execution automatically falls + back to the interpretive code. If you want to know whether JIT was + actually used for a particular match, you should arrange for a JIT + callback function to be set up as described in the section entitled + "Controlling the JIT stack" below, even if you do not need to supply a + non-default JIT stack. Such a callback function is called whenever JIT + code is about to be obeyed. If the execution options are not right for + JIT execution, the callback function is not obeyed. + + If the JIT compiler finds an unsupported item, no JIT data is gener- + ated. You can find out if JIT execution is available after studying a + pattern by calling pcre_fullinfo() with the PCRE_INFO_JIT option. A + result of 1 means that JIT compilation was successful. A result of 0 + means that JIT support is not available, or the pattern was not studied + with PCRE_STUDY_JIT_COMPILE etc., or the JIT compiler was not able to + handle the pattern. + + Once a pattern has been studied, with or without JIT, it can be used as + many times as you like for matching different subject strings. + + +UNSUPPORTED OPTIONS AND PATTERN ITEMS + + The only pcre_exec() options that are supported for JIT execution are + PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NO_UTF32_CHECK, PCRE_NOT- + BOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PAR- + TIAL_HARD, and PCRE_PARTIAL_SOFT. + + The only unsupported pattern items are \C (match a single data unit) + when running in a UTF mode, and a callout immediately before an asser- + tion condition in a conditional group. + + +RETURN VALUES FROM JIT EXECUTION + + When a pattern is matched using JIT execution, the return values are + the same as those given by the interpretive pcre_exec() code, with the + addition of one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means + that the memory used for the JIT stack was insufficient. See "Control- + ling the JIT stack" below for a discussion of JIT stack usage. For com- + patibility with the interpretive pcre_exec() code, no more than two- + thirds of the ovector argument is used for passing back captured sub- + strings. + + The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if + searching a very large pattern tree goes on for too long, as it is in + the same circumstance when JIT is not used, but the details of exactly + what is counted are not the same. The PCRE_ERROR_RECURSIONLIMIT error + code is never returned by JIT execution. + + +SAVING AND RESTORING COMPILED PATTERNS + + The code that is generated by the JIT compiler is architecture-spe- + cific, and is also position dependent. For those reasons it cannot be + saved (in a file or database) and restored later like the bytecode and + other data of a compiled pattern. Saving and restoring compiled pat- + terns is not something many people do. More detail about this facility + is given in the pcreprecompile documentation. It should be possible to + run pcre_study() on a saved and restored pattern, and thereby recreate + the JIT data, but because JIT compilation uses significant resources, + it is probably not worth doing this; you might as well recompile the + original pattern. + + +CONTROLLING THE JIT STACK + + When the compiled JIT code runs, it needs a block of memory to use as a + stack. By default, it uses 32K on the machine stack. However, some + large or complicated patterns need more than this. The error + PCRE_ERROR_JIT_STACKLIMIT is given when there is not enough stack. + Three functions are provided for managing blocks of memory for use as + JIT stacks. There is further discussion about the use of JIT stacks in + the section entitled "JIT stack FAQ" below. + + The pcre_jit_stack_alloc() function creates a JIT stack. Its arguments + are a starting size and a maximum size, and it returns a pointer to an + opaque structure of type pcre_jit_stack, or NULL if there is an error. + The pcre_jit_stack_free() function can be used to free a stack that is + no longer needed. (For the technically minded: the address space is + allocated by mmap or VirtualAlloc.) + + JIT uses far less memory for recursion than the interpretive code, and + a maximum stack size of 512K to 1M should be more than enough for any + pattern. + + The pcre_assign_jit_stack() function specifies which stack JIT code + should use. Its arguments are as follows: + + pcre_extra *extra + pcre_jit_callback callback + void *data + + The extra argument must be the result of studying a pattern with + PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the + other two options: + + (1) If callback is NULL and data is NULL, an internal 32K block + on the machine stack is used. + + (2) If callback is NULL and data is not NULL, data must be + a valid JIT stack, the result of calling pcre_jit_stack_alloc(). + + (3) If callback is not NULL, it must point to a function that is + called with data as an argument at the start of matching, in + order to set up a JIT stack. If the return from the callback + function is NULL, the internal 32K stack is used; otherwise the + return value must be a valid JIT stack, the result of calling + pcre_jit_stack_alloc(). + + A callback function is obeyed whenever JIT code is about to be run; it + is not obeyed when pcre_exec() is called with options that are incom- + patible for JIT execution. A callback function can therefore be used to + determine whether a match operation was executed by JIT or by the + interpreter. + + You may safely use the same JIT stack for more than one pattern (either + by assigning directly or by callback), as long as the patterns are all + matched sequentially in the same thread. In a multithread application, + if you do not specify a JIT stack, or if you assign or pass back NULL + from a callback, that is thread-safe, because each thread has its own + machine stack. However, if you assign or pass back a non-NULL JIT + stack, this must be a different stack for each thread so that the + application is thread-safe. + + Strictly speaking, even more is allowed. You can assign the same non- + NULL stack to any number of patterns as long as they are not used for + matching by multiple threads at the same time. For example, you can + assign the same stack to all compiled patterns, and use a global mutex + in the callback to wait until the stack is available for use. However, + this is an inefficient solution, and not recommended. + + This is a suggestion for how a multithreaded program that needs to set + up non-default JIT stacks might operate: + + During thread initalization + thread_local_var = pcre_jit_stack_alloc(...) + + During thread exit + pcre_jit_stack_free(thread_local_var) + + Use a one-line callback function + return thread_local_var + + All the functions described in this section do nothing if JIT is not + available, and pcre_assign_jit_stack() does nothing unless the extra + argument is non-NULL and points to a pcre_extra block that is the + result of a successful study with PCRE_STUDY_JIT_COMPILE etc. + + +JIT STACK FAQ + + (1) Why do we need JIT stacks? + + PCRE (and JIT) is a recursive, depth-first engine, so it needs a stack + where the local data of the current node is pushed before checking its + child nodes. Allocating real machine stack on some platforms is diffi- + cult. For example, the stack chain needs to be updated every time if we + extend the stack on PowerPC. Although it is possible, its updating + time overhead decreases performance. So we do the recursion in memory. + + (2) Why don't we simply allocate blocks of memory with malloc()? + + Modern operating systems have a nice feature: they can reserve an + address space instead of allocating memory. We can safely allocate mem- + ory pages inside this address space, so the stack could grow without + moving memory data (this is important because of pointers). Thus we can + allocate 1M address space, and use only a single memory page (usually + 4K) if that is enough. However, we can still grow up to 1M anytime if + needed. + + (3) Who "owns" a JIT stack? + + The owner of the stack is the user program, not the JIT studied pattern + or anything else. The user program must ensure that if a stack is used + by pcre_exec(), (that is, it is assigned to the pattern currently run- + ning), that stack must not be used by any other threads (to avoid over- + writing the same memory area). The best practice for multithreaded pro- + grams is to allocate a stack for each thread, and return this stack + through the JIT callback function. + + (4) When should a JIT stack be freed? + + You can free a JIT stack at any time, as long as it will not be used by + pcre_exec() again. When you assign the stack to a pattern, only a + pointer is set. There is no reference counting or any other magic. You + can free the patterns and stacks in any order, anytime. Just do not + call pcre_exec() with a pattern pointing to an already freed stack, as + that will cause SEGFAULT. (Also, do not free a stack currently used by + pcre_exec() in another thread). You can also replace the stack for a + pattern at any time. You can even free the previous stack before + assigning a replacement. + + (5) Should I allocate/free a stack every time before/after calling + pcre_exec()? + + No, because this is too costly in terms of resources. However, you + could implement some clever idea which release the stack if it is not + used in let's say two minutes. The JIT callback can help to achieve + this without keeping a list of the currently JIT studied patterns. + + (6) OK, the stack is for long term memory allocation. But what happens + if a pattern causes stack overflow with a stack of 1M? Is that 1M kept + until the stack is freed? + + Especially on embedded sytems, it might be a good idea to release mem- + ory sometimes without freeing the stack. There is no API for this at + the moment. Probably a function call which returns with the currently + allocated memory for any stack and another which allows releasing mem- + ory (shrinking the stack) would be a good idea if someone needs this. + + (7) This is too much of a headache. Isn't there any better solution for + JIT stack handling? + + No, thanks to Windows. If POSIX threads were used everywhere, we could + throw out this complicated API. + + +EXAMPLE CODE + + This is a single-threaded example that specifies a JIT stack without + using a callback. + + int rc; + int ovector[30]; + pcre *re; + pcre_extra *extra; + pcre_jit_stack *jit_stack; + + re = pcre_compile(pattern, 0, &error, &erroffset, NULL); + /* Check for errors */ + extra = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &error); + jit_stack = pcre_jit_stack_alloc(32*1024, 512*1024); + /* Check for error (NULL) */ + pcre_assign_jit_stack(extra, NULL, jit_stack); + rc = pcre_exec(re, extra, subject, length, 0, 0, ovector, 30); + /* Check results */ + pcre_free(re); + pcre_free_study(extra); + pcre_jit_stack_free(jit_stack); + + +JIT FAST PATH API + + Because the API described above falls back to interpreted execution + when JIT is not available, it is convenient for programs that are writ- + ten for general use in many environments. However, calling JIT via + pcre_exec() does have a performance impact. Programs that are written + for use where JIT is known to be available, and which need the best + possible performance, can instead use a "fast path" API to call JIT + execution directly instead of calling pcre_exec() (obviously only for + patterns that have been successfully studied by JIT). + + The fast path function is called pcre_jit_exec(), and it takes exactly + the same arguments as pcre_exec(), plus one additional argument that + must point to a JIT stack. The JIT stack arrangements described above + do not apply. The return values are the same as for pcre_exec(). + + When you call pcre_exec(), as well as testing for invalid options, a + number of other sanity checks are performed on the arguments. For exam- + ple, if the subject pointer is NULL, or its length is negative, an + immediate error is given. Also, unless PCRE_NO_UTF[8|16|32] is set, a + UTF subject string is tested for validity. In the interests of speed, + these checks do not happen on the JIT fast path, and if invalid data is + passed, the result is undefined. + + Bypassing the sanity checks and the pcre_exec() wrapping can give + speedups of more than 10%. + + +SEE ALSO + + pcreapi(3) + + +AUTHOR + + Philip Hazel (FAQ by Zoltan Herczeg) + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 17 March 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREPARTIAL(3) Library Functions Manual PCREPARTIAL(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PARTIAL MATCHING IN PCRE + + In normal use of PCRE, if the subject string that is passed to a match- + ing function matches as far as it goes, but is too short to match the + entire pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances + where it might be helpful to distinguish this case from other cases in + which there is no match. + + Consider, for example, an application where a human is required to type + in data for a field with specific formatting requirements. An example + might be a date in the form ddmmmyy, defined by this pattern: + + ^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$ + + If the application sees the user's keystrokes one by one, and can check + that what has been typed so far is potentially valid, it is able to + raise an error as soon as a mistake is made, by beeping and not + reflecting the character that has been typed, for example. This immedi- + ate feedback is likely to be a better user interface than a check that + is delayed until the entire string has been entered. Partial matching + can also be useful when the subject string is very long and is not all + available at once. + + PCRE supports partial matching by means of the PCRE_PARTIAL_SOFT and + PCRE_PARTIAL_HARD options, which can be set when calling any of the + matching functions. For backwards compatibility, PCRE_PARTIAL is a syn- + onym for PCRE_PARTIAL_SOFT. The essential difference between the two + options is whether or not a partial match is preferred to an alterna- + tive complete match, though the details differ between the two types of + matching function. If both options are set, PCRE_PARTIAL_HARD takes + precedence. + + If you want to use partial matching with just-in-time optimized code, + you must call pcre_study(), pcre16_study() or pcre32_study() with one + or both of these options: + + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + + PCRE_STUDY_JIT_COMPILE should also be set if you are going to run non- + partial matches on the same pattern. If the appropriate JIT study mode + has not been set for a match, the interpretive matching code is used. + + Setting a partial matching option disables two of PCRE's standard opti- + mizations. PCRE remembers the last literal data unit in a pattern, and + abandons matching immediately if it is not present in the subject + string. This optimization cannot be used for a subject string that + might match only partially. If the pattern was studied, PCRE knows the + minimum length of a matching string, and does not bother to run the + matching function on shorter strings. This optimization is also dis- + abled for partial matching. + + +PARTIAL MATCHING USING pcre_exec() OR pcre[16|32]_exec() + + A partial match occurs during a call to pcre_exec() or + pcre[16|32]_exec() when the end of the subject string is reached suc- + cessfully, but matching cannot continue because more characters are + needed. However, at least one character in the subject must have been + inspected. This character need not form part of the final matched + string; lookbehind assertions and the \K escape sequence provide ways + of inspecting characters before the start of a matched substring. The + requirement for inspecting at least one character exists because an + empty string can always be matched; without such a restriction there + would always be a partial match of an empty string at the end of the + subject. + + If there are at least two slots in the offsets vector when a partial + match is returned, the first slot is set to the offset of the earliest + character that was inspected. For convenience, the second offset points + to the end of the subject so that a substring can easily be identified. + If there are at least three slots in the offsets vector, the third slot + is set to the offset of the character where matching started. + + For the majority of patterns, the contents of the first and third slots + will be the same. However, for patterns that contain lookbehind asser- + tions, or begin with \b or \B, characters before the one where matching + started may have been inspected while carrying out the match. For exam- + ple, consider this pattern: + + /(?<=abc)123/ + + This pattern matches "123", but only if it is preceded by "abc". If the + subject string is "xyzabc12", the first two offsets after a partial + match are for the substring "abc12", because all these characters were + inspected. However, the third offset is set to 6, because that is the + offset where matching began. + + What happens when a partial match is identified depends on which of the + two partial matching options are set. + + PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre[16|32]_exec() + + If PCRE_PARTIAL_SOFT is set when pcre_exec() or pcre[16|32]_exec() + identifies a partial match, the partial match is remembered, but match- + ing continues as normal, and other alternatives in the pattern are + tried. If no complete match can be found, PCRE_ERROR_PARTIAL is + returned instead of PCRE_ERROR_NOMATCH. + + This option is "soft" because it prefers a complete match over a par- + tial match. All the various matching items in a pattern behave as if + the subject string is potentially complete. For example, \z, \Z, and $ + match at the end of the subject, as normal, and for \b and \B the end + of the subject is treated as a non-alphanumeric. + + If there is more than one partial match, the first one that was found + provides the data that is returned. Consider this pattern: + + /123\w+X|dogY/ + + If this is matched against the subject string "abc123dog", both alter- + natives fail to match, but the end of the subject is reached during + matching, so PCRE_ERROR_PARTIAL is returned. The offsets are set to 3 + and 9, identifying "123dog" as the first partial match that was found. + (In this example, there are two partial matches, because "dog" on its + own partially matches the second alternative.) + + PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre[16|32]_exec() + + If PCRE_PARTIAL_HARD is set for pcre_exec() or pcre[16|32]_exec(), + PCRE_ERROR_PARTIAL is returned as soon as a partial match is found, + without continuing to search for possible complete matches. This option + is "hard" because it prefers an earlier partial match over a later com- + plete match. For this reason, the assumption is made that the end of + the supplied subject string may not be the true end of the available + data, and so, if \z, \Z, \b, \B, or $ are encountered at the end of the + subject, the result is PCRE_ERROR_PARTIAL, provided that at least one + character in the subject has been inspected. + + Setting PCRE_PARTIAL_HARD also affects the way UTF-8 and UTF-16 subject + strings are checked for validity. Normally, an invalid sequence causes + the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the + special case of a truncated character at the end of the subject, + PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when + PCRE_PARTIAL_HARD is set. + + Comparing hard and soft partial matching + + The difference between the two partial matching options can be illus- + trated by a pattern such as: + + /dog(sbody)?/ + + This matches either "dog" or "dogsbody", greedily (that is, it prefers + the longer string if possible). If it is matched against the string + "dog" with PCRE_PARTIAL_SOFT, it yields a complete match for "dog". + However, if PCRE_PARTIAL_HARD is set, the result is PCRE_ERROR_PARTIAL. + On the other hand, if the pattern is made ungreedy the result is dif- + ferent: + + /dog(sbody)??/ + + In this case the result is always a complete match because that is + found first, and matching never continues after finding a complete + match. It might be easier to follow this explanation by thinking of the + two patterns like this: + + /dog(sbody)?/ is the same as /dogsbody|dog/ + /dog(sbody)??/ is the same as /dog|dogsbody/ + + The second pattern will never match "dogsbody", because it will always + find the shorter match first. + + +PARTIAL MATCHING USING pcre_dfa_exec() OR pcre[16|32]_dfa_exec() + + The DFA functions move along the subject string character by character, + without backtracking, searching for all possible matches simultane- + ously. If the end of the subject is reached before the end of the pat- + tern, there is the possibility of a partial match, again provided that + at least one character has been inspected. + + When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if + there have been no complete matches. Otherwise, the complete matches + are returned. However, if PCRE_PARTIAL_HARD is set, a partial match + takes precedence over any complete matches. The portion of the string + that was inspected when the longest partial match was found is set as + the first matching string, provided there are at least two slots in the + offsets vector. + + Because the DFA functions always search for all possible matches, and + there is no difference between greedy and ungreedy repetition, their + behaviour is different from the standard functions when PCRE_PAR- + TIAL_HARD is set. Consider the string "dog" matched against the + ungreedy pattern shown above: + + /dog(sbody)??/ + + Whereas the standard functions stop as soon as they find the complete + match for "dog", the DFA functions also find the partial match for + "dogsbody", and so return that when PCRE_PARTIAL_HARD is set. + + +PARTIAL MATCHING AND WORD BOUNDARIES + + If a pattern ends with one of sequences \b or \B, which test for word + boundaries, partial matching with PCRE_PARTIAL_SOFT can give counter- + intuitive results. Consider this pattern: + + /\bcat\b/ + + This matches "cat", provided there is a word boundary at either end. If + the subject string is "the cat", the comparison of the final "t" with a + following character cannot take place, so a partial match is found. + However, normal matching carries on, and \b matches at the end of the + subject when the last character is a letter, so a complete match is + found. The result, therefore, is not PCRE_ERROR_PARTIAL. Using + PCRE_PARTIAL_HARD in this case does yield PCRE_ERROR_PARTIAL, because + then the partial match takes precedence. + + +FORMERLY RESTRICTED PATTERNS + + For releases of PCRE prior to 8.00, because of the way certain internal + optimizations were implemented in the pcre_exec() function, the + PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be + used with all patterns. From release 8.00 onwards, the restrictions no + longer apply, and partial matching with can be requested for any pat- + tern. + + Items that were formerly restricted were repeated single characters and + repeated metasequences. If PCRE_PARTIAL was set for a pattern that did + not conform to the restrictions, pcre_exec() returned the error code + PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The + PCRE_INFO_OKPARTIAL call to pcre_fullinfo() to find out if a compiled + pattern can be used for partial matching now always returns 1. + + +EXAMPLE OF PARTIAL MATCHING USING PCRETEST + + If the escape sequence \P is present in a pcretest data line, the + PCRE_PARTIAL_SOFT option is used for the match. Here is a run of + pcretest that uses the date example quoted above: + + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 25jun04\P + 0: 25jun04 + 1: jun + data> 25dec3\P + Partial match: 23dec3 + data> 3ju\P + Partial match: 3ju + data> 3juj\P + No match + data> j\P + No match + + The first data string is matched completely, so pcretest shows the + matched substrings. The remaining four strings do not match the com- + plete pattern, but the first two are partial matches. Similar output is + obtained if DFA matching is used. + + If the escape sequence \P is present more than once in a pcretest data + line, the PCRE_PARTIAL_HARD option is set for the match. + + +MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec() + + When a partial match has been found using a DFA matching function, it + is possible to continue the match by providing additional subject data + and calling the function again with the same compiled regular expres- + sion, this time setting the PCRE_DFA_RESTART option. You must pass the + same working space as before, because this is where details of the pre- + vious partial match are stored. Here is an example using pcretest, + using the \R escape sequence to set the PCRE_DFA_RESTART option (\D + specifies the use of the DFA matching function): + + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 23ja\P\D + Partial match: 23ja + data> n05\R\D + 0: n05 + + The first call has "23ja" as the subject, and requests partial match- + ing; the second call has "n05" as the subject for the continued + (restarted) match. Notice that when the match is complete, only the + last part is shown; PCRE does not retain the previously partially- + matched string. It is up to the calling program to do that if it needs + to. + + That means that, for an unanchored pattern, if a continued match fails, + it is not possible to try again at a new starting point. All this + facility is capable of doing is continuing with the previous match + attempt. In the previous example, if the second set of data is "ug23" + the result is no match, even though there would be a match for "aug23" + if the entire string were given at once. Depending on the application, + this may or may not be what you want. The only way to allow for start- + ing again at the next character is to retain the matched part of the + subject and try a new complete match. + + You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with + PCRE_DFA_RESTART to continue partial matching over multiple segments. + This facility can be used to pass very long subject strings to the DFA + matching functions. + + +MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre[16|32]_exec() + + From release 8.00, the standard matching functions can also be used to + do multi-segment matching. Unlike the DFA functions, it is not possible + to restart the previous match with a new segment of data. Instead, new + data must be added to the previous subject string, and the entire match + re-run, starting from the point where the partial match occurred. Ear- + lier data can be discarded. + + It is best to use PCRE_PARTIAL_HARD in this situation, because it does + not treat the end of a segment as the end of the subject when matching + \z, \Z, \b, \B, and $. Consider an unanchored pattern that matches + dates: + + re> /\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d/ + data> The date is 23ja\P\P + Partial match: 23ja + + At this stage, an application could discard the text preceding "23ja", + add on text from the next segment, and call the matching function + again. Unlike the DFA matching functions, the entire matching string + must always be available, and the complete matching process occurs for + each call, so more memory and more processing time is needed. + + Note: If the pattern contains lookbehind assertions, or \K, or starts + with \b or \B, the string that is returned for a partial match includes + characters that precede the start of what would be returned for a com- + plete match, because it contains all the characters that were inspected + during the partial match. + + +ISSUES WITH MULTI-SEGMENT MATCHING + + Certain types of pattern may give problems with multi-segment matching, + whichever matching function is used. + + 1. If the pattern contains a test for the beginning of a line, you need + to pass the PCRE_NOTBOL option when the subject string for any call + does start at the beginning of a line. There is also a PCRE_NOTEOL + option, but in practice when doing multi-segment matching you should be + using PCRE_PARTIAL_HARD, which includes the effect of PCRE_NOTEOL. + + 2. Lookbehind assertions that have already been obeyed are catered for + in the offsets that are returned for a partial match. However a lookbe- + hind assertion later in the pattern could require even earlier charac- + ters to be inspected. You can handle this case by using the + PCRE_INFO_MAXLOOKBEHIND option of the pcre_fullinfo() or + pcre[16|32]_fullinfo() functions to obtain the length of the longest + lookbehind in the pattern. This length is given in characters, not + bytes. If you always retain at least that many characters before the + partially matched string, all should be well. (Of course, near the + start of the subject, fewer characters may be present; in that case all + characters should be retained.) + + From release 8.33, there is a more accurate way of deciding which char- + acters to retain. Instead of subtracting the length of the longest + lookbehind from the earliest inspected character (offsets[0]), the + match start position (offsets[2]) should be used, and the next match + attempt started at the offsets[2] character by setting the startoffset + argument of pcre_exec() or pcre_dfa_exec(). + + For example, if the pattern "(?<=123)abc" is partially matched against + the string "xx123a", the three offset values returned are 2, 6, and 5. + This indicates that the matching process that gave a partial match + started at offset 5, but the characters "123a" were all inspected. The + maximum lookbehind for that pattern is 3, so taking that away from 5 + shows that we need only keep "123a", and the next match attempt can be + started at offset 3 (that is, at "a") when further characters have been + added. When the match start is not the earliest inspected character, + pcretest shows it explicitly: + + re> "(?<=123)abc" + data> xx123a\P\P + Partial match at offset 5: 123a + + 3. Because a partial match must always contain at least one character, + what might be considered a partial match of an empty string actually + gives a "no match" result. For example: + + re> /c(?<=abc)x/ + data> ab\P + No match + + If the next segment begins "cx", a match should be found, but this will + only happen if characters from the previous segment are retained. For + this reason, a "no match" result should be interpreted as "partial + match of an empty string" when the pattern contains lookbehinds. + + 4. Matching a subject string that is split into multiple segments may + not always produce exactly the same result as matching over one single + long string, especially when PCRE_PARTIAL_SOFT is used. The section + "Partial Matching and Word Boundaries" above describes an issue that + arises if the pattern ends with \b or \B. Another kind of difference + may occur when there are multiple matching possibilities, because (for + PCRE_PARTIAL_SOFT) a partial match result is given only when there are + no completed matches. This means that as soon as the shortest match has + been found, continuation to a new subject segment is no longer possi- + ble. Consider again this pcretest example: + + re> /dog(sbody)?/ + data> dogsb\P + 0: dog + data> do\P\D + Partial match: do + data> gsb\R\P\D + 0: g + data> dogsbody\D + 0: dogsbody + 1: dog + + The first data line passes the string "dogsb" to a standard matching + function, setting the PCRE_PARTIAL_SOFT option. Although the string is + a partial match for "dogsbody", the result is not PCRE_ERROR_PARTIAL, + because the shorter string "dog" is a complete match. Similarly, when + the subject is presented to a DFA matching function in several parts + ("do" and "gsb" being the first two) the match stops when "dog" has + been found, and it is not possible to continue. On the other hand, if + "dogsbody" is presented as a single string, a DFA matching function + finds both matches. + + Because of these problems, it is best to use PCRE_PARTIAL_HARD when + matching multi-segment data. The example above then behaves differ- + ently: + + re> /dog(sbody)?/ + data> dogsb\P\P + Partial match: dogsb + data> do\P\D + Partial match: do + data> gsb\R\P\P\D + Partial match: gsb + + 5. Patterns that contain alternatives at the top level which do not all + start with the same pattern item may not work as expected when + PCRE_DFA_RESTART is used. For example, consider this pattern: + + 1234|3789 + + If the first part of the subject is "ABC123", a partial match of the + first alternative is found at offset 3. There is no partial match for + the second alternative, because such a match does not start at the same + point in the subject string. Attempting to continue with the string + "7890" does not yield a match because only those alternatives that + match at one point in the subject are remembered. The problem arises + because the start of the second alternative matches within the first + alternative. There is no problem with anchored patterns or patterns + such as: + + 1234|ABCD + + where no string can be a partial match for both alternatives. This is + not a problem if a standard matching function is used, because the + entire match has to be rerun each time: + + re> /1234|3789/ + data> ABC123\P\P + Partial match: 123 + data> 1237890 + 0: 3789 + + Of course, instead of using PCRE_DFA_RESTART, the same technique of re- + running the entire match can also be used with the DFA matching func- + tions. Another possibility is to work with two buffers. If a partial + match at offset n in the first buffer is followed by "no match" when + PCRE_DFA_RESTART is used on the second buffer, you can then try a new + match starting at offset n+1 in the first buffer. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 02 July 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREPRECOMPILE(3) Library Functions Manual PCREPRECOMPILE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +SAVING AND RE-USING PRECOMPILED PCRE PATTERNS + + If you are running an application that uses a large number of regular + expression patterns, it may be useful to store them in a precompiled + form instead of having to compile them every time the application is + run. If you are not using any private character tables (see the + pcre_maketables() documentation), this is relatively straightforward. + If you are using private tables, it is a little bit more complicated. + However, if you are using the just-in-time optimization feature, it is + not possible to save and reload the JIT data. + + If you save compiled patterns to a file, you can copy them to a differ- + ent host and run them there. If the two hosts have different endianness + (byte order), you should run the pcre[16|32]_pat- + tern_to_host_byte_order() function on the new host before trying to + match the pattern. The matching functions return PCRE_ERROR_BADENDIAN- + NESS if they detect a pattern with the wrong endianness. + + Compiling regular expressions with one version of PCRE for use with a + different version is not guaranteed to work and may cause crashes, and + saving and restoring a compiled pattern loses any JIT optimization + data. + + +SAVING A COMPILED PATTERN + + The value returned by pcre[16|32]_compile() points to a single block of + memory that holds the compiled pattern and associated data. You can + find the length of this block in bytes by calling + pcre[16|32]_fullinfo() with an argument of PCRE_INFO_SIZE. You can then + save the data in any appropriate manner. Here is sample code for the + 8-bit library that compiles a pattern and writes it to a file. It + assumes that the variable fd refers to a file that is open for output: + + int erroroffset, rc, size; + char *error; + pcre *re; + + re = pcre_compile("my pattern", 0, &error, &erroroffset, NULL); + if (re == NULL) { ... handle errors ... } + rc = pcre_fullinfo(re, NULL, PCRE_INFO_SIZE, &size); + if (rc < 0) { ... handle errors ... } + rc = fwrite(re, 1, size, fd); + if (rc != size) { ... handle errors ... } + + In this example, the bytes that comprise the compiled pattern are + copied exactly. Note that this is binary data that may contain any of + the 256 possible byte values. On systems that make a distinction + between binary and non-binary data, be sure that the file is opened for + binary output. + + If you want to write more than one pattern to a file, you will have to + devise a way of separating them. For binary data, preceding each pat- + tern with its length is probably the most straightforward approach. + Another possibility is to write out the data in hexadecimal instead of + binary, one pattern to a line. + + Saving compiled patterns in a file is only one possible way of storing + them for later use. They could equally well be saved in a database, or + in the memory of some daemon process that passes them via sockets to + the processes that want them. + + If the pattern has been studied, it is also possible to save the normal + study data in a similar way to the compiled pattern itself. However, if + the PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is cre- + ated cannot be saved because it is too dependent on the current envi- + ronment. When studying generates additional information, + pcre[16|32]_study() returns a pointer to a pcre[16|32]_extra data + block. Its format is defined in the section on matching a pattern in + the pcreapi documentation. The study_data field points to the binary + study data, and this is what you must save (not the pcre[16|32]_extra + block itself). The length of the study data can be obtained by calling + pcre[16|32]_fullinfo() with an argument of PCRE_INFO_STUDYSIZE. Remem- + ber to check that pcre[16|32]_study() did return a non-NULL value + before trying to save the study data. + + +RE-USING A PRECOMPILED PATTERN + + Re-using a precompiled pattern is straightforward. Having reloaded it + into main memory, called pcre[16|32]_pattern_to_host_byte_order() if + necessary, you pass its pointer to pcre[16|32]_exec() or + pcre[16|32]_dfa_exec() in the usual way. + + However, if you passed a pointer to custom character tables when the + pattern was compiled (the tableptr argument of pcre[16|32]_compile()), + you must now pass a similar pointer to pcre[16|32]_exec() or + pcre[16|32]_dfa_exec(), because the value saved with the compiled pat- + tern will obviously be nonsense. A field in a pcre[16|32]_extra() block + is used to pass this data, as described in the section on matching a + pattern in the pcreapi documentation. + + Warning: The tables that pcre_exec() and pcre_dfa_exec() use must be + the same as those that were used when the pattern was compiled. If this + is not the case, the behaviour is undefined. + + If you did not provide custom character tables when the pattern was + compiled, the pointer in the compiled pattern is NULL, which causes the + matching functions to use PCRE's internal tables. Thus, you do not need + to take any special action at run time in this case. + + If you saved study data with the compiled pattern, you need to create + your own pcre[16|32]_extra data block and set the study_data field to + point to the reloaded study data. You must also set the + PCRE_EXTRA_STUDY_DATA bit in the flags field to indicate that study + data is present. Then pass the pcre[16|32]_extra block to the matching + function in the usual way. If the pattern was studied for just-in-time + optimization, that data cannot be saved, and so is lost by a + save/restore cycle. + + +COMPATIBILITY WITH DIFFERENT PCRE RELEASES + + In general, it is safest to recompile all saved patterns when you + update to a new PCRE release, though not all updates actually require + this. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 12 November 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREPERFORM(3) Library Functions Manual PCREPERFORM(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE PERFORMANCE + + Two aspects of performance are discussed below: memory usage and pro- + cessing time. The way you express your pattern as a regular expression + can affect both of them. + + +COMPILED PATTERN MEMORY USAGE + + Patterns are compiled by PCRE into a reasonably efficient interpretive + code, so that most simple patterns do not use much memory. However, + there is one case where the memory usage of a compiled pattern can be + unexpectedly large. If a parenthesized subpattern has a quantifier with + a minimum greater than 1 and/or a limited maximum, the whole subpattern + is repeated in the compiled code. For example, the pattern + + (abc|def){2,4} + + is compiled as if it were + + (abc|def)(abc|def)((abc|def)(abc|def)?)? + + (Technical aside: It is done this way so that backtrack points within + each of the repetitions can be independently maintained.) + + For regular expressions whose quantifiers use only small numbers, this + is not usually a problem. However, if the numbers are large, and par- + ticularly if such repetitions are nested, the memory usage can become + an embarrassment. For example, the very simple pattern + + ((ab){1,1000}c){1,3} + + uses 51K bytes when compiled using the 8-bit library. When PCRE is com- + piled with its default internal pointer size of two bytes, the size + limit on a compiled pattern is 64K data units, and this is reached with + the above pattern if the outer repetition is increased from 3 to 4. + PCRE can be compiled to use larger internal pointers and thus handle + larger compiled patterns, but it is better to try to rewrite your pat- + tern to use less memory if you can. + + One way of reducing the memory usage for such patterns is to make use + of PCRE's "subroutine" facility. Re-writing the above pattern as + + ((ab)(?2){0,999}c)(?1){0,2} + + reduces the memory requirements to 18K, and indeed it remains under 20K + even with the outer repetition increased to 100. However, this pattern + is not exactly equivalent, because the "subroutine" calls are treated + as atomic groups into which there can be no backtracking if there is a + subsequent matching failure. Therefore, PCRE cannot do this kind of + rewriting automatically. Furthermore, there is a noticeable loss of + speed when executing the modified pattern. Nevertheless, if the atomic + grouping is not a problem and the loss of speed is acceptable, this + kind of rewriting will allow you to process patterns that PCRE cannot + otherwise handle. + + +STACK USAGE AT RUN TIME + + When pcre_exec() or pcre[16|32]_exec() is used for matching, certain + kinds of pattern can cause it to use large amounts of the process + stack. In some environments the default process stack is quite small, + and if it runs out the result is often SIGSEGV. This issue is probably + the most frequently raised problem with PCRE. Rewriting your pattern + can often help. The pcrestack documentation discusses this issue in + detail. + + +PROCESSING TIME + + Certain items in regular expression patterns are processed more effi- + ciently than others. It is more efficient to use a character class like + [aeiou] than a set of single-character alternatives such as + (a|e|i|o|u). In general, the simplest construction that provides the + required behaviour is usually the most efficient. Jeffrey Friedl's book + contains a lot of useful general discussion about optimizing regular + expressions for efficient performance. This document contains a few + observations about PCRE. + + Using Unicode character properties (the \p, \P, and \X escapes) is + slow, because PCRE has to use a multi-stage table lookup whenever it + needs a character's property. If you can find an alternative pattern + that does not use character properties, it will probably be faster. + + By default, the escape sequences \b, \d, \s, and \w, and the POSIX + character classes such as [:alpha:] do not use Unicode properties, + partly for backwards compatibility, and partly for performance reasons. + However, you can set PCRE_UCP if you want Unicode character properties + to be used. This can double the matching time for items such as \d, + when matched with a traditional matching function; the performance loss + is less with a DFA matching function, and in both cases there is not + much difference for \b. + + When a pattern begins with .* not in parentheses, or in parentheses + that are not the subject of a backreference, and the PCRE_DOTALL option + is set, the pattern is implicitly anchored by PCRE, since it can match + only at the start of a subject string. However, if PCRE_DOTALL is not + set, PCRE cannot make this optimization, because the . metacharacter + does not then match a newline, and if the subject string contains new- + lines, the pattern may match from the character immediately following + one of them instead of from the very start. For example, the pattern + + .*second + + matches the subject "first\nand second" (where \n stands for a newline + character), with the match starting at the seventh character. In order + to do this, PCRE has to retry the match starting after every newline in + the subject. + + If you are using such a pattern with subject strings that do not con- + tain newlines, the best performance is obtained by setting PCRE_DOTALL, + or starting the pattern with ^.* or ^.*? to indicate explicit anchor- + ing. That saves PCRE from having to scan along the subject looking for + a newline to restart at. + + Beware of patterns that contain nested indefinite repeats. These can + take a long time to run when applied to a string that does not match. + Consider the pattern fragment + + ^(a+)* + + This can match "aaaa" in 16 different ways, and this number increases + very rapidly as the string gets longer. (The * repeat can match 0, 1, + 2, 3, or 4 times, and for each of those cases other than 0 or 4, the + + repeats can match different numbers of times.) When the remainder of + the pattern is such that the entire match is going to fail, PCRE has in + principle to try every possible variation, and this can take an + extremely long time, even for relatively short strings. + + An optimization catches some of the more simple cases such as + + (a+)*b + + where a literal character follows. Before embarking on the standard + matching procedure, PCRE checks that there is a "b" later in the sub- + ject string, and if there is not, it fails the match immediately. How- + ever, when there is no following literal this optimization cannot be + used. You can see the difference by comparing the behaviour of + + (a+)*\d + + with the pattern above. The former gives a failure almost instantly + when applied to a whole line of "a" characters, whereas the latter + takes an appreciable time with strings longer than about 20 characters. + + In many cases, the solution to this kind of performance issue is to use + an atomic group or a possessive quantifier. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 25 August 2012 + Copyright (c) 1997-2012 University of Cambridge. +------------------------------------------------------------------------------ + + +PCREPOSIX(3) Library Functions Manual PCREPOSIX(3) + + + +NAME + PCRE - Perl-compatible regular expressions. + +SYNOPSIS + + #include <pcreposix.h> + + int regcomp(regex_t *preg, const char *pattern, + int cflags); + + int regexec(regex_t *preg, const char *string, + size_t nmatch, regmatch_t pmatch[], int eflags); + size_t regerror(int errcode, const regex_t *preg, + char *errbuf, size_t errbuf_size); + + void regfree(regex_t *preg); + + +DESCRIPTION + + This set of functions provides a POSIX-style API for the PCRE regular + expression 8-bit library. See the pcreapi documentation for a descrip- + tion of PCRE's native API, which contains much additional functional- + ity. There is no POSIX-style wrapper for PCRE's 16-bit and 32-bit + library. + + The functions described here are just wrapper functions that ultimately + call the PCRE native API. Their prototypes are defined in the + pcreposix.h header file, and on Unix systems the library itself is + called pcreposix.a, so can be accessed by adding -lpcreposix to the + command for linking an application that uses them. Because the POSIX + functions call the native ones, it is also necessary to add -lpcre. + + I have implemented only those POSIX option bits that can be reasonably + mapped to PCRE native options. In addition, the option REG_EXTENDED is + defined with the value zero. This has no effect, but since programs + that are written to the POSIX interface often use it, this makes it + easier to slot in PCRE as a replacement library. Other POSIX options + are not even defined. + + There are also some other options that are not defined by POSIX. These + have been added at the request of users who want to make use of certain + PCRE-specific features via the POSIX calling interface. + + When PCRE is called via these functions, it is only the API that is + POSIX-like in style. The syntax and semantics of the regular expres- + sions themselves are still those of Perl, subject to the setting of + various PCRE options, as described below. "POSIX-like in style" means + that the API approximates to the POSIX definition; it is not fully + POSIX-compatible, and in multi-byte encoding domains it is probably + even less compatible. + + The header for these functions is supplied as pcreposix.h to avoid any + potential clash with other POSIX libraries. It can, of course, be + renamed or aliased as regex.h, which is the "correct" name. It provides + two structure types, regex_t for compiled internal forms, and reg- + match_t for returning captured substrings. It also defines some con- + stants whose names start with "REG_"; these are used for setting + options and identifying error codes. + + +COMPILING A PATTERN + + The function regcomp() is called to compile a pattern into an internal + form. The pattern is a C string terminated by a binary zero, and is + passed in the argument pattern. The preg argument is a pointer to a + regex_t structure that is used as a base for storing information about + the compiled regular expression. + + The argument cflags is either zero, or contains one or more of the bits + defined by the following macros: + + REG_DOTALL + + The PCRE_DOTALL option is set when the regular expression is passed for + compilation to the native function. Note that REG_DOTALL is not part of + the POSIX standard. + + REG_ICASE + + The PCRE_CASELESS option is set when the regular expression is passed + for compilation to the native function. + + REG_NEWLINE + + The PCRE_MULTILINE option is set when the regular expression is passed + for compilation to the native function. Note that this does not mimic + the defined POSIX behaviour for REG_NEWLINE (see the following sec- + tion). + + REG_NOSUB + + The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is + passed for compilation to the native function. In addition, when a pat- + tern that is compiled with this flag is passed to regexec() for match- + ing, the nmatch and pmatch arguments are ignored, and no captured + strings are returned. + + REG_UCP + + The PCRE_UCP option is set when the regular expression is passed for + compilation to the native function. This causes PCRE to use Unicode + properties when matchine \d, \w, etc., instead of just recognizing + ASCII values. Note that REG_UTF8 is not part of the POSIX standard. + + REG_UNGREEDY + + The PCRE_UNGREEDY option is set when the regular expression is passed + for compilation to the native function. Note that REG_UNGREEDY is not + part of the POSIX standard. + + REG_UTF8 + + The PCRE_UTF8 option is set when the regular expression is passed for + compilation to the native function. This causes the pattern itself and + all data strings used for matching it to be treated as UTF-8 strings. + Note that REG_UTF8 is not part of the POSIX standard. + + In the absence of these flags, no options are passed to the native + function. This means the the regex is compiled with PCRE default + semantics. In particular, the way it handles newline characters in the + subject string is the Perl way, not the POSIX way. Note that setting + PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE. + It does not affect the way newlines are matched by . (they are not) or + by a negative class such as [^a] (they are). + + The yield of regcomp() is zero on success, and non-zero otherwise. The + preg structure is filled in on success, and one member of the structure + is public: re_nsub contains the number of capturing subpatterns in the + regular expression. Various error codes are defined in the header file. + + NOTE: If the yield of regcomp() is non-zero, you must not attempt to + use the contents of the preg structure. If, for example, you pass it to + regexec(), the result is undefined and your program is likely to crash. + + +MATCHING NEWLINE CHARACTERS + + This area is not simple, because POSIX and Perl take different views of + things. It is not possible to get PCRE to obey POSIX semantics, but + then PCRE was never intended to be a POSIX engine. The following table + lists the different possibilities for matching newline characters in + PCRE: + + Default Change with + + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \n at end yes PCRE_DOLLARENDONLY + $ matches \n in middle no PCRE_MULTILINE + ^ matches \n in middle no PCRE_MULTILINE + + This is the equivalent table for POSIX: + + Default Change with + + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \n at end no REG_NEWLINE + $ matches \n in middle no REG_NEWLINE + ^ matches \n in middle no REG_NEWLINE + + PCRE's behaviour is the same as Perl's, except that there is no equiva- + lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is + no way to stop newline from matching [^a]. + + The default POSIX newline handling can be obtained by setting + PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE + behave exactly as for the REG_NEWLINE action. + + +MATCHING A PATTERN + + The function regexec() is called to match a compiled pattern preg + against a given string, which is by default terminated by a zero byte + (but see REG_STARTEND below), subject to the options in eflags. These + can be: + + REG_NOTBOL + + The PCRE_NOTBOL option is set when calling the underlying PCRE matching + function. + + REG_NOTEMPTY + + The PCRE_NOTEMPTY option is set when calling the underlying PCRE match- + ing function. Note that REG_NOTEMPTY is not part of the POSIX standard. + However, setting this option can give more POSIX-like behaviour in some + situations. + + REG_NOTEOL + + The PCRE_NOTEOL option is set when calling the underlying PCRE matching + function. + + REG_STARTEND + + The string is considered to start at string + pmatch[0].rm_so and to + have a terminating NUL located at string + pmatch[0].rm_eo (there need + not actually be a NUL at that location), regardless of the value of + nmatch. This is a BSD extension, compatible with but not specified by + IEEE Standard 1003.2 (POSIX.2), and should be used with caution in + software intended to be portable to other systems. Note that a non-zero + rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location + of the string, not how it is matched. + + If the pattern was compiled with the REG_NOSUB flag, no data about any + matched strings is returned. The nmatch and pmatch arguments of + regexec() are ignored. + + If the value of nmatch is zero, or if the value pmatch is NULL, no data + about any matched strings is returned. + + Otherwise,the portion of the string that was matched, and also any cap- + tured substrings, are returned via the pmatch argument, which points to + an array of nmatch structures of type regmatch_t, containing the mem- + bers rm_so and rm_eo. These contain the offset to the first character + of each substring and the offset to the first character after the end + of each substring, respectively. The 0th element of the vector relates + to the entire portion of string that was matched; subsequent elements + relate to the capturing subpatterns of the regular expression. Unused + entries in the array have both structure members set to -1. + + A successful match yields a zero return; various error codes are + defined in the header file, of which REG_NOMATCH is the "expected" + failure code. + + +ERROR MESSAGES + + The regerror() function maps a non-zero errorcode from either regcomp() + or regexec() to a printable message. If preg is not NULL, the error + should have arisen from the use of that structure. A message terminated + by a binary zero is placed in errbuf. The length of the message, + including the zero, is limited to errbuf_size. The yield of the func- + tion is the size of buffer needed to hold the whole message. + + +MEMORY USAGE + + Compiling a regular expression causes memory to be allocated and asso- + ciated with the preg structure. The function regfree() frees all such + memory, after which preg may no longer be used as a compiled expres- + sion. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 09 January 2012 + Copyright (c) 1997-2012 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRECPP(3) Library Functions Manual PCRECPP(3) + + + +NAME + PCRE - Perl-compatible regular expressions. + +SYNOPSIS OF C++ WRAPPER + + #include <pcrecpp.h> + + +DESCRIPTION + + The C++ wrapper for PCRE was provided by Google Inc. Some additional + functionality was added by Giuseppe Maxia. This brief man page was con- + structed from the notes in the pcrecpp.h file, which should be con- + sulted for further details. Note that the C++ wrapper supports only the + original 8-bit PCRE library. There is no 16-bit or 32-bit support at + present. + + +MATCHING INTERFACE + + The "FullMatch" operation checks that supplied text matches a supplied + pattern exactly. If pointer arguments are supplied, it copies matched + sub-strings that match sub-patterns into them. + + Example: successful match + pcrecpp::RE re("h.*o"); + re.FullMatch("hello"); + + Example: unsuccessful match (requires full match): + pcrecpp::RE re("e"); + !re.FullMatch("hello"); + + Example: creating a temporary RE object: + pcrecpp::RE("h.*o").FullMatch("hello"); + + You can pass in a "const char*" or a "string" for "text". The examples + below tend to use a const char*. You can, as in the different examples + above, store the RE object explicitly in a variable or use a temporary + RE object. The examples below use one mode or the other arbitrarily. + Either could correctly be used for any of these examples. + + You must supply extra pointer arguments to extract matched subpieces. + + Example: extracts "ruby" into "s" and 1234 into "i" + int i; + string s; + pcrecpp::RE re("(\\w+):(\\d+)"); + re.FullMatch("ruby:1234", &s, &i); + + Example: does not try to extract any extra sub-patterns + re.FullMatch("ruby:1234", &s); + + Example: does not try to extract into NULL + re.FullMatch("ruby:1234", NULL, &i); + + Example: integer overflow causes failure + !re.FullMatch("ruby:1234567891234", NULL, &i); + + Example: fails because there aren't enough sub-patterns: + !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s); + + Example: fails because string cannot be stored in integer + !pcrecpp::RE("(.*)").FullMatch("ruby", &i); + + The provided pointer arguments can be pointers to any scalar numeric + type, or one of: + + string (matched piece is copied to string) + StringPiece (StringPiece is mutated to point to matched piece) + T (where "bool T::ParseFrom(const char*, int)" exists) + NULL (the corresponding matched sub-pattern is not copied) + + The function returns true iff all of the following conditions are sat- + isfied: + + a. "text" matches "pattern" exactly; + + b. The number of matched sub-patterns is >= number of supplied + pointers; + + c. The "i"th argument has a suitable type for holding the + string captured as the "i"th sub-pattern. If you pass in + void * NULL for the "i"th argument, or a non-void * NULL + of the correct type, or pass fewer arguments than the + number of sub-patterns, "i"th captured sub-pattern is + ignored. + + CAVEAT: An optional sub-pattern that does not exist in the matched + string is assigned the empty string. Therefore, the following will + return false (because the empty string is not a valid number): + + int number; + pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number); + + The matching interface supports at most 16 arguments per call. If you + need more, consider using the more general interface + pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch. + + NOTE: Do not use no_arg, which is used internally to mark the end of a + list of optional arguments, as a placeholder for missing arguments, as + this can lead to segfaults. + + +QUOTING METACHARACTERS + + You can use the "QuoteMeta" operation to insert backslashes before all + potentially meaningful characters in a string. The returned string, + used as a regular expression, will exactly match the original string. + + Example: + string quoted = RE::QuoteMeta(unquoted); + + Note that it's legal to escape a character even if it has no special + meaning in a regular expression -- so this function does that. (This + also makes it identical to the perl function of the same name; see + "perldoc -f quotemeta".) For example, "1.5-2.0?" becomes + "1\.5\-2\.0\?". + + +PARTIAL MATCHES + + You can use the "PartialMatch" operation when you want the pattern to + match any substring of the text. + + Example: simple search for a string: + pcrecpp::RE("ell").PartialMatch("hello"); + + Example: find first number in a string: + int number; + pcrecpp::RE re("(\\d+)"); + re.PartialMatch("x*100 + 20", &number); + assert(number == 100); + + +UTF-8 AND THE MATCHING INTERFACE + + By default, pattern and text are plain text, one byte per character. + The UTF8 flag, passed to the constructor, causes both pattern and + string to be treated as UTF-8 text, still a byte stream but potentially + multiple bytes per character. In practice, the text is likelier to be + UTF-8 than the pattern, but the match returned may depend on the UTF8 + flag, so always use it when matching UTF8 text. For example, "." will + match one byte normally but with UTF8 set may match up to three bytes + of a multi-byte character. + + Example: + pcrecpp::RE_Options options; + options.set_utf8(); + pcrecpp::RE re(utf8_pattern, options); + re.FullMatch(utf8_string); + + Example: using the convenience function UTF8(): + pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8()); + re.FullMatch(utf8_string); + + NOTE: The UTF8 flag is ignored if pcre was not configured with the + --enable-utf8 flag. + + +PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE + + PCRE defines some modifiers to change the behavior of the regular + expression engine. The C++ wrapper defines an auxiliary class, + RE_Options, as a vehicle to pass such modifiers to a RE class. Cur- + rently, the following modifiers are supported: + + modifier description Perl corresponding + + PCRE_CASELESS case insensitive match /i + PCRE_MULTILINE multiple lines match /m + PCRE_DOTALL dot matches newlines /s + PCRE_DOLLAR_ENDONLY $ matches only at end N/A + PCRE_EXTRA strict escape parsing N/A + PCRE_EXTENDED ignore white spaces /x + PCRE_UTF8 handles UTF8 chars built-in + PCRE_UNGREEDY reverses * and *? N/A + PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*) + + (*) Both Perl and PCRE allow non capturing parentheses by means of the + "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not cap- + ture, while (ab|cd) does. + + For a full account on how each modifier works, please check the PCRE + API reference page. + + For each modifier, there are two member functions whose name is made + out of the modifier in lowercase, without the "PCRE_" prefix. For + instance, PCRE_CASELESS is handled by + + bool caseless() + + which returns true if the modifier is set, and + + RE_Options & set_caseless(bool) + + which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can + be accessed through the set_match_limit() and match_limit() member + functions. Setting match_limit to a non-zero value will limit the exe- + cution of pcre to keep it from doing bad things like blowing the stack + or taking an eternity to return a result. A value of 5000 is good + enough to stop stack blowup in a 2MB thread stack. Setting match_limit + to zero disables match limiting. Alternatively, you can call + match_limit_recursion() which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to + limit how much PCRE recurses. match_limit() limits the number of + matches PCRE does; match_limit_recursion() limits the depth of internal + recursion, and therefore the amount of stack that is used. + + Normally, to pass one or more modifiers to a RE class, you declare a + RE_Options object, set the appropriate options, and pass this object to + a RE constructor. Example: + + RE_Options opt; + opt.set_caseless(true); + if (RE("HELLO", opt).PartialMatch("hello world")) ... + + RE_options has two constructors. The default constructor takes no argu- + ments and creates a set of flags that are off by default. The optional + parameter option_flags is to facilitate transfer of legacy code from C + programs. This lets you do + + RE(pattern, + RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str); + + However, new code is better off doing + + RE(pattern, + RE_Options().set_caseless(true).set_multiline(true)) + .PartialMatch(str); + + If you are going to pass one of the most used modifiers, there are some + convenience functions that return a RE_Options class with the appropri- + ate modifier already set: CASELESS(), UTF8(), MULTILINE(), DOTALL(), + and EXTENDED(). + + If you need to set several options at once, and you don't want to go + through the pains of declaring a RE_Options object and setting several + options, there is a parallel method that give you such ability on the + fly. You can concatenate several set_xxxxx() member functions, since + each of them returns a reference to its class object. For example, to + pass PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one + statement, you may write: + + RE(" ^ xyz \\s+ .* blah$", + RE_Options() + .set_caseless(true) + .set_extended(true) + .set_multiline(true)).PartialMatch(sometext); + + +SCANNING TEXT INCREMENTALLY + + The "Consume" operation may be useful if you want to repeatedly match + regular expressions at the front of a string and skip over them as they + match. This requires use of the "StringPiece" type, which represents a + sub-range of a real string. Like RE, StringPiece is defined in the + pcrecpp namespace. + + Example: read lines of the form "var = value" from a string. + string contents = ...; // Fill string somehow + pcrecpp::StringPiece input(contents); // Wrap in a StringPiece + + string var; + int value; + pcrecpp::RE re("(\\w+) = (\\d+)\n"); + while (re.Consume(&input, &var, &value)) { + ...; + } + + Each successful call to "Consume" will set "var/value", and also + advance "input" so it points past the matched text. + + The "FindAndConsume" operation is similar to "Consume" but does not + anchor your match at the beginning of the string. For example, you + could extract all words from a string by repeatedly calling + + pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word) + + +PARSING HEX/OCTAL/C-RADIX NUMBERS + + By default, if you pass a pointer to a numeric value, the corresponding + text is interpreted as a base-10 number. You can instead wrap the + pointer with a call to one of the operators Hex(), Octal(), or CRadix() + to interpret the text in another base. The CRadix operator interprets + C-style "0" (base-8) and "0x" (base-16) prefixes, but defaults to + base-10. + + Example: + int a, b, c, d; + pcrecpp::RE re("(.*) (.*) (.*) (.*)"); + re.FullMatch("100 40 0100 0x40", + pcrecpp::Octal(&a), pcrecpp::Hex(&b), + pcrecpp::CRadix(&c), pcrecpp::CRadix(&d)); + + will leave 64 in a, b, c, and d. + + +REPLACING PARTS OF STRINGS + + You can replace the first match of "pattern" in "str" with "rewrite". + Within "rewrite", backslash-escaped digits (\1 to \9) can be used to + insert text matching corresponding parenthesized group from the pat- + tern. \0 in "rewrite" refers to the entire matching text. For example: + + string s = "yabba dabba doo"; + pcrecpp::RE("b+").Replace("d", &s); + + will leave "s" containing "yada dabba doo". The result is true if the + pattern matches and a replacement occurs, false otherwise. + + GlobalReplace is like Replace except that it replaces all occurrences + of the pattern in the string with the rewrite. Replacements are not + subject to re-matching. For example: + + string s = "yabba dabba doo"; + pcrecpp::RE("b+").GlobalReplace("d", &s); + + will leave "s" containing "yada dada doo". It returns the number of + replacements made. + + Extract is like Replace, except that if the pattern matches, "rewrite" + is copied into "out" (an additional argument) with substitutions. The + non-matching portions of "text" are ignored. Returns true iff a match + occurred and the extraction happened successfully; if no match occurs, + the string is left unaffected. + + +AUTHOR + + The C++ wrapper was contributed by Google Inc. + Copyright (c) 2007 Google Inc. + + +REVISION + + Last updated: 08 January 2012 +------------------------------------------------------------------------------ + + +PCRESAMPLE(3) Library Functions Manual PCRESAMPLE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE SAMPLE PROGRAM + + A simple, complete demonstration program, to get you started with using + PCRE, is supplied in the file pcredemo.c in the PCRE distribution. A + listing of this program is given in the pcredemo documentation. If you + do not have a copy of the PCRE distribution, you can save this listing + to re-create pcredemo.c. + + The demonstration program, which uses the original PCRE 8-bit library, + compiles the regular expression that is its first argument, and matches + it against the subject string in its second argument. No PCRE options + are set, and default character tables are used. If matching succeeds, + the program outputs the portion of the subject that matched, together + with the contents of any captured substrings. + + If the -g option is given on the command line, the program then goes on + to check for further matches of the same regular expression in the same + subject string. The logic is a little bit tricky because of the possi- + bility of matching an empty string. Comments in the code explain what + is going on. + + If PCRE is installed in the standard include and library directories + for your operating system, you should be able to compile the demonstra- + tion program using this command: + + gcc -o pcredemo pcredemo.c -lpcre + + If PCRE is installed elsewhere, you may need to add additional options + to the command line. For example, on a Unix-like system that has PCRE + installed in /usr/local, you can compile the demonstration program + using a command like this: + + gcc -o pcredemo -I/usr/local/include pcredemo.c \ + -L/usr/local/lib -lpcre + + In a Windows environment, if you want to statically link the program + against a non-dll pcre.a file, you must uncomment the line that defines + PCRE_STATIC before including pcre.h, because otherwise the pcre_mal- + loc() and pcre_free() exported functions will be declared + __declspec(dllimport), with unwanted results. + + Once you have compiled and linked the demonstration program, you can + run simple tests like this: + + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' + + Note that there is a much more comprehensive test program, called + pcretest, which supports many more facilities for testing regular + expressions and both PCRE libraries. The pcredemo program is provided + as a simple coding example. + + If you try to run pcredemo when PCRE is not installed in the standard + library directory, you may get an error like this on some operating + systems (e.g. Solaris): + + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or + directory + + This is caused by the way shared library support works on those sys- + tems. You need to add + + -R/usr/local/lib + + (for example) to the compile command to get round this problem. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 10 January 2012 + Copyright (c) 1997-2012 University of Cambridge. +------------------------------------------------------------------------------ +PCRELIMITS(3) Library Functions Manual PCRELIMITS(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +SIZE AND OTHER LIMITATIONS + + There are some size limitations in PCRE but it is hoped that they will + never in practice be relevant. + + The maximum length of a compiled pattern is approximately 64K data + units (bytes for the 8-bit library, 16-bit units for the 16-bit + library, and 32-bit units for the 32-bit library) if PCRE is compiled + with the default internal linkage size, which is 2 bytes for the 8-bit + and 16-bit libraries, and 4 bytes for the 32-bit library. If you want + to process regular expressions that are truly enormous, you can compile + PCRE with an internal linkage size of 3 or 4 (when building the 16-bit + or 32-bit library, 3 is rounded up to 4). See the README file in the + source distribution and the pcrebuild documentation for details. In + these cases the limit is substantially larger. However, the speed of + execution is slower. + + All values in repeating quantifiers must be less than 65536. + + There is no limit to the number of parenthesized subpatterns, but there + can be no more than 65535 capturing subpatterns. There is, however, a + limit to the depth of nesting of parenthesized subpatterns of all + kinds. This is imposed in order to limit the amount of system stack + used at compile time. The limit can be specified when PCRE is built; + the default is 250. + + There is a limit to the number of forward references to subsequent sub- + patterns of around 200,000. Repeated forward references with fixed + upper limits, for example, (?2){0,100} when subpattern number 2 is to + the right, are included in the count. There is no limit to the number + of backward references. + + The maximum length of name for a named subpattern is 32 characters, and + the maximum number of named subpatterns is 10000. + + The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or + (*THEN) verb is 255 for the 8-bit library and 65535 for the 16-bit and + 32-bit libraries. + + The maximum length of a subject string is the largest positive number + that an integer variable can hold. However, when using the traditional + matching function, PCRE uses recursion to handle subpatterns and indef- + inite repetition. This means that the available stack space may limit + the size of a subject string that can be processed by certain patterns. + For a discussion of stack issues, see the pcrestack documentation. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 05 November 2013 + Copyright (c) 1997-2013 University of Cambridge. +------------------------------------------------------------------------------ + + +PCRESTACK(3) Library Functions Manual PCRESTACK(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE DISCUSSION OF STACK USAGE + + When you call pcre[16|32]_exec(), it makes use of an internal function + called match(). This calls itself recursively at branch points in the + pattern, in order to remember the state of the match so that it can + back up and try a different alternative if the first one fails. As + matching proceeds deeper and deeper into the tree of possibilities, the + recursion depth increases. The match() function is also called in other + circumstances, for example, whenever a parenthesized sub-pattern is + entered, and in certain cases of repetition. + + Not all calls of match() increase the recursion depth; for an item such + as a* it may be called several times at the same level, after matching + different numbers of a's. Furthermore, in a number of cases where the + result of the recursive call would immediately be passed back as the + result of the current call (a "tail recursion"), the function is just + restarted instead. + + The above comments apply when pcre[16|32]_exec() is run in its normal + interpretive manner. If the pattern was studied with the + PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling was success- + ful, and the options passed to pcre[16|32]_exec() were not incompati- + ble, the matching process uses the JIT-compiled code instead of the + match() function. In this case, the memory requirements are handled + entirely differently. See the pcrejit documentation for details. + + The pcre[16|32]_dfa_exec() function operates in an entirely different + way, and uses recursion only when there is a regular expression recur- + sion or subroutine call in the pattern. This includes the processing of + assertion and "once-only" subpatterns, which are handled like subrou- + tine calls. Normally, these are never very deep, and the limit on the + complexity of pcre[16|32]_dfa_exec() is controlled by the amount of + workspace it is given. However, it is possible to write patterns with + runaway infinite recursions; such patterns will cause + pcre[16|32]_dfa_exec() to run out of stack. At present, there is no + protection against this. + + The comments that follow do NOT apply to pcre[16|32]_dfa_exec(); they + are relevant only for pcre[16|32]_exec() without the JIT optimization. + + Reducing pcre[16|32]_exec()'s stack usage + + Each time that match() is actually called recursively, it uses memory + from the process stack. For certain kinds of pattern and data, very + large amounts of stack may be needed, despite the recognition of "tail + recursion". You can often reduce the amount of recursion, and there- + fore the amount of stack used, by modifying the pattern that is being + matched. Consider, for example, this pattern: + + ([^<]|<(?!inet))+ + + It matches from wherever it starts until it encounters "<inet" or the + end of the data, and is the kind of pattern that might be used when + processing an XML file. Each iteration of the outer parentheses matches + either one character that is not "<" or a "<" that is not followed by + "inet". However, each time a parenthesis is processed, a recursion + occurs, so this formulation uses a stack frame for each matched charac- + ter. For a long string, a lot of stack is required. Consider now this + rewritten pattern, which matches exactly the same strings: + + ([^<]++|<(?!inet))+ + + This uses very much less stack, because runs of characters that do not + contain "<" are "swallowed" in one item inside the parentheses. Recur- + sion happens only when a "<" character that is not followed by "inet" + is encountered (and we assume this is relatively rare). A possessive + quantifier is used to stop any backtracking into the runs of non-"<" + characters, but that is not related to stack usage. + + This example shows that one way of avoiding stack problems when match- + ing long subject strings is to write repeated parenthesized subpatterns + to match more than one character whenever possible. + + Compiling PCRE to use heap instead of stack for pcre[16|32]_exec() + + In environments where stack memory is constrained, you might want to + compile PCRE to use heap memory instead of stack for remembering back- + up points when pcre[16|32]_exec() is running. This makes it run a lot + more slowly, however. Details of how to do this are given in the pcre- + build documentation. When built in this way, instead of using the + stack, PCRE obtains and frees memory by calling the functions that are + pointed to by the pcre[16|32]_stack_malloc and pcre[16|32]_stack_free + variables. By default, these point to malloc() and free(), but you can + replace the pointers to cause PCRE to use your own functions. Since the + block sizes are always the same, and are always freed in reverse order, + it may be possible to implement customized memory handlers that are + more efficient than the standard functions. + + Limiting pcre[16|32]_exec()'s stack usage + + You can set limits on the number of times that match() is called, both + in total and recursively. If a limit is exceeded, pcre[16|32]_exec() + returns an error code. Setting suitable limits should prevent it from + running out of stack. The default values of the limits are very large, + and unlikely ever to operate. They can be changed when PCRE is built, + and they can also be set when pcre[16|32]_exec() is called. For details + of these interfaces, see the pcrebuild documentation and the section on + extra data for pcre[16|32]_exec() in the pcreapi documentation. + + As a very rough rule of thumb, you should reckon on about 500 bytes per + recursion. Thus, if you want to limit your stack usage to 8Mb, you + should set the limit at 16000 recursions. A 64Mb stack, on the other + hand, can support around 128000 recursions. + + In Unix-like environments, the pcretest test program has a command line + option (-S) that can be used to increase the size of its stack. As long + as the stack is large enough, another option (-M) can be used to find + the smallest limits that allow a particular pattern to match a given + subject string. This is done by calling pcre[16|32]_exec() repeatedly + with different limits. + + Obtaining an estimate of stack usage + + The actual amount of stack used per recursion can vary quite a lot, + depending on the compiler that was used to build PCRE and the optimiza- + tion or debugging options that were set for it. The rule of thumb value + of 500 bytes mentioned above may be larger or smaller than what is + actually needed. A better approximation can be obtained by running this + command: + + pcretest -m -C + + The -C option causes pcretest to output information about the options + with which PCRE was compiled. When -m is also given (before -C), infor- + mation about stack use is given in a line like this: + + Match recursion uses stack: approximate frame size = 640 bytes + + The value is approximate because some recursions need a bit more (up to + perhaps 16 more bytes). + + If the above command is given when PCRE is compiled to use the heap + instead of the stack for recursion, the value that is output is the + size of each block that is obtained from the heap. + + Changing stack size in Unix-like systems + + In Unix-like environments, there is not often a problem with the stack + unless very long strings are involved, though the default limit on + stack size varies from system to system. Values from 8Mb to 64Mb are + common. You can find your default limit by running the command: + + ulimit -s + + Unfortunately, the effect of running out of stack is often SIGSEGV, + though sometimes a more explicit error message is given. You can nor- + mally increase the limit on stack size by code such as this: + + struct rlimit rlim; + getrlimit(RLIMIT_STACK, &rlim); + rlim.rlim_cur = 100*1024*1024; + setrlimit(RLIMIT_STACK, &rlim); + + This reads the current limits (soft and hard) using getrlimit(), then + attempts to increase the soft limit to 100Mb using setrlimit(). You + must do this before calling pcre[16|32]_exec(). + + Changing stack size in Mac OS X + + Using setrlimit(), as described above, should also work on Mac OS X. It + is also possible to set a stack size when linking a program. There is a + discussion about stack sizes in Mac OS X at this web site: + http://developer.apple.com/qa/qa2005/qa1419.html. + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 24 June 2012 + Copyright (c) 1997-2012 University of Cambridge. +------------------------------------------------------------------------------ + + diff --git a/doc/pcre16.3 b/doc/pcre16.3 new file mode 100644 index 0000000..85126a6 --- /dev/null +++ b/doc/pcre16.3 @@ -0,0 +1,371 @@ +.TH PCRE 3 "12 May 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.sp +.B #include <pcre.h> +. +. +.SH "PCRE 16-BIT API BASIC FUNCTIONS" +.rs +.sp +.nf +.B pcre16 *pcre16_compile(PCRE_SPTR16 \fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre16 *pcre16_compile2(PCRE_SPTR16 \fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre16_extra *pcre16_study(const pcre16 *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.sp +.B void pcre16_free_study(pcre16_extra *\fIextra\fP); +.sp +.B int pcre16_exec(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " PCRE_SPTR16 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.sp +.B int pcre16_dfa_exec(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " PCRE_SPTR16 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.fi +. +. +.SH "PCRE 16-BIT API STRING EXTRACTION FUNCTIONS" +.rs +.sp +.nf +.B int pcre16_copy_named_substring(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR16 \fIstringname\fP," +.B " PCRE_UCHAR16 *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre16_copy_substring(PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, PCRE_UCHAR16 *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre16_get_named_substring(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR16 \fIstringname\fP," +.B " PCRE_SPTR16 *\fIstringptr\fP);" +.sp +.B int pcre16_get_stringnumber(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIname\fP); +.sp +.B int pcre16_get_stringtable_entries(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIname\fP, PCRE_UCHAR16 **\fIfirst\fP, PCRE_UCHAR16 **\fIlast\fP);" +.sp +.B int pcre16_get_substring(PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " PCRE_SPTR16 *\fIstringptr\fP);" +.sp +.B int pcre16_get_substring_list(PCRE_SPTR16 \fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, PCRE_SPTR16 **\fIlistptr\fP);" +.sp +.B void pcre16_free_substring(PCRE_SPTR16 \fIstringptr\fP); +.sp +.B void pcre16_free_substring_list(PCRE_SPTR16 *\fIstringptr\fP); +.fi +. +. +.SH "PCRE 16-BIT API AUXILIARY FUNCTIONS" +.rs +.sp +.nf +.B pcre16_jit_stack *pcre16_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP); +.sp +.B void pcre16_jit_stack_free(pcre16_jit_stack *\fIstack\fP); +.sp +.B void pcre16_assign_jit_stack(pcre16_extra *\fIextra\fP, +.B " pcre16_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.sp +.B const unsigned char *pcre16_maketables(void); +.sp +.B int pcre16_fullinfo(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.sp +.B int pcre16_refcount(pcre16 *\fIcode\fP, int \fIadjust\fP); +.sp +.B int pcre16_config(int \fIwhat\fP, void *\fIwhere\fP); +.sp +.B const char *pcre16_version(void); +.sp +.B int pcre16_pattern_to_host_byte_order(pcre16 *\fIcode\fP, +.B " pcre16_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.fi +. +. +.SH "PCRE 16-BIT API INDIRECTED FUNCTIONS" +.rs +.sp +.nf +.B void *(*pcre16_malloc)(size_t); +.sp +.B void (*pcre16_free)(void *); +.sp +.B void *(*pcre16_stack_malloc)(size_t); +.sp +.B void (*pcre16_stack_free)(void *); +.sp +.B int (*pcre16_callout)(pcre16_callout_block *); +.fi +. +. +.SH "PCRE 16-BIT API 16-BIT-ONLY FUNCTION" +.rs +.sp +.nf +.B int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *\fIoutput\fP, +.B " PCRE_SPTR16 \fIinput\fP, int \fIlength\fP, int *\fIbyte_order\fP," +.B " int \fIkeep_boms\fP);" +.fi +. +. +.SH "THE PCRE 16-BIT LIBRARY" +.rs +.sp +Starting with release 8.30, it is possible to compile a PCRE library that +supports 16-bit character strings, including UTF-16 strings, as well as or +instead of the original 8-bit library. The majority of the work to make this +possible was done by Zoltan Herczeg. The two libraries contain identical sets +of functions, used in exactly the same way. Only the names of the functions and +the data types of their arguments and results are different. To avoid +over-complication and reduce the documentation maintenance load, most of the +PCRE documentation describes the 8-bit library, with only occasional references +to the 16-bit library. This page describes what is different when you use the +16-bit library. +.P +WARNING: A single application can be linked with both libraries, but you must +take care when processing any particular pattern to use functions from just one +library. For example, if you want to study a pattern that was compiled with +\fBpcre16_compile()\fP, you must do so with \fBpcre16_study()\fP, not +\fBpcre_study()\fP, and you must free the study data with +\fBpcre16_free_study()\fP. +. +. +.SH "THE HEADER FILE" +.rs +.sp +There is only one header file, \fBpcre.h\fP. It contains prototypes for all the +functions in all libraries, as well as definitions of flags, structures, error +codes, etc. +. +. +.SH "THE LIBRARY NAME" +.rs +.sp +In Unix-like systems, the 16-bit library is called \fBlibpcre16\fP, and can +normally be accesss by adding \fB-lpcre16\fP to the command for linking an +application that uses PCRE. +. +. +.SH "STRING TYPES" +.rs +.sp +In the 8-bit library, strings are passed to PCRE library functions as vectors +of bytes with the C type "char *". In the 16-bit library, strings are passed as +vectors of unsigned 16-bit quantities. The macro PCRE_UCHAR16 specifies an +appropriate data type, and PCRE_SPTR16 is defined as "const PCRE_UCHAR16 *". In +very many environments, "short int" is a 16-bit data type. When PCRE is built, +it defines PCRE_UCHAR16 as "unsigned short int", but checks that it really is a +16-bit data type. If it is not, the build fails with an error message telling +the maintainer to modify the definition appropriately. +. +. +.SH "STRUCTURE TYPES" +.rs +.sp +The types of the opaque structures that are used for compiled 16-bit patterns +and JIT stacks are \fBpcre16\fP and \fBpcre16_jit_stack\fP respectively. The +type of the user-accessible structure that is returned by \fBpcre16_study()\fP +is \fBpcre16_extra\fP, and the type of the structure that is used for passing +data to a callout function is \fBpcre16_callout_block\fP. These structures +contain the same fields, with the same names, as their 8-bit counterparts. The +only difference is that pointers to character strings are 16-bit instead of +8-bit types. +. +. +.SH "16-BIT FUNCTIONS" +.rs +.sp +For every function in the 8-bit library there is a corresponding function in +the 16-bit library with a name that starts with \fBpcre16_\fP instead of +\fBpcre_\fP. The prototypes are listed above. In addition, there is one extra +function, \fBpcre16_utf16_to_host_byte_order()\fP. This is a utility function +that converts a UTF-16 character string to host byte order if necessary. The +other 16-bit functions expect the strings they are passed to be in host byte +order. +.P +The \fIinput\fP and \fIoutput\fP arguments of +\fBpcre16_utf16_to_host_byte_order()\fP may point to the same address, that is, +conversion in place is supported. The output buffer must be at least as long as +the input. +.P +The \fIlength\fP argument specifies the number of 16-bit data units in the +input string; a negative value specifies a zero-terminated string. +.P +If \fIbyte_order\fP is NULL, it is assumed that the string starts off in host +byte order. This may be changed by byte-order marks (BOMs) anywhere in the +string (commonly as the first character). +.P +If \fIbyte_order\fP is not NULL, a non-zero value of the integer to which it +points means that the input starts off in host byte order, otherwise the +opposite order is assumed. Again, BOMs in the string can change this. The final +byte order is passed back at the end of processing. +.P +If \fIkeep_boms\fP is not zero, byte-order mark characters (0xfeff) are copied +into the output string. Otherwise they are discarded. +.P +The result of the function is the number of 16-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +. +. +.SH "SUBJECT STRING OFFSETS" +.rs +.sp +The lengths and starting offsets of subject strings must be specified in 16-bit +data units, and the offsets within subject strings that are returned by the +matching functions are in also 16-bit units rather than bytes. +. +. +.SH "NAMED SUBPATTERNS" +.rs +.sp +The name-to-number translation table that is maintained for named subpatterns +uses 16-bit characters. The \fBpcre16_get_stringtable_entries()\fP function +returns the length of each entry in the table as the number of 16-bit data +units. +. +. +.SH "OPTION NAMES" +.rs +.sp +There are two new general option names, PCRE_UTF16 and PCRE_NO_UTF16_CHECK, +which correspond to PCRE_UTF8 and PCRE_NO_UTF8_CHECK in the 8-bit library. In +fact, these new options define the same bits in the options word. There is a +discussion about the +.\" HTML <a href="pcreunicode.html#utf16strings"> +.\" </a> +validity of UTF-16 strings +.\" +in the +.\" HREF +\fBpcreunicode\fP +.\" +page. +.P +For the \fBpcre16_config()\fP function there is an option PCRE_CONFIG_UTF16 +that returns 1 if UTF-16 support is configured, otherwise 0. If this option is +given to \fBpcre_config()\fP or \fBpcre32_config()\fP, or if the +PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 option is given to \fBpcre16_config()\fP, +the result is the PCRE_ERROR_BADOPTION error. +. +. +.SH "CHARACTER CODES" +.rs +.sp +In 16-bit mode, when PCRE_UTF16 is not set, character values are treated in the +same way as in 8-bit, non UTF-8 mode, except, of course, that they can range +from 0 to 0xffff instead of 0 to 0xff. Character types for characters less than +0xff can therefore be influenced by the locale in the same way as before. +Characters greater than 0xff have only one case, and no "type" (such as letter +or digit). +.P +In UTF-16 mode, the character code is Unicode, in the range 0 to 0x10ffff, with +the exception of values in the range 0xd800 to 0xdfff because those are +"surrogate" values that are used in pairs to encode values greater than 0xffff. +.P +A UTF-16 string can indicate its endianness by special code knows as a +byte-order mark (BOM). The PCRE functions do not handle this, expecting strings +to be in host byte order. A utility function called +\fBpcre16_utf16_to_host_byte_order()\fP is provided to help with this (see +above). +. +. +.SH "ERROR NAMES" +.rs +.sp +The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 correspond to +their 8-bit counterparts. The error PCRE_ERROR_BADMODE is given when a compiled +pattern is passed to a function that processes patterns in the other +mode, for example, if a pattern compiled with \fBpcre_compile()\fP is passed to +\fBpcre16_exec()\fP. +.P +There are new error codes whose names begin with PCRE_UTF16_ERR for invalid +UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for UTF-8 strings that +are described in the section entitled +.\" HTML <a href="pcreapi.html#badutf8reasons"> +.\" </a> +"Reason codes for invalid UTF-8 strings" +.\" +in the main +.\" HREF +\fBpcreapi\fP +.\" +page. The UTF-16 errors are: +.sp + PCRE_UTF16_ERR1 Missing low surrogate at end of string + PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate + PCRE_UTF16_ERR3 Isolated low surrogate + PCRE_UTF16_ERR4 Non-character +. +. +.SH "ERROR TEXTS" +.rs +.sp +If there is an error while compiling a pattern, the error text that is passed +back by \fBpcre16_compile()\fP or \fBpcre16_compile2()\fP is still an 8-bit +character string, zero-terminated. +. +. +.SH "CALLOUTS" +.rs +.sp +The \fIsubject\fP and \fImark\fP fields in the callout block that is passed to +a callout function point to 16-bit vectors. +. +. +.SH "TESTING" +.rs +.sp +The \fBpcretest\fP program continues to operate with 8-bit input and output +files, but it can be used for testing the 16-bit library. If it is run with the +command line option \fB-16\fP, patterns and subject strings are converted from +8-bit to 16-bit before being passed to PCRE, and the 16-bit library functions +are used instead of the 8-bit ones. Returned 16-bit strings are converted to +8-bit for output. If both the 8-bit and the 32-bit libraries were not compiled, +\fBpcretest\fP defaults to 16-bit and the \fB-16\fP option is ignored. +.P +When PCRE is being built, the \fBRunTest\fP script that is called by "make +check" uses the \fBpcretest\fP \fB-C\fP option to discover which of the 8-bit, +16-bit and 32-bit libraries has been built, and runs the tests appropriately. +. +. +.SH "NOT SUPPORTED IN 16-BIT MODE" +.rs +.sp +Not all the features of the 8-bit library are available with the 16-bit +library. The C++ and POSIX wrapper functions support only the 8-bit library, +and the \fBpcregrep\fP program is at present 8-bit only. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 May 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcre32.3 b/doc/pcre32.3 new file mode 100644 index 0000000..7cde8c0 --- /dev/null +++ b/doc/pcre32.3 @@ -0,0 +1,369 @@ +.TH PCRE 3 "12 May 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.sp +.B #include <pcre.h> +. +. +.SH "PCRE 32-BIT API BASIC FUNCTIONS" +.rs +.sp +.nf +.B pcre32 *pcre32_compile(PCRE_SPTR32 \fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre32 *pcre32_compile2(PCRE_SPTR32 \fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre32_extra *pcre32_study(const pcre32 *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.sp +.B void pcre32_free_study(pcre32_extra *\fIextra\fP); +.sp +.B int pcre32_exec(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " PCRE_SPTR32 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.sp +.B int pcre32_dfa_exec(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " PCRE_SPTR32 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.fi +. +. +.SH "PCRE 32-BIT API STRING EXTRACTION FUNCTIONS" +.rs +.sp +.nf +.B int pcre32_copy_named_substring(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR32 \fIstringname\fP," +.B " PCRE_UCHAR32 *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre32_copy_substring(PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, PCRE_UCHAR32 *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre32_get_named_substring(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR32 \fIstringname\fP," +.B " PCRE_SPTR32 *\fIstringptr\fP);" +.sp +.B int pcre32_get_stringnumber(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIname\fP);" +.sp +.B int pcre32_get_stringtable_entries(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIname\fP, PCRE_UCHAR32 **\fIfirst\fP, PCRE_UCHAR32 **\fIlast\fP);" +.sp +.B int pcre32_get_substring(PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " PCRE_SPTR32 *\fIstringptr\fP);" +.sp +.B int pcre32_get_substring_list(PCRE_SPTR32 \fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, PCRE_SPTR32 **\fIlistptr\fP);" +.sp +.B void pcre32_free_substring(PCRE_SPTR32 \fIstringptr\fP); +.sp +.B void pcre32_free_substring_list(PCRE_SPTR32 *\fIstringptr\fP); +.fi +. +. +.SH "PCRE 32-BIT API AUXILIARY FUNCTIONS" +.rs +.sp +.nf +.B pcre32_jit_stack *pcre32_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP); +.sp +.B void pcre32_jit_stack_free(pcre32_jit_stack *\fIstack\fP); +.sp +.B void pcre32_assign_jit_stack(pcre32_extra *\fIextra\fP, +.B " pcre32_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.sp +.B const unsigned char *pcre32_maketables(void); +.sp +.B int pcre32_fullinfo(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.sp +.B int pcre32_refcount(pcre32 *\fIcode\fP, int \fIadjust\fP); +.sp +.B int pcre32_config(int \fIwhat\fP, void *\fIwhere\fP); +.sp +.B const char *pcre32_version(void); +.sp +.B int pcre32_pattern_to_host_byte_order(pcre32 *\fIcode\fP, +.B " pcre32_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.fi +. +. +.SH "PCRE 32-BIT API INDIRECTED FUNCTIONS" +.rs +.sp +.nf +.B void *(*pcre32_malloc)(size_t); +.sp +.B void (*pcre32_free)(void *); +.sp +.B void *(*pcre32_stack_malloc)(size_t); +.sp +.B void (*pcre32_stack_free)(void *); +.sp +.B int (*pcre32_callout)(pcre32_callout_block *); +.fi +. +. +.SH "PCRE 32-BIT API 32-BIT-ONLY FUNCTION" +.rs +.sp +.nf +.B int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *\fIoutput\fP, +.B " PCRE_SPTR32 \fIinput\fP, int \fIlength\fP, int *\fIbyte_order\fP," +.B " int \fIkeep_boms\fP);" +.fi +. +. +.SH "THE PCRE 32-BIT LIBRARY" +.rs +.sp +Starting with release 8.32, it is possible to compile a PCRE library that +supports 32-bit character strings, including UTF-32 strings, as well as or +instead of the original 8-bit library. This work was done by Christian Persch, +based on the work done by Zoltan Herczeg for the 16-bit library. All three +libraries contain identical sets of functions, used in exactly the same way. +Only the names of the functions and the data types of their arguments and +results are different. To avoid over-complication and reduce the documentation +maintenance load, most of the PCRE documentation describes the 8-bit library, +with only occasional references to the 16-bit and 32-bit libraries. This page +describes what is different when you use the 32-bit library. +.P +WARNING: A single application can be linked with all or any of the three +libraries, but you must take care when processing any particular pattern +to use functions from just one library. For example, if you want to study +a pattern that was compiled with \fBpcre32_compile()\fP, you must do so +with \fBpcre32_study()\fP, not \fBpcre_study()\fP, and you must free the +study data with \fBpcre32_free_study()\fP. +. +. +.SH "THE HEADER FILE" +.rs +.sp +There is only one header file, \fBpcre.h\fP. It contains prototypes for all the +functions in all libraries, as well as definitions of flags, structures, error +codes, etc. +. +. +.SH "THE LIBRARY NAME" +.rs +.sp +In Unix-like systems, the 32-bit library is called \fBlibpcre32\fP, and can +normally be accesss by adding \fB-lpcre32\fP to the command for linking an +application that uses PCRE. +. +. +.SH "STRING TYPES" +.rs +.sp +In the 8-bit library, strings are passed to PCRE library functions as vectors +of bytes with the C type "char *". In the 32-bit library, strings are passed as +vectors of unsigned 32-bit quantities. The macro PCRE_UCHAR32 specifies an +appropriate data type, and PCRE_SPTR32 is defined as "const PCRE_UCHAR32 *". In +very many environments, "unsigned int" is a 32-bit data type. When PCRE is +built, it defines PCRE_UCHAR32 as "unsigned int", but checks that it really is +a 32-bit data type. If it is not, the build fails with an error message telling +the maintainer to modify the definition appropriately. +. +. +.SH "STRUCTURE TYPES" +.rs +.sp +The types of the opaque structures that are used for compiled 32-bit patterns +and JIT stacks are \fBpcre32\fP and \fBpcre32_jit_stack\fP respectively. The +type of the user-accessible structure that is returned by \fBpcre32_study()\fP +is \fBpcre32_extra\fP, and the type of the structure that is used for passing +data to a callout function is \fBpcre32_callout_block\fP. These structures +contain the same fields, with the same names, as their 8-bit counterparts. The +only difference is that pointers to character strings are 32-bit instead of +8-bit types. +. +. +.SH "32-BIT FUNCTIONS" +.rs +.sp +For every function in the 8-bit library there is a corresponding function in +the 32-bit library with a name that starts with \fBpcre32_\fP instead of +\fBpcre_\fP. The prototypes are listed above. In addition, there is one extra +function, \fBpcre32_utf32_to_host_byte_order()\fP. This is a utility function +that converts a UTF-32 character string to host byte order if necessary. The +other 32-bit functions expect the strings they are passed to be in host byte +order. +.P +The \fIinput\fP and \fIoutput\fP arguments of +\fBpcre32_utf32_to_host_byte_order()\fP may point to the same address, that is, +conversion in place is supported. The output buffer must be at least as long as +the input. +.P +The \fIlength\fP argument specifies the number of 32-bit data units in the +input string; a negative value specifies a zero-terminated string. +.P +If \fIbyte_order\fP is NULL, it is assumed that the string starts off in host +byte order. This may be changed by byte-order marks (BOMs) anywhere in the +string (commonly as the first character). +.P +If \fIbyte_order\fP is not NULL, a non-zero value of the integer to which it +points means that the input starts off in host byte order, otherwise the +opposite order is assumed. Again, BOMs in the string can change this. The final +byte order is passed back at the end of processing. +.P +If \fIkeep_boms\fP is not zero, byte-order mark characters (0xfeff) are copied +into the output string. Otherwise they are discarded. +.P +The result of the function is the number of 32-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +. +. +.SH "SUBJECT STRING OFFSETS" +.rs +.sp +The lengths and starting offsets of subject strings must be specified in 32-bit +data units, and the offsets within subject strings that are returned by the +matching functions are in also 32-bit units rather than bytes. +. +. +.SH "NAMED SUBPATTERNS" +.rs +.sp +The name-to-number translation table that is maintained for named subpatterns +uses 32-bit characters. The \fBpcre32_get_stringtable_entries()\fP function +returns the length of each entry in the table as the number of 32-bit data +units. +. +. +.SH "OPTION NAMES" +.rs +.sp +There are two new general option names, PCRE_UTF32 and PCRE_NO_UTF32_CHECK, +which correspond to PCRE_UTF8 and PCRE_NO_UTF8_CHECK in the 8-bit library. In +fact, these new options define the same bits in the options word. There is a +discussion about the +.\" HTML <a href="pcreunicode.html#utf32strings"> +.\" </a> +validity of UTF-32 strings +.\" +in the +.\" HREF +\fBpcreunicode\fP +.\" +page. +.P +For the \fBpcre32_config()\fP function there is an option PCRE_CONFIG_UTF32 +that returns 1 if UTF-32 support is configured, otherwise 0. If this option is +given to \fBpcre_config()\fP or \fBpcre16_config()\fP, or if the +PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 option is given to \fBpcre32_config()\fP, +the result is the PCRE_ERROR_BADOPTION error. +. +. +.SH "CHARACTER CODES" +.rs +.sp +In 32-bit mode, when PCRE_UTF32 is not set, character values are treated in the +same way as in 8-bit, non UTF-8 mode, except, of course, that they can range +from 0 to 0x7fffffff instead of 0 to 0xff. Character types for characters less +than 0xff can therefore be influenced by the locale in the same way as before. +Characters greater than 0xff have only one case, and no "type" (such as letter +or digit). +.P +In UTF-32 mode, the character code is Unicode, in the range 0 to 0x10ffff, with +the exception of values in the range 0xd800 to 0xdfff because those are +"surrogate" values that are ill-formed in UTF-32. +.P +A UTF-32 string can indicate its endianness by special code knows as a +byte-order mark (BOM). The PCRE functions do not handle this, expecting strings +to be in host byte order. A utility function called +\fBpcre32_utf32_to_host_byte_order()\fP is provided to help with this (see +above). +. +. +.SH "ERROR NAMES" +.rs +.sp +The error PCRE_ERROR_BADUTF32 corresponds to its 8-bit counterpart. +The error PCRE_ERROR_BADMODE is given when a compiled +pattern is passed to a function that processes patterns in the other +mode, for example, if a pattern compiled with \fBpcre_compile()\fP is passed to +\fBpcre32_exec()\fP. +.P +There are new error codes whose names begin with PCRE_UTF32_ERR for invalid +UTF-32 strings, corresponding to the PCRE_UTF8_ERR codes for UTF-8 strings that +are described in the section entitled +.\" HTML <a href="pcreapi.html#badutf8reasons"> +.\" </a> +"Reason codes for invalid UTF-8 strings" +.\" +in the main +.\" HREF +\fBpcreapi\fP +.\" +page. The UTF-32 errors are: +.sp + PCRE_UTF32_ERR1 Surrogate character (range from 0xd800 to 0xdfff) + PCRE_UTF32_ERR2 Non-character + PCRE_UTF32_ERR3 Character > 0x10ffff +. +. +.SH "ERROR TEXTS" +.rs +.sp +If there is an error while compiling a pattern, the error text that is passed +back by \fBpcre32_compile()\fP or \fBpcre32_compile2()\fP is still an 8-bit +character string, zero-terminated. +. +. +.SH "CALLOUTS" +.rs +.sp +The \fIsubject\fP and \fImark\fP fields in the callout block that is passed to +a callout function point to 32-bit vectors. +. +. +.SH "TESTING" +.rs +.sp +The \fBpcretest\fP program continues to operate with 8-bit input and output +files, but it can be used for testing the 32-bit library. If it is run with the +command line option \fB-32\fP, patterns and subject strings are converted from +8-bit to 32-bit before being passed to PCRE, and the 32-bit library functions +are used instead of the 8-bit ones. Returned 32-bit strings are converted to +8-bit for output. If both the 8-bit and the 16-bit libraries were not compiled, +\fBpcretest\fP defaults to 32-bit and the \fB-32\fP option is ignored. +.P +When PCRE is being built, the \fBRunTest\fP script that is called by "make +check" uses the \fBpcretest\fP \fB-C\fP option to discover which of the 8-bit, +16-bit and 32-bit libraries has been built, and runs the tests appropriately. +. +. +.SH "NOT SUPPORTED IN 32-BIT MODE" +.rs +.sp +Not all the features of the 8-bit library are available with the 32-bit +library. The C++ and POSIX wrapper functions support only the 8-bit library, +and the \fBpcregrep\fP program is at present 8-bit only. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 May 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcre_assign_jit_stack.3 b/doc/pcre_assign_jit_stack.3 new file mode 100644 index 0000000..0ecf6f2 --- /dev/null +++ b/doc/pcre_assign_jit_stack.3 @@ -0,0 +1,59 @@ +.TH PCRE_ASSIGN_JIT_STACK 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP, +.B " pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.sp +.B void pcre16_assign_jit_stack(pcre16_extra *\fIextra\fP, +.B " pcre16_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.sp +.B void pcre32_assign_jit_stack(pcre32_extra *\fIextra\fP, +.B " pcre32_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function provides control over the memory used as a stack at run-time by a +call to \fBpcre[16|32]_exec()\fP with a pattern that has been successfully +compiled with JIT optimization. The arguments are: +.sp + extra the data pointer returned by \fBpcre[16|32]_study()\fP + callback a callback function + data a JIT stack or a value to be passed to the callback + function +.P +If \fIcallback\fP is NULL and \fIdata\fP is NULL, an internal 32K block on +the machine stack is used. +.P +If \fIcallback\fP is NULL and \fIdata\fP is not NULL, \fIdata\fP must +be a valid JIT stack, the result of calling \fBpcre[16|32]_jit_stack_alloc()\fP. +.P +If \fIcallback\fP not NULL, it is called with \fIdata\fP as an argument at +the start of matching, in order to set up a JIT stack. If the result is NULL, +the internal 32K stack is used; otherwise the return value must be a valid JIT +stack, the result of calling \fBpcre[16|32]_jit_stack_alloc()\fP. +.P +You may safely assign the same JIT stack to multiple patterns, as long as they +are all matched in the same thread. In a multithread application, each thread +must use its own JIT stack. For more details, see the +.\" HREF +\fBpcrejit\fP +.\" +page. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_compile.3 b/doc/pcre_compile.3 new file mode 100644 index 0000000..5c16ebe --- /dev/null +++ b/doc/pcre_compile.3 @@ -0,0 +1,96 @@ +.TH PCRE_COMPILE 3 "01 October 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre16 *pcre16_compile(PCRE_SPTR16 \fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre32 *pcre32_compile(PCRE_SPTR32 \fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function compiles a regular expression into an internal form. It is the +same as \fBpcre[16|32]_compile2()\fP, except for the absence of the +\fIerrorcodeptr\fP argument. Its arguments are: +.sp + \fIpattern\fP A zero-terminated string containing the + regular expression to be compiled + \fIoptions\fP Zero or more option bits + \fIerrptr\fP Where to put an error message + \fIerroffset\fP Offset in pattern where error was found + \fItableptr\fP Pointer to character tables, or NULL to + use the built-in default +.sp +The option bits are: +.sp + PCRE_ANCHORED Force pattern anchoring + PCRE_AUTO_CALLOUT Compile automatic callouts + PCRE_BSR_ANYCRLF \eR matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \eR matches all Unicode line endings + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_DUPNAMES Allow duplicate names for subpatterns + PCRE_EXTENDED Ignore white space and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_FIRSTLINE Force matching to be before newline + PCRE_JAVASCRIPT_COMPAT JavaScript compatibility + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NEVER_UTF Lock out UTF, e.g. via (*UTF) + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, and CRLF as newline + sequences + PCRE_NEWLINE_CR Set CR as the newline sequence + PCRE_NEWLINE_CRLF Set CRLF as the newline sequence + PCRE_NEWLINE_LF Set LF as the newline sequence + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_NO_AUTO_POSSESS Disable auto-possessification + PCRE_NO_START_OPTIMIZE Disable match-time start optimizations + PCRE_NO_UTF16_CHECK Do not check the pattern for UTF-16 + validity (only relevant if + PCRE_UTF16 is set) + PCRE_NO_UTF32_CHECK Do not check the pattern for UTF-32 + validity (only relevant if + PCRE_UTF32 is set) + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) + PCRE_UCP Use Unicode properties for \ed, \ew, etc. + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF16 Run in \fBpcre16_compile()\fP UTF-16 mode + PCRE_UTF32 Run in \fBpcre32_compile()\fP UTF-32 mode + PCRE_UTF8 Run in \fBpcre_compile()\fP UTF-8 mode +.sp +PCRE must be built with UTF support in order to use PCRE_UTF8/16/32 and +PCRE_NO_UTF8/16/32_CHECK, and with UCP support if PCRE_UCP is used. +.P +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. Note that +compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_compile2.3 b/doc/pcre_compile2.3 new file mode 100644 index 0000000..3774201 --- /dev/null +++ b/doc/pcre_compile2.3 @@ -0,0 +1,101 @@ +.TH PCRE_COMPILE2 3 "01 October 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre16 *pcre16_compile2(PCRE_SPTR16 \fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre32 *pcre32_compile2(PCRE_SPTR32 \fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP,£ +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function compiles a regular expression into an internal form. It is the +same as \fBpcre[16|32]_compile()\fP, except for the addition of the +\fIerrorcodeptr\fP argument. The arguments are: +. +.sp + \fIpattern\fP A zero-terminated string containing the + regular expression to be compiled + \fIoptions\fP Zero or more option bits + \fIerrorcodeptr\fP Where to put an error code + \fIerrptr\fP Where to put an error message + \fIerroffset\fP Offset in pattern where error was found + \fItableptr\fP Pointer to character tables, or NULL to + use the built-in default +.sp +The option bits are: +.sp + PCRE_ANCHORED Force pattern anchoring + PCRE_AUTO_CALLOUT Compile automatic callouts + PCRE_BSR_ANYCRLF \eR matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \eR matches all Unicode line endings + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_DUPNAMES Allow duplicate names for subpatterns + PCRE_EXTENDED Ignore white space and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_FIRSTLINE Force matching to be before newline + PCRE_JAVASCRIPT_COMPAT JavaScript compatibility + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NEVER_UTF Lock out UTF, e.g. via (*UTF) + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, and CRLF as newline + sequences + PCRE_NEWLINE_CR Set CR as the newline sequence + PCRE_NEWLINE_CRLF Set CRLF as the newline sequence + PCRE_NEWLINE_LF Set LF as the newline sequence + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_NO_AUTO_POSSESS Disable auto-possessification + PCRE_NO_START_OPTIMIZE Disable match-time start optimizations + PCRE_NO_UTF16_CHECK Do not check the pattern for UTF-16 + validity (only relevant if + PCRE_UTF16 is set) + PCRE_NO_UTF32_CHECK Do not check the pattern for UTF-32 + validity (only relevant if + PCRE_UTF32 is set) + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) + PCRE_UCP Use Unicode properties for \ed, \ew, etc. + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF16 Run \fBpcre16_compile()\fP in UTF-16 mode + PCRE_UTF32 Run \fBpcre32_compile()\fP in UTF-32 mode + PCRE_UTF8 Run \fBpcre_compile()\fP in UTF-8 mode +.sp +PCRE must be built with UTF support in order to use PCRE_UTF8/16/32 and +PCRE_NO_UTF8/16/32_CHECK, and with UCP support if PCRE_UCP is used. +.P +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. Note that +compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_config.3 b/doc/pcre_config.3 new file mode 100644 index 0000000..d14ffda --- /dev/null +++ b/doc/pcre_config.3 @@ -0,0 +1,79 @@ +.TH PCRE_CONFIG 3 "20 April 2014" "PCRE 8.36" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP); +.PP +.B int pcre16_config(int \fIwhat\fP, void *\fIwhere\fP); +.PP +.B int pcre32_config(int \fIwhat\fP, void *\fIwhere\fP); +. +.SH DESCRIPTION +.rs +.sp +This function makes it possible for a client program to find out which optional +features are available in the version of the PCRE library it is using. The +arguments are as follows: +.sp + \fIwhat\fP A code specifying what information is required + \fIwhere\fP Points to where to put the data +.sp +The \fIwhere\fP argument must point to an integer variable, except for +PCRE_CONFIG_MATCH_LIMIT, PCRE_CONFIG_MATCH_LIMIT_RECURSION, and +PCRE_CONFIG_PARENS_LIMIT, when it must point to an unsigned long integer, +and for PCRE_CONFIG_JITTARGET, when it must point to a const char*. +The available codes are: +.sp + PCRE_CONFIG_JIT Availability of just-in-time compiler + support (1=yes 0=no) + PCRE_CONFIG_JITTARGET String containing information about the + target architecture for the JIT compiler, + or NULL if there is no JIT support + PCRE_CONFIG_LINK_SIZE Internal link size: 2, 3, or 4 + PCRE_CONFIG_PARENS_LIMIT Parentheses nesting limit + PCRE_CONFIG_MATCH_LIMIT Internal resource limit + PCRE_CONFIG_MATCH_LIMIT_RECURSION + Internal recursion depth limit + PCRE_CONFIG_NEWLINE Value of the default newline sequence: + 13 (0x000d) for CR + 10 (0x000a) for LF + 3338 (0x0d0a) for CRLF + -2 for ANYCRLF + -1 for ANY + PCRE_CONFIG_BSR Indicates what \eR matches by default: + 0 all Unicode line endings + 1 CR, LF, or CRLF only + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + Threshold of return slots, above which + \fBmalloc()\fP is used by the POSIX API + PCRE_CONFIG_STACKRECURSE Recursion implementation (1=stack 0=heap) + PCRE_CONFIG_UTF16 Availability of UTF-16 support (1=yes + 0=no); option for \fBpcre16_config()\fP + PCRE_CONFIG_UTF32 Availability of UTF-32 support (1=yes + 0=no); option for \fBpcre32_config()\fP + PCRE_CONFIG_UTF8 Availability of UTF-8 support (1=yes 0=no); + option for \fBpcre_config()\fP + PCRE_CONFIG_UNICODE_PROPERTIES + Availability of Unicode property support + (1=yes 0=no) +.sp +The function yields 0 on success or PCRE_ERROR_BADOPTION otherwise. That error +is also given if PCRE_CONFIG_UTF16 or PCRE_CONFIG_UTF32 is passed to +\fBpcre_config()\fP, if PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF32 is passed to +\fBpcre16_config()\fP, or if PCRE_CONFIG_UTF8 or PCRE_CONFIG_UTF16 is passed to +\fBpcre32_config()\fP. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_copy_named_substring.3 b/doc/pcre_copy_named_substring.3 new file mode 100644 index 0000000..52582ae --- /dev/null +++ b/doc/pcre_copy_named_substring.3 @@ -0,0 +1,51 @@ +.TH PCRE_COPY_NAMED_SUBSTRING 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_copy_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " char *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre16_copy_named_substring(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR16 \fIstringname\fP," +.B " PCRE_UCHAR16 *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre32_copy_named_substring(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR32 \fIstringname\fP," +.B " PCRE_UCHAR32 *\fIbuffer\fP, int \fIbuffersize\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring, identified +by name, into a given buffer. The arguments are: +.sp + \fIcode\fP Pattern that was successfully matched + \fIsubject\fP Subject that has been successfully matched + \fIovector\fP Offset vector that \fBpcre[16|32]_exec()\fP used + \fIstringcount\fP Value returned by \fBpcre[16|32]_exec()\fP + \fIstringname\fP Name of the required substring + \fIbuffer\fP Buffer to receive the string + \fIbuffersize\fP Size of buffer +.sp +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string name is invalid. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_copy_substring.3 b/doc/pcre_copy_substring.3 new file mode 100644 index 0000000..83af6e8 --- /dev/null +++ b/doc/pcre_copy_substring.3 @@ -0,0 +1,47 @@ +.TH PCRE_COPY_SUBSTRING 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre16_copy_substring(PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, PCRE_UCHAR16 *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre32_copy_substring(PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, PCRE_UCHAR32 *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring into a given +buffer. The arguments are: +.sp + \fIsubject\fP Subject that has been successfully matched + \fIovector\fP Offset vector that \fBpcre[16|32]_exec()\fP used + \fIstringcount\fP Value returned by \fBpcre[16|32]_exec()\fP + \fIstringnumber\fP Number of the required substring + \fIbuffer\fP Buffer to receive the string + \fIbuffersize\fP Size of buffer +.sp +The yield is the length of the string, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string number is invalid. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_dfa_exec.3 b/doc/pcre_dfa_exec.3 new file mode 100644 index 0000000..39c2e83 --- /dev/null +++ b/doc/pcre_dfa_exec.3 @@ -0,0 +1,118 @@ +.TH PCRE_DFA_EXEC 3 "12 May 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.sp +.B int pcre16_dfa_exec(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " PCRE_SPTR16 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.sp +.B int pcre32_dfa_exec(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " PCRE_SPTR32 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function matches a compiled regular expression against a given subject +string, using an alternative matching algorithm that scans the subject string +just once (\fInot\fP Perl-compatible). Note that the main, Perl-compatible, +matching function is \fBpcre[16|32]_exec()\fP. The arguments for this function +are: +.sp + \fIcode\fP Points to the compiled pattern + \fIextra\fP Points to an associated \fBpcre[16|32]_extra\fP structure, + or is NULL + \fIsubject\fP Points to the subject string + \fIlength\fP Length of the subject string + \fIstartoffset\fP Offset in the subject at which to start matching + \fIoptions\fP Option bits + \fIovector\fP Points to a vector of ints for result offsets + \fIovecsize\fP Number of elements in the vector + \fIworkspace\fP Points to a vector of ints used as working space + \fIwscount\fP Number of elements in the vector +.sp +The units for \fIlength\fP and \fIstartoffset\fP are bytes for +\fBpcre_exec()\fP, 16-bit data items for \fBpcre16_exec()\fP, and 32-bit items +for \fBpcre32_exec()\fP. The options are: +.sp + PCRE_ANCHORED Match only at the first position + PCRE_BSR_ANYCRLF \eR matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \eR matches all Unicode line endings + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, & CRLF as newline sequences + PCRE_NEWLINE_CR Recognize CR as the only newline sequence + PCRE_NEWLINE_CRLF Recognize CRLF as the only newline sequence + PCRE_NEWLINE_LF Recognize LF as the only newline sequence + PCRE_NOTBOL Subject is not the beginning of a line + PCRE_NOTEOL Subject is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_START_OPTIMIZE Do not do "start-match" optimizations + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + even if there is a full match as well + PCRE_DFA_SHORTEST Return only the shortest match + PCRE_DFA_RESTART Restart after a partial match +.sp +There are restrictions on what may appear in a pattern when using this matching +function. Details are given in the +.\" HREF +\fBpcrematching\fP +.\" +documentation. For details of partial matching, see the +.\" HREF +\fBpcrepartial\fP +.\" +page. +.P +A \fBpcre[16|32]_extra\fP structure contains the following fields: +.sp + \fIflags\fP Bits indicating which fields are set + \fIstudy_data\fP Opaque data from \fBpcre[16|32]_study()\fP + \fImatch_limit\fP Limit on internal resource use + \fImatch_limit_recursion\fP Limit on internal recursion depth + \fIcallout_data\fP Opaque data passed back to callouts + \fItables\fP Points to character tables or is NULL + \fImark\fP For passing back a *MARK pointer + \fIexecutable_jit\fP Opaque data from JIT compilation +.sp +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. For this +matching function, the \fImatch_limit\fP and \fImatch_limit_recursion\fP fields +are not used, and must not be set. The PCRE_EXTRA_EXECUTABLE_JIT flag and +the corresponding variable are ignored. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_exec.3 b/doc/pcre_exec.3 new file mode 100644 index 0000000..4686bd6 --- /dev/null +++ b/doc/pcre_exec.3 @@ -0,0 +1,99 @@ +.TH PCRE_EXEC 3 "12 May 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.sp +.B int pcre16_exec(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " PCRE_SPTR16 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.sp +.B int pcre32_exec(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " PCRE_SPTR32 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function matches a compiled regular expression against a given subject +string, using a matching algorithm that is similar to Perl's. It returns +offsets to captured substrings. Its arguments are: +.sp + \fIcode\fP Points to the compiled pattern + \fIextra\fP Points to an associated \fBpcre[16|32]_extra\fP structure, + or is NULL + \fIsubject\fP Points to the subject string + \fIlength\fP Length of the subject string + \fIstartoffset\fP Offset in the subject at which to start matching + \fIoptions\fP Option bits + \fIovector\fP Points to a vector of ints for result offsets + \fIovecsize\fP Number of elements in the vector (a multiple of 3) +.sp +The units for \fIlength\fP and \fIstartoffset\fP are bytes for +\fBpcre_exec()\fP, 16-bit data items for \fBpcre16_exec()\fP, and 32-bit items +for \fBpcre32_exec()\fP. The options are: +.sp + PCRE_ANCHORED Match only at the first position + PCRE_BSR_ANYCRLF \eR matches only CR, LF, or CRLF + PCRE_BSR_UNICODE \eR matches all Unicode line endings + PCRE_NEWLINE_ANY Recognize any Unicode newline sequence + PCRE_NEWLINE_ANYCRLF Recognize CR, LF, & CRLF as newline sequences + PCRE_NEWLINE_CR Recognize CR as the only newline sequence + PCRE_NEWLINE_CRLF Recognize CRLF as the only newline sequence + PCRE_NEWLINE_LF Recognize LF as the only newline sequence + PCRE_NOTBOL Subject string is not the beginning of a line + PCRE_NOTEOL Subject string is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_START_OPTIMIZE Do not do "start-match" optimizations + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + if that is found before a full match +.sp +For details of partial matching, see the +.\" HREF +\fBpcrepartial\fP +.\" +page. A \fBpcre_extra\fP structure contains the following fields: +.sp + \fIflags\fP Bits indicating which fields are set + \fIstudy_data\fP Opaque data from \fBpcre[16|32]_study()\fP + \fImatch_limit\fP Limit on internal resource use + \fImatch_limit_recursion\fP Limit on internal recursion depth + \fIcallout_data\fP Opaque data passed back to callouts + \fItables\fP Points to character tables or is NULL + \fImark\fP For passing back a *MARK pointer + \fIexecutable_jit\fP Opaque data from JIT compilation +.sp +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_free_study.3 b/doc/pcre_free_study.3 new file mode 100644 index 0000000..8826b73 --- /dev/null +++ b/doc/pcre_free_study.3 @@ -0,0 +1,31 @@ +.TH PCRE_FREE_STUDY 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B void pcre_free_study(pcre_extra *\fIextra\fP); +.PP +.B void pcre16_free_study(pcre16_extra *\fIextra\fP); +.PP +.B void pcre32_free_study(pcre32_extra *\fIextra\fP); +. +.SH DESCRIPTION +.rs +.sp +This function is used to free the memory used for the data generated by a call +to \fBpcre[16|32]_study()\fP when it is no longer needed. The argument must be the +result of such a call. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_free_substring.3 b/doc/pcre_free_substring.3 new file mode 100644 index 0000000..88c0401 --- /dev/null +++ b/doc/pcre_free_substring.3 @@ -0,0 +1,31 @@ +.TH PCRE_FREE_SUBSTRING 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B void pcre_free_substring(const char *\fIstringptr\fP); +.PP +.B void pcre16_free_substring(PCRE_SPTR16 \fIstringptr\fP); +.PP +.B void pcre32_free_substring(PCRE_SPTR32 \fIstringptr\fP); +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for freeing the store obtained by a previous +call to \fBpcre[16|32]_get_substring()\fP or \fBpcre[16|32]_get_named_substring()\fP. +Its only argument is a pointer to the string. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_free_substring_list.3 b/doc/pcre_free_substring_list.3 new file mode 100644 index 0000000..248b4bd --- /dev/null +++ b/doc/pcre_free_substring_list.3 @@ -0,0 +1,31 @@ +.TH PCRE_FREE_SUBSTRING_LIST 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B void pcre_free_substring_list(const char **\fIstringptr\fP); +.PP +.B void pcre16_free_substring_list(PCRE_SPTR16 *\fIstringptr\fP); +.PP +.B void pcre32_free_substring_list(PCRE_SPTR32 *\fIstringptr\fP); +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for freeing the store obtained by a previous +call to \fBpcre[16|32]_get_substring_list()\fP. Its only argument is a pointer to +the list of string pointers. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_fullinfo.3 b/doc/pcre_fullinfo.3 new file mode 100644 index 0000000..c9b2c65 --- /dev/null +++ b/doc/pcre_fullinfo.3 @@ -0,0 +1,103 @@ +.TH PCRE_FULLINFO 3 "21 April 2014" "PCRE 8.36" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.sp +.B int pcre16_fullinfo(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.sp +.B int pcre32_fullinfo(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function returns information about a compiled pattern. Its arguments are: +.sp + \fIcode\fP Compiled regular expression + \fIextra\fP Result of \fBpcre[16|32]_study()\fP or NULL + \fIwhat\fP What information is required + \fIwhere\fP Where to put the information +.sp +The following information is available: +.sp + PCRE_INFO_BACKREFMAX Number of highest back reference + PCRE_INFO_CAPTURECOUNT Number of capturing subpatterns + PCRE_INFO_DEFAULT_TABLES Pointer to default tables + PCRE_INFO_FIRSTBYTE Fixed first data unit for a match, or + -1 for start of string + or after newline, or + -2 otherwise + PCRE_INFO_FIRSTTABLE Table of first data units (after studying) + PCRE_INFO_HASCRORLF Return 1 if explicit CR or LF matches exist + PCRE_INFO_JCHANGED Return 1 if (?J) or (?-J) was used + PCRE_INFO_JIT Return 1 after successful JIT compilation + PCRE_INFO_JITSIZE Size of JIT compiled code + PCRE_INFO_LASTLITERAL Literal last data unit required + PCRE_INFO_MINLENGTH Lower bound length of matching strings + PCRE_INFO_MATCHEMPTY Return 1 if the pattern can match an empty string, + 0 otherwise + PCRE_INFO_MATCHLIMIT Match limit if set, otherwise PCRE_RROR_UNSET + PCRE_INFO_MAXLOOKBEHIND Length (in characters) of the longest lookbehind assertion + PCRE_INFO_NAMECOUNT Number of named subpatterns + PCRE_INFO_NAMEENTRYSIZE Size of name table entry + PCRE_INFO_NAMETABLE Pointer to name table + PCRE_INFO_OKPARTIAL Return 1 if partial matching can be tried + (always returns 1 after release 8.00) + PCRE_INFO_OPTIONS Option bits used for compilation + PCRE_INFO_SIZE Size of compiled pattern + PCRE_INFO_STUDYSIZE Size of study data + PCRE_INFO_FIRSTCHARACTER Fixed first data unit for a match + PCRE_INFO_FIRSTCHARACTERFLAGS Returns + 1 if there is a first data character set, which can + then be retrieved using PCRE_INFO_FIRSTCHARACTER, + 2 if the first character is at the start of the data + string or after a newline, and + 0 otherwise + PCRE_INFO_RECURSIONLIMIT Recursion limit if set, otherwise PCRE_ERROR_UNSET + PCRE_INFO_REQUIREDCHAR Literal last data unit required + PCRE_INFO_REQUIREDCHARFLAGS Returns 1 if the last data character is set (which can then + be retrieved using PCRE_INFO_REQUIREDCHAR); 0 otherwise +.sp +The \fIwhere\fP argument must point to an integer variable, except for the +following \fIwhat\fP values: +.sp + PCRE_INFO_DEFAULT_TABLES const uint8_t * + PCRE_INFO_FIRSTCHARACTER uint32_t + PCRE_INFO_FIRSTTABLE const uint8_t * + PCRE_INFO_JITSIZE size_t + PCRE_INFO_MATCHLIMIT uint32_t + PCRE_INFO_NAMETABLE PCRE_SPTR16 (16-bit library) + PCRE_INFO_NAMETABLE PCRE_SPTR32 (32-bit library) + PCRE_INFO_NAMETABLE const unsigned char * (8-bit library) + PCRE_INFO_OPTIONS unsigned long int + PCRE_INFO_SIZE size_t + PCRE_INFO_STUDYSIZE size_t + PCRE_INFO_RECURSIONLIMIT uint32_t + PCRE_INFO_REQUIREDCHAR uint32_t +.sp +The yield of the function is zero on success or: +.sp + PCRE_ERROR_NULL the argument \fIcode\fP was NULL + the argument \fIwhere\fP was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid + PCRE_ERROR_UNSET the option was not set +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_get_named_substring.3 b/doc/pcre_get_named_substring.3 new file mode 100644 index 0000000..84d4ee7 --- /dev/null +++ b/doc/pcre_get_named_substring.3 @@ -0,0 +1,54 @@ +.TH PCRE_GET_NAMED_SUBSTRING 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_get_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " const char **\fIstringptr\fP);" +.sp +.B int pcre16_get_named_substring(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR16 \fIstringname\fP," +.B " PCRE_SPTR16 *\fIstringptr\fP);" +.sp +.B int pcre32_get_named_substring(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, PCRE_SPTR32 \fIstringname\fP," +.B " PCRE_SPTR32 *\fIstringptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring by name. The +arguments are: +.sp + \fIcode\fP Compiled pattern + \fIsubject\fP Subject that has been successfully matched + \fIovector\fP Offset vector that \fBpcre[16|32]_exec()\fP used + \fIstringcount\fP Value returned by \fBpcre[16|32]_exec()\fP + \fIstringname\fP Name of the required substring + \fIstringptr\fP Where to put the string pointer +.sp +The memory in which the substring is placed is obtained by calling +\fBpcre[16|32]_malloc()\fP. The convenience function +\fBpcre[16|32]_free_substring()\fP can be used to free it when it is no longer +needed. The yield of the function is the length of the extracted substring, +PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or +PCRE_ERROR_NOSUBSTRING if the string name is invalid. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_get_stringnumber.3 b/doc/pcre_get_stringnumber.3 new file mode 100644 index 0000000..9fc5291 --- /dev/null +++ b/doc/pcre_get_stringnumber.3 @@ -0,0 +1,43 @@ +.TH PCRE_GET_STRINGNUMBER 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_get_stringnumber(const pcre *\fIcode\fP, +.B " const char *\fIname\fP);" +.sp +.B int pcre16_get_stringnumber(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIname\fP);" +.sp +.B int pcre32_get_stringnumber(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIname\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This convenience function finds the number of a named substring capturing +parenthesis in a compiled pattern. Its arguments are: +.sp + \fIcode\fP Compiled regular expression + \fIname\fP Name whose number is required +.sp +The yield of the function is the number of the parenthesis if the name is +found, or PCRE_ERROR_NOSUBSTRING otherwise. When duplicate names are allowed +(PCRE_DUPNAMES is set), it is not defined which of the numbers is returned by +\fBpcre[16|32]_get_stringnumber()\fP. You can obtain the complete list by calling +\fBpcre[16|32]_get_stringtable_entries()\fP. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_get_stringtable_entries.3 b/doc/pcre_get_stringtable_entries.3 new file mode 100644 index 0000000..5c58c90 --- /dev/null +++ b/doc/pcre_get_stringtable_entries.3 @@ -0,0 +1,46 @@ +.TH PCRE_GET_STRINGTABLE_ENTRIES 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_get_stringtable_entries(const pcre *\fIcode\fP, +.B " const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);" +.sp +.B int pcre16_get_stringtable_entries(const pcre16 *\fIcode\fP, +.B " PCRE_SPTR16 \fIname\fP, PCRE_UCHAR16 **\fIfirst\fP, PCRE_UCHAR16 **\fIlast\fP);" +.sp +.B int pcre32_get_stringtable_entries(const pcre32 *\fIcode\fP, +.B " PCRE_SPTR32 \fIname\fP, PCRE_UCHAR32 **\fIfirst\fP, PCRE_UCHAR32 **\fIlast\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This convenience function finds, for a compiled pattern, the first and last +entries for a given name in the table that translates capturing parenthesis +names into numbers. When names are required to be unique (PCRE_DUPNAMES is +\fInot\fP set), it is usually easier to use \fBpcre[16|32]_get_stringnumber()\fP +instead. +.sp + \fIcode\fP Compiled regular expression + \fIname\fP Name whose entries required + \fIfirst\fP Where to return a pointer to the first entry + \fIlast\fP Where to return a pointer to the last entry +.sp +The yield of the function is the length of each entry, or +PCRE_ERROR_NOSUBSTRING if none are found. +.P +There is a complete description of the PCRE native API, including the format of +the table entries, in the +.\" HREF +\fBpcreapi\fP +.\" +page, and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_get_substring.3 b/doc/pcre_get_substring.3 new file mode 100644 index 0000000..1e62b2c --- /dev/null +++ b/doc/pcre_get_substring.3 @@ -0,0 +1,50 @@ +.TH PCRE_GET_SUBSTRING 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " const char **\fIstringptr\fP);" +.sp +.B int pcre16_get_substring(PCRE_SPTR16 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " PCRE_SPTR16 *\fIstringptr\fP);" +.sp +.B int pcre32_get_substring(PCRE_SPTR32 \fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " PCRE_SPTR32 *\fIstringptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring. The +arguments are: +.sp + \fIsubject\fP Subject that has been successfully matched + \fIovector\fP Offset vector that \fBpcre[16|32]_exec()\fP used + \fIstringcount\fP Value returned by \fBpcre[16|32]_exec()\fP + \fIstringnumber\fP Number of the required substring + \fIstringptr\fP Where to put the string pointer +.sp +The memory in which the substring is placed is obtained by calling +\fBpcre[16|32]_malloc()\fP. The convenience function +\fBpcre[16|32]_free_substring()\fP can be used to free it when it is no longer +needed. The yield of the function is the length of the substring, +PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or +PCRE_ERROR_NOSUBSTRING if the string number is invalid. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_get_substring_list.3 b/doc/pcre_get_substring_list.3 new file mode 100644 index 0000000..511a4a3 --- /dev/null +++ b/doc/pcre_get_substring_list.3 @@ -0,0 +1,47 @@ +.TH PCRE_GET_SUBSTRING_LIST 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_get_substring_list(const char *\fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, const char ***\fIlistptr\fP);" +.sp +.B int pcre16_get_substring_list(PCRE_SPTR16 \fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, PCRE_SPTR16 **\fIlistptr\fP);" +.sp +.B int pcre32_get_substring_list(PCRE_SPTR32 \fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, PCRE_SPTR32 **\fIlistptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a list of all the captured +substrings. The arguments are: +.sp + \fIsubject\fP Subject that has been successfully matched + \fIovector\fP Offset vector that \fBpcre[16|32]_exec\fP used + \fIstringcount\fP Value returned by \fBpcre[16|32]_exec\fP + \fIlistptr\fP Where to put a pointer to the list +.sp +The memory in which the substrings and the list are placed is obtained by +calling \fBpcre[16|32]_malloc()\fP. The convenience function +\fBpcre[16|32]_free_substring_list()\fP can be used to free it when it is no +longer needed. A pointer to a list of pointers is put in the variable whose +address is in \fIlistptr\fP. The list is terminated by a NULL pointer. The +yield of the function is zero on success or PCRE_ERROR_NOMEMORY if sufficient +memory could not be obtained. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_jit_exec.3 b/doc/pcre_jit_exec.3 new file mode 100644 index 0000000..ba85168 --- /dev/null +++ b/doc/pcre_jit_exec.3 @@ -0,0 +1,96 @@ +.TH PCRE_EXEC 3 "31 October 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_jit_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " pcre_jit_stack *\fIjstack\fP);" +.sp +.B int pcre16_jit_exec(const pcre16 *\fIcode\fP, "const pcre16_extra *\fIextra\fP," +.B " PCRE_SPTR16 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " pcre_jit_stack *\fIjstack\fP);" +.sp +.B int pcre32_jit_exec(const pcre32 *\fIcode\fP, "const pcre32_extra *\fIextra\fP," +.B " PCRE_SPTR32 \fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " pcre_jit_stack *\fIjstack\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function matches a compiled regular expression that has been successfully +studied with one of the JIT options against a given subject string, using a +matching algorithm that is similar to Perl's. It is a "fast path" interface to +JIT, and it bypasses some of the sanity checks that \fBpcre_exec()\fP applies. +It returns offsets to captured substrings. Its arguments are: +.sp + \fIcode\fP Points to the compiled pattern + \fIextra\fP Points to an associated \fBpcre[16|32]_extra\fP structure, + or is NULL + \fIsubject\fP Points to the subject string + \fIlength\fP Length of the subject string, in bytes + \fIstartoffset\fP Offset in bytes in the subject at which to + start matching + \fIoptions\fP Option bits + \fIovector\fP Points to a vector of ints for result offsets + \fIovecsize\fP Number of elements in the vector (a multiple of 3) + \fIjstack\fP Pointer to a JIT stack +.sp +The allowed options are: +.sp + PCRE_NOTBOL Subject string is not the beginning of a line + PCRE_NOTEOL Subject string is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NOTEMPTY_ATSTART An empty string at the start of the subject + is not a valid match + PCRE_NO_UTF16_CHECK Do not check the subject for UTF-16 + validity (only relevant if PCRE_UTF16 + was set at compile time) + PCRE_NO_UTF32_CHECK Do not check the subject for UTF-32 + validity (only relevant if PCRE_UTF32 + was set at compile time) + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + PCRE_PARTIAL ) Return PCRE_ERROR_PARTIAL for a partial + PCRE_PARTIAL_SOFT ) match if no full matches are found + PCRE_PARTIAL_HARD Return PCRE_ERROR_PARTIAL for a partial match + if that is found before a full match +.sp +However, the PCRE_NO_UTF[8|16|32]_CHECK options have no effect, as this check +is never applied. For details of partial matching, see the +.\" HREF +\fBpcrepartial\fP +.\" +page. A \fBpcre_extra\fP structure contains the following fields: +.sp + \fIflags\fP Bits indicating which fields are set + \fIstudy_data\fP Opaque data from \fBpcre[16|32]_study()\fP + \fImatch_limit\fP Limit on internal resource use + \fImatch_limit_recursion\fP Limit on internal recursion depth + \fIcallout_data\fP Opaque data passed back to callouts + \fItables\fP Points to character tables or is NULL + \fImark\fP For passing back a *MARK pointer + \fIexecutable_jit\fP Opaque data from JIT compilation +.sp +The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT, +PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, +PCRE_EXTRA_TABLES, PCRE_EXTRA_MARK and PCRE_EXTRA_EXECUTABLE_JIT. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the JIT API in the +.\" HREF +\fBpcrejit\fP +.\" +page. diff --git a/doc/pcre_jit_stack_alloc.3 b/doc/pcre_jit_stack_alloc.3 new file mode 100644 index 0000000..11c97a0 --- /dev/null +++ b/doc/pcre_jit_stack_alloc.3 @@ -0,0 +1,43 @@ +.TH PCRE_JIT_STACK_ALLOC 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, +.B " int \fImaxsize\fP);" +.sp +.B pcre16_jit_stack *pcre16_jit_stack_alloc(int \fIstartsize\fP, +.B " int \fImaxsize\fP);" +.sp +.B pcre32_jit_stack *pcre32_jit_stack_alloc(int \fIstartsize\fP, +.B " int \fImaxsize\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function is used to create a stack for use by the code compiled by the JIT +optimization of \fBpcre[16|32]_study()\fP. The arguments are a starting size for +the stack, and a maximum size to which it is allowed to grow. The result can be +passed to the JIT run-time code by \fBpcre[16|32]_assign_jit_stack()\fP, or that +function can set up a callback for obtaining a stack. A maximum stack size of +512K to 1M should be more than enough for any pattern. For more details, see +the +.\" HREF +\fBpcrejit\fP +.\" +page. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_jit_stack_free.3 b/doc/pcre_jit_stack_free.3 new file mode 100644 index 0000000..494724e --- /dev/null +++ b/doc/pcre_jit_stack_free.3 @@ -0,0 +1,35 @@ +.TH PCRE_JIT_STACK_FREE 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP); +.PP +.B void pcre16_jit_stack_free(pcre16_jit_stack *\fIstack\fP); +.PP +.B void pcre32_jit_stack_free(pcre32_jit_stack *\fIstack\fP); +. +.SH DESCRIPTION +.rs +.sp +This function is used to free a JIT stack that was created by +\fBpcre[16|32]_jit_stack_alloc()\fP when it is no longer needed. For more details, +see the +.\" HREF +\fBpcrejit\fP +.\" +page. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_maketables.3 b/doc/pcre_maketables.3 new file mode 100644 index 0000000..b2c3d23 --- /dev/null +++ b/doc/pcre_maketables.3 @@ -0,0 +1,33 @@ +.TH PCRE_MAKETABLES 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B const unsigned char *pcre_maketables(void); +.PP +.B const unsigned char *pcre16_maketables(void); +.PP +.B const unsigned char *pcre32_maketables(void); +. +.SH DESCRIPTION +.rs +.sp +This function builds a set of character tables for character values less than +256. These can be passed to \fBpcre[16|32]_compile()\fP to override PCRE's +internal, built-in tables (which were made by \fBpcre[16|32]_maketables()\fP when +PCRE was compiled). You might want to do this if you are using a non-standard +locale. The function yields a pointer to the tables. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_pattern_to_host_byte_order.3 b/doc/pcre_pattern_to_host_byte_order.3 new file mode 100644 index 0000000..b0c41c3 --- /dev/null +++ b/doc/pcre_pattern_to_host_byte_order.3 @@ -0,0 +1,44 @@ +.TH PCRE_PATTERN_TO_HOST_BYTE_ORDER 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP, +.B " pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.sp +.B int pcre16_pattern_to_host_byte_order(pcre16 *\fIcode\fP, +.B " pcre16_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.sp +.B int pcre32_pattern_to_host_byte_order(pcre32 *\fIcode\fP, +.B " pcre32_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function ensures that the bytes in 2-byte and 4-byte values in a compiled +pattern are in the correct order for the current host. It is useful when a +pattern that has been compiled on one host is transferred to another that might +have different endianness. The arguments are: +.sp + \fIcode\fP A compiled regular expression + \fIextra\fP Points to an associated \fBpcre[16|32]_extra\fP structure, + or is NULL + \fItables\fP Pointer to character tables, or NULL to + set the built-in default +.sp +The result is 0 for success, a negative PCRE_ERROR_xxx value otherwise. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_refcount.3 b/doc/pcre_refcount.3 new file mode 100644 index 0000000..45a41fe --- /dev/null +++ b/doc/pcre_refcount.3 @@ -0,0 +1,36 @@ +.TH PCRE_REFCOUNT 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP); +.PP +.B int pcre16_refcount(pcre16 *\fIcode\fP, int \fIadjust\fP); +.PP +.B int pcre32_refcount(pcre32 *\fIcode\fP, int \fIadjust\fP); +. +.SH DESCRIPTION +.rs +.sp +This function is used to maintain a reference count inside a data block that +contains a compiled pattern. Its arguments are: +.sp + \fIcode\fP Compiled regular expression + \fIadjust\fP Adjustment to reference value +.sp +The yield of the function is the adjusted reference value, which is constrained +to lie between 0 and 65535. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_study.3 b/doc/pcre_study.3 new file mode 100644 index 0000000..1200e0a --- /dev/null +++ b/doc/pcre_study.3 @@ -0,0 +1,54 @@ +.TH PCRE_STUDY 3 " 24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.sp +.B pcre16_extra *pcre16_study(const pcre16 *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.sp +.B pcre32_extra *pcre32_study(const pcre32 *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.fi +. +.SH DESCRIPTION +.rs +.sp +This function studies a compiled pattern, to see if additional information can +be extracted that might speed up matching. Its arguments are: +.sp + \fIcode\fP A compiled regular expression + \fIoptions\fP Options for \fBpcre[16|32]_study()\fP + \fIerrptr\fP Where to put an error message +.sp +If the function succeeds, it returns a value that can be passed to +\fBpcre[16|32]_exec()\fP or \fBpcre[16|32]_dfa_exec()\fP via their \fIextra\fP +arguments. +.P +If the function returns NULL, either it could not find any additional +information, or there was an error. You can tell the difference by looking at +the error value. It is NULL in first case. +.P +The only option is PCRE_STUDY_JIT_COMPILE. It requests just-in-time compilation +if possible. If PCRE has been compiled without JIT support, this option is +ignored. See the +.\" HREF +\fBpcrejit\fP +.\" +page for further details. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_utf16_to_host_byte_order.3 b/doc/pcre_utf16_to_host_byte_order.3 new file mode 100644 index 0000000..1851b61 --- /dev/null +++ b/doc/pcre_utf16_to_host_byte_order.3 @@ -0,0 +1,45 @@ +.TH PCRE_UTF16_TO_HOST_BYTE_ORDER 3 "21 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *\fIoutput\fP, +.B " PCRE_SPTR16 \fIinput\fP, int \fIlength\fP, int *\fIhost_byte_order\fP," +.B " int \fIkeep_boms\fP);" +.fi +. +. +.SH DESCRIPTION +.rs +.sp +This function, which exists only in the 16-bit library, converts a UTF-16 +string to the correct order for the current host, taking account of any byte +order marks (BOMs) within the string. Its arguments are: +.sp + \fIoutput\fP pointer to output buffer, may be the same as \fIinput\fP + \fIinput\fP pointer to input buffer + \fIlength\fP number of 16-bit units in the input, or negative for + a zero-terminated string + \fIhost_byte_order\fP a NULL value or a non-zero value pointed to means + start in host byte order + \fIkeep_boms\fP if non-zero, BOMs are copied to the output string +.sp +The result of the function is the number of 16-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +.P +If \fIhost_byte_order\fP is not NULL, it is set to indicate the byte order that +is current at the end of the string. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_utf32_to_host_byte_order.3 b/doc/pcre_utf32_to_host_byte_order.3 new file mode 100644 index 0000000..a415dcf --- /dev/null +++ b/doc/pcre_utf32_to_host_byte_order.3 @@ -0,0 +1,45 @@ +.TH PCRE_UTF32_TO_HOST_BYTE_ORDER 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.nf +.B int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *\fIoutput\fP, +.B " PCRE_SPTR32 \fIinput\fP, int \fIlength\fP, int *\fIhost_byte_order\fP," +.B " int \fIkeep_boms\fP);" +.fi +. +. +.SH DESCRIPTION +.rs +.sp +This function, which exists only in the 32-bit library, converts a UTF-32 +string to the correct order for the current host, taking account of any byte +order marks (BOMs) within the string. Its arguments are: +.sp + \fIoutput\fP pointer to output buffer, may be the same as \fIinput\fP + \fIinput\fP pointer to input buffer + \fIlength\fP number of 32-bit units in the input, or negative for + a zero-terminated string + \fIhost_byte_order\fP a NULL value or a non-zero value pointed to means + start in host byte order + \fIkeep_boms\fP if non-zero, BOMs are copied to the output string +.sp +The result of the function is the number of 32-bit units placed into the output +buffer, including the zero terminator if the string was zero-terminated. +.P +If \fIhost_byte_order\fP is not NULL, it is set to indicate the byte order that +is current at the end of the string. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcre_version.3 b/doc/pcre_version.3 new file mode 100644 index 0000000..0f4973f --- /dev/null +++ b/doc/pcre_version.3 @@ -0,0 +1,31 @@ +.TH PCRE_VERSION 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B const char *pcre_version(void); +.PP +.B const char *pcre16_version(void); +.PP +.B const char *pcre32_version(void); +. +.SH DESCRIPTION +.rs +.sp +This function (even in the 16-bit and 32-bit libraries) returns a +zero-terminated, 8-bit character string that gives the version number of the +PCRE library and the date of its release. +.P +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fP +.\" +page and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fP +.\" +page. diff --git a/doc/pcreapi.3 b/doc/pcreapi.3 new file mode 100644 index 0000000..ab3eaa0 --- /dev/null +++ b/doc/pcreapi.3 @@ -0,0 +1,2919 @@ +.TH PCREAPI 3 "09 February 2014" "PCRE 8.35" +.SH NAME +PCRE - Perl-compatible regular expressions +.sp +.B #include <pcre.h> +. +. +.SH "PCRE NATIVE API BASIC FUNCTIONS" +.rs +.sp +.nf +.B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.sp +.B void pcre_free_study(pcre_extra *\fIextra\fP); +.sp +.B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.sp +.B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.fi +. +. +.SH "PCRE NATIVE API STRING EXTRACTION FUNCTIONS" +.rs +.sp +.nf +.B int pcre_copy_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " char *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre_get_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " const char **\fIstringptr\fP);" +.sp +.B int pcre_get_stringnumber(const pcre *\fIcode\fP, +.B " const char *\fIname\fP);" +.sp +.B int pcre_get_stringtable_entries(const pcre *\fIcode\fP, +.B " const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);" +.sp +.B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " const char **\fIstringptr\fP);" +.sp +.B int pcre_get_substring_list(const char *\fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, const char ***\fIlistptr\fP);" +.sp +.B void pcre_free_substring(const char *\fIstringptr\fP); +.sp +.B void pcre_free_substring_list(const char **\fIstringptr\fP); +.fi +. +. +.SH "PCRE NATIVE API AUXILIARY FUNCTIONS" +.rs +.sp +.nf +.B int pcre_jit_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " pcre_jit_stack *\fIjstack\fP);" +.sp +.B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP); +.sp +.B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP); +.sp +.B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP, +.B " pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);" +.sp +.B const unsigned char *pcre_maketables(void); +.sp +.B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.sp +.B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP); +.sp +.B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP); +.sp +.B const char *pcre_version(void); +.sp +.B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP, +.B " pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);" +.fi +. +. +.SH "PCRE NATIVE API INDIRECTED FUNCTIONS" +.rs +.sp +.nf +.B void *(*pcre_malloc)(size_t); +.sp +.B void (*pcre_free)(void *); +.sp +.B void *(*pcre_stack_malloc)(size_t); +.sp +.B void (*pcre_stack_free)(void *); +.sp +.B int (*pcre_callout)(pcre_callout_block *); +.sp +.B int (*pcre_stack_guard)(void); +.fi +. +. +.SH "PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES" +.rs +.sp +As well as support for 8-bit character strings, PCRE also supports 16-bit +strings (from release 8.30) and 32-bit strings (from release 8.32), by means of +two additional libraries. They can be built as well as, or instead of, the +8-bit library. To avoid too much complication, this document describes the +8-bit versions of the functions, with only occasional references to the 16-bit +and 32-bit libraries. +.P +The 16-bit and 32-bit functions operate in the same way as their 8-bit +counterparts; they just use different data types for their arguments and +results, and their names start with \fBpcre16_\fP or \fBpcre32_\fP instead of +\fBpcre_\fP. For every option that has UTF8 in its name (for example, +PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced +by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the +16-bit and 32-bit option names define the same bit values. +.P +References to bytes and UTF-8 in this document should be read as references to +16-bit data units and UTF-16 when using the 16-bit library, or 32-bit data +units and UTF-32 when using the 32-bit library, unless specified otherwise. +More details of the specific differences for the 16-bit and 32-bit libraries +are given in the +.\" HREF +\fBpcre16\fP +.\" +and +.\" HREF +\fBpcre32\fP +.\" +pages. +. +. +.SH "PCRE API OVERVIEW" +.rs +.sp +PCRE has its own native API, which is described in this document. There are +also some wrapper functions (for the 8-bit library only) that correspond to the +POSIX regular expression API, but they do not give access to all the +functionality. They are described in the +.\" HREF +\fBpcreposix\fP +.\" +documentation. Both of these APIs define a set of C function calls. A C++ +wrapper (again for the 8-bit library only) is also distributed with PCRE. It is +documented in the +.\" HREF +\fBpcrecpp\fP +.\" +page. +.P +The native API C function prototypes are defined in the header file +\fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called +\fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the +command for linking an application that uses PCRE. The header file defines the +macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers +for the library. Applications can use these to include support for different +releases of PCRE. +.P +In a Windows environment, if you want to statically link an application program +against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before +including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the +\fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared +\fB__declspec(dllimport)\fP, with unwanted results. +.P +The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP, +and \fBpcre_exec()\fP are used for compiling and matching regular expressions +in a Perl-compatible manner. A sample program that demonstrates the simplest +way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE +source distribution. A listing of this program is given in the +.\" HREF +\fBpcredemo\fP +.\" +documentation, and the +.\" HREF +\fBpcresample\fP +.\" +documentation describes how to compile and run it. +.P +Just-in-time compiler support is an optional feature of PCRE that can be built +in appropriate hardware environments. It greatly speeds up the matching +performance of many patterns. Simple programs can easily request that it be +used if available, by setting an option that is ignored when it is not +relevant. More complicated programs might need to make use of the functions +\fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and +\fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage. +.P +From release 8.32 there is also a direct interface for JIT execution, which +gives improved performance. The JIT-specific functions are discussed in the +.\" HREF +\fBpcrejit\fP +.\" +documentation. +.P +A second matching function, \fBpcre_dfa_exec()\fP, which is not +Perl-compatible, is also provided. This uses a different algorithm for the +matching. The alternative algorithm finds all possible matches (at a given +point in the subject), and scans the subject just once (unless there are +lookbehind assertions). However, this algorithm does not return captured +substrings. A description of the two matching algorithms and their advantages +and disadvantages is given in the +.\" HREF +\fBpcrematching\fP +.\" +documentation. +.P +In addition to the main compiling and matching functions, there are convenience +functions for extracting captured substrings from a subject string that is +matched by \fBpcre_exec()\fP. They are: +.sp + \fBpcre_copy_substring()\fP + \fBpcre_copy_named_substring()\fP + \fBpcre_get_substring()\fP + \fBpcre_get_named_substring()\fP + \fBpcre_get_substring_list()\fP + \fBpcre_get_stringnumber()\fP + \fBpcre_get_stringtable_entries()\fP +.sp +\fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also +provided, to free the memory used for extracted strings. +.P +The function \fBpcre_maketables()\fP is used to build a set of character tables +in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP, +or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for +specialist use. Most commonly, no special tables are passed, in which case +internal tables that are generated when PCRE is built are used. +.P +The function \fBpcre_fullinfo()\fP is used to find out information about a +compiled pattern. The function \fBpcre_version()\fP returns a pointer to a +string containing the version of PCRE and its date of release. +.P +The function \fBpcre_refcount()\fP maintains a reference count in a data block +containing a compiled pattern. This is provided for the benefit of +object-oriented applications. +.P +The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain +the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions, +respectively. PCRE calls the memory management functions via these variables, +so a calling program can replace them if it wishes to intercept the calls. This +should be done before calling any PCRE functions. +.P +The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also +indirections to memory management functions. These special functions are used +only when PCRE is compiled to use the heap for remembering data, instead of +recursive function calls, when running the \fBpcre_exec()\fP function. See the +.\" HREF +\fBpcrebuild\fP +.\" +documentation for details of how to do this. It is a non-standard way of +building PCRE, for use in environments that have limited stacks. Because of the +greater use of memory management, it runs more slowly. Separate functions are +provided so that special-purpose external code can be used for this case. When +used, these functions are always called in a stack-like manner (last obtained, +first freed), and always for memory blocks of the same size. There is a +discussion about PCRE's stack usage in the +.\" HREF +\fBpcrestack\fP +.\" +documentation. +.P +The global variable \fBpcre_callout\fP initially contains NULL. It can be set +by the caller to a "callout" function, which PCRE will then call at specified +points during a matching operation. Details are given in the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.P +The global variable \fBpcre_stack_guard\fP initially contains NULL. It can be +set by the caller to a function that is called by PCRE whenever it starts +to compile a parenthesized part of a pattern. When parentheses are nested, PCRE +uses recursive function calls, which use up the system stack. This function is +provided so that applications with restricted stacks can force a compilation +error if the stack runs out. The function should return zero if all is well, or +non-zero to force an error. +. +. +.\" HTML <a name="newlines"></a> +.SH NEWLINES +.rs +.sp +PCRE supports five different conventions for indicating line breaks in +strings: a single CR (carriage return) character, a single LF (linefeed) +character, the two-character sequence CRLF, any of the three preceding, or any +Unicode newline sequence. The Unicode newline sequences are the three just +mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, +U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). +.P +Each of the first three conventions is used by at least one operating system as +its standard newline sequence. When PCRE is built, a default can be specified. +The default default is LF, which is the Unix standard. When PCRE is run, the +default can be overridden, either when a pattern is compiled, or when it is +matched. +.P +At compile time, the newline convention can be specified by the \fIoptions\fP +argument of \fBpcre_compile()\fP, or it can be specified by special text at the +start of the pattern itself; this overrides any other settings. See the +.\" HREF +\fBpcrepattern\fP +.\" +page for details of the special character sequences. +.P +In the PCRE documentation the word "newline" is used to mean "the character or +pair of characters that indicate a line break". The choice of newline +convention affects the handling of the dot, circumflex, and dollar +metacharacters, the handling of #-comments in /x mode, and, when CRLF is a +recognized line ending sequence, the match position advancement for a +non-anchored pattern. There is more detail about this in the +.\" HTML <a href="#execoptions"> +.\" </a> +section on \fBpcre_exec()\fP options +.\" +below. +.P +The choice of newline convention does not affect the interpretation of +the \en or \er escape sequences, nor does it affect what \eR matches, which is +controlled in a similar way, but by separate options. +. +. +.SH MULTITHREADING +.rs +.sp +The PCRE functions can be used in multi-threading applications, with the +proviso that the memory management functions pointed to by \fBpcre_malloc\fP, +\fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the +callout and stack-checking functions pointed to by \fBpcre_callout\fP and +\fBpcre_stack_guard\fP, are shared by all threads. +.P +The compiled form of a regular expression is not altered during matching, so +the same compiled pattern can safely be used by several threads at once. +.P +If the just-in-time optimization feature is being used, it needs separate +memory stack areas for each thread. See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for more details. +. +. +.SH "SAVING PRECOMPILED PATTERNS FOR LATER USE" +.rs +.sp +The compiled form of a regular expression can be saved and re-used at a later +time, possibly by a different program, and even on a host other than the one on +which it was compiled. Details are given in the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation, which includes a description of the +\fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular +expression with one version of PCRE for use with a different version is not +guaranteed to work and may cause crashes. +. +. +.SH "CHECKING BUILD-TIME OPTIONS" +.rs +.sp +.B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP); +.PP +The function \fBpcre_config()\fP makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +.\" HREF +\fBpcrebuild\fP +.\" +documentation has more details about these optional features. +.P +The first argument for \fBpcre_config()\fP is an integer, specifying which +information is required; the second argument is a pointer to a variable into +which the information is placed. The returned value is zero on success, or the +negative error code PCRE_ERROR_BADOPTION if the value in the first argument is +not recognized. The following information is available: +.sp + PCRE_CONFIG_UTF8 +.sp +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. This value should normally be given to the 8-bit +version of this function, \fBpcre_config()\fP. If it is given to the 16-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +.sp + PCRE_CONFIG_UTF16 +.sp +The output is an integer that is set to one if UTF-16 support is available; +otherwise it is set to zero. This value should normally be given to the 16-bit +version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit +or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. +.sp + PCRE_CONFIG_UTF32 +.sp +The output is an integer that is set to one if UTF-32 support is available; +otherwise it is set to zero. This value should normally be given to the 32-bit +version of this function, \fBpcre32_config()\fP. If it is given to the 8-bit +or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION. +.sp + PCRE_CONFIG_UNICODE_PROPERTIES +.sp +The output is an integer that is set to one if support for Unicode character +properties is available; otherwise it is set to zero. +.sp + PCRE_CONFIG_JIT +.sp +The output is an integer that is set to one if support for just-in-time +compiling is available; otherwise it is set to zero. +.sp + PCRE_CONFIG_JITTARGET +.sp +The output is a pointer to a zero-terminated "const char *" string. If JIT +support is available, the string contains the name of the architecture for +which the JIT compiler is configured, for example "x86 32bit (little endian + +unaligned)". If JIT support is not available, the result is NULL. +.sp + PCRE_CONFIG_NEWLINE +.sp +The output is an integer whose value specifies the default character sequence +that is recognized as meaning "newline". The values that are supported in +ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for +ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the +same values. However, the value for LF is normally 21, though some EBCDIC +environments use 37. The corresponding values for CRLF are 3349 and 3365. The +default should normally correspond to the standard sequence for your operating +system. +.sp + PCRE_CONFIG_BSR +.sp +The output is an integer whose value indicates what character sequences the \eR +escape sequence matches by default. A value of 0 means that \eR matches any +Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF, +or CRLF. The default can be overridden when a pattern is compiled or matched. +.sp + PCRE_CONFIG_LINK_SIZE +.sp +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. For the 8-bit library, the value can +be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still +a number of bytes. For the 32-bit library, the value is either 2 or 4 and is +still a number of bytes. The default value of 2 is sufficient for all but the +most massive patterns, since it allows the compiled pattern to be up to 64K in +size. Larger values allow larger regular expressions to be compiled, at the +expense of slower matching. +.sp + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD +.sp +The output is an integer that contains the threshold above which the POSIX +interface uses \fBmalloc()\fP for output vectors. Further details are given in +the +.\" HREF +\fBpcreposix\fP +.\" +documentation. +.sp + PCRE_CONFIG_PARENS_LIMIT +.sp +The output is a long integer that gives the maximum depth of nesting of +parentheses (of any kind) in a pattern. This limit is imposed to cap the amount +of system stack used when a pattern is compiled. It is specified when PCRE is +built; the default is 250. This limit does not take into account the stack that +may already be used by the calling application. For finer control over +compilation stack usage, you can set a pointer to an external checking function +in \fBpcre_stack_guard\fP. +.sp + PCRE_CONFIG_MATCH_LIMIT +.sp +The output is a long integer that gives the default limit for the number of +internal matching function calls in a \fBpcre_exec()\fP execution. Further +details are given with \fBpcre_exec()\fP below. +.sp + PCRE_CONFIG_MATCH_LIMIT_RECURSION +.sp +The output is a long integer that gives the default limit for the depth of +recursion when calling the internal matching function in a \fBpcre_exec()\fP +execution. Further details are given with \fBpcre_exec()\fP below. +.sp + PCRE_CONFIG_STACKRECURSE +.sp +The output is an integer that is set to one if internal recursion when running +\fBpcre_exec()\fP is implemented by recursive function calls that use the stack +to remember their state. This is the usual way that PCRE is compiled. The +output is zero if PCRE was compiled to use blocks of data on the heap instead +of recursive function calls. In this case, \fBpcre_stack_malloc\fP and +\fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus +avoiding the use of the stack. +. +. +.SH "COMPILING A PATTERN" +.rs +.sp +.nf +.B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.sp +.B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP, +.B " int *\fIerrorcodeptr\fP," +.B " const char **\fIerrptr\fP, int *\fIerroffset\fP," +.B " const unsigned char *\fItableptr\fP);" +.fi +.P +Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be +called to compile a pattern into an internal form. The only difference between +the two interfaces is that \fBpcre_compile2()\fP has an additional argument, +\fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid +too much repetition, we refer just to \fBpcre_compile()\fP below, but the +information applies equally to \fBpcre_compile2()\fP. +.P +The pattern is a C string terminated by a binary zero, and is passed in the +\fIpattern\fP argument. A pointer to a single block of memory that is obtained +via \fBpcre_malloc\fP is returned. This contains the compiled code and related +data. The \fBpcre\fP type is defined for the returned block; this is a typedef +for a structure whose contents are not externally defined. It is up to the +caller to free the memory (via \fBpcre_free\fP) when it is no longer required. +.P +Although the compiled code of a PCRE regex is relocatable, that is, it does not +depend on memory location, the complete \fBpcre\fP data block is not +fully relocatable, because it may contain a copy of the \fItableptr\fP +argument, which is an address (see below). +.P +The \fIoptions\fP argument contains various bit settings that affect the +compilation. It should be zero if no options are required. The available +options are described below. Some of them (in particular, those that are +compatible with Perl, but some others as well) can also be set and unset from +within the pattern (see the detailed description in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation). For those options that can be different in different parts of +the pattern, the contents of the \fIoptions\fP argument specifies their +settings at the start of compilation and execution. The PCRE_ANCHORED, +PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and +PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at +compile time. +.P +If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately. +Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns +NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual +error message. This is a static string that is part of the library. You must +not try to free it. Normally, the offset from the start of the pattern to the +data unit that was being processed when the error was discovered is placed in +the variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, +an immediate error is given). However, for an invalid UTF-8 or UTF-16 string, +the offset is that of the first data unit of the failing character. +.P +Some errors are not detected until the whole pattern has been scanned; in these +cases, the offset passed back is the length of the pattern. Note that the +offset is in data units, not characters, even in a UTF mode. It may sometimes +point into the middle of a UTF-8 or UTF-16 character. +.P +If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the +\fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is +returned via this argument in the event of an error. This is in addition to the +textual error message. Error codes and messages are listed below. +.P +If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of +character tables that are built when PCRE is compiled, using the default C +locale. Otherwise, \fItableptr\fP must be an address that is the result of a +call to \fBpcre_maketables()\fP. This value is stored with the compiled +pattern, and used again by \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP when the +pattern is matched. For more discussion, see the section on locale support +below. +.P +This code fragment shows a typical straightforward call to \fBpcre_compile()\fP: +.sp + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ +.sp +The following names for option bits are defined in the \fBpcre.h\fP header +file: +.sp + PCRE_ANCHORED +.sp +If this bit is set, the pattern is forced to be "anchored", that is, it is +constrained to match only at the first matching point in the string that is +being searched (the "subject string"). This effect can also be achieved by +appropriate constructs in the pattern itself, which is the only way to do it in +Perl. +.sp + PCRE_AUTO_CALLOUT +.sp +If this bit is set, \fBpcre_compile()\fP automatically inserts callout items, +all with number 255, before each pattern item. For discussion of the callout +facility, see the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.sp + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE +.sp +These options (which are mutually exclusive) control what the \eR escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. The default is specified when PCRE is +built. It can be overridden from within the pattern, or by setting an option +when a compiled pattern is matched. +.sp + PCRE_CASELESS +.sp +If this bit is set, letters in the pattern match both upper and lower case +letters. It is equivalent to Perl's /i option, and it can be changed within a +pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the +concept of case for characters whose values are less than 128, so caseless +matching is always possible. For characters with higher values, the concept of +case is supported if PCRE is compiled with Unicode property support, but not +otherwise. If you want to use caseless matching for characters 128 and above, +you must ensure that PCRE is compiled with Unicode property support as well as +with UTF-8 support. +.sp + PCRE_DOLLAR_ENDONLY +.sp +If this bit is set, a dollar metacharacter in the pattern matches only at the +end of the subject string. Without this option, a dollar also matches +immediately before a newline at the end of the string (but not before any other +newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set. +There is no equivalent to this option in Perl, and no way to set it within a +pattern. +.sp + PCRE_DOTALL +.sp +If this bit is set, a dot metacharacter in the pattern matches a character of +any value, including one that indicates a newline. However, it only ever +matches one character, even if newlines are coded as CRLF. Without this option, +a dot does not match when the current position is at a newline. This option is +equivalent to Perl's /s option, and it can be changed within a pattern by a +(?s) option setting. A negative class such as [^a] always matches newline +characters, independent of the setting of this option. +.sp + PCRE_DUPNAMES +.sp +If this bit is set, names used to identify capturing subpatterns need not be +unique. This can be helpful for certain types of pattern when it is known that +only one instance of the named subpattern can ever be matched. There are more +details of named subpatterns below; see also the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +.sp + PCRE_EXTENDED +.sp +If this bit is set, most white space characters in the pattern are totally +ignored except when escaped or inside a character class. However, white space +is not allowed within sequences such as (?> that introduce various +parenthesized subpatterns, nor within a numerical quantifier such as {1,3}. +However, ignorable white space is permitted between an item and a following +quantifier and between a quantifier and a following + that indicates +possessiveness. +.P +White space did not used to include the VT character (code 11), because Perl +did not treat this character as white space. However, Perl changed at release +5.18, so PCRE followed at release 8.34, and VT is now treated as white space. +.P +PCRE_EXTENDED also causes characters between an unescaped # outside a character +class and the next newline, inclusive, to be ignored. PCRE_EXTENDED is +equivalent to Perl's /x option, and it can be changed within a pattern by a +(?x) option setting. +.P +Which characters are interpreted as newlines is controlled by the options +passed to \fBpcre_compile()\fP or by a special sequence at the start of the +pattern, as described in the section entitled +.\" HTML <a href="pcrepattern.html#newlines"> +.\" </a> +"Newline conventions" +.\" +in the \fBpcrepattern\fP documentation. Note that the end of this type of +comment is a literal newline sequence in the pattern; escape sequences that +happen to represent a newline do not count. +.P +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. White space characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( that introduces a conditional subpattern. +.sp + PCRE_EXTRA +.sp +This option was invented in order to turn on additional functionality of PCRE +that is incompatible with Perl, but it is currently of very little use. When +set, any backslash in a pattern that is followed by a letter that has no +special meaning causes an error, thus reserving these combinations for future +expansion. By default, as in Perl, a backslash followed by a letter with no +special meaning is treated as a literal. (Perl can, however, be persuaded to +give an error for this, by running it with the -w option.) There are at present +no other features controlled by this option. It can also be set by a (?X) +option setting within a pattern. +.sp + PCRE_FIRSTLINE +.sp +If this option is set, an unanchored pattern is required to match before or at +the first newline in the subject string, though the matched text may continue +over the newline. +.sp + PCRE_JAVASCRIPT_COMPAT +.sp +If this option is set, PCRE's behaviour is changed in some ways so that it is +compatible with JavaScript rather than Perl. The changes are as follows: +.P +(1) A lone closing square bracket in a pattern causes a compile-time error, +because this is illegal in JavaScript (by default it is treated as a data +character). Thus, the pattern AB]CD becomes illegal when this option is set. +.P +(2) At run time, a back reference to an unset subpattern group matches an empty +string (by default this causes the current matching alternative to fail). A +pattern such as (\e1)(a) succeeds when this option is set (assuming it can find +an "a" in the subject), whereas it fails by default, for Perl compatibility. +.P +(3) \eU matches an upper case "U" character; by default \eU causes a compile +time error (Perl uses \eU to upper case subsequent characters). +.P +(4) \eu matches a lower case "u" character unless it is followed by four +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, \eu causes a compile time error (Perl uses it to upper +case the following character). +.P +(5) \ex matches a lower case "x" character unless it is followed by two +hexadecimal digits, in which case the hexadecimal number defines the code point +to match. By default, as in Perl, a hexadecimal number is always expected after +\ex, but it may have zero, one, or two digits (so, for example, \exz matches a +binary zero character followed by z). +.sp + PCRE_MULTILINE +.sp +By default, for the purposes of matching "start of line" and "end of line", +PCRE treats the subject string as consisting of a single line of characters, +even if it actually contains newlines. The "start of line" metacharacter (^) +matches only at the start of the string, and the "end of line" metacharacter +($) matches only at the end of the string, or before a terminating newline +(except when PCRE_DOLLAR_ENDONLY is set). Note, however, that unless +PCRE_DOTALL is set, the "any character" metacharacter (.) does not match at a +newline. This behaviour (for ^, $, and dot) is the same as Perl. +.P +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before internal newlines in the +subject string, respectively, as well as at the very start and end. This is +equivalent to Perl's /m option, and it can be changed within a pattern by a +(?m) option setting. If there are no newlines in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. +.sp + PCRE_NEVER_UTF +.sp +This option locks out interpretation of the pattern as UTF-8 (or UTF-16 or +UTF-32 in the 16-bit and 32-bit libraries). In particular, it prevents the +creator of the pattern from switching to UTF interpretation by starting the +pattern with (*UTF). This may be useful in applications that process patterns +from external sources. The combination of PCRE_UTF8 and PCRE_NEVER_UTF also +causes an error. +.sp + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +.sp +These options override the default newline definition that was chosen when PCRE +was built. Setting the first or the second specifies that a newline is +indicated by a single character (CR or LF, respectively). Setting +PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character +CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three +preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies +that any Unicode newline sequence should be recognized. +.P +In an ASCII/Unicode environment, the Unicode newline sequences are the three +just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form +feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS +(paragraph separator, U+2029). For the 8-bit library, the last two are +recognized only in UTF-8 mode. +.P +When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for +CR is 0x0d, the same as ASCII. However, the character code for LF is normally +0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is +not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all +less than 256. For more details, see the +.\" HREF +\fBpcrebuild\fP +.\" +documentation. +.P +The newline setting in the options word uses three bits that are treated +as a number, giving eight possibilities. Currently only six are used (default +plus the five values above). This means that if you set more than one newline +option, the combination may or may not be sensible. For example, +PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but +other combinations may yield unused numbers and cause an error. +.P +The only time that a line break in a pattern is specially recognized when +compiling is when PCRE_EXTENDED is set. CR and LF are white space characters, +and so are ignored in this mode. Also, an unescaped # outside a character class +indicates a comment that lasts until after the next line break sequence. In +other circumstances, line break sequences in patterns are treated as literal +data. +.P +The newline option that is set at compile time becomes the default that is used +for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden. +.sp + PCRE_NO_AUTO_CAPTURE +.sp +If this option is set, it disables the use of numbered capturing parentheses in +the pattern. Any opening parenthesis that is not followed by ? behaves as if it +were followed by ?: but named parentheses can still be used for capturing (and +they acquire numbers in the usual way). There is no equivalent of this option +in Perl. +.sp + PCRE_NO_AUTO_POSSESS +.sp +If this option is set, it disables "auto-possessification". This is an +optimization that, for example, turns a+b into a++b in order to avoid +backtracks into a+ that can never be successful. However, if callouts are in +use, auto-possessification means that some of them are never taken. You can set +this option if you want the matching functions to do a full unoptimized search +and run all the callouts, but it is mainly provided for testing purposes. +.sp + PCRE_NO_START_OPTIMIZE +.sp +This is an option that acts at matching time; that is, it is really an option +for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time, +it is remembered with the compiled pattern and assumed at matching time. This +is necessary if you want to use JIT execution, because the JIT compiler needs +to know whether or not this option is set. For details see the discussion of +PCRE_NO_START_OPTIMIZE +.\" HTML <a href="#execoptions"> +.\" </a> +below. +.\" +.sp + PCRE_UCP +.sp +This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW, +\ew, and some of the POSIX character classes. By default, only ASCII characters +are recognized, but if PCRE_UCP is set, Unicode properties are used instead to +classify characters. More details are given in the section on +.\" HTML <a href="pcre.html#genericchartypes"> +.\" </a> +generic character types +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +page. If you set PCRE_UCP, matching one of the items it affects takes much +longer. The option is available only if PCRE has been compiled with Unicode +property support. +.sp + PCRE_UNGREEDY +.sp +This option inverts the "greediness" of the quantifiers so that they are not +greedy by default, but become greedy if followed by "?". It is not compatible +with Perl. It can also be set by a (?U) option setting within the pattern. +.sp + PCRE_UTF8 +.sp +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte strings. However, it is available +only when PCRE is built to include UTF support. If not, the use of this option +provokes an error. Details of how this option changes the behaviour of PCRE are +given in the +.\" HREF +\fBpcreunicode\fP +.\" +page. +.sp + PCRE_NO_UTF8_CHECK +.sp +When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is +automatically checked. There is a discussion about the +.\" HTML <a href="pcreunicode.html#utf8strings"> +.\" </a> +validity of UTF-8 strings +.\" +in the +.\" HREF +\fBpcreunicode\fP +.\" +page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an +error. If you already know that your pattern is valid, and you want to skip +this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option. +When it is set, the effect of passing an invalid UTF-8 string as a pattern is +undefined. It may cause your program to crash or loop. Note that this option +can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress +the validity checking of subject strings only. If the same string is being +matched many times, the option can be safely set for the second and subsequent +matchings to improve performance. +. +. +.SH "COMPILATION ERROR CODES" +.rs +.sp +The following table lists the error codes than may be returned by +\fBpcre_compile2()\fP, along with the error messages that may be returned by +both compiling functions. Note that error messages are always 8-bit ASCII +strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes +have fallen out of use. To avoid confusion, they have not been re-used. +.sp + 0 no error + 1 \e at end of pattern + 2 \ec at end of pattern + 3 unrecognized character follows \e + 4 numbers out of order in {} quantifier + 5 number too big in {} quantifier + 6 missing terminating ] for character class + 7 invalid escape sequence in character class + 8 range out of order in character class + 9 nothing to repeat + 10 [this code is not in use] + 11 internal error: unexpected repeat + 12 unrecognized character after (? or (?- + 13 POSIX named classes are supported only within a class + 14 missing ) + 15 reference to non-existent subpattern + 16 erroffset passed as NULL + 17 unknown option bit(s) set + 18 missing ) after comment + 19 [this code is not in use] + 20 regular expression is too large + 21 failed to get memory + 22 unmatched parentheses + 23 internal error: code overflow + 24 unrecognized character after (?< + 25 lookbehind assertion is not fixed length + 26 malformed number or name after (?( + 27 conditional group contains more than two branches + 28 assertion expected after (?( + 29 (?R or (?[+-]digits must be followed by ) + 30 unknown POSIX class name + 31 POSIX collating elements are not supported + 32 this version of PCRE is compiled without UTF support + 33 [this code is not in use] + 34 character value in \ex{} or \eo{} is too large + 35 invalid condition (?(0) + 36 \eC not allowed in lookbehind assertion + 37 PCRE does not support \eL, \el, \eN{name}, \eU, or \eu + 38 number after (?C is > 255 + 39 closing ) for (?C expected + 40 recursive call could loop indefinitely + 41 unrecognized character after (?P + 42 syntax error in subpattern name (missing terminator) + 43 two named subpatterns have the same name + 44 invalid UTF-8 string (specifically UTF-8) + 45 support for \eP, \ep, and \eX has not been compiled + 46 malformed \eP or \ep sequence + 47 unknown property name after \eP or \ep + 48 subpattern name is too long (maximum 32 characters) + 49 too many named subpatterns (maximum 10000) + 50 [this code is not in use] + 51 octal value is greater than \e377 in 8-bit non-UTF-8 mode + 52 internal error: overran compiling workspace + 53 internal error: previously-checked referenced subpattern + not found + 54 DEFINE group contains more than one branch + 55 repeating a DEFINE group is not allowed + 56 inconsistent NEWLINE options + 57 \eg is not followed by a braced, angle-bracketed, or quoted + name/number or by a plain number + 58 a numbered reference must not be zero + 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT) + 60 (*VERB) not recognized or malformed + 61 number is too big + 62 subpattern name expected + 63 digit expected after (?+ + 64 ] is an invalid data character in JavaScript compatibility mode + 65 different names for subpatterns of the same number are + not allowed + 66 (*MARK) must have an argument + 67 this version of PCRE is not compiled with Unicode property + support + 68 \ec must be followed by an ASCII character + 69 \ek is not followed by a braced, angle-bracketed, or quoted name + 70 internal error: unknown opcode in find_fixedlength() + 71 \eN is not supported in a class + 72 too many forward references + 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff) + 74 invalid UTF-16 string (specifically UTF-16) + 75 name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN) + 76 character value in \eu.... sequence is too large + 77 invalid UTF-32 string (specifically UTF-32) + 78 setting UTF is disabled by the application + 79 non-hex character in \ex{} (closing brace missing?) + 80 non-octal character in \eo{} (closing brace missing?) + 81 missing opening brace after \eo + 82 parentheses are too deeply nested + 83 invalid range in character class + 84 group name must start with a non-digit + 85 parentheses are too deeply nested (stack check) +.sp +The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may +be used if the limits were changed when PCRE was built. +. +. +.\" HTML <a name="studyingapattern"></a> +.SH "STUDYING A PATTERN" +.rs +.sp +.nf +.B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP, +.B " const char **\fIerrptr\fP);" +.fi +.PP +If a compiled pattern is going to be used several times, it is worth spending +more time analyzing it in order to speed up the time taken for matching. The +function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first +argument. If studying the pattern produces additional information that will +help speed up matching, \fBpcre_study()\fP returns a pointer to a +\fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the +results of the study. +.P +The returned value from \fBpcre_study()\fP can be passed directly to +\fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block +also contains other fields that can be set by the caller before the block is +passed; these are described +.\" HTML <a href="#extradata"> +.\" </a> +below +.\" +in the section on matching a pattern. +.P +If studying the pattern does not produce any useful information, +\fBpcre_study()\fP returns NULL by default. In that circumstance, if the +calling program wants to pass any of the other fields to \fBpcre_exec()\fP or +\fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block. However, +if \fBpcre_study()\fP is called with the PCRE_STUDY_EXTRA_NEEDED option, it +returns a \fBpcre_extra\fP block even if studying did not find any additional +information. It may still return NULL, however, if an error occurs in +\fBpcre_study()\fP. +.P +The second argument of \fBpcre_study()\fP contains option bits. There are three +further options in addition to PCRE_STUDY_EXTRA_NEEDED: +.sp + PCRE_STUDY_JIT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE +.sp +If any of these are set, and the just-in-time compiler is available, the +pattern is further compiled into machine code that executes much faster than +the \fBpcre_exec()\fP interpretive matching function. If the just-in-time +compiler is not available, these options are ignored. All undefined bits in the +\fIoptions\fP argument must be zero. +.P +JIT compilation is a heavyweight optimization. It can take some time for +patterns to be analyzed, and for one-off matches and simple patterns the +benefit of faster execution might be offset by a much slower study time. +Not all patterns can be optimized by the JIT compiler. For those that cannot be +handled, matching automatically falls back to the \fBpcre_exec()\fP +interpreter. For more details, see the +.\" HREF +\fBpcrejit\fP +.\" +documentation. +.P +The third argument for \fBpcre_study()\fP is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it is set to point to a textual error message. This is a +static string that is part of the library. You must not try to free it. You +should test the error pointer for NULL after calling \fBpcre_study()\fP, to be +sure that it has run successfully. +.P +When you are finished with a pattern, you can free the memory used for the +study data by calling \fBpcre_free_study()\fP. This function was added to the +API for release 8.20. For earlier versions, the memory could be freed with +\fBpcre_free()\fP, just like the pattern itself. This will still work in cases +where JIT optimization is not used, but it is advisable to change to the new +function when convenient. +.P +This is a typical way in which \fBpcre_study\fP() is used (except that in a +real application there should be tests for errors): +.sp + int rc; + pcre *re; + pcre_extra *sd; + re = pcre_compile("pattern", 0, &error, &erroroffset, NULL); + sd = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options */ + &error); /* set to NULL or points to a message */ + rc = pcre_exec( /* see below for details of pcre_exec() options */ + re, sd, "subject", 7, 0, 0, ovector, 30); + ... + pcre_free_study(sd); + pcre_free(re); +.sp +Studying a pattern does two things: first, a lower bound for the length of +subject string that is needed to match the pattern is computed. This does not +mean that there are any strings of that length that match, but it does +guarantee that no shorter strings match. The value is used to avoid wasting +time by trying to match strings that are shorter than the lower bound. You can +find out the value in a calling program via the \fBpcre_fullinfo()\fP function. +.P +Studying a pattern is also useful for non-anchored patterns that do not have a +single fixed starting character. A bitmap of possible starting bytes is +created. This speeds up finding a position in the subject at which to start +matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256. +In 32-bit mode, the bitmap is used for 32-bit values less than 256.) +.P +These two optimizations apply to both \fBpcre_exec()\fP and +\fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler. +The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option. +You might want to do this if your pattern contains callouts or (*MARK) and you +want to make use of these facilities in cases where matching fails. +.P +PCRE_NO_START_OPTIMIZE can be specified at either compile time or execution +time. However, if PCRE_NO_START_OPTIMIZE is passed to \fBpcre_exec()\fP, (that +is, after any JIT compilation has happened) JIT execution is disabled. For JIT +execution to work with PCRE_NO_START_OPTIMIZE, the option must be set at +compile time. +.P +There is a longer discussion of PCRE_NO_START_OPTIMIZE +.\" HTML <a href="#execoptions"> +.\" </a> +below. +.\" +. +. +.\" HTML <a name="localesupport"></a> +.SH "LOCALE SUPPORT" +.rs +.sp +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables, indexed by character +code point. When running in UTF-8 mode, or in the 16- or 32-bit libraries, this +applies only to characters with code points less than 256. By default, +higher-valued code points never match escapes such as \ew or \ed. However, if +PCRE is built with Unicode property support, all characters can be tested with +\ep and \eP, or, alternatively, the PCRE_UCP option can be set when a pattern +is compiled; this causes \ew and friends to use Unicode property support +instead of the built-in tables. +.P +The use of locales with Unicode is discouraged. If you are handling characters +with code points greater than 128, you should either use Unicode support, or +use locales, but not try to mix the two. +.P +PCRE contains an internal set of tables that are used when the final argument +of \fBpcre_compile()\fP is NULL. These are sufficient for many applications. +Normally, the internal tables recognize only ASCII characters. However, when +PCRE is built, it is possible to cause the internal tables to be rebuilt in the +default "C" locale of the local system, which may cause them to be different. +.P +The internal tables can always be overridden by tables supplied by the +application that calls PCRE. These may be created in a different locale from +the default. As more and more applications change to using Unicode, the need +for this locale support is expected to die away. +.P +External tables are built by calling the \fBpcre_maketables()\fP function, +which has no arguments, in the relevant locale. The result can then be passed +to \fBpcre_compile()\fP as often as necessary. For example, to build and use +tables that are appropriate for the French locale (where accented characters +with values greater than 128 are treated as letters), the following code could +be used: +.sp + setlocale(LC_CTYPE, "fr_FR"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); +.sp +The locale name "fr_FR" is used on Linux and other Unix-like systems; if you +are using Windows, the name for the French locale is "french". +.P +When \fBpcre_maketables()\fP runs, the tables are built in memory that is +obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure +that the memory containing the tables remains available for as long as it is +needed. +.P +The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled +pattern, and the same tables are used via this pointer by \fBpcre_study()\fP +and also by \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP. Thus, for any single +pattern, compilation, studying and matching all happen in the same locale, but +different patterns can be processed in different locales. +.P +It is possible to pass a table pointer or NULL (indicating the use of the +internal tables) to \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP (see the +discussion below in the section on matching a pattern). This facility is +provided for use with pre-compiled patterns that have been saved and reloaded. +Character tables are not saved with patterns, so if a non-standard table was +used at compile time, it must be provided again when the reloaded pattern is +matched. Attempting to use this facility to match a pattern in a different +locale from the one in which it was compiled is likely to lead to anomalous +(usually incorrect) results. +. +. +.\" HTML <a name="infoaboutpattern"></a> +.SH "INFORMATION ABOUT A PATTERN" +.rs +.sp +.nf +.B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " int \fIwhat\fP, void *\fIwhere\fP);" +.fi +.PP +The \fBpcre_fullinfo()\fP function returns information about a compiled +pattern. It replaces the \fBpcre_info()\fP function, which was removed from the +library at version 8.30, after more than 10 years of obsolescence. +.P +The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled +pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if +the pattern was not studied. The third argument specifies which piece of +information is required, and the fourth argument is a pointer to a variable +to receive the data. The yield of the function is zero for success, or one of +the following negative numbers: +.sp + PCRE_ERROR_NULL the argument \fIcode\fP was NULL + the argument \fIwhere\fP was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADENDIANNESS the pattern was compiled with different + endianness + PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid + PCRE_ERROR_UNSET the requested field is not set +.sp +The "magic number" is placed at the start of each compiled pattern as an simple +check against passing an arbitrary memory pointer. The endianness error can +occur if a compiled pattern is saved and reloaded on a different host. Here is +a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled +pattern: +.sp + int rc; + size_t length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + sd, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ +.sp +The possible values for the third argument are defined in \fBpcre.h\fP, and are +as follows: +.sp + PCRE_INFO_BACKREFMAX +.sp +Return the number of the highest back reference in the pattern. The fourth +argument should point to an \fBint\fP variable. Zero is returned if there are +no back references. +.sp + PCRE_INFO_CAPTURECOUNT +.sp +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an \fBint\fP variable. +.sp + PCRE_INFO_DEFAULT_TABLES +.sp +Return a pointer to the internal default character tables within PCRE. The +fourth argument should point to an \fBunsigned char *\fP variable. This +information call is provided for internal use by the \fBpcre_study()\fP +function. External callers can cause PCRE to use its internal tables by passing +a NULL table pointer. +.sp + PCRE_INFO_FIRSTBYTE (deprecated) +.sp +Return information about the first data unit of any matched string, for a +non-anchored pattern. The name of this option refers to the 8-bit library, +where data units are bytes. The fourth argument should point to an \fBint\fP +variable. Negative values are used for special cases. However, this means that +when the 32-bit library is in non-UTF-32 mode, the full 32-bit range of +characters cannot be returned. For this reason, this value is deprecated; use +PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER instead. +.P +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), its value is returned. In the 8-bit library, the +value is always less than 256. In the 16-bit library the value can be up to +0xffff. In the 32-bit library the value can be up to 0x10ffff. +.P +If there is no fixed first value, and if either +.sp +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +.sp +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +.sp +-1 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise -2 is +returned. For anchored patterns, -2 is returned. +.sp + PCRE_INFO_FIRSTCHARACTER +.sp +Return the value of the first data unit (non-UTF character) of any matched +string in the situation where PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; +otherwise return 0. The fourth argument should point to an \fBuint_t\fP +variable. +.P +In the 8-bit library, the value is always less than 256. In the 16-bit library +the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value +can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode. +.sp + PCRE_INFO_FIRSTCHARACTERFLAGS +.sp +Return information about the first data unit of any matched string, for a +non-anchored pattern. The fourth argument should point to an \fBint\fP +variable. +.P +If there is a fixed first value, for example, the letter "c" from a pattern +such as (cat|cow|coyote), 1 is returned, and the character value can be +retrieved using PCRE_INFO_FIRSTCHARACTER. If there is no fixed first value, and +if either +.sp +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +.sp +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +.sp +2 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise 0 is +returned. For anchored patterns, 0 is returned. +.sp + PCRE_INFO_FIRSTTABLE +.sp +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of values for the first data unit in any matching +string, a pointer to the table is returned. Otherwise NULL is returned. The +fourth argument should point to an \fBunsigned char *\fP variable. +.sp + PCRE_INFO_HASCRORLF +.sp +Return 1 if the pattern contains any explicit matches for CR or LF characters, +otherwise 0. The fourth argument should point to an \fBint\fP variable. An +explicit match is either a literal CR or LF character, or \er or \en. +.sp + PCRE_INFO_JCHANGED +.sp +Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise +0. The fourth argument should point to an \fBint\fP variable. (?J) and +(?-J) set and unset the local PCRE_DUPNAMES option, respectively. +.sp + PCRE_INFO_JIT +.sp +Return 1 if the pattern was studied with one of the JIT options, and +just-in-time compiling was successful. The fourth argument should point to an +\fBint\fP variable. A return value of 0 means that JIT support is not available +in this version of PCRE, or that the pattern was not studied with a JIT option, +or that the JIT compiler could not handle this particular pattern. See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for details of what can and cannot be handled. +.sp + PCRE_INFO_JITSIZE +.sp +If the pattern was successfully studied with a JIT option, return the size of +the JIT compiled code, otherwise return zero. The fourth argument should point +to a \fBsize_t\fP variable. +.sp + PCRE_INFO_LASTLITERAL +.sp +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an \fBint\fP variable. If there is no such +value, -1 is returned. For anchored patterns, a last literal value is recorded +only if it follows something of variable length. For example, for the pattern +/^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value +is -1. +.P +Since for the 32-bit library using the non-UTF-32 mode, this function is unable +to return the full 32-bit range of characters, this value is deprecated; +instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should +be used. +.sp + PCRE_INFO_MATCH_EMPTY +.sp +Return 1 if the pattern can match an empty string, otherwise 0. The fourth +argument should point to an \fBint\fP variable. +.sp + PCRE_INFO_MATCHLIMIT +.sp +If the pattern set a match limit by including an item of the form +(*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth argument +should point to an unsigned 32-bit integer. If no such value has been set, the +call to \fBpcre_fullinfo()\fP returns the error PCRE_ERROR_UNSET. +.sp + PCRE_INFO_MAXLOOKBEHIND +.sp +Return the number of characters (NB not data units) in the longest lookbehind +assertion in the pattern. This information is useful when doing multi-segment +matching using the partial matching facilities. Note that the simple assertions +\eb and \eB require a one-character lookbehind. \eA also registers a +one-character lookbehind, though it does not actually inspect the previous +character. This is to ensure that at least one character from the old segment +is retained when a new segment is processed. Otherwise, if there are no +lookbehinds in the pattern, \eA might match incorrectly at the start of a new +segment. +.sp + PCRE_INFO_MINLENGTH +.sp +If the pattern was studied and a minimum length for matching subject strings +was computed, its value is returned. Otherwise the returned value is -1. The +value is a number of characters, which in UTF mode may be different from the +number of data units. The fourth argument should point to an \fBint\fP +variable. A non-negative value is a lower bound to the length of any matching +string. There may not be any strings of that length that do actually match, but +every string that does match is at least that long. +.sp + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE +.sp +PCRE supports the use of named as well as numbered capturing parentheses. The +names are just an additional way of identifying the parentheses, which still +acquire numbers. Several convenience functions such as +\fBpcre_get_named_substring()\fP are provided for extracting captured +substrings by name. It is also possible to extract the data directly, by first +converting the name to a number in order to access the correct pointers in the +output vector (described with \fBpcre_exec()\fP below). To do the conversion, +you need to use the name-to-number map, which is described by these three +values. +.P +The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an \fBint\fP value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where +the first two bytes of each entry are the number of the capturing parenthesis, +most significant byte first. In the 16-bit library, the pointer points to +16-bit data units, the first of which contains the parenthesis number. In the +32-bit library, the pointer points to 32-bit data units, the first of which +contains the parenthesis number. The rest of the entry is the corresponding +name, zero terminated. +.P +The names are in alphabetical order. If (?| is used to create multiple groups +with the same number, as described in the +.\" HTML <a href="pcrepattern.html#dupsubpatternnumber"> +.\" </a> +section on duplicate subpattern numbers +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +page, the groups may be given the same name, but there is only one entry in the +table. Different names for groups of the same number are not permitted. +Duplicate names for subpatterns with different numbers are permitted, +but only if PCRE_DUPNAMES is set. They appear in the table in the order in +which they were found in the pattern. In the absence of (?| this is the order +of increasing number; when (?| is used this is not necessarily the case because +later subpatterns may have lower numbers. +.P +As a simple example of the name/number table, consider the following pattern +after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white +space - including newlines - is ignored): +.sp +.\" JOIN + (?<date> (?<year>(\ed\ed)?\ed\ed) - + (?<month>\ed\ed) - (?<day>\ed\ed) ) +.sp +There are four named subpatterns, so the table has four entries, and each entry +in the table is eight bytes long. The table is as follows, with non-printing +bytes shows in hexadecimal, and undefined bytes shown as ??: +.sp + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? +.sp +When writing code to extract data from named subpatterns using the +name-to-number map, remember that the length of the entries is likely to be +different for each compiled pattern. +.sp + PCRE_INFO_OKPARTIAL +.sp +Return 1 if the pattern can be used for partial matching with +\fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an +\fBint\fP variable. From release 8.00, this always returns 1, because the +restrictions that previously applied to partial matching have been lifted. The +.\" HREF +\fBpcrepartial\fP +.\" +documentation gives details of partial matching. +.sp + PCRE_INFO_OPTIONS +.sp +Return a copy of the options with which the pattern was compiled. The fourth +argument should point to an \fBunsigned long int\fP variable. These option bits +are those specified in the call to \fBpcre_compile()\fP, modified by any +top-level option settings at the start of the pattern itself. In other words, +they are the options that will be in force when matching starts. For example, +if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the +result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED. +.P +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: +.sp + ^ unless PCRE_MULTILINE is set + \eA always + \eG always +.\" JOIN + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears +.sp +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +\fBpcre_fullinfo()\fP. +.sp + PCRE_INFO_RECURSIONLIMIT +.sp +If the pattern set a recursion limit by including an item of the form +(*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth +argument should point to an unsigned 32-bit integer. If no such value has been +set, the call to \fBpcre_fullinfo()\fP returns the error PCRE_ERROR_UNSET. +.sp + PCRE_INFO_SIZE +.sp +Return the size of the compiled pattern in bytes (for all three libraries). The +fourth argument should point to a \fBsize_t\fP variable. This value does not +include the size of the \fBpcre\fP structure that is returned by +\fBpcre_compile()\fP. The value that is passed as the argument to +\fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to +place the compiled data is the value returned by this option plus the size of +the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT, +does not alter the value returned by this option. +.sp + PCRE_INFO_STUDYSIZE +.sp +Return the size in bytes (for all three libraries) of the data block pointed to +by the \fIstudy_data\fP field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP +is NULL, or there is no study data, zero is returned. The fourth argument +should point to a \fBsize_t\fP variable. The \fIstudy_data\fP field is set by +\fBpcre_study()\fP to record information that will speed up matching (see the +section entitled +.\" HTML <a href="#studyingapattern"> +.\" </a> +"Studying a pattern" +.\" +above). The format of the \fIstudy_data\fP block is private, but its length +is made available via this option so that it can be saved and restored (see the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation for details). +.sp + PCRE_INFO_REQUIREDCHARFLAGS +.sp +Returns 1 if there is a rightmost literal data unit that must exist in any +matched string, other than at its start. The fourth argument should point to +an \fBint\fP variable. If there is no such value, 0 is returned. If returning +1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR. +.P +For anchored patterns, a last literal value is recorded only if it follows +something of variable length. For example, for the pattern /^a\ed+z\ed+/ the +returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for +/^a\edz\ed/ the returned value is 0. +.sp + PCRE_INFO_REQUIREDCHAR +.sp +Return the value of the rightmost literal data unit that must exist in any +matched string, other than at its start, if such a value has been recorded. The +fourth argument should point to an \fBuint32_t\fP variable. If there is no such +value, 0 is returned. +. +. +.SH "REFERENCE COUNTS" +.rs +.sp +.B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP); +.PP +The \fBpcre_refcount()\fP function is used to maintain a reference count in the +data block that contains a compiled pattern. It is provided for the benefit of +applications that operate in an object-oriented manner, where different parts +of the application may be using the same compiled pattern, but you want to free +the block when they are all done. +.P +When a pattern is compiled, the reference count field is initialized to zero. +It is changed only by calling this function, whose action is to add the +\fIadjust\fP value (which may be positive or negative) to it. The yield of the +function is the new value. However, the value of the count is constrained to +lie between 0 and 65535, inclusive. If the new value is outside these limits, +it is forced to the appropriate limit value. +.P +Except when it is zero, the reference count is not correctly preserved if a +pattern is compiled on one host and then transferred to a host whose byte-order +is different. (This seems a highly unlikely scenario.) +. +. +.SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION" +.rs +.sp +.nf +.B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP, +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);" +.fi +.P +The function \fBpcre_exec()\fP is called to match a subject string against a +compiled pattern, which is passed in the \fIcode\fP argument. If the +pattern was studied, the result of the study should be passed in the +\fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP +and \fIextra\fP arguments as many times as you like, in order to match +different subject strings with the same pattern. +.P +This function is the main matching facility of the library, and it operates in +a Perl-like manner. For specialist use there is also an alternative matching +function, which is described +.\" HTML <a href="#dfamatch"> +.\" </a> +below +.\" +in the section about the \fBpcre_dfa_exec()\fP function. +.P +In most applications, the pattern will have been compiled (and optionally +studied) in the same process that calls \fBpcre_exec()\fP. However, it is +possible to save compiled patterns and study data, and then use them later +in different processes, possibly even on different hosts. For a discussion +about this, see the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation. +.P +Here is an example of a simple call to \fBpcre_exec()\fP: +.sp + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 30); /* number of elements (NOT size in bytes) */ +. +. +.\" HTML <a name="extradata"></a> +.SS "Extra data for \fBpcre_exec()\fR" +.rs +.sp +If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP +data block. The \fBpcre_study()\fP function returns such a block (when it +doesn't return NULL), but you can also create one for yourself, and pass +additional information in it. The \fBpcre_extra\fP block contains the following +fields (not necessarily in this order): +.sp + unsigned long int \fIflags\fP; + void *\fIstudy_data\fP; + void *\fIexecutable_jit\fP; + unsigned long int \fImatch_limit\fP; + unsigned long int \fImatch_limit_recursion\fP; + void *\fIcallout_data\fP; + const unsigned char *\fItables\fP; + unsigned char **\fImark\fP; +.sp +In the 16-bit version of this structure, the \fImark\fP field has type +"PCRE_UCHAR16 **". +.sp +In the 32-bit version of this structure, the \fImark\fP field has type +"PCRE_UCHAR32 **". +.P +The \fIflags\fP field is used to specify which of the other fields are set. The +flag bits are: +.sp + PCRE_EXTRA_CALLOUT_DATA + PCRE_EXTRA_EXECUTABLE_JIT + PCRE_EXTRA_MARK + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_MATCH_LIMIT_RECURSION + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_TABLES +.sp +Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes +the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is +returned by \fBpcre_study()\fP, together with the appropriate flag bits. You +should not set these yourself, but you may add to the block by setting other +fields and their corresponding flag bits. +.P +The \fImatch_limit\fP field provides a means of preventing PCRE from using up a +vast amount of resources when running patterns that are not going to match, +but which have a very large number of possibilities in their search trees. The +classic example is a pattern that uses nested unlimited repeats. +.P +Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it +calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is +imposed on the number of times this function is called during a match, which +has the effect of limiting the amount of backtracking that can take place. For +patterns that are not anchored, the count restarts from zero for each position +in the subject string. +.P +When \fBpcre_exec()\fP is called with a pattern that was successfully studied +with a JIT option, the way that the matching is executed is entirely different. +However, there is still the possibility of runaway matching that goes on for a +very long time, and so the \fImatch_limit\fP value is also used in this case +(but in a different way) to limit how long the matching can continue. +.P +The default value for the limit can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP +block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in +the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns +PCRE_ERROR_MATCHLIMIT. +.P +A value for the match limit may also be supplied by an item at the start of a +pattern of the form +.sp + (*LIMIT_MATCH=d) +.sp +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of \fBpcre_exec()\fP or, if no such limit +is set, less than the default. +.P +The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but +instead of limiting the total number of times that \fBmatch()\fP is called, it +limits the depth of recursion. The recursion depth is a smaller number than the +total number of calls, because not all calls to \fBmatch()\fP are recursive. +This limit is of use only if it is set smaller than \fImatch_limit\fP. +.P +Limiting the recursion depth limits the amount of machine stack that can be +used, or, when PCRE has been compiled to use memory on the heap instead of the +stack, the amount of heap memory that can be used. This limit is not relevant, +and is ignored, when matching is done using JIT compiled code. +.P +The default value for \fImatch_limit_recursion\fP can be set when PCRE is +built; the default default is the same value as the default for +\fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP +with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and +PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit +is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT. +.P +A value for the recursion limit may also be supplied by an item at the start of +a pattern of the form +.sp + (*LIMIT_RECURSION=d) +.sp +where d is a decimal number. However, such a setting is ignored unless d is +less than the limit set by the caller of \fBpcre_exec()\fP or, if no such limit +is set, less than the default. +.P +The \fIcallout_data\fP field is used in conjunction with the "callout" feature, +and is described in the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.P +The \fItables\fP field is provided for use with patterns that have been +pre-compiled using custom character tables, saved to disc or elsewhere, and +then reloaded, because the tables that were used to compile a pattern are not +saved with it. See the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation for a discussion of saving compiled patterns for later use. If +NULL is passed using this mechanism, it forces PCRE's internal tables to be +used. +.P +\fBWarning:\fP The tables that \fBpcre_exec()\fP uses must be the same as those +that were used when the pattern was compiled. If this is not the case, the +behaviour of \fBpcre_exec()\fP is undefined. Therefore, when a pattern is +compiled and matched in the same process, this field should never be set. In +this (the most common) case, the correct table pointer is automatically passed +with the compiled pattern from \fBpcre_compile()\fP to \fBpcre_exec()\fP. +.P +If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must +be set to point to a suitable variable. If the pattern contains any +backtracking control verbs such as (*MARK:NAME), and the execution ends up with +a name to pass back, a pointer to the name string (zero terminated) is placed +in the variable pointed to by the \fImark\fP field. The names are within the +compiled pattern; if you wish to retain such a name you must copy it before +freeing the memory of a compiled pattern. If there is no name to pass back, the +variable pointed to by the \fImark\fP field is set to NULL. For details of the +backtracking control verbs, see the section entitled +.\" HTML <a href="pcrepattern#backtrackcontrol"> +.\" </a> +"Backtracking control" +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +. +. +.\" HTML <a name="execoptions"></a> +.SS "Option bits for \fBpcre_exec()\fP" +.rs +.sp +The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be +zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and +PCRE_PARTIAL_SOFT. +.P +If the pattern was successfully studied with one of the just-in-time (JIT) +compile options, the only supported options for JIT execution are +PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, +PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an +unsupported option is used, JIT execution is disabled and the normal +interpretive code in \fBpcre_exec()\fP is run. +.sp + PCRE_ANCHORED +.sp +The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first +matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out +to be anchored by virtue of its contents, it cannot be made unachored at +matching time. +.sp + PCRE_BSR_ANYCRLF + PCRE_BSR_UNICODE +.sp +These options (which are mutually exclusive) control what the \eR escape +sequence matches. The choice is either to match only CR, LF, or CRLF, or to +match any Unicode newline sequence. These options override the choice that was +made or defaulted when the pattern was compiled. +.sp + PCRE_NEWLINE_CR + PCRE_NEWLINE_LF + PCRE_NEWLINE_CRLF + PCRE_NEWLINE_ANYCRLF + PCRE_NEWLINE_ANY +.sp +These options override the newline definition that was chosen or defaulted when +the pattern was compiled. For details, see the description of +\fBpcre_compile()\fP above. During matching, the newline choice affects the +behaviour of the dot, circumflex, and dollar metacharacters. It may also alter +the way the match position is advanced after a match failure for an unanchored +pattern. +.P +When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a +match attempt for an unanchored pattern fails when the current position is at a +CRLF sequence, and the pattern contains no explicit matches for CR or LF +characters, the match position is advanced by two characters instead of one, in +other words, to after the CRLF. +.P +The above rule is a compromise that makes the most common cases work as +expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not +set), it does not match the string "\er\enA" because, after failing at the +start, it skips both the CR and the LF before retrying. However, the pattern +[\er\en]A does match that string, because it contains an explicit CR or LF +reference, and so advances only by one character after the first failure. +.P +An explicit match for CR of LF is either a literal appearance of one of those +characters, or one of the \er or \en escape sequences. Implicit matches such as +[^X] do not count, nor does \es (which includes CR and LF in the characters +that it matches). +.P +Notwithstanding the above, anomalous effects may still occur when CRLF is a +valid newline sequence and explicit \er or \en escapes appear in the pattern. +.sp + PCRE_NOTBOL +.sp +This option specifies that first character of the subject string is not the +beginning of a line, so the circumflex metacharacter should not match before +it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex +never to match. This option affects only the behaviour of the circumflex +metacharacter. It does not affect \eA. +.sp + PCRE_NOTEOL +.sp +This option specifies that the end of the subject string is not the end of a +line, so the dollar metacharacter should not match it nor (except in multiline +mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at +compile time) causes dollar never to match. This option affects only the +behaviour of the dollar metacharacter. It does not affect \eZ or \ez. +.sp + PCRE_NOTEMPTY +.sp +An empty string is not considered to be a valid match if this option is set. If +there are alternatives in the pattern, they are tried. If all the alternatives +match the empty string, the entire match fails. For example, if the pattern +.sp + a?b? +.sp +is applied to a string not beginning with "a" or "b", it matches an empty +string at the start of the subject. With PCRE_NOTEMPTY set, this match is not +valid, so PCRE searches further into the string for occurrences of "a" or "b". +.sp + PCRE_NOTEMPTY_ATSTART +.sp +This is like PCRE_NOTEMPTY, except that an empty string match that is not at +the start of the subject is permitted. If the pattern is anchored, such a match +can occur only if the pattern contains \eK. +.P +Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it +does make a special case of a pattern match of the empty string within its +\fBsplit()\fP function, and when using the /g modifier. It is possible to +emulate Perl's behaviour after matching a null string by first trying the match +again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then +if that fails, by advancing the starting offset (see below) and trying an +ordinary match again. There is some code that demonstrates how to do this in +the +.\" HREF +\fBpcredemo\fP +.\" +sample program. In the most general case, you have to check to see if the +newline convention recognizes CRLF as a newline, and if so, and the current +character is CR followed by LF, advance the starting offset by two characters +instead of one. +.sp + PCRE_NO_START_OPTIMIZE +.sp +There are a number of optimizations that \fBpcre_exec()\fP uses at the start of +a match, in order to speed up the process. For example, if it is known that an +unanchored match must start with a specific character, it searches the subject +for that character, and fails immediately if it cannot find it, without +actually running the main matching function. This means that a special item +such as (*COMMIT) at the start of a pattern is not considered until after a +suitable starting point for the match has been found. Also, when callouts or +(*MARK) items are in use, these "start-up" optimizations can cause them to be +skipped if the pattern is never actually used. The start-up optimizations are +in effect a pre-scan of the subject that takes place before the pattern is run. +.P +The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly +causing performance to suffer, but ensuring that in cases where the result is +"no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK) +are considered at every possible starting position in the subject string. If +PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching +time. The use of PCRE_NO_START_OPTIMIZE at matching time (that is, passing it +to \fBpcre_exec()\fP) disables JIT execution; in this situation, matching is +always done using interpretively. +.P +Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation. +Consider the pattern +.sp + (*COMMIT)ABC +.sp +When this is compiled, PCRE records the fact that a match must start with the +character "A". Suppose the subject string is "DEFABC". The start-up +optimization scans along the subject, finds "A" and runs the first match +attempt from there. The (*COMMIT) item means that the pattern must match the +current starting position, which in this case, it does. However, if the same +match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the +subject string does not happen. The first match attempt is run starting from +"D" and when this fails, (*COMMIT) prevents any further matches being tried, so +the overall result is "no match". If the pattern is studied, more start-up +optimizations may be used. For example, a minimum length for the subject may be +recorded. Consider the pattern +.sp + (*MARK:A)(X|Y) +.sp +The minimum length for a match is one character. If the subject is "ABC", there +will be attempts to match "ABC", "BC", "C", and then finally an empty string. +If the pattern is studied, the final attempt does not take place, because PCRE +knows that the subject is too short, and so the (*MARK) is never encountered. +In this case, studying the pattern does not affect the overall match result, +which is still "no match", but it does affect the auxiliary information that is +returned. +.sp + PCRE_NO_UTF8_CHECK +.sp +When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8 +string is automatically checked when \fBpcre_exec()\fP is subsequently called. +The entire string is checked before any other processing takes place. The value +of \fIstartoffset\fP is also checked to ensure that it points to the start of a +UTF-8 character. There is a discussion about the +.\" HTML <a href="pcreunicode.html#utf8strings"> +.\" </a> +validity of UTF-8 strings +.\" +in the +.\" HREF +\fBpcreunicode\fP +.\" +page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the +error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a +truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both +cases, information about the precise nature of the error may also be returned +(see the descriptions of these errors in the section entitled \fIError return +values from\fP \fBpcre_exec()\fP +.\" HTML <a href="#errorlist"> +.\" </a> +below). +.\" +If \fIstartoffset\fP contains a value that does not point to the start of a +UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is +returned. +.P +If you already know that your subject is valid, and you want to skip these +checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when +calling \fBpcre_exec()\fP. You might want to do this for the second and +subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find +all the matches in a single subject string. However, you should be sure that +the value of \fIstartoffset\fP points to the start of a character (or the end +of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an +invalid string as a subject or an invalid value of \fIstartoffset\fP is +undefined. Your program may crash or loop. +.sp + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +.sp +These options turn on the partial matching feature. For backwards +compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match +occurs if the end of the subject string is reached successfully, but there are +not enough subject characters to complete the match. If this happens when +PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by +testing any remaining alternatives. Only if no complete match can be found is +PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words, +PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match, +but only if no complete match can be found. +.P +If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a +partial match is found, \fBpcre_exec()\fP immediately returns +PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words, +when PCRE_PARTIAL_HARD is set, a partial match is considered to be more +important that an alternative complete match. +.P +In both cases, the portion of the string that was inspected when the partial +match was found is set as the first matching string. There is a more detailed +discussion of partial and multi-segment matching, with examples, in the +.\" HREF +\fBpcrepartial\fP +.\" +documentation. +. +. +.SS "The string to be matched by \fBpcre_exec()\fP" +.rs +.sp +The subject string is passed to \fBpcre_exec()\fP as a pointer in +\fIsubject\fP, a length in \fIlength\fP, and a starting offset in +\fIstartoffset\fP. The units for \fIlength\fP and \fIstartoffset\fP are bytes +for the 8-bit library, 16-bit data items for the 16-bit library, and 32-bit +data items for the 32-bit library. +.P +If \fIstartoffset\fP is negative or greater than the length of the subject, +\fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting offset is +zero, the search for a match starts at the beginning of the subject, and this +is by far the most common case. In UTF-8 or UTF-16 mode, the offset must point +to the start of a character, or the end of the subject (in UTF-32 mode, one +data unit equals one character, so all offsets are valid). Unlike the pattern +string, the subject may contain binary zeroes. +.P +A non-zero starting offset is useful when searching for another match in the +same subject by calling \fBpcre_exec()\fP again after a previous success. +Setting \fIstartoffset\fP differs from just passing over a shortened string and +setting PCRE_NOTBOL in the case of a pattern that begins with any kind of +lookbehind. For example, consider the pattern +.sp + \eBiss\eB +.sp +which finds occurrences of "iss" in the middle of words. (\eB matches only if +the current position in the subject is not a word boundary.) When applied to +the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first +occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the +subject, namely "issipi", it does not match, because \eB is always false at the +start of the subject, which is deemed to be a word boundary. However, if +\fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP +set to 4, it finds the second occurrence of "iss" because it is able to look +behind the starting point to discover that it is preceded by a letter. +.P +Finding all the matches in a subject is tricky when the pattern can match an +empty string. It is possible to emulate Perl's /g behaviour by first trying the +match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and +PCRE_ANCHORED options, and then if that fails, advancing the starting offset +and trying an ordinary match again. There is some code that demonstrates how to +do this in the +.\" HREF +\fBpcredemo\fP +.\" +sample program. In the most general case, you have to check to see if the +newline convention recognizes CRLF as a newline, and if so, and the current +character is CR followed by LF, advance the starting offset by two characters +instead of one. +.P +If a non-zero starting offset is passed when the pattern is anchored, one +attempt to match at the given offset is made. This can only succeed if the +pattern does not require the match to be at the start of the subject. +. +. +.SS "How \fBpcre_exec()\fP returns captured substrings" +.rs +.sp +In general, a pattern matches a certain portion of the subject, and in +addition, further substrings from the subject may be picked out by parts of the +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. +.P +Captured substrings are returned to the caller via a vector of integers whose +address is passed in \fIovector\fP. The number of elements in the vector is +passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this +argument is NOT the size of \fIovector\fP in bytes. +.P +The first two-thirds of the vector is used to pass back captured substrings, +each substring using a pair of integers. The remaining third of the vector is +used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns, +and is not available for passing back information. The number passed in +\fIovecsize\fP should always be a multiple of three. If it is not, it is +rounded down. +.P +When a match is successful, information about captured substrings is returned +in pairs of integers, starting at the beginning of \fIovector\fP, and +continuing up to two-thirds of its length at the most. The first element of +each pair is set to the offset of the first character in a substring, and the +second is set to the offset of the first character after the end of a +substring. These values are always data unit offsets, even in UTF mode. They +are byte offsets in the 8-bit library, 16-bit data item offsets in the 16-bit +library, and 32-bit data item offsets in the 32-bit library. \fBNote\fP: they +are not character counts. +.P +The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the +portion of the subject string matched by the entire pattern. The next pair is +used for the first capturing subpattern, and so on. The value returned by +\fBpcre_exec()\fP is one more than the highest numbered pair that has been set. +For example, if two substrings have been captured, the returned value is 3. If +there are no capturing subpatterns, the return value from a successful match is +1, indicating that just the first pair of offsets has been set. +.P +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that is returned. +.P +If the vector is too small to hold all the captured substring offsets, it is +used as far as possible (up to two-thirds of its length), and the function +returns a value of zero. If neither the actual string matched nor any captured +substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP +passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains +back references and the \fIovector\fP is not big enough to remember the related +substrings, PCRE has to get additional memory for use during matching. Thus it +is usually advisable to supply an \fIovector\fP of reasonable size. +.P +There are some cases where zero is returned (indicating vector overflow) when +in fact the vector is exactly the right size for the final match. For example, +consider the pattern +.sp + (a)(?:(b)c|bd) +.sp +If a vector of 6 elements (allowing for only 1 captured substring) is given +with subject string "abd", \fBpcre_exec()\fP will try to set the second +captured string, thereby recording a vector overflow, before failing to match +"c" and backing up to try the second alternative. The zero return, however, +does correctly indicate that the maximum number of slots (namely 2) have been +filled. In similar cases where there is temporary overflow, but the final +number of used slots is actually less than the maximum, a non-zero value is +returned. +.P +The \fBpcre_fullinfo()\fP function can be used to find out how many capturing +subpatterns there are in a compiled pattern. The smallest size for +\fIovector\fP that will allow for \fIn\fP captured substrings, in addition to +the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3. +.P +It is possible for capturing subpattern number \fIn+1\fP to match some part of +the subject when subpattern \fIn\fP has not been used at all. For example, if +the string "abc" is matched against the pattern (a|(z))(bc) the return from the +function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this +happens, both values in the offset pairs corresponding to unused subpatterns +are set to -1. +.P +Offset values that correspond to unused subpatterns at the end of the +expression are also set to -1. For example, if the string "abc" is matched +against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The +return from the function is 2, because the highest used capturing subpattern +number is 1, and the offsets for for the second and third capturing subpatterns +(assuming the vector is large enough, of course) are set to -1. +.P +\fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not +correspond to capturing parentheses in the pattern are never changed. That is, +if a pattern contains \fIn\fP capturing parentheses, no more than +\fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other +elements (in the first two-thirds) retain whatever values they previously had. +.P +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described below. +. +. +.\" HTML <a name="errorlist"></a> +.SS "Error return values from \fBpcre_exec()\fP" +.rs +.sp +If \fBpcre_exec()\fP fails, it returns a negative number. The following are +defined in the header file: +.sp + PCRE_ERROR_NOMATCH (-1) +.sp +The subject string did not match the pattern. +.sp + PCRE_ERROR_NULL (-2) +.sp +Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was +NULL and \fIovecsize\fP was not zero. +.sp + PCRE_ERROR_BADOPTION (-3) +.sp +An unrecognized bit was set in the \fIoptions\fP argument. +.sp + PCRE_ERROR_BADMAGIC (-4) +.sp +PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch +the case when it is passed a junk pointer and to detect when a pattern that was +compiled in an environment of one endianness is run in an environment with the +other endianness. This is the error that PCRE gives when the magic number is +not present. +.sp + PCRE_ERROR_UNKNOWN_OPCODE (-5) +.sp +While running the pattern match, an unknown item was encountered in the +compiled pattern. This error could be caused by a bug in PCRE or by overwriting +of the compiled pattern. +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +If a pattern contains back references, but the \fIovector\fP that is passed to +\fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE +gets a block of memory at the start of matching to use for this purpose. If the +call via \fBpcre_malloc()\fP fails, this error is given. The memory is +automatically freed at the end of matching. +.P +This error is also given if \fBpcre_stack_malloc()\fP fails in +\fBpcre_exec()\fP. This can happen only when PCRE has been compiled with +\fB--disable-stack-for-recursion\fP. +.sp + PCRE_ERROR_NOSUBSTRING (-7) +.sp +This error is used by the \fBpcre_copy_substring()\fP, +\fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see +below). It is never returned by \fBpcre_exec()\fP. +.sp + PCRE_ERROR_MATCHLIMIT (-8) +.sp +The backtracking limit, as specified by the \fImatch_limit\fP field in a +\fBpcre_extra\fP structure (or defaulted) was reached. See the description +above. +.sp + PCRE_ERROR_CALLOUT (-9) +.sp +This error is never generated by \fBpcre_exec()\fP itself. It is provided for +use by callout functions that want to yield a distinctive error code. See the +.\" HREF +\fBpcrecallout\fP +.\" +documentation for details. +.sp + PCRE_ERROR_BADUTF8 (-10) +.sp +A string that contains an invalid UTF-8 byte sequence was passed as a subject, +and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector +(\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid +UTF-8 character is placed in the first element, and a reason code is placed in +the second element. The reason codes are listed in the +.\" HTML <a href="#badutf8reasons"> +.\" </a> +following section. +.\" +For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a +truncated UTF-8 character at the end of the subject (reason codes 1 to 5), +PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. +.sp + PCRE_ERROR_BADUTF8_OFFSET (-11) +.sp +The UTF-8 byte sequence that was passed as a subject was checked and found to +be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of +\fIstartoffset\fP did not point to the beginning of a UTF-8 character or the +end of the subject. +.sp + PCRE_ERROR_PARTIAL (-12) +.sp +The subject string did not match, but it did match partially. See the +.\" HREF +\fBpcrepartial\fP +.\" +documentation for details of partial matching. +.sp + PCRE_ERROR_BADPARTIAL (-13) +.sp +This code is no longer in use. It was formerly returned when the PCRE_PARTIAL +option was used with a compiled pattern containing items that were not +supported for partial matching. From release 8.00 onwards, there are no +restrictions on partial matching. +.sp + PCRE_ERROR_INTERNAL (-14) +.sp +An unexpected internal error has occurred. This error could be caused by a bug +in PCRE or by overwriting of the compiled pattern. +.sp + PCRE_ERROR_BADCOUNT (-15) +.sp +This error is given if the value of the \fIovecsize\fP argument is negative. +.sp + PCRE_ERROR_RECURSIONLIMIT (-21) +.sp +The internal recursion limit, as specified by the \fImatch_limit_recursion\fP +field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the +description above. +.sp + PCRE_ERROR_BADNEWLINE (-23) +.sp +An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given. +.sp + PCRE_ERROR_BADOFFSET (-24) +.sp +The value of \fIstartoffset\fP was negative or greater than the length of the +subject, that is, the value in \fIlength\fP. +.sp + PCRE_ERROR_SHORTUTF8 (-25) +.sp +This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string +ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set. +Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in +fact sufficient to detect this case, but this special error code for +PCRE_PARTIAL_HARD precedes the implementation of returned information; it is +retained for backwards compatibility. +.sp + PCRE_ERROR_RECURSELOOP (-26) +.sp +This error is returned when \fBpcre_exec()\fP detects a recursion loop within +the pattern. Specifically, it means that either the whole pattern or a +subpattern has been called recursively for the second time at the same position +in the subject string. Some simple patterns that might do this are detected and +faulted at compile time, but more complicated cases, in particular mutual +recursions between two different subpatterns, cannot be detected until run +time. +.sp + PCRE_ERROR_JIT_STACKLIMIT (-27) +.sp +This error is returned when a pattern that was successfully studied using a +JIT compile option is being matched, but the memory available for the +just-in-time processing stack is not large enough. See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for more details. +.sp + PCRE_ERROR_BADMODE (-28) +.sp +This error is given if a pattern that was compiled by the 8-bit library is +passed to a 16-bit or 32-bit library function, or vice versa. +.sp + PCRE_ERROR_BADENDIANNESS (-29) +.sp +This error is given if a pattern that was compiled and saved is reloaded on a +host with different endianness. The utility function +\fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern +so that it runs on the new host. +.sp + PCRE_ERROR_JIT_BADOPTION +.sp +This error is returned when a pattern that was successfully studied using a JIT +compile option is being matched, but the matching mode (partial or complete +match) does not correspond to any JIT compilation mode. When the JIT fast path +function is used, this error may be also given for invalid options. See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for more details. +.sp + PCRE_ERROR_BADLENGTH (-32) +.sp +This error is given if \fBpcre_exec()\fP is called with a negative value for +the \fIlength\fP argument. +.P +Error numbers -16 to -20, -22, and 30 are not used by \fBpcre_exec()\fP. +. +. +.\" HTML <a name="badutf8reasons"></a> +.SS "Reason codes for invalid UTF-8 strings" +.rs +.sp +This section applies only to the 8-bit library. The corresponding information +for the 16-bit and 32-bit libraries is given in the +.\" HREF +\fBpcre16\fP +.\" +and +.\" HREF +\fBpcre32\fP +.\" +pages. +.P +When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or +PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at +least 2, the offset of the start of the invalid UTF-8 character is placed in +the first output vector element (\fIovector[0]\fP) and a reason code is placed +in the second element (\fIovector[1]\fP). The reason codes are given names in +the \fBpcre.h\fP header file: +.sp + PCRE_UTF8_ERR1 + PCRE_UTF8_ERR2 + PCRE_UTF8_ERR3 + PCRE_UTF8_ERR4 + PCRE_UTF8_ERR5 +.sp +The string ends with a truncated UTF-8 character; the code specifies how many +bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be +no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279) +allows for up to 6 bytes, and this is checked first; hence the possibility of +4 or 5 missing bytes. +.sp + PCRE_UTF8_ERR6 + PCRE_UTF8_ERR7 + PCRE_UTF8_ERR8 + PCRE_UTF8_ERR9 + PCRE_UTF8_ERR10 +.sp +The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the +character do not have the binary value 0b10 (that is, either the most +significant bit is 0, or the next bit is 1). +.sp + PCRE_UTF8_ERR11 + PCRE_UTF8_ERR12 +.sp +A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long; +these code points are excluded by RFC 3629. +.sp + PCRE_UTF8_ERR13 +.sp +A 4-byte character has a value greater than 0x10fff; these code points are +excluded by RFC 3629. +.sp + PCRE_UTF8_ERR14 +.sp +A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of +code points are reserved by RFC 3629 for use with UTF-16, and so are excluded +from UTF-8. +.sp + PCRE_UTF8_ERR15 + PCRE_UTF8_ERR16 + PCRE_UTF8_ERR17 + PCRE_UTF8_ERR18 + PCRE_UTF8_ERR19 +.sp +A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a +value that can be represented by fewer bytes, which is invalid. For example, +the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just +one byte. +.sp + PCRE_UTF8_ERR20 +.sp +The two most significant bits of the first byte of a character have the binary +value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a +byte can only validly occur as the second or subsequent byte of a multi-byte +character. +.sp + PCRE_UTF8_ERR21 +.sp +The first byte of a character has the value 0xfe or 0xff. These values can +never occur in a valid UTF-8 string. +.sp + PCRE_UTF8_ERR22 +.sp +This error code was formerly used when the presence of a so-called +"non-character" caused an error. Unicode corrigendum #9 makes it clear that +such characters should not cause a string to be rejected, and so this code is +no longer in use and is never returned. +. +. +.SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER" +.rs +.sp +.nf +.B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP," +.B " int \fIbuffersize\fP);" +.sp +.B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP, +.B " int \fIstringcount\fP, int \fIstringnumber\fP," +.B " const char **\fIstringptr\fP);" +.sp +.B int pcre_get_substring_list(const char *\fIsubject\fP, +.B " int *\fIovector\fP, int \fIstringcount\fP, const char ***\fIlistptr\fP);" +.fi +.PP +Captured substrings can be accessed directly by using the offsets returned by +\fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions +\fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and +\fBpcre_get_substring_list()\fP are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. +.P +A substring that contains a binary zero is correctly extracted and has a +further zero added on the end, but the result is not, of course, a C string. +However, you can process such a string by referring to the length that is +returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP. +Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate +for handling strings containing binary zeros, because the end of the final +string is not independently indicated. +.P +The first three arguments are the same for all three of these functions: +\fIsubject\fP is the subject string that has just been successfully matched, +\fIovector\fP is a pointer to the vector of integer offsets that was passed to +\fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were +captured by the match, including the substring that matched the entire regular +expression. This is the value returned by \fBpcre_exec()\fP if it is greater +than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of +space in \fIovector\fP, the value passed as \fIstringcount\fP should be the +number of elements in the vector divided by three. +.P +The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP +extract a single substring, whose number is given as \fIstringnumber\fP. A +value of zero extracts the substring that matched the entire pattern, whereas +higher values extract the captured substrings. For \fBpcre_copy_substring()\fP, +the string is placed in \fIbuffer\fP, whose length is given by +\fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is +obtained via \fBpcre_malloc\fP, and its address is returned via +\fIstringptr\fP. The yield of the function is the length of the string, not +including the terminating zero, or one of these error codes: +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get +memory failed for \fBpcre_get_substring()\fP. +.sp + PCRE_ERROR_NOSUBSTRING (-7) +.sp +There is no substring whose number is \fIstringnumber\fP. +.P +The \fBpcre_get_substring_list()\fP function extracts all available substrings +and builds a list of pointers to them. All this is done in a single block of +memory that is obtained via \fBpcre_malloc\fP. The address of the memory block +is returned via \fIlistptr\fP, which is also the start of the list of string +pointers. The end of the list is marked by a NULL pointer. The yield of the +function is zero if all went well, or the error code +.sp + PCRE_ERROR_NOMEMORY (-6) +.sp +if the attempt to get the memory block failed. +.P +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number \fIn+1\fP matches some part of the +subject, but subpattern \fIn\fP has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in \fIovector\fP, which is negative for unset +substrings. +.P +The two convenience functions \fBpcre_free_substring()\fP and +\fBpcre_free_substring_list()\fP can be used to free the memory returned by +a previous call of \fBpcre_get_substring()\fP or +\fBpcre_get_substring_list()\fP, respectively. They do nothing more than call +the function pointed to by \fBpcre_free\fP, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language that cannot use +\fBpcre_free\fP directly; it is for these cases that the functions are +provided. +. +. +.SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME" +.rs +.sp +.nf +.B int pcre_get_stringnumber(const pcre *\fIcode\fP, +.B " const char *\fIname\fP);" +.sp +.B int pcre_copy_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " char *\fIbuffer\fP, int \fIbuffersize\fP);" +.sp +.B int pcre_get_named_substring(const pcre *\fIcode\fP, +.B " const char *\fIsubject\fP, int *\fIovector\fP," +.B " int \fIstringcount\fP, const char *\fIstringname\fP," +.B " const char **\fIstringptr\fP);" +.fi +.PP +To extract a substring by name, you first have to find associated number. +For example, for this pattern +.sp + (a+)b(?<xxx>\ed+)... +.sp +the number of the subpattern called "xxx" is 2. If the name is known to be +unique (PCRE_DUPNAMES was not set), you can find the number from the name by +calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled +pattern, and the second is the name. The yield of the function is the +subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of +that name. +.P +Given the number, you can extract the substring directly, or use one of the +functions described in the previous section. For convenience, there are also +two functions that do the whole job. +.P +Most of the arguments of \fBpcre_copy_named_substring()\fP and +\fBpcre_get_named_substring()\fP are the same as those for the similarly named +functions that extract by number. As these are described in the previous +section, they are not re-described here. There are just two differences: +.P +First, instead of a substring number, a substring name is given. Second, there +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. +.P +These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they +then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as +appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names, +the behaviour may not be what you want (see the next section). +.P +\fBWarning:\fP If the pattern uses the (?| feature to set up multiple +subpatterns with the same number, as described in the +.\" HTML <a href="pcrepattern.html#dupsubpatternnumber"> +.\" </a> +section on duplicate subpattern numbers +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +page, you cannot use names to distinguish the different subpatterns, because +names are not included in the compiled code. The matching process uses only +numbers. For this reason, the use of different names for subpatterns of the +same number causes an error at compile time. +. +. +.SH "DUPLICATE SUBPATTERN NAMES" +.rs +.sp +.nf +.B int pcre_get_stringtable_entries(const pcre *\fIcode\fP, +.B " const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);" +.fi +.PP +When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns +are not required to be unique. (Duplicate names are always allowed for +subpatterns with the same number, created by using the (?| feature. Indeed, if +such subpatterns are named, they are required to use the same names.) +.P +Normally, patterns with duplicate names are such that in any one match, only +one of the named subpatterns participates. An example is shown in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +.P +When duplicates are present, \fBpcre_copy_named_substring()\fP and +\fBpcre_get_named_substring()\fP return the first substring corresponding to +the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is +returned; no data is returned. The \fBpcre_get_stringnumber()\fP function +returns one of the numbers that are associated with the name, but it is not +defined which it is. +.P +If you want to get full details of all captured substrings for a given name, +you must use the \fBpcre_get_stringtable_entries()\fP function. The first +argument is the compiled pattern, and the second is the name. The third and +fourth are pointers to variables which are updated by the function. After it +has run, they point to the first and last entries in the name-to-number table +for the given name. The function itself returns the length of each entry, or +PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is +described above in the section entitled \fIInformation about a pattern\fP +.\" HTML <a href="#infoaboutpattern"> +.\" </a> +above. +.\" +Given all the relevant entries for the name, you can extract each of their +numbers, and hence the captured data, if any. +. +. +.SH "FINDING ALL POSSIBLE MATCHES" +.rs +.sp +The traditional matching function uses a similar algorithm to Perl, which stops +when it finds the first match, starting at a given point in the subject. If you +want to find all possible matches, or the longest possible match, consider +using the alternative matching function (see below) instead. If you cannot use +the alternative function, but still need to find all possible matches, you +can kludge it up by making use of the callout facility, which is described in +the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +.P +What you have to do is to insert a callout right at the end of the pattern. +When your callout function is called, extract and save the current matched +substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try +other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP +will yield PCRE_ERROR_NOMATCH. +. +. +.SH "OBTAINING AN ESTIMATE OF STACK USAGE" +.rs +.sp +Matching certain patterns using \fBpcre_exec()\fP can use a lot of process +stack, which in certain environments can be rather limited in size. Some users +find it helpful to have an estimate of the amount of stack that is used by +\fBpcre_exec()\fP, to help them set recursion limits, as described in the +.\" HREF +\fBpcrestack\fP +.\" +documentation. The estimate that is output by \fBpcretest\fP when called with +the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with +the values NULL, NULL, NULL, -999, and -999 for its first five arguments. +.P +Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns +the negative error code PCRE_ERROR_NULL, but with this special combination of +arguments, it returns instead a negative number whose absolute value is the +approximate stack frame size in bytes. (A negative number is used so that it is +clear that no match has happened.) The value is approximate because in some +cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two +additional variables on the stack. +.P +If PCRE has been compiled to use the heap instead of the stack for recursion, +the value returned is the size of each block that is obtained from the heap. +. +. +.\" HTML <a name="dfamatch"></a> +.SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION" +.rs +.sp +.nf +.B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP," +.B " const char *\fIsubject\fP, int \fIlength\fP, int \fIstartoffset\fP," +.B " int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP," +.B " int *\fIworkspace\fP, int \fIwscount\fP);" +.fi +.P +The function \fBpcre_dfa_exec()\fP is called to match a subject string against +a compiled pattern, using a matching algorithm that scans the subject string +just once, and does not backtrack. This has different characteristics to the +normal algorithm, and is not compatible with Perl. Some of the features of PCRE +patterns are not supported. Nevertheless, there are times when this kind of +matching can be useful. For a discussion of the two matching algorithms, and a +list of features that \fBpcre_dfa_exec()\fP does not support, see the +.\" HREF +\fBpcrematching\fP +.\" +documentation. +.P +The arguments for the \fBpcre_dfa_exec()\fP function are the same as for +\fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a +different way, and this is described below. The other common arguments are used +in the same way as for \fBpcre_exec()\fP, so their description is not repeated +here. +.P +The two additional arguments provide workspace for the function. The workspace +vector should contain at least 20 elements. It is used for keeping track of +multiple paths through the pattern tree. More workspace will be needed for +patterns and subjects where there are a lot of potential matches. +.P +Here is an example of a simple call to \fBpcre_dfa_exec()\fP: +.sp + int rc; + int ovector[10]; + int wspace[20]; + rc = pcre_dfa_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector of integers for substring information */ + 10, /* number of elements (NOT size in bytes) */ + wspace, /* working space vector */ + 20); /* number of elements (NOT size in bytes) */ +. +.SS "Option bits for \fBpcre_dfa_exec()\fP" +.rs +.sp +The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be +zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP, +PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, +PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, +PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. +All but the last four of these are exactly the same as for \fBpcre_exec()\fP, +so their description is not repeated here. +.sp + PCRE_PARTIAL_HARD + PCRE_PARTIAL_SOFT +.sp +These have the same general effect as they do for \fBpcre_exec()\fP, but the +details are slightly different. When PCRE_PARTIAL_HARD is set for +\fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject +is reached and there is still at least one matching possibility that requires +additional characters. This happens even if some complete matches have also +been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH +is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached, +there have been no complete matches, but there is still at least one matching +possibility. The portion of the string that was inspected when the longest +partial match was found is set as the first matching string in both cases. +There is a more detailed discussion of partial and multi-segment matching, with +examples, in the +.\" HREF +\fBpcrepartial\fP +.\" +documentation. +.sp + PCRE_DFA_SHORTEST +.sp +Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as +soon as it has found one match. Because of the way the alternative algorithm +works, this is necessarily the shortest possible match at the first possible +matching point in the subject string. +.sp + PCRE_DFA_RESTART +.sp +When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it +again, with additional subject characters, and have it continue with the same +match. The PCRE_DFA_RESTART option requests this action; when it is set, the +\fIworkspace\fP and \fIwscount\fP options must reference the same vector as +before because data about the match so far is left in them after a partial +match. There is more discussion of this facility in the +.\" HREF +\fBpcrepartial\fP +.\" +documentation. +. +. +.SS "Successful returns from \fBpcre_dfa_exec()\fP" +.rs +.sp +When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one +substring in the subject. Note, however, that all the matches from one run of +the function start at the same point in the subject. The shorter matches are +all initial substrings of the longer matches. For example, if the pattern +.sp + <.*> +.sp +is matched against the string +.sp + This is <something> <something else> <something further> no more +.sp +the three matched strings are +.sp + <something> + <something> <something else> + <something> <something else> <something further> +.sp +On success, the yield of the function is a number greater than zero, which is +the number of matched substrings. The substrings themselves are returned in +\fIovector\fP. Each string uses two elements; the first is the offset to the +start, and the second is the offset to the end. In fact, all the strings have +the same start offset. (Space could have been saved by giving this only once, +but it was decided to retain some compatibility with the way \fBpcre_exec()\fP +returns data, even though the meaning of the strings is different.) +.P +The strings are returned in reverse order of length; that is, the longest +matching string is given first. If there were too many matches to fit into +\fIovector\fP, the yield of the function is zero, and the vector is filled with +the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use +the entire \fIovector\fP for returning matched strings. +.P +NOTE: PCRE's "auto-possessification" optimization usually applies to character +repeats at the end of a pattern (as well as internally). For example, the +pattern "a\ed+" is compiled as if it were "a\ed++" because there is no point +even considering the possibility of backtracking into the repeated digits. For +DFA matching, this means that only one possible match is found. If you really +do want multiple matches in such cases, either use an ungreedy repeat +("a\ed+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. +. +. +.SS "Error returns from \fBpcre_dfa_exec()\fP" +.rs +.sp +The \fBpcre_dfa_exec()\fP function returns a negative number when it fails. +Many of the errors are the same as for \fBpcre_exec()\fP, and these are +described +.\" HTML <a href="#errorlist"> +.\" </a> +above. +.\" +There are in addition the following errors that are specific to +\fBpcre_dfa_exec()\fP: +.sp + PCRE_ERROR_DFA_UITEM (-16) +.sp +This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern +that it does not support, for instance, the use of \eC or a back reference. +.sp + PCRE_ERROR_DFA_UCOND (-17) +.sp +This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that +uses a back reference for the condition, or a test for recursion in a specific +group. These are not supported. +.sp + PCRE_ERROR_DFA_UMLIMIT (-18) +.sp +This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP +block that contains a setting of the \fImatch_limit\fP or +\fImatch_limit_recursion\fP fields. This is not supported (these fields are +meaningless for DFA matching). +.sp + PCRE_ERROR_DFA_WSSIZE (-19) +.sp +This return is given if \fBpcre_dfa_exec()\fP runs out of space in the +\fIworkspace\fP vector. +.sp + PCRE_ERROR_DFA_RECURSE (-20) +.sp +When a recursive subpattern is processed, the matching function calls itself +recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This +error is given if the output vector is not large enough. This should be +extremely rare, as a vector of size 1000 is used. +.sp + PCRE_ERROR_DFA_BADRESTART (-30) +.sp +When \fBpcre_dfa_exec()\fP is called with the \fBPCRE_DFA_RESTART\fP option, +some plausibility checks are made on the contents of the workspace, which +should contain data about the previous partial match. If any of these checks +fail, this error is given. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), +\fBpcrecpp(3)\fP(3), \fBpcrematching\fP(3), \fBpcrepartial\fP(3), +\fBpcreposix\fP(3), \fBpcreprecompile\fP(3), \fBpcresample\fP(3), +\fBpcrestack\fP(3). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 09 February 2014 +Copyright (c) 1997-2014 University of Cambridge. +.fi diff --git a/doc/pcrebuild.3 b/doc/pcrebuild.3 new file mode 100644 index 0000000..403f2ae --- /dev/null +++ b/doc/pcrebuild.3 @@ -0,0 +1,550 @@ +.TH PCREBUILD 3 "12 May 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +. +. +.SH "BUILDING PCRE" +.rs +.sp +PCRE is distributed with a \fBconfigure\fP script that can be used to build the +library in Unix-like environments using the applications known as Autotools. +Also in the distribution are files to support building using \fBCMake\fP +instead of \fBconfigure\fP. The text file +.\" HTML <a href="README.txt"> +.\" </a> +\fBREADME\fP +.\" +contains general information about building with Autotools (some of which is +repeated below), and also has some comments about building on various operating +systems. There is a lot more information about building PCRE without using +Autotools (including information about using \fBCMake\fP and building "by +hand") in the text file called +.\" HTML <a href="NON-AUTOTOOLS-BUILD.txt"> +.\" </a> +\fBNON-AUTOTOOLS-BUILD\fP. +.\" +You should consult this file as well as the +.\" HTML <a href="README.txt"> +.\" </a> +\fBREADME\fP +.\" +file if you are building in a non-Unix-like environment. +. +. +.SH "PCRE BUILD-TIME OPTIONS" +.rs +.sp +The rest of this document describes the optional features of PCRE that can be +selected when the library is compiled. It assumes use of the \fBconfigure\fP +script, where the optional features are selected or deselected by providing +options to \fBconfigure\fP before running the \fBmake\fP command. However, the +same options can be selected in both Unix-like and non-Unix-like environments +using the GUI facility of \fBcmake-gui\fP if you are using \fBCMake\fP instead +of \fBconfigure\fP to build PCRE. +.P +If you are not using Autotools or \fBCMake\fP, option selection can be done by +editing the \fBconfig.h\fP file, or by passing parameter settings to the +compiler, as described in +.\" HTML <a href="NON-AUTOTOOLS-BUILD.txt"> +.\" </a> +\fBNON-AUTOTOOLS-BUILD\fP. +.\" +.P +The complete list of options for \fBconfigure\fP (which includes the standard +ones such as the selection of the installation directory) can be obtained by +running +.sp + ./configure --help +.sp +The following sections include descriptions of options whose names begin with +--enable or --disable. These settings specify changes to the defaults for the +\fBconfigure\fP command. Because of the way that \fBconfigure\fP works, +--enable and --disable always come in pairs, so the complementary option always +exists as well, but as it specifies the default, it is not described. +. +. +.SH "BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES" +.rs +.sp +By default, a library called \fBlibpcre\fP is built, containing functions that +take string arguments contained in vectors of bytes, either as single-byte +characters, or interpreted as UTF-8 strings. You can also build a separate +library, called \fBlibpcre16\fP, in which strings are contained in vectors of +16-bit data units and interpreted either as single-unit characters or UTF-16 +strings, by adding +.sp + --enable-pcre16 +.sp +to the \fBconfigure\fP command. You can also build yet another separate +library, called \fBlibpcre32\fP, in which strings are contained in vectors of +32-bit data units and interpreted either as single-unit characters or UTF-32 +strings, by adding +.sp + --enable-pcre32 +.sp +to the \fBconfigure\fP command. If you do not want the 8-bit library, add +.sp + --disable-pcre8 +.sp +as well. At least one of the three libraries must be built. Note that the C++ +and POSIX wrappers are for the 8-bit library only, and that \fBpcregrep\fP is +an 8-bit program. None of these are built if you select only the 16-bit or +32-bit libraries. +. +. +.SH "BUILDING SHARED AND STATIC LIBRARIES" +.rs +.sp +The Autotools PCRE building process uses \fBlibtool\fP to build both shared and +static libraries by default. You can suppress one of these by adding one of +.sp + --disable-shared + --disable-static +.sp +to the \fBconfigure\fP command, as required. +. +. +.SH "C++ SUPPORT" +.rs +.sp +By default, if the 8-bit library is being built, the \fBconfigure\fP script +will search for a C++ compiler and C++ header files. If it finds them, it +automatically builds the C++ wrapper library (which supports only 8-bit +strings). You can disable this by adding +.sp + --disable-cpp +.sp +to the \fBconfigure\fP command. +. +. +.SH "UTF-8, UTF-16 AND UTF-32 SUPPORT" +.rs +.sp +To build PCRE with support for UTF Unicode character strings, add +.sp + --enable-utf +.sp +to the \fBconfigure\fP command. This setting applies to all three libraries, +adding support for UTF-8 to the 8-bit library, support for UTF-16 to the 16-bit +library, and support for UTF-32 to the to the 32-bit library. There are no +separate options for enabling UTF-8, UTF-16 and UTF-32 independently because +that would allow ridiculous settings such as requesting UTF-16 support while +building only the 8-bit library. It is not possible to build one library with +UTF support and another without in the same configuration. (For backwards +compatibility, --enable-utf8 is a synonym of --enable-utf.) +.P +Of itself, this setting does not make PCRE treat strings as UTF-8, UTF-16 or +UTF-32. As well as compiling PCRE with this option, you also have have to set +the PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as appropriate) when you call +one of the pattern compiling functions. +.P +If you set --enable-utf when compiling in an EBCDIC environment, PCRE expects +its input to be either ASCII or UTF-8 (depending on the run-time option). It is +not possible to support both EBCDIC and UTF-8 codes in the same version of the +library. Consequently, --enable-utf and --enable-ebcdic are mutually +exclusive. +. +. +.SH "UNICODE CHARACTER PROPERTY SUPPORT" +.rs +.sp +UTF support allows the libraries to process character codepoints up to 0x10ffff +in the strings that they handle. On its own, however, it does not provide any +facilities for accessing the properties of such characters. If you want to be +able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode +character properties, you must add +.sp + --enable-unicode-properties +.sp +to the \fBconfigure\fP command. This implies UTF support, even if you have +not explicitly requested it. +.P +Including Unicode property support adds around 30K of tables to the PCRE +library. Only the general category properties such as \fILu\fP and \fINd\fP are +supported. Details are given in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +. +. +.SH "JUST-IN-TIME COMPILER SUPPORT" +.rs +.sp +Just-in-time compiler support is included in the build by specifying +.sp + --enable-jit +.sp +This support is available only for certain hardware architectures. If this +option is set for an unsupported architecture, a compile time error occurs. +See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for a discussion of JIT usage. When JIT support is enabled, +pcregrep automatically makes use of it, unless you add +.sp + --disable-pcregrep-jit +.sp +to the "configure" command. +. +. +.SH "CODE VALUE OF NEWLINE" +.rs +.sp +By default, PCRE interprets the linefeed (LF) character as indicating the end +of a line. This is the normal newline character on Unix-like systems. You can +compile PCRE to use carriage return (CR) instead, by adding +.sp + --enable-newline-is-cr +.sp +to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option, +which explicitly specifies linefeed as the newline character. +.sp +Alternatively, you can specify that line endings are to be indicated by the two +character sequence CRLF. If you want this, add +.sp + --enable-newline-is-crlf +.sp +to the \fBconfigure\fP command. There is a fourth option, specified by +.sp + --enable-newline-is-anycrlf +.sp +which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as +indicating a line ending. Finally, a fifth option, specified by +.sp + --enable-newline-is-any +.sp +causes PCRE to recognize any Unicode newline sequence. +.P +Whatever line ending convention is selected when PCRE is built can be +overridden when the library functions are called. At build time it is +conventional to use the standard for your operating system. +. +. +.SH "WHAT \eR MATCHES" +.rs +.sp +By default, the sequence \eR in a pattern matches any Unicode newline sequence, +whatever has been selected as the line ending sequence. If you specify +.sp + --enable-bsr-anycrlf +.sp +the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is +selected when PCRE is built can be overridden when the library functions are +called. +. +. +.SH "POSIX MALLOC USAGE" +.rs +.sp +When the 8-bit library is called through the POSIX interface (see the +.\" HREF +\fBpcreposix\fP +.\" +documentation), additional working storage is required for holding the pointers +to capturing substrings, because PCRE requires three integers per substring, +whereas the POSIX interface provides only two. If the number of expected +substrings is small, the wrapper function uses space on the stack, because this +is faster than using \fBmalloc()\fP for each call. The default threshold above +which the stack is no longer used is 10; it can be changed by adding a setting +such as +.sp + --with-posix-malloc-threshold=20 +.sp +to the \fBconfigure\fP command. +. +. +.SH "HANDLING VERY LARGE PATTERNS" +.rs +.sp +Within a compiled pattern, offset values are used to point from one part to +another (for example, from an opening parenthesis to an alternation +metacharacter). By default, in the 8-bit and 16-bit libraries, two-byte values +are used for these offsets, leading to a maximum size for a compiled pattern of +around 64K. This is sufficient to handle all but the most gigantic patterns. +Nevertheless, some people do want to process truly enormous patterns, so it is +possible to compile PCRE to use three-byte or four-byte offsets by adding a +setting such as +.sp + --with-link-size=3 +.sp +to the \fBconfigure\fP command. The value given must be 2, 3, or 4. For the +16-bit library, a value of 3 is rounded up to 4. In these libraries, using +longer offsets slows down the operation of PCRE because it has to load +additional data when handling them. For the 32-bit library the value is always +4 and cannot be overridden; the value of --with-link-size is ignored. +. +. +.SH "AVOIDING EXCESSIVE STACK USAGE" +.rs +.sp +When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking +by making recursive calls to an internal function called \fBmatch()\fP. In +environments where the size of the stack is limited, this can severely limit +PCRE's operation. (The Unix environment does not usually suffer from this +problem, but it may sometimes be necessary to increase the maximum stack size. +There is a discussion in the +.\" HREF +\fBpcrestack\fP +.\" +documentation.) An alternative approach to recursion that uses memory from the +heap to remember data, instead of using recursive function calls, has been +implemented to work round the problem of limited stack size. If you want to +build a version of PCRE that works this way, add +.sp + --disable-stack-for-recursion +.sp +to the \fBconfigure\fP command. With this configuration, PCRE will use the +\fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory +management functions. By default these point to \fBmalloc()\fP and +\fBfree()\fP, but you can replace the pointers so that your own functions are +used instead. +.P +Separate functions are provided rather than using \fBpcre_malloc\fP and +\fBpcre_free\fP because the usage is very predictable: the block sizes +requested are always the same, and the blocks are always freed in reverse +order. A calling program might be able to implement optimized functions that +perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more +slowly when built in this way. This option affects only the \fBpcre_exec()\fP +function; it is not relevant for \fBpcre_dfa_exec()\fP. +. +. +.SH "LIMITING PCRE RESOURCE USAGE" +.rs +.sp +Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly +(sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP +function. By controlling the maximum number of times this function may be +called during a single matching operation, a limit can be placed on the +resources used by a single call to \fBpcre_exec()\fP. The limit can be changed +at run time, as described in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. The default is 10 million, but this can be changed by adding a +setting such as +.sp + --with-match-limit=500000 +.sp +to the \fBconfigure\fP command. This setting has no effect on the +\fBpcre_dfa_exec()\fP matching function. +.P +In some environments it is desirable to limit the depth of recursive calls of +\fBmatch()\fP more strictly than the total number of calls, in order to +restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion +is specified) that is used. A second limit controls this; it defaults to the +value that is set for --with-match-limit, which imposes no additional +constraints. However, you can set a lower limit by adding, for example, +.sp + --with-match-limit-recursion=10000 +.sp +to the \fBconfigure\fP command. This value can also be overridden at run time. +. +. +.SH "CREATING CHARACTER TABLES AT BUILD TIME" +.rs +.sp +PCRE uses fixed tables for processing characters whose code values are less +than 256. By default, PCRE is built with a set of tables that are distributed +in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes +only. If you add +.sp + --enable-rebuild-chartables +.sp +to the \fBconfigure\fP command, the distributed tables are no longer used. +Instead, a program called \fBdftables\fP is compiled and run. This outputs the +source for new set of tables, created in the default locale of your C run-time +system. (This method of replacing the tables does not work if you are cross +compiling, because \fBdftables\fP is run on the local host. If you need to +create alternative tables when cross compiling, you will have to do so "by +hand".) +. +. +.SH "USING EBCDIC CODE" +.rs +.sp +PCRE assumes by default that it will run in an environment where the character +code is ASCII (or Unicode, which is a superset of ASCII). This is the case for +most computer operating systems. PCRE can, however, be compiled to run in an +EBCDIC environment by adding +.sp + --enable-ebcdic +.sp +to the \fBconfigure\fP command. This setting implies +--enable-rebuild-chartables. You should only use it if you know that you are in +an EBCDIC environment (for example, an IBM mainframe operating system). The +--enable-ebcdic option is incompatible with --enable-utf. +.P +The EBCDIC character that corresponds to an ASCII LF is assumed to have the +value 0x15 by default. However, in some EBCDIC environments, 0x25 is used. In +such an environment you should use +.sp + --enable-ebcdic-nl25 +.sp +as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR has the +same value as in ASCII, namely, 0x0d. Whichever of 0x15 and 0x25 is \fInot\fP +chosen as LF is made to correspond to the Unicode NEL character (which, in +Unicode, is 0x85). +.P +The options that select newline behaviour, such as --enable-newline-is-cr, +and equivalent run-time options, refer to these character values in an EBCDIC +environment. +. +. +.SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT" +.rs +.sp +By default, \fBpcregrep\fP reads all files as plain text. You can build it so +that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads +them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of +.sp + --enable-pcregrep-libz + --enable-pcregrep-libbz2 +.sp +to the \fBconfigure\fP command. These options naturally require that the +relevant libraries are installed on your system. Configuration will fail if +they are not. +. +. +.SH "PCREGREP BUFFER SIZE" +.rs +.sp +\fBpcregrep\fP uses an internal buffer to hold a "window" on the file it is +scanning, in order to be able to output "before" and "after" lines when it +finds a match. The size of the buffer is controlled by a parameter whose +default value is 20K. The buffer itself is three times this size, but because +of the way it is used for holding "before" lines, the longest line that is +guaranteed to be processable is the parameter size. You can change the default +parameter value by adding, for example, +.sp + --with-pcregrep-bufsize=50K +.sp +to the \fBconfigure\fP command. The caller of \fPpcregrep\fP can, however, +override this value by specifying a run-time option. +. +. +.SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT" +.rs +.sp +If you add +.sp + --enable-pcretest-libreadline +.sp +to the \fBconfigure\fP command, \fBpcretest\fP is linked with the +\fBlibreadline\fP library, and when its input is from a terminal, it reads it +using the \fBreadline()\fP function. This provides line-editing and history +facilities. Note that \fBlibreadline\fP is GPL-licensed, so if you distribute a +binary of \fBpcretest\fP linked in this way, there may be licensing issues. +.P +Setting this option causes the \fB-lreadline\fP option to be added to the +\fBpcretest\fP build. In many operating environments with a sytem-installed +\fBlibreadline\fP this is sufficient. However, in some environments (e.g. +if an unmodified distribution version of readline is in use), some extra +configuration may be necessary. The INSTALL file for \fBlibreadline\fP says +this: +.sp + "Readline uses the termcap functions, but does not link with the + termcap or curses library itself, allowing applications which link + with readline the to choose an appropriate library." +.sp +If your environment has not been set up so that an appropriate library is +automatically included, you may need to add something like +.sp + LIBS="-ncurses" +.sp +immediately before the \fBconfigure\fP command. +. +. +.SH "DEBUGGING WITH VALGRIND SUPPORT" +.rs +.sp +By adding the +.sp + --enable-valgrind +.sp +option to to the \fBconfigure\fP command, PCRE will use valgrind annotations +to mark certain memory regions as unaddressable. This allows it to detect +invalid memory accesses, and is mostly useful for debugging PCRE itself. +. +. +.SH "CODE COVERAGE REPORTING" +.rs +.sp +If your C compiler is gcc, you can build a version of PCRE that can generate a +code coverage report for its test suite. To enable this, you must install +\fBlcov\fP version 1.6 or above. Then specify +.sp + --enable-coverage +.sp +to the \fBconfigure\fP command and build PCRE in the usual way. +.P +Note that using \fBccache\fP (a caching C compiler) is incompatible with code +coverage reporting. If you have configured \fBccache\fP to run automatically +on your system, you must set the environment variable +.sp + CCACHE_DISABLE=1 +.sp +before running \fBmake\fP to build PCRE, so that \fBccache\fP is not used. +.P +When --enable-coverage is used, the following addition targets are added to the +\fIMakefile\fP: +.sp + make coverage +.sp +This creates a fresh coverage report for the PCRE test suite. It is equivalent +to running "make coverage-reset", "make coverage-baseline", "make check", and +then "make coverage-report". +.sp + make coverage-reset +.sp +This zeroes the coverage counters, but does nothing else. +.sp + make coverage-baseline +.sp +This captures baseline coverage information. +.sp + make coverage-report +.sp +This creates the coverage report. +.sp + make coverage-clean-report +.sp +This removes the generated coverage report without cleaning the coverage data +itself. +.sp + make coverage-clean-data +.sp +This removes the captured coverage data without removing the coverage files +created at compile time (*.gcno). +.sp + make coverage-clean +.sp +This cleans all coverage data including the generated coverage report. For more +information about code coverage, see the \fBgcov\fP and \fBlcov\fP +documentation. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcreapi\fP(3), \fBpcre16\fP, \fBpcre32\fP, \fBpcre_config\fP(3). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 May 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrecallout.3 b/doc/pcrecallout.3 new file mode 100644 index 0000000..8ebc995 --- /dev/null +++ b/doc/pcrecallout.3 @@ -0,0 +1,255 @@ +.TH PCRECALLOUT 3 "12 November 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.B int (*pcre_callout)(pcre_callout_block *); +.PP +.B int (*pcre16_callout)(pcre16_callout_block *); +.PP +.B int (*pcre32_callout)(pcre32_callout_block *); +. +.SH DESCRIPTION +.rs +.sp +PCRE provides a feature called "callout", which is a means of temporarily +passing control to the caller of PCRE in the middle of pattern matching. The +caller of PCRE provides an external function by putting its entry point in the +global variable \fIpcre_callout\fP (\fIpcre16_callout\fP for the 16-bit +library, \fIpcre32_callout\fP for the 32-bit library). By default, this +variable contains NULL, which disables all calling out. +.P +Within a regular expression, (?C) indicates the points at which the external +function is to be called. Different callout points can be identified by putting +a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +.sp + (?C1)abc(?C2)def +.sp +If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled, PCRE +automatically inserts callouts, all with number 255, before each item in the +pattern. For example, if PCRE_AUTO_CALLOUT is used with the pattern +.sp + A(\ed{2}|--) +.sp +it is processed as if it were +.sp +(?C255)A(?C255)((?C255)\ed{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255) +.sp +Notice that there is a callout before and after each parenthesis and +alternation bar. If the pattern contains a conditional group whose condition is +an assertion, an automatic callout is inserted immediately before the +condition. Such a callout may also be inserted explicitly, for example: +.sp + (?(?C9)(?=a)ab|de) +.sp +This applies only to assertion conditions (because they are themselves +independent groups). +.P +Automatic callouts can be used for tracking the progress of pattern matching. +The +.\" HREF +\fBpcretest\fP +.\" +program has a pattern qualifier (/C) that sets automatic callouts; when it is +used, the output indicates how the pattern is being matched. This is useful +information when you are trying to optimize the performance of a particular +pattern. +. +. +.SH "MISSING CALLOUTS" +.rs +.sp +You should be aware that, because of optimizations in the way PCRE compiles and +matches patterns, callouts sometimes do not happen exactly as you might expect. +.P +At compile time, PCRE "auto-possessifies" repeated items when it knows that +what follows cannot be part of the repeat. For example, a+[bc] is compiled as +if it were a++[bc]. The \fBpcretest\fP output when this pattern is anchored and +then applied with automatic callouts to the string "aaaa" is: +.sp + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + No match +.sp +This indicates that when matching [bc] fails, there is no backtracking into a+ +and therefore the callouts that would be taken for the backtracks do not occur. +You can disable the auto-possessify feature by passing PCRE_NO_AUTO_POSSESS +to \fBpcre_compile()\fP, or starting the pattern with (*NO_AUTO_POSSESS). If +this is done in \fBpcretest\fP (using the /O qualifier), the output changes to +this: +.sp + --->aaaa + +0 ^ ^ + +1 ^ a+ + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^ ^ [bc] + +3 ^^ [bc] + No match +.sp +This time, when matching [bc] fails, the matcher backtracks into a+ and tries +again, repeatedly, until a+ itself fails. +.P +Other optimizations that provide fast "no match" results also affect callouts. +For example, if the pattern is +.sp + ab(?C4)cd +.sp +PCRE knows that any matching string must contain the letter "d". If the subject +string is "abyz", the lack of "d" means that matching doesn't ever start, and +the callout is never reached. However, with "abyd", though the result is still +no match, the callout is obeyed. +.P +If the pattern is studied, PCRE knows the minimum length of a matching string, +and will immediately give a "no match" return without actually running a match +if the subject is not long enough, or, for unanchored patterns, if it has +been scanned far enough. +.P +You can disable these optimizations by passing the PCRE_NO_START_OPTIMIZE +option to the matching function, or by starting the pattern with +(*NO_START_OPT). This slows down the matching process, but does ensure that +callouts such as the example above are obeyed. +. +. +.SH "THE CALLOUT INTERFACE" +.rs +.sp +During matching, when PCRE reaches a callout point, the external function +defined by \fIpcre_callout\fP or \fIpcre[16|32]_callout\fP is called (if it is +set). This applies to both normal and DFA matching. The only argument to the +callout function is a pointer to a \fBpcre_callout\fP or +\fBpcre[16|32]_callout\fP block. These structures contains the following +fields: +.sp + int \fIversion\fP; + int \fIcallout_number\fP; + int *\fIoffset_vector\fP; + const char *\fIsubject\fP; (8-bit version) + PCRE_SPTR16 \fIsubject\fP; (16-bit version) + PCRE_SPTR32 \fIsubject\fP; (32-bit version) + int \fIsubject_length\fP; + int \fIstart_match\fP; + int \fIcurrent_position\fP; + int \fIcapture_top\fP; + int \fIcapture_last\fP; + void *\fIcallout_data\fP; + int \fIpattern_position\fP; + int \fInext_item_length\fP; + const unsigned char *\fImark\fP; (8-bit version) + const PCRE_UCHAR16 *\fImark\fP; (16-bit version) + const PCRE_UCHAR32 *\fImark\fP; (32-bit version) +.sp +The \fIversion\fP field is an integer containing the version number of the +block format. The initial version was 0; the current version is 2. The version +number will change again in future if additional fields are added, but the +intention is never to remove any of the existing fields. +.P +The \fIcallout_number\fP field contains the number of the callout, as compiled +into the pattern (that is, the number after ?C for manual callouts, and 255 for +automatically generated callouts). +.P +The \fIoffset_vector\fP field is a pointer to the vector of offsets that was +passed by the caller to the matching function. When \fBpcre_exec()\fP or +\fBpcre[16|32]_exec()\fP is used, the contents can be inspected, in order to +extract substrings that have been matched so far, in the same way as for +extracting substrings after a match has completed. For the DFA matching +functions, this field is not useful. +.P +The \fIsubject\fP and \fIsubject_length\fP fields contain copies of the values +that were passed to the matching function. +.P +The \fIstart_match\fP field normally contains the offset within the subject at +which the current match attempt started. However, if the escape sequence \eK +has been encountered, this value is changed to reflect the modified starting +point. If the pattern is not anchored, the callout function may be called +several times from the same point in the pattern for different starting points +in the subject. +.P +The \fIcurrent_position\fP field contains the offset within the subject of the +current match pointer. +.P +When the \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP is used, the +\fIcapture_top\fP field contains one more than the number of the highest +numbered captured substring so far. If no substrings have been captured, the +value of \fIcapture_top\fP is one. This is always the case when the DFA +functions are used, because they do not support captured substrings. +.P +The \fIcapture_last\fP field contains the number of the most recently captured +substring. However, when a recursion exits, the value reverts to what it was +outside the recursion, as do the values of all captured substrings. If no +substrings have been captured, the value of \fIcapture_last\fP is -1. This is +always the case for the DFA matching functions. +.P +The \fIcallout_data\fP field contains a value that is passed to a matching +function specifically so that it can be passed back in callouts. It is passed +in the \fIcallout_data\fP field of a \fBpcre_extra\fP or \fBpcre[16|32]_extra\fP +data structure. If no such data was passed, the value of \fIcallout_data\fP in +a callout block is NULL. There is a description of the \fBpcre_extra\fP +structure in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +.P +The \fIpattern_position\fP field is present from version 1 of the callout +structure. It contains the offset to the next item to be matched in the pattern +string. +.P +The \fInext_item_length\fP field is present from version 1 of the callout +structure. It contains the length of the next item to be matched in the pattern +string. When the callout immediately precedes an alternation bar, a closing +parenthesis, or the end of the pattern, the length is zero. When the callout +precedes an opening parenthesis, the length is that of the entire subpattern. +.P +The \fIpattern_position\fP and \fInext_item_length\fP fields are intended to +help in distinguishing between different automatic callouts, which all have the +same callout number. However, they are set for all callouts. +.P +The \fImark\fP field is present from version 2 of the callout structure. In +callouts from \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP it contains a +pointer to the zero-terminated name of the most recently passed (*MARK), +(*PRUNE), or (*THEN) item in the match, or NULL if no such items have been +passed. Instances of (*PRUNE) or (*THEN) without a name do not obliterate a +previous (*MARK). In callouts from the DFA matching functions this field always +contains NULL. +. +. +.SH "RETURN VALUES" +.rs +.sp +The external callout function returns an integer to PCRE. If the value is zero, +matching proceeds as normal. If the value is greater than zero, matching fails +at the current point, but the testing of other matching possibilities goes +ahead, just as if a lookahead assertion had failed. If the value is less than +zero, the match is abandoned, the matching function returns the negative value. +.P +Negative values should normally be chosen from the set of PCRE_ERROR_xxx +values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure. +The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; +it will never be used by PCRE itself. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 November 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrecompat.3 b/doc/pcrecompat.3 new file mode 100644 index 0000000..0cc4019 --- /dev/null +++ b/doc/pcrecompat.3 @@ -0,0 +1,200 @@ +.TH PCRECOMPAT 3 "10 November 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "DIFFERENCES BETWEEN PCRE AND PERL" +.rs +.sp +This document describes the differences in the ways that PCRE and Perl handle +regular expressions. The differences described here are with respect to Perl +versions 5.10 and above. +.P +1. PCRE has only a subset of Perl's Unicode support. Details of what it does +have are given in the +.\" HREF +\fBpcreunicode\fP +.\" +page. +.P +2. PCRE allows repeat quantifiers only on parenthesized assertions, but they do +not mean what you might think. For example, (?!a){3} does not assert that the +next three characters are not "a". It just asserts that the next character is +not "a" three times (in principle: PCRE optimizes this to run the assertion +just once). Perl allows repeat quantifiers on other assertions such as \eb, but +these do not seem to have any use. +.P +3. Capturing subpatterns that occur inside negative lookahead assertions are +counted, but their entries in the offsets vector are never set. Perl sometimes +(but not always) sets its numerical variables from inside negative assertions. +.P +4. Though binary zero characters are supported in the subject string, they are +not allowed in a pattern string because it is passed as a normal C string, +terminated by zero. The escape sequence \e0 can be used in the pattern to +represent a binary zero. +.P +5. The following Perl escape sequences are not supported: \el, \eu, \eL, +\eU, and \eN when followed by a character name or Unicode value. (\eN on its +own, matching a non-newline character, is supported.) In fact these are +implemented by Perl's general string-handling and are not part of its pattern +matching engine. If any of these are encountered by PCRE, an error is +generated by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set, +\eU and \eu are interpreted as JavaScript interprets them. +.P +6. The Perl escape sequences \ep, \eP, and \eX are supported only if PCRE is +built with Unicode character property support. The properties that can be +tested with \ep and \eP are limited to the general category properties such as +Lu and Nd, script names such as Greek or Han, and the derived properties Any +and L&. PCRE does support the Cs (surrogate) property, which Perl does not; the +Perl documentation says "Because Perl hides the need for the user to understand +the internal representation of Unicode characters, there is no need to +implement the somewhat messy concept of surrogates." +.P +7. PCRE does support the \eQ...\eE escape for quoting substrings. Characters in +between are treated as literals. This is slightly different from Perl in that $ +and @ are also handled as literals inside the quotes. In Perl, they cause +variable interpolation (but of course PCRE does not have variables). Note the +following examples: +.sp + Pattern PCRE matches Perl matches +.sp +.\" JOIN + \eQabc$xyz\eE abc$xyz abc followed by the + contents of $xyz + \eQabc\e$xyz\eE abc\e$xyz abc\e$xyz + \eQabc\eE\e$\eQxyz\eE abc$xyz abc$xyz +.sp +The \eQ...\eE sequence is recognized both inside and outside character classes. +.P +8. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) +constructions. However, there is support for recursive patterns. This is not +available in Perl 5.8, but it is in Perl 5.10. Also, the PCRE "callout" +feature allows an external function to be called during pattern matching. See +the +.\" HREF +\fBpcrecallout\fP +.\" +documentation for details. +.P +9. Subpatterns that are called as subroutines (whether or not recursively) are +always treated as atomic groups in PCRE. This is like Python, but unlike Perl. +Captured values that are set outside a subroutine call can be reference from +inside in PCRE, but not in Perl. There is a discussion that explains these +differences in more detail in the +.\" HTML <a href="pcrepattern.html#recursiondifference"> +.\" </a> +section on recursion differences from Perl +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +page. +.P +10. If any of the backtracking control verbs are used in a subpattern that is +called as a subroutine (whether or not recursively), their effect is confined +to that subpattern; it does not extend to the surrounding pattern. This is not +always the case in Perl. In particular, if (*THEN) is present in a group that +is called as a subroutine, its action is limited to that group, even if the +group does not contain any | characters. Note that such subpatterns are +processed as anchored at the point where they are tested. +.P +11. If a pattern contains more than one backtracking control verb, the first +one that is backtracked onto acts. For example, in the pattern +A(*COMMIT)B(*PRUNE)C a failure in B triggers (*COMMIT), but a failure in C +triggers (*PRUNE). Perl's behaviour is more complex; in many cases it is the +same as PCRE, but there are examples where it differs. +.P +12. Most backtracking verbs in assertions have their normal actions. They are +not confined to the assertion. +.P +13. There are some differences that are concerned with the settings of captured +strings when part of a pattern is repeated. For example, matching "aba" against +the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". +.P +14. PCRE's handling of duplicate subpattern numbers and duplicate subpattern +names is not as general as Perl's. This is a consequence of the fact the PCRE +works internally just with numbers, using an external table to translate +between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B), +where the two capturing parentheses have the same number but different names, +is not supported, and causes an error at compile time. If it were allowed, it +would not be possible to distinguish which parentheses matched, because both +names map to capturing subpattern number 1. To avoid this confusing situation, +an error is given at compile time. +.P +15. Perl recognizes comments in some places that PCRE does not, for example, +between the ( and ? at the start of a subpattern. If the /x modifier is set, +Perl allows white space between ( and ? (though current Perls warn that this is +deprecated) but PCRE never does, even if the PCRE_EXTENDED option is set. +.P +16. Perl, when in warning mode, gives warnings for character classes such as +[A-\ed] or [a-[:digit:]]. It then treats the hyphens as literals. PCRE has no +warning features, so it gives an error in these cases because they are almost +certainly user mistakes. +.P +17. In PCRE, the upper/lower case character properties Lu and Ll are not +affected when case-independent matching is specified. For example, \ep{Lu} +always matches an upper case letter. I think Perl has changed in this respect; +in the release at the time of writing (5.16), \ep{Lu} and \ep{Ll} match all +letters, regardless of case, when case independence is specified. +.P +18. PCRE provides some extensions to the Perl regular expression facilities. +Perl 5.10 includes new features that are not in earlier versions of Perl, some +of which (such as named parentheses) have been in PCRE for some time. This list +is with respect to Perl 5.10: +.sp +(a) Although lookbehind assertions in PCRE must match fixed length strings, +each alternative branch of a lookbehind assertion can match a different length +of string. Perl requires them all to have the same length. +.sp +(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ +meta-character matches only at the very end of the string. +.sp +(c) If PCRE_EXTRA is set, a backslash followed by a letter with no special +meaning is faulted. Otherwise, like Perl, the backslash is quietly ignored. +(Perl can be made to issue a warning.) +.sp +(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is +inverted, that is, by default they are not greedy, but if followed by a +question mark they are. +.sp +(e) PCRE_ANCHORED can be used at matching time to force a pattern to be tried +only at the first matching position in the subject string. +.sp +(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, and +PCRE_NO_AUTO_CAPTURE options for \fBpcre_exec()\fP have no Perl equivalents. +.sp +(g) The \eR escape sequence can be restricted to match only CR, LF, or CRLF +by the PCRE_BSR_ANYCRLF option. +.sp +(h) The callout facility is PCRE-specific. +.sp +(i) The partial matching facility is PCRE-specific. +.sp +(j) Patterns compiled by PCRE can be saved and re-used at a later time, even on +different hosts that have the other endianness. However, this does not apply to +optimized data created by the just-in-time compiler. +.sp +(k) The alternative matching functions (\fBpcre_dfa_exec()\fP, +\fBpcre16_dfa_exec()\fP and \fBpcre32_dfa_exec()\fP,) match in a different way +and are not Perl-compatible. +.sp +(l) PCRE recognizes some special sequences such as (*CR) at the start of +a pattern that set overall options that cannot be changed within the pattern. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 10 November 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrecpp.3 b/doc/pcrecpp.3 new file mode 100644 index 0000000..fbddd86 --- /dev/null +++ b/doc/pcrecpp.3 @@ -0,0 +1,348 @@ +.TH PCRECPP 3 "08 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions. +.SH "SYNOPSIS OF C++ WRAPPER" +.rs +.sp +.B #include <pcrecpp.h> +. +.SH DESCRIPTION +.rs +.sp +The C++ wrapper for PCRE was provided by Google Inc. Some additional +functionality was added by Giuseppe Maxia. This brief man page was constructed +from the notes in the \fIpcrecpp.h\fP file, which should be consulted for +further details. Note that the C++ wrapper supports only the original 8-bit +PCRE library. There is no 16-bit or 32-bit support at present. +. +. +.SH "MATCHING INTERFACE" +.rs +.sp +The "FullMatch" operation checks that supplied text matches a supplied pattern +exactly. If pointer arguments are supplied, it copies matched sub-strings that +match sub-patterns into them. +.sp + Example: successful match + pcrecpp::RE re("h.*o"); + re.FullMatch("hello"); +.sp + Example: unsuccessful match (requires full match): + pcrecpp::RE re("e"); + !re.FullMatch("hello"); +.sp + Example: creating a temporary RE object: + pcrecpp::RE("h.*o").FullMatch("hello"); +.sp +You can pass in a "const char*" or a "string" for "text". The examples below +tend to use a const char*. You can, as in the different examples above, store +the RE object explicitly in a variable or use a temporary RE object. The +examples below use one mode or the other arbitrarily. Either could correctly be +used for any of these examples. +.P +You must supply extra pointer arguments to extract matched subpieces. +.sp + Example: extracts "ruby" into "s" and 1234 into "i" + int i; + string s; + pcrecpp::RE re("(\e\ew+):(\e\ed+)"); + re.FullMatch("ruby:1234", &s, &i); +.sp + Example: does not try to extract any extra sub-patterns + re.FullMatch("ruby:1234", &s); +.sp + Example: does not try to extract into NULL + re.FullMatch("ruby:1234", NULL, &i); +.sp + Example: integer overflow causes failure + !re.FullMatch("ruby:1234567891234", NULL, &i); +.sp + Example: fails because there aren't enough sub-patterns: + !pcrecpp::RE("\e\ew+:\e\ed+").FullMatch("ruby:1234", &s); +.sp + Example: fails because string cannot be stored in integer + !pcrecpp::RE("(.*)").FullMatch("ruby", &i); +.sp +The provided pointer arguments can be pointers to any scalar numeric +type, or one of: +.sp + string (matched piece is copied to string) + StringPiece (StringPiece is mutated to point to matched piece) + T (where "bool T::ParseFrom(const char*, int)" exists) + NULL (the corresponding matched sub-pattern is not copied) +.sp +The function returns true iff all of the following conditions are satisfied: +.sp + a. "text" matches "pattern" exactly; +.sp + b. The number of matched sub-patterns is >= number of supplied + pointers; +.sp + c. The "i"th argument has a suitable type for holding the + string captured as the "i"th sub-pattern. If you pass in + void * NULL for the "i"th argument, or a non-void * NULL + of the correct type, or pass fewer arguments than the + number of sub-patterns, "i"th captured sub-pattern is + ignored. +.sp +CAVEAT: An optional sub-pattern that does not exist in the matched +string is assigned the empty string. Therefore, the following will +return false (because the empty string is not a valid number): +.sp + int number; + pcrecpp::RE::FullMatch("abc", "[a-z]+(\e\ed+)?", &number); +.sp +The matching interface supports at most 16 arguments per call. +If you need more, consider using the more general interface +\fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for +\fBDoMatch\fP. +.P +NOTE: Do not use \fBno_arg\fP, which is used internally to mark the end of a +list of optional arguments, as a placeholder for missing arguments, as this can +lead to segfaults. +. +. +.SH "QUOTING METACHARACTERS" +.rs +.sp +You can use the "QuoteMeta" operation to insert backslashes before all +potentially meaningful characters in a string. The returned string, used as a +regular expression, will exactly match the original string. +.sp + Example: + string quoted = RE::QuoteMeta(unquoted); +.sp +Note that it's legal to escape a character even if it has no special meaning in +a regular expression -- so this function does that. (This also makes it +identical to the perl function of the same name; see "perldoc -f quotemeta".) +For example, "1.5-2.0?" becomes "1\e.5\e-2\e.0\e?". +. +.SH "PARTIAL MATCHES" +.rs +.sp +You can use the "PartialMatch" operation when you want the pattern +to match any substring of the text. +.sp + Example: simple search for a string: + pcrecpp::RE("ell").PartialMatch("hello"); +.sp + Example: find first number in a string: + int number; + pcrecpp::RE re("(\e\ed+)"); + re.PartialMatch("x*100 + 20", &number); + assert(number == 100); +. +. +.SH "UTF-8 AND THE MATCHING INTERFACE" +.rs +.sp +By default, pattern and text are plain text, one byte per character. The UTF8 +flag, passed to the constructor, causes both pattern and string to be treated +as UTF-8 text, still a byte stream but potentially multiple bytes per +character. In practice, the text is likelier to be UTF-8 than the pattern, but +the match returned may depend on the UTF8 flag, so always use it when matching +UTF8 text. For example, "." will match one byte normally but with UTF8 set may +match up to three bytes of a multi-byte character. +.sp + Example: + pcrecpp::RE_Options options; + options.set_utf8(); + pcrecpp::RE re(utf8_pattern, options); + re.FullMatch(utf8_string); +.sp + Example: using the convenience function UTF8(): + pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8()); + re.FullMatch(utf8_string); +.sp +NOTE: The UTF8 flag is ignored if pcre was not configured with the + --enable-utf8 flag. +. +. +.SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE" +.rs +.sp +PCRE defines some modifiers to change the behavior of the regular expression +engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to +pass such modifiers to a RE class. Currently, the following modifiers are +supported: +.sp + modifier description Perl corresponding +.sp + PCRE_CASELESS case insensitive match /i + PCRE_MULTILINE multiple lines match /m + PCRE_DOTALL dot matches newlines /s + PCRE_DOLLAR_ENDONLY $ matches only at end N/A + PCRE_EXTRA strict escape parsing N/A + PCRE_EXTENDED ignore white spaces /x + PCRE_UTF8 handles UTF8 chars built-in + PCRE_UNGREEDY reverses * and *? N/A + PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*) +.sp +(*) Both Perl and PCRE allow non capturing parentheses by means of the +"?:" modifier within the pattern itself. e.g. (?:ab|cd) does not +capture, while (ab|cd) does. +.P +For a full account on how each modifier works, please check the +PCRE API reference page. +.P +For each modifier, there are two member functions whose name is made +out of the modifier in lowercase, without the "PCRE_" prefix. For +instance, PCRE_CASELESS is handled by +.sp + bool caseless() +.sp +which returns true if the modifier is set, and +.sp + RE_Options & set_caseless(bool) +.sp +which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be +accessed through the \fBset_match_limit()\fP and \fBmatch_limit()\fP member +functions. Setting \fImatch_limit\fP to a non-zero value will limit the +execution of pcre to keep it from doing bad things like blowing the stack or +taking an eternity to return a result. A value of 5000 is good enough to stop +stack blowup in a 2MB thread stack. Setting \fImatch_limit\fP to zero disables +match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP +which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE +recurses. \fBmatch_limit()\fP limits the number of matches PCRE does; +\fBmatch_limit_recursion()\fP limits the depth of internal recursion, and +therefore the amount of stack that is used. +.P +Normally, to pass one or more modifiers to a RE class, you declare +a \fIRE_Options\fP object, set the appropriate options, and pass this +object to a RE constructor. Example: +.sp + RE_Options opt; + opt.set_caseless(true); + if (RE("HELLO", opt).PartialMatch("hello world")) ... +.sp +RE_options has two constructors. The default constructor takes no arguments and +creates a set of flags that are off by default. The optional parameter +\fIoption_flags\fP is to facilitate transfer of legacy code from C programs. +This lets you do +.sp + RE(pattern, + RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str); +.sp +However, new code is better off doing +.sp + RE(pattern, + RE_Options().set_caseless(true).set_multiline(true)) + .PartialMatch(str); +.sp +If you are going to pass one of the most used modifiers, there are some +convenience functions that return a RE_Options class with the +appropriate modifier already set: \fBCASELESS()\fP, \fBUTF8()\fP, +\fBMULTILINE()\fP, \fBDOTALL\fP(), and \fBEXTENDED()\fP. +.P +If you need to set several options at once, and you don't want to go through +the pains of declaring a RE_Options object and setting several options, there +is a parallel method that give you such ability on the fly. You can concatenate +several \fBset_xxxxx()\fP member functions, since each of them returns a +reference to its class object. For example, to pass PCRE_CASELESS, +PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write: +.sp + RE(" ^ xyz \e\es+ .* blah$", + RE_Options() + .set_caseless(true) + .set_extended(true) + .set_multiline(true)).PartialMatch(sometext); +.sp +. +. +.SH "SCANNING TEXT INCREMENTALLY" +.rs +.sp +The "Consume" operation may be useful if you want to repeatedly +match regular expressions at the front of a string and skip over +them as they match. This requires use of the "StringPiece" type, +which represents a sub-range of a real string. Like RE, StringPiece +is defined in the pcrecpp namespace. +.sp + Example: read lines of the form "var = value" from a string. + string contents = ...; // Fill string somehow + pcrecpp::StringPiece input(contents); // Wrap in a StringPiece +.sp + string var; + int value; + pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en"); + while (re.Consume(&input, &var, &value)) { + ...; + } +.sp +Each successful call to "Consume" will set "var/value", and also +advance "input" so it points past the matched text. +.P +The "FindAndConsume" operation is similar to "Consume" but does not +anchor your match at the beginning of the string. For example, you +could extract all words from a string by repeatedly calling +.sp + pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word) +. +. +.SH "PARSING HEX/OCTAL/C-RADIX NUMBERS" +.rs +.sp +By default, if you pass a pointer to a numeric value, the +corresponding text is interpreted as a base-10 number. You can +instead wrap the pointer with a call to one of the operators Hex(), +Octal(), or CRadix() to interpret the text in another base. The +CRadix operator interprets C-style "0" (base-8) and "0x" (base-16) +prefixes, but defaults to base-10. +.sp + Example: + int a, b, c, d; + pcrecpp::RE re("(.*) (.*) (.*) (.*)"); + re.FullMatch("100 40 0100 0x40", + pcrecpp::Octal(&a), pcrecpp::Hex(&b), + pcrecpp::CRadix(&c), pcrecpp::CRadix(&d)); +.sp +will leave 64 in a, b, c, and d. +. +. +.SH "REPLACING PARTS OF STRINGS" +.rs +.sp +You can replace the first match of "pattern" in "str" with "rewrite". +Within "rewrite", backslash-escaped digits (\e1 to \e9) can be +used to insert text matching corresponding parenthesized group +from the pattern. \e0 in "rewrite" refers to the entire matching +text. For example: +.sp + string s = "yabba dabba doo"; + pcrecpp::RE("b+").Replace("d", &s); +.sp +will leave "s" containing "yada dabba doo". The result is true if the pattern +matches and a replacement occurs, false otherwise. +.P +\fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all +occurrences of the pattern in the string with the rewrite. Replacements are +not subject to re-matching. For example: +.sp + string s = "yabba dabba doo"; + pcrecpp::RE("b+").GlobalReplace("d", &s); +.sp +will leave "s" containing "yada dada doo". It returns the number of +replacements made. +.P +\fBExtract\fP is like \fBReplace\fP, except that if the pattern matches, +"rewrite" is copied into "out" (an additional argument) with substitutions. +The non-matching portions of "text" are ignored. Returns true iff a match +occurred and the extraction happened successfully; if no match occurs, the +string is left unaffected. +. +. +.SH AUTHOR +.rs +.sp +.nf +The C++ wrapper was contributed by Google Inc. +Copyright (c) 2007 Google Inc. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 08 January 2012 +.fi diff --git a/doc/pcredemo.3 b/doc/pcredemo.3 new file mode 100644 index 0000000..194629b --- /dev/null +++ b/doc/pcredemo.3 @@ -0,0 +1,424 @@ +.\" Start example. +.de EX +. nr mE \\n(.f +. nf +. nh +. ft CW +.. +. +. +.\" End example. +.de EE +. ft \\n(mE +. fi +. hy \\n(HY +.. +. +.EX +/************************************************* +* PCRE DEMONSTRATION PROGRAM * +*************************************************/ + +/* This is a demonstration program to illustrate the most straightforward ways +of calling the PCRE regular expression library from a C program. See the +pcresample documentation for a short discussion ("man pcresample" if you have +the PCRE man pages installed). + +In Unix-like environments, if PCRE is installed in your standard system +libraries, you should be able to compile this program using this command: + +gcc -Wall pcredemo.c -lpcre -o pcredemo + +If PCRE is not installed in a standard place, it is likely to be installed with +support for the pkg-config mechanism. If you have pkg-config, you can compile +this program using this command: + +gcc -Wall pcredemo.c `pkg-config --cflags --libs libpcre` -o pcredemo + +If you do not have pkg-config, you may have to use this: + +gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \e + -R/usr/local/lib -lpcre -o pcredemo + +Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and +library files for PCRE are installed on your system. Only some operating +systems (e.g. Solaris) use the -R option. + +Building under Windows: + +If you want to statically link this program against a non-dll .a file, you must +define PCRE_STATIC before including pcre.h, otherwise the pcre_malloc() and +pcre_free() exported functions will be declared __declspec(dllimport), with +unwanted results. So in this environment, uncomment the following line. */ + +/* #define PCRE_STATIC */ + +#include <stdio.h> +#include <string.h> +#include <pcre.h> + +#define OVECCOUNT 30 /* should be a multiple of 3 */ + + +int main(int argc, char **argv) +{ +pcre *re; +const char *error; +char *pattern; +char *subject; +unsigned char *name_table; +unsigned int option_bits; +int erroffset; +int find_all; +int crlf_is_newline; +int namecount; +int name_entry_size; +int ovector[OVECCOUNT]; +int subject_length; +int rc, i; +int utf8; + + +/************************************************************************** +* First, sort out the command line. There is only one possible option at * +* the moment, "-g" to request repeated matching to find all occurrences, * +* like Perl's /g option. We set the variable find_all to a non-zero value * +* if the -g option is present. Apart from that, there must be exactly two * +* arguments. * +**************************************************************************/ + +find_all = 0; +for (i = 1; i < argc; i++) + { + if (strcmp(argv[i], "-g") == 0) find_all = 1; + else break; + } + +/* After the options, we require exactly two arguments, which are the pattern, +and the subject string. */ + +if (argc - i != 2) + { + printf("Two arguments required: a regex and a subject string\en"); + return 1; + } + +pattern = argv[i]; +subject = argv[i+1]; +subject_length = (int)strlen(subject); + + +/************************************************************************* +* Now we are going to compile the regular expression pattern, and handle * +* and errors that are detected. * +*************************************************************************/ + +re = pcre_compile( + pattern, /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ + +/* Compilation failed: print the error message and exit */ + +if (re == NULL) + { + printf("PCRE compilation failed at offset %d: %s\en", erroffset, error); + return 1; + } + + +/************************************************************************* +* If the compilation succeeded, we call PCRE again, in order to do a * +* pattern match against the subject string. This does just ONE match. If * +* further matching is needed, it will be done below. * +*************************************************************************/ + +rc = pcre_exec( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + subject, /* the subject string */ + subject_length, /* the length of the subject */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* output vector for substring information */ + OVECCOUNT); /* number of elements in the output vector */ + +/* Matching failed: handle error cases */ + +if (rc < 0) + { + switch(rc) + { + case PCRE_ERROR_NOMATCH: printf("No match\en"); break; + /* + Handle other special cases if you like + */ + default: printf("Matching error %d\en", rc); break; + } + pcre_free(re); /* Release memory used for the compiled pattern */ + return 1; + } + +/* Match succeded */ + +printf("\enMatch succeeded at offset %d\en", ovector[0]); + + +/************************************************************************* +* We have found the first match within the subject string. If the output * +* vector wasn't big enough, say so. Then output any substrings that were * +* captured. * +*************************************************************************/ + +/* The output vector wasn't big enough */ + +if (rc == 0) + { + rc = OVECCOUNT/3; + printf("ovector only has room for %d captured substrings\en", rc - 1); + } + +/* Show substrings stored in the output vector by number. Obviously, in a real +application you might want to do things other than print them. */ + +for (i = 0; i < rc; i++) + { + char *substring_start = subject + ovector[2*i]; + int substring_length = ovector[2*i+1] - ovector[2*i]; + printf("%2d: %.*s\en", i, substring_length, substring_start); + } + + +/************************************************************************** +* That concludes the basic part of this demonstration program. We have * +* compiled a pattern, and performed a single match. The code that follows * +* shows first how to access named substrings, and then how to code for * +* repeated matches on the same subject. * +**************************************************************************/ + +/* See if there are any named substrings, and if so, show them by name. First +we have to extract the count of named parentheses from the pattern. */ + +(void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMECOUNT, /* number of named substrings */ + &namecount); /* where to put the answer */ + +if (namecount <= 0) printf("No named substrings\en"); else + { + unsigned char *tabptr; + printf("Named substrings\en"); + + /* Before we can access the substrings, we must extract the table for + translating names to numbers, and the size of each entry in the table. */ + + (void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMETABLE, /* address of the table */ + &name_table); /* where to put the answer */ + + (void)pcre_fullinfo( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + PCRE_INFO_NAMEENTRYSIZE, /* size of each entry in the table */ + &name_entry_size); /* where to put the answer */ + + /* Now we can scan the table and, for each entry, print the number, the name, + and the substring itself. */ + + tabptr = name_table; + for (i = 0; i < namecount; i++) + { + int n = (tabptr[0] << 8) | tabptr[1]; + printf("(%d) %*s: %.*s\en", n, name_entry_size - 3, tabptr + 2, + ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]); + tabptr += name_entry_size; + } + } + + +/************************************************************************* +* If the "-g" option was given on the command line, we want to continue * +* to search for additional matches in the subject string, in a similar * +* way to the /g option in Perl. This turns out to be trickier than you * +* might think because of the possibility of matching an empty string. * +* What happens is as follows: * +* * +* If the previous match was NOT for an empty string, we can just start * +* the next match at the end of the previous one. * +* * +* If the previous match WAS for an empty string, we can't do that, as it * +* would lead to an infinite loop. Instead, a special call of pcre_exec() * +* is made with the PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED flags set. * +* The first of these tells PCRE that an empty string at the start of the * +* subject is not a valid match; other possibilities must be tried. The * +* second flag restricts PCRE to one match attempt at the initial string * +* position. If this match succeeds, an alternative to the empty string * +* match has been found, and we can print it and proceed round the loop, * +* advancing by the length of whatever was found. If this match does not * +* succeed, we still stay in the loop, advancing by just one character. * +* In UTF-8 mode, which can be set by (*UTF8) in the pattern, this may be * +* more than one byte. * +* * +* However, there is a complication concerned with newlines. When the * +* newline convention is such that CRLF is a valid newline, we must * +* advance by two characters rather than one. The newline convention can * +* be set in the regex by (*CR), etc.; if not, we must find the default. * +*************************************************************************/ + +if (!find_all) /* Check for -g */ + { + pcre_free(re); /* Release the memory used for the compiled pattern */ + return 0; /* Finish unless -g was given */ + } + +/* Before running the loop, check for UTF-8 and whether CRLF is a valid newline +sequence. First, find the options with which the regex was compiled; extract +the UTF-8 state, and mask off all but the newline options. */ + +(void)pcre_fullinfo(re, NULL, PCRE_INFO_OPTIONS, &option_bits); +utf8 = option_bits & PCRE_UTF8; +option_bits &= PCRE_NEWLINE_CR|PCRE_NEWLINE_LF|PCRE_NEWLINE_CRLF| + PCRE_NEWLINE_ANY|PCRE_NEWLINE_ANYCRLF; + +/* If no newline options were set, find the default newline convention from the +build configuration. */ + +if (option_bits == 0) + { + int d; + (void)pcre_config(PCRE_CONFIG_NEWLINE, &d); + /* Note that these values are always the ASCII ones, even in + EBCDIC environments. CR = 13, NL = 10. */ + option_bits = (d == 13)? PCRE_NEWLINE_CR : + (d == 10)? PCRE_NEWLINE_LF : + (d == (13<<8 | 10))? PCRE_NEWLINE_CRLF : + (d == -2)? PCRE_NEWLINE_ANYCRLF : + (d == -1)? PCRE_NEWLINE_ANY : 0; + } + +/* See if CRLF is a valid newline sequence. */ + +crlf_is_newline = + option_bits == PCRE_NEWLINE_ANY || + option_bits == PCRE_NEWLINE_CRLF || + option_bits == PCRE_NEWLINE_ANYCRLF; + +/* Loop for second and subsequent matches */ + +for (;;) + { + int options = 0; /* Normally no options */ + int start_offset = ovector[1]; /* Start at end of previous match */ + + /* If the previous match was for an empty string, we are finished if we are + at the end of the subject. Otherwise, arrange to run another match at the + same point to see if a non-empty match can be found. */ + + if (ovector[0] == ovector[1]) + { + if (ovector[0] == subject_length) break; + options = PCRE_NOTEMPTY_ATSTART | PCRE_ANCHORED; + } + + /* Run the next matching operation */ + + rc = pcre_exec( + re, /* the compiled pattern */ + NULL, /* no extra data - we didn't study the pattern */ + subject, /* the subject string */ + subject_length, /* the length of the subject */ + start_offset, /* starting offset in the subject */ + options, /* options */ + ovector, /* output vector for substring information */ + OVECCOUNT); /* number of elements in the output vector */ + + /* This time, a result of NOMATCH isn't an error. If the value in "options" + is zero, it just means we have found all possible matches, so the loop ends. + Otherwise, it means we have failed to find a non-empty-string match at a + point where there was a previous empty-string match. In this case, we do what + Perl does: advance the matching position by one character, and continue. We + do this by setting the "end of previous match" offset, because that is picked + up at the top of the loop as the point at which to start again. + + There are two complications: (a) When CRLF is a valid newline sequence, and + the current position is just before it, advance by an extra byte. (b) + Otherwise we must ensure that we skip an entire UTF-8 character if we are in + UTF-8 mode. */ + + if (rc == PCRE_ERROR_NOMATCH) + { + if (options == 0) break; /* All matches found */ + ovector[1] = start_offset + 1; /* Advance one byte */ + if (crlf_is_newline && /* If CRLF is newline & */ + start_offset < subject_length - 1 && /* we are at CRLF, */ + subject[start_offset] == '\er' && + subject[start_offset + 1] == '\en') + ovector[1] += 1; /* Advance by one more. */ + else if (utf8) /* Otherwise, ensure we */ + { /* advance a whole UTF-8 */ + while (ovector[1] < subject_length) /* character. */ + { + if ((subject[ovector[1]] & 0xc0) != 0x80) break; + ovector[1] += 1; + } + } + continue; /* Go round the loop again */ + } + + /* Other matching errors are not recoverable. */ + + if (rc < 0) + { + printf("Matching error %d\en", rc); + pcre_free(re); /* Release memory used for the compiled pattern */ + return 1; + } + + /* Match succeded */ + + printf("\enMatch succeeded again at offset %d\en", ovector[0]); + + /* The match succeeded, but the output vector wasn't big enough. */ + + if (rc == 0) + { + rc = OVECCOUNT/3; + printf("ovector only has room for %d captured substrings\en", rc - 1); + } + + /* As before, show substrings stored in the output vector by number, and then + also any named substrings. */ + + for (i = 0; i < rc; i++) + { + char *substring_start = subject + ovector[2*i]; + int substring_length = ovector[2*i+1] - ovector[2*i]; + printf("%2d: %.*s\en", i, substring_length, substring_start); + } + + if (namecount <= 0) printf("No named substrings\en"); else + { + unsigned char *tabptr = name_table; + printf("Named substrings\en"); + for (i = 0; i < namecount; i++) + { + int n = (tabptr[0] << 8) | tabptr[1]; + printf("(%d) %*s: %.*s\en", n, name_entry_size - 3, tabptr + 2, + ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]); + tabptr += name_entry_size; + } + } + } /* End of loop to find second and subsequent matches */ + +printf("\en"); +pcre_free(re); /* Release memory used for the compiled pattern */ +return 0; +} + +/* End of pcredemo.c */ +.EE diff --git a/doc/pcregrep.1 b/doc/pcregrep.1 new file mode 100644 index 0000000..07b8f57 --- /dev/null +++ b/doc/pcregrep.1 @@ -0,0 +1,687 @@ +.TH PCREGREP 1 "03 April 2014" "PCRE 8.35" +.SH NAME +pcregrep - a grep with Perl-compatible regular expressions. +.SH SYNOPSIS +.B pcregrep [options] [long options] [pattern] [path1 path2 ...] +.B zpcregrep [options] [long options] [pattern] [file1 file2 ...] +. +.SH DESCRIPTION +.rs +.sp +\fBpcregrep\fP searches files for character patterns, in the same way as other +grep commands do, but it uses the PCRE regular expression library to support +patterns that are compatible with the regular expressions of Perl 5. See +.\" HREF +\fBpcresyntax\fP(3) +.\" +for a quick-reference summary of pattern syntax, or +.\" HREF +\fBpcrepattern\fP(3) +.\" +for a full description of the syntax and semantics of the regular expressions +that PCRE supports. +.P +Patterns, whether supplied on the command line or in a separate file, are given +without delimiters. For example: +.sp + pcregrep Thursday /etc/motd +.sp +If you attempt to use delimiters (for example, by surrounding a pattern with +slashes, as is common in Perl scripts), they are interpreted as part of the +pattern. Quotes can of course be used to delimit patterns on the command line +because they are interpreted by the shell, and indeed quotes are required if a +pattern contains white space or shell metacharacters. +.P +The first argument that follows any option settings is treated as the single +pattern to be matched when neither \fB-e\fP nor \fB-f\fP is present. +Conversely, when one or both of these options are used to specify patterns, all +arguments are treated as path names. At least one of \fB-e\fP, \fB-f\fP, or an +argument pattern must be provided. +.P +If no files are specified, \fBpcregrep\fP reads the standard input. The +standard input can also be referenced by a name consisting of a single hyphen. +For example: +.sp + pcregrep some-pattern /file1 - /file3 +.sp +By default, each line that matches a pattern is copied to the standard +output, and if there is more than one file, the file name is output at the +start of each line, followed by a colon. However, there are options that can +change how \fBpcregrep\fP behaves. In particular, the \fB-M\fP option makes it +possible to search for patterns that span line boundaries. What defines a line +boundary is controlled by the \fB-N\fP (\fB--newline\fP) option. +.P +The amount of memory used for buffering files that are being scanned is +controlled by a parameter that can be set by the \fB--buffer-size\fP option. +The default value for this parameter is specified when \fBpcregrep\fP is built, +with the default default being 20K. A block of memory three times this size is +used (to allow for buffering "before" and "after" lines). An error occurs if a +line overflows the buffer. +.P +Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the greater. +BUFSIZ is defined in \fB<stdio.h>\fP. When there is more than one pattern +(specified by the use of \fB-e\fP and/or \fB-f\fP), each pattern is applied to +each line in the order in which they are defined, except that all the \fB-e\fP +patterns are tried before the \fB-f\fP patterns. +.P +By default, as soon as one pattern matches a line, no further patterns are +considered. However, if \fB--colour\fP (or \fB--color\fP) is used to colour the +matching substrings, or if \fB--only-matching\fP, \fB--file-offsets\fP, or +\fB--line-offsets\fP is used to output only the part of the line that matched +(either shown literally, or as an offset), scanning resumes immediately +following the match, so that further matches on the same line can be found. If +there are multiple patterns, they are all tried on the remainder of the line, +but patterns that follow the one that matched are not tried on the earlier part +of the line. +.P +This behaviour means that the order in which multiple patterns are specified +can affect the output when one of the above options is used. This is no longer +the same behaviour as GNU grep, which now manages to display earlier matches +for later patterns (as long as there is no overlap). +.P +Patterns that can match an empty string are accepted, but empty string +matches are never recognized. An example is the pattern "(super)?(man)?", in +which all components are optional. This pattern finds all occurrences of both +"super" and "man"; the output differs from matching with "super|man" when only +the matching substrings are being shown. +.P +If the \fBLC_ALL\fP or \fBLC_CTYPE\fP environment variable is set, +\fBpcregrep\fP uses the value to set a locale when calling the PCRE library. +The \fB--locale\fP option can be used to override this. +.P +\fBzpcregrep\fR is a wrapper script that allows pcregrep to work on +gzip compressed files. +. +. +.SH "SUPPORT FOR COMPRESSED FILES" +.rs +.sp +It is possible to compile \fBpcregrep\fP so that it uses \fBlibz\fP or +\fBlibbz2\fP to read files whose names end in \fB.gz\fP or \fB.bz2\fP, +respectively. You can find out whether your binary has support for one or both +of these file types by running it with the \fB--help\fP option. If the +appropriate support is not present, files are treated as plain text. The +standard input is always so treated. +. +. +.SH "BINARY FILES" +.rs +.sp +By default, a file that contains a binary zero byte within the first 1024 bytes +is identified as a binary file, and is processed specially. (GNU grep also +identifies binary files in this manner.) See the \fB--binary-files\fP option +for a means of changing the way binary files are handled. +. +. +.SH OPTIONS +.rs +.sp +The order in which some of the options appear can affect the output. For +example, both the \fB-h\fP and \fB-l\fP options affect the printing of file +names. Whichever comes later in the command line will be the one that takes +effect. Similarly, except where noted below, if an option is given twice, the +later setting is used. Numerical values for options may be followed by K or M, +to signify multiplication by 1024 or 1024*1024 respectively. +.TP 10 +\fB--\fP +This terminates the list of options. It is useful if the next item on the +command line starts with a hyphen but is not an option. This allows for the +processing of patterns and filenames that start with hyphens. +.TP +\fB-A\fP \fInumber\fP, \fB--after-context=\fP\fInumber\fP +Output \fInumber\fP lines of context after each matching line. If filenames +and/or line numbers are being output, a hyphen separator is used instead of a +colon for the context lines. A line containing "--" is output between each +group of lines, unless they are in fact contiguous in the input file. The value +of \fInumber\fP is expected to be relatively small. However, \fBpcregrep\fP +guarantees to have up to 8K of following text available for context output. +.TP +\fB-a\fP, \fB--text\fP +Treat binary files as text. This is equivalent to +\fB--binary-files\fP=\fItext\fP. +.TP +\fB-B\fP \fInumber\fP, \fB--before-context=\fP\fInumber\fP +Output \fInumber\fP lines of context before each matching line. If filenames +and/or line numbers are being output, a hyphen separator is used instead of a +colon for the context lines. A line containing "--" is output between each +group of lines, unless they are in fact contiguous in the input file. The value +of \fInumber\fP is expected to be relatively small. However, \fBpcregrep\fP +guarantees to have up to 8K of preceding text available for context output. +.TP +\fB--binary-files=\fP\fIword\fP +Specify how binary files are to be processed. If the word is "binary" (the +default), pattern matching is performed on binary files, but the only output is +"Binary file <name> matches" when a match succeeds. If the word is "text", +which is equivalent to the \fB-a\fP or \fB--text\fP option, binary files are +processed in the same way as any other file. In this case, when a match +succeeds, the output may be binary garbage, which can have nasty effects if +sent to a terminal. If the word is "without-match", which is equivalent to the +\fB-I\fP option, binary files are not processed at all; they are assumed not to +be of interest. +.TP +\fB--buffer-size=\fP\fInumber\fP +Set the parameter that controls how much memory is used for buffering files +that are being scanned. +.TP +\fB-C\fP \fInumber\fP, \fB--context=\fP\fInumber\fP +Output \fInumber\fP lines of context both before and after each matching line. +This is equivalent to setting both \fB-A\fP and \fB-B\fP to the same value. +.TP +\fB-c\fP, \fB--count\fP +Do not output individual lines from the files that are being scanned; instead +output the number of lines that would otherwise have been shown. If no lines +are selected, the number zero is output. If several files are are being +scanned, a count is output for each of them. However, if the +\fB--files-with-matches\fP option is also used, only those files whose counts +are greater than zero are listed. When \fB-c\fP is used, the \fB-A\fP, +\fB-B\fP, and \fB-C\fP options are ignored. +.TP +\fB--colour\fP, \fB--color\fP +If this option is given without any data, it is equivalent to "--colour=auto". +If data is required, it must be given in the same shell item, separated by an +equals sign. +.TP +\fB--colour=\fP\fIvalue\fP, \fB--color=\fP\fIvalue\fP +This option specifies under what circumstances the parts of a line that matched +a pattern should be coloured in the output. By default, the output is not +coloured. The value (which is optional, see above) may be "never", "always", or +"auto". In the latter case, colouring happens only if the standard output is +connected to a terminal. More resources are used when colouring is enabled, +because \fBpcregrep\fP has to search for all possible matches in a line, not +just one, in order to colour them all. +.sp +The colour that is used can be specified by setting the environment variable +PCREGREP_COLOUR or PCREGREP_COLOR. The value of this variable should be a +string of two numbers, separated by a semicolon. They are copied directly into +the control string for setting colour on a terminal, so it is your +responsibility to ensure that they make sense. If neither of the environment +variables is set, the default is "1;31", which gives red. +.TP +\fB-D\fP \fIaction\fP, \fB--devices=\fP\fIaction\fP +If an input path is not a regular file or a directory, "action" specifies how +it is to be processed. Valid values are "read" (the default) or "skip" +(silently skip the path). +.TP +\fB-d\fP \fIaction\fP, \fB--directories=\fP\fIaction\fP +If an input path is a directory, "action" specifies how it is to be processed. +Valid values are "read" (the default in non-Windows environments, for +compatibility with GNU grep), "recurse" (equivalent to the \fB-r\fP option), or +"skip" (silently skip the path, the default in Windows environments). In the +"read" case, directories are read as if they were ordinary files. In some +operating systems the effect of reading a directory like this is an immediate +end-of-file; in others it may provoke an error. +.TP +\fB-e\fP \fIpattern\fP, \fB--regex=\fP\fIpattern\fP, \fB--regexp=\fP\fIpattern\fP +Specify a pattern to be matched. This option can be used multiple times in +order to specify several patterns. It can also be used as a way of specifying a +single pattern that starts with a hyphen. When \fB-e\fP is used, no argument +pattern is taken from the command line; all arguments are treated as file +names. There is no limit to the number of patterns. They are applied to each +line in the order in which they are defined until one matches. +.sp +If \fB-f\fP is used with \fB-e\fP, the command line patterns are matched first, +followed by the patterns from the file(s), independent of the order in which +these options are specified. Note that multiple use of \fB-e\fP is not the same +as a single pattern with alternatives. For example, X|Y finds the first +character in a line that is X or Y, whereas if the two patterns are given +separately, with X first, \fBpcregrep\fP finds X if it is present, even if it +follows Y in the line. It finds Y only if there is no X in the line. This +matters only if you are using \fB-o\fP or \fB--colo(u)r\fP to show the part(s) +of the line that matched. +.TP +\fB--exclude\fP=\fIpattern\fP +Files (but not directories) whose names match the pattern are skipped without +being processed. This applies to all files, whether listed on the command line, +obtained from \fB--file-list\fP, or by scanning a directory. The pattern is a +PCRE regular expression, and is matched against the final component of the file +name, not the entire path. The \fB-F\fP, \fB-w\fP, and \fB-x\fP options do not +apply to this pattern. The option may be given any number of times in order to +specify multiple patterns. If a file name matches both an \fB--include\fP +and an \fB--exclude\fP pattern, it is excluded. There is no short form for this +option. +.TP +\fB--exclude-from=\fP\fIfilename\fP +Treat each non-empty line of the file as the data for an \fB--exclude\fP +option. What constitutes a newline when reading the file is the operating +system's default. The \fB--newline\fP option has no effect on this option. This +option may be given more than once in order to specify a number of files to +read. +.TP +\fB--exclude-dir\fP=\fIpattern\fP +Directories whose names match the pattern are skipped without being processed, +whatever the setting of the \fB--recursive\fP option. This applies to all +directories, whether listed on the command line, obtained from +\fB--file-list\fP, or by scanning a parent directory. The pattern is a PCRE +regular expression, and is matched against the final component of the directory +name, not the entire path. The \fB-F\fP, \fB-w\fP, and \fB-x\fP options do not +apply to this pattern. The option may be given any number of times in order to +specify more than one pattern. If a directory matches both \fB--include-dir\fP +and \fB--exclude-dir\fP, it is excluded. There is no short form for this +option. +.TP +\fB-F\fP, \fB--fixed-strings\fP +Interpret each data-matching pattern as a list of fixed strings, separated by +newlines, instead of as a regular expression. What constitutes a newline for +this purpose is controlled by the \fB--newline\fP option. The \fB-w\fP (match +as a word) and \fB-x\fP (match whole line) options can be used with \fB-F\fP. +They apply to each of the fixed strings. A line is selected if any of the fixed +strings are found in it (subject to \fB-w\fP or \fB-x\fP, if present). This +option applies only to the patterns that are matched against the contents of +files; it does not apply to patterns specified by any of the \fB--include\fP or +\fB--exclude\fP options. +.TP +\fB-f\fP \fIfilename\fP, \fB--file=\fP\fIfilename\fP +Read patterns from the file, one per line, and match them against +each line of input. What constitutes a newline when reading the file is the +operating system's default. The \fB--newline\fP option has no effect on this +option. Trailing white space is removed from each line, and blank lines are +ignored. An empty file contains no patterns and therefore matches nothing. See +also the comments about multiple patterns versus a single pattern with +alternatives in the description of \fB-e\fP above. +.sp +If this option is given more than once, all the specified files are +read. A data line is output if any of the patterns match it. A filename can +be given as "-" to refer to the standard input. When \fB-f\fP is used, patterns +specified on the command line using \fB-e\fP may also be present; they are +tested before the file's patterns. However, no other pattern is taken from the +command line; all arguments are treated as the names of paths to be searched. +.TP +\fB--file-list\fP=\fIfilename\fP +Read a list of files and/or directories that are to be scanned from the given +file, one per line. Trailing white space is removed from each line, and blank +lines are ignored. These paths are processed before any that are listed on the +command line. The filename can be given as "-" to refer to the standard input. +If \fB--file\fP and \fB--file-list\fP are both specified as "-", patterns are +read first. This is useful only when the standard input is a terminal, from +which further lines (the list of files) can be read after an end-of-file +indication. If this option is given more than once, all the specified files are +read. +.TP +\fB--file-offsets\fP +Instead of showing lines or parts of lines that match, show each match as an +offset from the start of the file and a length, separated by a comma. In this +mode, no context is shown. That is, the \fB-A\fP, \fB-B\fP, and \fB-C\fP +options are ignored. If there is more than one match in a line, each of them is +shown separately. This option is mutually exclusive with \fB--line-offsets\fP +and \fB--only-matching\fP. +.TP +\fB-H\fP, \fB--with-filename\fP +Force the inclusion of the filename at the start of output lines when searching +a single file. By default, the filename is not shown in this case. For matching +lines, the filename is followed by a colon; for context lines, a hyphen +separator is used. If a line number is also being output, it follows the file +name. +.TP +\fB-h\fP, \fB--no-filename\fP +Suppress the output filenames when searching multiple files. By default, +filenames are shown when multiple files are searched. For matching lines, the +filename is followed by a colon; for context lines, a hyphen separator is used. +If a line number is also being output, it follows the file name. +.TP +\fB--help\fP +Output a help message, giving brief details of the command options and file +type support, and then exit. Anything else on the command line is +ignored. +.TP +\fB-I\fP +Treat binary files as never matching. This is equivalent to +\fB--binary-files\fP=\fIwithout-match\fP. +.TP +\fB-i\fP, \fB--ignore-case\fP +Ignore upper/lower case distinctions during comparisons. +.TP +\fB--include\fP=\fIpattern\fP +If any \fB--include\fP patterns are specified, the only files that are +processed are those that match one of the patterns (and do not match an +\fB--exclude\fP pattern). This option does not affect directories, but it +applies to all files, whether listed on the command line, obtained from +\fB--file-list\fP, or by scanning a directory. The pattern is a PCRE regular +expression, and is matched against the final component of the file name, not +the entire path. The \fB-F\fP, \fB-w\fP, and \fB-x\fP options do not apply to +this pattern. The option may be given any number of times. If a file name +matches both an \fB--include\fP and an \fB--exclude\fP pattern, it is excluded. +There is no short form for this option. +.TP +\fB--include-from=\fP\fIfilename\fP +Treat each non-empty line of the file as the data for an \fB--include\fP +option. What constitutes a newline for this purpose is the operating system's +default. The \fB--newline\fP option has no effect on this option. This option +may be given any number of times; all the files are read. +.TP +\fB--include-dir\fP=\fIpattern\fP +If any \fB--include-dir\fP patterns are specified, the only directories that +are processed are those that match one of the patterns (and do not match an +\fB--exclude-dir\fP pattern). This applies to all directories, whether listed +on the command line, obtained from \fB--file-list\fP, or by scanning a parent +directory. The pattern is a PCRE regular expression, and is matched against the +final component of the directory name, not the entire path. The \fB-F\fP, +\fB-w\fP, and \fB-x\fP options do not apply to this pattern. The option may be +given any number of times. If a directory matches both \fB--include-dir\fP and +\fB--exclude-dir\fP, it is excluded. There is no short form for this option. +.TP +\fB-L\fP, \fB--files-without-match\fP +Instead of outputting lines from the files, just output the names of the files +that do not contain any lines that would have been output. Each file name is +output once, on a separate line. +.TP +\fB-l\fP, \fB--files-with-matches\fP +Instead of outputting lines from the files, just output the names of the files +containing lines that would have been output. Each file name is output +once, on a separate line. Searching normally stops as soon as a matching line +is found in a file. However, if the \fB-c\fP (count) option is also used, +matching continues in order to obtain the correct count, and those files that +have at least one match are listed along with their counts. Using this option +with \fB-c\fP is a way of suppressing the listing of files with no matches. +.TP +\fB--label\fP=\fIname\fP +This option supplies a name to be used for the standard input when file names +are being output. If not supplied, "(standard input)" is used. There is no +short form for this option. +.TP +\fB--line-buffered\fP +When this option is given, input is read and processed line by line, and the +output is flushed after each write. By default, input is read in large chunks, +unless \fBpcregrep\fP can determine that it is reading from a terminal (which +is currently possible only in Unix-like environments). Output to terminal is +normally automatically flushed by the operating system. This option can be +useful when the input or output is attached to a pipe and you do not want +\fBpcregrep\fP to buffer up large amounts of data. However, its use will affect +performance, and the \fB-M\fP (multiline) option ceases to work. +.TP +\fB--line-offsets\fP +Instead of showing lines or parts of lines that match, show each match as a +line number, the offset from the start of the line, and a length. The line +number is terminated by a colon (as usual; see the \fB-n\fP option), and the +offset and length are separated by a comma. In this mode, no context is shown. +That is, the \fB-A\fP, \fB-B\fP, and \fB-C\fP options are ignored. If there is +more than one match in a line, each of them is shown separately. This option is +mutually exclusive with \fB--file-offsets\fP and \fB--only-matching\fP. +.TP +\fB--locale\fP=\fIlocale-name\fP +This option specifies a locale to be used for pattern matching. It overrides +the value in the \fBLC_ALL\fP or \fBLC_CTYPE\fP environment variables. If no +locale is specified, the PCRE library's default (usually the "C" locale) is +used. There is no short form for this option. +.TP +\fB--match-limit\fP=\fInumber\fP +Processing some regular expression patterns can require a very large amount of +memory, leading in some cases to a program crash if not enough is available. +Other patterns may take a very long time to search for all possible matching +strings. The \fBpcre_exec()\fP function that is called by \fBpcregrep\fP to do +the matching has two parameters that can limit the resources that it uses. +.sp +The \fB--match-limit\fP option provides a means of limiting resource usage +when processing patterns that are not going to match, but which have a very +large number of possibilities in their search trees. The classic example is a +pattern that uses nested unlimited repeats. Internally, PCRE uses a function +called \fBmatch()\fP which it calls repeatedly (sometimes recursively). The +limit set by \fB--match-limit\fP is imposed on the number of times this +function is called during a match, which has the effect of limiting the amount +of backtracking that can take place. +.sp +The \fB--recursion-limit\fP option is similar to \fB--match-limit\fP, but +instead of limiting the total number of times that \fBmatch()\fP is called, it +limits the depth of recursive calls, which in turn limits the amount of memory +that can be used. The recursion depth is a smaller number than the total number +of calls, because not all calls to \fBmatch()\fP are recursive. This limit is +of use only if it is set smaller than \fB--match-limit\fP. +.sp +There are no short forms for these options. The default settings are specified +when the PCRE library is compiled, with the default default being 10 million. +.TP +\fB-M\fP, \fB--multiline\fP +Allow patterns to match more than one line. When this option is given, patterns +may usefully contain literal newline characters and internal occurrences of ^ +and $ characters. The output for a successful match may consist of more than +one line, the last of which is the one in which the match ended. If the matched +string ends with a newline sequence the output ends at the end of that line. +.sp +When this option is set, the PCRE library is called in "multiline" mode. +There is a limit to the number of lines that can be matched, imposed by the way +that \fBpcregrep\fP buffers the input file as it scans it. However, +\fBpcregrep\fP ensures that at least 8K characters or the rest of the document +(whichever is the shorter) are available for forward matching, and similarly +the previous 8K characters (or all the previous characters, if fewer than 8K) +are guaranteed to be available for lookbehind assertions. This option does not +work when input is read line by line (see \fP--line-buffered\fP.) +.TP +\fB-N\fP \fInewline-type\fP, \fB--newline\fP=\fInewline-type\fP +The PCRE library supports five different conventions for indicating +the ends of lines. They are the single-character sequences CR (carriage return) +and LF (linefeed), the two-character sequence CRLF, an "anycrlf" convention, +which recognizes any of the preceding three types, and an "any" convention, in +which any Unicode line ending sequence is assumed to end a line. The Unicode +sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF +(form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and +PS (paragraph separator, U+2029). +.sp +When the PCRE library is built, a default line-ending sequence is specified. +This is normally the standard sequence for the operating system. Unless +otherwise specified by this option, \fBpcregrep\fP uses the library's default. +The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This +makes it possible to use \fBpcregrep\fP to scan files that have come from other +environments without having to modify their line endings. If the data that is +being scanned does not agree with the convention set by this option, +\fBpcregrep\fP may behave in strange ways. Note that this option does not +apply to files specified by the \fB-f\fP, \fB--exclude-from\fP, or +\fB--include-from\fP options, which are expected to use the operating system's +standard newline sequence. +.TP +\fB-n\fP, \fB--line-number\fP +Precede each output line by its line number in the file, followed by a colon +for matching lines or a hyphen for context lines. If the filename is also being +output, it precedes the line number. This option is forced if +\fB--line-offsets\fP is used. +.TP +\fB--no-jit\fP +If the PCRE library is built with support for just-in-time compiling (which +speeds up matching), \fBpcregrep\fP automatically makes use of this, unless it +was explicitly disabled at build time. This option can be used to disable the +use of JIT at run time. It is provided for testing and working round problems. +It should never be needed in normal use. +.TP +\fB-o\fP, \fB--only-matching\fP +Show only the part of the line that matched a pattern instead of the whole +line. In this mode, no context is shown. That is, the \fB-A\fP, \fB-B\fP, and +\fB-C\fP options are ignored. If there is more than one match in a line, each +of them is shown separately. If \fB-o\fP is combined with \fB-v\fP (invert the +sense of the match to find non-matching lines), no output is generated, but the +return code is set appropriately. If the matched portion of the line is empty, +nothing is output unless the file name or line number are being printed, in +which case they are shown on an otherwise empty line. This option is mutually +exclusive with \fB--file-offsets\fP and \fB--line-offsets\fP. +.TP +\fB-o\fP\fInumber\fP, \fB--only-matching\fP=\fInumber\fP +Show only the part of the line that matched the capturing parentheses of the +given number. Up to 32 capturing parentheses are supported, and -o0 is +equivalent to \fB-o\fP without a number. Because these options can be given +without an argument (see above), if an argument is present, it must be given in +the same shell item, for example, -o3 or --only-matching=2. The comments given +for the non-argument case above also apply to this case. If the specified +capturing parentheses do not exist in the pattern, or were not set in the +match, nothing is output unless the file name or line number are being printed. +.sp +If this option is given multiple times, multiple substrings are output, in the +order the options are given. For example, -o3 -o1 -o3 causes the substrings +matched by capturing parentheses 3 and 1 and then 3 again to be output. By +default, there is no separator (but see the next option). +.TP +\fB--om-separator\fP=\fItext\fP +Specify a separating string for multiple occurrences of \fB-o\fP. The default +is an empty string. Separating strings are never coloured. +.TP +\fB-q\fP, \fB--quiet\fP +Work quietly, that is, display nothing except error messages. The exit +status indicates whether or not any matches were found. +.TP +\fB-r\fP, \fB--recursive\fP +If any given path is a directory, recursively scan the files it contains, +taking note of any \fB--include\fP and \fB--exclude\fP settings. By default, a +directory is read as a normal file; in some operating systems this gives an +immediate end-of-file. This option is a shorthand for setting the \fB-d\fP +option to "recurse". +.TP +\fB--recursion-limit\fP=\fInumber\fP +See \fB--match-limit\fP above. +.TP +\fB-s\fP, \fB--no-messages\fP +Suppress error messages about non-existent or unreadable files. Such files are +quietly skipped. However, the return code is still 2, even if matches were +found in other files. +.TP +\fB-u\fP, \fB--utf-8\fP +Operate in UTF-8 mode. This option is available only if PCRE has been compiled +with UTF-8 support. All patterns (including those for any \fB--exclude\fP and +\fB--include\fP options) and all subject lines that are scanned must be valid +strings of UTF-8 characters. +.TP +\fB-V\fP, \fB--version\fP +Write the version numbers of \fBpcregrep\fP and the PCRE library to the +standard output and then exit. Anything else on the command line is +ignored. +.TP +\fB-v\fP, \fB--invert-match\fP +Invert the sense of the match, so that lines which do \fInot\fP match any of +the patterns are the ones that are found. +.TP +\fB-w\fP, \fB--word-regex\fP, \fB--word-regexp\fP +Force the patterns to match only whole words. This is equivalent to having \eb +at the start and end of the pattern. This option applies only to the patterns +that are matched against the contents of files; it does not apply to patterns +specified by any of the \fB--include\fP or \fB--exclude\fP options. +.TP +\fB-x\fP, \fB--line-regex\fP, \fB--line-regexp\fP +Force the patterns to be anchored (each must start matching at the beginning of +a line) and in addition, require them to match entire lines. This is equivalent +to having ^ and $ characters at the start and end of each alternative branch in +every pattern. This option applies only to the patterns that are matched +against the contents of files; it does not apply to patterns specified by any +of the \fB--include\fP or \fB--exclude\fP options. +. +. +.SH "ENVIRONMENT VARIABLES" +.rs +.sp +The environment variables \fBLC_ALL\fP and \fBLC_CTYPE\fP are examined, in that +order, for a locale. The first one that is set is used. This can be overridden +by the \fB--locale\fP option. If no locale is set, the PCRE library's default +(usually the "C" locale) is used. +. +. +.SH "NEWLINES" +.rs +.sp +The \fB-N\fP (\fB--newline\fP) option allows \fBpcregrep\fP to scan files with +different newline conventions from the default. Any parts of the input files +that are written to the standard output are copied identically, with whatever +newline sequences they have in the input. However, the setting of this option +does not affect the interpretation of files specified by the \fB-f\fP, +\fB--exclude-from\fP, or \fB--include-from\fP options, which are assumed to use +the operating system's standard newline sequence, nor does it affect the way in +which \fBpcregrep\fP writes informational messages to the standard error and +output streams. For these it uses the string "\en" to indicate newlines, +relying on the C I/O library to convert this to an appropriate sequence. +. +. +.SH "OPTIONS COMPATIBILITY" +.rs +.sp +Many of the short and long forms of \fBpcregrep\fP's options are the same +as in the GNU \fBgrep\fP program. Any long option of the form +\fB--xxx-regexp\fP (GNU terminology) is also available as \fB--xxx-regex\fP +(PCRE terminology). However, the \fB--file-list\fP, \fB--file-offsets\fP, +\fB--include-dir\fP, \fB--line-offsets\fP, \fB--locale\fP, \fB--match-limit\fP, +\fB-M\fP, \fB--multiline\fP, \fB-N\fP, \fB--newline\fP, \fB--om-separator\fP, +\fB--recursion-limit\fP, \fB-u\fP, and \fB--utf-8\fP options are specific to +\fBpcregrep\fP, as is the use of the \fB--only-matching\fP option with a +capturing parentheses number. +.P +Although most of the common options work the same way, a few are different in +\fBpcregrep\fP. For example, the \fB--include\fP option's argument is a glob +for GNU \fBgrep\fP, but a regular expression for \fBpcregrep\fP. If both the +\fB-c\fP and \fB-l\fP options are given, GNU grep lists only file names, +without counts, but \fBpcregrep\fP gives the counts. +. +. +.SH "OPTIONS WITH DATA" +.rs +.sp +There are four different ways in which an option with data can be specified. +If a short form option is used, the data may follow immediately, or (with one +exception) in the next command line item. For example: +.sp + -f/some/file + -f /some/file +.sp +The exception is the \fB-o\fP option, which may appear with or without data. +Because of this, if data is present, it must follow immediately in the same +item, for example -o3. +.P +If a long form option is used, the data may appear in the same command line +item, separated by an equals character, or (with two exceptions) it may appear +in the next command line item. For example: +.sp + --file=/some/file + --file /some/file +.sp +Note, however, that if you want to supply a file name beginning with ~ as data +in a shell command, and have the shell expand ~ to a home directory, you must +separate the file name from the option, because the shell does not treat ~ +specially unless it is at the start of an item. +.P +The exceptions to the above are the \fB--colour\fP (or \fB--color\fP) and +\fB--only-matching\fP options, for which the data is optional. If one of these +options does have data, it must be given in the first form, using an equals +character. Otherwise \fBpcregrep\fP will assume that it has no data. +. +. +.SH "MATCHING ERRORS" +.rs +.sp +It is possible to supply a regular expression that takes a very long time to +fail to match certain lines. Such patterns normally involve nested indefinite +repeats, for example: (a+)*\ed when matched against a line of a's with no final +digit. The PCRE matching function has a resource limit that causes it to abort +in these circumstances. If this happens, \fBpcregrep\fP outputs an error +message and the line that caused the problem to the standard error stream. If +there are more than 20 such errors, \fBpcregrep\fP gives up. +.P +The \fB--match-limit\fP option of \fBpcregrep\fP can be used to set the overall +resource limit; there is a second option called \fB--recursion-limit\fP that +sets a limit on the amount of memory (usually stack) that is used (see the +discussion of these options above). +. +. +.SH DIAGNOSTICS +.rs +.sp +Exit status is 0 if any matches were found, 1 if no matches were found, and 2 +for syntax errors, overlong lines, non-existent or inaccessible files (even if +matches were found in other files) or too many matching errors. Using the +\fB-s\fP option to suppress error messages about inaccessible files does not +affect the return code. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcrepattern\fP(3), \fBpcresyntax\fP(3), \fBpcretest\fP(1). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 03 April 2014 +Copyright (c) 1997-2014 University of Cambridge. +.fi diff --git a/doc/pcregrep.txt b/doc/pcregrep.txt new file mode 100644 index 0000000..97d9a7b --- /dev/null +++ b/doc/pcregrep.txt @@ -0,0 +1,741 @@ +PCREGREP(1) General Commands Manual PCREGREP(1) + + + +NAME + pcregrep - a grep with Perl-compatible regular expressions. + +SYNOPSIS + pcregrep [options] [long options] [pattern] [path1 path2 ...] + + +DESCRIPTION + + pcregrep searches files for character patterns, in the same way as + other grep commands do, but it uses the PCRE regular expression library + to support patterns that are compatible with the regular expressions of + Perl 5. See pcresyntax(3) for a quick-reference summary of pattern syn- + tax, or pcrepattern(3) for a full description of the syntax and seman- + tics of the regular expressions that PCRE supports. + + Patterns, whether supplied on the command line or in a separate file, + are given without delimiters. For example: + + pcregrep Thursday /etc/motd + + If you attempt to use delimiters (for example, by surrounding a pattern + with slashes, as is common in Perl scripts), they are interpreted as + part of the pattern. Quotes can of course be used to delimit patterns + on the command line because they are interpreted by the shell, and + indeed quotes are required if a pattern contains white space or shell + metacharacters. + + The first argument that follows any option settings is treated as the + single pattern to be matched when neither -e nor -f is present. Con- + versely, when one or both of these options are used to specify pat- + terns, all arguments are treated as path names. At least one of -e, -f, + or an argument pattern must be provided. + + If no files are specified, pcregrep reads the standard input. The stan- + dard input can also be referenced by a name consisting of a single + hyphen. For example: + + pcregrep some-pattern /file1 - /file3 + + By default, each line that matches a pattern is copied to the standard + output, and if there is more than one file, the file name is output at + the start of each line, followed by a colon. However, there are options + that can change how pcregrep behaves. In particular, the -M option + makes it possible to search for patterns that span line boundaries. + What defines a line boundary is controlled by the -N (--newline) + option. + + The amount of memory used for buffering files that are being scanned is + controlled by a parameter that can be set by the --buffer-size option. + The default value for this parameter is specified when pcregrep is + built, with the default default being 20K. A block of memory three + times this size is used (to allow for buffering "before" and "after" + lines). An error occurs if a line overflows the buffer. + + Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the + greater. BUFSIZ is defined in <stdio.h>. When there is more than one + pattern (specified by the use of -e and/or -f), each pattern is applied + to each line in the order in which they are defined, except that all + the -e patterns are tried before the -f patterns. + + By default, as soon as one pattern matches a line, no further patterns + are considered. However, if --colour (or --color) is used to colour the + matching substrings, or if --only-matching, --file-offsets, or --line- + offsets is used to output only the part of the line that matched + (either shown literally, or as an offset), scanning resumes immediately + following the match, so that further matches on the same line can be + found. If there are multiple patterns, they are all tried on the + remainder of the line, but patterns that follow the one that matched + are not tried on the earlier part of the line. + + This behaviour means that the order in which multiple patterns are + specified can affect the output when one of the above options is used. + This is no longer the same behaviour as GNU grep, which now manages to + display earlier matches for later patterns (as long as there is no + overlap). + + Patterns that can match an empty string are accepted, but empty string + matches are never recognized. An example is the pattern + "(super)?(man)?", in which all components are optional. This pattern + finds all occurrences of both "super" and "man"; the output differs + from matching with "super|man" when only the matching substrings are + being shown. + + If the LC_ALL or LC_CTYPE environment variable is set, pcregrep uses + the value to set a locale when calling the PCRE library. The --locale + option can be used to override this. + + +SUPPORT FOR COMPRESSED FILES + + It is possible to compile pcregrep so that it uses libz or libbz2 to + read files whose names end in .gz or .bz2, respectively. You can find + out whether your binary has support for one or both of these file types + by running it with the --help option. If the appropriate support is not + present, files are treated as plain text. The standard input is always + so treated. + + +BINARY FILES + + By default, a file that contains a binary zero byte within the first + 1024 bytes is identified as a binary file, and is processed specially. + (GNU grep also identifies binary files in this manner.) See the + --binary-files option for a means of changing the way binary files are + handled. + + +OPTIONS + + The order in which some of the options appear can affect the output. + For example, both the -h and -l options affect the printing of file + names. Whichever comes later in the command line will be the one that + takes effect. Similarly, except where noted below, if an option is + given twice, the later setting is used. Numerical values for options + may be followed by K or M, to signify multiplication by 1024 or + 1024*1024 respectively. + + -- This terminates the list of options. It is useful if the next + item on the command line starts with a hyphen but is not an + option. This allows for the processing of patterns and file- + names that start with hyphens. + + -A number, --after-context=number + Output number lines of context after each matching line. If + filenames and/or line numbers are being output, a hyphen sep- + arator is used instead of a colon for the context lines. A + line containing "--" is output between each group of lines, + unless they are in fact contiguous in the input file. The + value of number is expected to be relatively small. However, + pcregrep guarantees to have up to 8K of following text avail- + able for context output. + + -a, --text + Treat binary files as text. This is equivalent to --binary- + files=text. + + -B number, --before-context=number + Output number lines of context before each matching line. If + filenames and/or line numbers are being output, a hyphen sep- + arator is used instead of a colon for the context lines. A + line containing "--" is output between each group of lines, + unless they are in fact contiguous in the input file. The + value of number is expected to be relatively small. However, + pcregrep guarantees to have up to 8K of preceding text avail- + able for context output. + + --binary-files=word + Specify how binary files are to be processed. If the word is + "binary" (the default), pattern matching is performed on + binary files, but the only output is "Binary file <name> + matches" when a match succeeds. If the word is "text", which + is equivalent to the -a or --text option, binary files are + processed in the same way as any other file. In this case, + when a match succeeds, the output may be binary garbage, + which can have nasty effects if sent to a terminal. If the + word is "without-match", which is equivalent to the -I + option, binary files are not processed at all; they are + assumed not to be of interest. + + --buffer-size=number + Set the parameter that controls how much memory is used for + buffering files that are being scanned. + + -C number, --context=number + Output number lines of context both before and after each + matching line. This is equivalent to setting both -A and -B + to the same value. + + -c, --count + Do not output individual lines from the files that are being + scanned; instead output the number of lines that would other- + wise have been shown. If no lines are selected, the number + zero is output. If several files are are being scanned, a + count is output for each of them. However, if the --files- + with-matches option is also used, only those files whose + counts are greater than zero are listed. When -c is used, the + -A, -B, and -C options are ignored. + + --colour, --color + If this option is given without any data, it is equivalent to + "--colour=auto". If data is required, it must be given in + the same shell item, separated by an equals sign. + + --colour=value, --color=value + This option specifies under what circumstances the parts of a + line that matched a pattern should be coloured in the output. + By default, the output is not coloured. The value (which is + optional, see above) may be "never", "always", or "auto". In + the latter case, colouring happens only if the standard out- + put is connected to a terminal. More resources are used when + colouring is enabled, because pcregrep has to search for all + possible matches in a line, not just one, in order to colour + them all. + + The colour that is used can be specified by setting the envi- + ronment variable PCREGREP_COLOUR or PCREGREP_COLOR. The value + of this variable should be a string of two numbers, separated + by a semicolon. They are copied directly into the control + string for setting colour on a terminal, so it is your + responsibility to ensure that they make sense. If neither of + the environment variables is set, the default is "1;31", + which gives red. + + -D action, --devices=action + If an input path is not a regular file or a directory, + "action" specifies how it is to be processed. Valid values + are "read" (the default) or "skip" (silently skip the path). + + -d action, --directories=action + If an input path is a directory, "action" specifies how it is + to be processed. Valid values are "read" (the default in + non-Windows environments, for compatibility with GNU grep), + "recurse" (equivalent to the -r option), or "skip" (silently + skip the path, the default in Windows environments). In the + "read" case, directories are read as if they were ordinary + files. In some operating systems the effect of reading a + directory like this is an immediate end-of-file; in others it + may provoke an error. + + -e pattern, --regex=pattern, --regexp=pattern + Specify a pattern to be matched. This option can be used mul- + tiple times in order to specify several patterns. It can also + be used as a way of specifying a single pattern that starts + with a hyphen. When -e is used, no argument pattern is taken + from the command line; all arguments are treated as file + names. There is no limit to the number of patterns. They are + applied to each line in the order in which they are defined + until one matches. + + If -f is used with -e, the command line patterns are matched + first, followed by the patterns from the file(s), independent + of the order in which these options are specified. Note that + multiple use of -e is not the same as a single pattern with + alternatives. For example, X|Y finds the first character in a + line that is X or Y, whereas if the two patterns are given + separately, with X first, pcregrep finds X if it is present, + even if it follows Y in the line. It finds Y only if there is + no X in the line. This matters only if you are using -o or + --colo(u)r to show the part(s) of the line that matched. + + --exclude=pattern + Files (but not directories) whose names match the pattern are + skipped without being processed. This applies to all files, + whether listed on the command line, obtained from --file- + list, or by scanning a directory. The pattern is a PCRE regu- + lar expression, and is matched against the final component of + the file name, not the entire path. The -F, -w, and -x + options do not apply to this pattern. The option may be given + any number of times in order to specify multiple patterns. If + a file name matches both an --include and an --exclude pat- + tern, it is excluded. There is no short form for this option. + + --exclude-from=filename + Treat each non-empty line of the file as the data for an + --exclude option. What constitutes a newline when reading the + file is the operating system's default. The --newline option + has no effect on this option. This option may be given more + than once in order to specify a number of files to read. + + --exclude-dir=pattern + Directories whose names match the pattern are skipped without + being processed, whatever the setting of the --recursive + option. This applies to all directories, whether listed on + the command line, obtained from --file-list, or by scanning a + parent directory. The pattern is a PCRE regular expression, + and is matched against the final component of the directory + name, not the entire path. The -F, -w, and -x options do not + apply to this pattern. The option may be given any number of + times in order to specify more than one pattern. If a direc- + tory matches both --include-dir and --exclude-dir, it is + excluded. There is no short form for this option. + + -F, --fixed-strings + Interpret each data-matching pattern as a list of fixed + strings, separated by newlines, instead of as a regular + expression. What constitutes a newline for this purpose is + controlled by the --newline option. The -w (match as a word) + and -x (match whole line) options can be used with -F. They + apply to each of the fixed strings. A line is selected if any + of the fixed strings are found in it (subject to -w or -x, if + present). This option applies only to the patterns that are + matched against the contents of files; it does not apply to + patterns specified by any of the --include or --exclude + options. + + -f filename, --file=filename + Read patterns from the file, one per line, and match them + against each line of input. What constitutes a newline when + reading the file is the operating system's default. The + --newline option has no effect on this option. Trailing white + space is removed from each line, and blank lines are ignored. + An empty file contains no patterns and therefore matches + nothing. See also the comments about multiple patterns versus + a single pattern with alternatives in the description of -e + above. + + If this option is given more than once, all the specified + files are read. A data line is output if any of the patterns + match it. A filename can be given as "-" to refer to the + standard input. When -f is used, patterns specified on the + command line using -e may also be present; they are tested + before the file's patterns. However, no other pattern is + taken from the command line; all arguments are treated as the + names of paths to be searched. + + --file-list=filename + Read a list of files and/or directories that are to be + scanned from the given file, one per line. Trailing white + space is removed from each line, and blank lines are ignored. + These paths are processed before any that are listed on the + command line. The filename can be given as "-" to refer to + the standard input. If --file and --file-list are both spec- + ified as "-", patterns are read first. This is useful only + when the standard input is a terminal, from which further + lines (the list of files) can be read after an end-of-file + indication. If this option is given more than once, all the + specified files are read. + + --file-offsets + Instead of showing lines or parts of lines that match, show + each match as an offset from the start of the file and a + length, separated by a comma. In this mode, no context is + shown. That is, the -A, -B, and -C options are ignored. If + there is more than one match in a line, each of them is shown + separately. This option is mutually exclusive with --line- + offsets and --only-matching. + + -H, --with-filename + Force the inclusion of the filename at the start of output + lines when searching a single file. By default, the filename + is not shown in this case. For matching lines, the filename + is followed by a colon; for context lines, a hyphen separator + is used. If a line number is also being output, it follows + the file name. + + -h, --no-filename + Suppress the output filenames when searching multiple files. + By default, filenames are shown when multiple files are + searched. For matching lines, the filename is followed by a + colon; for context lines, a hyphen separator is used. If a + line number is also being output, it follows the file name. + + --help Output a help message, giving brief details of the command + options and file type support, and then exit. Anything else + on the command line is ignored. + + -I Treat binary files as never matching. This is equivalent to + --binary-files=without-match. + + -i, --ignore-case + Ignore upper/lower case distinctions during comparisons. + + --include=pattern + If any --include patterns are specified, the only files that + are processed are those that match one of the patterns (and + do not match an --exclude pattern). This option does not + affect directories, but it applies to all files, whether + listed on the command line, obtained from --file-list, or by + scanning a directory. The pattern is a PCRE regular expres- + sion, and is matched against the final component of the file + name, not the entire path. The -F, -w, and -x options do not + apply to this pattern. The option may be given any number of + times. If a file name matches both an --include and an + --exclude pattern, it is excluded. There is no short form + for this option. + + --include-from=filename + Treat each non-empty line of the file as the data for an + --include option. What constitutes a newline for this purpose + is the operating system's default. The --newline option has + no effect on this option. This option may be given any number + of times; all the files are read. + + --include-dir=pattern + If any --include-dir patterns are specified, the only direc- + tories that are processed are those that match one of the + patterns (and do not match an --exclude-dir pattern). This + applies to all directories, whether listed on the command + line, obtained from --file-list, or by scanning a parent + directory. The pattern is a PCRE regular expression, and is + matched against the final component of the directory name, + not the entire path. The -F, -w, and -x options do not apply + to this pattern. The option may be given any number of times. + If a directory matches both --include-dir and --exclude-dir, + it is excluded. There is no short form for this option. + + -L, --files-without-match + Instead of outputting lines from the files, just output the + names of the files that do not contain any lines that would + have been output. Each file name is output once, on a sepa- + rate line. + + -l, --files-with-matches + Instead of outputting lines from the files, just output the + names of the files containing lines that would have been out- + put. Each file name is output once, on a separate line. + Searching normally stops as soon as a matching line is found + in a file. However, if the -c (count) option is also used, + matching continues in order to obtain the correct count, and + those files that have at least one match are listed along + with their counts. Using this option with -c is a way of sup- + pressing the listing of files with no matches. + + --label=name + This option supplies a name to be used for the standard input + when file names are being output. If not supplied, "(standard + input)" is used. There is no short form for this option. + + --line-buffered + When this option is given, input is read and processed line + by line, and the output is flushed after each write. By + default, input is read in large chunks, unless pcregrep can + determine that it is reading from a terminal (which is cur- + rently possible only in Unix-like environments). Output to + terminal is normally automatically flushed by the operating + system. This option can be useful when the input or output is + attached to a pipe and you do not want pcregrep to buffer up + large amounts of data. However, its use will affect perfor- + mance, and the -M (multiline) option ceases to work. + + --line-offsets + Instead of showing lines or parts of lines that match, show + each match as a line number, the offset from the start of the + line, and a length. The line number is terminated by a colon + (as usual; see the -n option), and the offset and length are + separated by a comma. In this mode, no context is shown. + That is, the -A, -B, and -C options are ignored. If there is + more than one match in a line, each of them is shown sepa- + rately. This option is mutually exclusive with --file-offsets + and --only-matching. + + --locale=locale-name + This option specifies a locale to be used for pattern match- + ing. It overrides the value in the LC_ALL or LC_CTYPE envi- + ronment variables. If no locale is specified, the PCRE + library's default (usually the "C" locale) is used. There is + no short form for this option. + + --match-limit=number + Processing some regular expression patterns can require a + very large amount of memory, leading in some cases to a pro- + gram crash if not enough is available. Other patterns may + take a very long time to search for all possible matching + strings. The pcre_exec() function that is called by pcregrep + to do the matching has two parameters that can limit the + resources that it uses. + + The --match-limit option provides a means of limiting + resource usage when processing patterns that are not going to + match, but which have a very large number of possibilities in + their search trees. The classic example is a pattern that + uses nested unlimited repeats. Internally, PCRE uses a func- + tion called match() which it calls repeatedly (sometimes + recursively). The limit set by --match-limit is imposed on + the number of times this function is called during a match, + which has the effect of limiting the amount of backtracking + that can take place. + + The --recursion-limit option is similar to --match-limit, but + instead of limiting the total number of times that match() is + called, it limits the depth of recursive calls, which in turn + limits the amount of memory that can be used. The recursion + depth is a smaller number than the total number of calls, + because not all calls to match() are recursive. This limit is + of use only if it is set smaller than --match-limit. + + There are no short forms for these options. The default set- + tings are specified when the PCRE library is compiled, with + the default default being 10 million. + + -M, --multiline + Allow patterns to match more than one line. When this option + is given, patterns may usefully contain literal newline char- + acters and internal occurrences of ^ and $ characters. The + output for a successful match may consist of more than one + line, the last of which is the one in which the match ended. + If the matched string ends with a newline sequence the output + ends at the end of that line. + + When this option is set, the PCRE library is called in "mul- + tiline" mode. There is a limit to the number of lines that + can be matched, imposed by the way that pcregrep buffers the + input file as it scans it. However, pcregrep ensures that at + least 8K characters or the rest of the document (whichever is + the shorter) are available for forward matching, and simi- + larly the previous 8K characters (or all the previous charac- + ters, if fewer than 8K) are guaranteed to be available for + lookbehind assertions. This option does not work when input + is read line by line (see --line-buffered.) + + -N newline-type, --newline=newline-type + The PCRE library supports five different conventions for + indicating the ends of lines. They are the single-character + sequences CR (carriage return) and LF (linefeed), the two- + character sequence CRLF, an "anycrlf" convention, which rec- + ognizes any of the preceding three types, and an "any" con- + vention, in which any Unicode line ending sequence is assumed + to end a line. The Unicode sequences are the three just men- + tioned, plus VT (vertical tab, U+000B), FF (form feed, + U+000C), NEL (next line, U+0085), LS (line separator, + U+2028), and PS (paragraph separator, U+2029). + + When the PCRE library is built, a default line-ending + sequence is specified. This is normally the standard + sequence for the operating system. Unless otherwise specified + by this option, pcregrep uses the library's default. The + possible values for this option are CR, LF, CRLF, ANYCRLF, or + ANY. This makes it possible to use pcregrep to scan files + that have come from other environments without having to mod- + ify their line endings. If the data that is being scanned + does not agree with the convention set by this option, pcre- + grep may behave in strange ways. Note that this option does + not apply to files specified by the -f, --exclude-from, or + --include-from options, which are expected to use the operat- + ing system's standard newline sequence. + + -n, --line-number + Precede each output line by its line number in the file, fol- + lowed by a colon for matching lines or a hyphen for context + lines. If the filename is also being output, it precedes the + line number. This option is forced if --line-offsets is used. + + --no-jit If the PCRE library is built with support for just-in-time + compiling (which speeds up matching), pcregrep automatically + makes use of this, unless it was explicitly disabled at build + time. This option can be used to disable the use of JIT at + run time. It is provided for testing and working round prob- + lems. It should never be needed in normal use. + + -o, --only-matching + Show only the part of the line that matched a pattern instead + of the whole line. In this mode, no context is shown. That + is, the -A, -B, and -C options are ignored. If there is more + than one match in a line, each of them is shown separately. + If -o is combined with -v (invert the sense of the match to + find non-matching lines), no output is generated, but the + return code is set appropriately. If the matched portion of + the line is empty, nothing is output unless the file name or + line number are being printed, in which case they are shown + on an otherwise empty line. This option is mutually exclusive + with --file-offsets and --line-offsets. + + -onumber, --only-matching=number + Show only the part of the line that matched the capturing + parentheses of the given number. Up to 32 capturing parenthe- + ses are supported, and -o0 is equivalent to -o without a num- + ber. Because these options can be given without an argument + (see above), if an argument is present, it must be given in + the same shell item, for example, -o3 or --only-matching=2. + The comments given for the non-argument case above also apply + to this case. If the specified capturing parentheses do not + exist in the pattern, or were not set in the match, nothing + is output unless the file name or line number are being + printed. + + If this option is given multiple times, multiple substrings + are output, in the order the options are given. For example, + -o3 -o1 -o3 causes the substrings matched by capturing paren- + theses 3 and 1 and then 3 again to be output. By default, + there is no separator (but see the next option). + + --om-separator=text + Specify a separating string for multiple occurrences of -o. + The default is an empty string. Separating strings are never + coloured. + + -q, --quiet + Work quietly, that is, display nothing except error messages. + The exit status indicates whether or not any matches were + found. + + -r, --recursive + If any given path is a directory, recursively scan the files + it contains, taking note of any --include and --exclude set- + tings. By default, a directory is read as a normal file; in + some operating systems this gives an immediate end-of-file. + This option is a shorthand for setting the -d option to + "recurse". + + --recursion-limit=number + See --match-limit above. + + -s, --no-messages + Suppress error messages about non-existent or unreadable + files. Such files are quietly skipped. However, the return + code is still 2, even if matches were found in other files. + + -u, --utf-8 + Operate in UTF-8 mode. This option is available only if PCRE + has been compiled with UTF-8 support. All patterns (including + those for any --exclude and --include options) and all sub- + ject lines that are scanned must be valid strings of UTF-8 + characters. + + -V, --version + Write the version numbers of pcregrep and the PCRE library to + the standard output and then exit. Anything else on the com- + mand line is ignored. + + -v, --invert-match + Invert the sense of the match, so that lines which do not + match any of the patterns are the ones that are found. + + -w, --word-regex, --word-regexp + Force the patterns to match only whole words. This is equiva- + lent to having \b at the start and end of the pattern. This + option applies only to the patterns that are matched against + the contents of files; it does not apply to patterns speci- + fied by any of the --include or --exclude options. + + -x, --line-regex, --line-regexp + Force the patterns to be anchored (each must start matching + at the beginning of a line) and in addition, require them to + match entire lines. This is equivalent to having ^ and $ + characters at the start and end of each alternative branch in + every pattern. This option applies only to the patterns that + are matched against the contents of files; it does not apply + to patterns specified by any of the --include or --exclude + options. + + +ENVIRONMENT VARIABLES + + The environment variables LC_ALL and LC_CTYPE are examined, in that + order, for a locale. The first one that is set is used. This can be + overridden by the --locale option. If no locale is set, the PCRE + library's default (usually the "C" locale) is used. + + +NEWLINES + + The -N (--newline) option allows pcregrep to scan files with different + newline conventions from the default. Any parts of the input files that + are written to the standard output are copied identically, with what- + ever newline sequences they have in the input. However, the setting of + this option does not affect the interpretation of files specified by + the -f, --exclude-from, or --include-from options, which are assumed to + use the operating system's standard newline sequence, nor does it + affect the way in which pcregrep writes informational messages to the + standard error and output streams. For these it uses the string "\n" to + indicate newlines, relying on the C I/O library to convert this to an + appropriate sequence. + + +OPTIONS COMPATIBILITY + + Many of the short and long forms of pcregrep's options are the same as + in the GNU grep program. Any long option of the form --xxx-regexp (GNU + terminology) is also available as --xxx-regex (PCRE terminology). How- + ever, the --file-list, --file-offsets, --include-dir, --line-offsets, + --locale, --match-limit, -M, --multiline, -N, --newline, --om-separa- + tor, --recursion-limit, -u, and --utf-8 options are specific to pcre- + grep, as is the use of the --only-matching option with a capturing + parentheses number. + + Although most of the common options work the same way, a few are dif- + ferent in pcregrep. For example, the --include option's argument is a + glob for GNU grep, but a regular expression for pcregrep. If both the + -c and -l options are given, GNU grep lists only file names, without + counts, but pcregrep gives the counts. + + +OPTIONS WITH DATA + + There are four different ways in which an option with data can be spec- + ified. If a short form option is used, the data may follow immedi- + ately, or (with one exception) in the next command line item. For exam- + ple: + + -f/some/file + -f /some/file + + The exception is the -o option, which may appear with or without data. + Because of this, if data is present, it must follow immediately in the + same item, for example -o3. + + If a long form option is used, the data may appear in the same command + line item, separated by an equals character, or (with two exceptions) + it may appear in the next command line item. For example: + + --file=/some/file + --file /some/file + + Note, however, that if you want to supply a file name beginning with ~ + as data in a shell command, and have the shell expand ~ to a home + directory, you must separate the file name from the option, because the + shell does not treat ~ specially unless it is at the start of an item. + + The exceptions to the above are the --colour (or --color) and --only- + matching options, for which the data is optional. If one of these + options does have data, it must be given in the first form, using an + equals character. Otherwise pcregrep will assume that it has no data. + + +MATCHING ERRORS + + It is possible to supply a regular expression that takes a very long + time to fail to match certain lines. Such patterns normally involve + nested indefinite repeats, for example: (a+)*\d when matched against a + line of a's with no final digit. The PCRE matching function has a + resource limit that causes it to abort in these circumstances. If this + happens, pcregrep outputs an error message and the line that caused the + problem to the standard error stream. If there are more than 20 such + errors, pcregrep gives up. + + The --match-limit option of pcregrep can be used to set the overall + resource limit; there is a second option called --recursion-limit that + sets a limit on the amount of memory (usually stack) that is used (see + the discussion of these options above). + + +DIAGNOSTICS + + Exit status is 0 if any matches were found, 1 if no matches were found, + and 2 for syntax errors, overlong lines, non-existent or inaccessible + files (even if matches were found in other files) or too many matching + errors. Using the -s option to suppress error messages about inaccessi- + ble files does not affect the return code. + + +SEE ALSO + + pcrepattern(3), pcresyntax(3), pcretest(1). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 03 April 2014 + Copyright (c) 1997-2014 University of Cambridge. diff --git a/doc/pcrejit.3 b/doc/pcrejit.3 new file mode 100644 index 0000000..341403f --- /dev/null +++ b/doc/pcrejit.3 @@ -0,0 +1,431 @@ +.TH PCREJIT 3 "17 March 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE JUST-IN-TIME COMPILER SUPPORT" +.rs +.sp +Just-in-time compiling is a heavyweight optimization that can greatly speed up +pattern matching. However, it comes at the cost of extra processing before the +match is performed. Therefore, it is of most benefit when the same pattern is +going to be matched many times. This does not necessarily mean many calls of a +matching function; if the pattern is not anchored, matching attempts may take +place many times at various positions in the subject, even for a single call. +Therefore, if the subject string is very long, it may still pay to use JIT for +one-off matches. +.P +JIT support applies only to the traditional Perl-compatible matching function. +It does not apply when the DFA matching function is being used. The code for +this support was written by Zoltan Herczeg. +. +. +.SH "8-BIT, 16-BIT AND 32-BIT SUPPORT" +.rs +.sp +JIT support is available for all of the 8-bit, 16-bit and 32-bit PCRE +libraries. To keep this documentation simple, only the 8-bit interface is +described in what follows. If you are using the 16-bit library, substitute the +16-bit functions and 16-bit structures (for example, \fIpcre16_jit_stack\fP +instead of \fIpcre_jit_stack\fP). If you are using the 32-bit library, +substitute the 32-bit functions and 32-bit structures (for example, +\fIpcre32_jit_stack\fP instead of \fIpcre_jit_stack\fP). +. +. +.SH "AVAILABILITY OF JIT SUPPORT" +.rs +.sp +JIT support is an optional feature of PCRE. The "configure" option --enable-jit +(or equivalent CMake option) must be set when PCRE is built if you want to use +JIT. The support is limited to the following hardware platforms: +.sp + ARM v5, v7, and Thumb2 + Intel x86 32-bit and 64-bit + MIPS 32-bit + Power PC 32-bit and 64-bit + SPARC 32-bit (experimental) +.sp +If --enable-jit is set on an unsupported platform, compilation fails. +.P +A program that is linked with PCRE 8.20 or later can tell if JIT support is +available by calling \fBpcre_config()\fP with the PCRE_CONFIG_JIT option. The +result is 1 when JIT is available, and 0 otherwise. However, a simple program +does not need to check this in order to use JIT. The normal API is implemented +in a way that falls back to the interpretive code if JIT is not available. For +programs that need the best possible performance, there is also a "fast path" +API that is JIT-specific. +.P +If your program may sometimes be linked with versions of PCRE that are older +than 8.20, but you want to use JIT when it is available, you can test +the values of PCRE_MAJOR and PCRE_MINOR, or the existence of a JIT macro such +as PCRE_CONFIG_JIT, for compile-time control of your code. +. +. +.SH "SIMPLE USE OF JIT" +.rs +.sp +You have to do two things to make use of the JIT support in the simplest way: +.sp + (1) Call \fBpcre_study()\fP with the PCRE_STUDY_JIT_COMPILE option for + each compiled pattern, and pass the resulting \fBpcre_extra\fP block to + \fBpcre_exec()\fP. +.sp + (2) Use \fBpcre_free_study()\fP to free the \fBpcre_extra\fP block when it is + no longer needed, instead of just freeing it yourself. This ensures that + any JIT data is also freed. +.sp +For a program that may be linked with pre-8.20 versions of PCRE, you can insert +.sp + #ifndef PCRE_STUDY_JIT_COMPILE + #define PCRE_STUDY_JIT_COMPILE 0 + #endif +.sp +so that no option is passed to \fBpcre_study()\fP, and then use something like +this to free the study data: +.sp + #ifdef PCRE_CONFIG_JIT + pcre_free_study(study_ptr); + #else + pcre_free(study_ptr); + #endif +.sp +PCRE_STUDY_JIT_COMPILE requests the JIT compiler to generate code for complete +matches. If you want to run partial matches using the PCRE_PARTIAL_HARD or +PCRE_PARTIAL_SOFT options of \fBpcre_exec()\fP, you should set one or both of +the following options in addition to, or instead of, PCRE_STUDY_JIT_COMPILE +when you call \fBpcre_study()\fP: +.sp + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE +.sp +The JIT compiler generates different optimized code for each of the three +modes (normal, soft partial, hard partial). When \fBpcre_exec()\fP is called, +the appropriate code is run if it is available. Otherwise, the pattern is +matched using interpretive code. +.P +In some circumstances you may need to call additional functions. These are +described in the section entitled +.\" HTML <a href="#stackcontrol"> +.\" </a> +"Controlling the JIT stack" +.\" +below. +.P +If JIT support is not available, PCRE_STUDY_JIT_COMPILE etc. are ignored, and +no JIT data is created. Otherwise, the compiled pattern is passed to the JIT +compiler, which turns it into machine code that executes much faster than the +normal interpretive code. When \fBpcre_exec()\fP is passed a \fBpcre_extra\fP +block containing a pointer to JIT code of the appropriate mode (normal or +hard/soft partial), it obeys that code instead of running the interpreter. The +result is identical, but the compiled JIT code runs much faster. +.P +There are some \fBpcre_exec()\fP options that are not supported for JIT +execution. There are also some pattern items that JIT cannot handle. Details +are given below. In both cases, execution automatically falls back to the +interpretive code. If you want to know whether JIT was actually used for a +particular match, you should arrange for a JIT callback function to be set up +as described in the section entitled +.\" HTML <a href="#stackcontrol"> +.\" </a> +"Controlling the JIT stack" +.\" +below, even if you do not need to supply a non-default JIT stack. Such a +callback function is called whenever JIT code is about to be obeyed. If the +execution options are not right for JIT execution, the callback function is not +obeyed. +.P +If the JIT compiler finds an unsupported item, no JIT data is generated. You +can find out if JIT execution is available after studying a pattern by calling +\fBpcre_fullinfo()\fP with the PCRE_INFO_JIT option. A result of 1 means that +JIT compilation was successful. A result of 0 means that JIT support is not +available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE etc., or +the JIT compiler was not able to handle the pattern. +.P +Once a pattern has been studied, with or without JIT, it can be used as many +times as you like for matching different subject strings. +. +. +.SH "UNSUPPORTED OPTIONS AND PATTERN ITEMS" +.rs +.sp +The only \fBpcre_exec()\fP options that are supported for JIT execution are +PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK, PCRE_NO_UTF32_CHECK, PCRE_NOTBOL, +PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and +PCRE_PARTIAL_SOFT. +.P +The only unsupported pattern items are \eC (match a single data unit) when +running in a UTF mode, and a callout immediately before an assertion condition +in a conditional group. +. +. +.SH "RETURN VALUES FROM JIT EXECUTION" +.rs +.sp +When a pattern is matched using JIT execution, the return values are the same +as those given by the interpretive \fBpcre_exec()\fP code, with the addition of +one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means that the memory used +for the JIT stack was insufficient. See +.\" HTML <a href="#stackcontrol"> +.\" </a> +"Controlling the JIT stack" +.\" +below for a discussion of JIT stack usage. For compatibility with the +interpretive \fBpcre_exec()\fP code, no more than two-thirds of the +\fIovector\fP argument is used for passing back captured substrings. +.P +The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if searching a +very large pattern tree goes on for too long, as it is in the same circumstance +when JIT is not used, but the details of exactly what is counted are not the +same. The PCRE_ERROR_RECURSIONLIMIT error code is never returned by JIT +execution. +. +. +.SH "SAVING AND RESTORING COMPILED PATTERNS" +.rs +.sp +The code that is generated by the JIT compiler is architecture-specific, and is +also position dependent. For those reasons it cannot be saved (in a file or +database) and restored later like the bytecode and other data of a compiled +pattern. Saving and restoring compiled patterns is not something many people +do. More detail about this facility is given in the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation. It should be possible to run \fBpcre_study()\fP on a saved and +restored pattern, and thereby recreate the JIT data, but because JIT +compilation uses significant resources, it is probably not worth doing this; +you might as well recompile the original pattern. +. +. +.\" HTML <a name="stackcontrol"></a> +.SH "CONTROLLING THE JIT STACK" +.rs +.sp +When the compiled JIT code runs, it needs a block of memory to use as a stack. +By default, it uses 32K on the machine stack. However, some large or +complicated patterns need more than this. The error PCRE_ERROR_JIT_STACKLIMIT +is given when there is not enough stack. Three functions are provided for +managing blocks of memory for use as JIT stacks. There is further discussion +about the use of JIT stacks in the section entitled +.\" HTML <a href="#stackcontrol"> +.\" </a> +"JIT stack FAQ" +.\" +below. +.P +The \fBpcre_jit_stack_alloc()\fP function creates a JIT stack. Its arguments +are a starting size and a maximum size, and it returns a pointer to an opaque +structure of type \fBpcre_jit_stack\fP, or NULL if there is an error. The +\fBpcre_jit_stack_free()\fP function can be used to free a stack that is no +longer needed. (For the technically minded: the address space is allocated by +mmap or VirtualAlloc.) +.P +JIT uses far less memory for recursion than the interpretive code, +and a maximum stack size of 512K to 1M should be more than enough for any +pattern. +.P +The \fBpcre_assign_jit_stack()\fP function specifies which stack JIT code +should use. Its arguments are as follows: +.sp + pcre_extra *extra + pcre_jit_callback callback + void *data +.sp +The \fIextra\fP argument must be the result of studying a pattern with +PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the other +two options: +.sp + (1) If \fIcallback\fP is NULL and \fIdata\fP is NULL, an internal 32K block + on the machine stack is used. +.sp + (2) If \fIcallback\fP is NULL and \fIdata\fP is not NULL, \fIdata\fP must be + a valid JIT stack, the result of calling \fBpcre_jit_stack_alloc()\fP. +.sp + (3) If \fIcallback\fP is not NULL, it must point to a function that is + called with \fIdata\fP as an argument at the start of matching, in + order to set up a JIT stack. If the return from the callback + function is NULL, the internal 32K stack is used; otherwise the + return value must be a valid JIT stack, the result of calling + \fBpcre_jit_stack_alloc()\fP. +.sp +A callback function is obeyed whenever JIT code is about to be run; it is not +obeyed when \fBpcre_exec()\fP is called with options that are incompatible for +JIT execution. A callback function can therefore be used to determine whether a +match operation was executed by JIT or by the interpreter. +.P +You may safely use the same JIT stack for more than one pattern (either by +assigning directly or by callback), as long as the patterns are all matched +sequentially in the same thread. In a multithread application, if you do not +specify a JIT stack, or if you assign or pass back NULL from a callback, that +is thread-safe, because each thread has its own machine stack. However, if you +assign or pass back a non-NULL JIT stack, this must be a different stack for +each thread so that the application is thread-safe. +.P +Strictly speaking, even more is allowed. You can assign the same non-NULL stack +to any number of patterns as long as they are not used for matching by multiple +threads at the same time. For example, you can assign the same stack to all +compiled patterns, and use a global mutex in the callback to wait until the +stack is available for use. However, this is an inefficient solution, and not +recommended. +.P +This is a suggestion for how a multithreaded program that needs to set up +non-default JIT stacks might operate: +.sp + During thread initalization + thread_local_var = pcre_jit_stack_alloc(...) +.sp + During thread exit + pcre_jit_stack_free(thread_local_var) +.sp + Use a one-line callback function + return thread_local_var +.sp +All the functions described in this section do nothing if JIT is not available, +and \fBpcre_assign_jit_stack()\fP does nothing unless the \fBextra\fP argument +is non-NULL and points to a \fBpcre_extra\fP block that is the result of a +successful study with PCRE_STUDY_JIT_COMPILE etc. +. +. +.\" HTML <a name="stackfaq"></a> +.SH "JIT STACK FAQ" +.rs +.sp +(1) Why do we need JIT stacks? +.sp +PCRE (and JIT) is a recursive, depth-first engine, so it needs a stack where +the local data of the current node is pushed before checking its child nodes. +Allocating real machine stack on some platforms is difficult. For example, the +stack chain needs to be updated every time if we extend the stack on PowerPC. +Although it is possible, its updating time overhead decreases performance. So +we do the recursion in memory. +.P +(2) Why don't we simply allocate blocks of memory with \fBmalloc()\fP? +.sp +Modern operating systems have a nice feature: they can reserve an address space +instead of allocating memory. We can safely allocate memory pages inside this +address space, so the stack could grow without moving memory data (this is +important because of pointers). Thus we can allocate 1M address space, and use +only a single memory page (usually 4K) if that is enough. However, we can still +grow up to 1M anytime if needed. +.P +(3) Who "owns" a JIT stack? +.sp +The owner of the stack is the user program, not the JIT studied pattern or +anything else. The user program must ensure that if a stack is used by +\fBpcre_exec()\fP, (that is, it is assigned to the pattern currently running), +that stack must not be used by any other threads (to avoid overwriting the same +memory area). The best practice for multithreaded programs is to allocate a +stack for each thread, and return this stack through the JIT callback function. +.P +(4) When should a JIT stack be freed? +.sp +You can free a JIT stack at any time, as long as it will not be used by +\fBpcre_exec()\fP again. When you assign the stack to a pattern, only a pointer +is set. There is no reference counting or any other magic. You can free the +patterns and stacks in any order, anytime. Just \fIdo not\fP call +\fBpcre_exec()\fP with a pattern pointing to an already freed stack, as that +will cause SEGFAULT. (Also, do not free a stack currently used by +\fBpcre_exec()\fP in another thread). You can also replace the stack for a +pattern at any time. You can even free the previous stack before assigning a +replacement. +.P +(5) Should I allocate/free a stack every time before/after calling +\fBpcre_exec()\fP? +.sp +No, because this is too costly in terms of resources. However, you could +implement some clever idea which release the stack if it is not used in let's +say two minutes. The JIT callback can help to achieve this without keeping a +list of the currently JIT studied patterns. +.P +(6) OK, the stack is for long term memory allocation. But what happens if a +pattern causes stack overflow with a stack of 1M? Is that 1M kept until the +stack is freed? +.sp +Especially on embedded sytems, it might be a good idea to release memory +sometimes without freeing the stack. There is no API for this at the moment. +Probably a function call which returns with the currently allocated memory for +any stack and another which allows releasing memory (shrinking the stack) would +be a good idea if someone needs this. +.P +(7) This is too much of a headache. Isn't there any better solution for JIT +stack handling? +.sp +No, thanks to Windows. If POSIX threads were used everywhere, we could throw +out this complicated API. +. +. +.SH "EXAMPLE CODE" +.rs +.sp +This is a single-threaded example that specifies a JIT stack without using a +callback. +.sp + int rc; + int ovector[30]; + pcre *re; + pcre_extra *extra; + pcre_jit_stack *jit_stack; +.sp + re = pcre_compile(pattern, 0, &error, &erroffset, NULL); + /* Check for errors */ + extra = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &error); + jit_stack = pcre_jit_stack_alloc(32*1024, 512*1024); + /* Check for error (NULL) */ + pcre_assign_jit_stack(extra, NULL, jit_stack); + rc = pcre_exec(re, extra, subject, length, 0, 0, ovector, 30); + /* Check results */ + pcre_free(re); + pcre_free_study(extra); + pcre_jit_stack_free(jit_stack); +.sp +. +. +.SH "JIT FAST PATH API" +.rs +.sp +Because the API described above falls back to interpreted execution when JIT is +not available, it is convenient for programs that are written for general use +in many environments. However, calling JIT via \fBpcre_exec()\fP does have a +performance impact. Programs that are written for use where JIT is known to be +available, and which need the best possible performance, can instead use a +"fast path" API to call JIT execution directly instead of calling +\fBpcre_exec()\fP (obviously only for patterns that have been successfully +studied by JIT). +.P +The fast path function is called \fBpcre_jit_exec()\fP, and it takes exactly +the same arguments as \fBpcre_exec()\fP, plus one additional argument that +must point to a JIT stack. The JIT stack arrangements described above do not +apply. The return values are the same as for \fBpcre_exec()\fP. +.P +When you call \fBpcre_exec()\fP, as well as testing for invalid options, a +number of other sanity checks are performed on the arguments. For example, if +the subject pointer is NULL, or its length is negative, an immediate error is +given. Also, unless PCRE_NO_UTF[8|16|32] is set, a UTF subject string is tested +for validity. In the interests of speed, these checks do not happen on the JIT +fast path, and if invalid data is passed, the result is undefined. +.P +Bypassing the sanity checks and the \fBpcre_exec()\fP wrapping can give +speedups of more than 10%. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcreapi\fP(3) +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel (FAQ by Zoltan Herczeg) +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 17 March 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrelimits.3 b/doc/pcrelimits.3 new file mode 100644 index 0000000..423d6a2 --- /dev/null +++ b/doc/pcrelimits.3 @@ -0,0 +1,71 @@ +.TH PCRELIMITS 3 "05 November 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "SIZE AND OTHER LIMITATIONS" +.rs +.sp +There are some size limitations in PCRE but it is hoped that they will never in +practice be relevant. +.P +The maximum length of a compiled pattern is approximately 64K data units (bytes +for the 8-bit library, 16-bit units for the 16-bit library, and 32-bit units for +the 32-bit library) if PCRE is compiled with the default internal linkage size, +which is 2 bytes for the 8-bit and 16-bit libraries, and 4 bytes for the 32-bit +library. If you want to process regular expressions that are truly enormous, +you can compile PCRE with an internal linkage size of 3 or 4 (when building the +16-bit or 32-bit library, 3 is rounded up to 4). See the \fBREADME\fP file in +the source distribution and the +.\" HREF +\fBpcrebuild\fP +.\" +documentation for details. In these cases the limit is substantially larger. +However, the speed of execution is slower. +.P +All values in repeating quantifiers must be less than 65536. +.P +There is no limit to the number of parenthesized subpatterns, but there can be +no more than 65535 capturing subpatterns. There is, however, a limit to the +depth of nesting of parenthesized subpatterns of all kinds. This is imposed in +order to limit the amount of system stack used at compile time. The limit can +be specified when PCRE is built; the default is 250. +.P +There is a limit to the number of forward references to subsequent subpatterns +of around 200,000. Repeated forward references with fixed upper limits, for +example, (?2){0,100} when subpattern number 2 is to the right, are included in +the count. There is no limit to the number of backward references. +.P +The maximum length of name for a named subpattern is 32 characters, and the +maximum number of named subpatterns is 10000. +.P +The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb +is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries. +.P +The maximum length of a subject string is the largest positive number that an +integer variable can hold. However, when using the traditional matching +function, PCRE uses recursion to handle subpatterns and indefinite repetition. +This means that the available stack space may limit the size of a subject +string that can be processed by certain patterns. For a discussion of stack +issues, see the +.\" HREF +\fBpcrestack\fP +.\" +documentation. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 05 November 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrematching.3 b/doc/pcrematching.3 new file mode 100644 index 0000000..268baf9 --- /dev/null +++ b/doc/pcrematching.3 @@ -0,0 +1,214 @@ +.TH PCREMATCHING 3 "12 November 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE MATCHING ALGORITHMS" +.rs +.sp +This document describes the two different algorithms that are available in PCRE +for matching a compiled regular expression against a given subject string. The +"standard" algorithm is the one provided by the \fBpcre_exec()\fP, +\fBpcre16_exec()\fP and \fBpcre32_exec()\fP functions. These work in the same +as as Perl's matching function, and provide a Perl-compatible matching operation. +The just-in-time (JIT) optimization that is described in the +.\" HREF +\fBpcrejit\fP +.\" +documentation is compatible with these functions. +.P +An alternative algorithm is provided by the \fBpcre_dfa_exec()\fP, +\fBpcre16_dfa_exec()\fP and \fBpcre32_dfa_exec()\fP functions; they operate in +a different way, and are not Perl-compatible. This alternative has advantages +and disadvantages compared with the standard algorithm, and these are described +below. +.P +When there is only one possible way in which a given subject string can match a +pattern, the two algorithms give the same answer. A difference arises, however, +when there are multiple possibilities. For example, if the pattern +.sp + ^<.*> +.sp +is matched against the string +.sp + <something> <something else> <something further> +.sp +there are three possible answers. The standard algorithm finds only one of +them, whereas the alternative algorithm finds all three. +. +. +.SH "REGULAR EXPRESSIONS AS TREES" +.rs +.sp +The set of strings that are matched by a regular expression can be represented +as a tree structure. An unlimited repetition in the pattern makes the tree of +infinite size, but it is still a tree. Matching the pattern to a given subject +string (from a given starting point) can be thought of as a search of the tree. +There are two ways to search a tree: depth-first and breadth-first, and these +correspond to the two matching algorithms provided by PCRE. +. +. +.SH "THE STANDARD MATCHING ALGORITHM" +.rs +.sp +In the terminology of Jeffrey Friedl's book "Mastering Regular +Expressions", the standard algorithm is an "NFA algorithm". It conducts a +depth-first search of the pattern tree. That is, it proceeds along a single +path through the tree, checking that the subject matches what is required. When +there is a mismatch, the algorithm tries any alternatives at the current point, +and if they all fail, it backs up to the previous branch point in the tree, and +tries the next alternative branch at that level. This often involves backing up +(moving to the left) in the subject string as well. The order in which +repetition branches are tried is controlled by the greedy or ungreedy nature of +the quantifier. +.P +If a leaf node is reached, a matching string has been found, and at that point +the algorithm stops. Thus, if there is more than one possible match, this +algorithm returns the first one that it finds. Whether this is the shortest, +the longest, or some intermediate length depends on the way the greedy and +ungreedy repetition quantifiers are specified in the pattern. +.P +Because it ends up with a single path through the tree, it is relatively +straightforward for this algorithm to keep track of the substrings that are +matched by portions of the pattern in parentheses. This provides support for +capturing parentheses and back references. +. +. +.SH "THE ALTERNATIVE MATCHING ALGORITHM" +.rs +.sp +This algorithm conducts a breadth-first search of the tree. Starting from the +first matching point in the subject, it scans the subject string from left to +right, once, character by character, and as it does this, it remembers all the +paths through the tree that represent valid matches. In Friedl's terminology, +this is a kind of "DFA algorithm", though it is not implemented as a +traditional finite state machine (it keeps multiple states active +simultaneously). +.P +Although the general principle of this matching algorithm is that it scans the +subject string only once, without backtracking, there is one exception: when a +lookaround assertion is encountered, the characters following or preceding the +current point have to be independently inspected. +.P +The scan continues until either the end of the subject is reached, or there are +no more unterminated paths. At this point, terminated paths represent the +different matching possibilities (if there are none, the match has failed). +Thus, if there is more than one possible match, this algorithm finds all of +them, and in particular, it finds the longest. The matches are returned in +decreasing order of length. There is an option to stop the algorithm after the +first match (which is necessarily the shortest) is found. +.P +Note that all the matches that are found start at the same point in the +subject. If the pattern +.sp + cat(er(pillar)?)? +.sp +is matched against the string "the caterpillar catchment", the result will be +the three strings "caterpillar", "cater", and "cat" that start at the fifth +character of the subject. The algorithm does not automatically move on to find +matches that start at later positions. +.P +PCRE's "auto-possessification" optimization usually applies to character +repeats at the end of a pattern (as well as internally). For example, the +pattern "a\ed+" is compiled as if it were "a\ed++" because there is no point +even considering the possibility of backtracking into the repeated digits. For +DFA matching, this means that only one possible match is found. If you really +do want multiple matches in such cases, either use an ungreedy repeat +("a\ed+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. +.P +There are a number of features of PCRE regular expressions that are not +supported by the alternative matching algorithm. They are as follows: +.P +1. Because the algorithm finds all possible matches, the greedy or ungreedy +nature of repetition quantifiers is not relevant. Greedy and ungreedy +quantifiers are treated in exactly the same way. However, possessive +quantifiers can make a difference when what follows could also match what is +quantified, for example in a pattern like this: +.sp + ^a++\ew! +.sp +This pattern matches "aaab!" but not "aaa!", which would be matched by a +non-possessive quantifier. Similarly, if an atomic group is present, it is +matched as if it were a standalone pattern at the current point, and the +longest match is then "locked in" for the rest of the overall pattern. +.P +2. When dealing with multiple paths through the tree simultaneously, it is not +straightforward to keep track of captured substrings for the different matching +possibilities, and PCRE's implementation of this algorithm does not attempt to +do this. This means that no captured substrings are available. +.P +3. Because no substrings are captured, back references within the pattern are +not supported, and cause errors if encountered. +.P +4. For the same reason, conditional expressions that use a backreference as the +condition or test for a specific group recursion are not supported. +.P +5. Because many paths through the tree may be active, the \eK escape sequence, +which resets the start of the match when encountered (but may be on some paths +and not on others), is not supported. It causes an error if encountered. +.P +6. Callouts are supported, but the value of the \fIcapture_top\fP field is +always 1, and the value of the \fIcapture_last\fP field is always -1. +.P +7. The \eC escape sequence, which (in the standard algorithm) always matches a +single data unit, even in UTF-8, UTF-16 or UTF-32 modes, is not supported in +these modes, because the alternative algorithm moves through the subject string +one character (not data unit) at a time, for all active paths through the tree. +.P +8. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not +supported. (*FAIL) is supported, and behaves like a failing negative assertion. +. +. +.SH "ADVANTAGES OF THE ALTERNATIVE ALGORITHM" +.rs +.sp +Using the alternative matching algorithm provides the following advantages: +.P +1. All possible matches (at a single point in the subject) are automatically +found, and in particular, the longest match is found. To find more than one +match using the standard algorithm, you have to do kludgy things with +callouts. +.P +2. Because the alternative algorithm scans the subject string just once, and +never needs to backtrack (except for lookbehinds), it is possible to pass very +long subject strings to the matching function in several pieces, checking for +partial matching each time. Although it is possible to do multi-segment +matching using the standard algorithm by retaining partially matched +substrings, it is more complicated. The +.\" HREF +\fBpcrepartial\fP +.\" +documentation gives details of partial matching and discusses multi-segment +matching. +. +. +.SH "DISADVANTAGES OF THE ALTERNATIVE ALGORITHM" +.rs +.sp +The alternative algorithm suffers from a number of disadvantages: +.P +1. It is substantially slower than the standard algorithm. This is partly +because it has to search for all possible matches, but is also because it is +less susceptible to optimization. +.P +2. Capturing parentheses and back references are not supported. +.P +3. Although atomic groups are supported, their use does not provide the +performance advantage that it does for the standard algorithm. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 November 2013 +Copyright (c) 1997-2012 University of Cambridge. +.fi diff --git a/doc/pcrepartial.3 b/doc/pcrepartial.3 new file mode 100644 index 0000000..14d0124 --- /dev/null +++ b/doc/pcrepartial.3 @@ -0,0 +1,476 @@ +.TH PCREPARTIAL 3 "02 July 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PARTIAL MATCHING IN PCRE" +.rs +.sp +In normal use of PCRE, if the subject string that is passed to a matching +function matches as far as it goes, but is too short to match the entire +pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances where it might +be helpful to distinguish this case from other cases in which there is no +match. +.P +Consider, for example, an application where a human is required to type in data +for a field with specific formatting requirements. An example might be a date +in the form \fIddmmmyy\fP, defined by this pattern: +.sp + ^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$ +.sp +If the application sees the user's keystrokes one by one, and can check that +what has been typed so far is potentially valid, it is able to raise an error +as soon as a mistake is made, by beeping and not reflecting the character that +has been typed, for example. This immediate feedback is likely to be a better +user interface than a check that is delayed until the entire string has been +entered. Partial matching can also be useful when the subject string is very +long and is not all available at once. +.P +PCRE supports partial matching by means of the PCRE_PARTIAL_SOFT and +PCRE_PARTIAL_HARD options, which can be set when calling any of the matching +functions. For backwards compatibility, PCRE_PARTIAL is a synonym for +PCRE_PARTIAL_SOFT. The essential difference between the two options is whether +or not a partial match is preferred to an alternative complete match, though +the details differ between the two types of matching function. If both options +are set, PCRE_PARTIAL_HARD takes precedence. +.P +If you want to use partial matching with just-in-time optimized code, you must +call \fBpcre_study()\fP, \fBpcre16_study()\fP or \fBpcre32_study()\fP with one +or both of these options: +.sp + PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE +.sp +PCRE_STUDY_JIT_COMPILE should also be set if you are going to run non-partial +matches on the same pattern. If the appropriate JIT study mode has not been set +for a match, the interpretive matching code is used. +.P +Setting a partial matching option disables two of PCRE's standard +optimizations. PCRE remembers the last literal data unit in a pattern, and +abandons matching immediately if it is not present in the subject string. This +optimization cannot be used for a subject string that might match only +partially. If the pattern was studied, PCRE knows the minimum length of a +matching string, and does not bother to run the matching function on shorter +strings. This optimization is also disabled for partial matching. +. +. +.SH "PARTIAL MATCHING USING pcre_exec() OR pcre[16|32]_exec()" +.rs +.sp +A partial match occurs during a call to \fBpcre_exec()\fP or +\fBpcre[16|32]_exec()\fP when the end of the subject string is reached +successfully, but matching cannot continue because more characters are needed. +However, at least one character in the subject must have been inspected. This +character need not form part of the final matched string; lookbehind assertions +and the \eK escape sequence provide ways of inspecting characters before the +start of a matched substring. The requirement for inspecting at least one +character exists because an empty string can always be matched; without such a +restriction there would always be a partial match of an empty string at the end +of the subject. +.P +If there are at least two slots in the offsets vector when a partial match is +returned, the first slot is set to the offset of the earliest character that +was inspected. For convenience, the second offset points to the end of the +subject so that a substring can easily be identified. If there are at least +three slots in the offsets vector, the third slot is set to the offset of the +character where matching started. +.P +For the majority of patterns, the contents of the first and third slots will be +the same. However, for patterns that contain lookbehind assertions, or begin +with \eb or \eB, characters before the one where matching started may have been +inspected while carrying out the match. For example, consider this pattern: +.sp + /(?<=abc)123/ +.sp +This pattern matches "123", but only if it is preceded by "abc". If the subject +string is "xyzabc12", the first two offsets after a partial match are for the +substring "abc12", because all these characters were inspected. However, the +third offset is set to 6, because that is the offset where matching began. +.P +What happens when a partial match is identified depends on which of the two +partial matching options are set. +. +. +.SS "PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre[16|32]_exec()" +.rs +.sp +If PCRE_PARTIAL_SOFT is set when \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP +identifies a partial match, the partial match is remembered, but matching +continues as normal, and other alternatives in the pattern are tried. If no +complete match can be found, PCRE_ERROR_PARTIAL is returned instead of +PCRE_ERROR_NOMATCH. +.P +This option is "soft" because it prefers a complete match over a partial match. +All the various matching items in a pattern behave as if the subject string is +potentially complete. For example, \ez, \eZ, and $ match at the end of the +subject, as normal, and for \eb and \eB the end of the subject is treated as a +non-alphanumeric. +.P +If there is more than one partial match, the first one that was found provides +the data that is returned. Consider this pattern: +.sp + /123\ew+X|dogY/ +.sp +If this is matched against the subject string "abc123dog", both +alternatives fail to match, but the end of the subject is reached during +matching, so PCRE_ERROR_PARTIAL is returned. The offsets are set to 3 and 9, +identifying "123dog" as the first partial match that was found. (In this +example, there are two partial matches, because "dog" on its own partially +matches the second alternative.) +. +. +.SS "PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre[16|32]_exec()" +.rs +.sp +If PCRE_PARTIAL_HARD is set for \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP, +PCRE_ERROR_PARTIAL is returned as soon as a partial match is found, without +continuing to search for possible complete matches. This option is "hard" +because it prefers an earlier partial match over a later complete match. For +this reason, the assumption is made that the end of the supplied subject string +may not be the true end of the available data, and so, if \ez, \eZ, \eb, \eB, +or $ are encountered at the end of the subject, the result is +PCRE_ERROR_PARTIAL, provided that at least one character in the subject has +been inspected. +.P +Setting PCRE_PARTIAL_HARD also affects the way UTF-8 and UTF-16 +subject strings are checked for validity. Normally, an invalid sequence +causes the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the +special case of a truncated character at the end of the subject, +PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when +PCRE_PARTIAL_HARD is set. +. +. +.SS "Comparing hard and soft partial matching" +.rs +.sp +The difference between the two partial matching options can be illustrated by a +pattern such as: +.sp + /dog(sbody)?/ +.sp +This matches either "dog" or "dogsbody", greedily (that is, it prefers the +longer string if possible). If it is matched against the string "dog" with +PCRE_PARTIAL_SOFT, it yields a complete match for "dog". However, if +PCRE_PARTIAL_HARD is set, the result is PCRE_ERROR_PARTIAL. On the other hand, +if the pattern is made ungreedy the result is different: +.sp + /dog(sbody)??/ +.sp +In this case the result is always a complete match because that is found first, +and matching never continues after finding a complete match. It might be easier +to follow this explanation by thinking of the two patterns like this: +.sp + /dog(sbody)?/ is the same as /dogsbody|dog/ + /dog(sbody)??/ is the same as /dog|dogsbody/ +.sp +The second pattern will never match "dogsbody", because it will always find the +shorter match first. +. +. +.SH "PARTIAL MATCHING USING pcre_dfa_exec() OR pcre[16|32]_dfa_exec()" +.rs +.sp +The DFA functions move along the subject string character by character, without +backtracking, searching for all possible matches simultaneously. If the end of +the subject is reached before the end of the pattern, there is the possibility +of a partial match, again provided that at least one character has been +inspected. +.P +When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if there +have been no complete matches. Otherwise, the complete matches are returned. +However, if PCRE_PARTIAL_HARD is set, a partial match takes precedence over any +complete matches. The portion of the string that was inspected when the longest +partial match was found is set as the first matching string, provided there are +at least two slots in the offsets vector. +.P +Because the DFA functions always search for all possible matches, and there is +no difference between greedy and ungreedy repetition, their behaviour is +different from the standard functions when PCRE_PARTIAL_HARD is set. Consider +the string "dog" matched against the ungreedy pattern shown above: +.sp + /dog(sbody)??/ +.sp +Whereas the standard functions stop as soon as they find the complete match for +"dog", the DFA functions also find the partial match for "dogsbody", and so +return that when PCRE_PARTIAL_HARD is set. +. +. +.SH "PARTIAL MATCHING AND WORD BOUNDARIES" +.rs +.sp +If a pattern ends with one of sequences \eb or \eB, which test for word +boundaries, partial matching with PCRE_PARTIAL_SOFT can give counter-intuitive +results. Consider this pattern: +.sp + /\ebcat\eb/ +.sp +This matches "cat", provided there is a word boundary at either end. If the +subject string is "the cat", the comparison of the final "t" with a following +character cannot take place, so a partial match is found. However, normal +matching carries on, and \eb matches at the end of the subject when the last +character is a letter, so a complete match is found. The result, therefore, is +\fInot\fP PCRE_ERROR_PARTIAL. Using PCRE_PARTIAL_HARD in this case does yield +PCRE_ERROR_PARTIAL, because then the partial match takes precedence. +. +. +.SH "FORMERLY RESTRICTED PATTERNS" +.rs +.sp +For releases of PCRE prior to 8.00, because of the way certain internal +optimizations were implemented in the \fBpcre_exec()\fP function, the +PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be used with +all patterns. From release 8.00 onwards, the restrictions no longer apply, and +partial matching with can be requested for any pattern. +.P +Items that were formerly restricted were repeated single characters and +repeated metasequences. If PCRE_PARTIAL was set for a pattern that did not +conform to the restrictions, \fBpcre_exec()\fP returned the error code +PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The +PCRE_INFO_OKPARTIAL call to \fBpcre_fullinfo()\fP to find out if a compiled +pattern can be used for partial matching now always returns 1. +. +. +.SH "EXAMPLE OF PARTIAL MATCHING USING PCRETEST" +.rs +.sp +If the escape sequence \eP is present in a \fBpcretest\fP data line, the +PCRE_PARTIAL_SOFT option is used for the match. Here is a run of \fBpcretest\fP +that uses the date example quoted above: +.sp + re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/ + data> 25jun04\eP + 0: 25jun04 + 1: jun + data> 25dec3\eP + Partial match: 23dec3 + data> 3ju\eP + Partial match: 3ju + data> 3juj\eP + No match + data> j\eP + No match +.sp +The first data string is matched completely, so \fBpcretest\fP shows the +matched substrings. The remaining four strings do not match the complete +pattern, but the first two are partial matches. Similar output is obtained +if DFA matching is used. +.P +If the escape sequence \eP is present more than once in a \fBpcretest\fP data +line, the PCRE_PARTIAL_HARD option is set for the match. +. +. +.SH "MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre[16|32]_dfa_exec()" +.rs +.sp +When a partial match has been found using a DFA matching function, it is +possible to continue the match by providing additional subject data and calling +the function again with the same compiled regular expression, this time setting +the PCRE_DFA_RESTART option. You must pass the same working space as before, +because this is where details of the previous partial match are stored. Here is +an example using \fBpcretest\fP, using the \eR escape sequence to set the +PCRE_DFA_RESTART option (\eD specifies the use of the DFA matching function): +.sp + re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/ + data> 23ja\eP\eD + Partial match: 23ja + data> n05\eR\eD + 0: n05 +.sp +The first call has "23ja" as the subject, and requests partial matching; the +second call has "n05" as the subject for the continued (restarted) match. +Notice that when the match is complete, only the last part is shown; PCRE does +not retain the previously partially-matched string. It is up to the calling +program to do that if it needs to. +.P +That means that, for an unanchored pattern, if a continued match fails, it is +not possible to try again at a new starting point. All this facility is capable +of doing is continuing with the previous match attempt. In the previous +example, if the second set of data is "ug23" the result is no match, even +though there would be a match for "aug23" if the entire string were given at +once. Depending on the application, this may or may not be what you want. +The only way to allow for starting again at the next character is to retain the +matched part of the subject and try a new complete match. +.P +You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with +PCRE_DFA_RESTART to continue partial matching over multiple segments. This +facility can be used to pass very long subject strings to the DFA matching +functions. +. +. +.SH "MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre[16|32]_exec()" +.rs +.sp +From release 8.00, the standard matching functions can also be used to do +multi-segment matching. Unlike the DFA functions, it is not possible to +restart the previous match with a new segment of data. Instead, new data must +be added to the previous subject string, and the entire match re-run, starting +from the point where the partial match occurred. Earlier data can be discarded. +.P +It is best to use PCRE_PARTIAL_HARD in this situation, because it does not +treat the end of a segment as the end of the subject when matching \ez, \eZ, +\eb, \eB, and $. Consider an unanchored pattern that matches dates: +.sp + re> /\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed/ + data> The date is 23ja\eP\eP + Partial match: 23ja +.sp +At this stage, an application could discard the text preceding "23ja", add on +text from the next segment, and call the matching function again. Unlike the +DFA matching functions, the entire matching string must always be available, +and the complete matching process occurs for each call, so more memory and more +processing time is needed. +.P +\fBNote:\fP If the pattern contains lookbehind assertions, or \eK, or starts +with \eb or \eB, the string that is returned for a partial match includes +characters that precede the start of what would be returned for a complete +match, because it contains all the characters that were inspected during the +partial match. +. +. +.SH "ISSUES WITH MULTI-SEGMENT MATCHING" +.rs +.sp +Certain types of pattern may give problems with multi-segment matching, +whichever matching function is used. +.P +1. If the pattern contains a test for the beginning of a line, you need to pass +the PCRE_NOTBOL option when the subject string for any call does start at the +beginning of a line. There is also a PCRE_NOTEOL option, but in practice when +doing multi-segment matching you should be using PCRE_PARTIAL_HARD, which +includes the effect of PCRE_NOTEOL. +.P +2. Lookbehind assertions that have already been obeyed are catered for in the +offsets that are returned for a partial match. However a lookbehind assertion +later in the pattern could require even earlier characters to be inspected. You +can handle this case by using the PCRE_INFO_MAXLOOKBEHIND option of the +\fBpcre_fullinfo()\fP or \fBpcre[16|32]_fullinfo()\fP functions to obtain the +length of the longest lookbehind in the pattern. This length is given in +characters, not bytes. If you always retain at least that many characters +before the partially matched string, all should be well. (Of course, near the +start of the subject, fewer characters may be present; in that case all +characters should be retained.) +.P +From release 8.33, there is a more accurate way of deciding which characters to +retain. Instead of subtracting the length of the longest lookbehind from the +earliest inspected character (\fIoffsets[0]\fP), the match start position +(\fIoffsets[2]\fP) should be used, and the next match attempt started at the +\fIoffsets[2]\fP character by setting the \fIstartoffset\fP argument of +\fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. +.P +For example, if the pattern "(?<=123)abc" is partially +matched against the string "xx123a", the three offset values returned are 2, 6, +and 5. This indicates that the matching process that gave a partial match +started at offset 5, but the characters "123a" were all inspected. The maximum +lookbehind for that pattern is 3, so taking that away from 5 shows that we need +only keep "123a", and the next match attempt can be started at offset 3 (that +is, at "a") when further characters have been added. When the match start is +not the earliest inspected character, \fBpcretest\fP shows it explicitly: +.sp + re> "(?<=123)abc" + data> xx123a\eP\eP + Partial match at offset 5: 123a +.P +3. Because a partial match must always contain at least one character, what +might be considered a partial match of an empty string actually gives a "no +match" result. For example: +.sp + re> /c(?<=abc)x/ + data> ab\eP + No match +.sp +If the next segment begins "cx", a match should be found, but this will only +happen if characters from the previous segment are retained. For this reason, a +"no match" result should be interpreted as "partial match of an empty string" +when the pattern contains lookbehinds. +.P +4. Matching a subject string that is split into multiple segments may not +always produce exactly the same result as matching over one single long string, +especially when PCRE_PARTIAL_SOFT is used. The section "Partial Matching and +Word Boundaries" above describes an issue that arises if the pattern ends with +\eb or \eB. Another kind of difference may occur when there are multiple +matching possibilities, because (for PCRE_PARTIAL_SOFT) a partial match result +is given only when there are no completed matches. This means that as soon as +the shortest match has been found, continuation to a new subject segment is no +longer possible. Consider again this \fBpcretest\fP example: +.sp + re> /dog(sbody)?/ + data> dogsb\eP + 0: dog + data> do\eP\eD + Partial match: do + data> gsb\eR\eP\eD + 0: g + data> dogsbody\eD + 0: dogsbody + 1: dog +.sp +The first data line passes the string "dogsb" to a standard matching function, +setting the PCRE_PARTIAL_SOFT option. Although the string is a partial match +for "dogsbody", the result is not PCRE_ERROR_PARTIAL, because the shorter +string "dog" is a complete match. Similarly, when the subject is presented to +a DFA matching function in several parts ("do" and "gsb" being the first two) +the match stops when "dog" has been found, and it is not possible to continue. +On the other hand, if "dogsbody" is presented as a single string, a DFA +matching function finds both matches. +.P +Because of these problems, it is best to use PCRE_PARTIAL_HARD when matching +multi-segment data. The example above then behaves differently: +.sp + re> /dog(sbody)?/ + data> dogsb\eP\eP + Partial match: dogsb + data> do\eP\eD + Partial match: do + data> gsb\eR\eP\eP\eD + Partial match: gsb +.sp +5. Patterns that contain alternatives at the top level which do not all start +with the same pattern item may not work as expected when PCRE_DFA_RESTART is +used. For example, consider this pattern: +.sp + 1234|3789 +.sp +If the first part of the subject is "ABC123", a partial match of the first +alternative is found at offset 3. There is no partial match for the second +alternative, because such a match does not start at the same point in the +subject string. Attempting to continue with the string "7890" does not yield a +match because only those alternatives that match at one point in the subject +are remembered. The problem arises because the start of the second alternative +matches within the first alternative. There is no problem with anchored +patterns or patterns such as: +.sp + 1234|ABCD +.sp +where no string can be a partial match for both alternatives. This is not a +problem if a standard matching function is used, because the entire match has +to be rerun each time: +.sp + re> /1234|3789/ + data> ABC123\eP\eP + Partial match: 123 + data> 1237890 + 0: 3789 +.sp +Of course, instead of using PCRE_DFA_RESTART, the same technique of re-running +the entire match can also be used with the DFA matching functions. Another +possibility is to work with two buffers. If a partial match at offset \fIn\fP +in the first buffer is followed by "no match" when PCRE_DFA_RESTART is used on +the second buffer, you can then try a new match starting at offset \fIn+1\fP in +the first buffer. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 02 July 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcrepattern.3 b/doc/pcrepattern.3 new file mode 100644 index 0000000..3b8c639 --- /dev/null +++ b/doc/pcrepattern.3 @@ -0,0 +1,3301 @@ +.TH PCREPATTERN 3 "14 June 2015" "PCRE 8.38" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE REGULAR EXPRESSION DETAILS" +.rs +.sp +The syntax and semantics of the regular expressions that are supported by PCRE +are described in detail below. There is a quick-reference syntax summary in the +.\" HREF +\fBpcresyntax\fP +.\" +page. PCRE tries to match Perl syntax and semantics as closely as it can. PCRE +also supports some alternative regular expression syntax (which does not +conflict with the Perl syntax) in order to provide some compatibility with +regular expressions in Python, .NET, and Oniguruma. +.P +Perl's regular expressions are described in its own documentation, and +regular expressions in general are covered in a number of books, some of which +have copious examples. Jeffrey Friedl's "Mastering Regular Expressions", +published by O'Reilly, covers regular expressions in great detail. This +description of PCRE's regular expressions is intended as reference material. +.P +This document discusses the patterns that are supported by PCRE when one its +main matching functions, \fBpcre_exec()\fP (8-bit) or \fBpcre[16|32]_exec()\fP +(16- or 32-bit), is used. PCRE also has alternative matching functions, +\fBpcre_dfa_exec()\fP and \fBpcre[16|32_dfa_exec()\fP, which match using a +different algorithm that is not Perl-compatible. Some of the features discussed +below are not available when DFA matching is used. The advantages and +disadvantages of the alternative functions, and how they differ from the normal +functions, are discussed in the +.\" HREF +\fBpcrematching\fP +.\" +page. +. +. +.SH "SPECIAL START-OF-PATTERN ITEMS" +.rs +.sp +A number of options that can be passed to \fBpcre_compile()\fP can also be set +by special items at the start of a pattern. These are not Perl-compatible, but +are provided to make these options accessible to pattern writers who are not +able to change the program that processes the pattern. Any number of these +items may appear, but they must all be together right at the start of the +pattern string, and the letters must be in upper case. +. +. +.SS "UTF support" +.rs +.sp +The original operation of PCRE was on strings of one-byte characters. However, +there is now also support for UTF-8 strings in the original library, an +extra library that supports 16-bit and UTF-16 character strings, and a +third library that supports 32-bit and UTF-32 character strings. To use these +features, PCRE must be built to include appropriate support. When using UTF +strings you must either call the compiling function with the PCRE_UTF8, +PCRE_UTF16, or PCRE_UTF32 option, or the pattern must start with one of +these special sequences: +.sp + (*UTF8) + (*UTF16) + (*UTF32) + (*UTF) +.sp +(*UTF) is a generic sequence that can be used with any of the libraries. +Starting a pattern with such a sequence is equivalent to setting the relevant +option. How setting a UTF mode affects pattern matching is mentioned in several +places below. There is also a summary of features in the +.\" HREF +\fBpcreunicode\fP +.\" +page. +.P +Some applications that allow their users to supply patterns may wish to +restrict them to non-UTF data for security reasons. If the PCRE_NEVER_UTF +option is set at compile time, (*UTF) etc. are not allowed, and their +appearance causes an error. +. +. +.SS "Unicode property support" +.rs +.sp +Another special sequence that may appear at the start of a pattern is (*UCP). +This has the same effect as setting the PCRE_UCP option: it causes sequences +such as \ed and \ew to use Unicode properties to determine character types, +instead of recognizing only characters with codes less than 128 via a lookup +table. +. +. +.SS "Disabling auto-possessification" +.rs +.sp +If a pattern starts with (*NO_AUTO_POSSESS), it has the same effect as setting +the PCRE_NO_AUTO_POSSESS option at compile time. This stops PCRE from making +quantifiers possessive when what follows cannot match the repeated item. For +example, by default a+b is treated as a++b. For more details, see the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +. +. +.SS "Disabling start-up optimizations" +.rs +.sp +If a pattern starts with (*NO_START_OPT), it has the same effect as setting the +PCRE_NO_START_OPTIMIZE option either at compile or matching time. This disables +several optimizations for quickly reaching "no match" results. For more +details, see the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +. +. +.\" HTML <a name="newlines"></a> +.SS "Newline conventions" +.rs +.sp +PCRE supports five different conventions for indicating line breaks in +strings: a single CR (carriage return) character, a single LF (linefeed) +character, the two-character sequence CRLF, any of the three preceding, or any +Unicode newline sequence. The +.\" HREF +\fBpcreapi\fP +.\" +page has +.\" HTML <a href="pcreapi.html#newlines"> +.\" </a> +further discussion +.\" +about newlines, and shows how to set the newline convention in the +\fIoptions\fP arguments for the compiling and matching functions. +.P +It is also possible to specify a newline convention by starting a pattern +string with one of the following five sequences: +.sp + (*CR) carriage return + (*LF) linefeed + (*CRLF) carriage return, followed by linefeed + (*ANYCRLF) any of the three above + (*ANY) all Unicode newline sequences +.sp +These override the default and the options given to the compiling function. For +example, on a Unix system where LF is the default newline sequence, the pattern +.sp + (*CR)a.b +.sp +changes the convention to CR. That pattern matches "a\enb" because LF is no +longer a newline. If more than one of these settings is present, the last one +is used. +.P +The newline convention affects where the circumflex and dollar assertions are +true. It also affects the interpretation of the dot metacharacter when +PCRE_DOTALL is not set, and the behaviour of \eN. However, it does not affect +what the \eR escape sequence matches. By default, this is any Unicode newline +sequence, for Perl compatibility. However, this can be changed; see the +description of \eR in the section entitled +.\" HTML <a href="#newlineseq"> +.\" </a> +"Newline sequences" +.\" +below. A change of \eR setting can be combined with a change of newline +convention. +. +. +.SS "Setting match and recursion limits" +.rs +.sp +The caller of \fBpcre_exec()\fP can set a limit on the number of times the +internal \fBmatch()\fP function is called and on the maximum depth of +recursive calls. These facilities are provided to catch runaway matches that +are provoked by patterns with huge matching trees (a typical example is a +pattern with nested unlimited repeats) and to avoid running out of system stack +by too much recursion. When one of these limits is reached, \fBpcre_exec()\fP +gives an error return. The limits can also be set by items at the start of the +pattern of the form +.sp + (*LIMIT_MATCH=d) + (*LIMIT_RECURSION=d) +.sp +where d is any number of decimal digits. However, the value of the setting must +be less than the value set (or defaulted) by the caller of \fBpcre_exec()\fP +for it to have any effect. In other words, the pattern writer can lower the +limits set by the programmer, but not raise them. If there is more than one +setting of one of these limits, the lower value is used. +. +. +.SH "EBCDIC CHARACTER CODES" +.rs +.sp +PCRE can be compiled to run in an environment that uses EBCDIC as its character +code rather than ASCII or Unicode (typically a mainframe system). In the +sections below, character code values are ASCII or Unicode; in an EBCDIC +environment these characters may have different code values, and there are no +code points greater than 255. +. +. +.SH "CHARACTERS AND METACHARACTERS" +.rs +.sp +A regular expression is a pattern that is matched against a subject string from +left to right. Most characters stand for themselves in a pattern, and match the +corresponding characters in the subject. As a trivial example, the pattern +.sp + The quick brown fox +.sp +matches a portion of a subject string that is identical to itself. When +caseless matching is specified (the PCRE_CASELESS option), letters are matched +independently of case. In a UTF mode, PCRE always understands the concept of +case for characters whose values are less than 128, so caseless matching is +always possible. For characters with higher values, the concept of case is +supported if PCRE is compiled with Unicode property support, but not otherwise. +If you want to use caseless matching for characters 128 and above, you must +ensure that PCRE is compiled with Unicode property support as well as with +UTF support. +.P +The power of regular expressions comes from the ability to include alternatives +and repetitions in the pattern. These are encoded in the pattern by the use of +\fImetacharacters\fP, which do not stand for themselves but instead are +interpreted in some special way. +.P +There are two different sets of metacharacters: those that are recognized +anywhere in the pattern except within square brackets, and those that are +recognized within square brackets. Outside square brackets, the metacharacters +are as follows: +.sp + \e general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier +.sp +Part of a pattern that is in square brackets is called a "character class". In +a character class the only metacharacters are: +.sp + \e general escape character + ^ negate the class, but only if the first character + - indicates character range +.\" JOIN + [ POSIX character class (only if followed by POSIX + syntax) + ] terminates the character class +.sp +The following sections describe the use of each of the metacharacters. +. +. +.SH BACKSLASH +.rs +.sp +The backslash character has several uses. Firstly, if it is followed by a +character that is not a number or a letter, it takes away any special meaning +that character may have. This use of backslash as an escape character applies +both inside and outside character classes. +.P +For example, if you want to match a * character, you write \e* in the pattern. +This escaping action applies whether or not the following character would +otherwise be interpreted as a metacharacter, so it is always safe to precede a +non-alphanumeric with backslash to specify that it stands for itself. In +particular, if you want to match a backslash, you write \e\e. +.P +In a UTF mode, only ASCII numbers and letters have any special meaning after a +backslash. All other characters (in particular, those whose codepoints are +greater than 127) are treated as literals. +.P +If a pattern is compiled with the PCRE_EXTENDED option, most white space in the +pattern (other than in a character class), and characters between a # outside a +character class and the next newline, inclusive, are ignored. An escaping +backslash can be used to include a white space or # character as part of the +pattern. +.P +If you want to remove the special meaning from a sequence of characters, you +can do so by putting them between \eQ and \eE. This is different from Perl in +that $ and @ are handled as literals in \eQ...\eE sequences in PCRE, whereas in +Perl, $ and @ cause variable interpolation. Note the following examples: +.sp + Pattern PCRE matches Perl matches +.sp +.\" JOIN + \eQabc$xyz\eE abc$xyz abc followed by the + contents of $xyz + \eQabc\e$xyz\eE abc\e$xyz abc\e$xyz + \eQabc\eE\e$\eQxyz\eE abc$xyz abc$xyz +.sp +The \eQ...\eE sequence is recognized both inside and outside character classes. +An isolated \eE that is not preceded by \eQ is ignored. If \eQ is not followed +by \eE later in the pattern, the literal interpretation continues to the end of +the pattern (that is, \eE is assumed at the end). If the isolated \eQ is inside +a character class, this causes an error, because the character class is not +terminated. +. +. +.\" HTML <a name="digitsafterbackslash"></a> +.SS "Non-printing characters" +.rs +.sp +A second use of backslash provides a way of encoding non-printing characters +in patterns in a visible manner. There is no restriction on the appearance of +non-printing characters, apart from the binary zero that terminates a pattern, +but when a pattern is being prepared by text editing, it is often easier to use +one of the following escape sequences than the binary character it represents. +In an ASCII or Unicode environment, these escapes are as follows: +.sp + \ea alarm, that is, the BEL character (hex 07) + \ecx "control-x", where x is any ASCII character + \ee escape (hex 1B) + \ef form feed (hex 0C) + \en linefeed (hex 0A) + \er carriage return (hex 0D) + \et tab (hex 09) + \e0dd character with octal code 0dd + \eddd character with octal code ddd, or back reference + \eo{ddd..} character with octal code ddd.. + \exhh character with hex code hh + \ex{hhh..} character with hex code hhh.. (non-JavaScript mode) + \euhhhh character with hex code hhhh (JavaScript mode only) +.sp +The precise effect of \ecx on ASCII characters is as follows: if x is a lower +case letter, it is converted to upper case. Then bit 6 of the character (hex +40) is inverted. Thus \ecA to \ecZ become hex 01 to hex 1A (A is 41, Z is 5A), +but \ec{ becomes hex 3B ({ is 7B), and \ec; becomes hex 7B (; is 3B). If the +data item (byte or 16-bit value) following \ec has a value greater than 127, a +compile-time error occurs. This locks out non-ASCII characters in all modes. +.P +When PCRE is compiled in EBCDIC mode, \ea, \ee, \ef, \en, \er, and \et +generate the appropriate EBCDIC code values. The \ec escape is processed +as specified for Perl in the \fBperlebcdic\fP document. The only characters +that are allowed after \ec are A-Z, a-z, or one of @, [, \e, ], ^, _, or ?. Any +other character provokes a compile-time error. The sequence \e@ encodes +character code 0; the letters (in either case) encode characters 1-26 (hex 01 +to hex 1A); [, \e, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and +\e? becomes either 255 (hex FF) or 95 (hex 5F). +.P +Thus, apart from \e?, these escapes generate the same character code values as +they do in an ASCII environment, though the meanings of the values mostly +differ. For example, \eG always generates code value 7, which is BEL in ASCII +but DEL in EBCDIC. +.P +The sequence \e? generates DEL (127, hex 7F) in an ASCII environment, but +because 127 is not a control character in EBCDIC, Perl makes it generate the +APC character. Unfortunately, there are several variants of EBCDIC. In most of +them the APC character has the value 255 (hex FF), but in the one Perl calls +POSIX-BC its value is 95 (hex 5F). If certain other characters have POSIX-BC +values, PCRE makes \e? generate 95; otherwise it generates 255. +.P +After \e0 up to two further octal digits are read. If there are fewer than two +digits, just those that are present are used. Thus the sequence \e0\ex\e015 +specifies two binary zeros followed by a CR character (code value 13). Make +sure you supply two digits after the initial zero if the pattern character that +follows is itself an octal digit. +.P +The escape \eo must be followed by a sequence of octal digits, enclosed in +braces. An error occurs if this is not the case. This escape is a recent +addition to Perl; it provides way of specifying character code points as octal +numbers greater than 0777, and it also allows octal numbers and back references +to be unambiguously specified. +.P +For greater clarity and unambiguity, it is best to avoid following \e by a +digit greater than zero. Instead, use \eo{} or \ex{} to specify character +numbers, and \eg{} to specify back references. The following paragraphs +describe the old, ambiguous syntax. +.P +The handling of a backslash followed by a digit other than 0 is complicated, +and Perl has changed in recent releases, causing PCRE also to change. Outside a +character class, PCRE reads the digit and any following digits as a decimal +number. If the number is less than 8, or if there have been at least that many +previous capturing left parentheses in the expression, the entire sequence is +taken as a \fIback reference\fP. A description of how this works is given +.\" HTML <a href="#backreferences"> +.\" </a> +later, +.\" +following the discussion of +.\" HTML <a href="#subpattern"> +.\" </a> +parenthesized subpatterns. +.\" +.P +Inside a character class, or if the decimal number following \e is greater than +7 and there have not been that many capturing subpatterns, PCRE handles \e8 and +\e9 as the literal characters "8" and "9", and otherwise re-reads up to three +octal digits following the backslash, using them to generate a data character. +Any subsequent digits stand for themselves. For example: +.sp + \e040 is another way of writing an ASCII space +.\" JOIN + \e40 is the same, provided there are fewer than 40 + previous capturing subpatterns + \e7 is always a back reference +.\" JOIN + \e11 might be a back reference, or another way of + writing a tab + \e011 is always a tab + \e0113 is a tab followed by the character "3" +.\" JOIN + \e113 might be a back reference, otherwise the + character with octal code 113 +.\" JOIN + \e377 might be a back reference, otherwise + the value 255 (decimal) +.\" JOIN + \e81 is either a back reference, or the two + characters "8" and "1" +.sp +Note that octal values of 100 or greater that are specified using this syntax +must not be introduced by a leading zero, because no more than three octal +digits are ever read. +.P +By default, after \ex that is not followed by {, from zero to two hexadecimal +digits are read (letters can be in upper or lower case). Any number of +hexadecimal digits may appear between \ex{ and }. If a character other than +a hexadecimal digit appears between \ex{ and }, or if there is no terminating +}, an error occurs. +.P +If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \ex is +as just described only when it is followed by two hexadecimal digits. +Otherwise, it matches a literal "x" character. In JavaScript mode, support for +code points greater than 256 is provided by \eu, which must be followed by +four hexadecimal digits; otherwise it matches a literal "u" character. +.P +Characters whose value is less than 256 can be defined by either of the two +syntaxes for \ex (or by \eu in JavaScript mode). There is no difference in the +way they are handled. For example, \exdc is exactly the same as \ex{dc} (or +\eu00dc in JavaScript mode). +. +. +.SS "Constraints on character values" +.rs +.sp +Characters that are specified using octal or hexadecimal numbers are +limited to certain values, as follows: +.sp + 8-bit non-UTF mode less than 0x100 + 8-bit UTF-8 mode less than 0x10ffff and a valid codepoint + 16-bit non-UTF mode less than 0x10000 + 16-bit UTF-16 mode less than 0x10ffff and a valid codepoint + 32-bit non-UTF mode less than 0x100000000 + 32-bit UTF-32 mode less than 0x10ffff and a valid codepoint +.sp +Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called +"surrogate" codepoints), and 0xffef. +. +. +.SS "Escape sequences in character classes" +.rs +.sp +All the sequences that define a single character value can be used both inside +and outside character classes. In addition, inside a character class, \eb is +interpreted as the backspace character (hex 08). +.P +\eN is not allowed in a character class. \eB, \eR, and \eX are not special +inside a character class. Like other unrecognized escape sequences, they are +treated as the literal characters "B", "R", and "X" by default, but cause an +error if the PCRE_EXTRA option is set. Outside a character class, these +sequences have different meanings. +. +. +.SS "Unsupported escape sequences" +.rs +.sp +In Perl, the sequences \el, \eL, \eu, and \eU are recognized by its string +handler and used to modify the case of following characters. By default, PCRE +does not support these escape sequences. However, if the PCRE_JAVASCRIPT_COMPAT +option is set, \eU matches a "U" character, and \eu can be used to define a +character by code point, as described in the previous section. +. +. +.SS "Absolute and relative back references" +.rs +.sp +The sequence \eg followed by an unsigned or a negative number, optionally +enclosed in braces, is an absolute or relative back reference. A named back +reference can be coded as \eg{name}. Back references are discussed +.\" HTML <a href="#backreferences"> +.\" </a> +later, +.\" +following the discussion of +.\" HTML <a href="#subpattern"> +.\" </a> +parenthesized subpatterns. +.\" +. +. +.SS "Absolute and relative subroutine calls" +.rs +.sp +For compatibility with Oniguruma, the non-Perl syntax \eg followed by a name or +a number enclosed either in angle brackets or single quotes, is an alternative +syntax for referencing a subpattern as a "subroutine". Details are discussed +.\" HTML <a href="#onigurumasubroutines"> +.\" </a> +later. +.\" +Note that \eg{...} (Perl syntax) and \eg<...> (Oniguruma syntax) are \fInot\fP +synonymous. The former is a back reference; the latter is a +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +subroutine +.\" +call. +. +. +.\" HTML <a name="genericchartypes"></a> +.SS "Generic character types" +.rs +.sp +Another use of backslash is for specifying generic character types: +.sp + \ed any decimal digit + \eD any character that is not a decimal digit + \eh any horizontal white space character + \eH any character that is not a horizontal white space character + \es any white space character + \eS any character that is not a white space character + \ev any vertical white space character + \eV any character that is not a vertical white space character + \ew any "word" character + \eW any "non-word" character +.sp +There is also the single sequence \eN, which matches a non-newline character. +This is the same as +.\" HTML <a href="#fullstopdot"> +.\" </a> +the "." metacharacter +.\" +when PCRE_DOTALL is not set. Perl also uses \eN to match characters by name; +PCRE does not support this. +.P +Each pair of lower and upper case escape sequences partitions the complete set +of characters into two disjoint sets. Any given character matches one, and only +one, of each pair. The sequences can appear both inside and outside character +classes. They each match one character of the appropriate type. If the current +matching point is at the end of the subject string, all of them fail, because +there is no character to match. +.P +For compatibility with Perl, \es did not used to match the VT character (code +11), which made it different from the the POSIX "space" class. However, Perl +added VT at release 5.18, and PCRE followed suit at release 8.34. The default +\es characters are now HT (9), LF (10), VT (11), FF (12), CR (13), and space +(32), which are defined as white space in the "C" locale. This list may vary if +locale-specific matching is taking place. For example, in some locales the +"non-breaking space" character (\exA0) is recognized as white space, and in +others the VT character is not. +.P +A "word" character is an underscore or any character that is a letter or digit. +By default, the definition of letters and digits is controlled by PCRE's +low-valued character tables, and may vary if locale-specific matching is taking +place (see +.\" HTML <a href="pcreapi.html#localesupport"> +.\" </a> +"Locale support" +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +page). For example, in a French locale such as "fr_FR" in Unix-like systems, +or "french" in Windows, some character codes greater than 127 are used for +accented letters, and these are then matched by \ew. The use of locales with +Unicode is discouraged. +.P +By default, characters whose code points are greater than 127 never match \ed, +\es, or \ew, and always match \eD, \eS, and \eW, although this may vary for +characters in the range 128-255 when locale-specific matching is happening. +These escape sequences retain their original meanings from before Unicode +support was available, mainly for efficiency reasons. If PCRE is compiled with +Unicode property support, and the PCRE_UCP option is set, the behaviour is +changed so that Unicode properties are used to determine character types, as +follows: +.sp + \ed any character that matches \ep{Nd} (decimal digit) + \es any character that matches \ep{Z} or \eh or \ev + \ew any character that matches \ep{L} or \ep{N}, plus underscore +.sp +The upper case escapes match the inverse sets of characters. Note that \ed +matches only decimal digits, whereas \ew matches any Unicode digit, as well as +any Unicode letter, and underscore. Note also that PCRE_UCP affects \eb, and +\eB because they are defined in terms of \ew and \eW. Matching these sequences +is noticeably slower when PCRE_UCP is set. +.P +The sequences \eh, \eH, \ev, and \eV are features that were added to Perl at +release 5.10. In contrast to the other sequences, which match only ASCII +characters by default, these always match certain high-valued code points, +whether or not PCRE_UCP is set. The horizontal space characters are: +.sp + U+0009 Horizontal tab (HT) + U+0020 Space + U+00A0 Non-break space + U+1680 Ogham space mark + U+180E Mongolian vowel separator + U+2000 En quad + U+2001 Em quad + U+2002 En space + U+2003 Em space + U+2004 Three-per-em space + U+2005 Four-per-em space + U+2006 Six-per-em space + U+2007 Figure space + U+2008 Punctuation space + U+2009 Thin space + U+200A Hair space + U+202F Narrow no-break space + U+205F Medium mathematical space + U+3000 Ideographic space +.sp +The vertical space characters are: +.sp + U+000A Linefeed (LF) + U+000B Vertical tab (VT) + U+000C Form feed (FF) + U+000D Carriage return (CR) + U+0085 Next line (NEL) + U+2028 Line separator + U+2029 Paragraph separator +.sp +In 8-bit, non-UTF-8 mode, only the characters with codepoints less than 256 are +relevant. +. +. +.\" HTML <a name="newlineseq"></a> +.SS "Newline sequences" +.rs +.sp +Outside a character class, by default, the escape sequence \eR matches any +Unicode newline sequence. In 8-bit non-UTF-8 mode \eR is equivalent to the +following: +.sp + (?>\er\en|\en|\ex0b|\ef|\er|\ex85) +.sp +This is an example of an "atomic group", details of which are given +.\" HTML <a href="#atomicgroup"> +.\" </a> +below. +.\" +This particular group matches either the two-character sequence CR followed by +LF, or one of the single characters LF (linefeed, U+000A), VT (vertical tab, +U+000B), FF (form feed, U+000C), CR (carriage return, U+000D), or NEL (next +line, U+0085). The two-character sequence is treated as a single unit that +cannot be split. +.P +In other modes, two additional characters whose codepoints are greater than 255 +are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029). +Unicode character property support is not needed for these characters to be +recognized. +.P +It is possible to restrict \eR to match only CR, LF, or CRLF (instead of the +complete set of Unicode line endings) by setting the option PCRE_BSR_ANYCRLF +either at compile time or when the pattern is matched. (BSR is an abbrevation +for "backslash R".) This can be made the default when PCRE is built; if this is +the case, the other behaviour can be requested via the PCRE_BSR_UNICODE option. +It is also possible to specify these settings by starting a pattern string with +one of the following sequences: +.sp + (*BSR_ANYCRLF) CR, LF, or CRLF only + (*BSR_UNICODE) any Unicode newline sequence +.sp +These override the default and the options given to the compiling function, but +they can themselves be overridden by options given to a matching function. Note +that these special settings, which are not Perl-compatible, are recognized only +at the very start of a pattern, and that they must be in upper case. If more +than one of them is present, the last one is used. They can be combined with a +change of newline convention; for example, a pattern can start with: +.sp + (*ANY)(*BSR_ANYCRLF) +.sp +They can also be combined with the (*UTF8), (*UTF16), (*UTF32), (*UTF) or +(*UCP) special sequences. Inside a character class, \eR is treated as an +unrecognized escape sequence, and so matches the letter "R" by default, but +causes an error if PCRE_EXTRA is set. +. +. +.\" HTML <a name="uniextseq"></a> +.SS Unicode character properties +.rs +.sp +When PCRE is built with Unicode character property support, three additional +escape sequences that match characters with specific properties are available. +When in 8-bit non-UTF-8 mode, these sequences are of course limited to testing +characters whose codepoints are less than 256, but they do work in this mode. +The extra escape sequences are: +.sp + \ep{\fIxx\fP} a character with the \fIxx\fP property + \eP{\fIxx\fP} a character without the \fIxx\fP property + \eX a Unicode extended grapheme cluster +.sp +The property names represented by \fIxx\fP above are limited to the Unicode +script names, the general category properties, "Any", which matches any +character (including newline), and some special PCRE properties (described +in the +.\" HTML <a href="#extraprops"> +.\" </a> +next section). +.\" +Other Perl properties such as "InMusicalSymbols" are not currently supported by +PCRE. Note that \eP{Any} does not match any characters, so always causes a +match failure. +.P +Sets of Unicode characters are defined as belonging to certain scripts. A +character from one of these sets can be matched using a script name. For +example: +.sp + \ep{Greek} + \eP{Han} +.sp +Those that are not part of an identified script are lumped together as +"Common". The current list of scripts is: +.P +Arabic, +Armenian, +Avestan, +Balinese, +Bamum, +Bassa_Vah, +Batak, +Bengali, +Bopomofo, +Brahmi, +Braille, +Buginese, +Buhid, +Canadian_Aboriginal, +Carian, +Caucasian_Albanian, +Chakma, +Cham, +Cherokee, +Common, +Coptic, +Cuneiform, +Cypriot, +Cyrillic, +Deseret, +Devanagari, +Duployan, +Egyptian_Hieroglyphs, +Elbasan, +Ethiopic, +Georgian, +Glagolitic, +Gothic, +Grantha, +Greek, +Gujarati, +Gurmukhi, +Han, +Hangul, +Hanunoo, +Hebrew, +Hiragana, +Imperial_Aramaic, +Inherited, +Inscriptional_Pahlavi, +Inscriptional_Parthian, +Javanese, +Kaithi, +Kannada, +Katakana, +Kayah_Li, +Kharoshthi, +Khmer, +Khojki, +Khudawadi, +Lao, +Latin, +Lepcha, +Limbu, +Linear_A, +Linear_B, +Lisu, +Lycian, +Lydian, +Mahajani, +Malayalam, +Mandaic, +Manichaean, +Meetei_Mayek, +Mende_Kikakui, +Meroitic_Cursive, +Meroitic_Hieroglyphs, +Miao, +Modi, +Mongolian, +Mro, +Myanmar, +Nabataean, +New_Tai_Lue, +Nko, +Ogham, +Ol_Chiki, +Old_Italic, +Old_North_Arabian, +Old_Permic, +Old_Persian, +Old_South_Arabian, +Old_Turkic, +Oriya, +Osmanya, +Pahawh_Hmong, +Palmyrene, +Pau_Cin_Hau, +Phags_Pa, +Phoenician, +Psalter_Pahlavi, +Rejang, +Runic, +Samaritan, +Saurashtra, +Sharada, +Shavian, +Siddham, +Sinhala, +Sora_Sompeng, +Sundanese, +Syloti_Nagri, +Syriac, +Tagalog, +Tagbanwa, +Tai_Le, +Tai_Tham, +Tai_Viet, +Takri, +Tamil, +Telugu, +Thaana, +Thai, +Tibetan, +Tifinagh, +Tirhuta, +Ugaritic, +Vai, +Warang_Citi, +Yi. +.P +Each character has exactly one Unicode general category property, specified by +a two-letter abbreviation. For compatibility with Perl, negation can be +specified by including a circumflex between the opening brace and the property +name. For example, \ep{^Lu} is the same as \eP{Lu}. +.P +If only one letter is specified with \ep or \eP, it includes all the general +category properties that start with that letter. In this case, in the absence +of negation, the curly brackets in the escape sequence are optional; these two +examples have the same effect: +.sp + \ep{L} + \epL +.sp +The following general category property codes are supported: +.sp + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate +.sp + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter +.sp + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark +.sp + N Number + Nd Decimal number + Nl Letter number + No Other number +.sp + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation +.sp + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol +.sp + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator +.sp +The special property L& is also supported: it matches a character that has +the Lu, Ll, or Lt property, in other words, a letter that is not classified as +a modifier or "other". +.P +The Cs (Surrogate) property applies only to characters in the range U+D800 to +U+DFFF. Such characters are not valid in Unicode strings and so +cannot be tested by PCRE, unless UTF validity checking has been turned off +(see the discussion of PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK and +PCRE_NO_UTF32_CHECK in the +.\" HREF +\fBpcreapi\fP +.\" +page). Perl does not support the Cs property. +.P +The long synonyms for property names that Perl supports (such as \ep{Letter}) +are not supported by PCRE, nor is it permitted to prefix any of these +properties with "Is". +.P +No character that is in the Unicode table has the Cn (unassigned) property. +Instead, this property is assumed for any code point that is not in the +Unicode table. +.P +Specifying caseless matching does not affect these escape sequences. For +example, \ep{Lu} always matches only upper case letters. This is different from +the behaviour of current versions of Perl. +.P +Matching characters by Unicode property is not fast, because PCRE has to do a +multistage table lookup in order to find a character's property. That is why +the traditional escape sequences such as \ed and \ew do not use Unicode +properties in PCRE by default, though you can make them do so by setting the +PCRE_UCP option or by starting the pattern with (*UCP). +. +. +.SS Extended grapheme clusters +.rs +.sp +The \eX escape matches any number of Unicode characters that form an "extended +grapheme cluster", and treats the sequence as an atomic group +.\" HTML <a href="#atomicgroup"> +.\" </a> +(see below). +.\" +Up to and including release 8.31, PCRE matched an earlier, simpler definition +that was equivalent to +.sp + (?>\ePM\epM*) +.sp +That is, it matched a character without the "mark" property, followed by zero +or more characters with the "mark" property. Characters with the "mark" +property are typically non-spacing accents that affect the preceding character. +.P +This simple definition was extended in Unicode to include more complicated +kinds of composite character by giving each character a grapheme breaking +property, and creating rules that use these properties to define the boundaries +of extended grapheme clusters. In releases of PCRE later than 8.31, \eX matches +one of these clusters. +.P +\eX always matches at least one character. Then it decides whether to add +additional characters according to the following rules for ending a cluster: +.P +1. End at the end of the subject string. +.P +2. Do not end between CR and LF; otherwise end after any control character. +.P +3. Do not break Hangul (a Korean script) syllable sequences. Hangul characters +are of five types: L, V, T, LV, and LVT. An L character may be followed by an +L, V, LV, or LVT character; an LV or V character may be followed by a V or T +character; an LVT or T character may be follwed only by a T character. +.P +4. Do not end before extending characters or spacing marks. Characters with +the "mark" property always have the "extend" grapheme breaking property. +.P +5. Do not end after prepend characters. +.P +6. Otherwise, end the cluster. +. +. +.\" HTML <a name="extraprops"></a> +.SS PCRE's additional properties +.rs +.sp +As well as the standard Unicode properties described above, PCRE supports four +more that make it possible to convert traditional escape sequences such as \ew +and \es to use Unicode properties. PCRE uses these non-standard, non-Perl +properties internally when PCRE_UCP is set. However, they may also be used +explicitly. These properties are: +.sp + Xan Any alphanumeric character + Xps Any POSIX space character + Xsp Any Perl space character + Xwd Any Perl "word" character +.sp +Xan matches characters that have either the L (letter) or the N (number) +property. Xps matches the characters tab, linefeed, vertical tab, form feed, or +carriage return, and any other character that has the Z (separator) property. +Xsp is the same as Xps; it used to exclude vertical tab, for Perl +compatibility, but Perl changed, and so PCRE followed at release 8.34. Xwd +matches the same characters as Xan, plus underscore. +.P +There is another non-standard property, Xuc, which matches any character that +can be represented by a Universal Character Name in C++ and other programming +languages. These are the characters $, @, ` (grave accent), and all characters +with Unicode code points greater than or equal to U+00A0, except for the +surrogates U+D800 to U+DFFF. Note that most base (ASCII) characters are +excluded. (Universal Character Names are of the form \euHHHH or \eUHHHHHHHH +where H is a hexadecimal digit. Note that the Xuc property does not match these +sequences but the characters that they represent.) +. +. +.\" HTML <a name="resetmatchstart"></a> +.SS "Resetting the match start" +.rs +.sp +The escape sequence \eK causes any previously matched characters not to be +included in the final matched sequence. For example, the pattern: +.sp + foo\eKbar +.sp +matches "foobar", but reports that it has matched "bar". This feature is +similar to a lookbehind assertion +.\" HTML <a href="#lookbehind"> +.\" </a> +(described below). +.\" +However, in this case, the part of the subject before the real match does not +have to be of fixed length, as lookbehind assertions do. The use of \eK does +not interfere with the setting of +.\" HTML <a href="#subpattern"> +.\" </a> +captured substrings. +.\" +For example, when the pattern +.sp + (foo)\eKbar +.sp +matches "foobar", the first substring is still set to "foo". +.P +Perl documents that the use of \eK within assertions is "not well defined". In +PCRE, \eK is acted upon when it occurs inside positive assertions, but is +ignored in negative assertions. Note that when a pattern such as (?=ab\eK) +matches, the reported start of the match can be greater than the end of the +match. +. +. +.\" HTML <a name="smallassertions"></a> +.SS "Simple assertions" +.rs +.sp +The final use of backslash is for certain simple assertions. An assertion +specifies a condition that has to be met at a particular point in a match, +without consuming any characters from the subject string. The use of +subpatterns for more complicated assertions is described +.\" HTML <a href="#bigassertions"> +.\" </a> +below. +.\" +The backslashed assertions are: +.sp + \eb matches at a word boundary + \eB matches when not at a word boundary + \eA matches at the start of the subject + \eZ matches at the end of the subject + also matches before a newline at the end of the subject + \ez matches only at the end of the subject + \eG matches at the first matching position in the subject +.sp +Inside a character class, \eb has a different meaning; it matches the backspace +character. If any other of these assertions appears in a character class, by +default it matches the corresponding literal character (for example, \eB +matches the letter B). However, if the PCRE_EXTRA option is set, an "invalid +escape sequence" error is generated instead. +.P +A word boundary is a position in the subject string where the current character +and the previous character do not both match \ew or \eW (i.e. one matches +\ew and the other matches \eW), or the start or end of the string if the +first or last character matches \ew, respectively. In a UTF mode, the meanings +of \ew and \eW can be changed by setting the PCRE_UCP option. When this is +done, it also affects \eb and \eB. Neither PCRE nor Perl has a separate "start +of word" or "end of word" metasequence. However, whatever follows \eb normally +determines which it is. For example, the fragment \eba matches "a" at the start +of a word. +.P +The \eA, \eZ, and \ez assertions differ from the traditional circumflex and +dollar (described in the next section) in that they only ever match at the very +start and end of the subject string, whatever options are set. Thus, they are +independent of multiline mode. These three assertions are not affected by the +PCRE_NOTBOL or PCRE_NOTEOL options, which affect only the behaviour of the +circumflex and dollar metacharacters. However, if the \fIstartoffset\fP +argument of \fBpcre_exec()\fP is non-zero, indicating that matching is to start +at a point other than the beginning of the subject, \eA can never match. The +difference between \eZ and \ez is that \eZ matches before a newline at the end +of the string as well as at the very end, whereas \ez matches only at the end. +.P +The \eG assertion is true only when the current matching position is at the +start point of the match, as specified by the \fIstartoffset\fP argument of +\fBpcre_exec()\fP. It differs from \eA when the value of \fIstartoffset\fP is +non-zero. By calling \fBpcre_exec()\fP multiple times with appropriate +arguments, you can mimic Perl's /g option, and it is in this kind of +implementation where \eG can be useful. +.P +Note, however, that PCRE's interpretation of \eG, as the start of the current +match, is subtly different from Perl's, which defines it as the end of the +previous match. In Perl, these can be different when the previously matched +string was empty. Because PCRE does just one match at a time, it cannot +reproduce this behaviour. +.P +If all the alternatives of a pattern begin with \eG, the expression is anchored +to the starting match position, and the "anchored" flag is set in the compiled +regular expression. +. +. +.SH "CIRCUMFLEX AND DOLLAR" +.rs +.sp +The circumflex and dollar metacharacters are zero-width assertions. That is, +they test for a particular condition being true without consuming any +characters from the subject string. +.P +Outside a character class, in the default matching mode, the circumflex +character is an assertion that is true only if the current matching point is at +the start of the subject string. If the \fIstartoffset\fP argument of +\fBpcre_exec()\fP is non-zero, circumflex can never match if the PCRE_MULTILINE +option is unset. Inside a character class, circumflex has an entirely different +meaning +.\" HTML <a href="#characterclass"> +.\" </a> +(see below). +.\" +.P +Circumflex need not be the first character of the pattern if a number of +alternatives are involved, but it should be the first thing in each alternative +in which it appears if the pattern is ever to match that branch. If all +possible alternatives start with a circumflex, that is, if the pattern is +constrained to match only at the start of the subject, it is said to be an +"anchored" pattern. (There are also other constructs that can cause a pattern +to be anchored.) +.P +The dollar character is an assertion that is true only if the current matching +point is at the end of the subject string, or immediately before a newline at +the end of the string (by default). Note, however, that it does not actually +match the newline. Dollar need not be the last character of the pattern if a +number of alternatives are involved, but it should be the last item in any +branch in which it appears. Dollar has no special meaning in a character class. +.P +The meaning of dollar can be changed so that it matches only at the very end of +the string, by setting the PCRE_DOLLAR_ENDONLY option at compile time. This +does not affect the \eZ assertion. +.P +The meanings of the circumflex and dollar characters are changed if the +PCRE_MULTILINE option is set. When this is the case, a circumflex matches +immediately after internal newlines as well as at the start of the subject +string. It does not match after a newline that ends the string. A dollar +matches before any newlines in the string, as well as at the very end, when +PCRE_MULTILINE is set. When newline is specified as the two-character +sequence CRLF, isolated CR and LF characters do not indicate newlines. +.P +For example, the pattern /^abc$/ matches the subject string "def\enabc" (where +\en represents a newline) in multiline mode, but not otherwise. Consequently, +patterns that are anchored in single line mode because all branches start with +^ are not anchored in multiline mode, and a match for circumflex is possible +when the \fIstartoffset\fP argument of \fBpcre_exec()\fP is non-zero. The +PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set. +.P +Note that the sequences \eA, \eZ, and \ez can be used to match the start and +end of the subject in both modes, and if all branches of a pattern start with +\eA it is always anchored, whether or not PCRE_MULTILINE is set. +. +. +.\" HTML <a name="fullstopdot"></a> +.SH "FULL STOP (PERIOD, DOT) AND \eN" +.rs +.sp +Outside a character class, a dot in the pattern matches any one character in +the subject string except (by default) a character that signifies the end of a +line. +.P +When a line ending is defined as a single character, dot never matches that +character; when the two-character sequence CRLF is used, dot does not match CR +if it is immediately followed by LF, but otherwise it matches all characters +(including isolated CRs and LFs). When any Unicode line endings are being +recognized, dot does not match CR or LF or any of the other line ending +characters. +.P +The behaviour of dot with regard to newlines can be changed. If the PCRE_DOTALL +option is set, a dot matches any one character, without exception. If the +two-character sequence CRLF is present in the subject string, it takes two dots +to match it. +.P +The handling of dot is entirely independent of the handling of circumflex and +dollar, the only relationship being that they both involve newlines. Dot has no +special meaning in a character class. +.P +The escape sequence \eN behaves like a dot, except that it is not affected by +the PCRE_DOTALL option. In other words, it matches any character except one +that signifies the end of a line. Perl also uses \eN to match characters by +name; PCRE does not support this. +. +. +.SH "MATCHING A SINGLE DATA UNIT" +.rs +.sp +Outside a character class, the escape sequence \eC matches any one data unit, +whether or not a UTF mode is set. In the 8-bit library, one data unit is one +byte; in the 16-bit library it is a 16-bit unit; in the 32-bit library it is +a 32-bit unit. Unlike a dot, \eC always +matches line-ending characters. The feature is provided in Perl in order to +match individual bytes in UTF-8 mode, but it is unclear how it can usefully be +used. Because \eC breaks up characters into individual data units, matching one +unit with \eC in a UTF mode means that the rest of the string may start with a +malformed UTF character. This has undefined results, because PCRE assumes that +it is dealing with valid UTF strings (and by default it checks this at the +start of processing unless the PCRE_NO_UTF8_CHECK, PCRE_NO_UTF16_CHECK or +PCRE_NO_UTF32_CHECK option is used). +.P +PCRE does not allow \eC to appear in lookbehind assertions +.\" HTML <a href="#lookbehind"> +.\" </a> +(described below) +.\" +in a UTF mode, because this would make it impossible to calculate the length of +the lookbehind. +.P +In general, the \eC escape sequence is best avoided. However, one +way of using it that avoids the problem of malformed UTF characters is to use a +lookahead to check the length of the next character, as in this pattern, which +could be used with a UTF-8 string (ignore white space and line breaks): +.sp + (?| (?=[\ex00-\ex7f])(\eC) | + (?=[\ex80-\ex{7ff}])(\eC)(\eC) | + (?=[\ex{800}-\ex{ffff}])(\eC)(\eC)(\eC) | + (?=[\ex{10000}-\ex{1fffff}])(\eC)(\eC)(\eC)(\eC)) +.sp +A group that starts with (?| resets the capturing parentheses numbers in each +alternative (see +.\" HTML <a href="#dupsubpatternnumber"> +.\" </a> +"Duplicate Subpattern Numbers" +.\" +below). The assertions at the start of each branch check the next UTF-8 +character for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The +character's individual bytes are then captured by the appropriate number of +groups. +. +. +.\" HTML <a name="characterclass"></a> +.SH "SQUARE BRACKETS AND CHARACTER CLASSES" +.rs +.sp +An opening square bracket introduces a character class, terminated by a closing +square bracket. A closing square bracket on its own is not special by default. +However, if the PCRE_JAVASCRIPT_COMPAT option is set, a lone closing square +bracket causes a compile-time error. If a closing square bracket is required as +a member of the class, it should be the first data character in the class +(after an initial circumflex, if present) or escaped with a backslash. +.P +A character class matches a single character in the subject. In a UTF mode, the +character may be more than one data unit long. A matched character must be in +the set of characters defined by the class, unless the first character in the +class definition is a circumflex, in which case the subject character must not +be in the set defined by the class. If a circumflex is actually required as a +member of the class, ensure it is not the first character, or escape it with a +backslash. +.P +For example, the character class [aeiou] matches any lower case vowel, while +[^aeiou] matches any character that is not a lower case vowel. Note that a +circumflex is just a convenient notation for specifying the characters that +are in the class by enumerating those that are not. A class that starts with a +circumflex is not an assertion; it still consumes a character from the subject +string, and therefore it fails if the current pointer is at the end of the +string. +.P +In UTF-8 (UTF-16, UTF-32) mode, characters with values greater than 255 (0xffff) +can be included in a class as a literal string of data units, or by using the +\ex{ escaping mechanism. +.P +When caseless matching is set, any letters in a class represent both their +upper case and lower case versions, so for example, a caseless [aeiou] matches +"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a +caseful version would. In a UTF mode, PCRE always understands the concept of +case for characters whose values are less than 128, so caseless matching is +always possible. For characters with higher values, the concept of case is +supported if PCRE is compiled with Unicode property support, but not otherwise. +If you want to use caseless matching in a UTF mode for characters 128 and +above, you must ensure that PCRE is compiled with Unicode property support as +well as with UTF support. +.P +Characters that might indicate line breaks are never treated in any special way +when matching character classes, whatever line-ending sequence is in use, and +whatever setting of the PCRE_DOTALL and PCRE_MULTILINE options is used. A class +such as [^a] always matches one of these characters. +.P +The minus (hyphen) character can be used to specify a range of characters in a +character class. For example, [d-m] matches any letter between d and m, +inclusive. If a minus character is required in a class, it must be escaped with +a backslash or appear in a position where it cannot be interpreted as +indicating a range, typically as the first or last character in the class, or +immediately after a range. For example, [b-d-z] matches letters in the range b +to d, a hyphen character, or z. +.P +It is not possible to have the literal character "]" as the end character of a +range. A pattern such as [W-]46] is interpreted as a class of two characters +("W" and "-") followed by a literal string "46]", so it would match "W46]" or +"-46]". However, if the "]" is escaped with a backslash it is interpreted as +the end of range, so [W-\e]46] is interpreted as a class containing a range +followed by two other characters. The octal or hexadecimal representation of +"]" can also be used to end a range. +.P +An error is generated if a POSIX character class (see below) or an escape +sequence other than one that defines a single character appears at a point +where a range ending character is expected. For example, [z-\exff] is valid, +but [A-\ed] and [A-[:digit:]] are not. +.P +Ranges operate in the collating sequence of character values. They can also be +used for characters specified numerically, for example [\e000-\e037]. Ranges +can include any characters that are valid for the current mode. +.P +If a range that includes letters is used when caseless matching is set, it +matches the letters in either case. For example, [W-c] is equivalent to +[][\e\e^_`wxyzabc], matched caselessly, and in a non-UTF mode, if character +tables for a French locale are in use, [\exc8-\excb] matches accented E +characters in both cases. In UTF modes, PCRE supports the concept of case for +characters with values greater than 128 only when it is compiled with Unicode +property support. +.P +The character escape sequences \ed, \eD, \eh, \eH, \ep, \eP, \es, \eS, \ev, +\eV, \ew, and \eW may appear in a character class, and add the characters that +they match to the class. For example, [\edABCDEF] matches any hexadecimal +digit. In UTF modes, the PCRE_UCP option affects the meanings of \ed, \es, \ew +and their upper case partners, just as it does when they appear outside a +character class, as described in the section entitled +.\" HTML <a href="#genericchartypes"> +.\" </a> +"Generic character types" +.\" +above. The escape sequence \eb has a different meaning inside a character +class; it matches the backspace character. The sequences \eB, \eN, \eR, and \eX +are not special inside a character class. Like any other unrecognized escape +sequences, they are treated as the literal characters "B", "N", "R", and "X" by +default, but cause an error if the PCRE_EXTRA option is set. +.P +A circumflex can conveniently be used with the upper case character types to +specify a more restricted set of characters than the matching lower case type. +For example, the class [^\eW_] matches any letter or digit, but not underscore, +whereas [\ew] includes underscore. A positive character class should be read as +"something OR something OR ..." and a negative class as "NOT something AND NOT +something AND NOT ...". +.P +The only metacharacters that are recognized in character classes are backslash, +hyphen (only where it can be interpreted as specifying a range), circumflex +(only at the start), opening square bracket (only when it can be interpreted as +introducing a POSIX class name, or for a special compatibility feature - see +the next two sections), and the terminating closing square bracket. However, +escaping other non-alphanumeric characters does no harm. +. +. +.SH "POSIX CHARACTER CLASSES" +.rs +.sp +Perl supports the POSIX notation for character classes. This uses names +enclosed by [: and :] within the enclosing square brackets. PCRE also supports +this notation. For example, +.sp + [01[:alpha:]%] +.sp +matches "0", "1", any alphabetic character, or "%". The supported class names +are: +.sp + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \ed) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits and space + space white space (the same as \es from PCRE 8.34) + upper upper case letters + word "word" characters (same as \ew) + xdigit hexadecimal digits +.sp +The default "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), +and space (32). If locale-specific matching is taking place, the list of space +characters may be different; there may be fewer or more of them. "Space" used +to be different to \es, which did not include VT, for Perl compatibility. +However, Perl changed at release 5.18, and PCRE followed at release 8.34. +"Space" and \es now match the same set of characters. +.P +The name "word" is a Perl extension, and "blank" is a GNU extension from Perl +5.8. Another Perl extension is negation, which is indicated by a ^ character +after the colon. For example, +.sp + [12[:^digit:]] +.sp +matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX +syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not +supported, and an error is given if they are encountered. +.P +By default, characters with values greater than 128 do not match any of the +POSIX character classes. However, if the PCRE_UCP option is passed to +\fBpcre_compile()\fP, some of the classes are changed so that Unicode character +properties are used. This is achieved by replacing certain POSIX classes by +other sequences, as follows: +.sp + [:alnum:] becomes \ep{Xan} + [:alpha:] becomes \ep{L} + [:blank:] becomes \eh + [:digit:] becomes \ep{Nd} + [:lower:] becomes \ep{Ll} + [:space:] becomes \ep{Xps} + [:upper:] becomes \ep{Lu} + [:word:] becomes \ep{Xwd} +.sp +Negated versions, such as [:^alpha:] use \eP instead of \ep. Three other POSIX +classes are handled specially in UCP mode: +.TP 10 +[:graph:] +This matches characters that have glyphs that mark the page when printed. In +Unicode property terms, it matches all characters with the L, M, N, P, S, or Cf +properties, except for: +.sp + U+061C Arabic Letter Mark + U+180E Mongolian Vowel Separator + U+2066 - U+2069 Various "isolate"s +.sp +.TP 10 +[:print:] +This matches the same characters as [:graph:] plus space characters that are +not controls, that is, characters with the Zs property. +.TP 10 +[:punct:] +This matches all characters that have the Unicode P (punctuation) property, +plus those characters whose code points are less than 128 that have the S +(Symbol) property. +.P +The other POSIX classes are unchanged, and match only characters with code +points less than 128. +. +. +.SH "COMPATIBILITY FEATURE FOR WORD BOUNDARIES" +.rs +.sp +In the POSIX.2 compliant library that was included in 4.4BSD Unix, the ugly +syntax [[:<:]] and [[:>:]] is used for matching "start of word" and "end of +word". PCRE treats these items as follows: +.sp + [[:<:]] is converted to \eb(?=\ew) + [[:>:]] is converted to \eb(?<=\ew) +.sp +Only these exact character sequences are recognized. A sequence such as +[a[:<:]b] provokes error for an unrecognized POSIX class name. This support is +not compatible with Perl. It is provided to help migrations from other +environments, and is best not used in any new patterns. Note that \eb matches +at the start and the end of a word (see +.\" HTML <a href="#smallassertions"> +.\" </a> +"Simple assertions" +.\" +above), and in a Perl-style pattern the preceding or following character +normally shows which is wanted, without the need for the assertions that are +used above in order to give exactly the POSIX behaviour. +. +. +.SH "VERTICAL BAR" +.rs +.sp +Vertical bar characters are used to separate alternative patterns. For example, +the pattern +.sp + gilbert|sullivan +.sp +matches either "gilbert" or "sullivan". Any number of alternatives may appear, +and an empty alternative is permitted (matching the empty string). The matching +process tries each alternative in turn, from left to right, and the first one +that succeeds is used. If the alternatives are within a subpattern +.\" HTML <a href="#subpattern"> +.\" </a> +(defined below), +.\" +"succeeds" means matching the rest of the main pattern as well as the +alternative in the subpattern. +. +. +.SH "INTERNAL OPTION SETTING" +.rs +.sp +The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and +PCRE_EXTENDED options (which are Perl-compatible) can be changed from within +the pattern by a sequence of Perl option letters enclosed between "(?" and ")". +The option letters are +.sp + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED +.sp +For example, (?im) sets caseless, multiline matching. It is also possible to +unset these options by preceding the letter with a hyphen, and a combined +setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and +PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also +permitted. If a letter appears both before and after the hyphen, the option is +unset. +.P +The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA can be +changed in the same way as the Perl-compatible options by using the characters +J, U and X respectively. +.P +When one of these option changes occurs at top level (that is, not inside +subpattern parentheses), the change applies to the remainder of the pattern +that follows. If the change is placed right at the start of a pattern, PCRE +extracts it into the global options (and it will therefore show up in data +extracted by the \fBpcre_fullinfo()\fP function). +.P +An option change within a subpattern (see below for a description of +subpatterns) affects only that part of the subpattern that follows it, so +.sp + (a(?i)b)c +.sp +matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). +By this means, options can be made to have different settings in different +parts of the pattern. Any changes made in one alternative do carry on +into subsequent branches within the same subpattern. For example, +.sp + (a(?i)b|c) +.sp +matches "ab", "aB", "c", and "C", even though when matching "C" the first +branch is abandoned before the option setting. This is because the effects of +option settings happen at compile time. There would be some very weird +behaviour otherwise. +.P +\fBNote:\fP There are other PCRE-specific options that can be set by the +application when the compiling or matching functions are called. In some cases +the pattern can contain special leading sequences such as (*CRLF) to override +what the application has set or what has been defaulted. Details are given in +the section entitled +.\" HTML <a href="#newlineseq"> +.\" </a> +"Newline sequences" +.\" +above. There are also the (*UTF8), (*UTF16),(*UTF32), and (*UCP) leading +sequences that can be used to set UTF and Unicode property modes; they are +equivalent to setting the PCRE_UTF8, PCRE_UTF16, PCRE_UTF32 and the PCRE_UCP +options, respectively. The (*UTF) sequence is a generic version that can be +used with any of the libraries. However, the application can set the +PCRE_NEVER_UTF option, which locks out the use of the (*UTF) sequences. +. +. +.\" HTML <a name="subpattern"></a> +.SH SUBPATTERNS +.rs +.sp +Subpatterns are delimited by parentheses (round brackets), which can be nested. +Turning part of a pattern into a subpattern does two things: +.sp +1. It localizes a set of alternatives. For example, the pattern +.sp + cat(aract|erpillar|) +.sp +matches "cataract", "caterpillar", or "cat". Without the parentheses, it would +match "cataract", "erpillar" or an empty string. +.sp +2. It sets up the subpattern as a capturing subpattern. This means that, when +the whole pattern matches, that portion of the subject string that matched the +subpattern is passed back to the caller via the \fIovector\fP argument of the +matching function. (This applies only to the traditional matching functions; +the DFA matching functions do not support capturing.) +.P +Opening parentheses are counted from left to right (starting from 1) to obtain +numbers for the capturing subpatterns. For example, if the string "the red +king" is matched against the pattern +.sp + the ((red|white) (king|queen)) +.sp +the captured substrings are "red king", "red", and "king", and are numbered 1, +2, and 3, respectively. +.P +The fact that plain parentheses fulfil two functions is not always helpful. +There are often times when a grouping subpattern is required without a +capturing requirement. If an opening parenthesis is followed by a question mark +and a colon, the subpattern does not do any capturing, and is not counted when +computing the number of any subsequent capturing subpatterns. For example, if +the string "the white queen" is matched against the pattern +.sp + the ((?:red|white) (king|queen)) +.sp +the captured substrings are "white queen" and "queen", and are numbered 1 and +2. The maximum number of capturing subpatterns is 65535. +.P +As a convenient shorthand, if any option settings are required at the start of +a non-capturing subpattern, the option letters may appear between the "?" and +the ":". Thus the two patterns +.sp + (?i:saturday|sunday) + (?:(?i)saturday|sunday) +.sp +match exactly the same set of strings. Because alternative branches are tried +from left to right, and options are not reset until the end of the subpattern +is reached, an option setting in one branch does affect subsequent branches, so +the above patterns match "SUNDAY" as well as "Saturday". +. +. +.\" HTML <a name="dupsubpatternnumber"></a> +.SH "DUPLICATE SUBPATTERN NUMBERS" +.rs +.sp +Perl 5.10 introduced a feature whereby each alternative in a subpattern uses +the same numbers for its capturing parentheses. Such a subpattern starts with +(?| and is itself a non-capturing subpattern. For example, consider this +pattern: +.sp + (?|(Sat)ur|(Sun))day +.sp +Because the two alternatives are inside a (?| group, both sets of capturing +parentheses are numbered one. Thus, when the pattern matches, you can look +at captured substring number one, whichever alternative matched. This construct +is useful when you want to capture part, but not all, of one of a number of +alternatives. Inside a (?| group, parentheses are numbered as usual, but the +number is reset at the start of each branch. The numbers of any capturing +parentheses that follow the subpattern start after the highest number used in +any branch. The following example is taken from the Perl documentation. The +numbers underneath show in which buffer the captured content will be stored. +.sp + # before ---------------branch-reset----------- after + / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x + # 1 2 2 3 2 3 4 +.sp +A back reference to a numbered subpattern uses the most recent value that is +set for that number by any subpattern. The following pattern matches "abcabc" +or "defdef": +.sp + /(?|(abc)|(def))\e1/ +.sp +In contrast, a subroutine call to a numbered subpattern always refers to the +first one in the pattern with the given number. The following pattern matches +"abcabc" or "defabc": +.sp + /(?|(abc)|(def))(?1)/ +.sp +If a +.\" HTML <a href="#conditions"> +.\" </a> +condition test +.\" +for a subpattern's having matched refers to a non-unique number, the test is +true if any of the subpatterns of that number have matched. +.P +An alternative approach to using this "branch reset" feature is to use +duplicate named subpatterns, as described in the next section. +. +. +.SH "NAMED SUBPATTERNS" +.rs +.sp +Identifying capturing parentheses by number is simple, but it can be very hard +to keep track of the numbers in complicated regular expressions. Furthermore, +if an expression is modified, the numbers may change. To help with this +difficulty, PCRE supports the naming of subpatterns. This feature was not +added to Perl until release 5.10. Python had the feature earlier, and PCRE +introduced it at release 4.0, using the Python syntax. PCRE now supports both +the Perl and the Python syntax. Perl allows identically numbered subpatterns to +have different names, but PCRE does not. +.P +In PCRE, a subpattern can be named in one of three ways: (?<name>...) or +(?'name'...) as in Perl, or (?P<name>...) as in Python. References to capturing +parentheses from other parts of the pattern, such as +.\" HTML <a href="#backreferences"> +.\" </a> +back references, +.\" +.\" HTML <a href="#recursion"> +.\" </a> +recursion, +.\" +and +.\" HTML <a href="#conditions"> +.\" </a> +conditions, +.\" +can be made by name as well as by number. +.P +Names consist of up to 32 alphanumeric characters and underscores, but must +start with a non-digit. Named capturing parentheses are still allocated numbers +as well as names, exactly as if the names were not present. The PCRE API +provides function calls for extracting the name-to-number translation table +from a compiled pattern. There is also a convenience function for extracting a +captured substring by name. +.P +By default, a name must be unique within a pattern, but it is possible to relax +this constraint by setting the PCRE_DUPNAMES option at compile time. (Duplicate +names are also always permitted for subpatterns with the same number, set up as +described in the previous section.) Duplicate names can be useful for patterns +where only one instance of the named parentheses can match. Suppose you want to +match the name of a weekday, either as a 3-letter abbreviation or as the full +name, and in both cases you want to extract the abbreviation. This pattern +(ignoring the line breaks) does the job: +.sp + (?<DN>Mon|Fri|Sun)(?:day)?| + (?<DN>Tue)(?:sday)?| + (?<DN>Wed)(?:nesday)?| + (?<DN>Thu)(?:rsday)?| + (?<DN>Sat)(?:urday)? +.sp +There are five capturing substrings, but only one is ever set after a match. +(An alternative way of solving this problem is to use a "branch reset" +subpattern, as described in the previous section.) +.P +The convenience function for extracting the data by name returns the substring +for the first (and in this example, the only) subpattern of that name that +matched. This saves searching to find which numbered subpattern it was. +.P +If you make a back reference to a non-unique named subpattern from elsewhere in +the pattern, the subpatterns to which the name refers are checked in the order +in which they appear in the overall pattern. The first one that is set is used +for the reference. For example, this pattern matches both "foofoo" and +"barbar" but not "foobar" or "barfoo": +.sp + (?:(?<n>foo)|(?<n>bar))\ek<n> +.sp +.P +If you make a subroutine call to a non-unique named subpattern, the one that +corresponds to the first occurrence of the name is used. In the absence of +duplicate numbers (see the previous section) this is the one with the lowest +number. +.P +If you use a named reference in a condition +test (see the +.\" +.\" HTML <a href="#conditions"> +.\" </a> +section about conditions +.\" +below), either to check whether a subpattern has matched, or to check for +recursion, all subpatterns with the same name are tested. If the condition is +true for any one of them, the overall condition is true. This is the same +behaviour as testing by number. For further details of the interfaces for +handling named subpatterns, see the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +.P +\fBWarning:\fP You cannot use different names to distinguish between two +subpatterns with the same number because PCRE uses only the numbers when +matching. For this reason, an error is given at compile time if different names +are given to subpatterns with the same number. However, you can always give the +same name to subpatterns with the same number, even when PCRE_DUPNAMES is not +set. +. +. +.SH REPETITION +.rs +.sp +Repetition is specified by quantifiers, which can follow any of the following +items: +.sp + a literal data character + the dot metacharacter + the \eC escape sequence + the \eX escape sequence + the \eR escape sequence + an escape such as \ed or \epL that matches a single character + a character class + a back reference (see next section) + a parenthesized subpattern (including assertions) + a subroutine call to a subpattern (recursive or otherwise) +.sp +The general repetition quantifier specifies a minimum and maximum number of +permitted matches, by giving the two numbers in curly brackets (braces), +separated by a comma. The numbers must be less than 65536, and the first must +be less than or equal to the second. For example: +.sp + z{2,4} +.sp +matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special +character. If the second number is omitted, but the comma is present, there is +no upper limit; if the second number and the comma are both omitted, the +quantifier specifies an exact number of required matches. Thus +.sp + [aeiou]{3,} +.sp +matches at least 3 successive vowels, but may match many more, while +.sp + \ed{8} +.sp +matches exactly 8 digits. An opening curly bracket that appears in a position +where a quantifier is not allowed, or one that does not match the syntax of a +quantifier, is taken as a literal character. For example, {,6} is not a +quantifier, but a literal string of four characters. +.P +In UTF modes, quantifiers apply to characters rather than to individual data +units. Thus, for example, \ex{100}{2} matches two characters, each of +which is represented by a two-byte sequence in a UTF-8 string. Similarly, +\eX{3} matches three Unicode extended grapheme clusters, each of which may be +several data units long (and they may be of different lengths). +.P +The quantifier {0} is permitted, causing the expression to behave as if the +previous item and the quantifier were not present. This may be useful for +subpatterns that are referenced as +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +subroutines +.\" +from elsewhere in the pattern (but see also the section entitled +.\" HTML <a href="#subdefine"> +.\" </a> +"Defining subpatterns for use by reference only" +.\" +below). Items other than subpatterns that have a {0} quantifier are omitted +from the compiled pattern. +.P +For convenience, the three most common quantifiers have single-character +abbreviations: +.sp + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} +.sp +It is possible to construct infinite loops by following a subpattern that can +match no characters with a quantifier that has no upper limit, for example: +.sp + (a?)* +.sp +Earlier versions of Perl and PCRE used to give an error at compile time for +such patterns. However, because there are cases where this can be useful, such +patterns are now accepted, but if any repetition of the subpattern does in fact +match no characters, the loop is forcibly broken. +.P +By default, the quantifiers are "greedy", that is, they match as much as +possible (up to the maximum number of permitted times), without causing the +rest of the pattern to fail. The classic example of where this gives problems +is in trying to match comments in C programs. These appear between /* and */ +and within the comment, individual * and / characters may appear. An attempt to +match C comments by applying the pattern +.sp + /\e*.*\e*/ +.sp +to the string +.sp + /* first comment */ not comment /* second comment */ +.sp +fails, because it matches the entire string owing to the greediness of the .* +item. +.P +However, if a quantifier is followed by a question mark, it ceases to be +greedy, and instead matches the minimum number of times possible, so the +pattern +.sp + /\e*.*?\e*/ +.sp +does the right thing with the C comments. The meaning of the various +quantifiers is not otherwise changed, just the preferred number of matches. +Do not confuse this use of question mark with its use as a quantifier in its +own right. Because it has two uses, it can sometimes appear doubled, as in +.sp + \ed??\ed +.sp +which matches one digit by preference, but can match two if that is the only +way the rest of the pattern matches. +.P +If the PCRE_UNGREEDY option is set (an option that is not available in Perl), +the quantifiers are not greedy by default, but individual ones can be made +greedy by following them with a question mark. In other words, it inverts the +default behaviour. +.P +When a parenthesized subpattern is quantified with a minimum repeat count that +is greater than 1 or with a limited maximum, more memory is required for the +compiled pattern, in proportion to the size of the minimum or maximum. +.P +If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent +to Perl's /s) is set, thus allowing the dot to match newlines, the pattern is +implicitly anchored, because whatever follows will be tried against every +character position in the subject string, so there is no point in retrying the +overall match at any position after the first. PCRE normally treats such a +pattern as though it were preceded by \eA. +.P +In cases where it is known that the subject string contains no newlines, it is +worth setting PCRE_DOTALL in order to obtain this optimization, or +alternatively using ^ to indicate anchoring explicitly. +.P +However, there are some cases where the optimization cannot be used. When .* +is inside capturing parentheses that are the subject of a back reference +elsewhere in the pattern, a match at the start may fail where a later one +succeeds. Consider, for example: +.sp + (.*)abc\e1 +.sp +If the subject is "xyz123abc123" the match point is the fourth character. For +this reason, such a pattern is not implicitly anchored. +.P +Another case where implicit anchoring is not applied is when the leading .* is +inside an atomic group. Once again, a match at the start may fail where a later +one succeeds. Consider this pattern: +.sp + (?>.*?a)b +.sp +It matches "ab" in the subject "aab". The use of the backtracking control verbs +(*PRUNE) and (*SKIP) also disable this optimization. +.P +When a capturing subpattern is repeated, the value captured is the substring +that matched the final iteration. For example, after +.sp + (tweedle[dume]{3}\es*)+ +.sp +has matched "tweedledum tweedledee" the value of the captured substring is +"tweedledee". However, if there are nested capturing subpatterns, the +corresponding captured values may have been set in previous iterations. For +example, after +.sp + /(a|(b))+/ +.sp +matches "aba" the value of the second captured substring is "b". +. +. +.\" HTML <a name="atomicgroup"></a> +.SH "ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS" +.rs +.sp +With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") +repetition, failure of what follows normally causes the repeated item to be +re-evaluated to see if a different number of repeats allows the rest of the +pattern to match. Sometimes it is useful to prevent this, either to change the +nature of the match, or to cause it fail earlier than it otherwise might, when +the author of the pattern knows there is no point in carrying on. +.P +Consider, for example, the pattern \ed+foo when applied to the subject line +.sp + 123456bar +.sp +After matching all 6 digits and then failing to match "foo", the normal +action of the matcher is to try again with only 5 digits matching the \ed+ +item, and then with 4, and so on, before ultimately failing. "Atomic grouping" +(a term taken from Jeffrey Friedl's book) provides the means for specifying +that once a subpattern has matched, it is not to be re-evaluated in this way. +.P +If we use atomic grouping for the previous example, the matcher gives up +immediately on failing to match "foo" the first time. The notation is a kind of +special parenthesis, starting with (?> as in this example: +.sp + (?>\ed+)foo +.sp +This kind of parenthesis "locks up" the part of the pattern it contains once +it has matched, and a failure further into the pattern is prevented from +backtracking into it. Backtracking past it to previous items, however, works as +normal. +.P +An alternative description is that a subpattern of this type matches the string +of characters that an identical standalone pattern would match, if anchored at +the current point in the subject string. +.P +Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as +the above example can be thought of as a maximizing repeat that must swallow +everything it can. So, while both \ed+ and \ed+? are prepared to adjust the +number of digits they match in order to make the rest of the pattern match, +(?>\ed+) can only match an entire sequence of digits. +.P +Atomic groups in general can of course contain arbitrarily complicated +subpatterns, and can be nested. However, when the subpattern for an atomic +group is just a single repeated item, as in the example above, a simpler +notation, called a "possessive quantifier" can be used. This consists of an +additional + character following a quantifier. Using this notation, the +previous example can be rewritten as +.sp + \ed++foo +.sp +Note that a possessive quantifier can be used with an entire group, for +example: +.sp + (abc|xyz){2,3}+ +.sp +Possessive quantifiers are always greedy; the setting of the PCRE_UNGREEDY +option is ignored. They are a convenient notation for the simpler forms of +atomic group. However, there is no difference in the meaning of a possessive +quantifier and the equivalent atomic group, though there may be a performance +difference; possessive quantifiers should be slightly faster. +.P +The possessive quantifier syntax is an extension to the Perl 5.8 syntax. +Jeffrey Friedl originated the idea (and the name) in the first edition of his +book. Mike McCloskey liked it, so implemented it when he built Sun's Java +package, and PCRE copied it from there. It ultimately found its way into Perl +at release 5.10. +.P +PCRE has an optimization that automatically "possessifies" certain simple +pattern constructs. For example, the sequence A+B is treated as A++B because +there is no point in backtracking into a sequence of A's when B must follow. +.P +When a pattern contains an unlimited repeat inside a subpattern that can itself +be repeated an unlimited number of times, the use of an atomic group is the +only way to avoid some failing matches taking a very long time indeed. The +pattern +.sp + (\eD+|<\ed+>)*[!?] +.sp +matches an unlimited number of substrings that either consist of non-digits, or +digits enclosed in <>, followed by either ! or ?. When it matches, it runs +quickly. However, if it is applied to +.sp + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +.sp +it takes a long time before reporting failure. This is because the string can +be divided between the internal \eD+ repeat and the external * repeat in a +large number of ways, and all have to be tried. (The example uses [!?] rather +than a single character at the end, because both PCRE and Perl have an +optimization that allows for fast failure when a single character is used. They +remember the last single character that is required for a match, and fail early +if it is not present in the string.) If the pattern is changed so that it uses +an atomic group, like this: +.sp + ((?>\eD+)|<\ed+>)*[!?] +.sp +sequences of non-digits cannot be broken, and failure happens quickly. +. +. +.\" HTML <a name="backreferences"></a> +.SH "BACK REFERENCES" +.rs +.sp +Outside a character class, a backslash followed by a digit greater than 0 (and +possibly further digits) is a back reference to a capturing subpattern earlier +(that is, to its left) in the pattern, provided there have been that many +previous capturing left parentheses. +.P +However, if the decimal number following the backslash is less than 10, it is +always taken as a back reference, and causes an error only if there are not +that many capturing left parentheses in the entire pattern. In other words, the +parentheses that are referenced need not be to the left of the reference for +numbers less than 10. A "forward back reference" of this type can make sense +when a repetition is involved and the subpattern to the right has participated +in an earlier iteration. +.P +It is not possible to have a numerical "forward back reference" to a subpattern +whose number is 10 or more using this syntax because a sequence such as \e50 is +interpreted as a character defined in octal. See the subsection entitled +"Non-printing characters" +.\" HTML <a href="#digitsafterbackslash"> +.\" </a> +above +.\" +for further details of the handling of digits following a backslash. There is +no such problem when named parentheses are used. A back reference to any +subpattern is possible using named parentheses (see below). +.P +Another way of avoiding the ambiguity inherent in the use of digits following a +backslash is to use the \eg escape sequence. This escape must be followed by an +unsigned number or a negative number, optionally enclosed in braces. These +examples are all identical: +.sp + (ring), \e1 + (ring), \eg1 + (ring), \eg{1} +.sp +An unsigned number specifies an absolute reference without the ambiguity that +is present in the older syntax. It is also useful when literal digits follow +the reference. A negative number is a relative reference. Consider this +example: +.sp + (abc(def)ghi)\eg{-1} +.sp +The sequence \eg{-1} is a reference to the most recently started capturing +subpattern before \eg, that is, is it equivalent to \e2 in this example. +Similarly, \eg{-2} would be equivalent to \e1. The use of relative references +can be helpful in long patterns, and also in patterns that are created by +joining together fragments that contain references within themselves. +.P +A back reference matches whatever actually matched the capturing subpattern in +the current subject string, rather than anything matching the subpattern +itself (see +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +"Subpatterns as subroutines" +.\" +below for a way of doing that). So the pattern +.sp + (sens|respons)e and \e1ibility +.sp +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If caseful matching is in force at the time of the +back reference, the case of letters is relevant. For example, +.sp + ((?i)rah)\es+\e1 +.sp +matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original +capturing subpattern is matched caselessly. +.P +There are several different ways of writing back references to named +subpatterns. The .NET syntax \ek{name} and the Perl syntax \ek<name> or +\ek'name' are supported, as is the Python syntax (?P=name). Perl 5.10's unified +back reference syntax, in which \eg can be used for both numeric and named +references, is also supported. We could rewrite the above example in any of +the following ways: +.sp + (?<p1>(?i)rah)\es+\ek<p1> + (?'p1'(?i)rah)\es+\ek{p1} + (?P<p1>(?i)rah)\es+(?P=p1) + (?<p1>(?i)rah)\es+\eg{p1} +.sp +A subpattern that is referenced by name may appear in the pattern before or +after the reference. +.P +There may be more than one back reference to the same subpattern. If a +subpattern has not actually been used in a particular match, any back +references to it always fail by default. For example, the pattern +.sp + (a|(bc))\e2 +.sp +always fails if it starts to match "a" rather than "bc". However, if the +PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back reference to an +unset value matches an empty string. +.P +Because there may be many capturing parentheses in a pattern, all digits +following a backslash are taken as part of a potential back reference number. +If the pattern continues with a digit character, some delimiter must be used to +terminate the back reference. If the PCRE_EXTENDED option is set, this can be +white space. Otherwise, the \eg{ syntax or an empty comment (see +.\" HTML <a href="#comments"> +.\" </a> +"Comments" +.\" +below) can be used. +. +.SS "Recursive back references" +.rs +.sp +A back reference that occurs inside the parentheses to which it refers fails +when the subpattern is first used, so, for example, (a\e1) never matches. +However, such references can be useful inside repeated subpatterns. For +example, the pattern +.sp + (a|b\e1)+ +.sp +matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of +the subpattern, the back reference matches the character string corresponding +to the previous iteration. In order for this to work, the pattern must be such +that the first iteration does not need to match the back reference. This can be +done using alternation, as in the example above, or by a quantifier with a +minimum of zero. +.P +Back references of this type cause the group that they reference to be treated +as an +.\" HTML <a href="#atomicgroup"> +.\" </a> +atomic group. +.\" +Once the whole group has been matched, a subsequent matching failure cannot +cause backtracking into the middle of the group. +. +. +.\" HTML <a name="bigassertions"></a> +.SH ASSERTIONS +.rs +.sp +An assertion is a test on the characters following or preceding the current +matching point that does not actually consume any characters. The simple +assertions coded as \eb, \eB, \eA, \eG, \eZ, \ez, ^ and $ are described +.\" HTML <a href="#smallassertions"> +.\" </a> +above. +.\" +.P +More complicated assertions are coded as subpatterns. There are two kinds: +those that look ahead of the current position in the subject string, and those +that look behind it. An assertion subpattern is matched in the normal way, +except that it does not cause the current matching position to be changed. +.P +Assertion subpatterns are not capturing subpatterns. If such an assertion +contains capturing subpatterns within it, these are counted for the purposes of +numbering the capturing subpatterns in the whole pattern. However, substring +capturing is carried out only for positive assertions. (Perl sometimes, but not +always, does do capturing in negative assertions.) +.P +For compatibility with Perl, assertion subpatterns may be repeated; though +it makes no sense to assert the same thing several times, the side effect of +capturing parentheses may occasionally be useful. In practice, there only three +cases: +.sp +(1) If the quantifier is {0}, the assertion is never obeyed during matching. +However, it may contain internal capturing parenthesized groups that are called +from elsewhere via the +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +subroutine mechanism. +.\" +.sp +(2) If quantifier is {0,n} where n is greater than zero, it is treated as if it +were {0,1}. At run time, the rest of the pattern match is tried with and +without the assertion, the order depending on the greediness of the quantifier. +.sp +(3) If the minimum repetition is greater than zero, the quantifier is ignored. +The assertion is obeyed just once when encountered during matching. +. +. +.SS "Lookahead assertions" +.rs +.sp +Lookahead assertions start with (?= for positive assertions and (?! for +negative assertions. For example, +.sp + \ew+(?=;) +.sp +matches a word followed by a semicolon, but does not include the semicolon in +the match, and +.sp + foo(?!bar) +.sp +matches any occurrence of "foo" that is not followed by "bar". Note that the +apparently similar pattern +.sp + (?!foo)bar +.sp +does not find an occurrence of "bar" that is preceded by something other than +"foo"; it finds any occurrence of "bar" whatsoever, because the assertion +(?!foo) is always true when the next three characters are "bar". A +lookbehind assertion is needed to achieve the other effect. +.P +If you want to force a matching failure at some point in a pattern, the most +convenient way to do it is with (?!) because an empty string always matches, so +an assertion that requires there not to be an empty string must always fail. +The backtracking control verb (*FAIL) or (*F) is a synonym for (?!). +. +. +.\" HTML <a name="lookbehind"></a> +.SS "Lookbehind assertions" +.rs +.sp +Lookbehind assertions start with (?<= for positive assertions and (?<! for +negative assertions. For example, +.sp + (?<!foo)bar +.sp +does find an occurrence of "bar" that is not preceded by "foo". The contents of +a lookbehind assertion are restricted such that all the strings it matches must +have a fixed length. However, if there are several top-level alternatives, they +do not all have to have the same fixed length. Thus +.sp + (?<=bullock|donkey) +.sp +is permitted, but +.sp + (?<!dogs?|cats?) +.sp +causes an error at compile time. Branches that match different length strings +are permitted only at the top level of a lookbehind assertion. This is an +extension compared with Perl, which requires all branches to match the same +length of string. An assertion such as +.sp + (?<=ab(c|de)) +.sp +is not permitted, because its single top-level branch can match two different +lengths, but it is acceptable to PCRE if rewritten to use two top-level +branches: +.sp + (?<=abc|abde) +.sp +In some cases, the escape sequence \eK +.\" HTML <a href="#resetmatchstart"> +.\" </a> +(see above) +.\" +can be used instead of a lookbehind assertion to get round the fixed-length +restriction. +.P +The implementation of lookbehind assertions is, for each alternative, to +temporarily move the current position back by the fixed length and then try to +match. If there are insufficient characters before the current position, the +assertion fails. +.P +In a UTF mode, PCRE does not allow the \eC escape (which matches a single data +unit even in a UTF mode) to appear in lookbehind assertions, because it makes +it impossible to calculate the length of the lookbehind. The \eX and \eR +escapes, which can match different numbers of data units, are also not +permitted. +.P +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +"Subroutine" +.\" +calls (see below) such as (?2) or (?&X) are permitted in lookbehinds, as long +as the subpattern matches a fixed-length string. +.\" HTML <a href="#recursion"> +.\" </a> +Recursion, +.\" +however, is not supported. +.P +Possessive quantifiers can be used in conjunction with lookbehind assertions to +specify efficient matching of fixed-length strings at the end of subject +strings. Consider a simple pattern such as +.sp + abcd$ +.sp +when applied to a long string that does not match. Because matching proceeds +from left to right, PCRE will look for each "a" in the subject and then see if +what follows matches the rest of the pattern. If the pattern is specified as +.sp + ^.*abcd$ +.sp +the initial .* matches the entire string at first, but when this fails (because +there is no following "a"), it backtracks to match all but the last character, +then all but the last two characters, and so on. Once again the search for "a" +covers the entire string, from right to left, so we are no better off. However, +if the pattern is written as +.sp + ^.*+(?<=abcd) +.sp +there can be no backtracking for the .*+ item; it can match only the entire +string. The subsequent lookbehind assertion does a single test on the last four +characters. If it fails, the match fails immediately. For long strings, this +approach makes a significant difference to the processing time. +. +. +.SS "Using multiple assertions" +.rs +.sp +Several assertions (of any sort) may occur in succession. For example, +.sp + (?<=\ed{3})(?<!999)foo +.sp +matches "foo" preceded by three digits that are not "999". Notice that each of +the assertions is applied independently at the same point in the subject +string. First there is a check that the previous three characters are all +digits, and then there is a check that the same three characters are not "999". +This pattern does \fInot\fP match "foo" preceded by six characters, the first +of which are digits and the last three of which are not "999". For example, it +doesn't match "123abcfoo". A pattern to do that is +.sp + (?<=\ed{3}...)(?<!999)foo +.sp +This time the first assertion looks at the preceding six characters, checking +that the first three are digits, and then the second assertion checks that the +preceding three characters are not "999". +.P +Assertions can be nested in any combination. For example, +.sp + (?<=(?<!foo)bar)baz +.sp +matches an occurrence of "baz" that is preceded by "bar" which in turn is not +preceded by "foo", while +.sp + (?<=\ed{3}(?!999)...)foo +.sp +is another pattern that matches "foo" preceded by three digits and any three +characters that are not "999". +. +. +.\" HTML <a name="conditions"></a> +.SH "CONDITIONAL SUBPATTERNS" +.rs +.sp +It is possible to cause the matching process to obey a subpattern +conditionally or to choose between two alternative subpatterns, depending on +the result of an assertion, or whether a specific capturing subpattern has +already been matched. The two possible forms of conditional subpattern are: +.sp + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) +.sp +If the condition is satisfied, the yes-pattern is used; otherwise the +no-pattern (if present) is used. If there are more than two alternatives in the +subpattern, a compile-time error occurs. Each of the two alternatives may +itself contain nested subpatterns of any form, including conditional +subpatterns; the restriction to two alternatives applies only at the level of +the condition. This pattern fragment is an example where the alternatives are +complex: +.sp + (?(1) (A|B|C) | (D | (?(2)E|F) | E) ) +.sp +.P +There are four kinds of condition: references to subpatterns, references to +recursion, a pseudo-condition called DEFINE, and assertions. +. +.SS "Checking for a used subpattern by number" +.rs +.sp +If the text between the parentheses consists of a sequence of digits, the +condition is true if a capturing subpattern of that number has previously +matched. If there is more than one capturing subpattern with the same number +(see the earlier +.\" +.\" HTML <a href="#recursion"> +.\" </a> +section about duplicate subpattern numbers), +.\" +the condition is true if any of them have matched. An alternative notation is +to precede the digits with a plus or minus sign. In this case, the subpattern +number is relative rather than absolute. The most recently opened parentheses +can be referenced by (?(-1), the next most recent by (?(-2), and so on. Inside +loops it can also make sense to refer to subsequent groups. The next +parentheses to be opened can be referenced as (?(+1), and so on. (The value +zero in any of these forms is not used; it provokes a compile-time error.) +.P +Consider the following pattern, which contains non-significant white space to +make it more readable (assume the PCRE_EXTENDED option) and to divide it into +three parts for ease of discussion: +.sp + ( \e( )? [^()]+ (?(1) \e) ) +.sp +The first part matches an optional opening parenthesis, and if that +character is present, sets it as the first captured substring. The second part +matches one or more characters that are not parentheses. The third part is a +conditional subpattern that tests whether or not the first set of parentheses +matched. If they did, that is, if subject started with an opening parenthesis, +the condition is true, and so the yes-pattern is executed and a closing +parenthesis is required. Otherwise, since no-pattern is not present, the +subpattern matches nothing. In other words, this pattern matches a sequence of +non-parentheses, optionally enclosed in parentheses. +.P +If you were embedding this pattern in a larger one, you could use a relative +reference: +.sp + ...other stuff... ( \e( )? [^()]+ (?(-1) \e) ) ... +.sp +This makes the fragment independent of the parentheses in the larger pattern. +. +.SS "Checking for a used subpattern by name" +.rs +.sp +Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used +subpattern by name. For compatibility with earlier versions of PCRE, which had +this facility before Perl, the syntax (?(name)...) is also recognized. +.P +Rewriting the above example to use a named subpattern gives this: +.sp + (?<OPEN> \e( )? [^()]+ (?(<OPEN>) \e) ) +.sp +If the name used in a condition of this kind is a duplicate, the test is +applied to all subpatterns of the same name, and is true if any one of them has +matched. +. +.SS "Checking for pattern recursion" +.rs +.sp +If the condition is the string (R), and there is no subpattern with the name R, +the condition is true if a recursive call to the whole pattern or any +subpattern has been made. If digits or a name preceded by ampersand follow the +letter R, for example: +.sp + (?(R3)...) or (?(R&name)...) +.sp +the condition is true if the most recent recursion is into a subpattern whose +number or name is given. This condition does not check the entire recursion +stack. If the name used in a condition of this kind is a duplicate, the test is +applied to all subpatterns of the same name, and is true if any one of them is +the most recent recursion. +.P +At "top level", all these recursion test conditions are false. +.\" HTML <a href="#recursion"> +.\" </a> +The syntax for recursive patterns +.\" +is described below. +. +.\" HTML <a name="subdefine"></a> +.SS "Defining subpatterns for use by reference only" +.rs +.sp +If the condition is the string (DEFINE), and there is no subpattern with the +name DEFINE, the condition is always false. In this case, there may be only one +alternative in the subpattern. It is always skipped if control reaches this +point in the pattern; the idea of DEFINE is that it can be used to define +subroutines that can be referenced from elsewhere. (The use of +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +subroutines +.\" +is described below.) For example, a pattern to match an IPv4 address such as +"192.168.23.245" could be written like this (ignore white space and line +breaks): +.sp + (?(DEFINE) (?<byte> 2[0-4]\ed | 25[0-5] | 1\ed\ed | [1-9]?\ed) ) + \eb (?&byte) (\e.(?&byte)){3} \eb +.sp +The first part of the pattern is a DEFINE group inside which a another group +named "byte" is defined. This matches an individual component of an IPv4 +address (a number less than 256). When matching takes place, this part of the +pattern is skipped because DEFINE acts like a false condition. The rest of the +pattern uses references to the named group to match the four dot-separated +components of an IPv4 address, insisting on a word boundary at each end. +. +.SS "Assertion conditions" +.rs +.sp +If the condition is not in any of the above formats, it must be an assertion. +This may be a positive or negative lookahead or lookbehind assertion. Consider +this pattern, again containing non-significant white space, and with the two +alternatives on the second line: +.sp + (?(?=[^a-z]*[a-z]) + \ed{2}-[a-z]{3}-\ed{2} | \ed{2}-\ed{2}-\ed{2} ) +.sp +The condition is a positive lookahead assertion that matches an optional +sequence of non-letters followed by a letter. In other words, it tests for the +presence of at least one letter in the subject. If a letter is found, the +subject is matched against the first alternative; otherwise it is matched +against the second. This pattern matches strings in one of the two forms +dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. +. +. +.\" HTML <a name="comments"></a> +.SH COMMENTS +.rs +.sp +There are two ways of including comments in patterns that are processed by +PCRE. In both cases, the start of the comment must not be in a character class, +nor in the middle of any other sequence of related characters such as (?: or a +subpattern name or number. The characters that make up a comment play no part +in the pattern matching. +.P +The sequence (?# marks the start of a comment that continues up to the next +closing parenthesis. Nested parentheses are not permitted. If the PCRE_EXTENDED +option is set, an unescaped # character also introduces a comment, which in +this case continues to immediately after the next newline character or +character sequence in the pattern. Which characters are interpreted as newlines +is controlled by the options passed to a compiling function or by a special +sequence at the start of the pattern, as described in the section entitled +.\" HTML <a href="#newlines"> +.\" </a> +"Newline conventions" +.\" +above. Note that the end of this type of comment is a literal newline sequence +in the pattern; escape sequences that happen to represent a newline do not +count. For example, consider this pattern when PCRE_EXTENDED is set, and the +default newline convention is in force: +.sp + abc #comment \en still comment +.sp +On encountering the # character, \fBpcre_compile()\fP skips along, looking for +a newline in the pattern. The sequence \en is still literal at this stage, so +it does not terminate the comment. Only an actual character with the code value +0x0a (the default newline) does so. +. +. +.\" HTML <a name="recursion"></a> +.SH "RECURSIVE PATTERNS" +.rs +.sp +Consider the problem of matching a string in parentheses, allowing for +unlimited nested parentheses. Without the use of recursion, the best that can +be done is to use a pattern that matches up to some fixed depth of nesting. It +is not possible to handle an arbitrary nesting depth. +.P +For some time, Perl has provided a facility that allows regular expressions to +recurse (amongst other things). It does this by interpolating Perl code in the +expression at run time, and the code can refer to the expression itself. A Perl +pattern using code interpolation to solve the parentheses problem can be +created like this: +.sp + $re = qr{\e( (?: (?>[^()]+) | (?p{$re}) )* \e)}x; +.sp +The (?p{...}) item interpolates Perl code at run time, and in this case refers +recursively to the pattern in which it appears. +.P +Obviously, PCRE cannot support the interpolation of Perl code. Instead, it +supports special syntax for recursion of the entire pattern, and also for +individual subpattern recursion. After its introduction in PCRE and Python, +this kind of recursion was subsequently introduced into Perl at release 5.10. +.P +A special item that consists of (? followed by a number greater than zero and a +closing parenthesis is a recursive subroutine call of the subpattern of the +given number, provided that it occurs inside that subpattern. (If not, it is a +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +non-recursive subroutine +.\" +call, which is described in the next section.) The special item (?R) or (?0) is +a recursive call of the entire regular expression. +.P +This PCRE pattern solves the nested parentheses problem (assume the +PCRE_EXTENDED option is set so that white space is ignored): +.sp + \e( ( [^()]++ | (?R) )* \e) +.sp +First it matches an opening parenthesis. Then it matches any number of +substrings which can either be a sequence of non-parentheses, or a recursive +match of the pattern itself (that is, a correctly parenthesized substring). +Finally there is a closing parenthesis. Note the use of a possessive quantifier +to avoid backtracking into sequences of non-parentheses. +.P +If this were part of a larger pattern, you would not want to recurse the entire +pattern, so instead you could use this: +.sp + ( \e( ( [^()]++ | (?1) )* \e) ) +.sp +We have put the pattern into parentheses, and caused the recursion to refer to +them instead of the whole pattern. +.P +In a larger pattern, keeping track of parenthesis numbers can be tricky. This +is made easier by the use of relative references. Instead of (?1) in the +pattern above you can write (?-2) to refer to the second most recently opened +parentheses preceding the recursion. In other words, a negative number counts +capturing parentheses leftwards from the point at which it is encountered. +.P +It is also possible to refer to subsequently opened parentheses, by writing +references such as (?+2). However, these cannot be recursive because the +reference is not inside the parentheses that are referenced. They are always +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +non-recursive subroutine +.\" +calls, as described in the next section. +.P +An alternative approach is to use named parentheses instead. The Perl syntax +for this is (?&name); PCRE's earlier syntax (?P>name) is also supported. We +could rewrite the above example as follows: +.sp + (?<pn> \e( ( [^()]++ | (?&pn) )* \e) ) +.sp +If there is more than one subpattern with the same name, the earliest one is +used. +.P +This particular example pattern that we have been looking at contains nested +unlimited repeats, and so the use of a possessive quantifier for matching +strings of non-parentheses is important when applying the pattern to strings +that do not match. For example, when this pattern is applied to +.sp + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() +.sp +it yields "no match" quickly. However, if a possessive quantifier is not used, +the match runs for a very long time indeed because there are so many different +ways the + and * repeats can carve up the subject, and all have to be tested +before failure can be reported. +.P +At the end of a match, the values of capturing parentheses are those from +the outermost level. If you want to obtain intermediate values, a callout +function can be used (see below and the +.\" HREF +\fBpcrecallout\fP +.\" +documentation). If the pattern above is matched against +.sp + (ab(cd)ef) +.sp +the value for the inner capturing parentheses (numbered 2) is "ef", which is +the last value taken on at the top level. If a capturing subpattern is not +matched at the top level, its final captured value is unset, even if it was +(temporarily) set at a deeper level during the matching process. +.P +If there are more than 15 capturing parentheses in a pattern, PCRE has to +obtain extra memory to store data during a recursion, which it does by using +\fBpcre_malloc\fP, freeing it via \fBpcre_free\fP afterwards. If no memory can +be obtained, the match fails with the PCRE_ERROR_NOMEMORY error. +.P +Do not confuse the (?R) item with the condition (R), which tests for recursion. +Consider this pattern, which matches text in angle brackets, allowing for +arbitrary nesting. Only digits are allowed in nested brackets (that is, when +recursing), whereas any characters are permitted at the outer level. +.sp + < (?: (?(R) \ed++ | [^<>]*+) | (?R)) * > +.sp +In this pattern, (?(R) is the start of a conditional subpattern, with two +different alternatives for the recursive and non-recursive cases. The (?R) item +is the actual recursive call. +. +. +.\" HTML <a name="recursiondifference"></a> +.SS "Differences in recursion processing between PCRE and Perl" +.rs +.sp +Recursion processing in PCRE differs from Perl in two important ways. In PCRE +(like Python, but unlike Perl), a recursive subpattern call is always treated +as an atomic group. That is, once it has matched some of the subject string, it +is never re-entered, even if it contains untried alternatives and there is a +subsequent matching failure. This can be illustrated by the following pattern, +which purports to match a palindromic string that contains an odd number of +characters (for example, "a", "aba", "abcba", "abcdcba"): +.sp + ^(.|(.)(?1)\e2)$ +.sp +The idea is that it either matches a single character, or two identical +characters surrounding a sub-palindrome. In Perl, this pattern works; in PCRE +it does not if the pattern is longer than three characters. Consider the +subject string "abcba": +.P +At the top level, the first character is matched, but as it is not at the end +of the string, the first alternative fails; the second alternative is taken +and the recursion kicks in. The recursive call to subpattern 1 successfully +matches the next character ("b"). (Note that the beginning and end of line +tests are not part of the recursion). +.P +Back at the top level, the next character ("c") is compared with what +subpattern 2 matched, which was "a". This fails. Because the recursion is +treated as an atomic group, there are now no backtracking points, and so the +entire match fails. (Perl is able, at this point, to re-enter the recursion and +try the second alternative.) However, if the pattern is written with the +alternatives in the other order, things are different: +.sp + ^((.)(?1)\e2|.)$ +.sp +This time, the recursing alternative is tried first, and continues to recurse +until it runs out of characters, at which point the recursion fails. But this +time we do have another alternative to try at the higher level. That is the big +difference: in the previous case the remaining alternative is at a deeper +recursion level, which PCRE cannot use. +.P +To change the pattern so that it matches all palindromic strings, not just +those with an odd number of characters, it is tempting to change the pattern to +this: +.sp + ^((.)(?1)\e2|.?)$ +.sp +Again, this works in Perl, but not in PCRE, and for the same reason. When a +deeper recursion has matched a single character, it cannot be entered again in +order to match an empty string. The solution is to separate the two cases, and +write out the odd and even cases as alternatives at the higher level: +.sp + ^(?:((.)(?1)\e2|)|((.)(?3)\e4|.)) +.sp +If you want to match typical palindromic phrases, the pattern has to ignore all +non-word characters, which can be done like this: +.sp + ^\eW*+(?:((.)\eW*+(?1)\eW*+\e2|)|((.)\eW*+(?3)\eW*+\e4|\eW*+.\eW*+))\eW*+$ +.sp +If run with the PCRE_CASELESS option, this pattern matches phrases such as "A +man, a plan, a canal: Panama!" and it works well in both PCRE and Perl. Note +the use of the possessive quantifier *+ to avoid backtracking into sequences of +non-word characters. Without this, PCRE takes a great deal longer (ten times or +more) to match typical phrases, and Perl takes so long that you think it has +gone into a loop. +.P +\fBWARNING\fP: The palindrome-matching patterns above work only if the subject +string does not start with a palindrome that is shorter than the entire string. +For example, although "abcba" is correctly matched, if the subject is "ababa", +PCRE finds the palindrome "aba" at the start, then fails at top level because +the end of the string does not follow. Once again, it cannot jump back into the +recursion to try other alternatives, so the entire match fails. +.P +The second way in which PCRE and Perl differ in their recursion processing is +in the handling of captured values. In Perl, when a subpattern is called +recursively or as a subpattern (see the next section), it has no access to any +values that were captured outside the recursion, whereas in PCRE these values +can be referenced. Consider this pattern: +.sp + ^(.)(\e1|a(?2)) +.sp +In PCRE, this pattern matches "bab". The first capturing parentheses match "b", +then in the second group, when the back reference \e1 fails to match "b", the +second alternative matches "a" and then recurses. In the recursion, \e1 does +now match "b" and so the whole match succeeds. In Perl, the pattern fails to +match because inside the recursive call \e1 cannot access the externally set +value. +. +. +.\" HTML <a name="subpatternsassubroutines"></a> +.SH "SUBPATTERNS AS SUBROUTINES" +.rs +.sp +If the syntax for a recursive subpattern call (either by number or by +name) is used outside the parentheses to which it refers, it operates like a +subroutine in a programming language. The called subpattern may be defined +before or after the reference. A numbered reference can be absolute or +relative, as in these examples: +.sp + (...(absolute)...)...(?2)... + (...(relative)...)...(?-1)... + (...(?+1)...(relative)... +.sp +An earlier example pointed out that the pattern +.sp + (sens|respons)e and \e1ibility +.sp +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If instead the pattern +.sp + (sens|respons)e and (?1)ibility +.sp +is used, it does match "sense and responsibility" as well as the other two +strings. Another example is given in the discussion of DEFINE above. +.P +All subroutine calls, whether recursive or not, are always treated as atomic +groups. That is, once a subroutine has matched some of the subject string, it +is never re-entered, even if it contains untried alternatives and there is a +subsequent matching failure. Any capturing parentheses that are set during the +subroutine call revert to their previous values afterwards. +.P +Processing options such as case-independence are fixed when a subpattern is +defined, so if it is used as a subroutine, such options cannot be changed for +different calls. For example, consider this pattern: +.sp + (abc)(?i:(?-1)) +.sp +It matches "abcabc". It does not match "abcABC" because the change of +processing option does not affect the called subpattern. +. +. +.\" HTML <a name="onigurumasubroutines"></a> +.SH "ONIGURUMA SUBROUTINE SYNTAX" +.rs +.sp +For compatibility with Oniguruma, the non-Perl syntax \eg followed by a name or +a number enclosed either in angle brackets or single quotes, is an alternative +syntax for referencing a subpattern as a subroutine, possibly recursively. Here +are two of the examples used above, rewritten using this syntax: +.sp + (?<pn> \e( ( (?>[^()]+) | \eg<pn> )* \e) ) + (sens|respons)e and \eg'1'ibility +.sp +PCRE supports an extension to Oniguruma: if a number is preceded by a +plus or a minus sign it is taken as a relative reference. For example: +.sp + (abc)(?i:\eg<-1>) +.sp +Note that \eg{...} (Perl syntax) and \eg<...> (Oniguruma syntax) are \fInot\fP +synonymous. The former is a back reference; the latter is a subroutine call. +. +. +.SH CALLOUTS +.rs +.sp +Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl +code to be obeyed in the middle of matching a regular expression. This makes it +possible, amongst other things, to extract different substrings that match the +same pair of parentheses when there is a repetition. +.P +PCRE provides a similar feature, but of course it cannot obey arbitrary Perl +code. The feature is called "callout". The caller of PCRE provides an external +function by putting its entry point in the global variable \fIpcre_callout\fP +(8-bit library) or \fIpcre[16|32]_callout\fP (16-bit or 32-bit library). +By default, this variable contains NULL, which disables all calling out. +.P +Within a regular expression, (?C) indicates the points at which the external +function is to be called. If you want to identify different callout points, you +can put a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +.sp + (?C1)abc(?C2)def +.sp +If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, callouts are +automatically installed before each item in the pattern. They are all numbered +255. If there is a conditional group in the pattern whose condition is an +assertion, an additional callout is inserted just before the condition. An +explicit callout may also be set at this position, as in this example: +.sp + (?(?C9)(?=a)abc|def) +.sp +Note that this applies only to assertion conditions, not to other types of +condition. +.P +During matching, when PCRE reaches a callout point, the external function is +called. It is provided with the number of the callout, the position in the +pattern, and, optionally, one item of data originally supplied by the caller of +the matching function. The callout function may cause matching to proceed, to +backtrack, or to fail altogether. +.P +By default, PCRE implements a number of optimizations at compile time and +matching time, and one side-effect is that sometimes callouts are skipped. If +you need all possible callouts to happen, you need to set options that disable +the relevant optimizations. More details, and a complete description of the +interface to the callout function, are given in the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +. +. +.\" HTML <a name="backtrackcontrol"></a> +.SH "BACKTRACKING CONTROL" +.rs +.sp +Perl 5.10 introduced a number of "Special Backtracking Control Verbs", which +are still described in the Perl documentation as "experimental and subject to +change or removal in a future version of Perl". It goes on to say: "Their usage +in production code should be noted to avoid problems during upgrades." The same +remarks apply to the PCRE features described in this section. +.P +The new verbs make use of what was previously invalid syntax: an opening +parenthesis followed by an asterisk. They are generally of the form +(*VERB) or (*VERB:NAME). Some may take either form, possibly behaving +differently depending on whether or not a name is present. A name is any +sequence of characters that does not include a closing parenthesis. The maximum +length of name is 255 in the 8-bit library and 65535 in the 16-bit and 32-bit +libraries. If the name is empty, that is, if the closing parenthesis +immediately follows the colon, the effect is as if the colon were not there. +Any number of these verbs may occur in a pattern. +.P +Since these verbs are specifically related to backtracking, most of them can be +used only when the pattern is to be matched using one of the traditional +matching functions, because these use a backtracking algorithm. With the +exception of (*FAIL), which behaves like a failing negative assertion, the +backtracking control verbs cause an error if encountered by a DFA matching +function. +.P +The behaviour of these verbs in +.\" HTML <a href="#btrepeat"> +.\" </a> +repeated groups, +.\" +.\" HTML <a href="#btassert"> +.\" </a> +assertions, +.\" +and in +.\" HTML <a href="#btsub"> +.\" </a> +subpatterns called as subroutines +.\" +(whether or not recursively) is documented below. +. +. +.\" HTML <a name="nooptimize"></a> +.SS "Optimizations that affect backtracking verbs" +.rs +.sp +PCRE contains some optimizations that are used to speed up matching by running +some checks at the start of each match attempt. For example, it may know the +minimum length of matching subject, or that a particular character must be +present. When one of these optimizations bypasses the running of a match, any +included backtracking verbs will not, of course, be processed. You can suppress +the start-of-match optimizations by setting the PCRE_NO_START_OPTIMIZE option +when calling \fBpcre_compile()\fP or \fBpcre_exec()\fP, or by starting the +pattern with (*NO_START_OPT). There is more discussion of this option in the +section entitled +.\" HTML <a href="pcreapi.html#execoptions"> +.\" </a> +"Option bits for \fBpcre_exec()\fP" +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +.P +Experiments with Perl suggest that it too has similar optimizations, sometimes +leading to anomalous results. +. +. +.SS "Verbs that act immediately" +.rs +.sp +The following verbs act as soon as they are encountered. They may not be +followed by a name. +.sp + (*ACCEPT) +.sp +This verb causes the match to end successfully, skipping the remainder of the +pattern. However, when it is inside a subpattern that is called as a +subroutine, only that subpattern is ended successfully. Matching then continues +at the outer level. If (*ACCEPT) in triggered in a positive assertion, the +assertion succeeds; in a negative assertion, the assertion fails. +.P +If (*ACCEPT) is inside capturing parentheses, the data so far is captured. For +example: +.sp + A((?:A|B(*ACCEPT)|C)D) +.sp +This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is captured by +the outer parentheses. +.sp + (*FAIL) or (*F) +.sp +This verb causes a matching failure, forcing backtracking to occur. It is +equivalent to (?!) but easier to read. The Perl documentation notes that it is +probably useful only when combined with (?{}) or (??{}). Those are, of course, +Perl features that are not present in PCRE. The nearest equivalent is the +callout feature, as for example in this pattern: +.sp + a+(?C)(*FAIL) +.sp +A match with the string "aaaa" always fails, but the callout is taken before +each backtrack happens (in this example, 10 times). +. +. +.SS "Recording which path was taken" +.rs +.sp +There is one verb whose main purpose is to track how a match was arrived at, +though it also has a secondary use in conjunction with advancing the match +starting point (see (*SKIP) below). +.sp + (*MARK:NAME) or (*:NAME) +.sp +A name is always required with this verb. There may be as many instances of +(*MARK) as you like in a pattern, and their names do not have to be unique. +.P +When a match succeeds, the name of the last-encountered (*MARK:NAME), +(*PRUNE:NAME), or (*THEN:NAME) on the matching path is passed back to the +caller as described in the section entitled +.\" HTML <a href="pcreapi.html#extradata"> +.\" </a> +"Extra data for \fBpcre_exec()\fP" +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. Here is an example of \fBpcretest\fP output, where the /K +modifier requests the retrieval and outputting of (*MARK) data: +.sp + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XY + 0: XY + MK: A + XZ + 0: XZ + MK: B +.sp +The (*MARK) name is tagged with "MK:" in this output, and in this example it +indicates which of the two alternatives matched. This is a more efficient way +of obtaining this information than putting each alternative in its own +capturing parentheses. +.P +If a verb with a name is encountered in a positive assertion that is true, the +name is recorded and passed back if it is the last-encountered. This does not +happen for negative assertions or failing positive assertions. +.P +After a partial match or a failed match, the last encountered name in the +entire match process is returned. For example: +.sp + re> /X(*MARK:A)Y|X(*MARK:B)Z/K + data> XP + No match, mark = B +.sp +Note that in this unanchored example the mark is retained from the match +attempt that started at the letter "X" in the subject. Subsequent match +attempts starting at "P" and then with an empty string do not get as far as the +(*MARK) item, but nevertheless do not reset it. +.P +If you are interested in (*MARK) values after failed matches, you should +probably set the PCRE_NO_START_OPTIMIZE option +.\" HTML <a href="#nooptimize"> +.\" </a> +(see above) +.\" +to ensure that the match is always attempted. +. +. +.SS "Verbs that act after backtracking" +.rs +.sp +The following verbs do nothing when they are encountered. Matching continues +with what follows, but if there is no subsequent match, causing a backtrack to +the verb, a failure is forced. That is, backtracking cannot pass to the left of +the verb. However, when one of these verbs appears inside an atomic group or an +assertion that is true, its effect is confined to that group, because once the +group has been matched, there is never any backtracking into it. In this +situation, backtracking can "jump back" to the left of the entire atomic group +or assertion. (Remember also, as stated above, that this localization also +applies in subroutine calls.) +.P +These verbs differ in exactly what kind of failure occurs when backtracking +reaches them. The behaviour described below is what happens when the verb is +not in a subroutine or an assertion. Subsequent sections cover these special +cases. +.sp + (*COMMIT) +.sp +This verb, which may not be followed by a name, causes the whole match to fail +outright if there is a later matching failure that causes backtracking to reach +it. Even if the pattern is unanchored, no further attempts to find a match by +advancing the starting point take place. If (*COMMIT) is the only backtracking +verb that is encountered, once it has been passed \fBpcre_exec()\fP is +committed to finding a match at the current starting point, or not at all. For +example: +.sp + a+(*COMMIT)b +.sp +This matches "xxaab" but not "aacaab". It can be thought of as a kind of +dynamic anchor, or "I've started, so I must finish." The name of the most +recently passed (*MARK) in the path is passed back when (*COMMIT) forces a +match failure. +.P +If there is more than one backtracking verb in a pattern, a different one that +follows (*COMMIT) may be triggered first, so merely passing (*COMMIT) during a +match does not always guarantee that a match must be at this starting point. +.P +Note that (*COMMIT) at the start of a pattern is not the same as an anchor, +unless PCRE's start-of-match optimizations are turned off, as shown in this +output from \fBpcretest\fP: +.sp + re> /(*COMMIT)abc/ + data> xyzabc + 0: abc + data> xyzabc\eY + No match +.sp +For this pattern, PCRE knows that any match must start with "a", so the +optimization skips along the subject to "a" before applying the pattern to the +first set of data. The match attempt then succeeds. In the second set of data, +the escape sequence \eY is interpreted by the \fBpcretest\fP program. It causes +the PCRE_NO_START_OPTIMIZE option to be set when \fBpcre_exec()\fP is called. +This disables the optimization that skips along to the first character. The +pattern is now applied starting at "x", and so the (*COMMIT) causes the match +to fail without trying any other starting points. +.sp + (*PRUNE) or (*PRUNE:NAME) +.sp +This verb causes the match to fail at the current starting position in the +subject if there is a later matching failure that causes backtracking to reach +it. If the pattern is unanchored, the normal "bumpalong" advance to the next +starting character then happens. Backtracking can occur as usual to the left of +(*PRUNE), before it is reached, or when matching to the right of (*PRUNE), but +if there is no match to the right, backtracking cannot cross (*PRUNE). In +simple cases, the use of (*PRUNE) is just an alternative to an atomic group or +possessive quantifier, but there are some uses of (*PRUNE) that cannot be +expressed in any other way. In an anchored pattern (*PRUNE) has the same effect +as (*COMMIT). +.P +The behaviour of (*PRUNE:NAME) is the not the same as (*MARK:NAME)(*PRUNE). +It is like (*MARK:NAME) in that the name is remembered for passing back to the +caller. However, (*SKIP:NAME) searches only for names set with (*MARK). +.sp + (*SKIP) +.sp +This verb, when given without a name, is like (*PRUNE), except that if the +pattern is unanchored, the "bumpalong" advance is not to the next character, +but to the position in the subject where (*SKIP) was encountered. (*SKIP) +signifies that whatever text was matched leading up to it cannot be part of a +successful match. Consider: +.sp + a+(*SKIP)b +.sp +If the subject is "aaaac...", after the first match attempt fails (starting at +the first character in the string), the starting point skips on to start the +next attempt at "c". Note that a possessive quantifer does not have the same +effect as this example; although it would suppress backtracking during the +first match attempt, the second attempt would start at the second character +instead of skipping on to "c". +.sp + (*SKIP:NAME) +.sp +When (*SKIP) has an associated name, its behaviour is modified. When it is +triggered, the previous path through the pattern is searched for the most +recent (*MARK) that has the same name. If one is found, the "bumpalong" advance +is to the subject position that corresponds to that (*MARK) instead of to where +(*SKIP) was encountered. If no (*MARK) with a matching name is found, the +(*SKIP) is ignored. +.P +Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It ignores +names that are set by (*PRUNE:NAME) or (*THEN:NAME). +.sp + (*THEN) or (*THEN:NAME) +.sp +This verb causes a skip to the next innermost alternative when backtracking +reaches it. That is, it cancels any further backtracking within the current +alternative. Its name comes from the observation that it can be used for a +pattern-based if-then-else block: +.sp + ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ... +.sp +If the COND1 pattern matches, FOO is tried (and possibly further items after +the end of the group if FOO succeeds); on failure, the matcher skips to the +second alternative and tries COND2, without backtracking into COND1. If that +succeeds and BAR fails, COND3 is tried. If subsequently BAZ fails, there are no +more alternatives, so there is a backtrack to whatever came before the entire +group. If (*THEN) is not inside an alternation, it acts like (*PRUNE). +.P +The behaviour of (*THEN:NAME) is the not the same as (*MARK:NAME)(*THEN). +It is like (*MARK:NAME) in that the name is remembered for passing back to the +caller. However, (*SKIP:NAME) searches only for names set with (*MARK). +.P +A subpattern that does not contain a | character is just a part of the +enclosing alternative; it is not a nested alternation with only one +alternative. The effect of (*THEN) extends beyond such a subpattern to the +enclosing alternative. Consider this pattern, where A, B, etc. are complex +pattern fragments that do not contain any | characters at this level: +.sp + A (B(*THEN)C) | D +.sp +If A and B are matched, but there is a failure in C, matching does not +backtrack into A; instead it moves to the next alternative, that is, D. +However, if the subpattern containing (*THEN) is given an alternative, it +behaves differently: +.sp + A (B(*THEN)C | (*FAIL)) | D +.sp +The effect of (*THEN) is now confined to the inner subpattern. After a failure +in C, matching moves to (*FAIL), which causes the whole subpattern to fail +because there are no more alternatives to try. In this case, matching does now +backtrack into A. +.P +Note that a conditional subpattern is not considered as having two +alternatives, because only one is ever used. In other words, the | character in +a conditional subpattern has a different meaning. Ignoring white space, +consider: +.sp + ^.*? (?(?=a) a | b(*THEN)c ) +.sp +If the subject is "ba", this pattern does not match. Because .*? is ungreedy, +it initially matches zero characters. The condition (?=a) then fails, the +character "b" is matched, but "c" is not. At this point, matching does not +backtrack to .*? as might perhaps be expected from the presence of the | +character. The conditional subpattern is part of the single alternative that +comprises the whole pattern, and so the match fails. (If there was a backtrack +into .*?, allowing it to match "b", the match would succeed.) +.P +The verbs just described provide four different "strengths" of control when +subsequent matching fails. (*THEN) is the weakest, carrying on the match at the +next alternative. (*PRUNE) comes next, failing the match at the current +starting position, but allowing an advance to the next character (for an +unanchored pattern). (*SKIP) is similar, except that the advance may be more +than one character. (*COMMIT) is the strongest, causing the entire match to +fail. +. +. +.SS "More than one backtracking verb" +.rs +.sp +If more than one backtracking verb is present in a pattern, the one that is +backtracked onto first acts. For example, consider this pattern, where A, B, +etc. are complex pattern fragments: +.sp + (A(*COMMIT)B(*THEN)C|ABD) +.sp +If A matches but B fails, the backtrack to (*COMMIT) causes the entire match to +fail. However, if A and B match, but C fails, the backtrack to (*THEN) causes +the next alternative (ABD) to be tried. This behaviour is consistent, but is +not always the same as Perl's. It means that if two or more backtracking verbs +appear in succession, all the the last of them has no effect. Consider this +example: +.sp + ...(*COMMIT)(*PRUNE)... +.sp +If there is a matching failure to the right, backtracking onto (*PRUNE) causes +it to be triggered, and its action is taken. There can never be a backtrack +onto (*COMMIT). +. +. +.\" HTML <a name="btrepeat"></a> +.SS "Backtracking verbs in repeated groups" +.rs +.sp +PCRE differs from Perl in its handling of backtracking verbs in repeated +groups. For example, consider: +.sp + /(a(*COMMIT)b)+ac/ +.sp +If the subject is "abac", Perl matches, but PCRE fails because the (*COMMIT) in +the second repeat of the group acts. +. +. +.\" HTML <a name="btassert"></a> +.SS "Backtracking verbs in assertions" +.rs +.sp +(*FAIL) in an assertion has its normal effect: it forces an immediate backtrack. +.P +(*ACCEPT) in a positive assertion causes the assertion to succeed without any +further processing. In a negative assertion, (*ACCEPT) causes the assertion to +fail without any further processing. +.P +The other backtracking verbs are not treated specially if they appear in a +positive assertion. In particular, (*THEN) skips to the next alternative in the +innermost enclosing group that has alternations, whether or not this is within +the assertion. +.P +Negative assertions are, however, different, in order to ensure that changing a +positive assertion into a negative assertion changes its result. Backtracking +into (*COMMIT), (*SKIP), or (*PRUNE) causes a negative assertion to be true, +without considering any further alternative branches in the assertion. +Backtracking into (*THEN) causes it to skip to the next enclosing alternative +within the assertion (the normal behaviour), but if the assertion does not have +such an alternative, (*THEN) behaves like (*PRUNE). +. +. +.\" HTML <a name="btsub"></a> +.SS "Backtracking verbs in subroutines" +.rs +.sp +These behaviours occur whether or not the subpattern is called recursively. +Perl's treatment of subroutines is different in some cases. +.P +(*FAIL) in a subpattern called as a subroutine has its normal effect: it forces +an immediate backtrack. +.P +(*ACCEPT) in a subpattern called as a subroutine causes the subroutine match to +succeed without any further processing. Matching then continues after the +subroutine call. +.P +(*COMMIT), (*SKIP), and (*PRUNE) in a subpattern called as a subroutine cause +the subroutine match to fail. +.P +(*THEN) skips to the next alternative in the innermost enclosing group within +the subpattern that has alternatives. If there is no such group within the +subpattern, (*THEN) causes the subroutine match to fail. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3), +\fBpcresyntax\fP(3), \fBpcre\fP(3), \fBpcre16(3)\fP, \fBpcre32(3)\fP. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 14 June 2015 +Copyright (c) 1997-2015 University of Cambridge. +.fi diff --git a/doc/pcreperform.3 b/doc/pcreperform.3 new file mode 100644 index 0000000..fb2aa95 --- /dev/null +++ b/doc/pcreperform.3 @@ -0,0 +1,177 @@ +.TH PCREPERFORM 3 "09 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE PERFORMANCE" +.rs +.sp +Two aspects of performance are discussed below: memory usage and processing +time. The way you express your pattern as a regular expression can affect both +of them. +. +.SH "COMPILED PATTERN MEMORY USAGE" +.rs +.sp +Patterns are compiled by PCRE into a reasonably efficient interpretive code, so +that most simple patterns do not use much memory. However, there is one case +where the memory usage of a compiled pattern can be unexpectedly large. If a +parenthesized subpattern has a quantifier with a minimum greater than 1 and/or +a limited maximum, the whole subpattern is repeated in the compiled code. For +example, the pattern +.sp + (abc|def){2,4} +.sp +is compiled as if it were +.sp + (abc|def)(abc|def)((abc|def)(abc|def)?)? +.sp +(Technical aside: It is done this way so that backtrack points within each of +the repetitions can be independently maintained.) +.P +For regular expressions whose quantifiers use only small numbers, this is not +usually a problem. However, if the numbers are large, and particularly if such +repetitions are nested, the memory usage can become an embarrassment. For +example, the very simple pattern +.sp + ((ab){1,1000}c){1,3} +.sp +uses 51K bytes when compiled using the 8-bit library. When PCRE is compiled +with its default internal pointer size of two bytes, the size limit on a +compiled pattern is 64K data units, and this is reached with the above pattern +if the outer repetition is increased from 3 to 4. PCRE can be compiled to use +larger internal pointers and thus handle larger compiled patterns, but it is +better to try to rewrite your pattern to use less memory if you can. +.P +One way of reducing the memory usage for such patterns is to make use of PCRE's +.\" HTML <a href="pcrepattern.html#subpatternsassubroutines"> +.\" </a> +"subroutine" +.\" +facility. Re-writing the above pattern as +.sp + ((ab)(?2){0,999}c)(?1){0,2} +.sp +reduces the memory requirements to 18K, and indeed it remains under 20K even +with the outer repetition increased to 100. However, this pattern is not +exactly equivalent, because the "subroutine" calls are treated as +.\" HTML <a href="pcrepattern.html#atomicgroup"> +.\" </a> +atomic groups +.\" +into which there can be no backtracking if there is a subsequent matching +failure. Therefore, PCRE cannot do this kind of rewriting automatically. +Furthermore, there is a noticeable loss of speed when executing the modified +pattern. Nevertheless, if the atomic grouping is not a problem and the loss of +speed is acceptable, this kind of rewriting will allow you to process patterns +that PCRE cannot otherwise handle. +. +. +.SH "STACK USAGE AT RUN TIME" +.rs +.sp +When \fBpcre_exec()\fP or \fBpcre[16|32]_exec()\fP is used for matching, certain +kinds of pattern can cause it to use large amounts of the process stack. In +some environments the default process stack is quite small, and if it runs out +the result is often SIGSEGV. This issue is probably the most frequently raised +problem with PCRE. Rewriting your pattern can often help. The +.\" HREF +\fBpcrestack\fP +.\" +documentation discusses this issue in detail. +. +. +.SH "PROCESSING TIME" +.rs +.sp +Certain items in regular expression patterns are processed more efficiently +than others. It is more efficient to use a character class like [aeiou] than a +set of single-character alternatives such as (a|e|i|o|u). In general, the +simplest construction that provides the required behaviour is usually the most +efficient. Jeffrey Friedl's book contains a lot of useful general discussion +about optimizing regular expressions for efficient performance. This document +contains a few observations about PCRE. +.P +Using Unicode character properties (the \ep, \eP, and \eX escapes) is slow, +because PCRE has to use a multi-stage table lookup whenever it needs a +character's property. If you can find an alternative pattern that does not use +character properties, it will probably be faster. +.P +By default, the escape sequences \eb, \ed, \es, and \ew, and the POSIX +character classes such as [:alpha:] do not use Unicode properties, partly for +backwards compatibility, and partly for performance reasons. However, you can +set PCRE_UCP if you want Unicode character properties to be used. This can +double the matching time for items such as \ed, when matched with +a traditional matching function; the performance loss is less with +a DFA matching function, and in both cases there is not much difference for +\eb. +.P +When a pattern begins with .* not in parentheses, or in parentheses that are +not the subject of a backreference, and the PCRE_DOTALL option is set, the +pattern is implicitly anchored by PCRE, since it can match only at the start of +a subject string. However, if PCRE_DOTALL is not set, PCRE cannot make this +optimization, because the . metacharacter does not then match a newline, and if +the subject string contains newlines, the pattern may match from the character +immediately following one of them instead of from the very start. For example, +the pattern +.sp + .*second +.sp +matches the subject "first\enand second" (where \en stands for a newline +character), with the match starting at the seventh character. In order to do +this, PCRE has to retry the match starting after every newline in the subject. +.P +If you are using such a pattern with subject strings that do not contain +newlines, the best performance is obtained by setting PCRE_DOTALL, or starting +the pattern with ^.* or ^.*? to indicate explicit anchoring. That saves PCRE +from having to scan along the subject looking for a newline to restart at. +.P +Beware of patterns that contain nested indefinite repeats. These can take a +long time to run when applied to a string that does not match. Consider the +pattern fragment +.sp + ^(a+)* +.sp +This can match "aaaa" in 16 different ways, and this number increases very +rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 +times, and for each of those cases other than 0 or 4, the + repeats can match +different numbers of times.) When the remainder of the pattern is such that the +entire match is going to fail, PCRE has in principle to try every possible +variation, and this can take an extremely long time, even for relatively short +strings. +.P +An optimization catches some of the more simple cases such as +.sp + (a+)*b +.sp +where a literal character follows. Before embarking on the standard matching +procedure, PCRE checks that there is a "b" later in the subject string, and if +there is not, it fails the match immediately. However, when there is no +following literal this optimization cannot be used. You can see the difference +by comparing the behaviour of +.sp + (a+)*\ed +.sp +with the pattern above. The former gives a failure almost instantly when +applied to a whole line of "a" characters, whereas the latter takes an +appreciable time with strings longer than about 20 characters. +.P +In many cases, the solution to this kind of performance issue is to use an +atomic group or a possessive quantifier. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 25 August 2012 +Copyright (c) 1997-2012 University of Cambridge. +.fi diff --git a/doc/pcreposix.3 b/doc/pcreposix.3 new file mode 100644 index 0000000..77890f3 --- /dev/null +++ b/doc/pcreposix.3 @@ -0,0 +1,267 @@ +.TH PCREPOSIX 3 "09 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions. +.SH "SYNOPSIS" +.rs +.sp +.B #include <pcreposix.h> +.PP +.nf +.B int regcomp(regex_t *\fIpreg\fP, const char *\fIpattern\fP, +.B " int \fIcflags\fP);" +.sp +.B int regexec(regex_t *\fIpreg\fP, const char *\fIstring\fP, +.B " size_t \fInmatch\fP, regmatch_t \fIpmatch\fP[], int \fIeflags\fP);" +.B " size_t regerror(int \fIerrcode\fP, const regex_t *\fIpreg\fP," +.B " char *\fIerrbuf\fP, size_t \fIerrbuf_size\fP);" +.sp +.B void regfree(regex_t *\fIpreg\fP); +.fi +. +.SH DESCRIPTION +.rs +.sp +This set of functions provides a POSIX-style API for the PCRE regular +expression 8-bit library. See the +.\" HREF +\fBpcreapi\fP +.\" +documentation for a description of PCRE's native API, which contains much +additional functionality. There is no POSIX-style wrapper for PCRE's 16-bit +and 32-bit library. +.P +The functions described here are just wrapper functions that ultimately call +the PCRE native API. Their prototypes are defined in the \fBpcreposix.h\fP +header file, and on Unix systems the library itself is called +\fBpcreposix.a\fP, so can be accessed by adding \fB-lpcreposix\fP to the +command for linking an application that uses them. Because the POSIX functions +call the native ones, it is also necessary to add \fB-lpcre\fP. +.P +I have implemented only those POSIX option bits that can be reasonably mapped +to PCRE native options. In addition, the option REG_EXTENDED is defined with +the value zero. This has no effect, but since programs that are written to the +POSIX interface often use it, this makes it easier to slot in PCRE as a +replacement library. Other POSIX options are not even defined. +.P +There are also some other options that are not defined by POSIX. These have +been added at the request of users who want to make use of certain +PCRE-specific features via the POSIX calling interface. +.P +When PCRE is called via these functions, it is only the API that is POSIX-like +in style. The syntax and semantics of the regular expressions themselves are +still those of Perl, subject to the setting of various PCRE options, as +described below. "POSIX-like in style" means that the API approximates to the +POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding +domains it is probably even less compatible. +.P +The header for these functions is supplied as \fBpcreposix.h\fP to avoid any +potential clash with other POSIX libraries. It can, of course, be renamed or +aliased as \fBregex.h\fP, which is the "correct" name. It provides two +structure types, \fIregex_t\fP for compiled internal forms, and +\fIregmatch_t\fP for returning captured substrings. It also defines some +constants whose names start with "REG_"; these are used for setting options and +identifying error codes. +. +. +.SH "COMPILING A PATTERN" +.rs +.sp +The function \fBregcomp()\fP is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument \fIpattern\fP. The \fIpreg\fP argument is a pointer +to a \fBregex_t\fP structure that is used as a base for storing information +about the compiled regular expression. +.P +The argument \fIcflags\fP is either zero, or contains one or more of the bits +defined by the following macros: +.sp + REG_DOTALL +.sp +The PCRE_DOTALL option is set when the regular expression is passed for +compilation to the native function. Note that REG_DOTALL is not part of the +POSIX standard. +.sp + REG_ICASE +.sp +The PCRE_CASELESS option is set when the regular expression is passed for +compilation to the native function. +.sp + REG_NEWLINE +.sp +The PCRE_MULTILINE option is set when the regular expression is passed for +compilation to the native function. Note that this does \fInot\fP mimic the +defined POSIX behaviour for REG_NEWLINE (see the following section). +.sp + REG_NOSUB +.sp +The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed +for compilation to the native function. In addition, when a pattern that is +compiled with this flag is passed to \fBregexec()\fP for matching, the +\fInmatch\fP and \fIpmatch\fP arguments are ignored, and no captured strings +are returned. +.sp + REG_UCP +.sp +The PCRE_UCP option is set when the regular expression is passed for +compilation to the native function. This causes PCRE to use Unicode properties +when matchine \ed, \ew, etc., instead of just recognizing ASCII values. Note +that REG_UTF8 is not part of the POSIX standard. +.sp + REG_UNGREEDY +.sp +The PCRE_UNGREEDY option is set when the regular expression is passed for +compilation to the native function. Note that REG_UNGREEDY is not part of the +POSIX standard. +.sp + REG_UTF8 +.sp +The PCRE_UTF8 option is set when the regular expression is passed for +compilation to the native function. This causes the pattern itself and all data +strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 +is not part of the POSIX standard. +.P +In the absence of these flags, no options are passed to the native function. +This means the the regex is compiled with PCRE default semantics. In +particular, the way it handles newline characters in the subject string is the +Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only +\fIsome\fP of the effects specified for REG_NEWLINE. It does not affect the way +newlines are matched by . (they are not) or by a negative class such as [^a] +(they are). +.P +The yield of \fBregcomp()\fP is zero on success, and non-zero otherwise. The +\fIpreg\fP structure is filled in on success, and one member of the structure +is public: \fIre_nsub\fP contains the number of capturing subpatterns in +the regular expression. Various error codes are defined in the header file. +.P +NOTE: If the yield of \fBregcomp()\fP is non-zero, you must not attempt to +use the contents of the \fIpreg\fP structure. If, for example, you pass it to +\fBregexec()\fP, the result is undefined and your program is likely to crash. +. +. +.SH "MATCHING NEWLINE CHARACTERS" +.rs +.sp +This area is not simple, because POSIX and Perl take different views of things. +It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never +intended to be a POSIX engine. The following table lists the different +possibilities for matching newline characters in PCRE: +.sp + Default Change with +.sp + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \en at end yes PCRE_DOLLARENDONLY + $ matches \en in middle no PCRE_MULTILINE + ^ matches \en in middle no PCRE_MULTILINE +.sp +This is the equivalent table for POSIX: +.sp + Default Change with +.sp + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \en at end no REG_NEWLINE + $ matches \en in middle no REG_NEWLINE + ^ matches \en in middle no REG_NEWLINE +.sp +PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop +newline from matching [^a]. +.P +The default POSIX newline handling can be obtained by setting PCRE_DOTALL and +PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the +REG_NEWLINE action. +. +. +.SH "MATCHING A PATTERN" +.rs +.sp +The function \fBregexec()\fP is called to match a compiled pattern \fIpreg\fP +against a given \fIstring\fP, which is by default terminated by a zero byte +(but see REG_STARTEND below), subject to the options in \fIeflags\fP. These can +be: +.sp + REG_NOTBOL +.sp +The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. +.sp + REG_NOTEMPTY +.sp +The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching +function. Note that REG_NOTEMPTY is not part of the POSIX standard. However, +setting this option can give more POSIX-like behaviour in some situations. +.sp + REG_NOTEOL +.sp +The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. +.sp + REG_STARTEND +.sp +The string is considered to start at \fIstring\fP + \fIpmatch[0].rm_so\fP and +to have a terminating NUL located at \fIstring\fP + \fIpmatch[0].rm_eo\fP +(there need not actually be a NUL at that location), regardless of the value of +\fInmatch\fP. This is a BSD extension, compatible with but not specified by +IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software +intended to be portable to other systems. Note that a non-zero \fIrm_so\fP does +not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not +how it is matched. +.P +If the pattern was compiled with the REG_NOSUB flag, no data about any matched +strings is returned. The \fInmatch\fP and \fIpmatch\fP arguments of +\fBregexec()\fP are ignored. +.P +If the value of \fInmatch\fP is zero, or if the value \fIpmatch\fP is NULL, +no data about any matched strings is returned. +.P +Otherwise,the portion of the string that was matched, and also any captured +substrings, are returned via the \fIpmatch\fP argument, which points to an +array of \fInmatch\fP structures of type \fIregmatch_t\fP, containing the +members \fIrm_so\fP and \fIrm_eo\fP. These contain the offset to the first +character of each substring and the offset to the first character after the end +of each substring, respectively. The 0th element of the vector relates to the +entire portion of \fIstring\fP that was matched; subsequent elements relate to +the capturing subpatterns of the regular expression. Unused entries in the +array have both structure members set to -1. +.P +A successful match yields a zero return; various error codes are defined in the +header file, of which REG_NOMATCH is the "expected" failure code. +. +. +.SH "ERROR MESSAGES" +.rs +.sp +The \fBregerror()\fP function maps a non-zero errorcode from either +\fBregcomp()\fP or \fBregexec()\fP to a printable message. If \fIpreg\fP is not +NULL, the error should have arisen from the use of that structure. A message +terminated by a binary zero is placed in \fIerrbuf\fP. The length of the +message, including the zero, is limited to \fIerrbuf_size\fP. The yield of the +function is the size of buffer needed to hold the whole message. +. +. +.SH MEMORY USAGE +.rs +.sp +Compiling a regular expression causes memory to be allocated and associated +with the \fIpreg\fP structure. The function \fBregfree()\fP frees all such +memory, after which \fIpreg\fP may no longer be used as a compiled expression. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 09 January 2012 +Copyright (c) 1997-2012 University of Cambridge. +.fi diff --git a/doc/pcreprecompile.3 b/doc/pcreprecompile.3 new file mode 100644 index 0000000..40f257a --- /dev/null +++ b/doc/pcreprecompile.3 @@ -0,0 +1,155 @@ +.TH PCREPRECOMPILE 3 "12 November 2013" "PCRE 8.34" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "SAVING AND RE-USING PRECOMPILED PCRE PATTERNS" +.rs +.sp +If you are running an application that uses a large number of regular +expression patterns, it may be useful to store them in a precompiled form +instead of having to compile them every time the application is run. +If you are not using any private character tables (see the +.\" HREF +\fBpcre_maketables()\fP +.\" +documentation), this is relatively straightforward. If you are using private +tables, it is a little bit more complicated. However, if you are using the +just-in-time optimization feature, it is not possible to save and reload the +JIT data. +.P +If you save compiled patterns to a file, you can copy them to a different host +and run them there. If the two hosts have different endianness (byte order), +you should run the \fBpcre[16|32]_pattern_to_host_byte_order()\fP function on the +new host before trying to match the pattern. The matching functions return +PCRE_ERROR_BADENDIANNESS if they detect a pattern with the wrong endianness. +.P +Compiling regular expressions with one version of PCRE for use with a different +version is not guaranteed to work and may cause crashes, and saving and +restoring a compiled pattern loses any JIT optimization data. +. +. +.SH "SAVING A COMPILED PATTERN" +.rs +.sp +The value returned by \fBpcre[16|32]_compile()\fP points to a single block of +memory that holds the compiled pattern and associated data. You can find the +length of this block in bytes by calling \fBpcre[16|32]_fullinfo()\fP with an +argument of PCRE_INFO_SIZE. You can then save the data in any appropriate +manner. Here is sample code for the 8-bit library that compiles a pattern and +writes it to a file. It assumes that the variable \fIfd\fP refers to a file +that is open for output: +.sp + int erroroffset, rc, size; + char *error; + pcre *re; +.sp + re = pcre_compile("my pattern", 0, &error, &erroroffset, NULL); + if (re == NULL) { ... handle errors ... } + rc = pcre_fullinfo(re, NULL, PCRE_INFO_SIZE, &size); + if (rc < 0) { ... handle errors ... } + rc = fwrite(re, 1, size, fd); + if (rc != size) { ... handle errors ... } +.sp +In this example, the bytes that comprise the compiled pattern are copied +exactly. Note that this is binary data that may contain any of the 256 possible +byte values. On systems that make a distinction between binary and non-binary +data, be sure that the file is opened for binary output. +.P +If you want to write more than one pattern to a file, you will have to devise a +way of separating them. For binary data, preceding each pattern with its length +is probably the most straightforward approach. Another possibility is to write +out the data in hexadecimal instead of binary, one pattern to a line. +.P +Saving compiled patterns in a file is only one possible way of storing them for +later use. They could equally well be saved in a database, or in the memory of +some daemon process that passes them via sockets to the processes that want +them. +.P +If the pattern has been studied, it is also possible to save the normal study +data in a similar way to the compiled pattern itself. However, if the +PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is created cannot +be saved because it is too dependent on the current environment. When studying +generates additional information, \fBpcre[16|32]_study()\fP returns a pointer to a +\fBpcre[16|32]_extra\fP data block. Its format is defined in the +.\" HTML <a href="pcreapi.html#extradata"> +.\" </a> +section on matching a pattern +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. The \fIstudy_data\fP field points to the binary study data, and +this is what you must save (not the \fBpcre[16|32]_extra\fP block itself). The +length of the study data can be obtained by calling \fBpcre[16|32]_fullinfo()\fP +with an argument of PCRE_INFO_STUDYSIZE. Remember to check that +\fBpcre[16|32]_study()\fP did return a non-NULL value before trying to save the +study data. +. +. +.SH "RE-USING A PRECOMPILED PATTERN" +.rs +.sp +Re-using a precompiled pattern is straightforward. Having reloaded it into main +memory, called \fBpcre[16|32]_pattern_to_host_byte_order()\fP if necessary, you +pass its pointer to \fBpcre[16|32]_exec()\fP or \fBpcre[16|32]_dfa_exec()\fP in +the usual way. +.P +However, if you passed a pointer to custom character tables when the pattern +was compiled (the \fItableptr\fP argument of \fBpcre[16|32]_compile()\fP), you +must now pass a similar pointer to \fBpcre[16|32]_exec()\fP or +\fBpcre[16|32]_dfa_exec()\fP, because the value saved with the compiled pattern +will obviously be nonsense. A field in a \fBpcre[16|32]_extra()\fP block is used +to pass this data, as described in the +.\" HTML <a href="pcreapi.html#extradata"> +.\" </a> +section on matching a pattern +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +.P +\fBWarning:\fP The tables that \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP use +must be the same as those that were used when the pattern was compiled. If this +is not the case, the behaviour is undefined. +.P +If you did not provide custom character tables when the pattern was compiled, +the pointer in the compiled pattern is NULL, which causes the matching +functions to use PCRE's internal tables. Thus, you do not need to take any +special action at run time in this case. +.P +If you saved study data with the compiled pattern, you need to create your own +\fBpcre[16|32]_extra\fP data block and set the \fIstudy_data\fP field to point +to the reloaded study data. You must also set the PCRE_EXTRA_STUDY_DATA bit in +the \fIflags\fP field to indicate that study data is present. Then pass the +\fBpcre[16|32]_extra\fP block to the matching function in the usual way. If the +pattern was studied for just-in-time optimization, that data cannot be saved, +and so is lost by a save/restore cycle. +. +. +.SH "COMPATIBILITY WITH DIFFERENT PCRE RELEASES" +.rs +.sp +In general, it is safest to recompile all saved patterns when you update to a +new PCRE release, though not all updates actually require this. +. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 12 November 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/pcresample.3 b/doc/pcresample.3 new file mode 100644 index 0000000..d7fe7ec --- /dev/null +++ b/doc/pcresample.3 @@ -0,0 +1,99 @@ +.TH PCRESAMPLE 3 "10 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE SAMPLE PROGRAM" +.rs +.sp +A simple, complete demonstration program, to get you started with using PCRE, +is supplied in the file \fIpcredemo.c\fP in the PCRE distribution. A listing of +this program is given in the +.\" HREF +\fBpcredemo\fP +.\" +documentation. If you do not have a copy of the PCRE distribution, you can save +this listing to re-create \fIpcredemo.c\fP. +.P +The demonstration program, which uses the original PCRE 8-bit library, compiles +the regular expression that is its first argument, and matches it against the +subject string in its second argument. No PCRE options are set, and default +character tables are used. If matching succeeds, the program outputs the +portion of the subject that matched, together with the contents of any captured +substrings. +.P +If the -g option is given on the command line, the program then goes on to +check for further matches of the same regular expression in the same subject +string. The logic is a little bit tricky because of the possibility of matching +an empty string. Comments in the code explain what is going on. +.P +If PCRE is installed in the standard include and library directories for your +operating system, you should be able to compile the demonstration program using +this command: +.sp + gcc -o pcredemo pcredemo.c -lpcre +.sp +If PCRE is installed elsewhere, you may need to add additional options to the +command line. For example, on a Unix-like system that has PCRE installed in +\fI/usr/local\fP, you can compile the demonstration program using a command +like this: +.sp +.\" JOINSH + gcc -o pcredemo -I/usr/local/include pcredemo.c \e + -L/usr/local/lib -lpcre +.sp +In a Windows environment, if you want to statically link the program against a +non-dll \fBpcre.a\fP file, you must uncomment the line that defines PCRE_STATIC +before including \fBpcre.h\fP, because otherwise the \fBpcre_malloc()\fP and +\fBpcre_free()\fP exported functions will be declared +\fB__declspec(dllimport)\fP, with unwanted results. +.P +Once you have compiled and linked the demonstration program, you can run simple +tests like this: +.sp + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' +.sp +Note that there is a much more comprehensive test program, called +.\" HREF +\fBpcretest\fP, +.\" +which supports many more facilities for testing regular expressions and both +PCRE libraries. The +.\" HREF +\fBpcredemo\fP +.\" +program is provided as a simple coding example. +.P +If you try to run +.\" HREF +\fBpcredemo\fP +.\" +when PCRE is not installed in the standard library directory, you may get an +error like this on some operating systems (e.g. Solaris): +.sp + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory +.sp +This is caused by the way shared library support works on those systems. You +need to add +.sp + -R/usr/local/lib +.sp +(for example) to the compile command to get round this problem. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 10 January 2012 +Copyright (c) 1997-2012 University of Cambridge. +.fi diff --git a/doc/pcrestack.3 b/doc/pcrestack.3 new file mode 100644 index 0000000..798f0bc --- /dev/null +++ b/doc/pcrestack.3 @@ -0,0 +1,215 @@ +.TH PCRESTACK 3 "24 June 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE DISCUSSION OF STACK USAGE" +.rs +.sp +When you call \fBpcre[16|32]_exec()\fP, it makes use of an internal function +called \fBmatch()\fP. This calls itself recursively at branch points in the +pattern, in order to remember the state of the match so that it can back up and +try a different alternative if the first one fails. As matching proceeds deeper +and deeper into the tree of possibilities, the recursion depth increases. The +\fBmatch()\fP function is also called in other circumstances, for example, +whenever a parenthesized sub-pattern is entered, and in certain cases of +repetition. +.P +Not all calls of \fBmatch()\fP increase the recursion depth; for an item such +as a* it may be called several times at the same level, after matching +different numbers of a's. Furthermore, in a number of cases where the result of +the recursive call would immediately be passed back as the result of the +current call (a "tail recursion"), the function is just restarted instead. +.P +The above comments apply when \fBpcre[16|32]_exec()\fP is run in its normal +interpretive manner. If the pattern was studied with the +PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling was successful, and +the options passed to \fBpcre[16|32]_exec()\fP were not incompatible, the matching +process uses the JIT-compiled code instead of the \fBmatch()\fP function. In +this case, the memory requirements are handled entirely differently. See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for details. +.P +The \fBpcre[16|32]_dfa_exec()\fP function operates in an entirely different way, +and uses recursion only when there is a regular expression recursion or +subroutine call in the pattern. This includes the processing of assertion and +"once-only" subpatterns, which are handled like subroutine calls. Normally, +these are never very deep, and the limit on the complexity of +\fBpcre[16|32]_dfa_exec()\fP is controlled by the amount of workspace it is given. +However, it is possible to write patterns with runaway infinite recursions; +such patterns will cause \fBpcre[16|32]_dfa_exec()\fP to run out of stack. At +present, there is no protection against this. +.P +The comments that follow do NOT apply to \fBpcre[16|32]_dfa_exec()\fP; they are +relevant only for \fBpcre[16|32]_exec()\fP without the JIT optimization. +. +. +.SS "Reducing \fBpcre[16|32]_exec()\fP's stack usage" +.rs +.sp +Each time that \fBmatch()\fP is actually called recursively, it uses memory +from the process stack. For certain kinds of pattern and data, very large +amounts of stack may be needed, despite the recognition of "tail recursion". +You can often reduce the amount of recursion, and therefore the amount of stack +used, by modifying the pattern that is being matched. Consider, for example, +this pattern: +.sp + ([^<]|<(?!inet))+ +.sp +It matches from wherever it starts until it encounters "<inet" or the end of +the data, and is the kind of pattern that might be used when processing an XML +file. Each iteration of the outer parentheses matches either one character that +is not "<" or a "<" that is not followed by "inet". However, each time a +parenthesis is processed, a recursion occurs, so this formulation uses a stack +frame for each matched character. For a long string, a lot of stack is +required. Consider now this rewritten pattern, which matches exactly the same +strings: +.sp + ([^<]++|<(?!inet))+ +.sp +This uses very much less stack, because runs of characters that do not contain +"<" are "swallowed" in one item inside the parentheses. Recursion happens only +when a "<" character that is not followed by "inet" is encountered (and we +assume this is relatively rare). A possessive quantifier is used to stop any +backtracking into the runs of non-"<" characters, but that is not related to +stack usage. +.P +This example shows that one way of avoiding stack problems when matching long +subject strings is to write repeated parenthesized subpatterns to match more +than one character whenever possible. +. +. +.SS "Compiling PCRE to use heap instead of stack for \fBpcre[16|32]_exec()\fP" +.rs +.sp +In environments where stack memory is constrained, you might want to compile +PCRE to use heap memory instead of stack for remembering back-up points when +\fBpcre[16|32]_exec()\fP is running. This makes it run a lot more slowly, however. +Details of how to do this are given in the +.\" HREF +\fBpcrebuild\fP +.\" +documentation. When built in this way, instead of using the stack, PCRE obtains +and frees memory by calling the functions that are pointed to by the +\fBpcre[16|32]_stack_malloc\fP and \fBpcre[16|32]_stack_free\fP variables. By +default, these point to \fBmalloc()\fP and \fBfree()\fP, but you can replace +the pointers to cause PCRE to use your own functions. Since the block sizes are +always the same, and are always freed in reverse order, it may be possible to +implement customized memory handlers that are more efficient than the standard +functions. +. +. +.SS "Limiting \fBpcre[16|32]_exec()\fP's stack usage" +.rs +.sp +You can set limits on the number of times that \fBmatch()\fP is called, both in +total and recursively. If a limit is exceeded, \fBpcre[16|32]_exec()\fP returns an +error code. Setting suitable limits should prevent it from running out of +stack. The default values of the limits are very large, and unlikely ever to +operate. They can be changed when PCRE is built, and they can also be set when +\fBpcre[16|32]_exec()\fP is called. For details of these interfaces, see the +.\" HREF +\fBpcrebuild\fP +.\" +documentation and the +.\" HTML <a href="pcreapi.html#extradata"> +.\" </a> +section on extra data for \fBpcre[16|32]_exec()\fP +.\" +in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +.P +As a very rough rule of thumb, you should reckon on about 500 bytes per +recursion. Thus, if you want to limit your stack usage to 8Mb, you should set +the limit at 16000 recursions. A 64Mb stack, on the other hand, can support +around 128000 recursions. +.P +In Unix-like environments, the \fBpcretest\fP test program has a command line +option (\fB-S\fP) that can be used to increase the size of its stack. As long +as the stack is large enough, another option (\fB-M\fP) can be used to find the +smallest limits that allow a particular pattern to match a given subject +string. This is done by calling \fBpcre[16|32]_exec()\fP repeatedly with different +limits. +. +. +.SS "Obtaining an estimate of stack usage" +.rs +.sp +The actual amount of stack used per recursion can vary quite a lot, depending +on the compiler that was used to build PCRE and the optimization or debugging +options that were set for it. The rule of thumb value of 500 bytes mentioned +above may be larger or smaller than what is actually needed. A better +approximation can be obtained by running this command: +.sp + pcretest -m -C +.sp +The \fB-C\fP option causes \fBpcretest\fP to output information about the +options with which PCRE was compiled. When \fB-m\fP is also given (before +\fB-C\fP), information about stack use is given in a line like this: +.sp + Match recursion uses stack: approximate frame size = 640 bytes +.sp +The value is approximate because some recursions need a bit more (up to perhaps +16 more bytes). +.P +If the above command is given when PCRE is compiled to use the heap instead of +the stack for recursion, the value that is output is the size of each block +that is obtained from the heap. +. +. +.SS "Changing stack size in Unix-like systems" +.rs +.sp +In Unix-like environments, there is not often a problem with the stack unless +very long strings are involved, though the default limit on stack size varies +from system to system. Values from 8Mb to 64Mb are common. You can find your +default limit by running the command: +.sp + ulimit -s +.sp +Unfortunately, the effect of running out of stack is often SIGSEGV, though +sometimes a more explicit error message is given. You can normally increase the +limit on stack size by code such as this: +.sp + struct rlimit rlim; + getrlimit(RLIMIT_STACK, &rlim); + rlim.rlim_cur = 100*1024*1024; + setrlimit(RLIMIT_STACK, &rlim); +.sp +This reads the current limits (soft and hard) using \fBgetrlimit()\fP, then +attempts to increase the soft limit to 100Mb using \fBsetrlimit()\fP. You must +do this before calling \fBpcre[16|32]_exec()\fP. +. +. +.SS "Changing stack size in Mac OS X" +.rs +.sp +Using \fBsetrlimit()\fP, as described above, should also work on Mac OS X. It +is also possible to set a stack size when linking a program. There is a +discussion about stack sizes in Mac OS X at this web site: +.\" HTML <a href="http://developer.apple.com/qa/qa2005/qa1419.html"> +.\" </a> +http://developer.apple.com/qa/qa2005/qa1419.html. +.\" +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 24 June 2012 +Copyright (c) 1997-2012 University of Cambridge. +.fi diff --git a/doc/pcresyntax.3 b/doc/pcresyntax.3 new file mode 100644 index 0000000..0850369 --- /dev/null +++ b/doc/pcresyntax.3 @@ -0,0 +1,540 @@ +.TH PCRESYNTAX 3 "08 January 2014" "PCRE 8.35" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "PCRE REGULAR EXPRESSION SYNTAX SUMMARY" +.rs +.sp +The full syntax and semantics of the regular expressions that are supported by +PCRE are described in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. This document contains a quick-reference summary of the syntax. +. +. +.SH "QUOTING" +.rs +.sp + \ex where x is non-alphanumeric is a literal x + \eQ...\eE treat enclosed characters as literal +. +. +.SH "CHARACTERS" +.rs +.sp + \ea alarm, that is, the BEL character (hex 07) + \ecx "control-x", where x is any ASCII character + \ee escape (hex 1B) + \ef form feed (hex 0C) + \en newline (hex 0A) + \er carriage return (hex 0D) + \et tab (hex 09) + \e0dd character with octal code 0dd + \eddd character with octal code ddd, or backreference + \eo{ddd..} character with octal code ddd.. + \exhh character with hex code hh + \ex{hhh..} character with hex code hhh.. +.sp +Note that \e0dd is always an octal code, and that \e8 and \e9 are the literal +characters "8" and "9". +. +. +.SH "CHARACTER TYPES" +.rs +.sp + . any character except newline; + in dotall mode, any character whatsoever + \eC one data unit, even in UTF mode (best avoided) + \ed a decimal digit + \eD a character that is not a decimal digit + \eh a horizontal white space character + \eH a character that is not a horizontal white space character + \eN a character that is not a newline + \ep{\fIxx\fP} a character with the \fIxx\fP property + \eP{\fIxx\fP} a character without the \fIxx\fP property + \eR a newline sequence + \es a white space character + \eS a character that is not a white space character + \ev a vertical white space character + \eV a character that is not a vertical white space character + \ew a "word" character + \eW a "non-word" character + \eX a Unicode extended grapheme cluster +.sp +By default, \ed, \es, and \ew match only ASCII characters, even in UTF-8 mode +or in the 16- bit and 32-bit libraries. However, if locale-specific matching is +happening, \es and \ew may also match characters with code points in the range +128-255. If the PCRE_UCP option is set, the behaviour of these escape sequences +is changed to use Unicode properties and they match many more characters. +. +. +.SH "GENERAL CATEGORY PROPERTIES FOR \ep and \eP" +.rs +.sp + C Other + Cc Control + Cf Format + Cn Unassigned + Co Private use + Cs Surrogate +.sp + L Letter + Ll Lower case letter + Lm Modifier letter + Lo Other letter + Lt Title case letter + Lu Upper case letter + L& Ll, Lu, or Lt +.sp + M Mark + Mc Spacing mark + Me Enclosing mark + Mn Non-spacing mark +.sp + N Number + Nd Decimal number + Nl Letter number + No Other number +.sp + P Punctuation + Pc Connector punctuation + Pd Dash punctuation + Pe Close punctuation + Pf Final punctuation + Pi Initial punctuation + Po Other punctuation + Ps Open punctuation +.sp + S Symbol + Sc Currency symbol + Sk Modifier symbol + Sm Mathematical symbol + So Other symbol +.sp + Z Separator + Zl Line separator + Zp Paragraph separator + Zs Space separator +. +. +.SH "PCRE SPECIAL CATEGORY PROPERTIES FOR \ep and \eP" +.rs +.sp + Xan Alphanumeric: union of properties L and N + Xps POSIX space: property Z or tab, NL, VT, FF, CR + Xsp Perl space: property Z or tab, NL, VT, FF, CR + Xuc Univerally-named character: one that can be + represented by a Universal Character Name + Xwd Perl word: property Xan or underscore +.sp +Perl and POSIX space are now the same. Perl added VT to its space character set +at release 5.18 and PCRE changed at release 8.34. +. +. +.SH "SCRIPT NAMES FOR \ep AND \eP" +.rs +.sp +Arabic, +Armenian, +Avestan, +Balinese, +Bamum, +Bassa_Vah, +Batak, +Bengali, +Bopomofo, +Brahmi, +Braille, +Buginese, +Buhid, +Canadian_Aboriginal, +Carian, +Caucasian_Albanian, +Chakma, +Cham, +Cherokee, +Common, +Coptic, +Cuneiform, +Cypriot, +Cyrillic, +Deseret, +Devanagari, +Duployan, +Egyptian_Hieroglyphs, +Elbasan, +Ethiopic, +Georgian, +Glagolitic, +Gothic, +Grantha, +Greek, +Gujarati, +Gurmukhi, +Han, +Hangul, +Hanunoo, +Hebrew, +Hiragana, +Imperial_Aramaic, +Inherited, +Inscriptional_Pahlavi, +Inscriptional_Parthian, +Javanese, +Kaithi, +Kannada, +Katakana, +Kayah_Li, +Kharoshthi, +Khmer, +Khojki, +Khudawadi, +Lao, +Latin, +Lepcha, +Limbu, +Linear_A, +Linear_B, +Lisu, +Lycian, +Lydian, +Mahajani, +Malayalam, +Mandaic, +Manichaean, +Meetei_Mayek, +Mende_Kikakui, +Meroitic_Cursive, +Meroitic_Hieroglyphs, +Miao, +Modi, +Mongolian, +Mro, +Myanmar, +Nabataean, +New_Tai_Lue, +Nko, +Ogham, +Ol_Chiki, +Old_Italic, +Old_North_Arabian, +Old_Permic, +Old_Persian, +Old_South_Arabian, +Old_Turkic, +Oriya, +Osmanya, +Pahawh_Hmong, +Palmyrene, +Pau_Cin_Hau, +Phags_Pa, +Phoenician, +Psalter_Pahlavi, +Rejang, +Runic, +Samaritan, +Saurashtra, +Sharada, +Shavian, +Siddham, +Sinhala, +Sora_Sompeng, +Sundanese, +Syloti_Nagri, +Syriac, +Tagalog, +Tagbanwa, +Tai_Le, +Tai_Tham, +Tai_Viet, +Takri, +Tamil, +Telugu, +Thaana, +Thai, +Tibetan, +Tifinagh, +Tirhuta, +Ugaritic, +Vai, +Warang_Citi, +Yi. +. +. +.SH "CHARACTER CLASSES" +.rs +.sp + [...] positive character class + [^...] negative character class + [x-y] range (can be used for hex characters) + [[:xxx:]] positive POSIX named set + [[:^xxx:]] negative POSIX named set +.sp + alnum alphanumeric + alpha alphabetic + ascii 0-127 + blank space or tab + cntrl control character + digit decimal digit + graph printing, excluding space + lower lower case letter + print printing, including space + punct printing, excluding alphanumeric + space white space + upper upper case letter + word same as \ew + xdigit hexadecimal digit +.sp +In PCRE, POSIX character set names recognize only ASCII characters by default, +but some of them use Unicode properties if PCRE_UCP is set. You can use +\eQ...\eE inside a character class. +. +. +.SH "QUANTIFIERS" +.rs +.sp + ? 0 or 1, greedy + ?+ 0 or 1, possessive + ?? 0 or 1, lazy + * 0 or more, greedy + *+ 0 or more, possessive + *? 0 or more, lazy + + 1 or more, greedy + ++ 1 or more, possessive + +? 1 or more, lazy + {n} exactly n + {n,m} at least n, no more than m, greedy + {n,m}+ at least n, no more than m, possessive + {n,m}? at least n, no more than m, lazy + {n,} n or more, greedy + {n,}+ n or more, possessive + {n,}? n or more, lazy +. +. +.SH "ANCHORS AND SIMPLE ASSERTIONS" +.rs +.sp + \eb word boundary + \eB not a word boundary + ^ start of subject + also after internal newline in multiline mode + \eA start of subject + $ end of subject + also before newline at end of subject + also before internal newline in multiline mode + \eZ end of subject + also before newline at end of subject + \ez end of subject + \eG first matching position in subject +. +. +.SH "MATCH POINT RESET" +.rs +.sp + \eK reset start of match +.sp +\eK is honoured in positive assertions, but ignored in negative ones. +. +. +.SH "ALTERNATION" +.rs +.sp + expr|expr|expr... +. +. +.SH "CAPTURING" +.rs +.sp + (...) capturing group + (?<name>...) named capturing group (Perl) + (?'name'...) named capturing group (Perl) + (?P<name>...) named capturing group (Python) + (?:...) non-capturing group + (?|...) non-capturing group; reset group numbers for + capturing groups in each alternative +. +. +.SH "ATOMIC GROUPS" +.rs +.sp + (?>...) atomic, non-capturing group +. +. +. +. +.SH "COMMENT" +.rs +.sp + (?#....) comment (not nestable) +. +. +.SH "OPTION SETTING" +.rs +.sp + (?i) caseless + (?J) allow duplicate names + (?m) multiline + (?s) single line (dotall) + (?U) default ungreedy (lazy) + (?x) extended (ignore white space) + (?-...) unset option(s) +.sp +The following are recognized only at the very start of a pattern or after one +of the newline or \eR options with similar syntax. More than one of them may +appear. +.sp + (*LIMIT_MATCH=d) set the match limit to d (decimal number) + (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number) + (*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS) + (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE) + (*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8) + (*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16) + (*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32) + (*UTF) set appropriate UTF mode for the library in use + (*UCP) set PCRE_UCP (use Unicode properties for \ed etc) +.sp +Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the +limits set by the caller of pcre_exec(), not increase them. +. +. +.SH "NEWLINE CONVENTION" +.rs +.sp +These are recognized only at the very start of the pattern or after option +settings with a similar syntax. +.sp + (*CR) carriage return only + (*LF) linefeed only + (*CRLF) carriage return followed by linefeed + (*ANYCRLF) all three of the above + (*ANY) any Unicode newline sequence +. +. +.SH "WHAT \eR MATCHES" +.rs +.sp +These are recognized only at the very start of the pattern or after option +setting with a similar syntax. +.sp + (*BSR_ANYCRLF) CR, LF, or CRLF + (*BSR_UNICODE) any Unicode newline sequence +. +. +.SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS" +.rs +.sp + (?=...) positive look ahead + (?!...) negative look ahead + (?<=...) positive look behind + (?<!...) negative look behind +.sp +Each top-level branch of a look behind must be of a fixed length. +. +. +.SH "BACKREFERENCES" +.rs +.sp + \en reference by number (can be ambiguous) + \egn reference by number + \eg{n} reference by number + \eg{-n} relative reference by number + \ek<name> reference by name (Perl) + \ek'name' reference by name (Perl) + \eg{name} reference by name (Perl) + \ek{name} reference by name (.NET) + (?P=name) reference by name (Python) +. +. +.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)" +.rs +.sp + (?R) recurse whole pattern + (?n) call subpattern by absolute number + (?+n) call subpattern by relative number + (?-n) call subpattern by relative number + (?&name) call subpattern by name (Perl) + (?P>name) call subpattern by name (Python) + \eg<name> call subpattern by name (Oniguruma) + \eg'name' call subpattern by name (Oniguruma) + \eg<n> call subpattern by absolute number (Oniguruma) + \eg'n' call subpattern by absolute number (Oniguruma) + \eg<+n> call subpattern by relative number (PCRE extension) + \eg'+n' call subpattern by relative number (PCRE extension) + \eg<-n> call subpattern by relative number (PCRE extension) + \eg'-n' call subpattern by relative number (PCRE extension) +. +. +.SH "CONDITIONAL PATTERNS" +.rs +.sp + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) +.sp + (?(n)... absolute reference condition + (?(+n)... relative reference condition + (?(-n)... relative reference condition + (?(<name>)... named reference condition (Perl) + (?('name')... named reference condition (Perl) + (?(name)... named reference condition (PCRE) + (?(R)... overall recursion condition + (?(Rn)... specific group recursion condition + (?(R&name)... specific recursion condition + (?(DEFINE)... define subpattern for reference + (?(assert)... assertion condition +. +. +.SH "BACKTRACKING CONTROL" +.rs +.sp +The following act immediately they are reached: +.sp + (*ACCEPT) force successful match + (*FAIL) force backtrack; synonym (*F) + (*MARK:NAME) set name to be passed back; synonym (*:NAME) +.sp +The following act only when a subsequent match failure causes a backtrack to +reach them. They all force a match failure, but they differ in what happens +afterwards. Those that advance the start-of-match point do so only if the +pattern is not anchored. +.sp + (*COMMIT) overall failure, no advance of starting point + (*PRUNE) advance to next starting character + (*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE) + (*SKIP) advance to current matching position + (*SKIP:NAME) advance to position corresponding to an earlier + (*MARK:NAME); if not found, the (*SKIP) is ignored + (*THEN) local failure, backtrack to next alternation + (*THEN:NAME) equivalent to (*MARK:NAME)(*THEN) +. +. +.SH "CALLOUTS" +.rs +.sp + (?C) callout + (?Cn) callout with data n +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcrepattern\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), +\fBpcrematching\fP(3), \fBpcre\fP(3). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 08 January 2014 +Copyright (c) 1997-2014 University of Cambridge. +.fi diff --git a/doc/pcretest.1 b/doc/pcretest.1 new file mode 100644 index 0000000..92640da --- /dev/null +++ b/doc/pcretest.1 @@ -0,0 +1,1156 @@ +.TH PCRETEST 1 "09 February 2014" "PCRE 8.35" +.SH NAME +pcretest - a program for testing Perl-compatible regular expressions. +.SH SYNOPSIS +.rs +.sp +.B pcretest "[options] [input file [output file]]" +.sp +\fBpcretest\fP was written as a test program for the PCRE regular expression +library itself, but it can also be used for experimenting with regular +expressions. This document describes the features of the test program; for +details of the regular expressions themselves, see the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. For details of the PCRE library function calls and their +options, see the +.\" HREF +\fBpcreapi\fP +.\" +, +.\" HREF +\fBpcre16\fP +and +.\" HREF +\fBpcre32\fP +.\" +documentation. +.P +The input for \fBpcretest\fP is a sequence of regular expression patterns and +strings to be matched, as described below. The output shows the result of each +match. Options on the command line and the patterns control PCRE options and +exactly what is output. +.P +As PCRE has evolved, it has acquired many different features, and as a result, +\fBpcretest\fP now has rather a lot of obscure options for testing every +possible feature. Some of these options are specifically designed for use in +conjunction with the test script and data files that are distributed as part of +PCRE, and are unlikely to be of use otherwise. They are all documented here, +but without much justification. +. +. +.SH "INPUT DATA FORMAT" +.rs +.sp +Input to \fBpcretest\fP is processed line by line, either by calling the C +library's \fBfgets()\fP function, or via the \fBlibreadline\fP library (see +below). In Unix-like environments, \fBfgets()\fP treats any bytes other than +newline as data characters. However, in some Windows environments character 26 +(hex 1A) causes an immediate end of file, and no further data is read. For +maximum portability, therefore, it is safest to use only ASCII characters in +\fBpcretest\fP input files. +. +. +.SH "PCRE's 8-BIT, 16-BIT AND 32-BIT LIBRARIES" +.rs +.sp +From release 8.30, two separate PCRE libraries can be built. The original one +supports 8-bit character strings, whereas the newer 16-bit library supports +character strings encoded in 16-bit units. From release 8.32, a third library +can be built, supporting character strings encoded in 32-bit units. The +\fBpcretest\fP program can be used to test all three libraries. However, it is +itself still an 8-bit program, reading 8-bit input and writing 8-bit output. +When testing the 16-bit or 32-bit library, the patterns and data strings are +converted to 16- or 32-bit format before being passed to the PCRE library +functions. Results are converted to 8-bit for output. +.P +References to functions and structures of the form \fBpcre[16|32]_xx\fP below +mean "\fBpcre_xx\fP when using the 8-bit library, \fBpcre16_xx\fP when using +the 16-bit library, or \fBpcre32_xx\fP when using the 32-bit library". +. +. +.SH "COMMAND LINE OPTIONS" +.rs +.TP 10 +\fB-8\fP +If both the 8-bit library has been built, this option causes the 8-bit library +to be used (which is the default); if the 8-bit library has not been built, +this option causes an error. +.TP 10 +\fB-16\fP +If both the 8-bit or the 32-bit, and the 16-bit libraries have been built, this +option causes the 16-bit library to be used. If only the 16-bit library has been +built, this is the default (so has no effect). If only the 8-bit or the 32-bit +library has been built, this option causes an error. +.TP 10 +\fB-32\fP +If both the 8-bit or the 16-bit, and the 32-bit libraries have been built, this +option causes the 32-bit library to be used. If only the 32-bit library has been +built, this is the default (so has no effect). If only the 8-bit or the 16-bit +library has been built, this option causes an error. +.TP 10 +\fB-b\fP +Behave as if each pattern has the \fB/B\fP (show byte code) modifier; the +internal form is output after compilation. +.TP 10 +\fB-C\fP +Output the version number of the PCRE library, and all available information +about the optional features that are included, and then exit with zero exit +code. All other options are ignored. +.TP 10 +\fB-C\fP \fIoption\fP +Output information about a specific build-time option, then exit. This +functionality is intended for use in scripts such as \fBRunTest\fP. The +following options output the value and set the exit code as indicated: +.sp + ebcdic-nl the code for LF (= NL) in an EBCDIC environment: + 0x15 or 0x25 + 0 if used in an ASCII environment + exit code is always 0 + linksize the configured internal link size (2, 3, or 4) + exit code is set to the link size + newline the default newline setting: + CR, LF, CRLF, ANYCRLF, or ANY + exit code is always 0 + bsr the default setting for what \eR matches: + ANYCRLF or ANY + exit code is always 0 +.sp +The following options output 1 for true or 0 for false, and set the exit code +to the same value: +.sp + ebcdic compiled for an EBCDIC environment + jit just-in-time support is available + pcre16 the 16-bit library was built + pcre32 the 32-bit library was built + pcre8 the 8-bit library was built + ucp Unicode property support is available + utf UTF-8 and/or UTF-16 and/or UTF-32 support + is available +.sp +If an unknown option is given, an error message is output; the exit code is 0. +.TP 10 +\fB-d\fP +Behave as if each pattern has the \fB/D\fP (debug) modifier; the internal +form and information about the compiled pattern is output after compilation; +\fB-d\fP is equivalent to \fB-b -i\fP. +.TP 10 +\fB-dfa\fP +Behave as if each data line contains the \eD escape sequence; this causes the +alternative matching function, \fBpcre[16|32]_dfa_exec()\fP, to be used instead +of the standard \fBpcre[16|32]_exec()\fP function (more detail is given below). +.TP 10 +\fB-help\fP +Output a brief summary these options and then exit. +.TP 10 +\fB-i\fP +Behave as if each pattern has the \fB/I\fP modifier; information about the +compiled pattern is given after compilation. +.TP 10 +\fB-M\fP +Behave as if each data line contains the \eM escape sequence; this causes +PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by +calling \fBpcre[16|32]_exec()\fP repeatedly with different limits. +.TP 10 +\fB-m\fP +Output the size of each compiled pattern after it has been compiled. This is +equivalent to adding \fB/M\fP to each regular expression. The size is given in +bytes for both libraries. +.TP 10 +\fB-O\fP +Behave as if each pattern has the \fB/O\fP modifier, that is disable +auto-possessification for all patterns. +.TP 10 +\fB-o\fP \fIosize\fP +Set the number of elements in the output vector that is used when calling +\fBpcre[16|32]_exec()\fP or \fBpcre[16|32]_dfa_exec()\fP to be \fIosize\fP. The +default value is 45, which is enough for 14 capturing subexpressions for +\fBpcre[16|32]_exec()\fP or 22 different matches for +\fBpcre[16|32]_dfa_exec()\fP. +The vector size can be changed for individual matching calls by including \eO +in the data line (see below). +.TP 10 +\fB-p\fP +Behave as if each pattern has the \fB/P\fP modifier; the POSIX wrapper API is +used to call PCRE. None of the other options has any effect when \fB-p\fP is +set. This option can be used only with the 8-bit library. +.TP 10 +\fB-q\fP +Do not output the version number of \fBpcretest\fP at the start of execution. +.TP 10 +\fB-S\fP \fIsize\fP +On Unix-like systems, set the size of the run-time stack to \fIsize\fP +megabytes. +.TP 10 +\fB-s\fP or \fB-s+\fP +Behave as if each pattern has the \fB/S\fP modifier; in other words, force each +pattern to be studied. If \fB-s+\fP is used, all the JIT compile options are +passed to \fBpcre[16|32]_study()\fP, causing just-in-time optimization to be set +up if it is available, for both full and partial matching. Specific JIT compile +options can be selected by following \fB-s+\fP with a digit in the range 1 to +7, which selects the JIT compile modes as follows: +.sp + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) +.sp +If \fB-s++\fP is used instead of \fB-s+\fP (with or without a following digit), +the text "(JIT)" is added to the first output line after a match or no match +when JIT-compiled code was actually used. +.sp +Note that there are pattern options that can override \fB-s\fP, either +specifying no studying at all, or suppressing JIT compilation. +.sp +If the \fB/I\fP or \fB/D\fP option is present on a pattern (requesting output +about the compiled pattern), information about the result of studying is not +included when studying is caused only by \fB-s\fP and neither \fB-i\fP nor +\fB-d\fP is present on the command line. This behaviour means that the output +from tests that are run with and without \fB-s\fP should be identical, except +when options that output information about the actual running of a match are +set. +.sp +The \fB-M\fP, \fB-t\fP, and \fB-tm\fP options, which give information about +resources used, are likely to produce different output with and without +\fB-s\fP. Output may also differ if the \fB/C\fP option is present on an +individual pattern. This uses callouts to trace the the matching process, and +this may be different between studied and non-studied patterns. If the pattern +contains (*MARK) items there may also be differences, for the same reason. The +\fB-s\fP command line option can be overridden for specific patterns that +should never be studied (see the \fB/S\fP pattern modifier below). +.TP 10 +\fB-t\fP +Run each compile, study, and match many times with a timer, and output the +resulting times per compile, study, or match (in milliseconds). Do not set +\fB-m\fP with \fB-t\fP, because you will then get the size output a zillion +times, and the timing will be distorted. You can control the number of +iterations that are used for timing by following \fB-t\fP with a number (as a +separate item on the command line). For example, "-t 1000" iterates 1000 times. +The default is to iterate 500000 times. +.TP 10 +\fB-tm\fP +This is like \fB-t\fP except that it times only the matching phase, not the +compile or study phases. +.TP 10 +\fB-T\fP \fB-TM\fP +These behave like \fB-t\fP and \fB-tm\fP, but in addition, at the end of a run, +the total times for all compiles, studies, and matches are output. +. +. +.SH DESCRIPTION +.rs +.sp +If \fBpcretest\fP is given two filename arguments, it reads from the first and +writes to the second. If it is given only one filename argument, it reads from +that file and writes to stdout. Otherwise, it reads from stdin and writes to +stdout, and prompts for each line of input, using "re>" to prompt for regular +expressions, and "data>" to prompt for data lines. +.P +When \fBpcretest\fP is built, a configuration option can specify that it should +be linked with the \fBlibreadline\fP library. When this is done, if the input +is from a terminal, it is read using the \fBreadline()\fP function. This +provides line-editing and history facilities. The output from the \fB-help\fP +option states whether or not \fBreadline()\fP will be used. +.P +The program handles any number of sets of input on a single input file. Each +set starts with a regular expression, and continues with any number of data +lines to be matched against that pattern. +.P +Each data line is matched separately and independently. If you want to do +multi-line matches, you have to use the \en escape sequence (or \er or \er\en, +etc., depending on the newline setting) in a single line of input to encode the +newline sequences. There is no limit on the length of data lines; the input +buffer is automatically extended if it is too small. +.P +An empty line signals the end of the data lines, at which point a new regular +expression is read. The regular expressions are given enclosed in any +non-alphanumeric delimiters other than backslash, for example: +.sp + /(a|bc)x+yz/ +.sp +White space before the initial delimiter is ignored. A regular expression may +be continued over several input lines, in which case the newline characters are +included within it. It is possible to include the delimiter within the pattern +by escaping it, for example +.sp + /abc\e/def/ +.sp +If you do so, the escape and the delimiter form part of the pattern, but since +delimiters are always non-alphanumeric, this does not affect its interpretation. +If the terminating delimiter is immediately followed by a backslash, for +example, +.sp + /abc/\e +.sp +then a backslash is added to the end of the pattern. This is done to provide a +way of testing the error condition that arises if a pattern finishes with a +backslash, because +.sp + /abc\e/ +.sp +is interpreted as the first line of a pattern that starts with "abc/", causing +pcretest to read the next line as a continuation of the regular expression. +. +. +.SH "PATTERN MODIFIERS" +.rs +.sp +A pattern may be followed by any number of modifiers, which are mostly single +characters, though some of these can be qualified by further characters. +Following Perl usage, these are referred to below as, for example, "the +\fB/i\fP modifier", even though the delimiter of the pattern need not always be +a slash, and no slash is used when writing modifiers. White space may appear +between the final pattern delimiter and the first modifier, and between the +modifiers themselves. For reference, here is a complete list of modifiers. They +fall into several groups that are described in detail in the following +sections. +.sp + \fB/8\fP set UTF mode + \fB/9\fP set PCRE_NEVER_UTF (locks out UTF mode) + \fB/?\fP disable UTF validity check + \fB/+\fP show remainder of subject after match + \fB/=\fP show all captures (not just those that are set) +.sp + \fB/A\fP set PCRE_ANCHORED + \fB/B\fP show compiled code + \fB/C\fP set PCRE_AUTO_CALLOUT + \fB/D\fP same as \fB/B\fP plus \fB/I\fP + \fB/E\fP set PCRE_DOLLAR_ENDONLY + \fB/F\fP flip byte order in compiled pattern + \fB/f\fP set PCRE_FIRSTLINE + \fB/G\fP find all matches (shorten string) + \fB/g\fP find all matches (use startoffset) + \fB/I\fP show information about pattern + \fB/i\fP set PCRE_CASELESS + \fB/J\fP set PCRE_DUPNAMES + \fB/K\fP show backtracking control names + \fB/L\fP set locale + \fB/M\fP show compiled memory size + \fB/m\fP set PCRE_MULTILINE + \fB/N\fP set PCRE_NO_AUTO_CAPTURE + \fB/O\fP set PCRE_NO_AUTO_POSSESS + \fB/P\fP use the POSIX wrapper + \fB/Q\fP test external stack check function + \fB/S\fP study the pattern after compilation + \fB/s\fP set PCRE_DOTALL + \fB/T\fP select character tables + \fB/U\fP set PCRE_UNGREEDY + \fB/W\fP set PCRE_UCP + \fB/X\fP set PCRE_EXTRA + \fB/x\fP set PCRE_EXTENDED + \fB/Y\fP set PCRE_NO_START_OPTIMIZE + \fB/Z\fP don't show lengths in \fB/B\fP output +.sp + \fB/<any>\fP set PCRE_NEWLINE_ANY + \fB/<anycrlf>\fP set PCRE_NEWLINE_ANYCRLF + \fB/<cr>\fP set PCRE_NEWLINE_CR + \fB/<crlf>\fP set PCRE_NEWLINE_CRLF + \fB/<lf>\fP set PCRE_NEWLINE_LF + \fB/<bsr_anycrlf>\fP set PCRE_BSR_ANYCRLF + \fB/<bsr_unicode>\fP set PCRE_BSR_UNICODE + \fB/<JS>\fP set PCRE_JAVASCRIPT_COMPAT +.sp +. +. +.SS "Perl-compatible modifiers" +.rs +.sp +The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS, +PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when +\fBpcre[16|32]_compile()\fP is called. These four modifier letters have the same +effect as they do in Perl. For example: +.sp + /caseless/i +.sp +. +. +.SS "Modifiers for other PCRE options" +.rs +.sp +The following table shows additional modifiers for setting PCRE compile-time +options that do not correspond to anything in Perl: +.sp + \fB/8\fP PCRE_UTF8 ) when using the 8-bit + \fB/?\fP PCRE_NO_UTF8_CHECK ) library +.sp + \fB/8\fP PCRE_UTF16 ) when using the 16-bit + \fB/?\fP PCRE_NO_UTF16_CHECK ) library +.sp + \fB/8\fP PCRE_UTF32 ) when using the 32-bit + \fB/?\fP PCRE_NO_UTF32_CHECK ) library +.sp + \fB/9\fP PCRE_NEVER_UTF + \fB/A\fP PCRE_ANCHORED + \fB/C\fP PCRE_AUTO_CALLOUT + \fB/E\fP PCRE_DOLLAR_ENDONLY + \fB/f\fP PCRE_FIRSTLINE + \fB/J\fP PCRE_DUPNAMES + \fB/N\fP PCRE_NO_AUTO_CAPTURE + \fB/O\fP PCRE_NO_AUTO_POSSESS + \fB/U\fP PCRE_UNGREEDY + \fB/W\fP PCRE_UCP + \fB/X\fP PCRE_EXTRA + \fB/Y\fP PCRE_NO_START_OPTIMIZE + \fB/<any>\fP PCRE_NEWLINE_ANY + \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF + \fB/<cr>\fP PCRE_NEWLINE_CR + \fB/<crlf>\fP PCRE_NEWLINE_CRLF + \fB/<lf>\fP PCRE_NEWLINE_LF + \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF + \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE + \fB/<JS>\fP PCRE_JAVASCRIPT_COMPAT +.sp +The modifiers that are enclosed in angle brackets are literal strings as shown, +including the angle brackets, but the letters within can be in either case. +This example sets multiline matching with CRLF as the line ending sequence: +.sp + /^abc/m<CRLF> +.sp +As well as turning on the PCRE_UTF8/16/32 option, the \fB/8\fP modifier causes +all non-printing characters in output strings to be printed using the +\ex{hh...} notation. Otherwise, those less than 0x100 are output in hex without +the curly brackets. +.P +Full details of the PCRE options are given in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. +. +. +.SS "Finding all matches in a string" +.rs +.sp +Searching for all possible matches within each subject string can be requested +by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called +again to search the remainder of the subject string. The difference between +\fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to +\fBpcre[16|32]_exec()\fP to start searching at a new point within the entire +string (which is in effect what Perl does), whereas the latter passes over a +shortened substring. This makes a difference to the matching process if the +pattern begins with a lookbehind assertion (including \eb or \eB). +.P +If any call to \fBpcre[16|32]_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches +an empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and +PCRE_ANCHORED flags set in order to search for another, non-empty, match at the +same point. If this second match fails, the start offset is advanced, and the +normal match is retried. This imitates the way Perl handles such cases when +using the \fB/g\fP modifier or the \fBsplit()\fP function. Normally, the start +offset is advanced by one character, but if the newline convention recognizes +CRLF as a newline, and the current character is CR followed by LF, an advance +of two is used. +. +. +.SS "Other modifiers" +.rs +.sp +There are yet more modifiers for controlling the way \fBpcretest\fP +operates. +.P +The \fB/+\fP modifier requests that as well as outputting the substring that +matched the entire pattern, \fBpcretest\fP should in addition output the +remainder of the subject string. This is useful for tests where the subject +contains multiple copies of the same substring. If the \fB+\fP modifier appears +twice, the same action is taken for captured substrings. In each case the +remainder is output on the following line with a plus character following the +capture number. Note that this modifier must not immediately follow the /S +modifier because /S+ and /S++ have other meanings. +.P +The \fB/=\fP modifier requests that the values of all potential captured +parentheses be output after a match. By default, only those up to the highest +one actually used in the match are output (corresponding to the return code +from \fBpcre[16|32]_exec()\fP). Values in the offsets vector corresponding to +higher numbers should be set to -1, and these are output as "<unset>". This +modifier gives a way of checking that this is happening. +.P +The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP +output a representation of the compiled code after compilation. Normally this +information contains length and offset values; however, if \fB/Z\fP is also +present, this data is replaced by spaces. This is a special feature for use in +the automatic test scripts; it ensures that the same output is generated for +different internal link sizes. +.P +The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to +\fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers. +.P +The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the +2-byte and 4-byte fields in the compiled pattern. This facility is for testing +the feature in PCRE that allows it to execute patterns that were compiled on a +host with a different endianness. This feature is not available when the POSIX +interface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is +specified. See also the section about saving and reloading compiled patterns +below. +.P +The \fB/I\fP modifier requests that \fBpcretest\fP output information about the +compiled pattern (whether it is anchored, has a fixed first character, and +so on). It does this by calling \fBpcre[16|32]_fullinfo()\fP after compiling a +pattern. If the pattern is studied, the results of that are also output. In +this output, the word "char" means a non-UTF character, that is, the value of a +single data item (8-bit, 16-bit, or 32-bit, depending on the library that is +being tested). +.P +The \fB/K\fP modifier requests \fBpcretest\fP to show names from backtracking +control verbs that are returned from calls to \fBpcre[16|32]_exec()\fP. It causes +\fBpcretest\fP to create a \fBpcre[16|32]_extra\fP block if one has not already +been created by a call to \fBpcre[16|32]_study()\fP, and to set the +PCRE_EXTRA_MARK flag and the \fBmark\fP field within it, every time that +\fBpcre[16|32]_exec()\fP is called. If the variable that the \fBmark\fP field +points to is non-NULL for a match, non-match, or partial match, \fBpcretest\fP +prints the string to which it points. For a match, this is shown on a line by +itself, tagged with "MK:". For a non-match it is added to the message. +.P +The \fB/L\fP modifier must be followed directly by the name of a locale, for +example, +.sp + /pattern/Lfr_FR +.sp +For this reason, it must be the last modifier. The given locale is set, +\fBpcre[16|32]_maketables()\fP is called to build a set of character tables for +the locale, and this is then passed to \fBpcre[16|32]_compile()\fP when compiling +the regular expression. Without an \fB/L\fP (or \fB/T\fP) modifier, NULL is +passed as the tables pointer; that is, \fB/L\fP applies only to the expression +on which it appears. +.P +The \fB/M\fP modifier causes the size in bytes of the memory block used to hold +the compiled pattern to be output. This does not include the size of the +\fBpcre[16|32]\fP block; it is just the actual compiled data. If the pattern is +successfully studied with the PCRE_STUDY_JIT_COMPILE option, the size of the +JIT compiled code is also output. +.P +The \fB/Q\fP modifier is used to test the use of \fBpcre_stack_guard\fP. It +must be followed by '0' or '1', specifying the return code to be given from an +external function that is passed to PCRE and used for stack checking during +compilation (see the +.\" HREF +\fBpcreapi\fP +.\" +documentation for details). +.P +The \fB/S\fP modifier causes \fBpcre[16|32]_study()\fP to be called after the +expression has been compiled, and the results used when the expression is +matched. There are a number of qualifying characters that may follow \fB/S\fP. +They may appear in any order. +.P +If \fB/S\fP is followed by an exclamation mark, \fBpcre[16|32]_study()\fP is +called with the PCRE_STUDY_EXTRA_NEEDED option, causing it always to return a +\fBpcre_extra\fP block, even when studying discovers no useful information. +.P +If \fB/S\fP is followed by a second S character, it suppresses studying, even +if it was requested externally by the \fB-s\fP command line option. This makes +it possible to specify that certain patterns are always studied, and others are +never studied, independently of \fB-s\fP. This feature is used in the test +files in a few cases where the output is different when the pattern is studied. +.P +If the \fB/S\fP modifier is followed by a + character, the call to +\fBpcre[16|32]_study()\fP is made with all the JIT study options, requesting +just-in-time optimization support if it is available, for both normal and +partial matching. If you want to restrict the JIT compiling modes, you can +follow \fB/S+\fP with a digit in the range 1 to 7: +.sp + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) +.sp +If \fB/S++\fP is used instead of \fB/S+\fP (with or without a following digit), +the text "(JIT)" is added to the first output line after a match or no match +when JIT-compiled code was actually used. +.P +Note that there is also an independent \fB/+\fP modifier; it must not be given +immediately after \fB/S\fP or \fB/S+\fP because this will be misinterpreted. +.P +If JIT studying is successful, the compiled JIT code will automatically be used +when \fBpcre[16|32]_exec()\fP is run, except when incompatible run-time options +are specified. For more details, see the +.\" HREF +\fBpcrejit\fP +.\" +documentation. See also the \fB\eJ\fP escape sequence below for a way of +setting the size of the JIT stack. +.P +Finally, if \fB/S\fP is followed by a minus character, JIT compilation is +suppressed, even if it was requested externally by the \fB-s\fP command line +option. This makes it possible to specify that JIT is never to be used for +certain patterns. +.P +The \fB/T\fP modifier must be followed by a single digit. It causes a specific +set of built-in character tables to be passed to \fBpcre[16|32]_compile()\fP. It +is used in the standard PCRE tests to check behaviour with different character +tables. The digit specifies the tables as follows: +.sp + 0 the default ASCII tables, as distributed in + pcre_chartables.c.dist + 1 a set of tables defining ISO 8859 characters +.sp +In table 1, some characters whose codes are greater than 128 are identified as +letters, digits, spaces, etc. +. +. +.SS "Using the POSIX wrapper API" +.rs +.sp +The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper +API rather than its native API. This supports only the 8-bit library. When +\fB/P\fP is set, the following modifiers set options for the \fBregcomp()\fP +function: +.sp + /i REG_ICASE + /m REG_NEWLINE + /N REG_NOSUB + /s REG_DOTALL ) + /U REG_UNGREEDY ) These options are not part of + /W REG_UCP ) the POSIX standard + /8 REG_UTF8 ) +.sp +The \fB/+\fP modifier works as described above. All other modifiers are +ignored. +. +. +.SS "Locking out certain modifiers" +.rs +.sp +PCRE can be compiled with or without support for certain features such as +UTF-8/16/32 or Unicode properties. Accordingly, the standard tests are split up +into a number of different files that are selected for running depending on +which features are available. When updating the tests, it is all too easy to +put a new test into the wrong file by mistake; for example, to put a test that +requires UTF support into a file that is used when it is not available. To help +detect such mistakes as early as possible, there is a facility for locking out +specific modifiers. If an input line for \fBpcretest\fP starts with the string +"< forbid " the following sequence of characters is taken as a list of +forbidden modifiers. For example, in the test files that must not use UTF or +Unicode property support, this line appears: +.sp + < forbid 8W +.sp +This locks out the /8 and /W modifiers. An immediate error is given if they are +subsequently encountered. If the character string contains < but not >, all the +multi-character modifiers that begin with < are locked out. Otherwise, such +modifiers must be explicitly listed, for example: +.sp + < forbid <JS><cr> +.sp +There must be a single space between < and "forbid" for this feature to be +recognised. If there is not, the line is interpreted either as a request to +re-load a pre-compiled pattern (see "SAVING AND RELOADING COMPILED PATTERNS" +below) or, if there is a another < character, as a pattern that uses < as its +delimiter. +. +. +.SH "DATA LINES" +.rs +.sp +Before each data line is passed to \fBpcre[16|32]_exec()\fP, leading and trailing +white space is removed, and it is then scanned for \e escapes. Some of these +are pretty esoteric features, intended for checking out some of the more +complicated features of PCRE. If you are just testing "ordinary" regular +expressions, you probably don't need any of these. The following escapes are +recognized: +.sp + \ea alarm (BEL, \ex07) + \eb backspace (\ex08) + \ee escape (\ex27) + \ef form feed (\ex0c) + \en newline (\ex0a) +.\" JOIN + \eqdd set the PCRE_MATCH_LIMIT limit to dd + (any number of digits) + \er carriage return (\ex0d) + \et tab (\ex09) + \ev vertical tab (\ex0b) + \ennn octal character (up to 3 octal digits); always + a byte unless > 255 in UTF-8 or 16-bit or 32-bit mode + \eo{dd...} octal character (any number of octal digits} + \exhh hexadecimal byte (up to 2 hex digits) + \ex{hh...} hexadecimal character (any number of hex digits) +.\" JOIN + \eA pass the PCRE_ANCHORED option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \eB pass the PCRE_NOTBOL option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \eCdd call pcre[16|32]_copy_substring() for substring dd + after a successful match (number less than 32) +.\" JOIN + \eCname call pcre[16|32]_copy_named_substring() for substring + "name" after a successful match (name termin- + ated by next non alphanumeric character) +.\" JOIN + \eC+ show the current captured substrings at callout + time + \eC- do not supply a callout function +.\" JOIN + \eC!n return 1 instead of 0 when callout number n is + reached +.\" JOIN + \eC!n!m return 1 instead of 0 when callout number n is + reached for the nth time +.\" JOIN + \eC*n pass the number n (may be negative) as callout + data; this is used as the callout return value + \eD use the \fBpcre[16|32]_dfa_exec()\fP match function + \eF only shortest match for \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \eGdd call pcre[16|32]_get_substring() for substring dd + after a successful match (number less than 32) +.\" JOIN + \eGname call pcre[16|32]_get_named_substring() for substring + "name" after a successful match (name termin- + ated by next non-alphanumeric character) +.\" JOIN + \eJdd set up a JIT stack of dd kilobytes maximum (any + number of digits) +.\" JOIN + \eL call pcre[16|32]_get_substringlist() after a + successful match +.\" JOIN + \eM discover the minimum MATCH_LIMIT and + MATCH_LIMIT_RECURSION settings +.\" JOIN + \eN pass the PCRE_NOTEMPTY option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP; if used twice, pass the + PCRE_NOTEMPTY_ATSTART option +.\" JOIN + \eOdd set the size of the output vector passed to + \fBpcre[16|32]_exec()\fP to dd (any number of digits) +.\" JOIN + \eP pass the PCRE_PARTIAL_SOFT option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP; if used twice, pass the + PCRE_PARTIAL_HARD option +.\" JOIN + \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd + (any number of digits) + \eR pass the PCRE_DFA_RESTART option to \fBpcre[16|32]_dfa_exec()\fP + \eS output details of memory get/free calls during matching +.\" JOIN + \eY pass the PCRE_NO_START_OPTIMIZE option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \eZ pass the PCRE_NOTEOL option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e? pass the PCRE_NO_UTF[8|16|32]_CHECK option to + \fBpcre[16|32]_exec()\fP or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e>dd start the match at offset dd (optional "-"; then + any number of digits); this sets the \fIstartoffset\fP + argument for \fBpcre[16|32]_exec()\fP or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.\" JOIN + \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre[16|32]_exec()\fP + or \fBpcre[16|32]_dfa_exec()\fP +.sp +The use of \ex{hh...} is not dependent on the use of the \fB/8\fP modifier on +the pattern. It is recognized always. There may be any number of hexadecimal +digits inside the braces; invalid values provoke error messages. +.P +Note that \exhh specifies one byte rather than one character in UTF-8 mode; +this makes it possible to construct invalid UTF-8 sequences for testing +purposes. On the other hand, \ex{hh} is interpreted as a UTF-8 character in +UTF-8 mode, generating more than one byte if the value is greater than 127. +When testing the 8-bit library not in UTF-8 mode, \ex{hh} generates one byte +for values less than 256, and causes an error for greater values. +.P +In UTF-16 mode, all 4-digit \ex{hhhh} values are accepted. This makes it +possible to construct invalid UTF-16 sequences for testing purposes. +.P +In UTF-32 mode, all 4- to 8-digit \ex{...} values are accepted. This makes it +possible to construct invalid UTF-32 sequences for testing purposes. +.P +The escapes that specify line ending sequences are literal strings, exactly as +shown. No more than one newline setting should be present in any data line. +.P +A backslash followed by anything else just escapes the anything else. If +the very last character is a backslash, it is ignored. This gives a way of +passing an empty line as data, since a real empty line terminates the data +input. +.P +The \fB\eJ\fP escape provides a way of setting the maximum stack size that is +used by the just-in-time optimization code. It is ignored if JIT optimization +is not being used. Providing a stack that is larger than the default 32K is +necessary only for very complicated patterns. +.P +If \eM is present, \fBpcretest\fP calls \fBpcre[16|32]_exec()\fP several times, +with different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP +fields of the \fBpcre[16|32]_extra\fP data structure, until it finds the minimum +numbers for each parameter that allow \fBpcre[16|32]_exec()\fP to complete without +error. Because this is testing a specific feature of the normal interpretive +\fBpcre[16|32]_exec()\fP execution, the use of any JIT optimization that might +have been set up by the \fB/S+\fP qualifier of \fB-s+\fP option is disabled. +.P +The \fImatch_limit\fP number is a measure of the amount of backtracking +that takes place, and checking it out can be instructive. For most simple +matches, the number is quite small, but for patterns with very large numbers of +matching possibilities, it can become large very quickly with increasing length +of subject string. The \fImatch_limit_recursion\fP number is a measure of how +much stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is +needed to complete the match attempt. +.P +When \eO is used, the value specified may be higher or lower than the size set +by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to +the call of \fBpcre[16|32]_exec()\fP for the line in which it appears. +.P +If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper +API to be used, the only option-setting sequences that have any effect are \eB, +\eN, and \eZ, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively, +to be passed to \fBregexec()\fP. +. +. +.SH "THE ALTERNATIVE MATCHING FUNCTION" +.rs +.sp +By default, \fBpcretest\fP uses the standard PCRE matching function, +\fBpcre[16|32]_exec()\fP to match each data line. PCRE also supports an +alternative matching function, \fBpcre[16|32]_dfa_test()\fP, which operates in a +different way, and has some restrictions. The differences between the two +functions are described in the +.\" HREF +\fBpcrematching\fP +.\" +documentation. +.P +If a data line contains the \eD escape sequence, or if the command line +contains the \fB-dfa\fP option, the alternative matching function is used. +This function finds all possible matches at a given point. If, however, the \eF +escape sequence is present in the data line, it stops after the first match is +found. This is always the shortest possible match. +. +. +.SH "DEFAULT OUTPUT FROM PCRETEST" +.rs +.sp +This section describes the output when the normal matching function, +\fBpcre[16|32]_exec()\fP, is being used. +.P +When a match succeeds, \fBpcretest\fP outputs the list of captured substrings +that \fBpcre[16|32]_exec()\fP returns, starting with number 0 for the string that +matched the whole pattern. Otherwise, it outputs "No match" when the return is +PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching +substring when \fBpcre[16|32]_exec()\fP returns PCRE_ERROR_PARTIAL. (Note that +this is the entire substring that was inspected during the partial match; it +may include characters before the actual match start if a lookbehind assertion, +\eK, \eb, or \eB was involved.) For any other return, \fBpcretest\fP outputs +the PCRE negative error number and a short descriptive phrase. If the error is +a failed UTF string check, the offset of the start of the failing character and +the reason code are also output, provided that the size of the output vector is +at least two. Here is an example of an interactive \fBpcretest\fP run. +.sp + $ pcretest + PCRE version 8.13 2011-04-30 +.sp + re> /^abc(\ed+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match +.sp +Unset capturing substrings that are not followed by one that is set are not +returned by \fBpcre[16|32]_exec()\fP, and are not shown by \fBpcretest\fP. In the +following example, there are two capturing substrings, but when the first data +line is matched, the second, unset substring is not shown. An "internal" unset +substring is shown as "<unset>", as for the second data line. +.sp + re> /(a)|(b)/ + data> a + 0: a + 1: a + data> b + 0: b + 1: <unset> + 2: b +.sp +If the strings contain any non-printing characters, they are output as \exhh +escapes if the value is less than 256 and UTF mode is not set. Otherwise they +are output as \ex{hh...} escapes. See below for the definition of non-printing +characters. If the pattern has the \fB/+\fP modifier, the output for substring +0 is followed by the the rest of the subject string, identified by "0+" like +this: +.sp + re> /cat/+ + data> cataract + 0: cat + 0+ aract +.sp +If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive +matching attempts are output in sequence, like this: +.sp + re> /\eBi(\ew\ew)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp +.sp +"No match" is output only if the first match attempt fails. Here is an example +of a failure message (the offset 4 that is specified by \e>4 is past the end of +the subject string): +.sp + re> /xyz/ + data> xyz\e>4 + Error -24 (bad offset value) +.P +If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a +data line that is successfully matched, the substrings extracted by the +convenience functions are output with C, G, or L after the string number +instead of a colon. This is in addition to the normal full list. The string +length (that is, the return from the extraction function) is given in +parentheses after each string for \fB\eC\fP and \fB\eG\fP. +.P +Note that whereas patterns can be continued over several lines (a plain ">" +prompt is used for continuations), data lines may not. However newlines can be +included in data by means of the \en escape (or \er, \er\en, etc., depending on +the newline sequence setting). +. +. +. +.SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION" +.rs +.sp +When the alternative matching function, \fBpcre[16|32]_dfa_exec()\fP, is used (by +means of the \eD escape sequence or the \fB-dfa\fP command line option), the +output consists of a list of all the matches that start at the first point in +the subject where there is at least one match. For example: +.sp + re> /(tang|tangerine|tan)/ + data> yellow tangerine\eD + 0: tangerine + 1: tang + 2: tan +.sp +(Using the normal matching function on this data finds only "tang".) The +longest matching string is always given first (and numbered zero). After a +PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the +partially matching substring. (Note that this is the entire substring that was +inspected during the partial match; it may include characters before the actual +match start if a lookbehind assertion, \eK, \eb, or \eB was involved.) +.P +If \fB/g\fP is present on the pattern, the search for further matches resumes +at the end of the longest match. For example: +.sp + re> /(tang|tangerine|tan)/g + data> yellow tangerine and tangy sultana\eD + 0: tangerine + 1: tang + 2: tan + 0: tang + 1: tan + 0: tan +.sp +Since the matching function does not support substring capture, the escape +sequences that are concerned with captured substrings are not relevant. +. +. +.SH "RESTARTING AFTER A PARTIAL MATCH" +.rs +.sp +When the alternative matching function has given the PCRE_ERROR_PARTIAL return, +indicating that the subject partially matched the pattern, you can restart the +match with additional subject data by means of the \eR escape sequence. For +example: +.sp + re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/ + data> 23ja\eP\eD + Partial match: 23ja + data> n05\eR\eD + 0: n05 +.sp +For further information about partial matching, see the +.\" HREF +\fBpcrepartial\fP +.\" +documentation. +. +. +.SH CALLOUTS +.rs +.sp +If the pattern contains any callout requests, \fBpcretest\fP's callout function +is called during matching. This works with both matching functions. By default, +the called function displays the callout number, the start and current +positions in the text at the callout time, and the next pattern item to be +tested. For example: +.sp + --->pqrabcdef + 0 ^ ^ \ed +.sp +This output indicates that callout number 0 occurred for a match attempt +starting at the fourth character of the subject string, when the pointer was at +the seventh character of the data, and when the next pattern item was \ed. Just +one circumflex is output if the start and current positions are the same. +.P +Callouts numbered 255 are assumed to be automatic callouts, inserted as a +result of the \fB/C\fP pattern modifier. In this case, instead of showing the +callout number, the offset in the pattern, preceded by a plus, is output. For +example: +.sp + re> /\ed?[A-E]\e*/C + data> E* + --->E* + +0 ^ \ed? + +3 ^ [A-E] + +8 ^^ \e* + +10 ^ ^ + 0: E* +.sp +If a pattern contains (*MARK) items, an additional line is output whenever +a change of latest mark is passed to the callout function. For example: +.sp + re> /a(*MARK:X)bc/C + data> abc + --->abc + +0 ^ a + +1 ^^ (*MARK:X) + +10 ^^ b + Latest Mark: X + +11 ^ ^ c + +12 ^ ^ + 0: abc +.sp +The mark changes between matching "a" and "b", but stays the same for the rest +of the match, so nothing more is output. If, as a result of backtracking, the +mark reverts to being unset, the text "<unset>" is output. +.P +The callout function in \fBpcretest\fP returns zero (carry on matching) by +default, but you can use a \eC item in a data line (as described above) to +change this and other parameters of the callout. +.P +Inserting callouts can be helpful when using \fBpcretest\fP to check +complicated regular expressions. For further information about callouts, see +the +.\" HREF +\fBpcrecallout\fP +.\" +documentation. +. +. +. +.SH "NON-PRINTING CHARACTERS" +.rs +.sp +When \fBpcretest\fP is outputting text in the compiled version of a pattern, +bytes other than 32-126 are always treated as non-printing characters are are +therefore shown as hex escapes. +.P +When \fBpcretest\fP is outputting text that is a matched part of a subject +string, it behaves in the same way, unless a different locale has been set for +the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP +function to distinguish printing and non-printing characters. +. +. +. +.SH "SAVING AND RELOADING COMPILED PATTERNS" +.rs +.sp +The facilities described in this section are not available when the POSIX +interface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is +specified. +.P +When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a +compiled pattern to a file, by following the modifiers with > and a file name. +For example: +.sp + /pattern/im >/some/file +.sp +See the +.\" HREF +\fBpcreprecompile\fP +.\" +documentation for a discussion about saving and re-using compiled patterns. +Note that if the pattern was successfully studied with JIT optimization, the +JIT data cannot be saved. +.P +The data that is written is binary. The first eight bytes are the length of the +compiled pattern data followed by the length of the optional study data, each +written as four bytes in big-endian order (most significant byte first). If +there is no study data (either the pattern was not studied, or studying did not +return any data), the second length is zero. The lengths are followed by an +exact copy of the compiled pattern. If there is additional study data, this +(excluding any JIT data) follows immediately after the compiled pattern. After +writing the file, \fBpcretest\fP expects to read a new pattern. +.P +A saved pattern can be reloaded into \fBpcretest\fP by specifying < and a file +name instead of a pattern. There must be no space between < and the file name, +which must not contain a < character, as otherwise \fBpcretest\fP will +interpret the line as a pattern delimited by < characters. For example: +.sp + re> </some/file + Compiled pattern loaded from /some/file + No study data +.sp +If the pattern was previously studied with the JIT optimization, the JIT +information cannot be saved and restored, and so is lost. When the pattern has +been loaded, \fBpcretest\fP proceeds to read data lines in the usual way. +.P +You can copy a file written by \fBpcretest\fP to a different host and reload it +there, even if the new host has opposite endianness to the one on which the +pattern was compiled. For example, you can compile on an i86 machine and run on +a SPARC machine. When a pattern is reloaded on a host with different +endianness, the confirmation message is changed to: +.sp + Compiled pattern (byte-inverted) loaded from /some/file +.sp +The test suite contains some saved pre-compiled patterns with different +endianness. These are reloaded using "<!" instead of just "<". This suppresses +the "(byte-inverted)" text so that the output is the same on all hosts. It also +forces debugging output once the pattern has been reloaded. +.P +File names for saving and reloading can be absolute or relative, but note that +the shell facility of expanding a file name that starts with a tilde (~) is not +available. +.P +The ability to save and reload files in \fBpcretest\fP is intended for testing +and experimentation. It is not intended for production use because only a +single pattern can be written to a file. Furthermore, there is no facility for +supplying custom character tables for use with a reloaded pattern. If the +original pattern was compiled with custom tables, an attempt to match a subject +string using a reloaded pattern is likely to cause \fBpcretest\fP to crash. +Finally, if you attempt to load a file that is not in the correct format, the +result is undefined. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcre\fP(3), \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcreapi\fP(3), +\fBpcrecallout\fP(3), +\fBpcrejit\fP, \fBpcrematching\fP(3), \fBpcrepartial\fP(d), +\fBpcrepattern\fP(3), \fBpcreprecompile\fP(3). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 09 February 2014 +Copyright (c) 1997-2014 University of Cambridge. +.fi diff --git a/doc/pcretest.txt b/doc/pcretest.txt new file mode 100644 index 0000000..55de502 --- /dev/null +++ b/doc/pcretest.txt @@ -0,0 +1,1087 @@ +PCRETEST(1) General Commands Manual PCRETEST(1) + + + +NAME + pcretest - a program for testing Perl-compatible regular expressions. + +SYNOPSIS + + pcretest [options] [input file [output file]] + + pcretest was written as a test program for the PCRE regular expression + library itself, but it can also be used for experimenting with regular + expressions. This document describes the features of the test program; + for details of the regular expressions themselves, see the pcrepattern + documentation. For details of the PCRE library function calls and their + options, see the pcreapi , pcre16 and pcre32 documentation. + + The input for pcretest is a sequence of regular expression patterns and + strings to be matched, as described below. The output shows the result + of each match. Options on the command line and the patterns control + PCRE options and exactly what is output. + + As PCRE has evolved, it has acquired many different features, and as a + result, pcretest now has rather a lot of obscure options for testing + every possible feature. Some of these options are specifically designed + for use in conjunction with the test script and data files that are + distributed as part of PCRE, and are unlikely to be of use otherwise. + They are all documented here, but without much justification. + + +INPUT DATA FORMAT + + Input to pcretest is processed line by line, either by calling the C + library's fgets() function, or via the libreadline library (see below). + In Unix-like environments, fgets() treats any bytes other than newline + as data characters. However, in some Windows environments character 26 + (hex 1A) causes an immediate end of file, and no further data is read. + For maximum portability, therefore, it is safest to use only ASCII + characters in pcretest input files. + + +PCRE's 8-BIT, 16-BIT AND 32-BIT LIBRARIES + + From release 8.30, two separate PCRE libraries can be built. The origi- + nal one supports 8-bit character strings, whereas the newer 16-bit + library supports character strings encoded in 16-bit units. From + release 8.32, a third library can be built, supporting character + strings encoded in 32-bit units. The pcretest program can be used to + test all three libraries. However, it is itself still an 8-bit program, + reading 8-bit input and writing 8-bit output. When testing the 16-bit + or 32-bit library, the patterns and data strings are converted to 16- + or 32-bit format before being passed to the PCRE library functions. + Results are converted to 8-bit for output. + + References to functions and structures of the form pcre[16|32]_xx below + mean "pcre_xx when using the 8-bit library, pcre16_xx when using the + 16-bit library, or pcre32_xx when using the 32-bit library". + + +COMMAND LINE OPTIONS + + -8 If both the 8-bit library has been built, this option causes + the 8-bit library to be used (which is the default); if the + 8-bit library has not been built, this option causes an + error. + + -16 If both the 8-bit or the 32-bit, and the 16-bit libraries + have been built, this option causes the 16-bit library to be + used. If only the 16-bit library has been built, this is the + default (so has no effect). If only the 8-bit or the 32-bit + library has been built, this option causes an error. + + -32 If both the 8-bit or the 16-bit, and the 32-bit libraries + have been built, this option causes the 32-bit library to be + used. If only the 32-bit library has been built, this is the + default (so has no effect). If only the 8-bit or the 16-bit + library has been built, this option causes an error. + + -b Behave as if each pattern has the /B (show byte code) modi- + fier; the internal form is output after compilation. + + -C Output the version number of the PCRE library, and all avail- + able information about the optional features that are + included, and then exit with zero exit code. All other + options are ignored. + + -C option Output information about a specific build-time option, then + exit. This functionality is intended for use in scripts such + as RunTest. The following options output the value and set + the exit code as indicated: + + ebcdic-nl the code for LF (= NL) in an EBCDIC environment: + 0x15 or 0x25 + 0 if used in an ASCII environment + exit code is always 0 + linksize the configured internal link size (2, 3, or 4) + exit code is set to the link size + newline the default newline setting: + CR, LF, CRLF, ANYCRLF, or ANY + exit code is always 0 + bsr the default setting for what \R matches: + ANYCRLF or ANY + exit code is always 0 + + The following options output 1 for true or 0 for false, and + set the exit code to the same value: + + ebcdic compiled for an EBCDIC environment + jit just-in-time support is available + pcre16 the 16-bit library was built + pcre32 the 32-bit library was built + pcre8 the 8-bit library was built + ucp Unicode property support is available + utf UTF-8 and/or UTF-16 and/or UTF-32 support + is available + + If an unknown option is given, an error message is output; + the exit code is 0. + + -d Behave as if each pattern has the /D (debug) modifier; the + internal form and information about the compiled pattern is + output after compilation; -d is equivalent to -b -i. + + -dfa Behave as if each data line contains the \D escape sequence; + this causes the alternative matching function, + pcre[16|32]_dfa_exec(), to be used instead of the standard + pcre[16|32]_exec() function (more detail is given below). + + -help Output a brief summary these options and then exit. + + -i Behave as if each pattern has the /I modifier; information + about the compiled pattern is given after compilation. + + -M Behave as if each data line contains the \M escape sequence; + this causes PCRE to discover the minimum MATCH_LIMIT and + MATCH_LIMIT_RECURSION settings by calling pcre[16|32]_exec() + repeatedly with different limits. + + -m Output the size of each compiled pattern after it has been + compiled. This is equivalent to adding /M to each regular + expression. The size is given in bytes for both libraries. + + -O Behave as if each pattern has the /O modifier, that is dis- + able auto-possessification for all patterns. + + -o osize Set the number of elements in the output vector that is used + when calling pcre[16|32]_exec() or pcre[16|32]_dfa_exec() to + be osize. The default value is 45, which is enough for 14 + capturing subexpressions for pcre[16|32]_exec() or 22 differ- + ent matches for pcre[16|32]_dfa_exec(). The vector size can + be changed for individual matching calls by including \O in + the data line (see below). + + -p Behave as if each pattern has the /P modifier; the POSIX + wrapper API is used to call PCRE. None of the other options + has any effect when -p is set. This option can be used only + with the 8-bit library. + + -q Do not output the version number of pcretest at the start of + execution. + + -S size On Unix-like systems, set the size of the run-time stack to + size megabytes. + + -s or -s+ Behave as if each pattern has the /S modifier; in other + words, force each pattern to be studied. If -s+ is used, all + the JIT compile options are passed to pcre[16|32]_study(), + causing just-in-time optimization to be set up if it is + available, for both full and partial matching. Specific JIT + compile options can be selected by following -s+ with a digit + in the range 1 to 7, which selects the JIT compile modes as + follows: + + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) + + If -s++ is used instead of -s+ (with or without a following + digit), the text "(JIT)" is added to the first output line + after a match or no match when JIT-compiled code was actually + used. + + Note that there are pattern options that can override -s, + either specifying no studying at all, or suppressing JIT com- + pilation. + + If the /I or /D option is present on a pattern (requesting + output about the compiled pattern), information about the + result of studying is not included when studying is caused + only by -s and neither -i nor -d is present on the command + line. This behaviour means that the output from tests that + are run with and without -s should be identical, except when + options that output information about the actual running of a + match are set. + + The -M, -t, and -tm options, which give information about + resources used, are likely to produce different output with + and without -s. Output may also differ if the /C option is + present on an individual pattern. This uses callouts to trace + the the matching process, and this may be different between + studied and non-studied patterns. If the pattern contains + (*MARK) items there may also be differences, for the same + reason. The -s command line option can be overridden for spe- + cific patterns that should never be studied (see the /S pat- + tern modifier below). + + -t Run each compile, study, and match many times with a timer, + and output the resulting times per compile, study, or match + (in milliseconds). Do not set -m with -t, because you will + then get the size output a zillion times, and the timing will + be distorted. You can control the number of iterations that + are used for timing by following -t with a number (as a sepa- + rate item on the command line). For example, "-t 1000" iter- + ates 1000 times. The default is to iterate 500000 times. + + -tm This is like -t except that it times only the matching phase, + not the compile or study phases. + + -T -TM These behave like -t and -tm, but in addition, at the end of + a run, the total times for all compiles, studies, and matches + are output. + + +DESCRIPTION + + If pcretest is given two filename arguments, it reads from the first + and writes to the second. If it is given only one filename argument, it + reads from that file and writes to stdout. Otherwise, it reads from + stdin and writes to stdout, and prompts for each line of input, using + "re>" to prompt for regular expressions, and "data>" to prompt for data + lines. + + When pcretest is built, a configuration option can specify that it + should be linked with the libreadline library. When this is done, if + the input is from a terminal, it is read using the readline() function. + This provides line-editing and history facilities. The output from the + -help option states whether or not readline() will be used. + + The program handles any number of sets of input on a single input file. + Each set starts with a regular expression, and continues with any num- + ber of data lines to be matched against that pattern. + + Each data line is matched separately and independently. If you want to + do multi-line matches, you have to use the \n escape sequence (or \r or + \r\n, etc., depending on the newline setting) in a single line of input + to encode the newline sequences. There is no limit on the length of + data lines; the input buffer is automatically extended if it is too + small. + + An empty line signals the end of the data lines, at which point a new + regular expression is read. The regular expressions are given enclosed + in any non-alphanumeric delimiters other than backslash, for example: + + /(a|bc)x+yz/ + + White space before the initial delimiter is ignored. A regular expres- + sion may be continued over several input lines, in which case the new- + line characters are included within it. It is possible to include the + delimiter within the pattern by escaping it, for example + + /abc\/def/ + + If you do so, the escape and the delimiter form part of the pattern, + but since delimiters are always non-alphanumeric, this does not affect + its interpretation. If the terminating delimiter is immediately fol- + lowed by a backslash, for example, + + /abc/\ + + then a backslash is added to the end of the pattern. This is done to + provide a way of testing the error condition that arises if a pattern + finishes with a backslash, because + + /abc\/ + + is interpreted as the first line of a pattern that starts with "abc/", + causing pcretest to read the next line as a continuation of the regular + expression. + + +PATTERN MODIFIERS + + A pattern may be followed by any number of modifiers, which are mostly + single characters, though some of these can be qualified by further + characters. Following Perl usage, these are referred to below as, for + example, "the /i modifier", even though the delimiter of the pattern + need not always be a slash, and no slash is used when writing modi- + fiers. White space may appear between the final pattern delimiter and + the first modifier, and between the modifiers themselves. For refer- + ence, here is a complete list of modifiers. They fall into several + groups that are described in detail in the following sections. + + /8 set UTF mode + /9 set PCRE_NEVER_UTF (locks out UTF mode) + /? disable UTF validity check + /+ show remainder of subject after match + /= show all captures (not just those that are set) + + /A set PCRE_ANCHORED + /B show compiled code + /C set PCRE_AUTO_CALLOUT + /D same as /B plus /I + /E set PCRE_DOLLAR_ENDONLY + /F flip byte order in compiled pattern + /f set PCRE_FIRSTLINE + /G find all matches (shorten string) + /g find all matches (use startoffset) + /I show information about pattern + /i set PCRE_CASELESS + /J set PCRE_DUPNAMES + /K show backtracking control names + /L set locale + /M show compiled memory size + /m set PCRE_MULTILINE + /N set PCRE_NO_AUTO_CAPTURE + /O set PCRE_NO_AUTO_POSSESS + /P use the POSIX wrapper + /Q test external stack check function + /S study the pattern after compilation + /s set PCRE_DOTALL + /T select character tables + /U set PCRE_UNGREEDY + /W set PCRE_UCP + /X set PCRE_EXTRA + /x set PCRE_EXTENDED + /Y set PCRE_NO_START_OPTIMIZE + /Z don't show lengths in /B output + + /<any> set PCRE_NEWLINE_ANY + /<anycrlf> set PCRE_NEWLINE_ANYCRLF + /<cr> set PCRE_NEWLINE_CR + /<crlf> set PCRE_NEWLINE_CRLF + /<lf> set PCRE_NEWLINE_LF + /<bsr_anycrlf> set PCRE_BSR_ANYCRLF + /<bsr_unicode> set PCRE_BSR_UNICODE + /<JS> set PCRE_JAVASCRIPT_COMPAT + + + Perl-compatible modifiers + + The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE, + PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when + pcre[16|32]_compile() is called. These four modifier letters have the + same effect as they do in Perl. For example: + + /caseless/i + + + Modifiers for other PCRE options + + The following table shows additional modifiers for setting PCRE com- + pile-time options that do not correspond to anything in Perl: + + /8 PCRE_UTF8 ) when using the 8-bit + /? PCRE_NO_UTF8_CHECK ) library + + /8 PCRE_UTF16 ) when using the 16-bit + /? PCRE_NO_UTF16_CHECK ) library + + /8 PCRE_UTF32 ) when using the 32-bit + /? PCRE_NO_UTF32_CHECK ) library + + /9 PCRE_NEVER_UTF + /A PCRE_ANCHORED + /C PCRE_AUTO_CALLOUT + /E PCRE_DOLLAR_ENDONLY + /f PCRE_FIRSTLINE + /J PCRE_DUPNAMES + /N PCRE_NO_AUTO_CAPTURE + /O PCRE_NO_AUTO_POSSESS + /U PCRE_UNGREEDY + /W PCRE_UCP + /X PCRE_EXTRA + /Y PCRE_NO_START_OPTIMIZE + /<any> PCRE_NEWLINE_ANY + /<anycrlf> PCRE_NEWLINE_ANYCRLF + /<cr> PCRE_NEWLINE_CR + /<crlf> PCRE_NEWLINE_CRLF + /<lf> PCRE_NEWLINE_LF + /<bsr_anycrlf> PCRE_BSR_ANYCRLF + /<bsr_unicode> PCRE_BSR_UNICODE + /<JS> PCRE_JAVASCRIPT_COMPAT + + The modifiers that are enclosed in angle brackets are literal strings + as shown, including the angle brackets, but the letters within can be + in either case. This example sets multiline matching with CRLF as the + line ending sequence: + + /^abc/m<CRLF> + + As well as turning on the PCRE_UTF8/16/32 option, the /8 modifier + causes all non-printing characters in output strings to be printed + using the \x{hh...} notation. Otherwise, those less than 0x100 are out- + put in hex without the curly brackets. + + Full details of the PCRE options are given in the pcreapi documenta- + tion. + + Finding all matches in a string + + Searching for all possible matches within each subject string can be + requested by the /g or /G modifier. After finding a match, PCRE is + called again to search the remainder of the subject string. The differ- + ence between /g and /G is that the former uses the startoffset argument + to pcre[16|32]_exec() to start searching at a new point within the + entire string (which is in effect what Perl does), whereas the latter + passes over a shortened substring. This makes a difference to the + matching process if the pattern begins with a lookbehind assertion + (including \b or \B). + + If any call to pcre[16|32]_exec() in a /g or /G sequence matches an + empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and + PCRE_ANCHORED flags set in order to search for another, non-empty, + match at the same point. If this second match fails, the start offset + is advanced, and the normal match is retried. This imitates the way + Perl handles such cases when using the /g modifier or the split() func- + tion. Normally, the start offset is advanced by one character, but if + the newline convention recognizes CRLF as a newline, and the current + character is CR followed by LF, an advance of two is used. + + Other modifiers + + There are yet more modifiers for controlling the way pcretest operates. + + The /+ modifier requests that as well as outputting the substring that + matched the entire pattern, pcretest should in addition output the + remainder of the subject string. This is useful for tests where the + subject contains multiple copies of the same substring. If the + modi- + fier appears twice, the same action is taken for captured substrings. + In each case the remainder is output on the following line with a plus + character following the capture number. Note that this modifier must + not immediately follow the /S modifier because /S+ and /S++ have other + meanings. + + The /= modifier requests that the values of all potential captured + parentheses be output after a match. By default, only those up to the + highest one actually used in the match are output (corresponding to the + return code from pcre[16|32]_exec()). Values in the offsets vector cor- + responding to higher numbers should be set to -1, and these are output + as "<unset>". This modifier gives a way of checking that this is hap- + pening. + + The /B modifier is a debugging feature. It requests that pcretest out- + put a representation of the compiled code after compilation. Normally + this information contains length and offset values; however, if /Z is + also present, this data is replaced by spaces. This is a special fea- + ture for use in the automatic test scripts; it ensures that the same + output is generated for different internal link sizes. + + The /D modifier is a PCRE debugging feature, and is equivalent to /BI, + that is, both the /B and the /I modifiers. + + The /F modifier causes pcretest to flip the byte order of the 2-byte + and 4-byte fields in the compiled pattern. This facility is for testing + the feature in PCRE that allows it to execute patterns that were com- + piled on a host with a different endianness. This feature is not avail- + able when the POSIX interface to PCRE is being used, that is, when the + /P pattern modifier is specified. See also the section about saving and + reloading compiled patterns below. + + The /I modifier requests that pcretest output information about the + compiled pattern (whether it is anchored, has a fixed first character, + and so on). It does this by calling pcre[16|32]_fullinfo() after com- + piling a pattern. If the pattern is studied, the results of that are + also output. In this output, the word "char" means a non-UTF character, + that is, the value of a single data item (8-bit, 16-bit, or 32-bit, + depending on the library that is being tested). + + The /K modifier requests pcretest to show names from backtracking con- + trol verbs that are returned from calls to pcre[16|32]_exec(). It + causes pcretest to create a pcre[16|32]_extra block if one has not + already been created by a call to pcre[16|32]_study(), and to set the + PCRE_EXTRA_MARK flag and the mark field within it, every time that + pcre[16|32]_exec() is called. If the variable that the mark field + points to is non-NULL for a match, non-match, or partial match, + pcretest prints the string to which it points. For a match, this is + shown on a line by itself, tagged with "MK:". For a non-match it is + added to the message. + + The /L modifier must be followed directly by the name of a locale, for + example, + + /pattern/Lfr_FR + + For this reason, it must be the last modifier. The given locale is set, + pcre[16|32]_maketables() is called to build a set of character tables + for the locale, and this is then passed to pcre[16|32]_compile() when + compiling the regular expression. Without an /L (or /T) modifier, NULL + is passed as the tables pointer; that is, /L applies only to the + expression on which it appears. + + The /M modifier causes the size in bytes of the memory block used to + hold the compiled pattern to be output. This does not include the size + of the pcre[16|32] block; it is just the actual compiled data. If the + pattern is successfully studied with the PCRE_STUDY_JIT_COMPILE option, + the size of the JIT compiled code is also output. + + The /Q modifier is used to test the use of pcre_stack_guard. It must be + followed by '0' or '1', specifying the return code to be given from an + external function that is passed to PCRE and used for stack checking + during compilation (see the pcreapi documentation for details). + + The /S modifier causes pcre[16|32]_study() to be called after the + expression has been compiled, and the results used when the expression + is matched. There are a number of qualifying characters that may follow + /S. They may appear in any order. + + If /S is followed by an exclamation mark, pcre[16|32]_study() is called + with the PCRE_STUDY_EXTRA_NEEDED option, causing it always to return a + pcre_extra block, even when studying discovers no useful information. + + If /S is followed by a second S character, it suppresses studying, even + if it was requested externally by the -s command line option. This + makes it possible to specify that certain patterns are always studied, + and others are never studied, independently of -s. This feature is used + in the test files in a few cases where the output is different when the + pattern is studied. + + If the /S modifier is followed by a + character, the call to + pcre[16|32]_study() is made with all the JIT study options, requesting + just-in-time optimization support if it is available, for both normal + and partial matching. If you want to restrict the JIT compiling modes, + you can follow /S+ with a digit in the range 1 to 7: + + 1 normal match only + 2 soft partial match only + 3 normal match and soft partial match + 4 hard partial match only + 6 soft and hard partial match + 7 all three modes (default) + + If /S++ is used instead of /S+ (with or without a following digit), the + text "(JIT)" is added to the first output line after a match or no + match when JIT-compiled code was actually used. + + Note that there is also an independent /+ modifier; it must not be + given immediately after /S or /S+ because this will be misinterpreted. + + If JIT studying is successful, the compiled JIT code will automatically + be used when pcre[16|32]_exec() is run, except when incompatible run- + time options are specified. For more details, see the pcrejit documen- + tation. See also the \J escape sequence below for a way of setting the + size of the JIT stack. + + Finally, if /S is followed by a minus character, JIT compilation is + suppressed, even if it was requested externally by the -s command line + option. This makes it possible to specify that JIT is never to be used + for certain patterns. + + The /T modifier must be followed by a single digit. It causes a spe- + cific set of built-in character tables to be passed to pcre[16|32]_com- + pile(). It is used in the standard PCRE tests to check behaviour with + different character tables. The digit specifies the tables as follows: + + 0 the default ASCII tables, as distributed in + pcre_chartables.c.dist + 1 a set of tables defining ISO 8859 characters + + In table 1, some characters whose codes are greater than 128 are iden- + tified as letters, digits, spaces, etc. + + Using the POSIX wrapper API + + The /P modifier causes pcretest to call PCRE via the POSIX wrapper API + rather than its native API. This supports only the 8-bit library. When + /P is set, the following modifiers set options for the regcomp() func- + tion: + + /i REG_ICASE + /m REG_NEWLINE + /N REG_NOSUB + /s REG_DOTALL ) + /U REG_UNGREEDY ) These options are not part of + /W REG_UCP ) the POSIX standard + /8 REG_UTF8 ) + + The /+ modifier works as described above. All other modifiers are + ignored. + + Locking out certain modifiers + + PCRE can be compiled with or without support for certain features such + as UTF-8/16/32 or Unicode properties. Accordingly, the standard tests + are split up into a number of different files that are selected for + running depending on which features are available. When updating the + tests, it is all too easy to put a new test into the wrong file by mis- + take; for example, to put a test that requires UTF support into a file + that is used when it is not available. To help detect such mistakes as + early as possible, there is a facility for locking out specific modi- + fiers. If an input line for pcretest starts with the string "< forbid " + the following sequence of characters is taken as a list of forbidden + modifiers. For example, in the test files that must not use UTF or Uni- + code property support, this line appears: + + < forbid 8W + + This locks out the /8 and /W modifiers. An immediate error is given if + they are subsequently encountered. If the character string contains < + but not >, all the multi-character modifiers that begin with < are + locked out. Otherwise, such modifiers must be explicitly listed, for + example: + + < forbid <JS><cr> + + There must be a single space between < and "forbid" for this feature to + be recognised. If there is not, the line is interpreted either as a + request to re-load a pre-compiled pattern (see "SAVING AND RELOADING + COMPILED PATTERNS" below) or, if there is a another < character, as a + pattern that uses < as its delimiter. + + +DATA LINES + + Before each data line is passed to pcre[16|32]_exec(), leading and + trailing white space is removed, and it is then scanned for \ escapes. + Some of these are pretty esoteric features, intended for checking out + some of the more complicated features of PCRE. If you are just testing + "ordinary" regular expressions, you probably don't need any of these. + The following escapes are recognized: + + \a alarm (BEL, \x07) + \b backspace (\x08) + \e escape (\x27) + \f form feed (\x0c) + \n newline (\x0a) + \qdd set the PCRE_MATCH_LIMIT limit to dd + (any number of digits) + \r carriage return (\x0d) + \t tab (\x09) + \v vertical tab (\x0b) + \nnn octal character (up to 3 octal digits); always + a byte unless > 255 in UTF-8 or 16-bit or 32-bit mode + \o{dd...} octal character (any number of octal digits} + \xhh hexadecimal byte (up to 2 hex digits) + \x{hh...} hexadecimal character (any number of hex digits) + \A pass the PCRE_ANCHORED option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \B pass the PCRE_NOTBOL option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \Cdd call pcre[16|32]_copy_substring() for substring dd + after a successful match (number less than 32) + \Cname call pcre[16|32]_copy_named_substring() for substring + "name" after a successful match (name termin- + ated by next non alphanumeric character) + \C+ show the current captured substrings at callout + time + \C- do not supply a callout function + \C!n return 1 instead of 0 when callout number n is + reached + \C!n!m return 1 instead of 0 when callout number n is + reached for the nth time + \C*n pass the number n (may be negative) as callout + data; this is used as the callout return value + \D use the pcre[16|32]_dfa_exec() match function + \F only shortest match for pcre[16|32]_dfa_exec() + \Gdd call pcre[16|32]_get_substring() for substring dd + after a successful match (number less than 32) + \Gname call pcre[16|32]_get_named_substring() for substring + "name" after a successful match (name termin- + ated by next non-alphanumeric character) + \Jdd set up a JIT stack of dd kilobytes maximum (any + number of digits) + \L call pcre[16|32]_get_substringlist() after a + successful match + \M discover the minimum MATCH_LIMIT and + MATCH_LIMIT_RECURSION settings + \N pass the PCRE_NOTEMPTY option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec(); if used twice, pass the + PCRE_NOTEMPTY_ATSTART option + \Odd set the size of the output vector passed to + pcre[16|32]_exec() to dd (any number of digits) + \P pass the PCRE_PARTIAL_SOFT option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec(); if used twice, pass the + PCRE_PARTIAL_HARD option + \Qdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd + (any number of digits) + \R pass the PCRE_DFA_RESTART option to pcre[16|32]_dfa_exec() + \S output details of memory get/free calls during matching + \Y pass the PCRE_NO_START_OPTIMIZE option to + pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \Z pass the PCRE_NOTEOL option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \? pass the PCRE_NO_UTF[8|16|32]_CHECK option to + pcre[16|32]_exec() or pcre[16|32]_dfa_exec() + \>dd start the match at offset dd (optional "-"; then + any number of digits); this sets the startoffset + argument for pcre[16|32]_exec() or + pcre[16|32]_dfa_exec() + \<cr> pass the PCRE_NEWLINE_CR option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \<lf> pass the PCRE_NEWLINE_LF option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \<crlf> pass the PCRE_NEWLINE_CRLF option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + \<any> pass the PCRE_NEWLINE_ANY option to pcre[16|32]_exec() + or pcre[16|32]_dfa_exec() + + The use of \x{hh...} is not dependent on the use of the /8 modifier on + the pattern. It is recognized always. There may be any number of hexa- + decimal digits inside the braces; invalid values provoke error mes- + sages. + + Note that \xhh specifies one byte rather than one character in UTF-8 + mode; this makes it possible to construct invalid UTF-8 sequences for + testing purposes. On the other hand, \x{hh} is interpreted as a UTF-8 + character in UTF-8 mode, generating more than one byte if the value is + greater than 127. When testing the 8-bit library not in UTF-8 mode, + \x{hh} generates one byte for values less than 256, and causes an error + for greater values. + + In UTF-16 mode, all 4-digit \x{hhhh} values are accepted. This makes it + possible to construct invalid UTF-16 sequences for testing purposes. + + In UTF-32 mode, all 4- to 8-digit \x{...} values are accepted. This + makes it possible to construct invalid UTF-32 sequences for testing + purposes. + + The escapes that specify line ending sequences are literal strings, + exactly as shown. No more than one newline setting should be present in + any data line. + + A backslash followed by anything else just escapes the anything else. + If the very last character is a backslash, it is ignored. This gives a + way of passing an empty line as data, since a real empty line termi- + nates the data input. + + The \J escape provides a way of setting the maximum stack size that is + used by the just-in-time optimization code. It is ignored if JIT opti- + mization is not being used. Providing a stack that is larger than the + default 32K is necessary only for very complicated patterns. + + If \M is present, pcretest calls pcre[16|32]_exec() several times, with + different values in the match_limit and match_limit_recursion fields of + the pcre[16|32]_extra data structure, until it finds the minimum num- + bers for each parameter that allow pcre[16|32]_exec() to complete with- + out error. Because this is testing a specific feature of the normal + interpretive pcre[16|32]_exec() execution, the use of any JIT optimiza- + tion that might have been set up by the /S+ qualifier of -s+ option is + disabled. + + The match_limit number is a measure of the amount of backtracking that + takes place, and checking it out can be instructive. For most simple + matches, the number is quite small, but for patterns with very large + numbers of matching possibilities, it can become large very quickly + with increasing length of subject string. The match_limit_recursion + number is a measure of how much stack (or, if PCRE is compiled with + NO_RECURSE, how much heap) memory is needed to complete the match + attempt. + + When \O is used, the value specified may be higher or lower than the + size set by the -O command line option (or defaulted to 45); \O applies + only to the call of pcre[16|32]_exec() for the line in which it + appears. + + If the /P modifier was present on the pattern, causing the POSIX wrap- + per API to be used, the only option-setting sequences that have any + effect are \B, \N, and \Z, causing REG_NOTBOL, REG_NOTEMPTY, and + REG_NOTEOL, respectively, to be passed to regexec(). + + +THE ALTERNATIVE MATCHING FUNCTION + + By default, pcretest uses the standard PCRE matching function, + pcre[16|32]_exec() to match each data line. PCRE also supports an + alternative matching function, pcre[16|32]_dfa_test(), which operates + in a different way, and has some restrictions. The differences between + the two functions are described in the pcrematching documentation. + + If a data line contains the \D escape sequence, or if the command line + contains the -dfa option, the alternative matching function is used. + This function finds all possible matches at a given point. If, however, + the \F escape sequence is present in the data line, it stops after the + first match is found. This is always the shortest possible match. + + +DEFAULT OUTPUT FROM PCRETEST + + This section describes the output when the normal matching function, + pcre[16|32]_exec(), is being used. + + When a match succeeds, pcretest outputs the list of captured substrings + that pcre[16|32]_exec() returns, starting with number 0 for the string + that matched the whole pattern. Otherwise, it outputs "No match" when + the return is PCRE_ERROR_NOMATCH, and "Partial match:" followed by the + partially matching substring when pcre[16|32]_exec() returns + PCRE_ERROR_PARTIAL. (Note that this is the entire substring that was + inspected during the partial match; it may include characters before + the actual match start if a lookbehind assertion, \K, \b, or \B was + involved.) For any other return, pcretest outputs the PCRE negative + error number and a short descriptive phrase. If the error is a failed + UTF string check, the offset of the start of the failing character and + the reason code are also output, provided that the size of the output + vector is at least two. Here is an example of an interactive pcretest + run. + + $ pcretest + PCRE version 8.13 2011-04-30 + + re> /^abc(\d+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match + + Unset capturing substrings that are not followed by one that is set are + not returned by pcre[16|32]_exec(), and are not shown by pcretest. In + the following example, there are two capturing substrings, but when the + first data line is matched, the second, unset substring is not shown. + An "internal" unset substring is shown as "<unset>", as for the second + data line. + + re> /(a)|(b)/ + data> a + 0: a + 1: a + data> b + 0: b + 1: <unset> + 2: b + + If the strings contain any non-printing characters, they are output as + \xhh escapes if the value is less than 256 and UTF mode is not set. + Otherwise they are output as \x{hh...} escapes. See below for the defi- + nition of non-printing characters. If the pattern has the /+ modifier, + the output for substring 0 is followed by the the rest of the subject + string, identified by "0+" like this: + + re> /cat/+ + data> cataract + 0: cat + 0+ aract + + If the pattern has the /g or /G modifier, the results of successive + matching attempts are output in sequence, like this: + + re> /\Bi(\w\w)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp + + "No match" is output only if the first match attempt fails. Here is an + example of a failure message (the offset 4 that is specified by \>4 is + past the end of the subject string): + + re> /xyz/ + data> xyz\>4 + Error -24 (bad offset value) + + If any of the sequences \C, \G, or \L are present in a data line that + is successfully matched, the substrings extracted by the convenience + functions are output with C, G, or L after the string number instead of + a colon. This is in addition to the normal full list. The string length + (that is, the return from the extraction function) is given in paren- + theses after each string for \C and \G. + + Note that whereas patterns can be continued over several lines (a plain + ">" prompt is used for continuations), data lines may not. However new- + lines can be included in data by means of the \n escape (or \r, \r\n, + etc., depending on the newline sequence setting). + + +OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION + + When the alternative matching function, pcre[16|32]_dfa_exec(), is used + (by means of the \D escape sequence or the -dfa command line option), + the output consists of a list of all the matches that start at the + first point in the subject where there is at least one match. For exam- + ple: + + re> /(tang|tangerine|tan)/ + data> yellow tangerine\D + 0: tangerine + 1: tang + 2: tan + + (Using the normal matching function on this data finds only "tang".) + The longest matching string is always given first (and numbered zero). + After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", fol- + lowed by the partially matching substring. (Note that this is the + entire substring that was inspected during the partial match; it may + include characters before the actual match start if a lookbehind asser- + tion, \K, \b, or \B was involved.) + + If /g is present on the pattern, the search for further matches resumes + at the end of the longest match. For example: + + re> /(tang|tangerine|tan)/g + data> yellow tangerine and tangy sultana\D + 0: tangerine + 1: tang + 2: tan + 0: tang + 1: tan + 0: tan + + Since the matching function does not support substring capture, the + escape sequences that are concerned with captured substrings are not + relevant. + + +RESTARTING AFTER A PARTIAL MATCH + + When the alternative matching function has given the PCRE_ERROR_PARTIAL + return, indicating that the subject partially matched the pattern, you + can restart the match with additional subject data by means of the \R + escape sequence. For example: + + re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/ + data> 23ja\P\D + Partial match: 23ja + data> n05\R\D + 0: n05 + + For further information about partial matching, see the pcrepartial + documentation. + + +CALLOUTS + + If the pattern contains any callout requests, pcretest's callout func- + tion is called during matching. This works with both matching func- + tions. By default, the called function displays the callout number, the + start and current positions in the text at the callout time, and the + next pattern item to be tested. For example: + + --->pqrabcdef + 0 ^ ^ \d + + This output indicates that callout number 0 occurred for a match + attempt starting at the fourth character of the subject string, when + the pointer was at the seventh character of the data, and when the next + pattern item was \d. Just one circumflex is output if the start and + current positions are the same. + + Callouts numbered 255 are assumed to be automatic callouts, inserted as + a result of the /C pattern modifier. In this case, instead of showing + the callout number, the offset in the pattern, preceded by a plus, is + output. For example: + + re> /\d?[A-E]\*/C + data> E* + --->E* + +0 ^ \d? + +3 ^ [A-E] + +8 ^^ \* + +10 ^ ^ + 0: E* + + If a pattern contains (*MARK) items, an additional line is output when- + ever a change of latest mark is passed to the callout function. For + example: + + re> /a(*MARK:X)bc/C + data> abc + --->abc + +0 ^ a + +1 ^^ (*MARK:X) + +10 ^^ b + Latest Mark: X + +11 ^ ^ c + +12 ^ ^ + 0: abc + + The mark changes between matching "a" and "b", but stays the same for + the rest of the match, so nothing more is output. If, as a result of + backtracking, the mark reverts to being unset, the text "<unset>" is + output. + + The callout function in pcretest returns zero (carry on matching) by + default, but you can use a \C item in a data line (as described above) + to change this and other parameters of the callout. + + Inserting callouts can be helpful when using pcretest to check compli- + cated regular expressions. For further information about callouts, see + the pcrecallout documentation. + + +NON-PRINTING CHARACTERS + + When pcretest is outputting text in the compiled version of a pattern, + bytes other than 32-126 are always treated as non-printing characters + are are therefore shown as hex escapes. + + When pcretest is outputting text that is a matched part of a subject + string, it behaves in the same way, unless a different locale has been + set for the pattern (using the /L modifier). In this case, the + isprint() function to distinguish printing and non-printing characters. + + +SAVING AND RELOADING COMPILED PATTERNS + + The facilities described in this section are not available when the + POSIX interface to PCRE is being used, that is, when the /P pattern + modifier is specified. + + When the POSIX interface is not in use, you can cause pcretest to write + a compiled pattern to a file, by following the modifiers with > and a + file name. For example: + + /pattern/im >/some/file + + See the pcreprecompile documentation for a discussion about saving and + re-using compiled patterns. Note that if the pattern was successfully + studied with JIT optimization, the JIT data cannot be saved. + + The data that is written is binary. The first eight bytes are the + length of the compiled pattern data followed by the length of the + optional study data, each written as four bytes in big-endian order + (most significant byte first). If there is no study data (either the + pattern was not studied, or studying did not return any data), the sec- + ond length is zero. The lengths are followed by an exact copy of the + compiled pattern. If there is additional study data, this (excluding + any JIT data) follows immediately after the compiled pattern. After + writing the file, pcretest expects to read a new pattern. + + A saved pattern can be reloaded into pcretest by specifying < and a + file name instead of a pattern. There must be no space between < and + the file name, which must not contain a < character, as otherwise + pcretest will interpret the line as a pattern delimited by < charac- + ters. For example: + + re> </some/file + Compiled pattern loaded from /some/file + No study data + + If the pattern was previously studied with the JIT optimization, the + JIT information cannot be saved and restored, and so is lost. When the + pattern has been loaded, pcretest proceeds to read data lines in the + usual way. + + You can copy a file written by pcretest to a different host and reload + it there, even if the new host has opposite endianness to the one on + which the pattern was compiled. For example, you can compile on an i86 + machine and run on a SPARC machine. When a pattern is reloaded on a + host with different endianness, the confirmation message is changed to: + + Compiled pattern (byte-inverted) loaded from /some/file + + The test suite contains some saved pre-compiled patterns with different + endianness. These are reloaded using "<!" instead of just "<". This + suppresses the "(byte-inverted)" text so that the output is the same on + all hosts. It also forces debugging output once the pattern has been + reloaded. + + File names for saving and reloading can be absolute or relative, but + note that the shell facility of expanding a file name that starts with + a tilde (~) is not available. + + The ability to save and reload files in pcretest is intended for test- + ing and experimentation. It is not intended for production use because + only a single pattern can be written to a file. Furthermore, there is + no facility for supplying custom character tables for use with a + reloaded pattern. If the original pattern was compiled with custom + tables, an attempt to match a subject string using a reloaded pattern + is likely to cause pcretest to crash. Finally, if you attempt to load + a file that is not in the correct format, the result is undefined. + + +SEE ALSO + + pcre(3), pcre16(3), pcre32(3), pcreapi(3), pcrecallout(3), pcrejit, + pcrematching(3), pcrepartial(d), pcrepattern(3), pcreprecompile(3). + + +AUTHOR + + Philip Hazel + University Computing Service + Cambridge CB2 3QH, England. + + +REVISION + + Last updated: 09 February 2014 + Copyright (c) 1997-2014 University of Cambridge. diff --git a/doc/pcreunicode.3 b/doc/pcreunicode.3 new file mode 100644 index 0000000..cb5e526 --- /dev/null +++ b/doc/pcreunicode.3 @@ -0,0 +1,249 @@ +.TH PCREUNICODE 3 "27 February 2013" "PCRE 8.33" +.SH NAME +PCRE - Perl-compatible regular expressions +.SH "UTF-8, UTF-16, UTF-32, AND UNICODE PROPERTY SUPPORT" +.rs +.sp +As well as UTF-8 support, PCRE also supports UTF-16 (from release 8.30) and +UTF-32 (from release 8.32), by means of two additional libraries. They can be +built as well as, or instead of, the 8-bit library. +. +. +.SH "UTF-8 SUPPORT" +.rs +.sp +In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF +support, and, in addition, you must call +.\" HREF +\fBpcre_compile()\fP +.\" +with the PCRE_UTF8 option flag, or the pattern must start with the sequence +(*UTF8) or (*UTF). When either of these is the case, both the pattern and any +subject strings that are matched against it are treated as UTF-8 strings +instead of strings of individual 1-byte characters. +. +. +.SH "UTF-16 AND UTF-32 SUPPORT" +.rs +.sp +In order process UTF-16 or UTF-32 strings, you must build PCRE's 16-bit or +32-bit library with UTF support, and, in addition, you must call +.\" HREF +\fBpcre16_compile()\fP +.\" +or +.\" HREF +\fBpcre32_compile()\fP +.\" +with the PCRE_UTF16 or PCRE_UTF32 option flag, as appropriate. Alternatively, +the pattern must start with the sequence (*UTF16), (*UTF32), as appropriate, or +(*UTF), which can be used with either library. When UTF mode is set, both the +pattern and any subject strings that are matched against it are treated as +UTF-16 or UTF-32 strings instead of strings of individual 16-bit or 32-bit +characters. +. +. +.SH "UTF SUPPORT OVERHEAD" +.rs +.sp +If you compile PCRE with UTF support, but do not use it at run time, the +library will be a bit bigger, but the additional run time overhead is limited +to testing the PCRE_UTF[8|16|32] flag occasionally, so should not be very big. +. +. +.SH "UNICODE PROPERTY SUPPORT" +.rs +.sp +If PCRE is built with Unicode character property support (which implies UTF +support), the escape sequences \ep{..}, \eP{..}, and \eX can be used. +The available properties that can be tested are limited to the general +category properties such as Lu for an upper case letter or Nd for a decimal +number, the Unicode script names such as Arabic or Han, and the derived +properties Any and L&. Full lists is given in the +.\" HREF +\fBpcrepattern\fP +.\" +and +.\" HREF +\fBpcresyntax\fP +.\" +documentation. Only the short names for properties are supported. For example, +\ep{L} matches a letter. Its Perl synonym, \ep{Letter}, is not supported. +Furthermore, in Perl, many properties may optionally be prefixed by "Is", for +compatibility with Perl 5.6. PCRE does not support this. +. +. +.\" HTML <a name="utf8strings"></a> +.SS "Validity of UTF-8 strings" +.rs +.sp +When you set the PCRE_UTF8 flag, the byte strings passed as patterns and +subjects are (by default) checked for validity on entry to the relevant +functions. The entire string is checked before any other processing takes +place. From release 7.3 of PCRE, the check is according the rules of RFC 3629, +which are themselves derived from the Unicode specification. Earlier releases +of PCRE followed the rules of RFC 2279, which allows the full range of 31-bit +values (0 to 0x7FFFFFFF). The current check allows only values in the range U+0 +to U+10FFFF, excluding the surrogate area. (From release 8.33 the so-called +"non-character" code points are no longer excluded because Unicode corrigendum +#9 makes it clear that they should not be.) +.P +Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16, +where they are used in pairs to encode codepoints with values greater than +0xFFFF. The code points that are encoded by UTF-16 pairs are available +independently in the UTF-8 and UTF-32 encodings. (In other words, the whole +surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8 and +UTF-32.) +.P +If an invalid UTF-8 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first byte +of the failing character. The run-time functions \fBpcre_exec()\fP and +\fBpcre_dfa_exec()\fP also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +.P +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance, for +example in the case of a long subject string that is being scanned repeatedly. +If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, PCRE +assumes that the pattern or subject it is given (respectively) contains only +valid UTF-8 codes. In this case, it does not diagnose an invalid UTF-8 string. +.P +Note that passing PCRE_NO_UTF8_CHECK to \fBpcre_compile()\fP just disables the +check for the pattern; it does not also apply to subject strings. If you want +to disable the check for a subject string you must pass this option to +\fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. +.P +If you pass an invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set, the result +is undefined and your program may crash. +. +. +.\" HTML <a name="utf16strings"></a> +.SS "Validity of UTF-16 strings" +.rs +.sp +When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are +passed as patterns and subjects are (by default) checked for validity on entry +to the relevant functions. Values other than those in the surrogate range +U+D800 to U+DFFF are independent code points. Values in the surrogate range +must be used in pairs in the correct manner. +.P +If an invalid UTF-16 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first data +unit of the failing character. The run-time functions \fBpcre16_exec()\fP and +\fBpcre16_dfa_exec()\fP also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +.P +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance. If you set +the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that +the pattern or subject it is given (respectively) contains only valid UTF-16 +sequences. In this case, it does not diagnose an invalid UTF-16 string. +However, if an invalid string is passed, the result is undefined. +. +. +.\" HTML <a name="utf32strings"></a> +.SS "Validity of UTF-32 strings" +.rs +.sp +When you set the PCRE_UTF32 flag, the strings of 32-bit data units that are +passed as patterns and subjects are (by default) checked for validity on entry +to the relevant functions. This check allows only values in the range U+0 +to U+10FFFF, excluding the surrogate area U+D800 to U+DFFF. +.P +If an invalid UTF-32 string is passed to PCRE, an error return is given. At +compile time, the only additional information is the offset to the first data +unit of the failing character. The run-time functions \fBpcre32_exec()\fP and +\fBpcre32_dfa_exec()\fP also pass back this information, as well as a more +detailed reason code if the caller has provided memory in which to do this. +.P +In some situations, you may already know that your strings are valid, and +therefore want to skip these checks in order to improve performance. If you set +the PCRE_NO_UTF32_CHECK flag at compile time or at run time, PCRE assumes that +the pattern or subject it is given (respectively) contains only valid UTF-32 +sequences. In this case, it does not diagnose an invalid UTF-32 string. +However, if an invalid string is passed, the result is undefined. +. +. +.SS "General comments about UTF modes" +.rs +.sp +1. Codepoints less than 256 can be specified in patterns by either braced or +unbraced hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger +values have to use braced sequences. +.P +2. Octal numbers up to \e777 are recognized, and in UTF-8 mode they match +two-byte characters for values greater than \e177. +.P +3. Repeat quantifiers apply to complete UTF characters, not to individual +data units, for example: \ex{100}{3}. +.P +4. The dot metacharacter matches one UTF character instead of a single data +unit. +.P +5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, or +a single 16-bit data unit in UTF-16 mode, or a single 32-bit data unit in +UTF-32 mode, but its use can lead to some strange effects because it breaks up +multi-unit characters (see the description of \eC in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation). The use of \eC is not supported in the alternative matching +function \fBpcre[16|32]_dfa_exec()\fP, nor is it supported in UTF mode by the +JIT optimization of \fBpcre[16|32]_exec()\fP. If JIT optimization is requested +for a UTF pattern that contains \eC, it will not succeed, and so the matching +will be carried out by the normal interpretive function. +.P +6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly +test characters of any code value, but, by default, the characters that PCRE +recognizes as digits, spaces, or word characters remain the same set as in +non-UTF mode, all with values less than 256. This remains true even when PCRE +is built to include Unicode property support, because to do otherwise would +slow down PCRE in many common cases. Note in particular that this applies to +\eb and \eB, because they are defined in terms of \ew and \eW. If you really +want to test for a wider sense of, say, "digit", you can use explicit Unicode +property tests such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option, +the way that the character escapes work is changed so that Unicode properties +are used to determine which characters match. There are more details in the +section on +.\" HTML <a href="pcrepattern.html#genericchartypes"> +.\" </a> +generic character types +.\" +in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +.P +7. Similarly, characters that match the POSIX named character classes are all +low-valued characters, unless the PCRE_UCP option is set. +.P +8. However, the horizontal and vertical white space matching escapes (\eh, \eH, +\ev, and \eV) do match all the appropriate Unicode characters, whether or not +PCRE_UCP is set. +.P +9. Case-insensitive matching applies only to characters whose values are less +than 128, unless PCRE is built with Unicode property support. A few Unicode +characters such as Greek sigma have more than two codepoints that are +case-equivalent. Up to and including PCRE release 8.31, only one-to-one case +mappings were supported, but later releases (with Unicode property support) do +treat as case-equivalent all versions of characters such as Greek sigma. +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 27 February 2013 +Copyright (c) 1997-2013 University of Cambridge. +.fi diff --git a/doc/perltest.txt b/doc/perltest.txt new file mode 100644 index 0000000..bb1a52a --- /dev/null +++ b/doc/perltest.txt @@ -0,0 +1,42 @@ +The perltest program +-------------------- + +The perltest.pl script tests Perl's regular expressions; it has the same +specification as pcretest, and so can be given identical input, except that +input patterns can be followed only by Perl's lower case modifiers and certain +other pcretest modifiers that are either handled or ignored: + + /+ recognized and handled by perltest + /++ the second + is ignored + /8 recognized and handled by perltest + /J ignored + /K ignored + /W ignored + /S ignored + /SS ignored + /Y ignored + +The pcretest \Y escape in data lines is removed before matching. The data lines +are processed as Perl double-quoted strings, so if they contain " $ or @ +characters, these have to be escaped. For this reason, all such characters in +the Perl-compatible testinput1 file are escaped so that they can be used for +perltest as well as for pcretest. The special upper case pattern modifiers such +as /A that pcretest recognizes, and its special data line escapes, are not used +in the Perl-compatible test file. The output should be identical, apart from +the initial identifying banner. + +The perltest.pl script can also test UTF-8 features. It recognizes the special +modifier /8 that pcretest uses to invoke UTF-8 functionality. The testinput4 +and testinput6 files can be fed to perltest to run compatible UTF-8 tests. +However, it is necessary to add "use utf8; require Encode" to the script to +make this work correctly. I have not managed to find a way to handle this +automatically. + +The other testinput files are not suitable for feeding to perltest.pl, since +they make use of the special upper case modifiers and escapes that pcretest +uses to test certain features of PCRE. Some of these files also contain +malformed regular expressions, in order to check that PCRE diagnoses them +correctly. + +Philip Hazel +January 2012 |