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diff --git a/doc/pcre.3 b/doc/pcre.3 new file mode 100644 index 0000000..4eda404 --- /dev/null +++ b/doc/pcre.3 @@ -0,0 +1,218 @@ +.TH PCRE 3 "08 January 2014" "PCRE 8.35" +.SH NAME +PCRE - Perl-compatible regular expressions +.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: 08 January 2014 +Copyright (c) 1997-2014 University of Cambridge. +.fi |