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+<title>pcre specification</title>
+<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
+<h1>pcre man page</h1>
+Return to the <a href="index.html">PCRE index page</a>.
+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.
+<li><a name="TOC1" href="#SEC1">INTRODUCTION</a>
+<li><a name="TOC2" href="#SEC2">SECURITY CONSIDERATIONS</a>
+<li><a name="TOC3" href="#SEC3">USER DOCUMENTATION</a>
+<li><a name="TOC4" href="#SEC4">AUTHOR</a>
+<li><a name="TOC5" href="#SEC5">REVISION</a>
+<br><a name="SEC1" href="#TOC1">INTRODUCTION</a><br>
+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.
+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
+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 <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>
+<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".
+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 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>
+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=""></a>
+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>
+<a href="pcrecompat.html"><b>pcrecompat</b></a>
+pages. There is a syntax summary in the
+<a href="pcresyntax.html"><b>pcresyntax</b></a>
+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>
+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.
+<br><a name="SEC2" href="#TOC1">SECURITY CONSIDERATIONS</a><br>
+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
+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.
+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 provides some protection
+against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the
+<a href="pcreapi.html"><b>pcreapi</b></a>
+<br><a name="SEC3" href="#TOC1">USER DOCUMENTATION</a><br>
+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
+ 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
+In the "man" and HTML formats, there is also a short page for each C library
+function, listing its arguments and results.
+<br><a name="SEC4" href="#TOC1">AUTHOR</a><br>
+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
+<br><a name="SEC5" href="#TOC1">REVISION</a><br>
+Last updated: 08 January 2014
+Copyright &copy; 1997-2014 University of Cambridge.
+Return to the <a href="index.html">PCRE index page</a>.