1<html> 2<head> 3<title>pcre specification</title> 4</head> 5<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6<h1>pcre man page</h1> 7<p> 8Return to the <a href="index.html">PCRE index page</a>. 9</p> 10<p> 11This page is part of the PCRE HTML documentation. It was generated automatically 12from the original man page. If there is any nonsense in it, please consult the 13man page, in case the conversion went wrong. 14<br> 15<ul> 16<li><a name="TOC1" href="#SEC1">INTRODUCTION</a> 17<li><a name="TOC2" href="#SEC2">USER DOCUMENTATION</a> 18<li><a name="TOC3" href="#SEC3">AUTHOR</a> 19<li><a name="TOC4" href="#SEC4">REVISION</a> 20</ul> 21<br><a name="SEC1" href="#TOC1">INTRODUCTION</a><br> 22<P> 23The PCRE library is a set of functions that implement regular expression 24pattern matching using the same syntax and semantics as Perl, with just a few 25differences. Some features that appeared in Python and PCRE before they 26appeared in Perl are also available using the Python syntax, there is some 27support for one or two .NET and Oniguruma syntax items, and there is an option 28for requesting some minor changes that give better JavaScript compatibility. 29</P> 30<P> 31Starting with release 8.30, it is possible to compile two separate PCRE 32libraries: the original, which supports 8-bit character strings (including 33UTF-8 strings), and a second library that supports 16-bit character strings 34(including UTF-16 strings). The build process allows either one or both to be 35built. The majority of the work to make this possible was done by Zoltan 36Herczeg. 37</P> 38<P> 39The two libraries contain identical sets of functions, except that the names in 40the 16-bit library start with <b>pcre16_</b> instead of <b>pcre_</b>. To avoid 41over-complication and reduce the documentation maintenance load, most of the 42documentation describes the 8-bit library, with the differences for the 16-bit 43library described separately in the 44<a href="pcre16.html"><b>pcre16</b></a> 45page. References to functions or structures of the form <i>pcre[16]_xxx</i> 46should be read as meaning "<i>pcre_xxx</i> when using the 8-bit library and 47<i>pcre16_xxx</i> when using the 16-bit library". 48</P> 49<P> 50The current implementation of PCRE corresponds approximately with Perl 5.12, 51including support for UTF-8/16 encoded strings and Unicode general category 52properties. However, UTF-8/16 and Unicode support has to be explicitly enabled; 53it is not the default. The Unicode tables correspond to Unicode release 6.0.0. 54</P> 55<P> 56In addition to the Perl-compatible matching function, PCRE contains an 57alternative function that matches the same compiled patterns in a different 58way. In certain circumstances, the alternative function has some advantages. 59For a discussion of the two matching algorithms, see the 60<a href="pcrematching.html"><b>pcrematching</b></a> 61page. 62</P> 63<P> 64PCRE is written in C and released as a C library. A number of people have 65written wrappers and interfaces of various kinds. In particular, Google Inc. 66have provided a comprehensive C++ wrapper for the 8-bit library. This is now 67included as part of the PCRE distribution. The 68<a href="pcrecpp.html"><b>pcrecpp</b></a> 69page has details of this interface. Other people's contributions can be found 70in the <i>Contrib</i> directory at the primary FTP site, which is: 71<a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre</a> 72</P> 73<P> 74Details of exactly which Perl regular expression features are and are not 75supported by PCRE are given in separate documents. See the 76<a href="pcrepattern.html"><b>pcrepattern</b></a> 77and 78<a href="pcrecompat.html"><b>pcrecompat</b></a> 79pages. There is a syntax summary in the 80<a href="pcresyntax.html"><b>pcresyntax</b></a> 81page. 82</P> 83<P> 84Some features of PCRE can be included, excluded, or changed when the library is 85built. The 86<a href="pcre_config.html"><b>pcre_config()</b></a> 87function makes it possible for a client to discover which features are 88available. The features themselves are described in the 89<a href="pcrebuild.html"><b>pcrebuild</b></a> 90page. Documentation about building PCRE for various operating systems can be 91found in the <b>README</b> and <b>NON-UNIX-USE</b> files in the source 92distribution. 93</P> 94<P> 95The libraries contains a number of undocumented internal functions and data 96tables that are used by more than one of the exported external functions, but 97which are not intended for use by external callers. Their names all begin with 98"_pcre_" or "_pcre16_", which hopefully will not provoke any name clashes. In 99some environments, it is possible to control which external symbols are 100exported when a shared library is built, and in these cases the undocumented 101symbols are not exported. 102</P> 103<br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br> 104<P> 105The user documentation for PCRE comprises a number of different sections. In 106the "man" format, each of these is a separate "man page". In the HTML format, 107each is a separate page, linked from the index page. In the plain text format, 108all the sections, except the <b>pcredemo</b> section, are concatenated, for ease 109of searching. The sections are as follows: 110<pre> 111 pcre this document 112 pcre16 details of the 16-bit library 113 pcre-config show PCRE installation configuration information 114 pcreapi details of PCRE's native C API 115 pcrebuild options for building PCRE 116 pcrecallout details of the callout feature 117 pcrecompat discussion of Perl compatibility 118 pcrecpp details of the C++ wrapper for the 8-bit library 119 pcredemo a demonstration C program that uses PCRE 120 pcregrep description of the <b>pcregrep</b> command (8-bit only) 121 pcrejit discussion of the just-in-time optimization support 122 pcrelimits details of size and other limits 123 pcrematching discussion of the two matching algorithms 124 pcrepartial details of the partial matching facility 125 pcrepattern syntax and semantics of supported regular expressions 126 pcreperform discussion of performance issues 127 pcreposix the POSIX-compatible C API for the 8-bit library 128 pcreprecompile details of saving and re-using precompiled patterns 129 pcresample discussion of the pcredemo program 130 pcrestack discussion of stack usage 131 pcresyntax quick syntax reference 132 pcretest description of the <b>pcretest</b> testing command 133 pcreunicode discussion of Unicode and UTF-8/16 support 134</pre> 135In addition, in the "man" and HTML formats, there is a short page for each 1368-bit C library function, listing its arguments and results. 137</P> 138<br><a name="SEC3" href="#TOC1">AUTHOR</a><br> 139<P> 140Philip Hazel 141<br> 142University Computing Service 143<br> 144Cambridge CB2 3QH, England. 145<br> 146</P> 147<P> 148Putting an actual email address here seems to have been a spam magnet, so I've 149taken it away. If you want to email me, use my two initials, followed by the 150two digits 10, at the domain cam.ac.uk. 151</P> 152<br><a name="SEC4" href="#TOC1">REVISION</a><br> 153<P> 154Last updated: 10 January 2012 155<br> 156Copyright © 1997-2012 University of Cambridge. 157<br> 158<p> 159Return to the <a href="index.html">PCRE index page</a>. 160</p> 161