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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>
8 Return to the <a href="index.html">PCRE index page</a>.
9 </p>
10 <p>
11 This page is part of the PCRE HTML documentation. It was generated automatically
12 from the original man page. If there is any nonsense in it, please consult the
13 man 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>
23 The PCRE library is a set of functions that implement regular expression
24 pattern matching using the same syntax and semantics as Perl, with just a few
25 differences. Some features that appeared in Python and PCRE before they
26 appeared in Perl are also available using the Python syntax, there is some
27 support for one or two .NET and Oniguruma syntax items, and there is an option
28 for requesting some minor changes that give better JavaScript compatibility.
29 </P>
30 <P>
31 Starting with release 8.30, it is possible to compile two separate PCRE
32 libraries: the original, which supports 8-bit character strings (including
33 UTF-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
35 built. The majority of the work to make this possible was done by Zoltan
36 Herczeg.
37 </P>
38 <P>
39 The two libraries contain identical sets of functions, except that the names in
40 the 16-bit library start with <b>pcre16_</b> instead of <b>pcre_</b>. To avoid
41 over-complication and reduce the documentation maintenance load, most of the
42 documentation describes the 8-bit library, with the differences for the 16-bit
43 library described separately in the
44 <a href="pcre16.html"><b>pcre16</b></a>
45 page. References to functions or structures of the form <i>pcre[16]_xxx</i>
46 should 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>
50 The current implementation of PCRE corresponds approximately with Perl 5.12,
51 including support for UTF-8/16 encoded strings and Unicode general category
52 properties. However, UTF-8/16 and Unicode support has to be explicitly enabled;
53 it is not the default. The Unicode tables correspond to Unicode release 6.0.0.
54 </P>
55 <P>
56 In addition to the Perl-compatible matching function, PCRE contains an
57 alternative function that matches the same compiled patterns in a different
58 way. In certain circumstances, the alternative function has some advantages.
59 For a discussion of the two matching algorithms, see the
60 <a href="pcrematching.html"><b>pcrematching</b></a>
61 page.
62 </P>
63 <P>
64 PCRE is written in C and released as a C library. A number of people have
65 written wrappers and interfaces of various kinds. In particular, Google Inc.
66 have provided a comprehensive C++ wrapper for the 8-bit library. This is now
67 included as part of the PCRE distribution. The
68 <a href="pcrecpp.html"><b>pcrecpp</b></a>
69 page has details of this interface. Other people's contributions can be found
70 in 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>
74 Details of exactly which Perl regular expression features are and are not
75 supported by PCRE are given in separate documents. See the
76 <a href="pcrepattern.html"><b>pcrepattern</b></a>
77 and
78 <a href="pcrecompat.html"><b>pcrecompat</b></a>
79 pages. There is a syntax summary in the
80 <a href="pcresyntax.html"><b>pcresyntax</b></a>
81 page.
82 </P>
83 <P>
84 Some features of PCRE can be included, excluded, or changed when the library is
85 built. The
86 <a href="pcre_config.html"><b>pcre_config()</b></a>
87 function makes it possible for a client to discover which features are
88 available. The features themselves are described in the
89 <a href="pcrebuild.html"><b>pcrebuild</b></a>
90 page. Documentation about building PCRE for various operating systems can be
91 found in the <b>README</b> and <b>NON-UNIX-USE</b> files in the source
92 distribution.
93 </P>
94 <P>
95 The libraries contains a number of undocumented internal functions and data
96 tables that are used by more than one of the exported external functions, but
97 which 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
99 some environments, it is possible to control which external symbols are
100 exported when a shared library is built, and in these cases the undocumented
101 symbols are not exported.
102 </P>
103 <br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br>
104 <P>
105 The user documentation for PCRE comprises a number of different sections. In
106 the "man" format, each of these is a separate "man page". In the HTML format,
107 each is a separate page, linked from the index page. In the plain text format,
108 all the sections, except the <b>pcredemo</b> section, are concatenated, for ease
109 of 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>
135 In addition, in the "man" and HTML formats, there is a short page for each
136 8-bit C library function, listing its arguments and results.
137 </P>
138 <br><a name="SEC3" href="#TOC1">AUTHOR</a><br>
139 <P>
140 Philip Hazel
141 <br>
142 University Computing Service
143 <br>
144 Cambridge CB2 3QH, England.
145 <br>
146 </P>
147 <P>
148 Putting an actual email address here seems to have been a spam magnet, so I've
149 taken it away. If you want to email me, use my two initials, followed by the
150 two digits 10, at the domain cam.ac.uk.
151 </P>
152 <br><a name="SEC4" href="#TOC1">REVISION</a><br>
153 <P>
154 Last updated: 10 January 2012
155 <br>
156 Copyright &copy; 1997-2012 University of Cambridge.
157 <br>
158 <p>
159 Return to the <a href="index.html">PCRE index page</a>.
160 </p>

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