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1 .TH PCRE 3 "10 January 2012" "PCRE 8.30"
2 .SH NAME
3 PCRE - Perl-compatible regular expressions
4 .SH INTRODUCTION
5 .rs
6 .sp
7 The PCRE library is a set of functions that implement regular expression
8 pattern matching using the same syntax and semantics as Perl, with just a few
9 differences. Some features that appeared in Python and PCRE before they
10 appeared in Perl are also available using the Python syntax, there is some
11 support for one or two .NET and Oniguruma syntax items, and there is an option
12 for requesting some minor changes that give better JavaScript compatibility.
13 .P
14 Starting with release 8.30, it is possible to compile two separate PCRE
15 libraries: the original, which supports 8-bit character strings (including
16 UTF-8 strings), and a second library that supports 16-bit character strings
17 (including UTF-16 strings). The build process allows either one or both to be
18 built. The majority of the work to make this possible was done by Zoltan
19 Herczeg.
20 .P
21 The two libraries contain identical sets of functions, except that the names in
22 the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP. To avoid
23 over-complication and reduce the documentation maintenance load, most of the
24 documentation describes the 8-bit library, with the differences for the 16-bit
25 library described separately in the
26 .\" HREF
27 \fBpcre16\fP
28 .\"
29 page. References to functions or structures of the form \fIpcre[16]_xxx\fP
30 should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library and
31 \fIpcre16_xxx\fP when using the 16-bit library".
32 .P
33 The current implementation of PCRE corresponds approximately with Perl 5.12,
34 including support for UTF-8/16 encoded strings and Unicode general category
35 properties. However, UTF-8/16 and Unicode support has to be explicitly enabled;
36 it is not the default. The Unicode tables correspond to Unicode release 6.0.0.
37 .P
38 In addition to the Perl-compatible matching function, PCRE contains an
39 alternative function that matches the same compiled patterns in a different
40 way. In certain circumstances, the alternative function has some advantages.
41 For a discussion of the two matching algorithms, see the
42 .\" HREF
43 \fBpcrematching\fP
44 .\"
45 page.
46 .P
47 PCRE is written in C and released as a C library. A number of people have
48 written wrappers and interfaces of various kinds. In particular, Google Inc.
49 have provided a comprehensive C++ wrapper for the 8-bit library. This is now
50 included as part of the PCRE distribution. The
51 .\" HREF
52 \fBpcrecpp\fP
53 .\"
54 page has details of this interface. Other people's contributions can be found
55 in the \fIContrib\fP directory at the primary FTP site, which is:
56 .sp
57 .\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">
58 .\" </a>
59 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
60 .P
61 Details of exactly which Perl regular expression features are and are not
62 supported by PCRE are given in separate documents. See the
63 .\" HREF
64 \fBpcrepattern\fP
65 .\"
66 and
67 .\" HREF
68 \fBpcrecompat\fP
69 .\"
70 pages. There is a syntax summary in the
71 .\" HREF
72 \fBpcresyntax\fP
73 .\"
74 page.
75 .P
76 Some features of PCRE can be included, excluded, or changed when the library is
77 built. The
78 .\" HREF
79 \fBpcre_config()\fP
80 .\"
81 function makes it possible for a client to discover which features are
82 available. The features themselves are described in the
83 .\" HREF
84 \fBpcrebuild\fP
85 .\"
86 page. Documentation about building PCRE for various operating systems can be
87 found in the \fBREADME\fP and \fBNON-UNIX-USE\fP files in the source
88 distribution.
89 .P
90 The libraries contains a number of undocumented internal functions and data
91 tables that are used by more than one of the exported external functions, but
92 which are not intended for use by external callers. Their names all begin with
93 "_pcre_" or "_pcre16_", which hopefully will not provoke any name clashes. In
94 some environments, it is possible to control which external symbols are
95 exported when a shared library is built, and in these cases the undocumented
96 symbols are not exported.
97 .
98 .
99 .SH "USER DOCUMENTATION"
100 .rs
101 .sp
102 The user documentation for PCRE comprises a number of different sections. In
103 the "man" format, each of these is a separate "man page". In the HTML format,
104 each is a separate page, linked from the index page. In the plain text format,
105 all the sections, except the \fBpcredemo\fP section, are concatenated, for ease
106 of searching. The sections are as follows:
107 .sp
108 pcre this document
109 pcre16 details of the 16-bit library
110 pcre-config show PCRE installation configuration information
111 pcreapi details of PCRE's native C API
112 pcrebuild options for building PCRE
113 pcrecallout details of the callout feature
114 pcrecompat discussion of Perl compatibility
115 pcrecpp details of the C++ wrapper for the 8-bit library
116 pcredemo a demonstration C program that uses PCRE
117 pcregrep description of the \fBpcregrep\fP command (8-bit only)
118 pcrejit discussion of the just-in-time optimization support
119 pcrelimits details of size and other limits
120 pcrematching discussion of the two matching algorithms
121 pcrepartial details of the partial matching facility
122 .\" JOIN
123 pcrepattern syntax and semantics of supported
124 regular expressions
125 pcreperform discussion of performance issues
126 pcreposix the POSIX-compatible C API for the 8-bit library
127 pcreprecompile details of saving and re-using precompiled patterns
128 pcresample discussion of the pcredemo program
129 pcrestack discussion of stack usage
130 pcresyntax quick syntax reference
131 pcretest description of the \fBpcretest\fP testing command
132 pcreunicode discussion of Unicode and UTF-8/16 support
133 .sp
134 In addition, in the "man" and HTML formats, there is a short page for each
135 8-bit C library function, listing its arguments and results.
136 .
137 .
138 .SH AUTHOR
139 .rs
140 .sp
141 .nf
142 Philip Hazel
143 University Computing Service
144 Cambridge CB2 3QH, England.
145 .fi
146 .P
147 Putting an actual email address here seems to have been a spam magnet, so I've
148 taken it away. If you want to email me, use my two initials, followed by the
149 two digits 10, at the domain cam.ac.uk.
150 .
151 .
152 .SH REVISION
153 .rs
154 .sp
155 .nf
156 Last updated: 10 January 2012
157 Copyright (c) 1997-2012 University of Cambridge.
158 .fi

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