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Some documentation updates.
1 .TH PCRE 3 "29 October 2012" "PCRE 8.32"
3 PCRE - Perl-compatible regular expressions
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 Starting with release 8.32 it is possible to compile a third separate PCRE
22 library, which supports 32-bit character strings (including
23 UTF-32 strings). The build process allows any set of the 8-, 16- and 32-bit
24 libraries. The work to make this possible was done by Christian Persch.
25 .P
26 The three libraries contain identical sets of functions, except that the names
27 in the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP, and the
28 names in the 32-bit library start with \fBpcre32_\fP instead of \fBpcre_\fP. To
29 avoid over-complication and reduce the documentation maintenance load, most of
30 the documentation describes the 8-bit library, with the differences for the
31 16-bit and 32-bit libraries described separately in the
32 .\" HREF
33 \fBpcre16\fP
34 and
35 .\" HREF
36 \fBpcre32\fP
37 .\"
38 pages. References to functions or structures of the form \fIpcre[16|32]_xxx\fP
39 should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library,
40 \fIpcre16_xxx\fP when using the 16-bit library, or \fIpcre32_xxx\fP when using
41 the 32-bit library".
42 .P
43 The current implementation of PCRE corresponds approximately with Perl 5.12,
44 including support for UTF-8/16/32 encoded strings and Unicode general category
45 properties. However, UTF-8/16/32 and Unicode support has to be explicitly
46 enabled; it is not the default. The Unicode tables correspond to Unicode
47 release 6.2.0.
48 .P
49 In addition to the Perl-compatible matching function, PCRE contains an
50 alternative function that matches the same compiled patterns in a different
51 way. In certain circumstances, the alternative function has some advantages.
52 For a discussion of the two matching algorithms, see the
53 .\" HREF
54 \fBpcrematching\fP
55 .\"
56 page.
57 .P
58 PCRE is written in C and released as a C library. A number of people have
59 written wrappers and interfaces of various kinds. In particular, Google Inc.
60 have provided a comprehensive C++ wrapper for the 8-bit library. This is now
61 included as part of the PCRE distribution. The
62 .\" HREF
63 \fBpcrecpp\fP
64 .\"
65 page has details of this interface. Other people's contributions can be found
66 in the \fIContrib\fP directory at the primary FTP site, which is:
67 .sp
68 .\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">
69 .\" </a>
70 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
71 .P
72 Details of exactly which Perl regular expression features are and are not
73 supported by PCRE are given in separate documents. See the
74 .\" HREF
75 \fBpcrepattern\fP
76 .\"
77 and
78 .\" HREF
79 \fBpcrecompat\fP
80 .\"
81 pages. There is a syntax summary in the
82 .\" HREF
83 \fBpcresyntax\fP
84 .\"
85 page.
86 .P
87 Some features of PCRE can be included, excluded, or changed when the library is
88 built. The
89 .\" HREF
90 \fBpcre_config()\fP
91 .\"
92 function makes it possible for a client to discover which features are
93 available. The features themselves are described in the
94 .\" HREF
95 \fBpcrebuild\fP
96 .\"
97 page. Documentation about building PCRE for various operating systems can be
98 found in the \fBREADME\fP and \fBNON-AUTOTOOLS_BUILD\fP files in the source
99 distribution.
100 .P
101 The libraries contains a number of undocumented internal functions and data
102 tables that are used by more than one of the exported external functions, but
103 which are not intended for use by external callers. Their names all begin with
104 "_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name
105 clashes. In some environments, it is possible to control which external symbols
106 are exported when a shared library is built, and in these cases the
107 undocumented symbols are not exported.
108 .
109 .
111 .rs
112 .sp
113 The user documentation for PCRE comprises a number of different sections. In
114 the "man" format, each of these is a separate "man page". In the HTML format,
115 each is a separate page, linked from the index page. In the plain text format,
116 all the sections, except the \fBpcredemo\fP section, are concatenated, for ease
117 of searching. The sections are as follows:
118 .sp
119 pcre this document
120 pcre16 details of the 16-bit library
121 pcre32 details of the 32-bit library
122 pcre-config show PCRE installation configuration information
123 pcreapi details of PCRE's native C API
124 pcrebuild options for building PCRE
125 pcrecallout details of the callout feature
126 pcrecompat discussion of Perl compatibility
127 pcrecpp details of the C++ wrapper for the 8-bit library
128 pcredemo a demonstration C program that uses PCRE
129 pcregrep description of the \fBpcregrep\fP command (8-bit only)
130 pcrejit discussion of the just-in-time optimization support
131 pcrelimits details of size and other limits
132 pcrematching discussion of the two matching algorithms
133 pcrepartial details of the partial matching facility
134 .\" JOIN
135 pcrepattern syntax and semantics of supported
136 regular expressions
137 pcreperform discussion of performance issues
138 pcreposix the POSIX-compatible C API for the 8-bit library
139 pcreprecompile details of saving and re-using precompiled patterns
140 pcresample discussion of the pcredemo program
141 pcrestack discussion of stack usage
142 pcresyntax quick syntax reference
143 pcretest description of the \fBpcretest\fP testing command
144 pcreunicode discussion of Unicode and UTF-8/16/32 support
145 .sp
146 In addition, in the "man" and HTML formats, there is a short page for each
147 C library function, listing its arguments and results.
148 .
149 .
151 .rs
152 .sp
153 .nf
154 Philip Hazel
155 University Computing Service
156 Cambridge CB2 3QH, England.
157 .fi
158 .P
159 Putting an actual email address here seems to have been a spam magnet, so I've
160 taken it away. If you want to email me, use my two initials, followed by the
161 two digits 10, at the domain cam.ac.uk.
162 .
163 .
165 .rs
166 .sp
167 .nf
168 Last updated: 29 October 2012
169 Copyright (c) 1997-2012 University of Cambridge.
170 .fi


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