Annotation of embedaddon/pcre/doc/html/pcre.html, revision 1.1.1.4
1.1 misho 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>
1.1.1.3 misho 17: <li><a name="TOC2" href="#SEC2">SECURITY CONSIDERATIONS</a>
18: <li><a name="TOC3" href="#SEC3">USER DOCUMENTATION</a>
19: <li><a name="TOC4" href="#SEC4">AUTHOR</a>
20: <li><a name="TOC5" href="#SEC5">REVISION</a>
1.1 misho 21: </ul>
22: <br><a name="SEC1" href="#TOC1">INTRODUCTION</a><br>
23: <P>
24: The PCRE library is a set of functions that implement regular expression
25: pattern matching using the same syntax and semantics as Perl, with just a few
26: differences. Some features that appeared in Python and PCRE before they
27: appeared in Perl are also available using the Python syntax, there is some
28: support for one or two .NET and Oniguruma syntax items, and there is an option
29: for requesting some minor changes that give better JavaScript compatibility.
30: </P>
31: <P>
1.1.1.2 misho 32: Starting with release 8.30, it is possible to compile two separate PCRE
33: libraries: the original, which supports 8-bit character strings (including
34: UTF-8 strings), and a second library that supports 16-bit character strings
35: (including UTF-16 strings). The build process allows either one or both to be
36: built. The majority of the work to make this possible was done by Zoltan
37: Herczeg.
38: </P>
39: <P>
1.1.1.3 misho 40: Starting with release 8.32 it is possible to compile a third separate PCRE
41: library that supports 32-bit character strings (including UTF-32 strings). The
42: build process allows any combination of the 8-, 16- and 32-bit libraries. The
43: work to make this possible was done by Christian Persch.
44: </P>
45: <P>
46: The three libraries contain identical sets of functions, except that the names
47: in the 16-bit library start with <b>pcre16_</b> instead of <b>pcre_</b>, and the
48: names in the 32-bit library start with <b>pcre32_</b> instead of <b>pcre_</b>. To
49: avoid over-complication and reduce the documentation maintenance load, most of
50: the documentation describes the 8-bit library, with the differences for the
51: 16-bit and 32-bit libraries described separately in the
1.1.1.2 misho 52: <a href="pcre16.html"><b>pcre16</b></a>
1.1.1.3 misho 53: and
54: <a href="pcre32.html"><b>pcre32</b></a>
55: pages. References to functions or structures of the form <i>pcre[16|32]_xxx</i>
56: should be read as meaning "<i>pcre_xxx</i> when using the 8-bit library,
57: <i>pcre16_xxx</i> when using the 16-bit library, or <i>pcre32_xxx</i> when using
58: the 32-bit library".
1.1.1.2 misho 59: </P>
60: <P>
1.1 misho 61: The current implementation of PCRE corresponds approximately with Perl 5.12,
1.1.1.3 misho 62: including support for UTF-8/16/32 encoded strings and Unicode general category
63: properties. However, UTF-8/16/32 and Unicode support has to be explicitly
64: enabled; it is not the default. The Unicode tables correspond to Unicode
1.1.1.4 ! misho 65: release 6.3.0.
1.1 misho 66: </P>
67: <P>
68: In addition to the Perl-compatible matching function, PCRE contains an
69: alternative function that matches the same compiled patterns in a different
70: way. In certain circumstances, the alternative function has some advantages.
71: For a discussion of the two matching algorithms, see the
72: <a href="pcrematching.html"><b>pcrematching</b></a>
73: page.
74: </P>
75: <P>
76: PCRE is written in C and released as a C library. A number of people have
77: written wrappers and interfaces of various kinds. In particular, Google Inc.
1.1.1.2 misho 78: have provided a comprehensive C++ wrapper for the 8-bit library. This is now
79: included as part of the PCRE distribution. The
1.1 misho 80: <a href="pcrecpp.html"><b>pcrecpp</b></a>
81: page has details of this interface. Other people's contributions can be found
82: in the <i>Contrib</i> directory at the primary FTP site, which is:
83: <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre</a>
84: </P>
85: <P>
86: Details of exactly which Perl regular expression features are and are not
87: supported by PCRE are given in separate documents. See the
88: <a href="pcrepattern.html"><b>pcrepattern</b></a>
89: and
90: <a href="pcrecompat.html"><b>pcrecompat</b></a>
91: pages. There is a syntax summary in the
92: <a href="pcresyntax.html"><b>pcresyntax</b></a>
93: page.
94: </P>
95: <P>
96: Some features of PCRE can be included, excluded, or changed when the library is
97: built. The
98: <a href="pcre_config.html"><b>pcre_config()</b></a>
99: function makes it possible for a client to discover which features are
100: available. The features themselves are described in the
101: <a href="pcrebuild.html"><b>pcrebuild</b></a>
102: page. Documentation about building PCRE for various operating systems can be
1.1.1.3 misho 103: found in the
104: <a href="README.txt"><b>README</b></a>
105: and
106: <a href="NON-AUTOTOOLS-BUILD.txt"><b>NON-AUTOTOOLS_BUILD</b></a>
107: files in the source distribution.
1.1 misho 108: </P>
109: <P>
1.1.1.2 misho 110: The libraries contains a number of undocumented internal functions and data
1.1 misho 111: tables that are used by more than one of the exported external functions, but
112: which are not intended for use by external callers. Their names all begin with
1.1.1.3 misho 113: "_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name
114: clashes. In some environments, it is possible to control which external symbols
115: are exported when a shared library is built, and in these cases the
116: undocumented symbols are not exported.
117: </P>
118: <br><a name="SEC2" href="#TOC1">SECURITY CONSIDERATIONS</a><br>
119: <P>
120: If you are using PCRE in a non-UTF application that permits users to supply
121: arbitrary patterns for compilation, you should be aware of a feature that
122: allows users to turn on UTF support from within a pattern, provided that PCRE
123: was built with UTF support. For example, an 8-bit pattern that begins with
124: "(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and
125: subjects as strings of UTF-8 characters instead of individual 8-bit characters.
126: This causes both the pattern and any data against which it is matched to be
127: checked for UTF-8 validity. If the data string is very long, such a check might
128: use sufficiently many resources as to cause your application to lose
129: performance.
130: </P>
131: <P>
132: One way of guarding against this possibility is to use the
133: <b>pcre_fullinfo()</b> function to check the compiled pattern's options for UTF.
134: Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at
135: compile time. This causes an compile time error if a pattern contains a
136: UTF-setting sequence.
137: </P>
138: <P>
139: If your application is one that supports UTF, be aware that validity checking
140: can take time. If the same data string is to be matched many times, you can use
141: the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to
142: save redundant checks.
143: </P>
144: <P>
145: Another way that performance can be hit is by running a pattern that has a very
146: large search tree against a string that will never match. Nested unlimited
147: repeats in a pattern are a common example. PCRE provides some protection
148: against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the
149: <a href="pcreapi.html"><b>pcreapi</b></a>
150: page.
1.1 misho 151: </P>
1.1.1.3 misho 152: <br><a name="SEC3" href="#TOC1">USER DOCUMENTATION</a><br>
1.1 misho 153: <P>
154: The user documentation for PCRE comprises a number of different sections. In
155: the "man" format, each of these is a separate "man page". In the HTML format,
156: each is a separate page, linked from the index page. In the plain text format,
157: all the sections, except the <b>pcredemo</b> section, are concatenated, for ease
158: of searching. The sections are as follows:
159: <pre>
160: pcre this document
161: pcre-config show PCRE installation configuration information
1.1.1.3 misho 162: pcre16 details of the 16-bit library
163: pcre32 details of the 32-bit library
1.1 misho 164: pcreapi details of PCRE's native C API
1.1.1.3 misho 165: pcrebuild building PCRE
1.1 misho 166: pcrecallout details of the callout feature
167: pcrecompat discussion of Perl compatibility
1.1.1.2 misho 168: pcrecpp details of the C++ wrapper for the 8-bit library
1.1 misho 169: pcredemo a demonstration C program that uses PCRE
1.1.1.2 misho 170: pcregrep description of the <b>pcregrep</b> command (8-bit only)
1.1 misho 171: pcrejit discussion of the just-in-time optimization support
172: pcrelimits details of size and other limits
173: pcrematching discussion of the two matching algorithms
174: pcrepartial details of the partial matching facility
175: pcrepattern syntax and semantics of supported regular expressions
176: pcreperform discussion of performance issues
1.1.1.2 misho 177: pcreposix the POSIX-compatible C API for the 8-bit library
1.1 misho 178: pcreprecompile details of saving and re-using precompiled patterns
179: pcresample discussion of the pcredemo program
180: pcrestack discussion of stack usage
181: pcresyntax quick syntax reference
182: pcretest description of the <b>pcretest</b> testing command
1.1.1.3 misho 183: pcreunicode discussion of Unicode and UTF-8/16/32 support
1.1 misho 184: </pre>
185: In addition, in the "man" and HTML formats, there is a short page for each
1.1.1.3 misho 186: C library function, listing its arguments and results.
1.1 misho 187: </P>
1.1.1.3 misho 188: <br><a name="SEC4" href="#TOC1">AUTHOR</a><br>
1.1 misho 189: <P>
190: Philip Hazel
191: <br>
192: University Computing Service
193: <br>
194: Cambridge CB2 3QH, England.
195: <br>
196: </P>
197: <P>
198: Putting an actual email address here seems to have been a spam magnet, so I've
199: taken it away. If you want to email me, use my two initials, followed by the
200: two digits 10, at the domain cam.ac.uk.
201: </P>
1.1.1.3 misho 202: <br><a name="SEC5" href="#TOC1">REVISION</a><br>
1.1 misho 203: <P>
1.1.1.3 misho 204: Last updated: 13 May 2013
1.1 misho 205: <br>
1.1.1.3 misho 206: Copyright © 1997-2013 University of Cambridge.
1.1 misho 207: <br>
208: <p>
209: Return to the <a href="index.html">PCRE index page</a>.
210: </p>
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