Annotation of embedaddon/pcre/doc/pcre.3, revision 1.1.1.4
1.1.1.4 ! misho 1: .TH PCRE 3 "13 May 2013" "PCRE 8.33"
1.1 misho 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
1.1.1.2 misho 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
1.1.1.4 ! misho 21: Starting with release 8.32 it is possible to compile a third separate PCRE
! 22: library that supports 32-bit character strings (including UTF-32 strings). The
! 23: build process allows any combination of the 8-, 16- and 32-bit libraries. The
! 24: 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
1.1.1.2 misho 32: .\" HREF
33: \fBpcre16\fP
1.1.1.4 ! misho 34: and
! 35: .\" HREF
! 36: \fBpcre32\fP
1.1.1.2 misho 37: .\"
1.1.1.4 ! misho 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".
1.1.1.2 misho 42: .P
1.1 misho 43: The current implementation of PCRE corresponds approximately with Perl 5.12,
1.1.1.4 ! misho 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.
1.1 misho 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.
1.1.1.2 misho 60: have provided a comprehensive C++ wrapper for the 8-bit library. This is now
61: included as part of the PCRE distribution. The
1.1 misho 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
1.1.1.4 ! misho 71: .\"
1.1 misho 72: .P
73: Details of exactly which Perl regular expression features are and are not
74: supported by PCRE are given in separate documents. See the
75: .\" HREF
76: \fBpcrepattern\fP
77: .\"
78: and
79: .\" HREF
80: \fBpcrecompat\fP
81: .\"
82: pages. There is a syntax summary in the
83: .\" HREF
84: \fBpcresyntax\fP
85: .\"
86: page.
87: .P
88: Some features of PCRE can be included, excluded, or changed when the library is
89: built. The
90: .\" HREF
91: \fBpcre_config()\fP
92: .\"
93: function makes it possible for a client to discover which features are
94: available. The features themselves are described in the
95: .\" HREF
96: \fBpcrebuild\fP
97: .\"
98: page. Documentation about building PCRE for various operating systems can be
1.1.1.4 ! misho 99: found in the
! 100: .\" HTML <a href="README.txt">
! 101: .\" </a>
! 102: \fBREADME\fP
! 103: .\"
! 104: and
! 105: .\" HTML <a href="NON-AUTOTOOLS-BUILD.txt">
! 106: .\" </a>
! 107: \fBNON-AUTOTOOLS_BUILD\fP
! 108: .\"
! 109: files in the source distribution.
1.1 misho 110: .P
1.1.1.2 misho 111: The libraries contains a number of undocumented internal functions and data
1.1 misho 112: tables that are used by more than one of the exported external functions, but
113: which are not intended for use by external callers. Their names all begin with
1.1.1.4 ! misho 114: "_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name
! 115: clashes. In some environments, it is possible to control which external symbols
! 116: are exported when a shared library is built, and in these cases the
! 117: undocumented symbols are not exported.
! 118: .
! 119: .
! 120: .SH "SECURITY CONSIDERATIONS"
! 121: .rs
! 122: .sp
! 123: If you are using PCRE in a non-UTF application that permits users to supply
! 124: arbitrary patterns for compilation, you should be aware of a feature that
! 125: allows users to turn on UTF support from within a pattern, provided that PCRE
! 126: was built with UTF support. For example, an 8-bit pattern that begins with
! 127: "(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and
! 128: subjects as strings of UTF-8 characters instead of individual 8-bit characters.
! 129: This causes both the pattern and any data against which it is matched to be
! 130: checked for UTF-8 validity. If the data string is very long, such a check might
! 131: use sufficiently many resources as to cause your application to lose
! 132: performance.
! 133: .P
! 134: One way of guarding against this possibility is to use the
! 135: \fBpcre_fullinfo()\fP function to check the compiled pattern's options for UTF.
! 136: Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at
! 137: compile time. This causes an compile time error if a pattern contains a
! 138: UTF-setting sequence.
! 139: .P
! 140: If your application is one that supports UTF, be aware that validity checking
! 141: can take time. If the same data string is to be matched many times, you can use
! 142: the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to
! 143: save redundant checks.
! 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: .\" HREF
! 150: \fBpcreapi\fP
! 151: .\"
! 152: page.
1.1 misho 153: .
154: .
155: .SH "USER DOCUMENTATION"
156: .rs
157: .sp
158: The user documentation for PCRE comprises a number of different sections. In
159: the "man" format, each of these is a separate "man page". In the HTML format,
160: each is a separate page, linked from the index page. In the plain text format,
161: all the sections, except the \fBpcredemo\fP section, are concatenated, for ease
162: of searching. The sections are as follows:
163: .sp
164: pcre this document
165: pcre-config show PCRE installation configuration information
1.1.1.4 ! misho 166: pcre16 details of the 16-bit library
! 167: pcre32 details of the 32-bit library
1.1 misho 168: pcreapi details of PCRE's native C API
1.1.1.4 ! misho 169: pcrebuild building PCRE
1.1 misho 170: pcrecallout details of the callout feature
171: pcrecompat discussion of Perl compatibility
1.1.1.2 misho 172: pcrecpp details of the C++ wrapper for the 8-bit library
1.1 misho 173: pcredemo a demonstration C program that uses PCRE
1.1.1.2 misho 174: pcregrep description of the \fBpcregrep\fP command (8-bit only)
1.1 misho 175: pcrejit discussion of the just-in-time optimization support
176: pcrelimits details of size and other limits
177: pcrematching discussion of the two matching algorithms
178: pcrepartial details of the partial matching facility
179: .\" JOIN
180: pcrepattern syntax and semantics of supported
181: regular expressions
182: pcreperform discussion of performance issues
1.1.1.2 misho 183: pcreposix the POSIX-compatible C API for the 8-bit library
1.1 misho 184: pcreprecompile details of saving and re-using precompiled patterns
185: pcresample discussion of the pcredemo program
186: pcrestack discussion of stack usage
187: pcresyntax quick syntax reference
188: pcretest description of the \fBpcretest\fP testing command
1.1.1.4 ! misho 189: pcreunicode discussion of Unicode and UTF-8/16/32 support
1.1 misho 190: .sp
191: In addition, in the "man" and HTML formats, there is a short page for each
1.1.1.4 ! misho 192: C library function, listing its arguments and results.
1.1 misho 193: .
194: .
195: .SH AUTHOR
196: .rs
197: .sp
198: .nf
199: Philip Hazel
200: University Computing Service
201: Cambridge CB2 3QH, England.
202: .fi
203: .P
204: Putting an actual email address here seems to have been a spam magnet, so I've
205: taken it away. If you want to email me, use my two initials, followed by the
206: two digits 10, at the domain cam.ac.uk.
207: .
208: .
209: .SH REVISION
210: .rs
211: .sp
212: .nf
1.1.1.4 ! misho 213: Last updated: 13 May 2013
! 214: Copyright (c) 1997-2013 University of Cambridge.
1.1 misho 215: .fi
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