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.TH PCRE 3	.TH PCRE 3 "13 May 2013" "PCRE 8.33"
.SH NAME	.SH NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions
.SH INTRODUCTION	.SH INTRODUCTION
Line 11 appeared in Perl are also available using the Python s	Line 11 appeared in Perl are also available using the Python s
support for one or two .NET and Oniguruma syntax items, and there is an option	support for one or two .NET and Oniguruma syntax items, and there is an option
for requesting some minor changes that give better JavaScript compatibility.	for requesting some minor changes that give better JavaScript compatibility.
.P	.P
	Starting with release 8.30, it is possible to compile two separate PCRE
	libraries: the original, which supports 8-bit character strings (including
	UTF-8 strings), and a second library that supports 16-bit character strings
	(including UTF-16 strings). The build process allows either one or both to be
	built. The majority of the work to make this possible was done by Zoltan
	Herczeg.
	.P
	Starting with release 8.32 it is possible to compile a third separate PCRE
	library that supports 32-bit character strings (including UTF-32 strings). The
	build process allows any combination of the 8-, 16- and 32-bit libraries. The
	work to make this possible was done by Christian Persch.
	.P
	The three libraries contain identical sets of functions, except that the names
	in the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP, and the
	names in the 32-bit library start with \fBpcre32_\fP instead of \fBpcre_\fP. To
	avoid over-complication and reduce the documentation maintenance load, most of
	the documentation describes the 8-bit library, with the differences for the
	16-bit and 32-bit libraries described separately in the
	.\" HREF
	\fBpcre16\fP
	and
	.\" HREF
	\fBpcre32\fP
	.\"
	pages. References to functions or structures of the form \fIpcre[16\|32]_xxx\fP
	should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library,
	\fIpcre16_xxx\fP when using the 16-bit library, or \fIpcre32_xxx\fP when using
	the 32-bit library".
	.P
The current implementation of PCRE corresponds approximately with Perl 5.12,	The current implementation of PCRE corresponds approximately with Perl 5.12,
including support for UTF-8 encoded strings and Unicode general category	including support for UTF-8/16/32 encoded strings and Unicode general category
properties. However, UTF-8 and Unicode support has to be explicitly enabled; it	properties. However, UTF-8/16/32 and Unicode support has to be explicitly
is not the default. The Unicode tables correspond to Unicode release 6.0.0.	enabled; it is not the default. The Unicode tables correspond to Unicode
	release 6.2.0.
.P	.P
In addition to the Perl-compatible matching function, PCRE contains an	In addition to the Perl-compatible matching function, PCRE contains an
alternative function that matches the same compiled patterns in a different	alternative function that matches the same compiled patterns in a different
Line 27 page.	Line 57 page.
.P	.P
PCRE is written in C and released as a C library. A number of people have	PCRE is written in C and released as a C library. A number of people have
written wrappers and interfaces of various kinds. In particular, Google Inc.	written wrappers and interfaces of various kinds. In particular, Google Inc.
have provided a comprehensive C++ wrapper. This is now included as part of the	have provided a comprehensive C++ wrapper for the 8-bit library. This is now
PCRE distribution. The	included as part of the PCRE distribution. The
.\" HREF	.\" HREF
\fBpcrecpp\fP	\fBpcrecpp\fP
.\"	.\"
Line 38 in the \fIContrib\fP directory at the primary FTP site	Line 68 in the \fIContrib\fP directory at the primary FTP site
.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">	.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">
.\" </a>	.\" </a>
ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre	ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
	.\"
.P	.P
Details of exactly which Perl regular expression features are and are not	Details of exactly which Perl regular expression features are and are not
supported by PCRE are given in separate documents. See the	supported by PCRE are given in separate documents. See the
Line 65 available. The features themselves are described in th	Line 96 available. The features themselves are described in th
\fBpcrebuild\fP	\fBpcrebuild\fP
.\"	.\"
page. Documentation about building PCRE for various operating systems can be	page. Documentation about building PCRE for various operating systems can be
found in the \fBREADME\fP and \fBNON-UNIX-USE\fP files in the source	found in the
distribution.	.\" HTML <a href="README.txt">
	.\" </a>
	\fBREADME\fP
	.\"
	and
	.\" HTML <a href="NON-AUTOTOOLS-BUILD.txt">
	.\" </a>
	\fBNON-AUTOTOOLS_BUILD\fP
	.\"
	files in the source distribution.
.P	.P
The library contains a number of undocumented internal functions and data	The libraries contains a number of undocumented internal functions and data
tables that are used by more than one of the exported external functions, but	tables that are used by more than one of the exported external functions, but
which are not intended for use by external callers. Their names all begin with	which are not intended for use by external callers. Their names all begin with
"_pcre_", which hopefully will not provoke any name clashes. In some	"_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name
environments, it is possible to control which external symbols are exported	clashes. In some environments, it is possible to control which external symbols
when a shared library is built, and in these cases the undocumented symbols are	are exported when a shared library is built, and in these cases the
not exported.	undocumented symbols are not exported.
.	.
.	.
	.SH "SECURITY CONSIDERATIONS"
	.rs
	.sp
	If you are using PCRE in a non-UTF application that permits users to supply
	arbitrary patterns for compilation, you should be aware of a feature that
	allows users to turn on UTF support from within a pattern, provided that PCRE
	was built with UTF support. For example, an 8-bit pattern that begins with
	"(UTF8)" or "(UTF)" turns on UTF-8 mode, which interprets patterns and
	subjects as strings of UTF-8 characters instead of individual 8-bit characters.
	This causes both the pattern and any data against which it is matched to be
	checked for UTF-8 validity. If the data string is very long, such a check might
	use sufficiently many resources as to cause your application to lose
	performance.
	.P
	One way of guarding against this possibility is to use the
	\fBpcre_fullinfo()\fP function to check the compiled pattern's options for UTF.
	Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at
	compile time. This causes an compile time error if a pattern contains a
	UTF-setting sequence.
	.P
	If your application is one that supports UTF, be aware that validity checking
	can take time. If the same data string is to be matched many times, you can use
	the PCRE_NO_UTF[8\|16\|32]_CHECK option for the second and subsequent matches to
	save redundant checks.
	.P
	Another way that performance can be hit is by running a pattern that has a very
	large search tree against a string that will never match. Nested unlimited
	repeats in a pattern are a common example. PCRE provides some protection
	against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the
	.\" HREF
	\fBpcreapi\fP
	.\"
	page.
	.
	.
.SH "USER DOCUMENTATION"	.SH "USER DOCUMENTATION"
.rs	.rs
.sp	.sp
Line 88 of searching. The sections are as follows:	Line 163 of searching. The sections are as follows:
.sp	.sp
pcre this document	pcre this document
pcre-config show PCRE installation configuration information	pcre-config show PCRE installation configuration information
	pcre16 details of the 16-bit library
	pcre32 details of the 32-bit library
pcreapi details of PCRE's native C API	pcreapi details of PCRE's native C API
pcrebuild options for building PCRE	pcrebuild building PCRE
pcrecallout details of the callout feature	pcrecallout details of the callout feature
pcrecompat discussion of Perl compatibility	pcrecompat discussion of Perl compatibility
pcrecpp details of the C++ wrapper	pcrecpp details of the C++ wrapper for the 8-bit library
pcredemo a demonstration C program that uses PCRE	pcredemo a demonstration C program that uses PCRE
pcregrep description of the \fBpcregrep\fP command	pcregrep description of the \fBpcregrep\fP command (8-bit only)
pcrejit discussion of the just-in-time optimization support	pcrejit discussion of the just-in-time optimization support
pcrelimits details of size and other limits	pcrelimits details of size and other limits
pcrematching discussion of the two matching algorithms	pcrematching discussion of the two matching algorithms
Line 103 of searching. The sections are as follows:	Line 180 of searching. The sections are as follows:
pcrepattern syntax and semantics of supported	pcrepattern syntax and semantics of supported
regular expressions	regular expressions
pcreperform discussion of performance issues	pcreperform discussion of performance issues
pcreposix the POSIX-compatible C API	pcreposix the POSIX-compatible C API for the 8-bit library
pcreprecompile details of saving and re-using precompiled patterns	pcreprecompile details of saving and re-using precompiled patterns
pcresample discussion of the pcredemo program	pcresample discussion of the pcredemo program
pcrestack discussion of stack usage	pcrestack discussion of stack usage
pcresyntax quick syntax reference	pcresyntax quick syntax reference
pcretest description of the \fBpcretest\fP testing command	pcretest description of the \fBpcretest\fP testing command
pcreunicode discussion of Unicode and UTF-8 support	pcreunicode discussion of Unicode and UTF-8/16/32 support
.sp	.sp
In addition, in the "man" and HTML formats, there is a short page for each	In addition, in the "man" and HTML formats, there is a short page for each
C library function, listing its arguments and results.	C library function, listing its arguments and results.
Line 133 two digits 10, at the domain cam.ac.uk.	Line 210 two digits 10, at the domain cam.ac.uk.
.rs	.rs
.sp	.sp
.nf	.nf
Last updated: 24 August 2011	Last updated: 13 May 2013
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2013 University of Cambridge.
.fi	.fi

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