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.TH PCRE 3 "10 January 2012" "PCRE 8.30"	.TH PCRE 3 "01 Oct 2013" "PCRE 8.33"
.SH NAME	.SH NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions
.SH INTRODUCTION	.SH INTRODUCTION
Line 18 UTF-8 strings), and a second library that supports 16-	Line 18 UTF-8 strings), and a second library that supports 16-
built. The majority of the work to make this possible was done by Zoltan	built. The majority of the work to make this possible was done by Zoltan
Herczeg.	Herczeg.
.P	.P
The two libraries contain identical sets of functions, except that the names in	Starting with release 8.32 it is possible to compile a third separate PCRE
the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP. To avoid	library that supports 32-bit character strings (including UTF-32 strings). The
over-complication and reduce the documentation maintenance load, most of the	build process allows any combination of the 8-, 16- and 32-bit libraries. The
documentation describes the 8-bit library, with the differences for the 16-bit	work to make this possible was done by Christian Persch.
library described separately in the	.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	.\" HREF
\fBpcre16\fP	\fBpcre16\fP
	and
	.\" HREF
	\fBpcre32\fP
.\"	.\"
page. References to functions or structures of the form \fIpcre[16]_xxx\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 and	should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library,
\fIpcre16_xxx\fP when using the 16-bit library".	\fIpcre16_xxx\fP when using the 16-bit library, or \fIpcre32_xxx\fP when using
	the 32-bit library".
.P	.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-8/16 encoded strings and Unicode general category	including support for UTF-8/16/32 encoded strings and Unicode general category
properties. However, UTF-8/16 and Unicode support has to be explicitly enabled;	properties. However, UTF-8/16/32 and Unicode support has to be explicitly
it 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 6.3.0.
.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 57 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 84 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 libraries 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_" or "_pcre16_", which hopefully will not provoke any name clashes. In	"_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name
some environments, it is possible to control which external symbols are	clashes. In some environments, it is possible to control which external symbols
exported when a shared library is built, and in these cases the undocumented	are exported when a shared library is built, and in these cases the
symbols are 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 106 all the sections, except the \fBpcredemo\fP section, a	Line 162 all the sections, except the \fBpcredemo\fP section, a
of searching. The sections are as follows:	of searching. The sections are as follows:
.sp	.sp
pcre this document	pcre this document
pcre16 details of the 16-bit library
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 for the 8-bit library	pcrecpp details of the C++ wrapper for the 8-bit library
Line 129 of searching. The sections are as follows:	Line 186 of searching. The sections are as follows:
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-8/16 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
8-bit C library function, listing its arguments and results.	C library function, listing its arguments and results.
.	.
.	.
.SH AUTHOR	.SH AUTHOR
Line 153 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: 10 January 2012	Last updated: 13 May 2013
Copyright (c) 1997-2012 University of Cambridge.	Copyright (c) 1997-2013 University of Cambridge.
.fi	.fi

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