PCRE(3)PCRE(3)NAME
PCRE - Perl-compatible regular expressions
INTRODUCTION
The PCRE library is a set of functions that implement regular expres‐
sion pattern matching using the same syntax and semantics as Perl, with
just a few differences. Some features that appeared in Python and PCRE
before they appeared in Perl are also available using the Python syn‐
tax, there is some 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.
The current implementation of PCRE corresponds approximately with Perl
5.12, including support for UTF-8 encoded strings and Unicode general
category properties. However, UTF-8 and Unicode support has to be
explicitly enabled; it is not the default. The Unicode tables corre‐
spond to Unicode release 6.0.0.
In addition to the Perl-compatible matching function, PCRE contains an
alternative function that matches the same compiled patterns in a dif‐
ferent way. In certain circumstances, the alternative function has some
advantages. For a discussion of the two matching algorithms, see the
pcrematching page.
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. have provided a comprehensive C++ wrapper. This is now
included as part of the PCRE distribution. The pcrecpp page has details
of this interface. Other people's contributions can be found in the
Contrib directory at the primary FTP site, which is:
ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
Details of exactly which Perl regular expression features are and are
not supported by PCRE are given in separate documents. See the pcrepat‐
tern and pcrecompat pages. There is a syntax summary in the pcresyntax
page.
Some features of PCRE can be included, excluded, or changed when the
library is built. The pcre_config() function makes it possible for a
client to discover which features are available. The features them‐
selves are described in the pcrebuild page. Documentation about build‐
ing PCRE for various operating systems can be found in the README and
NON-UNIX-USE files in the source distribution.
The library contains a number of undocumented internal functions and
data 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 "_pcre_", which hopefully will not provoke
any name clashes. In some environments, it is possible to control which
external symbols are exported when a shared library is built, and in
these cases the undocumented symbols are not exported.
USER DOCUMENTATION
The user documentation for PCRE comprises a number of different sec‐
tions. In the "man" format, each of these is a separate "man page". In
the HTML format, each is a separate page, linked from the index page.
In the plain text format, all the sections, except the pcredemo sec‐
tion, are concatenated, for ease of searching. The sections are as fol‐
lows:
pcre this document
pcre-config show PCRE installation configuration information
pcreapi details of PCRE's native C API
pcrebuild options for building PCRE
pcrecallout details of the callout feature
pcrecompat discussion of Perl compatibility
pcrecpp details of the C++ wrapper
pcredemo a demonstration C program that uses PCRE
pcregrep description of the pcregrep command
pcrejit discussion of the just-in-time optimization support
pcrelimits details of size and other limits
pcrematching discussion of the two matching algorithms
pcrepartial details of the partial matching facility
pcrepattern syntax and semantics of supported
regular expressions
pcreperform discussion of performance issues
pcreposix the POSIX-compatible C API
pcreprecompile details of saving and re-using precompiled patterns
pcresample discussion of the pcredemo program
pcrestack discussion of stack usage
pcresyntax quick syntax reference
pcretest description of the pcretest testing command
pcreunicode discussion of Unicode and UTF-8 support
In addition, in the "man" and HTML formats, there is a short page for
each C library function, listing its arguments and results.
AUTHOR
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
Putting an actual email address here seems to have been a spam magnet,
so I've taken it away. If you want to email me, use my two initials,
followed by the two digits 10, at the domain cam.ac.uk.
REVISION
Last updated: 24 August 2011
Copyright (c) 1997-2011 University of Cambridge.
PCRE(3)
