# pcre man page

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This page is part of the PCRE HTML documentation. It was generated automatically from the original man page. If there is any nonsense in it, please consult the man page, in case the conversion went wrong.

- INTRODUCTION
- USER DOCUMENTATION
- AUTHOR
- REVISION

INTRODUCTION

The PCRE library is a set of functions that implement regular expression 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 syntax, 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 correspond 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 different 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 pcrepattern 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 themselves are described in the pcrebuild page. Documentation about building 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 sections. 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 section, are concatenated, for ease of searching. The sections are as follows:

      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 © 1997-2011 University of Cambridge.

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