PCRE(3)                   OpenBSD Programmer's Manual                  PCRE(3)



NAME
       PCRE - Perl-compatible regular expressions

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.

       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.

       The two libraries contain identical sets of functions, except that the
       names in the 16-bit library start with pcre16_ instead of pcre_. 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 library described separately in the pcre16
       page. References to functions or structures of the form pcre[16]_xxx
       should be read as meaning "pcre_xxx when using the 8-bit library and
       pcre16_xxx when using the 16-bit library".

       The current implementation of PCRE corresponds approximately with Perl
       5.12, including support for UTF-8/16 encoded strings and Unicode
       general category properties. However, UTF-8/16 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 for the 8-bit
       library. 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 libraries 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_" or "_pcre16_", 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
         pcre16            details of the 16-bit library
         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 for the 8-bit library
         pcredemo          a demonstration C program that uses PCRE
         pcregrep          description of the pcregrep command (8-bit only)
         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 for the 8-bit library
         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-8/16 support

       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.

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: 10 January 2012
       Copyright (c) 1997-2012 University of Cambridge.



                                                                       PCRE(3)
