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PCRE(3)                                                                PCRE(3)

       PCRE - Perl-compatible regular expressions


       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

       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  explic-
       itly 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  advan-
       tages.  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:

       Details of exactly which Perl regular expression features are and are not supported by PCRE are given in  sepa-
       rate 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() func-
       tion 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.


       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  sec-
       tions 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.


       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


       Last updated: 24 August 2011
       Copyright (c) 1997-2011 University of Cambridge.