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.

       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 differ-
       ences 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  gen-
       eral  category properties. However, UTF-8/16 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 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 contribu-
       tions 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 separate documents. See the pcrepat-
       tern  and pcrecompat pages. There is a syntax summary in the pcresyntax

       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 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-

         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.


       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.


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