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<title>pcre specification</title>
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<h1>pcre man page</h1>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
<p>
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.
<br>
<ul>
<li><a name="TOC1" href="#SEC1">INTRODUCTION</a>
<li><a name="TOC2" href="#SEC2">USER DOCUMENTATION</a>
<li><a name="TOC3" href="#SEC3">AUTHOR</a>
<li><a name="TOC4" href="#SEC4">REVISION</a>
</ul>
<br><a name="SEC1" href="#TOC1">INTRODUCTION</a><br>
<P>
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.
</P>
<P>
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.
</P>
<P>
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
<a href="pcrematching.html"><b>pcrematching</b></a>
page.
</P>
<P>
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
<a href="pcrecpp.html"><b>pcrecpp</b></a>
page has details of this interface. Other people's contributions can be found
in the <i>Contrib</i> directory at the primary FTP site, which is:
<a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre</a>
</P>
<P>
Details of exactly which Perl regular expression features are and are not
supported by PCRE are given in separate documents. See the
<a href="pcrepattern.html"><b>pcrepattern</b></a>
and
<a href="pcrecompat.html"><b>pcrecompat</b></a>
pages. There is a syntax summary in the
<a href="pcresyntax.html"><b>pcresyntax</b></a>
page.
</P>
<P>
Some features of PCRE can be included, excluded, or changed when the library is
built. The
<a href="pcre_config.html"><b>pcre_config()</b></a>
function makes it possible for a client to discover which features are
available. The features themselves are described in the
<a href="pcrebuild.html"><b>pcrebuild</b></a>
page. Documentation about building PCRE for various operating systems can be
found in the <b>README</b> and <b>NON-UNIX-USE</b> files in the source
distribution.
</P>
<P>
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.
</P>
<br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br>
<P>
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 <b>pcredemo</b> section, are concatenated, for ease
of searching. The sections are as follows:
<pre>
  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 <b>pcregrep</b> 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 <b>pcretest</b> testing command
  pcreunicode       discussion of Unicode and UTF-8 support
</pre>
In addition, in the "man" and HTML formats, there is a short page for each
C library function, listing its arguments and results.
</P>
<br><a name="SEC3" href="#TOC1">AUTHOR</a><br>
<P>
Philip Hazel
<br>
University Computing Service
<br>
Cambridge CB2 3QH, England.
<br>
</P>
<P>
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.
</P>
<br><a name="SEC4" href="#TOC1">REVISION</a><br>
<P>
Last updated: 24 August 2011
<br>
Copyright &copy; 1997-2011 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.
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