.TH PCRE 3 "10 January 2012" "PCRE 8.30"
.SH NAME
PCRE - Perl-compatible regular expressions
.SH INTRODUCTION
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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
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.
.P
The two libraries contain identical sets of functions, except that the names in
the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP. 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
.\" HREF
\fBpcre16\fP
.\"
page. References to functions or structures of the form \fIpcre[16]_xxx\fP
should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library and
\fIpcre16_xxx\fP when using the 16-bit library".
.P
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.
.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
.\" HREF
\fBpcrematching\fP
.\"
page.
.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 for the 8-bit library. This is now
included as part of the PCRE distribution. The
.\" HREF
\fBpcrecpp\fP
.\"
page has details of this interface. Other people's contributions can be found
in the \fIContrib\fP directory at the primary FTP site, which is:
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.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">
.\" </a>
ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
.P
Details of exactly which Perl regular expression features are and are not
supported by PCRE are given in separate documents. See the
.\" HREF
\fBpcrepattern\fP
.\"
and
.\" HREF
\fBpcrecompat\fP
.\"
pages. There is a syntax summary in the
.\" HREF
\fBpcresyntax\fP
.\"
page.
.P
Some features of PCRE can be included, excluded, or changed when the library is
built. The
.\" HREF
\fBpcre_config()\fP
.\"
function makes it possible for a client to discover which features are
available. The features themselves are described in the
.\" HREF
\fBpcrebuild\fP
.\"
page. Documentation about building PCRE for various operating systems can be
found in the \fBREADME\fP and \fBNON-UNIX-USE\fP files in the source
distribution.
.P
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.
.
.
.SH "USER DOCUMENTATION"
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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 \fBpcredemo\fP section, are concatenated, for ease
of searching. The sections are as follows:
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  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 \fBpcregrep\fP 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
.\" JOIN
  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 \fBpcretest\fP testing command
  pcreunicode       discussion of Unicode and UTF-8/16 support
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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.
.
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.SH AUTHOR
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Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
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.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.
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.SH REVISION
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Last updated: 10 January 2012
Copyright (c) 1997-2012 University of Cambridge.
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