/[pcre]/code/trunk/doc/html/pcre.html

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-revision 71 by nigel,
Sat Feb 24 21:40:24 2007 UTC
+revision 83 by nigel,
Sat Feb 24 21:41:06 2007 UTC
 Line 3
  <title>pcre specification</title>
  </head>
  <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
- This HTML document has been generated automatically from the original man page.
+ <h1>pcre man page</h1>
- If there is any nonsense in it, please consult the man page, in case the
+ <p>
- conversion went wrong.<br>
+ 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">DESCRIPTION</a>
+ <li><a name="TOC1" href="#SEC1">INTRODUCTION</a>
  <li><a name="TOC2" href="#SEC2">USER DOCUMENTATION</a>
  <li><a name="TOC3" href="#SEC3">LIMITATIONS</a>
- <li><a name="TOC4" href="#SEC4">UTF-8 SUPPORT</a>
+ <li><a name="TOC4" href="#SEC4">UTF-8 AND UNICODE PROPERTY SUPPORT</a>
  <li><a name="TOC5" href="#SEC5">AUTHOR</a>
  </ul>
- <br><a name="SEC1" href="#TOC1">DESCRIPTION</a><br>
+ <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. The current implementation of PCRE (release 4.x) corresponds
+ differences. The current implementation of PCRE (release 6.x) corresponds
- approximately with Perl 5.8, including support for UTF-8 encoded strings.
+ approximately with Perl 5.8, including support for UTF-8 encoded strings and
- However, this support has to be explicitly enabled; it is not the default.
+ Unicode general category properties. However, this support has to be explicitly
- </P>
+ enabled; it is not the default.
- <P>
+ </P>
- PCRE is written in C and released as a C library. However, a number of people
+ <P>
- have written wrappers and interfaces of various kinds. A C++ class is included
+ In addition to the Perl-compatible matching function, PCRE also contains an
- in these contributions, which can be found in the <i>Contrib</i> directory at
+ alternative matching function that matches the same compiled patterns in a
- the primary FTP site, which is:
+ different way. In certain circumstances, the alternative function has some
- </P>
+ 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
-Line 41 
 Some features of PCRE can be included, e
+Line 59 
 Some features of PCRE can be included, e
  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. Documentation about building PCRE for various operating systems can
+ available. The features themselves are described in the
- be found in the <b>README</b> file in the source distribution.
+ <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> file in the source distribution.
  </P>
- <br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br>
  <P>
- The user documentation for PCRE has been split up into a number of different
+ The library contains a number of undocumented internal functions and data
- sections. In the "man" format, each of these is a separate "man page". In the
+ tables that are used by more than one of the exported external functions, but
- HTML format, each is a separate page, linked from the index page. In the plain
+ which are not intended for use by external callers. Their names all begin with
- text format, all the sections are concatenated, for ease of searching. The
+ "_pcre_", which hopefully will not provoke any name clashes. In some
- sections are as follows:
+ 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 are concatenated, for ease of searching. The sections are as
+ follows:
  <pre>
    pcre              this document
-   pcreapi           details of PCRE's native API
+   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
    pcregrep          description of the <b>pcregrep</b> command
-   pcrepattern       syntax and semantics of supported
+   pcrematching      discussion of the two matching algorithms
-                       regular expressions
+   pcrepartial       details of the partial matching facility
+   pcrepattern       syntax and semantics of supported regular expressions
    pcreperform       discussion of performance issues
-   pcreposix         the POSIX-compatible API
+   pcreposix         the POSIX-compatible C API
+   pcreprecompile    details of saving and re-using precompiled patterns
    pcresample        discussion of the sample program
-   pcretest          the <b>pcretest</b> testing command
+   pcretest          description of the <b>pcretest</b> testing command
- </PRE>
+ </pre>
- </P>
- <P>
  In addition, in the "man" and HTML formats, there is a short page for each
- library function, listing its arguments and results.
+ C library function, listing its arguments and results.
  </P>
  <br><a name="SEC3" href="#TOC1">LIMITATIONS</a><br>
  <P>
-Line 84 
 regular expressions that are truly enorm
+Line 112 
 regular expressions that are truly enorm
  internal linkage size of 3 or 4 (see the <b>README</b> file in the source
  distribution and the
  <a href="pcrebuild.html"><b>pcrebuild</b></a>
- documentation for details). If these cases the limit is substantially larger.
+ documentation for details). In these cases the limit is substantially larger.
  However, the speed of execution will be slower.
  </P>
  <P>
-Line 98 
 subpatterns, assertions, and other types
+Line 126 
 subpatterns, assertions, and other types
  </P>
  <P>
  The maximum length of a subject string is the largest positive number that an
- integer variable can hold. However, PCRE uses recursion to handle subpatterns
+ integer variable can hold. However, when using the traditional matching
- and indefinite repetition. This means that the available stack space may limit
+ function, PCRE uses recursion to handle subpatterns and indefinite repetition.
- the size of a subject string that can be processed by certain patterns.
+ This means that the available stack space may limit the size of a subject
- </P>
+ string that can be processed by certain patterns.
- <a name="utf8support"></a><br><a name="SEC4" href="#TOC1">UTF-8 SUPPORT</a><br>
+ <a name="utf8support"></a></P>
- <P>
+ <br><a name="SEC4" href="#TOC1">UTF-8 AND UNICODE PROPERTY SUPPORT</a><br>
- Starting at release 3.3, PCRE has had some support for character strings
+ <P>
- encoded in the UTF-8 format. For release 4.0 this has been greatly extended to
+ From release 3.3, PCRE has had some support for character strings encoded in
- cover most common requirements.
+ the UTF-8 format. For release 4.0 this was greatly extended to cover most
+ common requirements, and in release 5.0 additional support for Unicode general
+ category properties was added.
  </P>
  <P>
  In order process UTF-8 strings, you must build PCRE to include UTF-8 support in
-Line 122 
 library will be a bit bigger, but the ad
+Line 152 
 library will be a bit bigger, but the ad
  to testing the PCRE_UTF8 flag in several places, so should not be very large.
  </P>
  <P>
+ If PCRE is built with Unicode character property support (which implies UTF-8
+ support), the escape sequences \p{..}, \P{..}, and \X are supported.
+ The available properties that can be tested are limited to the general
+ category properties such as Lu for an upper case letter or Nd for a decimal
+ number. A full list is given in the
+ <a href="pcrepattern.html"><b>pcrepattern</b></a>
+ documentation. The PCRE library is increased in size by about 90K when Unicode
+ property support is included.
+ </P>
+ <P>
  The following comments apply when PCRE is running in UTF-8 mode:
  </P>
  <P>
-Line 157 
 bytes, for example: \x{100}{3}.
+Line 197 
 bytes, for example: \x{100}{3}.
  </P>
  <P>
 . The escape sequence \C can be used to match a single byte in UTF-8 mode,
- but its use can lead to some strange effects.
+ but its use can lead to some strange effects. This facility is not available in
+ the alternative matching function, <b>pcre_dfa_exec()</b>.
  </P>
  <P>
 . The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
  test characters of any code value, but the characters that PCRE recognizes as
  digits, spaces, or word characters remain the same set as before, all with
- values less than 256.
+ values less than 256. This remains true even when PCRE includes Unicode
- </P>
+ property support, because to do otherwise would slow down PCRE in many common
- <P>
+ cases. If you really want to test for a wider sense of, say, "digit", you
-. Case-insensitive matching applies only to characters whose values are less
+ must use Unicode property tests such as \p{Nd}.
- than 256. PCRE does not support the notion of "case" for higher-valued
+ </P>
- characters.
+ <P>
- </P>
+. Similarly, characters that match the POSIX named character classes are all
- <P>
+ low-valued characters.
-. PCRE does not support the use of Unicode tables and properties or the Perl
+ </P>
- escapes \p, \P, and \X.
+ <P>
+. Case-insensitive matching applies only to characters whose values are less
+ than 128, unless PCRE is built with Unicode property support. Even when Unicode
+ property support is available, PCRE still uses its own character tables when
+ checking the case of low-valued characters, so as not to degrade performance.
+ The Unicode property information is used only for characters with higher
+ values.
  </P>
  <br><a name="SEC5" href="#TOC1">AUTHOR</a><br>
  <P>
- Philip Hazel &#60;ph10@cam.ac.uk&#62;
+ Philip Hazel
  <br>
  University Computing Service,
  <br>
  Cambridge CB2 3QG, England.
- <br>
- Phone: +44 1223 334714
  </P>
  <P>
- Last updated: 20 August 2003
+ 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 initial and surname, separated
+ by a dot, at the domain ucs.cam.ac.uk.
+ Last updated: 07 March 2005
  <br>
- Copyright &copy; 1997-2003 University of Cambridge.
+ Copyright &copy; 1997-2005 University of Cambridge.
+ <p>
+ Return to the <a href="index.html">PCRE index page</a>.
+ </p>

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