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

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-revision 77 by nigel,
Sat Feb 24 21:40:45 2007 UTC
+revision 96 by nigel,
Fri Mar  2 13:10:43 2007 UTC
 Line 23 
 man page, in case the conversion went wr
  <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 6.x) corresponds
+ differences. (Certain features that appeared in Python and PCRE before they
- approximately with Perl 5.8, including support for UTF-8 encoded strings and
+ appeared in Perl are also available using the Python syntax.)
- Unicode general category properties. However, this support has to be explicitly
- enabled; it is not the default.
  </P>
  <P>
- In addition to the Perl-compatible matching function, PCRE also contains an
+ The current implementation of PCRE (release 7.x) corresponds approximately with
+ Perl 5.10, 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 5.0.0.
+ </P>
+ <P>
+ In addition to the Perl-compatible matching function, PCRE contains an
  alternative matching 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
-Line 68 
 found in the <b>README</b> file in the s
+Line 73 
 found in the <b>README</b> file in the s
  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.
+ "_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>
-Line 92 
 follows:
+Line 100 
 follows:
    pcreposix         the POSIX-compatible C API
    pcreprecompile    details of saving and re-using precompiled patterns
    pcresample        discussion of the sample program
+   pcrestack         discussion of stack usage
    pcretest          description of the <b>pcretest</b> testing command
  </pre>
  In addition, in the "man" and HTML formats, there is a short page for each
-Line 110 
 internal linkage size of 3 or 4 (see the
+Line 119 
 internal linkage size of 3 or 4 (see the
  distribution and the
  <a href="pcrebuild.html"><b>pcrebuild</b></a>
  documentation for details). In these cases the limit is substantially larger.
- However, the speed of execution will be slower.
+ However, the speed of execution is slower.
+ </P>
+ <P>
+ All values in repeating quantifiers must be less than 65536. The maximum
+ compiled length of subpattern with an explicit repeat count is 30000 bytes. The
+ maximum number of capturing subpatterns is 65535.
  </P>
  <P>
- All values in repeating quantifiers must be less than 65536.
+ There is no limit to the number of parenthesized subpatterns, but there can be
- The maximum number of capturing subpatterns is 65535.
+ no more than 65535 capturing subpatterns.
  </P>
  <P>
- There is no limit to the number of non-capturing subpatterns, but the maximum
+ The maximum length of name for a named subpattern is 32 characters, and the
- depth of nesting of all kinds of parenthesized subpattern, including capturing
+ maximum number of named subpatterns is 10000.
- subpatterns, assertions, and other types of subpattern, is 200.
  </P>
  <P>
  The maximum length of a subject string is the largest positive number that an
  integer variable can hold. However, when using the traditional matching
  function, PCRE uses recursion to handle subpatterns and indefinite repetition.
  This means that the available stack space may limit the size of a subject
- string that can be processed by certain patterns.
+ string that can be processed by certain patterns. For a discussion of stack
+ issues, see the
+ <a href="pcrestack.html"><b>pcrestack</b></a>
+ documentation.
  <a name="utf8support"></a></P>
  <br><a name="SEC4" href="#TOC1">UTF-8 AND UNICODE PROPERTY SUPPORT</a><br>
  <P>
-Line 146 
 instead of just strings of bytes.
+Line 162 
 instead of just strings of bytes.
  <P>
  If you compile PCRE with UTF-8 support, but do not use it at run time, the
  library will be a bit bigger, but the additional run time overhead is limited
- to testing the PCRE_UTF8 flag in several places, so should not be very large.
+ to testing the PCRE_UTF8 flag occasionally, so should not be very big.
  </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
+ number, the Unicode script names such as Arabic or Han, and the derived
+ properties Any and L&. 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
+ documentation. Only the short names for properties are supported. For example,
- property support is included.
+ \p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported.
+ Furthermore, in Perl, many properties may optionally be prefixed by "Is", for
+ compatibility with Perl 5.6. PCRE does not support this.
  </P>
  <P>
  The following comments apply when PCRE is running in UTF-8 mode:
-Line 174 
 PCRE when PCRE_NO_UTF8_CHECK is set, the
+Line 193 
 PCRE when PCRE_NO_UTF8_CHECK is set, the
  may crash.
  </P>
  <P>
-. In a pattern, the escape sequence \x{...}, where the contents of the braces
+. An unbraced hexadecimal escape sequence (such as \xb3) matches a two-byte
- is a string of hexadecimal digits, is interpreted as a UTF-8 character whose
+ UTF-8 character if the value is greater than 127.
- code number is the given hexadecimal number, for example: \x{1234}. If a
- non-hexadecimal digit appears between the braces, the item is not recognized.
- This escape sequence can be used either as a literal, or within a character
- class.
  </P>
  <P>
-. The original hexadecimal escape sequence, \xhh, matches a two-byte UTF-8
+. Octal numbers up to \777 are recognized, and match two-byte UTF-8
- character if the value is greater than 127.
+ characters for values greater than \177.
  </P>
  <P>
 . Repeat quantifiers apply to complete UTF-8 characters, not to individual
-Line 216 
 than 128, unless PCRE is built with Unic
+Line 231 
 than 128, unless PCRE is built with Unic
  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.
+ values. Even when Unicode property support is available, PCRE supports
+ case-insensitive matching only when there is a one-to-one mapping between a
+ letter's cases. There are a small number of many-to-one mappings in Unicode;
+ these are not supported by PCRE.
  </P>
  <br><a name="SEC5" href="#TOC1">AUTHOR</a><br>
  <P>
-Line 224 
 Philip Hazel
+Line 242 
 Philip Hazel
  <br>
  University Computing Service,
  <br>
- Cambridge CB2 3QG, England.
+ Cambridge CB2 3QH, England.
  </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 initial and surname, separated
  by a dot, at the domain ucs.cam.ac.uk.
- Last updated: 07 March 2005
+ Last updated: 23 November 2006
  <br>
- Copyright &copy; 1997-2005 University of Cambridge.
+ Copyright &copy; 1997-2006 University of Cambridge.
  <p>
  Return to the <a href="index.html">PCRE index page</a>.
  </p>

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