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

Diff of /code/trunk/doc/html/pcre.html

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

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 Line 23  man page, in case the conversion went wr
23  <P>  <P>
24  The PCRE library is a set of functions that implement regular expression  The PCRE library is a set of functions that implement regular expression
25  pattern matching using the same syntax and semantics as Perl, with just a few  pattern matching using the same syntax and semantics as Perl, with just a few
26  differences. The current implementation of PCRE (release 6.x) corresponds  differences. (Certain features that appeared in Python and PCRE before they
27  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.  
28  </P>  </P>
29  <P>  <P>
30  In addition to the Perl-compatible matching function, PCRE also contains an  The current implementation of PCRE (release 7.x) corresponds approximately with
31    Perl 5.10, including support for UTF-8 encoded strings and Unicode general
32    category properties. However, UTF-8 and Unicode support has to be explicitly
33    enabled; it is not the default. The Unicode tables correspond to Unicode
34    release 5.0.0.
35    </P>
36    <P>
37    In addition to the Perl-compatible matching function, PCRE contains an
38  alternative matching function that matches the same compiled patterns in a  alternative matching function that matches the same compiled patterns in a
39  different way. In certain circumstances, the alternative function has some  different way. In certain circumstances, the alternative function has some
40  advantages. For a discussion of the two matching algorithms, see the  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
73  The library contains a number of undocumented internal functions and data  The library contains a number of undocumented internal functions and data
74  tables that are used by more than one of the exported external functions, but  tables that are used by more than one of the exported external functions, but
75  which are not intended for use by external callers. Their names all begin with  which are not intended for use by external callers. Their names all begin with
76  "_pcre_", which hopefully will not provoke any name clashes.  "_pcre_", which hopefully will not provoke any name clashes. In some
77    environments, it is possible to control which external symbols are exported
78    when a shared library is built, and in these cases the undocumented symbols are
79    not exported.
80  </P>  </P>
81  <br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br>  <br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br>
82  <P>  <P>
# Line 92  follows: Line 100  follows:
100    pcreposix         the POSIX-compatible C API    pcreposix         the POSIX-compatible C API
101    pcreprecompile    details of saving and re-using precompiled patterns    pcreprecompile    details of saving and re-using precompiled patterns
102    pcresample        discussion of the sample program    pcresample        discussion of the sample program
103      pcrestack         discussion of stack usage
104    pcretest          description of the <b>pcretest</b> testing command    pcretest          description of the <b>pcretest</b> testing command
105  </pre>  </pre>
106  In addition, in the "man" and HTML formats, there is a short page for each  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
119  distribution and the  distribution and the
120  <a href="pcrebuild.html"><b>pcrebuild</b></a>  <a href="pcrebuild.html"><b>pcrebuild</b></a>
121  documentation for details). In these cases the limit is substantially larger.  documentation for details). In these cases the limit is substantially larger.
122  However, the speed of execution will be slower.  However, the speed of execution is slower.
123    </P>
124    <P>
125    All values in repeating quantifiers must be less than 65536. The maximum
126    compiled length of subpattern with an explicit repeat count is 30000 bytes. The
127    maximum number of capturing subpatterns is 65535.
128  </P>  </P>
129  <P>  <P>
130  All values in repeating quantifiers must be less than 65536.  There is no limit to the number of parenthesized subpatterns, but there can be
131  The maximum number of capturing subpatterns is 65535.  no more than 65535 capturing subpatterns.
132  </P>  </P>
133  <P>  <P>
134  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
135  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.  
136  </P>  </P>
137  <P>  <P>
138  The maximum length of a subject string is the largest positive number that an  The maximum length of a subject string is the largest positive number that an
139  integer variable can hold. However, when using the traditional matching  integer variable can hold. However, when using the traditional matching
140  function, PCRE uses recursion to handle subpatterns and indefinite repetition.  function, PCRE uses recursion to handle subpatterns and indefinite repetition.
141  This means that the available stack space may limit the size of a subject  This means that the available stack space may limit the size of a subject
142  string that can be processed by certain patterns.  string that can be processed by certain patterns. For a discussion of stack
143    issues, see the
144    <a href="pcrestack.html"><b>pcrestack</b></a>
145    documentation.
146  <a name="utf8support"></a></P>  <a name="utf8support"></a></P>
147  <br><a name="SEC4" href="#TOC1">UTF-8 AND UNICODE PROPERTY SUPPORT</a><br>  <br><a name="SEC4" href="#TOC1">UTF-8 AND UNICODE PROPERTY SUPPORT</a><br>
148  <P>  <P>
# Line 146  instead of just strings of bytes. Line 162  instead of just strings of bytes.
162  <P>  <P>
163  If you compile PCRE with UTF-8 support, but do not use it at run time, the  If you compile PCRE with UTF-8 support, but do not use it at run time, the
164  library will be a bit bigger, but the additional run time overhead is limited  library will be a bit bigger, but the additional run time overhead is limited
165  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.
166  </P>  </P>
167  <P>  <P>
168  If PCRE is built with Unicode character property support (which implies UTF-8  If PCRE is built with Unicode character property support (which implies UTF-8
169  support), the escape sequences \p{..}, \P{..}, and \X are supported.  support), the escape sequences \p{..}, \P{..}, and \X are supported.
170  The available properties that can be tested are limited to the general  The available properties that can be tested are limited to the general
171  category properties such as Lu for an upper case letter or Nd for a decimal  category properties such as Lu for an upper case letter or Nd for a decimal
172  number. A full list is given in the  number, the Unicode script names such as Arabic or Han, and the derived
173    properties Any and L&. A full list is given in the
174  <a href="pcrepattern.html"><b>pcrepattern</b></a>  <a href="pcrepattern.html"><b>pcrepattern</b></a>
175  documentation. The PCRE library is increased in size by about 90K when Unicode  documentation. Only the short names for properties are supported. For example,
176  property support is included.  \p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported.
177    Furthermore, in Perl, many properties may optionally be prefixed by "Is", for
178    compatibility with Perl 5.6. PCRE does not support this.
179  </P>  </P>
180  <P>  <P>
181  The following comments apply when PCRE is running in UTF-8 mode:  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
193  may crash.  may crash.
194  </P>  </P>
195  <P>  <P>
196  2. In a pattern, the escape sequence \x{...}, where the contents of the braces  2. An unbraced hexadecimal escape sequence (such as \xb3) matches a two-byte
197  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.  
198  </P>  </P>
199  <P>  <P>
200  3. The original hexadecimal escape sequence, \xhh, matches a two-byte UTF-8  3. Octal numbers up to \777 are recognized, and match two-byte UTF-8
201  character if the value is greater than 127.  characters for values greater than \177.
202  </P>  </P>
203  <P>  <P>
204  4. Repeat quantifiers apply to complete UTF-8 characters, not to individual  4. 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
231  property support is available, PCRE still uses its own character tables when  property support is available, PCRE still uses its own character tables when
232  checking the case of low-valued characters, so as not to degrade performance.  checking the case of low-valued characters, so as not to degrade performance.
233  The Unicode property information is used only for characters with higher  The Unicode property information is used only for characters with higher
234  values.  values. Even when Unicode property support is available, PCRE supports
235    case-insensitive matching only when there is a one-to-one mapping between a
236    letter's cases. There are a small number of many-to-one mappings in Unicode;
237    these are not supported by PCRE.
238  </P>  </P>
239  <br><a name="SEC5" href="#TOC1">AUTHOR</a><br>  <br><a name="SEC5" href="#TOC1">AUTHOR</a><br>
240  <P>  <P>
# Line 224  Philip Hazel Line 242  Philip Hazel
242  <br>  <br>
243  University Computing Service,  University Computing Service,
244  <br>  <br>
245  Cambridge CB2 3QG, England.  Cambridge CB2 3QH, England.
246  </P>  </P>
247  <P>  <P>
248  Putting an actual email address here seems to have been a spam magnet, so I've  Putting an actual email address here seems to have been a spam magnet, so I've
249  taken it away. If you want to email me, use my initial and surname, separated  taken it away. If you want to email me, use my initial and surname, separated
250  by a dot, at the domain ucs.cam.ac.uk.  by a dot, at the domain ucs.cam.ac.uk.
251  Last updated: 07 March 2005  Last updated: 23 November 2006
252  <br>  <br>
253  Copyright &copy; 1997-2005 University of Cambridge.  Copyright &copy; 1997-2006 University of Cambridge.
254  <p>  <p>
255  Return to the <a href="index.html">PCRE index page</a>.  Return to the <a href="index.html">PCRE index page</a>.
256  </p>  </p>

Legend:
Removed from v.77  
changed lines
  Added in v.96

  ViewVC Help
Powered by ViewVC 1.1.5