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revision 254 by ph10, Mon Sep 17 11:05:37 2007 UTC revision 392 by ph10, Tue Mar 17 21:30:30 2009 UTC
# Line 35  man page, in case the conversion went wr Line 35  man page, in case the conversion went wr
35  <li><a name="TOC20" href="#SEC20">COMMENTS</a>  <li><a name="TOC20" href="#SEC20">COMMENTS</a>
36  <li><a name="TOC21" href="#SEC21">RECURSIVE PATTERNS</a>  <li><a name="TOC21" href="#SEC21">RECURSIVE PATTERNS</a>
37  <li><a name="TOC22" href="#SEC22">SUBPATTERNS AS SUBROUTINES</a>  <li><a name="TOC22" href="#SEC22">SUBPATTERNS AS SUBROUTINES</a>
38  <li><a name="TOC23" href="#SEC23">CALLOUTS</a>  <li><a name="TOC23" href="#SEC23">ONIGURUMA SUBROUTINE SYNTAX</a>
39  <li><a name="TOC24" href="#SEC24">BACKTRACKING CONTROL</a>  <li><a name="TOC24" href="#SEC24">CALLOUTS</a>
40  <li><a name="TOC25" href="#SEC25">SEE ALSO</a>  <li><a name="TOC25" href="#SEC25">BACKTRACKING CONTROL</a>
41  <li><a name="TOC26" href="#SEC26">AUTHOR</a>  <li><a name="TOC26" href="#SEC26">SEE ALSO</a>
42  <li><a name="TOC27" href="#SEC27">REVISION</a>  <li><a name="TOC27" href="#SEC27">AUTHOR</a>
43    <li><a name="TOC28" href="#SEC28">REVISION</a>
44  </ul>  </ul>
45  <br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION DETAILS</a><br>  <br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION DETAILS</a><br>
46  <P>  <P>
47  The syntax and semantics of the regular expressions that are supported by PCRE  The syntax and semantics of the regular expressions that are supported by PCRE
48  are described in detail below. There is a quick-reference syntax summary in the  are described in detail below. There is a quick-reference syntax summary in the
49  <a href="pcresyntax.html"><b>pcresyntax</b></a>  <a href="pcresyntax.html"><b>pcresyntax</b></a>
50  page. Perl's regular expressions are described in its own documentation, and  page. PCRE tries to match Perl syntax and semantics as closely as it can. PCRE
51    also supports some alternative regular expression syntax (which does not
52    conflict with the Perl syntax) in order to provide some compatibility with
53    regular expressions in Python, .NET, and Oniguruma.
54    </P>
55    <P>
56    Perl's regular expressions are described in its own documentation, and
57  regular expressions in general are covered in a number of books, some of which  regular expressions in general are covered in a number of books, some of which
58  have copious examples. Jeffrey Friedl's "Mastering Regular Expressions",  have copious examples. Jeffrey Friedl's "Mastering Regular Expressions",
59  published by O'Reilly, covers regular expressions in great detail. This  published by O'Reilly, covers regular expressions in great detail. This
# Line 312  following the discussion of Line 319  following the discussion of
319  <a href="#subpattern">parenthesized subpatterns.</a>  <a href="#subpattern">parenthesized subpatterns.</a>
320  </P>  </P>
321  <br><b>  <br><b>
322    Absolute and relative subroutine calls
323    </b><br>
324    <P>
325    For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or
326    a number enclosed either in angle brackets or single quotes, is an alternative
327    syntax for referencing a subpattern as a "subroutine". Details are discussed
328    <a href="#onigurumasubroutines">later.</a>
329    Note that \g{...} (Perl syntax) and \g&#60;...&#62; (Oniguruma syntax) are <i>not</i>
330    synonymous. The former is a back reference; the latter is a subroutine call.
331    </P>
332    <br><b>
333  Generic character types  Generic character types
334  </b><br>  </b><br>
335  <P>  <P>
# Line 1042  application when the compile or match fu Line 1060  application when the compile or match fu
1060  pattern can contain special leading sequences to override what the application  pattern can contain special leading sequences to override what the application
1061  has set or what has been defaulted. Details are given in the section entitled  has set or what has been defaulted. Details are given in the section entitled
1062  <a href="#newlineseq">"Newline sequences"</a>  <a href="#newlineseq">"Newline sequences"</a>
1063  above.  above.
1064  <a name="subpattern"></a></P>  <a name="subpattern"></a></P>
1065  <br><a name="SEC12" href="#TOC1">SUBPATTERNS</a><br>  <br><a name="SEC12" href="#TOC1">SUBPATTERNS</a><br>
1066  <P>  <P>
# Line 1184  details of the interfaces for handling n Line 1202  details of the interfaces for handling n
1202  <a href="pcreapi.html"><b>pcreapi</b></a>  <a href="pcreapi.html"><b>pcreapi</b></a>
1203  documentation.  documentation.
1204  </P>  </P>
1205    <P>
1206    <b>Warning:</b> You cannot use different names to distinguish between two
1207    subpatterns with the same number (see the previous section) because PCRE uses
1208    only the numbers when matching.
1209    </P>
1210  <br><a name="SEC15" href="#TOC1">REPETITION</a><br>  <br><a name="SEC15" href="#TOC1">REPETITION</a><br>
1211  <P>  <P>
1212  Repetition is specified by quantifiers, which can follow any of the following  Repetition is specified by quantifiers, which can follow any of the following
# Line 1231  which may be several bytes long (and the Line 1254  which may be several bytes long (and the
1254  </P>  </P>
1255  <P>  <P>
1256  The quantifier {0} is permitted, causing the expression to behave as if the  The quantifier {0} is permitted, causing the expression to behave as if the
1257  previous item and the quantifier were not present.  previous item and the quantifier were not present. This may be useful for
1258    subpatterns that are referenced as
1259    <a href="#subpatternsassubroutines">subroutines</a>
1260    from elsewhere in the pattern. Items other than subpatterns that have a {0}
1261    quantifier are omitted from the compiled pattern.
1262  </P>  </P>
1263  <P>  <P>
1264  For convenience, the three most common quantifiers have single-character  For convenience, the three most common quantifiers have single-character
# Line 2031  changed for different calls. For example Line 2058  changed for different calls. For example
2058  </pre>  </pre>
2059  It matches "abcabc". It does not match "abcABC" because the change of  It matches "abcabc". It does not match "abcABC" because the change of
2060  processing option does not affect the called subpattern.  processing option does not affect the called subpattern.
2061    <a name="onigurumasubroutines"></a></P>
2062    <br><a name="SEC23" href="#TOC1">ONIGURUMA SUBROUTINE SYNTAX</a><br>
2063    <P>
2064    For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or
2065    a number enclosed either in angle brackets or single quotes, is an alternative
2066    syntax for referencing a subpattern as a subroutine, possibly recursively. Here
2067    are two of the examples used above, rewritten using this syntax:
2068    <pre>
2069      (?&#60;pn&#62; \( ( (?&#62;[^()]+) | \g&#60;pn&#62; )* \) )
2070      (sens|respons)e and \g'1'ibility
2071    </pre>
2072    PCRE supports an extension to Oniguruma: if a number is preceded by a
2073    plus or a minus sign it is taken as a relative reference. For example:
2074    <pre>
2075      (abc)(?i:\g&#60;-1&#62;)
2076    </pre>
2077    Note that \g{...} (Perl syntax) and \g&#60;...&#62; (Oniguruma syntax) are <i>not</i>
2078    synonymous. The former is a back reference; the latter is a subroutine call.
2079  </P>  </P>
2080  <br><a name="SEC23" href="#TOC1">CALLOUTS</a><br>  <br><a name="SEC24" href="#TOC1">CALLOUTS</a><br>
2081  <P>  <P>
2082  Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl  Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl
2083  code to be obeyed in the middle of matching a regular expression. This makes it  code to be obeyed in the middle of matching a regular expression. This makes it
# Line 2067  description of the interface to the call Line 2112  description of the interface to the call
2112  <a href="pcrecallout.html"><b>pcrecallout</b></a>  <a href="pcrecallout.html"><b>pcrecallout</b></a>
2113  documentation.  documentation.
2114  </P>  </P>
2115  <br><a name="SEC24" href="#TOC1">BACKTRACKING CONTROL</a><br>  <br><a name="SEC25" href="#TOC1">BACKTRACKING CONTROL</a><br>
2116  <P>  <P>
2117  Perl 5.10 introduced a number of "Special Backtracking Control Verbs", which  Perl 5.10 introduced a number of "Special Backtracking Control Verbs", which
2118  are described in the Perl documentation as "experimental and subject to change  are described in the Perl documentation as "experimental and subject to change
# Line 2076  production code should be noted to avoid Line 2121  production code should be noted to avoid
2121  remarks apply to the PCRE features described in this section.  remarks apply to the PCRE features described in this section.
2122  </P>  </P>
2123  <P>  <P>
2124  Since these verbs are specifically related to backtracking, they can be used  Since these verbs are specifically related to backtracking, most of them can be
2125  only when the pattern is to be matched using <b>pcre_exec()</b>, which uses a  used only when the pattern is to be matched using <b>pcre_exec()</b>, which uses
2126  backtracking algorithm. They cause an error if encountered by  a backtracking algorithm. With the exception of (*FAIL), which behaves like a
2127    failing negative assertion, they cause an error if encountered by
2128  <b>pcre_dfa_exec()</b>.  <b>pcre_dfa_exec()</b>.
2129  </P>  </P>
2130  <P>  <P>
# Line 2182  the end of the group if FOO succeeds); o Line 2228  the end of the group if FOO succeeds); o
2228  second alternative and tries COND2, without backtracking into COND1. If (*THEN)  second alternative and tries COND2, without backtracking into COND1. If (*THEN)
2229  is used outside of any alternation, it acts exactly like (*PRUNE).  is used outside of any alternation, it acts exactly like (*PRUNE).
2230  </P>  </P>
2231  <br><a name="SEC25" href="#TOC1">SEE ALSO</a><br>  <br><a name="SEC26" href="#TOC1">SEE ALSO</a><br>
2232  <P>  <P>
2233  <b>pcreapi</b>(3), <b>pcrecallout</b>(3), <b>pcrematching</b>(3), <b>pcre</b>(3).  <b>pcreapi</b>(3), <b>pcrecallout</b>(3), <b>pcrematching</b>(3), <b>pcre</b>(3).
2234  </P>  </P>
2235  <br><a name="SEC26" href="#TOC1">AUTHOR</a><br>  <br><a name="SEC27" href="#TOC1">AUTHOR</a><br>
2236  <P>  <P>
2237  Philip Hazel  Philip Hazel
2238  <br>  <br>
# Line 2195  University Computing Service Line 2241  University Computing Service
2241  Cambridge CB2 3QH, England.  Cambridge CB2 3QH, England.
2242  <br>  <br>
2243  </P>  </P>
2244  <br><a name="SEC27" href="#TOC1">REVISION</a><br>  <br><a name="SEC28" href="#TOC1">REVISION</a><br>
2245  <P>  <P>
2246  Last updated: 17 September 2007  Last updated: 08 March 2009
2247  <br>  <br>
2248  Copyright &copy; 1997-2007 University of Cambridge.  Copyright &copy; 1997-2009 University of Cambridge.
2249  <br>  <br>
2250  <p>  <p>
2251  Return to the <a href="index.html">PCRE index page</a>.  Return to the <a href="index.html">PCRE index page</a>.
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