/[pcre]/code/trunk/pcre.3
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revision 18 by nigel, Sat Feb 24 21:38:25 2007 UTC revision 19 by nigel, Sat Feb 24 21:38:33 2007 UTC
# Line 104  The \fIoptions\fR argument contains inde Line 104  The \fIoptions\fR argument contains inde
104  compilation. It should be zero if no options are required. Those options that  compilation. It should be zero if no options are required. Those options that
105  are compabible with Perl can also be set at compile time from within the  are compabible with Perl can also be set at compile time from within the
106  pattern (see the detailed description of regular expressions below) and all  pattern (see the detailed description of regular expressions below) and all
107  options except PCRE_EXTENDED and PCRE_EXTRA can be set at the time of matching.  options except PCRE_EXTENDED, PCRE_EXTRA and PCRE_UNGREEDY can be set at the
108    time of matching.
109  .PP  .PP
110  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.
111  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns
# Line 182  influencing the progress of a match. Line 183  influencing the progress of a match.
183    (2) Once a subpattern enclosed in (?>subpat) brackets has matched,    (2) Once a subpattern enclosed in (?>subpat) brackets has matched,
184        backtracking never goes back into the pattern.        backtracking never goes back into the pattern.
185    
186  See below for further details of both of these.  See below for further details of both of these. PCRE_EXTRA can be set by a (?X)
187    option setting within the pattern, but this must precede anything in the
188    pattern which relies on its being set.
189    
190      PCRE_UNGREEDY
191    
192    This option inverts the "greediness" of the quantifiers so that they are not
193    greedy by default, but become greedy if followed by "?". It is not compatible
194    with Perl. It can also be set by a (?U) option setting within the pattern.
195    
196    
197    
# Line 419  recognized, and a backslash followed by Line 428  recognized, and a backslash followed by
428  faulted. There is also a new kind of parenthesized subpattern starting with (?>  faulted. There is also a new kind of parenthesized subpattern starting with (?>
429  which has a block on backtracking into it once it has matched.  which has a block on backtracking into it once it has matched.
430    
431    (c) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is
432    inverted, that is, by default they are not greedy, but if followed by a
433    question mark they are.
434    
435    
436  .SH REGULAR EXPRESSION DETAILS  .SH REGULAR EXPRESSION DETAILS
437  The syntax and semantics of the regular expressions supported by PCRE are  The syntax and semantics of the regular expressions supported by PCRE are
# Line 866  own right. Because it has two uses, it c Line 879  own right. Because it has two uses, it c
879  which matches one digit by preference, but can match two if that is the only  which matches one digit by preference, but can match two if that is the only
880  way the rest of the pattern matches.  way the rest of the pattern matches.
881    
882    If the PCRE_UNGREEDY option is set (an option which is not available in Perl)
883    then the quantifiers are not greedy by default, but individual ones can be made
884    greedy by following they by a question mark. In other words, it inverts the
885    default behaviour.
886    
887  When a parenthesized subpattern is quantified with a minimum repeat count that  When a parenthesized subpattern is quantified with a minimum repeat count that
888  is greater than 1 or with a limited maximum, more store is required for the  is greater than 1 or with a limited maximum, more store is required for the
889  compiled pattern, in proportion to the size of the minimum or maximum.  compiled pattern, in proportion to the size of the minimum or maximum.
# Line 986  the PCRE_EXTENDED option, that is, white Line 1004  the PCRE_EXTENDED option, that is, white
1004  comment that lasts till the next newline. The option applies to the whole  comment that lasts till the next newline. The option applies to the whole
1005  pattern, not just to the portion that follows it.  pattern, not just to the portion that follows it.
1006    
1007    If the sequence (?U) occurs anywhere in a pattern, it has the effect of setting
1008    the PCRE_UNGREEDY option which inverts the greediness of quantifiers. This is
1009    an extension to Perl's facilities.
1010    
1011    If the sequence (?X) occurs in a pattern, it has the effect of setting the
1012    PCRE_EXTRA flag, which turns on some additional features not found in Perl.
1013    This flag setting is special in that it must occur earlier in the pattern than
1014    any of the additional features. It is best put at the start.
1015    
1016  If more than one option is required, they can be specified jointly, for example  If more than one option is required, they can be specified jointly, for example
1017  as (?ix) or (?mi).  as (?ix) or (?mi).
1018    
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