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revision 211 by ph10, Thu Aug 9 09:52:43 2007 UTC revision 450 by ph10, Wed Sep 16 10:56:40 2009 UTC
# Line 7  PCRE - Perl-compatible regular expressio Line 7  PCRE - Perl-compatible regular expressio
7  This document describes the differences in the ways that PCRE and Perl handle  This document describes the differences in the ways that PCRE and Perl handle
8  regular expressions. The differences described here are mainly with respect to  regular expressions. The differences described here are mainly with respect to
9  Perl 5.8, though PCRE versions 7.0 and later contain some features that are  Perl 5.8, though PCRE versions 7.0 and later contain some features that are
10  expected to be in the forthcoming Perl 5.10.  in Perl 5.10.
11  .P  .P
12  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what
13  it does have are given in the  it does have are given in the
# Line 46  encountered by PCRE, an error is generat Line 46  encountered by PCRE, an error is generat
46  built with Unicode character property support. The properties that can be  built with Unicode character property support. The properties that can be
47  tested with \ep and \eP are limited to the general category properties such as  tested with \ep and \eP are limited to the general category properties such as
48  Lu and Nd, script names such as Greek or Han, and the derived properties Any  Lu and Nd, script names such as Greek or Han, and the derived properties Any
49  and L&.  and L&. PCRE does support the Cs (surrogate) property, which Perl does not; the
50    Perl documentation says "Because Perl hides the need for the user to understand
51    the internal representation of Unicode characters, there is no need to
52    implement the somewhat messy concept of surrogates."
53  .P  .P
54  7. PCRE does support the \eQ...\eE escape for quoting substrings. Characters in  7. PCRE does support the \eQ...\eE escape for quoting substrings. Characters in
55  between are treated as literals. This is slightly different from Perl in that $  between are treated as literals. This is slightly different from Perl in that $
# Line 83  the pattern /^(a(b)?)+$/ in Perl leaves Line 86  the pattern /^(a(b)?)+$/ in Perl leaves
86  .P  .P
87  11. PCRE does support Perl 5.10's backtracking verbs (*ACCEPT), (*FAIL), (*F),  11. PCRE does support Perl 5.10's backtracking verbs (*ACCEPT), (*FAIL), (*F),
88  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in the forms without an  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in the forms without an
89  argument. PCRE does not support (*MARK). If (*ACCEPT) is within capturing  argument. PCRE does not support (*MARK).
 parentheses, PCRE does not set that capture group; this is different to Perl.  
90  .P  .P
91  12. PCRE provides some extensions to the Perl regular expression facilities.  12. PCRE provides some extensions to the Perl regular expression facilities.
92  Perl 5.10 will include new features that are not in earlier versions, some of  Perl 5.10 will include new features that are not in earlier versions, some of
# Line 109  question mark they are. Line 111  question mark they are.
111  (e) PCRE_ANCHORED can be used at matching time to force a pattern to be tried  (e) PCRE_ANCHORED can be used at matching time to force a pattern to be tried
112  only at the first matching position in the subject string.  only at the first matching position in the subject string.
113  .sp  .sp
114  (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAPTURE  (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, and
115  options for \fBpcre_exec()\fP have no Perl equivalents.  PCRE_NO_AUTO_CAPTURE options for \fBpcre_exec()\fP have no Perl equivalents.
116  .sp  .sp
117  (g) The callout facility is PCRE-specific.  (g) The \eR escape sequence can be restricted to match only CR, LF, or CRLF
118    by the PCRE_BSR_ANYCRLF option.
119  .sp  .sp
120  (h) The partial matching facility is PCRE-specific.  (h) The callout facility is PCRE-specific.
121  .sp  .sp
122  (i) Patterns compiled by PCRE can be saved and re-used at a later time, even on  (i) The partial matching facility is PCRE-specific.
123    .sp
124    (j) Patterns compiled by PCRE can be saved and re-used at a later time, even on
125  different hosts that have the other endianness.  different hosts that have the other endianness.
126  .sp  .sp
127  (j) The alternative matching function (\fBpcre_dfa_exec()\fP) matches in a  (k) The alternative matching function (\fBpcre_dfa_exec()\fP) matches in a
128  different way and is not Perl-compatible.  different way and is not Perl-compatible.
129    .sp
130    (l) PCRE recognizes some special sequences such as (*CR) at the start of
131    a pattern that set overall options that cannot be changed within the pattern.
132  .  .
133  .  .
134  .SH AUTHOR  .SH AUTHOR
# Line 137  Cambridge CB2 3QH, England. Line 145  Cambridge CB2 3QH, England.
145  .rs  .rs
146  .sp  .sp
147  .nf  .nf
148  Last updated: 08 August 2007  Last updated: 16 September 2009
149  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
150  .fi  .fi

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