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# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a  few  differences. Certain features that appeared in Python and
23         PCRE before they appeared in Perl are also available using  the  Python         PCRE before they appeared in Perl are also available using  the  Python
24         syntax.)         syntax.  There is also some support for certain .NET and Oniguruma syn-
25           tax items, and there is an option for  requesting  some  minor  changes
26           that give better JavaScript compatibility.
27    
28         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current implementation of PCRE (release 8.xx) corresponds approxi-
29         mately with Perl 5.10, including support for UTF-8 encoded strings  and         mately with Perl 5.10, including support for UTF-8 encoded strings  and
30         Unicode general category properties. However, UTF-8 and Unicode support         Unicode general category properties. However, UTF-8 and Unicode support
31         has to be explicitly enabled; it is not the default. The Unicode tables         has to be explicitly enabled; it is not the default. The Unicode tables
32         correspond to Unicode release 5.0.0.         correspond to Unicode release 5.1.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative matching function that matches the same  compiled  patterns
# Line 69  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 79  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
# Line 88  USER DOCUMENTATION Line 93  USER DOCUMENTATION
93           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
94           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
95           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
96           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
97           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
98           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
99    
# Line 134  UTF-8 AND UNICODE PROPERTY SUPPORT Line 139  UTF-8 AND UNICODE PROPERTY SUPPORT
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any subject strings that are matched against it are  treated  as  UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of just strings of bytes.
146    
147         If  you compile PCRE with UTF-8 support, but do not use it at run time,         If you compile PCRE with UTF-8 support, but do not use it at run  time,
148         the library will be a bit bigger, but the additional run time  overhead         the  library will be a bit bigger, but the additional run time overhead
149         is limited to testing the PCRE_UTF8 flag occasionally, so should not be         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
150         very big.         very big.
151    
152         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
153         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
155         general  category  properties such as Lu for an upper case letter or Nd         general category properties such as Lu for an upper case letter  or  Nd
156         for a decimal number, the Unicode script names such as Arabic  or  Han,         for  a  decimal number, the Unicode script names such as Arabic or Han,
157         and  the  derived  properties  Any  and L&. A full list is given in the         and the derived properties Any and L&. A full  list  is  given  in  the
158         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
159         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
160         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         does not support this.         does not support this.
163    
164     Validity of UTF-8 strings     Validity of UTF-8 strings
165    
166         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167         subjects are (by default) checked for validity on entry to the relevant         subjects are (by default) checked for validity on entry to the relevant
168         functions. From release 7.3 of PCRE, the check is according  the  rules         functions.  From  release 7.3 of PCRE, the check is according the rules
169         of  RFC  3629, which are themselves derived from the Unicode specifica-         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172         check allows only values in the range U+0 to U+10FFFF, excluding U+D800         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173         to U+DFFF.         to U+DFFF.
174    
175         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176         which the Unicode Standard says this: "The Low Surrogate Area does  not         which  the Unicode Standard says this: "The Low Surrogate Area does not
177         contain  any  character  assignments,  consequently  no  character code         contain any  character  assignments,  consequently  no  character  code
178         charts or namelists are provided for this area. Surrogates are reserved         charts or namelists are provided for this area. Surrogates are reserved
179         for  use  with  UTF-16 and then must be used in pairs." The code points         for use with UTF-16 and then must be used in pairs."  The  code  points
180         that are encoded by UTF-16 pairs  are  available  as  independent  code         that  are  encoded  by  UTF-16  pairs are available as independent code
181         points  in  the  UTF-8  encoding.  (In other words, the whole surrogate         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184         If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return         If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186         that your strings are valid, and therefore want to skip these checks in         that your strings are valid, and therefore want to skip these checks in
187         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188         compile time or at run time, PCRE assumes that the pattern  or  subject         compile  time  or at run time, PCRE assumes that the pattern or subject
189         it  is  given  (respectively)  contains only valid UTF-8 codes. In this         it is given (respectively) contains only valid  UTF-8  codes.  In  this
190         case, it does not diagnose an invalid UTF-8 string.         case, it does not diagnose an invalid UTF-8 string.
191    
192         If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193         what  happens  depends on why the string is invalid. If the string con-         what happens depends on why the string is invalid. If the  string  con-
194         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195         string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,         string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196         apart from the initial validity test, PCRE (when in UTF-8 mode) handles         apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197         strings  according  to  the more liberal rules of RFC 2279. However, if         strings according to the more liberal rules of RFC  2279.  However,  if
198         the string does not even conform to RFC 2279, the result is  undefined.         the  string does not even conform to RFC 2279, the result is undefined.
199         Your program may crash.         Your program may crash.
200    
201         If  you  want  to  process  strings  of  values  in the full range 0 to         If you want to process strings  of  values  in  the  full  range  0  to
202         0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can         0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204         this situation, you will have to apply your own validity check.         this situation, you will have to apply your own validity check.
205    
206     General comments about UTF-8 mode     General comments about UTF-8 mode
207    
208         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
210    
211         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212         characters for values greater than \177.         characters for values greater than \177.
213    
214         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         4.  The dot metacharacter matches one UTF-8 character instead of a sin-         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         gle byte.         gle byte.
219    
220         5. The escape sequence \C can be used to match a single byte  in  UTF-8         5.  The  escape sequence \C can be used to match a single byte in UTF-8
221         mode,  but  its  use can lead to some strange effects. This facility is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         6. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but the characters that PCRE  recog-
226         nizes as digits, spaces, or word characters  remain  the  same  set  as         nizes  as  digits,  spaces,  or  word characters remain the same set as
227         before, all with values less than 256. This remains true even when PCRE         before, all with values less than 256. This remains true even when PCRE
228         includes Unicode property support, because to do otherwise  would  slow         includes  Unicode  property support, because to do otherwise would slow
229         down  PCRE in many common cases. If you really want to test for a wider         down PCRE in many common cases. If you really want to test for a  wider
230         sense of, say, "digit", you must use Unicode  property  tests  such  as         sense  of,  say,  "digit",  you must use Unicode property tests such as
231         \p{Nd}.         \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
232           terms of \w and \W.
233    
234         7.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
235         are all low-valued characters.         are all low-valued characters.
# Line 256  AUTHOR Line 263  AUTHOR
263    
264  REVISION  REVISION
265    
266         Last updated: 09 August 2007         Last updated: 01 September 2009
267         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
268  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
269    
270    
271  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
272    
273    
# Line 275  PCRE BUILD-TIME OPTIONS Line 282  PCRE BUILD-TIME OPTIONS
282         script,  where the optional features are selected or deselected by pro-         script,  where the optional features are selected or deselected by pro-
283         viding options to configure before running the make  command.  However,         viding options to configure before running the make  command.  However,
284         the  same  options  can be selected in both Unix-like and non-Unix-like         the  same  options  can be selected in both Unix-like and non-Unix-like
285         environments using the GUI facility of  CMakeSetup  if  you  are  using         environments using the GUI facility of cmake-gui if you are using CMake
286         CMake instead of configure to build PCRE.         instead of configure to build PCRE.
287    
288           There  is  a  lot more information about building PCRE in non-Unix-like
289           environments in the file called NON_UNIX_USE, which is part of the PCRE
290           distribution.  You  should consult this file as well as the README file
291           if you are building in a non-Unix-like environment.
292    
293         The complete list of options for configure (which includes the standard         The complete list of options for configure (which includes the standard
294         ones such as the  selection  of  the  installation  directory)  can  be         ones  such  as  the  selection  of  the  installation directory) can be
295         obtained by running         obtained by running
296    
297           ./configure --help           ./configure --help
298    
299         The  following  sections  include  descriptions  of options whose names         The following sections include  descriptions  of  options  whose  names
300         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
301         defaults  for  the configure command. Because of the way that configure         defaults for the configure command. Because of the way  that  configure
302         works, --enable and --disable always come in pairs, so  the  complemen-         works,  --enable  and --disable always come in pairs, so the complemen-
303         tary  option always exists as well, but as it specifies the default, it         tary option always exists as well, but as it specifies the default,  it
304         is not described.         is not described.
305    
306    
# Line 305  C++ SUPPORT Line 317  C++ SUPPORT
317    
318  UTF-8 SUPPORT  UTF-8 SUPPORT
319    
320         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
321    
322           --enable-utf8           --enable-utf8
323    
324         to the configure command. Of itself, this  does  not  make  PCRE  treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
325         strings  as UTF-8. As well as compiling PCRE with this option, you also         strings as UTF-8. As well as compiling PCRE with this option, you  also
326         have have to set the PCRE_UTF8 option when you call the  pcre_compile()         have  have to set the PCRE_UTF8 option when you call the pcre_compile()
327         function.         function.
328    
329           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
330           expects its input to be either ASCII or UTF-8 (depending on the runtime
331           option). It is not possible to support both EBCDIC and UTF-8  codes  in
332           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
333           --enable-ebcdic are mutually exclusive.
334    
335    
336  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
337    
338         UTF-8  support allows PCRE to process character values greater than 255         UTF-8 support allows PCRE to process character values greater than  255
339         in the strings that it handles. On its own, however, it does  not  pro-         in  the  strings that it handles. On its own, however, it does not pro-
340         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
341         you want to be able to use the pattern escapes \P, \p,  and  \X,  which         you  want  to  be able to use the pattern escapes \P, \p, and \X, which
342         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
343    
344           --enable-unicode-properties           --enable-unicode-properties
345    
346         to  the configure command. This implies UTF-8 support, even if you have         to the configure command. This implies UTF-8 support, even if you  have
347         not explicitly requested it.         not explicitly requested it.
348    
349         Including Unicode property support adds around 30K  of  tables  to  the         Including  Unicode  property  support  adds around 30K of tables to the
350         PCRE  library.  Only  the general category properties such as Lu and Nd         PCRE library. Only the general category properties such as  Lu  and  Nd
351         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
352    
353    
354  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
355    
356         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
357         the  end  of  a line. This is the normal newline character on Unix-like         the end of a line. This is the normal newline  character  on  Unix-like
358         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
359         instead, by adding         adding
360    
361           --enable-newline-is-cr           --enable-newline-is-cr
362    
363         to  the  configure  command.  There  is  also  a --enable-newline-is-lf         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
364         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
365    
366         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 354  CODE VALUE OF NEWLINE Line 372  CODE VALUE OF NEWLINE
372    
373           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
374    
375         which  causes  PCRE  to recognize any of the three sequences CR, LF, or         which causes PCRE to recognize any of the three sequences  CR,  LF,  or
376         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
377    
378           --enable-newline-is-any           --enable-newline-is-any
# Line 514  USING EBCDIC CODE Line 532  USING EBCDIC CODE
532    
533         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
534         bles. You should only use it if you know that  you  are  in  an  EBCDIC         bles. You should only use it if you know that  you  are  in  an  EBCDIC
535         environment (for example, an IBM mainframe operating system).         environment  (for  example,  an  IBM  mainframe  operating system). The
536           --enable-ebcdic option is incompatible with --enable-utf8.
537    
538    
539  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
# Line 527  PCREGREP OPTIONS FOR COMPRESSED FILE SUP Line 546  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
546           --enable-pcregrep-libbz2           --enable-pcregrep-libbz2
547    
548         to the configure command. These options naturally require that the rel-         to the configure command. These options naturally require that the rel-
549         evant libraries are installed on your system. Configuration  will  fail         evant  libraries  are installed on your system. Configuration will fail
550         if they are not.         if they are not.
551    
552    
553    PCRETEST OPTION FOR LIBREADLINE SUPPORT
554    
555           If you add
556    
557             --enable-pcretest-libreadline
558    
559           to the configure command,  pcretest  is  linked  with  the  libreadline
560           library,  and  when its input is from a terminal, it reads it using the
561           readline() function. This provides line-editing and history facilities.
562           Note that libreadline is GPL-licenced, so if you distribute a binary of
563           pcretest linked in this way, there may be licensing issues.
564    
565           Setting this option causes the -lreadline option to  be  added  to  the
566           pcretest  build.  In many operating environments with a sytem-installed
567           libreadline this is sufficient. However, in some environments (e.g.  if
568           an  unmodified  distribution version of readline is in use), some extra
569           configuration may be necessary. The INSTALL file for  libreadline  says
570           this:
571    
572             "Readline uses the termcap functions, but does not link with the
573             termcap or curses library itself, allowing applications which link
574             with readline the to choose an appropriate library."
575    
576           If  your environment has not been set up so that an appropriate library
577           is automatically included, you may need to add something like
578    
579             LIBS="-ncurses"
580    
581           immediately before the configure command.
582    
583    
584  SEE ALSO  SEE ALSO
585    
586         pcreapi(3), pcre_config(3).         pcreapi(3), pcre_config(3).
# Line 545  AUTHOR Line 595  AUTHOR
595    
596  REVISION  REVISION
597    
598         Last updated: 17 December 2007         Last updated: 06 September 2009
599         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
600  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
601    
602    
603  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
604    
605    
# Line 651  THE ALTERNATIVE MATCHING ALGORITHM Line 701  THE ALTERNATIVE MATCHING ALGORITHM
701         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
702         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
703    
704           Although the general principle of this matching algorithm  is  that  it
705           scans  the subject string only once, without backtracking, there is one
706           exception: when a lookbehind assertion is  encountered,  the  preceding
707           characters have to be re-inspected.
708    
709         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
710         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
711    
712         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
713         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
714         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
715         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
716         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
717    
718           ^a++\w!           ^a++\w!
719    
720         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
721         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
722         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
723         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
724         pattern.         pattern.
725    
726         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
727         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
728         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
729         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
730         strings are available.         strings are available.
731    
732         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
733         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
734    
735         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
736         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
737         supported.         supported.
738    
739         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
740         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
741         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
742         error if encountered.         error if encountered.
743    
744         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
745         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
746    
747         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
748         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8 mode, is not supported because the  alterna-
749         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
750         time, for all active paths through the tree.         time, for all active paths through the tree.
751    
752         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
753         ported.         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
754           negative assertion.
755    
756    
757  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 708  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 764  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
764         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
765         things with callouts.         things with callouts.
766    
767         2. There is much better support for partial matching. The  restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
        on  the content of the pattern that apply when using the standard algo-  
        rithm for partial matching do not apply to the  alternative  algorithm.  
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
768         once,  and  never  needs to backtrack, it is possible to pass very long         once,  and  never  needs to backtrack, it is possible to pass very long
769         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
770         for partial matching each time.         for partial matching each time.
# Line 743  AUTHOR Line 793  AUTHOR
793    
794  REVISION  REVISION
795    
796         Last updated: 08 August 2007         Last updated: 05 September 2009
797         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
798  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
799    
800    
801  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
802    
803    
# Line 855  PCRE API OVERVIEW Line 905  PCRE API OVERVIEW
905         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
906         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
907         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
908         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
909         run it.         pcredemo documentation, and the pcresample documentation describes  how
910           to compile and run it.
911    
912         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
913         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
914         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
915         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
916         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
917         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
918         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
919           mentation.
920    
921         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
922         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 965  MULTITHREADING Line 1017  MULTITHREADING
1017         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1018         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1019    
1020         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
1021         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1022         at once.         at once.
1023    
# Line 973  MULTITHREADING Line 1025  MULTITHREADING
1025  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1026    
1027         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1028         later  time,  possibly by a different program, and even on a host other         later time, possibly by a different program, and even on a  host  other
1029         than the one on which  it  was  compiled.  Details  are  given  in  the         than  the  one  on  which  it  was  compiled.  Details are given in the
1030         pcreprecompile  documentation.  However, compiling a regular expression         pcreprecompile documentation. However, compiling a  regular  expression
1031         with one version of PCRE for use with a different version is not  guar-         with  one version of PCRE for use with a different version is not guar-
1032         anteed to work and may cause crashes.         anteed to work and may cause crashes.
1033    
1034    
# Line 984  CHECKING BUILD-TIME OPTIONS Line 1036  CHECKING BUILD-TIME OPTIONS
1036    
1037         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1038    
1039         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
1040         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1041         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
1042         tures.         tures.
1043    
1044         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
1045         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1046         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
1047         available:         available:
1048    
1049           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1050    
1051         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
1052         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1053    
1054           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1055    
1056         The output is an integer that is set to  one  if  support  for  Unicode         The  output  is  an  integer  that is set to one if support for Unicode
1057         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1058    
1059           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1060    
1061         The  output  is  an integer whose value specifies the default character         The output is an integer whose value specifies  the  default  character
1062         sequence that is recognized as meaning "newline". The four values  that         sequence  that is recognized as meaning "newline". The four values that
1063         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1064         and -1 for ANY. The default should normally be  the  standard  sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1065         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1066           spond to the standard sequence for your operating system.
1067    
1068           PCRE_CONFIG_BSR           PCRE_CONFIG_BSR
1069    
# Line 1037  CHECKING BUILD-TIME OPTIONS Line 1090  CHECKING BUILD-TIME OPTIONS
1090    
1091           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1092    
1093         The output is an integer that gives the default limit for the number of         The output is a long integer that gives the default limit for the  num-
1094         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1095         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1096    
1097           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1098    
1099         The output is an integer that gives the default limit for the depth  of         The output is a long integer that gives the default limit for the depth
1100         recursion  when calling the internal matching function in a pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1101         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1102           below.
1103    
1104           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1105    
1106         The output is an integer that is set to one if internal recursion  when         The  output is an integer that is set to one if internal recursion when
1107         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1108         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1109         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1110         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1111         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1112         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1113    
1114    
# Line 1071  COMPILING A PATTERN Line 1125  COMPILING A PATTERN
1125    
1126         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1127         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1128         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1129         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1130    
1131         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1132         the pattern argument. A pointer to a single block  of  memory  that  is         the  pattern  argument.  A  pointer to a single block of memory that is
1133         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1134         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1135         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1136         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1137         longer required.         longer required.
1138    
1139         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although the compiled code of a PCRE regex is relocatable, that is,  it
1140         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1141         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1142         ment, which is an address (see below).         ment, which is an address (see below).
1143    
1144         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1145         pilation.  It  should be zero if no options are required. The available         pilation. It should be zero if no options are required.  The  available
1146         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them (in particular, those that
1147         are  compatible  with  Perl,  can also be set and unset from within the         are compatible with Perl, but also some others) can  also  be  set  and
1148         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset  from  within  the  pattern  (see the detailed description in the
1149         tion).  For  these options, the contents of the options argument speci-         pcrepattern documentation). For those options that can be different  in
1150         fies their initial settings at the start of compilation and  execution.         different  parts  of  the pattern, the contents of the options argument
1151         The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time         specifies their initial settings at the start of compilation and execu-
1152         of matching as well as at compile time.         tion.  The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the
1153           time of matching as well as at compile time.
1154    
1155         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1156         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1157         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1158         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1159         try to free it. The offset from the start of the pattern to the charac-         try to free it. The byte offset from the start of the  pattern  to  the
1160         ter where the error was discovered is placed in the variable pointed to         character  that  was  being  processes when the error was discovered is
1161         by erroffset, which must not be NULL. If it is, an immediate  error  is         placed in the variable pointed to by erroffset, which must not be NULL.
1162         given.         If  it  is,  an  immediate error is given. Some errors are not detected
1163           until checks are carried out when the whole pattern has  been  scanned;
1164           in this case the offset is set to the end of the pattern.
1165    
1166         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1167         codeptr argument is not NULL, a non-zero error code number is  returned         codeptr argument is not NULL, a non-zero error code number is  returned
# Line 1231  COMPILING A PATTERN Line 1288  COMPILING A PATTERN
1288         before or at the first  newline  in  the  subject  string,  though  the         before or at the first  newline  in  the  subject  string,  though  the
1289         matched text may continue over the newline.         matched text may continue over the newline.
1290    
1291             PCRE_JAVASCRIPT_COMPAT
1292    
1293           If this option is set, PCRE's behaviour is changed in some ways so that
1294           it is compatible with JavaScript rather than Perl. The changes  are  as
1295           follows:
1296    
1297           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1298           error, because this is illegal in JavaScript (by default it is  treated
1299           as a data character). Thus, the pattern AB]CD becomes illegal when this
1300           option is set.
1301    
1302           (2) At run time, a back reference to an unset subpattern group  matches
1303           an  empty  string (by default this causes the current matching alterna-
1304           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1305           set  (assuming  it can find an "a" in the subject), whereas it fails by
1306           default, for Perl compatibility.
1307    
1308           PCRE_MULTILINE           PCRE_MULTILINE
1309    
1310         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1311         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1312         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1313         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1314         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1315         is set). This is the same as Perl.         is set). This is the same as Perl.
1316    
1317         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1318         constructs  match  immediately following or immediately before internal         constructs match immediately following or immediately  before  internal
1319         newlines in the subject string, respectively, as well as  at  the  very         newlines  in  the  subject string, respectively, as well as at the very
1320         start  and  end.  This is equivalent to Perl's /m option, and it can be         start and end. This is equivalent to Perl's /m option, and  it  can  be
1321         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1322         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1323         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1324    
1325           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1254  COMPILING A PATTERN Line 1328  COMPILING A PATTERN
1328           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1329           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1330    
1331         These options override the default newline definition that  was  chosen         These  options  override the default newline definition that was chosen
1332         when  PCRE  was built. Setting the first or the second specifies that a         when PCRE was built. Setting the first or the second specifies  that  a
1333         newline is indicated by a single character (CR  or  LF,  respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1334         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1335         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1336         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1337         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1338         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1339         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1340         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1341         (paragraph separator, U+2029). The last  two  are  recognized  only  in         (paragraph  separator,  U+2029).  The  last  two are recognized only in
1342         UTF-8 mode.         UTF-8 mode.
1343    
1344         The  newline  setting  in  the  options  word  uses three bits that are         The newline setting in the  options  word  uses  three  bits  that  are
1345         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1346         used  (default  plus the five values above). This means that if you set         used (default plus the five values above). This means that if  you  set
1347         more than one newline option, the combination may or may not be  sensi-         more  than one newline option, the combination may or may not be sensi-
1348         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1349         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1350         cause an error.         cause an error.
1351    
1352         The  only time that a line break is specially recognized when compiling         The only time that a line break is specially recognized when  compiling
1353         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
1354         character  class  is  encountered.  This indicates a comment that lasts         character class is encountered. This indicates  a  comment  that  lasts
1355         until after the next line break sequence. In other circumstances,  line         until  after the next line break sequence. In other circumstances, line
1356         break   sequences   are   treated  as  literal  data,  except  that  in         break  sequences  are  treated  as  literal  data,   except   that   in
1357         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1358         and are therefore ignored.         and are therefore ignored.
1359    
1360         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1361         is used for pcre_exec() and pcre_dfa_exec(), but it can be  overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1362    
1363           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1364    
# Line 1343  COMPILATION ERROR CODES Line 1417  COMPILATION ERROR CODES
1417            9  nothing to repeat            9  nothing to repeat
1418           10  [this code is not in use]           10  [this code is not in use]
1419           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1420           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1421           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1422           14  missing )           14  missing )
1423           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1351  COMPILATION ERROR CODES Line 1425  COMPILATION ERROR CODES
1425           17  unknown option bit(s) set           17  unknown option bit(s) set
1426           18  missing ) after comment           18  missing ) after comment
1427           19  [this code is not in use]           19  [this code is not in use]
1428           20  regular expression too large           20  regular expression is too large
1429           21  failed to get memory           21  failed to get memory
1430           22  unmatched parentheses           22  unmatched parentheses
1431           23  internal error: code overflow           23  internal error: code overflow
# Line 1380  COMPILATION ERROR CODES Line 1454  COMPILATION ERROR CODES
1454           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1455           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1456           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1457           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1458           50  [this code is not in use]           50  [this code is not in use]
1459           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1460           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
# Line 1389  COMPILATION ERROR CODES Line 1463  COMPILATION ERROR CODES
1463           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1464           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1465           56  inconsistent NEWLINE options           56  inconsistent NEWLINE options
1466           57  \g is not followed by a braced name or an optionally braced           57  \g is not followed by a braced, angle-bracketed, or quoted
1467                 non-zero number                 name/number or by a plain number
1468           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1469             59  (*VERB) with an argument is not supported
1470             60  (*VERB) not recognized
1471             61  number is too big
1472             62  subpattern name expected
1473             63  digit expected after (?+
1474             64  ] is an invalid data character in JavaScript compatibility mode
1475    
1476           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1477           values may be used if the limits were changed when PCRE was built.
1478    
1479    
1480  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1399  STUDYING A PATTERN Line 1482  STUDYING A PATTERN
1482         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1483              const char **errptr);              const char **errptr);
1484    
1485         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1486         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1487         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1488         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1489         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1490         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
1491         the results of the study.         the results of the study.
1492    
1493         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1494         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1495         that can be set by the caller before the block  is  passed;  these  are         that  can  be  set  by the caller before the block is passed; these are
1496         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1497    
1498         If  studying  the  pattern  does not produce any additional information         If studying the pattern does not  produce  any  additional  information
1499         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1500         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants to pass any of the other fields to pcre_exec(), it  must  set  up
1501         its own pcre_extra block.         its own pcre_extra block.
1502    
1503         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1504         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1505    
1506         The  third argument for pcre_study() is a pointer for an error message.         The third argument for pcre_study() is a pointer for an error  message.
1507         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1508         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1509         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1510         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1511         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1512    
1513         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1436  STUDYING A PATTERN Line 1519  STUDYING A PATTERN
1519             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1520    
1521         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1522         that  do not have a single fixed starting character. A bitmap of possi-         that do not have a single fixed starting character. A bitmap of  possi-
1523         ble starting bytes is created.         ble starting bytes is created.
1524    
1525    
1526  LOCALE SUPPORT  LOCALE SUPPORT
1527    
1528         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1529         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1530         by character value. When running in UTF-8 mode, this  applies  only  to         by  character  value.  When running in UTF-8 mode, this applies only to
1531         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1532         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1533         with  Unicode  character property support. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1534         code is discouraged. If you are handling characters with codes  greater         code  is discouraged. If you are handling characters with codes greater
1535         than  128, you should either use UTF-8 and Unicode, or use locales, but         than 128, you should either use UTF-8 and Unicode, or use locales,  but
1536         not try to mix the two.         not try to mix the two.
1537    
1538         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1539         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1540         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1541         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1542         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1543         which may cause them to be different.         which may cause them to be different.
1544    
1545         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1546         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1547         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1548         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1549    
1550         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1551         which  has no arguments, in the relevant locale. The result can then be         which has no arguments, in the relevant locale. The result can then  be
1552         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1553         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1554         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1555         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1556    
1557           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1558           tables = pcre_maketables();           tables = pcre_maketables();
1559           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1560    
1561         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1562         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1563    
1564         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1565         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1566         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1567         it is needed.         it is needed.
1568    
1569         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1570         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
1571         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1572         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1573         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1574    
1575         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1576         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1577         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1578         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1579         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1580    
# Line 1501  INFORMATION ABOUT A PATTERN Line 1584  INFORMATION ABOUT A PATTERN
1584         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1585              int what, void *where);              int what, void *where);
1586    
1587         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1588         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1589         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1590    
1591         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1592         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
1593         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1594         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
1595         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
1596         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1597    
1598           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1517  INFORMATION ABOUT A PATTERN Line 1600  INFORMATION ABOUT A PATTERN
1600           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1601           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1602    
1603         The "magic number" is placed at the start of each compiled  pattern  as         The  "magic  number" is placed at the start of each compiled pattern as
1604         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1605         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1606         pattern:         pattern:
1607    
1608           int rc;           int rc;
# Line 1530  INFORMATION ABOUT A PATTERN Line 1613  INFORMATION ABOUT A PATTERN
1613             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1614             &length);         /* where to put the data */             &length);         /* where to put the data */
1615    
1616         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1617         are as follows:         are as follows:
1618    
1619           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1620    
1621         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1622         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1623         there are no back references.         there are no back references.
1624    
1625           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1626    
1627         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1628         argument should point to an int variable.         argument should point to an int variable.
1629    
1630           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1631    
1632         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1633         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1634         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1635         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1636         passing a NULL table pointer.         passing a NULL table pointer.
1637    
1638           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1639    
1640         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1641         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1642         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1643         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1644    
1645         If there is a fixed first byte, for example, from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1646         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1647    
1648         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1649         branch starts with "^", or         branch starts with "^", or
1650    
1651         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1652         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1653    
1654         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1655         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1656         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1657    
1658           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1659    
1660         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1661         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1662         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1663         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1664         able.         able.
1665    
1666           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1667    
1668         Return  1  if  the  pattern  contains any explicit matches for CR or LF         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1669         characters, otherwise 0. The fourth argument should  point  to  an  int         characters,  otherwise  0.  The  fourth argument should point to an int
1670         variable.  An explicit match is either a literal CR or LF character, or         variable. An explicit match is either a literal CR or LF character,  or
1671         \r or \n.         \r or \n.
1672    
1673           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1674    
1675         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1676         otherwise  0. The fourth argument should point to an int variable. (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1677         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1678    
1679           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1680    
1681         Return the value of the rightmost literal byte that must exist  in  any         Return  the  value of the rightmost literal byte that must exist in any
1682         matched  string,  other  than  at  its  start,  if such a byte has been         matched string, other than at its  start,  if  such  a  byte  has  been
1683         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1684         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such byte, -1 is returned. For anchored patterns, a last  literal
1685         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1686         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1687         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1688    
# Line 1607  INFORMATION ABOUT A PATTERN Line 1690  INFORMATION ABOUT A PATTERN
1690           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1691           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1692    
1693         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1694         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1695         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1696         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1697         strings by name. It is also possible to extract the data  directly,  by         strings  by  name. It is also possible to extract the data directly, by
1698         first  converting  the  name to a number in order to access the correct         first converting the name to a number in order to  access  the  correct
1699         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1700         the  conversion,  you  need  to  use  the  name-to-number map, which is         the conversion, you need  to  use  the  name-to-number  map,  which  is
1701         described by these three values.         described by these three values.
1702    
1703         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1704         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1705         of each entry; both of these  return  an  int  value.  The  entry  size         of  each  entry;  both  of  these  return  an int value. The entry size
1706         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1707         a pointer to the first entry of the table  (a  pointer  to  char).  The         a  pointer  to  the  first  entry of the table (a pointer to char). The
1708         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1709         sis, most significant byte first. The rest of the entry is  the  corre-         sis,  most  significant byte first. The rest of the entry is the corre-
1710         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated. The names are  in  alphabetical  order.
1711         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1712         theses  numbers.  For  example,  consider the following pattern (assume         theses numbers. For example, consider  the  following  pattern  (assume
1713         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is
1714         ignored):         ignored):
1715    
1716           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1717           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1718    
1719         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1720         each entry in the table is eight bytes long. The table is  as  follows,         each  entry  in the table is eight bytes long. The table is as follows,
1721         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1722         as ??:         as ??:
1723    
# Line 1643  INFORMATION ABOUT A PATTERN Line 1726  INFORMATION ABOUT A PATTERN
1726           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1727           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1728    
1729         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1730         name-to-number  map,  remember that the length of the entries is likely         name-to-number map, remember that the length of the entries  is  likely
1731         to be different for each compiled pattern.         to be different for each compiled pattern.
1732    
1733           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1734    
1735         Return 1 if the pattern can be used for partial matching, otherwise  0.         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1736         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1737         documentation lists the restrictions that apply to patterns  when  par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1738         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1739           lifted.  The  pcrepartial documentation gives details of partial match-
1740           ing.
1741    
1742           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1743    
1744         Return  a  copy of the options with which the pattern was compiled. The         Return a copy of the options with which the pattern was  compiled.  The
1745         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1746         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1747         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1748         other  words,  they are the options that will be in force when matching         other words, they are the options that will be in force  when  matching
1749         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1750         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1751         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1752    
1753         A pattern is automatically anchored by PCRE if  all  of  its  top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1754         alternatives begin with one of the following:         alternatives begin with one of the following:
1755    
1756           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1679  INFORMATION ABOUT A PATTERN Line 1764  INFORMATION ABOUT A PATTERN
1764    
1765           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1766    
1767         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1768         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1769         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1770         size_t variable.         size_t variable.
# Line 1687  INFORMATION ABOUT A PATTERN Line 1772  INFORMATION ABOUT A PATTERN
1772           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1773    
1774         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1775         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1776         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1777         created by pcre_study(). The fourth argument should point to  a  size_t         created  by  pcre_study(). The fourth argument should point to a size_t
1778         variable.         variable.
1779    
1780    
# Line 1697  OBSOLETE INFO FUNCTION Line 1782  OBSOLETE INFO FUNCTION
1782    
1783         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1784    
1785         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1786         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1787         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1788         pcre_info() is the number of capturing subpatterns, or one of the  fol-         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1789         lowing negative numbers:         lowing negative numbers:
1790    
1791           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1792           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1793    
1794         If  the  optptr  argument is not NULL, a copy of the options with which         If the optptr argument is not NULL, a copy of the  options  with  which
1795         the pattern was compiled is placed in the integer  it  points  to  (see         the  pattern  was  compiled  is placed in the integer it points to (see
1796         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1797    
1798         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1799         NULL, it is used to pass back information about the first character  of         NULL,  it is used to pass back information about the first character of
1800         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1801    
1802    
# Line 1719  REFERENCE COUNTS Line 1804  REFERENCE COUNTS
1804    
1805         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1806    
1807         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1808         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1809         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1810         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1811         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1812    
1813         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1814         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1815         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1816         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1817         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1818         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1819    
1820         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1821         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1822         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1823    
1824    
# Line 1827  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1912  MATCHING A PATTERN: THE TRADITIONAL FUNC
1912         the  total number of calls, because not all calls to match() are recur-         the  total number of calls, because not all calls to match() are recur-
1913         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
1914    
1915         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1916         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
1917         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1918    
1919         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
1920         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1921         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1922         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1923         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1924         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1925    
1926         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
1927         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1928    
1929         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1930         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1931         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
1932         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1933         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
1934         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
1935         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1936         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1937         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1938         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1939    
1940     Option bits for pcre_exec()     Option bits for pcre_exec()
1941    
1942         The unused bits of the options argument for pcre_exec() must  be  zero.         The  unused  bits of the options argument for pcre_exec() must be zero.
1943         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
1944         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
1945         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
1946           PCRE_PARTIAL_HARD.
1947    
1948           PCRE_ANCHORED           PCRE_ANCHORED
1949    
# Line 1937  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2023  MATCHING A PATTERN: THE TRADITIONAL FUNC
2023    
2024           a?b?           a?b?
2025    
2026         is applied to a string not beginning with "a" or "b",  it  matches  the         is applied to a string not beginning with "a" or  "b",  it  matches  an
2027         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
2028         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2029         rences of "a" or "b".         rences of "a" or "b".
2030    
2031         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2032         cial case of a pattern match of the empty  string  within  its  split()  
2033         function,  and  when  using  the /g modifier. It is possible to emulate         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2034         Perl's behaviour after matching a null string by first trying the match         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2035         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2036         if that fails by advancing the starting offset (see below)  and  trying  
2037         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2038         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2039           match  of  the empty string within its split() function, and when using
2040           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2041           matching a null string by first trying the match again at the same off-
2042           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2043           fails, by advancing the starting offset (see below) and trying an ordi-
2044           nary match again. There is some code that demonstrates how to  do  this
2045           in the pcredemo sample program.
2046    
2047             PCRE_NO_START_OPTIMIZE
2048    
2049           There  are a number of optimizations that pcre_exec() uses at the start
2050           of a match, in order to speed up the process. For  example,  if  it  is
2051           known  that  a  match must start with a specific character, it searches
2052           the subject for that character, and fails immediately if it cannot find
2053           it,  without actually running the main matching function. When callouts
2054           are in use, these optimizations can cause  them  to  be  skipped.  This
2055           option  disables  the  "start-up" optimizations, causing performance to
2056           suffer, but ensuring that the callouts do occur.
2057    
2058           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2059    
# Line 1973  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2077  MATCHING A PATTERN: THE TRADITIONAL FUNC
2077         value  of startoffset that does not point to the start of a UTF-8 char-         value  of startoffset that does not point to the start of a UTF-8 char-
2078         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2079    
2080           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2081             PCRE_PARTIAL_SOFT
2082    
2083         This option turns on the  partial  matching  feature.  If  the  subject         These options turn on the partial matching feature. For backwards  com-
2084         string  fails to match the pattern, but at some point during the match-         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2085         ing process the end of the subject was reached (that  is,  the  subject         match occurs if the end of the subject string is reached  successfully,
2086         partially  matches  the  pattern and the failure to match occurred only         but  there  are not enough subject characters to complete the match. If
2087         because there were not enough subject characters), pcre_exec()  returns         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
2088         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
2089         used, there are restrictions on what may appear in the  pattern.  These         matching continues by testing any other alternatives. Only if they  all
2090         are discussed in the pcrepartial documentation.         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
2091           The portion of the string that was inspected when the partial match was
2092           found  is  set  as  the first matching string. There is a more detailed
2093           discussion in the pcrepartial documentation.
2094    
2095     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2096    
2097         The  subject string is passed to pcre_exec() as a pointer in subject, a         The subject string is passed to pcre_exec() as a pointer in subject,  a
2098         length in length, and a starting byte offset in startoffset.  In  UTF-8         length (in bytes) in length, and a starting byte offset in startoffset.
2099         mode,  the  byte  offset  must point to the start of a UTF-8 character.         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2100         Unlike the pattern string, the subject may contain binary  zero  bytes.         acter.  Unlike  the pattern string, the subject may contain binary zero
2101         When  the starting offset is zero, the search for a match starts at the         bytes. When the starting offset is zero, the search for a match  starts
2102         beginning of the subject, and this is by far the most common case.         at  the  beginning  of  the subject, and this is by far the most common
2103           case.
2104    
2105         A non-zero starting offset is useful when searching for  another  match         A non-zero starting offset is useful when searching for  another  match
2106         in  the same subject by calling pcre_exec() again after a previous suc-         in  the same subject by calling pcre_exec() again after a previous suc-
# Line 2027  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2136  MATCHING A PATTERN: THE TRADITIONAL FUNC
2136         string.  PCRE  supports several other kinds of parenthesized subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2137         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2138    
2139         Captured substrings are returned to the caller via a vector of  integer         Captured substrings are returned to the caller via a vector of integers
2140         offsets  whose  address is passed in ovector. The number of elements in         whose  address is passed in ovector. The number of elements in the vec-
2141         the vector is passed in ovecsize, which must be a non-negative  number.         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2142         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2143    
2144         The  first  two-thirds of the vector is used to pass back captured sub-         The  first  two-thirds of the vector is used to pass back captured sub-
2145         strings, each substring using a pair of integers. The  remaining  third         strings, each substring using a pair of integers. The  remaining  third
2146         of  the  vector is used as workspace by pcre_exec() while matching cap-         of  the  vector is used as workspace by pcre_exec() while matching cap-
2147         turing subpatterns, and is not available for passing back  information.         turing subpatterns, and is not available for passing back  information.
2148         The  length passed in ovecsize should always be a multiple of three. If         The  number passed in ovecsize should always be a multiple of three. If
2149         it is not, it is rounded down.         it is not, it is rounded down.
2150    
2151         When a match is successful, information about  captured  substrings  is         When a match is successful, information about  captured  substrings  is
2152         returned  in  pairs  of integers, starting at the beginning of ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2153         and continuing up to two-thirds of its length at the  most.  The  first         and continuing up to two-thirds of its length at the  most.  The  first
2154         element of a pair is set to the offset of the first character in a sub-         element  of  each pair is set to the byte offset of the first character
2155         string, and the second is set to the  offset  of  the  first  character         in a substring, and the second is set to the byte offset of  the  first
2156         after  the  end  of  a  substring. The first pair, ovector[0] and ovec-         character  after  the end of a substring. Note: these values are always
2157         tor[1], identify the portion of  the  subject  string  matched  by  the         byte offsets, even in UTF-8 mode. They are not character counts.
2158         entire  pattern.  The next pair is used for the first capturing subpat-  
2159         tern, and so on. The value returned by pcre_exec() is one more than the         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2160         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2161         have been captured, the returned value is 3. If there are no  capturing         pair is used for the first capturing subpattern, and so on.  The  value
2162         subpatterns,  the return value from a successful match is 1, indicating         returned by pcre_exec() is one more than the highest numbered pair that
2163         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2164           returned  value is 3. If there are no capturing subpatterns, the return
2165           value from a successful match is 1, indicating that just the first pair
2166           of offsets has been set.
2167    
2168         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2169         of the string that it matched that is returned.         of the string that it matched that is returned.
2170    
2171         If  the vector is too small to hold all the captured substring offsets,         If the vector is too small to hold all the captured substring  offsets,
2172         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2173         function  returns a value of zero. In particular, if the substring off-         function returns a value of zero. If the substring offsets are  not  of
2174         sets are not of interest, pcre_exec() may be called with ovector passed         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2175         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         ovecsize as zero. However, if the pattern contains back references  and
2176         references and the ovector is not big enough to  remember  the  related         the  ovector is not big enough to remember the related substrings, PCRE
2177         substrings,  PCRE has to get additional memory for use during matching.         has to get additional memory for use during matching. Thus it  is  usu-
2178         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2179    
2180         The pcre_info() function can be used to find  out  how  many  capturing         The  pcre_info()  function  can  be used to find out how many capturing
2181         subpatterns  there  are  in  a  compiled pattern. The smallest size for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2182         ovector that will allow for n captured substrings, in addition  to  the         ovector  that  will allow for n captured substrings, in addition to the
2183         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2184    
2185         It  is  possible for capturing subpattern number n+1 to match some part         It is possible for capturing subpattern number n+1 to match  some  part
2186         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2187         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2188         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2189         2  is  not.  When  this happens, both values in the offset pairs corre-         2 is not. When this happens, both values in  the  offset  pairs  corre-
2190         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2191    
2192         Offset values that correspond to unused subpatterns at the end  of  the         Offset  values  that correspond to unused subpatterns at the end of the
2193         expression  are  also  set  to  -1. For example, if the string "abc" is         expression are also set to -1. For example,  if  the  string  "abc"  is
2194         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2195         matched.  The  return  from the function is 2, because the highest used         matched. The return from the function is 2, because  the  highest  used
2196         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2197         for  the  second  and third capturing subpatterns if you wish (assuming         for the second and third capturing subpatterns if  you  wish  (assuming
2198         the vector is large enough, of course).         the vector is large enough, of course).
2199    
2200         Some convenience functions are provided  for  extracting  the  captured         Some  convenience  functions  are  provided for extracting the captured
2201         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2202    
2203     Error return values from pcre_exec()     Error return values from pcre_exec()
2204    
2205         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2206         defined in the header file:         defined in the header file:
2207    
2208           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2099  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2211  MATCHING A PATTERN: THE TRADITIONAL FUNC
2211    
2212           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2213    
2214         Either code or subject was passed as NULL,  or  ovector  was  NULL  and         Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2215         ovecsize was not zero.         ovecsize was not zero.
2216    
2217           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2108  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2220  MATCHING A PATTERN: THE TRADITIONAL FUNC
2220    
2221           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2222    
2223         PCRE  stores a 4-byte "magic number" at the start of the compiled code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2224         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2225         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2226         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2227         gives when the magic number is not present.         gives when the magic number is not present.
2228    
2229           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2230    
2231         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2232         compiled pattern. This error could be caused by a bug  in  PCRE  or  by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2233         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2234    
2235           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2236    
2237         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2238         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2239         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
2240         purpose. If the call via pcre_malloc() fails, this error is given.  The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2241         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2242    
2243           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2244    
2245         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2246         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2247         returned by pcre_exec().         returned by pcre_exec().
2248    
2249           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2250    
2251         The  backtracking  limit,  as  specified  by the match_limit field in a         The backtracking limit, as specified by  the  match_limit  field  in  a
2252         pcre_extra structure (or defaulted) was reached.  See  the  description         pcre_extra  structure  (or  defaulted) was reached. See the description
2253         above.         above.
2254    
2255           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2256    
2257         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2258         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2259         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2260    
2261           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2262    
2263         A  string  that contains an invalid UTF-8 byte sequence was passed as a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2264         subject.         subject.
2265    
2266           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2267    
2268         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2269         value  of startoffset did not point to the beginning of a UTF-8 charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2270         ter.         ter.
2271    
2272           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2273    
2274         The subject string did not match, but it did match partially.  See  the         The  subject  string did not match, but it did match partially. See the
2275         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2276    
2277           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2278    
2279         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2280         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2281         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2282           onwards, there are no restrictions on partial matching.
2283    
2284           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2285    
# Line 2175  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2288  MATCHING A PATTERN: THE TRADITIONAL FUNC
2288    
2289           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2290    
2291         This error is given if the value of the ovecsize argument is  negative.         This error is given if the value of the ovecsize argument is negative.
2292    
2293           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2294    
2295         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2296         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2297         description above.         description above.
2298    
2299           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
# Line 2203  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2316  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2316         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2317              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2318    
2319         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2320         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2321         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2322         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2323         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2324         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2325         substrings.         substrings.
2326    
2327         A  substring that contains a binary zero is correctly extracted and has         A substring that contains a binary zero is correctly extracted and  has
2328         a further zero added on the end, but the result is not, of course, a  C         a  further zero added on the end, but the result is not, of course, a C
2329         string.   However,  you  can  process such a string by referring to the         string.  However, you can process such a string  by  referring  to  the
2330         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2331         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2332         not adequate for handling strings containing binary zeros, because  the         not  adequate for handling strings containing binary zeros, because the
2333         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2334    
2335         The  first  three  arguments  are the same for all three of these func-         The first three arguments are the same for all  three  of  these  func-
2336         tions: subject is the subject string that has  just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2337         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2338         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2339         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2340         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2341         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2342         it ran out of space in ovector, the value passed as stringcount  should         it  ran out of space in ovector, the value passed as stringcount should
2343         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2344    
2345         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2346         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2347         zero  extracts  the  substring that matched the entire pattern, whereas         zero extracts the substring that matched the  entire  pattern,  whereas
2348         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2349         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2350         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2351         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2352         The yield of the function is the length of the  string,  not  including         The  yield  of  the function is the length of the string, not including
2353         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2354    
2355           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2356    
2357         The  buffer  was too small for pcre_copy_substring(), or the attempt to         The buffer was too small for pcre_copy_substring(), or the  attempt  to
2358         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2359    
2360           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2361    
2362         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2363    
2364         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2365         strings  and  builds  a list of pointers to them. All this is done in a         strings and builds a list of pointers to them. All this is  done  in  a
2366         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2367         the  memory  block  is returned via listptr, which is also the start of         the memory block is returned via listptr, which is also  the  start  of
2368         the list of string pointers. The end of the list is marked  by  a  NULL         the  list  of  string pointers. The end of the list is marked by a NULL
2369         pointer.  The  yield  of  the function is zero if all went well, or the         pointer. The yield of the function is zero if all  went  well,  or  the
2370         error code         error code
2371    
2372           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2373    
2374         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2375    
2376         When any of these functions encounter a substring that is unset,  which         When  any of these functions encounter a substring that is unset, which
2377         can  happen  when  capturing subpattern number n+1 matches some part of         can happen when capturing subpattern number n+1 matches  some  part  of
2378         the subject, but subpattern n has not been used at all, they return  an         the  subject, but subpattern n has not been used at all, they return an
2379         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2380         string by inspecting the appropriate offset in ovector, which is  nega-         string  by inspecting the appropriate offset in ovector, which is nega-
2381         tive for unset substrings.         tive for unset substrings.
2382    
2383         The  two convenience functions pcre_free_substring() and pcre_free_sub-         The two convenience functions pcre_free_substring() and  pcre_free_sub-
2384         string_list() can be used to free the memory  returned  by  a  previous         string_list()  can  be  used  to free the memory returned by a previous
2385         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2386         tively. They do nothing more than  call  the  function  pointed  to  by         tively.  They  do  nothing  more  than  call the function pointed to by
2387         pcre_free,  which  of course could be called directly from a C program.         pcre_free, which of course could be called directly from a  C  program.
2388         However, PCRE is used in some situations where it is linked via a  spe-         However,  PCRE is used in some situations where it is linked via a spe-
2389         cial   interface  to  another  programming  language  that  cannot  use         cial  interface  to  another  programming  language  that  cannot   use
2390         pcre_free directly; it is for these cases that the functions  are  pro-         pcre_free  directly;  it is for these cases that the functions are pro-
2391         vided.         vided.
2392    
2393    
# Line 2293  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2406  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2406              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2407              const char **stringptr);              const char **stringptr);
2408    
2409         To  extract a substring by name, you first have to find associated num-         To extract a substring by name, you first have to find associated  num-
2410         ber.  For example, for this pattern         ber.  For example, for this pattern
2411    
2412           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2302  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2415  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2415         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2416         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2417         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2418         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
2419         subpattern of that name.         subpattern of that name.
2420    
2421         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2422         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2423         are also two functions that do the whole job.         are also two functions that do the whole job.
2424    
2425         Most    of    the    arguments   of   pcre_copy_named_substring()   and         Most   of   the   arguments    of    pcre_copy_named_substring()    and
2426         pcre_get_named_substring() are the same  as  those  for  the  similarly         pcre_get_named_substring()  are  the  same  as  those for the similarly
2427         named  functions  that extract by number. As these are described in the         named functions that extract by number. As these are described  in  the
2428         previous section, they are not re-described here. There  are  just  two         previous  section,  they  are not re-described here. There are just two
2429         differences:         differences:
2430    
2431         First,  instead  of a substring number, a substring name is given. Sec-         First, instead of a substring number, a substring name is  given.  Sec-
2432         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2433         to  the compiled pattern. This is needed in order to gain access to the         to the compiled pattern. This is needed in order to gain access to  the
2434         name-to-number translation table.         name-to-number translation table.
2435    
2436         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2437         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2438         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2439         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2440    
2441           Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
2442           patterns  with  the  same  number,  you cannot use names to distinguish
2443           them, because names are not included in the compiled code. The matching
2444           process uses only numbers.
2445    
2446    
2447  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2448    
# Line 2388  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2506  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2506         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics to the normal algorithm, and  is  not  compatible  with
2507         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2508         theless, there are times when this kind of matching can be useful.  For         theless, there are times when this kind of matching can be useful.  For
2509         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2510         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2511           tion.
2512    
2513         The arguments for the pcre_dfa_exec() function  are  the  same  as  for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2514         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2515         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2516         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2517         repeated here.         repeated here.
2518    
2519         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2520         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2521         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2522         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2523         lot of potential matches.         lot of potential matches.
2524    
2525         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2422  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2541  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2541    
2542     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2543    
2544         The unused bits of the options argument  for  pcre_dfa_exec()  must  be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2545         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2546         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2547         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
2548         three of these are the same as for pcre_exec(), so their description is         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and  PCRE_DFA_RESTART. All but the last
2549         not repeated here.         four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
2550           description is not repeated here.
2551           PCRE_PARTIAL  
2552             PCRE_PARTIAL_HARD
2553         This  has  the  same general effect as it does for pcre_exec(), but the           PCRE_PARTIAL_SOFT
2554         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for  
2555         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into         These  have the same general effect as they do for pcre_exec(), but the
2556         PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2557         been no complete matches, but there is still at least one matching pos-         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2558         sibility. The portion of the string that provided the partial match  is         ject is reached and there is still at least  one  matching  possibility
2559         set as the first matching string.         that requires additional characters. This happens even if some complete
2560           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2561           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2562           of the subject is reached, there have been  no  complete  matches,  but
2563           there  is  still  at least one matching possibility. The portion of the
2564           string that was inspected when the longest partial match was  found  is
2565           set as the first matching string in both cases.
2566    
2567           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2568    
# Line 2448  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2573  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2573    
2574           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2575    
2576         When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2577         returns  a  partial  match, it is possible to call it again, with addi-         again,  with  additional  subject characters, and have it continue with
2578         tional subject characters, and have it continue with  the  same  match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
2579         The  PCRE_DFA_RESTART  option requests this action; when it is set, the         it  is  set,  the workspace and wscount options must reference the same
2580         workspace and wscount options must reference the same vector as  before         vector as before because data about the match so far is  left  in  them
2581         because  data  about  the  match so far is left in them after a partial         after a partial match. There is more discussion of this facility in the
2582         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2583    
2584     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2585    
2586         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
2587         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2588         of  the  function  start  at the same point in the subject. The shorter         of the function start at the same point in  the  subject.  The  shorter
2589         matches are all initial substrings of the longer matches. For  example,         matches  are all initial substrings of the longer matches. For example,
2590         if the pattern         if the pattern
2591    
2592           <.*>           <.*>
# Line 2477  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2601  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2601           <something> <something else>           <something> <something else>
2602           <something> <something else> <something further>           <something> <something else> <something further>
2603    
2604         On  success,  the  yield of the function is a number greater than zero,         On success, the yield of the function is a number  greater  than  zero,
2605         which is the number of matched substrings.  The  substrings  themselves         which  is  the  number of matched substrings. The substrings themselves
2606         are  returned  in  ovector. Each string uses two elements; the first is         are returned in ovector. Each string uses two elements;  the  first  is
2607         the offset to the start, and the second is the offset to  the  end.  In         the  offset  to  the start, and the second is the offset to the end. In
2608         fact,  all  the  strings  have the same start offset. (Space could have         fact, all the strings have the same start  offset.  (Space  could  have
2609         been saved by giving this only once, but it was decided to retain  some         been  saved by giving this only once, but it was decided to retain some
2610         compatibility  with  the  way pcre_exec() returns data, even though the         compatibility with the way pcre_exec() returns data,  even  though  the
2611         meaning of the strings is different.)         meaning of the strings is different.)
2612    
2613         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2614         est  matching  string is given first. If there were too many matches to         est matching string is given first. If there were too many  matches  to
2615         fit into ovector, the yield of the function is zero, and the vector  is         fit  into ovector, the yield of the function is zero, and the vector is
2616         filled with the longest matches.         filled with the longest matches.
2617    
2618     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2619    
2620         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2621         Many of the errors are the same  as  for  pcre_exec(),  and  these  are         Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2622         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2623         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2624    
2625           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2626    
2627         This return is given if pcre_dfa_exec() encounters an item in the  pat-         This  return is given if pcre_dfa_exec() encounters an item in the pat-
2628         tern  that  it  does not support, for instance, the use of \C or a back         tern that it does not support, for instance, the use of \C  or  a  back
2629         reference.         reference.
2630    
2631           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2632    
2633         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2634         that  uses  a back reference for the condition, or a test for recursion         that uses a back reference for the condition, or a test  for  recursion
2635         in a specific group. These are not supported.         in a specific group. These are not supported.
2636    
2637           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2638    
2639         This return is given if pcre_dfa_exec() is called with an  extra  block         This  return  is given if pcre_dfa_exec() is called with an extra block
2640         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2641         (it is meaningless).         (it is meaningless).
2642    
2643           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2644    
2645         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2646         workspace vector.         workspace vector.
2647    
2648           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2649    
2650         When  a  recursive subpattern is processed, the matching function calls         When a recursive subpattern is processed, the matching  function  calls
2651         itself recursively, using private vectors for  ovector  and  workspace.         itself  recursively,  using  private vectors for ovector and workspace.
2652         This  error  is  given  if  the output vector is not large enough. This         This error is given if the output vector  is  not  large  enough.  This
2653         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2654    
2655    
2656  SEE ALSO  SEE ALSO
2657    
2658         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2659         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2660    
2661    
2662  AUTHOR  AUTHOR
# Line 2544  AUTHOR Line 2668  AUTHOR
2668    
2669  REVISION  REVISION
2670    
2671         Last updated: 27 November 2007         Last updated: 22 September 2009
2672         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2673  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2674    
2675    
2676  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2677    
2678    
# Line 2596  PCRE CALLOUTS Line 2720  PCRE CALLOUTS
2720  MISSING CALLOUTS  MISSING CALLOUTS
2721    
2722         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2723         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2724         pattern is         example, if the pattern is
2725    
2726           ab(?C4)cd           ab(?C4)cd
2727    
# Line 2606  MISSING CALLOUTS Line 2730  MISSING CALLOUTS
2730         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2731         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2732    
2733           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2734           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2735           matching process, but does ensure that callouts  such  as  the  example
2736           above are obeyed.
2737    
2738    
2739  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2740    
2741         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2742         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2743         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2744         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2745         block. This structure contains the following fields:         block. This structure contains the following fields:
2746    
2747           int          version;           int          version;
# Line 2628  THE CALLOUT INTERFACE Line 2757  THE CALLOUT INTERFACE
2757           int          pattern_position;           int          pattern_position;
2758           int          next_item_length;           int          next_item_length;
2759    
2760         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2761         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2762         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2763         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2764    
2765         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2715  AUTHOR Line 2844  AUTHOR
2844    
2845  REVISION  REVISION
2846    
2847         Last updated: 29 May 2007         Last updated: 15 March 2009
2848         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2849  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2850    
2851    
2852  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2853    
2854    
# Line 2732  DIFFERENCES BETWEEN PCRE AND PERL Line 2861  DIFFERENCES BETWEEN PCRE AND PERL
2861         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2862         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences described here  are  mainly
2863         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2864         some features that are expected to be in the forthcoming Perl 5.10.         some features that are in Perl 5.10.
2865    
2866         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2867         of  what  it does have are given in the section on UTF-8 support in the         of  what  it does have are given in the section on UTF-8 support in the
# Line 2764  DIFFERENCES BETWEEN PCRE AND PERL Line 2893  DIFFERENCES BETWEEN PCRE AND PERL
2893         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
2894         can be tested with \p and \P are limited to the general category  prop-         can be tested with \p and \P are limited to the general category  prop-
2895         erties  such  as  Lu and Nd, script names such as Greek or Han, and the         erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2896         derived properties Any and L&.         derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
2897           property,  which  Perl  does  not; the Perl documentation says "Because
2898           Perl hides the need for the user to understand the internal representa-
2899           tion  of Unicode characters, there is no need to implement the somewhat
2900           messy concept of surrogates."
2901    
2902         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2903         ters  in  between  are  treated as literals. This is slightly different         ters  in  between  are  treated as literals. This is slightly different
# Line 2784  DIFFERENCES BETWEEN PCRE AND PERL Line 2917  DIFFERENCES BETWEEN PCRE AND PERL
2917    
2918         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2919         constructions. However, there is support for recursive  patterns.  This         constructions. However, there is support for recursive  patterns.  This
2920         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE         is  not  available  in Perl 5.8, but it is in Perl 5.10. Also, the PCRE
2921         "callout" feature allows an external function to be called during  pat-         "callout" feature allows an external function to be called during  pat-
2922         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
2923    
2924         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2925         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2926         unlike Perl.         unlike  Perl. There is a discussion of an example that explains this in
2927           more detail in the section on recursion differences from  Perl  in  the
2928           pcrecompat page.
2929    
2930         10.  There are some differences that are concerned with the settings of         10.  There are some differences that are concerned with the settings of
2931         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
# Line 2799  DIFFERENCES BETWEEN PCRE AND PERL Line 2934  DIFFERENCES BETWEEN PCRE AND PERL
2934    
2935         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2936         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2937         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         the forms without an argument. PCRE does not support (*MARK).
        (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-  
        ture group; this is different to Perl.  
2938    
2939         12. PCRE provides some extensions to the Perl regular expression facil-         12. PCRE provides some extensions to the Perl regular expression facil-
2940         ities.   Perl  5.10  will  include new features that are not in earlier         ities.   Perl  5.10  will  include new features that are not in earlier
# Line 2826  DIFFERENCES BETWEEN PCRE AND PERL Line 2959  DIFFERENCES BETWEEN PCRE AND PERL
2959         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
2960         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
2961    
2962         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2963         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
2964           lents.
2965    
2966         (g) The \R escape sequence can be restricted to match only CR,  LF,  or         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
2967         CRLF by the PCRE_BSR_ANYCRLF option.         CRLF by the PCRE_BSR_ANYCRLF option.
2968    
2969         (h) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
# Line 2839  DIFFERENCES BETWEEN PCRE AND PERL Line 2973  DIFFERENCES BETWEEN PCRE AND PERL
2973         (j) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2974         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2975    
2976         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2977         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2978    
2979         (l)  PCRE  recognizes some special sequences such as (*CR) at the start         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
2980         of a pattern that set overall options that cannot be changed within the         of a pattern that set overall options that cannot be changed within the
2981         pattern.         pattern.
2982    
# Line 2856  AUTHOR Line 2990  AUTHOR
2990    
2991  REVISION  REVISION
2992    
2993         Last updated: 11 September 2007         Last updated: 18 September 2009
2994         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2995  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2996    
2997    
2998  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
2999    
3000    
# Line 2872  PCRE REGULAR EXPRESSION DETAILS Line 3006  PCRE REGULAR EXPRESSION DETAILS
3006    
3007         The  syntax and semantics of the regular expressions that are supported         The  syntax and semantics of the regular expressions that are supported
3008         by PCRE are described in detail below. There is a quick-reference  syn-         by PCRE are described in detail below. There is a quick-reference  syn-
3009         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3010         described in its own documentation, and regular expressions in  general         semantics as closely as it can. PCRE  also  supports  some  alternative
3011         are  covered in a number of books, some of which have copious examples.         regular  expression  syntax (which does not conflict with the Perl syn-
3012         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by         tax) in order to provide some compatibility with regular expressions in
3013         O'Reilly,  covers regular expressions in great detail. This description         Python, .NET, and Oniguruma.
3014         of PCRE's regular expressions is intended as reference material.  
3015           Perl's  regular expressions are described in its own documentation, and
3016           regular expressions in general are covered in a number of  books,  some
3017           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3018           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3019           great  detail.  This  description  of  PCRE's  regular  expressions  is
3020           intended as reference material.
3021    
3022         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3023         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
3024         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, you must build PCRE to  include  UTF-8  support,  and  then  call
3025         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
3026         matching is mentioned in several places below. There is also a  summary         sequence that can be given at the start of a pattern:
3027         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3028         page.           (*UTF8)
3029    
3030           Starting a pattern with this sequence  is  equivalent  to  setting  the
3031           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3032           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3033           below.  There  is  also  a  summary of UTF-8 features in the section on
3034           UTF-8 support in the main pcre page.
3035    
3036         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3037         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
# Line 2989  CHARACTERS AND METACHARACTERS Line 3135  CHARACTERS AND METACHARACTERS
3135                    syntax)                    syntax)
3136           ]      terminates the character class           ]      terminates the character class
3137    
3138         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3139    
3140    
3141  BACKSLASH  BACKSLASH
3142    
3143         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3144         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3145         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3146         applies both inside and outside character classes.         applies both inside and outside character classes.
3147    
3148         For  example,  if  you want to match a * character, you write \* in the         For example, if you want to match a * character, you write  \*  in  the
3149         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3150         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3151         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3152         that  it stands for itself. In particular, if you want to match a back-         that it stands for itself. In particular, if you want to match a  back-
3153         slash, you write \\.         slash, you write \\.
3154    
3155         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3156         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3157         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3158         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3159         part of the pattern.         part of the pattern.
3160    
3161         If you want to remove the special meaning from a  sequence  of  charac-         If  you  want  to remove the special meaning from a sequence of charac-
3162         ters,  you can do so by putting them between \Q and \E. This is differ-         ters, you can do so by putting them between \Q and \E. This is  differ-
3163         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E
3164         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3165         tion. Note the following examples:         tion. Note the following examples:
3166    
3167           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3025  BACKSLASH Line 3171  BACKSLASH
3171           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3172           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3173    
3174         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3175         classes.         classes.
3176    
3177     Non-printing characters     Non-printing characters
3178    
3179         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3180         acters in patterns in a visible manner. There is no restriction on  the         acters  in patterns in a visible manner. There is no restriction on the
3181         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3182         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3183         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
3184         sequences than the binary character it represents:         sequences than the binary character it represents:
3185    
3186           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 3048  BACKSLASH Line 3194  BACKSLASH
3194           \xhh      character with hex code hh           \xhh      character with hex code hh
3195           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3196    
3197         The precise effect of \cx is as follows: if x is a lower  case  letter,         The  precise  effect of \cx is as follows: if x is a lower case letter,
3198         it  is converted to upper case. Then bit 6 of the character (hex 40) is         it is converted to upper case. Then bit 6 of the character (hex 40)  is
3199         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
3200         becomes hex 7B.         becomes hex 7B.
3201    
3202         After  \x, from zero to two hexadecimal digits are read (letters can be         After \x, from zero to two hexadecimal digits are read (letters can  be
3203         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3204         between  \x{  and  },  but the value of the character code must be less         between \x{ and }, but the value of the character  code  must  be  less
3205         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3206         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3207         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3208    
3209         If characters other than hexadecimal digits appear between \x{  and  },         If  characters  other than hexadecimal digits appear between \x{ and },
3210         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3211         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3212         escape,  with  no  following  digits, giving a character whose value is         escape, with no following digits, giving a  character  whose  value  is
3213         zero.         zero.
3214    
3215         Characters whose value is less than 256 can be defined by either of the         Characters whose value is less than 256 can be defined by either of the
3216         two  syntaxes  for  \x. There is no difference in the way they are han-         two syntaxes for \x. There is no difference in the way  they  are  han-
3217         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3218    
3219         After \0 up to two further octal digits are read. If  there  are  fewer         After  \0  up  to two further octal digits are read. If there are fewer
3220         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3221         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3222         (code  value 7). Make sure you supply two digits after the initial zero         (code value 7). Make sure you supply two digits after the initial  zero
3223         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3224    
3225         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3226         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3227         its as a decimal number. If the number is less than  10,  or  if  there         its  as  a  decimal  number. If the number is less than 10, or if there
3228         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3229         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3230         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3231         of parenthesized subpatterns.         of parenthesized subpatterns.
3232    
3233         Inside a character class, or if the decimal number is  greater  than  9         Inside  a  character  class, or if the decimal number is greater than 9
3234         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3235         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3236         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3237         non-UTF-8 mode, the value of a character specified  in  octal  must  be         non-UTF-8  mode,  the  value  of a character specified in octal must be
3238         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
3239         example:         example:
3240    
3241           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3107  BACKSLASH Line 3253  BACKSLASH
3253           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3254                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3255    
3256         Note that octal values of 100 or greater must not be  introduced  by  a         Note  that  octal  values of 100 or greater must not be introduced by a
3257         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3258    
3259         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3260         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3261         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3262         08), and the sequences \R and \X are interpreted as the characters  "R"         08),  and the sequences \R and \X are interpreted as the characters "R"
3263         and  "X", respectively. Outside a character class, these sequences have         and "X", respectively. Outside a character class, these sequences  have
3264         different meanings (see below).         different meanings (see below).
3265    
3266     Absolute and relative back references     Absolute and relative back references
3267    
3268         The sequence \g followed by an unsigned or a negative  number,  option-         The  sequence  \g followed by an unsigned or a negative number, option-
3269         ally  enclosed  in braces, is an absolute or relative back reference. A         ally enclosed in braces, is an absolute or relative back  reference.  A
3270         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3271         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3272    
3273       Absolute and relative subroutine calls
3274    
3275           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3276           name or a number enclosed either in angle brackets or single quotes, is
3277           an alternative syntax for referencing a subpattern as  a  "subroutine".
3278           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3279           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3280           reference; the latter is a subroutine call.
3281    
3282     Generic character types     Generic character types
3283    
3284         Another use of backslash is for specifying generic character types. The         Another use of backslash is for specifying generic character types. The
# Line 3159  BACKSLASH Line 3314  BACKSLASH
3314         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3315         code  character  property  support is available. These sequences retain         code  character  property  support is available. These sequences retain
3316         their original meanings from before UTF-8 support was available, mainly         their original meanings from before UTF-8 support was available, mainly
3317         for efficiency reasons.         for  efficiency  reasons. Note that this also affects \b, because it is
3318           defined in terms of \w and \W.
3319    
3320         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3321         the other sequences, these do match certain high-valued  codepoints  in         the  other  sequences, these do match certain high-valued codepoints in
3322         UTF-8 mode.  The horizontal space characters are:         UTF-8 mode.  The horizontal space characters are:
3323    
3324           U+0009     Horizontal tab           U+0009     Horizontal tab
# Line 3196  BACKSLASH Line 3352  BACKSLASH
3352           U+2029     Paragraph separator           U+2029     Paragraph separator
3353    
3354         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character less than 256 that
3355         is a letter or digit. The definition of  letters  and  digits  is  con-         is  a  letter  or  digit.  The definition of letters and digits is con-
3356         trolled  by PCRE's low-valued character tables, and may vary if locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3357         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3358         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3359         systems, or "french" in Windows, some character codes greater than  128         systems,  or "french" in Windows, some character codes greater than 128
3360         are  used for accented letters, and these are matched by \w. The use of         are used for accented letters, and these are matched by \w. The use  of
3361         locales with Unicode is discouraged.         locales with Unicode is discouraged.
3362    
3363     Newline sequences     Newline sequences
3364    
3365         Outside a character class, by default, the escape sequence  \R  matches         Outside  a  character class, by default, the escape sequence \R matches
3366         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3367         mode \R is equivalent to the following:         mode \R is equivalent to the following:
3368    
3369           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3370    
3371         This is an example of an "atomic group", details  of  which  are  given         This  is  an  example  of an "atomic group", details of which are given
3372         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3373         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3374         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3375         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3376         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3377    
3378         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3379         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3380         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3381         these characters to be recognized.         these characters to be recognized.
3382    
3383         It is possible to restrict \R to match only CR, LF, or CRLF (instead of         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3384         the  complete  set  of  Unicode  line  endings)  by  setting the option         the complete set  of  Unicode  line  endings)  by  setting  the  option
3385         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3386         (BSR is an abbrevation for "backslash R".) This can be made the default         (BSR is an abbrevation for "backslash R".) This can be made the default
3387         when PCRE is built; if this is the case, the  other  behaviour  can  be         when  PCRE  is  built;  if this is the case, the other behaviour can be
3388         requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to         requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3389         specify these settings by starting a pattern string  with  one  of  the         specify  these  settings  by  starting a pattern string with one of the
3390         following sequences:         following sequences:
3391    
3392           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
# Line 3239  BACKSLASH Line 3395  BACKSLASH
3395         These override the default and the options given to pcre_compile(), but         These override the default and the options given to pcre_compile(), but
3396         they can be overridden by options given to pcre_exec(). Note that these         they can be overridden by options given to pcre_exec(). Note that these
3397         special settings, which are not Perl-compatible, are recognized only at         special settings, which are not Perl-compatible, are recognized only at
3398         the very start of a pattern, and that they must be in  upper  case.  If         the  very  start  of a pattern, and that they must be in upper case. If
3399         more  than  one  of  them is present, the last one is used. They can be         more than one of them is present, the last one is  used.  They  can  be
3400         combined with a change of newline convention, for  example,  a  pattern         combined  with  a  change of newline convention, for example, a pattern
3401         can start with:         can start with:
3402    
3403           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
# Line 3251  BACKSLASH Line 3407  BACKSLASH
3407     Unicode character properties     Unicode character properties
3408    
3409         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3410         tional escape sequences that match characters with specific  properties         tional  escape sequences that match characters with specific properties
3411         are  available.   When not in UTF-8 mode, these sequences are of course         are available.  When not in UTF-8 mode, these sequences are  of  course
3412         limited to testing characters whose codepoints are less than  256,  but         limited  to  testing characters whose codepoints are less than 256, but
3413         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3414    
3415           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3416           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3417           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3418    
3419         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
3420         script names, the general category properties, and "Any", which matches         script names, the general category properties, and "Any", which matches
3421         any character (including newline). Other properties such as "InMusical-         any character (including newline). Other properties such as "InMusical-
3422         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
3423         not match any characters, so always causes a match failure.         not match any characters, so always causes a match failure.
3424    
3425         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3426         A character from one of these sets can be matched using a script  name.         A  character from one of these sets can be matched using a script name.
3427         For example:         For example:
3428    
3429           \p{Greek}           \p{Greek}
3430           \P{Han}           \P{Han}
3431    
3432         Those  that are not part of an identified script are lumped together as         Those that are not part of an identified script are lumped together  as
3433         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3434    
3435         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3436         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
3437         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3438         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
3439         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
3440         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3441         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
3442         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3443         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3444    
3445         Each character has exactly one general category property, specified  by         Each  character has exactly one general category property, specified by
3446         a two-letter abbreviation. For compatibility with Perl, negation can be         a two-letter abbreviation. For compatibility with Perl, negation can be
3447         specified by including a circumflex between the opening brace  and  the         specified  by  including a circumflex between the opening brace and the
3448         property name. For example, \p{^Lu} is the same as \P{Lu}.         property name. For example, \p{^Lu} is the same as \P{Lu}.
3449    
3450         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3451         eral category properties that start with that letter. In this case,  in         eral  category properties that start with that letter. In this case, in
3452         the  absence of negation, the curly brackets in the escape sequence are         the absence of negation, the curly brackets in the escape sequence  are
3453         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3454    
3455           \p{L}           \p{L}
# Line 3345  BACKSLASH Line 3501  BACKSLASH
3501           Zp    Paragraph separator           Zp    Paragraph separator
3502           Zs    Space separator           Zs    Space separator
3503    
3504         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3505         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3506         classified as a modifier or "other".         classified as a modifier or "other".
3507    
3508         The Cs (Surrogate) property applies only to  characters  in  the  range         The  Cs  (Surrogate)  property  applies only to characters in the range
3509         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3510         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3511         ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3512         the pcreapi page).         the pcreapi page). Perl does not support the Cs property.
3513    
3514         The long synonyms for these properties  that  Perl  supports  (such  as         The  long  synonyms  for  property  names  that  Perl supports (such as
3515         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3516         any of these properties with "Is".         any of these properties with "Is".
3517    
3518         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3519         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3520         in the Unicode table.         in the Unicode table.
3521    
3522         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3523         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3524    
3525         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3526         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3527    
3528           (?>\PM\pM*)           (?>\PM\pM*)
3529    
3530         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
3531         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
3532         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3533         property  are  typically  accents  that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3534         None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3535         matches any one character.         matches any one character.
3536    
3537         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
3538         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
3539         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3540         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3541    
3542     Resetting the match start     Resetting the match start
3543    
3544         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3545         ously  matched  characters  not  to  be  included  in the final matched         ously matched characters not  to  be  included  in  the  final  matched
3546         sequence. For example, the pattern:         sequence. For example, the pattern:
3547    
3548           foo\Kbar           foo\Kbar
3549    
3550         matches "foobar", but reports that it has matched "bar".  This  feature         matches  "foobar",  but reports that it has matched "bar". This feature
3551         is  similar  to  a lookbehind assertion (described below).  However, in         is similar to a lookbehind assertion (described  below).   However,  in
3552         this case, the part of the subject before the real match does not  have         this  case, the part of the subject before the real match does not have
3553         to  be of fixed length, as lookbehind assertions do. The use of \K does         to be of fixed length, as lookbehind assertions do. The use of \K  does
3554         not interfere with the setting of captured  substrings.   For  example,         not  interfere  with  the setting of captured substrings.  For example,
3555         when the pattern         when the pattern
3556    
3557           (foo)\Kbar           (foo)\Kbar
# Line 3404  BACKSLASH Line 3560  BACKSLASH
3560    
3561     Simple assertions     Simple assertions
3562    
3563         The  final use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3564         tion specifies a condition that has to be met at a particular point  in         tion  specifies a condition that has to be met at a particular point in
3565         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3566         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3567         The backslashed assertions are:         The backslashed assertions are:
3568    
3569           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3418  BACKSLASH Line 3574  BACKSLASH
3574           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3575           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3576    
3577         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3578         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3579         acter class).         acter class).
3580    
3581         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3582         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3583         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3584         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3585    
3586         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3587         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3588         at the very start and end of the subject string, whatever  options  are         at  the  very start and end of the subject string, whatever options are
3589         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3590         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3591         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3592         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3593         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3594         the subject, \A can never match. The difference between \Z  and  \z  is         the  subject,  \A  can never match. The difference between \Z and \z is
3595         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3596         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3597    
3598         The \G assertion is true only when the current matching position is  at         The  \G assertion is true only when the current matching position is at
3599         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
3600         of pcre_exec(). It differs from \A when the  value  of  startoffset  is         of  pcre_exec().  It  differs  from \A when the value of startoffset is
3601         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
3602         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3603         mentation where \G can be useful.         mentation where \G can be useful.
3604    
3605         Note,  however,  that  PCRE's interpretation of \G, as the start of the         Note, however, that PCRE's interpretation of \G, as the  start  of  the
3606         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3607         end  of  the  previous  match. In Perl, these can be different when the         end of the previous match. In Perl, these can  be  different  when  the
3608         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
3609         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3610    
3611         If  all  the alternatives of a pattern begin with \G, the expression is         If all the alternatives of a pattern begin with \G, the  expression  is
3612         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3613         in the compiled regular expression.         in the compiled regular expression.
3614    
# Line 3460  BACKSLASH Line 3616  BACKSLASH
3616  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3617    
3618         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3619         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
3620         point  is  at the start of the subject string. If the startoffset argu-         point is at the start of the subject string. If the  startoffset  argu-
3621         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the
3622         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
3623         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3624    
3625         Circumflex need not be the first character of the pattern if  a  number         Circumflex  need  not be the first character of the pattern if a number
3626         of  alternatives are involved, but it should be the first thing in each         of alternatives are involved, but it should be the first thing in  each
3627         alternative in which it appears if the pattern is ever  to  match  that         alternative  in  which  it appears if the pattern is ever to match that
3628         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
3629         if the pattern is constrained to match only at the start  of  the  sub-         if  the  pattern  is constrained to match only at the start of the sub-
3630         ject,  it  is  said  to be an "anchored" pattern. (There are also other         ject, it is said to be an "anchored" pattern.  (There  are  also  other
3631         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3632    
3633         A dollar character is an assertion that is true  only  if  the  current         A  dollar  character  is  an assertion that is true only if the current
3634         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
3635         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3636         be  the  last  character of the pattern if a number of alternatives are         be the last character of the pattern if a number  of  alternatives  are
3637         involved, but it should be the last item in  any  branch  in  which  it         involved,  but  it  should  be  the last item in any branch in which it
3638         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3639    
3640         The  meaning  of  dollar  can be changed so that it matches only at the         The meaning of dollar can be changed so that it  matches  only  at  the
3641         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at
3642         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3643    
3644         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3645         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3646         matches  immediately after internal newlines as well as at the start of         matches immediately after internal newlines as well as at the start  of
3647         the subject string. It does not match after a  newline  that  ends  the         the  subject  string.  It  does not match after a newline that ends the
3648         string.  A dollar matches before any newlines in the string, as well as         string. A dollar matches before any newlines in the string, as well  as
3649         at the very end, when PCRE_MULTILINE is set. When newline is  specified         at  the very end, when PCRE_MULTILINE is set. When newline is specified
3650         as  the  two-character  sequence CRLF, isolated CR and LF characters do         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3651         not indicate newlines.         not indicate newlines.
3652    
3653         For example, the pattern /^abc$/ matches the subject string  "def\nabc"         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3654         (where  \n  represents a newline) in multiline mode, but not otherwise.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3655         Consequently, patterns that are anchored in single  line  mode  because         Consequently,  patterns  that  are anchored in single line mode because
3656         all  branches  start  with  ^ are not anchored in multiline mode, and a         all branches start with ^ are not anchored in  multiline  mode,  and  a
3657         match for circumflex is  possible  when  the  startoffset  argument  of         match  for  circumflex  is  possible  when  the startoffset argument of
3658         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if
3659         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3660    
3661         Note that the sequences \A, \Z, and \z can be used to match  the  start         Note  that  the sequences \A, \Z, and \z can be used to match the start
3662         and  end of the subject in both modes, and if all branches of a pattern         and end of the subject in both modes, and if all branches of a  pattern
3663         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
3664         set.         set.
3665    
3666    
3667  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3668    
3669         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3670         ter in the subject string except (by default) a character  that  signi-         ter  in  the subject string except (by default) a character that signi-
3671         fies  the  end  of  a line. In UTF-8 mode, the matched character may be         fies the end of a line. In UTF-8 mode, the  matched  character  may  be
3672         more than one byte long.         more than one byte long.
3673    
3674         When a line ending is defined as a single character, dot never  matches         When  a line ending is defined as a single character, dot never matches
3675         that  character; when the two-character sequence CRLF is used, dot does         that character; when the two-character sequence CRLF is used, dot  does
3676         not match CR if it is immediately followed  by  LF,  but  otherwise  it         not  match  CR  if  it  is immediately followed by LF, but otherwise it
3677         matches  all characters (including isolated CRs and LFs). When any Uni-         matches all characters (including isolated CRs and LFs). When any  Uni-
3678         code line endings are being recognized, dot does not match CR or LF  or         code  line endings are being recognized, dot does not match CR or LF or
3679         any of the other line ending characters.         any of the other line ending characters.
3680    
3681         The  behaviour  of  dot  with regard to newlines can be changed. If the         The behaviour of dot with regard to newlines can  be  changed.  If  the
3682         PCRE_DOTALL option is set, a dot matches  any  one  character,  without         PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3683         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3684         string, it takes two dots to match it.         string, it takes two dots to match it.
3685    
3686         The handling of dot is entirely independent of the handling of  circum-         The  handling of dot is entirely independent of the handling of circum-
3687         flex  and  dollar,  the  only relationship being that they both involve         flex and dollar, the only relationship being  that  they  both  involve
3688         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3689    
3690    
3691  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3692    
3693         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3694         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
3695         line-ending characters. The feature is provided in  Perl  in  order  to         line-ending  characters.  The  feature  is provided in Perl in order to
3696         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-
3697         acters into individual bytes, what remains in the string may be a  mal-         acters  into individual bytes, what remains in the string may be a mal-
3698         formed  UTF-8  string.  For this reason, the \C escape sequence is best         formed UTF-8 string. For this reason, the \C escape  sequence  is  best
3699         avoided.         avoided.
3700    
3701         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3702         below),  because  in UTF-8 mode this would make it impossible to calcu-         below), because in UTF-8 mode this would make it impossible  to  calcu-
3703         late the length of the lookbehind.         late the length of the lookbehind.
3704    
3705    
# Line 3552  SQUARE BRACKETS AND CHARACTER CLASSES Line 3708  SQUARE BRACKETS AND CHARACTER CLASSES
3708         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3709         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
3710         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
3711         it  should  be  the first data character in the class (after an initial         it should be the first data character in the class  (after  an  initial
3712         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3713    
3714         A character class matches a single character in the subject.  In  UTF-8         A  character  class matches a single character in the subject. In UTF-8
3715         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3716         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
3717         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3718         subject character must not be in the set defined by  the  class.  If  a         subject  character  must  not  be in the set defined by the class. If a
3719         circumflex  is actually required as a member of the class, ensure it is         circumflex is actually required as a member of the class, ensure it  is
3720         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3721    
3722         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3723         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3724         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3725         characters  that  are in the class by enumerating those that are not. A         characters that are in the class by enumerating those that are  not.  A
3726         class that starts with a circumflex is not an assertion: it still  con-         class  that starts with a circumflex is not an assertion: it still con-
3727         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3728         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3729    
3730         In UTF-8 mode, characters with values greater than 255 can be  included         In  UTF-8 mode, characters with values greater than 255 can be included
3731         in  a  class as a literal string of bytes, or by using the \x{ escaping         in a class as a literal string of bytes, or by using the  \x{  escaping
3732         mechanism.         mechanism.
3733    
3734         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3735         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3736         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
3737         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always
3738         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3739         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3740         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3741         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3742         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3743         PCRE  is  compiled  with Unicode property support as well as with UTF-8         PCRE is compiled with Unicode property support as well  as  with  UTF-8
3744         support.         support.
3745    
3746         Characters that might indicate line breaks are  never  treated  in  any         Characters  that  might  indicate  line breaks are never treated in any
3747         special  way  when  matching  character  classes,  whatever line-ending         special way  when  matching  character  classes,  whatever  line-ending
3748         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3749         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
3750         of these characters.         of these characters.
3751    
3752         The minus (hyphen) character can be used to specify a range of  charac-         The  minus (hyphen) character can be used to specify a range of charac-
3753         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3754         between d and m, inclusive. If a  minus  character  is  required  in  a         between  d  and  m,  inclusive.  If  a minus character is required in a
3755         class,  it  must  be  escaped  with a backslash or appear in a position         class, it must be escaped with a backslash  or  appear  in  a  position
3756         where it cannot be interpreted as indicating a range, typically as  the         where  it cannot be interpreted as indicating a range, typically as the
3757         first or last character in the class.         first or last character in the class.
3758    
3759         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
3760         ter of a range. A pattern such as [W-]46] is interpreted as a class  of         ter  of a range. A pattern such as [W-]46] is interpreted as a class of
3761         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3762         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3763         backslash  it is interpreted as the end of range, so [W-\]46] is inter-         backslash it is interpreted as the end of range, so [W-\]46] is  inter-
3764         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3765         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3766         a range.         a range.
3767    
3768         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3769         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3770         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3771         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3772    
3773         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
3774         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
3775         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3776         character tables for a French locale are in  use,  [\xc8-\xcb]  matches         character  tables  for  a French locale are in use, [\xc8-\xcb] matches
3777         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the
3778         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3779         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3780    
3781         The  character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear         The character types \d, \D, \p, \P, \s, \S, \w, and \W may also  appear
3782         in a character class, and add the characters that  they  match  to  the         in  a  character  class,  and add the characters that they match to the
3783         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3784         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3785         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3786         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3787         but not underscore.         but not underscore.
3788    
3789         The  only  metacharacters  that are recognized in character classes are         The only metacharacters that are recognized in  character  classes  are
3790         backslash, hyphen (only where it can be  interpreted  as  specifying  a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
3791         range),  circumflex  (only  at the start), opening square bracket (only         range), circumflex (only at the start), opening  square  bracket  (only
3792         when it can be interpreted as introducing a POSIX class name - see  the         when  it can be interpreted as introducing a POSIX class name - see the
3793         next  section),  and  the  terminating closing square bracket. However,         next section), and the terminating  closing  square  bracket.  However,
3794         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3795    
3796    
3797  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3798    
3799         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3800         enclosed  by  [: and :] within the enclosing square brackets. PCRE also         enclosed by [: and :] within the enclosing square brackets.  PCRE  also
3801         supports this notation. For example,         supports this notation. For example,
3802    
3803           [01[:alpha:]%]           [01[:alpha:]%]
# Line 3664  POSIX CHARACTER CLASSES Line 3820  POSIX CHARACTER CLASSES
3820           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3821           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3822    
3823         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),
3824         and space (32). Notice that this list includes the VT  character  (code         and  space  (32). Notice that this list includes the VT character (code
3825         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
3826         Perl compatibility).         Perl compatibility).
3827    
3828         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension
3829         from  Perl  5.8. Another Perl extension is negation, which is indicated         from Perl 5.8. Another Perl extension is negation, which  is  indicated
3830         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3831    
3832           [12[:^digit:]]           [12[:^digit:]]
3833    
3834         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the
3835         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3836         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
3837    
# Line 3695  VERTICAL BAR Line 3851  VERTICAL BAR
3851         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3852         to right, and the first one that succeeds is used. If the  alternatives         to right, and the first one that succeeds is used. If the  alternatives
3853         are  within a subpattern (defined below), "succeeds" means matching the         are  within a subpattern (defined below), "succeeds" means matching the
3854         rest of the main pattern as well as the alternative in the  subpattern.         rest of the main pattern as well as the alternative in the subpattern.
3855    
3856    
3857  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3858    
3859         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3860         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
3861         within  the  pattern  by  a  sequence  of  Perl option letters enclosed         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
3862         between "(?" and ")".  The option letters are         between "(?" and ")".  The option letters are
3863    
3864           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 3712  INTERNAL OPTION SETTING Line 3868  INTERNAL OPTION SETTING
3868    
3869         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3870         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
3871         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
3872         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
3873         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
3874         hyphen, the option is unset.         hyphen, the option is unset.
3875    
3876         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
3877         can be changed in the same way as the Perl-compatible options by  using         can  be changed in the same way as the Perl-compatible options by using
3878         the characters J, U and X respectively.         the characters J, U and X respectively.
3879    
3880         When  an option change occurs at top level (that is, not inside subpat-         When one of these option changes occurs at  top  level  (that  is,  not
3881         tern parentheses), the change applies to the remainder of  the  pattern         inside  subpattern parentheses), the change applies to the remainder of
3882         that follows.  If the change is placed right at the start of a pattern,         the pattern that follows. If the change is placed right at the start of
3883         PCRE extracts it into the global options (and it will therefore show up         a pattern, PCRE extracts it into the global options (and it will there-
3884         in data extracted by the pcre_fullinfo() function).         fore show up in data extracted by the pcre_fullinfo() function).
3885    
3886         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
3887         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3888         it, so         it, so
3889    
3890           (a(?i)b)c           (a(?i)b)c
3891    
3892         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
3893         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
3894         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
3895         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
3896         example,         example,
3897    
3898           (a(?i)b|c)           (a(?i)b|c)
3899    
3900         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
3901         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
3902         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
3903         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3904    
3905         Note: There are other PCRE-specific options that  can  be  set  by  the         Note:  There  are  other  PCRE-specific  options that can be set by the
3906         application  when  the  compile  or match functions are called. In some         application when the compile or match functions  are  called.  In  some
3907         cases the pattern can contain special  leading  sequences  to  override         cases the pattern can contain special leading sequences such as (*CRLF)
3908         what  the  application  has set or what has been defaulted. Details are         to override what the application has set or what  has  been  defaulted.
3909         given in the section entitled "Newline sequences" above.         Details  are  given  in the section entitled "Newline sequences" above.
3910           There is also the (*UTF8) leading sequence that  can  be  used  to  set
3911           UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
3912    
3913    
3914  SUBPATTERNS  SUBPATTERNS
# Line 3762  SUBPATTERNS Line 3920  SUBPATTERNS
3920    
3921           cat(aract|erpillar|)           cat(aract|erpillar|)
3922    
3923         matches  one  of the words "cat", "cataract", or "caterpillar". Without         matches one of the words "cat", "cataract", or  "caterpillar".  Without
3924         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
3925         string.         string.
3926    
3927         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
3928         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
3929         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
3930         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
3931         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
3932         subpatterns.         subpatterns.
3933    
3934         For example, if the string "the red king" is matched against  the  pat-         For  example,  if the string "the red king" is matched against the pat-
3935         tern         tern
3936    
3937           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3781  SUBPATTERNS Line 3939  SUBPATTERNS
3939         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3940         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3941    
3942         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
3943         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
3944         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
3945         by  a question mark and a colon, the subpattern does not do any captur-         by a question mark and a colon, the subpattern does not do any  captur-
3946         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
3947         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
3948         matched against the pattern         matched against the pattern
3949    
3950           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 3794  SUBPATTERNS Line 3952  SUBPATTERNS
3952         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3953         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
3954    
3955         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
3956         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
3957         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3958    
3959           (?i:saturday|sunday)           (?i:saturday|sunday)
3960           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3961    
3962         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3963         tried from left to right, and options are not reset until  the  end  of         tried  from  left  to right, and options are not reset until the end of
3964         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
3965         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
3966         "Saturday".         "Saturday".
3967    
3968    
3969  DUPLICATE SUBPATTERN NUMBERS  DUPLICATE SUBPATTERN NUMBERS
3970    
3971         Perl 5.10 introduced a feature whereby each alternative in a subpattern         Perl 5.10 introduced a feature whereby each alternative in a subpattern
3972         uses the same numbers for its capturing parentheses. Such a  subpattern         uses  the same numbers for its capturing parentheses. Such a subpattern
3973         starts  with (?| and is itself a non-capturing subpattern. For example,         starts with (?| and is itself a non-capturing subpattern. For  example,
3974         consider this pattern:         consider this pattern:
3975    
3976           (?|(Sat)ur|(Sun))day           (?|(Sat)ur|(Sun))day
3977    
3978         Because the two alternatives are inside a (?| group, both sets of  cap-         Because  the two alternatives are inside a (?| group, both sets of cap-
3979         turing  parentheses  are  numbered one. Thus, when the pattern matches,         turing parentheses are numbered one. Thus, when  the  pattern  matches,
3980         you can look at captured substring number  one,  whichever  alternative         you  can  look  at captured substring number one, whichever alternative
3981         matched.  This  construct  is useful when you want to capture part, but         matched. This construct is useful when you want to  capture  part,  but
3982         not all, of one of a number of alternatives. Inside a (?| group, paren-         not all, of one of a number of alternatives. Inside a (?| group, paren-
3983         theses  are  numbered as usual, but the number is reset at the start of         theses are numbered as usual, but the number is reset at the  start  of
3984         each branch. The numbers of any capturing buffers that follow the  sub-         each  branch. The numbers of any capturing buffers that follow the sub-
3985         pattern  start after the highest number used in any branch. The follow-         pattern start after the highest number used in any branch. The  follow-
3986         ing example is taken from the Perl documentation.  The  numbers  under-         ing  example  is taken from the Perl documentation.  The numbers under-
3987         neath show in which buffer the captured content will be stored.         neath show in which buffer the captured content will be stored.
3988    
3989           # before  ---------------branch-reset----------- after           # before  ---------------branch-reset----------- after
3990           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3991           # 1            2         2  3        2     3     4           # 1            2         2  3        2     3     4
3992    
3993         A  backreference  or  a  recursive call to a numbered subpattern always         A backreference or a recursive call to  a  numbered  subpattern  always
3994         refers to the first one in the pattern with the given number.         refers to the first one in the pattern with the given number.
3995    
3996         An alternative approach to using this "branch reset" feature is to  use         An  alternative approach to using this "branch reset" feature is to use
3997         duplicate named subpatterns, as described in the next section.         duplicate named subpatterns, as described in the next section.
3998    
3999    
4000  NAMED SUBPATTERNS  NAMED SUBPATTERNS
4001    
4002         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
4003         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
4004         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
4005         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
4006         patterns. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
4007         had the feature earlier, and PCRE introduced it at release  4.0,  using         had  the  feature earlier, and PCRE introduced it at release 4.0, using
4008         the  Python syntax. PCRE now supports both the Perl and the Python syn-         the Python syntax. PCRE now supports both the Perl and the Python  syn-
4009         tax.         tax.
4010    
4011         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
4012         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
4013         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
4014         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
4015         by number.         by number.
4016    
4017         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
4018         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
4019         names, exactly as if the names were not present. The PCRE API  provides         names,  exactly as if the names were not present. The PCRE API provides
4020         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
4021         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
4022         a captured substring by name.         a captured substring by name.
4023    
4024         By  default, a name must be unique within a pattern, but it is possible         By default, a name must be unique within a pattern, but it is  possible
4025         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
4026         time.  This  can  be useful for patterns where only one instance of the         time. This can be useful for patterns where only one  instance  of  the
4027         named parentheses can match. Suppose you want to match the  name  of  a         named  parentheses  can  match. Suppose you want to match the name of a
4028         weekday,  either as a 3-letter abbreviation or as the full name, and in         weekday, either as a 3-letter abbreviation or as the full name, and  in
4029         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
4030         the line breaks) does the job:         the line breaks) does the job:
4031    
# Line 3877  NAMED SUBPATTERNS Line 4035  NAMED SUBPATTERNS
4035           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
4036           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
4037    
4038         There  are  five capturing substrings, but only one is ever set after a         There are five capturing substrings, but only one is ever set  after  a
4039         match.  (An alternative way of solving this problem is to use a "branch         match.  (An alternative way of solving this problem is to use a "branch
4040         reset" subpattern, as described in the previous section.)         reset" subpattern, as described in the previous section.)
4041    
4042         The  convenience  function  for extracting the data by name returns the         The convenience function for extracting the data by  name  returns  the
4043         substring for the first (and in this example, the only)  subpattern  of         substring  for  the first (and in this example, the only) subpattern of
4044         that  name  that  matched.  This saves searching to find which numbered         that name that matched. This saves searching  to  find  which  numbered
4045         subpattern it was. If you make a reference to a non-unique  named  sub-         subpattern  it  was. If you make a reference to a non-unique named sub-
4046         pattern  from elsewhere in the pattern, the one that corresponds to the         pattern from elsewhere in the pattern, the one that corresponds to  the
4047         lowest number is used. For further details of the interfaces  for  han-         lowest  number  is used. For further details of the interfaces for han-
4048         dling named subpatterns, see the pcreapi documentation.         dling named subpatterns, see the pcreapi documentation.
4049    
4050           Warning: You cannot use different names to distinguish between two sub-
4051           patterns  with  the same number (see the previous section) because PCRE
4052           uses only the numbers when matching.
4053    
4054    
4055  REPETITION  REPETITION
4056    
4057         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
4058         following items:         following items:
4059    
4060           a literal data character           a literal data character
# Line 3905  REPETITION Line 4067  REPETITION
4067           a back reference (see next section)           a back reference (see next section)
4068           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4069    
4070         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
4071         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
4072         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
4073         and the first must be less than or equal to the second. For example:         and the first must be less than or equal to the second. For example:
4074    
4075           z{2,4}           z{2,4}
4076    
4077         matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a         matches "zz", "zzz", or "zzzz". A closing brace on its  own  is  not  a
4078         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
4079         present,  there  is  no upper limit; if the second number and the comma         present, there is no upper limit; if the second number  and  the  comma
4080         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
4081         matches. Thus         matches. Thus
4082    
4083           [aeiou]{3,}           [aeiou]{3,}
# Line 3924  REPETITION Line 4086  REPETITION
4086    
4087           \d{8}           \d{8}
4088    
4089         matches  exactly  8  digits. An opening curly bracket that appears in a         matches exactly 8 digits. An opening curly bracket that  appears  in  a
4090         position where a quantifier is not allowed, or one that does not  match         position  where a quantifier is not allowed, or one that does not match
4091         the  syntax of a quantifier, is taken as a literal character. For exam-         the syntax of a quantifier, is taken as a literal character. For  exam-
4092         ple, {,6} is not a quantifier, but a literal string of four characters.         ple, {,6} is not a quantifier, but a literal string of four characters.
4093    
4094         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
# Line 3937  REPETITION Line 4099  REPETITION
4099         may be of different lengths).         may be of different lengths).
4100    
4101         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4102         the previous item and the quantifier were not present.         the previous item and the quantifier were not present. This may be use-
4103           ful for subpatterns that are referenced as subroutines  from  elsewhere
4104           in the pattern. Items other than subpatterns that have a {0} quantifier
4105           are omitted from the compiled pattern.
4106    
4107         For  convenience, the three most common quantifiers have single-charac-         For convenience, the three most common quantifiers have  single-charac-
4108         ter abbreviations:         ter abbreviations:
4109    
4110           *    is equivalent to {0,}           *    is equivalent to {0,}
4111           +    is equivalent to {1,}           +    is equivalent to {1,}
4112           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
4113    
4114         It is possible to construct infinite loops by  following  a  subpattern         It  is  possible  to construct infinite loops by following a subpattern
4115         that can match no characters with a quantifier that has no upper limit,         that can match no characters with a quantifier that has no upper limit,
4116         for example:         for example:
4117    
4118           (a?)*           (a?)*
4119    
4120         Earlier versions of Perl and PCRE used to give an error at compile time         Earlier versions of Perl and PCRE used to give an error at compile time
4121         for  such  patterns. However, because there are cases where this can be         for such patterns. However, because there are cases where this  can  be
4122         useful, such patterns are now accepted, but if any  repetition  of  the         useful,  such  patterns  are now accepted, but if any repetition of the
4123         subpattern  does in fact match no characters, the loop is forcibly bro-         subpattern does in fact match no characters, the loop is forcibly  bro-
4124         ken.         ken.
4125    
4126         By default, the quantifiers are "greedy", that is, they match  as  much         By  default,  the quantifiers are "greedy", that is, they match as much
4127         as  possible  (up  to  the  maximum number of permitted times), without         as possible (up to the maximum  number  of  permitted  times),  without
4128         causing the rest of the pattern to fail. The classic example  of  where         causing  the  rest of the pattern to fail. The classic example of where
4129         this gives problems is in trying to match comments in C programs. These         this gives problems is in trying to match comments in C programs. These
4130         appear between /* and */ and within the comment,  individual  *  and  /         appear  between  /*  and  */ and within the comment, individual * and /
4131         characters  may  appear. An attempt to match C comments by applying the         characters may appear. An attempt to match C comments by  applying  the
4132         pattern         pattern
4133    
4134           /\*.*\*/           /\*.*\*/
# Line 3972  REPETITION Line 4137  REPETITION
4137    
4138           /* first comment */  not comment  /* second comment */           /* first comment */  not comment  /* second comment */
4139    
4140         fails, because it matches the entire string owing to the greediness  of         fails,  because it matches the entire string owing to the greediness of
4141         the .*  item.         the .*  item.
4142    
4143         However,  if  a quantifier is followed by a question mark, it ceases to         However, if a quantifier is followed by a question mark, it  ceases  to
4144         be greedy, and instead matches the minimum number of times possible, so         be greedy, and instead matches the minimum number of times possible, so
4145         the pattern         the pattern
4146    
4147           /\*.*?\*/           /\*.*?\*/
4148    
4149         does  the  right  thing with the C comments. The meaning of the various         does the right thing with the C comments. The meaning  of  the  various
4150         quantifiers is not otherwise changed,  just  the  preferred  number  of         quantifiers  is  not  otherwise  changed,  just the preferred number of
4151         matches.   Do  not  confuse this use of question mark with its use as a         matches.  Do not confuse this use of question mark with its  use  as  a
4152         quantifier in its own right. Because it has two uses, it can  sometimes         quantifier  in its own right. Because it has two uses, it can sometimes
4153         appear doubled, as in         appear doubled, as in
4154    
4155           \d??\d           \d??\d
# Line 3992  REPETITION Line 4157  REPETITION
4157         which matches one digit by preference, but can match two if that is the         which matches one digit by preference, but can match two if that is the
4158         only way the rest of the pattern matches.         only way the rest of the pattern matches.
4159    
4160         If the PCRE_UNGREEDY option is set (an option that is not available  in         If  the PCRE_UNGREEDY option is set (an option that is not available in
4161         Perl),  the  quantifiers are not greedy by default, but individual ones         Perl), the quantifiers are not greedy by default, but  individual  ones
4162         can be made greedy by following them with a  question  mark.  In  other         can  be  made  greedy  by following them with a question mark. In other
4163         words, it inverts the default behaviour.         words, it inverts the default behaviour.
4164    
4165         When  a  parenthesized  subpattern  is quantified with a minimum repeat         When a parenthesized subpattern is quantified  with  a  minimum  repeat
4166         count that is greater than 1 or with a limited maximum, more memory  is         count  that is greater than 1 or with a limited maximum, more memory is
4167         required  for  the  compiled  pattern, in proportion to the size of the         required for the compiled pattern, in proportion to  the  size  of  the
4168         minimum or maximum.         minimum or maximum.
4169    
4170         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
4171         alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,         alent to Perl's /s) is set, thus allowing the dot  to  match  newlines,
4172         the pattern is implicitly anchored, because whatever  follows  will  be         the  pattern  is  implicitly anchored, because whatever follows will be
4173         tried  against every character position in the subject string, so there         tried against every character position in the subject string, so  there
4174         is no point in retrying the overall match at  any  position  after  the         is  no  point  in  retrying the overall match at any position after the
4175         first.  PCRE  normally treats such a pattern as though it were preceded         first. PCRE normally treats such a pattern as though it  were  preceded
4176         by \A.         by \A.
4177    
4178         In cases where it is known that the subject  string  contains  no  new-         In  cases  where  it  is known that the subject string contains no new-
4179         lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-         lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
4180         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
4181    
4182         However, there is one situation where the optimization cannot be  used.         However,  there is one situation where the optimization cannot be used.
4183         When  .*   is  inside  capturing  parentheses that are the subject of a         When .*  is inside capturing parentheses that  are  the  subject  of  a
4184         backreference elsewhere in the pattern, a match at the start  may  fail         backreference  elsewhere  in the pattern, a match at the start may fail
4185         where a later one succeeds. Consider, for example:         where a later one succeeds. Consider, for example:
4186    
4187           (.*)abc\1           (.*)abc\1
4188    
4189         If  the subject is "xyz123abc123" the match point is the fourth charac-         If the subject is "xyz123abc123" the match point is the fourth  charac-
4190         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
4191    
4192         When a capturing subpattern is repeated, the value captured is the sub-         When a capturing subpattern is repeated, the value captured is the sub-
# Line 4030  REPETITION Line 4195  REPETITION
4195           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+
4196    
4197         has matched "tweedledum tweedledee" the value of the captured substring         has matched "tweedledum tweedledee" the value of the captured substring
4198         is "tweedledee". However, if there are  nested  capturing  subpatterns,         is  "tweedledee".  However,  if there are nested capturing subpatterns,
4199         the  corresponding captured values may have been set in previous itera-         the corresponding captured values may have been set in previous  itera-
4200         tions. For example, after         tions. For example, after
4201    
4202           /(a|(b))+/           /(a|(b))+/
# Line 4041  REPETITION Line 4206  REPETITION
4206    
4207  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
4208    
4209         With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")         With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
4210         repetition,  failure  of what follows normally causes the repeated item         repetition, failure of what follows normally causes the  repeated  item
4211         to be re-evaluated to see if a different number of repeats  allows  the         to  be  re-evaluated to see if a different number of repeats allows the
4212         rest  of  the pattern to match. Sometimes it is useful to prevent this,         rest of the pattern to match. Sometimes it is useful to  prevent  this,
4213         either to change the nature of the match, or to cause it  fail  earlier         either  to  change the nature of the match, or to cause it fail earlier
4214         than  it otherwise might, when the author of the pattern knows there is         than it otherwise might, when the author of the pattern knows there  is
4215         no point in carrying on.         no point in carrying on.
4216    
4217         Consider, for example, the pattern \d+foo when applied to  the  subject         Consider,  for  example, the pattern \d+foo when applied to the subject
4218         line         line
4219    
4220           123456bar           123456bar
4221    
4222         After matching all 6 digits and then failing to match "foo", the normal         After matching all 6 digits and then failing to match "foo", the normal
4223         action of the matcher is to try again with only 5 digits  matching  the         action  of  the matcher is to try again with only 5 digits matching the
4224         \d+  item,  and  then  with  4,  and  so on, before ultimately failing.         \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.
4225         "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides         "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides
4226         the  means for specifying that once a subpattern has matched, it is not         the means for specifying that once a subpattern has matched, it is  not
4227         to be re-evaluated in this way.         to be re-evaluated in this way.
4228    
4229         If we use atomic grouping for the previous example, the  matcher  gives         If  we  use atomic grouping for the previous example, the matcher gives
4230         up  immediately  on failing to match "foo" the first time. The notation         up immediately on failing to match "foo" the first time.  The  notation
4231         is a kind of special parenthesis, starting with (?> as in this example:         is a kind of special parenthesis, starting with (?> as in this example:
4232    
4233           (?>\d+)foo           (?>\d+)foo
# Line 4140  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4305  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4305    
4306           ((?>\D+)|<\d+>)*[!?]           ((?>\D+)|<\d+>)*[!?]
4307    
4308         sequences of non-digits cannot be broken, and failure happens  quickly.         sequences of non-digits cannot be broken, and failure happens quickly.
4309    
4310    
4311  BACK REFERENCES  BACK REFERENCES
4312    
4313         Outside a character class, a backslash followed by a digit greater than         Outside a character class, a backslash followed by a digit greater than
4314         0 (and possibly further digits) is a back reference to a capturing sub-         0 (and possibly further digits) is a back reference to a capturing sub-
4315         pattern  earlier  (that is, to its left) in the pattern, provided there         pattern earlier (that is, to its left) in the pattern,  provided  there
4316         have been that many previous capturing left parentheses.         have been that many previous capturing left parentheses.
4317    
4318         However, if the decimal number following the backslash is less than 10,         However, if the decimal number following the backslash is less than 10,
4319         it  is  always  taken  as a back reference, and causes an error only if         it is always taken as a back reference, and causes  an  error  only  if
4320         there are not that many capturing left parentheses in the  entire  pat-         there  are  not that many capturing left parentheses in the entire pat-
4321         tern.  In  other words, the parentheses that are referenced need not be         tern. In other words, the parentheses that are referenced need  not  be
4322         to the left of the reference for numbers less than 10. A "forward  back         to  the left of the reference for numbers less than 10. A "forward back
4323         reference"  of  this  type can make sense when a repetition is involved         reference" of this type can make sense when a  repetition  is  involved
4324         and the subpattern to the right has participated in an  earlier  itera-         and  the  subpattern to the right has participated in an earlier itera-
4325         tion.         tion.
4326    
4327         It  is  not  possible to have a numerical "forward back reference" to a         It is not possible to have a numerical "forward back  reference"  to  a
4328         subpattern whose number is 10 or  more  using  this  syntax  because  a         subpattern  whose  number  is  10  or  more using this syntax because a
4329         sequence  such  as  \50 is interpreted as a character defined in octal.         sequence such as \50 is interpreted as a character  defined  in  octal.
4330         See the subsection entitled "Non-printing characters" above for further         See the subsection entitled "Non-printing characters" above for further
4331         details  of  the  handling of digits following a backslash. There is no         details of the handling of digits following a backslash.  There  is  no
4332         such problem when named parentheses are used. A back reference  to  any         such  problem  when named parentheses are used. A back reference to any
4333         subpattern is possible using named parentheses (see below).         subpattern is possible using named parentheses (see below).
4334    
4335         Another  way  of  avoiding  the ambiguity inherent in the use of digits         Another way of avoiding the ambiguity inherent in  the  use  of  digits
4336         following a backslash is to use the \g escape sequence, which is a fea-         following a backslash is to use the \g escape sequence, which is a fea-
4337         ture  introduced  in  Perl  5.10.  This  escape  must be followed by an         ture introduced in Perl 5.10.  This  escape  must  be  followed  by  an
4338         unsigned number or a negative number, optionally  enclosed  in  braces.         unsigned  number  or  a negative number, optionally enclosed in braces.
4339         These examples are all identical:         These examples are all identical:
4340    
4341           (ring), \1           (ring), \1
4342           (ring), \g1           (ring), \g1
4343           (ring), \g{1}           (ring), \g{1}
4344    
4345         An  unsigned number specifies an absolute reference without the ambigu-         An unsigned number specifies an absolute reference without the  ambigu-
4346         ity that is present in the older syntax. It is also useful when literal         ity that is present in the older syntax. It is also useful when literal
4347         digits follow the reference. A negative number is a relative reference.         digits follow the reference. A negative number is a relative reference.
4348         Consider this example:         Consider this example:
# Line 4185  BACK REFERENCES Line 4350  BACK REFERENCES
4350           (abc(def)ghi)\g{-1}           (abc(def)ghi)\g{-1}
4351    
4352         The sequence \g{-1} is a reference to the most recently started captur-         The sequence \g{-1} is a reference to the most recently started captur-
4353         ing  subpattern  before \g, that is, is it equivalent to \2. Similarly,         ing subpattern before \g, that is, is it equivalent to  \2.  Similarly,
4354         \g{-2} would be equivalent to \1. The use of relative references can be         \g{-2} would be equivalent to \1. The use of relative references can be
4355         helpful  in  long  patterns,  and  also in patterns that are created by         helpful in long patterns, and also in  patterns  that  are  created  by
4356         joining together fragments that contain references within themselves.         joining together fragments that contain references within themselves.
4357    
4358         A back refere