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# Line 18  INTRODUCTION Line 18  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few differences. (Certain features that appeared in Python and         just  a  few  differences. Certain features that appeared in Python and
22         PCRE before they appeared in Perl are also available using  the  Python         PCRE before they appeared in Perl are also available using  the  Python
23         syntax.)         syntax.  There is also some support for certain .NET and Oniguruma syn-
24           tax items, and there is an option for  requesting  some  minor  changes
25           that give better JavaScript compatibility.
26    
27         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current  implementation of PCRE (release 7.x) corresponds approxi-
28         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
29         Unicode general category properties. However, UTF-8 and Unicode support         Unicode general category properties. However, UTF-8 and Unicode support
30         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
31         correspond to Unicode release 5.0.0.         correspond to Unicode release 5.1.
32    
33         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
34         alternative matching function that matches the same  compiled  patterns         alternative matching function that matches the same  compiled  patterns
# Line 45  INTRODUCTION Line 47  INTRODUCTION
47    
48         Details of exactly which Perl regular expression features are  and  are         Details of exactly which Perl regular expression features are  and  are
49         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
50         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
51           page.
52    
53         Some features of PCRE can be included, excluded, or  changed  when  the         Some  features  of  PCRE can be included, excluded, or changed when the
54         library  is  built.  The pcre_config() function makes it possible for a         library is built. The pcre_config() function makes it  possible  for  a
55         client to discover which features are  available.  The  features  them-         client  to  discover  which  features are available. The features them-
56         selves  are described in the pcrebuild page. Documentation about build-         selves are described in the pcrebuild page. Documentation about  build-
57         ing PCRE for various operating systems can be found in the README  file         ing  PCRE for various operating systems can be found in the README file
58         in the source distribution.         in the source distribution.
59    
60         The  library  contains  a number of undocumented internal functions and         The library contains a number of undocumented  internal  functions  and
61         data tables that are used by more than one  of  the  exported  external         data  tables  that  are  used by more than one of the exported external
62         functions,  but  which  are  not  intended for use by external callers.         functions, but which are not intended  for  use  by  external  callers.
63         Their names all begin with "_pcre_", which hopefully will  not  provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
64         any name clashes. In some environments, it is possible to control which         any name clashes. In some environments, it is possible to control which
65         external symbols are exported when a shared library is  built,  and  in         external  symbols  are  exported when a shared library is built, and in
66         these cases the undocumented symbols are not exported.         these cases the undocumented symbols are not exported.
67    
68    
69  USER DOCUMENTATION  USER DOCUMENTATION
70    
71         The  user  documentation  for PCRE comprises a number of different sec-         The user documentation for PCRE comprises a number  of  different  sec-
72         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
73         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.
74         In the plain text format, all the sections are concatenated,  for  ease         In  the  plain text format, all the sections are concatenated, for ease
75         of searching. The sections are as follows:         of searching. The sections are as follows:
76    
77           pcre              this document           pcre              this document
# Line 83  USER DOCUMENTATION Line 86  USER DOCUMENTATION
86           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
87           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
88                               regular expressions                               regular expressions
89             pcresyntax        quick syntax reference
90           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
91           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
92           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
# Line 107  LIMITATIONS Line 111  LIMITATIONS
111         In  these  cases the limit is substantially larger.  However, the speed         In  these  cases the limit is substantially larger.  However, the speed
112         of execution is slower.         of execution is slower.
113    
114         All values in repeating quantifiers must be less than 65536. The  maxi-         All values in repeating quantifiers must be less than 65536.
        mum  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
115    
116         There is no limit to the number of parenthesized subpatterns, but there         There is no limit to the number of parenthesized subpatterns, but there
117         can be no more than 65535 capturing subpatterns.         can be no more than 65535 capturing subpatterns.
# Line 134  UTF-8 AND UNICODE PROPERTY SUPPORT Line 136  UTF-8 AND UNICODE PROPERTY SUPPORT
136    
137         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
138         support  in  the  code,  and, in addition, you must call pcre_compile()         support  in  the  code,  and, in addition, you must call pcre_compile()
139         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
140         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
141         strings instead of just strings of bytes.         and any subject strings that are matched  against  it  are  treated  as
142           UTF-8 strings instead of just strings of bytes.
143    
144         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,
145         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
146         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
147         very big.         very big.
148    
149         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
150         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
151         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
152         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
153         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,
154         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
155         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
156         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-
157         ter},  is  not  supported.   Furthermore,  in Perl, many properties may         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
158         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
159         does not support this.         does not support this.
160    
161         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
162    
163           When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
164           subjects are (by default) checked for validity on entry to the relevant
165           functions. From release 7.3 of PCRE, the check is according  the  rules
166           of  RFC  3629, which are themselves derived from the Unicode specifica-
167           tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
168           allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
169           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
170           to U+DFFF.
171    
172           The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
173           which the Unicode Standard says this: "The Low Surrogate Area does  not
174           contain  any  character  assignments,  consequently  no  character code
175           charts or namelists are provided for this area. Surrogates are reserved
176           for  use  with  UTF-16 and then must be used in pairs." The code points
177           that are encoded by UTF-16 pairs  are  available  as  independent  code
178           points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
179           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
180    
181           If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
182           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
183           that your strings are valid, and therefore want to skip these checks in
184           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
185           compile time or at run time, PCRE assumes that the pattern  or  subject
186           it  is  given  (respectively)  contains only valid UTF-8 codes. In this
187           case, it does not diagnose an invalid UTF-8 string.
188    
189           If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
190           what  happens  depends on why the string is invalid. If the string con-
191           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
192           string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
193           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
194           strings  according  to  the more liberal rules of RFC 2279. However, if
195           the string does not even conform to RFC 2279, the result is  undefined.
196           Your program may crash.
197    
198           If  you  want  to  process  strings  of  values  in the full range 0 to
199           0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
200           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
201           this situation, you will have to apply your own validity check.
202    
203         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and     General comments about UTF-8 mode
        subjects are checked for validity on entry to the  relevant  functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations, you may already know  that  your  strings  are  valid,  and  
        therefore want to skip these checks in order to improve performance. If  
        you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,  
        PCRE  assumes  that  the  pattern or subject it is given (respectively)  
        contains only valid UTF-8 codes. In this case, it does not diagnose  an  
        invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when  
        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may  
        crash.  
204    
205         2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
206         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
207    
208         3. 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
209         characters for values greater than \177.         characters for values greater than \177.
210    
211         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
212         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
213    
214         5. 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-
215         gle byte.         gle byte.
216    
217         6.  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
218         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
219         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
220    
221         7.  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
222         test characters of any code value, but the characters that PCRE  recog-         test  characters of any code value, but the characters that PCRE recog-
223         nizes  as  digits,  spaces,  or  word characters remain the same set as         nizes as digits, spaces, or word characters  remain  the  same  set  as
224         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
225         includes  Unicode  property support, because to do otherwise would slow         includes Unicode property support, because to do otherwise  would  slow
226         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
227         sense  of,  say,  "digit",  you must use Unicode property tests such as         sense of, say, "digit", you must use Unicode  property  tests  such  as
228         \p{Nd}.         \p{Nd}.  Note  that  this  also applies to \b, because it is defined in
229           terms of \w and \W.
230    
231         8. Similarly, characters that match the POSIX named  character  classes         7. Similarly, characters that match the POSIX named  character  classes
232         are all low-valued characters.         are all low-valued characters.
233    
234           8.  However,  the Perl 5.10 horizontal and vertical whitespace matching
235           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
236           acters.
237    
238         9.  Case-insensitive  matching  applies only to characters whose values         9.  Case-insensitive  matching  applies only to characters whose values
239         are less than 128, unless PCRE is built with Unicode property  support.         are less than 128, unless PCRE is built with Unicode property  support.
240         Even  when  Unicode  property support is available, PCRE still uses its         Even  when  Unicode  property support is available, PCRE still uses its
# Line 222  AUTHOR Line 260  AUTHOR
260    
261  REVISION  REVISION
262    
263         Last updated: 18 April 2007         Last updated: 11 April 2009
264         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
265  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
266    
267    
# Line 237  NAME Line 275  NAME
275  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
276    
277         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
278         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
279         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
280         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
281         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
282         directory) can be obtained by running         environments using the GUI facility of  CMakeSetup  if  you  are  using
283           CMake instead of configure to build PCRE.
284    
285           The complete list of options for configure (which includes the standard
286           ones such as the  selection  of  the  installation  directory)  can  be
287           obtained by running
288    
289           ./configure --help           ./configure --help
290    
291         The following sections include  descriptions  of  options  whose  names         The  following  sections  include  descriptions  of options whose names
292         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
293         defaults for the configure command. Because of the way  that  configure         defaults  for  the configure command. Because of the way that configure
294         works,  --enable  and --disable always come in pairs, so the complemen-         works, --enable and --disable always come in pairs, so  the  complemen-
295         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
296         is not described.         is not described.
297    
298    
# Line 266  C++ SUPPORT Line 309  C++ SUPPORT
309    
310  UTF-8 SUPPORT  UTF-8 SUPPORT
311    
312         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
313    
314           --enable-utf8           --enable-utf8
315    
316         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
317         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
318         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()
319         function.         function.
320    
321           If  you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
322           expects its input to be either ASCII or UTF-8 (depending on the runtime
323           option).  It  is not possible to support both EBCDIC and UTF-8 codes in
324           the same  version  of  the  library.  Consequently,  --enable-utf8  and
325           --enable-ebcdic are mutually exclusive.
326    
327    
328  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
329    
330         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
331         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-
332         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
333         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
334         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
335    
336           --enable-unicode-properties           --enable-unicode-properties
337    
338         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
339         not explicitly requested it.         not explicitly requested it.
340    
341         Including  Unicode  property  support  adds around 30K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
342         PCRE library. Only the general category properties such as  Lu  and  Nd         PCRE  library.  Only  the general category properties such as Lu and Nd
343         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
344    
345    
346  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
347    
348         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By default, PCRE interprets the linefeed (LF) character  as  indicating
349         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
350         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems. You can compile PCRE to use carriage return (CR)  instead,  by
351         instead, by adding         adding
352    
353           --enable-newline-is-cr           --enable-newline-is-cr
354    
355         to the  configure  command.  There  is  also  a  --enable-newline-is-lf         to  the  configure  command.  There  is  also  a --enable-newline-is-lf
356         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
357    
358         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 315  CODE VALUE OF NEWLINE Line 364  CODE VALUE OF NEWLINE
364    
365           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
366    
367         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
368         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
369    
370           --enable-newline-is-any           --enable-newline-is-any
# Line 327  CODE VALUE OF NEWLINE Line 376  CODE VALUE OF NEWLINE
376         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
377    
378    
379    WHAT \R MATCHES
380    
381           By default, the sequence \R in a pattern matches  any  Unicode  newline
382           sequence,  whatever  has  been selected as the line ending sequence. If
383           you specify
384    
385             --enable-bsr-anycrlf
386    
387           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
388           ever  is selected when PCRE is built can be overridden when the library
389           functions are called.
390    
391    
392  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
393    
394         The PCRE building process uses libtool to build both shared and  static         The PCRE building process uses libtool to build both shared and  static
# Line 390  AVOIDING EXCESSIVE STACK USAGE Line 452  AVOIDING EXCESSIVE STACK USAGE
452    
453         to  the  configure  command. With this configuration, PCRE will use the         to  the  configure  command. With this configuration, PCRE will use the
454         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
455         ment  functions.  Separate  functions are provided because the usage is         ment  functions. By default these point to malloc() and free(), but you
456         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used.
457         the  blocks  are always freed in reverse order. A calling program might  
458         be able to implement optimized functions that perform better  than  the         Separate functions are  provided  rather  than  using  pcre_malloc  and
459         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
460         slowly when built in this way. This option affects only the pcre_exec()         requested are always the same, and  the  blocks  are  always  freed  in
461         function; it is not relevant for the the pcre_dfa_exec() function.         reverse  order.  A calling program might be able to implement optimized
462           functions that perform better  than  malloc()  and  free().  PCRE  runs
463           noticeably more slowly when built in this way. This option affects only
464           the  pcre_exec()  function;  it   is   not   relevant   for   the   the
465           pcre_dfa_exec() function.
466    
467    
468  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 451  USING EBCDIC CODE Line 517  USING EBCDIC CODE
517    
518         PCRE  assumes  by  default that it will run in an environment where the         PCRE  assumes  by  default that it will run in an environment where the
519         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
520         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         This  is  the  case for most computer operating systems. PCRE can, how-
521         adding         ever, be compiled to run in an EBCDIC environment by adding
522    
523           --enable-ebcdic           --enable-ebcdic
524    
525         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
526         bles.         bles.  You  should  only  use  it if you know that you are in an EBCDIC
527           environment (for example,  an  IBM  mainframe  operating  system).  The
528           --enable-ebcdic option is incompatible with --enable-utf8.
529    
530    
531    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
532    
533           By default, pcregrep reads all files as plain text. You can build it so
534           that it recognizes files whose names end in .gz or .bz2, and reads them
535           with libz or libbz2, respectively, by adding one or both of
536    
537             --enable-pcregrep-libz
538             --enable-pcregrep-libbz2
539    
540           to the configure command. These options naturally require that the rel-
541           evant libraries are installed on your system. Configuration  will  fail
542           if they are not.
543    
544    
545    PCRETEST OPTION FOR LIBREADLINE SUPPORT
546    
547           If you add
548    
549             --enable-pcretest-libreadline
550    
551           to  the  configure  command,  pcretest  is  linked with the libreadline
552           library, and when its input is from a terminal, it reads it  using  the
553           readline() function. This provides line-editing and history facilities.
554           Note that libreadline is GPL-licenced, so if you distribute a binary of
555           pcretest linked in this way, there may be licensing issues.
556    
557           Setting  this  option  causes  the -lreadline option to be added to the
558           pcretest build. In many operating environments with  a  sytem-installed
559           libreadline this is sufficient. However, in some environments (e.g.  if
560           an unmodified distribution version of readline is in use),  some  extra
561           configuration  may  be necessary. The INSTALL file for libreadline says
562           this:
563    
564             "Readline uses the termcap functions, but does not link with the
565             termcap or curses library itself, allowing applications which link
566             with readline the to choose an appropriate library."
567    
568           If your environment has not been set up so that an appropriate  library
569           is automatically included, you may need to add something like
570    
571             LIBS="-ncurses"
572    
573           immediately before the configure command.
574    
575    
576  SEE ALSO  SEE ALSO
# Line 474  AUTHOR Line 587  AUTHOR
587    
588  REVISION  REVISION
589    
590         Last updated: 16 April 2007         Last updated: 17 March 2009
591         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
592  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
593    
594    
# Line 618  THE ALTERNATIVE MATCHING ALGORITHM Line 731  THE ALTERNATIVE MATCHING ALGORITHM
731         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
732         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.
733    
734         7.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
735         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-
736         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
737         time, for all active paths through the tree.         time, for all active paths through the tree.
738    
739           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
740           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
741           negative assertion.
742    
743    
744  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
745    
# Line 669  AUTHOR Line 786  AUTHOR
786    
787  REVISION  REVISION
788    
789         Last updated: 29 May 2007         Last updated: 19 April 2008
790         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
791  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
792    
793    
# Line 782  PCRE API OVERVIEW Line 899  PCRE API OVERVIEW
899         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
900         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
901         the  source distribution. The pcresample documentation describes how to         the  source distribution. The pcresample documentation describes how to
902         run it.         compile and run it.
903    
904         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
905         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
# Line 866  NEWLINES Line 983  NEWLINES
983         dard. When PCRE is run, the default can be overridden,  either  when  a         dard. When PCRE is run, the default can be overridden,  either  when  a
984         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
985    
986           At compile time, the newline convention can be specified by the options
987           argument of pcre_compile(), or it can be specified by special  text  at
988           the start of the pattern itself; this overrides any other settings. See
989           the pcrepattern page for details of the special character sequences.
990    
991         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
992         acter or pair of characters that indicate a line break". The choice  of         acter  or pair of characters that indicate a line break". The choice of
993         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
994         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
995         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
996         ment for a non-anchored pattern. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
997         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
998    
999           The choice of newline convention does not affect the interpretation  of
1000           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1001           which is controlled in a similar way, but by separate options.
1002    
1003    
1004  MULTITHREADING  MULTITHREADING
1005    
1006         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1007         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1008         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
1009         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 926  CHECKING BUILD-TIME OPTIONS Line 1052  CHECKING BUILD-TIME OPTIONS
1052         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1053         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1054         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,
1055         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
1056         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1057           spond to the standard sequence for your operating system.
1058    
1059             PCRE_CONFIG_BSR
1060    
1061           The output is an integer whose value indicates what character sequences
1062           the \R escape sequence matches by default. A value of 0 means  that  \R
1063           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1064           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1065           tern is compiled or matched.
1066    
1067           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1068    
1069         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
1070         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1071         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1072         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1073         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1074         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1075    
1076           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1077    
1078         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1079         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1080         given in the pcreposix documentation.         given in the pcreposix documentation.
1081    
1082           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1083    
1084         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-
1085         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1086         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1087    
1088           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1089    
1090         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
1091         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1092         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1093           below.
1094    
1095           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1096    
# Line 998  COMPILING A PATTERN Line 1134  COMPILING A PATTERN
1134    
1135         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1136         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1137         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1138         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
1139         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1140         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1141         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1142         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-
1143         of matching as well as at compile time.         tion.  The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the
1144           time of matching as well as at compile time.
1145    
1146         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1147         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1148         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-
1149         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
1150         try to free it. The offset from the start of the pattern to the charac-         try to free it. The offset from the start of the pattern to the charac-
1151         ter where the error was discovered is placed in the variable pointed to         ter where the error was discovered is placed in the variable pointed to
1152         by  erroffset,  which must not be NULL. If it is, an immediate error is         by erroffset, which must not be NULL. If it is, an immediate  error  is
1153         given.         given.
1154    
1155         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1156         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
1157         via this argument in the event of an error. This is in addition to  the         via  this argument in the event of an error. This is in addition to the
1158         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1159    
1160         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1161         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1162         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1163         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1164         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1165         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1166         support below.         support below.
1167    
1168         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1169         pile():         pile():
1170    
1171           pcre *re;           pcre *re;
# Line 1041  COMPILING A PATTERN Line 1178  COMPILING A PATTERN
1178             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1179             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1180    
1181         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1182         file:         file:
1183    
1184           PCRE_ANCHORED           PCRE_ANCHORED
1185    
1186         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1187         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1188         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1189         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1190         only way to do it in Perl.         only way to do it in Perl.
1191    
1192           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1193    
1194         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1195         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1196         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1197    
1198             PCRE_BSR_ANYCRLF
1199             PCRE_BSR_UNICODE
1200    
1201           These options (which are mutually exclusive) control what the \R escape
1202           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1203           or to match any Unicode newline sequence. The default is specified when
1204           PCRE is built. It can be overridden from within the pattern, or by set-
1205           ting an option when a compiled pattern is matched.
1206    
1207           PCRE_CASELESS           PCRE_CASELESS
1208    
1209         If  this  bit is set, letters in the pattern match both upper and lower         If this bit is set, letters in the pattern match both upper  and  lower
1210         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1211         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1212         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1213         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1214         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1215         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1216         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1217         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1218         UTF-8 support.         UTF-8 support.
1219    
1220           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1221    
1222         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1223         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1224         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1225         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1226         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1227         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1228    
1229           PCRE_DOTALL           PCRE_DOTALL
1230    
1231         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharater in the pattern matches all char-
1232         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1233         not  match  when  the  current position is at a newline. This option is         not match when the current position is at a  newline.  This  option  is
1234         equivalent to Perl's /s option, and it can be changed within a  pattern         equivalent  to Perl's /s option, and it can be changed within a pattern
1235         by  a (?s) option setting. A negative class such as [^a] always matches         by a (?s) option setting. A negative class such as [^a] always  matches
1236         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1237    
1238           PCRE_DUPNAMES           PCRE_DUPNAMES
1239    
1240         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1241         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1242         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1243         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1244         the pcrepattern documentation.         the pcrepattern documentation.
1245    
1246           PCRE_EXTENDED           PCRE_EXTENDED
1247    
1248         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1249         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1250         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1251         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1252         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1253         option,  and  it  can be changed within a pattern by a (?x) option set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1254         ting.         ting.
1255    
1256         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1257         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1258         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1259         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1260         introduces a conditional subpattern.         introduces a conditional subpattern.
1261    
1262           PCRE_EXTRA           PCRE_EXTRA
1263    
1264         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1265         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1266         little use. When set, any backslash in a pattern that is followed by  a         little  use. When set, any backslash in a pattern that is followed by a
1267         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1268         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1269         backslash  followed by a letter with no special meaning is treated as a         backslash followed by a letter with no special meaning is treated as  a
1270         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal.  (Perl can, however, be persuaded to give a warning for this.)
1271         There  are  at  present no other features controlled by this option. It         There are at present no other features controlled by  this  option.  It
1272         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1273    
1274           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1275    
1276         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1277         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1278         matched text may continue over the newline.         matched text may continue over the newline.
1279    
1280             PCRE_JAVASCRIPT_COMPAT
1281    
1282           If this option is set, PCRE's behaviour is changed in some ways so that
1283           it is compatible with JavaScript rather than Perl. The changes  are  as
1284           follows:
1285    
1286           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1287           error, because this is illegal in JavaScript (by default it is  treated
1288           as a data character). Thus, the pattern AB]CD becomes illegal when this
1289           option is set.
1290    
1291           (2) At run time, a back reference to an unset subpattern group  matches
1292           an  empty  string (by default this causes the current matching alterna-
1293           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1294           set  (assuming  it can find an "a" in the subject), whereas it fails by
1295           default, for Perl compatibility.
1296    
1297           PCRE_MULTILINE           PCRE_MULTILINE
1298    
1299         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1184  COMPILING A PATTERN Line 1347  COMPILING A PATTERN
1347         and are therefore ignored.         and are therefore ignored.
1348    
1349         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
1350         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.
1351    
1352           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1353    
1354         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1355         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1356         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1357         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1358         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1359    
1360           PCRE_UNGREEDY           PCRE_UNGREEDY
1361    
1362         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1363         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1364         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1365         within the pattern.         within the pattern.
1366    
1367           PCRE_UTF8           PCRE_UTF8
1368    
1369         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1370         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1371         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1372         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1373         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  section  on
1374         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1375    
1376           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1377    
1378         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1379         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1380         pcre_compile() returns an error. If you already know that your  pattern         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1381         is  valid, and you want to skip this check for performance reasons, you         bytes is found, pcre_compile() returns an error. If  you  already  know
1382         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1383         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1384         your program to crash.  Note that this option can  also  be  passed  to         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1385         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined. It may cause your program to crash. Note  that  this  option
1386         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1387           UTF-8 validity checking of subject strings.
1388    
1389    
1390  COMPILATION ERROR CODES  COMPILATION ERROR CODES
# Line 1242  COMPILATION ERROR CODES Line 1406  COMPILATION ERROR CODES
1406            9  nothing to repeat            9  nothing to repeat
1407           10  [this code is not in use]           10  [this code is not in use]
1408           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1409           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1410           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1411           14  missing )           14  missing )
1412           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1250  COMPILATION ERROR CODES Line 1414  COMPILATION ERROR CODES
1414           17  unknown option bit(s) set           17  unknown option bit(s) set
1415           18  missing ) after comment           18  missing ) after comment
1416           19  [this code is not in use]           19  [this code is not in use]
1417           20  regular expression too large           20  regular expression is too large
1418           21  failed to get memory           21  failed to get memory
1419           22  unmatched parentheses           22  unmatched parentheses
1420           23  internal error: code overflow           23  internal error: code overflow
# Line 1259  COMPILATION ERROR CODES Line 1423  COMPILATION ERROR CODES
1423           26  malformed number or name after (?(           26  malformed number or name after (?(
1424           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1425           28  assertion expected after (?(           28  assertion expected after (?(
1426           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1427           30  unknown POSIX class name           30  unknown POSIX class name
1428           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1429           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
# Line 1279  COMPILATION ERROR CODES Line 1443  COMPILATION ERROR CODES
1443           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1444           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1445           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1446           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1447           50  repeated subpattern is too long           50  [this code is not in use]
1448           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1449           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1450           53   internal  error:  previously-checked  referenced  subpattern not           53   internal  error:  previously-checked  referenced  subpattern not
1451         found         found
1452           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1453           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1454           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1455             57  \g is not followed by a braced, angle-bracketed, or quoted
1456                   name/number or by a plain number
1457             58  a numbered reference must not be zero
1458             59  (*VERB) with an argument is not supported
1459             60  (*VERB) not recognized
1460             61  number is too big
1461             62  subpattern name expected
1462             63  digit expected after (?+
1463             64  ] is an invalid data character in JavaScript compatibility mode
1464    
1465           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1466           values may be used if the limits were changed when PCRE was built.
1467    
1468    
1469  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1295  STUDYING A PATTERN Line 1471  STUDYING A PATTERN
1471         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1472              const char **errptr);              const char **errptr);
1473    
1474         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
1475         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
1476         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1477         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1478         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1479         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
1480         the results of the study.         the results of the study.
1481    
1482         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1483         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1484         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
1485         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1486    
1487         If  studying  the  pattern  does not produce any additional information         If studying the pattern does not  produce  any  additional  information
1488         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1489         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
1490         its own pcre_extra block.         its own pcre_extra block.
1491    
1492         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1493         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1494    
1495         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.
1496         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1497         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
1498         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
1499         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
1500         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1501    
1502         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1332  STUDYING A PATTERN Line 1508  STUDYING A PATTERN
1508             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1509    
1510         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1511         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-
1512         ble starting bytes is created.         ble starting bytes is created.
1513    
1514    
1515  LOCALE SUPPORT  LOCALE SUPPORT
1516    
1517         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1518         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1519         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
1520         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1521         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
1522         with  Unicode  character property support. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1523         code is discouraged. If you are handling characters with codes  greater         code  is discouraged. If you are handling characters with codes greater
1524         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
1525         not try to mix the two.         not try to mix the two.
1526    
1527         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
1528         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1529         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1530         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-
1531         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,
1532         which may cause them to be different.         which may cause them to be different.
1533    
1534         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1535         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1536         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1537         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1538    
1539         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1540         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
1541         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1542         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1543         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1544         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1545    
1546           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1547           tables = pcre_maketables();           tables = pcre_maketables();
1548           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1549    
1550         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;
1551         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".
1552    
1553         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1554         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1555         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1556         it is needed.         it is needed.
1557    
1558         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
1559         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()
1560         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-
1561         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1562         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1563    
1564         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
1565         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1566         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
1567         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
1568         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1569    
# Line 1397  INFORMATION ABOUT A PATTERN Line 1573  INFORMATION ABOUT A PATTERN
1573         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1574              int what, void *where);              int what, void *where);
1575    
1576         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1577         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1578         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1579    
1580         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1581         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
1582         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1583         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
1584         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
1585         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1586    
1587           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1413  INFORMATION ABOUT A PATTERN Line 1589  INFORMATION ABOUT A PATTERN
1589           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1590           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1591    
1592         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
1593         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1594         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1595         pattern:         pattern:
1596    
1597           int rc;           int rc;
# Line 1426  INFORMATION ABOUT A PATTERN Line 1602  INFORMATION ABOUT A PATTERN
1602             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1603             &length);         /* where to put the data */             &length);         /* where to put the data */
1604    
1605         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
1606         are as follows:         are as follows:
1607    
1608           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1609    
1610         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1611         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1612         there are no back references.         there are no back references.
1613    
1614           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1615    
1616         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1617         argument should point to an int variable.         argument should point to an int variable.
1618    
1619           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1620    
1621         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1622         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1623         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1624         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1625         passing a NULL table pointer.         passing a NULL table pointer.
1626    
1627           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1628    
1629         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1630         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1631         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
1632         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1633    
1634         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
1635         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1636    
1637         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1638         branch starts with "^", or         branch starts with "^", or
1639    
1640         (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
1641         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1642    
1643         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1644         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1645         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1646    
1647           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1648    
1649         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
1650         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
1651         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1652         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1653         able.         able.
1654    
1655             PCRE_INFO_HASCRORLF
1656    
1657           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1658           characters,  otherwise  0.  The  fourth argument should point to an int
1659           variable. An explicit match is either a literal CR or LF character,  or
1660           \r or \n.
1661    
1662           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1663    
1664         Return  1  if the (?J) option setting is used in the pattern, otherwise         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1665         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise 0. The fourth argument should point to an int variable.  (?J)
1666         nal option setting changes the local PCRE_DUPNAMES value.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1667    
1668           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1669    
# Line 1548  INFORMATION ABOUT A PATTERN Line 1731  INFORMATION ABOUT A PATTERN
1731         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
1732         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
1733         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1734         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1735           other words, they are the options that will be in force  when  matching
1736           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1737           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1738           and PCRE_EXTENDED.
1739    
1740         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
1741         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1628  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1815  MATCHING A PATTERN: THE TRADITIONAL FUNC
1815              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1816              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1817    
1818         The function pcre_exec() is called to match a subject string against  a         The  function pcre_exec() is called to match a subject string against a
1819         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1820         has been studied, the result of the study should be passed in the extra         has been studied, the result of the study should be passed in the extra
1821         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1822         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1823         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1824         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1825    
1826         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1827         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1828         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1829         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1830         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1831    
1832         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1658  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1845  MATCHING A PATTERN: THE TRADITIONAL FUNC
1845    
1846     Extra data for pcre_exec()     Extra data for pcre_exec()
1847    
1848         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
1849         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
1850         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
1851         tional  information  in it. The pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
1852         fields (not necessarily in this order):         fields (not necessarily in this order):
1853    
1854           unsigned long int flags;           unsigned long int flags;
# Line 1671  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1858  MATCHING A PATTERN: THE TRADITIONAL FUNC
1858           void *callout_data;           void *callout_data;
1859           const unsigned char *tables;           const unsigned char *tables;
1860    
1861         The flags field is a bitmap that specifies which of  the  other  fields         The  flags  field  is a bitmap that specifies which of the other fields
1862         are set. The flag bits are:         are set. The flag bits are:
1863    
1864           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1680  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1867  MATCHING A PATTERN: THE TRADITIONAL FUNC
1867           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1868           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1869    
1870         Other  flag  bits should be set to zero. The study_data field is set in         Other flag bits should be set to zero. The study_data field is  set  in
1871         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1872         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1873         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1874         flag bits.         flag bits.
1875    
1876         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1877         a vast amount of resources when running patterns that are not going  to         a  vast amount of resources when running patterns that are not going to
1878         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1879         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees.  The  classic  example  is  the  use of nested unlimited
1880         repeats.         repeats.
1881    
1882         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1883         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
1884         on  the  number  of times this function is called during a match, which         on the number of times this function is called during  a  match,  which
1885         has the effect of limiting the amount of  backtracking  that  can  take         has  the  effect  of  limiting the amount of backtracking that can take
1886         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1887         for each position in the subject string.         for each position in the subject string.
1888    
1889         The default value for the limit can be set  when  PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
1890         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1891         cases. You can override the default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1892         pcre_extra     block    in    which    match_limit    is    set,    and         pcre_extra    block    in    which    match_limit    is    set,     and
1893         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
1894         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1895    
1896         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
1897         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
1898         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
1899         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-
1900         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.
1901    
1902         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting the recursion depth limits the amount of  stack  that  can  be
# Line 1741  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1928  MATCHING A PATTERN: THE TRADITIONAL FUNC
1928    
1929         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.
1930         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,
1931         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_START_OPTIMIZE,
1932         PCRE_PARTIAL.         PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1933    
1934           PCRE_ANCHORED           PCRE_ANCHORED
1935    
# Line 1751  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1938  MATCHING A PATTERN: THE TRADITIONAL FUNC
1938         turned out to be anchored by virtue of its contents, it cannot be  made         turned out to be anchored by virtue of its contents, it cannot be  made
1939         unachored at matching time.         unachored at matching time.
1940    
1941             PCRE_BSR_ANYCRLF
1942             PCRE_BSR_UNICODE
1943    
1944           These options (which are mutually exclusive) control what the \R escape
1945           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1946           or  to  match  any Unicode newline sequence. These options override the
1947           choice that was made or defaulted when the pattern was compiled.
1948    
1949           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1950           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1951           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1952           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1953           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1954    
1955         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
1956         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
1957         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
1958         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
1959         ters.  It may also alter the way the match position is advanced after a         ters. It may also alter the way the match position is advanced after  a
1960         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
1961         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
1962         fails when the current position is at a CRLF sequence, the match  posi-         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
1963         tion  is  advanced by two characters instead of one, in other words, to         set, and a match attempt for an unanchored pattern fails when the  cur-
1964         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
1965           explicit matches for  CR  or  LF  characters,  the  match  position  is
1966           advanced by two characters instead of one, in other words, to after the
1967           CRLF.
1968    
1969           The above rule is a compromise that makes the most common cases work as
1970           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
1971           option is not set), it does not match the string "\r\nA" because, after
1972           failing  at the start, it skips both the CR and the LF before retrying.
1973           However, the pattern [\r\n]A does match that string,  because  it  con-
1974           tains an explicit CR or LF reference, and so advances only by one char-
1975           acter after the first failure.
1976    
1977           An explicit match for CR of LF is either a literal appearance of one of
1978           those  characters,  or  one  of the \r or \n escape sequences. Implicit
1979           matches such as [^X] do not count, nor does \s (which includes  CR  and
1980           LF in the characters that it matches).
1981    
1982           Notwithstanding  the above, anomalous effects may still occur when CRLF
1983           is a valid newline sequence and explicit \r or \n escapes appear in the
1984           pattern.
1985    
1986           PCRE_NOTBOL           PCRE_NOTBOL
1987    
1988         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1989         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
1990         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
1991         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
1992         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1993    
1994           PCRE_NOTEOL           PCRE_NOTEOL
1995    
1996         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
1997         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
1998         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
1999         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2000         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2001         not affect \Z or \z.         not affect \Z or \z.
2002    
2003           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2004    
2005         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2006         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2007         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2008         example, if the pattern         example, if the pattern
2009    
2010           a?b?           a?b?
2011    
2012         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 the
2013         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
2014         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-
2015         rences of "a" or "b".         rences of "a" or "b".
2016    
2017         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
2018         cial case of a pattern match of the empty  string  within  its  split()         cial  case  of  a  pattern match of the empty string within its split()
2019         function,  and  when  using  the /g modifier. It is possible to emulate         function, and when using the /g modifier. It  is  possible  to  emulate
2020         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
2021         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
2022         if that fails by advancing the starting offset (see below)  and  trying         if  that  fails by advancing the starting offset (see below) and trying
2023         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
2024         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
2025    
2026             PCRE_NO_START_OPTIMIZE
2027    
2028           There  are a number of optimizations that pcre_exec() uses at the start
2029           of a match, in order to speed up the process. For  example,  if  it  is
2030           known  that  a  match must start with a specific character, it searches
2031           the subject for that character, and fails immediately if it cannot find
2032           it,  without actually running the main matching function. When callouts
2033           are in use, these optimizations can cause  them  to  be  skipped.  This
2034           option  disables  the  "start-up" optimizations, causing performance to
2035           suffer, but ensuring that the callouts do occur.
2036    
2037           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2038    
2039         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2040         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2041         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2042         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2043         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2044         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2045         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2046           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2047         If you already know that your subject is valid, and you  want  to  skip  
2048         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
2049         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
2050         do  this  for the second and subsequent calls to pcre_exec() if you are         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2051         making repeated calls to find all  the  matches  in  a  single  subject         do this for the second and subsequent calls to pcre_exec() if  you  are
2052         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
2053         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         string. However, you should be  sure  that  the  value  of  startoffset
2054         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
2055         value of startoffset that does not point to the start of a UTF-8  char-         set, the effect of passing an invalid UTF-8 string as a subject,  or  a
2056           value  of startoffset that does not point to the start of a UTF-8 char-
2057         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2058    
2059           PCRE_PARTIAL           PCRE_PARTIAL
2060    
2061         This  option  turns  on  the  partial  matching feature. If the subject         This option turns on the  partial  matching  feature.  If  the  subject
2062         string fails to match the pattern, but at some point during the  match-         string  fails to match the pattern, but at some point during the match-
2063         ing  process  the  end of the subject was reached (that is, the subject         ing process the end of the subject was reached (that  is,  the  subject
2064         partially matches the pattern and the failure to  match  occurred  only         partially  matches  the  pattern and the failure to match occurred only
2065         because  there were not enough subject characters), pcre_exec() returns         because there were not enough subject characters), pcre_exec()  returns
2066         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
2067         used,  there  are restrictions on what may appear in the pattern. These         used, there are restrictions on what may appear in the  pattern.  These
2068         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
2069    
2070     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2071    
2072         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
2073         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.
2074         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-
2075         Unlike  the  pattern string, the subject may contain binary zero bytes.         acter. Unlike the pattern string, the subject may contain  binary  zero
2076         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
2077         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
2078           case.
2079    
2080         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2081         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 1883  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2111  MATCHING A PATTERN: THE TRADITIONAL FUNC
2111         string. PCRE supports several other kinds of  parenthesized  subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2112         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2113    
2114         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2115         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-
2116         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:
2117         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2118    
2119         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-
2120         strings,  each  substring using a pair of integers. The remaining third         strings,  each  substring using a pair of integers. The remaining third
2121         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-
2122         turing  subpatterns, and is not available for passing back information.         turing  subpatterns, and is not available for passing back information.
2123         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
2124         it is not, it is rounded down.         it is not, it is rounded down.
2125    
2126         When  a  match  is successful, information about captured substrings is         When  a  match  is successful, information about captured substrings is
2127         returned in pairs of integers, starting at the  beginning  of  ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2128         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
2129         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
2130         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
2131         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
2132         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2133         entire pattern. The next pair is used for the first  capturing  subpat-  
2134         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
2135         highest numbered pair that has been set. For example, if two substrings         portion of the subject string matched by the entire pattern.  The  next
2136         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
2137         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2138         that just the first pair of offsets has been set.         has  been  set.  For example, if two substrings have been captured, the
2139           returned value is 3. If there are no capturing subpatterns, the  return
2140           value from a successful match is 1, indicating that just the first pair
2141           of offsets has been set.
2142    
2143         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2144         of the string that it matched that is returned.         of the string that it matched that is returned.
2145    
2146         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,
2147         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
2148         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
2149         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
2150         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize  as zero. However, if the pattern contains back references and
2151         references  and  the  ovector is not big enough to remember the related         the ovector is not big enough to remember the related substrings,  PCRE
2152         substrings, PCRE has to get additional memory for use during  matching.         has  to  get additional memory for use during matching. Thus it is usu-
2153         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2154    
2155         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
2156         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2157         ovector  that  will allow for n captured substrings, in addition to the         ovector that will allow for n captured substrings, in addition  to  the
2158         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.
2159    
2160         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
2161         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,
2162         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
2163         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
2164         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-
2165         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2166    
2167         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2168         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
2169         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
2170         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2171         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2172         for the second and third capturing subpatterns if  you  wish  (assuming         for  the  second  and third capturing subpatterns if you wish (assuming
2173         the vector is large enough, of course).         the vector is large enough, of course).
2174    
2175         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2176         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2177    
2178     Error return values from pcre_exec()     Error return values from pcre_exec()
2179    
2180         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2181         defined in the header file:         defined in the header file:
2182    
2183           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1955  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2186  MATCHING A PATTERN: THE TRADITIONAL FUNC
2186    
2187           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2188    
2189         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
2190         ovecsize was not zero.         ovecsize was not zero.
2191    
2192           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1964  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2195  MATCHING A PATTERN: THE TRADITIONAL FUNC
2195    
2196           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2197    
2198         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,
2199         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
2200         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
2201         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2202         gives when the magic number is not present.         gives when the magic number is not present.
2203    
2204           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2205    
2206         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2207         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
2208         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2209    
2210           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2211    
2212         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2213         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2214         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
2215         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
2216         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2217    
2218           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2219    
2220         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2221         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2222         returned by pcre_exec().         returned by pcre_exec().
2223    
2224           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2225    
2226         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2227         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2228         above.         above.
2229    
2230           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2231    
2232         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
2233         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2234         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2235    
2236           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2237    
2238         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
2239         subject.         subject.
2240    
2241           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2242    
2243         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
2244         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-
2245         ter.         ter.
2246    
2247           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2248    
2249         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
2250         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2251    
2252           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2253    
2254         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
2255         items  that are not supported for partial matching. See the pcrepartial         items that are not supported for partial matching. See the  pcrepartial
2256         documentation for details of partial matching.         documentation for details of partial matching.
2257    
2258           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2259    
2260         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2261         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2262    
2263           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2264    
2265         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.
2266    
2267           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2268    
# Line 2039  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2270  MATCHING A PATTERN: THE TRADITIONAL FUNC
2270         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2271         description above.         description above.
2272    
          PCRE_ERROR_NULLWSLIMIT    (-22)  
   
        When a group that can match an empty  substring  is  repeated  with  an  
        unbounded  upper  limit, the subject position at the start of the group  
        must be remembered, so that a test for an empty string can be made when  
        the  end  of the group is reached. Some workspace is required for this;  
        if it runs out, this error is given.  
   
2273           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2274    
2275         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2276    
2277         Error numbers -16 to -20 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2278    
2279    
2280  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2189  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2412  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2412         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
2413         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2414    
2415           Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
2416           patterns  with  the  same  number,  you cannot use names to distinguish
2417           them, because names are not included in the compiled code. The matching
2418           process uses only numbers.
2419    
2420    
2421  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2422    
2423         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2424              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2425    
2426         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2427         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to  be  unique.  Normally,  patterns  with
2428         duplicate names are such that in any one match, only one of  the  named         duplicate  names  are such that in any one match, only one of the named
2429         subpatterns  participates. An example is shown in the pcrepattern docu-         subpatterns participates. An example is shown in the pcrepattern  docu-
2430         mentation. When duplicates are present, pcre_copy_named_substring() and         mentation.
2431         pcre_get_named_substring()  return the first substring corresponding to  
2432         the given name that is set.  If  none  are  set,  an  empty  string  is         When    duplicates   are   present,   pcre_copy_named_substring()   and
2433         returned.  The pcre_get_stringnumber() function returns one of the num-         pcre_get_named_substring() return the first substring corresponding  to
2434         bers that are associated with the name, but it is not defined which  it         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2435         is.         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2436           function  returns one of the numbers that are associated with the name,
2437           but it is not defined which it is.
2438    
2439         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2440         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2441         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2442         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2443         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2444         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2445         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2446         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2447         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2448         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2449         the captured data, if any.         the captured data, if any.
2450    
2451    
2452  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2453    
2454         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2455         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2456         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2457         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2458         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2459         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2460         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2461         tation.         tation.
2462    
2463         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2464         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2465         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2466         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2467         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2468    
2469    
# Line 2244  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2474  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2474              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2475              int *workspace, int wscount);              int *workspace, int wscount);
2476    
2477         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2478         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2479         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2480         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2481         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2482         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
2483         a discussion of the two matching algorithms, see the pcrematching docu-         a discussion of the two matching algorithms, see the pcrematching docu-
2484         mentation.         mentation.
2485    
2486         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
2487         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-
2488         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
2489         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
2490         repeated here.         repeated here.
2491    
2492         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
2493         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
2494         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2495         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
2496         lot of potential matches.         lot of potential matches.
2497    
2498         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 2284  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2514  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2514    
2515     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2516    
2517         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
2518         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-
2519         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
2520         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
2521         three of these are the same as for pcre_exec(), so their description is         three of these are the same as for pcre_exec(), so their description is
2522         not repeated here.         not repeated here.
2523    
2524           PCRE_PARTIAL           PCRE_PARTIAL
2525    
2526         This has the same general effect as it does for  pcre_exec(),  but  the         This  has  the  same general effect as it does for pcre_exec(), but the
2527         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
2528         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
2529         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have
2530         been no complete matches, but there is still at least one matching pos-         been no complete matches, but there is still at least one matching pos-
2531         sibility.  The portion of the string that provided the partial match is         sibility. The portion of the string that provided the partial match  is
2532         set as the first matching string.         set as the first matching string.
2533    
2534           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2535    
2536         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2537         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2538         tive algorithm works, this is necessarily the shortest  possible  match         tive  algorithm  works, this is necessarily the shortest possible match
2539         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2540    
2541           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2542    
2543         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
2544         returns a partial match, it is possible to call it  again,  with  addi-         returns  a  partial  match, it is possible to call it again, with addi-
2545         tional  subject  characters,  and have it continue with the same match.         tional subject characters, and have it continue with  the  same  match.
2546         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         The  PCRE_DFA_RESTART  option requests this action; when it is set, the
2547         workspace  and wscount options must reference the same vector as before         workspace and wscount options must reference the same vector as  before
2548         because data about the match so far is left in  them  after  a  partial         because  data  about  the  match so far is left in them after a partial
2549         match.  There  is  more  discussion of this facility in the pcrepartial         match. There is more discussion of this  facility  in  the  pcrepartial
2550         documentation.         documentation.
2551    
2552     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2553    
2554         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-
2555         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
2556         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
2557         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2558         if the pattern         if the pattern
2559    
2560           <.*>           <.*>
# Line 2339  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2569  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2569           <something> <something else>           <something> <something else>
2570           <something> <something else> <something further>           <something> <something else> <something further>
2571    
2572         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,
2573         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2574         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2575         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
2576         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2577         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
2578         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2579         meaning of the strings is different.)         meaning of the strings is different.)
2580    
2581         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-
2582         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
2583         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
2584         filled with the longest matches.         filled with the longest matches.
2585    
2586     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2587    
2588         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2589         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
2590         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2591         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2592    
2593           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2594    
2595         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-
2596         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
2597         reference.         reference.
2598    
2599           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2600    
2601         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2602         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
2603         in a specific group. These are not supported.         in a specific group. These are not supported.
2604    
2605           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2606    
2607         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
2608         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
2609         (it is meaningless).         (it is meaningless).
2610    
2611           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2612    
2613         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
2614         workspace vector.         workspace vector.
2615    
2616           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2617    
2618         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2619         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2620         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
2621         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2622    
2623    
2624  SEE ALSO  SEE ALSO
2625    
2626         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2627         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2628    
2629    
2630  AUTHOR  AUTHOR
# Line 2406  AUTHOR Line 2636  AUTHOR
2636    
2637  REVISION  REVISION
2638    
2639         Last updated: 04 June 2007         Last updated: 11 April 2009
2640         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2641  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2642    
2643    
# Line 2458  PCRE CALLOUTS Line 2688  PCRE CALLOUTS
2688  MISSING CALLOUTS  MISSING CALLOUTS
2689    
2690         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2691         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2692         pattern is         example, if the pattern is
2693    
2694           ab(?C4)cd           ab(?C4)cd
2695    
# Line 2468  MISSING CALLOUTS Line 2698  MISSING CALLOUTS
2698         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2699         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2700    
2701           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2702           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2703           matching process, but does ensure that callouts  such  as  the  example
2704           above are obeyed.
2705    
2706    
2707  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2708    
2709         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2710         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
2711         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2712         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
2713         block. This structure contains the following fields:         block. This structure contains the following fields:
2714    
2715           int          version;           int          version;
# Line 2490  THE CALLOUT INTERFACE Line 2725  THE CALLOUT INTERFACE
2725           int          pattern_position;           int          pattern_position;
2726           int          next_item_length;           int          next_item_length;
2727    
2728         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2729         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
2730         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2731         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.
2732    
2733         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 2577  AUTHOR Line 2812  AUTHOR
2812    
2813  REVISION  REVISION
2814    
2815         Last updated: 29 May 2007         Last updated: 15 March 2009
2816         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2817  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2818    
2819    
# Line 2593  DIFFERENCES BETWEEN PCRE AND PERL Line 2828  DIFFERENCES BETWEEN PCRE AND PERL
2828    
2829         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2830         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences described here  are  mainly
2831         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2832         tures that are expected to be in the forthcoming Perl 5.10.         some features that are expected to be in the forthcoming Perl 5.10.
2833    
2834         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
2835         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 2659  DIFFERENCES BETWEEN PCRE AND PERL Line 2894  DIFFERENCES BETWEEN PCRE AND PERL
2894         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2895         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2896    
2897         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2898           (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2899           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2900           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2901           ture group; this is different to Perl.
2902    
2903           12. PCRE provides some extensions to the Perl regular expression facil-
2904         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
2905         versions, some of which (such as named parentheses) have been  in  PCRE         versions, some of which (such as named parentheses) have been  in  PCRE
2906         for some time. This list is with respect to Perl 5.10:         for some time. This list is with respect to Perl 5.10:
# Line 2672  DIFFERENCES BETWEEN PCRE AND PERL Line 2913  DIFFERENCES BETWEEN PCRE AND PERL
2913         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2914    
2915         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
2916         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2917         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
2918    
2919         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2920         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2685  DIFFERENCES BETWEEN PCRE AND PERL Line 2926  DIFFERENCES BETWEEN PCRE AND PERL
2926         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
2927         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2928    
2929         (g) The callout facility is PCRE-specific.         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2930           CRLF by the PCRE_BSR_ANYCRLF option.
2931    
2932         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
2933    
2934         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
2935    
2936           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2937         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2938    
2939         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2940         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2941    
2942           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2943           of a pattern that set overall options that cannot be changed within the
2944           pattern.
2945    
2946    
2947  AUTHOR  AUTHOR
2948    
# Line 2705  AUTHOR Line 2953  AUTHOR
2953    
2954  REVISION  REVISION
2955    
2956         Last updated: 06 March 2007         Last updated: 11 September 2007
2957         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2958  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2959    
# Line 2719  NAME Line 2967  NAME
2967    
2968  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2969    
2970         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
2971         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
2972         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
2973         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
2974         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
2975         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
2976           Python, .NET, and Oniguruma.
2977    
2978           Perl's  regular expressions are described in its own documentation, and
2979           regular expressions in general are covered in a number of  books,  some
2980           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
2981           Expressions", published by  O'Reilly,  covers  regular  expressions  in
2982           great  detail.  This  description  of  PCRE's  regular  expressions  is
2983           intended as reference material.
2984    
2985         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2986         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
2987         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
2988         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
2989         matching is mentioned in several places below. There is also a  summary         sequence that can be given at the start of a pattern:
2990         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
2991         page.           (*UTF8)
2992    
2993           Starting a pattern with this sequence  is  equivalent  to  setting  the
2994           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
2995           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
2996           below.  There  is  also  a  summary of UTF-8 features in the section on
2997           UTF-8 support in the main pcre page.
2998    
2999         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3000         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 2744  PCRE REGULAR EXPRESSION DETAILS Line 3006  PCRE REGULAR EXPRESSION DETAILS
3006         discussed in the pcrematching page.         discussed in the pcrematching page.
3007    
3008    
3009    NEWLINE CONVENTIONS
3010    
3011           PCRE  supports five different conventions for indicating line breaks in
3012           strings: a single CR (carriage return) character, a  single  LF  (line-
3013           feed) character, the two-character sequence CRLF, any of the three pre-
3014           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3015           discussion  about newlines, and shows how to set the newline convention
3016           in the options arguments for the compiling and matching functions.
3017    
3018           It is also possible to specify a newline convention by starting a  pat-
3019           tern string with one of the following five sequences:
3020    
3021             (*CR)        carriage return
3022             (*LF)        linefeed
3023             (*CRLF)      carriage return, followed by linefeed
3024             (*ANYCRLF)   any of the three above
3025             (*ANY)       all Unicode newline sequences
3026    
3027           These override the default and the options given to pcre_compile(). For
3028           example, on a Unix system where LF is the default newline sequence, the
3029           pattern
3030    
3031             (*CR)a.b
3032    
3033           changes the convention to CR. That pattern matches "a\nb" because LF is
3034           no longer a newline. Note that these special settings,  which  are  not
3035           Perl-compatible,  are  recognized  only at the very start of a pattern,
3036           and that they must be in upper case.  If  more  than  one  of  them  is
3037           present, the last one is used.
3038    
3039           The  newline  convention  does  not  affect what the \R escape sequence
3040           matches. By default, this is any Unicode  newline  sequence,  for  Perl
3041           compatibility.  However, this can be changed; see the description of \R
3042           in the section entitled "Newline sequences" below. A change of \R  set-
3043           ting can be combined with a change of newline convention.
3044    
3045    
3046  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3047    
3048         A  regular  expression  is  a pattern that is matched against a subject         A  regular  expression  is  a pattern that is matched against a subject
# Line 2799  CHARACTERS AND METACHARACTERS Line 3098  CHARACTERS AND METACHARACTERS
3098                    syntax)                    syntax)
3099           ]      terminates the character class           ]      terminates the character class
3100    
3101         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3102    
3103    
3104  BACKSLASH  BACKSLASH
3105    
3106         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3107         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3108         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3109         applies both inside and outside character classes.         applies both inside and outside character classes.
3110    
3111         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
3112         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3113         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3114         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3115         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-
3116         slash, you write \\.         slash, you write \\.
3117    
3118         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3119         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3120         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3121         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3122         part of the pattern.         part of the pattern.
3123    
3124         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-
3125         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-
3126         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
3127         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3128         tion. Note the following examples:         tion. Note the following examples:
3129    
3130           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2835  BACKSLASH Line 3134  BACKSLASH
3134           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3135           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3136    
3137         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3138         classes.         classes.
3139    
3140     Non-printing characters     Non-printing characters
3141    
3142         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-
3143         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
3144         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3145         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3146         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
3147         sequences than the binary character it represents:         sequences than the binary character it represents:
3148    
3149           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3150           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3151           \e        escape (hex 1B)           \e        escape (hex 1B)
3152           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3153           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3154           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3155           \t        tab (hex 09)           \t        tab (hex 09)
3156           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
3157           \xhh      character with hex code hh           \xhh      character with hex code hh
3158           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3159    
3160         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,
3161         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
3162         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;
3163         becomes hex 7B.         becomes hex 7B.
3164    
3165         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
3166         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3167         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
3168         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,
3169         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3170         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
3171         nating  }, this form of escape is not recognized.  Instead, the initial  
3172         \x will be interpreted as a basic hexadecimal escape, with no following         If  characters  other than hexadecimal digits appear between \x{ and },
3173         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3174           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3175           escape, with no following digits, giving a  character  whose  value  is
3176           zero.
3177    
3178         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
3179         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-
# Line 2926  BACKSLASH Line 3228  BACKSLASH
3228    
3229     Absolute and relative back references     Absolute and relative back references
3230    
3231         The  sequence  \g followed by a positive or negative number, optionally         The  sequence  \g followed by an unsigned or a negative number, option-
3232         enclosed in braces, is an absolute or relative back reference. A  named         ally enclosed in braces, is an absolute or relative back  reference.  A
3233         back  reference can be coded as \g{name}. Back references are discussed         named back reference can be coded as \g{name}. Back references are dis-
3234         later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3235    
3236       Absolute and relative subroutine calls
3237    
3238           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3239           name or a number enclosed either in angle brackets or single quotes, is
3240           an alternative syntax for referencing a subpattern as  a  "subroutine".
3241           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3242           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3243           reference; the latter is a subroutine call.
3244    
3245     Generic character types     Generic character types
3246    
# Line 2938  BACKSLASH Line 3249  BACKSLASH
3249    
3250           \d     any decimal digit           \d     any decimal digit
3251           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3252             \h     any horizontal whitespace character
3253             \H     any character that is not a horizontal whitespace character
3254           \s     any whitespace character           \s     any whitespace character
3255           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3256             \v     any vertical whitespace character
3257             \V     any character that is not a vertical whitespace character
3258           \w     any "word" character           \w     any "word" character
3259           \W     any "non-word" character           \W     any "non-word" character
3260    
3261         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
3262         into two disjoint sets. Any given character matches one, and only  one,         into  two disjoint sets. Any given character matches one, and only one,
3263         of each pair.         of each pair.
3264    
3265         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
3266         acter classes. They each match one character of the  appropriate  type.         acter  classes.  They each match one character of the appropriate type.
3267         If  the current matching point is at the end of the subject string, all         If the current matching point is at the end of the subject string,  all
3268         of them fail, since there is no character to match.         of them fail, since there is no character to match.
3269    
3270         For compatibility with Perl, \s does not match the VT  character  (code         For  compatibility  with Perl, \s does not match the VT character (code
3271         11).   This makes it different from the the POSIX "space" class. The \s         11).  This makes it different from the the POSIX "space" class. The  \s
3272         characters are HT (9), LF (10), FF (12), CR (13), and space  (32).  (If         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3273         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3274         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3275    
3276           In  UTF-8 mode, characters with values greater than 128 never match \d,
3277           \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3278           code  character  property  support is available. These sequences retain
3279           their original meanings from before UTF-8 support was available, mainly
3280           for  efficiency  reasons. Note that this also affects \b, because it is
3281           defined in terms of \w and \W.
3282    
3283           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3284           the  other  sequences, these do match certain high-valued codepoints in
3285           UTF-8 mode.  The horizontal space characters are:
3286    
3287             U+0009     Horizontal tab
3288             U+0020     Space
3289             U+00A0     Non-break space
3290             U+1680     Ogham space mark
3291             U+180E     Mongolian vowel separator
3292             U+2000     En quad
3293             U+2001     Em quad
3294             U+2002     En space
3295             U+2003     Em space
3296             U+2004     Three-per-em space
3297             U+2005     Four-per-em space
3298             U+2006     Six-per-em space
3299             U+2007     Figure space
3300             U+2008     Punctuation space
3301             U+2009     Thin space
3302             U+200A     Hair space
3303             U+202F     Narrow no-break space
3304             U+205F     Medium mathematical space
3305             U+3000     Ideographic space
3306    
3307           The vertical space characters are:
3308    
3309             U+000A     Linefeed
3310             U+000B     Vertical tab
3311             U+000C     Formfeed
3312             U+000D     Carriage return
3313             U+0085     Next line
3314             U+2028     Line separator
3315             U+2029     Paragraph separator
3316    
3317         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
3318         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-
# Line 2964  BACKSLASH Line 3320  BACKSLASH
3320         specific  matching is taking place (see "Locale support" in the pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3321         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
3322         systems,  or "french" in Windows, some character codes greater than 128         systems,  or "french" in Windows, some character codes greater than 128
3323         are used for accented letters, and these are matched by \w.         are used for accented letters, and these are matched by \w. The use  of
3324           locales with Unicode is discouraged.
        In UTF-8 mode, characters with values greater than 128 never match  \d,  
        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-  
        code character property support is available. The use of  locales  with  
        Unicode is discouraged.  
3325    
3326     Newline sequences     Newline sequences
3327    
3328         Outside  a  character class, the escape sequence \R matches any Unicode         Outside  a  character class, by default, the escape sequence \R matches
3329         newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3330         equivalent to the following:         mode \R is equivalent to the following:
3331    
3332           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3333    
# Line 2991  BACKSLASH Line 3343  BACKSLASH
3343         rator, U+2029).  Unicode character property support is not  needed  for         rator, U+2029).  Unicode character property support is not  needed  for
3344         these characters to be recognized.         these characters to be recognized.
3345    
3346           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3347           the complete set  of  Unicode  line  endings)  by  setting  the  option
3348           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3349           (BSR is an abbrevation for "backslash R".) This can be made the default
3350           when  PCRE  is  built;  if this is the case, the other behaviour can be
3351           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3352           specify  these  settings  by  starting a pattern string with one of the
3353           following sequences:
3354    
3355             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3356             (*BSR_UNICODE)   any Unicode newline sequence
3357    
3358           These override the default and the options given to pcre_compile(), but
3359           they can be overridden by options given to pcre_exec(). Note that these
3360           special settings, which are not Perl-compatible, are recognized only at
3361           the  very  start  of a pattern, and that they must be in upper case. If
3362           more than one of them is present, the last one is  used.  They  can  be
3363           combined  with  a  change of newline convention, for example, a pattern
3364           can start with:
3365    
3366             (*ANY)(*BSR_ANYCRLF)
3367    
3368         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3369    
3370     Unicode character properties     Unicode character properties
3371    
3372         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3373         tional escape sequences to match  character  properties  are  available         tional  escape sequences that match characters with specific properties
3374         when UTF-8 mode is selected. They are:         are available.  When not in UTF-8 mode, these sequences are  of  course
3375           limited  to  testing characters whose codepoints are less than 256, but
3376           they do work in this mode.  The extra escape sequences are:
3377    
3378           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3379           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3380           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3381    
3382         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
3383         script names, the general category properties, and "Any", which matches         script names, the general category properties, and "Any", which matches
3384         any character (including newline). Other properties such as "InMusical-         any character (including newline). Other properties such as "InMusical-
3385         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
3386         not match any characters, so always causes a match failure.         not match any characters, so always causes a match failure.
3387    
3388         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3389         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.
3390         For example:         For example:
3391    
3392           \p{Greek}           \p{Greek}
3393           \P{Han}           \P{Han}
3394    
3395         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
3396         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3397    
3398         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3399         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
3400         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3401         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
3402         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
3403         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3404         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
3405         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3406         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3407    
3408         Each character has exactly one general category property, specified  by         Each  character has exactly one general category property, specified by
3409         a two-letter abbreviation. For compatibility with Perl, negation can be         a two-letter abbreviation. For compatibility with Perl, negation can be
3410         specified by including a circumflex between the opening brace  and  the         specified  by  including a circumflex between the opening brace and the
3411         property name. For example, \p{^Lu} is the same as \P{Lu}.         property name. For example, \p{^Lu} is the same as \P{Lu}.
3412    
3413         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-
3414         eral category properties that start with that letter. In this case,  in         eral  category properties that start with that letter. In this case, in
3415         the  absence of negation, the curly brackets in the escape sequence are         the absence of negation, the curly brackets in the escape sequence  are
3416         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3417    
3418           \p{L}           \p{L}
# Line 3088  BACKSLASH Line 3464  BACKSLASH
3464           Zp    Paragraph separator           Zp    Paragraph separator
3465           Zs    Space separator           Zs    Space separator
3466    
3467         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3468         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
3469         classified as a modifier or "other".         classified as a modifier or "other".
3470    
3471         The long synonyms for these properties  that  Perl  supports  (such  as         The  Cs  (Surrogate)  property  applies only to characters in the range
3472         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3473           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3474           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3475           the pcreapi page).
3476    
3477           The  long  synonyms  for  these  properties that Perl supports (such as
3478           \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3479         any of these properties with "Is".         any of these properties with "Is".
3480    
3481         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-
3482         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
3483         in the Unicode table.         in the Unicode table.
3484    
3485         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3486         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3487    
3488         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3489         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3490    
3491           (?>\PM\pM*)           (?>\PM\pM*)
3492    
3493         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
3494         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
3495         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3496         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3497           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3498           matches any one character.
3499    
3500         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
3501         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
3502         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3503         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3504    
3505     Resetting the match start     Resetting the match start
3506    
3507         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-
3508         ously  matched  characters  not  to  be  included  in the final matched         ously matched characters not  to  be  included  in  the  final  matched
3509         sequence. For example, the pattern:         sequence. For example, the pattern:
3510    
3511           foo\Kbar           foo\Kbar
3512    
3513         matches "foobar", but reports that it has matched "bar".  This  feature         matches  "foobar",  but reports that it has matched "bar". This feature
3514         is  similar  to  a lookbehind assertion (described below).  However, in         is similar to a lookbehind assertion (described  below).   However,  in
3515         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
3516         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
3517         not interfere with the setting of captured  substrings.   For  example,         not  interfere  with  the setting of captured substrings.  For example,
3518         when the pattern         when the pattern
3519    
3520           (foo)\Kbar           (foo)\Kbar
# Line 3139  BACKSLASH Line 3523  BACKSLASH
3523    
3524     Simple assertions     Simple assertions
3525    
3526         The  final use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3527         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
3528         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3529         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3530         The backslashed assertions are:         The backslashed assertions are:
3531    
3532           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3153  BACKSLASH Line 3537  BACKSLASH
3537           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3538           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3539    
3540         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3541         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3542         acter class).         acter class).
3543    
3544         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
3545         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.
3546         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
3547         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3548    
3549         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3550         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
3551         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
3552         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3553         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
3554         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3555         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3556         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
3557         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
3558         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
3559         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3560    
3561         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
3562         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
3563         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
3564         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
3565         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-
3566         mentation where \G can be useful.         mentation where \G can be useful.
3567    
3568         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
3569         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
3570         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
3571         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
3572         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3573    
3574         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
3575         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3576         in the compiled regular expression.         in the compiled regular expression.
3577    
# Line 3195  BACKSLASH Line 3579  BACKSLASH
3579  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3580    
3581         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3582         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
3583         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-
3584         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
3585         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
3586         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3587    
3588         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
3589         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
3590         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
3591         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
3592         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-
3593         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
3594         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3595    
3596         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
3597         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
3598         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
3599         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
3600         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
3601         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3602    
3603         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
3604         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
3605         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3606    
3607         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3608         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3609         matches  immediately after internal newlines as well as at the start of         matches immediately after internal newlines as well as at the start  of
3610         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
3611         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
3612         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
3613         as  the  two-character  sequence CRLF, isolated CR and LF characters do         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3614         not indicate newlines.         not indicate newlines.
3615    
3616         For example, the pattern /^abc$/ matches the subject string  "def\nabc"         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3617         (where  \n  represents a newline) in multiline mode, but not otherwise.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3618         Consequently, patterns that are anchored in single  line  mode  because         Consequently,  patterns  that  are anchored in single line mode because
3619         all  branches  start  with  ^ are not anchored in multiline mode, and a         all branches start with ^ are not anchored in  multiline  mode,  and  a
3620         match for circumflex is  possible  when  the  startoffset  argument  of         match  for  circumflex  is  possible  when  the startoffset argument of
3621         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
3622         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3623    
3624         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
3625         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
3626         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
3627         set.         set.
3628    
3629    
3630  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3631    
3632         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-
3633         ter in the subject string except (by default) a character  that  signi-         ter  in  the subject string except (by default) a character that signi-
3634         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
3635         more than one byte long.         more than one byte long.
3636    
3637         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
3638         that  character; when the two-character sequence CRLF is used, dot does         that character; when the two-character sequence CRLF is used, dot  does
3639         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
3640         matches  all characters (including isolated CRs and LFs). When any Uni-         matches all characters (including isolated CRs and LFs). When any  Uni-
3641         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
3642         any of the other line ending characters.         any of the other line ending characters.
3643    
3644         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
3645         PCRE_DOTALL option is set, a dot matches  any  one  character,  without         PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3646         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3647         string, it takes two dots to match it.         string, it takes two dots to match it.
3648    
3649         The handling of dot is entirely independent of the handling of  circum-         The  handling of dot is entirely independent of the handling of circum-
3650         flex  and  dollar,  the  only relationship being that they both involve         flex and dollar, the only relationship being  that  they  both  involve
3651         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3652    
3653    
3654  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3655    
3656         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3657         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
3658         line-ending characters. The feature is provided in  Perl  in  order  to         line-ending  characters.  The  feature  is provided in Perl in order to
3659         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-
3660         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-
3661         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
3662         avoided.         avoided.
3663    
3664         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3665         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-
3666         late the length of the lookbehind.         late the length of the lookbehind.
3667    
3668    
# Line 3287  SQUARE BRACKETS AND CHARACTER CLASSES Line 3671  SQUARE BRACKETS AND CHARACTER CLASSES
3671         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3672         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-
3673         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,
3674         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
3675         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3676    
3677         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
3678         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3679         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
3680         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3681         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
3682         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
3683         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3684    
3685         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3686         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3687         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3688         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
3689         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-
3690         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3691         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3692    
3693         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
3694         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
3695         mechanism.         mechanism.
3696    
3697         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3698         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3699         [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
3700         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
3701         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3702         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3703         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3704         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3705         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3706         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
3707         support.         support.
3708    
3709         Characters that might indicate line breaks are  never  treated  in  any         Characters  that  might  indicate  line breaks are never treated in any
3710         special  way  when  matching  character  classes,  whatever line-ending         special way  when  matching  character  classes,  whatever  line-ending
3711         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3712         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
3713         of these characters.         of these characters.
3714    
3715         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-
3716         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3717         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
3718         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
3719         where it cannot be interpreted as indicating a range, typically as  the         where  it cannot be interpreted as indicating a range, typically as the
3720         first or last character in the class.         first or last character in the class.
3721    
3722         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-
3723         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
3724         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3725         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3726         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-
3727         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3728         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3729         a range.         a range.
3730    
3731         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3732         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3733         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3734         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3735    
3736         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,
3737         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
3738         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3739         character tables for a French locale are in  use,  [\xc8-\xcb]  matches         character  tables  for  a French locale are in use, [\xc8-\xcb] matches
3740         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
3741         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3742         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3743    
3744         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
3745         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
3746         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3747         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3748         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3749         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3750         but not underscore.         but not underscore.
3751    
3752         The  only  metacharacters  that are recognized in character classes are         The only metacharacters that are recognized in  character  classes  are
3753         backslash, hyphen (only where it can be  interpreted  as  specifying  a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
3754         range),  circumflex  (only  at the start), opening square bracket (only         range), circumflex (only at the start), opening  square  bracket  (only
3755         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
3756         next  section),  and  the  terminating closing square bracket. However,         next section), and the terminating  closing  square  bracket.  However,
3757         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3758    
3759    
3760  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3761    
3762         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3763         enclosed  by  [: and :] within the enclosing square brackets. PCRE also         enclosed by [: and :] within the enclosing square brackets.  PCRE  also
3764         supports this notation. For example,         supports this notation. For example,
3765    
3766           [01[:alpha:]%]           [01[:alpha:]%]
# Line 3399  POSIX CHARACTER CLASSES Line 3783  POSIX CHARACTER CLASSES
3783           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3784           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3785    
3786         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),
3787         and space (32). Notice that this list includes the VT  character  (code         and  space  (32). Notice that this list includes the VT character (code
3788         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
3789         Perl compatibility).         Perl compatibility).
3790    
3791         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
3792         from  Perl  5.8. Another Perl extension is negation, which is indicated         from Perl 5.8. Another Perl extension is negation, which  is  indicated
3793         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3794    
3795           [12[:^digit:]]           [12[:^digit:]]
3796    
3797         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
3798         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3799         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.
3800    
# Line 3430  VERTICAL BAR Line 3814  VERTICAL BAR
3814         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3815         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
3816         are  within a subpattern (defined below), "succeeds" means matching the         are  within a subpattern (defined below), "succeeds" means matching the
3817         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.
3818    
3819    
3820  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3821    
3822         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3823         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
3824         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
3825         option letters are         between "(?" and ")".  The option letters are
3826    
3827           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3828           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3447  INTERNAL OPTION SETTING Line 3831  INTERNAL OPTION SETTING
3831    
3832         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3833         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
3834         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
3835         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
3836         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
3837         hyphen, the option is unset.         hyphen, the option is unset.
3838    
3839         When  an option change occurs at top level (that is, not inside subpat-         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
3840         tern parentheses), the change applies to the remainder of  the  pattern         can  be changed in the same way as the Perl-compatible options by using
3841         that follows.  If the change is placed right at the start of a pattern,         the characters J, U and X respectively.
3842         PCRE extracts it into the global options (and it will therefore show up  
3843         in data extracted by the pcre_fullinfo() function).         When one of these option changes occurs at  top  level  (that  is,  not
3844           inside  subpattern parentheses), the change applies to the remainder of
3845           the pattern that follows. If the change is placed right at the start of
3846           a pattern, PCRE extracts it into the global options (and it will there-
3847           fore show up in data extracted by the pcre_fullinfo() function).
3848    
3849         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
3850         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3851         it, so         it, so
3852    
3853           (a(?i)b)c           (a(?i)b)c
3854    
3855         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
3856         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
3857         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
3858         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
3859         example,         example,
3860    
3861           (a(?i)b|c)           (a(?i)b|c)
3862    
3863         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
3864         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
3865         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
3866         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3867    
3868         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         Note:  There  are  other  PCRE-specific  options that can be set by the
3869         can  be changed in the same way as the Perl-compatible options by using         application when the compile or match functions  are  called.  In  some
3870         the characters J, U and X respectively.         cases the pattern can contain special leading sequences such as (*CRLF)
3871           to override what the application has set or what  has  been  defaulted.
3872           Details  are  given  in the section entitled "Newline sequences" above.
3873           There is also the (*UTF8) leading sequence that  can  be  used  to  set
3874           UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
3875    
3876    
3877  SUBPATTERNS  SUBPATTERNS
# Line 3491  SUBPATTERNS Line 3883  SUBPATTERNS
3883    
3884           cat(aract|erpillar|)           cat(aract|erpillar|)
3885    
3886         matches  one  of the words "cat", "cataract", or "caterpillar". Without         matches one of the words "cat", "cataract", or  "caterpillar".  Without
3887         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
3888         string.         string.
3889    
3890         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
3891         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
3892         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
3893         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
3894         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
3895         subpatterns.         subpatterns.
3896    
3897         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-
3898         tern         tern
3899    
3900           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3510  SUBPATTERNS Line 3902  SUBPATTERNS
3902         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3903         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3904    
3905         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
3906         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
3907         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
3908         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-
3909         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
3910         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
3911         matched against the pattern         matched against the pattern
3912    
3913           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 3523  SUBPATTERNS Line 3915  SUBPATTERNS
3915         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3916         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
3917    
3918         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
3919         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
3920         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3921    
3922           (?i:saturday|sunday)           (?i:saturday|sunday)
3923           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3924    
3925         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3926         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
3927         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
3928         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
3929         "Saturday".         "Saturday".
3930    
3931    
3932    DUPLICATE SUBPATTERN NUMBERS
3933    
3934           Perl 5.10 introduced a feature whereby each alternative in a subpattern
3935           uses  the same numbers for its capturing parentheses. Such a subpattern
3936           starts with (?| and is itself a non-capturing subpattern. For  example,
3937           consider this pattern:
3938    
3939             (?|(Sat)ur|(Sun))day
3940    
3941           Because  the two alternatives are inside a (?| group, both sets of cap-
3942           turing parentheses are numbered one. Thus, when  the  pattern  matches,
3943           you  can  look  at captured substring number one, whichever alternative
3944           matched. This construct is useful when you want to  capture  part,  but
3945           not all, of one of a number of alternatives. Inside a (?| group, paren-
3946           theses are numbered as usual, but the number is reset at the  start  of
3947           each  branch. The numbers of any capturing buffers that follow the sub-
3948           pattern start after the highest number used in any branch. The  follow-
3949           ing  example  is taken from the Perl documentation.  The numbers under-
3950           neath show in which buffer the captured content will be stored.
3951    
3952             # before  ---------------branch-reset----------- after
3953             / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3954             # 1            2         2  3        2     3     4
3955    
3956           A backreference or a recursive call to  a  numbered  subpattern  always
3957           refers to the first one in the pattern with the given number.
3958    
3959           An  alternative approach to using this "branch reset" feature is to use
3960           duplicate named subpatterns, as described in the next section.
3961    
3962    
3963  NAMED SUBPATTERNS  NAMED SUBPATTERNS
3964    
3965         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
3966         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
3967         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
3968         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
3969         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
3970         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
3971         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-
3972         tax.         tax.
3973    
3974         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>...)
3975         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
3976         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
3977         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
3978         by number.         by number.
3979    
3980         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
3981         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
3982         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
3983         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
3984         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
3985         a captured substring by name.         a captured substring by name.
3986    
3987         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
3988         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
3989         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
3990         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
3991         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
3992         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
3993         the line breaks) does the job:         the line breaks) does the job:
3994    
# Line 3575  NAMED SUBPATTERNS Line 3998  NAMED SUBPATTERNS
3998           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
3999           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
4000    
4001         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
4002         match.  The convenience  function  for  extracting  the  data  by  name         match.  (An alternative way of solving this problem is to use a "branch
4003         returns  the  substring  for  the first (and in this example, the only)         reset" subpattern, as described in the previous section.)
4004         subpattern of that name that matched.  This  saves  searching  to  find  
4005         which  numbered  subpattern  it  was. If you make a reference to a non-         The convenience function for extracting the data by  name  returns  the
4006         unique named subpattern from elsewhere in the  pattern,  the  one  that         substring  for  the first (and in this example, the only) subpattern of
4007         corresponds  to  the  lowest number is used. For further details of the         that name that matched. This saves searching  to  find  which  numbered
4008         interfaces for handling named subpatterns, see the  pcreapi  documenta-         subpattern  it  was. If you make a reference to a non-unique named sub-
4009         tion.         pattern from elsewhere in the pattern, the one that corresponds to  the
4010           lowest  number  is used. For further details of the interfaces for han-
4011           dling named subpatterns, see the pcreapi documentation.
4012    
4013           Warning: You cannot use different names to distinguish between two sub-
4014           patterns  with  the same number (see the previous section) because PCRE
4015           uses only the numbers when matching.
4016    
4017    
4018  REPETITION  REPETITION
4019    
4020         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
4021         following items:         following items:
4022    
4023           a literal data character           a literal data character
# Line 3601  REPETITION Line 4030  REPETITION
4030           a back reference (see next section)           a back reference (see next section)
4031           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4032    
4033         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
4034         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
4035         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
4036         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:
4037    
4038           z{2,4}           z{2,4}
4039    
4040         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
4041         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
4042         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
4043         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
4044         matches. Thus         matches. Thus
4045    
4046           [aeiou]{3,}           [aeiou]{3,}
# Line 3620  REPETITION Line 4049  REPETITION
4049    
4050           \d{8}           \d{8}
4051    
4052         matches  exactly  8  digits. An opening curly bracket that appears in a         matches exactly 8 digits. An opening curly bracket that  appears  in  a
4053         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
4054         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-
4055         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.
4056    
4057         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 3633  REPETITION Line 4062  REPETITION
4062         may be of different lengths).         may be of different lengths).
4063    
4064         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4065         the previous item and the quantifier were not present.         the previous item and the quantifier were not present. This may be use-
4066           ful for subpatterns that are referenced as subroutines  from  elsewhere
4067           in the pattern. Items other than subpatterns that have a {0} quantifier
4068           are omitted from the compiled pattern.
4069    
4070         For  convenience, the three most common quantifiers have single-charac-         For convenience, the three most common quantifiers have  single-charac-
4071         ter abbreviations:         ter abbreviations:
4072    
4073           *    is equivalent to {0,}           *    is equivalent to {0,}
4074           +    is equivalent to {1,}           +    is equivalent to {1,}
4075           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
4076    
4077         It is possible to construct infinite loops by  following  a  subpattern         It  is  possible  to construct infinite loops by following a subpattern
4078         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,
4079         for example:         for example:
4080    
4081           (a?)*           (a?)*
4082    
4083         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
4084         for  such  patterns. However, because there are cases where this can be         for such patterns. However, because there are cases where this  can  be
4085         useful, such patterns are now accepted, but if any  repetition  of  the         useful,  such  patterns  are now accepted, but if any repetition of the
4086         subpattern  does in fact match no characters, the loop is forcibly bro-         subpattern does in fact match no characters, the loop is forcibly  bro-
4087         ken.         ken.
4088    
4089         By default, the quantifiers are "greedy", that is, they match  as  much         By  default,  the quantifiers are "greedy", that is, they match as much
4090         as  possible  (up  to  the  maximum number of permitted times), without         as possible (up to the maximum  number  of  permitted  times),  without
4091         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
4092         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
4093         appear between /* and */ and within the comment,  individual  *  and  /         appear  between  /*  and  */ and within the comment, individual * and /
4094         characters  may  appear. An attempt to match C comments by applying the         characters may appear. An attempt to match C comments by  applying  the
4095         pattern         pattern
4096    
4097           /\*.*\*/           /\*.*\*/
# Line 3668  REPETITION Line 4100  REPETITION
4100    
4101           /* first comment */  not comment  /* second comment */           /* first comment */  not comment  /* second comment */
4102    
4103         fails, because it matches the entire string owing to the greediness  of         fails,  because it matches the entire string owing to the greediness of
4104         the .*  item.         the .*  item.
4105    
4106         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
4107         be greedy, and instead matches the minimum number of times possible, so         be greedy, and instead matches the minimum number of times possible, so
4108         the pattern         the pattern
4109    
4110           /\*.*?\*/           /\*.*?\*/
4111    
4112         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
4113         quantifiers is not otherwise changed,  just  the  preferred  number  of         quantifiers  is  not  otherwise  changed,  just the preferred number of
4114         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
4115         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
4116         appear doubled, as in         appear doubled, as in
4117    
4118           \d??\d           \d??\d
# Line 3688  REPETITION Line 4120  REPETITION
4120         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
4121         only way the rest of the pattern matches.         only way the rest of the pattern matches.
4122    
4123         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
4124         Perl),  the  quantifiers are not greedy by default, but individual ones         Perl), the quantifiers are not greedy by default, but  individual  ones
4125         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
4126         words, it inverts the default behaviour.         words, it inverts the default behaviour.
4127    
4128         When  a  parenthesized  subpattern  is quantified with a minimum repeat         When a parenthesized subpattern is quantified  with  a  minimum  repeat
4129         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
4130         required  for  the  compiled  pattern, in proportion to the size of the         required for the compiled pattern, in proportion to  the  size  of  the
4131         minimum or maximum.         minimum or maximum.
4132    
4133         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-
4134         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,
4135         the pattern is implicitly anchored, because whatever  follows  will  be         the  pattern  is  implicitly anchored, because whatever follows will be
4136         tried  against every character position in the subject string, so there         tried against every character position in the subject string, so  there
4137         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
4138         first.  PCRE  normally treats such a pattern as though it were preceded         first. PCRE normally treats such a pattern as though it  were  preceded
4139         by \A.         by \A.
4140    
4141         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-
4142         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-
4143         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
4144    
4145         However, there is one situation where the optimization cannot be  used.         However,  there is one situation where the optimization cannot be used.
4146         When  .*   is  inside  capturing  parentheses that are the subject of a         When .*  is inside capturing parentheses that  are  the  subject  of  a
4147         backreference elsewhere in the pattern, a match at the start  may  fail         backreference  elsewhere  in the pattern, a match at the start may fail
4148         where a later one succeeds. Consider, for example:         where a later one succeeds. Consider, for example:
4149    
4150           (.*)abc\1           (.*)abc\1
4151    
4152         If  the subject is "xyz123abc123" the match point is the fourth charac-         If the subject is "xyz123abc123" the match point is the fourth  charac-
4153         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
4154    
4155         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 3726  REPETITION Line 4158  REPETITION
4158           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+
4159    
4160         has matched "tweedledum tweedledee" the value of the captured substring         has matched "tweedledum tweedledee" the value of the captured substring
4161         is "tweedledee". However, if there are  nested  capturing  subpatterns,         is  "tweedledee".  However,  if there are nested capturing subpatterns,
4162         the  corresponding captured values may have been set in previous itera-         the corresponding captured values may have been set in previous  itera-
4163         tions. For example, after         tions. For example, after
4164    
4165           /(a|(b))+/           /(a|(b))+/
# Line 3737  REPETITION Line 4169  REPETITION
4169    
4170  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
4171    
4172         With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")         With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
4173         repetition,  failure  of what follows normally causes the repeated item         repetition, failure of what follows normally causes the  repeated  item
4174         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
4175         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,
4176         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
4177         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
4178         no point in carrying on.         no point in carrying on.
4179    
4180         Consider, for example, the pattern \d+foo when applied to  the  subject         Consider,  for  example, the pattern \d+foo when applied to the subject
4181         line         line
4182    
4183           123456bar           123456bar
4184    
4185         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
4186         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
4187         \d+  item,  and  then  with  4,  and  so on, before ultimately failing.         \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.
4188         "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides         "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides
4189         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
4190         to be re-evaluated in this way.         to be re-evaluated in this way.
4191    
4192         If we use atomic grouping for the previous example, the  matcher  gives         If  we  use atomic grouping for the previous example, the matcher gives
4193         up  immediately  on failing to match "foo" the first time. The notation         up immediately on failing to match "foo" the first time.  The  notation
4194         is a kind of special parenthesis, starting with (?> as in this example:         is a kind of special parenthesis, starting with (?> as in this example:
4195    
4196           (?>\d+)foo           (?>\d+)foo
# Line 3788  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4220  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4220    
4221           \d++foo           \d++foo
4222    
4223         Possessive  quantifiers  are  always  greedy;  the   setting   of   the         Note that a possessive quantifier can be used with an entire group, for
4224           example:
4225    
4226             (abc|xyz){2,3}+
4227    
4228           Possessive   quantifiers   are   always  greedy;  the  setting  of  the
4229         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
4230         simpler forms of atomic group. However, there is no difference  in  the         simpler  forms  of atomic group. However, there is no difference in the
4231         meaning  of  a  possessive  quantifier and the equivalent atomic group,         meaning of a possessive quantifier and  the  equivalent  atomic  group,
4232         though there may be a performance  difference;  possessive  quantifiers         though  there  may  be a performance difference; possessive quantifiers
4233         should be slightly faster.         should be slightly faster.
4234    
4235         The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-         The possessive quantifier syntax is an extension to the Perl  5.8  syn-
4236         tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first         tax.   Jeffrey  Friedl  originated the idea (and the name) in the first
4237         edition of his book. Mike McCloskey liked it, so implemented it when he         edition of his book. Mike McCloskey liked it, so implemented it when he
4238         built Sun's Java package, and PCRE copied it from there. It  ultimately         built  Sun's Java package, and PCRE copied it from there. It ultimately
4239         found its way into Perl at release 5.10.         found its way into Perl at release 5.10.
4240    
4241         PCRE has an optimization that automatically "possessifies" certain sim-         PCRE has an optimization that automatically "possessifies" certain sim-
4242         ple pattern constructs. For example, the sequence  A+B  is  treated  as         ple  pattern  constructs.  For  example, the sequence A+B is treated as
4243         A++B  because  there is no point in backtracking into a sequence of A's         A++B because there is no point in backtracking into a sequence  of  A's
4244         when B must follow.         when B must follow.
4245    
4246         When a pattern contains an unlimited repeat inside  a  subpattern  that         When  a  pattern  contains an unlimited repeat inside a subpattern that
4247         can  itself  be  repeated  an  unlimited number of times, the use of an         can itself be repeated an unlimited number of  times,  the  use  of  an
4248         atomic group is the only way to avoid some  failing  matches  taking  a         atomic  group  is  the  only way to avoid some failing matches taking a
4249         very long time indeed. The pattern         very long time indeed. The pattern
4250    
4251           (\D+|<\d+>)*[!?]           (\D+|<\d+>)*[!?]
4252    
4253         matches  an  unlimited number of substrings that either consist of non-         matches an unlimited number of substrings that either consist  of  non-
4254         digits, or digits enclosed in <>, followed by either ! or  ?.  When  it         digits,  or  digits  enclosed in <>, followed by either ! or ?. When it
4255         matches, it runs quickly. However, if it is applied to         matches, it runs quickly. However, if it is applied to
4256    
4257           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
4258    
4259         it  takes  a  long  time  before reporting failure. This is because the         it takes a long time before reporting  failure.  This  is  because  the
4260         string can be divided between the internal \D+ repeat and the  external         string  can be divided between the internal \D+ repeat and the external
4261         *  repeat  in  a  large  number of ways, and all have to be tried. (The         * repeat in a large number of ways, and all  have  to  be  tried.  (The
4262         example uses [!?] rather than a single character at  the  end,  because         example  uses  [!?]  rather than a single character at the end, because
4263         both  PCRE  and  Perl have an optimization that allows for fast failure         both PCRE and Perl have an optimization that allows  for  fast  failure
4264         when a single character is used. They remember the last single  charac-         when  a single character is used. They remember the last single charac-
4265         ter  that  is required for a match, and fail early if it is not present         ter that is required for a match, and fail early if it is  not  present
4266         in the string.) If the pattern is changed so that  it  uses  an  atomic         in  the  string.)  If  the pattern is changed so that it uses an atomic
4267         group, like this:         group, like this:
4268    
4269           ((?>\D+)|<\d+>)*[!?]           ((?>\D+)|<\d+>)*[!?]
4270    
4271         sequences  of non-digits cannot be broken, and failure happens quickly.         sequences of non-digits cannot be broken, and failure happens quickly.
4272    
4273    
4274  BACK REFERENCES  BACK REFERENCES
# Line 3860  BACK REFERENCES Line 4297  BACK REFERENCES
4297    
4298         Another way of avoiding the ambiguity inherent in  the  use  of  digits         Another way of avoiding the ambiguity inherent in  the  use  of  digits
4299         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-
4300         ture introduced in Perl 5.10. This escape must be followed by  a  posi-         ture introduced in Perl 5.10.  This  escape  must  be  followed  by  an
4301         tive  or  a negative number, optionally enclosed in braces. These exam-         unsigned  number  or  a negative number, optionally enclosed in braces.
4302         ples are all identical:         These examples are all identical:
4303    
4304           (ring), \1           (ring), \1
4305           (ring), \g1           (ring), \g1
4306           (ring), \g{1}           (ring), \g{1}
4307    
4308         A positive number specifies an absolute reference without the ambiguity         An unsigned number specifies an absolute reference without the  ambigu-
4309         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
4310         digits follow the reference. A negative number is a relative reference.         digits follow the reference. A negative number is a relative reference.
4311         Consider this example:         Consider this example:
4312    
# Line 4406  SUBPATTERNS AS SUBROUTINES Line 4843  SUBPATTERNS AS SUBROUTINES