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revision 208 by ph10, Mon Aug 6 15:23:29 2007 UTC revision 261 by ph10, Fri Sep 21 08:37:48 2007 UTC
# Line 155  UTF-8 AND UNICODE PROPERTY SUPPORT Line 155  UTF-8 AND UNICODE PROPERTY SUPPORT
155         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
156         does not support this.         does not support this.
157    
158         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
159    
160         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
161         subjects  are  checked for validity on entry to the relevant functions.         subjects are (by default) checked for validity on entry to the relevant
162         If an invalid UTF-8 string is passed, an error return is given. In some         functions. From release 7.3 of PCRE, the check is according  the  rules
163         situations,  you  may  already  know  that  your strings are valid, and         of  RFC  3629, which are themselves derived from the Unicode specifica-
164         therefore want to skip these checks in order to improve performance. If         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
165         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
166         PCRE assumes that the pattern or subject  it  is  given  (respectively)         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
167         contains  only valid UTF-8 codes. In this case, it does not diagnose an         to U+DFFF.
168         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when  
169         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
170         crash.         which the Unicode Standard says this: "The Low Surrogate Area does  not
171           contain  any  character  assignments,  consequently  no  character code
172           charts or namelists are provided for this area. Surrogates are reserved
173           for  use  with  UTF-16 and then must be used in pairs." The code points
174           that are encoded by UTF-16 pairs  are  available  as  independent  code
175           points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
176           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
177    
178           If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
179           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
180           that your strings are valid, and therefore want to skip these checks in
181           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
182           compile time or at run time, PCRE assumes that the pattern  or  subject
183           it  is  given  (respectively)  contains only valid UTF-8 codes. In this
184           case, it does not diagnose an invalid UTF-8 string.
185    
186           If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
187           what  happens  depends on why the string is invalid. If the string con-
188           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
189           string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
190           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
191           strings  according  to  the more liberal rules of RFC 2279. However, if
192           the string does not even conform to RFC 2279, the result is  undefined.
193           Your program may crash.
194    
195           If  you  want  to  process  strings  of  values  in the full range 0 to
196           0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
197           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
198           this situation, you will have to apply your own validity check.
199    
200         2. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a     General comments about UTF-8 mode
201    
202           1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
203         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
204    
205         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
206         characters for values greater than \177.         characters for values greater than \177.
207    
208         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
209         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
210    
211         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-
212         gle byte.         gle byte.
213    
214         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
215         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
216         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
217    
218         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
219         test  characters of any code value, but the characters that PCRE recog-         test  characters of any code value, but the characters that PCRE recog-
220         nizes as digits, spaces, or word characters  remain  the  same  set  as         nizes as digits, spaces, or word characters  remain  the  same  set  as
221         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
# Line 194  UTF-8 AND UNICODE PROPERTY SUPPORT Line 224  UTF-8 AND UNICODE PROPERTY SUPPORT
224         sense of, say, "digit", you must use Unicode  property  tests  such  as         sense of, say, "digit", you must use Unicode  property  tests  such  as
225         \p{Nd}.         \p{Nd}.
226    
227         8.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
228         are all low-valued characters.         are all low-valued characters.
229    
230         9. However, the Perl 5.10 horizontal and vertical  whitespace  matching         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
231         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
232         acters.         acters.
233    
234         10. Case-insensitive matching applies only to characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
235         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
236         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
237         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
# Line 226  AUTHOR Line 256  AUTHOR
256    
257  REVISION  REVISION
258    
259         Last updated: 06 August 2007         Last updated: 09 August 2007
260         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
261  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
262    
# Line 241  NAME Line 271  NAME
271  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
272    
273         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
274         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
275         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
276         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
277         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
278         directory) can be obtained by running         environments using the GUI facility of  CMakeSetup  if  you  are  using
279           CMake instead of configure to build PCRE.
280    
281           The complete list of options for configure (which includes the standard
282           ones such as the  selection  of  the  installation  directory)  can  be
283           obtained by running
284    
285           ./configure --help           ./configure --help
286    
287         The following sections include  descriptions  of  options  whose  names         The  following  sections  include  descriptions  of options whose names
288         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
289         defaults for the configure command. Because of the way  that  configure         defaults  for  the configure command. Because of the way that configure
290         works,  --enable  and --disable always come in pairs, so the complemen-         works, --enable and --disable always come in pairs, so  the  complemen-
291         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
292         is not described.         is not described.
293    
294    
# Line 274  UTF-8 SUPPORT Line 309  UTF-8 SUPPORT
309    
310           --enable-utf8           --enable-utf8
311    
312         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
313         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
314         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()
315         function.         function.
316    
317    
318  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
319    
320         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
321         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-
322         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
323         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
324         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
325    
326           --enable-unicode-properties           --enable-unicode-properties
327    
328         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
329         not explicitly requested it.         not explicitly requested it.
330    
331         Including  Unicode  property  support  adds around 30K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
332         PCRE library. Only the general category properties such as  Lu  and  Nd         PCRE  library.  Only  the general category properties such as Lu and Nd
333         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
334    
335    
336  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
337    
338         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating
339         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
340         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems. You can compile PCRE to use character 13 (carriage return, CR)
341         instead, by adding         instead, by adding
342    
343           --enable-newline-is-cr           --enable-newline-is-cr
344    
345         to the  configure  command.  There  is  also  a  --enable-newline-is-lf         to  the  configure  command.  There  is  also  a --enable-newline-is-lf
346         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
347    
348         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 319  CODE VALUE OF NEWLINE Line 354  CODE VALUE OF NEWLINE
354    
355           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
356    
357         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
358         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
359    
360           --enable-newline-is-any           --enable-newline-is-any
361    
362         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
363    
364         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
365         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
366         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
367    
368    
369    WHAT \R MATCHES
370    
371           By  default,  the  sequence \R in a pattern matches any Unicode newline
372           sequence, whatever has been selected as the line  ending  sequence.  If
373           you specify
374    
375             --enable-bsr-anycrlf
376    
377           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
378           ever is selected when PCRE is built can be overridden when the  library
379           functions are called.
380    
381    
382  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
383    
384         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
385         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
386         of         of
387    
388           --disable-shared           --disable-shared
# Line 346  BUILDING SHARED AND STATIC LIBRARIES Line 394  BUILDING SHARED AND STATIC LIBRARIES
394  POSIX MALLOC USAGE  POSIX MALLOC USAGE
395    
396         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
397         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
398         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
399         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
400         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
401         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
402         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 361  POSIX MALLOC USAGE Line 409  POSIX MALLOC USAGE
409    
410  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
411    
412         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
413         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
414         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
415         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
416         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
417         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process enormous patterns, so it
418         is  possible  to compile PCRE to use three-byte or four-byte offsets by         is possible to compile PCRE to use three-byte or four-byte  offsets  by
419         adding a setting such as         adding a setting such as
420    
421           --with-link-size=3           --with-link-size=3
422    
423         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
424         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
425         additional bytes when handling them.         additional bytes when handling them.
426    
427    
428  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
429    
430         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
431         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
432         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
433         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
434         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
435         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
436         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
437         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
438         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
439         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
440    
441           --disable-stack-for-recursion           --disable-stack-for-recursion
442    
443         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
444         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
445         ment  functions. By default these point to malloc() and free(), but you         ment functions. By default these point to malloc() and free(), but  you
446         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used.
447    
448         Separate functions are  provided  rather  than  using  pcre_malloc  and         Separate  functions  are  provided  rather  than  using pcre_malloc and
449         pcre_free  because  the  usage  is  very  predictable:  the block sizes         pcre_free because the  usage  is  very  predictable:  the  block  sizes
450         requested are always the same, and  the  blocks  are  always  freed  in         requested  are  always  the  same,  and  the blocks are always freed in
451         reverse  order.  A calling program might be able to implement optimized         reverse order. A calling program might be able to  implement  optimized
452         functions that perform better  than  malloc()  and  free().  PCRE  runs         functions  that  perform  better  than  malloc()  and free(). PCRE runs
453         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
454         the  pcre_exec()  function;  it   is   not   relevant   for   the   the         the   pcre_exec()   function;   it   is   not   relevant  for  the  the
455         pcre_dfa_exec() function.         pcre_dfa_exec() function.
456    
457    
458  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
459    
460         Internally,  PCRE has a function called match(), which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
461         edly  (sometimes  recursively)  when  matching  a  pattern   with   the         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
462         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec() function. By controlling the maximum number of  times  this
463         function may be called during a single matching operation, a limit  can         function  may be called during a single matching operation, a limit can
464         be  placed  on  the resources used by a single call to pcre_exec(). The         be placed on the resources used by a single call  to  pcre_exec().  The
465         limit can be changed at run time, as described in the pcreapi  documen-         limit  can be changed at run time, as described in the pcreapi documen-
466         tation.  The default is 10 million, but this can be changed by adding a         tation. The default is 10 million, but this can be changed by adding  a
467         setting such as         setting such as
468    
469           --with-match-limit=500000           --with-match-limit=500000
470    
471         to  the  configure  command.  This  setting  has  no  effect   on   the         to   the   configure  command.  This  setting  has  no  effect  on  the
472         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
473    
474         In  some  environments  it is desirable to limit the depth of recursive         In some environments it is desirable to limit the  depth  of  recursive
475         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
476         to  restrict  the maximum amount of stack (or heap, if --disable-stack-         to restrict the maximum amount of stack (or heap,  if  --disable-stack-
477         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
478         it  defaults  to  the  value  that is set for --with-match-limit, which         it defaults to the value that  is  set  for  --with-match-limit,  which
479         imposes no additional constraints. However, you can set a  lower  limit         imposes  no  additional constraints. However, you can set a lower limit
480         by adding, for example,         by adding, for example,
481    
482           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
483    
484         to  the  configure  command.  This  value can also be overridden at run         to the configure command. This value can  also  be  overridden  at  run
485         time.         time.
486    
487    
488  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
489    
490         PCRE uses fixed tables for processing characters whose code values  are         PCRE  uses fixed tables for processing characters whose code values are
491         less  than 256. By default, PCRE is built with a set of tables that are         less than 256. By default, PCRE is built with a set of tables that  are
492         distributed in the file pcre_chartables.c.dist. These  tables  are  for         distributed  in  the  file pcre_chartables.c.dist. These tables are for
493         ASCII codes only. If you add         ASCII codes only. If you add
494    
495           --enable-rebuild-chartables           --enable-rebuild-chartables
496    
497         to  the  configure  command, the distributed tables are no longer used.         to the configure command, the distributed tables are  no  longer  used.
498         Instead, a program called dftables is compiled and  run.  This  outputs         Instead,  a  program  called dftables is compiled and run. This outputs
499         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
500         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
501         you  are cross compiling, because dftables is run on the local host. If         you are cross compiling, because dftables is run on the local host.  If
502         you need to create alternative tables when cross  compiling,  you  will         you  need  to  create alternative tables when cross compiling, you will
503         have to do so "by hand".)         have to do so "by hand".)
504    
505    
506  USING EBCDIC CODE  USING EBCDIC CODE
507    
508         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
509         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
510         This  is  the  case for most computer operating systems. PCRE can, how-         This is the case for most computer operating systems.  PCRE  can,  how-
511         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
512    
513           --enable-ebcdic           --enable-ebcdic
514    
515         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
516         bles.  You  should  only  use  it if you know that you are in an EBCDIC         bles. You should only use it if you know that  you  are  in  an  EBCDIC
517         environment (for example, an IBM mainframe operating system).         environment (for example, an IBM mainframe operating system).
518    
519    
# Line 483  AUTHOR Line 531  AUTHOR
531    
532  REVISION  REVISION
533    
534         Last updated: 30 July 2007         Last updated: 21 September 2007
535         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
536  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
537    
# Line 627  THE ALTERNATIVE MATCHING ALGORITHM Line 675  THE ALTERNATIVE MATCHING ALGORITHM
675         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
676         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.
677    
678         7.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
679         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-
680         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
681         time, for all active paths through the tree.         time, for all active paths through the tree.
682    
683           8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-
684           ported.
685    
686    
687  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
688    
689         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
690         tages:         tages:
691    
692         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
693         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
694         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
695         things with callouts.         things with callouts.
696    
697         2.  There is much better support for partial matching. The restrictions         2. There is much better support for partial matching. The  restrictions
698         on the content of the pattern that apply when using the standard  algo-         on  the content of the pattern that apply when using the standard algo-
699         rithm  for  partial matching do not apply to the alternative algorithm.         rithm for partial matching do not apply to the  alternative  algorithm.
700         For non-anchored patterns, the starting position of a partial match  is         For  non-anchored patterns, the starting position of a partial match is
701         available.         available.
702    
703         3.  Because  the  alternative  algorithm  scans the subject string just         3. Because the alternative algorithm  scans  the  subject  string  just
704         once, and never needs to backtrack, it is possible to  pass  very  long         once,  and  never  needs to backtrack, it is possible to pass very long
705         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
706         for partial matching each time.         for partial matching each time.
707    
708    
# Line 659  DISADVANTAGES OF THE ALTERNATIVE ALGORIT Line 710  DISADVANTAGES OF THE ALTERNATIVE ALGORIT
710    
711         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
712    
713         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
714         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
715         because it is less susceptible to optimization.         because it is less susceptible to optimization.
716    
717         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 678  AUTHOR Line 729  AUTHOR
729    
730  REVISION  REVISION
731    
732         Last updated: 29 May 2007         Last updated: 08 August 2007
733         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
734  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
735    
# Line 875  NEWLINES Line 926  NEWLINES
926         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
927         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
928    
929           At compile time, the newline convention can be specified by the options
930           argument of pcre_compile(), or it can be specified by special  text  at
931           the start of the pattern itself; this overrides any other settings. See
932           the pcrepattern page for details of the special character sequences.
933    
934         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-
935         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
936         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
937         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
938         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
939         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
940         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
941    
942           The choice of newline convention does not affect the interpretation  of
943           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
944           which is controlled in a similar way, but by separate options.
945    
946    
947  MULTITHREADING  MULTITHREADING
948    
949         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
950         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
951         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
952         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
953    
954         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
955         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
956         at once.         at once.
957    
# Line 899  MULTITHREADING Line 959  MULTITHREADING
959  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
960    
961         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
962         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
963         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
964         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation.  However, compiling a regular expression
965         with  one version of PCRE for use with a different version is not guar-         with one version of PCRE for use with a different version is not  guar-
966         anteed to work and may cause crashes.         anteed to work and may cause crashes.
967    
968    
# Line 910  CHECKING BUILD-TIME OPTIONS Line 970  CHECKING BUILD-TIME OPTIONS
970    
971         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
972    
973         The function pcre_config() makes it possible for a PCRE client to  dis-         The  function pcre_config() makes it possible for a PCRE client to dis-
974         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
975         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
976         tures.         tures.
977    
978         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
979         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
980         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
981         available:         available:
982    
983           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
984    
985         The output is an integer that is set to one if UTF-8 support is  avail-         The  output is an integer that is set to one if UTF-8 support is avail-
986         able; otherwise it is set to zero.         able; otherwise it is set to zero.
987    
988           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
989    
990         The  output  is  an  integer  that is set to one if support for Unicode         The output is an integer that is set to  one  if  support  for  Unicode
991         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
992    
993           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
994    
995         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
996         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
997         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,
998         and  -1  for  ANY. The default should normally be the standard sequence         and -1 for ANY. The default should normally be  the  standard  sequence
999         for your operating system.         for your operating system.
1000    
1001             PCRE_CONFIG_BSR
1002    
1003           The output is an integer whose value indicates what character sequences
1004           the \R escape sequence matches by default. A value of 0 means  that  \R
1005           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1006           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1007           tern is compiled or matched.
1008    
1009           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1010    
1011         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
1012         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1013         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1014         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1015         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1016         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1017    
1018           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1019    
1020         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1021         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1022         given in the pcreposix documentation.         given in the pcreposix documentation.
1023    
1024           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1025    
1026         The output is an integer that gives the default limit for the number of         The output is an integer that gives the default limit for the number of
1027         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
1028         details are given with pcre_exec() below.         details are given with pcre_exec() below.
1029    
1030           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1031    
1032         The  output is an integer that gives the default limit for the depth of         The output is an integer that gives the default limit for the depth  of
1033         recursion when calling the internal matching function in a  pcre_exec()         recursion  when calling the internal matching function in a pcre_exec()
1034         execution. Further details are given with pcre_exec() below.         execution. Further details are given with pcre_exec() below.
1035    
1036           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1037    
1038         The  output is an integer that is set to one if internal recursion when         The output is an integer that is set to one if internal recursion  when
1039         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1040         the  stack  to remember their state. This is the usual way that PCRE is         the stack to remember their state. This is the usual way that  PCRE  is
1041         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1042         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1043         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1044         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1045    
1046    
# Line 989  COMPILING A PATTERN Line 1057  COMPILING A PATTERN
1057    
1058         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1059         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1060         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1061         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1062    
1063         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1064         the  pattern  argument.  A  pointer to a single block of memory that is         the pattern argument. A pointer to a single block  of  memory  that  is
1065         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1066         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1067         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1068         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1069         longer required.         longer required.
1070    
1071         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
1072         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1073         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1074         ment, which is an address (see below).         ment, which is an address (see below).
1075    
1076         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1077         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1078         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
1079         are compatible with Perl, can also be set and  unset  from  within  the         are  compatible  with  Perl,  can also be set and unset from within the
1080         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
1081         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
1082         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
1083         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time
1084         of matching as well as at compile time.         of matching as well as at compile time.
1085    
1086         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1087         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1088         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-
1089         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
1090         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-
1091         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
1092         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
1093         given.         given.
1094    
1095         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1096         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
1097         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
1098         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1099    
1100         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
1101         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1102         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1103         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
1104         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1105         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
1106         support below.         support below.
1107    
1108         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1109         pile():         pile():
1110    
1111           pcre *re;           pcre *re;
# Line 1050  COMPILING A PATTERN Line 1118  COMPILING A PATTERN
1118             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1119             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1120    
1121         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
1122         file:         file:
1123    
1124           PCRE_ANCHORED           PCRE_ANCHORED
1125    
1126         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
1127         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
1128         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1129         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1130         only way to do it in Perl.         only way to do it in Perl.
1131    
1132           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1133    
1134         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1135         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1136         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1137    
1138             PCRE_BSR_ANYCRLF
1139             PCRE_BSR_UNICODE
1140    
1141           These options (which are mutually exclusive) control what the \R escape
1142           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1143           or to match any Unicode newline sequence. The default is specified when
1144           PCRE is built. It can be overridden from within the pattern, or by set-
1145           ting an option when a compiled pattern is matched.
1146    
1147           PCRE_CASELESS           PCRE_CASELESS
1148    
1149         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
1150         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
1151         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
1152         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1153         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1154         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-
1155         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1156         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1157         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1158         UTF-8 support.         UTF-8 support.
1159    
1160           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1161    
1162         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
1163         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
1164         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
1165         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1166         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
1167         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1168    
1169           PCRE_DOTALL           PCRE_DOTALL
1170    
1171         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-
1172         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1173         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
1174         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
1175         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
1176         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1177    
1178           PCRE_DUPNAMES           PCRE_DUPNAMES
1179    
1180         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1181         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
1182         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
1183         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1184         the pcrepattern documentation.         the pcrepattern documentation.
1185    
1186           PCRE_EXTENDED           PCRE_EXTENDED
1187    
1188         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1189         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1190         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1191         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1192         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1193         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-
1194         ting.         ting.
1195    
1196         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1197         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1198         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1199         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1200         introduces a conditional subpattern.         introduces a conditional subpattern.
1201    
1202           PCRE_EXTRA           PCRE_EXTRA
1203    
1204         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1205         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
1206         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
1207         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1208         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1209         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
1210         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal.  (Perl can, however, be persuaded to give a warning for this.)
1211         There  are  at  present no other features controlled by this option. It         There are at present no other features controlled by  this  option.  It
1212         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1213    
1214           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1215    
1216         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1217         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1218         matched text may continue over the newline.         matched text may continue over the newline.
1219    
1220           PCRE_MULTILINE           PCRE_MULTILINE
1221    
1222         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1223         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1224         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1225         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1226         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1227         is set). This is the same as Perl.         is set). This is the same as Perl.
1228    
1229         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1230         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1231         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1232         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1233         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1234         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1235         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1236    
1237           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1163  COMPILING A PATTERN Line 1240  COMPILING A PATTERN
1240           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1241           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1242    
1243         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1244         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1245         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1246         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1247         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1248         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1249         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1250         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1251         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1252         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1253         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1254         UTF-8 mode.         UTF-8 mode.
1255    
1256         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1257         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1258         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1259         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1260         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1261         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1262         cause an error.         cause an error.
1263    
1264         The only time that a line break is specially recognized when  compiling         The  only time that a line break is specially recognized when compiling
1265         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1266         character class is encountered. This indicates  a  comment  that  lasts         character  class  is  encountered.  This indicates a comment that lasts
1267         until  after the next line break sequence. In other circumstances, line         until after the next line break sequence. In other circumstances,  line
1268         break  sequences  are  treated  as  literal  data,   except   that   in         break   sequences   are   treated  as  literal  data,  except  that  in
1269         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1270         and are therefore ignored.         and are therefore ignored.
1271    
1272         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
1273         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.
1274    
1275           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1276    
1277         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-
1278         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1279         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1280         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1281         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1282    
1283           PCRE_UNGREEDY           PCRE_UNGREEDY
1284    
1285         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1286         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
1287         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
1288         within the pattern.         within the pattern.
1289    
1290           PCRE_UTF8           PCRE_UTF8
1291    
1292         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
1293         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1294         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-
1295         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
1296         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
1297         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1298    
1299           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1300    
1301         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
1302         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1303         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
1304         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
1305         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-
1306         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
1307         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
1308         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
1309         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1310           UTF-8 validity checking of subject strings.
1311    
1312    
1313  COMPILATION ERROR CODES  COMPILATION ERROR CODES
# Line 1296  COMPILATION ERROR CODES Line 1374  COMPILATION ERROR CODES
1374         found         found
1375           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1376           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1377           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1378           57  \g is not followed by a braced name or an optionally braced           57  \g is not followed by a braced name or an optionally braced
1379                 non-zero number                 non-zero number
1380           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
# Line 1488  INFORMATION ABOUT A PATTERN Line 1566  INFORMATION ABOUT A PATTERN
1566         returned. The fourth argument should point to an unsigned char *  vari-         returned. The fourth argument should point to an unsigned char *  vari-
1567         able.         able.
1568    
1569             PCRE_INFO_HASCRORLF
1570    
1571           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1572           characters, otherwise 0. The fourth argument should  point  to  an  int
1573           variable.  An explicit match is either a literal CR or LF character, or
1574           \r or \n.
1575    
1576           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1577    
1578         Return  1  if the (?J) option setting is used in the pattern, otherwise         Return 1 if the (?J) option setting is used in the  pattern,  otherwise
1579         0. The fourth argument should point to an int variable. The (?J) inter-         0. The fourth argument should point to an int variable. The (?J) inter-
1580         nal option setting changes the local PCRE_DUPNAMES option.         nal option setting changes the local PCRE_DUPNAMES option.
1581    
1582           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1583    
1584         Return  the  value of the rightmost literal byte that must exist in any         Return the value of the rightmost literal byte that must exist  in  any
1585         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1586         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1587         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1588         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1589         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1590         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1591    
# Line 1508  INFORMATION ABOUT A PATTERN Line 1593  INFORMATION ABOUT A PATTERN
1593           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1594           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1595    
1596         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1597         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1598         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1599         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1600         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1601         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1602         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1603         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1604         described by these three values.         described by these three values.
1605    
1606         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1607         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1608         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1609         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1610         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1611         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1612         sis,  most  significant byte first. The rest of the entry is the corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1613         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1614         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1615         theses numbers. For example, consider  the  following  pattern  (assume         theses  numbers.  For  example,  consider the following pattern (assume
1616         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
1617         ignored):         ignored):
1618    
1619           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1620           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1621    
1622         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1623         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
1624         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1625         as ??:         as ??:
1626    
# Line 1544  INFORMATION ABOUT A PATTERN Line 1629  INFORMATION ABOUT A PATTERN
1629           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1630           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1631    
1632         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1633         name-to-number map, remember that the length of the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
1634         to be different for each compiled pattern.         to be different for each compiled pattern.
1635    
1636           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1637    
1638         Return  1 if the pattern can be used for partial matching, otherwise 0.         Return 1 if the pattern can be used for partial matching, otherwise  0.
1639         The fourth argument should point to an int  variable.  The  pcrepartial         The  fourth  argument  should point to an int variable. The pcrepartial
1640         documentation  lists  the restrictions that apply to patterns when par-         documentation lists the restrictions that apply to patterns  when  par-
1641         tial matching is used.         tial matching is used.
1642    
1643           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1644    
1645         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
1646         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1647         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1648         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1649         other words, they are the options that will be in force  when  matching         other  words,  they are the options that will be in force when matching
1650         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1651         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1652         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1653    
1654         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
1655         alternatives begin with one of the following:         alternatives begin with one of the following:
1656    
1657           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1580  INFORMATION ABOUT A PATTERN Line 1665  INFORMATION ABOUT A PATTERN
1665    
1666           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1667    
1668         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of the compiled pattern, that is, the  value  that  was
1669         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1670         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1671         size_t variable.         size_t variable.
# Line 1588  INFORMATION ABOUT A PATTERN Line 1673  INFORMATION ABOUT A PATTERN
1673           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1674    
1675         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1676         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
1677         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1678         created  by  pcre_study(). The fourth argument should point to a size_t         created by pcre_study(). The fourth argument should point to  a  size_t
1679         variable.         variable.
1680    
1681    
# Line 1598  OBSOLETE INFO FUNCTION Line 1683  OBSOLETE INFO FUNCTION
1683    
1684         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1685    
1686         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1687         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1688         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1689         pcre_info()  is the number of capturing subpatterns, or one of the fol-         pcre_info() is the number of capturing subpatterns, or one of the  fol-
1690         lowing negative numbers:         lowing negative numbers:
1691    
1692           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1693           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1694    
1695         If the optptr argument is not NULL, a copy of the  options  with  which         If  the  optptr  argument is not NULL, a copy of the options with which
1696         the  pattern  was  compiled  is placed in the integer it points to (see         the pattern was compiled is placed in the integer  it  points  to  (see
1697         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1698    
1699         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1700         NULL,  it is used to pass back information about the first character of         NULL, it is used to pass back information about the first character  of
1701         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1702    
1703    
# Line 1620  REFERENCE COUNTS Line 1705  REFERENCE COUNTS
1705    
1706         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1707    
1708         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1709         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1710         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1711         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1712         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1713    
1714         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1715         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1716         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1717         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1718         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1719         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1720    
1721         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1722         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1723         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1724    
1725    
# Line 1644  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1729  MATCHING A PATTERN: THE TRADITIONAL FUNC
1729              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1730              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1731    
1732         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
1733         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1734         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
1735         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1736         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
1737         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1738         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1739    
1740         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1741         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1742         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
1743         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1744         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1745    
1746         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1674  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1759  MATCHING A PATTERN: THE TRADITIONAL FUNC
1759    
1760     Extra data for pcre_exec()     Extra data for pcre_exec()
1761    
1762         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
1763         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
1764         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-
1765         tional  information  in it. The pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
1766         fields (not necessarily in this order):         fields (not necessarily in this order):
1767    
1768           unsigned long int flags;           unsigned long int flags;
# Line 1687  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1772  MATCHING A PATTERN: THE TRADITIONAL FUNC
1772           void *callout_data;           void *callout_data;
1773           const unsigned char *tables;           const unsigned char *tables;
1774    
1775         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
1776         are set. The flag bits are:         are set. The flag bits are:
1777    
1778           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1696  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1781  MATCHING A PATTERN: THE TRADITIONAL FUNC
1781           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1782           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1783    
1784         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
1785         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1786         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
1787         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1788         flag bits.         flag bits.
1789    
1790         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
1791         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
1792         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1793         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees.  The  classic  example  is  the  use of nested unlimited
1794         repeats.         repeats.
1795    
1796         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1797         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
1798         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
1799         has the effect of limiting the amount of  backtracking  that  can  take         has  the  effect  of  limiting the amount of backtracking that can take
1800         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1801         for each position in the subject string.         for each position in the subject string.
1802    
1803         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
1804         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1805         cases. You can override the default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1806         pcre_extra     block    in    which    match_limit    is    set,    and         pcre_extra    block    in    which    match_limit    is    set,     and
1807         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
1808         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1809    
1810         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
1811         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
1812         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
1813         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-
1814         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.
1815    
1816         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth  limits the amount of stack that can be
1817         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
1818         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1819    
1820         The default value for match_limit_recursion can be  set  when  PCRE  is         The  default  value  for  match_limit_recursion can be set when PCRE is
1821         built;  the  default  default  is  the  same  value  as the default for         built; the default default  is  the  same  value  as  the  default  for
1822         match_limit. You can override the default by suppling pcre_exec()  with         match_limit.  You can override the default by suppling pcre_exec() with
1823         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1824         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1825         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1826    
1827         The  pcre_callout  field is used in conjunction with the "callout" fea-         The pcre_callout field is used in conjunction with the  "callout"  fea-
1828         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1829    
1830         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
1831         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
1832         pattern. A non-NULL value is stored with the compiled pattern  only  if         pattern.  A  non-NULL value is stored with the compiled pattern only if
1833         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
1834         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
1835         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
1836         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
1837         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
1838         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
1839         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1840    
1841     Option bits for pcre_exec()     Option bits for pcre_exec()
1842    
1843         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.
1844         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,
1845         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1846         PCRE_PARTIAL.         PCRE_PARTIAL.
1847    
1848           PCRE_ANCHORED           PCRE_ANCHORED
1849    
1850         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1851         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1852         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
1853         unachored at matching time.         unachored at matching time.
1854    
1855             PCRE_BSR_ANYCRLF
1856             PCRE_BSR_UNICODE
1857    
1858           These options (which are mutually exclusive) control what the \R escape
1859           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1860           or to match any Unicode newline sequence. These  options  override  the
1861           choice that was made or defaulted when the pattern was compiled.
1862    
1863           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1864           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1865           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
# Line 1778  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1871  MATCHING A PATTERN: THE TRADITIONAL FUNC
1871         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
1872         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1873         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
1874         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
1875         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
1876         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
1877         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-
1878         after the CRLF.         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1879           explicit  matches  for  CR  or  LF  characters,  the  match position is
1880           advanced by two characters instead of one, in other words, to after the
1881           CRLF.
1882    
1883           The above rule is a compromise that makes the most common cases work as
1884           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1885           option is not set), it does not match the string "\r\nA" because, after
1886           failing at the start, it skips both the CR and the LF before  retrying.
1887           However,  the  pattern  [\r\n]A does match that string, because it con-
1888           tains an explicit CR or LF reference, and so advances only by one char-
1889           acter after the first failure.
1890    
1891           An explicit match for CR of LF is either a literal appearance of one of
1892           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1893           matches  such  as [^X] do not count, nor does \s (which includes CR and
1894           LF in the characters that it matches).
1895    
1896           Notwithstanding the above, anomalous effects may still occur when  CRLF
1897           is a valid newline sequence and explicit \r or \n escapes appear in the
1898           pattern.
1899    
1900           PCRE_NOTBOL           PCRE_NOTBOL
1901    
# Line 1829  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1942  MATCHING A PATTERN: THE TRADITIONAL FUNC
1942         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
1943         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
1944         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
1945         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
1946         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
1947         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
1948         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
1949           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1950         If you already know that your subject is valid, and you  want  to  skip  
1951         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
1952         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
1953         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
1954         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
1955         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
1956         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
1957         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
1958         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
1959           value  of startoffset that does not point to the start of a UTF-8 char-
1960         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
1961    
1962           PCRE_PARTIAL           PCRE_PARTIAL
1963    
1964         This  option  turns  on  the  partial  matching feature. If the subject         This option turns on the  partial  matching  feature.  If  the  subject
1965         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-
1966         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
1967         partially matches the pattern and the failure to  match  occurred  only         partially  matches  the  pattern and the failure to match occurred only
1968         because  there were not enough subject characters), pcre_exec() returns         because there were not enough subject characters), pcre_exec()  returns
1969         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
1970         used,  there  are restrictions on what may appear in the pattern. These         used, there are restrictions on what may appear in the  pattern.  These
1971         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
1972    
1973     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
1974    
1975         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
1976         length  in  length, and a starting byte offset in startoffset. In UTF-8         length in length, and a starting byte offset in startoffset.  In  UTF-8
1977         mode, the byte offset must point to the start  of  a  UTF-8  character.         mode,  the  byte  offset  must point to the start of a UTF-8 character.
1978         Unlike  the  pattern string, the subject may contain binary zero bytes.         Unlike the pattern string, the subject may contain binary  zero  bytes.
1979         When the starting offset is zero, the search for a match starts at  the         When  the starting offset is zero, the search for a match starts at the
1980         beginning of the subject, and this is by far the most common case.         beginning of the subject, and this is by far the most common case.
1981    
1982         A  non-zero  starting offset is useful when searching for another match         A non-zero starting offset is useful when searching for  another  match
1983         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-
1984         cess.   Setting  startoffset differs from just passing over a shortened         cess.  Setting startoffset differs from just passing over  a  shortened
1985         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
1986         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
1987    
1988           \Biss\B           \Biss\B
1989    
1990         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
1991         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
1992         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
1993         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
1994         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
1995         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
1996         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
1997         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
1998         rence  of "iss" because it is able to look behind the starting point to         rence of "iss" because it is able to look behind the starting point  to
1999         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2000    
2001         If a non-zero starting offset is passed when the pattern  is  anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2002         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2003         if the pattern does not require the match to be at  the  start  of  the         if  the  pattern  does  not require the match to be at the start of the
2004         subject.         subject.
2005    
2006     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2007    
2008         In  general, a pattern matches a certain portion of the subject, and in         In general, a pattern matches a certain portion of the subject, and  in
2009         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2010         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2011         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2012         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2013         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2014         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2015    
2016         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of  integer
2017         offsets whose address is passed in ovector. The number of  elements  in         offsets  whose  address is passed in ovector. The number of elements in
2018         the  vector is passed in ovecsize, which must be a non-negative number.         the vector is passed in ovecsize, which must be a non-negative  number.
2019         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
2020    
2021         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-
2022         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2023         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-
2024         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2025         The length passed in ovecsize should always be a multiple of three.  If         The  length passed in ovecsize should always be a multiple of three. If
2026         it is not, it is rounded down.         it is not, it is rounded down.
2027    
2028         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2029         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2030         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
2031         element of a pair is set to the offset of the first character in a sub-         element of a pair is set to the offset of the first character in a sub-
2032         string,  and  the  second  is  set to the offset of the first character         string, and the second is set to the  offset  of  the  first  character
2033         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
2034         tor[1],  identify  the  portion  of  the  subject string matched by the         tor[1], identify the portion of  the  subject  string  matched  by  the
2035         entire pattern. The next pair is used for the first  capturing  subpat-         entire  pattern.  The next pair is used for the first capturing subpat-
2036         tern, and so on. The value returned by pcre_exec() is one more than the         tern, and so on. The value returned by pcre_exec() is one more than the
2037         highest numbered pair that has been set. For example, if two substrings         highest numbered pair that has been set. For example, if two substrings
2038         have  been captured, the returned value is 3. If there are no capturing         have been captured, the returned value is 3. If there are no  capturing
2039         subpatterns, the return value from a successful match is 1,  indicating         subpatterns,  the return value from a successful match is 1, indicating
2040         that just the first pair of offsets has been set.         that just the first pair of offsets has been set.
2041    
2042         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2043         of the string that it matched that is returned.         of the string that it matched that is returned.
2044    
2045         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,
2046         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
2047         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. In particular, if the substring off-
2048         sets are not of interest, pcre_exec() may be called with ovector passed         sets are not of interest, pcre_exec() may be called with ovector passed
2049         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         as  NULL  and  ovecsize  as zero. However, if the pattern contains back
2050         references  and  the  ovector is not big enough to remember the related         references and the ovector is not big enough to  remember  the  related
2051         substrings, PCRE has to get additional memory for use during  matching.         substrings,  PCRE has to get additional memory for use during matching.
2052         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
2053    
2054         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
2055         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2056         ovector  that  will allow for n captured substrings, in addition to the         ovector that will allow for n captured substrings, in addition  to  the
2057         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.
2058    
2059         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
2060         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,
2061         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
2062         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
2063         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-
2064         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2065    
2066         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2067         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
2068         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
2069         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2070         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2071         for the second and third capturing subpatterns if  you  wish  (assuming         for  the  second  and third capturing subpatterns if you wish (assuming
2072         the vector is large enough, of course).         the vector is large enough, of course).
2073    
2074         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2075         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2076    
2077     Error return values from pcre_exec()     Error return values from pcre_exec()
2078    
2079         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2080         defined in the header file:         defined in the header file:
2081    
2082           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1971  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2085  MATCHING A PATTERN: THE TRADITIONAL FUNC
2085    
2086           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2087    
2088         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
2089         ovecsize was not zero.         ovecsize was not zero.
2090    
2091           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1980  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2094  MATCHING A PATTERN: THE TRADITIONAL FUNC
2094    
2095           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2096    
2097         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,
2098         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
2099         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
2100         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2101         gives when the magic number is not present.         gives when the magic number is not present.
2102    
2103           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2104    
2105         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2106         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
2107         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2108    
2109           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2110    
2111         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2112         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2113         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
2114         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
2115         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2116    
2117           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2118    
2119         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2120         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2121         returned by pcre_exec().         returned by pcre_exec().
2122    
2123           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2124    
2125         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2126         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2127         above.         above.
2128    
2129           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2130    
2131         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
2132         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2133         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2134    
2135           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2136    
2137         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
2138         subject.         subject.
2139    
2140           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2141    
2142         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
2143         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-
2144         ter.         ter.
2145    
2146           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2147    
2148         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
2149         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2150    
2151           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2152    
2153         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
2154         items  that are not supported for partial matching. See the pcrepartial         items that are not supported for partial matching. See the  pcrepartial
2155         documentation for details of partial matching.         documentation for details of partial matching.
2156    
2157           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2158    
2159         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2160         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2161    
2162           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2163    
2164         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.
2165    
2166           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2167    
2168         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2169         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2170         description above.         description above.
2171    
2172           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
# Line 2075  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2189  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2189         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2190              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2191    
2192         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2193         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2194         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2195         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2196         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2197         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2198         substrings.         substrings.
2199    
2200         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2201         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2202         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2203         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2204         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2205         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2206         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2207    
2208         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2209         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2210         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2211         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2212         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2213         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2214         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2215         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2216         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2217    
2218         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2219         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2220         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2221         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2222         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2223         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2224         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2225         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2226         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2227    
2228           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2229    
2230         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2231         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2232    
2233           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2234    
2235         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2236    
2237         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2238         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2239         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2240         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2241         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2242         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2243         error code         error code
2244    
2245           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2246    
2247         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2248    
2249         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2250         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2251         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2252         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2253         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2254         tive for unset substrings.         tive for unset substrings.
2255    
2256         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2257         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2258         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2259         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2260         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2261         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2262         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2263         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2264         vided.         vided.
2265    
2266    
# Line 2165  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2279  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2279              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2280              const char **stringptr);              const char **stringptr);
2281    
2282         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2283         ber.  For example, for this pattern         ber.  For example, for this pattern
2284    
2285           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2174  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2288  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2288         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2289         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2290         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2291         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2292         subpattern of that name.         subpattern of that name.
2293    
2294         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2295         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2296         are also two functions that do the whole job.         are also two functions that do the whole job.
2297    
2298         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2299         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2300         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2301         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2302         differences:         differences:
2303    
2304         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2305         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2306         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2307         name-to-number translation table.         name-to-number translation table.
2308    
2309         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2310         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2311         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
2312         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2313    
2314    
# Line 2203  DUPLICATE SUBPATTERN NAMES Line 2317  DUPLICATE SUBPATTERN NAMES
2317         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2318              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2319    
2320         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2321         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to  be  unique.  Normally,  patterns  with
2322         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
2323         subpatterns  participates. An example is shown in the pcrepattern docu-         subpatterns participates. An example is shown in the pcrepattern  docu-
2324         mentation.         mentation.
2325    
2326         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2327         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2328         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2329         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2330         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2331         but it is not defined which it is.         but it is not defined which it is.
2332    
2333         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
2334         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2335         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
2336         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2337         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
2338         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2339         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2340         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-
2341         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2342         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
2343         the captured data, if any.         the captured data, if any.
2344    
2345    
2346  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2347    
2348         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2349         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
2350         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
2351         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2352         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2353         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
2354         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2355         tation.         tation.
2356    
2357         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-
2358         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2359         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2360         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2361         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2362    
2363    
# Line 2254  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2368  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2368              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2369              int *workspace, int wscount);              int *workspace, int wscount);
2370    
2371         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2372         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2373         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2374         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2375         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2376         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
2377         a discussion of the two matching algorithms, see the pcrematching docu-         a discussion of the two matching algorithms, see the pcrematching docu-
2378         mentation.         mentation.
2379    
2380         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
2381         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-
2382         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
2383         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
2384         repeated here.         repeated here.
2385    
2386         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
2387         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
2388         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2389         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
2390         lot of potential matches.         lot of potential matches.
2391    
2392         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 2294  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2408  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2408    
2409     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2410    
2411         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
2412         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-
2413         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
2414         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
2415         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
2416         not repeated here.         not repeated here.
2417    
2418           PCRE_PARTIAL           PCRE_PARTIAL
2419    
2420         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
2421         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
2422         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
2423         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
2424         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-
2425         sibility.  The portion of the string that provided the partial match is         sibility. The portion of the string that provided the partial match  is
2426         set as the first matching string.         set as the first matching string.
2427    
2428           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2429    
2430         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2431         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-
2432         tive algorithm works, this is necessarily the shortest  possible  match         tive  algorithm  works, this is necessarily the shortest possible match
2433         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2434    
2435           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2436    
2437         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
2438         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-
2439         tional  subject  characters,  and have it continue with the same match.         tional subject characters, and have it continue with  the  same  match.
2440         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
2441         workspace  and wscount options must reference the same vector as before         workspace and wscount options must reference the same vector as  before
2442         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
2443         match.  There  is  more  discussion of this facility in the pcrepartial         match. There is more discussion of this  facility  in  the  pcrepartial
2444         documentation.         documentation.
2445    
2446     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2447    
2448         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-
2449         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
2450         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
2451         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2452         if the pattern         if the pattern
2453    
2454           <.*>           <.*>
# Line 2349  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2463  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2463           <something> <something else>           <something> <something else>
2464           <something> <something else> <something further>           <something> <something else> <something further>
2465    
2466         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,
2467         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2468         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2469         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
2470         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2471         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
2472         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2473         meaning of the strings is different.)         meaning of the strings is different.)
2474    
2475         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-
2476         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
2477         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
2478         filled with the longest matches.         filled with the longest matches.
2479    
2480     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2481    
2482         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2483         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
2484         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2485         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2486    
2487           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2488    
2489         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-
2490         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
2491         reference.         reference.
2492    
2493           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2494    
2495         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2496         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
2497         in a specific group. These are not supported.         in a specific group. These are not supported.
2498    
2499           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2500    
2501         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
2502         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
2503         (it is meaningless).         (it is meaningless).
2504    
2505           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2506    
2507         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
2508         workspace vector.         workspace vector.
2509    
2510           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2511    
2512         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2513         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2514         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
2515         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2516    
2517    
2518  SEE ALSO  SEE ALSO
2519    
2520         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2521         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2522    
2523    
2524  AUTHOR  AUTHOR
# Line 2416  AUTHOR Line 2530  AUTHOR
2530    
2531  REVISION  REVISION
2532    
2533         Last updated: 30 July 2007         Last updated: 11 September 2007
2534         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2535  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2536    
# Line 2669  DIFFERENCES BETWEEN PCRE AND PERL Line 2783  DIFFERENCES BETWEEN PCRE AND PERL
2783         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2784         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2785    
2786         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2787           (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2788           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2789           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2790           ture group; this is different to Perl.
2791    
2792           12. PCRE provides some extensions to the Perl regular expression facil-
2793         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
2794         versions, some of which (such as named parentheses) have been  in  PCRE         versions, some of which (such as named parentheses) have been  in  PCRE
2795         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 2695  DIFFERENCES BETWEEN PCRE AND PERL Line 2815  DIFFERENCES BETWEEN PCRE AND PERL
2815         (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-
2816         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2817    
2818         (g) The callout facility is PCRE-specific.         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2819           CRLF by the PCRE_BSR_ANYCRLF option.
2820    
2821           (h) The callout facility is PCRE-specific.
2822    
2823         (h) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
2824    
2825         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2826         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2827    
2828         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2829         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2830    
2831           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2832           of a pattern that set overall options that cannot be changed within the
2833           pattern.
2834    
2835    
2836  AUTHOR  AUTHOR
2837    
# Line 2715  AUTHOR Line 2842  AUTHOR
2842    
2843  REVISION  REVISION
2844    
2845         Last updated: 13 June 2007         Last updated: 11 September 2007
2846         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2847  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2848    
# Line 2756  PCRE REGULAR EXPRESSION DETAILS Line 2883  PCRE REGULAR EXPRESSION DETAILS
2883         discussed in the pcrematching page.         discussed in the pcrematching page.
2884    
2885    
2886    NEWLINE CONVENTIONS
2887    
2888           PCRE  supports five different conventions for indicating line breaks in
2889           strings: a single CR (carriage return) character, a  single  LF  (line-
2890           feed) character, the two-character sequence CRLF, any of the three pre-
2891           ceding, or any Unicode newline sequence. The pcreapi page  has  further
2892           discussion  about newlines, and shows how to set the newline convention
2893           in the options arguments for the compiling and matching functions.
2894    
2895           It is also possible to specify a newline convention by starting a  pat-
2896           tern string with one of the following five sequences:
2897    
2898             (*CR)        carriage return
2899             (*LF)        linefeed
2900             (*CRLF)      carriage return, followed by linefeed
2901             (*ANYCRLF)   any of the three above
2902             (*ANY)       all Unicode newline sequences
2903    
2904           These override the default and the options given to pcre_compile(). For
2905           example, on a Unix system where LF is the default newline sequence, the
2906           pattern
2907    
2908             (*CR)a.b
2909    
2910           changes the convention to CR. That pattern matches "a\nb" because LF is
2911           no longer a newline. Note that these special settings,  which  are  not
2912           Perl-compatible,  are  recognized  only at the very start of a pattern,
2913           and that they must be in upper case.  If  more  than  one  of  them  is
2914           present, the last one is used.
2915    
2916           The  newline  convention  does  not  affect what the \R escape sequence
2917           matches. By default, this is any Unicode  newline  sequence,  for  Perl
2918           compatibility.  However, this can be changed; see the description of \R
2919           in the section entitled "Newline sequences" below. A change of \R  set-
2920           ting can be combined with a change of newline convention.
2921    
2922    
2923  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
2924    
2925         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 2863  BACKSLASH Line 3027  BACKSLASH
3027           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3028           \e        escape (hex 1B)           \e        escape (hex 1B)
3029           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3030           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3031           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3032           \t        tab (hex 09)           \t        tab (hex 09)
3033           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
# Line 2878  BACKSLASH Line 3042  BACKSLASH
3042         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
3043         in upper or lower case). Any number of hexadecimal  digits  may  appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
3044         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
3045         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,
3046         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3047         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
3048         nating  }, this form of escape is not recognized.  Instead, the initial  
3049         \x will be interpreted as a basic hexadecimal escape, with no following         If characters other than hexadecimal digits appear between \x{  and  },
3050         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3051           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3052           escape,  with  no  following  digits, giving a character whose value is
3053           zero.
3054    
3055         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
3056         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-
3057         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3058    
3059         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3060         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3061         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3062         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
3063         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3064    
3065         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3066         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3067         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
3068         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3069         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3070         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3071         of parenthesized subpatterns.         of parenthesized subpatterns.
3072    
3073         Inside  a  character  class, or if the decimal number is greater than 9         Inside a character class, or if the decimal number is  greater  than  9
3074         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3075         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3076         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3077         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3078         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3079         example:         example:
3080    
3081           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2926  BACKSLASH Line 3093  BACKSLASH
3093           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3094                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3095    
3096         Note  that  octal  values of 100 or greater must not be introduced by a         Note that octal values of 100 or greater must not be  introduced  by  a
3097         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3098    
3099         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3100         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3101         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3102         08),  and the sequences \R and \X are interpreted as the characters "R"         08), and the sequences \R and \X are interpreted as the characters  "R"
3103         and "X", respectively. Outside a character class, these sequences  have         and  "X", respectively. Outside a character class, these sequences have
3104         different meanings (see below).         different meanings (see below).
3105    
3106     Absolute and relative back references     Absolute and relative back references
3107    
3108         The  sequence  \g followed by an unsigned or a negative number, option-         The sequence \g followed by an unsigned or a negative  number,  option-
3109         ally enclosed in braces, is an absolute or relative back  reference.  A         ally  enclosed  in braces, is an absolute or relative back reference. A
3110         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3111         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3112    
# Line 2960  BACKSLASH Line 3127  BACKSLASH
3127           \W     any "non-word" character           \W     any "non-word" character
3128    
3129         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
3130         into two disjoint sets. Any given character matches one, and only  one,         into  two disjoint sets. Any given character matches one, and only one,
3131         of each pair.         of each pair.
3132    
3133         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
3134         acter classes. They each match one character of the  appropriate  type.         acter  classes.  They each match one character of the appropriate type.
3135         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
3136         of them fail, since there is no character to match.         of them fail, since there is no character to match.
3137    
3138         For compatibility with Perl, \s does not match the VT  character  (code         For  compatibility  with Perl, \s does not match the VT character (code
3139         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
3140         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
3141         "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-
3142         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3143    
3144         In UTF-8 mode, characters with values greater than 128 never match  \d,         In  UTF-8 mode, characters with values greater than 128 never match \d,
3145         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3146         code character property support is available.  These  sequences  retain         code  character  property  support is available. These sequences retain
3147         their original meanings from before UTF-8 support was available, mainly         their original meanings from before UTF-8 support was available, mainly
3148         for efficiency reasons.         for efficiency reasons.
3149    
3150         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3151         the  other  sequences, these do match certain high-valued codepoints in         the other sequences, these do match certain high-valued  codepoints  in
3152         UTF-8 mode.  The horizontal space characters are:         UTF-8 mode.  The horizontal space characters are:
3153    
3154           U+0009     Horizontal tab           U+0009     Horizontal tab
# Line 3015  BACKSLASH Line 3182  BACKSLASH
3182           U+2029     Paragraph separator           U+2029     Paragraph separator
3183    
3184         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
3185         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-
3186         trolled by PCRE's low-valued character tables, and may vary if  locale-         trolled  by PCRE's low-valued character tables, and may vary if locale-
3187         specific  matching is taking place (see "Locale support" in the pcreapi         specific matching is taking place (see "Locale support" in the  pcreapi
3188         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
3189         systems,  or "french" in Windows, some character codes greater than 128         systems, or "french" in Windows, some character codes greater than  128
3190         are used for accented letters, and these are matched by \w. The use  of         are  used for accented letters, and these are matched by \w. The use of
3191         locales with Unicode is discouraged.         locales with Unicode is discouraged.
3192    
3193     Newline sequences     Newline sequences
3194    
3195         Outside  a  character class, the escape sequence \R matches any Unicode         Outside a character class, by default, the escape sequence  \R  matches
3196         newline sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R  is         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3197         equivalent to the following:         mode \R is equivalent to the following:
3198    
3199           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3200    
3201         This  is  an  example  of an "atomic group", details of which are given         This is an example of an "atomic group", details  of  which  are  given
3202         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3203         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3204         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3205         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3206         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3207    
3208         In UTF-8 mode, two additional characters whose codepoints  are  greater         In  UTF-8  mode, two additional characters whose codepoints are greater
3209         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3210         rator, U+2029).  Unicode character property support is not  needed  for         rator,  U+2029).   Unicode character property support is not needed for
3211         these characters to be recognized.         these characters to be recognized.
3212    
3213           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3214           the  complete  set  of  Unicode  line  endings)  by  setting the option
3215           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3216           (BSR is an abbrevation for "backslash R".) This can be made the default
3217           when PCRE is built; if this is the case, the  other  behaviour  can  be
3218           requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3219           specify these settings by starting a pattern string  with  one  of  the
3220           following sequences:
3221    
3222             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3223             (*BSR_UNICODE)   any Unicode newline sequence
3224    
3225           These override the default and the options given to pcre_compile(), but
3226           they can be overridden by options given to pcre_exec(). Note that these
3227           special settings, which are not Perl-compatible, are recognized only at
3228           the very start of a pattern, and that they must be in  upper  case.  If
3229           more  than  one  of  them is present, the last one is used. They can be
3230           combined with a change of newline convention, for  example,  a  pattern
3231           can start with:
3232    
3233             (*ANY)(*BSR_ANYCRLF)
3234    
3235         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3236    
3237     Unicode character properties     Unicode character properties
# Line 3146  BACKSLASH Line 3335  BACKSLASH
3335         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
3336         classified as a modifier or "other".         classified as a modifier or "other".
3337    
3338           The Cs (Surrogate) property applies only to  characters  in  the  range
3339           U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3340           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3341           ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3342           the pcreapi page).
3343    
3344         The long synonyms for these properties  that  Perl  supports  (such  as         The long synonyms for these properties  that  Perl  supports  (such  as
3345         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3346         any of these properties with "Is".         any of these properties with "Is".
# Line 3492  VERTICAL BAR Line 3687  VERTICAL BAR
3687  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3688    
3689         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
3690         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
3691         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         within  the  pattern  by  a  sequence  of  Perl option letters enclosed
3692         option letters are         between "(?" and ")".  The option letters are
3693    
3694           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3695           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3508  INTERNAL OPTION SETTING Line 3703  INTERNAL OPTION SETTING
3703         is also permitted. If a  letter  appears  both  before  and  after  the         is also permitted. If a  letter  appears  both  before  and  after  the
3704         hyphen, the option is unset.         hyphen, the option is unset.
3705    
3706           The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
3707           can be changed in the same way as the Perl-compatible options by  using
3708           the characters J, U and X respectively.
3709    
3710         When  an option change occurs at top level (that is, not inside subpat-         When  an option change occurs at top level (that is, not inside subpat-
3711         tern parentheses), the change applies to the remainder of  the  pattern         tern parentheses), the change applies to the remainder of  the  pattern
3712         that follows.  If the change is placed right at the start of a pattern,         that follows.  If the change is placed right at the start of a pattern,
# Line 3533  INTERNAL OPTION SETTING Line 3732  INTERNAL OPTION SETTING
3732         the  effects  of option settings happen at compile time. There would be         the  effects  of option settings happen at compile time. There would be
3733         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3734    
3735         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         Note: There are other PCRE-specific options that  can  be  set  by  the
3736         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
3737         the characters J, U and X respectively.         cases the pattern can contain special  leading  sequences  to  override
3738           what  the  application  has set or what has been defaulted. Details are
3739           given in the section entitled "Newline sequences" above.
3740    
3741    
3742  SUBPATTERNS  SUBPATTERNS
# Line 4535  CALLOUTS Line 4736  CALLOUTS
4736         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
4737    
4738    
4739    BACKTRACKING CONTROL
4740    
4741           Perl 5.10 introduced a number of "Special Backtracking Control  Verbs",
4742           which are described in the Perl documentation as "experimental and sub-
4743           ject to change or removal in a future version of Perl". It goes  on  to
4744           say:  "Their usage in production code should be noted to avoid problems
4745           during upgrades." The same remarks apply to the PCRE features described
4746           in this section.
4747    
4748           Since these verbs are specifically related to backtracking, they can be
4749           used only when the pattern is to be matched  using  pcre_exec(),  which
4750           uses  a  backtracking  algorithm. They cause an error if encountered by
4751           pcre_dfa_exec().
4752    
4753           The new verbs make use of what was previously invalid syntax: an  open-
4754           ing parenthesis followed by an asterisk. In Perl, they are generally of
4755           the form (*VERB:ARG) but PCRE does not support the use of arguments, so
4756           its  general  form is just (*VERB). Any number of these verbs may occur
4757           in a pattern. There are two kinds:
4758    
4759       Verbs that act immediately
4760    
4761           The following verbs act as soon as they are encountered:
4762    
4763              (*ACCEPT)
4764    
4765           This verb causes the match to end successfully, skipping the  remainder
4766           of  the pattern. When inside a recursion, only the innermost pattern is
4767           ended immediately. PCRE differs  from  Perl  in  what  happens  if  the
4768           (*ACCEPT)  is inside capturing parentheses. In Perl, the data so far is
4769           captured: in PCRE no data is captured. For example:
4770    
4771             A(A|B(*ACCEPT)|C)D
4772    
4773           This matches "AB", "AAD", or "ACD", but when it matches "AB",  no  data
4774           is captured.
4775    
4776             (*FAIL) or (*F)
4777    
4778           This  verb  causes the match to fail, forcing backtracking to occur. It
4779           is equivalent to (?!) but easier to read. The Perl documentation  notes
4780           that  it  is  probably  useful only when combined with (?{}) or (??{}).
4781           Those are, of course, Perl features that are not present in  PCRE.  The
4782           nearest  equivalent is the callout feature, as for example in this pat-
4783           tern:
4784    
4785             a+(?C)(*FAIL)
4786    
4787           A match with the string "aaaa" always fails, but the callout  is  taken
4788           before each backtrack happens (in this example, 10 times).
4789    
4790       Verbs that act after backtracking
4791    
4792           The following verbs do nothing when they are encountered. Matching con-
4793           tinues with what follows, but if there is no subsequent match, a  fail-
4794           ure  is  forced.   The  verbs  differ  in  exactly what kind of failure
4795           occurs.
4796    
4797             (*COMMIT)
4798    
4799           This verb causes the whole match to fail outright if the  rest  of  the
4800           pattern  does  not match. Even if the pattern is unanchored, no further
4801           attempts to find a match by advancing the start point take place.  Once
4802           (*COMMIT)  has been passed, pcre_exec() is committed to finding a match
4803           at the current starting point, or not at all. For example:
4804    
4805             a+(*COMMIT)b
4806    
4807           This matches "xxaab" but not "aacaab". It can be thought of as  a  kind
4808           of dynamic anchor, or "I've started, so I must finish."
4809    
4810             (*PRUNE)
4811    
4812           This  verb causes the match to fail at the current position if the rest
4813           of the pattern does not match. If the pattern is unanchored, the normal
4814           "bumpalong"  advance to the next starting character then happens. Back-
4815           tracking can occur as usual to the left of (*PRUNE), or  when  matching
4816           to  the right of (*PRUNE), but if there is no match to the right, back-
4817           tracking cannot cross (*PRUNE).  In simple cases, the use  of  (*PRUNE)
4818           is just an alternative to an atomic group or possessive quantifier, but
4819           there are some uses of (*PRUNE) that cannot be expressed in  any  other
4820           way.
4821    
4822             (*SKIP)
4823    
4824           This  verb  is like (*PRUNE), except that if the pattern is unanchored,
4825           the "bumpalong" advance is not to the next character, but to the  posi-
4826           tion  in  the  subject where (*SKIP) was encountered. (*SKIP) signifies
4827           that whatever text was matched leading up to it cannot  be  part  of  a
4828           successful match. Consider:
4829    
4830             a+(*SKIP)b
4831    
4832           If  the  subject  is  "aaaac...",  after  the first match attempt fails
4833           (starting at the first character in the  string),  the  starting  point
4834           skips on to start the next attempt at "c". Note that a possessive quan-
4835           tifer does not have the same effect in this example; although it  would
4836           suppress  backtracking  during  the  first  match  attempt,  the second
4837           attempt would start at the second character instead of skipping  on  to
4838           "c".
4839    
4840             (*THEN)
4841    
4842           This verb causes a skip to the next alternation if the rest of the pat-
4843           tern does not match. That is, it cancels pending backtracking, but only
4844           within  the  current  alternation.  Its name comes from the observation
4845           that it can be used for a pattern-based if-then-else block:
4846    
4847             ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
4848    
4849           If the COND1 pattern matches, FOO is tried (and possibly further  items
4850           after  the  end  of  the group if FOO succeeds); on failure the matcher
4851           skips to the second alternative and tries COND2,  without  backtracking
4852           into  COND1.  If  (*THEN)  is  used outside of any alternation, it acts
4853           exactly like (*PRUNE).
4854    
4855    
4856  SEE ALSO  SEE ALSO
4857    
4858         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
# Line 4549  AUTHOR Line 4867  AUTHOR
4867    
4868  REVISION  REVISION
4869    
4870         Last updated: 06 August 2007         Last updated: 17 September 2007
4871         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
4872  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
4873    
# Line 4828  CONDITIONAL PATTERNS Line 5146  CONDITIONAL PATTERNS
5146           (?(assert)...  assertion condition           (?(assert)...  assertion condition
5147    
5148    
5149    BACKTRACKING CONTROL
5150    
5151           The following act immediately they are reached:
5152    
5153             (*ACCEPT)      force successful match
5154             (*FAIL)        force backtrack; synonym (*F)
5155    
5156           The following act only when a subsequent match failure causes  a  back-
5157           track to reach them. They all force a match failure, but they differ in
5158           what happens afterwards. Those that advance the start-of-match point do
5159           so only if the pattern is not anchored.
5160    
5161             (*COMMIT)      overall failure, no advance of starting point
5162             (*PRUNE)       advance to next starting character
5163             (*SKIP)        advance start to current matching position
5164             (*THEN)        local failure, backtrack to next alternation
5165    
5166    
5167    NEWLINE CONVENTIONS
5168    
5169           These  are  recognized only at the very start of the pattern or after a
5170           (*BSR_...) option.
5171    
5172             (*CR)
5173             (*LF)
5174             (*CRLF)
5175             (*ANYCRLF)
5176             (*ANY)
5177    
5178    
5179    WHAT \R MATCHES
5180    
5181           These are recognized only at the very start of the pattern or  after  a
5182           (*...) option that sets the newline convention.
5183    
5184             (*BSR_ANYCRLF)
5185             (*BSR_UNICODE)
5186    
5187    
5188  CALLOUTS  CALLOUTS
5189    
5190           (?C)      callout           (?C)      callout
# Line 4848  AUTHOR Line 5205  AUTHOR
5205    
5206  REVISION  REVISION
5207    
5208         Last updated: 06 August 2007         Last updated: 21 September 2007
5209         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
5210  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5211    

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