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revision 208 by ph10, Mon Aug 6 15:23:29 2007 UTC revision 231 by ph10, Tue Sep 11 11:15:33 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 331  CODE VALUE OF NEWLINE Line 361  CODE VALUE OF NEWLINE
361         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
362    
363    
364    WHAT \R MATCHES
365    
366           By default, the sequence \R in a pattern matches  any  Unicode  newline
367           sequence,  whatever  has  been selected as the line ending sequence. If
368           you specify
369    
370             --enable-bsr-anycrlf
371    
372           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
373           ever  is selected when PCRE is built can be overridden when the library
374           functions are called.
375    
376    
377  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
378    
379         The PCRE building process uses libtool to build both shared and  static         The PCRE building process uses libtool to build both shared and  static
# Line 483  AUTHOR Line 526  AUTHOR
526    
527  REVISION  REVISION
528    
529         Last updated: 30 July 2007         Last updated: 11 September 2007
530         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
531  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
532    
# Line 627  THE ALTERNATIVE MATCHING ALGORITHM Line 670  THE ALTERNATIVE MATCHING ALGORITHM
670         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
671         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.
672    
673         7.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
674         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-
675         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
676         time, for all active paths through the tree.         time, for all active paths through the tree.
677    
678           8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-
679           ported.
680    
681    
682  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
683    
684         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
685         tages:         tages:
686    
687         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-
688         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
689         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
690         things with callouts.         things with callouts.
691    
692         2.  There is much better support for partial matching. The restrictions         2. There is much better support for partial matching. The  restrictions
693         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-
694         rithm  for  partial matching do not apply to the alternative algorithm.         rithm for partial matching do not apply to the  alternative  algorithm.
695         For non-anchored patterns, the starting position of a partial match  is         For  non-anchored patterns, the starting position of a partial match is
696         available.         available.
697    
698         3.  Because  the  alternative  algorithm  scans the subject string just         3. Because the alternative algorithm  scans  the  subject  string  just
699         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
700         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
701         for partial matching each time.         for partial matching each time.
702    
703    
# Line 659  DISADVANTAGES OF THE ALTERNATIVE ALGORIT Line 705  DISADVANTAGES OF THE ALTERNATIVE ALGORIT
705    
706         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
707    
708         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
709         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
710         because it is less susceptible to optimization.         because it is less susceptible to optimization.
711    
712         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 678  AUTHOR Line 724  AUTHOR
724    
725  REVISION  REVISION
726    
727         Last updated: 29 May 2007         Last updated: 08 August 2007
728         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
729  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
730    
# Line 875  NEWLINES Line 921  NEWLINES
921         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
922         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
923    
924           At compile time, the newline convention can be specified by the options
925           argument of pcre_compile(), or it can be specified by special  text  at
926           the start of the pattern itself; this overrides any other settings. See
927           the pcrepattern page for details of the special character sequences.
928    
929         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-
930         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
931         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
932         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
933         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
934         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
935         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
936    
937           The choice of newline convention does not affect the interpretation  of
938           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
939           which is controlled in a similar way, but by separate options.
940    
941    
942  MULTITHREADING  MULTITHREADING
943    
944         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
945         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
946         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
947         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
948    
949         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
950         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
951         at once.         at once.
952    
# Line 899  MULTITHREADING Line 954  MULTITHREADING
954  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
955    
956         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
957         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
958         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
959         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation.  However, compiling a regular expression
960         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-
961         anteed to work and may cause crashes.         anteed to work and may cause crashes.
962    
963    
# Line 910  CHECKING BUILD-TIME OPTIONS Line 965  CHECKING BUILD-TIME OPTIONS
965    
966         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
967    
968         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-
969         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
970         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
971         tures.         tures.
972    
973         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
974         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
975         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
976         available:         available:
977    
978           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
979    
980         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-
981         able; otherwise it is set to zero.         able; otherwise it is set to zero.
982    
983           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
984    
985         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
986         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
987    
988           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
989    
990         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
991         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
992         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,
993         and  -1  for  ANY. The default should normally be the standard sequence         and -1 for ANY. The default should normally be  the  standard  sequence
994         for your operating system.         for your operating system.
995    
996             PCRE_CONFIG_BSR
997    
998           The output is an integer whose value indicates what character sequences
999           the \R escape sequence matches by default. A value of 0 means  that  \R
1000           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1001           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1002           tern is compiled or matched.
1003    
1004           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1005    
1006         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
1007         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1008         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1009         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1010         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1011         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1012    
1013           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1014    
1015         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1016         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1017         given in the pcreposix documentation.         given in the pcreposix documentation.
1018    
1019           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1020    
1021         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
1022         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
1023         details are given with pcre_exec() below.         details are given with pcre_exec() below.
1024    
1025           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1026    
1027         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
1028         recursion when calling the internal matching function in a  pcre_exec()         recursion  when calling the internal matching function in a pcre_exec()
1029         execution. Further details are given with pcre_exec() below.         execution. Further details are given with pcre_exec() below.
1030    
1031           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1032    
1033         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
1034         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1035         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
1036         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
1037         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1038         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1039         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1040    
1041    
# Line 989  COMPILING A PATTERN Line 1052  COMPILING A PATTERN
1052    
1053         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1054         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1055         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1056         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1057    
1058         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
1059         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
1060         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1061         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
1062         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1063         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
1064         longer required.         longer required.
1065    
1066         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
1067         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
1068         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1069         ment, which is an address (see below).         ment, which is an address (see below).
1070    
1071         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1072         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1073         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
1074         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
1075         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
1076         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
1077         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
1078         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
1079         of matching as well as at compile time.         of matching as well as at compile time.
1080    
1081         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1082         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1083         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-
1084         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
1085         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-
1086         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
1087         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
1088         given.         given.
1089    
1090         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1091         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
1092         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
1093         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1094    
1095         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
1096         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1097         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1098         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
1099         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1100         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
1101         support below.         support below.
1102    
1103         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1104         pile():         pile():
1105    
1106           pcre *re;           pcre *re;
# Line 1050  COMPILING A PATTERN Line 1113  COMPILING A PATTERN
1113             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1114             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1115    
1116         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
1117         file:         file:
1118    
1119           PCRE_ANCHORED           PCRE_ANCHORED
1120    
1121         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
1122         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
1123         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1124         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1125         only way to do it in Perl.         only way to do it in Perl.
1126    
1127           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1128    
1129         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1130         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1131         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1132    
1133             PCRE_BSR_ANYCRLF
1134             PCRE_BSR_UNICODE
1135    
1136           These options (which are mutually exclusive) control what the \R escape
1137           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1138           or to match any Unicode newline sequence. The default is specified when
1139           PCRE is built. It can be overridden from within the pattern, or by set-
1140           ting an option when a compiled pattern is matched.
1141    
1142           PCRE_CASELESS           PCRE_CASELESS
1143    
1144         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
1145         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
1146         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
1147         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1148         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1149         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-
1150         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1151         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1152         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1153         UTF-8 support.         UTF-8 support.
1154    
1155           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1156    
1157         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
1158         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
1159         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
1160         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1161         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
1162         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1163    
1164           PCRE_DOTALL           PCRE_DOTALL
1165    
1166         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-
1167         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1168         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
1169         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
1170         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
1171         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1172    
1173           PCRE_DUPNAMES           PCRE_DUPNAMES
1174    
1175         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1176         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
1177         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
1178         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1179         the pcrepattern documentation.         the pcrepattern documentation.
1180    
1181           PCRE_EXTENDED           PCRE_EXTENDED
1182    
1183         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1184         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1185         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1186         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1187         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1188         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-
1189         ting.         ting.
1190    
1191         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1192         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1193         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1194         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1195         introduces a conditional subpattern.         introduces a conditional subpattern.
1196    
1197           PCRE_EXTRA           PCRE_EXTRA
1198    
1199         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1200         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
1201         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
1202         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1203         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1204         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
1205         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal.  (Perl can, however, be persuaded to give a warning for this.)
1206         There  are  at  present no other features controlled by this option. It         There are at present no other features controlled by  this  option.  It
1207         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1208    
1209           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1210    
1211         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1212         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1213         matched text may continue over the newline.         matched text may continue over the newline.
1214    
1215           PCRE_MULTILINE           PCRE_MULTILINE
1216    
1217         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1218         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1219         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1220         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1221         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1222         is set). This is the same as Perl.         is set). This is the same as Perl.
1223    
1224         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"
1225         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1226         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1227         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
1228         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-
1229         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,
1230         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1231    
1232           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1163  COMPILING A PATTERN Line 1235  COMPILING A PATTERN
1235           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1236           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1237    
1238         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1239         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
1240         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1241         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1242         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1243         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1244         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1245         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1246         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1247         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
1248         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1249         UTF-8 mode.         UTF-8 mode.
1250    
1251         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1252         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1253         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
1254         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-
1255         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
1256         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1257         cause an error.         cause an error.
1258    
1259         The only time that a line break is specially recognized when  compiling         The  only time that a line break is specially recognized when compiling
1260         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
1261         character class is encountered. This indicates  a  comment  that  lasts         character  class  is  encountered.  This indicates a comment that lasts
1262         until  after the next line break sequence. In other circumstances, line         until after the next line break sequence. In other circumstances,  line
1263         break  sequences  are  treated  as  literal  data,   except   that   in         break   sequences   are   treated  as  literal  data,  except  that  in
1264         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1265         and are therefore ignored.         and are therefore ignored.
1266    
1267         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
1268         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.
1269    
1270           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1271    
1272         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-
1273         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1274         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1275         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1276         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1277    
1278           PCRE_UNGREEDY           PCRE_UNGREEDY
1279    
1280         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1281         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
1282         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
1283         within the pattern.         within the pattern.
1284    
1285           PCRE_UTF8           PCRE_UTF8
1286    
1287         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
1288         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1289         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-
1290         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
1291         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
1292         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1293    
1294           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1295    
1296         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
1297         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1298         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
1299         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
1300         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-
1301         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
1302         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
1303         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
1304         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1305           UTF-8 validity checking of subject strings.
1306    
1307    
1308  COMPILATION ERROR CODES  COMPILATION ERROR CODES
# Line 1296  COMPILATION ERROR CODES Line 1369  COMPILATION ERROR CODES
1369         found         found
1370           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1371           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1372           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1373           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
1374                 non-zero number                 non-zero number
1375           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 1561  INFORMATION ABOUT A PATTERN
1561         returned. The fourth argument should point to an unsigned char *  vari-         returned. The fourth argument should point to an unsigned char *  vari-
1562         able.         able.
1563    
1564             PCRE_INFO_HASCRORLF
1565    
1566           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1567           characters, otherwise 0. The fourth argument should  point  to  an  int
1568           variable.
1569    
1570           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1571    
1572         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
# Line 1767  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1846  MATCHING A PATTERN: THE TRADITIONAL FUNC
1846         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
1847         unachored at matching time.         unachored at matching time.
1848    
1849             PCRE_BSR_ANYCRLF
1850             PCRE_BSR_UNICODE
1851    
1852           These options (which are mutually exclusive) control what the \R escape
1853           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1854           or  to  match  any Unicode newline sequence. These options override the
1855           choice that was made or defaulted when the pattern was compiled.
1856    
1857           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1858           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1859           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1860           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1861           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1862    
1863         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
1864         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
1865         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
1866         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
1867         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
1868         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
1869         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
1870         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
1871         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-
1872         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
1873           explicit matches for  CR  or  LF  characters,  the  match  position  is
1874           advanced by two characters instead of one, in other words, to after the
1875           CRLF.
1876    
1877           The above rule is a compromise that makes the most common cases work as
1878           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
1879           option is not set), it does not match the string "\r\nA" because, after
1880           failing  at the start, it skips both the CR and the LF before retrying.
1881           However, the pattern [\r\n]A does match that string,  because  it  con-
1882           tains an explicit CR or LF reference, and so advances only by one char-
1883           acter after the first failure.
1884    
1885           An explicit match for CR of LF is either a literal appearance of one of
1886           those  characters,  or  one  of the \r or \n escape sequences. Implicit
1887           matches such as [^X] do not count, nor does \s (which includes  CR  and
1888           LF in the characters that it matches).
1889    
1890           Notwithstanding  the above, anomalous effects may still occur when CRLF
1891           is a valid newline sequence and explicit \r or \n escapes appear in the
1892           pattern.
1893    
1894           PCRE_NOTBOL           PCRE_NOTBOL
1895    
1896         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1897         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
1898         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
1899         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
1900         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1901    
1902           PCRE_NOTEOL           PCRE_NOTEOL
1903    
1904         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
1905         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
1906         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
1907         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1908         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
1909         not affect \Z or \z.         not affect \Z or \z.
1910    
1911           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1912    
1913         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
1914         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
1915         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
1916         example, if the pattern         example, if the pattern
1917    
1918           a?b?           a?b?
1919    
1920         is applied to a string not beginning with "a" or "b",  it  matches  the         is  applied  to  a string not beginning with "a" or "b", it matches the
1921         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
1922         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
1923         rences of "a" or "b".         rences of "a" or "b".
1924    
1925         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
1926         cial case of a pattern match of the empty  string  within  its  split()         cial  case  of  a  pattern match of the empty string within its split()
1927         function,  and  when  using  the /g modifier. It is possible to emulate         function, and when using the /g modifier. It  is  possible  to  emulate
1928         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
1929         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
1930         if that fails by advancing the starting offset (see below)  and  trying         if  that  fails by advancing the starting offset (see below) and trying
1931         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
1932         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
1933    
1934           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1935    
1936         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
1937         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
1938         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
1939         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
1940         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
1941         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
1942         returned.         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
1943           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1944    
1945         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
1946         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 2416  AUTHOR Line 2524  AUTHOR
2524    
2525  REVISION  REVISION
2526    
2527         Last updated: 30 July 2007         Last updated: 11 September 2007
2528         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2529  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2530    
# Line 2669  DIFFERENCES BETWEEN PCRE AND PERL Line 2777  DIFFERENCES BETWEEN PCRE AND PERL
2777         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2778         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2779    
2780         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2781           (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2782           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2783           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2784           ture group; this is different to Perl.
2785    
2786           12. PCRE provides some extensions to the Perl regular expression facil-
2787         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
2788         versions, some of which (such as named parentheses) have been  in  PCRE         versions, some of which (such as named parentheses) have been  in  PCRE
2789         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 2809  DIFFERENCES BETWEEN PCRE AND PERL
2809         (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-
2810         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2811    
2812         (g) The callout facility is PCRE-specific.         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2813           CRLF by the PCRE_BSR_ANYCRLF option.
2814    
2815         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
2816    
2817         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
2818    
2819           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2820         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2821    
2822         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2823         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2824    
2825           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2826           of a pattern that set overall options that cannot be changed within the
2827           pattern.
2828    
2829    
2830  AUTHOR  AUTHOR
2831    
# Line 2715  AUTHOR Line 2836  AUTHOR
2836    
2837  REVISION  REVISION
2838    
2839         Last updated: 13 June 2007         Last updated: 11 September 2007
2840         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2841  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2842    
# Line 2756  PCRE REGULAR EXPRESSION DETAILS Line 2877  PCRE REGULAR EXPRESSION DETAILS
2877         discussed in the pcrematching page.         discussed in the pcrematching page.
2878    
2879    
2880    NEWLINE CONVENTIONS
2881    
2882           PCRE  supports five different conventions for indicating line breaks in
2883           strings: a single CR (carriage return) character, a  single  LF  (line-
2884           feed) character, the two-character sequence CRLF, any of the three pre-
2885           ceding, or any Unicode newline sequence. The pcreapi page  has  further
2886           discussion  about newlines, and shows how to set the newline convention
2887           in the options arguments for the compiling and matching functions.
2888    
2889           It is also possible to specify a newline convention by starting a  pat-
2890           tern string with one of the following five sequences:
2891    
2892             (*CR)        carriage return
2893             (*LF)        linefeed
2894             (*CRLF)      carriage return, followed by linefeed
2895             (*ANYCRLF)   any of the three above
2896             (*ANY)       all Unicode newline sequences
2897    
2898           These override the default and the options given to pcre_compile(). For
2899           example, on a Unix system where LF is the default newline sequence, the
2900           pattern
2901    
2902             (*CR)a.b
2903    
2904           changes the convention to CR. That pattern matches "a\nb" because LF is
2905           no longer a newline. Note that these special settings,  which  are  not
2906           Perl-compatible,  are  recognized  only at the very start of a pattern,
2907           and that they must be in upper case.  If  more  than  one  of  them  is
2908           present, the last one is used.
2909    
2910           The  newline  convention  does  not  affect what the \R escape sequence
2911           matches. By default, this is any Unicode  newline  sequence,  for  Perl
2912           compatibility.  However, this can be changed; see the description of \R
2913           in the section entitled "Newline sequences" below.
2914    
2915    
2916  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
2917    
2918         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
2919         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
2920         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
2921         trivial example, the pattern         trivial example, the pattern
2922    
2923           The quick brown fox           The quick brown fox
2924    
2925         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
2926         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
2927         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
2928         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
2929         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
2930         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
2931         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
2932         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
2933         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
2934    
2935         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
2936         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
2937         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
2938         but instead are interpreted in some special way.         but instead are interpreted in some special way.
2939    
2940         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
2941         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
2942         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
2943         the metacharacters are as follows:         the metacharacters are as follows:
2944    
2945           \      general escape character with several uses           \      general escape character with several uses
# Line 2801  CHARACTERS AND METACHARACTERS Line 2958  CHARACTERS AND METACHARACTERS
2958                  also "possessive quantifier"                  also "possessive quantifier"
2959           {      start min/max quantifier           {      start min/max quantifier
2960    
2961         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
2962         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
2963    
2964           \      general escape character           \      general escape character
# Line 2811  CHARACTERS AND METACHARACTERS Line 2968  CHARACTERS AND METACHARACTERS
2968                    syntax)                    syntax)
2969           ]      terminates the character class           ]      terminates the character class
2970    
2971         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the  metacharacters.
2972    
2973    
2974  BACKSLASH  BACKSLASH
2975    
2976         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2977         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
2978         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
2979         applies both inside and outside character classes.         applies both inside and outside character classes.
2980    
2981         For  example,  if  you want to match a * character, you write \* in the         For example, if you want to match a * character, you write  \*  in  the
2982         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
2983         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
2984         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
2985         that  it stands for itself. In particular, if you want to match a back-         that it stands for itself. In particular, if you want to match a  back-
2986         slash, you write \\.         slash, you write \\.
2987    
2988         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
2989         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
2990         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
2991         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
2992         part of the pattern.         part of the pattern.
2993    
2994         If you want to remove the special meaning from a  sequence  of  charac-         If  you  want  to remove the special meaning from a sequence of charac-
2995         ters,  you can do so by putting them between \Q and \E. This is differ-         ters, you can do so by putting them between \Q and \E. This is  differ-
2996         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E
2997         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
2998         tion. Note the following examples:         tion. Note the following examples:
2999    
3000           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2847  BACKSLASH Line 3004  BACKSLASH
3004           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3005           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3006    
3007         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3008         classes.         classes.
3009    
3010     Non-printing characters     Non-printing characters
3011    
3012         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3013         acters in patterns in a visible manner. There is no restriction on  the         acters  in patterns in a visible manner. There is no restriction on the
3014         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3015         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3016         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
3017         sequences than the binary character it represents:         sequences than the binary character it represents:
3018    
3019           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3020           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3021           \e        escape (hex 1B)           \e        escape (hex 1B)
3022           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3023           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3024           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3025           \t        tab (hex 09)           \t        tab (hex 09)
3026           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
3027           \xhh      character with hex code hh           \xhh      character with hex code hh
3028           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3029    
3030         The precise effect of \cx is as follows: if x is a lower  case  letter,         The  precise  effect of \cx is as follows: if x is a lower case letter,
3031         it  is converted to upper case. Then bit 6 of the character (hex 40) is         it is converted to upper case. Then bit 6 of the character (hex 40)  is
3032         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
3033         becomes hex 7B.         becomes hex 7B.
3034    
3035         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
3036         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3037         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
3038         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,
3039         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3040         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
3041         nating  }, this form of escape is not recognized.  Instead, the initial  
3042         \x will be interpreted as a basic hexadecimal escape, with no following         If  characters  other than hexadecimal digits appear between \x{ and },
3043         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3044           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3045           escape, with no following digits, giving a  character  whose  value  is
3046           zero.
3047    
3048         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
3049         two syntaxes for \x. There is no difference in the way  they  are  han-         two syntaxes for \x. There is no difference in the way  they  are  han-
# Line 3025  BACKSLASH Line 3185  BACKSLASH
3185    
3186     Newline sequences     Newline sequences
3187    
3188         Outside  a  character class, the escape sequence \R matches any Unicode         Outside  a  character class, by default, the escape sequence \R matches
3189         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
3190         equivalent to the following:         mode \R is equivalent to the following:
3191    
3192           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3193    
# Line 3043  BACKSLASH Line 3203  BACKSLASH
3203         rator, U+2029).  Unicode character property support is not  needed  for         rator, U+2029).  Unicode character property support is not  needed  for
3204         these characters to be recognized.         these characters to be recognized.
3205    
3206           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3207           the complete set  of  Unicode  line  endings)  by  setting  the  option
3208           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3209           This can be made the default when PCRE is built; if this is  the  case,
3210           the  other  behaviour can be requested via the PCRE_BSR_UNICODE option.
3211           It is also possible to specify these settings  by  starting  a  pattern
3212           string with one of the following sequences:
3213    
3214             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3215             (*BSR_UNICODE)   any Unicode newline sequence
3216    
3217           These override the default and the options given to pcre_compile(), but
3218           they can be overridden by options given to pcre_exec(). Note that these
3219           special settings, which are not Perl-compatible, are recognized only at
3220           the very start of a pattern, and that they must be in  upper  case.  If
3221           more than one of them is present, the last one is used.
3222    
3223         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3224    
3225     Unicode character properties     Unicode character properties
# Line 3146  BACKSLASH Line 3323  BACKSLASH
3323         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
3324         classified as a modifier or "other".         classified as a modifier or "other".
3325    
3326           The Cs (Surrogate) property applies only to  characters  in  the  range
3327           U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3328           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3329           ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3330           the pcreapi page).
3331    
3332         The long synonyms for these properties  that  Perl  supports  (such  as         The long synonyms for these properties  that  Perl  supports  (such  as
3333         \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
3334         any of these properties with "Is".         any of these properties with "Is".
# Line 4535  CALLOUTS Line 4718  CALLOUTS
4718         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
4719    
4720    
4721    BACTRACKING CONTROL
4722    
4723           Perl 5.10 introduced a number of "Special Backtracking Control  Verbs",
4724           which are described in the Perl documentation as "experimental and sub-
4725           ject to change or removal in a future version of Perl". It goes  on  to
4726           say:  "Their usage in production code should be noted to avoid problems
4727           during upgrades." The same remarks apply to the PCRE features described
4728           in this section.
4729    
4730           Since these verbs are specifically related to backtracking, they can be
4731           used only when the pattern is to be matched  using  pcre_exec(),  which
4732           uses  a  backtracking  algorithm. They cause an error if encountered by
4733           pcre_dfa_exec().
4734    
4735           The new verbs make use of what was previously invalid syntax: an  open-
4736           ing parenthesis followed by an asterisk. In Perl, they are generally of
4737           the form (*VERB:ARG) but PCRE does not support the use of arguments, so
4738           its  general  form is just (*VERB). Any number of these verbs may occur
4739           in a pattern. There are two kinds:
4740    
4741       Verbs that act immediately
4742    
4743           The following verbs act as soon as they are encountered:
4744    
4745              (*ACCEPT)
4746    
4747           This verb causes the match to end successfully, skipping the  remainder
4748           of  the pattern. When inside a recursion, only the innermost pattern is
4749           ended immediately. PCRE differs  from  Perl  in  what  happens  if  the
4750           (*ACCEPT)  is inside capturing parentheses. In Perl, the data so far is
4751           captured: in PCRE no data is captured. For example:
4752    
4753             A(A|B(*ACCEPT)|C)D
4754    
4755           This matches "AB", "AAD", or "ACD", but when it matches "AB",  no  data
4756           is captured.
4757    
4758             (*FAIL) or (*F)
4759    
4760           This  verb  causes the match to fail, forcing backtracking to occur. It
4761           is equivalent to (?!) but easier to read. The Perl documentation  notes
4762           that  it  is  probably  useful only when combined with (?{}) or (??{}).
4763           Those are, of course, Perl features that are not present in  PCRE.  The
4764           nearest  equivalent is the callout feature, as for example in this pat-
4765           tern:
4766    
4767             a+(?C)(*FAIL)
4768    
4769           A match with the string "aaaa" always fails, but the callout  is  taken
4770           before each backtrack happens (in this example, 10 times).
4771    
4772       Verbs that act after backtracking
4773    
4774           The following verbs do nothing when they are encountered. Matching con-
4775           tinues with what follows, but if there is no subsequent match, a  fail-
4776           ure  is  forced.   The  verbs  differ  in  exactly what kind of failure
4777           occurs.
4778    
4779             (*COMMIT)
4780    
4781           This verb causes the whole match to fail outright if the  rest  of  the
4782           pattern  does  not match. Even if the pattern is unanchored, no further
4783           attempts to find a match by advancing the start point take place.  Once
4784           (*COMMIT)  has been passed, pcre_exec() is committed to finding a match
4785           at the current starting point, or not at all. For example:
4786    
4787             a+(*COMMIT)b
4788    
4789           This matches "xxaab" but not "aacaab". It can be thought of as  a  kind
4790           of dynamic anchor, or "I've started, so I must finish."
4791    
4792             (*PRUNE)
4793    
4794           This  verb causes the match to fail at the current position if the rest
4795           of the pattern does not match. If the pattern is unanchored, the normal
4796           "bumpalong"  advance to the next starting character then happens. Back-
4797           tracking can occur as usual to the left of (*PRUNE), or  when  matching
4798           to  the right of (*PRUNE), but if there is no match to the right, back-
4799           tracking cannot cross (*PRUNE).  In simple cases, the use  of  (*PRUNE)
4800           is just an alternative to an atomic group or possessive quantifier, but
4801           there are some uses of (*PRUNE) that cannot be expressed in  any  other
4802           way.
4803    
4804             (*SKIP)
4805    
4806           This  verb  is like (*PRUNE), except that if the pattern is unanchored,
4807           the "bumpalong" advance is not to the next character, but to the  posi-
4808           tion  in  the  subject where (*SKIP) was encountered. (*SKIP) signifies
4809           that whatever text was matched leading up to it cannot  be  part  of  a
4810           successful match. Consider:
4811    
4812             a+(*SKIP)b
4813    
4814           If  the  subject  is  "aaaac...",  after  the first match attempt fails
4815           (starting at the first character in the  string),  the  starting  point
4816           skips on to start the next attempt at "c". Note that a possessive quan-
4817           tifer does not have the same effect in this example; although it  would
4818           suppress  backtracking  during  the  first  match  attempt,  the second
4819           attempt would start at the second character instead of skipping  on  to
4820           "c".
4821    
4822             (*THEN)
4823    
4824           This verb causes a skip to the next alternation if the rest of the pat-
4825           tern does not match. That is, it cancels pending backtracking, but only
4826           within  the  current  alternation.  Its name comes from the observation
4827           that it can be used for a pattern-based if-then-else block:
4828    
4829             ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
4830    
4831           If the COND1 pattern matches, FOO is tried (and possibly further  items
4832           after  the  end  of  the group if FOO succeeds); on failure the matcher
4833           skips to the second alternative and tries COND2,  without  backtracking
4834           into  COND1.  If  (*THEN)  is  used outside of any alternation, it acts
4835           exactly like (*PRUNE).
4836    
4837    
4838  SEE ALSO  SEE ALSO
4839    
4840         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
# Line 4549  AUTHOR Line 4849  AUTHOR
4849    
4850  REVISION  REVISION
4851    
4852         Last updated: 06 August 2007         Last updated: 11 September 2007
4853         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
4854  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
4855    
# Line 4828  CONDITIONAL PATTERNS Line 5128  CONDITIONAL PATTERNS
5128           (?(assert)...  assertion condition           (?(assert)...  assertion condition
5129    
5130    
5131    BACKTRACKING CONTROL
5132    
5133           The following act immediately they are reached:
5134    
5135             (*ACCEPT)      force successful match
5136             (*FAIL)        force backtrack; synonym (*F)
5137    
5138           The following act only when a subsequent match failure causes  a  back-
5139           track to reach them. They all force a match failure, but they differ in
5140           what happens afterwards. Those that advance the start-of-match point do
5141           so only if the pattern is not anchored.
5142    
5143             (*COMMIT)      overall failure, no advance of starting point
5144             (*PRUNE)       advance to next starting character
5145             (*SKIP)        advance start to current matching position
5146             (*THEN)        local failure, backtrack to next alternation
5147    
5148    
5149    NEWLINE CONVENTIONS
5150    
5151           These are recognized only at the very start of a pattern.
5152    
5153             (*CR)
5154             (*LF)
5155             (*CRLF)
5156             (*ANYCRLF)
5157             (*ANY)
5158    
5159    
5160    WHAT \R MATCHES
5161    
5162           These are recognized only at the very start of a pattern.
5163    
5164             (*BSR_ANYCRLF)
5165             (*BSR_UNICODE)
5166    
5167    
5168  CALLOUTS  CALLOUTS
5169    
5170           (?C)      callout           (?C)      callout
# Line 4848  AUTHOR Line 5185  AUTHOR
5185    
5186  REVISION  REVISION
5187    
5188         Last updated: 06 August 2007         Last updated: 11 September 2007
5189         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
5190  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5191    

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