/[pcre]/code/trunk/doc/pcre.txt
ViewVC logotype

Diff of /code/trunk/doc/pcre.txt

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 548 by ph10, Fri Jun 25 14:42:00 2010 UTC revision 659 by ph10, Tue Aug 16 09:48:29 2011 UTC
# Line 26  INTRODUCTION Line 26  INTRODUCTION
26         give better JavaScript compatibility.         give better JavaScript compatibility.
27    
28         The  current implementation of PCRE corresponds approximately with Perl         The  current implementation of PCRE corresponds approximately with Perl
29         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         eral  category properties. However, UTF-8 and Unicode support has to be         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         explicitly enabled; it is not the default. The  Unicode  tables  corre-         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32         spond to Unicode release 5.2.0.         spond to Unicode release 6.0.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative function that matches the same compiled patterns in a  dif-         alternative function that matches the same compiled patterns in a  dif-
# Line 181  UTF-8 AND UNICODE PROPERTY SUPPORT Line 181  UTF-8 AND UNICODE PROPERTY SUPPORT
181         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184         If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return         If an invalid UTF-8 string is passed to PCRE, an error return is given.
185         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know         At compile time, the only additional information is the offset  to  the
186         that your strings are valid, and therefore want to skip these checks in         first byte of the failing character. The runtime functions (pcre_exec()
187         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at         and pcre_dfa_exec()), pass back this information  as  well  as  a  more
188         compile  time  or at run time, PCRE assumes that the pattern or subject         detailed  reason  code if the caller has provided memory in which to do
189         it is given (respectively) contains only valid  UTF-8  codes.  In  this         this.
190         case, it does not diagnose an invalid UTF-8 string.  
191           In some situations, you may already know that your strings  are  valid,
192           and  therefore  want  to  skip these checks in order to improve perfor-
193           mance. If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run
194           time,  PCRE  assumes  that  the pattern or subject it is given (respec-
195           tively) contains only valid UTF-8 codes. In  this  case,  it  does  not
196           diagnose an invalid UTF-8 string.
197    
198         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
199         what happens depends on why the string is invalid. If the  string  con-         what happens depends on why the string is invalid. If the  string  con-
# Line 226  UTF-8 AND UNICODE PROPERTY SUPPORT Line 232  UTF-8 AND UNICODE PROPERTY SUPPORT
232         PCRE  recognizes  as digits, spaces, or word characters remain the same         PCRE  recognizes  as digits, spaces, or word characters remain the same
233         set as before, all with values less than 256. This  remains  true  even         set as before, all with values less than 256. This  remains  true  even
234         when  PCRE  is built to include Unicode property support, because to do         when  PCRE  is built to include Unicode property support, because to do
235         otherwise would slow down PCRE in many common  cases.  Note  that  this         otherwise would slow down PCRE in many common cases. Note in particular
236         also applies to \b, because it is defined in terms of \w and \W. If you         that this applies to \b and \B, because they are defined in terms of \w
237         really want to test for a wider sense of, say,  "digit",  you  can  use         and \W. If you really want to test for a wider sense of, say,  "digit",
238         explicit  Unicode property tests such as \p{Nd}.  Alternatively, if you         you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
239         set the PCRE_UCP option, the way that the  character  escapes  work  is         tively, if you set the PCRE_UCP option,  the  way  that  the  character
240         changed  so that Unicode properties are used to determine which charac-         escapes  work  is changed so that Unicode properties are used to deter-
241         ters match. There are more details in the section on generic  character         mine which characters match. There are more details in the  section  on
242         types in the pcrepattern documentation.         generic character types in the pcrepattern documentation.
243    
244         7.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
245         are all low-valued characters, unless the PCRE_UCP option is set.         are all low-valued characters, unless the PCRE_UCP option is set.
246    
247         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching         8. However, the horizontal and  vertical  whitespace  matching  escapes
248         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-         (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
249         acters, whether or not PCRE_UCP is set.         whether or not PCRE_UCP is set.
250    
251         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
252         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
253         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
254         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
255         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
256         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Furthermore, PCRE supports
257         support is available, PCRE supports case-insensitive matching only when         case-insensitive matching only  when  there  is  a  one-to-one  mapping
258         there  is  a  one-to-one  mapping between a letter's cases. There are a         between  a letter's cases. There are a small number of many-to-one map-
259         small number of many-to-one mappings in Unicode;  these  are  not  sup-         pings in Unicode; these are not supported by PCRE.
        ported by PCRE.  
260    
261    
262  AUTHOR  AUTHOR
# Line 260  AUTHOR Line 265  AUTHOR
265         University Computing Service         University Computing Service
266         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
267    
268         Putting  an actual email address here seems to have been a spam magnet,         Putting an actual email address here seems to have been a spam  magnet,
269         so I've taken it away. If you want to email me, use  my  two  initials,         so  I've  taken  it away. If you want to email me, use my two initials,
270         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
271    
272    
273  REVISION  REVISION
274    
275         Last updated: 12 May 2010         Last updated: 07 May 2011
276         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
277  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
278    
279    
# Line 308  PCRE BUILD-TIME OPTIONS Line 313  PCRE BUILD-TIME OPTIONS
313         is not described.         is not described.
314    
315    
316    BUILDING SHARED AND STATIC LIBRARIES
317    
318           The  PCRE building process uses libtool to build both shared and static
319           Unix libraries by default. You can suppress one of these by adding  one
320           of
321    
322             --disable-shared
323             --disable-static
324    
325           to the configure command, as required.
326    
327    
328  C++ SUPPORT  C++ SUPPORT
329    
330         By default, the configure script will search for a C++ compiler and C++         By default, the configure script will search for a C++ compiler and C++
# Line 401  WHAT \R MATCHES Line 418  WHAT \R MATCHES
418         functions are called.         functions are called.
419    
420    
 BUILDING SHARED AND STATIC LIBRARIES  
   
        The  PCRE building process uses libtool to build both shared and static  
        Unix libraries by default. You can suppress one of these by adding  one  
        of  
   
          --disable-shared  
          --disable-static  
   
        to the configure command, as required.  
   
   
421  POSIX MALLOC USAGE  POSIX MALLOC USAGE
422    
423         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
# Line 553  PCREGREP OPTIONS FOR COMPRESSED FILE SUP Line 558  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
558         if they are not.         if they are not.
559    
560    
561    PCREGREP BUFFER SIZE
562    
563           pcregrep  uses  an internal buffer to hold a "window" on the file it is
564           scanning, in order to be able to output "before" and "after" lines when
565           it  finds  a match. The size of the buffer is controlled by a parameter
566           whose default value is 20K. The buffer itself is three times this size,
567           but because of the way it is used for holding "before" lines, the long-
568           est line that is guaranteed to be processable is  the  parameter  size.
569           You can change the default parameter value by adding, for example,
570    
571             --with-pcregrep-bufsize=50K
572    
573           to the configure command. The caller of pcregrep can, however, override
574           this value by specifying a run-time option.
575    
576    
577  PCRETEST OPTION FOR LIBREADLINE SUPPORT  PCRETEST OPTION FOR LIBREADLINE SUPPORT
578    
579         If you add         If you add
580    
581           --enable-pcretest-libreadline           --enable-pcretest-libreadline
582    
583         to  the  configure  command,  pcretest  is  linked with the libreadline         to the configure command,  pcretest  is  linked  with  the  libreadline
584         library, and when its input is from a terminal, it reads it  using  the         library,  and  when its input is from a terminal, it reads it using the
585         readline() function. This provides line-editing and history facilities.         readline() function. This provides line-editing and history facilities.
586         Note that libreadline is GPL-licensed, so if you distribute a binary of         Note that libreadline is GPL-licensed, so if you distribute a binary of
587         pcretest linked in this way, there may be licensing issues.         pcretest linked in this way, there may be licensing issues.
588    
589         Setting  this  option  causes  the -lreadline option to be added to the         Setting this option causes the -lreadline option to  be  added  to  the
590         pcretest build. In many operating environments with  a  sytem-installed         pcretest  build.  In many operating environments with a sytem-installed
591         libreadline this is sufficient. However, in some environments (e.g.  if         libreadline this is sufficient. However, in some environments (e.g.  if
592         an unmodified distribution version of readline is in use),  some  extra         an  unmodified  distribution version of readline is in use), some extra
593         configuration  may  be necessary. The INSTALL file for libreadline says         configuration may be necessary. The INSTALL file for  libreadline  says
594         this:         this:
595    
596           "Readline uses the termcap functions, but does not link with the           "Readline uses the termcap functions, but does not link with the
597           termcap or curses library itself, allowing applications which link           termcap or curses library itself, allowing applications which link
598           with readline the to choose an appropriate library."           with readline the to choose an appropriate library."
599    
600         If your environment has not been set up so that an appropriate  library         If  your environment has not been set up so that an appropriate library
601         is automatically included, you may need to add something like         is automatically included, you may need to add something like
602    
603           LIBS="-ncurses"           LIBS="-ncurses"
# Line 598  AUTHOR Line 619  AUTHOR
619    
620  REVISION  REVISION
621    
622         Last updated: 29 September 2009         Last updated: 02 August 2011
623         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
624  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
625    
626    
# Line 697  THE ALTERNATIVE MATCHING ALGORITHM Line 718  THE ALTERNATIVE MATCHING ALGORITHM
718         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
719         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
720         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
721         est.  There  is  an  option to stop the algorithm after the first match         est.  The  matches are returned in decreasing order of length. There is
722         (which is necessarily the shortest) is found.         an option to stop the algorithm after the first match (which is  neces-
723           sarily the shortest) is found.
724    
725         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
726         subject. If the pattern         subject. If the pattern
727    
728           cat(er(pillar)?)           cat(er(pillar)?)?
729    
730         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
731         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
732         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
733         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
734    
735         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
736         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
737    
738         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
739         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
740         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
741         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
742         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
743    
744           ^a++\w!           ^a++\w!
745    
746         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
747         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
748         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
749         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
750         pattern.         pattern.
751    
752         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
753         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
754         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
755         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
756         strings are available.         strings are available.
757    
758         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
759         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
760    
761         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
762         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
763         supported.         supported.
764    
765         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
766         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
767         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
768         error if encountered.         error if encountered.
769    
770         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
771         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.
772    
773         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
774         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-
775         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
776         time, for all active paths through the tree.         time, for all active paths through the tree.
777    
778         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
779         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
780         negative assertion.         negative assertion.
781    
782    
783  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
784    
785         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
786         tages:         tages:
787    
788         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-
789         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
790         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
791         things with callouts.         things with callouts.
792    
793         2.  Because  the  alternative  algorithm  scans the subject string just         2. Because the alternative algorithm  scans  the  subject  string  just
794         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
795         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
796         for partial matching each time.  The  pcrepartial  documentation  gives         for  partial  matching  each time. Although it is possible to do multi-
797         details of partial matching.         segment matching using the standard algorithm (pcre_exec()), by retain-
798           ing  partially matched substrings, it is more complicated. The pcrepar-
799           tial documentation gives details  of  partial  matching  and  discusses
800           multi-segment matching.
801    
802    
803  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 798  AUTHOR Line 823  AUTHOR
823    
824  REVISION  REVISION
825    
826         Last updated: 29 September 2009         Last updated: 17 November 2010
827         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
828  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
829    
830    
# Line 1162  COMPILING A PATTERN Line 1187  COMPILING A PATTERN
1187         pcrepattern documentation). For those options that can be different  in         pcrepattern documentation). For those options that can be different  in
1188         different  parts  of  the pattern, the contents of the options argument         different  parts  of  the pattern, the contents of the options argument
1189         specifies their settings at the start of compilation and execution. The         specifies their settings at the start of compilation and execution. The
1190         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1191         the time of matching as well as at compile time.         PCRE_NO_START_OPT options can be set at the time of matching as well as
1192           at compile time.
1193    
1194         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1195         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1196         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-
1197         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
1198         try to free it. The byte offset from the start of the  pattern  to  the         try  to  free it. Normally, the offset from the start of the pattern to
1199         character  that  was  being  processed when the error was discovered is         the byte that was being processed when  the  error  was  discovered  is
1200         placed in the variable pointed to by erroffset, which must not be NULL.         placed  in the variable pointed to by erroffset, which must not be NULL
1201         If  it  is,  an  immediate error is given. Some errors are not detected         (if it is, an immediate error is given). However, for an invalid  UTF-8
1202         until checks are carried out when the whole pattern has  been  scanned;         string,  the offset is that of the first byte of the failing character.
1203         in this case the offset is set to the end of the pattern.         Also, some errors are not detected until checks are  carried  out  when
1204           the  whole  pattern  has been scanned; in these cases the offset passed
1205           back is the length of the pattern.
1206    
1207           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1208           It may sometimes point into the middle of a UTF-8 character.
1209    
1210         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1211         codeptr argument is not NULL, a non-zero error code number is  returned         codeptr argument is not NULL, a non-zero error code number is  returned
# Line 1252  COMPILING A PATTERN Line 1283  COMPILING A PATTERN
1283    
1284           PCRE_DOTALL           PCRE_DOTALL
1285    
1286         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
1287         acters,  including  those that indicate newline. Without it, a dot does         acter of any value, including one that indicates a newline. However, it
1288         not match when the current position is at a  newline.  This  option  is         only ever matches one character, even if newlines are  coded  as  CRLF.
1289         equivalent  to Perl's /s option, and it can be changed within a pattern         Without  this option, a dot does not match when the current position is
1290         by a (?s) option setting. A negative class such as [^a] always  matches         at a newline. This option is equivalent to Perl's /s option, and it can
1291         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1292           such as [^a] always matches newline characters, independent of the set-
1293           ting of this option.
1294    
1295           PCRE_DUPNAMES           PCRE_DUPNAMES
1296    
# Line 1277  COMPILING A PATTERN Line 1310  COMPILING A PATTERN
1310         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-
1311         ting.         ting.
1312    
1313         This  option  makes  it possible to include comments inside complicated         Which  characters  are  interpreted  as  newlines  is controlled by the
1314         patterns.  Note, however, that this applies only  to  data  characters.         options passed to pcre_compile() or by a special sequence at the  start
1315         Whitespace   characters  may  never  appear  within  special  character         of  the  pattern, as described in the section entitled "Newline conven-
1316         sequences in a pattern, for  example  within  the  sequence  (?(  which         tions" in the pcrepattern documentation. Note that the end of this type
1317         introduces a conditional subpattern.         of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1318           sequences that happen to represent a newline do not count.
1319    
1320           This option makes it possible to include  comments  inside  complicated
1321           patterns.   Note,  however,  that this applies only to data characters.
1322           Whitespace  characters  may  never  appear  within  special   character
1323           sequences in a pattern, for example within the sequence (?( that intro-
1324           duces a conditional subpattern.
1325    
1326           PCRE_EXTRA           PCRE_EXTRA
1327    
1328         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1329         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
1330         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
1331         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1332         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1333         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
1334         literal. (Perl can, however, be persuaded to give an error for this, by         literal. (Perl can, however, be persuaded to give an error for this, by
1335         running it with the -w option.) There are at present no other  features         running  it with the -w option.) There are at present no other features
1336         controlled  by this option. It can also be set by a (?X) option setting         controlled by this option. It can also be set by a (?X) option  setting
1337         within a pattern.         within a pattern.
1338    
1339           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1340    
1341         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1342         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1343         matched text may continue over the newline.         matched text may continue over the newline.
1344    
1345           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1346    
1347         If this option is set, PCRE's behaviour is changed in some ways so that         If this option is set, PCRE's behaviour is changed in some ways so that
1348         it  is  compatible with JavaScript rather than Perl. The changes are as         it is compatible with JavaScript rather than Perl. The changes  are  as
1349         follows:         follows:
1350    
1351         (1) A lone closing square bracket in a pattern  causes  a  compile-time         (1)  A  lone  closing square bracket in a pattern causes a compile-time
1352         error,  because this is illegal in JavaScript (by default it is treated         error, because this is illegal in JavaScript (by default it is  treated
1353         as a data character). Thus, the pattern AB]CD becomes illegal when this         as a data character). Thus, the pattern AB]CD becomes illegal when this
1354         option is set.         option is set.
1355    
1356         (2)  At run time, a back reference to an unset subpattern group matches         (2) At run time, a back reference to an unset subpattern group  matches
1357         an empty string (by default this causes the current  matching  alterna-         an  empty  string (by default this causes the current matching alterna-
1358         tive  to  fail). A pattern such as (\1)(a) succeeds when this option is         tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1359         set (assuming it can find an "a" in the subject), whereas it  fails  by         set  (assuming  it can find an "a" in the subject), whereas it fails by
1360         default, for Perl compatibility.         default, for Perl compatibility.
1361    
1362           PCRE_MULTILINE           PCRE_MULTILINE
1363    
1364         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1365         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1366         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1367         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1368         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1369         is set). This is the same as Perl.         is set). This is the same as Perl.
1370    
1371         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"
1372         constructs  match  immediately following or immediately before internal         constructs match immediately following or immediately  before  internal
1373         newlines in the subject string, respectively, as well as  at  the  very         newlines  in  the  subject string, respectively, as well as at the very
1374         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
1375         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-
1376         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,
1377         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1378    
1379           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1342  COMPILING A PATTERN Line 1382  COMPILING A PATTERN
1382           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1383           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1384    
1385         These options override the default newline definition that  was  chosen         These  options  override the default newline definition that was chosen
1386         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
1387         newline is indicated by a single character (CR  or  LF,  respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1388         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1389         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1390         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1391         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1392         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1393         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1394         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
1395         (paragraph separator, U+2029). The last  two  are  recognized  only  in         (paragraph  separator,  U+2029).  The  last  two are recognized only in
1396         UTF-8 mode.         UTF-8 mode.
1397    
1398         The  newline  setting  in  the  options  word  uses three bits that are         The newline setting in the  options  word  uses  three  bits  that  are
1399         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1400         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
1401         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-
1402         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
1403         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1404         cause an error.         cause an error.
1405    
1406         The  only time that a line break is specially recognized when compiling         The only time that a line break in a pattern  is  specially  recognized
1407         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a         when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1408         character  class  is  encountered.  This indicates a comment that lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1409         until after the next line break sequence. In other circumstances,  line         side  a  character class indicates a comment that lasts until after the
1410         break   sequences   are   treated  as  literal  data,  except  that  in         next line break sequence. In other circumstances, line break  sequences
1411         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1412    
1413         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
1414         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.
# Line 1382  COMPILING A PATTERN Line 1421  COMPILING A PATTERN
1421         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1422         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1423    
1424             NO_START_OPTIMIZE
1425    
1426           This is an option that acts at matching time; that is, it is really  an
1427           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1428           time, it is remembered with the compiled pattern and assumed at  match-
1429           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1430           below.
1431    
1432           PCRE_UCP           PCRE_UCP
1433    
1434         This option changes the way PCRE processes \b, \d, \s, \w, and some  of         This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1435         the POSIX character classes. By default, only ASCII characters are rec-         \w,  and  some  of  the POSIX character classes. By default, only ASCII
1436         ognized, but if PCRE_UCP is set, Unicode properties are used instead to         characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1437         classify  characters.  More details are given in the section on generic         are  used instead to classify characters. More details are given in the
1438         character types in the pcrepattern page. If you set PCRE_UCP,  matching         section on generic character types in the pcrepattern page. If you  set
1439         one  of the items it affects takes much longer. The option is available         PCRE_UCP,  matching  one of the items it affects takes much longer. The
1440         only if PCRE has been compiled with Unicode property support.         option is available only if PCRE has been compiled with  Unicode  prop-
1441           erty support.
1442    
1443           PCRE_UNGREEDY           PCRE_UNGREEDY
1444    
1445         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1446         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
1447         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
1448         within the pattern.         within the pattern.
1449    
1450           PCRE_UTF8           PCRE_UTF8
1451    
1452         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
1453         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1454         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-
1455         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
1456         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
1457         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1458    
1459           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1460    
1461         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
1462         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1463         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1464         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1465         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1466         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1467         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1468         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1469         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1470         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1471    
1472    
1473  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1474    
1475         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1476         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1477         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1478         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1479    
1480            0  no error            0  no error
# Line 1466  COMPILATION ERROR CODES Line 1514  COMPILATION ERROR CODES
1514           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1515           35  invalid condition (?(0)           35  invalid condition (?(0)
1516           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1517           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1518           38  number after (?C is > 255           38  number after (?C is > 255
1519           39  closing ) for (?C expected           39  closing ) for (?C expected
1520           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1500  COMPILATION ERROR CODES Line 1548  COMPILATION ERROR CODES
1548                 not allowed                 not allowed
1549           66  (*MARK) must have an argument           66  (*MARK) must have an argument
1550           67  this version of PCRE is not compiled with PCRE_UCP support           67  this version of PCRE is not compiled with PCRE_UCP support
1551             68  \c must be followed by an ASCII character
1552             69  \k is not followed by a braced, angle-bracketed, or quoted name
1553    
1554         The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1555         values may be used if the limits were changed when PCRE was built.         values may be used if the limits were changed when PCRE was built.
1556    
1557    
# Line 1510  STUDYING A PATTERN Line 1560  STUDYING A PATTERN
1560         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1561              const char **errptr);              const char **errptr);
1562    
1563         If  a  compiled  pattern is going to be used several times, it is worth         If a compiled pattern is going to be used several times,  it  is  worth
1564         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1565         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1566         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1567         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1568         pointer to a pcre_extra block, in which the study_data field points  to         pointer  to a pcre_extra block, in which the study_data field points to
1569         the results of the study.         the results of the study.
1570    
1571         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1572         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1573         tains  other  fields  that can be set by the caller before the block is         tains other fields that can be set by the caller before  the  block  is
1574         passed; these are described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1575    
1576         If studying the  pattern  does  not  produce  any  useful  information,         If  studying  the  pattern  does  not  produce  any useful information,
1577         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1578         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1579         pcre_dfa_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1580    
1581         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1582         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1583    
1584         The third argument for pcre_study() is a pointer for an error  message.         The  third argument for pcre_study() is a pointer for an error message.
1585         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1586         points to is set to NULL. Otherwise it is set to  point  to  a  textual         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1587         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1588         must not try to free it. You should test the  error  pointer  for  NULL         must  not  try  to  free it. You should test the error pointer for NULL
1589         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1590    
1591         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1549  STUDYING A PATTERN Line 1599  STUDYING A PATTERN
1599         Studying a pattern does two things: first, a lower bound for the length         Studying a pattern does two things: first, a lower bound for the length
1600         of subject string that is needed to match the pattern is computed. This         of subject string that is needed to match the pattern is computed. This
1601         does not mean that there are any strings of that length that match, but         does not mean that there are any strings of that length that match, but
1602         it does guarantee that no shorter strings match. The value is  used  by         it  does  guarantee that no shorter strings match. The value is used by
1603         pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to         pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1604         match strings that are shorter than the lower bound. You can  find  out         match  strings  that are shorter than the lower bound. You can find out
1605         the value in a calling program via the pcre_fullinfo() function.         the value in a calling program via the pcre_fullinfo() function.
1606    
1607         Studying a pattern is also useful for non-anchored patterns that do not         Studying a pattern is also useful for non-anchored patterns that do not
1608         have a single fixed starting character. A bitmap of  possible  starting         have  a  single fixed starting character. A bitmap of possible starting
1609         bytes  is  created. This speeds up finding a position in the subject at         bytes is created. This speeds up finding a position in the  subject  at
1610         which to start matching.         which to start matching.
1611    
1612         The two optimizations just described can be  disabled  by  setting  the         The  two  optimizations  just  described can be disabled by setting the
1613         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or         PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1614         pcre_dfa_exec(). You might want to do this  if  your  pattern  contains         pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1615         callouts,  or  make  use of (*MARK), and you make use of these in cases         callouts or (*MARK), and you want to make use of  these  facilities  in
1616         where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE         cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1617         below.         MIZE below.
1618    
1619    
1620  LOCALE SUPPORT  LOCALE SUPPORT
1621    
1622         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1623         letters, digits, or whatever, by reference to a set of tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1624         by  character  value.  When running in UTF-8 mode, this applies only to         by character value. When running in UTF-8 mode, this  applies  only  to
1625         characters with codes less than 128. By  default,  higher-valued  codes         characters  with  codes  less than 128. By default, higher-valued codes
1626         never match escapes such as \w or \d, but they can be tested with \p if         never match escapes such as \w or \d, but they can be tested with \p if
1627         PCRE is built with Unicode character property  support.  Alternatively,         PCRE  is  built with Unicode character property support. Alternatively,
1628         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1629         friends to use Unicode property support instead of built-in tables. The         friends to use Unicode property support instead of built-in tables. The
1630         use of locales with Unicode is discouraged. If you are handling charac-         use of locales with Unicode is discouraged. If you are handling charac-
1631         ters with codes greater than 128, you should either use UTF-8 and  Uni-         ters  with codes greater than 128, you should either use UTF-8 and Uni-
1632         code, or use locales, but not try to mix the two.         code, or use locales, but not try to mix the two.
1633    
1634         PCRE  contains  an  internal set of tables that are used when the final         PCRE contains an internal set of tables that are used  when  the  final
1635         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1636         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1637         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1638         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1639         which may cause them to be different.         which may cause them to be different.
1640    
1641         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
1642         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1643         from the default. As more and more applications change  to  using  Uni-         from  the  default.  As more and more applications change to using Uni-
1644         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1645    
1646         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
1647         which has no arguments, in the relevant locale. The result can then  be         which  has no arguments, in the relevant locale. The result can then be
1648         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1649         example, to build and use tables that are appropriate  for  the  French         example,  to  build  and use tables that are appropriate for the French
1650         locale  (where  accented  characters  with  values greater than 128 are         locale (where accented characters with  values  greater  than  128  are
1651         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1652    
1653           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1654           tables = pcre_maketables();           tables = pcre_maketables();
1655           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1656    
1657         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1658         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1659    
1660         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1661         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1662         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1663         it is needed.         it is needed.
1664    
1665         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1666         pattern,  and the same tables are used via this pointer by pcre_study()         pattern, and the same tables are used via this pointer by  pcre_study()
1667         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1668         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1669         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1670    
1671         It is possible to pass a table pointer or NULL (indicating the  use  of         It  is  possible to pass a table pointer or NULL (indicating the use of
1672         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1673         purpose, this facility could be used to match a pattern in a  different         purpose,  this facility could be used to match a pattern in a different
1674         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1675         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1676    
# Line 1630  INFORMATION ABOUT A PATTERN Line 1680  INFORMATION ABOUT A PATTERN
1680         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1681              int what, void *where);              int what, void *where);
1682    
1683         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1684         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1685         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1686    
1687         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1688         pattern.  The second argument is the result of pcre_study(), or NULL if         pattern. The second argument is the result of pcre_study(), or NULL  if
1689         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1690         of  information  is required, and the fourth argument is a pointer to a         of information is required, and the fourth argument is a pointer  to  a
1691         variable to receive the data. The yield of the  function  is  zero  for         variable  to  receive  the  data. The yield of the function is zero for
1692         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1693    
1694           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1646  INFORMATION ABOUT A PATTERN Line 1696  INFORMATION ABOUT A PATTERN
1696           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1697           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1698    
1699         The  "magic  number" is placed at the start of each compiled pattern as         The "magic number" is placed at the start of each compiled  pattern  as
1700         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1701         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1702         pattern:         pattern:
1703    
1704           int rc;           int rc;
# Line 1659  INFORMATION ABOUT A PATTERN Line 1709  INFORMATION ABOUT A PATTERN
1709             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1710             &length);         /* where to put the data */             &length);         /* where to put the data */
1711    
1712         The possible values for the third argument are defined in  pcre.h,  and         The  possible  values for the third argument are defined in pcre.h, and
1713         are as follows:         are as follows:
1714    
1715           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1716    
1717         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1718         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1719         there are no back references.         there are no back references.
1720    
1721           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1722    
1723         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1724         argument should point to an int variable.         argument should point to an int variable.
1725    
1726           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1727    
1728         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1729         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1730         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1731         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1732         passing a NULL table pointer.         passing a NULL table pointer.
1733    
1734           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1735    
1736         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1737         non-anchored  pattern. The fourth argument should point to an int vari-         non-anchored pattern. The fourth argument should point to an int  vari-
1738         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1739         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1740    
1741         If  there  is  a  fixed first byte, for example, from a pattern such as         If there is a fixed first byte, for example, from  a  pattern  such  as
1742         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1743    
1744         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1745         branch starts with "^", or         branch starts with "^", or
1746    
1747         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1748         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1749    
1750         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1751         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1752         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1753    
1754           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1755    
1756         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
1757         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1758         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1759         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1760         able.         able.
1761    
1762           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1763    
1764         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF         Return  1  if  the  pattern  contains any explicit matches for CR or LF
1765         characters,  otherwise  0.  The  fourth argument should point to an int         characters, otherwise 0. The fourth argument should  point  to  an  int
1766         variable. An explicit match is either a literal CR or LF character,  or         variable.  An explicit match is either a literal CR or LF character, or
1767         \r or \n.         \r or \n.
1768    
1769           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1770    
1771         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1772         otherwise 0. The fourth argument should point to an int variable.  (?J)         otherwise  0. The fourth argument should point to an int variable. (?J)
1773         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1774    
1775           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1776    
1777         Return  the  value of the rightmost literal byte that must exist in any         Return the value of the rightmost literal byte that must exist  in  any
1778         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1779         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1780         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1781         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1782         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1783         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1784    
1785           PCRE_INFO_MINLENGTH           PCRE_INFO_MINLENGTH
1786    
1787         If  the  pattern  was studied and a minimum length for matching subject         If the pattern was studied and a minimum length  for  matching  subject
1788         strings was computed, its value is  returned.  Otherwise  the  returned         strings  was  computed,  its  value is returned. Otherwise the returned
1789         value  is  -1. The value is a number of characters, not bytes (this may         value is -1. The value is a number of characters, not bytes  (this  may
1790         be relevant in UTF-8 mode). The fourth argument should point to an  int         be  relevant in UTF-8 mode). The fourth argument should point to an int
1791         variable.  A  non-negative  value is a lower bound to the length of any         variable. A non-negative value is a lower bound to the  length  of  any
1792         matching string. There may not be any strings of that  length  that  do         matching  string.  There  may not be any strings of that length that do
1793         actually match, but every string that does match is at least that long.         actually match, but every string that does match is at least that long.
1794    
1795           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1796           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1797           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1798    
1799         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1800         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1801         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1802         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1803         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1804         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1805         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1806         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1807         described by these three values.         described by these three values.
1808    
1809         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1810         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1811         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1812         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1813         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1814         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1815         sis,  most  significant byte first. The rest of the entry is the corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1816         sponding name, zero terminated.         sponding name, zero terminated.
1817    
1818         The names are in alphabetical order. Duplicate names may appear if  (?|         The  names are in alphabetical order. Duplicate names may appear if (?|
1819         is used to create multiple groups with the same number, as described in         is used to create multiple groups with the same number, as described in
1820         the section on duplicate subpattern numbers in  the  pcrepattern  page.         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1821         Duplicate  names  for  subpatterns with different numbers are permitted         Duplicate names for subpatterns with different  numbers  are  permitted
1822         only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they         only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1823         appear  in  the table in the order in which they were found in the pat-         appear in the table in the order in which they were found in  the  pat-
1824         tern. In the absence of (?| this is the  order  of  increasing  number;         tern.  In  the  absence  of (?| this is the order of increasing number;
1825         when (?| is used this is not necessarily the case because later subpat-         when (?| is used this is not necessarily the case because later subpat-
1826         terns may have lower numbers.         terns may have lower numbers.
1827    
1828         As a simple example of the name/number table,  consider  the  following         As  a  simple  example of the name/number table, consider the following
1829         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-         pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1830         lines - is ignored):         lines - is ignored):
1831    
1832           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1833           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1834    
1835         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1836         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
1837         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1838         as ??:         as ??:
1839    
# Line 1792  INFORMATION ABOUT A PATTERN Line 1842  INFORMATION ABOUT A PATTERN
1842           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1843           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1844    
1845         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1846         name-to-number map, remember that the length of the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
1847         to be different for each compiled pattern.         to be different for each compiled pattern.
1848    
1849           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1850    
1851         Return  1  if  the  pattern  can  be  used  for  partial  matching with         Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1852         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int         pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1853         variable.  From  release  8.00,  this  always  returns  1,  because the         variable. From  release  8.00,  this  always  returns  1,  because  the
1854         restrictions that previously applied  to  partial  matching  have  been         restrictions  that  previously  applied  to  partial matching have been
1855         lifted.  The  pcrepartial documentation gives details of partial match-         lifted. The pcrepartial documentation gives details of  partial  match-
1856         ing.         ing.
1857    
1858           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1859    
1860         Return a copy of the options with which the pattern was  compiled.  The         Return  a  copy of the options with which the pattern was compiled. The
1861         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1862         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1863         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1864         other words, they are the options that will be in force  when  matching         other  words,  they are the options that will be in force when matching
1865         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1866         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1867         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1868    
1869         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A pattern is automatically anchored by PCRE if  all  of  its  top-level
1870         alternatives begin with one of the following:         alternatives begin with one of the following:
1871    
1872           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1830  INFORMATION ABOUT A PATTERN Line 1880  INFORMATION ABOUT A PATTERN
1880    
1881           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1882    
1883         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of the compiled pattern, that is, the  value  that  was
1884         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1885         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1886         size_t variable.         size_t variable.
# Line 1838  INFORMATION ABOUT A PATTERN Line 1888  INFORMATION ABOUT A PATTERN
1888           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1889    
1890         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1891         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a pcre_extra block. If pcre_extra is NULL, or there is no  study  data,
1892         pcre_malloc() when PCRE was getting memory into which to place the data         zero  is  returned.  The fourth argument should point to a size_t vari-
1893         created  by  pcre_study().  If pcre_extra is NULL, or there is no study         able.  The study_data field is set by pcre_study() to  record  informa-
1894         data, zero is returned. The fourth argument should point  to  a  size_t         tion  that will speed up matching (see the section entitled "Studying a
1895         variable.         pattern" above). The format of the study_data block is private, but its
1896           length  is  made  available via this option so that it can be saved and
1897           restored (see the pcreprecompile documentation for details).
1898    
1899    
1900  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
1901    
1902         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1903    
1904         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1905         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1906         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1907         pcre_info() is the number of capturing subpatterns, or one of the  fol-         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1908         lowing negative numbers:         lowing negative numbers:
1909    
1910           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1911           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1912    
1913         If  the  optptr  argument is not NULL, a copy of the options with which         If the optptr argument is not NULL, a copy of the  options  with  which
1914         the pattern was compiled is placed in the integer  it  points  to  (see         the  pattern  was  compiled  is placed in the integer it points to (see
1915         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1916    
1917         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1918         NULL, it is used to pass back information about the first character  of         NULL,  it is used to pass back information about the first character of
1919         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1920    
1921    
# Line 1871  REFERENCE COUNTS Line 1923  REFERENCE COUNTS
1923    
1924         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1925    
1926         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1927         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1928         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1929         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1930         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1931    
1932         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1933         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1934         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1935         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1936         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1937         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1938    
1939         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1940         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1941         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1942    
1943    
# Line 1895  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1947  MATCHING A PATTERN: THE TRADITIONAL FUNC
1947              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1948              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1949    
1950         The function pcre_exec() is called to match a subject string against  a         The  function pcre_exec() is called to match a subject string against a
1951         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1952         was studied, the result of the study should  be  passed  in  the  extra         was  studied,  the  result  of  the study should be passed in the extra
1953         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1954         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1955         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1956         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1957    
1958         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1959         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1960         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1961         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1962         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1963    
1964         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1925  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1977  MATCHING A PATTERN: THE TRADITIONAL FUNC
1977    
1978     Extra data for pcre_exec()     Extra data for pcre_exec()
1979    
1980         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
1981         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
1982         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
1983         tional  information  in it. The pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
1984         fields (not necessarily in this order):         fields (not necessarily in this order):
1985    
1986           unsigned long int flags;           unsigned long int flags;
# Line 1939  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1991  MATCHING A PATTERN: THE TRADITIONAL FUNC
1991           const unsigned char *tables;           const unsigned char *tables;
1992           unsigned char **mark;           unsigned char **mark;
1993    
1994         The flags field is a bitmap that specifies which of  the  other  fields         The  flags  field  is a bitmap that specifies which of the other fields
1995         are set. The flag bits are:         are set. The flag bits are:
1996    
1997           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1949  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2001  MATCHING A PATTERN: THE TRADITIONAL FUNC
2001           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
2002           PCRE_EXTRA_MARK           PCRE_EXTRA_MARK
2003    
2004         Other  flag  bits should be set to zero. The study_data field is set in         Other flag bits should be set to zero. The study_data field is  set  in
2005         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
2006         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
2007         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
2008         flag bits.         flag bits.
2009    
2010         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
2011         a vast amount of resources when running patterns that are not going  to         a  vast amount of resources when running patterns that are not going to
2012         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
2013         search trees. The classic example is a pattern that uses nested  unlim-         search  trees. The classic example is a pattern that uses nested unlim-
2014         ited repeats.         ited repeats.
2015    
2016         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
2017         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
2018         on  the  number  of times this function is called during a match, which         on the number of times this function is called during  a  match,  which
2019         has the effect of limiting the amount of  backtracking  that  can  take         has  the  effect  of  limiting the amount of backtracking that can take
2020         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
2021         for each position in the subject string.         for each position in the subject string.
2022    
2023         The default value for the limit can be set  when  PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
2024         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
2025         cases. You can override the default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
2026         pcre_extra     block    in    which    match_limit    is    set,    and         pcre_extra    block    in    which    match_limit    is    set,     and
2027         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
2028         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2029    
2030         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
2031         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
2032         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
2033         the total number of calls, because not all calls to match() are  recur-         the  total number of calls, because not all calls to match() are recur-
2034         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
2035    
2036         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
2037         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
2038         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
2039    
2040         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
2041         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
2042         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
2043         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2044         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2045         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2046    
2047         The callout_data field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2048         ture, and is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2049    
2050         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2051         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2052         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
2053         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2054         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2055         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
2056         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2057         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2058         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2059         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2060    
2061         If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be         If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2062         set  to  point  to a char * variable. If the pattern contains any back-         set to point to a char * variable. If the pattern  contains  any  back-
2063         tracking control verbs such as (*MARK:NAME), and the execution ends  up         tracking  control verbs such as (*MARK:NAME), and the execution ends up
2064         with  a  name  to  pass back, a pointer to the name string (zero termi-         with a name to pass back, a pointer to the  name  string  (zero  termi-
2065         nated) is placed in the variable pointed to  by  the  mark  field.  The         nated)  is  placed  in  the  variable pointed to by the mark field. The
2066         names  are  within  the  compiled pattern; if you wish to retain such a         names are within the compiled pattern; if you wish  to  retain  such  a
2067         name you must copy it before freeing the memory of a compiled  pattern.         name  you must copy it before freeing the memory of a compiled pattern.
2068         If  there  is no name to pass back, the variable pointed to by the mark         If there is no name to pass back, the variable pointed to by  the  mark
2069         field set to NULL. For details of the backtracking control  verbs,  see         field  set  to NULL. For details of the backtracking control verbs, see
2070         the section entitled "Backtracking control" in the pcrepattern documen-         the section entitled "Backtracking control" in the pcrepattern documen-
2071         tation.         tation.
2072    
2073     Option bits for pcre_exec()     Option bits for pcre_exec()
2074    
2075         The unused bits of the options argument for pcre_exec() must  be  zero.         The  unused  bits of the options argument for pcre_exec() must be zero.
2076         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
2077         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2078         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2079         PCRE_PARTIAL_HARD.         PCRE_PARTIAL_HARD.
2080    
2081           PCRE_ANCHORED           PCRE_ANCHORED
2082    
2083         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
2084         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
2085         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
2086         unachored at matching time.         unachored at matching time.
2087    
2088           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
2089           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
2090    
2091         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
2092         sequence matches. The choice is either to match only CR, LF,  or  CRLF,         sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2093         or  to  match  any Unicode newline sequence. These options override the         or to match any Unicode newline sequence. These  options  override  the
2094         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
2095    
2096           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 2047  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2099  MATCHING A PATTERN: THE TRADITIONAL FUNC
2099           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2100           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2101    
2102         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
2103         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
2104         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
2105         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2106         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
2107         match failure for an unanchored pattern.         match failure for an unanchored pattern.
2108    
2109         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
2110         set, and a match attempt for an unanchored pattern fails when the  cur-         set,  and a match attempt for an unanchored pattern fails when the cur-
2111         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2112         explicit matches for  CR  or  LF  characters,  the  match  position  is         explicit  matches  for  CR  or  LF  characters,  the  match position is
2113         advanced by two characters instead of one, in other words, to after the         advanced by two characters instead of one, in other words, to after the
2114         CRLF.         CRLF.
2115    
2116         The above rule is a compromise that makes the most common cases work as         The above rule is a compromise that makes the most common cases work as
2117         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2118         option is not set), it does not match the string "\r\nA" because, after         option is not set), it does not match the string "\r\nA" because, after
2119         failing  at the start, it skips both the CR and the LF before retrying.         failing at the start, it skips both the CR and the LF before  retrying.
2120         However, the pattern [\r\n]A does match that string,  because  it  con-         However,  the  pattern  [\r\n]A does match that string, because it con-
2121         tains an explicit CR or LF reference, and so advances only by one char-         tains an explicit CR or LF reference, and so advances only by one char-
2122         acter after the first failure.         acter after the first failure.
2123    
2124         An explicit match for CR of LF is either a literal appearance of one of         An explicit match for CR of LF is either a literal appearance of one of
2125         those  characters,  or  one  of the \r or \n escape sequences. Implicit         those characters, or one of the \r or  \n  escape  sequences.  Implicit
2126         matches such as [^X] do not count, nor does \s (which includes  CR  and         matches  such  as [^X] do not count, nor does \s (which includes CR and
2127         LF in the characters that it matches).         LF in the characters that it matches).
2128    
2129         Notwithstanding  the above, anomalous effects may still occur when CRLF         Notwithstanding the above, anomalous effects may still occur when  CRLF
2130         is a valid newline sequence and explicit \r or \n escapes appear in the         is a valid newline sequence and explicit \r or \n escapes appear in the
2131         pattern.         pattern.
2132    
2133           PCRE_NOTBOL           PCRE_NOTBOL
2134    
2135         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2136         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
2137         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
2138         causes circumflex never to match. This option affects only  the  behav-         causes  circumflex  never to match. This option affects only the behav-
2139         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2140    
2141           PCRE_NOTEOL           PCRE_NOTEOL
2142    
2143         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
2144         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
2145         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
2146         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2147         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
2148         not affect \Z or \z.         not affect \Z or \z.
2149    
2150           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2151    
2152         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
2153         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
2154         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
2155         example, if the pattern         example, if the pattern
2156    
2157           a?b?           a?b?
2158    
2159         is  applied  to  a  string not beginning with "a" or "b", it matches an         is applied to a string not beginning with "a" or  "b",  it  matches  an
2160         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
2161         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-
2162         rences of "a" or "b".         rences of "a" or "b".
2163    
2164           PCRE_NOTEMPTY_ATSTART           PCRE_NOTEMPTY_ATSTART
2165    
2166         This is like PCRE_NOTEMPTY, except that an empty string match  that  is         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2167         not  at  the  start  of  the  subject  is  permitted. If the pattern is         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2168         anchored, such a match can occur only if the pattern contains \K.         anchored, such a match can occur only if the pattern contains \K.
2169    
2170         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2171         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2172         match of the empty string within its split() function, and  when  using         match  of  the empty string within its split() function, and when using
2173         the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after         the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2174         matching a null string by first trying the match again at the same off-         matching a null string by first trying the match again at the same off-
2175         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that         set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2176         fails, by advancing the starting offset (see below) and trying an ordi-         fails, by advancing the starting offset (see below) and trying an ordi-
2177         nary  match  again. There is some code that demonstrates how to do this         nary match again. There is some code that demonstrates how to  do  this
2178         in the pcredemo sample program.         in  the  pcredemo sample program. In the most general case, you have to
2179           check to see if the newline convention recognizes CRLF  as  a  newline,
2180           and  if so, and the current character is CR followed by LF, advance the
2181           starting offset by two characters instead of one.
2182    
2183           PCRE_NO_START_OPTIMIZE           PCRE_NO_START_OPTIMIZE
2184    
# Line 2143  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2198  MATCHING A PATTERN: THE TRADITIONAL FUNC
2198         possibly  causing  performance  to  suffer,  but ensuring that in cases         possibly  causing  performance  to  suffer,  but ensuring that in cases
2199         where the result is "no match", the callouts do occur, and  that  items         where the result is "no match", the callouts do occur, and  that  items
2200         such as (*COMMIT) and (*MARK) are considered at every possible starting         such as (*COMMIT) and (*MARK) are considered at every possible starting
2201         position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can         position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2202         change the outcome of a matching operation.  Consider the pattern         compile time, it cannot be unset at matching time.
2203    
2204           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2205           operation.  Consider the pattern
2206    
2207           (*COMMIT)ABC           (*COMMIT)ABC
2208    
2209         When  this  is  compiled, PCRE records the fact that a match must start         When this is compiled, PCRE records the fact that a  match  must  start
2210         with the character "A". Suppose the subject  string  is  "DEFABC".  The         with  the  character  "A".  Suppose the subject string is "DEFABC". The
2211         start-up  optimization  scans along the subject, finds "A" and runs the         start-up optimization scans along the subject, finds "A" and  runs  the
2212         first match attempt from there. The (*COMMIT) item means that the  pat-         first  match attempt from there. The (*COMMIT) item means that the pat-
2213         tern  must  match the current starting position, which in this case, it         tern must match the current starting position, which in this  case,  it
2214         does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE         does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2215         set,  the  initial  scan  along the subject string does not happen. The         set, the initial scan along the subject string  does  not  happen.  The
2216         first match attempt is run starting  from  "D"  and  when  this  fails,         first  match  attempt  is  run  starting  from "D" and when this fails,
2217         (*COMMIT)  prevents  any  further  matches  being tried, so the overall         (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2218         result is "no match". If the pattern is studied,  more  start-up  opti-         result  is  "no  match". If the pattern is studied, more start-up opti-
2219         mizations  may  be  used. For example, a minimum length for the subject         mizations may be used. For example, a minimum length  for  the  subject
2220         may be recorded. Consider the pattern         may be recorded. Consider the pattern
2221    
2222           (*MARK:A)(X|Y)           (*MARK:A)(X|Y)
2223    
2224         The minimum length for a match is one  character.  If  the  subject  is         The  minimum  length  for  a  match is one character. If the subject is
2225         "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then         "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2226         finally an empty string.  If the pattern is studied, the final  attempt         finally  an empty string.  If the pattern is studied, the final attempt
2227         does  not take place, because PCRE knows that the subject is too short,         does not take place, because PCRE knows that the subject is too  short,
2228         and so the (*MARK) is never encountered.  In this  case,  studying  the         and  so  the  (*MARK) is never encountered.  In this case, studying the
2229         pattern  does  not  affect the overall match result, which is still "no         pattern does not affect the overall match result, which  is  still  "no
2230         match", but it does affect the auxiliary information that is returned.         match", but it does affect the auxiliary information that is returned.
2231    
2232           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2233    
2234         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
2235         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2236         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2237         points  to  the start of a UTF-8 character. There is a discussion about         points to the start of a UTF-8 character. There is a  discussion  about
2238         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2239         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2240         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec()  returns  the  error  PCRE_ERROR_BADUTF8  or,  if PCRE_PAR-
2241         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         TIAL_HARD is set and the problem is a truncated UTF-8 character at  the
2242           end  of  the  subject, PCRE_ERROR_SHORTUTF8. In both cases, information
2243         If  you  already  know that your subject is valid, and you want to skip         about the precise nature of the error may also  be  returned  (see  the
2244         these   checks   for   performance   reasons,   you   can    set    the         descriptions  of these errors in the section entitled Error return val-
2245         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         ues from pcre_exec() below).  If startoffset contains a value that does
2246         do this for the second and subsequent calls to pcre_exec() if  you  are         not  point to the start of a UTF-8 character (or to the end of the sub-
2247         making  repeated  calls  to  find  all  the matches in a single subject         ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2248         string. However, you should be  sure  that  the  value  of  startoffset  
2249         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         If you already know that your subject is valid, and you  want  to  skip
2250         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         these    checks    for   performance   reasons,   you   can   set   the
2251         value  of startoffset that does not point to the start of a UTF-8 char-         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2252         acter, is undefined. Your program may crash.         do  this  for the second and subsequent calls to pcre_exec() if you are
2253           making repeated calls to find all  the  matches  in  a  single  subject
2254           string.  However,  you  should  be  sure  that the value of startoffset
2255           points to the start of a UTF-8 character (or the end of  the  subject).
2256           When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2257           string as a subject or an invalid value of  startoffset  is  undefined.
2258           Your program may crash.
2259    
2260           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2261           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2262    
2263         These options turn on the partial matching feature. For backwards  com-         These  options turn on the partial matching feature. For backwards com-
2264         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2265         match occurs if the end of the subject string is reached  successfully,         match  occurs if the end of the subject string is reached successfully,
2266         but  there  are not enough subject characters to complete the match. If         but there are not enough subject characters to complete the  match.  If
2267         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2268         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         matching continues by testing any remaining alternatives.  Only  if  no
2269         matching continues by testing any other alternatives. Only if they  all         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2270         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2271         The portion of the string that was inspected when the partial match was         caller  is  prepared to handle a partial match, but only if no complete
2272         found  is  set  as  the first matching string. There is a more detailed         match can be found.
2273         discussion in the pcrepartial documentation.  
2274           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2275           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2276           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2277           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2278           ered to be more important that an alternative complete match.
2279    
2280           In both cases, the portion of the string that was  inspected  when  the
2281           partial match was found is set as the first matching string. There is a
2282           more detailed discussion of partial and  multi-segment  matching,  with
2283           examples, in the pcrepartial documentation.
2284    
2285     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2286    
2287         The subject string is passed to pcre_exec() as a pointer in subject,  a         The  subject string is passed to pcre_exec() as a pointer in subject, a
2288         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2289         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         If  this  is  negative  or  greater  than  the  length  of the subject,
2290         acter.  Unlike  the pattern string, the subject may contain binary zero         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2291         bytes. When the starting offset is zero, the search for a match  starts         zero,  the  search  for a match starts at the beginning of the subject,
2292         at  the  beginning  of  the subject, and this is by far the most common         and this is by far the most common case. In UTF-8 mode, the byte offset
2293         case.         must  point  to  the start of a UTF-8 character (or the end of the sub-
2294           ject). Unlike the pattern string, the subject may contain  binary  zero
2295         A non-zero starting offset is useful when searching for  another  match         bytes.
2296         in  the same subject by calling pcre_exec() again after a previous suc-  
2297         cess.  Setting startoffset differs from just passing over  a  shortened         A  non-zero  starting offset is useful when searching for another match
2298         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         in the same subject by calling pcre_exec() again after a previous  suc-
2299           cess.   Setting  startoffset differs from just passing over a shortened
2300           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2301         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2302    
2303           \Biss\B           \Biss\B
2304    
2305         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2306         only  if  the  current position in the subject is not a word boundary.)         only if the current position in the subject is not  a  word  boundary.)
2307         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2308         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2309         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2310         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2311         to be a word boundary. However, if pcre_exec()  is  passed  the  entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2312         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2313         rence of "iss" because it is able to look behind the starting point  to         rence  of "iss" because it is able to look behind the starting point to
2314         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2315    
2316           Finding all the matches in a subject is tricky  when  the  pattern  can
2317           match an empty string. It is possible to emulate Perl's /g behaviour by
2318           first  trying  the  match  again  at  the   same   offset,   with   the
2319           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2320           fails, advancing the starting  offset  and  trying  an  ordinary  match
2321           again. There is some code that demonstrates how to do this in the pcre-
2322           demo sample program. In the most general case, you have to check to see
2323           if  the newline convention recognizes CRLF as a newline, and if so, and
2324           the current character is CR followed by LF, advance the starting offset
2325           by two characters instead of one.
2326    
2327         If  a  non-zero starting offset is passed when the pattern is anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2328         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2329         if  the  pattern  does  not require the match to be at the start of the         if  the  pattern  does  not require the match to be at the start of the
# Line 2309  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2396  MATCHING A PATTERN: THE TRADITIONAL FUNC
2396         expression are also set to -1. For example,  if  the  string  "abc"  is         expression are also set to -1. For example,  if  the  string  "abc"  is
2397         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2398         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2399         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2400         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2401         the vector is large enough, of course).         of course) are set to -1.
2402    
2403           Note: Elements of ovector that do not correspond to capturing parenthe-
2404           ses in the pattern are never changed. That is, if a pattern contains  n
2405           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2406           by pcre_exec(). The other elements retain whatever values  they  previ-
2407           ously had.
2408    
2409         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2410         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2381  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2474  MATCHING A PATTERN: THE TRADITIONAL FUNC
2474           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2475    
2476         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2477         subject.         subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2478           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2479           start  of  the  the invalid UTF-8 character is placed in the first ele-
2480           ment, and a reason code is placed in the  second  element.  The  reason
2481           codes are listed in the following section.  For backward compatibility,
2482           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2483           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2484           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2485    
2486           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2487    
2488         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject  was  checked  and
2489           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2490         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2491         ter.         ter or the end of the subject.
2492    
2493           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2494    
# Line 2420  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2521  MATCHING A PATTERN: THE TRADITIONAL FUNC
2521    
2522         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2523    
2524             PCRE_ERROR_BADOFFSET      (-24)
2525    
2526           The value of startoffset was negative or greater than the length of the
2527           subject, that is, the value in length.
2528    
2529             PCRE_ERROR_SHORTUTF8      (-25)
2530    
2531           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2532           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2533           option  is  set.   Information  about  the  failure  is returned as for
2534           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2535           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2536           tion of returned information; it is retained for backwards  compatibil-
2537           ity.
2538    
2539             PCRE_ERROR_RECURSELOOP    (-26)
2540    
2541           This error is returned when pcre_exec() detects a recursion loop within
2542           the pattern. Specifically, it means that either the whole pattern or  a
2543           subpattern  has been called recursively for the second time at the same
2544           position in the subject string. Some simple patterns that might do this
2545           are  detected  and faulted at compile time, but more complicated cases,
2546           in particular mutual recursions between two different subpatterns, can-
2547           not be detected until run time.
2548    
2549         Error numbers -16 to -20 and -22 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2550    
2551       Reason codes for invalid UTF-8 strings
2552    
2553           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2554           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2555           offset  of  the  start  of the invalid UTF-8 character is placed in the
2556           first output vector element (ovector[0]) and a reason code is placed in
2557           the  second  element  (ovector[1]). The reason codes are given names in
2558           the pcre.h header file:
2559    
2560             PCRE_UTF8_ERR1
2561             PCRE_UTF8_ERR2
2562             PCRE_UTF8_ERR3
2563             PCRE_UTF8_ERR4
2564             PCRE_UTF8_ERR5
2565    
2566           The string ends with a truncated UTF-8 character;  the  code  specifies
2567           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2568           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2569           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2570           checked first; hence the possibility of 4 or 5 missing bytes.
2571    
2572             PCRE_UTF8_ERR6
2573             PCRE_UTF8_ERR7
2574             PCRE_UTF8_ERR8
2575             PCRE_UTF8_ERR9
2576             PCRE_UTF8_ERR10
2577    
2578           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2579           the  character  do  not have the binary value 0b10 (that is, either the
2580           most significant bit is 0, or the next bit is 1).
2581    
2582             PCRE_UTF8_ERR11
2583             PCRE_UTF8_ERR12
2584    
2585           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2586           long; these code points are excluded by RFC 3629.
2587    
2588             PCRE_UTF8_ERR13
2589    
2590           A  4-byte character has a value greater than 0x10fff; these code points
2591           are excluded by RFC 3629.
2592    
2593             PCRE_UTF8_ERR14
2594    
2595           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2596           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2597           so are excluded from UTF-8.
2598    
2599             PCRE_UTF8_ERR15
2600             PCRE_UTF8_ERR16
2601             PCRE_UTF8_ERR17
2602             PCRE_UTF8_ERR18
2603             PCRE_UTF8_ERR19
2604    
2605           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2606           for  a  value that can be represented by fewer bytes, which is invalid.
2607           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2608           rect coding uses just one byte.
2609    
2610             PCRE_UTF8_ERR20
2611    
2612           The two most significant bits of the first byte of a character have the
2613           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2614           ond  is  0). Such a byte can only validly occur as the second or subse-
2615           quent byte of a multi-byte character.
2616    
2617             PCRE_UTF8_ERR21
2618    
2619           The first byte of a character has the value 0xfe or 0xff. These  values
2620           can never occur in a valid UTF-8 string.
2621    
2622    
2623  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2624    
# Line 2436  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2633  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2633         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2634              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2635    
2636         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2637         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2638         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2639         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2640         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2641         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2642         substrings.         substrings.
2643    
2644         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2645         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2646         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2647         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2648         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2649         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2650         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2651    
2652         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2653         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2654         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2655         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2656         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2657         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2658         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2659         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2660         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2661    
2662         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2663         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2664         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2665         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2666         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2667         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2668         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2669         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2670         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2671    
2672           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2673    
2674         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2675         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2676    
2677           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2678    
2679         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2680    
2681         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2682         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2683         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2684         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2685         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2686         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2687         error code         error code
2688    
2689           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2690    
2691         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2692    
2693         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2694         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2695         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2696         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2697         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2698         tive for unset substrings.         tive for unset substrings.
2699    
2700         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2701         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2702         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2703         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2704         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2705         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2706         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2707         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2708         vided.         vided.
2709    
2710    
# Line 2526  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2723  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2723              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2724              const char **stringptr);              const char **stringptr);
2725    
2726         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2727         ber.  For example, for this pattern         ber.  For example, for this pattern
2728    
2729           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2535  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2732  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2732         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2733         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2734         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2735         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2736         subpattern of that name.         subpattern of that name.
2737    
2738         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2739         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2740         are also two functions that do the whole job.         are also two functions that do the whole job.
2741    
2742         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2743         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2744         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2745         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2746         differences:         differences:
2747    
2748         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2749         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2750         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2751         name-to-number translation table.         name-to-number translation table.
2752    
2753         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2754         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2755         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2756         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2757    
2758         Warning: If the pattern uses the (?| feature to set up multiple subpat-         Warning: If the pattern uses the (?| feature to set up multiple subpat-
2759         terns  with  the  same number, as described in the section on duplicate         terns with the same number, as described in the  section  on  duplicate
2760         subpattern numbers in the pcrepattern page, you  cannot  use  names  to         subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2761         distinguish  the  different subpatterns, because names are not included         distinguish the different subpatterns, because names are  not  included
2762         in the compiled code. The matching process uses only numbers. For  this         in  the compiled code. The matching process uses only numbers. For this
2763         reason,  the  use of different names for subpatterns of the same number         reason, the use of different names for subpatterns of the  same  number
2764         causes an error at compile time.         causes an error at compile time.
2765    
2766    
# Line 2572  DUPLICATE SUBPATTERN NAMES Line 2769  DUPLICATE SUBPATTERN NAMES
2769         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2770              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2771    
2772         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2773         subpatterns  are not required to be unique. (Duplicate names are always         subpatterns are not required to be unique. (Duplicate names are  always
2774         allowed for subpatterns with the same number, created by using the  (?|         allowed  for subpatterns with the same number, created by using the (?|
2775         feature.  Indeed,  if  such subpatterns are named, they are required to         feature. Indeed, if such subpatterns are named, they  are  required  to
2776         use the same names.)         use the same names.)
2777    
2778         Normally, patterns with duplicate names are such that in any one match,         Normally, patterns with duplicate names are such that in any one match,
2779         only  one of the named subpatterns participates. An example is shown in         only one of the named subpatterns participates. An example is shown  in
2780         the pcrepattern documentation.         the pcrepattern documentation.
2781    
2782         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2783         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2784         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2785         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2786         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2787         but it is not defined which it is.         but it is not defined which it is.
2788    
2789         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2790         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2791         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2792         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2793         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2794         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2795         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2796         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2797         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2798         entries for the name, you can extract each of their numbers, and  hence         vant  entries  for the name, you can extract each of their numbers, and
2799         the captured data, if any.         hence the captured data, if any.
2800    
2801    
2802  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2803    
2804         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2805         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2806         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2807         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2808         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2809         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2810         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2811         tation.         tation.
2812    
2813         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2814         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2815         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2816         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2817         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2818    
2819    
# Line 2627  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2824  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2824              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2825              int *workspace, int wscount);              int *workspace, int wscount);
2826    
2827         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2828         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2829         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2830         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2831         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2832         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2833         a discussion of the two matching algorithms, and  a  list  of  features         a  discussion  of  the  two matching algorithms, and a list of features
2834         that  pcre_dfa_exec() does not support, see the pcrematching documenta-         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2835         tion.         tion.
2836    
2837         The arguments for the pcre_dfa_exec() function  are  the  same  as  for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2838         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2839         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2840         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2841         repeated here.         repeated here.
2842    
2843         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2844         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2845         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2846         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2847         lot of potential matches.         lot of potential matches.
2848    
2849         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2668  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2865  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2865    
2866     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2867    
2868         The unused bits of the options argument  for  pcre_dfa_exec()  must  be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2869         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2870         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2871         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2872         PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD,  PCRE_PAR-         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2873         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and PCRE_DFA_RESTART.  All but the last         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2874         four of these are  exactly  the  same  as  for  pcre_exec(),  so  their         four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2875         description is not repeated here.         description is not repeated here.
2876    
2877           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2878           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2879    
2880         These  have the same general effect as they do for pcre_exec(), but the         These have the same general effect as they do for pcre_exec(), but  the
2881         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2882         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2883         ject is reached and there is still at least  one  matching  possibility         ject  is  reached  and there is still at least one matching possibility
2884         that requires additional characters. This happens even if some complete         that requires additional characters. This happens even if some complete
2885         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2886         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2887         of the subject is reached, there have been  no  complete  matches,  but         of  the  subject  is  reached, there have been no complete matches, but
2888         there  is  still  at least one matching possibility. The portion of the         there is still at least one matching possibility. The  portion  of  the
2889         string that was inspected when the longest partial match was  found  is         string  that  was inspected when the longest partial match was found is
2890         set as the first matching string in both cases.         set as the first matching string  in  both  cases.   There  is  a  more
2891           detailed  discussion  of partial and multi-segment matching, with exam-
2892           ples, in the pcrepartial documentation.
2893    
2894           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2895    
2896         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2897         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2898         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2899         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2900    
2901           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2902    
2903         When pcre_dfa_exec() returns a partial match, it is possible to call it         When pcre_dfa_exec() returns a partial match, it is possible to call it
2904         again,  with  additional  subject characters, and have it continue with         again, with additional subject characters, and have  it  continue  with
2905         the same match. The PCRE_DFA_RESTART option requests this action;  when         the  same match. The PCRE_DFA_RESTART option requests this action; when
2906         it  is  set,  the workspace and wscount options must reference the same         it is set, the workspace and wscount options must  reference  the  same
2907         vector as before because data about the match so far is  left  in  them         vector  as  before  because data about the match so far is left in them
2908         after a partial match. There is more discussion of this facility in the         after a partial match. There is more discussion of this facility in the
2909         pcrepartial documentation.         pcrepartial documentation.
2910    
2911     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2912    
2913         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2914         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2915         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2916         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2917         if the pattern         if the pattern
2918    
2919           <.*>           <.*>
# Line 2729  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2928  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2928           <something> <something else>           <something> <something else>
2929           <something> <something else> <something further>           <something> <something else> <something further>
2930    
2931         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2932         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2933         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2934         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2935         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2936         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2937         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2938         meaning of the strings is different.)         meaning of the strings is different.)
2939    
2940         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2941         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2942         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2943         filled with the longest matches.         filled with the longest matches.
2944    
2945     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2946    
2947         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2948         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2949         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2950         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2951    
2952           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2953    
2954         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2955         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2956         reference.         reference.
2957    
2958           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2959    
2960         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2961         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
2962         in a specific group. These are not supported.         in a specific group. These are not supported.
2963    
2964           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2965    
2966         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2967         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2968         (it is meaningless).         (it is meaningless).
2969    
2970           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2971    
2972         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2973         workspace vector.         workspace vector.
2974    
2975           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2976    
2977         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2978         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2979         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2980         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2981    
2982    
2983  SEE ALSO  SEE ALSO
2984    
2985         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2986         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2987    
2988    
# Line 2796  AUTHOR Line 2995  AUTHOR
2995    
2996  REVISION  REVISION
2997    
2998         Last updated: 21 June 2010         Last updated: 13 August 2011
2999         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3000  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3001    
3002    
# Line 2864  MISSING CALLOUTS Line 3063  MISSING CALLOUTS
3063         patterns, if it has been scanned far enough.         patterns, if it has been scanned far enough.
3064    
3065         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
3066         MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the         MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
3067         matching  process,  but  does  ensure that callouts such as the example         starting the pattern with (*NO_START_OPT). This slows down the matching
3068         above are obeyed.         process, but does ensure that callouts such as the  example  above  are
3069           obeyed.
3070    
3071    
3072  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3073    
3074         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3075         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
3076         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
3077         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
3078         block. This structure contains the following fields:         block. This structure contains the following fields:
3079    
3080           int          version;           int         version;
3081           int          callout_number;           int         callout_number;
3082           int         *offset_vector;           int        *offset_vector;
3083           const char  *subject;           const char *subject;
3084           int          subject_length;           int         subject_length;
3085           int          start_match;           int         start_match;
3086           int          current_position;           int         current_position;
3087           int          capture_top;           int         capture_top;
3088           int          capture_last;           int         capture_last;
3089           void        *callout_data;           void       *callout_data;
3090           int          pattern_position;           int         pattern_position;
3091           int          next_item_length;           int         next_item_length;
3092             const unsigned char *mark;
3093         The version field is an integer containing the version  number  of  the  
3094         block  format. The initial version was 0; the current version is 1. The         The  version  field  is an integer containing the version number of the
3095         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
3096           version  number  will  change  again in future if additional fields are
3097         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
3098    
3099         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
3100         piled into the pattern (that is, the number after ?C for  manual  call-         piled  into  the pattern (that is, the number after ?C for manual call-
3101         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
3102    
3103         The  offset_vector field is a pointer to the vector of offsets that was         The offset_vector field is a pointer to the vector of offsets that  was
3104         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
3105         pcre_exec()  is used, the contents can be inspected in order to extract         pcre_exec() is used, the contents can be inspected in order to  extract
3106         substrings that have been matched so  far,  in  the  same  way  as  for         substrings  that  have  been  matched  so  far,  in the same way as for
3107         extracting  substrings after a match has completed. For pcre_dfa_exec()         extracting substrings after a match has completed. For  pcre_dfa_exec()
3108         this field is not useful.         this field is not useful.
3109    
3110         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
3111         were passed to pcre_exec().         were passed to pcre_exec().
3112    
3113         The  start_match  field normally contains the offset within the subject         The start_match field normally contains the offset within  the  subject
3114         at which the current match attempt  started.  However,  if  the  escape         at  which  the  current  match  attempt started. However, if the escape
3115         sequence  \K has been encountered, this value is changed to reflect the         sequence \K has been encountered, this value is changed to reflect  the
3116         modified starting point. If the pattern is not  anchored,  the  callout         modified  starting  point.  If the pattern is not anchored, the callout
3117         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
3118         for different starting points in the subject.         for different starting points in the subject.
3119    
3120         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
3121         the current match pointer.         the current match pointer.
3122    
3123         When  the  pcre_exec() function is used, the capture_top field contains         When the pcre_exec() function is used, the capture_top  field  contains
3124         one more than the number of the highest numbered captured substring  so         one  more than the number of the highest numbered captured substring so
3125         far.  If  no substrings have been captured, the value of capture_top is         far. If no substrings have been captured, the value of  capture_top  is
3126         one. This is always the case when pcre_dfa_exec() is used,  because  it         one.  This  is always the case when pcre_dfa_exec() is used, because it
3127         does not support captured substrings.         does not support captured substrings.
3128    
3129         The  capture_last  field  contains the number of the most recently cap-         The capture_last field contains the number of the  most  recently  cap-
3130         tured substring. If no substrings have been captured, its value is  -1.         tured  substring. If no substrings have been captured, its value is -1.
3131         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
3132    
3133         The  callout_data  field contains a value that is passed to pcre_exec()         The callout_data field contains a value that is passed  to  pcre_exec()
3134         or pcre_dfa_exec() specifically so that it can be passed back in  call-         or  pcre_dfa_exec() specifically so that it can be passed back in call-
3135         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
3136         structure. If no such data was passed, the value of callout_data  in  a         structure.  If  no such data was passed, the value of callout_data in a
3137         pcre_callout  block  is  NULL. There is a description of the pcre_extra         pcre_callout block is NULL. There is a description  of  the  pcre_extra
3138         structure in the pcreapi documentation.         structure in the pcreapi documentation.
3139    
3140         The pattern_position field is present from version 1 of the  pcre_call-         The  pattern_position field is present from version 1 of the pcre_call-
3141         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
3142         the pattern string.         the pattern string.
3143    
3144         The next_item_length field is present from version 1 of the  pcre_call-         The  next_item_length field is present from version 1 of the pcre_call-
3145         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
3146         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
3147         tion  bar, a closing parenthesis, or the end of the pattern, the length         tion bar, a closing parenthesis, or the end of the pattern, the  length
3148         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
3149         is that of the entire subpattern.         is that of the entire subpattern.
3150    
3151         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
3152         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
3153         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3154    
3155           The mark field is present from version 2 of the pcre_callout structure.
3156           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3157           nated name of the most recently passed (*MARK) item in  the  match,  or
3158           NULL if there are no (*MARK)s in the current matching path. In callouts
3159           from pcre_dfa_exec() this field always contains NULL.
3160    
3161    
3162  RETURN VALUES  RETURN VALUES
3163    
3164         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
3165         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
3166         zero,  matching  fails  at  the current point, but the testing of other         zero, matching fails at the current point, but  the  testing  of  other
3167         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3168         failed.  If  the  value  is less than zero, the match is abandoned, and         failed. If the value is less than zero, the  match  is  abandoned,  and
3169         pcre_exec() or pcre_dfa_exec() returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3170    
3171         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
3172         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3173         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
3174         reserved  for  use  by callout functions; it will never be used by PCRE         reserved for use by callout functions; it will never be  used  by  PCRE
3175         itself.         itself.
3176    
3177    
# Line 2977  AUTHOR Line 3184  AUTHOR
3184    
3185  REVISION  REVISION
3186    
3187         Last updated: 29 September 2009         Last updated: 31 July 2011
3188         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3189  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3190    
3191    
# Line 2993  DIFFERENCES BETWEEN PCRE AND PERL Line 3200  DIFFERENCES BETWEEN PCRE AND PERL
3200    
3201         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3202         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3203         respect to Perl 5.10/5.11.         respect to Perl versions 5.10 and above.
3204    
3205         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3206         of what it does have are given in the section on UTF-8 support  in  the         of what it does have are given in the section on UTF-8 support  in  the
3207         main pcre page.         main pcre page.
3208    
3209         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3210         permits them, but they do not mean what you might think.  For  example,         they do not mean what you might think. For example, (?!a){3}  does  not
3211         (?!a){3} does not assert that the next three characters are not "a". It         assert that the next three characters are not "a". It just asserts that
3212         just asserts that the next character is not "a" three times.         the next character is not "a" three times (in principle: PCRE optimizes
3213           this to run the assertion just once). Perl allows repeat quantifiers on
3214           other assertions such as \b, but these do not seem to have any use.
3215    
3216         3. Capturing subpatterns that occur inside  negative  lookahead  asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3217         tions  are  counted,  but their entries in the offsets vector are never         tions  are  counted,  but their entries in the offsets vector are never
# Line 3017  DIFFERENCES BETWEEN PCRE AND PERL Line 3226  DIFFERENCES BETWEEN PCRE AND PERL
3226         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3227    
3228         5. The following Perl escape sequences are not supported: \l,  \u,  \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3229         \U, and \N. In fact these are implemented by Perl's general string-han-         \U,  and  \N when followed by a character name or Unicode value. (\N on
3230         dling and are not part of its pattern matching engine. If any of  these         its own, matching a non-newline character, is supported.) In fact these
3231         are encountered by PCRE, an error is generated.         are  implemented  by Perl's general string-handling and are not part of
3232           its pattern matching engine. If any of these are encountered  by  PCRE,
3233           an error is generated.
3234    
3235         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3236         is built with Unicode character property support. The  properties  that         is built with Unicode character property support. The  properties  that
# Line 3031  DIFFERENCES BETWEEN PCRE AND PERL Line 3242  DIFFERENCES BETWEEN PCRE AND PERL
3242         tion of Unicode characters, there is no need to implement the  somewhat         tion of Unicode characters, there is no need to implement the  somewhat
3243         messy concept of surrogates."         messy concept of surrogates."
3244    
3245         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7.  PCRE implements a simpler version of \X than Perl, which changed to
3246         ters in between are treated as literals.  This  is  slightly  different         make \X match what Unicode calls an "extended grapheme  cluster".  This
3247         from  Perl  in  that  $  and  @ are also handled as literals inside the         is  more  complicated  than an extended Unicode sequence, which is what
3248         quotes. In Perl, they cause variable interpolation (but of course  PCRE         PCRE matches.
3249    
3250           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3251           ters  in  between  are  treated as literals. This is slightly different
3252           from Perl in that $ and @ are  also  handled  as  literals  inside  the
3253           quotes.  In Perl, they cause variable interpolation (but of course PCRE
3254         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3255    
3256             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 3044  DIFFERENCES BETWEEN PCRE AND PERL Line 3260  DIFFERENCES BETWEEN PCRE AND PERL
3260             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3261             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3262    
3263         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3264         classes.         classes.
3265    
3266         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3267         constructions.  However,  there is support for recursive patterns. This         constructions. However, there is support for recursive  patterns.  This
3268         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE         is  not  available  in Perl 5.8, but it is in Perl 5.10. Also, the PCRE
3269         "callout"  feature allows an external function to be called during pat-         "callout" feature allows an external function to be called during  pat-
3270         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3271    
3272         9. Subpatterns that are called  recursively  or  as  "subroutines"  are         10.  Subpatterns  that  are  called recursively or as "subroutines" are
3273         always  treated  as  atomic  groups  in  PCRE. This is like Python, but         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
3274         unlike Perl. There is a discussion of an example that explains this  in         unlike  Perl. There is a discussion of an example that explains this in
3275         more  detail  in  the section on recursion differences from Perl in the         more detail in the section on recursion differences from  Perl  in  the
3276         pcrepattern page.         pcrepattern page.
3277    
3278         10. There are some differences that are concerned with the settings  of         11.  There are some differences that are concerned with the settings of
3279         captured  strings  when  part  of  a  pattern is repeated. For example,         captured strings when part of  a  pattern  is  repeated.  For  example,
3280         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
3281         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3282    
3283         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-         12. PCRE's handling of duplicate subpattern numbers and duplicate  sub-
3284         pattern names is not as general as Perl's. This is a consequence of the         pattern names is not as general as Perl's. This is a consequence of the
3285         fact the PCRE works internally just with numbers, using an external ta-         fact the PCRE works internally just with numbers, using an external ta-
3286         ble to translate between numbers and names. In  particular,  a  pattern         ble  to  translate  between numbers and names. In particular, a pattern
3287         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have         such as (?|(?<a>A)|(?<b)B), where the two  capturing  parentheses  have
3288         the same number but different names, is not supported,  and  causes  an         the  same  number  but different names, is not supported, and causes an
3289         error  at compile time. If it were allowed, it would not be possible to         error at compile time. If it were allowed, it would not be possible  to
3290         distinguish which parentheses matched, because both names map  to  cap-         distinguish  which  parentheses matched, because both names map to cap-
3291         turing subpattern number 1. To avoid this confusing situation, an error         turing subpattern number 1. To avoid this confusing situation, an error
3292         is given at compile time.         is given at compile time.
3293    
3294         12. PCRE provides some extensions to the Perl regular expression facil-         13.  Perl  recognizes  comments  in some places that PCRE does not, for
3295           example, between the ( and ? at the start of a subpattern.  If  the  /x
3296           modifier  is set, Perl allows whitespace between ( and ? but PCRE never
3297           does, even if the PCRE_EXTENDED option is set.
3298    
3299           14. PCRE provides some extensions to the Perl regular expression facil-
3300         ities.   Perl  5.10  includes new features that are not in earlier ver-         ities.   Perl  5.10  includes new features that are not in earlier ver-
3301         sions of Perl, some of which (such as named parentheses) have  been  in         sions of Perl, some of which (such as named parentheses) have  been  in
3302         PCRE for some time. This list is with respect to Perl 5.10:         PCRE for some time. This list is with respect to Perl 5.10:
# Line 3130  AUTHOR Line 3351  AUTHOR
3351    
3352  REVISION  REVISION
3353    
3354         Last updated: 12 May 2010         Last updated: 24 July 2011
3355         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3356  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3357    
3358    
# Line 3183  PCRE REGULAR EXPRESSION DETAILS Line 3404  PCRE REGULAR EXPRESSION DETAILS
3404         character types, instead of recognizing only characters with codes less         character types, instead of recognizing only characters with codes less
3405         than 128 via a lookup table.         than 128 via a lookup table.
3406    
3407         The remainder of this document discusses the  patterns  that  are  sup-         If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3408         ported  by  PCRE when its main matching function, pcre_exec(), is used.         setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3409         From  release  6.0,   PCRE   offers   a   second   matching   function,         time. There are also some more of these special sequences that are con-
3410         pcre_dfa_exec(),  which matches using a different algorithm that is not         cerned with the handling of newlines; they are described below.
3411    
3412           The  remainder  of  this  document discusses the patterns that are sup-
3413           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3414           From   release   6.0,   PCRE   offers   a   second  matching  function,
3415           pcre_dfa_exec(), which matches using a different algorithm that is  not
3416         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3417         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3418         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3419         discussed in the pcrematching page.         discussed in the pcrematching page.
3420    
3421    
3422  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3423    
3424         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3425         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3426         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3427         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3428         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3429         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3430    
3431         It is also possible to specify a newline convention by starting a  pat-         It  is also possible to specify a newline convention by starting a pat-
3432         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3433    
3434           (*CR)        carriage return           (*CR)        carriage return
# Line 3211  NEWLINE CONVENTIONS Line 3437  NEWLINE CONVENTIONS
3437           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3438           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3439    
3440         These  override  the default and the options given to pcre_compile() or         These override the default and the options given to  pcre_compile()  or
3441         pcre_compile2(). For example, on a Unix system where LF is the  default         pcre_compile2().  For example, on a Unix system where LF is the default
3442         newline sequence, the pattern         newline sequence, the pattern
3443    
3444           (*CR)a.b           (*CR)a.b
3445    
3446         changes the convention to CR. That pattern matches "a\nb" because LF is         changes the convention to CR. That pattern matches "a\nb" because LF is
3447         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3448         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3449         and that they must be in upper case.  If  more  than  one  of  them  is         and  that  they  must  be  in  upper  case. If more than one of them is
3450         present, the last one is used.         present, the last one is used.
3451    
3452         The  newline convention affects the interpretation of the dot metachar-         The newline convention affects the interpretation of the dot  metachar-
3453         acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-         acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3454         ever,  it  does  not  affect  what  the  \R escape sequence matches. By         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3455         default, this is any Unicode newline sequence, for Perl  compatibility.         default,  this is any Unicode newline sequence, for Perl compatibility.
3456         However,  this can be changed; see the description of \R in the section         However, this can be changed; see the description of \R in the  section
3457         entitled "Newline sequences" below. A change of \R setting can be  com-         entitled  "Newline sequences" below. A change of \R setting can be com-
3458         bined with a change of newline convention.         bined with a change of newline convention.
3459    
3460    
3461  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3462    
3463         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3464         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3465         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3466         trivial example, the pattern         trivial example, the pattern
3467    
3468           The quick brown fox           The quick brown fox
3469    
3470         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
3471         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3472         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3473         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
3474         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3475         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
3476         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3477         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3478         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3479    
3480         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3481         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3482         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3483         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3484    
3485         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3486         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3487         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3488         the metacharacters are as follows:         the metacharacters are as follows:
3489    
3490           \      general escape character with several uses           \      general escape character with several uses
# Line 3277  CHARACTERS AND METACHARACTERS Line 3503  CHARACTERS AND METACHARACTERS
3503                  also "possessive quantifier"                  also "possessive quantifier"
3504           {      start min/max quantifier           {      start min/max quantifier
3505    
3506         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
3507         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3508    
3509           \      general escape character           \      general escape character
# Line 3293  CHARACTERS AND METACHARACTERS Line 3519  CHARACTERS AND METACHARACTERS
3519  BACKSLASH  BACKSLASH
3520    
3521         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3522         a non-alphanumeric character, it takes away any  special  meaning  that         a character that is not a number or a letter, it takes away any special
3523         character  may  have.  This  use  of  backslash  as an escape character         meaning that character may have. This use of  backslash  as  an  escape
3524         applies both inside and outside character classes.         character applies both inside and outside character classes.
3525    
3526         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
3527         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3528         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3529         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3530         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-
3531         slash, you write \\.         slash, you write \\.
3532    
3533         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3534         the pattern (other than in a character class) and characters between  a         after  a  backslash.  All  other characters (in particular, those whose
3535           codepoints are greater than 127) are treated as literals.
3536    
3537           If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3538           the  pattern (other than in a character class) and characters between a
3539         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3540         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3541         part of the pattern.         part of the pattern.
3542    
3543         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-
3544         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-
3545         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
3546         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3547         tion. Note the following examples:         tion. Note the following examples:
3548    
3549           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3323  BACKSLASH Line 3553  BACKSLASH
3553           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3554           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3555    
3556         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3557         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3558           is not followed by \E later in the pattern, the literal  interpretation
3559           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3560           end). If the isolated \Q is inside a character class,  this  causes  an
3561           error, because the character class is not terminated.
3562    
3563     Non-printing characters     Non-printing characters
3564    
3565         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-
3566         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
3567         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3568         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3569         editing, it is  often  easier  to  use  one  of  the  following  escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3570         sequences than the binary character it represents:         sequences than the binary character it represents:
3571    
3572           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3573           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3574           \e        escape (hex 1B)           \e        escape (hex 1B)
3575           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3576           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
# Line 3346  BACKSLASH Line 3580  BACKSLASH
3580           \xhh      character with hex code hh           \xhh      character with hex code hh
3581           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3582    
3583         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,
3584         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
3585         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;         inverted.  Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
3586         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3587           has a value greater than 127, a compile-time error occurs.  This  locks
3588         After \x, from zero to two hexadecimal digits are read (letters can  be         out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3589         in  upper  or  lower case). Any number of hexadecimal digits may appear         is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3590         between \x{ and }, but the value of the character  code  must  be  less         letter is converted to upper case, and then the 0xc0 bits are flipped.)
3591    
3592           After  \x, from zero to two hexadecimal digits are read (letters can be
3593           in upper or lower case). Any number of hexadecimal  digits  may  appear
3594           between  \x{  and  },  but the value of the character code must be less
3595         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,
3596         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3597         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3598    
3599         If  characters  other than hexadecimal digits appear between \x{ and },         If characters other than hexadecimal digits appear between \x{  and  },
3600         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3601         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3602         escape, with no following digits, giving a  character  whose  value  is         escape,  with  no  following  digits, giving a character whose value is
3603         zero.         zero.
3604    
3605         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
3606         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-
3607         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3608    
3609         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3610         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3611         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3612         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
3613         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3614    
3615         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3616         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3617         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
3618         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3619         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3620         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3621         of parenthesized subpatterns.         of parenthesized subpatterns.
3622    
3623         Inside  a  character  class, or if the decimal number is greater than 9         Inside a character class, or if the decimal number is  greater  than  9
3624         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3625         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3626         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3627         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3628         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3629         example:         example:
3630    
3631           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3405  BACKSLASH Line 3643  BACKSLASH
3643           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3644                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3645    
3646         Note  that  octal  values of 100 or greater must not be introduced by a         Note that octal values of 100 or greater must not be  introduced  by  a
3647         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3648    
3649         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3650         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3651         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3652         08).  The sequences \B, \N, \R, and \X are not special inside a charac-         08). The sequences \B, \N, \R, and \X are not special inside a  charac-
3653         ter class. Like any  other  unrecognized  escape  sequences,  they  are         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3654         treated  as  the  literal characters "B", "N", "R", and "X" by default,         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3655         but cause an error if the PCRE_EXTRA option is set. Outside a character         but cause an error if the PCRE_EXTRA option is set. Outside a character
3656         class, these sequences have different meanings.         class, these sequences have different meanings.
3657    
3658     Absolute and relative back references     Absolute and relative back references
3659    
3660         The  sequence  \g followed by an unsigned or a negative number, option-         The sequence \g followed by an unsigned or a negative  number,  option-
3661         ally enclosed in braces, is an absolute or relative back  reference.  A         ally  enclosed  in braces, is an absolute or relative back reference. A
3662         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3663         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3664    
3665     Absolute and relative subroutine calls     Absolute and relative subroutine calls
3666    
3667         For compatibility with Oniguruma, the non-Perl syntax \g followed by  a         For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3668         name or a number enclosed either in angle brackets or single quotes, is         name or a number enclosed either in angle brackets or single quotes, is
3669         an alternative syntax for referencing a subpattern as  a  "subroutine".         an  alternative  syntax for referencing a subpattern as a "subroutine".
3670         Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and         Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3671         \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back         \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3672         reference; the latter is a subroutine call.         reference; the latter is a subroutine call.
3673    
3674     Generic character types     Generic character types
# Line 3449  BACKSLASH Line 3687  BACKSLASH
3687           \W     any "non-word" character           \W     any "non-word" character
3688    
3689         There is also the single sequence \N, which matches a non-newline char-         There is also the single sequence \N, which matches a non-newline char-
3690         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3691         not set.         not set.
3692    
3693         Each  pair of lower and upper case escape sequences partitions the com-         Each pair of lower and upper case escape sequences partitions the  com-
3694         plete set of characters into two disjoint  sets.  Any  given  character         plete  set  of  characters  into two disjoint sets. Any given character
3695         matches  one, and only one, of each pair. The sequences can appear both         matches one, and only one, of each pair. The sequences can appear  both
3696         inside and outside character classes. They each match one character  of         inside  and outside character classes. They each match one character of
3697         the  appropriate  type.  If the current matching point is at the end of         the appropriate type. If the current matching point is at  the  end  of
3698         the subject string, all of them fail, because there is no character  to         the  subject string, all of them fail, because there is no character to
3699         match.         match.
3700    
3701         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
3702         11).  This makes it different from the the POSIX "space" class. The  \s         11).   This makes it different from the the POSIX "space" class. The \s
3703         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3704         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3705         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3706    
3707         A  "word"  character is an underscore or any character that is a letter         A "word" character is an underscore or any character that is  a  letter
3708         or digit.  By default, the definition of letters  and  digits  is  con-         or  digit.   By  default,  the definition of letters and digits is con-
3709         trolled  by PCRE's low-valued character tables, and may vary if locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3710         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3711         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3712         systems, or "french" in Windows, some character codes greater than  128         systems,  or "french" in Windows, some character codes greater than 128
3713         are  used  for  accented letters, and these are then matched by \w. The         are used for accented letters, and these are then matched  by  \w.  The
3714         use of locales with Unicode is discouraged.         use of locales with Unicode is discouraged.
3715    
3716         By default, in UTF-8 mode, characters  with  values  greater  than  128         By  default,  in  UTF-8  mode,  characters with values greater than 128
3717         never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These         never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3718         sequences retain their original meanings from before UTF-8 support  was         sequences  retain their original meanings from before UTF-8 support was
3719         available,  mainly for efficiency reasons. However, if PCRE is compiled         available, mainly for efficiency reasons. However, if PCRE is  compiled
3720         with Unicode property support, and the PCRE_UCP option is set, the  be-         with  Unicode property support, and the PCRE_UCP option is set, the be-
3721         haviour  is  changed  so  that Unicode properties are used to determine         haviour is changed so that Unicode properties  are  used  to  determine
3722         character types, as follows:         character types, as follows:
3723    
3724           \d  any character that \p{Nd} matches (decimal digit)           \d  any character that \p{Nd} matches (decimal digit)
3725           \s  any character that \p{Z} matches, plus HT, LF, FF, CR           \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3726           \w  any character that \p{L} or \p{N} matches, plus underscore           \w  any character that \p{L} or \p{N} matches, plus underscore
3727    
3728         The upper case escapes match the inverse sets of characters. Note  that         The  upper case escapes match the inverse sets of characters. Note that
3729         \d  matches  only decimal digits, whereas \w matches any Unicode digit,         \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3730         as well as any Unicode letter, and underscore. Note also that  PCRE_UCP         as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3731         affects  \b,  and  \B  because  they are defined in terms of \w and \W.         affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3732         Matching these sequences is noticeably slower when PCRE_UCP is set.         Matching these sequences is noticeably slower when PCRE_UCP is set.
3733    
3734         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The  sequences  \h, \H, \v, and \V are features that were added to Perl
3735         the  other  sequences,  which  match  only ASCII characters by default,         at release 5.10. In contrast to the other sequences, which  match  only
3736         these always  match  certain  high-valued  codepoints  in  UTF-8  mode,         ASCII  characters  by  default,  these always match certain high-valued
3737         whether or not PCRE_UCP is set. The horizontal space characters are:         codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3738           tal space characters are:
3739    
3740           U+0009     Horizontal tab           U+0009     Horizontal tab
3741           U+0020     Space           U+0020     Space
# Line 3531  BACKSLASH Line 3770  BACKSLASH
3770     Newline sequences     Newline sequences
3771    
3772         Outside  a  character class, by default, the escape sequence \R matches         Outside  a  character class, by default, the escape sequence \R matches
3773         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3774         mode \R is equivalent to the following:         following:
3775    
3776           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3777    
# Line 3712  BACKSLASH Line 3951  BACKSLASH
3951         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3952         matches any one character.         matches any one character.
3953    
3954           Note that recent versions of Perl have changed \X to match what Unicode
3955           calls an "extended grapheme cluster", which has a more complicated def-
3956           inition.
3957    
3958         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3959         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3960         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
# Line 3740  BACKSLASH Line 3983  BACKSLASH
3983    
3984     Resetting the match start     Resetting the match start
3985    
3986         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The  escape sequence \K causes any previously matched characters not to
3987         ously matched characters not  to  be  included  in  the  final  matched         be included in the final matched sequence. For example, the pattern:
        sequence. For example, the pattern:  
3988    
3989           foo\Kbar           foo\Kbar
3990    
3991         matches  "foobar",  but reports that it has matched "bar". This feature         matches "foobar", but reports that it has matched "bar".  This  feature
3992         is similar to a lookbehind assertion (described  below).   However,  in         is  similar  to  a lookbehind assertion (described below).  However, in
3993         this  case, the part of the subject before the real match does not have         this case, the part of the subject before the real match does not  have
3994         to be of fixed length, as lookbehind assertions do. The use of \K  does         to  be of fixed length, as lookbehind assertions do. The use of \K does
3995         not  interfere  with  the setting of captured substrings.  For example,         not interfere with the setting of captured  substrings.   For  example,
3996         when the pattern         when the pattern
3997    
3998           (foo)\Kbar           (foo)\Kbar
3999    
4000         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
4001    
4002         Perl documents that the use  of  \K  within  assertions  is  "not  well         Perl  documents  that  the  use  of  \K  within assertions is "not well
4003         defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive         defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
4004         assertions, but is ignored in negative assertions.         assertions, but is ignored in negative assertions.
4005    
4006     Simple assertions     Simple assertions
4007    
4008         The final use of backslash is for certain simple assertions. An  asser-         The  final use of backslash is for certain simple assertions. An asser-
4009         tion  specifies a condition that has to be met at a particular point in         tion specifies a condition that has to be met at a particular point  in
4010         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
4011         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
4012         The backslashed assertions are:         The backslashed assertions are:
4013    
4014           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3777  BACKSLASH Line 4019  BACKSLASH
4019           \z     matches only at the end of the subject           \z     matches only at the end of the subject
4020           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
4021    
4022         Inside a character class, \b has a different meaning;  it  matches  the         Inside  a  character  class, \b has a different meaning; it matches the
4023         backspace  character.  If  any  other  of these assertions appears in a         backspace character. If any other of  these  assertions  appears  in  a
4024         character class, by default it matches the corresponding literal  char-         character  class, by default it matches the corresponding literal char-
4025         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
4026         PCRE_EXTRA option is set, an "invalid escape sequence" error is  gener-         PCRE_EXTRA  option is set, an "invalid escape sequence" error is gener-
4027         ated instead.         ated instead.
4028    
4029         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
4030         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
4031         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
4032         string if the first or last  character  matches  \w,  respectively.  In         string  if  the  first  or  last character matches \w, respectively. In
4033         UTF-8  mode,  the  meanings  of \w and \W can be changed by setting the         UTF-8 mode, the meanings of \w and \W can be  changed  by  setting  the
4034         PCRE_UCP option. When this is done, it also affects \b and \B.  Neither         PCRE_UCP  option. When this is done, it also affects \b and \B. Neither
4035         PCRE  nor  Perl has a separate "start of word" or "end of word" metase-         PCRE nor Perl has a separate "start of word" or "end of  word"  metase-
4036         quence. However, whatever follows \b normally determines which  it  is.         quence.  However,  whatever follows \b normally determines which it is.
4037         For example, the fragment \ba matches "a" at the start of a word.         For example, the fragment \ba matches "a" at the start of a word.
4038    
4039         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
4040         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
4041         at  the  very start and end of the subject string, whatever options are         at the very start and end of the subject string, whatever  options  are
4042         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
4043         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
4044         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
4045         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
4046         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
4047         the  subject,  \A  can never match. The difference between \Z and \z is         the subject, \A can never match. The difference between \Z  and  \z  is
4048         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
4049         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
4050    
4051         The  \G assertion is true only when the current matching position is at         The \G assertion is true only when the current matching position is  at
4052         the start point of the match, as specified by the startoffset  argument         the  start point of the match, as specified by the startoffset argument
4053         of  pcre_exec().  It  differs  from \A when the value of startoffset is         of pcre_exec(). It differs from \A when the  value  of  startoffset  is
4054         non-zero. By calling pcre_exec() multiple times with appropriate  argu-         non-zero.  By calling pcre_exec() multiple times with appropriate argu-
4055         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
4056         mentation where \G can be useful.         mentation where \G can be useful.
4057    
4058         Note, however, that PCRE's interpretation of \G, as the  start  of  the         Note,  however,  that  PCRE's interpretation of \G, as the start of the
4059         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
4060         end of the previous match. In Perl, these can  be  different  when  the         end  of  the  previous  match. In Perl, these can be different when the
4061         previously  matched  string was empty. Because PCRE does just one match         previously matched string was empty. Because PCRE does just  one  match
4062         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
4063    
4064         If all the alternatives of a pattern begin with \G, the  expression  is         If  all  the alternatives of a pattern begin with \G, the expression is
4065         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
4066         in the compiled regular expression.         in the compiled regular expression.
4067    
# Line 3827  BACKSLASH Line 4069  BACKSLASH
4069  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
4070    
4071         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
4072         character  is  an  assertion  that is true only if the current matching         character is an assertion that is true only  if  the  current  matching
4073         point is at the start of the subject string. If the  startoffset  argu-         point  is  at the start of the subject string. If the startoffset argu-
4074         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
4075         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
4076         has an entirely different meaning (see below).         has an entirely different meaning (see below).
4077    
4078         Circumflex  need  not be the first character of the pattern if a number         Circumflex need not be the first character of the pattern if  a  number
4079         of alternatives are involved, but it should be the first thing in  each         of  alternatives are involved, but it should be the first thing in each
4080         alternative  in  which  it appears if the pattern is ever to match that         alternative in which it appears if the pattern is ever  to  match  that
4081         branch. If all possible alternatives start with a circumflex, that  is,         branch.  If all possible alternatives start with a circumflex, that is,
4082         if  the  pattern  is constrained to match only at the start of the sub-         if the pattern is constrained to match only at the start  of  the  sub-
4083         ject, it is said to be an "anchored" pattern.  (There  are  also  other         ject,  it  is  said  to be an "anchored" pattern. (There are also other
4084         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
4085    
4086         A  dollar  character  is  an assertion that is true only if the current         A dollar character is an assertion that is true  only  if  the  current
4087         matching point is at the end of  the  subject  string,  or  immediately         matching  point  is  at  the  end of the subject string, or immediately
4088         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
4089         be the last character of the pattern if a number  of  alternatives  are         be  the  last  character of the pattern if a number of alternatives are
4090         involved,  but  it  should  be  the last item in any branch in which it         involved, but it should be the last item in  any  branch  in  which  it
4091         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
4092    
4093         The meaning of dollar can be changed so that it  matches  only  at  the         The  meaning  of  dollar  can be changed so that it matches only at the
4094         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at
4095         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
4096    
4097         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
4098         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex
4099         matches immediately after internal newlines as well as at the start  of         matches  immediately after internal newlines as well as at the start of
4100         the  subject  string.  It  does not match after a newline that ends the         the subject string. It does not match after a  newline  that  ends  the
4101         string. A dollar matches before any newlines in the string, as well  as         string.  A dollar matches before any newlines in the string, as well as
4102         at  the very end, when PCRE_MULTILINE is set. When newline is specified         at the very end, when PCRE_MULTILINE is set. When newline is  specified
4103         as the two-character sequence CRLF, isolated CR and  LF  characters  do         as  the  two-character  sequence CRLF, isolated CR and LF characters do
4104         not indicate newlines.         not indicate newlines.
4105    
4106         For  example, the pattern /^abc$/ matches the subject string "def\nabc"         For example, the pattern /^abc$/ matches the subject string  "def\nabc"
4107         (where \n represents a newline) in multiline mode, but  not  otherwise.         (where  \n  represents a newline) in multiline mode, but not otherwise.
4108         Consequently,  patterns  that  are anchored in single line mode because         Consequently, patterns that are anchored in single  line  mode  because
4109         all branches start with ^ are not anchored in  multiline  mode,  and  a         all  branches  start  with  ^ are not anchored in multiline mode, and a
4110         match  for  circumflex  is  possible  when  the startoffset argument of         match for circumflex is  possible  when  the  startoffset  argument  of
4111         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
4112         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
4113    
4114         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note that the sequences \A, \Z, and \z can be used to match  the  start
4115         and end of the subject in both modes, and if all branches of a  pattern         and  end of the subject in both modes, and if all branches of a pattern
4116         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
4117         set.         set.
4118    
4119    
4120  FULL STOP (PERIOD, DOT) AND \N  FULL STOP (PERIOD, DOT) AND \N
4121    
4122         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
4123         ter  in  the subject string except (by default) a character that signi-         ter in the subject string except (by default) a character  that  signi-
4124         fies the end of a line. In UTF-8 mode, the  matched  character  may  be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
4125         more than one byte long.         more than one byte long.
4126    
4127         When  a line ending is defined as a single character, dot never matches         When a line ending is defined as a single character, dot never  matches
4128         that character; when the two-character sequence CRLF is used, dot  does         that  character; when the two-character sequence CRLF is used, dot does
4129         not  match  CR  if  it  is immediately followed by LF, but otherwise it         not match CR if it is immediately followed  by  LF,  but  otherwise  it
4130         matches all characters (including isolated CRs and LFs). When any  Uni-         matches  all characters (including isolated CRs and LFs). When any Uni-
4131         code  line endings are being recognized, dot does not match CR or LF or         code line endings are being recognized, dot does not match CR or LF  or
4132         any of the other line ending characters.         any of the other line ending characters.
4133    
4134         The behaviour of dot with regard to newlines can  be  changed.  If  the         The  behaviour  of  dot  with regard to newlines can be changed. If the
4135         PCRE_DOTALL  option  is  set,  a dot matches any one character, without         PCRE_DOTALL option is set, a dot matches  any  one  character,  without
4136         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
4137         string, it takes two dots to match it.         string, it takes two dots to match it.
4138    
4139         The  handling of dot is entirely independent of the handling of circum-         The handling of dot is entirely independent of the handling of  circum-
4140         flex and dollar, the only relationship being  that  they  both  involve         flex  and  dollar,  the  only relationship being that they both involve
4141         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
4142    
4143         The escape sequence \N always behaves as a dot does when PCRE_DOTALL is         The escape sequence \N behaves like  a  dot,  except  that  it  is  not
4144         not set. In other words, it matches any one character except  one  that         affected  by  the  PCRE_DOTALL  option.  In other words, it matches any
4145         signifies the end of a line.         character except one that signifies the end of a line.
4146    
4147    
4148  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
4149    
4150         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
4151         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
4152         line-ending  characters.  The  feature  is provided in Perl in order to         line-ending characters. The feature is provided in  Perl  in  order  to
4153         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
4154         acters  into individual bytes, what remains in the string may be a mal-         acters into individual bytes, the rest of the string may start  with  a
4155         formed UTF-8 string. For this reason, the \C escape  sequence  is  best         malformed  UTF-8  character. For this reason, the \C escape sequence is
4156         avoided.         best avoided.
4157    
4158         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
4159         below), because in UTF-8 mode this would make it impossible  to  calcu-         below),  because  in UTF-8 mode this would make it impossible to calcu-
4160         late the length of the lookbehind.         late the length of the lookbehind.
4161    
4162    
# Line 3924  SQUARE BRACKETS AND CHARACTER CLASSES Line 4166  SQUARE BRACKETS AND CHARACTER CLASSES
4166         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
4167         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
4168         a lone closing square bracket causes a compile-time error. If a closing         a lone closing square bracket causes a compile-time error. If a closing
4169         square  bracket  is required as a member of the class, it should be the         square bracket is required as a member of the class, it should  be  the
4170         first data character in the class  (after  an  initial  circumflex,  if         first  data  character  in  the  class (after an initial circumflex, if
4171         present) or escaped with a backslash.         present) or escaped with a backslash.
4172    
4173         A  character  class matches a single character in the subject. In UTF-8         A character class matches a single character in the subject.  In  UTF-8
4174         mode, the character may be more than one byte long. A matched character         mode, the character may be more than one byte long. A matched character
4175         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
4176         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
4177         subject  character  must  not  be in the set defined by the class. If a         subject character must not be in the set defined by  the  class.  If  a
4178         circumflex is actually required as a member of the class, ensure it  is         circumflex  is actually required as a member of the class, ensure it is
4179         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
4180    
4181         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
4182         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
4183         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
4184         characters that are in the class by enumerating those that are  not.  A         characters  that  are in the class by enumerating those that are not. A
4185         class  that starts with a circumflex is not an assertion; it still con-         class that starts with a circumflex is not an assertion; it still  con-
4186         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
4187         the current pointer is at the end of the string.         the current pointer is at the end of the string.
4188    
4189         In  UTF-8 mode, characters with values greater than 255 can be included         In UTF-8 mode, characters with values greater than 255 can be  included
4190         in a class as a literal string of bytes, or by using the  \x{  escaping         in  a  class as a literal string of bytes, or by using the \x{ escaping
4191         mechanism.         mechanism.
4192    
4193         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
4194         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
4195         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not
4196         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
4197         understands  the  concept  of case for characters whose values are less         understands the concept of case for characters whose  values  are  less
4198         than 128, so caseless matching is always possible. For characters  with         than  128, so caseless matching is always possible. For characters with
4199         higher  values,  the  concept  of case is supported if PCRE is compiled         higher values, the concept of case is supported  if  PCRE  is  compiled
4200         with Unicode property support, but not otherwise.  If you want  to  use         with  Unicode  property support, but not otherwise.  If you want to use
4201         caseless  matching  in UTF8-mode for characters 128 and above, you must         caseless matching in UTF8-mode for characters 128 and above,  you  must
4202         ensure that PCRE is compiled with Unicode property support as  well  as         ensure  that  PCRE is compiled with Unicode property support as well as
4203         with UTF-8 support.         with UTF-8 support.
4204    
4205         Characters  that  might  indicate  line breaks are never treated in any         Characters that might indicate line breaks are  never  treated  in  any
4206         special way  when  matching  character  classes,  whatever  line-ending         special  way  when  matching  character  classes,  whatever line-ending
4207         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
4208         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
4209         of these characters.         of these characters.
4210    
4211         The  minus (hyphen) character can be used to specify a range of charac-         The minus (hyphen) character can be used to specify a range of  charac-
4212         ters in a character  class.  For  example,  [d-m]  matches  any  letter         ters  in  a  character  class.  For  example,  [d-m] matches any letter
4213         between  d  and  m,  inclusive.  If  a minus character is required in a         between d and m, inclusive. If a  minus  character  is  required  in  a
4214         class, it must be escaped with a backslash  or  appear  in  a  position         class,  it  must  be  escaped  with a backslash or appear in a position
4215         where  it cannot be interpreted as indicating a range, typically as the         where it cannot be interpreted as indicating a range, typically as  the
4216         first or last character in the class.         first or last character in the class.
4217    
4218         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
4219         ter  of a range. A pattern such as [W-]46] is interpreted as a class of         ter of a range. A pattern such as [W-]46] is interpreted as a class  of
4220         two characters ("W" and "-") followed by a literal string "46]", so  it         two  characters ("W" and "-") followed by a literal string "46]", so it
4221         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
4222         backslash it is interpreted as the end of range, so [W-\]46] is  inter-         backslash  it is interpreted as the end of range, so [W-\]46] is inter-
4223         preted  as a class containing a range followed by two other characters.         preted as a class containing a range followed by two other  characters.
4224         The octal or hexadecimal representation of "]" can also be used to  end         The  octal or hexadecimal representation of "]" can also be used to end
4225         a range.         a range.
4226    
4227         Ranges  operate in the collating sequence of character values. They can         Ranges operate in the collating sequence of character values. They  can
4228         also  be  used  for  characters  specified  numerically,  for   example         also   be  used  for  characters  specified  numerically,  for  example
4229         [\000-\037].  In UTF-8 mode, ranges can include characters whose values         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
4230         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
4231    
4232         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
4233         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
4234         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
4235         character  tables  for  a French locale are in use, [\xc8-\xcb] matches         character tables for a French locale are in  use,  [\xc8-\xcb]  matches
4236         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
4237         concept  of  case for characters with values greater than 128 only when         concept of case for characters with values greater than 128  only  when
4238         it is compiled with Unicode property support.         it is compiled with Unicode property support.
4239    
4240         The character types \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, \w, and  \W         The  character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V,
4241         may  also appear in a character class, and add the characters that they         \w, and \W may appear in a character class, and add the characters that
4242         match to the class. For example,  [\dABCDEF]  matches  any  hexadecimal         they  match to the class. For example, [\dABCDEF] matches any hexadeci-
4243         digit.  A circumflex can conveniently be used with the upper case char-         mal digit. In UTF-8 mode, the PCRE_UCP option affects the  meanings  of
4244         acter types to specify a more restricted set  of  characters  than  the         \d,  \s,  \w  and  their upper case partners, just as it does when they
4245         matching  lower  case  type.  For example, the class [^\W_] matches any         appear outside a character class, as described in the section  entitled
4246         letter or digit, but not underscore.         "Generic character types" above. The escape sequence \b has a different
4247           meaning inside a character class; it matches the  backspace  character.
4248         The only metacharacters that are recognized in  character  classes  are         The  sequences  \B,  \N,  \R, and \X are not special inside a character
4249         backslash,  hyphen  (only  where  it can be interpreted as specifying a         class. Like any other unrecognized escape sequences, they  are  treated
4250         range), circumflex (only at the start), opening  square  bracket  (only         as  the literal characters "B", "N", "R", and "X" by default, but cause
4251         when  it can be interpreted as introducing a POSIX class name - see the         an error if the PCRE_EXTRA option is set.
4252         next section), and the terminating  closing  square  bracket.  However,  
4253           A circumflex can conveniently be used with  the  upper  case  character
4254           types  to specify a more restricted set of characters than the matching
4255           lower case type.  For example, the class [^\W_] matches any  letter  or
4256           digit, but not underscore, whereas [\w] includes underscore. A positive
4257           character class should be read as "something OR something OR ..." and a
4258           negative class as "NOT something AND NOT something AND NOT ...".
4259    
4260           The  only  metacharacters  that are recognized in character classes are
4261           backslash, hyphen (only where it can be  interpreted  as  specifying  a
4262           range),  circumflex  (only  at the start), opening square bracket (only
4263           when it can be interpreted as introducing a POSIX class name - see  the
4264           next  section),  and  the  terminating closing square bracket. However,
4265         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
4266    
4267    
4268  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
4269    
4270         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
4271         enclosed by [: and :] within the enclosing square brackets.  PCRE  also         enclosed  by  [: and :] within the enclosing square brackets. PCRE also
4272         supports this notation. For example,         supports this notation. For example,
4273    
4274           [01[:alpha:]%]           [01[:alpha:]%]
# Line 4037  POSIX CHARACTER CLASSES Line 4291  POSIX CHARACTER CLASSES
4291           word     "word" characters (same as \w)           word     "word" characters (same as \w)
4292           xdigit   hexadecimal digits           xdigit   hexadecimal digits
4293    
4294         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
4295         and  space  (32). Notice that this list includes the VT character (code         and space (32). Notice that this list includes the VT  character  (code
4296         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
4297         Perl compatibility).         Perl compatibility).
4298    
4299         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension
4300         from Perl 5.8. Another Perl extension is negation, which  is  indicated         from  Perl  5.8. Another Perl extension is negation, which is indicated
4301         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
4302    
4303           [12[:^digit:]]           [12[:^digit:]]
4304    
4305         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the
4306         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
4307         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
4308    
4309         By  default,  in UTF-8 mode, characters with values greater than 128 do         By default, in UTF-8 mode, characters with values greater than  128  do
4310         not match any of the POSIX character classes. However, if the  PCRE_UCP         not  match any of the POSIX character classes. However, if the PCRE_UCP
4311         option  is passed to pcre_compile(), some of the classes are changed so         option is passed to pcre_compile(), some of the classes are changed  so
4312         that Unicode character properties are used. This is achieved by replac-         that Unicode character properties are used. This is achieved by replac-
4313         ing the POSIX classes by other sequences, as follows:         ing the POSIX classes by other sequences, as follows:
4314    
# Line 4067  POSIX CHARACTER CLASSES Line 4321  POSIX CHARACTER CLASSES
4321           [:upper:]  becomes  \p{Lu}           [:upper:]  becomes  \p{Lu}
4322           [:word:]   becomes  \p{Xwd}           [:word:]   becomes  \p{Xwd}
4323    
4324         Negated  versions,  such  as [:^alpha:] use \P instead of \p. The other         Negated versions, such as [:^alpha:] use \P instead of  \p.  The  other
4325         POSIX classes are unchanged, and match only characters with code points         POSIX classes are unchanged, and match only characters with code points
4326         less than 128.         less than 128.
4327    
4328    
4329  VERTICAL BAR  VERTICAL BAR
4330    
4331         Vertical  bar characters are used to separate alternative patterns. For         Vertical bar characters are used to separate alternative patterns.  For
4332         example, the pattern         example, the pattern
4333    
4334           gilbert|sullivan           gilbert|sullivan
4335    
4336         matches either "gilbert" or "sullivan". Any number of alternatives  may         matches  either "gilbert" or "sullivan". Any number of alternatives may
4337         appear,  and  an  empty  alternative  is  permitted (matching the empty         appear, and an empty  alternative  is  permitted  (matching  the  empty
4338         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
4339         to  right, and the first one that succeeds is used. If the alternatives         to right, and the first one that succeeds is used. If the  alternatives
4340         are within a subpattern (defined below), "succeeds" means matching  the         are  within a subpattern (defined below), "succeeds" means matching the
4341         rest of the main pattern as well as the alternative in the subpattern.         rest of the main pattern as well as the alternative in the subpattern.
4342    
4343    
4344  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
4345    
4346         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
4347         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
4348         within  the  pattern  by  a  sequence  of  Perl option letters enclosed         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
4349         between "(?" and ")".  The option letters are         between "(?" and ")".  The option letters are
4350    
4351           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 4101  INTERNAL OPTION SETTING Line 4355  INTERNAL OPTION SETTING
4355    
4356         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
4357         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
4358         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
4359         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
4360         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
4361         hyphen, the option is unset.         hyphen, the option is unset.
4362    
4363         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
4364         can be changed in the same way as the Perl-compatible options by  using         can  be changed in the same way as the Perl-compatible options by using
4365         the characters J, U and X respectively.         the characters J, U and X respectively.
4366    
4367         When  one  of  these  option  changes occurs at top level (that is, not         When one of these option changes occurs at  top  level  (that  is,  not
4368         inside subpattern parentheses), the change applies to the remainder  of         inside  subpattern parentheses), the change applies to the remainder of
4369         the pattern that follows. If the change is placed right at the start of         the pattern that follows. If the change is placed right at the start of
4370         a pattern, PCRE extracts it into the global options (and it will there-         a pattern, PCRE extracts it into the global options (and it will there-
4371         fore show up in data extracted by the pcre_fullinfo() function).         fore show up in data extracted by the pcre_fullinfo() function).
4372    
4373         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
4374         subpatterns) affects only that part of the current pattern that follows         subpatterns)  affects only that part of the subpattern that follows it,
4375         it, so         so
4376    
4377           (a(?i)b)c           (a(?i)b)c
4378    
4379         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
4380         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
4381         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
4382         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
4383         example,         example,
4384    
4385           (a(?i)b|c)           (a(?i)b|c)
4386    
4387         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
4388         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
4389         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
4390         some very weird behaviour otherwise.         some very weird behaviour otherwise.
4391    
4392         Note: There are other PCRE-specific options that  can  be  set  by  the         Note:  There  are  other  PCRE-specific  options that can be set by the
4393         application  when  the  compile  or match functions are called. In some         application when the compile or match functions  are  called.  In  some
4394         cases the pattern can contain special leading sequences such as (*CRLF)         cases the pattern can contain special leading sequences such as (*CRLF)
4395         to  override  what  the application has set or what has been defaulted.         to override what the application has set or what  has  been  defaulted.
4396         Details are given in the section entitled  "Newline  sequences"  above.         Details  are  given  in the section entitled "Newline sequences" above.
4397         There  are  also  the  (*UTF8) and (*UCP) leading sequences that can be         There are also the (*UTF8) and (*UCP) leading  sequences  that  can  be
4398         used to set UTF-8 and Unicode property modes; they  are  equivalent  to         used  to  set  UTF-8 and Unicode property modes; they are equivalent to
4399         setting the PCRE_UTF8 and the PCRE_UCP options, respectively.         setting the PCRE_UTF8 and the PCRE_UCP options, respectively.
4400    
4401    
# Line 4154  SUBPATTERNS Line 4408  SUBPATTERNS
4408    
4409           cat(aract|erpillar|)           cat(aract|erpillar|)
4410    
4411         matches one of the words "cat", "cataract", or  "caterpillar".  Without         matches  "cataract",  "caterpillar", or "cat". Without the parentheses,
4412         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty         it would match "cataract", "erpillar" or an empty string.
        string.  
4413    
4414         2. It sets up the subpattern as  a  capturing  subpattern.  This  means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
4415         that,  when  the  whole  pattern  matches,  that portion of the subject         that,  when  the  whole  pattern  matches,  that portion of the subject
4416         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
4417         ovector  argument  of pcre_exec(). Opening parentheses are counted from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
4418         left to right (starting from 1) to obtain  numbers  for  the  capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
4419         subpatterns.         subpatterns.  For  example,  if  the  string  "the red king" is matched
4420           against the pattern
        For  example,  if the string "the red king" is matched against the pat-  
        tern  
4421    
4422           the ((red|white) (king|queen))           the ((red|white) (king|queen))
4423    
# Line 4215  DUPLICATE SUBPATTERN NUMBERS Line 4466  DUPLICATE SUBPATTERN NUMBERS
4466         matched. This construct is useful when you want to  capture  part,  but         matched. This construct is useful when you want to  capture  part,  but
4467         not all, of one of a number of alternatives. Inside a (?| group, paren-         not all, of one of a number of alternatives. Inside a (?| group, paren-
4468         theses are numbered as usual, but the number is reset at the  start  of         theses are numbered as usual, but the number is reset at the  start  of
4469         each  branch. The numbers of any capturing buffers that follow the sub-         each  branch.  The numbers of any capturing parentheses that follow the
4470         pattern start after the highest number used in any branch. The  follow-         subpattern start after the highest number used in any branch. The  fol-
4471         ing  example  is taken from the Perl documentation.  The numbers under-         lowing example is taken from the Perl documentation. The numbers under-
4472         neath show in which buffer the captured content will be stored.         neath show in which buffer the captured content will be stored.
4473    
4474           # before  ---------------branch-reset----------- after           # before  ---------------branch-reset----------- after
# Line 4324  REPETITION Line 4575  REPETITION
4575           the \C escape sequence           the \C escape sequence
4576           the \X escape sequence (in UTF-8 mode with Unicode properties)           the \X escape sequence (in UTF-8 mode with Unicode properties)
4577           the \R escape sequence           the \R escape sequence
4578           an escape such as \d that matches a single character           an escape such as \d or \pL that matches a single character
4579           a character class           a character class
4580           a back reference (see next section)           a back reference (see next section)
4581           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (including assertions)
4582           a recursive or "subroutine" call to a subpattern           a recursive or "subroutine" call to a subpattern
4583    
4584         The  general repetition quantifier specifies a minimum and maximum num-         The  general repetition quantifier specifies a minimum and maximum num-
# Line 4364  REPETITION Line 4615  REPETITION
4615         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4616         the previous item and the quantifier were not present. This may be use-         the previous item and the quantifier were not present. This may be use-
4617         ful for subpatterns that are referenced as subroutines  from  elsewhere         ful for subpatterns that are referenced as subroutines  from  elsewhere
4618         in the pattern. Items other than subpatterns that have a {0} quantifier         in the pattern (but see also the section entitled "Defining subpatterns
4619         are omitted from the compiled pattern.         for use by reference only" below). Items other  than  subpatterns  that
4620           have a {0} quantifier are omitted from the compiled pattern.
4621    
4622         For convenience, the three most common quantifiers have  single-charac-         For  convenience, the three most common quantifiers have single-charac-
4623         ter abbreviations:         ter abbreviations:
4624    
4625           *    is equivalent to {0,}           *    is equivalent to {0,}
4626           +    is equivalent to {1,}           +    is equivalent to {1,}
4627           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
4628    
4629         It  is  possible  to construct infinite loops by following a subpattern         It is possible to construct infinite loops by  following  a  subpattern
4630         that can match no characters with a quantifier that has no upper limit,         that can match no characters with a quantifier that has no upper limit,
4631         for example:         for example:
4632    
4633           (a?)*           (a?)*
4634    
4635         Earlier versions of Perl and PCRE used to give an error at compile time         Earlier versions of Perl and PCRE used to give an error at compile time
4636         for such patterns. However, because there are cases where this  can  be         for  such  patterns. However, because there are cases where this can be
4637         useful,  such  patterns  are now accepted, but if any repetition of the         useful, such patterns are now accepted, but if any  repetition  of  the
4638         subpattern does in fact match no characters, the loop is forcibly  bro-         subpattern  does in fact match no characters, the loop is forcibly bro-
4639         ken.         ken.
4640    
4641         By  default,  the quantifiers are "greedy", that is, they match as much