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revision 75 by nigel, Sat Feb 24 21:40:37 2007 UTC revision 83 by nigel, Sat Feb 24 21:41:06 2007 UTC
# Line 6  synopses of each function in the library Line 6  synopses of each function in the library
6  separate text files for the pcregrep and pcretest commands.  separate text files for the pcregrep and pcretest commands.
7  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
8    
 PCRE(3)                                                                PCRE(3)  
9    
10    PCRE(3)                                                                PCRE(3)
11    
12    
13  NAME  NAME
14         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
15    
16    
17  INTRODUCTION  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few  differences.  The current implementation of PCRE (release         just  a  few  differences.  The current implementation of PCRE (release
22         5.x) corresponds approximately with Perl  5.8,  including  support  for         6.x) corresponds approximately with Perl  5.8,  including  support  for
23         UTF-8 encoded strings and Unicode general category properties. However,         UTF-8 encoded strings and Unicode general category properties. However,
24         this support has to be explicitly enabled; it is not the default.         this support has to be explicitly enabled; it is not the default.
25    
26           In addition to the Perl-compatible matching function,  PCRE  also  con-
27           tains  an  alternative matching function that matches the same compiled
28           patterns in a different way. In certain circumstances, the  alternative
29           function  has  some  advantages.  For  a discussion of the two matching
30           algorithms, see the pcrematching page.
31    
32         PCRE is written in C and released as a C library. A  number  of  people         PCRE is written in C and released as a C library. A  number  of  people
33         have  written  wrappers and interfaces of various kinds. A C++ class is         have  written  wrappers and interfaces of various kinds. In particular,
34         included in these contributions, which can  be  found  in  the  Contrib         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now
35         directory at the primary FTP site, which is:         included as part of the PCRE distribution. The pcrecpp page has details
36           of this interface. Other people's contributions can  be  found  in  the
37           Contrib directory at the primary FTP site, which is:
38    
39         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
40    
# Line 40  INTRODUCTION Line 49  INTRODUCTION
49         ing  PCRE for various operating systems can be found in the README file         ing  PCRE for various operating systems can be found in the README file
50         in the source distribution.         in the source distribution.
51    
52           The library contains a number of undocumented  internal  functions  and
53           data  tables  that  are  used by more than one of the exported external
54           functions, but which are not intended  for  use  by  external  callers.
55           Their  names  all begin with "_pcre_", which hopefully will not provoke
56           any name clashes. In some environments, it is possible to control which
57           external  symbols  are  exported when a shared library is built, and in
58           these cases the undocumented symbols are not exported.
59    
60    
61  USER DOCUMENTATION  USER DOCUMENTATION
62    
# Line 50  USER DOCUMENTATION Line 67  USER DOCUMENTATION
67         of searching. The sections are as follows:         of searching. The sections are as follows:
68    
69           pcre              this document           pcre              this document
70           pcreapi           details of PCRE's native API           pcreapi           details of PCRE's native C API
71           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
72           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
73           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
74             pcrecpp           details of the C++ wrapper
75           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
76             pcrematching      discussion of the two matching algorithms
77           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
78           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
79                               regular expressions                               regular expressions
80           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
81           pcreposix         the POSIX-compatible API           pcreposix         the POSIX-compatible C API
82           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
83           pcresample        discussion of the sample program           pcresample        discussion of the sample program
84           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
85    
86         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
87         each library function, listing its arguments and results.         each C library function, listing its arguments and results.
88    
89    
90  LIMITATIONS  LIMITATIONS
# Line 90  LIMITATIONS Line 109  LIMITATIONS
109         tern, is 200.         tern, is 200.
110    
111         The  maximum  length of a subject string is the largest positive number         The  maximum  length of a subject string is the largest positive number
112         that an integer variable can hold. However, PCRE uses recursion to han-         that an integer variable can hold. However, when using the  traditional
113         dle  subpatterns  and indefinite repetition. This means that the avail-         matching function, PCRE uses recursion to handle subpatterns and indef-
114         able stack space may limit the size of a subject  string  that  can  be         inite repetition.  This means that the available stack space may  limit
115         processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
116    
117    
118  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
119    
120         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
121         encoded in the UTF-8 format. For release 4.0 this was greatly  extended         encoded  in the UTF-8 format. For release 4.0 this was greatly extended
122         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
123         port for Unicode general category properties was added.         port for Unicode general category properties was added.
124    
125         In order process UTF-8 strings, you must build PCRE  to  include  UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
126         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
127         with the PCRE_UTF8 option flag. When you do this, both the pattern  and         with  the PCRE_UTF8 option flag. When you do this, both the pattern and
128         any  subject  strings  that are matched against it are treated as UTF-8         any subject strings that are matched against it are  treated  as  UTF-8
129         strings instead of just strings of bytes.         strings instead of just strings of bytes.
130    
131         If you compile PCRE with UTF-8 support, but do not use it at run  time,         If  you compile PCRE with UTF-8 support, but do not use it at run time,
132         the  library will be a bit bigger, but the additional run time overhead         the library will be a bit bigger, but the additional run time  overhead
133         is limited to testing the PCRE_UTF8 flag in several places,  so  should         is  limited  to testing the PCRE_UTF8 flag in several places, so should
134         not be very large.         not be very large.
135    
136         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
137         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
138         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
139         general category properties such as Lu for an upper case letter  or  Nd         general  category  properties such as Lu for an upper case letter or Nd
140         for  a decimal number. A full list is given in the pcrepattern documen-         for a decimal number. A full list is given in the pcrepattern  documen-
141         tation. The PCRE library is increased in size by about 90K when Unicode         tation. The PCRE library is increased in size by about 90K when Unicode
142         property support is included.         property support is included.
143    
144         The following comments apply when PCRE is running in UTF-8 mode:         The following comments apply when PCRE is running in UTF-8 mode:
145    
146         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and
147         subjects are checked for validity on entry to the  relevant  functions.         subjects  are  checked for validity on entry to the relevant functions.
148         If an invalid UTF-8 string is passed, an error return is given. In some         If an invalid UTF-8 string is passed, an error return is given. In some
149         situations, you may already know  that  your  strings  are  valid,  and         situations,  you  may  already  know  that  your strings are valid, and
150         therefore want to skip these checks in order to improve performance. If         therefore want to skip these checks in order to improve performance. If
151         you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,
152         PCRE  assumes  that  the  pattern or subject it is given (respectively)         PCRE assumes that the pattern or subject  it  is  given  (respectively)
153         contains only valid UTF-8 codes. In this case, it does not diagnose  an         contains  only valid UTF-8 codes. In this case, it does not diagnose an
154         invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when
155         PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may
156         crash.         crash.
157    
158         2. In a pattern, the escape sequence \x{...}, where the contents of the         2. In a pattern, the escape sequence \x{...}, where the contents of the
159         braces is a string of hexadecimal digits, is  interpreted  as  a  UTF-8         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8
160         character  whose code number is the given hexadecimal number, for exam-         character whose code number is the given hexadecimal number, for  exam-
161         ple: \x{1234}. If a non-hexadecimal digit appears between  the  braces,         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,
162         the item is not recognized.  This escape sequence can be used either as         the item is not recognized.  This escape sequence can be used either as
163         a literal, or within a character class.         a literal, or within a character class.
164    
165         3. The original hexadecimal escape sequence, \xhh, matches  a  two-byte         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte
166         UTF-8 character if the value is greater than 127.         UTF-8 character if the value is greater than 127.
167    
168         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
169         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
170    
171         5. The dot metacharacter matches one UTF-8 character instead of a  sin-         5.  The dot metacharacter matches one UTF-8 character instead of a sin-
172         gle byte.         gle byte.
173    
174         6.  The  escape sequence \C can be used to match a single byte in UTF-8         6. The escape sequence \C can be used to match a single byte  in  UTF-8
175         mode, but its use can lead to some strange effects.         mode,  but  its  use can lead to some strange effects. This facility is
176           not available in the alternative matching function, pcre_dfa_exec().
177    
178         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
179         test  characters of any code value, but the characters that PCRE recog-         test  characters of any code value, but the characters that PCRE recog-
# Line 177  UTF-8 AND UNICODE PROPERTY SUPPORT Line 197  UTF-8 AND UNICODE PROPERTY SUPPORT
197    
198  AUTHOR  AUTHOR
199    
200         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
201         University Computing Service,         University Computing Service,
202         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
        Phone: +44 1223 334714  
203    
204  Last updated: 09 September 2004         Putting  an actual email address here seems to have been a spam magnet,
205  Copyright (c) 1997-2004 University of Cambridge.         so I've taken it away. If you want to email me, use my initial and sur-
206  -----------------------------------------------------------------------------         name, separated by a dot, at the domain ucs.cam.ac.uk.
207    
208  PCRE(3)                                                                PCRE(3)  Last updated: 07 March 2005
209    Copyright (c) 1997-2005 University of Cambridge.
210    ------------------------------------------------------------------------------
211    
212    
213    PCREBUILD(3)                                                      PCREBUILD(3)
214    
215    
216  NAME  NAME
217         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
218    
219    
220  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
221    
222         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
# Line 212  PCRE BUILD-TIME OPTIONS Line 236  PCRE BUILD-TIME OPTIONS
236         not described.         not described.
237    
238    
239    C++ SUPPORT
240    
241           By default, the configure script will search for a C++ compiler and C++
242           header files. If it finds them, it automatically builds the C++ wrapper
243           library for PCRE. You can disable this by adding
244    
245             --disable-cpp
246    
247           to the configure command.
248    
249    
250  UTF-8 SUPPORT  UTF-8 SUPPORT
251    
252         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 character strings, add
# Line 287  POSIX MALLOC USAGE Line 322  POSIX MALLOC USAGE
322  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
323    
324         Internally,  PCRE has a function called match(), which it calls repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
325         edly (possibly recursively) when matching a pattern. By controlling the         edly  (possibly  recursively)  when  matching  a   pattern   with   the
326         maximum  number  of  times  this function may be called during a single         pcre_exec()  function.  By controlling the maximum number of times this
327         matching operation, a limit can be placed on the resources  used  by  a         function may be called during a single matching operation, a limit  can
328         single  call  to  pcre_exec(). The limit can be changed at run time, as         be  placed  on  the resources used by a single call to pcre_exec(). The
329         described in the pcreapi documentation. The default is 10 million,  but         limit can be changed at run time, as described in the pcreapi  documen-
330         this can be changed by adding a setting such as         tation.  The default is 10 million, but this can be changed by adding a
331           setting such as
332    
333           --with-match-limit=500000           --with-match-limit=500000
334    
335         to the configure command.         to  the  configure  command.  This  setting  has  no  effect   on   the
336           pcre_dfa_exec() matching function.
337    
338    
339  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
# Line 324  HANDLING VERY LARGE PATTERNS Line 361  HANDLING VERY LARGE PATTERNS
361    
362  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
363    
364         PCRE  implements  backtracking while matching by making recursive calls         When matching with the pcre_exec() function, PCRE implements backtrack-
365         to an internal function called match(). In environments where the  size         ing by making recursive calls to an internal function  called  match().
366         of the stack is limited, this can severely limit PCRE's operation. (The         In  environments  where  the size of the stack is limited, this can se-
367         Unix environment does not usually suffer from this problem.) An  alter-         verely limit PCRE's operation. (The Unix environment does  not  usually
368         native  approach  that  uses  memory  from  the  heap to remember data,         suffer  from  this  problem.)  An alternative approach that uses memory
369         instead of using recursive function calls, has been implemented to work         from the heap to remember data, instead  of  using  recursive  function
370         round  this  problem. If you want to build a version of PCRE that works         calls,  has been implemented to work round this problem. If you want to
371         this way, add         build a version of PCRE that works this way, add
372    
373           --disable-stack-for-recursion           --disable-stack-for-recursion
374    
# Line 342  AVOIDING EXCESSIVE STACK USAGE Line 379  AVOIDING EXCESSIVE STACK USAGE
379         the blocks are always freed in reverse order. A calling  program  might         the blocks are always freed in reverse order. A calling  program  might
380         be  able  to implement optimized functions that perform better than the         be  able  to implement optimized functions that perform better than the
381         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more
382         slowly when built in this way.         slowly when built in this way. This option affects only the pcre_exec()
383           function; it is not relevant for the the pcre_dfa_exec() function.
384    
385    
386  USING EBCDIC CODE  USING EBCDIC CODE
387    
388         PCRE  assumes  by  default that it will run in an environment where the         PCRE assumes by default that it will run in an  environment  where  the
389         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
390         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by
391         adding         adding
392    
393           --enable-ebcdic           --enable-ebcdic
394    
395         to the configure command.         to the configure command.
396    
397  Last updated: 09 September 2004  Last updated: 15 August 2005
398  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
399  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
400    
401    
402    PCREMATCHING(3)                                                PCREMATCHING(3)
403    
404    
405    NAME
406           PCRE - Perl-compatible regular expressions
407    
408    
409    PCRE MATCHING ALGORITHMS
410    
411           This document describes the two different algorithms that are available
412           in PCRE for matching a compiled regular expression against a given sub-
413           ject  string.  The  "standard"  algorithm  is  the  one provided by the
414           pcre_exec() function.  This works in the same was  as  Perl's  matching
415           function, and provides a Perl-compatible matching operation.
416    
417           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
418           this operates in a different way, and is not  Perl-compatible.  It  has
419           advantages  and disadvantages compared with the standard algorithm, and
420           these are described below.
421    
422           When there is only one possible way in which a given subject string can
423           match  a pattern, the two algorithms give the same answer. A difference
424           arises, however, when there are multiple possibilities. For example, if
425           the pattern
426    
427             ^<.*>
428    
429           is matched against the string
430    
431             <something> <something else> <something further>
432    
433           there are three possible answers. The standard algorithm finds only one
434           of them, whereas the DFA algorithm finds all three.
435    
436    
437    REGULAR EXPRESSIONS AS TREES
438    
439           The set of strings that are matched by a regular expression can be rep-
440           resented  as  a  tree structure. An unlimited repetition in the pattern
441           makes the tree of infinite size, but it is still a tree.  Matching  the
442           pattern  to a given subject string (from a given starting point) can be
443           thought of as a search of the tree.  There are  two  standard  ways  to
444           search  a  tree: depth-first and breadth-first, and these correspond to
445           the two matching algorithms provided by PCRE.
446    
447    
448    THE STANDARD MATCHING ALGORITHM
449    
450           In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-
451           sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a
452           depth-first search of the pattern tree. That is, it  proceeds  along  a
453           single path through the tree, checking that the subject matches what is
454           required. When there is a mismatch, the algorithm  tries  any  alterna-
455           tives  at  the  current point, and if they all fail, it backs up to the
456           previous branch point in the  tree,  and  tries  the  next  alternative
457           branch  at  that  level.  This often involves backing up (moving to the
458           left) in the subject string as well.  The  order  in  which  repetition
459           branches  are  tried  is controlled by the greedy or ungreedy nature of
460           the quantifier.
461    
462           If a leaf node is reached, a matching string has  been  found,  and  at
463           that  point the algorithm stops. Thus, if there is more than one possi-
464           ble match, this algorithm returns the first one that it finds.  Whether
465           this  is the shortest, the longest, or some intermediate length depends
466           on the way the greedy and ungreedy repetition quantifiers are specified
467           in the pattern.
468    
469           Because  it  ends  up  with a single path through the tree, it is rela-
470           tively straightforward for this algorithm to keep  track  of  the  sub-
471           strings  that  are  matched  by portions of the pattern in parentheses.
472           This provides support for capturing parentheses and back references.
473    
474    
475    THE DFA MATCHING ALGORITHM
476    
477           DFA stands for "deterministic finite automaton", but you do not need to
478           understand the origins of that name. This algorithm conducts a breadth-
479           first search of the tree. Starting from the first matching point in the
480           subject,  it scans the subject string from left to right, once, charac-
481           ter by character, and as it does  this,  it  remembers  all  the  paths
482           through the tree that represent valid matches.
483    
484           The  scan  continues until either the end of the subject is reached, or
485           there are no more unterminated paths. At this point,  terminated  paths
486           represent  the different matching possibilities (if there are none, the
487           match has failed).  Thus, if there is more  than  one  possible  match,
488           this algorithm finds all of them, and in particular, it finds the long-
489           est. In PCRE, there is an option to stop the algorithm after the  first
490           match (which is necessarily the shortest) has been found.
491    
492           Note that all the matches that are found start at the same point in the
493           subject. If the pattern
494    
495             cat(er(pillar)?)
496    
497           is matched against the string "the caterpillar catchment",  the  result
498           will  be the three strings "cat", "cater", and "caterpillar" that start
499           at the fourth character of the subject. The algorithm does not automat-
500           ically move on to find matches that start at later positions.
501    
502           There are a number of features of PCRE regular expressions that are not
503           supported by the DFA matching algorithm. They are as follows:
504    
505           1. Because the algorithm finds all  possible  matches,  the  greedy  or
506           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
507           ungreedy quantifiers are treated in exactly the same way.
508    
509           2. When dealing with multiple paths through the tree simultaneously, it
510           is  not  straightforward  to  keep track of captured substrings for the
511           different matching possibilities, and  PCRE's  implementation  of  this
512           algorithm does not attempt to do this. This means that no captured sub-
513           strings are available.
514    
515           3. Because no substrings are captured, back references within the  pat-
516           tern are not supported, and cause errors if encountered.
517    
518           4.  For  the same reason, conditional expressions that use a backrefer-
519           ence as the condition are not supported.
520    
521           5. Callouts are supported, but the value of the  capture_top  field  is
522           always 1, and the value of the capture_last field is always -1.
523    
524           6.  The \C escape sequence, which (in the standard algorithm) matches a
525           single byte, even in UTF-8 mode, is not supported because the DFA algo-
526           rithm moves through the subject string one character at a time, for all
527           active paths through the tree.
528    
529    
530    ADVANTAGES OF THE DFA ALGORITHM
531    
532           Using the DFA matching algorithm provides the following advantages:
533    
534           1. All possible matches (at a single point in the subject) are automat-
535           ically  found,  and  in particular, the longest match is found. To find
536           more than one match using the standard algorithm, you have to do kludgy
537           things with callouts.
538    
539           2.  There is much better support for partial matching. The restrictions
540           on the content of the pattern that apply when using the standard  algo-
541           rithm  for partial matching do not apply to the DFA algorithm. For non-
542           anchored patterns, the starting position of a partial match  is  avail-
543           able.
544    
545           3.  Because  the  DFA algorithm scans the subject string just once, and
546           never needs to backtrack, it is possible  to  pass  very  long  subject
547           strings  to  the matching function in several pieces, checking for par-
548           tial matching each time.
549    
550    
551    DISADVANTAGES OF THE DFA ALGORITHM
552    
553           The DFA algorithm suffers from a number of disadvantages:
554    
555           1. It is substantially slower than  the  standard  algorithm.  This  is
556           partly  because  it has to search for all possible matches, but is also
557           because it is less susceptible to optimization.
558    
559           2. Capturing parentheses and back references are not supported.
560    
561           3. The "atomic group" feature of PCRE regular expressions is supported,
562           but  does not provide the advantage that it does for the standard algo-
563           rithm.
564    
565    Last updated: 28 February 2005
566    Copyright (c) 1997-2005 University of Cambridge.
567    ------------------------------------------------------------------------------
568    
 PCRE(3)                                                                PCRE(3)  
569    
570    PCREAPI(3)                                                          PCREAPI(3)
571    
572    
573  NAME  NAME
574         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
575    
576    
577  PCRE NATIVE API  PCRE NATIVE API
578    
579         #include <pcre.h>         #include <pcre.h>
# Line 375  PCRE NATIVE API Line 582  PCRE NATIVE API
582              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
583              const unsigned char *tableptr);              const unsigned char *tableptr);
584    
585           pcre *pcre_compile2(const char *pattern, int options,
586                int *errorcodeptr,
587                const char **errptr, int *erroffset,
588                const unsigned char *tableptr);
589    
590         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
591              const char **errptr);              const char **errptr);
592    
# Line 382  PCRE NATIVE API Line 594  PCRE NATIVE API
594              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
595              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
596    
597           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
598                const char *subject, int length, int startoffset,
599                int options, int *ovector, int ovecsize,
600                int *workspace, int wscount);
601    
602         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
603              const char *subject, int *ovector,              const char *subject, int *ovector,
604              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 417  PCRE NATIVE API Line 634  PCRE NATIVE API
634    
635         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
636    
637           int pcre_refcount(pcre *code, int adjust);
638    
639         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
640    
641         char *pcre_version(void);         char *pcre_version(void);
# Line 436  PCRE API OVERVIEW Line 655  PCRE API OVERVIEW
655    
656         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
657         is also a set of wrapper functions that correspond to the POSIX regular         is also a set of wrapper functions that correspond to the POSIX regular
658         expression API.  These are described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
659           Both of these APIs define a set of C function calls. A C++  wrapper  is
660           distributed with PCRE. It is documented in the pcrecpp page.
661    
662         The  native  API  function  prototypes  are  defined in the header file         The  native  API  C  function prototypes are defined in the header file
663         pcre.h, and on Unix systems the library itself is  called  libpcre.  It         pcre.h, and on Unix systems the library itself is called  libpcre.   It
664         can normally be accessed by adding -lpcre to the command for linking an         can normally be accessed by adding -lpcre to the command for linking an
665         application  that  uses  PCRE.  The  header  file  defines  the  macros         application  that  uses  PCRE.  The  header  file  defines  the  macros
666         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
667         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
668         for different releases of PCRE.         for different releases of PCRE.
669    
670         The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
671         for compiling and matching regular expressions. A sample  program  that         pcre_exec() are used for compiling and matching regular expressions  in
672         demonstrates  the  simplest  way  of using them is provided in the file         a  Perl-compatible  manner. A sample program that demonstrates the sim-
673         called pcredemo.c in the source distribution. The pcresample documenta-         plest way of using them is provided in the file  called  pcredemo.c  in
674         tion describes how to run it.         the  source distribution. The pcresample documentation describes how to
675           run it.
676         In  addition  to  the  main compiling and matching functions, there are  
677         convenience functions for extracting captured substrings from a matched         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
678         subject string.  They are:         ble,  is  also provided. This uses a different algorithm for the match-
679           ing. This allows it to find all possible matches (at a given  point  in
680           the  subject),  not  just  one. However, this algorithm does not return
681           captured substrings. A description of the two matching  algorithms  and
682           their  advantages  and disadvantages is given in the pcrematching docu-
683           mentation.
684    
685           In addition to the main compiling and  matching  functions,  there  are
686           convenience functions for extracting captured substrings from a subject
687           string that is matched by pcre_exec(). They are:
688    
689           pcre_copy_substring()           pcre_copy_substring()
690           pcre_copy_named_substring()           pcre_copy_named_substring()
# Line 466  PCRE API OVERVIEW Line 696  PCRE API OVERVIEW
696         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
697         to free the memory used for extracted strings.         to free the memory used for extracted strings.
698    
699         The function pcre_maketables() is used to  build  a  set  of  character         The  function  pcre_maketables()  is  used  to build a set of character
700         tables   in  the  current  locale  for  passing  to  pcre_compile()  or         tables  in  the  current  locale   for   passing   to   pcre_compile(),
701         pcre_exec().  This is an optional facility that is  provided  for  spe-         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
702         cialist use. Most commonly, no special tables are passed, in which case         provided for specialist use.  Most  commonly,  no  special  tables  are
703         internal tables that are generated when PCRE is built are used.         passed,  in  which case internal tables that are generated when PCRE is
704           built are used.
705    
706         The function pcre_fullinfo() is used to find out  information  about  a         The function pcre_fullinfo() is used to find out  information  about  a
707         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled  pattern; pcre_info() is an obsolete version that returns only
# Line 478  PCRE API OVERVIEW Line 709  PCRE API OVERVIEW
709         patibility.   The function pcre_version() returns a pointer to a string         patibility.   The function pcre_version() returns a pointer to a string
710         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
711    
712           The function pcre_refcount() maintains a  reference  count  in  a  data
713           block  containing  a compiled pattern. This is provided for the benefit
714           of object-oriented applications.
715    
716         The global variables pcre_malloc and pcre_free  initially  contain  the         The global variables pcre_malloc and pcre_free  initially  contain  the
717         entry  points  of  the  standard malloc() and free() functions, respec-         entry  points  of  the  standard malloc() and free() functions, respec-
718         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
# Line 487  PCRE API OVERVIEW Line 722  PCRE API OVERVIEW
722         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
723         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
724         are used only when PCRE is compiled to use  the  heap  for  remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
725         data,  instead  of recursive function calls. This is a non-standard way         data, instead of recursive function calls, when running the pcre_exec()
726         of building PCRE, for use in environments  that  have  limited  stacks.         function. This is a non-standard way of building PCRE, for use in envi-
727         Because  of  the greater use of memory management, it runs more slowly.         ronments that have limited stacks. Because of the greater use of memory
728         Separate functions are provided so that special-purpose  external  code         management, it runs more slowly.  Separate functions  are  provided  so
729         can be used for this case. When used, these functions are always called         that  special-purpose  external  code  can  be used for this case. When
730         in a stack-like manner (last obtained, first  freed),  and  always  for         used, these functions are always called in a  stack-like  manner  (last
731         memory blocks of the same size.         obtained,  first freed), and always for memory blocks of the same size.
732    
733         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
734         by the caller to a "callout" function, which PCRE  will  then  call  at         by  the  caller  to  a "callout" function, which PCRE will then call at
735         specified  points during a matching operation. Details are given in the         specified points during a matching operation. Details are given in  the
736         pcrecallout documentation.         pcrecallout documentation.
737    
738    
739  MULTITHREADING  MULTITHREADING
740    
741         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
742         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
743         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
744         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
745    
746         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
747         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
748         at once.         at once.
749    
# Line 516  MULTITHREADING Line 751  MULTITHREADING
751  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
752    
753         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
754         later  time,  possibly by a different program, and even on a host other         later time, possibly by a different program, and even on a  host  other
755         than the one on which  it  was  compiled.  Details  are  given  in  the         than  the  one  on  which  it  was  compiled.  Details are given in the
756         pcreprecompile documentation.         pcreprecompile documentation.
757    
758    
# Line 525  CHECKING BUILD-TIME OPTIONS Line 760  CHECKING BUILD-TIME OPTIONS
760    
761         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
762    
763         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
764         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
765         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
766         tures.         tures.
767    
768         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
769         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
770         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
771         available:         available:
772    
773           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
774    
775         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
776         able; otherwise it is set to zero.         able; otherwise it is set to zero.
777    
778           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
779    
780         The output is an integer that is set to  one  if  support  for  Unicode         The  output  is  an  integer  that is set to one if support for Unicode
781         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
782    
783           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
784    
785         The  output  is an integer that is set to the value of the code that is         The output is an integer that is set to the value of the code  that  is
786         used for the newline character. It is either linefeed (10) or  carriage         used  for the newline character. It is either linefeed (10) or carriage
787         return  (13),  and  should  normally be the standard character for your         return (13), and should normally be the  standard  character  for  your
788         operating system.         operating system.
789    
790           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
791    
792         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
793         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
794         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
795         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
796         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
797         pattern to be up to 64K in size.         pattern to be up to 64K in size.
798    
799           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
800    
801         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
802         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
803         given in the pcreposix documentation.         given in the pcreposix documentation.
804    
805           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
806    
807         The output is an integer that gives the default limit for the number of         The output is an integer that gives the default limit for the number of
808         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
809         details are given with pcre_exec() below.         details are given with pcre_exec() below.
810    
811           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
812    
813         The  output  is  an integer that is set to one if internal recursion is         The output is an integer that is set to one if internal recursion  when
814         implemented by recursive function calls that use the stack to  remember         running pcre_exec() is implemented by recursive function calls that use
815         their state. This is the usual way that PCRE is compiled. The output is         the stack to remember their state. This is the usual way that  PCRE  is
816         zero if PCRE was compiled to use blocks of data on the heap instead  of         compiled. The output is zero if PCRE was compiled to use blocks of data
817         recursive   function   calls.   In  this  case,  pcre_stack_malloc  and         on the  heap  instead  of  recursive  function  calls.  In  this  case,
818         pcre_stack_free are called to manage memory blocks on  the  heap,  thus         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
819         avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
820    
821    
822  COMPILING A PATTERN  COMPILING A PATTERN
# Line 590  COMPILING A PATTERN Line 825  COMPILING A PATTERN
825              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
826              const unsigned char *tableptr);              const unsigned char *tableptr);
827    
828         The  function  pcre_compile()  is  called  to compile a pattern into an         pcre *pcre_compile2(const char *pattern, int options,
829         internal form. The pattern is a C string terminated by a  binary  zero,              int *errorcodeptr,
830         and  is  passed in the pattern argument. A pointer to a single block of              const char **errptr, int *erroffset,
831         memory that is obtained via pcre_malloc is returned. This contains  the              const unsigned char *tableptr);
832         compiled  code  and  related  data.  The  pcre  type is defined for the  
833         returned block; this is a typedef for a structure  whose  contents  are         Either of the functions pcre_compile() or pcre_compile2() can be called
834         not  externally defined. It is up to the caller to free the memory when         to compile a pattern into an internal form. The only difference between
835         it is no longer required.         the two interfaces is that pcre_compile2() has an additional  argument,
836           errorcodeptr, via which a numerical error code can be returned.
837    
838           The pattern is a C string terminated by a binary zero, and is passed in
839           the pattern argument. A pointer to a single block  of  memory  that  is
840           obtained  via  pcre_malloc is returned. This contains the compiled code
841           and related data. The pcre type is defined for the returned block; this
842           is a typedef for a structure whose contents are not externally defined.
843           It is up to the caller  to  free  the  memory  when  it  is  no  longer
844           required.
845    
846         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
847         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
848         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
849         ment, which is an address (see below).         ment, which is an address (see below).
850    
851         The options argument contains independent bits that affect the compila-         The options argument contains independent bits that affect the compila-
852         tion. It should be zero if  no  options  are  required.  The  available         tion.  It  should  be  zero  if  no options are required. The available
853         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
854         are compatible with Perl, can also be set and  unset  from  within  the         are  compatible  with  Perl,  can also be set and unset from within the
855         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
856         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
857         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
858         The PCRE_ANCHORED option can be set at the time of matching as well  as         The  PCRE_ANCHORED option can be set at the time of matching as well as
859         at compile time.         at compile time.
860    
861         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
862         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
863         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-
864         sage. The offset from the start of the pattern to the  character  where         sage.  The  offset from the start of the pattern to the character where
865         the  error  was  discovered  is  placed  in  the variable pointed to by         the error was discovered is  placed  in  the  variable  pointed  to  by
866         erroffset, which must not be NULL. If it  is,  an  immediate  error  is         erroffset,  which  must  not  be  NULL. If it is, an immediate error is
867         given.         given.
868    
869           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
870           codeptr  argument is not NULL, a non-zero error code number is returned
871           via this argument in the event of an error. This is in addition to  the
872           textual error message. Error codes and messages are listed below.
873    
874         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
875         character tables that are  built  when  PCRE  is  compiled,  using  the         character tables that are  built  when  PCRE  is  compiled,  using  the
876         default  C  locale.  Otherwise, tableptr must be an address that is the         default  C  locale.  Otherwise, tableptr must be an address that is the
# Line 664  COMPILING A PATTERN Line 913  COMPILING A PATTERN
913    
914         If  this  bit is set, letters in the pattern match both upper and lower         If  this  bit is set, letters in the pattern match both upper and lower
915         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
916         changed  within  a  pattern  by  a (?i) option setting. When running in         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
917         UTF-8 mode, case support for high-valued characters is  available  only         always understands the concept of case for characters whose values  are
918         when PCRE is built with Unicode character property support.         less  than 128, so caseless matching is always possible. For characters
919           with higher values, the concept of case is supported if  PCRE  is  com-
920           piled  with Unicode property support, but not otherwise. If you want to
921           use caseless matching for characters 128 and  above,  you  must  ensure
922           that  PCRE  is  compiled  with Unicode property support as well as with
923           UTF-8 support.
924    
925           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
926    
927         If  this bit is set, a dollar metacharacter in the pattern matches only         If this bit is set, a dollar metacharacter in the pattern matches  only
928         at the end of the subject string. Without this option,  a  dollar  also         at  the  end  of the subject string. Without this option, a dollar also
929         matches  immediately before the final character if it is a newline (but         matches immediately before the final character if it is a newline  (but
930         not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is
931         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         ignored if PCRE_MULTILINE is set. There is no equivalent to this option
932         in Perl, and no way to set it within a pattern.         in Perl, and no way to set it within a pattern.
933    
934           PCRE_DOTALL           PCRE_DOTALL
935    
936         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharater in the pattern matches all char-
937         acters,  including  newlines.  Without  it, newlines are excluded. This         acters, including newlines. Without it,  newlines  are  excluded.  This
938         option is equivalent to Perl's /s option, and it can be changed  within         option  is equivalent to Perl's /s option, and it can be changed within
939         a  pattern  by  a  (?s)  option  setting. A negative class such as [^a]         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]
940         always matches a newline character, independent of the setting of  this         always  matches a newline character, independent of the setting of this
941         option.         option.
942    
943           PCRE_EXTENDED           PCRE_EXTENDED
944    
945         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
946         totally ignored except  when  escaped  or  inside  a  character  class.         totally ignored except when escaped or inside a character class. White-
947         Whitespace  does  not  include the VT character (code 11). In addition,         space does not include the VT character (code 11). In addition, charac-
948         characters between an unescaped # outside a  character  class  and  the         ters between an unescaped # outside a character class and the next new-
949         next newline character, inclusive, are also ignored. This is equivalent         line character, inclusive, are also  ignored.  This  is  equivalent  to
950         to Perl's /x option, and it can be changed within a pattern by  a  (?x)         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)
951         option setting.         option setting.
952    
953         This  option  makes  it possible to include comments inside complicated         This option makes it possible to include  comments  inside  complicated
954         patterns.  Note, however, that this applies only  to  data  characters.         patterns.   Note,  however,  that this applies only to data characters.
955         Whitespace   characters  may  never  appear  within  special  character         Whitespace  characters  may  never  appear  within  special   character
956         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences  in  a  pattern,  for  example  within the sequence (?( which
957         introduces a conditional subpattern.         introduces a conditional subpattern.
958    
959           PCRE_EXTRA           PCRE_EXTRA
960    
961         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
962         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
963         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
964         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
965         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
966         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
967         literal.  There  are  at  present  no other features controlled by this         literal. There are at present no  other  features  controlled  by  this
968         option. It can also be set by a (?X) option setting within a pattern.         option. It can also be set by a (?X) option setting within a pattern.
969    
970             PCRE_FIRSTLINE
971    
972           If  this  option  is  set,  an  unanchored pattern is required to match
973           before or at the first newline character in the subject string,  though
974           the matched text may continue over the newline.
975    
976           PCRE_MULTILINE           PCRE_MULTILINE
977    
978         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
979         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
980         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
981         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
982         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
983         is set). This is the same as Perl.         is set). This is the same as Perl.
984    
985         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"
986         constructs match immediately following or immediately before  any  new-         constructs  match  immediately following or immediately before any new-
987         line  in the subject string, respectively, as well as at the very start         line in the subject string, respectively, as well as at the very  start
988         and end. This is equivalent to Perl's /m option, and it can be  changed         and  end. This is equivalent to Perl's /m option, and it can be changed
989         within a pattern by a (?m) option setting. If there are no "\n" charac-         within a pattern by a (?m) option setting. If there are no "\n" charac-
990         ters in a subject string, or no occurrences of ^ or  $  in  a  pattern,         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,
991         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
992    
993           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
994    
995         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
996         theses in the pattern. Any opening parenthesis that is not followed  by         theses  in the pattern. Any opening parenthesis that is not followed by
997         ?  behaves as if it were followed by ?: but named parentheses can still         ? behaves as if it were followed by ?: but named parentheses can  still
998         be used for capturing (and they acquire  numbers  in  the  usual  way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
999         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1000    
1001           PCRE_UNGREEDY           PCRE_UNGREEDY
1002    
1003         This  option  inverts  the "greediness" of the quantifiers so that they         This option inverts the "greediness" of the quantifiers  so  that  they
1004         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
1005         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
1006         within the pattern.         within the pattern.
1007    
1008           PCRE_UTF8           PCRE_UTF8
1009    
1010         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
1011         strings  of  UTF-8 characters instead of single-byte character strings.         strings of UTF-8 characters instead of single-byte  character  strings.
1012         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-
1013         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
1014         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
1015         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1016    
1017           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1018    
1019         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
1020         automatically checked. If an invalid UTF-8 sequence of bytes is  found,         automatically  checked. If an invalid UTF-8 sequence of bytes is found,
1021         pcre_compile()  returns an error. If you already know that your pattern         pcre_compile() returns an error. If you already know that your  pattern
1022         is valid, and you want to skip this check for performance reasons,  you         is  valid, and you want to skip this check for performance reasons, you
1023         can  set  the  PCRE_NO_UTF8_CHECK option. When it is set, the effect of         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of
1024         passing an invalid UTF-8 string as a pattern is undefined. It may cause         passing an invalid UTF-8 string as a pattern is undefined. It may cause
1025         your  program  to  crash.   Note that this option can also be passed to         your program to crash.  Note that this option can  also  be  passed  to
1026         pcre_exec(),  to  suppress  the  UTF-8  validity  checking  of  subject         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-
1027         strings.         ing of subject strings.
1028    
1029    
1030    COMPILATION ERROR CODES
1031    
1032           The following table lists the error  codes  than  may  be  returned  by
1033           pcre_compile2(),  along with the error messages that may be returned by
1034           both compiling functions.
1035    
1036              0  no error
1037              1  \ at end of pattern
1038              2  \c at end of pattern
1039              3  unrecognized character follows \
1040              4  numbers out of order in {} quantifier
1041              5  number too big in {} quantifier
1042              6  missing terminating ] for character class
1043              7  invalid escape sequence in character class
1044              8  range out of order in character class
1045              9  nothing to repeat
1046             10  operand of unlimited repeat could match the empty string
1047             11  internal error: unexpected repeat
1048             12  unrecognized character after (?
1049             13  POSIX named classes are supported only within a class
1050             14  missing )
1051             15  reference to non-existent subpattern
1052             16  erroffset passed as NULL
1053             17  unknown option bit(s) set
1054             18  missing ) after comment
1055             19  parentheses nested too deeply
1056             20  regular expression too large
1057             21  failed to get memory
1058             22  unmatched parentheses
1059             23  internal error: code overflow
1060             24  unrecognized character after (?<
1061             25  lookbehind assertion is not fixed length
1062             26  malformed number after (?(
1063             27  conditional group contains more than two branches
1064             28  assertion expected after (?(
1065             29  (?R or (?digits must be followed by )
1066             30  unknown POSIX class name
1067             31  POSIX collating elements are not supported
1068             32  this version of PCRE is not compiled with PCRE_UTF8 support
1069             33  spare error
1070             34  character value in \x{...} sequence is too large
1071             35  invalid condition (?(0)
1072             36  \C not allowed in lookbehind assertion
1073             37  PCRE does not support \L, \l, \N, \U, or \u
1074             38  number after (?C is > 255
1075             39  closing ) for (?C expected
1076             40  recursive call could loop indefinitely
1077             41  unrecognized character after (?P
1078             42  syntax error after (?P
1079             43  two named groups have the same name
1080             44  invalid UTF-8 string
1081             45  support for \P, \p, and \X has not been compiled
1082             46  malformed \P or \p sequence
1083             47  unknown property name after \P or \p
1084    
1085    
1086  STUDYING A PATTERN  STUDYING A PATTERN
1087    
1088         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1089              const char **errptr);              const char **errptr);
1090    
1091         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
1092         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
1093         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1094         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1095         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1096         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
1097         the results of the study.         the results of the study.
1098    
1099         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1100         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec().  However,  a  pcre_extra  block also contains other fields
1101         that  can  be  set  by the caller before the block is passed; these are         that can be set by the caller before the block  is  passed;  these  are
1102         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1103    
1104         If studying the pattern does not produce  any  additional  information,         If  studying  the  pattern  does not produce any additional information
1105         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1106         wants to pass any of the other fields to pcre_exec(), it  must  set  up         wants  to  pass  any of the other fields to pcre_exec(), it must set up
1107         its own pcre_extra block.         its own pcre_extra block.
1108    
1109         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1110         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1111    
1112         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.
1113         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1114         points to is set to NULL. Otherwise it points to a textual  error  mes-         points  to  is set to NULL. Otherwise it points to a textual error mes-
1115         sage.  You should therefore test the error pointer for NULL after call-         sage. You should therefore test the error pointer for NULL after  call-
1116         ing pcre_study(), to be sure that it has run successfully.         ing pcre_study(), to be sure that it has run successfully.
1117    
1118         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 808  STUDYING A PATTERN Line 1124  STUDYING A PATTERN
1124             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1125    
1126         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1127         that  do not have a single fixed starting character. A bitmap of possi-         that do not have a single fixed starting character. A bitmap of  possi-
1128         ble starting bytes is created.         ble starting bytes is created.
1129    
1130    
1131  LOCALE SUPPORT  LOCALE SUPPORT
1132    
1133         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1134         letters,  digits, or whatever, by reference to a set of tables, indexed         letters digits, or whatever, by reference to a set of  tables,  indexed
1135         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
1136         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1137         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1138         with Unicode character property support.)         with Unicode character property support.
1139    
1140         An  internal set of tables is created in the default C locale when PCRE         An internal set of tables is created in the default C locale when  PCRE
1141         is built. This is used when the final  argument  of  pcre_compile()  is         is  built.  This  is  used when the final argument of pcre_compile() is
1142         NULL,  and  is  sufficient for many applications. An alternative set of         NULL, and is sufficient for many applications. An  alternative  set  of
1143         tables can, however, be supplied. These may be created in  a  different         tables  can,  however, be supplied. These may be created in a different
1144         locale  from the default. As more and more applications change to using         locale from the default. As more and more applications change to  using
1145         Unicode, the need for this locale support is expected to die away.         Unicode, the need for this locale support is expected to die away.
1146    
1147         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1148         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
1149         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1150         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1151         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1152         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1153    
1154           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1155           tables = pcre_maketables();           tables = pcre_maketables();
1156           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1157    
1158         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1159         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1160         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1161         it is needed.         it is needed.
1162    
1163         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
1164         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()
1165         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-
1166         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1167         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1168    
1169         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
1170         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1171         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
1172         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
1173         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1174    
# Line 862  INFORMATION ABOUT A PATTERN Line 1178  INFORMATION ABOUT A PATTERN
1178         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1179              int what, void *where);              int what, void *where);
1180    
1181         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1182         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1183         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1184    
1185         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1186         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
1187         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1188         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
1189         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
1190         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1191    
1192           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 878  INFORMATION ABOUT A PATTERN Line 1194  INFORMATION ABOUT A PATTERN
1194           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1195           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1196    
1197         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
1198         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1199         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1200         pattern:         pattern:
1201    
1202           int rc;           int rc;
# Line 891  INFORMATION ABOUT A PATTERN Line 1207  INFORMATION ABOUT A PATTERN
1207             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1208             &length);         /* where to put the data */             &length);         /* where to put the data */
1209    
1210         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
1211         are as follows:         are as follows:
1212    
1213           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1214    
1215         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1216         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1217         there are no back references.         there are no back references.
1218    
1219           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1220    
1221         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1222         argument should point to an int variable.         argument should point to an int variable.
1223    
1224           PCRE_INFO_DEFAULTTABLES           PCRE_INFO_DEFAULT_TABLES
1225    
1226         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1227         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1228         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1229         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1230         passing a NULL table pointer.         passing a NULL table pointer.
1231    
1232           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1233    
1234         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1235         non-anchored    pattern.    (This    option    used    to   be   called         non-anchored   pattern.   (This    option    used    to    be    called
1236         PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards
1237         compatibility.)         compatibility.)
1238    
1239         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
1240         (cat|cow|coyote), it is returned in the integer pointed  to  by  where.         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.
1241         Otherwise, if either         Otherwise, if either
1242    
1243         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1244         branch starts with "^", or         branch starts with "^", or
1245    
1246         (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
1247         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1248    
1249         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1250         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1251         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1252    
1253           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1254    
1255         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
1256         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
1257         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1258         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1259         able.         able.
1260    
1261           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1262    
1263         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
1264         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
1265         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1266         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
1267         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1268         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
1269         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1270    
# Line 956  INFORMATION ABOUT A PATTERN Line 1272  INFORMATION ABOUT A PATTERN
1272           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1273           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1274    
1275         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1276         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1277         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses,  which  still  acquire  numbers.  A  convenience  function  called
1278         pcre_get_named_substring() is provided  for  extracting  an  individual         pcre_get_named_substring()  is  provided  for  extracting an individual
1279         captured  substring  by  name.  It is also possible to extract the data         captured substring by name. It is also possible  to  extract  the  data
1280         directly, by first converting the name to a number in order  to  access         directly,  by  first converting the name to a number in order to access
1281         the  correct  pointers in the output vector (described with pcre_exec()         the correct pointers in the output vector (described  with  pcre_exec()
1282         below). To do the conversion, you need to use the  name-to-number  map,         below).  To  do the conversion, you need to use the name-to-number map,
1283         which is described by these three values.         which is described by these three values.
1284    
1285         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
1286         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1287         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
1288         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1289         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
1290         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-
1291         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-
1292         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1293         For  example,  consider  the following pattern (assume PCRE_EXTENDED is         For example, consider the following pattern  (assume  PCRE_EXTENDED  is
1294         set, so white space - including newlines - is ignored):         set, so white space - including newlines - is ignored):
1295    
1296           (?P<date> (?P<year>(\d\d)?\d\d) -           (?P<date> (?P<year>(\d\d)?\d\d) -
1297           (?P<month>\d\d) - (?P<day>\d\d) )           (?P<month>\d\d) - (?P<day>\d\d) )
1298    
1299         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1300         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,
1301         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1302         as ??:         as ??:
1303    
# Line 990  INFORMATION ABOUT A PATTERN Line 1306  INFORMATION ABOUT A PATTERN
1306           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1307           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1308    
1309         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1310         name-to-number map, remember that the length of each entry is likely to         name-to-number map, remember that the length of each entry is likely to
1311         be different for each compiled pattern.         be different for each compiled pattern.
1312    
1313           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1314    
1315         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
1316         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1317         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1318         by any top-level option settings within the pattern itself.         by any top-level option settings within the pattern itself.
1319    
1320         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
1321         alternatives begin with one of the following:         alternatives begin with one of the following:
1322    
1323           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1015  INFORMATION ABOUT A PATTERN Line 1331  INFORMATION ABOUT A PATTERN
1331    
1332           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1333    
1334         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
1335         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
1336         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
1337         size_t variable.         size_t variable.
# Line 1023  INFORMATION ABOUT A PATTERN Line 1339  INFORMATION ABOUT A PATTERN
1339           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1340    
1341         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
1342         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1343         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1344         created by pcre_study(). The fourth argument should point to  a  size_t         created  by  pcre_study(). The fourth argument should point to a size_t
1345         variable.         variable.
1346    
1347    
# Line 1033  OBSOLETE INFO FUNCTION Line 1349  OBSOLETE INFO FUNCTION
1349    
1350         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1351    
1352         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1353         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1354         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1355         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-
1356         lowing negative numbers:         lowing negative numbers:
1357    
1358           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1359           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1360    
1361         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
1362         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
1363         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1364    
1365         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1366         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
1367         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1368    
1369    
1370  MATCHING A PATTERN  REFERENCE COUNTS
1371    
1372           int pcre_refcount(pcre *code, int adjust);
1373    
1374           The pcre_refcount() function is used to maintain a reference  count  in
1375           the data block that contains a compiled pattern. It is provided for the
1376           benefit of applications that  operate  in  an  object-oriented  manner,
1377           where different parts of the application may be using the same compiled
1378           pattern, but you want to free the block when they are all done.
1379    
1380           When a pattern is compiled, the reference count field is initialized to
1381           zero.   It is changed only by calling this function, whose action is to
1382           add the adjust value (which may be positive or  negative)  to  it.  The
1383           yield of the function is the new value. However, the value of the count
1384           is constrained to lie between 0 and 65535, inclusive. If the new  value
1385           is outside these limits, it is forced to the appropriate limit value.
1386    
1387           Except  when it is zero, the reference count is not correctly preserved
1388           if a pattern is compiled on one host and then  transferred  to  a  host
1389           whose byte-order is different. (This seems a highly unlikely scenario.)
1390    
1391    
1392    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1393    
1394         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1395              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1396              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1397    
1398         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
1399         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1400         has been studied, the result of the study should be passed in the extra         has been studied, the result of the study should be passed in the extra
1401         argument.         argument.  This  function is the main matching facility of the library,
1402           and it operates in a Perl-like manner. For specialist use there is also
1403           an  alternative matching function, which is described below in the sec-
1404           tion about the pcre_dfa_exec() function.
1405    
1406         In most applications, the pattern will have been compiled (and  option-         In most applications, the pattern will have been compiled (and  option-
1407         ally  studied)  in the same process that calls pcre_exec(). However, it         ally  studied)  in the same process that calls pcre_exec(). However, it
# Line 1080  MATCHING A PATTERN Line 1421  MATCHING A PATTERN
1421             0,              /* start at offset 0 in the subject */             0,              /* start at offset 0 in the subject */
1422             0,              /* default options */             0,              /* default options */
1423             ovector,        /* vector of integers for substring information */             ovector,        /* vector of integers for substring information */
1424             30);            /* number of elements in the vector  (NOT  size  in             30);            /* number of elements (NOT size in bytes) */
        bytes) */  
1425    
1426     Extra data for pcre_exec()     Extra data for pcre_exec()
1427    
1428         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
1429         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
1430         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-
1431         tional information in it. The fields in a pcre_extra block are as  fol-         tional  information in it. The fields in a pcre_extra block are as fol-
1432         lows:         lows:
1433    
1434           unsigned long int flags;           unsigned long int flags;
# Line 1097  MATCHING A PATTERN Line 1437  MATCHING A PATTERN
1437           void *callout_data;           void *callout_data;
1438           const unsigned char *tables;           const unsigned char *tables;
1439    
1440         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
1441         are set. The flag bits are:         are set. The flag bits are:
1442    
1443           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1105  MATCHING A PATTERN Line 1445  MATCHING A PATTERN
1445           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1446           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1447    
1448         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
1449         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1450         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
1451         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1452         flag bits.         flag bits.
1453    
1454         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
1455         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
1456         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1457         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1458         repeats.         repeats.
1459    
1460         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1461         edly  (sometimes  recursively).  The  limit is imposed on the number of         edly (sometimes recursively). The limit is imposed  on  the  number  of
1462         times this function is called during a match, which has the  effect  of         times  this  function is called during a match, which has the effect of
1463         limiting  the amount of recursion and backtracking that can take place.         limiting the amount of recursion and backtracking that can take  place.
1464         For patterns that are not anchored, the count starts from zero for each         For patterns that are not anchored, the count starts from zero for each
1465         position in the subject string.         position in the subject string.
1466    
1467         The  default  limit  for the library can be set when PCRE is built; the         The default limit for the library can be set when PCRE  is  built;  the
1468         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1469         cases.  You  can  reduce  the  default  by  suppling pcre_exec() with a         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a
1470         pcre_extra block in which match_limit is set to a  smaller  value,  and         pcre_extra  block  in  which match_limit is set to a smaller value, and
1471         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
1472         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1473    
1474         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1475         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1476    
1477         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1478         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1479         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
1480         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1481         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
1482         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-
1483         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1484         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1485         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1486         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1487    
1488     Option bits for pcre_exec()     Option bits for pcre_exec()
1489    
1490         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.
1491         The   only  bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,
1492         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1493    
1494           PCRE_ANCHORED           PCRE_ANCHORED
1495    
1496         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1497         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1498         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
1499         unachored at matching time.         unachored at matching time.
1500    
1501           PCRE_NOTBOL           PCRE_NOTBOL
1502    
1503         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1504         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
1505         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1506         causes  circumflex  never  to  match.  This  option  affects  only  the         causes  circumflex  never to match. This option affects only the behav-
1507         behaviour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1508    
1509           PCRE_NOTEOL           PCRE_NOTEOL
1510    
1511         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
1512         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
1513         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
1514         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1515         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
1516         not affect \Z or \z.         not affect \Z or \z.
1517    
1518           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1519    
1520         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
1521         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
1522         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
1523         example, if the pattern         example, if the pattern
1524    
1525           a?b?           a?b?
1526    
1527         is  applied  to  a string not beginning with "a" or "b", it matches the         is applied to a string not beginning with "a" or "b",  it  matches  the
1528         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
1529         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-
1530         rences of "a" or "b".         rences of "a" or "b".
1531    
1532         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
1533         cial  case  of  a  pattern match of the empty string within its split()         cial case of a pattern match of the empty  string  within  its  split()
1534         function, and when using the /g modifier. It  is  possible  to  emulate         function,  and  when  using  the /g modifier. It is possible to emulate
1535         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
1536         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
1537         if  that  fails by advancing the starting offset (see below) and trying         if that fails by advancing the starting offset (see below)  and  trying
1538         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
1539         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
1540    
1541           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1542    
1543         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
1544         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
1545         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
1546         points to the start of a UTF-8 character. If an invalid UTF-8  sequence         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence
1547         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
1548         startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
1549         returned.         returned.
1550    
1551         If  you  already  know that your subject is valid, and you want to skip         If you already know that your subject is valid, and you  want  to  skip
1552         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
1553         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
1554         do this for the second and subsequent calls to pcre_exec() if  you  are         do  this  for the second and subsequent calls to pcre_exec() if you are
1555         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
1556         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
1557         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
1558         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
1559         value  of startoffset that does not point to the start of a UTF-8 char-         value of startoffset that does not point to the start of a UTF-8  char-
1560         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
1561    
1562           PCRE_PARTIAL           PCRE_PARTIAL
1563    
1564         This option turns on the  partial  matching  feature.  If  the  subject         This  option  turns  on  the  partial  matching feature. If the subject
1565         string  fails to match the pattern, but at some point during the match-         string fails to match the pattern, but at some point during the  match-
1566         ing process the end of the subject was reached (that  is,  the  subject         ing  process  the  end of the subject was reached (that is, the subject
1567         partially  matches  the  pattern and the failure to match occurred only         partially matches the pattern and the failure to  match  occurred  only
1568         because there were not enough subject characters), pcre_exec()  returns         because  there were not enough subject characters), pcre_exec() returns
1569         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
1570         used, there are restrictions on what may appear in the  pattern.  These         used,  there  are restrictions on what may appear in the pattern. These
1571         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
1572    
1573     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
1574    
1575         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
1576         length in length, and a starting byte offset in startoffset.  In  UTF-8         length  in  length, and a starting byte offset in startoffset. In UTF-8
1577         mode,  the  byte  offset  must point to the start of a UTF-8 character.         mode, the byte offset must point to the start  of  a  UTF-8  character.
1578         Unlike the pattern string, the subject may contain binary  zero  bytes.         Unlike  the  pattern string, the subject may contain binary zero bytes.
1579         When  the starting offset is zero, the search for a match starts at the         When the starting offset is zero, the search for a match starts at  the
1580         beginning of the subject, and this is by far the most common case.         beginning of the subject, and this is by far the most common case.
1581    
1582         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
1583         in  the same subject by calling pcre_exec() again after a previous suc-         in the same subject by calling pcre_exec() again after a previous  suc-
1584         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
1585         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
1586         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
1587    
1588           \Biss\B           \Biss\B
1589    
1590         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
1591         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.)
1592         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
1593         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
1594         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
1595         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
1596         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
1597         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-
1598         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
1599         discover that it is preceded by a letter.         discover that it is preceded by a letter.
1600    
1601         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,
1602         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
1603         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
1604         subject.         subject.
1605    
1606     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
1607    
1608         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
1609         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
1610         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
1611         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
1612         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
1613         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
1614         that do not cause substrings to be captured.         that do not cause substrings to be captured.
1615    
1616         Captured substrings are returned to the caller via a vector of  integer         Captured  substrings are returned to the caller via a vector of integer
1617         offsets  whose  address is passed in ovector. The number of elements in         offsets whose address is passed in ovector. The number of  elements  in
1618         the vector is passed in ovecsize, which must be a non-negative  number.         the  vector is passed in ovecsize, which must be a non-negative number.
1619         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
1620    
1621         The  first  two-thirds of the vector is used to pass back captured sub-         The first two-thirds of the vector is used to pass back  captured  sub-
1622         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
1623         of  the  vector is used as workspace by pcre_exec() while matching cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
1624         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
1625         The  length passed in ovecsize should always be a multiple of three. If         The length passed in ovecsize should always be a multiple of three.  If
1626         it is not, it is rounded down.         it is not, it is rounded down.
1627    
1628         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
1629         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
1630         and continuing up to two-thirds of its length at the  most.  The  first         and  continuing  up  to two-thirds of its length at the most. The first
1631         element of a pair is set to the offset of the first character in a sub-         element of a pair is set to the offset of the first character in a sub-
1632         string, and the second is set to the  offset  of  the  first  character         string,  and  the  second  is  set to the offset of the first character
1633         after  the  end  of  a  substring. The first pair, ovector[0] and ovec-         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-
1634         tor[1], identify the portion of  the  subject  string  matched  by  the         tor[1],  identify  the  portion  of  the  subject string matched by the
1635         entire  pattern.  The next pair is used for the first capturing subpat-         entire pattern. The next pair is used for the first  capturing  subpat-
1636         tern, and so on. The value returned by pcre_exec()  is  the  number  of         tern,  and  so  on.  The value returned by pcre_exec() is the number of
1637         pairs  that  have  been set. If there are no capturing subpatterns, the         pairs that have been set. If there are no  capturing  subpatterns,  the
1638         return value from a successful match is 1,  indicating  that  just  the         return  value  from  a  successful match is 1, indicating that just the
1639         first pair of offsets has been set.         first pair of offsets has been set.
1640    
1641         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
1642         substrings as separate strings. These are described  in  the  following         substrings  as  separate  strings. These are described in the following
1643         section.         section.
1644    
1645         It  is  possible  for  an capturing subpattern number n+1 to match some         It is possible for an capturing subpattern number  n+1  to  match  some
1646         part of the subject when subpattern n has not been  used  at  all.  For         part  of  the  subject  when subpattern n has not been used at all. For
1647         example, if the string "abc" is matched against the pattern (a|(z))(bc)         example, if the string "abc" is matched against the pattern (a|(z))(bc)
1648         subpatterns 1 and 3 are matched, but 2 is not. When this happens,  both         subpatterns  1 and 3 are matched, but 2 is not. When this happens, both
1649         offset values corresponding to the unused subpattern are set to -1.         offset values corresponding to the unused subpattern are set to -1.
1650    
1651         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
1652         of the string that it matched that is returned.         of the string that it matched that is returned.
1653    
1654         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
1655         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
1656         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. In particular, if the substring off-
1657         sets are not of interest, pcre_exec() may be called with ovector passed         sets are not of interest, pcre_exec() may be called with ovector passed
1658         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         as  NULL  and  ovecsize  as zero. However, if the pattern contains back
1659         references  and  the  ovector is not big enough to remember the related         references and the ovector is not big enough to  remember  the  related
1660         substrings, PCRE has to get additional memory for use during  matching.         substrings,  PCRE has to get additional memory for use during matching.
1661         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
1662    
1663         Note  that  pcre_info() can be used to find out how many capturing sub-         Note that pcre_info() can be used to find out how many  capturing  sub-
1664         patterns there are in a compiled pattern. The smallest size for ovector         patterns there are in a compiled pattern. The smallest size for ovector
1665         that  will  allow for n captured substrings, in addition to the offsets         that will allow for n captured substrings, in addition to  the  offsets
1666         of the substring matched by the whole pattern, is (n+1)*3.         of the substring matched by the whole pattern, is (n+1)*3.
1667    
1668     Return values from pcre_exec()     Return values from pcre_exec()
1669    
1670         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
1671         defined in the header file:         defined in the header file:
1672    
1673           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1336  MATCHING A PATTERN Line 1676  MATCHING A PATTERN
1676    
1677           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
1678    
1679         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
1680         ovecsize was not zero.         ovecsize was not zero.
1681    
1682           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1345  MATCHING A PATTERN Line 1685  MATCHING A PATTERN
1685    
1686           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
1687    
1688         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
1689         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
1690         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
1691         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
1692         gives when the magic number is not present.         gives when the magic number is not present.
1693    
1694           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_NODE   (-5)
1695    
1696         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
1697         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
1698         overwriting of the compiled pattern.         overwriting of the compiled pattern.
1699    
1700           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1701    
1702         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
1703         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
1704         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
1705         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
1706         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
1707    
1708           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1709    
1710         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
1711         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
1712         returned by pcre_exec().         returned by pcre_exec().
1713    
1714           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
1715    
1716         The recursion and backtracking limit, as specified by  the  match_limit         The  recursion  and backtracking limit, as specified by the match_limit
1717         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
1718         description above.         description above.
1719    
1720           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
1721    
1722         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
1723         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
1724         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
1725    
1726           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
1727    
1728         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
1729         subject.         subject.
1730    
1731           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
1732    
1733         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
1734         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-
1735         ter.         ter.
1736    
1737           PCRE_ERROR_PARTIAL (-12)           PCRE_ERROR_PARTIAL        (-12)
1738    
1739         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
1740         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
1741    
1742           PCRE_ERROR_BAD_PARTIAL (-13)           PCRE_ERROR_BADPARTIAL     (-13)
1743    
1744         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
1745         items  that are not supported for partial matching. See the pcrepartial         items that are not supported for partial matching. See the  pcrepartial
1746         documentation for details of partial matching.         documentation for details of partial matching.
1747    
1748           PCRE_ERROR_INTERNAL (-14)           PCRE_ERROR_INTERNAL       (-14)
1749    
1750         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
1751         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
1752    
1753           PCRE_ERROR_BADCOUNT (-15)           PCRE_ERROR_BADCOUNT       (-15)
1754    
1755         This  error is given if the value of the ovecsize argument is negative.         This error is given if the value of the ovecsize argument is  negative.
1756    
1757    
1758  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1428  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 1768  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
1768         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
1769              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
1770    
1771         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
1772         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
1773         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
1774         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
1775         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
1776         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
1777         substrings. A substring  that  contains  a  binary  zero  is  correctly         substrings.  A  substring  that  contains  a  binary  zero is correctly
1778         extracted  and  has  a further zero added on the end, but the result is         extracted and has a further zero added on the end, but  the  result  is
1779         not, of course, a C string.         not, of course, a C string.
1780    
1781         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-
1782         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
1783         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
1784         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
1785         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
1786         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
1787         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
1788         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
1789         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
1790    
1791         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
1792         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
1793         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
1794         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
1795         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
1796         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
1797         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
1798         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
1799         the terminating zero, or one of         the terminating zero, or one of
1800    
1801           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1802    
1803         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
1804         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
1805    
1806           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1807    
1808         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
1809    
1810         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
1811         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
1812         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
1813         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
1814         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
1815         pointer. The yield of the function is zero if all went well, or         pointer. The yield of the function is zero if all went well, or
1816    
1817           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1818    
1819         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
1820    
1821         When any of these functions encounter a substring that is unset,  which         When  any of these functions encounter a substring that is unset, which
1822         can  happen  when  capturing subpattern number n+1 matches some part of         can happen when capturing subpattern number n+1 matches  some  part  of
1823         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
1824         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
1825         string by inspecting the appropriate offset in ovector, which is  nega-         string  by inspecting the appropriate offset in ovector, which is nega-
1826         tive for unset substrings.         tive for unset substrings.
1827    
1828         The  two convenience functions pcre_free_substring() and pcre_free_sub-         The two convenience functions pcre_free_substring() and  pcre_free_sub-
1829         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
1830         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
1831         tively. They do nothing more than  call  the  function  pointed  to  by         tively.  They  do  nothing  more  than  call the function pointed to by
1832         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.
1833         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-
1834         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  which  cannot  use
1835         pcre_free directly; it is  for  these  cases  that  the  functions  are         pcre_free  directly;  it is for these cases that the functions are pro-
1836         provided.         vided.
1837    
1838    
1839  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
# Line 1511  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 1851  EXTRACTING CAPTURED SUBSTRINGS BY NAME
1851              int stringcount, const char *stringname,              int stringcount, const char *stringname,
1852              const char **stringptr);              const char **stringptr);
1853    
1854         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-
1855         ber.  For example, for this pattern         ber.  For example, for this pattern
1856    
1857           (a+)b(?<xxx>\d+)...           (a+)b(?P<xxx>\d+)...
1858    
1859         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. You can find the number
1860         from the name by calling pcre_get_stringnumber(). The first argument is         from the name by calling pcre_get_stringnumber(). The first argument is
1861         the compiled pattern, and the second is the  name.  The  yield  of  the         the  compiled  pattern,  and  the  second is the name. The yield of the
1862         function  is  the  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if
1863         there is no subpattern of that name.         there is no subpattern of that name.
1864    
1865         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
1866         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
1867         are also two functions that do the whole job.         are also two functions that do the whole job.
1868    
1869         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
1870         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
1871         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
1872         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
1873         differences:         differences:
1874    
1875         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
1876         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
1877         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
1878         name-to-number translation table.         name-to-number translation table.
1879    
1880         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
1881         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
1882         ate.         ate.
1883    
 Last updated: 09 September 2004  
 Copyright (c) 1997-2004 University of Cambridge.  
 -----------------------------------------------------------------------------  
1884    
1885  PCRE(3)                                                                PCRE(3)  FINDING ALL POSSIBLE MATCHES
1886    
1887           The traditional matching function uses a  similar  algorithm  to  Perl,
1888           which stops when it finds the first match, starting at a given point in
1889           the subject. If you want to find all possible matches, or  the  longest
1890           possible  match,  consider using the alternative matching function (see
1891           below) instead. If you cannot use the alternative function,  but  still
1892           need  to  find all possible matches, you can kludge it up by making use
1893           of the callout facility, which is described in the pcrecallout documen-
1894           tation.
1895    
1896           What you have to do is to insert a callout right at the end of the pat-
1897           tern.  When your callout function is called, extract and save the  cur-
1898           rent  matched  substring.  Then  return  1, which forces pcre_exec() to
1899           backtrack and try other alternatives. Ultimately, when it runs  out  of
1900           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
1901    
1902    
1903    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
1904    
1905           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1906                const char *subject, int length, int startoffset,
1907                int options, int *ovector, int ovecsize,
1908                int *workspace, int wscount);
1909    
1910           The  function  pcre_dfa_exec()  is  called  to  match  a subject string
1911           against a compiled pattern, using a "DFA" matching algorithm. This  has
1912           different  characteristics to the normal algorithm, and is not compati-
1913           ble with Perl. Some of the features of PCRE patterns are not supported.
1914           Nevertheless, there are times when this kind of matching can be useful.
1915           For a discussion of the two matching algorithms, see  the  pcrematching
1916           documentation.
1917    
1918           The  arguments  for  the  pcre_dfa_exec()  function are the same as for
1919           pcre_exec(), plus two extras. The ovector argument is used in a differ-
1920           ent  way,  and  this is described below. The other common arguments are
1921           used in the same way as for pcre_exec(), so their  description  is  not
1922           repeated here.
1923    
1924           The  two  additional  arguments provide workspace for the function. The
1925           workspace vector should contain at least 20 elements. It  is  used  for
1926           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
1927           workspace will be needed for patterns and subjects where  there  are  a
1928           lot of possible matches.
1929    
1930           Here is an example of a simple call to pcre_exec():
1931    
1932             int rc;
1933             int ovector[10];
1934             int wspace[20];
1935             rc = pcre_exec(
1936               re,             /* result of pcre_compile() */
1937               NULL,           /* we didn't study the pattern */
1938               "some string",  /* the subject string */
1939               11,             /* the length of the subject string */
1940               0,              /* start at offset 0 in the subject */
1941               0,              /* default options */
1942               ovector,        /* vector of integers for substring information */
1943               10,             /* number of elements (NOT size in bytes) */
1944               wspace,         /* working space vector */
1945               20);            /* number of elements (NOT size in bytes) */
1946    
1947       Option bits for pcre_dfa_exec()
1948    
1949           The  unused  bits  of  the options argument for pcre_dfa_exec() must be
1950           zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,
1951           PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,
1952           PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of
1953           these  are  the  same  as  for pcre_exec(), so their description is not
1954           repeated here.
1955    
1956             PCRE_PARTIAL
1957    
1958           This has the same general effect as it does for  pcre_exec(),  but  the
1959           details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
1960           pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
1961           PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
1962           been no complete matches, but there is still at least one matching pos-
1963           sibility.  The portion of the string that provided the partial match is
1964           set as the first matching string.
1965    
1966             PCRE_DFA_SHORTEST
1967    
1968           Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
1969           stop  as  soon  as  it  has found one match. Because of the way the DFA
1970           algorithm works, this is necessarily the shortest possible match at the
1971           first possible matching point in the subject string.
1972    
1973             PCRE_DFA_RESTART
1974    
1975           When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
1976           returns a partial match, it is possible to call it  again,  with  addi-
1977           tional  subject  characters,  and have it continue with the same match.
1978           The PCRE_DFA_RESTART option requests this action; when it is  set,  the
1979           workspace  and wscount options must reference the same vector as before
1980           because data about the match so far is left in  them  after  a  partial
1981           match.  There  is  more  discussion of this facility in the pcrepartial
1982           documentation.
1983    
1984       Successful returns from pcre_dfa_exec()
1985    
1986           When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
1987           string in the subject. Note, however, that all the matches from one run
1988           of the function start at the same point in  the  subject.  The  shorter
1989           matches  are all initial substrings of the longer matches. For example,
1990           if the pattern
1991    
1992             <.*>
1993    
1994           is matched against the string
1995    
1996             This is <something> <something else> <something further> no more
1997    
1998           the three matched strings are
1999    
2000             <something>
2001             <something> <something else>
2002             <something> <something else> <something further>
2003    
2004           On success, the yield of the function is a number  greater  than  zero,
2005           which  is  the  number of matched substrings. The substrings themselves
2006           are returned in ovector. Each string uses two elements;  the  first  is
2007           the  offset  to the start, and the second is the offset to the end. All
2008           the strings have the same start offset. (Space could have been saved by
2009           giving  this only once, but it was decided to retain some compatibility
2010           with the way pcre_exec() returns data, even though the meaning  of  the
2011           strings is different.)
2012    
2013           The strings are returned in reverse order of length; that is, the long-
2014           est matching string is given first. If there were too many  matches  to
2015           fit  into ovector, the yield of the function is zero, and the vector is
2016           filled with the longest matches.
2017    
2018       Error returns from pcre_dfa_exec()
2019    
2020           The pcre_dfa_exec() function returns a negative number when  it  fails.
2021           Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2022           described above.  There are in addition the following errors  that  are
2023           specific to pcre_dfa_exec():
2024    
2025             PCRE_ERROR_DFA_UITEM      (-16)
2026    
2027           This  return is given if pcre_dfa_exec() encounters an item in the pat-
2028           tern that it does not support, for instance, the use of \C  or  a  back
2029           reference.
2030    
2031             PCRE_ERROR_DFA_UCOND      (-17)
2032    
2033           This  return is given if pcre_dfa_exec() encounters a condition item in
2034           a pattern that uses a back reference for the  condition.  This  is  not
2035           supported.
2036    
2037             PCRE_ERROR_DFA_UMLIMIT    (-18)
2038    
2039           This  return  is given if pcre_dfa_exec() is called with an extra block
2040           that contains a setting of the match_limit field. This is not supported
2041           (it is meaningless).
2042    
2043             PCRE_ERROR_DFA_WSSIZE     (-19)
2044    
2045           This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2046           workspace vector.
2047    
2048             PCRE_ERROR_DFA_RECURSE    (-20)
2049    
2050           When a recursive subpattern is processed, the matching  function  calls
2051           itself  recursively,  using  private vectors for ovector and workspace.
2052           This error is given if the output vector  is  not  large  enough.  This
2053           should be extremely rare, as a vector of size 1000 is used.
2054    
2055    Last updated: 16 May 2005
2056    Copyright (c) 1997-2005 University of Cambridge.
2057    ------------------------------------------------------------------------------
2058    
2059    
2060    PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2061    
2062    
2063  NAME  NAME
2064         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2065    
2066    
2067  PCRE CALLOUTS  PCRE CALLOUTS
2068    
2069         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
# Line 1606  MISSING CALLOUTS Line 2118  MISSING CALLOUTS
2118  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2119    
2120         During matching, when PCRE reaches a callout point, the external  func-         During matching, when PCRE reaches a callout point, the external  func-
2121         tion  defined  by pcre_callout is called (if it is set). The only argu-         tion  defined by pcre_callout is called (if it is set). This applies to
2122         ment is a pointer to a pcre_callout block. This structure contains  the         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The
2123         following fields:         only  argument  to  the callout function is a pointer to a pcre_callout
2124           block. This structure contains the following fields:
2125    
2126           int          version;           int          version;
2127           int          callout_number;           int          callout_number;
# Line 1623  THE CALLOUT INTERFACE Line 2136  THE CALLOUT INTERFACE
2136           int          pattern_position;           int          pattern_position;
2137           int          next_item_length;           int          next_item_length;
2138    
2139         The  version  field  is an integer containing the version number of the         The version field is an integer containing the version  number  of  the
2140         block format. The initial version was 0; the current version is 1.  The         block  format. The initial version was 0; the current version is 1. The
2141         version  number  will  change  again in future if additional fields are         version number will change again in future  if  additional  fields  are
2142         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.
2143    
2144         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
2145         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-
2146         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2147    
2148         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
2149         passed by the caller to pcre_exec(). The contents can be  inspected  in         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2150         order  to extract substrings that have been matched so far, in the same         pcre_exec() is used, the contents can be inspected in order to  extract
2151         way as for extracting substrings after a match has completed.         substrings  that  have  been  matched  so  far,  in the same way as for
2152           extracting substrings after a match has completed. For  pcre_dfa_exec()
2153           this field is not useful.
2154    
2155         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2156         were passed to pcre_exec().         were passed to pcre_exec().
2157    
2158         The  start_match  field contains the offset within the subject at which         The start_match field contains the offset within the subject  at  which
2159         the current match attempt started. If the pattern is not anchored,  the         the  current match attempt started. If the pattern is not anchored, the
2160         callout function may be called several times from the same point in the         callout function may be called several times from the same point in the
2161         pattern for different starting points in the subject.         pattern for different starting points in the subject.
2162    
2163         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2164         the current match pointer.         the current match pointer.
2165    
2166         The  capture_top field contains one more than the number of the highest         When the pcre_exec() function is used, the capture_top  field  contains
2167         numbered captured substring so far. If no  substrings  have  been  cap-         one  more than the number of the highest numbered captured substring so
2168         tured, the value of capture_top is one.         far. If no substrings have been captured, the value of  capture_top  is
2169           one.  This  is always the case when pcre_dfa_exec() is used, because it
2170         The  capture_last  field  contains the number of the most recently cap-         does not support captured substrings.
2171         tured substring. If no substrings have been captured, its value is  -1.  
2172           The capture_last field contains the number of the  most  recently  cap-
2173         The  callout_data  field contains a value that is passed to pcre_exec()         tured  substring. If no substrings have been captured, its value is -1.
2174         by the caller specifically so that it can be passed back  in  callouts.         This is always the case when pcre_dfa_exec() is used.
2175         It  is  passed  in the pcre_callout field of the pcre_extra data struc-  
2176         ture. If no such data was  passed,  the  value  of  callout_data  in  a         The callout_data field contains a value that is passed  to  pcre_exec()
2177         pcre_callout  block  is  NULL. There is a description of the pcre_extra         or  pcre_dfa_exec() specifically so that it can be passed back in call-
2178           outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
2179           structure.  If  no such data was passed, the value of callout_data in a
2180           pcre_callout block is NULL. There is a description  of  the  pcre_extra
2181         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2182    
2183         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-
2184         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
2185         the pattern string.         the pattern string.
2186    
2187         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-
2188         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
2189         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
2190         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
2191         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
2192         is that of the entire subpattern.         is that of the entire subpattern.
2193    
2194         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
2195         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
2196         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2197    
2198    
2199  RETURN VALUES  RETURN VALUES
2200    
2201         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
2202         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
2203         zero,  matching  fails  at  the current point, but backtracking to test         zero, matching fails at the current point, but  the  testing  of  other
2204         other matching possibilities goes ahead, just as if a lookahead  asser-         matching possibilities goes ahead, just as if a lookahead assertion had
2205         tion  had  failed.  If  the value is less than zero, the match is aban-         failed. If the value is less than zero, the  match  is  abandoned,  and
2206         doned, and pcre_exec() returns the negative value.         pcre_exec() (or pcre_dfa_exec()) returns the negative value.
2207    
2208         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
2209         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2210         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
2211         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
2212         itself.         itself.
2213    
2214  Last updated: 09 September 2004  Last updated: 28 February 2005
2215  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
2216  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
2217    
 PCRE(3)                                                                PCRE(3)  
2218    
2219    PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2220    
2221    
2222  NAME  NAME
2223         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2224    
2225    
2226  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2227    
2228         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
# Line 1808  DIFFERENCES BETWEEN PCRE AND PERL Line 2327  DIFFERENCES BETWEEN PCRE AND PERL
2327         (m) Patterns compiled by PCRE can be saved and re-used at a later time,         (m) Patterns compiled by PCRE can be saved and re-used at a later time,
2328         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2329    
2330  Last updated: 09 September 2004         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2331  Copyright (c) 1997-2004 University of Cambridge.         different way and is not Perl-compatible.
 -----------------------------------------------------------------------------  
2332    
2333  PCRE(3)                                                                PCRE(3)  Last updated: 28 February 2005
2334    Copyright (c) 1997-2005 University of Cambridge.
2335    ------------------------------------------------------------------------------
2336    
2337    
2338    PCREPATTERN(3)                                                  PCREPATTERN(3)
2339    
2340    
2341  NAME  NAME
2342         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2343    
2344    
2345  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2346    
2347         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax  and semantics of the regular expressions supported by PCRE
# Line 1836  PCRE REGULAR EXPRESSION DETAILS Line 2359  PCRE REGULAR EXPRESSION DETAILS
2359         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre
2360         page.         page.
2361    
2362           The remainder of this document discusses the  patterns  that  are  sup-
2363           ported  by  PCRE when its main matching function, pcre_exec(), is used.
2364           From  release  6.0,   PCRE   offers   a   second   matching   function,
2365           pcre_dfa_exec(),  which matches using a different algorithm that is not
2366           Perl-compatible. The advantages and disadvantages  of  the  alternative
2367           function, and how it differs from the normal function, are discussed in
2368           the pcrematching page.
2369    
2370         A regular expression is a pattern that is  matched  against  a  subject         A regular expression is a pattern that is  matched  against  a  subject
2371         string  from  left  to right. Most characters stand for themselves in a         string  from  left  to right. Most characters stand for themselves in a
2372         pattern, and match the corresponding characters in the  subject.  As  a         pattern, and match the corresponding characters in the  subject.  As  a
# Line 1843  PCRE REGULAR EXPRESSION DETAILS Line 2374  PCRE REGULAR EXPRESSION DETAILS
2374    
2375           The quick brown fox           The quick brown fox
2376    
2377         matches  a portion of a subject string that is identical to itself. The         matches a portion of a subject string that is identical to itself. When
2378         power of regular expressions comes from the ability to include alterna-         caseless matching is specified (the PCRE_CASELESS option), letters  are
2379         tives  and repetitions in the pattern. These are encoded in the pattern         matched  independently  of case. In UTF-8 mode, PCRE always understands
2380         by the use of metacharacters, which do not  stand  for  themselves  but         the concept of case for characters whose values are less than  128,  so
2381         instead are interpreted in some special way.         caseless  matching  is always possible. For characters with higher val-
2382           ues, the concept of case is supported if PCRE is compiled with  Unicode
2383         There  are  two different sets of metacharacters: those that are recog-         property  support,  but  not  otherwise.   If  you want to use caseless
2384         nized anywhere in the pattern except within square brackets, and  those         matching for characters 128 and above, you must  ensure  that  PCRE  is
2385         that  are  recognized  in square brackets. Outside square brackets, the         compiled with Unicode property support as well as with UTF-8 support.
2386    
2387           The  power  of  regular  expressions  comes from the ability to include
2388           alternatives and repetitions in the pattern. These are encoded  in  the
2389           pattern by the use of metacharacters, which do not stand for themselves
2390           but instead are interpreted in some special way.
2391    
2392           There are two different sets of metacharacters: those that  are  recog-
2393           nized  anywhere in the pattern except within square brackets, and those
2394           that are recognized in square brackets. Outside  square  brackets,  the
2395         metacharacters are as follows:         metacharacters are as follows:
2396    
2397           \      general escape character with several uses           \      general escape character with several uses
# Line 1870  PCRE REGULAR EXPRESSION DETAILS Line 2410  PCRE REGULAR EXPRESSION DETAILS
2410                  also "possessive quantifier"                  also "possessive quantifier"
2411           {      start min/max quantifier           {      start min/max quantifier
2412    
2413         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
2414         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
2415    
2416           \      general escape character           \      general escape character
# Line 1880  PCRE REGULAR EXPRESSION DETAILS Line 2420  PCRE REGULAR EXPRESSION DETAILS
2420                    syntax)                    syntax)
2421           ]      terminates the character class           ]      terminates the character class
2422    
2423         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the  metacharacters.
2424    
2425    
2426  BACKSLASH  BACKSLASH
2427    
2428         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2429         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
2430         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
2431         applies both inside and outside character classes.         applies both inside and outside character classes.
2432    
2433         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
2434         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
2435         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
2436         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
2437         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-
2438         slash, you write \\.         slash, you write \\.
2439    
2440         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
2441         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
2442         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline character are ignored.
2443         An  escaping backslash can be used to include a whitespace or # charac-         An escaping backslash can be used to include a whitespace or #  charac-
2444         ter as part of the pattern.         ter as part of the pattern.
2445    
2446         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-
2447         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-
2448         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
2449         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
2450         tion. Note the following examples:         tion. Note the following examples:
2451    
2452           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 1916  BACKSLASH Line 2456  BACKSLASH
2456           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
2457           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
2458    
2459         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
2460         classes.         classes.
2461    
2462     Non-printing characters     Non-printing characters
2463    
2464         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-
2465         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
2466         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
2467         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
2468         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
2469         sequences than the binary character it represents:         sequences than the binary character it represents:
2470    
2471           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 1939  BACKSLASH Line 2479  BACKSLASH
2479           \xhh      character with hex code hh           \xhh      character with hex code hh
2480           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh... (UTF-8 mode only)
2481    
2482         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,
2483         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
2484         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
2485         becomes hex 7B.         becomes hex 7B.
2486    
2487         After  \x, from zero to two hexadecimal digits are read (letters can be         After \x, from zero to two hexadecimal digits are read (letters can  be
2488         in upper or lower case). In UTF-8 mode, any number of hexadecimal  dig-         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-
2489         its  may  appear between \x{ and }, but the value of the character code         its may appear between \x{ and }, but the value of the  character  code
2490         must be less than 2**31 (that is,  the  maximum  hexadecimal  value  is         must  be  less  than  2**31  (that is, the maximum hexadecimal value is
2491         7FFFFFFF).  If  characters other than hexadecimal digits appear between         7FFFFFFF). If characters other than hexadecimal digits  appear  between
2492         \x{ and }, or if there is no terminating }, this form of escape is  not         \x{  and }, or if there is no terminating }, this form of escape is not
2493         recognized. Instead, the initial \x will be interpreted as a basic hex-         recognized. Instead, the initial \x will  be  interpreted  as  a  basic
2494         adecimal escape, with no following digits,  giving  a  character  whose         hexadecimal  escape, with no following digits, giving a character whose
2495         value is zero.         value is zero.
2496    
2497         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
2498         two syntaxes for \x when PCRE is in UTF-8 mode. There is no  difference         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference
2499         in  the  way they are handled. For example, \xdc is exactly the same as         in the way they are handled. For example, \xdc is exactly the  same  as
2500         \x{dc}.         \x{dc}.
2501    
2502         After \0 up to two further octal digits are read.  In  both  cases,  if         After  \0  up  to  two further octal digits are read. In both cases, if
2503         there  are fewer than two digits, just those that are present are used.         there are fewer than two digits, just those that are present are  used.
2504         Thus the sequence \0\x\07 specifies two binary zeros followed by a  BEL         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL
2505         character  (code  value  7).  Make sure you supply two digits after the         character (code value 7). Make sure you supply  two  digits  after  the
2506         initial zero if the pattern character that follows is itself  an  octal         initial  zero  if the pattern character that follows is itself an octal
2507         digit.         digit.
2508    
2509         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-
2510         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
2511         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
2512         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
2513         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
2514         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
2515         of parenthesized subpatterns.         of parenthesized subpatterns.
2516    
2517         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
2518         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
2519         up  to three octal digits following the backslash, and generates a sin-         up to three octal digits following the backslash, and generates a  sin-
2520         gle byte from the least significant 8 bits of the value. Any subsequent         gle byte from the least significant 8 bits of the value. Any subsequent
2521         digits stand for themselves.  For example:         digits stand for themselves.  For example:
2522    
# Line 1995  BACKSLASH Line 2535  BACKSLASH
2535           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
2536                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
2537    
2538         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
2539         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
2540    
2541         All the sequences that define a single byte value  or  a  single  UTF-8         All  the  sequences  that  define a single byte value or a single UTF-8
2542         character (in UTF-8 mode) can be used both inside and outside character         character (in UTF-8 mode) can be used both inside and outside character
2543         classes. In addition, inside a character  class,  the  sequence  \b  is         classes.  In  addition,  inside  a  character class, the sequence \b is
2544         interpreted as the backspace character (hex 08), and the sequence \X is         interpreted as the backspace character (hex 08), and the sequence \X is
2545         interpreted as the character "X".  Outside  a  character  class,  these         interpreted  as  the  character  "X".  Outside a character class, these
2546         sequences have different meanings (see below).         sequences have different meanings (see below).
2547    
2548     Generic character types     Generic character types
2549    
2550         The  third  use of backslash is for specifying generic character types.         The third use of backslash is for specifying generic  character  types.
2551         The following are always recognized:         The following are always recognized:
2552    
2553           \d     any decimal digit           \d     any decimal digit
# Line 2018  BACKSLASH Line 2558  BACKSLASH
2558           \W     any "non-word" character           \W     any "non-word" character
2559    
2560         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
2561         into  two disjoint sets. Any given character matches one, and only one,         into two disjoint sets. Any given character matches one, and only  one,
2562         of each pair.         of each pair.
2563    
2564         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
2565         acter  classes.  They each match one character of the appropriate type.         acter classes. They each match one character of the  appropriate  type.
2566         If the current matching point is at the end of the subject string,  all         If  the current matching point is at the end of the subject string, all
2567         of them fail, since there is no character to match.         of them fail, since there is no character to match.
2568    
2569         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
2570         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
2571         characters are HT (9), LF (10), FF (12), CR (13), and space (32).         characters are HT (9), LF (10), FF (12), CR (13), and space (32).
2572    
2573         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character less than 256 that
2574         is a letter or digit. The definition of  letters  and  digits  is  con-         is  a  letter  or  digit.  The definition of letters and digits is con-
2575         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-
2576         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
2577         page).  For  example,  in  the  "fr_FR" (French) locale, some character         page). For example, in the  "fr_FR"  (French)  locale,  some  character
2578         codes greater than 128 are used for accented  letters,  and  these  are         codes  greater  than  128  are used for accented letters, and these are
2579         matched by \w.         matched by \w.
2580    
2581         In  UTF-8 mode, characters with values greater than 128 never match \d,         In UTF-8 mode, characters with values greater than 128 never match  \d,
2582         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
2583         code character property support is available.         code character property support is available.
2584    
2585     Unicode character properties     Unicode character properties
2586    
2587         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
2588         tional escape sequences to match generic character types are  available         tional  escape sequences to match generic character types are available
2589         when UTF-8 mode is selected. They are:         when UTF-8 mode is selected. They are:
2590    
2591          \p{xx}   a character with the xx property          \p{xx}   a character with the xx property
2592          \P{xx}   a character without the xx property          \P{xx}   a character without the xx property
2593          \X       an extended Unicode sequence          \X       an extended Unicode sequence
2594    
2595         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
2596         general category properties. Each character has exactly one such  prop-         general  category properties. Each character has exactly one such prop-
2597         erty,  specified  by  a two-letter abbreviation. For compatibility with         erty, specified by a two-letter abbreviation.  For  compatibility  with
2598         Perl, negation can be specified by including a circumflex  between  the         Perl,  negation  can be specified by including a circumflex between the
2599         opening  brace  and the property name. For example, \p{^Lu} is the same         opening brace and the property name. For example, \p{^Lu} is  the  same
2600         as \P{Lu}.         as \P{Lu}.
2601    
2602         If only one letter is specified with \p or  \P,  it  includes  all  the         If  only  one  letter  is  specified with \p or \P, it includes all the
2603         properties that start with that letter. In this case, in the absence of         properties that start with that letter. In this case, in the absence of
2604         negation, the curly brackets in the escape sequence are optional; these         negation, the curly brackets in the escape sequence are optional; these
2605         two examples have the same effect:         two examples have the same effect:
# Line 2113  BACKSLASH Line 2653  BACKSLASH
2653           Zp    Paragraph separator           Zp    Paragraph separator
2654           Zs    Space separator           Zs    Space separator
2655    
2656         Extended  properties such as "Greek" or "InMusicalSymbols" are not sup-         Extended properties such as "Greek" or "InMusicalSymbols" are not  sup-
2657         ported by PCRE.         ported by PCRE.
2658    
2659         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
2660         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
2661    
2662         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
2663         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
2664    
2665           (?>\PM\pM*)           (?>\PM\pM*)
2666    
2667         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
2668         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
2669         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
2670         property are typically accents that affect the preceding character.         property are typically accents that affect the preceding character.
2671    
2672         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
2673         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
2674         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
2675         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
2676    
2677     Simple assertions     Simple assertions
2678    
2679         The fourth use of backslash is for certain simple assertions. An asser-         The fourth use of backslash is for certain simple assertions. An asser-
2680         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
2681         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
2682         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
2683         The backslashed assertions are:         The backslashed assertions are:
2684    
2685           \b     matches at a word boundary           \b     matches at a word boundary
# Line 2149  BACKSLASH Line 2689  BACKSLASH
2689           \z     matches at end of subject           \z     matches at end of subject
2690           \G     matches at first matching position in subject           \G     matches at first matching position in subject
2691    
2692         These assertions may not appear in character classes (but note that  \b         These  assertions may not appear in character classes (but note that \b
2693         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
2694         acter class).         acter class).
2695    
2696         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
2697         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.
2698         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
2699         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
2700    
2701         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
2702         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
2703         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
2704         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
2705         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
2706         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
2707         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
2708         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
2709         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
2710         that \Z matches before a newline that is  the  last  character  of  the         that  \Z  matches  before  a  newline that is the last character of the
2711         string  as well as at the end of the string, whereas \z matches only at         string as well as at the end of the string, whereas \z matches only  at
2712         the end.         the end.
2713    
2714         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
2715         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
2716         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
2717         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
2718         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-
2719         mentation where \G can be useful.         mentation where \G can be useful.
2720    
2721         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
2722         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
2723         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
2724         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
2725         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
2726    
2727         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
2728         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
2729         in the compiled regular expression.         in the compiled regular expression.
2730    
# Line 2192  BACKSLASH Line 2732  BACKSLASH
2732  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
2733    
2734         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
2735         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
2736         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-
2737         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
2738         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
2739         has an entirely different meaning (see below).         has an entirely different meaning (see below).
2740    
2741         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
2742         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
2743         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
2744         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
2745         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-
2746         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
2747         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
2748    
2749         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
2750         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
2751         before a newline character that is the last character in the string (by         before a newline character that is the last character in the string (by
2752         default).  Dollar  need  not  be the last character of the pattern if a         default). Dollar need not be the last character of  the  pattern  if  a
2753         number of alternatives are involved, but it should be the last item  in         number  of alternatives are involved, but it should be the last item in
2754         any  branch  in  which  it appears.  Dollar has no special meaning in a         any branch in which it appears.  Dollar has no  special  meaning  in  a
2755         character class.         character class.
2756    
2757         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
2758         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
2759         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
2760    
2761         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
2762         PCRE_MULTILINE option is set. When this is the case, they match immedi-         PCRE_MULTILINE option is set. When this is the case, they match immedi-
2763         ately after and  immediately  before  an  internal  newline  character,         ately  after  and  immediately  before  an  internal newline character,
2764         respectively,  in addition to matching at the start and end of the sub-         respectively, in addition to matching at the start and end of the  sub-
2765         ject string. For example,  the  pattern  /^abc$/  matches  the  subject         ject  string.  For  example,  the  pattern  /^abc$/ matches the subject
2766         string  "def\nabc"  (where \n represents a newline character) in multi-         string "def\nabc" (where \n represents a newline character)  in  multi-
2767         line mode, but not otherwise.  Consequently, patterns that are anchored         line mode, but not otherwise.  Consequently, patterns that are anchored
2768         in  single line mode because all branches start with ^ are not anchored         in single line mode because all branches start with ^ are not  anchored
2769         in multiline mode, and a match for  circumflex  is  possible  when  the         in  multiline  mode,  and  a  match for circumflex is possible when the
2770         startoffset   argument   of  pcre_exec()  is  non-zero.  The  PCRE_DOL-         startoffset  argument  of  pcre_exec()  is  non-zero.   The   PCRE_DOL-
2771         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
2772    
2773         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
2774         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
2775         start with \A it is always anchored, whether PCRE_MULTILINE is  set  or         start  with  \A it is always anchored, whether PCRE_MULTILINE is set or
2776         not.         not.
2777    
2778    
2779  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
2780    
2781         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-
2782         ter in the subject, including a non-printing  character,  but  not  (by         ter  in  the  subject,  including a non-printing character, but not (by
2783         default)  newline.   In  UTF-8 mode, a dot matches any UTF-8 character,         default) newline.  In UTF-8 mode, a dot matches  any  UTF-8  character,
2784         which might be more than one byte long, except (by default) newline. If         which might be more than one byte long, except (by default) newline. If
2785         the  PCRE_DOTALL  option  is set, dots match newlines as well. The han-         the PCRE_DOTALL option is set, dots match newlines as  well.  The  han-
2786         dling of dot is entirely independent of the handling of circumflex  and         dling  of dot is entirely independent of the handling of circumflex and
2787         dollar,  the  only  relationship  being  that they both involve newline         dollar, the only relationship being  that  they  both  involve  newline
2788         characters. Dot has no special meaning in a character class.         characters. Dot has no special meaning in a character class.
2789    
2790    
2791  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
2792    
2793         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
2794         both  in  and  out of UTF-8 mode. Unlike a dot, it can match a newline.         both in and out of UTF-8 mode. Unlike a dot, it can  match  a  newline.
2795         The feature is provided in Perl in order to match individual  bytes  in         The  feature  is provided in Perl in order to match individual bytes in
2796         UTF-8  mode.  Because  it  breaks  up  UTF-8 characters into individual         UTF-8 mode. Because it  breaks  up  UTF-8  characters  into  individual
2797         bytes, what remains in the string may be a malformed UTF-8 string.  For         bytes,  what remains in the string may be a malformed UTF-8 string. For
2798         this reason, the \C escape sequence is best avoided.         this reason, the \C escape sequence is best avoided.
2799    
2800         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
2801         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-
2802         late the length of the lookbehind.         late the length of the lookbehind.
2803    
2804    
# Line 2267  SQUARE BRACKETS AND CHARACTER CLASSES Line 2807  SQUARE BRACKETS AND CHARACTER CLASSES
2807         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
2808         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-
2809         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
2810         it should be the first data character in the class  (after  an  initial         it  should  be  the first data character in the class (after an initial
2811         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
2812    
2813         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
2814         mode, the character may occupy more than one byte. A matched  character         mode,  the character may occupy more than one byte. A matched character
2815         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
2816         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
2817         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
2818         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
2819         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
2820    
2821         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
2822         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
2823         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
2824         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
2825         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-
2826         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
2827         the current pointer is at the end of the string.         the current pointer is at the end of the string.
2828    
2829         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
2830         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
2831         mechanism.         mechanism.
2832    
2833         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
2834         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
2835         [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
2836         match "A", whereas a caseful version would. When running in UTF-8 mode,         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
2837         PCRE  supports  the  concept of case for characters with values greater         understands the concept of case for characters whose  values  are  less
2838         than 128 only when it is compiled with Unicode property support.         than  128, so caseless matching is always possible. For characters with
2839           higher values, the concept of case is supported  if  PCRE  is  compiled
2840           with  Unicode  property support, but not otherwise.  If you want to use
2841           caseless matching for characters 128 and above, you  must  ensure  that
2842           PCRE  is  compiled  with Unicode property support as well as with UTF-8
2843           support.
2844    
2845         The newline character is never treated in any special way in  character         The newline character is never treated in any special way in  character
2846         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE
# Line 3215  CALLOUTS Line 3760  CALLOUTS
3760         gether. A complete description of the interface to the callout function         gether. A complete description of the interface to the callout function
3761         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
3762    
3763  Last updated: 09 September 2004  Last updated: 28 February 2005
3764  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
3765  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
3766    
 PCRE(3)                                                                PCRE(3)  
3767    
3768    PCREPARTIAL(3)                                                  PCREPARTIAL(3)
3769    
3770    
3771  NAME  NAME
3772         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3773    
3774    
3775  PARTIAL MATCHING IN PCRE  PARTIAL MATCHING IN PCRE
3776    
3777         In  normal  use  of  PCRE,  if  the  subject  string  that is passed to         In  normal  use  of  PCRE,  if  the  subject  string  that is passed to
3778         pcre_exec() matches as far as it goes, but is too short  to  match  the         pcre_exec() or pcre_dfa_exec() matches as far as it goes,  but  is  too
3779         entire pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances         short  to  match  the  entire  pattern, PCRE_ERROR_NOMATCH is returned.
3780         where it might be helpful to distinguish this case from other cases  in         There are circumstances where it might be helpful to  distinguish  this
3781         which there is no match.         case from other cases in which there is no match.
3782    
3783         Consider, for example, an application where a human is required to type         Consider, for example, an application where a human is required to type
3784         in data for a field with specific formatting requirements.  An  example         in data for a field with specific formatting requirements.  An  example
# Line 3248  PARTIAL MATCHING IN PCRE Line 3794  PARTIAL MATCHING IN PCRE
3794         until the entire string has been entered.         until the entire string has been entered.
3795    
3796         PCRE supports the concept of partial matching by means of the PCRE_PAR-         PCRE supports the concept of partial matching by means of the PCRE_PAR-
3797         TIAL  option,  which  can be set when calling pcre_exec(). When this is         TIAL   option,   which   can   be   set  when  calling  pcre_exec()  or
3798         done,  the   return   code   PCRE_ERROR_NOMATCH   is   converted   into         pcre_dfa_exec(). When this flag is set for pcre_exec(), the return code
3799         PCRE_ERROR_PARTIAL  if  at  any  time  during  the matching process the         PCRE_ERROR_NOMATCH  is converted into PCRE_ERROR_PARTIAL if at any time
3800         entire subject string matched part of the pattern. No captured data  is         during the matching process the last part of the subject string matched
3801         set when this occurs.         part  of  the  pattern. Unfortunately, for non-anchored matching, it is
3802           not possible to obtain the position of the start of the partial  match.
3803           No captured data is set when PCRE_ERROR_PARTIAL is returned.
3804    
3805           When   PCRE_PARTIAL   is  set  for  pcre_dfa_exec(),  the  return  code
3806           PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the  end  of
3807           the  subject is reached, there have been no complete matches, but there
3808           is still at least one matching possibility. The portion of  the  string
3809           that provided the partial match is set as the first matching string.
3810    
3811         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers
3812         the last literal byte in a pattern, and abandons  matching  immediately         the last literal byte in a pattern, and abandons  matching  immediately
# Line 3263  PARTIAL MATCHING IN PCRE Line 3817  PARTIAL MATCHING IN PCRE
3817  RESTRICTED PATTERNS FOR PCRE_PARTIAL  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3818    
3819         Because of the way certain internal optimizations  are  implemented  in         Because of the way certain internal optimizations  are  implemented  in
3820         PCRE,  the  PCRE_PARTIAL  option  cannot  be  used  with  all patterns.         the  pcre_exec()  function, the PCRE_PARTIAL option cannot be used with
3821         Repeated single characters such as         all patterns. These restrictions do not apply when  pcre_dfa_exec()  is
3822           used.  For pcre_exec(), repeated single characters such as
3823    
3824           a{2,4}           a{2,4}
3825    
# Line 3272  RESTRICTED PATTERNS FOR PCRE_PARTIAL Line 3827  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3827    
3828           \d+           \d+
3829    
3830         are not permitted if the maximum number of occurrences is greater  than         are  not permitted if the maximum number of occurrences is greater than
3831         one.  Optional items such as \d? (where the maximum is one) are permit-         one.  Optional items such as \d? (where the maximum is one) are permit-
3832         ted.  Quantifiers with any values are permitted after  parentheses,  so         ted.   Quantifiers  with any values are permitted after parentheses, so
3833         the invalid examples above can be coded thus:         the invalid examples above can be coded thus:
3834    
3835           (a){2,4}           (a){2,4}
3836           (\d)+           (\d)+
3837    
3838         These  constructions  run more slowly, but for the kinds of application         These constructions run more slowly, but for the kinds  of  application
3839         that are envisaged for this facility, this is not felt to  be  a  major         that  are  envisaged  for this facility, this is not felt to be a major
3840         restriction.         restriction.
3841    
3842         If  PCRE_PARTIAL  is  set  for  a  pattern that does not conform to the         If PCRE_PARTIAL is set for a pattern  that  does  not  conform  to  the
3843         restrictions, pcre_exec() returns the error code  PCRE_ERROR_BADPARTIAL         restrictions,  pcre_exec() returns the error code PCRE_ERROR_BADPARTIAL
3844         (-13).         (-13).
3845    
3846    
3847  EXAMPLE OF PARTIAL MATCHING USING PCRETEST  EXAMPLE OF PARTIAL MATCHING USING PCRETEST
3848    
3849         If  the  escape  sequence  \P  is  present in a pcretest data line, the         If the escape sequence \P is present  in  a  pcretest  data  line,  the
3850         PCRE_PARTIAL flag is used for the match. Here is a run of pcretest that         PCRE_PARTIAL flag is used for the match. Here is a run of pcretest that
3851         uses the date example quoted above:         uses the date example quoted above:
3852    
# Line 3308  EXAMPLE OF PARTIAL MATCHING USING PCRETE Line 3863  EXAMPLE OF PARTIAL MATCHING USING PCRETE
3863           data> jP           data> jP
3864           No match           No match
3865    
3866         The  first  data  string  is  matched completely, so pcretest shows the         The first data string is matched  completely,  so  pcretest  shows  the
3867         matched substrings. The remaining four strings do not  match  the  com-         matched  substrings.  The  remaining four strings do not match the com-
3868         plete pattern, but the first two are partial matches.         plete pattern, but the first two are partial matches.  The  same  test,
3869           using  DFA  matching (by means of the \D escape sequence), produces the
3870           following output:
3871    
3872  Last updated: 08 September 2004             re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3873  Copyright (c) 1997-2004 University of Cambridge.           data> 25jun04\P\D
3874  -----------------------------------------------------------------------------            0: 25jun04
3875             data> 23dec3\P\D
3876             Partial match: 23dec3
3877             data> 3ju\P\D
3878             Partial match: 3ju
3879             data> 3juj\P\D
3880             No match
3881             data> j\P\D
3882             No match
3883    
3884  PCRE(3)                                                                PCRE(3)         Notice that in this case the portion of the string that was matched  is
3885           made available.
3886    
3887    
3888    MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()
3889    
3890           When a partial match has been found using pcre_dfa_exec(), it is possi-
3891           ble to continue the match by  providing  additional  subject  data  and
3892           calling  pcre_dfa_exec() again with the PCRE_DFA_RESTART option and the
3893           same working space (where details of the  previous  partial  match  are
3894           stored).  Here  is  an  example  using  pcretest,  where  the \R escape
3895           sequence sets the PCRE_DFA_RESTART option and the  \D  escape  sequence
3896           requests the use of pcre_dfa_exec():
3897    
3898               re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3899             data> 23ja\P\D
3900             Partial match: 23ja
3901             data> n05\R\D
3902              0: n05
3903    
3904           The  first  call has "23ja" as the subject, and requests partial match-
3905           ing; the second call  has  "n05"  as  the  subject  for  the  continued
3906           (restarted)  match.   Notice  that when the match is complete, only the
3907           last part is shown; PCRE does  not  retain  the  previously  partially-
3908           matched  string. It is up to the calling program to do that if it needs
3909           to.
3910    
3911           This facility can  be  used  to  pass  very  long  subject  strings  to
3912           pcre_dfa_exec(). However, some care is needed for certain types of pat-
3913           tern.
3914    
3915           1. If the pattern contains tests for the beginning or end  of  a  line,
3916           you  need  to pass the PCRE_NOTBOL or PCRE_NOTEOL options, as appropri-
3917           ate, when the subject string for any call does not contain  the  begin-
3918           ning or end of a line.
3919    
3920           2.  If  the  pattern contains backward assertions (including \b or \B),
3921           you need to arrange for some overlap in the subject  strings  to  allow
3922           for  this.  For example, you could pass the subject in chunks that were
3923           500 bytes long, but in a buffer of 700 bytes, with the starting  offset
3924           set to 200 and the previous 200 bytes at the start of the buffer.
3925    
3926           3.  Matching a subject string that is split into multiple segments does
3927           not always produce exactly the same result as matching over one  single
3928           long  string.   The  difference arises when there are multiple matching
3929           possibilities, because a partial match result is given only when  there
3930           are  no  completed  matches  in a call to fBpcre_dfa_exec(). This means
3931           that as soon as the shortest match has been found,  continuation  to  a
3932           new  subject  segment  is  no  longer possible.  Consider this pcretest
3933           example:
3934    
3935               re> /dog(sbody)?/
3936             data> do\P\D
3937             Partial match: do
3938             data> gsb\R\P\D
3939              0: g
3940             data> dogsbody\D
3941              0: dogsbody
3942              1: dog
3943    
3944           The pattern matches the words "dog" or "dogsbody". When the subject  is
3945           presented  in  several  parts  ("do" and "gsb" being the first two) the
3946           match stops when "dog" has been found, and it is not possible  to  con-
3947           tinue.  On  the  other  hand,  if  "dogsbody"  is presented as a single
3948           string, both matches are found.
3949    
3950           Because of this phenomenon, it does not usually make  sense  to  end  a
3951           pattern that is going to be matched in this way with a variable repeat.
3952    
3953    Last updated: 28 February 2005
3954    Copyright (c) 1997-2005 University of Cambridge.
3955    ------------------------------------------------------------------------------
3956    
3957    
3958    PCREPRECOMPILE(3)                                            PCREPRECOMPILE(3)
3959    
3960    
3961  NAME  NAME
3962         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3963    
3964    
3965  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS
3966    
3967         If  you  are running an application that uses a large number of regular         If  you  are running an application that uses a large number of regular
# Line 3391  SAVING A COMPILED PATTERN Line 4030  SAVING A COMPILED PATTERN
4030  RE-USING A PRECOMPILED PATTERN  RE-USING A PRECOMPILED PATTERN
4031    
4032         Re-using a precompiled pattern is straightforward. Having  reloaded  it         Re-using a precompiled pattern is straightforward. Having  reloaded  it
4033         into main memory, you pass its pointer to pcre_exec() in the usual way.         into   main   memory,   you   pass   its   pointer  to  pcre_exec()  or
4034         This should work even on another host, and even if that  host  has  the         pcre_dfa_exec() in the usual way. This  should  work  even  on  another
4035         opposite endianness to the one where the pattern was compiled.         host,  and  even  if  that  host has the opposite endianness to the one
4036           where the pattern was compiled.
4037         However,  if  you  passed a pointer to custom character tables when the  
4038         pattern was compiled (the tableptr  argument  of  pcre_compile()),  you         However, if you passed a pointer to custom character  tables  when  the
4039         must now pass a similar pointer to pcre_exec(), because the value saved         pattern  was  compiled  (the  tableptr argument of pcre_compile()), you
4040         with the compiled pattern will obviously be  nonsense.  A  field  in  a         must now pass a similar  pointer  to  pcre_exec()  or  pcre_dfa_exec(),
4041         pcre_extra()  block is used to pass this data, as described in the sec-         because  the  value  saved  with the compiled pattern will obviously be
4042         tion on matching a pattern in the pcreapi documentation.         nonsense. A field in a pcre_extra() block is used to pass this data, as
4043           described  in the section on matching a pattern in the pcreapi documen-
4044           tation.
4045    
4046         If you did not provide custom character tables  when  the  pattern  was         If you did not provide custom character tables  when  the  pattern  was
4047         compiled,  the  pointer  in  the compiled pattern is NULL, which causes         compiled,  the  pointer  in  the compiled pattern is NULL, which causes
# Line 3411  RE-USING A PRECOMPILED PATTERN Line 4052  RE-USING A PRECOMPILED PATTERN
4052         your own pcre_extra data block and set the study_data field to point to         your own pcre_extra data block and set the study_data field to point to
4053         the  reloaded  study  data. You must also set the PCRE_EXTRA_STUDY_DATA         the  reloaded  study  data. You must also set the PCRE_EXTRA_STUDY_DATA
4054         bit in the flags field to indicate that study  data  is  present.  Then         bit in the flags field to indicate that study  data  is  present.  Then
4055         pass the pcre_extra block to pcre_exec() in the usual way.         pass  the  pcre_extra  block  to  pcre_exec() or pcre_dfa_exec() in the
4056           usual way.
4057    
4058    
4059  COMPATIBILITY WITH DIFFERENT PCRE RELEASES  COMPATIBILITY WITH DIFFERENT PCRE RELEASES
4060    
4061         The  layout  of the control block that is at the start of the data that         The layout of the control block that is at the start of the  data  that
4062         makes up a compiled pattern was changed for release 5.0.  If  you  have         makes  up  a  compiled pattern was changed for release 5.0. If you have
4063         any  saved  patterns  that  were compiled with previous releases (not a         any saved patterns that were compiled with  previous  releases  (not  a
4064         facility that was previously advertised), you will  have  to  recompile         facility  that  was  previously advertised), you will have to recompile
4065         them  for  release  5.0. However, from now on, it should be possible to         them for release 5.0. However, from now on, it should  be  possible  to
4066         make changes in a compabible manner.         make changes in a compatible manner.
4067    
4068  Last updated: 10 September 2004  Last updated: 28 February 2005
4069  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4070  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
4071    
 PCRE(3)                                                                PCRE(3)  
4072    
4073    PCREPERFORM(3)                                                  PCREPERFORM(3)
4074    
4075    
4076  NAME  NAME
4077         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
4078    
4079    
4080  PCRE PERFORMANCE  PCRE PERFORMANCE
4081    
4082         Certain  items  that may appear in regular expression patterns are more         Certain  items  that may appear in regular expression patterns are more
# Line 3469  PCRE PERFORMANCE Line 4112  PCRE PERFORMANCE
4112    
4113         If you are using such a pattern with subject strings that do  not  con-         If you are using such a pattern with subject strings that do  not  con-
4114         tain newlines, the best performance is obtained by setting PCRE_DOTALL,         tain newlines, the best performance is obtained by setting PCRE_DOTALL,
4115         or starting the pattern with ^.* to indicate explicit  anchoring.  That         or starting the pattern with ^.* or ^.*? to indicate  explicit  anchor-
4116         saves  PCRE from having to scan along the subject looking for a newline         ing.  That saves PCRE from having to scan along the subject looking for
4117         to restart at.         a newline to restart at.
4118    
4119         Beware of patterns that contain nested indefinite  repeats.  These  can         Beware of patterns that contain nested indefinite  repeats.  These  can
4120         take  a  long time to run when applied to a string that does not match.         take  a  long time to run when applied to a string that does not match.
# Line 3492  PCRE PERFORMANCE Line 4135  PCRE PERFORMANCE
4135           (a+)*b           (a+)*b
4136    
4137         where a literal character follows. Before  embarking  on  the  standard         where a literal character follows. Before  embarking  on  the  standard
4138         matching  procedure,  PCRE  checks  that  there  is  a "b" later in the         matching  procedure,  PCRE checks that there is a "b" later in the sub-
4139         subject string, and if there is not, it fails  the  match  immediately.         ject string, and if there is not, it fails the match immediately.  How-
4140         However, when there is no following literal this optimization cannot be         ever,  when  there  is no following literal this optimization cannot be
4141         used. You can see the difference by comparing the behaviour of         used. You can see the difference by comparing the behaviour of
4142    
4143           (a+)*\d           (a+)*\d
# Line 3506  PCRE PERFORMANCE Line 4149  PCRE PERFORMANCE
4149         In many cases, the solution to this kind of performance issue is to use         In many cases, the solution to this kind of performance issue is to use
4150         an atomic group or a possessive quantifier.         an atomic group or a possessive quantifier.
4151    
4152  Last updated: 09 September 2004  Last updated: 28 February 2005
4153  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4154  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
4155    
 PCRE(3)                                                                PCRE(3)  
4156    
4157    PCREPOSIX(3)                                                      PCREPOSIX(3)
4158    
4159    
4160  NAME  NAME
4161         PCRE - Perl-compatible regular expressions.         PCRE - Perl-compatible regular expressions.
4162    
4163    
4164  SYNOPSIS OF POSIX API  SYNOPSIS OF POSIX API
4165    
4166         #include <pcreposix.h>         #include <pcreposix.h>
# Line 3537  DESCRIPTION Line 4181  DESCRIPTION
4181    
4182         This  set  of  functions provides a POSIX-style API to the PCRE regular         This  set  of  functions provides a POSIX-style API to the PCRE regular
4183         expression package. See the pcreapi documentation for a description  of         expression package. See the pcreapi documentation for a description  of
4184         PCRE's native API, which contains additional functionality.         PCRE's native API, which contains much additional functionality.
4185    
4186         The functions described here are just wrapper functions that ultimately         The functions described here are just wrapper functions that ultimately
4187         call  the  PCRE  native  API.  Their  prototypes  are  defined  in  the         call  the  PCRE  native  API.  Their  prototypes  are  defined  in  the
# Line 3581  COMPILING A PATTERN Line 4225  COMPILING A PATTERN
4225         The argument cflags is either zero, or contains one or more of the bits         The argument cflags is either zero, or contains one or more of the bits
4226         defined by the following macros:         defined by the following macros:
4227    
4228             REG_DOTALL
4229    
4230           The PCRE_DOTALL option is set when the expression is passed for  compi-
4231           lation  to the native function. Note that REG_DOTALL is not part of the
4232           POSIX standard.
4233    
4234           REG_ICASE           REG_ICASE
4235    
4236         The PCRE_CASELESS option is set when the expression is passed for  com-         The PCRE_CASELESS option is set when the expression is passed for  com-
# Line 3692  MEMORY USAGE Line 4342  MEMORY USAGE
4342    
4343  AUTHOR  AUTHOR
4344    
4345         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
4346         University Computing Service,         University Computing Service,
4347         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
4348    
4349  Last updated: 07 September 2004  Last updated: 28 February 2005
4350  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4351  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
4352    
 PCRE(3)                                                                PCRE(3)  
4353    
4354    PCRECPP(3)                                                          PCRECPP(3)
4355    
4356    
4357    NAME
4358           PCRE - Perl-compatible regular expressions.
4359    
4360    
4361    SYNOPSIS OF C++ WRAPPER
4362    
4363           #include <pcrecpp.h>
4364    
4365    
4366    DESCRIPTION
4367    
4368           The  C++  wrapper  for PCRE was provided by Google Inc. Some additional
4369           functionality was added by Giuseppe Maxia. This brief man page was con-
4370           structed  from  the  notes  in the pcrecpp.h file, which should be con-
4371           sulted for further details.
4372    
4373    
4374    MATCHING INTERFACE
4375    
4376           The "FullMatch" operation checks that supplied text matches a  supplied
4377           pattern  exactly.  If pointer arguments are supplied, it copies matched
4378           sub-strings that match sub-patterns into them.
4379    
4380             Example: successful match
4381                pcrecpp::RE re("h.*o");
4382                re.FullMatch("hello");
4383    
4384             Example: unsuccessful match (requires full match):
4385                pcrecpp::RE re("e");
4386                !re.FullMatch("hello");
4387    
4388             Example: creating a temporary RE object:
4389                pcrecpp::RE("h.*o").FullMatch("hello");
4390    
4391           You can pass in a "const char*" or a "string" for "text". The  examples
4392           below  tend to use a const char*. You can, as in the different examples
4393           above, store the RE object explicitly in a variable or use a  temporary
4394           RE  object.  The  examples below use one mode or the other arbitrarily.
4395           Either could correctly be used for any of these examples.
4396    
4397           You must supply extra pointer arguments to extract matched subpieces.
4398    
4399             Example: extracts "ruby" into "s" and 1234 into "i"
4400                int i;
4401                string s;
4402                pcrecpp::RE re("(\\w+):(\\d+)");
4403                re.FullMatch("ruby:1234", &s, &i);
4404    
4405             Example: does not try to extract any extra sub-patterns
4406                re.FullMatch("ruby:1234", &s);
4407    
4408             Example: does not try to extract into NULL
4409                re.FullMatch("ruby:1234", NULL, &i);
4410    
4411             Example: integer overflow causes failure
4412                !re.FullMatch("ruby:1234567891234", NULL, &i);
4413    
4414             Example: fails because there aren't enough sub-patterns:
4415                !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
4416    
4417             Example: fails because string cannot be stored in integer
4418                !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
4419    
4420           The provided pointer arguments can be pointers to  any  scalar  numeric
4421           type, or one of:
4422    
4423              string        (matched piece is copied to string)
4424              StringPiece   (StringPiece is mutated to point to matched piece)
4425              T             (where "bool T::ParseFrom(const char*, int)" exists)
4426              NULL          (the corresponding matched sub-pattern is not copied)
4427    
4428           The  function returns true iff all of the following conditions are sat-
4429           isfied:
4430    
4431             a. "text" matches "pattern" exactly;
4432    
4433             b. The number of matched sub-patterns is >= number of supplied
4434                pointers;
4435    
4436             c. The "i"th argument has a suitable type for holding the
4437                string captured as the "i"th sub-pattern. If you pass in
4438                NULL for the "i"th argument, or pass fewer arguments than
4439                number of sub-patterns, "i"th captured sub-pattern is
4440                ignored.
4441    
4442           The matching interface supports at most 16 arguments per call.  If  you
4443           need    more,    consider    using    the    more   general   interface
4444           pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
4445    
4446    
4447    PARTIAL MATCHES
4448    
4449           You can use the "PartialMatch" operation when you want the  pattern  to
4450           match any substring of the text.
4451    
4452             Example: simple search for a string:
4453                pcrecpp::RE("ell").PartialMatch("hello");
4454    
4455             Example: find first number in a string:
4456                int number;
4457                pcrecpp::RE re("(\\d+)");
4458                re.PartialMatch("x*100 + 20", &number);
4459                assert(number == 100);
4460    
4461    
4462    UTF-8 AND THE MATCHING INTERFACE
4463    
4464           By  default,  pattern  and text are plain text, one byte per character.
4465           The UTF8 flag, passed to  the  constructor,  causes  both  pattern  and
4466           string to be treated as UTF-8 text, still a byte stream but potentially
4467           multiple bytes per character. In practice, the text is likelier  to  be
4468           UTF-8  than  the pattern, but the match returned may depend on the UTF8
4469           flag, so always use it when matching UTF8 text. For example,  "."  will
4470           match  one  byte normally but with UTF8 set may match up to three bytes
4471           of a multi-byte character.
4472    
4473             Example:
4474                pcrecpp::RE_Options options;
4475                options.set_utf8();
4476                pcrecpp::RE re(utf8_pattern, options);
4477                re.FullMatch(utf8_string);
4478    
4479             Example: using the convenience function UTF8():
4480                pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
4481                re.FullMatch(utf8_string);
4482    
4483           NOTE: The UTF8 flag is ignored if pcre was not configured with the
4484                 --enable-utf8 flag.
4485    
4486    
4487    PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE
4488    
4489           PCRE defines some modifiers to  change  the  behavior  of  the  regular
4490           expression   engine.  The  C++  wrapper  defines  an  auxiliary  class,
4491           RE_Options, as a vehicle to pass such modifiers to  a  RE  class.  Cur-
4492           rently, the following modifiers are supported:
4493    
4494              modifier              description               Perl corresponding
4495    
4496              PCRE_CASELESS         case insensitive match      /i
4497              PCRE_MULTILINE        multiple lines match        /m
4498              PCRE_DOTALL           dot matches newlines        /s
4499              PCRE_DOLLAR_ENDONLY   $ matches only at end       N/A
4500              PCRE_EXTRA            strict escape parsing       N/A
4501              PCRE_EXTENDED         ignore whitespaces          /x
4502              PCRE_UTF8             handles UTF8 chars          built-in
4503              PCRE_UNGREEDY         reverses * and *?           N/A
4504              PCRE_NO_AUTO_CAPTURE  disables capturing parens   N/A (*)
4505    
4506           (*)  Both Perl and PCRE allow non capturing parentheses by means of the
4507           "?:" modifier within the pattern itself. e.g. (?:ab|cd) does  not  cap-
4508           ture, while (ab|cd) does.
4509    
4510           For  a  full  account on how each modifier works, please check the PCRE
4511           API reference page.
4512    
4513           For each modifier, there are two member functions whose  name  is  made
4514           out  of  the  modifier  in  lowercase,  without the "PCRE_" prefix. For
4515           instance, PCRE_CASELESS is handled by
4516    
4517             bool caseless()
4518    
4519           which returns true if the modifier is set, and
4520    
4521             RE_Options & set_caseless(bool)
4522    
4523           which sets or unsets the  modifier.  Moreover,  PCRE_CONFIG_MATCH_LIMIT
4524           can  be accessed through the set_match_limit() and match_limit() member
4525           functions. Setting match_limit to a non-zero value will limit the  exe-
4526           cution  of pcre to keep it from doing bad things like blowing the stack
4527           or taking an eternity to return a result.  A  value  of  5000  is  good
4528           enough  to stop stack blowup in a 2MB thread stack. Setting match_limit
4529           to zero disables match limiting.
4530    
4531           Normally, to pass one or more modifiers to a RE class,  you  declare  a
4532           RE_Options object, set the appropriate options, and pass this object to
4533           a RE constructor. Example:
4534    
4535              RE_options opt;
4536              opt.set_caseless(true);
4537              if (RE("HELLO", opt).PartialMatch("hello world")) ...
4538    
4539           RE_options has two constructors. The default constructor takes no argu-
4540           ments  and creates a set of flags that are off by default. The optional
4541           parameter option_flags is to facilitate transfer of legacy code from  C
4542           programs.  This lets you do
4543    
4544              RE(pattern,
4545                RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
4546    
4547           However, new code is better off doing
4548    
4549              RE(pattern,
4550                RE_Options().set_caseless(true).set_multiline(true))
4551                  .PartialMatch(str);
4552    
4553           If you are going to pass one of the most used modifiers, there are some
4554           convenience functions that return a RE_Options class with the appropri-
4555           ate  modifier  already  set: CASELESS(), UTF8(), MULTILINE(), DOTALL(),
4556           and EXTENDED().
4557    
4558           If you need to set several options at once, and you don't  want  to  go
4559           through  the pains of declaring a RE_Options object and setting several
4560           options, there is a parallel method that give you such ability  on  the
4561           fly.  You  can  concatenate several set_xxxxx() member functions, since
4562           each of them returns a reference to its class object. For  example,  to
4563           pass  PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one
4564           statement, you may write:
4565    
4566              RE(" ^ xyz \\s+ .* blah$",
4567                RE_Options()
4568                  .set_caseless(true)
4569                  .set_extended(true)
4570                  .set_multiline(true)).PartialMatch(sometext);
4571    
4572    
4573    SCANNING TEXT INCREMENTALLY
4574    
4575           The "Consume" operation may be useful if you want to  repeatedly  match
4576           regular expressions at the front of a string and skip over them as they
4577           match. This requires use of the "StringPiece" type, which represents  a
4578           sub-range  of  a  real  string.  Like RE, StringPiece is defined in the
4579           pcrecpp namespace.
4580    
4581             Example: read lines of the form "var = value" from a string.
4582                string contents = ...;                 // Fill string somehow
4583                pcrecpp::StringPiece input(contents);  // Wrap in a StringPiece
4584    
4585                string var;
4586