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# Line 18  INTRODUCTION Line 18  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few  differences.  The current implementation of PCRE (release         just  a  few differences. (Certain features that appeared in Python and
22         6.x) corresponds approximately with Perl  5.8,  including  support  for         PCRE before they appeared in Perl are also available using  the  Python
23         UTF-8 encoded strings and Unicode general category properties. However,         syntax.)
24         this support has to be explicitly enabled; it is not the default.  
25           The  current  implementation of PCRE (release 7.x) corresponds approxi-
26         In addition to the Perl-compatible matching function,  PCRE  also  con-         mately with Perl 5.10, including support for UTF-8 encoded strings  and
27         tains  an  alternative matching function that matches the same compiled         Unicode general category properties. However, UTF-8 and Unicode support
28         patterns in a different way. In certain circumstances, the  alternative         has to be explicitly enabled; it is not the default. The Unicode tables
29         function  has  some  advantages.  For  a discussion of the two matching         correspond to Unicode release 5.0.0.
30         algorithms, see the pcrematching page.  
31           In  addition to the Perl-compatible matching function, PCRE contains an
32         PCRE is written in C and released as a C library. A  number  of  people         alternative matching function that matches the same  compiled  patterns
33         have  written  wrappers and interfaces of various kinds. In particular,         in  a different way. In certain circumstances, the alternative function
34         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         has some advantages. For a discussion of the two  matching  algorithms,
35           see the pcrematching page.
36    
37           PCRE  is  written  in C and released as a C library. A number of people
38           have written wrappers and interfaces of various kinds.  In  particular,
39           Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
40         included as part of the PCRE distribution. The pcrecpp page has details         included as part of the PCRE distribution. The pcrecpp page has details
41         of this interface. Other people's contributions can  be  found  in  the         of  this  interface.  Other  people's contributions can be found in the
42         Contrib directory at the primary FTP site, which is:         Contrib directory at the primary FTP site, which is:
43    
44         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
45    
46         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
47         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
48         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
49           page.
50    
51         Some  features  of  PCRE can be included, excluded, or changed when the         Some  features  of  PCRE can be included, excluded, or changed when the
52         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
# Line 67  USER DOCUMENTATION Line 73  USER DOCUMENTATION
73         of searching. The sections are as follows:         of searching. The sections are as follows:
74    
75           pcre              this document           pcre              this document
76             pcre-config       show PCRE installation configuration information
77           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
78           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
79           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
# Line 77  USER DOCUMENTATION Line 84  USER DOCUMENTATION
84           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
85           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
86                               regular expressions                               regular expressions
87             pcresyntax        quick syntax reference
88           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
89           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
90           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
# Line 99  LIMITATIONS Line 107  LIMITATIONS
107         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
108         the  source  distribution and the pcrebuild documentation for details).         the  source  distribution and the pcrebuild documentation for details).
109         In these cases the limit is substantially larger.  However,  the  speed         In these cases the limit is substantially larger.  However,  the  speed
110         of execution will be slower.         of execution is slower.
111    
112           All values in repeating quantifiers must be less than 65536.
113    
114         All  values in repeating quantifiers must be less than 65536. The maxi-         There is no limit to the number of parenthesized subpatterns, but there
115         mum compiled length of subpattern with  an  explicit  repeat  count  is         can be no more than 65535 capturing subpatterns.
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
   
        There  is  no limit to the number of non-capturing subpatterns, but the  
        maximum depth of nesting of  all  kinds  of  parenthesized  subpattern,  
        including capturing subpatterns, assertions, and other types of subpat-  
        tern, is 200.  
116    
117         The maximum length of name for a named subpattern is 32, and the  maxi-         The maximum length of name for a named subpattern is 32 characters, and
118         mum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
119    
120         The  maximum  length of a subject string is the largest positive number         The  maximum  length of a subject string is the largest positive number
121         that an integer variable can hold. However, when using the  traditional         that an integer variable can hold. However, when using the  traditional
# Line 136  UTF-8 AND UNICODE PROPERTY SUPPORT Line 140  UTF-8 AND UNICODE PROPERTY SUPPORT
140    
141         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,
142         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
143         is  limited  to testing the PCRE_UTF8 flag in several places, so should         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
144         not be very large.         very big.
145    
146         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
147         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
# Line 151  UTF-8 AND UNICODE PROPERTY SUPPORT Line 155  UTF-8 AND UNICODE PROPERTY SUPPORT
155         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
156         does not support this.         does not support this.
157    
158         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
159    
160           When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
161           subjects are (by default) checked for validity on entry to the relevant
162           functions. From release 7.3 of PCRE, the check is according  the  rules
163           of  RFC  3629, which are themselves derived from the Unicode specifica-
164           tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
165           allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
166           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
167           to U+DFFF.
168    
169           The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
170           which the Unicode Standard says this: "The Low Surrogate Area does  not
171           contain  any  character  assignments,  consequently  no  character code
172           charts or namelists are provided for this area. Surrogates are reserved
173           for  use  with  UTF-16 and then must be used in pairs." The code points
174           that are encoded by UTF-16 pairs  are  available  as  independent  code
175           points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
176           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
177    
178           If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
179           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
180           that your strings are valid, and therefore want to skip these checks in
181           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
182           compile time or at run time, PCRE assumes that the pattern  or  subject
183           it  is  given  (respectively)  contains only valid UTF-8 codes. In this
184           case, it does not diagnose an invalid UTF-8 string.
185    
186           If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
187           what  happens  depends on why the string is invalid. If the string con-
188           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
189           string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
190           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
191           strings  according  to  the more liberal rules of RFC 2279. However, if
192           the string does not even conform to RFC 2279, the result is  undefined.
193           Your program may crash.
194    
195           If  you  want  to  process  strings  of  values  in the full range 0 to
196           0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
197           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
198           this situation, you will have to apply your own validity check.
199    
200         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and     General comments about UTF-8 mode
        subjects  are  checked for validity on entry to the relevant functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations,  you  may  already  know  that  your strings are valid, and  
        therefore want to skip these checks in order to improve performance. If  
        you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,  
        PCRE assumes that the pattern or subject  it  is  given  (respectively)  
        contains  only valid UTF-8 codes. In this case, it does not diagnose an  
        invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when  
        PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may  
        crash.  
201    
202         2. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
203         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
204    
205         3.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
206         characters for values greater than \177.         characters for values greater than \177.
207    
208         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
209         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
210    
211         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         4.  The dot metacharacter matches one UTF-8 character instead of a sin-
212         gle byte.         gle byte.
213    
214         6. The escape sequence \C can be used to match a single byte  in  UTF-8         5. The escape sequence \C can be used to match a single byte  in  UTF-8
215         mode,  but  its  use can lead to some strange effects. This facility is         mode,  but  its  use can lead to some strange effects. This facility is
216         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
217    
218         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         6. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
219         test  characters of any code value, but the characters that PCRE recog-         test  characters of any code value, but the characters that PCRE recog-
220         nizes as digits, spaces, or word characters  remain  the  same  set  as         nizes as digits, spaces, or word characters  remain  the  same  set  as
221         before, all with values less than 256. This remains true even when PCRE         before, all with values less than 256. This remains true even when PCRE
# Line 190  UTF-8 AND UNICODE PROPERTY SUPPORT Line 224  UTF-8 AND UNICODE PROPERTY SUPPORT
224         sense of, say, "digit", you must use Unicode  property  tests  such  as         sense of, say, "digit", you must use Unicode  property  tests  such  as
225         \p{Nd}.         \p{Nd}.
226    
227         8.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
228         are all low-valued characters.         are all low-valued characters.
229    
230           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
231           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
232           acters.
233    
234         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
235         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
236         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
# Line 208  UTF-8 AND UNICODE PROPERTY SUPPORT Line 246  UTF-8 AND UNICODE PROPERTY SUPPORT
246  AUTHOR  AUTHOR
247    
248         Philip Hazel         Philip Hazel
249         University Computing Service,         University Computing Service
250         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
251    
252         Putting  an actual email address here seems to have been a spam magnet,         Putting  an actual email address here seems to have been a spam magnet,
253         so I've taken it away. If you want to email me, use my initial and sur-         so I've taken it away. If you want to email me, use  my  two  initials,
254         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
255    
256    
257    REVISION
258    
259  Last updated: 05 June 2006         Last updated: 09 August 2007
260  Copyright (c) 1997-2006 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
261  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
262    
263    
# Line 230  NAME Line 271  NAME
271  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
272    
273         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
274         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
275         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
276         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
277         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
278         directory) can be obtained by running         environments using the GUI facility of  CMakeSetup  if  you  are  using
279           CMake instead of configure to build PCRE.
280    
281           The complete list of options for configure (which includes the standard
282           ones such as the  selection  of  the  installation  directory)  can  be
283           obtained by running
284    
285           ./configure --help           ./configure --help
286    
287         The following sections describe certain options whose names begin  with         The  following  sections  include  descriptions  of options whose names
288         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
289         for the configure command. Because of the  way  that  configure  works,         defaults  for  the configure command. Because of the way that configure
290         --enable  and  --disable  always  come  in  pairs, so the complementary         works, --enable and --disable always come in pairs, so  the  complemen-
291         option always exists as well, but as it specifies the  default,  it  is         tary  option always exists as well, but as it specifies the default, it
292         not described.         is not described.
293    
294    
295  C++ SUPPORT  C++ SUPPORT
# Line 263  UTF-8 SUPPORT Line 309  UTF-8 SUPPORT
309    
310           --enable-utf8           --enable-utf8
311    
312         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
313         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings  as UTF-8. As well as compiling PCRE with this option, you also
314         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         have have to set the PCRE_UTF8 option when you call the  pcre_compile()
315         function.         function.
316    
317    
318  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
319    
320         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
321         in  the  strings that it handles. On its own, however, it does not pro-         in the strings that it handles. On its own, however, it does  not  pro-
322         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
323         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         you want to be able to use the pattern escapes \P, \p,  and  \X,  which
324         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
325    
326           --enable-unicode-properties           --enable-unicode-properties
327    
328         to the configure command. This implies UTF-8 support, even if you  have         to  the configure command. This implies UTF-8 support, even if you have
329         not explicitly requested it.         not explicitly requested it.
330    
331         Including  Unicode  property  support  adds around 90K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
332         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE  library.  Only  the general category properties such as Lu and Nd
333         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
334    
335    
336  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
# Line 305  CODE VALUE OF NEWLINE Line 350  CODE VALUE OF NEWLINE
350    
351           --enable-newline-is-crlf           --enable-newline-is-crlf
352    
353         to  the  configure command. Whatever line ending convention is selected         to the configure command. There is a fourth option, specified by
354         when PCRE is built can be overridden when  the  library  functions  are  
355         called.  At  build time it is conventional to use the standard for your           --enable-newline-is-anycrlf
356         operating system.  
357           which  causes  PCRE  to recognize any of the three sequences CR, LF, or
358           CRLF as indicating a line ending. Finally, a fifth option, specified by
359    
360             --enable-newline-is-any
361    
362           causes PCRE to recognize any Unicode newline sequence.
363    
364           Whatever  line  ending convention is selected when PCRE is built can be
365           overridden when the library functions are called. At build time  it  is
366           conventional to use the standard for your operating system.
367    
368    
369    WHAT \R MATCHES
370    
371           By  default,  the  sequence \R in a pattern matches any Unicode newline
372           sequence, whatever has been selected as the line  ending  sequence.  If
373           you specify
374    
375             --enable-bsr-anycrlf
376    
377           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
378           ever is selected when PCRE is built can be overridden when the  library
379           functions are called.
380    
381    
382  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
383    
384         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
385         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
386         of         of
387    
388           --disable-shared           --disable-shared
# Line 326  BUILDING SHARED AND STATIC LIBRARIES Line 394  BUILDING SHARED AND STATIC LIBRARIES
394  POSIX MALLOC USAGE  POSIX MALLOC USAGE
395    
396         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
397         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
398         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
399         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
400         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
401         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
402         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 341  POSIX MALLOC USAGE Line 409  POSIX MALLOC USAGE
409    
410  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
411    
412         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
413         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
414         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
415         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
416         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
417         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process enormous patterns, so it
418         is  possible  to compile PCRE to use three-byte or four-byte offsets by         is possible to compile PCRE to use three-byte or four-byte  offsets  by
419         adding a setting such as         adding a setting such as
420    
421           --with-link-size=3           --with-link-size=3
422    
423         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
424         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
425         additional bytes when handling them.         additional bytes when handling them.
426    
        If you build PCRE with an increased link size, test 2 (and  test  5  if  
        you  are using UTF-8) will fail. Part of the output of these tests is a  
        representation of the compiled pattern, and this changes with the  link  
        size.  
   
427    
428  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
429    
# Line 379  AVOIDING EXCESSIVE STACK USAGE Line 442  AVOIDING EXCESSIVE STACK USAGE
442    
443         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. With this configuration, PCRE  will  use  the
444         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
445         ment functions. Separate functions are provided because  the  usage  is         ment functions. By default these point to malloc() and free(), but  you
446         very  predictable:  the  block sizes requested are always the same, and         can replace the pointers so that your own functions are used.
447         the blocks are always freed in reverse order. A calling  program  might  
448         be  able  to implement optimized functions that perform better than the         Separate  functions  are  provided  rather  than  using pcre_malloc and
449         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
450         slowly when built in this way. This option affects only the pcre_exec()         requested  are  always  the  same,  and  the blocks are always freed in
451         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
452           functions  that  perform  better  than  malloc()  and free(). PCRE runs
453           noticeably more slowly when built in this way. This option affects only
454           the   pcre_exec()   function;   it   is   not   relevant  for  the  the
455           pcre_dfa_exec() function.
456    
457    
458  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 418  LIMITING PCRE RESOURCE USAGE Line 485  LIMITING PCRE RESOURCE USAGE
485         time.         time.
486    
487    
488    CREATING CHARACTER TABLES AT BUILD TIME
489    
490           PCRE  uses fixed tables for processing characters whose code values are
491           less than 256. By default, PCRE is built with a set of tables that  are
492           distributed  in  the  file pcre_chartables.c.dist. These tables are for
493           ASCII codes only. If you add
494    
495             --enable-rebuild-chartables
496    
497           to the configure command, the distributed tables are  no  longer  used.
498           Instead,  a  program  called dftables is compiled and run. This outputs
499           the source for new set of tables, created in the default locale of your
500           C runtime system. (This method of replacing the tables does not work if
501           you are cross compiling, because dftables is run on the local host.  If
502           you  need  to  create alternative tables when cross compiling, you will
503           have to do so "by hand".)
504    
505    
506  USING EBCDIC CODE  USING EBCDIC CODE
507    
508         PCRE  assumes  by  default that it will run in an environment where the         PCRE assumes by default that it will run in an  environment  where  the
509         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
510         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         This is the case for most computer operating systems.  PCRE  can,  how-
511         adding         ever, be compiled to run in an EBCDIC environment by adding
512    
513           --enable-ebcdic           --enable-ebcdic
514    
515         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
516           bles. You should only use it if you know that  you  are  in  an  EBCDIC
517           environment (for example, an IBM mainframe operating system).
518    
519    
520  Last updated: 06 June 2006  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
521  Copyright (c) 1997-2006 University of Cambridge.  
522           By default, pcregrep reads all files as plain text. You can build it so
523           that it recognizes files whose names end in .gz or .bz2, and reads them
524           with libz or libbz2, respectively, by adding one or both of
525    
526             --enable-pcregrep-libz
527             --enable-pcregrep-libbz2
528    
529           to the configure command. These options naturally require that the rel-
530           evant libraries are installed on your system. Configuration  will  fail
531           if they are not.
532    
533    
534    PCRETEST OPTION FOR LIBREADLINE SUPPORT
535    
536           If you add
537    
538             --enable-pcretest-libreadline
539    
540           to  the  configure  command,  pcretest  is  linked with the libreadline
541           library, and when its input is from a terminal, it reads it  using  the
542           readline() function. This provides line-editing and history facilities.
543           Note that libreadline is GPL-licenced, so if you distribute a binary of
544           pcretest linked in this way, there may be licensing issues.
545    
546    
547    SEE ALSO
548    
549           pcreapi(3), pcre_config(3).
550    
551    
552    AUTHOR
553    
554           Philip Hazel
555           University Computing Service
556           Cambridge CB2 3QH, England.
557    
558    
559    REVISION
560    
561           Last updated: 18 December 2007
562           Copyright (c) 1997-2007 University of Cambridge.
563  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
564    
565    
# Line 466  PCRE MATCHING ALGORITHMS Line 595  PCRE MATCHING ALGORITHMS
595           <something> <something else> <something further>           <something> <something else> <something further>
596    
597         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
598         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
599    
600    
601  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 482  REGULAR EXPRESSIONS AS TREES Line 611  REGULAR EXPRESSIONS AS TREES
611    
612  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
613    
614         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
615         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
616         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
617         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
618         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 507  THE STANDARD MATCHING ALGORITHM Line 636  THE STANDARD MATCHING ALGORITHM
636         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
637    
638    
639  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
640    
641         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
642         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
643         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
644         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
645         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
646         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
647           keeps multiple states active simultaneously).
648         The  scan  continues until either the end of the subject is reached, or  
649         there are no more unterminated paths. At this point,  terminated  paths         The scan continues until either the end of the subject is  reached,  or
650         represent  the different matching possibilities (if there are none, the         there  are  no more unterminated paths. At this point, terminated paths
651         match has failed).  Thus, if there is more  than  one  possible  match,         represent the different matching possibilities (if there are none,  the
652           match  has  failed).   Thus,  if there is more than one possible match,
653         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
654         est. In PCRE, there is an option to stop the algorithm after the  first         est.  In PCRE, there is an option to stop the algorithm after the first
655         match (which is necessarily the shortest) has been found.         match (which is necessarily the shortest) has been found.
656    
657         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
# Line 529  THE DFA MATCHING ALGORITHM Line 659  THE DFA MATCHING ALGORITHM
659    
660           cat(er(pillar)?)           cat(er(pillar)?)
661    
662         is matched against the string "the caterpillar catchment",  the  result         is  matched  against the string "the caterpillar catchment", the result
663         will  be the three strings "cat", "cater", and "caterpillar" that start         will be the three strings "cat", "cater", and "caterpillar" that  start
664         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
665         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
666    
667         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
668         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
669    
670         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1.  Because  the  algorithm  finds  all possible matches, the greedy or
671         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
672         ungreedy quantifiers are treated in exactly the same way.         ungreedy quantifiers are treated in exactly the same way. However, pos-
673           sessive quantifiers can make a difference when what follows could  also
674           match what is quantified, for example in a pattern like this:
675    
676             ^a++\w!
677    
678           This  pattern matches "aaab!" but not "aaa!", which would be matched by
679           a non-possessive quantifier. Similarly, if an atomic group is  present,
680           it  is matched as if it were a standalone pattern at the current point,
681           and the longest match is then "locked in" for the rest of  the  overall
682           pattern.
683    
684         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
685         is  not  straightforward  to  keep track of captured substrings for the         is not straightforward to keep track of  captured  substrings  for  the
686         different matching possibilities, and  PCRE's  implementation  of  this         different  matching  possibilities,  and  PCRE's implementation of this
687         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
688         strings are available.         strings are available.
689    
690         3. Because no substrings are captured, back references within the  pat-         3.  Because no substrings are captured, back references within the pat-
691         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
692    
693         4.  For  the same reason, conditional expressions that use a backrefer-         4. For the same reason, conditional expressions that use  a  backrefer-
694         ence as the condition are not supported.         ence  as  the  condition or test for a specific group recursion are not
695           supported.
696    
697           5. Because many paths through the tree may be  active,  the  \K  escape
698           sequence, which resets the start of the match when encountered (but may
699           be on some paths and not on others), is not  supported.  It  causes  an
700           error if encountered.
701    
702         5. Callouts are supported, but the value of the  capture_top  field  is         6.  Callouts  are  supported, but the value of the capture_top field is
703         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
704    
705         6.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
706         single byte, even in UTF-8 mode, is not supported because the DFA algo-         single  byte, even in UTF-8 mode, is not supported because the alterna-
707         rithm moves through the subject string one character at a time, for all         tive algorithm moves through the subject  string  one  character  at  a
708         active paths through the tree.         time, for all active paths through the tree.
709    
710           8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-
711           ported.
712    
 ADVANTAGES OF THE DFA ALGORITHM  
713    
714         Using the DFA matching algorithm provides the following advantages:  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
715    
716           Using the alternative matching algorithm provides the following  advan-
717           tages:
718    
719         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
720         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
721         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
722         things with callouts.         things with callouts.
723    
724         2.  There is much better support for partial matching. The restrictions         2. There is much better support for partial matching. The  restrictions
725         on the content of the pattern that apply when using the standard  algo-         on  the content of the pattern that apply when using the standard algo-
726         rithm  for partial matching do not apply to the DFA algorithm. For non-         rithm for partial matching do not apply to the  alternative  algorithm.
727         anchored patterns, the starting position of a partial match  is  avail-         For  non-anchored patterns, the starting position of a partial match is
728         able.         available.
729    
730         3.  Because  the  DFA algorithm scans the subject string just once, and         3. Because the alternative algorithm  scans  the  subject  string  just
731         never needs to backtrack, it is possible  to  pass  very  long  subject         once,  and  never  needs to backtrack, it is possible to pass very long
732         strings  to  the matching function in several pieces, checking for par-         subject strings to the matching function in  several  pieces,  checking
733         tial matching each time.         for partial matching each time.
734    
735    
736  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
737    
738         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
739    
740         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
741         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
742         because it is less susceptible to optimization.         because it is less susceptible to optimization.
743    
744         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
745    
746         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
747         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
748         rithm.  
749    
750  Last updated: 06 June 2006  AUTHOR
751  Copyright (c) 1997-2006 University of Cambridge.  
752           Philip Hazel
753           University Computing Service
754           Cambridge CB2 3QH, England.
755    
756    
757    REVISION
758    
759           Last updated: 08 August 2007
760           Copyright (c) 1997-2007 University of Cambridge.
761  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
762    
763    
# Line 692  PCRE NATIVE API Line 851  PCRE NATIVE API
851  PCRE API OVERVIEW  PCRE API OVERVIEW
852    
853         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
854         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
855         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
856         Both of these APIs define a set of C function calls. A C++  wrapper  is         Both of these APIs define a set of C function calls. A C++  wrapper  is
857         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 715  PCRE API OVERVIEW Line 874  PCRE API OVERVIEW
874         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
875         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
876         ing. The alternative algorithm finds all possible matches (at  a  given         ing. The alternative algorithm finds all possible matches (at  a  given
877         point in the subject). However, this algorithm does not return captured         point  in  the subject), and scans the subject just once. However, this
878         substrings. A description of the  two  matching  algorithms  and  their         algorithm does not return captured substrings. A description of the two
879         advantages  and  disadvantages  is given in the pcrematching documenta-         matching  algorithms and their advantages and disadvantages is given in
880         tion.         the pcrematching documentation.
881    
882         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
883         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 779  PCRE API OVERVIEW Line 938  PCRE API OVERVIEW
938    
939    
940  NEWLINES  NEWLINES
941         PCRE supports three different conventions for indicating line breaks in  
942         strings: a single CR character, a single LF character, or the two-char-         PCRE  supports five different conventions for indicating line breaks in
943         acter  sequence  CRLF.  All  three  are used as "standard" by different         strings: a single CR (carriage return) character, a  single  LF  (line-
944         operating systems.  When PCRE is built, a default can be specified. The         feed) character, the two-character sequence CRLF, any of the three pre-
945         default  default  is  LF, which is the Unix standard. When PCRE is run,         ceding, or any Unicode newline sequence. The Unicode newline  sequences
946         the default can be overridden, either when a pattern  is  compiled,  or         are  the  three just mentioned, plus the single characters VT (vertical
947         when it is matched.         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
948           separator, U+2028), and PS (paragraph separator, U+2029).
949    
950           Each  of  the first three conventions is used by at least one operating
951           system as its standard newline sequence. When PCRE is built, a  default
952           can  be  specified.  The default default is LF, which is the Unix stan-
953           dard. When PCRE is run, the default can be overridden,  either  when  a
954           pattern is compiled, or when it is matched.
955    
956           At compile time, the newline convention can be specified by the options
957           argument of pcre_compile(), or it can be specified by special  text  at
958           the start of the pattern itself; this overrides any other settings. See
959           the pcrepattern page for details of the special character sequences.
960    
961         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
962         acter or pair of characters that indicate a line break".         acter  or pair of characters that indicate a line break". The choice of
963           newline convention affects the handling of  the  dot,  circumflex,  and
964           dollar metacharacters, the handling of #-comments in /x mode, and, when
965           CRLF is a recognized line ending sequence, the match position  advance-
966           ment for a non-anchored pattern. There is more detail about this in the
967           section on pcre_exec() options below.
968    
969           The choice of newline convention does not affect the interpretation  of
970           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
971           which is controlled in a similar way, but by separate options.
972    
973    
974  MULTITHREADING  MULTITHREADING
# Line 808  SAVING PRECOMPILED PATTERNS FOR LATER US Line 988  SAVING PRECOMPILED PATTERNS FOR LATER US
988         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
989         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
990         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
991         pcreprecompile documentation.         pcreprecompile  documentation.  However, compiling a regular expression
992           with one version of PCRE for use with a different version is not  guar-
993           anteed to work and may cause crashes.
994    
995    
996  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 838  CHECKING BUILD-TIME OPTIONS Line 1020  CHECKING BUILD-TIME OPTIONS
1020           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1021    
1022         The  output  is  an integer whose value specifies the default character         The  output  is  an integer whose value specifies the default character
1023         sequence that is recognized as meaning "newline". The three values that         sequence that is recognized as meaning "newline". The four values  that
1024         are supported are: 10 for LF, 13 for CR, and 3338 for CRLF. The default         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1025         should normally be the standard sequence for your operating system.         and -1 for ANY. The default should normally be  the  standard  sequence
1026           for your operating system.
1027    
1028             PCRE_CONFIG_BSR
1029    
1030           The output is an integer whose value indicates what character sequences
1031           the \R escape sequence matches by default. A value of 0 means  that  \R
1032           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1033           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1034           tern is compiled or matched.
1035    
1036           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1037    
1038         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
1039         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1040         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1041         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1042         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1043         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1044    
1045           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1046    
1047         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1048         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1049         given in the pcreposix documentation.         given in the pcreposix documentation.
1050    
1051           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1052    
1053         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
1054         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
1055         details are given with pcre_exec() below.         details are given with pcre_exec() below.
1056    
1057           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1058    
1059         The  output is an integer that gives the default limit for the depth of         The output is an integer that gives the default limit for the depth  of
1060         recursion when calling the internal matching function in a  pcre_exec()         recursion  when calling the internal matching function in a pcre_exec()
1061         execution. Further details are given with pcre_exec() below.         execution. Further details are given with pcre_exec() below.
1062    
1063           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1064    
1065         The  output is an integer that is set to one if internal recursion when         The output is an integer that is set to one if internal recursion  when
1066         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1067         the  stack  to remember their state. This is the usual way that PCRE is         the stack to remember their state. This is the usual way that  PCRE  is
1068         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1069         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1070         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1071         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1072    
1073    
# Line 893  COMPILING A PATTERN Line 1084  COMPILING A PATTERN
1084    
1085         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1086         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1087         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1088         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1089    
1090         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1091         the  pattern  argument.  A  pointer to a single block of memory that is         the pattern argument. A pointer to a single block  of  memory  that  is
1092         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1093         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1094         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1095         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1096         longer required.         longer required.
1097    
1098         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
1099         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
1100         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1101         ment, which is an address (see below).         ment, which is an address (see below).
1102    
1103         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1104         tion. It should be zero if  no  options  are  required.  The  available         pilation.  It  should be zero if no options are required. The available
1105         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
1106         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
1107         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
1108         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
1109         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
1110         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time
1111         of matching as well as at compile time.         of matching as well as at compile time.
1112    
1113         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1114         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1115         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-
1116         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1117         try to free it. The offset from the start of the pattern to the charac-         try to free it. The offset from the start of the pattern to the charac-
1118         ter where the error was discovered is placed in the variable pointed to         ter where the error was discovered is placed in the variable pointed to
1119         by  erroffset,  which must not be NULL. If it is, an immediate error is         by erroffset, which must not be NULL. If it is, an immediate  error  is
1120         given.         given.
1121    
1122         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1123         codeptr  argument is not NULL, a non-zero error code number is returned         codeptr argument is not NULL, a non-zero error code number is  returned
1124         via this argument in the event of an error. This is in addition to  the         via  this argument in the event of an error. This is in addition to the
1125         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1126    
1127         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
1128         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1129         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1130         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1131         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1132         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1133         support below.         support below.
1134    
1135         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1136         pile():         pile():
1137    
1138           pcre *re;           pcre *re;
# Line 954  COMPILING A PATTERN Line 1145  COMPILING A PATTERN
1145             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1146             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1147    
1148         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1149         file:         file:
1150    
1151           PCRE_ANCHORED           PCRE_ANCHORED
1152    
1153         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1154         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1155         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1156         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1157         only way to do it in Perl.         only way to do it in Perl.
1158    
1159           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1160    
1161         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1162         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1163         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1164    
1165             PCRE_BSR_ANYCRLF
1166             PCRE_BSR_UNICODE
1167    
1168           These options (which are mutually exclusive) control what the \R escape
1169           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1170           or to match any Unicode newline sequence. The default is specified when
1171           PCRE is built. It can be overridden from within the pattern, or by set-
1172           ting an option when a compiled pattern is matched.
1173    
1174           PCRE_CASELESS           PCRE_CASELESS
1175    
1176         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
1177         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
1178         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1179         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1180         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1181         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1182         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1183         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1184         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1185         UTF-8 support.         UTF-8 support.
1186    
1187           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1188    
1189         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
1190         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
1191         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1192         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1193         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1194         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1195    
1196           PCRE_DOTALL           PCRE_DOTALL
1197    
1198         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-
1199         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1200         not  match  when  the  current position is at a newline. This option is         not match when the current position is at a  newline.  This  option  is
1201         equivalent to Perl's /s option, and it can be changed within a  pattern         equivalent  to Perl's /s option, and it can be changed within a pattern
1202         by  a (?s) option setting. A negative class such as [^a] always matches         by a (?s) option setting. A negative class such as [^a] always  matches
1203         newlines, independent of the setting of this option.         newline characters, independent of the setting of this option.
1204    
1205           PCRE_DUPNAMES           PCRE_DUPNAMES
1206    
1207         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1208         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1209         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1210         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1211         the pcrepattern documentation.         the pcrepattern documentation.
1212    
1213           PCRE_EXTENDED           PCRE_EXTENDED
1214    
1215         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1216         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1217         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1218         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1219         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1220         option,  and  it  can be changed within a pattern by a (?x) option set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1221         ting.         ting.
1222    
1223         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1224         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1225         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1226         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1227         introduces a conditional subpattern.         introduces a conditional subpattern.
1228    
1229           PCRE_EXTRA           PCRE_EXTRA
1230    
1231         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1232         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
1233         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
1234         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1235         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1236         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
1237         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal.  (Perl can, however, be persuaded to give a warning for this.)
1238         There  are  at  present no other features controlled by this option. It         There are at present no other features controlled by  this  option.  It
1239         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1240    
1241           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1242    
1243         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1244         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1245         matched text may continue over the newline.         matched text may continue over the newline.
1246    
1247           PCRE_MULTILINE           PCRE_MULTILINE
1248    
1249         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1250         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1251         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1252         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1253         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1254         is set). This is the same as Perl.         is set). This is the same as Perl.
1255    
1256         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"
1257         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1258         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1259         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1260         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1261         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1262         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1263    
1264           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1265           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1266           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1267             PCRE_NEWLINE_ANYCRLF
1268             PCRE_NEWLINE_ANY
1269    
1270         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1271         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1272         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1273         Setting both of them specifies that a newline is indicated by the  two-         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1274         character  CRLF sequence. For convenience, PCRE_NEWLINE_CRLF is defined         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1275         to contain both bits. The only time that a line break is relevant  when         that any of the three preceding sequences should be recognized. Setting
1276         compiling a pattern is if PCRE_EXTENDED is set, and an unescaped # out-         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1277         side a character class is encountered. This indicates  a  comment  that         recognized. The Unicode newline sequences are the three just mentioned,
1278         lasts until after the next newline.         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1279           U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1280           (paragraph separator, U+2029). The last  two  are  recognized  only  in
1281           UTF-8 mode.
1282    
1283           The  newline  setting  in  the  options  word  uses three bits that are
1284           treated as a number, giving eight possibilities. Currently only six are
1285           used  (default  plus the five values above). This means that if you set
1286           more than one newline option, the combination may or may not be  sensi-
1287           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1288           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1289           cause an error.
1290    
1291           The  only time that a line break is specially recognized when compiling
1292           a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1293           character  class  is  encountered.  This indicates a comment that lasts
1294           until after the next line break sequence. In other circumstances,  line
1295           break   sequences   are   treated  as  literal  data,  except  that  in
1296           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1297           and are therefore ignored.
1298    
1299         The newline option set at compile time becomes the default that is used         The newline option that is set at compile time becomes the default that
1300         for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be  overridden.
1301    
1302           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1303    
1304         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-
1305         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1306         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1307         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1308         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1309    
1310           PCRE_UNGREEDY           PCRE_UNGREEDY
1311    
1312         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1313         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
1314         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
1315         within the pattern.         within the pattern.
1316    
1317           PCRE_UTF8           PCRE_UTF8
1318    
1319         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
1320         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1321         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-
1322         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
1323         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
1324         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1325    
1326           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1327    
1328         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
1329         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1330         pcre_compile() returns an error. If you already know that your  pattern         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1331         is  valid, and you want to skip this check for performance reasons, you         bytes is found, pcre_compile() returns an error. If  you  already  know
1332         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1333         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1334         your program to crash.  Note that this option can  also  be  passed  to         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1335         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined. It may cause your program to crash. Note  that  this  option
1336         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1337           UTF-8 validity checking of subject strings.
1338    
1339    
1340  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1341    
1342         The following table lists the error  codes  than  may  be  returned  by         The following table lists the error  codes  than  may  be  returned  by
1343         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(),  along with the error messages that may be returned by
1344         both compiling functions.         both compiling functions. As PCRE has developed, some error codes  have
1345           fallen out of use. To avoid confusion, they have not been re-used.
1346    
1347            0  no error            0  no error
1348            1  \ at end of pattern            1  \ at end of pattern
# Line 1131  COMPILATION ERROR CODES Line 1354  COMPILATION ERROR CODES
1354            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1355            8  range out of order in character class            8  range out of order in character class
1356            9  nothing to repeat            9  nothing to repeat
1357           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1358           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1359           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1360           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1361           14  missing )           14  missing )
1362           15  reference to non-existent subpattern           15  reference to non-existent subpattern
1363           16  erroffset passed as NULL           16  erroffset passed as NULL
1364           17  unknown option bit(s) set           17  unknown option bit(s) set
1365           18  missing ) after comment           18  missing ) after comment
1366           19  parentheses nested too deeply           19  [this code is not in use]
1367           20  regular expression too large           20  regular expression is too large
1368           21  failed to get memory           21  failed to get memory
1369           22  unmatched parentheses           22  unmatched parentheses
1370           23  internal error: code overflow           23  internal error: code overflow
# Line 1150  COMPILATION ERROR CODES Line 1373  COMPILATION ERROR CODES
1373           26  malformed number or name after (?(           26  malformed number or name after (?(
1374           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1375           28  assertion expected after (?(           28  assertion expected after (?(
1376           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1377           30  unknown POSIX class name           30  unknown POSIX class name
1378           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1379           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1380           33  spare error           33  [this code is not in use]
1381           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1382           35  invalid condition (?(0)           35  invalid condition (?(0)
1383           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1163  COMPILATION ERROR CODES Line 1386  COMPILATION ERROR CODES
1386           39  closing ) for (?C expected           39  closing ) for (?C expected
1387           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1388           41  unrecognized character after (?P           41  unrecognized character after (?P
1389           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1390           43  two named subpatterns have the same name           43  two named subpatterns have the same name
1391           44  invalid UTF-8 string           44  invalid UTF-8 string
1392           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1393           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1394           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1395           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1396           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1397           50  repeated subpattern is too long           50  [this code is not in use]
1398           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1399             52  internal error: overran compiling workspace
1400             53   internal  error:  previously-checked  referenced  subpattern not
1401           found
1402             54  DEFINE group contains more than one branch
1403             55  repeating a DEFINE group is not allowed
1404             56  inconsistent NEWLINE options
1405             57  \g is not followed by a braced name or an optionally braced
1406                   non-zero number
1407             58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
1408             59  (*VERB) with an argument is not supported
1409             60  (*VERB) not recognized
1410             61  number is too big
1411             62  subpattern name expected
1412             63  digit expected after (?+
1413    
1414           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1415           values may be used if the limits were changed when PCRE was built.
1416    
1417    
1418  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1180  STUDYING A PATTERN Line 1420  STUDYING A PATTERN
1420         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1421              const char **errptr);              const char **errptr);
1422    
1423         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
1424         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
1425         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1426         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1427         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1428         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
1429         the results of the study.         the results of the study.
1430    
1431         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1432         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1433         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
1434         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1435    
1436         If  studying  the  pattern  does not produce any additional information         If studying the pattern does not  produce  any  additional  information
1437         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1438         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
1439         its own pcre_extra block.         its own pcre_extra block.
1440    
1441         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1442         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1443    
1444         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.
1445         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1446         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1447         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1448         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1449         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1450    
1451         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1217  STUDYING A PATTERN Line 1457  STUDYING A PATTERN
1457             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1458    
1459         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1460         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-
1461         ble starting bytes is created.         ble starting bytes is created.
1462    
1463    
1464  LOCALE SUPPORT  LOCALE SUPPORT
1465    
1466         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1467         letters  digits,  or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1468         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
1469         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1470         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
1471         with  Unicode  character property support. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1472         code is discouraged.         code  is discouraged. If you are handling characters with codes greater
1473           than 128, you should either use UTF-8 and Unicode, or use locales,  but
1474         An internal set of tables is created in the default C locale when  PCRE         not try to mix the two.
1475         is  built.  This  is  used when the final argument of pcre_compile() is  
1476         NULL, and is sufficient for many applications. An  alternative  set  of         PCRE  contains  an  internal set of tables that are used when the final
1477         tables  can,  however, be supplied. These may be created in a different         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1478         locale from the default. As more and more applications change to  using         applications.  Normally, the internal tables recognize only ASCII char-
1479         Unicode, the need for this locale support is expected to die away.         acters. However, when PCRE is built, it is possible to cause the inter-
1480           nal tables to be rebuilt in the default "C" locale of the local system,
1481           which may cause them to be different.
1482    
1483           The internal tables can always be overridden by tables supplied by  the
1484           application that calls PCRE. These may be created in a different locale
1485           from the default. As more and more applications change  to  using  Uni-
1486           code, the need for this locale support is expected to die away.
1487    
1488         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
1489         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
# Line 1249  LOCALE SUPPORT Line 1496  LOCALE SUPPORT
1496           tables = pcre_maketables();           tables = pcre_maketables();
1497           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1498    
1499         When pcre_maketables() runs, the tables are built  in  memory  that  is         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1500         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         if you are using Windows, the name for the French locale is "french".
1501         that the memory containing the tables remains available for as long  as  
1502           When  pcre_maketables()  runs,  the  tables are built in memory that is
1503           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1504           that  the memory containing the tables remains available for as long as
1505         it is needed.         it is needed.
1506    
1507         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
1508         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()
1509         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-
1510         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1511         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1512    
1513         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
1514         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1515         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
1516         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
1517         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1518    
# Line 1272  INFORMATION ABOUT A PATTERN Line 1522  INFORMATION ABOUT A PATTERN
1522         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1523              int what, void *where);              int what, void *where);
1524    
1525         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1526         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1527         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1528    
1529         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1530         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
1531         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1532         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
1533         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
1534         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1535    
1536           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1288  INFORMATION ABOUT A PATTERN Line 1538  INFORMATION ABOUT A PATTERN
1538           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1539           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1540    
1541         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
1542         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1543         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1544         pattern:         pattern:
1545    
1546           int rc;           int rc;
# Line 1301  INFORMATION ABOUT A PATTERN Line 1551  INFORMATION ABOUT A PATTERN
1551             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1552             &length);         /* where to put the data */             &length);         /* where to put the data */
1553    
1554         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
1555         are as follows:         are as follows:
1556    
1557           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1558    
1559         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1560         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1561         there are no back references.         there are no back references.
1562    
1563           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1564    
1565         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1566         argument should point to an int variable.         argument should point to an int variable.
1567    
1568           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1569    
1570         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1571         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1572         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1573         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1574         passing a NULL table pointer.         passing a NULL table pointer.
1575    
1576           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1577    
1578         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1579         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1580         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1581         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1582    
1583         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
1584         (cat|cow|coyote). Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1585    
1586         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1587         branch starts with "^", or         branch starts with "^", or
1588    
1589         (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
1590         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1591    
1592         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1593         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1594         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1595    
1596           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1597    
1598         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
1599         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
1600         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1601         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1602         able.         able.
1603    
1604             PCRE_INFO_HASCRORLF
1605    
1606           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1607           characters,  otherwise  0.  The  fourth argument should point to an int
1608           variable. An explicit match is either a literal CR or LF character,  or
1609           \r or \n.
1610    
1611             PCRE_INFO_JCHANGED
1612    
1613           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1614           otherwise 0. The fourth argument should point to an int variable.  (?J)
1615           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1616    
1617           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1618    
1619         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
# Line 1388  INFORMATION ABOUT A PATTERN Line 1651  INFORMATION ABOUT A PATTERN
1651         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is
1652         ignored):         ignored):
1653    
1654           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1655           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1656    
1657         There are four named subpatterns, so the table has  four  entries,  and         There are four named subpatterns, so the table has  four  entries,  and
1658         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,
# Line 1405  INFORMATION ABOUT A PATTERN Line 1668  INFORMATION ABOUT A PATTERN
1668         name-to-number map, remember that the length of the entries  is  likely         name-to-number map, remember that the length of the entries  is  likely
1669         to be different for each compiled pattern.         to be different for each compiled pattern.
1670    
1671             PCRE_INFO_OKPARTIAL
1672    
1673           Return  1 if the pattern can be used for partial matching, otherwise 0.
1674           The fourth argument should point to an int  variable.  The  pcrepartial
1675           documentation  lists  the restrictions that apply to patterns when par-
1676           tial matching is used.
1677    
1678           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1679    
1680         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
1681         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1682         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1683         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1684           other words, they are the options that will be in force  when  matching
1685           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1686           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1687           and PCRE_EXTENDED.
1688    
1689         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
1690         alternatives begin with one of the following:         alternatives begin with one of the following:
1691    
1692           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1426  INFORMATION ABOUT A PATTERN Line 1700  INFORMATION ABOUT A PATTERN
1700    
1701           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1702    
1703         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
1704         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
1705         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
1706         size_t variable.         size_t variable.
# Line 1434  INFORMATION ABOUT A PATTERN Line 1708  INFORMATION ABOUT A PATTERN
1708           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1709    
1710         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
1711         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
1712         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
1713         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
1714         variable.         variable.
1715    
1716    
# Line 1444  OBSOLETE INFO FUNCTION Line 1718  OBSOLETE INFO FUNCTION
1718    
1719         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1720    
1721         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1722         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1723         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1724         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-
1725         lowing negative numbers:         lowing negative numbers:
1726    
1727           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1728           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1729    
1730         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
1731         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
1732         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1733    
1734         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1735         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
1736         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1737    
1738    
# Line 1466  REFERENCE COUNTS Line 1740  REFERENCE COUNTS
1740    
1741         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1742    
1743         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1744         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1745         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1746         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1747         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1748    
1749         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1750         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1751         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1752         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1753         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1754         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1755    
1756         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1757         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1758         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1759    
1760    
# Line 1490  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1764  MATCHING A PATTERN: THE TRADITIONAL FUNC
1764              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1765              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1766    
1767         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
1768         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1769         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
1770         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1771         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1772         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1773         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1774    
1775         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1776         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1777         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1778         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1779         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1780    
1781         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1520  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1794  MATCHING A PATTERN: THE TRADITIONAL FUNC
1794    
1795     Extra data for pcre_exec()     Extra data for pcre_exec()
1796    
1797         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
1798         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
1799         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-
1800         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1801         fields (not necessarily in this order):         fields (not necessarily in this order):
1802    
1803           unsigned long int flags;           unsigned long int flags;
# Line 1533  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1807  MATCHING A PATTERN: THE TRADITIONAL FUNC
1807           void *callout_data;           void *callout_data;
1808           const unsigned char *tables;           const unsigned char *tables;
1809    
1810         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
1811         are set. The flag bits are:         are set. The flag bits are:
1812    
1813           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1542  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1816  MATCHING A PATTERN: THE TRADITIONAL FUNC
1816           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1817           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1818    
1819         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
1820         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1821         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
1822         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1823         flag bits.         flag bits.
1824    
1825         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
1826         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
1827         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1828         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1829         repeats.         repeats.
1830    
1831         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1832         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1833         on the number of times this function is called during  a  match,  which         on  the  number  of times this function is called during a match, which
1834         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1835         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1836         for each position in the subject string.         for each position in the subject string.
1837    
1838         The  default  value  for  the  limit can be set when PCRE is built; the         The default value for the limit can be set  when  PCRE  is  built;  the
1839         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1840         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1841         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
1842         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
1843         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1844    
1845         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
1846         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
1847         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
1848         the  total number of calls, because not all calls to match() are recur-         the total number of calls, because not all calls to match() are  recur-
1849         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
1850    
1851         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1852         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
1853         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1854    
1855         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
1856         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1857         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1858         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1859         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1860         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1861    
1862         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1863         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1864    
1865         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1866         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1867         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
1868         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1869         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
1870         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-
1871         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1872         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1873         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1874         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1875    
1876     Option bits for pcre_exec()     Option bits for pcre_exec()
1877    
1878         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.
1879         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
1880         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1881         PCRE_PARTIAL.         PCRE_PARTIAL.
1882    
1883           PCRE_ANCHORED           PCRE_ANCHORED
1884    
1885         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
1886         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
1887         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
1888         unachored at matching time.         unachored at matching time.
1889    
1890             PCRE_BSR_ANYCRLF
1891             PCRE_BSR_UNICODE
1892    
1893           These options (which are mutually exclusive) control what the \R escape
1894           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1895           or  to  match  any Unicode newline sequence. These options override the
1896           choice that was made or defaulted when the pattern was compiled.
1897    
1898           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1899           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1900           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1901             PCRE_NEWLINE_ANYCRLF
1902             PCRE_NEWLINE_ANY
1903    
1904         These options override  the  newline  definition  that  was  chosen  or         These options override  the  newline  definition  that  was  chosen  or
1905         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
1906         tion pcre_compile() above. During matching, the newline choice  affects         tion of pcre_compile()  above.  During  matching,  the  newline  choice
1907         the behaviour of the dot, circumflex, and dollar metacharacters.         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
1908           ters. It may also alter the way the match position is advanced after  a
1909           match failure for an unanchored pattern.
1910    
1911           When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
1912           set, and a match attempt for an unanchored pattern fails when the  cur-
1913           rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
1914           explicit matches for  CR  or  LF  characters,  the  match  position  is
1915           advanced by two characters instead of one, in other words, to after the
1916           CRLF.
1917    
1918           The above rule is a compromise that makes the most common cases work as
1919           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
1920           option is not set), it does not match the string "\r\nA" because, after
1921           failing  at the start, it skips both the CR and the LF before retrying.
1922           However, the pattern [\r\n]A does match that string,  because  it  con-
1923           tains an explicit CR or LF reference, and so advances only by one char-
1924           acter after the first failure.
1925    
1926           An explicit match for CR of LF is either a literal appearance of one of
1927           those  characters,  or  one  of the \r or \n escape sequences. Implicit
1928           matches such as [^X] do not count, nor does \s (which includes  CR  and
1929           LF in the characters that it matches).
1930    
1931           Notwithstanding  the above, anomalous effects may still occur when CRLF
1932           is a valid newline sequence and explicit \r or \n escapes appear in the
1933           pattern.
1934    
1935           PCRE_NOTBOL           PCRE_NOTBOL
1936    
# Line 1667  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1977  MATCHING A PATTERN: THE TRADITIONAL FUNC
1977         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
1978         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
1979         called.   The  value  of  startoffset is also checked to ensure that it         called.   The  value  of  startoffset is also checked to ensure that it
1980         points to the start of a UTF-8 character. If an invalid UTF-8  sequence         points to the start of a UTF-8 character. There is a  discussion  about
1981         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
1982         startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
1983         returned.         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
1984           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1985         If  you  already  know that your subject is valid, and you want to skip  
1986         these   checks   for   performance   reasons,   you   can    set    the         If you already know that your subject is valid, and you  want  to  skip
1987         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         these    checks    for   performance   reasons,   you   can   set   the
1988         do this for the second and subsequent calls to pcre_exec() if  you  are         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
1989         making  repeated  calls  to  find  all  the matches in a single subject         do  this  for the second and subsequent calls to pcre_exec() if you are
1990         string. However, you should be  sure  that  the  value  of  startoffset         making repeated calls to find all  the  matches  in  a  single  subject
1991         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         string.  However,  you  should  be  sure  that the value of startoffset
1992         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
1993         value  of startoffset that does not point to the start of a UTF-8 char-         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
1994           value of startoffset that does not point to the start of a UTF-8  char-
1995         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
1996    
1997           PCRE_PARTIAL           PCRE_PARTIAL
1998    
1999         This option turns on the  partial  matching  feature.  If  the  subject         This  option  turns  on  the  partial  matching feature. If the subject
2000         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-
2001         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
2002         partially  matches  the  pattern and the failure to match occurred only         partially matches the pattern and the failure to  match  occurred  only
2003         because there were not enough subject characters), pcre_exec()  returns         because  there were not enough subject characters), pcre_exec() returns
2004         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
2005         used, there are restrictions on what may appear in the  pattern.  These         used,  there  are restrictions on what may appear in the pattern. These
2006         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
2007    
2008     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2009    
2010         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
2011         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
2012         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.
2013         Unlike the pattern string, the subject may contain binary  zero  bytes.         Unlike  the  pattern string, the subject may contain binary zero bytes.
2014         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
2015         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.
2016    
2017         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
2018         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-
2019         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
2020         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
2021         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2022    
2023           \Biss\B           \Biss\B
2024    
2025         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2026         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.)
2027         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2028         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2029         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2030         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
2031         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
2032         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-
2033         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
2034         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2035    
2036         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,
2037         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
2038         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
2039         subject.         subject.
2040    
2041     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2042    
2043         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
2044         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2045         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2046         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2047         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-
2048         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2049         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2050    
2051         Captured substrings are returned to the caller via a vector of  integer         Captured  substrings are returned to the caller via a vector of integer
2052         offsets  whose  address is passed in ovector. The number of elements in         offsets whose address is passed in ovector. The number of  elements  in
2053         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.
2054         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
2055    
2056         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-
2057         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
2058         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-
2059         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
2060         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
2061         it is not, it is rounded down.         it is not, it is rounded down.
2062    
2063         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
2064         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2065         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
2066         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-
2067         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
2068         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-
2069         tor[1], identify the portion of  the  subject  string  matched  by  the         tor[1],  identify  the  portion  of  the  subject string matched by the
2070         entire  pattern.  The next pair is used for the first capturing subpat-         entire pattern. The next pair is used for the first  capturing  subpat-
2071         tern, and so on. The value returned by pcre_exec() is one more than the         tern, and so on. The value returned by pcre_exec() is one more than the
2072         highest numbered pair that has been set. For example, if two substrings         highest numbered pair that has been set. For example, if two substrings
2073         have been captured, the returned value is 3. If there are no  capturing         have  been captured, the returned value is 3. If there are no capturing
2074         subpatterns,  the return value from a successful match is 1, indicating         subpatterns, the return value from a successful match is 1,  indicating
2075         that just the first pair of offsets has been set.         that just the first pair of offsets has been set.
2076    
2077         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2078         of the string that it matched that is returned.         of the string that it matched that is returned.
2079    
2080         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,
2081         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
2082         function  returns a value of zero. In particular, if the substring off-         function returns a value of zero. In particular, if the substring  off-
2083         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
2084         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         as NULL and ovecsize as zero. However, if  the  pattern  contains  back
2085         references and the ovector is not big enough to  remember  the  related         references  and  the  ovector is not big enough to remember the related
2086         substrings,  PCRE has to get additional memory for use during matching.         substrings, PCRE has to get additional memory for use during  matching.
2087         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
2088    
2089         The pcre_info() function can be used to find  out  how  many  capturing         The  pcre_info()  function  can  be used to find out how many capturing
2090         subpatterns  there  are  in  a  compiled pattern. The smallest size for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2091         ovector that will allow for n captured substrings, in addition  to  the         ovector  that  will allow for n captured substrings, in addition to the
2092         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2093    
2094         It  is  possible for capturing subpattern number n+1 to match some part         It is possible for capturing subpattern number n+1 to match  some  part
2095         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2096         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2097         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2098         2  is  not.  When  this happens, both values in the offset pairs corre-         2 is not. When this happens, both values in  the  offset  pairs  corre-
2099         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2100    
2101         Offset values that correspond to unused subpatterns at the end  of  the         Offset  values  that correspond to unused subpatterns at the end of the
2102         expression  are  also  set  to  -1. For example, if the string "abc" is         expression are also set to -1. For example,  if  the  string  "abc"  is
2103         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2104         matched.  The  return  from the function is 2, because the highest used         matched. The return from the function is 2, because  the  highest  used
2105         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2106         for  the  second  and third capturing subpatterns if you wish (assuming         for the second and third capturing subpatterns if  you  wish  (assuming
2107         the vector is large enough, of course).         the vector is large enough, of course).
2108    
2109         Some convenience functions are provided  for  extracting  the  captured         Some  convenience  functions  are  provided for extracting the captured
2110         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2111    
2112     Error return values from pcre_exec()     Error return values from pcre_exec()
2113    
2114         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2115         defined in the header file:         defined in the header file:
2116    
2117           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1809  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2120  MATCHING A PATTERN: THE TRADITIONAL FUNC
2120    
2121           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2122    
2123         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
2124         ovecsize was not zero.         ovecsize was not zero.
2125    
2126           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1818  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2129  MATCHING A PATTERN: THE TRADITIONAL FUNC
2129    
2130           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2131    
2132         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,
2133         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
2134         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
2135         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2136         gives when the magic number is not present.         gives when the magic number is not present.
2137    
2138           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2139    
2140         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2141         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
2142         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2143    
2144           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2145    
2146         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2147         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2148         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
2149         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
2150         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2151    
2152           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2153    
2154         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2155         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2156         returned by pcre_exec().         returned by pcre_exec().
2157    
2158           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2159    
2160         The  backtracking  limit,  as  specified  by the match_limit field in a         The backtracking limit, as specified by  the  match_limit  field  in  a
2161         pcre_extra structure (or defaulted) was reached.  See  the  description         pcre_extra  structure  (or  defaulted) was reached. See the description
2162         above.         above.
2163    
          PCRE_ERROR_RECURSIONLIMIT (-21)  
   
        The internal recursion limit, as specified by the match_limit_recursion  
        field in a pcre_extra structure (or defaulted)  was  reached.  See  the  
        description above.  
   
2164           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2165    
2166         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
2167         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2168         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2169    
2170           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2171    
2172         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
2173         subject.         subject.
2174    
2175           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2176    
2177         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
2178         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-
2179         ter.         ter.
2180    
2181           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2182    
2183         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
2184         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2185    
2186           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2187    
2188         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
2189         items that are not supported for partial matching. See the  pcrepartial         items  that are not supported for partial matching. See the pcrepartial
2190         documentation for details of partial matching.         documentation for details of partial matching.
2191    
2192           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2193    
2194         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2195         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2196    
2197           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2198    
2199         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.
2200    
2201             PCRE_ERROR_RECURSIONLIMIT (-21)
2202    
2203           The internal recursion limit, as specified by the match_limit_recursion
2204           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2205           description above.
2206    
2207             PCRE_ERROR_BADNEWLINE     (-23)
2208    
2209           An invalid combination of PCRE_NEWLINE_xxx options was given.
2210    
2211           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2212    
2213    
2214  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1907  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2224  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2224         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2225              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2226    
2227         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2228         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2229         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2230         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2231         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2232         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2233         substrings.         substrings.
2234    
2235         A  substring that contains a binary zero is correctly extracted and has         A substring that contains a binary zero is correctly extracted and  has
2236         a further zero added on the end, but the result is not, of course, a  C         a  further zero added on the end, but the result is not, of course, a C
2237         string.   However,  you  can  process such a string by referring to the         string.  However, you can process such a string  by  referring  to  the
2238         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2239         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2240         not adequate for handling strings containing binary zeros, because  the         not  adequate for handling strings containing binary zeros, because the
2241         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2242    
2243         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-
2244         tions: subject is the subject string that has  just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2245         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
2246         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2247         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2248         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2249         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2250         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
2251         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2252    
2253         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2254         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2255         zero  extracts  the  substring that matched the entire pattern, whereas         zero extracts the substring that matched the  entire  pattern,  whereas
2256         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2257         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2258         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2259         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2260         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
2261         the terminating zero, or one of         the terminating zero, or one of these error codes:
2262    
2263           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2264    
2265         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
2266         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2267    
2268           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2269    
2270         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2271    
2272         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2273         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
2274         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
2275         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
2276         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
2277         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  the
2278           error code
2279    
2280           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2281    
# Line 1999  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2317  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2317         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-
2318         ber.  For example, for this pattern         ber.  For example, for this pattern
2319    
2320           (a+)b(?P<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2321    
2322         the number of the subpattern called "xxx" is 2. If the name is known to         the number of the subpattern called "xxx" is 2. If the name is known to
2323         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
# Line 2025  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2343  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2343    
2344         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2345         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2346         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2347           behaviour may not be what you want (see the next section).
2348    
2349    
2350  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
# Line 2033  DUPLICATE SUBPATTERN NAMES Line 2352  DUPLICATE SUBPATTERN NAMES
2352         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2353              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2354    
2355         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
2356         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns  are  not  required  to  be unique. Normally, patterns with
2357         duplicate  names  are such that in any one match, only one of the named         duplicate names are such that in any one match, only one of  the  named
2358         subpatterns participates. An example is shown in the pcrepattern  docu-         subpatterns  participates. An example is shown in the pcrepattern docu-
2359         mentation. When duplicates are present, pcre_copy_named_substring() and         mentation.
2360         pcre_get_named_substring() return the first substring corresponding  to  
2361         the  given  name  that  is  set.  If  none  are set, an empty string is         When   duplicates   are   present,   pcre_copy_named_substring()    and
2362         returned.  The pcre_get_stringnumber() function returns one of the num-         pcre_get_named_substring()  return the first substring corresponding to
2363         bers  that are associated with the name, but it is not defined which it         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
2364         is.         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
2365           function returns one of the numbers that are associated with the  name,
2366           but it is not defined which it is.
2367    
2368         If you want to get full details of all captured substrings for a  given         If  you want to get full details of all captured substrings for a given
2369         name,  you  must  use  the pcre_get_stringtable_entries() function. The         name, you must use  the  pcre_get_stringtable_entries()  function.  The
2370         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2371         third  and  fourth  are  pointers to variables which are updated by the         third and fourth are pointers to variables which  are  updated  by  the
2372         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2373         the  name-to-number  table  for  the  given  name.  The function itself         the name-to-number table  for  the  given  name.  The  function  itself
2374         returns the length of each entry, or  PCRE_ERROR_NOSUBSTRING  if  there         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
2375         are  none.  The  format  of the table is described above in the section         there are none. The format of the table is described above in the  sec-
2376         entitled Information about a pattern. Given all  the  relevant  entries         tion  entitled  Information  about  a  pattern.  Given all the relevant
2377         for the name, you can extract each of their numbers, and hence the cap-         entries for the name, you can extract each of their numbers, and  hence
2378         tured data, if any.         the captured data, if any.
2379    
2380    
2381  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2382    
2383         The traditional matching function uses a  similar  algorithm  to  Perl,         The  traditional  matching  function  uses a similar algorithm to Perl,
2384         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2385         the subject. If you want to find all possible matches, or  the  longest         the  subject.  If you want to find all possible matches, or the longest
2386         possible  match,  consider using the alternative matching function (see         possible match, consider using the alternative matching  function  (see
2387         below) instead. If you cannot use the alternative function,  but  still         below)  instead.  If you cannot use the alternative function, but still
2388         need  to  find all possible matches, you can kludge it up by making use         need to find all possible matches, you can kludge it up by  making  use
2389         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2390         tation.         tation.
2391    
2392         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2393         tern.  When your callout function is called, extract and save the  cur-         tern.   When your callout function is called, extract and save the cur-
2394         rent  matched  substring.  Then  return  1, which forces pcre_exec() to         rent matched substring. Then return  1,  which  forces  pcre_exec()  to
2395         backtrack and try other alternatives. Ultimately, when it runs  out  of         backtrack  and  try other alternatives. Ultimately, when it runs out of
2396         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2397    
2398    
# Line 2082  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2403  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2403              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2404              int *workspace, int wscount);              int *workspace, int wscount);
2405    
2406         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The function pcre_dfa_exec()  is  called  to  match  a  subject  string
2407         against a compiled pattern, using a "DFA" matching algorithm. This  has         against  a  compiled pattern, using a matching algorithm that scans the
2408         different  characteristics to the normal algorithm, and is not compati-         subject string just once, and does not backtrack.  This  has  different
2409         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics  to  the  normal  algorithm, and is not compatible with
2410         Nevertheless, there are times when this kind of matching can be useful.         Perl. Some of the features of PCRE patterns are not  supported.  Never-
2411         For a discussion of the two matching algorithms, see  the  pcrematching         theless,  there are times when this kind of matching can be useful. For
2412         documentation.         a discussion of the two matching algorithms, see the pcrematching docu-
2413           mentation.
2414    
2415         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2416         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2141  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2463  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2463           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2464    
2465         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2466         stop  as  soon  as  it  has found one match. Because of the way the DFA         stop as soon as it has found one match. Because of the way the alterna-
2467         algorithm works, this is necessarily the shortest possible match at the         tive algorithm works, this is necessarily the shortest  possible  match
2468         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2469    
2470           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2471    
# Line 2179  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2501  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2501         On success, the yield of the function is a number  greater  than  zero,         On success, the yield of the function is a number  greater  than  zero,
2502         which  is  the  number of matched substrings. The substrings themselves         which  is  the  number of matched substrings. The substrings themselves
2503         are returned in ovector. Each string uses two elements;  the  first  is         are returned in ovector. Each string uses two elements;  the  first  is
2504         the  offset  to the start, and the second is the offset to the end. All         the  offset  to  the start, and the second is the offset to the end. In
2505         the strings have the same start offset. (Space could have been saved by         fact, all the strings have the same start  offset.  (Space  could  have
2506         giving  this only once, but it was decided to retain some compatibility         been  saved by giving this only once, but it was decided to retain some
2507         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility with the way pcre_exec() returns data,  even  though  the
2508         strings is different.)         meaning of the strings is different.)
2509    
2510         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2511         est matching string is given first. If there were too many  matches  to         est matching string is given first. If there were too many  matches  to
# Line 2205  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2527  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2527    
2528           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2529    
2530         This  return is given if pcre_dfa_exec() encounters a condition item in         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2531         a pattern that uses a back reference for the  condition.  This  is  not         that uses a back reference for the condition, or a test  for  recursion
2532         supported.         in a specific group. These are not supported.
2533    
2534           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2535    
# Line 2227  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2549  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2549         This error is given if the output vector  is  not  large  enough.  This         This error is given if the output vector  is  not  large  enough.  This
2550         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2551    
2552  Last updated: 08 June 2006  
2553  Copyright (c) 1997-2006 University of Cambridge.  SEE ALSO
2554    
2555           pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2556           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).
2557    
2558    
2559    AUTHOR
2560    
2561           Philip Hazel
2562           University Computing Service
2563           Cambridge CB2 3QH, England.
2564    
2565    
2566    REVISION
2567    
2568           Last updated: 26 December 2007
2569           Copyright (c) 1997-2007 University of Cambridge.
2570  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2571    
2572    
# Line 2255  PCRE CALLOUTS Line 2593  PCRE CALLOUTS
2593         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2594         points:         points:
2595    
2596           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2597    
2598         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
2599         called, PCRE automatically  inserts  callouts,  all  with  number  255,         called, PCRE automatically  inserts  callouts,  all  with  number  255,
# Line 2330  THE CALLOUT INTERFACE Line 2668  THE CALLOUT INTERFACE
2668         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2669         were passed to pcre_exec().         were passed to pcre_exec().
2670    
2671         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2672         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2673         callout function may be called several times from the same point in the         sequence \K has been encountered, this value is changed to reflect  the
2674         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2675           function may be called several times from the same point in the pattern
2676           for different starting points in the subject.
2677    
2678         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2679         the current match pointer.         the current match pointer.
# Line 2386  RETURN VALUES Line 2726  RETURN VALUES
2726         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
2727         itself.         itself.
2728    
2729  Last updated: 28 February 2005  
2730  Copyright (c) 1997-2005 University of Cambridge.  AUTHOR
2731    
2732           Philip Hazel
2733           University Computing Service
2734           Cambridge CB2 3QH, England.
2735    
2736    
2737    REVISION
2738    
2739           Last updated: 29 May 2007
2740           Copyright (c) 1997-2007 University of Cambridge.
2741  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2742    
2743    
# Line 2401  NAME Line 2751  NAME
2751  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2752    
2753         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2754         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences described here  are  mainly
2755         respect to Perl 5.8.         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2756           some features that are expected to be in the forthcoming Perl 5.10.
2757    
2758         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2759         of what it does have are given in the section on UTF-8 support  in  the         of  what  it does have are given in the section on UTF-8 support in the
2760         main pcre page.         main pcre page.
2761    
2762         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
2763         permits them, but they do not mean what you might think.  For  example,         permits  them,  but they do not mean what you might think. For example,
2764         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
2765         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
2766    
2767         3. Capturing subpatterns that occur inside  negative  lookahead  asser-         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
2768         tions  are  counted,  but their entries in the offsets vector are never         tions are counted, but their entries in the offsets  vector  are  never
2769         set. Perl sets its numerical variables from any such patterns that  are         set.  Perl sets its numerical variables from any such patterns that are
2770         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
2771         ing), but only if the negative lookahead assertion  contains  just  one         ing),  but  only  if the negative lookahead assertion contains just one
2772         branch.         branch.
2773    
2774         4.  Though  binary zero characters are supported in the subject string,         4. Though binary zero characters are supported in the  subject  string,
2775         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
2776         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
2777         the pattern to represent a binary zero.         the pattern to represent a binary zero.
2778    
2779         5. The following Perl escape sequences are not supported: \l,  \u,  \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
2780         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
2781         dling and are not part of its pattern matching engine. If any of  these         dling  and are not part of its pattern matching engine. If any of these
2782         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
2783    
2784         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
2785         is built with Unicode character property support. The  properties  that         is  built  with Unicode character property support. The properties that
2786         can  be tested with \p and \P are limited to the general category prop-         can be tested with \p and \P are limited to the general category  prop-
2787         erties such as Lu and Nd, script names such as Greek or  Han,  and  the         erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2788         derived properties Any and L&.         derived properties Any and L&.
2789    
2790         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2791         ters in between are treated as literals.  This  is  slightly  different         ters  in  between  are  treated as literals. This is slightly different
2792         from  Perl  in  that  $  and  @ are also handled as literals inside the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
2793         quotes. In Perl, they cause variable interpolation (but of course  PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
2794         does not have variables). Note the following examples:         does not have variables). Note the following examples:
2795    
2796             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2449  DIFFERENCES BETWEEN PCRE AND PERL Line 2800  DIFFERENCES BETWEEN PCRE AND PERL
2800             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
2801             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
2802    
2803         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
2804         classes.         classes.
2805    
2806         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2807         constructions.  However,  there is support for recursive patterns using         constructions. However, there is support for recursive  patterns.  This
2808         the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE
2809         "callout"  feature allows an external function to be called during pat-         "callout" feature allows an external function to be called during  pat-
2810         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
2811    
2812         9. There are some differences that are concerned with the  settings  of         9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2813         captured  strings  when  part  of  a  pattern is repeated. For example,         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2814         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         unlike Perl.
2815    
2816           10.  There are some differences that are concerned with the settings of
2817           captured strings when part of  a  pattern  is  repeated.  For  example,
2818           matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2819         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2820    
2821         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2822         ities:         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2823           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2824           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2825           ture group; this is different to Perl.
2826    
2827           12. PCRE provides some extensions to the Perl regular expression facil-
2828           ities.   Perl  5.10  will  include new features that are not in earlier
2829           versions, some of which (such as named parentheses) have been  in  PCRE
2830           for some time. This list is with respect to Perl 5.10:
2831    
2832         (a) Although lookbehind assertions must  match  fixed  length  strings,         (a)  Although  lookbehind  assertions  must match fixed length strings,
2833         each alternative branch of a lookbehind assertion can match a different         each alternative branch of a lookbehind assertion can match a different
2834         length of string. Perl requires them all to have the same length.         length of string. Perl requires them all to have the same length.
2835    
2836         (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
2837         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2838    
2839         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
2840         cial meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash  is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2841         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
2842    
2843         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2844         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
2845         lowed by a question mark they are.         lowed by a question mark they are.
2846    
2847         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
2848         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
2849    
2850         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and  PCRE_NO_AUTO_CAP-         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
2851         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2852    
2853         (g)  The (?R), (?number), and (?P>name) constructs allows for recursive         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2854         pattern matching (Perl can do  this  using  the  (?p{code})  construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
2855    
2856         (h)  PCRE supports named capturing substrings, using the Python syntax.         (h) The callout facility is PCRE-specific.
2857    
2858         (i) PCRE supports the possessive quantifier  "++"  syntax,  taken  from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
2859    
2860         (j) The (R) condition, for testing recursion, is a PCRE extension.         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2861           even on different hosts that have the other endianness.
2862    
2863         (k) The callout facility is PCRE-specific.         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2864           different way and is not Perl-compatible.
2865    
2866         (l) The partial matching facility is PCRE-specific.         (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2867           of a pattern that set overall options that cannot be changed within the
2868           pattern.
2869    
        (m) Patterns compiled by PCRE can be saved and re-used at a later time,  
        even on different hosts that have the other endianness.  
2870    
2871         (n) The alternative matching function (pcre_dfa_exec())  matches  in  a  AUTHOR
        different way and is not Perl-compatible.  
2872    
2873  Last updated: 06 June 2006         Philip Hazel
2874  Copyright (c) 1997-2006 University of Cambridge.         University Computing Service
2875           Cambridge CB2 3QH, England.
2876    
2877    
2878    REVISION
2879    
2880           Last updated: 11 September 2007
2881           Copyright (c) 1997-2007 University of Cambridge.
2882  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2883    
2884    
# Line 2522  NAME Line 2891  NAME
2891    
2892  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2893    
2894         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
2895         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
2896         documentation  and  in  a  number  of books, some of which have copious         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are
2897         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         described in its own documentation, and regular expressions in  general
2898         by  O'Reilly, covers regular expressions in great detail. This descrip-         are  covered in a number of books, some of which have copious examples.
2899         tion of PCRE's regular expressions is intended as reference material.         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by
2900           O'Reilly,  covers regular expressions in great detail. This description
2901           of PCRE's regular expressions is intended as reference material.
2902    
2903         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2904         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
# Line 2541  PCRE REGULAR EXPRESSION DETAILS Line 2912  PCRE REGULAR EXPRESSION DETAILS
2912         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
2913         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
2914         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
2915         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
2916         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
2917         the pcrematching page.         alternative function, and how it differs from the normal function,  are
2918           discussed in the pcrematching page.
2919         A regular expression is a pattern that is  matched  against  a  subject  
2920         string  from  left  to right. Most characters stand for themselves in a  
2921         pattern, and match the corresponding characters in the  subject.  As  a  NEWLINE CONVENTIONS
2922    
2923           PCRE  supports five different conventions for indicating line breaks in
2924           strings: a single CR (carriage return) character, a  single  LF  (line-
2925           feed) character, the two-character sequence CRLF, any of the three pre-
2926           ceding, or any Unicode newline sequence. The pcreapi page  has  further
2927           discussion  about newlines, and shows how to set the newline convention
2928           in the options arguments for the compiling and matching functions.
2929    
2930           It is also possible to specify a newline convention by starting a  pat-
2931           tern string with one of the following five sequences:
2932    
2933             (*CR)        carriage return
2934             (*LF)        linefeed
2935             (*CRLF)      carriage return, followed by linefeed
2936             (*ANYCRLF)   any of the three above
2937             (*ANY)       all Unicode newline sequences
2938    
2939           These override the default and the options given to pcre_compile(). For
2940           example, on a Unix system where LF is the default newline sequence, the
2941           pattern
2942    
2943             (*CR)a.b
2944    
2945           changes the convention to CR. That pattern matches "a\nb" because LF is
2946           no longer a newline. Note that these special settings,  which  are  not
2947           Perl-compatible,  are  recognized  only at the very start of a pattern,
2948           and that they must be in upper case.  If  more  than  one  of  them  is
2949           present, the last one is used.
2950    
2951           The  newline  convention  does  not  affect what the \R escape sequence
2952           matches. By default, this is any Unicode  newline  sequence,  for  Perl
2953           compatibility.  However, this can be changed; see the description of \R
2954           in the section entitled "Newline sequences" below. A change of \R  set-
2955           ting can be combined with a change of newline convention.
2956    
2957    
2958    CHARACTERS AND METACHARACTERS
2959    
2960           A  regular  expression  is  a pattern that is matched against a subject
2961           string from left to right. Most characters stand for  themselves  in  a
2962           pattern,  and  match  the corresponding characters in the subject. As a
2963         trivial example, the pattern         trivial example, the pattern
2964    
2965           The quick brown fox           The quick brown fox
2966    
2967         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
2968         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
2969         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
2970         the concept of case for characters whose values are less than  128,  so         the  concept  of case for characters whose values are less than 128, so
2971         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
2972         ues, the concept of case is supported if PCRE is compiled with  Unicode         ues,  the concept of case is supported if PCRE is compiled with Unicode
2973         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
2974         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
2975         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
2976    
2977         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
2978         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
2979         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
2980         but instead are interpreted in some special way.         but instead are interpreted in some special way.
2981    
2982         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
2983         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
2984         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
2985         metacharacters are as follows:         the metacharacters are as follows:
2986    
2987           \      general escape character with several uses           \      general escape character with several uses
2988           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2588  PCRE REGULAR EXPRESSION DETAILS Line 3000  PCRE REGULAR EXPRESSION DETAILS
3000                  also "possessive quantifier"                  also "possessive quantifier"
3001           {      start min/max quantifier           {      start min/max quantifier
3002    
3003         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
3004         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3005    
3006           \      general escape character           \      general escape character
# Line 2598  PCRE REGULAR EXPRESSION DETAILS Line 3010  PCRE REGULAR EXPRESSION DETAILS
3010                    syntax)                    syntax)
3011           ]      terminates the character class           ]      terminates the character class
3012    
3013         The following sections describe the use of each of the  metacharacters.         The  following sections describe the use of each of the metacharacters.
3014    
3015    
3016  BACKSLASH  BACKSLASH
3017    
3018         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3019         a non-alphanumeric character, it takes away any  special  meaning  that         a  non-alphanumeric  character,  it takes away any special meaning that
3020         character  may  have.  This  use  of  backslash  as an escape character         character may have. This  use  of  backslash  as  an  escape  character
3021         applies both inside and outside character classes.         applies both inside and outside character classes.
3022    
3023         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
3024         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3025         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3026         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3027         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-
3028         slash, you write \\.         slash, you write \\.
3029    
3030         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3031         the pattern (other than in a character class) and characters between  a         the  pattern (other than in a character class) and characters between a
3032         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3033         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3034         part of the pattern.         part of the pattern.
3035    
3036         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-
3037         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-
3038         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
3039         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3040         tion. Note the following examples:         tion. Note the following examples:
3041    
3042           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2634  BACKSLASH Line 3046  BACKSLASH
3046           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3047           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3048    
3049         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3050         classes.         classes.
3051    
3052     Non-printing characters     Non-printing characters
3053    
3054         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-
3055         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
3056         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3057         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3058         editing, it is usually easier  to  use  one  of  the  following  escape         editing,  it  is  usually  easier  to  use  one of the following escape
3059         sequences than the binary character it represents:         sequences than the binary character it represents:
3060    
3061           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3062           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3063           \e        escape (hex 1B)           \e        escape (hex 1B)
3064           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3065           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3066           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3067           \t        tab (hex 09)           \t        tab (hex 09)
3068           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
3069           \xhh      character with hex code hh           \xhh      character with hex code hh
3070           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3071    
3072         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,
3073         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
3074         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;
3075         becomes hex 7B.         becomes hex 7B.
3076    
3077         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
3078         in  upper  or  lower case). Any number of hexadecimal digits may appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
3079         between \x{ and }, but the value of the character  code  must  be  less         between  \x{  and  },  but the value of the character code must be less
3080         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3081         the maximum hexadecimal value is 7FFFFFFF). If  characters  other  than         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3082         hexadecimal  digits  appear between \x{ and }, or if there is no termi-         than the largest Unicode code point, which is 10FFFF.
3083         nating }, this form of escape is not recognized.  Instead, the  initial  
3084         \x will be interpreted as a basic hexadecimal escape, with no following         If characters other than hexadecimal digits appear between \x{  and  },
3085         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3086           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3087           escape,  with  no  following  digits, giving a character whose value is
3088           zero.
3089    
3090         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
3091         two  syntaxes  for  \x. There is no difference in the way they are han-         two  syntaxes  for  \x. There is no difference in the way they are han-
# Line 2692  BACKSLASH Line 3107  BACKSLASH
3107    
3108         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
3109         and  there have not been that many capturing subpatterns, PCRE re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3110         up to three octal digits following the backslash, ane uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3111         erate  a data character. Any subsequent digits stand for themselves. In         erate  a data character. Any subsequent digits stand for themselves. In
3112         non-UTF-8 mode, the value of a character specified  in  octal  must  be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3113         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
# Line 2719  BACKSLASH Line 3134  BACKSLASH
3134         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3135         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3136         class,  the  sequence \b is interpreted as the backspace character (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3137         08), and the sequence \X is interpreted as the character "X". Outside a         08), and the sequences \R and \X are interpreted as the characters  "R"
3138         character class, these sequences have different meanings (see below).         and  "X", respectively. Outside a character class, these sequences have
3139           different meanings (see below).
3140    
3141       Absolute and relative back references
3142    
3143           The sequence \g followed by an unsigned or a negative  number,  option-
3144           ally  enclosed  in braces, is an absolute or relative back reference. A
3145           named back reference can be coded as \g{name}. Back references are dis-
3146           cussed later, following the discussion of parenthesized subpatterns.
3147    
3148     Generic character types     Generic character types
3149    
3150         The  third  use of backslash is for specifying generic character types.         Another use of backslash is for specifying generic character types. The
3151         The following are always recognized:         following are always recognized:
3152    
3153           \d     any decimal digit           \d     any decimal digit
3154           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3155             \h     any horizontal whitespace character
3156             \H     any character that is not a horizontal whitespace character
3157           \s     any whitespace character           \s     any whitespace character
3158           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3159             \v     any vertical whitespace character
3160             \V     any character that is not a vertical whitespace character
3161           \w     any "word" character           \w     any "word" character
3162           \W     any "non-word" character           \W     any "non-word" character
3163    
# Line 2745  BACKSLASH Line 3172  BACKSLASH
3172    
3173         For  compatibility  with Perl, \s does not match the VT character (code         For  compatibility  with Perl, \s does not match the VT character (code
3174         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
3175         characters  are  HT (9), LF (10), FF (12), CR (13), and space (32). (If         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3176         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3177         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3178    
3179           In  UTF-8 mode, characters with values greater than 128 never match \d,
3180           \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3181           code  character  property  support is available. These sequences retain
3182           their original meanings from before UTF-8 support was available, mainly
3183           for efficiency reasons.
3184    
3185           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3186           the other sequences, these do match certain high-valued  codepoints  in
3187           UTF-8 mode.  The horizontal space characters are:
3188    
3189             U+0009     Horizontal tab
3190             U+0020     Space
3191             U+00A0     Non-break space
3192             U+1680     Ogham space mark
3193             U+180E     Mongolian vowel separator
3194             U+2000     En quad
3195             U+2001     Em quad
3196             U+2002     En space
3197             U+2003     Em space
3198             U+2004     Three-per-em space
3199             U+2005     Four-per-em space
3200             U+2006     Six-per-em space
3201             U+2007     Figure space
3202             U+2008     Punctuation space
3203             U+2009     Thin space
3204             U+200A     Hair space
3205             U+202F     Narrow no-break space
3206             U+205F     Medium mathematical space
3207             U+3000     Ideographic space
3208    
3209           The vertical space characters are:
3210    
3211             U+000A     Linefeed
3212             U+000B     Vertical tab
3213             U+000C     Formfeed
3214             U+000D     Carriage return
3215             U+0085     Next line
3216             U+2028     Line separator
3217             U+2029     Paragraph separator
3218    
3219         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
3220         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-
3221         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-
3222         specific matching is taking place (see "Locale support" in the  pcreapi         specific matching is taking place (see "Locale support" in the  pcreapi
3223         page).  For  example,  in  the  "fr_FR" (French) locale, some character         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3224         codes greater than 128 are used for accented  letters,  and  these  are         systems, or "french" in Windows, some character codes greater than  128
3225         matched by \w.         are  used for accented letters, and these are matched by \w. The use of
3226           locales with Unicode is discouraged.
3227    
3228       Newline sequences
3229    
3230           Outside a character class, by default, the escape sequence  \R  matches
3231           any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3232           mode \R is equivalent to the following:
3233    
3234             (?>\r\n|\n|\x0b|\f|\r|\x85)
3235    
3236           This is an example of an "atomic group", details  of  which  are  given
3237           below.  This particular group matches either the two-character sequence
3238           CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3239           U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3240           return, U+000D), or NEL (next line, U+0085). The two-character sequence
3241           is treated as a single unit that cannot be split.
3242    
3243           In  UTF-8  mode, two additional characters whose codepoints are greater
3244           than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3245           rator,  U+2029).   Unicode character property support is not needed for
3246           these characters to be recognized.
3247    
3248           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3249           the  complete  set  of  Unicode  line  endings)  by  setting the option
3250           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3251           (BSR is an abbrevation for "backslash R".) This can be made the default
3252           when PCRE is built; if this is the case, the  other  behaviour  can  be
3253           requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3254           specify these settings by starting a pattern string  with  one  of  the
3255           following sequences:
3256    
3257             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3258             (*BSR_UNICODE)   any Unicode newline sequence
3259    
3260           These override the default and the options given to pcre_compile(), but
3261           they can be overridden by options given to pcre_exec(). Note that these
3262           special settings, which are not Perl-compatible, are recognized only at
3263           the very start of a pattern, and that they must be in  upper  case.  If
3264           more  than  one  of  them is present, the last one is used. They can be
3265           combined with a change of newline convention, for  example,  a  pattern
3266           can start with:
3267    
3268         In  UTF-8 mode, characters with values greater than 128 never match \d,           (*ANY)(*BSR_ANYCRLF)
3269         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-  
3270         code  character  property support is available. The use of locales with         Inside a character class, \R matches the letter "R".
        Unicode is discouraged.  
3271    
3272     Unicode character properties     Unicode character properties
3273    
3274         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3275         tional  escape  sequences  to  match character properties are available         tional escape sequences that match characters with specific  properties
3276         when UTF-8 mode is selected. They are:         are  available.   When not in UTF-8 mode, these sequences are of course
3277           limited to testing characters whose codepoints are less than  256,  but
3278           they do work in this mode.  The extra escape sequences are:
3279    
3280           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3281           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3282           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3283    
3284         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3285         script names, the general category properties, and "Any", which matches         script names, the general category properties, and "Any", which matches
3286         any character (including newline). Other properties such as "InMusical-         any character (including newline). Other properties such as "InMusical-
3287         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does
3288         not match any characters, so always causes a match failure.         not match any characters, so always causes a match failure.
3289    
3290         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3291         A  character from one of these sets can be matched using a script name.         A character from one of these sets can be matched using a script  name.
3292         For example:         For example:
3293    
3294           \p{Greek}           \p{Greek}
3295           \P{Han}           \P{Han}
3296    
3297         Those that are not part of an identified script are lumped together  as         Those  that are not part of an identified script are lumped together as
3298         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3299    
3300         Arabic,  Armenian,  Bengali,  Bopomofo, Braille, Buginese, Buhid, Cana-         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3301         dian_Aboriginal, Cherokee, Common, Coptic, Cypriot, Cyrillic,  Deseret,         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,
3302         Devanagari,  Ethiopic,  Georgian,  Glagolitic, Gothic, Greek, Gujarati,         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3303         Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana,  Inherited,  Kannada,         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-
3304         Katakana,  Kharoshthi,  Khmer,  Lao, Latin, Limbu, Linear_B, Malayalam,         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,
3305         Mongolian, Myanmar, New_Tai_Lue, Ogham, Old_Italic, Old_Persian, Oriya,         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3306         Osmanya,  Runic,  Shavian, Sinhala, Syloti_Nagri, Syriac, Tagalog, Tag-         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,
3307         banwa,  Tai_Le,  Tamil,  Telugu,  Thaana,  Thai,   Tibetan,   Tifinagh,         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3308         Ugaritic, Yi.         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3309    
3310         Each  character has exactly one general category property, specified by         Each character has exactly one general category property, specified  by
3311         a two-letter abbreviation. For compatibility with Perl, negation can be         a two-letter abbreviation. For compatibility with Perl, negation can be
3312         specified  by  including a circumflex between the opening brace and the         specified by including a circumflex between the opening brace  and  the
3313         property name. For example, \p{^Lu} is the same as \P{Lu}.         property name. For example, \p{^Lu} is the same as \P{Lu}.
3314    
3315         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3316         eral  category properties that start with that letter. In this case, in         eral category properties that start with that letter. In this case,  in
3317         the absence of negation, the curly brackets in the escape sequence  are         the  absence of negation, the curly brackets in the escape sequence are
3318         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3319    
3320           \p{L}           \p{L}
# Line 2857  BACKSLASH Line 3366  BACKSLASH
3366           Zp    Paragraph separator           Zp    Paragraph separator
3367           Zs    Space separator           Zs    Space separator
3368    
3369         The  special property L& is also supported: it matches a character that         The special property L& is also supported: it matches a character  that
3370         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
3371         classified as a modifier or "other".         classified as a modifier or "other".
3372    
3373         The  long  synonyms  for  these  properties that Perl supports (such as         The Cs (Surrogate) property applies only to  characters  in  the  range
3374         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3375           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3376           ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3377           the pcreapi page).
3378    
3379           The long synonyms for these properties  that  Perl  supports  (such  as
3380           \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3381         any of these properties with "Is".         any of these properties with "Is".
3382    
3383         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3384         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3385         in the Unicode table.         in the Unicode table.
3386    
3387         Specifying  caseless  matching  does not affect these escape sequences.         Specifying caseless matching does not affect  these  escape  sequences.
3388         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3389    
3390         The \X escape matches any number of Unicode  characters  that  form  an         The  \X  escape  matches  any number of Unicode characters that form an
3391         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3392    
3393           (?>\PM\pM*)           (?>\PM\pM*)
3394    
3395         That  is,  it matches a character without the "mark" property, followed         That is, it matches a character without the "mark"  property,  followed
3396         by zero or more characters with the "mark"  property,  and  treats  the         by  zero  or  more  characters with the "mark" property, and treats the
3397         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence as an atomic group (see below).  Characters  with  the  "mark"
3398         property are typically accents that affect the preceding character.         property  are  typically  accents  that affect the preceding character.
3399           None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
3400           matches any one character.
3401    
3402         Matching characters by Unicode property is not fast, because  PCRE  has         Matching  characters  by Unicode property is not fast, because PCRE has
3403         to  search  a  structure  that  contains data for over fifteen thousand         to search a structure that contains  data  for  over  fifteen  thousand
3404         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3405         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3406    
3407       Resetting the match start
3408    
3409           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3410           ously  matched  characters  not  to  be  included  in the final matched
3411           sequence. For example, the pattern:
3412    
3413             foo\Kbar
3414    
3415           matches "foobar", but reports that it has matched "bar".  This  feature
3416           is  similar  to  a lookbehind assertion (described below).  However, in
3417           this case, the part of the subject before the real match does not  have
3418           to  be of fixed length, as lookbehind assertions do. The use of \K does
3419           not interfere with the setting of captured  substrings.   For  example,
3420           when the pattern
3421    
3422             (foo)\Kbar
3423    
3424           matches "foobar", the first substring is still set to "foo".
3425    
3426     Simple assertions     Simple assertions
3427    
3428         The fourth use of backslash is for certain simple assertions. An asser-         The  final use of backslash is for certain simple assertions. An asser-
3429         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
3430         a  match, without consuming any characters from the subject string. The         a  match, without consuming any characters from the subject string. The
3431         use of subpatterns for more complicated assertions is described  below.         use of subpatterns for more complicated assertions is described  below.
# Line 2897  BACKSLASH Line 3433  BACKSLASH
3433    
3434           \b     matches at a word boundary           \b     matches at a word boundary
3435           \B     matches when not at a word boundary           \B     matches when not at a word boundary
3436           \A     matches at start of subject           \A     matches at the start of the subject
3437           \Z     matches at end of subject or before newline at end           \Z     matches at the end of the subject
3438           \z     matches at end of subject                   also matches before a newline at the end of the subject
3439           \G     matches at first matching position in subject           \z     matches only at the end of the subject
3440             \G     matches at the first matching position in the subject
3441    
3442         These  assertions may not appear in character classes (but note that \b         These  assertions may not appear in character classes (but note that \b
3443         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
# Line 2997  FULL STOP (PERIOD, DOT) Line 3534  FULL STOP (PERIOD, DOT)
3534         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-
3535         ter in the subject string except (by default) a character  that  signi-         ter in the subject string except (by default) a character  that  signi-
3536         fies  the  end  of  a line. In UTF-8 mode, the matched character may be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
3537         more than one byte long. When a line ending  is  defined  as  a  single         more than one byte long.
        character  (CR  or LF), dot never matches that character; when the two-  
        character sequence CRLF is used, dot does not match CR if it is immedi-  
        ately  followed by LF, but otherwise it matches all characters (includ-  
        ing isolated CRs and LFs).  
   
        The behaviour of dot with regard to newlines can  be  changed.  If  the  
        PCRE_DOTALL  option  is  set,  a dot matches any one character, without  
        exception. If newline is defined as the two-character sequence CRLF, it  
        takes two dots to match it.  
3538    
3539         The  handling of dot is entirely independent of the handling of circum-         When a line ending is defined as a single character, dot never  matches
3540         flex and dollar, the only relationship being  that  they  both  involve         that  character; when the two-character sequence CRLF is used, dot does
3541           not match CR if it is immediately followed  by  LF,  but  otherwise  it
3542           matches  all characters (including isolated CRs and LFs). When any Uni-
3543           code line endings are being recognized, dot does not match CR or LF  or
3544           any of the other line ending characters.
3545    
3546           The  behaviour  of  dot  with regard to newlines can be changed. If the
3547           PCRE_DOTALL option is set, a dot matches  any  one  character,  without
3548           exception. If the two-character sequence CRLF is present in the subject
3549           string, it takes two dots to match it.
3550    
3551           The handling of dot is entirely independent of the handling of  circum-
3552           flex  and  dollar,  the  only relationship being that they both involve
3553         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3554    
3555    
3556  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3557    
3558         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3559         both in and out of UTF-8 mode. Unlike a dot, it always matches  CR  and         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
3560         LF.  The feature is provided in Perl in order to match individual bytes         line-ending characters. The feature is provided in  Perl  in  order  to
3561         in UTF-8 mode.  Because it breaks up UTF-8 characters  into  individual         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
3562         bytes,  what remains in the string may be a malformed UTF-8 string. For         acters into individual bytes, what remains in the string may be a  mal-
3563         this reason, the \C escape sequence is best avoided.         formed  UTF-8  string.  For this reason, the \C escape sequence is best
3564           avoided.
3565    
3566         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
3567         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-
# Line 3067  SQUARE BRACKETS AND CHARACTER CLASSES Line 3608  SQUARE BRACKETS AND CHARACTER CLASSES
3608         PCRE  is  compiled  with Unicode property support as well as with UTF-8         PCRE  is  compiled  with Unicode property support as well as with UTF-8
3609         support.         support.
3610    
3611         Characters that might indicate  line  breaks  (CR  and  LF)  are  never         Characters that might indicate line breaks are  never  treated  in  any
3612         treated  in  any  special way when matching character classes, whatever         special  way  when  matching  character  classes,  whatever line-ending
3613         line-ending sequence is in use, and whatever setting of the PCRE_DOTALL         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
3614         and PCRE_MULTILINE options is used. A class such as [^a] always matches         PCRE_MULTILINE options is used. A class such as [^a] always matches one
3615         one of these characters.         of these characters.
3616    
3617         The minus (hyphen) character can be used to specify a range of  charac-         The minus (hyphen) character can be used to specify a range of  charac-
3618         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters  in  a  character  class.  For  example,  [d-m] matches any letter
# Line 3097  SQUARE BRACKETS AND CHARACTER CLASSES Line 3638  SQUARE BRACKETS AND CHARACTER CLASSES
3638         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
3639         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
3640         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
3641         character tables for the "fr_FR" locale are in use, [\xc8-\xcb] matches         character tables for a French locale are in  use,  [\xc8-\xcb]  matches
3642         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
3643         concept of case for characters with values greater than 128  only  when         concept of case for characters with values greater than 128  only  when
3644         it is compiled with Unicode property support.         it is compiled with Unicode property support.
# Line 3181  VERTICAL BAR Line 3722  VERTICAL BAR
3722  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3723    
3724         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
3725         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
3726         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         within  the  pattern  by  a  sequence  of  Perl option letters enclosed
3727         option letters are         between "(?" and ")".  The option letters are
3728    
3729           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3730           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3197  INTERNAL OPTION SETTING Line 3738  INTERNAL OPTION SETTING
3738         is also permitted. If a  letter  appears  both  before  and  after  the         is also permitted. If a  letter  appears  both  before  and  after  the
3739         hyphen, the option is unset.         hyphen, the option is unset.
3740    
3741           The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
3742           can be changed in the same way as the Perl-compatible options by  using
3743           the characters J, U and X respectively.
3744    
3745         When  an option change occurs at top level (that is, not inside subpat-         When  an option change occurs at top level (that is, not inside subpat-
3746         tern parentheses), the change applies to the remainder of  the  pattern         tern parentheses), the change applies to the remainder of  the  pattern
3747         that follows.  If the change is placed right at the start of a pattern,         that follows.  If the change is placed right at the start of a pattern,
3748         PCRE extracts it into the global options (and it will therefore show up         PCRE extracts it into the global options (and it will therefore show up
3749         in data extracted by the pcre_fullinfo() function).         in data extracted by the pcre_fullinfo() function).
3750    
3751         An option change within a subpattern affects only that part of the cur-         An  option  change  within a subpattern (see below for a description of
3752         rent pattern that follows it, so         subpatterns) affects only that part of the current pattern that follows
3753           it, so
3754    
3755           (a(?i)b)c           (a(?i)b)c
3756    
3757         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
3758         used).   By  this means, options can be made to have different settings         used).  By this means, options can be made to have  different  settings
3759         in different parts of the pattern. Any changes made in one  alternative         in  different parts of the pattern. Any changes made in one alternative
3760         do  carry  on  into subsequent branches within the same subpattern. For         do carry on into subsequent branches within the  same  subpattern.  For
3761         example,         example,
3762    
3763           (a(?i)b|c)           (a(?i)b|c)
3764    
3765         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the
3766         first  branch  is  abandoned before the option setting. This is because         first branch is abandoned before the option setting.  This  is  because
3767         the effects of option settings happen at compile time. There  would  be         the  effects  of option settings happen at compile time. There would be
3768         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3769    
3770         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         Note: There are other PCRE-specific options that  can  be  set  by  the
3771         can be changed in the same way as the Perl-compatible options by  using         application  when  the  compile  or match functions are called. In some
3772         the characters J, U and X respectively.         cases the pattern can contain special  leading  sequences  to  override
3773           what  the  application  has set or what has been defaulted. Details are
3774           given in the section entitled "Newline sequences" above.
3775    
3776    
3777  SUBPATTERNS  SUBPATTERNS
# Line 3235  SUBPATTERNS Line 3783  SUBPATTERNS
3783    
3784           cat(aract|erpillar|)           cat(aract|erpillar|)
3785    
3786         matches one of the words "cat", "cataract", or  "caterpillar".  Without         matches  one  of the words "cat", "cataract", or "caterpillar". Without
3787         the  parentheses,  it  would  match "cataract", "erpillar" or the empty         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty
3788         string.         string.
3789    
3790         2. It sets up the subpattern as  a  capturing  subpattern.  This  means         2.  It  sets  up  the  subpattern as a capturing subpattern. This means
3791         that,  when  the  whole  pattern  matches,  that portion of the subject         that, when the whole pattern  matches,  that  portion  of  the  subject
3792         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
3793         ovector  argument  of pcre_exec(). Opening parentheses are counted from         ovector argument of pcre_exec(). Opening parentheses are  counted  from
3794         left to right (starting from 1) to obtain  numbers  for  the  capturing         left  to  right  (starting  from 1) to obtain numbers for the capturing
3795         subpatterns.         subpatterns.
3796    
3797         For  example,  if the string "the red king" is matched against the pat-         For example, if the string "the red king" is matched against  the  pat-
3798         tern         tern
3799    
3800           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3254  SUBPATTERNS Line 3802  SUBPATTERNS
3802         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3803         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3804    
3805         The  fact  that  plain  parentheses  fulfil two functions is not always         The fact that plain parentheses fulfil  two  functions  is  not  always
3806         helpful.  There are often times when a grouping subpattern is  required         helpful.   There are often times when a grouping subpattern is required
3807         without  a capturing requirement. If an opening parenthesis is followed         without a capturing requirement. If an opening parenthesis is  followed
3808         by a question mark and a colon, the subpattern does not do any  captur-         by  a question mark and a colon, the subpattern does not do any captur-
3809         ing,  and  is  not  counted when computing the number of any subsequent         ing, and is not counted when computing the  number  of  any  subsequent
3810         capturing subpatterns. For example, if the string "the white queen"  is         capturing  subpatterns. For example, if the string "the white queen" is
3811         matched against the pattern         matched against the pattern
3812    
3813           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
3814    
3815         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3816         1 and 2. The maximum number of capturing subpatterns is 65535, and  the         1 and 2. The maximum number of capturing subpatterns is 65535.
        maximum  depth  of  nesting of all subpatterns, both capturing and non-  
        capturing, is 200.  
3817    
3818         As a convenient shorthand, if any option settings are required  at  the         As  a  convenient shorthand, if any option settings are required at the
3819         start  of  a  non-capturing  subpattern,  the option letters may appear         start of a non-capturing subpattern,  the  option  letters  may  appear
3820         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3821    
3822           (?i:saturday|sunday)           (?i:saturday|sunday)
3823           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3824    
3825         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3826         tried  from  left  to right, and options are not reset until the end of         tried from left to right, and options are not reset until  the  end  of
3827         the subpattern is reached, an option setting in one branch does  affect         the  subpattern is reached, an option setting in one branch does affect
3828         subsequent  branches,  so  the above patterns match "SUNDAY" as well as         subsequent branches, so the above patterns match "SUNDAY"  as  well  as
3829         "Saturday".         "Saturday".
3830    
3831    
3832    DUPLICATE SUBPATTERN NUMBERS
3833    
3834           Perl 5.10 introduced a feature whereby each alternative in a subpattern
3835           uses the same numbers for its capturing parentheses. Such a  subpattern
3836           starts  with (?| and is itself a non-capturing subpattern. For example,
3837           consider this pattern:
3838    
3839             (?|(Sat)ur|(Sun))day
3840    
3841           Because the two alternatives are inside a (?| group, both sets of  cap-
3842           turing  parentheses  are  numbered one. Thus, when the pattern matches,
3843           you can look at captured substring number  one,  whichever  alternative
3844           matched.  This  construct  is useful when you want to capture part, but
3845           not all, of one of a number of alternatives. Inside a (?| group, paren-
3846           theses  are  numbered as usual, but the number is reset at the start of
3847           each branch. The numbers of any capturing buffers that follow the  sub-
3848           pattern  start after the highest number used in any branch. The follow-
3849           ing example is taken from the Perl documentation.  The  numbers  under-
3850           neath show in which buffer the captured content will be stored.
3851    
3852             # before  ---------------branch-reset----------- after
3853             / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3854             # 1            2         2  3        2     3     4
3855    
3856           A  backreference  or  a  recursive call to a numbered subpattern always
3857           refers to the first one in the pattern with the given number.
3858    
3859           An alternative approach to using this "branch reset" feature is to  use
3860           duplicate named subpatterns, as described in the next section.
3861    
3862    
3863  NAMED SUBPATTERNS  NAMED SUBPATTERNS
3864    
3865         Identifying capturing parentheses by number is simple, but  it  can  be         Identifying  capturing  parentheses  by number is simple, but it can be
3866         very  hard  to keep track of the numbers in complicated regular expres-         very hard to keep track of the numbers in complicated  regular  expres-
3867         sions. Furthermore, if an  expression  is  modified,  the  numbers  may         sions.  Furthermore,  if  an  expression  is  modified, the numbers may
3868         change.  To help with this difficulty, PCRE supports the naming of sub-         change. To help with this difficulty, PCRE supports the naming of  sub-
3869         patterns, something that Perl  does  not  provide.  The  Python  syntax         patterns. This feature was not added to Perl until release 5.10. Python
3870         (?P<name>...)  is  used. References to capturing parentheses from other         had the feature earlier, and PCRE introduced it at release  4.0,  using
3871         parts of the pattern, such as  backreferences,  recursion,  and  condi-         the  Python syntax. PCRE now supports both the Perl and the Python syn-
3872         tions, can be made by name as well as by number.         tax.
3873    
3874         Names  consist  of  up  to  32 alphanumeric characters and underscores.         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
3875         Named capturing parentheses are still  allocated  numbers  as  well  as         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References
3876         names. The PCRE API provides function calls for extracting the name-to-         to capturing parentheses from other parts of the pattern, such as back-
3877         number translation table from a compiled pattern. There is also a  con-         references,  recursion,  and conditions, can be made by name as well as
3878         venience function for extracting a captured substring by name.         by number.
3879    
3880           Names consist of up to  32  alphanumeric  characters  and  underscores.
3881           Named  capturing  parentheses  are  still  allocated numbers as well as
3882           names, exactly as if the names were not present. The PCRE API  provides
3883           function calls for extracting the name-to-number translation table from
3884           a compiled pattern. There is also a convenience function for extracting
3885           a captured substring by name.
3886    
3887         By  default, a name must be unique within a pattern, but it is possible         By  default, a name must be unique within a pattern, but it is possible
3888         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
# Line 3308  NAMED SUBPATTERNS Line 3892  NAMED SUBPATTERNS
3892         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
3893         the line breaks) does the job:         the line breaks) does the job:
3894    
3895           (?P<DN>Mon|Fri|Sun)(?:day)?|           (?<DN>Mon|Fri|Sun)(?:day)?|
3896           (?P<DN>Tue)(?:sday)?|           (?<DN>Tue)(?:sday)?|
3897           (?P<DN>Wed)(?:nesday)?|           (?<DN>Wed)(?:nesday)?|
3898           (?P<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
3899           (?P<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
3900    
3901         There  are  five capturing substrings, but only one is ever set after a         There  are  five capturing substrings, but only one is ever set after a
3902         match.  The convenience  function  for  extracting  the  data  by  name         match.  (An alternative way of solving this problem is to use a "branch
3903         returns  the  substring  for  the first, and in this example, the only,         reset" subpattern, as described in the previous section.)
3904         subpattern of that name that matched.  This  saves  searching  to  find  
3905         which  numbered  subpattern  it  was. If you make a reference to a non-         The  convenience  function  for extracting the data by name returns the
3906         unique named subpattern from elsewhere in the  pattern,  the  one  that         substring for the first (and in this example, the only)  subpattern  of
3907         corresponds  to  the  lowest number is used. For further details of the         that  name  that  matched.  This saves searching to find which numbered
3908         interfaces for handling named subpatterns, see the  pcreapi  documenta-         subpattern it was. If you make a reference to a non-unique  named  sub-
3909         tion.         pattern  from elsewhere in the pattern, the one that corresponds to the
3910           lowest number is used. For further details of the interfaces  for  han-
3911           dling named subpatterns, see the pcreapi documentation.
3912    
3913    
3914  REPETITION  REPETITION
# Line 3331  REPETITION Line 3917  REPETITION
3917         following items:         following items:
3918    
3919           a literal data character           a literal data character
3920           the . metacharacter           the dot metacharacter
3921           the \C escape sequence           the \C escape sequence
3922           the \X escape sequence (in UTF-8 mode with Unicode properties)           the \X escape sequence (in UTF-8 mode with Unicode properties)
3923             the \R escape sequence
3924           an escape such as \d that matches a single character           an escape such as \d that matches a single character
3925           a character class           a character class
3926           a back reference (see next section)           a back reference (see next section)
# Line 3373  REPETITION Line 3960  REPETITION
3960         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
3961         the previous item and the quantifier were not present.         the previous item and the quantifier were not present.
3962    
3963         For  convenience  (and  historical compatibility) the three most common         For  convenience, the three most common quantifiers have single-charac-
3964         quantifiers have single-character abbreviations:         ter abbreviations:
3965    
3966           *    is equivalent to {0,}           *    is equivalent to {0,}
3967           +    is equivalent to {1,}           +    is equivalent to {1,}
# Line 3426  REPETITION Line 4013  REPETITION
4013         which matches one digit by preference, but can match two if that is the         which matches one digit by preference, but can match two if that is the
4014         only way the rest of the pattern matches.         only way the rest of the pattern matches.
4015    
4016         If the PCRE_UNGREEDY option is set (an option which is not available in         If the PCRE_UNGREEDY option is set (an option that is not available  in
4017         Perl),  the  quantifiers are not greedy by default, but individual ones         Perl),  the  quantifiers are not greedy by default, but individual ones
4018         can be made greedy by following them with a  question  mark.  In  other         can be made greedy by following them with a  question  mark.  In  other
4019         words, it inverts the default behaviour.         words, it inverts the default behaviour.
# Line 3437  REPETITION Line 4024  REPETITION
4024         minimum or maximum.         minimum or maximum.
4025    
4026         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
4027         alent  to Perl's /s) is set, thus allowing the . to match newlines, the         alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,
4028         pattern is implicitly anchored, because whatever follows will be  tried         the pattern is implicitly anchored, because whatever  follows  will  be
4029         against  every character position in the subject string, so there is no         tried  against every character position in the subject string, so there
4030         point in retrying the overall match at any position  after  the  first.         is no point in retrying the overall match at  any  position  after  the
4031         PCRE normally treats such a pattern as though it were preceded by \A.         first.  PCRE  normally treats such a pattern as though it were preceded
4032           by \A.
4033    
4034         In  cases  where  it  is known that the subject string contains no new-         In cases where it is known that the subject  string  contains  no  new-
4035         lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-         lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-
4036         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
4037    
4038         However,  there is one situation where the optimization cannot be used.         However, there is one situation where the optimization cannot be  used.
4039         When .*  is inside capturing parentheses that  are  the  subject  of  a         When  .*   is  inside  capturing  parentheses that are the subject of a
4040         backreference  elsewhere in the pattern, a match at the start may fail,         backreference elsewhere in the pattern, a match at the start  may  fail
4041         and a later one succeed. Consider, for example:         where a later one succeeds. Consider, for example:
4042    
4043           (.*)abc\1           (.*)abc\1
4044    
4045         If the subject is "xyz123abc123" the match point is the fourth  charac-         If  the subject is "xyz123abc123" the match point is the fourth charac-
4046         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
4047    
4048         When a capturing subpattern is repeated, the value captured is the sub-         When a capturing subpattern is repeated, the value captured is the sub-
# Line 3463  REPETITION Line 4051  REPETITION
4051           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+