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revision 77 by nigel, Sat Feb 24 21:40:45 2007 UTC revision 211 by ph10, Thu Aug 9 09:52:43 2007 UTC
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7  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
8    
9    
10    PCRE(3)                                                                PCRE(3)
11    
12    
13  NAME  NAME
14         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
# Line 16  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 51  INTRODUCTION Line 59  INTRODUCTION
59         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
60         functions, but which are not intended  for  use  by  external  callers.         functions, but which are not intended  for  use  by  external  callers.
61         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
62         any name clashes.         any name clashes. In some environments, it is possible to control which
63           external  symbols  are  exported when a shared library is built, and in
64           these cases the undocumented symbols are not exported.
65    
66    
67  USER DOCUMENTATION  USER DOCUMENTATION
# Line 63  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 73  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
91           pcresample        discussion of the sample program           pcresample        discussion of the sample program
92             pcrestack         discussion of stack usage
93           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
94    
95         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 94  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.  The maxi-         All values in repeating quantifiers must be less than 65536.
        mum number of capturing subpatterns is 65535.  
113    
114         There is no limit to the number of non-capturing subpatterns,  but  the         There is no limit to the number of parenthesized subpatterns, but there
115         maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,         can be no more than 65535 capturing subpatterns.
116         including capturing subpatterns, assertions, and other types of subpat-  
117         tern, is 200.         The maximum length of name for a named subpattern is 32 characters, and
118           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
122         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
123         inite repetition.  This means that the available stack space may  limit         inite repetition.  This means that the available stack space may  limit
124         the size of a subject string that can be processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
125           For a discussion of stack issues, see the pcrestack documentation.
126    
127    
128  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
# Line 126  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-
148         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
149         general  category  properties such as Lu for an upper case letter or Nd         general  category  properties such as Lu for an upper case letter or Nd
150         for a decimal number. A full list is given in the pcrepattern  documen-         for a decimal number, the Unicode script names such as Arabic  or  Han,
151         tation. The PCRE library is increased in size by about 90K when Unicode         and  the  derived  properties  Any  and L&. A full list is given in the
152         property support is included.         pcrepattern documentation. Only the short names for properties are sup-
153           ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
154         The following comments apply when PCRE is running in UTF-8 mode:         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
155           optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
156         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         does not support this.
157         subjects  are  checked for validity on entry to the relevant functions.  
158         If an invalid UTF-8 string is passed, an error return is given. In some     Validity of UTF-8 strings
159         situations,  you  may  already  know  that  your strings are valid, and  
160         therefore want to skip these checks in order to improve performance. If         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
161         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         subjects are (by default) checked for validity on entry to the relevant
162         PCRE assumes that the pattern or subject  it  is  given  (respectively)         functions. From release 7.3 of PCRE, the check is according  the  rules
163         contains  only valid UTF-8 codes. In this case, it does not diagnose an         of  RFC  3629, which are themselves derived from the Unicode specifica-
164         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
165         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
166         crash.         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
167           to U+DFFF.
168         2. In a pattern, the escape sequence \x{...}, where the contents of the  
169         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
170         character whose code number is the given hexadecimal number, for  exam-         which the Unicode Standard says this: "The Low Surrogate Area does  not
171         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,         contain  any  character  assignments,  consequently  no  character code
172         the item is not recognized.  This escape sequence can be used either as         charts or namelists are provided for this area. Surrogates are reserved
173         a literal, or within a character class.         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       General comments about UTF-8 mode
201    
202           1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
203           two-byte UTF-8 character if the value is greater than 127.
204    
205         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
206         UTF-8 character if the value is greater than 127.         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 180  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
237         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
238         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
239         used only for characters with higher values.         used only for characters with higher values. Even when Unicode property
240           support is available, PCRE supports case-insensitive matching only when
241           there  is  a  one-to-one  mapping between a letter's cases. There are a
242           small number of many-to-one mappings in Unicode;  these  are  not  sup-
243           ported by PCRE.
244    
245    
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    
 Last updated: 07 March 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
256    
257    REVISION
258    
259           Last updated: 09 August 2007
260           Copyright (c) 1997-2007 University of Cambridge.
261    ------------------------------------------------------------------------------
262    
263    
264    PCREBUILD(3)                                                      PCREBUILD(3)
265    
266    
267  NAME  NAME
# Line 222  PCRE BUILD-TIME OPTIONS Line 279  PCRE BUILD-TIME OPTIONS
279    
280           ./configure --help           ./configure --help
281    
282         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
283         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
284         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
285         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
286         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
287         not described.         is not described.
288    
289    
290    C++ SUPPORT
291    
292           By default, the configure script will search for a C++ compiler and C++
293           header files. If it finds them, it automatically builds the C++ wrapper
294           library for PCRE. You can disable this by adding
295    
296             --disable-cpp
297    
298           to the configure command.
299    
300    
301  UTF-8 SUPPORT  UTF-8 SUPPORT
# Line 255  UNICODE CHARACTER PROPERTY SUPPORT Line 323  UNICODE CHARACTER PROPERTY SUPPORT
323         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
324         not explicitly requested it.         not explicitly requested it.
325    
326         Including  Unicode  property  support  adds around 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
327         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
328         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.  
329    
330    
331  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
332    
333         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating
334         ter. This is the normal newline character on Unix-like systems. You can         the end of a line. This is the normal newline  character  on  Unix-like
335         compile PCRE to use character 13 (carriage return) instead by adding         systems. You can compile PCRE to use character 13 (carriage return, CR)
336           instead, by adding
337    
338           --enable-newline-is-cr           --enable-newline-is-cr
339    
340         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
341         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
342         line character.  
343           Alternatively, you can specify that line endings are to be indicated by
344           the two character sequence CRLF. If you want this, add
345    
346             --enable-newline-is-crlf
347    
348           to the configure command. There is a fourth option, specified by
349    
350             --enable-newline-is-anycrlf
351    
352           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
353           CRLF as indicating a line ending. Finally, a fifth option, specified by
354    
355             --enable-newline-is-any
356    
357           causes PCRE to recognize any Unicode newline sequence.
358    
359           Whatever line ending convention is selected when PCRE is built  can  be
360           overridden  when  the library functions are called. At build time it is
361           conventional to use the standard for your operating system.
362    
363    
364  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
# Line 302  POSIX MALLOC USAGE Line 389  POSIX MALLOC USAGE
389         to the configure command.         to the configure command.
390    
391    
 LIMITING PCRE RESOURCE USAGE  
   
        Internally,  PCRE has a function called match(), which it calls repeat-  
        edly  (possibly  recursively)  when  matching  a   pattern   with   the  
        pcre_exec()  function.  By controlling the maximum number of times this  
        function may be called during a single matching operation, a limit  can  
        be  placed  on  the resources used by a single call to pcre_exec(). The  
        limit can be changed at run time, as described in the pcreapi  documen-  
        tation.  The default is 10 million, but this can be changed by adding a  
        setting such as  
   
          --with-match-limit=500000  
   
        to  the  configure  command.  This  setting  has  no  effect   on   the  
        pcre_dfa_exec() matching function.  
   
   
392  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
393    
394         Within  a  compiled  pattern,  offset values are used to point from one         Within  a  compiled  pattern,  offset values are used to point from one
# Line 336  HANDLING VERY LARGE PATTERNS Line 406  HANDLING VERY LARGE PATTERNS
406         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
407         additional bytes when handling them.         additional bytes when handling them.
408    
        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.  
   
409    
410  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
411    
412         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
413         ing by making recursive calls to an internal function  called  match().         ing  by  making recursive calls to an internal function called match().
414         In  environments  where  the size of the stack is limited, this can se-         In environments where the size of the stack is limited,  this  can  se-
415         verely limit PCRE's operation. (The Unix environment does  not  usually         verely  limit  PCRE's operation. (The Unix environment does not usually
416         suffer  from  this  problem.)  An alternative approach that uses memory         suffer from this problem, but it may sometimes be necessary to increase
417         from the heap to remember data, instead  of  using  recursive  function         the  maximum  stack size.  There is a discussion in the pcrestack docu-
418         calls,  has been implemented to work round this problem. If you want to         mentation.) An alternative approach to recursion that uses memory  from
419         build a version of PCRE that works this way, add         the  heap  to remember data, instead of using recursive function calls,
420           has been implemented to work round the problem of limited  stack  size.
421           If you want to build a version of PCRE that works this way, add
422    
423           --disable-stack-for-recursion           --disable-stack-for-recursion
424    
425         to the configure command. With this configuration, PCRE  will  use  the         to  the  configure  command. With this configuration, PCRE will use the
426         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
427         ment functions. Separate functions are provided because  the  usage  is         ment  functions. By default these point to malloc() and free(), but you
428         very  predictable:  the  block sizes requested are always the same, and         can replace the pointers so that your own functions are used.
429         the blocks are always freed in reverse order. A calling  program  might  
430         be  able  to implement optimized functions that perform better than the         Separate functions are  provided  rather  than  using  pcre_malloc  and
431         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
432         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
433         function; it is not relevant for the the pcre_dfa_exec() function.         reverse  order.  A calling program might be able to implement optimized
434           functions that perform better  than  malloc()  and  free().  PCRE  runs
435           noticeably more slowly when built in this way. This option affects only
436           the  pcre_exec()  function;  it   is   not   relevant   for   the   the
437           pcre_dfa_exec() function.
438    
439    
440    LIMITING PCRE RESOURCE USAGE
441    
442           Internally,  PCRE has a function called match(), which it calls repeat-
443           edly  (sometimes  recursively)  when  matching  a  pattern   with   the
444           pcre_exec()  function.  By controlling the maximum number of times this
445           function may be called during a single matching operation, a limit  can
446           be  placed  on  the resources used by a single call to pcre_exec(). The
447           limit can be changed at run time, as described in the pcreapi  documen-
448           tation.  The default is 10 million, but this can be changed by adding a
449           setting such as
450    
451             --with-match-limit=500000
452    
453           to  the  configure  command.  This  setting  has  no  effect   on   the
454           pcre_dfa_exec() matching function.
455    
456           In  some  environments  it is desirable to limit the depth of recursive
457           calls of match() more strictly than the total number of calls, in order
458           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
459           for-recursion is specified) that is used. A second limit controls this;
460           it  defaults  to  the  value  that is set for --with-match-limit, which
461           imposes no additional constraints. However, you can set a  lower  limit
462           by adding, for example,
463    
464             --with-match-limit-recursion=10000
465    
466           to  the  configure  command.  This  value can also be overridden at run
467           time.
468    
469    
470    CREATING CHARACTER TABLES AT BUILD TIME
471    
472           PCRE uses fixed tables for processing characters whose code values  are
473           less  than 256. By default, PCRE is built with a set of tables that are
474           distributed in the file pcre_chartables.c.dist. These  tables  are  for
475           ASCII codes only. If you add
476    
477             --enable-rebuild-chartables
478    
479           to  the  configure  command, the distributed tables are no longer used.
480           Instead, a program called dftables is compiled and  run.  This  outputs
481           the source for new set of tables, created in the default locale of your
482           C runtime system. (This method of replacing the tables does not work if
483           you  are cross compiling, because dftables is run on the local host. If
484           you need to create alternative tables when cross  compiling,  you  will
485           have to do so "by hand".)
486    
487    
488  USING EBCDIC CODE  USING EBCDIC CODE
489    
490         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
491         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
492         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This  is  the  case for most computer operating systems. PCRE can, how-
493         adding         ever, be compiled to run in an EBCDIC environment by adding
494    
495           --enable-ebcdic           --enable-ebcdic
496    
497         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
498           bles.  You  should  only  use  it if you know that you are in an EBCDIC
499           environment (for example, an IBM mainframe operating system).
500    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
501    
502    SEE ALSO
503    
504           pcreapi(3), pcre_config(3).
505    
506    
507    AUTHOR
508    
509           Philip Hazel
510           University Computing Service
511           Cambridge CB2 3QH, England.
512    
513    
514    REVISION
515    
516           Last updated: 30 July 2007
517           Copyright (c) 1997-2007 University of Cambridge.
518    ------------------------------------------------------------------------------
519    
520    
521    PCREMATCHING(3)                                                PCREMATCHING(3)
522    
523    
524  NAME  NAME
# Line 412  PCRE MATCHING ALGORITHMS Line 550  PCRE MATCHING ALGORITHMS
550           <something> <something else> <something further>           <something> <something else> <something further>
551    
552         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
553         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
554    
555    
556  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 421  REGULAR EXPRESSIONS AS TREES Line 559  REGULAR EXPRESSIONS AS TREES
559         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
560         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
561         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
562         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
563         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
564         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
565    
566    
567  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
568    
569         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
570         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
571         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
572         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
573         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 453  THE STANDARD MATCHING ALGORITHM Line 591  THE STANDARD MATCHING ALGORITHM
591         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
592    
593    
594  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
595    
596         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
597         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
598         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
599         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
600         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",
601         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
602           keeps multiple states active simultaneously).
603         The  scan  continues until either the end of the subject is reached, or  
604         there are no more unterminated paths. At this point,  terminated  paths         The scan continues until either the end of the subject is  reached,  or
605         represent  the different matching possibilities (if there are none, the         there  are  no more unterminated paths. At this point, terminated paths
606         match has failed).  Thus, if there is more  than  one  possible  match,         represent the different matching possibilities (if there are none,  the
607           match  has  failed).   Thus,  if there is more than one possible match,
608         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-
609         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
610         match (which is necessarily the shortest) has been found.         match (which is necessarily the shortest) has been found.
611    
612         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 475  THE DFA MATCHING ALGORITHM Line 614  THE DFA MATCHING ALGORITHM
614    
615           cat(er(pillar)?)           cat(er(pillar)?)
616    
617         is matched against the string "the caterpillar catchment",  the  result         is  matched  against the string "the caterpillar catchment", the result
618         will  be the three strings "cat", "cater", and "caterpillar" that start         will be the three strings "cat", "cater", and "caterpillar" that  start
619         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
620         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
621    
622         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
623         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
624    
625         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1.  Because  the  algorithm  finds  all possible matches, the greedy or
626         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
627         ungreedy quantifiers are treated in exactly the same way.         ungreedy quantifiers are treated in exactly the same way. However, pos-
628           sessive quantifiers can make a difference when what follows could  also
629           match what is quantified, for example in a pattern like this:
630    
631             ^a++\w!
632    
633           This  pattern matches "aaab!" but not "aaa!", which would be matched by
634           a non-possessive quantifier. Similarly, if an atomic group is  present,
635           it  is matched as if it were a standalone pattern at the current point,
636           and the longest match is then "locked in" for the rest of  the  overall
637           pattern.
638    
639         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
640         is  not  straightforward  to  keep track of captured substrings for the         is not straightforward to keep track of  captured  substrings  for  the
641         different matching possibilities, and  PCRE's  implementation  of  this         different  matching  possibilities,  and  PCRE's implementation of this
642         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-
643         strings are available.         strings are available.
644    
645         3. Because no substrings are captured, back references within the  pat-         3.  Because no substrings are captured, back references within the pat-
646         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
647    
648         4.  For  the same reason, conditional expressions that use a backrefer-         4. For the same reason, conditional expressions that use  a  backrefer-
649         ence as the condition are not supported.         ence  as  the  condition or test for a specific group recursion are not
650           supported.
651    
652         5. Callouts are supported, but the value of the  capture_top  field  is         5. Because many paths through the tree may be  active,  the  \K  escape
653           sequence, which resets the start of the match when encountered (but may
654           be on some paths and not on others), is not  supported.  It  causes  an
655           error if encountered.
656    
657           6.  Callouts  are  supported, but the value of the capture_top field is
658         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.
659    
660         6.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
661         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-
662         rithm moves through the subject string one character at a time, for all         tive algorithm moves through the subject  string  one  character  at  a
663         active paths through the tree.         time, for all active paths through the tree.
664    
665           8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-
666           ported.
667    
668    
669  ADVANTAGES OF THE DFA ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
670    
671         Using the DFA matching algorithm provides the following advantages:         Using the alternative matching algorithm provides the following  advan-
672           tages:
673    
674         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-
675         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
676         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
677         things with callouts.         things with callouts.
678    
679         2.  There is much better support for partial matching. The restrictions         2. There is much better support for partial matching. The  restrictions
680         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-
681         rithm  for partial matching do not apply to the DFA algorithm. For non-         rithm for partial matching do not apply to the  alternative  algorithm.
682         anchored patterns, the starting position of a partial match  is  avail-         For  non-anchored patterns, the starting position of a partial match is
683         able.         available.
684    
685         3.  Because  the  DFA algorithm scans the subject string just once, and         3. Because the alternative algorithm  scans  the  subject  string  just
686         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
687         strings  to  the matching function in several pieces, checking for par-         subject strings to the matching function in  several  pieces,  checking
688         tial matching each time.         for partial matching each time.
689    
690    
691  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
692    
693         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
694    
695         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
696         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
697         because it is less susceptible to optimization.         because it is less susceptible to optimization.
698    
699         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
700    
701         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
702         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
        rithm.  
703    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
704    
705    AUTHOR
706    
707           Philip Hazel
708           University Computing Service
709           Cambridge CB2 3QH, England.
710    
711    
712    REVISION
713    
714           Last updated: 08 August 2007
715           Copyright (c) 1997-2007 University of Cambridge.
716    ------------------------------------------------------------------------------
717    
718    
719    PCREAPI(3)                                                          PCREAPI(3)
720    
721    
722  NAME  NAME
# Line 595  PCRE NATIVE API Line 765  PCRE NATIVE API
765         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
766              const char *name);              const char *name);
767    
768           int pcre_get_stringtable_entries(const pcre *code,
769                const char *name, char **first, char **last);
770    
771         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
772              int stringcount, int stringnumber,              int stringcount, int stringnumber,
773              const char **stringptr);              const char **stringptr);
# Line 633  PCRE NATIVE API Line 806  PCRE NATIVE API
806  PCRE API OVERVIEW  PCRE API OVERVIEW
807    
808         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
809         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
810         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
811         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
812         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 655  PCRE API OVERVIEW Line 828  PCRE API OVERVIEW
828    
829         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
830         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
831         ing. This allows it to find all possible matches (at a given  point  in         ing. The alternative algorithm finds all possible matches (at  a  given
832         the  subject),  not  just  one. However, this algorithm does not return         point  in  the subject), and scans the subject just once. However, this
833         captured substrings. A description of the two matching  algorithms  and         algorithm does not return captured substrings. A description of the two
834         their  advantages  and disadvantages is given in the pcrematching docu-         matching  algorithms and their advantages and disadvantages is given in
835         mentation.         the pcrematching documentation.
836    
837         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
838         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 671  PCRE API OVERVIEW Line 844  PCRE API OVERVIEW
844           pcre_get_named_substring()           pcre_get_named_substring()
845           pcre_get_substring_list()           pcre_get_substring_list()
846           pcre_get_stringnumber()           pcre_get_stringnumber()
847             pcre_get_stringtable_entries()
848    
849         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
850         to free the memory used for extracted strings.         to free the memory used for extracted strings.
# Line 702  PCRE API OVERVIEW Line 876  PCRE API OVERVIEW
876         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
877         are used only when PCRE is compiled to use  the  heap  for  remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
878         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
879         function. This is a non-standard way of building PCRE, for use in envi-         function. See the pcrebuild documentation for  details  of  how  to  do
880         ronments that have limited stacks. Because of the greater use of memory         this.  It  is  a non-standard way of building PCRE, for use in environ-
881         management, it runs more slowly.  Separate functions  are  provided  so         ments that have limited stacks. Because of the greater  use  of  memory
882         that  special-purpose  external  code  can  be used for this case. When         management,  it  runs  more  slowly. Separate functions are provided so
883         used, these functions are always called in a  stack-like  manner  (last         that special-purpose external code can be  used  for  this  case.  When
884         obtained,  first freed), and always for memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
885           obtained, first freed), and always for memory blocks of the same  size.
886           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
887           mentation.
888    
889         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
890         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 715  PCRE API OVERVIEW Line 892  PCRE API OVERVIEW
892         pcrecallout documentation.         pcrecallout documentation.
893    
894    
895    NEWLINES
896    
897           PCRE  supports five different conventions for indicating line breaks in
898           strings: a single CR (carriage return) character, a  single  LF  (line-
899           feed) character, the two-character sequence CRLF, any of the three pre-
900           ceding, or any Unicode newline sequence. The Unicode newline  sequences
901           are  the  three just mentioned, plus the single characters VT (vertical
902           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
903           separator, U+2028), and PS (paragraph separator, U+2029).
904    
905           Each  of  the first three conventions is used by at least one operating
906           system as its standard newline sequence. When PCRE is built, a  default
907           can  be  specified.  The default default is LF, which is the Unix stan-
908           dard. When PCRE is run, the default can be overridden,  either  when  a
909           pattern is compiled, or when it is matched.
910    
911           In the PCRE documentation the word "newline" is used to mean "the char-
912           acter or pair of characters that indicate a line break". The choice  of
913           newline  convention  affects  the  handling of the dot, circumflex, and
914           dollar metacharacters, the handling of #-comments in /x mode, and, when
915           CRLF  is a recognized line ending sequence, the match position advance-
916           ment for a non-anchored pattern. The choice of newline convention  does
917           not affect the interpretation of the \n or \r escape sequences.
918    
919    
920  MULTITHREADING  MULTITHREADING
921    
922         The  PCRE  functions  can be used in multi-threading applications, with         The  PCRE  functions  can be used in multi-threading applications, with
# Line 732  SAVING PRECOMPILED PATTERNS FOR LATER US Line 934  SAVING PRECOMPILED PATTERNS FOR LATER US
934         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
935         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
936         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
937         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
938           with  one version of PCRE for use with a different version is not guar-
939           anteed to work and may cause crashes.
940    
941    
942  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 761  CHECKING BUILD-TIME OPTIONS Line 965  CHECKING BUILD-TIME OPTIONS
965    
966           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
967    
968         The output is an integer that is set to the value of the code  that  is         The output is an integer whose value specifies  the  default  character
969         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
970         return (13), and should normally be the  standard  character  for  your         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
971         operating system.         and  -1  for  ANY. The default should normally be the standard sequence
972           for your operating system.
973    
974           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
975    
976         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
977         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
978         4.  Larger  values  allow larger regular expressions to be compiled, at         4. Larger values allow larger regular expressions to  be  compiled,  at
979         the expense of slower matching. The default value of  2  is  sufficient         the  expense  of  slower matching. The default value of 2 is sufficient
980         for  all  but  the  most massive patterns, since it allows the compiled         for all but the most massive patterns, since  it  allows  the  compiled
981         pattern to be up to 64K in size.         pattern to be up to 64K in size.
982    
983           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
984    
985         The output is an integer that contains the threshold  above  which  the         The  output  is  an integer that contains the threshold above which the
986         POSIX  interface  uses malloc() for output vectors. Further details are         POSIX interface uses malloc() for output vectors. Further  details  are
987         given in the pcreposix documentation.         given in the pcreposix documentation.
988    
989           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
990    
991         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
992         internal  matching  function  calls in a pcre_exec() execution. Further         internal matching function calls in a  pcre_exec()  execution.  Further
993         details are given with pcre_exec() below.         details are given with pcre_exec() below.
994    
995             PCRE_CONFIG_MATCH_LIMIT_RECURSION
996    
997           The  output is an integer that gives the default limit for the depth of
998           recursion when calling the internal matching function in a  pcre_exec()
999           execution. Further details are given with pcre_exec() below.
1000    
1001           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1002    
1003         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
1004         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1005         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
1006         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
1007         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1008         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1009         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1010    
1011    
# Line 811  COMPILING A PATTERN Line 1022  COMPILING A PATTERN
1022    
1023         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1024         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1025         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1026         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1027    
1028         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
1029         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
1030         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1031         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
1032         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1033         It is up to the caller  to  free  the  memory  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1034         required.         longer required.
1035    
1036         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
1037         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
1038         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1039         ment, which is an address (see below).         ment, which is an address (see below).
1040    
1041         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1042         tion.  It  should  be  zero  if  no options are required. The available         pilation. It should be zero if no options are required.  The  available
1043         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them, in particular, those that
1044         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
1045         pattern (see the detailed description  in  the  pcrepattern  documenta-         pattern  (see  the  detailed  description in the pcrepattern documenta-
1046         tion).  For  these options, the contents of the options argument speci-         tion). For these options, the contents of the options  argument  speci-
1047         fies their initial settings at the start of compilation and  execution.         fies  their initial settings at the start of compilation and execution.
1048         The  PCRE_ANCHORED option can be set at the time of matching as well as         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time
1049         at compile time.         of matching as well as at compile time.
1050    
1051         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1052         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1053         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-
1054         sage.  The  offset from the start of the pattern to the character where         sage. This is a static string that is part of the library. You must not
1055         the error was discovered is  placed  in  the  variable  pointed  to  by         try to free it. The offset from the start of the pattern to the charac-
1056         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         ter where the error was discovered is placed in the variable pointed to
1057           by  erroffset,  which must not be NULL. If it is, an immediate error is
1058         given.         given.
1059    
1060         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
# Line 905  COMPILING A PATTERN Line 1117  COMPILING A PATTERN
1117    
1118         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
1119         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
1120         matches immediately before the final character if it is a newline  (but         matches immediately before a newline at the end of the string (but  not
1121         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
1122         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
1123         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1124    
1125           PCRE_DOTALL           PCRE_DOTALL
1126    
1127         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-
1128         acters, including newlines. Without it,  newlines  are  excluded.  This         acters, including those that indicate newline. Without it, a  dot  does
1129         option  is equivalent to Perl's /s option, and it can be changed within         not  match  when  the  current position is at a newline. This option is
1130         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]         equivalent to Perl's /s option, and it can be changed within a  pattern
1131         always  matches a newline character, independent of the setting of this         by  a (?s) option setting. A negative class such as [^a] always matches
1132         option.         newline characters, independent of the setting of this option.
1133    
1134             PCRE_DUPNAMES
1135    
1136           If this bit is set, names used to identify capturing  subpatterns  need
1137           not be unique. This can be helpful for certain types of pattern when it
1138           is known that only one instance of the named  subpattern  can  ever  be
1139           matched.  There  are  more details of named subpatterns below; see also
1140           the pcrepattern documentation.
1141    
1142           PCRE_EXTENDED           PCRE_EXTENDED
1143    
# Line 925  COMPILING A PATTERN Line 1145  COMPILING A PATTERN
1145         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1146         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1147         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1148         line character, inclusive, are also  ignored.  This  is  equivalent  to         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
1149         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)         option,  and  it  can be changed within a pattern by a (?x) option set-
1150         option setting.         ting.
1151    
1152         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1153         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
# Line 943  COMPILING A PATTERN Line 1163  COMPILING A PATTERN
1163         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1164         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1165         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
1166         literal. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give a warning for  this.)
1167         option. It can also be set by a (?X) option setting within a pattern.         There  are  at  present no other features controlled by this option. It
1168           can also be set by a (?X) option setting within a pattern.
1169    
1170           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1171    
1172         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1173         before or at the first newline character in the subject string,  though         before  or  at  the  first  newline  in  the subject string, though the
1174         the matched text may continue over the newline.         matched text may continue over the newline.
1175    
1176           PCRE_MULTILINE           PCRE_MULTILINE
1177    
1178         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1179         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1180         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1181         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1182         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1183         is set). This is the same as Perl.         is set). This is the same as Perl.
1184    
1185         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"
1186         constructs  match  immediately following or immediately before any new-         constructs match immediately following or immediately  before  internal
1187         line in the subject string, respectively, as well as at the very  start         newlines  in  the  subject string, respectively, as well as at the very
1188         and  end. This is equivalent to Perl's /m option, and it can be changed         start and end. This is equivalent to Perl's /m option, and  it  can  be
1189         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
1190         ters  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,
1191         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1192    
1193             PCRE_NEWLINE_CR
1194             PCRE_NEWLINE_LF
1195             PCRE_NEWLINE_CRLF
1196             PCRE_NEWLINE_ANYCRLF
1197             PCRE_NEWLINE_ANY
1198    
1199           These  options  override the default newline definition that was chosen
1200           when PCRE was built. Setting the first or the second specifies  that  a
1201           newline  is  indicated  by a single character (CR or LF, respectively).
1202           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1203           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1204           that any of the three preceding sequences should be recognized. Setting
1205           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1206           recognized. The Unicode newline sequences are the three just mentioned,
1207           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1208           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1209           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1210           UTF-8 mode.
1211    
1212           The newline setting in the  options  word  uses  three  bits  that  are
1213           treated as a number, giving eight possibilities. Currently only six are
1214           used (default plus the five values above). This means that if  you  set
1215           more  than one newline option, the combination may or may not be sensi-
1216           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1217           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1218           cause an error.
1219    
1220           The only time that a line break is specially recognized when  compiling
1221           a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
1222           character class is encountered. This indicates  a  comment  that  lasts
1223           until  after the next line break sequence. In other circumstances, line
1224           break  sequences  are  treated  as  literal  data,   except   that   in
1225           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1226           and are therefore ignored.
1227    
1228           The newline option that is set at compile time becomes the default that
1229           is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1230    
1231           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1232    
1233         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-
# Line 996  COMPILING A PATTERN Line 1255  COMPILING A PATTERN
1255           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1256    
1257         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
1258         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1259         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
1260         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
1261         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-
1262         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
1263         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
1264         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
1265         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1266           UTF-8 validity checking of subject strings.
1267    
1268    
1269  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1270    
1271         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1272         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1273         both compiling functions.         both  compiling functions. As PCRE has developed, some error codes have
1274           fallen out of use. To avoid confusion, they have not been re-used.
1275    
1276            0  no error            0  no error
1277            1  \ at end of pattern            1  \ at end of pattern
# Line 1022  COMPILATION ERROR CODES Line 1283  COMPILATION ERROR CODES
1283            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1284            8  range out of order in character class            8  range out of order in character class
1285            9  nothing to repeat            9  nothing to repeat
1286           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1287           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1288           12  unrecognized character after (?           12  unrecognized character after (?
1289           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
# Line 1031  COMPILATION ERROR CODES Line 1292  COMPILATION ERROR CODES
1292           16  erroffset passed as NULL           16  erroffset passed as NULL
1293           17  unknown option bit(s) set           17  unknown option bit(s) set
1294           18  missing ) after comment           18  missing ) after comment
1295           19  parentheses nested too deeply           19  [this code is not in use]
1296           20  regular expression too large           20  regular expression too large
1297           21  failed to get memory           21  failed to get memory
1298           22  unmatched parentheses           22  unmatched parentheses
1299           23  internal error: code overflow           23  internal error: code overflow
1300           24  unrecognized character after (?<           24  unrecognized character after (?<
1301           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1302           26  malformed number after (?(           26  malformed number or name after (?(
1303           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1304           28  assertion expected after (?(           28  assertion expected after (?(
1305           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1306           30  unknown POSIX class name           30  unknown POSIX class name
1307           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1308           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1309           33  spare error           33  [this code is not in use]
1310           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1311           35  invalid condition (?(0)           35  invalid condition (?(0)
1312           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1054  COMPILATION ERROR CODES Line 1315  COMPILATION ERROR CODES
1315           39  closing ) for (?C expected           39  closing ) for (?C expected
1316           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1317           41  unrecognized character after (?P           41  unrecognized character after (?P
1318           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1319           43  two named groups have the same name           43  two named subpatterns have the same name
1320           44  invalid UTF-8 string           44  invalid UTF-8 string
1321           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1322           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1323           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1324             48  subpattern name is too long (maximum 32 characters)
1325             49  too many named subpatterns (maximum 10,000)
1326             50  [this code is not in use]
1327             51  octal value is greater than \377 (not in UTF-8 mode)
1328             52  internal error: overran compiling workspace
1329             53  internal  error:  previously-checked  referenced  subpattern  not
1330           found
1331             54  DEFINE group contains more than one branch
1332             55  repeating a DEFINE group is not allowed
1333             56  inconsistent NEWLINE options"
1334             57  \g is not followed by a braced name or an optionally braced
1335                   non-zero number
1336             58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
1337    
1338    
1339  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1067  STUDYING A PATTERN Line 1341  STUDYING A PATTERN
1341         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1342              const char **errptr);              const char **errptr);
1343    
1344         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
1345         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
1346         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1347         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1348         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1349         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
1350         the results of the study.         the results of the study.
1351    
1352         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1353         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1354         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
1355         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1356    
1357         If  studying  the  pattern  does not produce any additional information         If studying the pattern does not  produce  any  additional  information
1358         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1359         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
1360         its own pcre_extra block.         its own pcre_extra block.
1361    
1362         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1363         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1364    
1365         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.
1366         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1367         points  to  is set to NULL. Otherwise it points to a textual error mes-         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1368         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1369         ing pcre_study(), to be sure that it has run successfully.         must not try to free it. You should test the  error  pointer  for  NULL
1370           after calling pcre_study(), to be sure that it has run successfully.
1371    
1372         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1373    
# Line 1110  STUDYING A PATTERN Line 1385  STUDYING A PATTERN
1385  LOCALE SUPPORT  LOCALE SUPPORT
1386    
1387         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1388         letters digits, or whatever, by reference to a set of  tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1389         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
1390         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. Higher-valued  codes  never  match
1391         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
1392         with Unicode character property support.         with Unicode character property support. The use of locales  with  Uni-
1393           code  is discouraged. If you are handling characters with codes greater
1394         An internal set of tables is created in the default C locale when  PCRE         than 128, you should either use UTF-8 and Unicode, or use locales,  but
1395         is  built.  This  is  used when the final argument of pcre_compile() is         not try to mix the two.
1396         NULL, and is sufficient for many applications. An  alternative  set  of  
1397         tables  can,  however, be supplied. These may be created in a different         PCRE  contains  an  internal set of tables that are used when the final
1398         locale from the default. As more and more applications change to  using         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1399         Unicode, the need for this locale support is expected to die away.         applications.  Normally, the internal tables recognize only ASCII char-
1400           acters. However, when PCRE is built, it is possible to cause the inter-
1401           nal tables to be rebuilt in the default "C" locale of the local system,
1402           which may cause them to be different.
1403    
1404           The internal tables can always be overridden by tables supplied by  the
1405           application that calls PCRE. These may be created in a different locale
1406           from the default. As more and more applications change  to  using  Uni-
1407           code, the need for this locale support is expected to die away.
1408    
1409         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
1410         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 1134  LOCALE SUPPORT Line 1417  LOCALE SUPPORT
1417           tables = pcre_maketables();           tables = pcre_maketables();
1418           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1419    
1420         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;
1421         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".
1422         that the memory containing the tables remains available for as long  as  
1423           When  pcre_maketables()  runs,  the  tables are built in memory that is
1424           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1425           that  the memory containing the tables remains available for as long as
1426         it is needed.         it is needed.
1427    
1428         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
1429         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()
1430         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-
1431         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1432         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1433    
1434         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
1435         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1436         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
1437         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
1438         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1439    
# Line 1157  INFORMATION ABOUT A PATTERN Line 1443  INFORMATION ABOUT A PATTERN
1443         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1444              int what, void *where);              int what, void *where);
1445    
1446         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1447         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1448         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1449    
1450         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1451         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
1452         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1453         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
1454         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
1455         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1456    
1457           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1173  INFORMATION ABOUT A PATTERN Line 1459  INFORMATION ABOUT A PATTERN
1459           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1460           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1461    
1462         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
1463         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1464         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1465         pattern:         pattern:
1466    
1467           int rc;           int rc;
1468           unsigned long int length;           size_t length;
1469           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1470             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1471             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1472             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1473             &length);         /* where to put the data */             &length);         /* where to put the data */
1474    
1475         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
1476         are as follows:         are as follows:
1477    
1478           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1479    
1480         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1481         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1482         there are no back references.         there are no back references.
1483    
1484           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1485    
1486         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1487         argument should point to an int variable.         argument should point to an int variable.
1488    
1489           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1490    
1491         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1492         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1493         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1494         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1495         passing a NULL table pointer.         passing a NULL table pointer.
1496    
1497           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1498    
1499         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1500         non-anchored   pattern.   (This    option    used    to    be    called         non-anchored  pattern. The fourth argument should point to an int vari-
1501         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1502         compatibility.)         is still recognized for backwards compatibility.)
1503    
1504         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
1505         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.         (cat|cow|coyote), its value is returned. Otherwise, if either
        Otherwise, if either  
1506    
1507         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1508         branch starts with "^", or         branch starts with "^", or
# Line 1237  INFORMATION ABOUT A PATTERN Line 1522  INFORMATION ABOUT A PATTERN
1522         returned.  The fourth argument should point to an unsigned char * vari-         returned.  The fourth argument should point to an unsigned char * vari-
1523         able.         able.
1524    
1525             PCRE_INFO_JCHANGED
1526    
1527           Return 1 if the (?J) option setting is used in the  pattern,  otherwise
1528           0. The fourth argument should point to an int variable. The (?J) inter-
1529           nal option setting changes the local PCRE_DUPNAMES option.
1530    
1531           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1532    
1533         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 1253  INFORMATION ABOUT A PATTERN Line 1544  INFORMATION ABOUT A PATTERN
1544    
1545         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1546         ses.  The names are just an additional way of identifying the parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1547         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
1548         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring()  are  provided  for extracting captured sub-
1549         captured substring by name. It is also possible  to  extract  the  data         strings by name. It is also possible to extract the data  directly,  by
1550         directly,  by  first converting the name to a number in order to access         first  converting  the  name to a number in order to access the correct
1551         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
1552         below).  To  do the conversion, you need to use the name-to-number map,         the  conversion,  you  need  to  use  the  name-to-number map, which is
1553         which is described by these three values.         described by these three values.
1554    
1555         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1556         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
# Line 1269  INFORMATION ABOUT A PATTERN Line 1560  INFORMATION ABOUT A PATTERN
1560         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1561         sis, most significant byte first. The rest of the entry is  the  corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1562         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1563         For example, consider the following pattern  (assume  PCRE_EXTENDED  is         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1564         set, so white space - including newlines - is ignored):         theses  numbers.  For  example,  consider the following pattern (assume
1565           PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
1566           ignored):
1567    
1568           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1569           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1570    
1571         There  are  four  named subpatterns, so the table has four entries, and         There  are  four  named subpatterns, so the table has four entries, and
1572         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 1286  INFORMATION ABOUT A PATTERN Line 1579  INFORMATION ABOUT A PATTERN
1579           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1580    
1581         When writing code to extract data  from  named  subpatterns  using  the         When writing code to extract data  from  named  subpatterns  using  the
1582         name-to-number map, remember that the length of each entry is likely to         name-to-number  map,  remember that the length of the entries is likely
1583         be different for each compiled pattern.         to be different for each compiled pattern.
1584    
1585             PCRE_INFO_OKPARTIAL
1586    
1587           Return 1 if the pattern can be used for partial matching, otherwise  0.
1588           The  fourth  argument  should point to an int variable. The pcrepartial
1589           documentation lists the restrictions that apply to patterns  when  par-
1590           tial matching is used.
1591    
1592           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1593    
1594         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
1595         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1596         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1597         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1598           other  words,  they are the options that will be in force when matching
1599           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1600           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1601           and PCRE_EXTENDED.
1602    
1603         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
1604         alternatives begin with one of the following:         alternatives begin with one of the following:
1605    
1606           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1310  INFORMATION ABOUT A PATTERN Line 1614  INFORMATION ABOUT A PATTERN
1614    
1615           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1616    
1617         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
1618         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
1619         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
1620         size_t variable.         size_t variable.
# Line 1318  INFORMATION ABOUT A PATTERN Line 1622  INFORMATION ABOUT A PATTERN
1622           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1623    
1624         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
1625         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
1626         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
1627         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
1628         variable.         variable.
1629    
1630    
# Line 1328  OBSOLETE INFO FUNCTION Line 1632  OBSOLETE INFO FUNCTION
1632    
1633         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1634    
1635         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1636         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1637         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1638         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-
1639         lowing negative numbers:         lowing negative numbers:
1640    
1641           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1642           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1643    
1644         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
1645         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
1646         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1647    
1648         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1649         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
1650         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1651    
1652    
# Line 1350  REFERENCE COUNTS Line 1654  REFERENCE COUNTS
1654    
1655         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1656    
1657         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1658         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
1659         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1660         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1661         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.
1662    
1663         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1664         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
1665         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
1666         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
1667         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
1668         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1669    
1670         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1671         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
1672         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1673    
1674    
# Line 1374  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1678  MATCHING A PATTERN: THE TRADITIONAL FUNC
1678              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1679              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1680    
1681         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
1682         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1683         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
1684         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1685         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
1686         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1687         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1688    
1689         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1690         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1691         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
1692         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1693         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1694    
1695         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1404  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1708  MATCHING A PATTERN: THE TRADITIONAL FUNC
1708    
1709     Extra data for pcre_exec()     Extra data for pcre_exec()
1710    
1711         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
1712         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
1713         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-
1714         tional  information in it. The fields in a pcre_extra block are as fol-         tional information in it. The pcre_extra block contains  the  following
1715         lows:         fields (not necessarily in this order):
1716    
1717           unsigned long int flags;           unsigned long int flags;
1718           void *study_data;           void *study_data;
1719           unsigned long int match_limit;           unsigned long int match_limit;
1720             unsigned long int match_limit_recursion;
1721           void *callout_data;           void *callout_data;
1722           const unsigned char *tables;           const unsigned char *tables;
1723    
1724         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
1725         are set. The flag bits are:         are set. The flag bits are:
1726    
1727           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1728           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1729             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1730           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1731           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1732    
1733         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
1734         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1735         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
1736         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1737         flag bits.         flag bits.
1738    
1739         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
1740         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
1741         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1742         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees.  The  classic  example  is  the  use of nested unlimited
1743         repeats.         repeats.
1744    
1745         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1746         edly (sometimes recursively). The limit is imposed  on  the  number  of         edly  (sometimes  recursively). The limit set by match_limit is imposed
1747         times  this  function is called during a match, which has the effect of         on the number of times this function is called during  a  match,  which
1748         limiting the amount of recursion and backtracking that can take  place.         has  the  effect  of  limiting the amount of backtracking that can take
1749         For patterns that are not anchored, the count starts from zero for each         place. For patterns that are not anchored, the count restarts from zero
1750         position in the subject string.         for each position in the subject string.
1751    
1752         The default limit for the library can be set when PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
1753         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1754         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1755         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra    block    in    which    match_limit    is    set,     and
1756         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
1757         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1758    
1759         The  pcre_callout  field is used in conjunction with the "callout" fea-         The match_limit_recursion field is similar to match_limit, but  instead
1760           of limiting the total number of times that match() is called, it limits
1761           the depth of recursion. The recursion depth is a  smaller  number  than
1762           the  total number of calls, because not all calls to match() are recur-
1763           sive.  This limit is of use only if it is set smaller than match_limit.
1764    
1765           Limiting  the  recursion  depth  limits the amount of stack that can be
1766           used, or, when PCRE has been compiled to use memory on the heap instead
1767           of the stack, the amount of heap memory that can be used.
1768    
1769           The  default  value  for  match_limit_recursion can be set when PCRE is
1770           built; the default default  is  the  same  value  as  the  default  for
1771           match_limit.  You can override the default by suppling pcre_exec() with
1772           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1773           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1774           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1775    
1776           The pcre_callout field is used in conjunction with the  "callout"  fea-
1777         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1778    
1779         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
1780         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
1781         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
1782         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
1783         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
1784         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-
1785         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
1786         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
1787         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
1788         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1789    
1790     Option bits for pcre_exec()     Option bits for pcre_exec()
1791    
1792         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.
1793         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
1794         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1795           PCRE_PARTIAL.
1796    
1797           PCRE_ANCHORED           PCRE_ANCHORED
1798    
# Line 1477  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1801  MATCHING A PATTERN: THE TRADITIONAL FUNC
1801         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
1802         unachored at matching time.         unachored at matching time.
1803    
1804             PCRE_NEWLINE_CR
1805             PCRE_NEWLINE_LF
1806             PCRE_NEWLINE_CRLF
1807             PCRE_NEWLINE_ANYCRLF
1808             PCRE_NEWLINE_ANY
1809    
1810           These options override  the  newline  definition  that  was  chosen  or
1811           defaulted  when the pattern was compiled. For details, see the descrip-
1812           tion of pcre_compile()  above.  During  matching,  the  newline  choice
1813           affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
1814           ters. It may also alter the way the match position is advanced after  a
1815           match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,
1816           PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt
1817           fails  when the current position is at a CRLF sequence, the match posi-
1818           tion is advanced by two characters instead of one, in other  words,  to
1819           after the CRLF.
1820    
1821           PCRE_NOTBOL           PCRE_NOTBOL
1822    
1823         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1824         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
1825         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
1826         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
1827         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1828    
1829           PCRE_NOTEOL           PCRE_NOTEOL
1830    
1831         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
1832         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
1833         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
1834         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1835         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
1836         not affect \Z or \z.         not affect \Z or \z.
1837    
1838           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1839    
1840         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
1841         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
1842         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
1843         example, if the pattern         example, if the pattern
1844    
1845           a?b?           a?b?
1846    
1847         is applied to a string not beginning with "a" or "b",  it  matches  the         is  applied  to  a string not beginning with "a" or "b", it matches the
1848         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
1849         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
1850         rences of "a" or "b".         rences of "a" or "b".
1851    
1852         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
1853         cial case of a pattern match of the empty  string  within  its  split()         cial  case  of  a  pattern match of the empty string within its split()
1854         function,  and  when  using  the /g modifier. It is possible to emulate         function, and when using the /g modifier. It  is  possible  to  emulate
1855         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
1856         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
1857         if that fails by advancing the starting offset (see below)  and  trying         if  that  fails by advancing the starting offset (see below) and trying
1858         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
1859         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
1860    
1861           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1862    
1863         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
1864         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
1865         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
1866         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
1867         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
1868         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
1869         returned.         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
1870           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1871    
1872         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
1873         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1612  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1954  MATCHING A PATTERN: THE TRADITIONAL FUNC
1954         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-
1955         tor[1],  identify  the  portion  of  the  subject string matched by the         tor[1],  identify  the  portion  of  the  subject string matched by the
1956         entire pattern. The next pair is used for the first  capturing  subpat-         entire pattern. The next pair is used for the first  capturing  subpat-
1957         tern,  and  so  on.  The value returned by pcre_exec() is the number of         tern, and so on. The value returned by pcre_exec() is one more than the
1958         pairs that have been set. If there are no  capturing  subpatterns,  the         highest numbered pair that has been set. For example, if two substrings
1959         return  value  from  a  successful match is 1, indicating that just the         have  been captured, the returned value is 3. If there are no capturing
1960         first pair of offsets has been set.         subpatterns, the return value from a successful match is 1,  indicating
1961           that just the first pair of offsets has been set.
        Some convenience functions are provided  for  extracting  the  captured  
        substrings  as  separate  strings. These are described in the following  
        section.  
   
        It is possible for an capturing subpattern number  n+1  to  match  some  
        part  of  the  subject  when subpattern n has not been used at all. For  
        example, if the string "abc" is matched against the pattern (a|(z))(bc)  
        subpatterns  1 and 3 are matched, but 2 is not. When this happens, both  
        offset values corresponding to the unused subpattern are set to -1.  
1962    
1963         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
1964         of the string that it matched that is returned.         of the string that it matched that is returned.
1965    
1966         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,
1967         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
1968         function  returns a value of zero. In particular, if the substring off-         function returns a value of zero. In particular, if the substring  off-
1969         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
1970         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         as NULL and ovecsize as zero. However, if  the  pattern  contains  back
1971         references and the ovector is not big enough to  remember  the  related         references  and  the  ovector is not big enough to remember the related
1972         substrings,  PCRE has to get additional memory for use during matching.         substrings, PCRE has to get additional memory for use during  matching.
1973         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
1974    
1975         Note that pcre_info() can be used to find out how many  capturing  sub-         The  pcre_info()  function  can  be used to find out how many capturing
1976         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns there are in a compiled  pattern.  The  smallest  size  for
1977         that will allow for n captured substrings, in addition to  the  offsets         ovector  that  will allow for n captured substrings, in addition to the
1978         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.
1979    
1980           It is possible for capturing subpattern number n+1 to match  some  part
1981           of the subject when subpattern n has not been used at all. For example,
1982           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
1983           return from the function is 4, and subpatterns 1 and 3 are matched, but
1984           2 is not. When this happens, both values in  the  offset  pairs  corre-
1985           sponding to unused subpatterns are set to -1.
1986    
1987           Offset  values  that correspond to unused subpatterns at the end of the
1988           expression are also set to -1. For example,  if  the  string  "abc"  is
1989           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
1990           matched. The return from the function is 2, because  the  highest  used
1991           capturing subpattern number is 1. However, you can refer to the offsets
1992           for the second and third capturing subpatterns if  you  wish  (assuming
1993           the vector is large enough, of course).
1994    
1995           Some  convenience  functions  are  provided for extracting the captured
1996           substrings as separate strings. These are described below.
1997    
1998     Return values from pcre_exec()     Error return values from pcre_exec()
1999    
2000         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2001         defined in the header file:         defined in the header file:
2002    
2003           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1655  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2006  MATCHING A PATTERN: THE TRADITIONAL FUNC
2006    
2007           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2008    
2009         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
2010         ovecsize was not zero.         ovecsize was not zero.
2011    
2012           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1664  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2015  MATCHING A PATTERN: THE TRADITIONAL FUNC
2015    
2016           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2017    
2018         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,
2019         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
2020         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
2021         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2022         gives when the magic number is not present.         gives when the magic number is not present.
2023    
2024           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2025    
2026         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2027         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
2028         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2029    
2030           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2031    
2032         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2033         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2034         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
2035         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
2036         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2037    
2038           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2039    
2040         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2041         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2042         returned by pcre_exec().         returned by pcre_exec().
2043    
2044           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2045    
2046         The  recursion  and backtracking limit, as specified by the match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2047         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra  structure  (or  defaulted) was reached. See the description
2048         description above.         above.
2049    
2050           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2051    
2052         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
2053         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2054         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2055    
2056           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2057    
2058         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
2059         subject.         subject.
2060    
2061           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2062    
2063         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
2064         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-
2065         ter.         ter.
2066    
2067           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2068    
2069         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
2070         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2071    
2072           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2073    
2074         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
2075         items that are not supported for partial matching. See the  pcrepartial         items  that are not supported for partial matching. See the pcrepartial
2076         documentation for details of partial matching.         documentation for details of partial matching.
2077    
2078           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2079    
2080         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2081         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2082    
2083           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2084    
2085         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.
2086    
2087             PCRE_ERROR_RECURSIONLIMIT (-21)
2088    
2089           The internal recursion limit, as specified by the match_limit_recursion
2090           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2091           description above.
2092    
2093             PCRE_ERROR_BADNEWLINE     (-23)
2094    
2095           An invalid combination of PCRE_NEWLINE_xxx options was given.
2096    
2097           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2098    
2099    
2100  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1747  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2110         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2111              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2112    
2113         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2114         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2115         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2116         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2117         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2118         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2119         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2120         extracted and has a further zero added on the end, but  the  result  is  
2121         not, of course, a C string.         A substring that contains a binary zero is correctly extracted and  has
2122           a  further zero added on the end, but the result is not, of course, a C
2123           string.  However, you can process such a string  by  referring  to  the
2124           length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2125           string().  Unfortunately, the interface to pcre_get_substring_list() is
2126           not  adequate for handling strings containing binary zeros, because the
2127           end of the final string is not independently indicated.
2128    
2129         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-
2130         tions: subject is the subject string that has  just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2131         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
2132         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2133         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2134         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2135         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2136         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
2137         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2138    
2139         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2140         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2141         zero  extracts  the  substring that matched the entire pattern, whereas         zero extracts the substring that matched the  entire  pattern,  whereas
2142         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2143         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2144         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2145         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2146         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
2147         the terminating zero, or one of         the terminating zero, or one of these error codes:
2148    
2149           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2150    
2151         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
2152         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2153    
2154           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2155    
2156         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2157    
2158         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2159         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
2160         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
2161         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
2162         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
2163         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
2164           error code
2165    
2166           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2167    
# Line 1810  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2180  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2180         tively.  They  do  nothing  more  than  call the function pointed to by         tively.  They  do  nothing  more  than  call the function pointed to by
2181         pcre_free, which of course could be called directly from a  C  program.         pcre_free, which of course could be called directly from a  C  program.
2182         However,  PCRE is used in some situations where it is linked via a spe-         However,  PCRE is used in some situations where it is linked via a spe-
2183         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  that  cannot   use
2184         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free  directly;  it is for these cases that the functions are pro-
2185         vided.         vided.
2186    
# Line 1835  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2205  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2205    
2206           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2207    
2208         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. If the name is known to
2209         from the name by calling pcre_get_stringnumber(). The first argument is         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2210         the  compiled  pattern,  and  the  second is the name. The yield of the         name by calling pcre_get_stringnumber(). The first argument is the com-
2211         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if         piled pattern, and the second is the name. The yield of the function is
2212         there is no subpattern of that name.         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
2213           subpattern of that name.
2214    
2215         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2216         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2217         are also two functions that do the whole job.         are also two functions that do the whole job.
2218    
2219         Most    of    the    arguments   of   pcre_copy_named_substring()   and         Most   of   the   arguments    of    pcre_copy_named_substring()    and
2220         pcre_get_named_substring() are the same  as  those  for  the  similarly         pcre_get_named_substring()  are  the  same  as  those for the similarly
2221         named  functions  that extract by number. As these are described in the         named functions that extract by number. As these are described  in  the
2222         previous section, they are not re-described here. There  are  just  two         previous  section,  they  are not re-described here. There are just two
2223         differences:         differences:
2224    
2225         First,  instead  of a substring number, a substring name is given. Sec-         First, instead of a substring number, a substring name is  given.  Sec-
2226         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2227         to  the compiled pattern. This is needed in order to gain access to the         to the compiled pattern. This is needed in order to gain access to  the
2228         name-to-number translation table.         name-to-number translation table.
2229    
2230         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2231         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2232         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2233           behaviour may not be what you want (see the next section).
2234    
2235    
2236    DUPLICATE SUBPATTERN NAMES
2237    
2238           int pcre_get_stringtable_entries(const pcre *code,
2239                const char *name, char **first, char **last);
2240    
2241           When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
2242           subpatterns  are  not  required  to  be unique. Normally, patterns with
2243           duplicate names are such that in any one match, only one of  the  named
2244           subpatterns  participates. An example is shown in the pcrepattern docu-
2245           mentation.
2246    
2247           When   duplicates   are   present,   pcre_copy_named_substring()    and
2248           pcre_get_named_substring()  return the first substring corresponding to
2249           the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
2250           (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
2251           function returns one of the numbers that are associated with the  name,
2252           but it is not defined which it is.
2253    
2254           If  you want to get full details of all captured substrings for a given
2255           name, you must use  the  pcre_get_stringtable_entries()  function.  The
2256           first argument is the compiled pattern, and the second is the name. The
2257           third and fourth are pointers to variables which  are  updated  by  the
2258           function. After it has run, they point to the first and last entries in
2259           the name-to-number table  for  the  given  name.  The  function  itself
2260           returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
2261           there are none. The format of the table is described above in the  sec-
2262           tion  entitled  Information  about  a  pattern.  Given all the relevant
2263           entries for the name, you can extract each of their numbers, and  hence
2264           the captured data, if any.
2265    
2266    
2267  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2268    
2269         The traditional matching function uses a  similar  algorithm  to  Perl,         The  traditional  matching  function  uses a similar algorithm to Perl,
2270         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
2271         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
2272         possible  match,  consider using the alternative matching function (see         possible match, consider using the alternative matching  function  (see
2273         below) instead. If you cannot use the alternative function,  but  still         below)  instead.  If you cannot use the alternative function, but still
2274         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
2275         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2276         tation.         tation.
2277    
2278         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-
2279         tern.  When your callout function is called, extract and save the  cur-         tern.   When your callout function is called, extract and save the cur-
2280         rent  matched  substring.  Then  return  1, which forces pcre_exec() to         rent matched substring. Then return  1,  which  forces  pcre_exec()  to
2281         backtrack and try other alternatives. Ultimately, when it runs  out  of         backtrack  and  try other alternatives. Ultimately, when it runs out of
2282         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2283    
2284    
# Line 1886  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2289  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2289              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2290              int *workspace, int wscount);              int *workspace, int wscount);
2291    
2292         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The function pcre_dfa_exec()  is  called  to  match  a  subject  string
2293         against a compiled pattern, using a "DFA" matching algorithm. This  has         against  a  compiled pattern, using a matching algorithm that scans the
2294         different  characteristics to the normal algorithm, and is not compati-         subject string just once, and does not backtrack.  This  has  different
2295         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics  to  the  normal  algorithm, and is not compatible with
2296         Nevertheless, there are times when this kind of matching can be useful.         Perl. Some of the features of PCRE patterns are not  supported.  Never-
2297         For a discussion of the two matching algorithms, see  the  pcrematching         theless,  there are times when this kind of matching can be useful. For
2298         documentation.         a discussion of the two matching algorithms, see the pcrematching docu-
2299           mentation.
2300    
2301         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
2302         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 1904  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2308  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2308         workspace vector should contain at least 20 elements. It  is  used  for         workspace vector should contain at least 20 elements. It  is  used  for
2309         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2310         workspace will be needed for patterns and subjects where  there  are  a         workspace will be needed for patterns and subjects where  there  are  a
2311         lot of possible matches.         lot of potential matches.
2312    
2313         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_dfa_exec():
2314    
2315           int rc;           int rc;
2316           int ovector[10];           int ovector[10];
2317           int wspace[20];           int wspace[20];
2318           rc = pcre_exec(           rc = pcre_dfa_exec(
2319             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2320             NULL,           /* we didn't study the pattern */             NULL,           /* we didn't study the pattern */
2321             "some string",  /* the subject string */             "some string",  /* the subject string */
# Line 1926  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2330  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2330     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2331    
2332         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2333         zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2334         PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,
2335         PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
2336         these  are  the  same  as  for pcre_exec(), so their description is not         three of these are the same as for pcre_exec(), so their description is
2337         repeated here.         not repeated here.
2338    
2339           PCRE_PARTIAL           PCRE_PARTIAL
2340    
# Line 1945  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2349  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2349           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2350    
2351         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2352         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-
2353         algorithm works, this is necessarily the shortest possible match at the         tive algorithm works, this is necessarily the shortest  possible  match
2354         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2355    
2356           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2357    
# Line 1983  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2387  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2387         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,
2388         which  is  the  number of matched substrings. The substrings themselves         which  is  the  number of matched substrings. The substrings themselves
2389         are returned in ovector. Each string uses two elements;  the  first  is         are returned in ovector. Each string uses two elements;  the  first  is
2390         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
2391         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
2392         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
2393         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility with the way pcre_exec() returns data,  even  though  the
2394         strings is different.)         meaning of the strings is different.)
2395    
2396         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-
2397         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 2009  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2413  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2413    
2414           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2415    
2416         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
2417         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
2418         supported.         in a specific group. These are not supported.
2419    
2420           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2421    
# Line 2031  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2435  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2435         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
2436         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2437    
 Last updated: 16 May 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
2438    
2439    SEE ALSO
2440    
2441           pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2442           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).
2443    
2444    
2445    AUTHOR
2446    
2447           Philip Hazel
2448           University Computing Service
2449           Cambridge CB2 3QH, England.
2450    
2451    
2452    REVISION
2453    
2454           Last updated: 09 August 2007
2455           Copyright (c) 1997-2007 University of Cambridge.
2456    ------------------------------------------------------------------------------
2457    
2458    
2459    PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2460    
2461    
2462  NAME  NAME
# Line 2057  PCRE CALLOUTS Line 2479  PCRE CALLOUTS
2479         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2480         points:         points:
2481    
2482           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2483    
2484         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
2485         called, PCRE automatically  inserts  callouts,  all  with  number  255,         called, PCRE automatically  inserts  callouts,  all  with  number  255,
# Line 2132  THE CALLOUT INTERFACE Line 2554  THE CALLOUT INTERFACE
2554         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2555         were passed to pcre_exec().         were passed to pcre_exec().
2556    
2557         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2558         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2559         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
2560         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2561           function may be called several times from the same point in the pattern
2562           for different starting points in the subject.
2563    
2564         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2565         the current match pointer.         the current match pointer.
# Line 2188  RETURN VALUES Line 2612  RETURN VALUES
2612         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
2613         itself.         itself.
2614    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
2615    
2616    AUTHOR
2617    
2618           Philip Hazel
2619           University Computing Service
2620           Cambridge CB2 3QH, England.
2621    
2622    
2623    REVISION
2624    
2625           Last updated: 29 May 2007
2626           Copyright (c) 1997-2007 University of Cambridge.
2627    ------------------------------------------------------------------------------
2628    
2629    
2630    PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2631    
2632    
2633  NAME  NAME
# Line 2201  NAME Line 2637  NAME
2637  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2638    
2639         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2640         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences described here  are  mainly
2641         respect to Perl 5.8.         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2642           some features that are expected to be in the forthcoming Perl 5.10.
2643         1.  PCRE does not have full UTF-8 support. Details of what it does have  
2644         are given in the section on UTF-8 support in the main pcre page.         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2645           of  what  it does have are given in the section on UTF-8 support in the
2646           main pcre page.
2647    
2648         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
2649         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,
# Line 2232  DIFFERENCES BETWEEN PCRE AND PERL Line 2670  DIFFERENCES BETWEEN PCRE AND PERL
2670         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
2671         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
2672         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-
2673         erties such as Lu and Nd.         erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2674           derived properties Any and L&.
2675    
2676         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2677         ters in between are treated as literals.  This  is  slightly  different         ters  in  between  are  treated as literals. This is slightly different
2678         from  Perl  in  that  $  and  @ are also handled as literals inside the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
2679         quotes. In Perl, they cause variable interpolation (but of course  PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
2680         does not have variables). Note the following examples:         does not have variables). Note the following examples:
2681    
2682             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2247  DIFFERENCES BETWEEN PCRE AND PERL Line 2686  DIFFERENCES BETWEEN PCRE AND PERL
2686             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
2687             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
2688    
2689         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
2690         classes.         classes.
2691    
2692         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2693         constructions.  However,  there is support for recursive patterns using         constructions. However, there is support for recursive  patterns.  This
2694         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
2695         "callout"  feature allows an external function to be called during pat-         "callout" feature allows an external function to be called during  pat-
2696         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
2697    
2698         9. There are some differences that are concerned with the  settings  of         9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2699         captured  strings  when  part  of  a  pattern is repeated. For example,         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2700         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         unlike Perl.
2701    
2702           10.  There are some differences that are concerned with the settings of
2703           captured strings when part of  a  pattern  is  repeated.  For  example,
2704           matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2705         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2706    
2707         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2708         ities:         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2709           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2710           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2711           ture group; this is different to Perl.
2712    
2713           12. PCRE provides some extensions to the Perl regular expression facil-
2714           ities.   Perl  5.10  will  include new features that are not in earlier
2715           versions, some of which (such as named parentheses) have been  in  PCRE
2716           for some time. This list is with respect to Perl 5.10:
2717    
2718         (a) Although lookbehind assertions must  match  fixed  length  strings,         (a)  Although  lookbehind  assertions  must match fixed length strings,
2719         each alternative branch of a lookbehind assertion can match a different         each alternative branch of a lookbehind assertion can match a different
2720         length of string. Perl requires them all to have the same length.         length of string. Perl requires them all to have the same length.
2721    
2722         (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 $
2723         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2724    
2725         (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-
2726         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2727           ignored.  (Perl can be made to issue a warning.)
2728    
2729         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2730         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-
# Line 2284  DIFFERENCES BETWEEN PCRE AND PERL Line 2736  DIFFERENCES BETWEEN PCRE AND PERL
2736         (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-
2737         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2738    
2739         (g) The (?R), (?number), and (?P>name) constructs allows for  recursive         (g) The callout facility is PCRE-specific.
        pattern  matching  (Perl  can  do  this using the (?p{code}) construct,  
        which PCRE cannot support.)  
2740    
2741         (h) PCRE supports named capturing substrings, using the Python  syntax.         (h) The partial matching facility is PCRE-specific.
2742    
2743         (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from         (i) Patterns compiled by PCRE can be saved and re-used at a later time,
2744         Sun's Java package.         even on different hosts that have the other endianness.
2745    
2746         (j) The (R) condition, for testing recursion, is a PCRE extension.         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2747           different way and is not Perl-compatible.
2748    
        (k) The callout facility is PCRE-specific.  
2749    
2750         (l) The partial matching facility is PCRE-specific.  AUTHOR
2751    
2752         (m) Patterns compiled by PCRE can be saved and re-used at a later time,         Philip Hazel
2753         even on different hosts that have the other endianness.         University Computing Service
2754           Cambridge CB2 3QH, England.
2755    
        (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a  
        different way and is not Perl-compatible.  
2756    
2757  Last updated: 28 February 2005  REVISION
 Copyright (c) 1997-2005 University of Cambridge.  
 -----------------------------------------------------------------------------  
2758    
2759           Last updated: 08 August 2007
2760           Copyright (c) 1997-2007 University of Cambridge.
2761    ------------------------------------------------------------------------------
2762    
2763    
2764    PCREPATTERN(3)                                                  PCREPATTERN(3)
2765    
2766    
2767  NAME  NAME
# Line 2317  NAME Line 2770  NAME
2770    
2771  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2772    
2773         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
2774         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
2775         documentation  and  in  a  number  of books, some of which have copious         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are
2776         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         described in its own documentation, and regular expressions in  general
2777         by  O'Reilly, covers regular expressions in great detail. This descrip-         are  covered in a number of books, some of which have copious examples.
2778         tion of PCRE's regular expressions is intended as reference material.         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by
2779           O'Reilly,  covers regular expressions in great detail. This description
2780           of PCRE's regular expressions is intended as reference material.
2781    
2782         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2783         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 2336  PCRE REGULAR EXPRESSION DETAILS Line 2791  PCRE REGULAR EXPRESSION DETAILS
2791         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
2792         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
2793         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
2794         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
2795         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
2796         the pcrematching page.         alternative function, and how it differs from the normal function,  are
2797           discussed in the pcrematching page.
2798         A regular expression is a pattern that is  matched  against  a  subject  
2799         string  from  left  to right. Most characters stand for themselves in a  
2800         pattern, and match the corresponding characters in the  subject.  As  a  CHARACTERS AND METACHARACTERS
2801    
2802           A  regular  expression  is  a pattern that is matched against a subject
2803           string from left to right. Most characters stand for  themselves  in  a
2804           pattern,  and  match  the corresponding characters in the subject. As a
2805         trivial example, the pattern         trivial example, the pattern
2806    
2807           The quick brown fox           The quick brown fox
2808    
2809         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
2810         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
2811         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
2812         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
2813         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
2814         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
2815         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
2816         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
2817         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
2818    
2819         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
2820         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
2821         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
2822         but instead are interpreted in some special way.         but instead are interpreted in some special way.
2823    
2824         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
2825         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
2826         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
2827         metacharacters are as follows:         the metacharacters are as follows:
2828    
2829           \      general escape character with several uses           \      general escape character with several uses
2830           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2383  PCRE REGULAR EXPRESSION DETAILS Line 2842  PCRE REGULAR EXPRESSION DETAILS
2842                  also "possessive quantifier"                  also "possessive quantifier"
2843           {      start min/max quantifier           {      start min/max quantifier
2844    
2845         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
2846         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
2847    
2848           \      general escape character           \      general escape character
# Line 2393  PCRE REGULAR EXPRESSION DETAILS Line 2852  PCRE REGULAR EXPRESSION DETAILS
2852                    syntax)                    syntax)
2853           ]      terminates the character class           ]      terminates the character class
2854    
2855         The following sections describe the use of each of the  metacharacters.         The  following sections describe the use of each of the metacharacters.
2856    
2857    
2858  BACKSLASH  BACKSLASH
2859    
2860         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2861         a non-alphanumeric character, it takes away any  special  meaning  that         a  non-alphanumeric  character,  it takes away any special meaning that
2862         character  may  have.  This  use  of  backslash  as an escape character         character may have. This  use  of  backslash  as  an  escape  character
2863         applies both inside and outside character classes.         applies both inside and outside character classes.
2864    
2865         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
2866         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
2867         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
2868         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
2869         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-
2870         slash, you write \\.         slash, you write \\.
2871    
2872         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
2873         the pattern (other than in a character class) and characters between  a         the  pattern (other than in a character class) and characters between a
2874         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
2875         An escaping backslash can be used to include a whitespace or #  charac-         ing  backslash  can  be  used to include a whitespace or # character as
2876         ter as part of the pattern.         part of the pattern.
2877    
2878         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-
2879         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-
2880         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
2881         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
2882         tion. Note the following examples:         tion. Note the following examples:
2883    
2884           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2429  BACKSLASH Line 2888  BACKSLASH
2888           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
2889           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
2890    
2891         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
2892         classes.         classes.
2893    
2894     Non-printing characters     Non-printing characters
2895    
2896         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-
2897         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
2898         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
2899         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
2900         editing, it is usually easier  to  use  one  of  the  following  escape         editing,  it  is  usually  easier  to  use  one of the following escape
2901         sequences than the binary character it represents:         sequences than the binary character it represents:
2902    
2903           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 2450  BACKSLASH Line 2909  BACKSLASH
2909           \t        tab (hex 09)           \t        tab (hex 09)
2910           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
2911           \xhh      character with hex code hh           \xhh      character with hex code hh
2912           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh..
2913    
2914         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,
2915         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
2916         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;
2917         becomes hex 7B.         becomes hex 7B.
2918    
2919         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
2920         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-         in upper or lower case). Any number of hexadecimal  digits  may  appear
2921         its may appear between \x{ and }, but the value of the  character  code         between  \x{  and  },  but the value of the character code must be less
2922         must  be  less  than  2**31  (that is, the maximum hexadecimal value is         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
2923         7FFFFFFF). If characters other than hexadecimal digits  appear  between         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
2924         \x{  and }, or if there is no terminating }, this form of escape is not         than the largest Unicode code point, which is 10FFFF.
2925         recognized. Instead, the initial \x will  be  interpreted  as  a  basic  
2926         hexadecimal  escape, with no following digits, giving a character whose         If characters other than hexadecimal digits appear between \x{  and  },
2927         value is zero.         or if there is no terminating }, this form of escape is not recognized.
2928           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
2929           escape,  with  no  following  digits, giving a character whose value is
2930           zero.
2931    
2932         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
2933         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference         two  syntaxes  for  \x. There is no difference in the way they are han-
2934         in the way they are handled. For example, \xdc is exactly the  same  as         dled. For example, \xdc is exactly the same as \x{dc}.
2935         \x{dc}.  
2936           After \0 up to two further octal digits are read. If  there  are  fewer
2937         After  \0  up  to  two further octal digits are read. In both cases, if         than  two  digits,  just  those  that  are  present  are used. Thus the
2938         there are fewer than two digits, just those that are present are  used.         sequence \0\x\07 specifies two binary zeros followed by a BEL character
2939         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL         (code  value 7). Make sure you supply two digits after the initial zero
2940         character (code value 7). Make sure you supply  two  digits  after  the         if the pattern character that follows is itself an octal digit.
        initial  zero  if the pattern character that follows is itself an octal  
        digit.  
2941    
2942         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
2943         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
# Line 2489  BACKSLASH Line 2949  BACKSLASH
2949    
2950         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
2951         and  there have not been that many capturing subpatterns, PCRE re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
2952         up to three octal digits following the backslash, and generates a  sin-         up to three octal digits following the backslash, and uses them to gen-
2953         gle byte from the least significant 8 bits of the value. Any subsequent         erate  a data character. Any subsequent digits stand for themselves. In
2954         digits stand for themselves.  For example:         non-UTF-8 mode, the value of a character specified  in  octal  must  be
2955           less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
2956           example:
2957    
2958           \040   is another way of writing a space           \040   is another way of writing a space
2959           \40    is the same, provided there are fewer than 40           \40    is the same, provided there are fewer than 40
# Line 2511  BACKSLASH Line 2973  BACKSLASH
2973         Note that octal values of 100 or greater must not be  introduced  by  a         Note that octal values of 100 or greater must not be  introduced  by  a
2974         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
2975    
2976         All  the  sequences  that  define a single byte value or a single UTF-8         All the sequences that define a single character value can be used both
2977         character (in UTF-8 mode) can be used both inside and outside character         inside and outside character classes. In addition, inside  a  character
2978         classes.  In  addition,  inside  a  character class, the sequence \b is         class,  the  sequence \b is interpreted as the backspace character (hex
2979         interpreted as the backspace character (hex 08), and the sequence \X is         08), and the sequences \R and \X are interpreted as the characters  "R"
2980         interpreted  as  the  character  "X".  Outside a character class, these         and  "X", respectively. Outside a character class, these sequences have
2981         sequences have different meanings (see below).         different meanings (see below).
2982    
2983       Absolute and relative back references
2984    
2985           The sequence \g followed by an unsigned or a negative  number,  option-
2986           ally  enclosed  in braces, is an absolute or relative back reference. A
2987           named back reference can be coded as \g{name}. Back references are dis-
2988           cussed later, following the discussion of parenthesized subpatterns.
2989    
2990     Generic character types     Generic character types
2991    
2992         The third use of backslash is for specifying generic  character  types.         Another use of backslash is for specifying generic character types. The
2993         The following are always recognized:         following are always recognized:
2994    
2995           \d     any decimal digit           \d     any decimal digit
2996           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
2997             \h     any horizontal whitespace character
2998             \H     any character that is not a horizontal whitespace character
2999           \s     any whitespace character           \s     any whitespace character
3000           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3001             \v     any vertical whitespace character
3002             \V     any character that is not a vertical whitespace character
3003           \w     any "word" character           \w     any "word" character
3004           \W     any "non-word" character           \W     any "non-word" character
3005    
3006         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
3007         into two disjoint sets. Any given character matches one, and only  one,         into  two disjoint sets. Any given character matches one, and only one,
3008         of each pair.         of each pair.
3009    
3010         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
3011         acter classes. They each match one character of the  appropriate  type.         acter  classes.  They each match one character of the appropriate type.
3012         If  the current matching point is at the end of the subject string, all         If the current matching point is at the end of the subject string,  all
3013         of them fail, since there is no character to match.         of them fail, since there is no character to match.
3014    
3015         For compatibility with Perl, \s does not match the VT  character  (code         For  compatibility  with Perl, \s does not match the VT character (code
3016         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
3017         characters are HT (9), LF (10), FF (12), CR (13), and space (32).         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3018           "use locale;" is included in a Perl script, \s may match the VT charac-
3019           ter. In PCRE, it never does.
3020    
3021           In  UTF-8 mode, characters with values greater than 128 never match \d,
3022           \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3023           code  character  property  support is available. These sequences retain
3024           their original meanings from before UTF-8 support was available, mainly
3025           for efficiency reasons.
3026    
3027           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3028           the other sequences, these do match certain high-valued  codepoints  in
3029           UTF-8 mode.  The horizontal space characters are:
3030    
3031             U+0009     Horizontal tab
3032             U+0020     Space
3033             U+00A0     Non-break space
3034             U+1680     Ogham space mark
3035             U+180E     Mongolian vowel separator
3036             U+2000     En quad
3037             U+2001     Em quad
3038             U+2002     En space
3039             U+2003     Em space
3040             U+2004     Three-per-em space
3041             U+2005     Four-per-em space
3042             U+2006     Six-per-em space
3043             U+2007     Figure space
3044             U+2008     Punctuation space
3045             U+2009     Thin space
3046             U+200A     Hair space
3047             U+202F     Narrow no-break space
3048             U+205F     Medium mathematical space
3049             U+3000     Ideographic space
3050    
3051           The vertical space characters are:
3052    
3053             U+000A     Linefeed
3054             U+000B     Vertical tab
3055             U+000C     Formfeed
3056             U+000D     Carriage return
3057             U+0085     Next line
3058             U+2028     Line separator
3059             U+2029     Paragraph separator
3060    
3061         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
3062         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-
3063         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-
3064         specific  matching is taking place (see "Locale support" in the pcreapi         specific matching is taking place (see "Locale support" in the  pcreapi
3065         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
3066         codes  greater  than  128  are used for accented letters, and these are         systems, or "french" in Windows, some character codes greater than  128
3067         matched by \w.         are  used for accented letters, and these are matched by \w. The use of
3068           locales with Unicode is discouraged.
3069    
3070       Newline sequences
3071    
3072           Outside a character class, the escape sequence \R matches  any  Unicode
3073           newline  sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is
3074           equivalent to the following:
3075    
3076             (?>\r\n|\n|\x0b|\f|\r|\x85)
3077    
3078           This is an example of an "atomic group", details  of  which  are  given
3079           below.  This particular group matches either the two-character sequence
3080           CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3081           U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3082           return, U+000D), or NEL (next line, U+0085). The two-character sequence
3083           is treated as a single unit that cannot be split.
3084    
3085           In  UTF-8  mode, two additional characters whose codepoints are greater
3086           than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3087           rator,  U+2029).   Unicode character property support is not needed for
3088           these characters to be recognized.
3089    
3090         In UTF-8 mode, characters with values greater than 128 never match  \d,         Inside a character class, \R matches the letter "R".
        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-  
        code character property support is available.  
3091    
3092     Unicode character properties     Unicode character properties
3093    
3094         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3095         tional  escape sequences to match generic character types are available         tional  escape sequences that match characters with specific properties
3096         when UTF-8 mode is selected. They are:         are available.  When not in UTF-8 mode, these sequences are  of  course
3097           limited  to  testing characters whose codepoints are less than 256, but
3098          \p{xx}   a character with the xx property         they do work in this mode.  The extra escape sequences are:
3099          \P{xx}   a character without the xx property  
3100          \X       an extended Unicode sequence           \p{xx}   a character with the xx property
3101             \P{xx}   a character without the xx property
3102             \X       an extended Unicode sequence
3103    
3104         The property names represented by xx above are limited to  the  Unicode         The property names represented by xx above are limited to  the  Unicode
3105         general  category properties. Each character has exactly one such prop-         script names, the general category properties, and "Any", which matches
3106         erty, specified by a two-letter abbreviation.  For  compatibility  with         any character (including newline). Other properties such as "InMusical-
3107         Perl,  negation  can be specified by including a circumflex between the         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
3108         opening brace and the property name. For example, \p{^Lu} is  the  same         not match any characters, so always causes a match failure.
3109         as \P{Lu}.  
3110           Sets of Unicode characters are defined as belonging to certain scripts.
3111         If  only  one  letter  is  specified with \p or \P, it includes all the         A  character from one of these sets can be matched using a script name.
3112         properties that start with that letter. In this case, in the absence of         For example:
3113         negation, the curly brackets in the escape sequence are optional; these  
3114         two examples have the same effect:           \p{Greek}
3115             \P{Han}
3116    
3117           Those that are not part of an identified script are lumped together  as
3118           "Common". The current list of scripts is:
3119    
3120           Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3121           Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
3122           Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3123           Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
3124           gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
3125           Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3126           Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
3127           Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3128           Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3129    
3130           Each  character has exactly one general category property, specified by
3131           a two-letter abbreviation. For compatibility with Perl, negation can be
3132           specified  by  including a circumflex between the opening brace and the
3133           property name. For example, \p{^Lu} is the same as \P{Lu}.
3134    
3135           If only one letter is specified with \p or \P, it includes all the gen-
3136           eral  category properties that start with that letter. In this case, in
3137           the absence of negation, the curly brackets in the escape sequence  are
3138           optional; these two examples have the same effect:
3139    
3140           \p{L}           \p{L}
3141           \pL           \pL
3142    
3143         The following property codes are supported:         The following general category property codes are supported:
3144    
3145           C     Other           C     Other
3146           Cc    Control           Cc    Control
# Line 2626  BACKSLASH Line 3186  BACKSLASH
3186           Zp    Paragraph separator           Zp    Paragraph separator
3187           Zs    Space separator           Zs    Space separator
3188    
3189         Extended properties such as "Greek" or "InMusicalSymbols" are not  sup-         The  special property L& is also supported: it matches a character that
3190         ported by PCRE.         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3191           classified as a modifier or "other".
3192    
3193           The  Cs  (Surrogate)  property  applies only to characters in the range
3194           U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3195           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3196           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3197           the pcreapi page).
3198    
3199           The  long  synonyms  for  these  properties that Perl supports (such as
3200           \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3201           any of these properties with "Is".
3202    
3203           No character that is in the Unicode table has the Cn (unassigned) prop-
3204           erty.  Instead, this property is assumed for any code point that is not
3205           in the Unicode table.
3206    
3207         Specifying  caseless  matching  does not affect these escape sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3208         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
# Line 2640  BACKSLASH Line 3215  BACKSLASH
3215         That  is,  it matches a character without the "mark" property, followed         That  is,  it matches a character without the "mark" property, followed
3216         by zero or more characters with the "mark"  property,  and  treats  the         by zero or more characters with the "mark"  property,  and  treats  the
3217         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3218         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3219           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3220           matches any one character.
3221    
3222         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3223         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3224         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3225         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3226    
3227       Resetting the match start
3228    
3229           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3230           ously matched characters not  to  be  included  in  the  final  matched
3231           sequence. For example, the pattern:
3232    
3233             foo\Kbar
3234    
3235           matches  "foobar",  but reports that it has matched "bar". This feature
3236           is similar to a lookbehind assertion (described  below).   However,  in
3237           this  case, the part of the subject before the real match does not have
3238           to be of fixed length, as lookbehind assertions do. The use of \K  does
3239           not  interfere  with  the setting of captured substrings.  For example,
3240           when the pattern
3241    
3242             (foo)\Kbar
3243    
3244           matches "foobar", the first substring is still set to "foo".
3245    
3246     Simple assertions     Simple assertions
3247    
3248         The fourth use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3249         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
3250         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3251         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3252         The backslashed assertions are:         The backslashed assertions are:
3253    
3254           \b     matches at a word boundary           \b     matches at a word boundary
3255           \B     matches when not at a word boundary           \B     matches when not at a word boundary
3256           \A     matches at start of subject           \A     matches at the start of the subject
3257           \Z     matches at end of subject or before newline at end           \Z     matches at the end of the subject
3258           \z     matches at end of subject                   also matches before a newline at the end of the subject
3259           \G     matches at first matching position in subject           \z     matches only at the end of the subject
3260             \G     matches at the first matching position in the subject
3261    
3262         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3263         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3264         acter class).         acter class).
3265    
3266         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3267         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3268         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3269         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3270    
3271         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3272         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3273         at the very start and end of the subject string, whatever  options  are         at  the  very start and end of the subject string, whatever options are
3274         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3275         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3276         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3277         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3278         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3279         the subject, \A can never match. The difference between \Z  and  \z  is         the  subject,  \A  can never match. The difference between \Z and \z is
3280         that  \Z  matches  before  a  newline that is the last character of the         that \Z matches before a newline at the end of the string as well as at
3281         string as well as at the end of the string, whereas \z matches only  at         the very end, whereas \z matches only at the end.
        the end.  
3282    
3283         The  \G assertion is true only when the current matching position is at         The  \G assertion is true only when the current matching position is at
3284         the start point of the match, as specified by the startoffset  argument         the start point of the match, as specified by the startoffset  argument
# Line 2721  CIRCUMFLEX AND DOLLAR Line 3317  CIRCUMFLEX AND DOLLAR
3317    
3318         A  dollar  character  is  an assertion that is true only if the current         A  dollar  character  is  an assertion that is true only if the current
3319         matching point is at the end of  the  subject  string,  or  immediately         matching point is at the end of  the  subject  string,  or  immediately
3320         before a newline character that is the last character in the string (by         before a newline at the end of the string (by default). Dollar need not
3321         default). Dollar need not be the last character of  the  pattern  if  a         be the last character of the pattern if a number  of  alternatives  are
3322         number  of alternatives are involved, but it should be the last item in         involved,  but  it  should  be  the last item in any branch in which it
3323         any branch in which it appears.  Dollar has no  special  meaning  in  a         appears. Dollar has no special meaning in a character class.
        character class.  
3324    
3325         The  meaning  of  dollar  can be changed so that it matches only at the         The meaning of dollar can be changed so that it  matches  only  at  the
3326         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at
3327         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3328    
3329         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3330         PCRE_MULTILINE option is set. When this is the case, they match immedi-         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3331         ately  after  and  immediately  before  an  internal newline character,         matches immediately after internal newlines as well as at the start  of
3332         respectively, in addition to matching at the start and end of the  sub-         the  subject  string.  It  does not match after a newline that ends the
3333         ject  string.  For  example,  the  pattern  /^abc$/ matches the subject         string. A dollar matches before any newlines in the string, as well  as
3334         string "def\nabc" (where \n represents a newline character)  in  multi-         at  the very end, when PCRE_MULTILINE is set. When newline is specified
3335         line mode, but not otherwise.  Consequently, patterns that are anchored         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3336         in single line mode because all branches start with ^ are not  anchored         not indicate newlines.
3337         in  multiline  mode,  and  a  match for circumflex is possible when the  
3338         startoffset  argument  of  pcre_exec()  is  non-zero.   The   PCRE_DOL-         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3339         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3340           Consequently,  patterns  that  are anchored in single line mode because
3341           all branches start with ^ are not anchored in  multiline  mode,  and  a
3342           match  for  circumflex  is  possible  when  the startoffset argument of
3343           pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if
3344           PCRE_MULTILINE is set.
3345    
3346         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note  that  the sequences \A, \Z, and \z can be used to match the start
3347         and end of the subject in both modes, and if all branches of a  pattern         and end of the subject in both modes, and if all branches of a  pattern
3348         start  with  \A it is always anchored, whether PCRE_MULTILINE is set or         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
3349         not.         set.
3350    
3351    
3352  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3353    
3354         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-
3355         ter  in  the  subject,  including a non-printing character, but not (by         ter  in  the subject string except (by default) a character that signi-
3356         default) newline.  In UTF-8 mode, a dot matches  any  UTF-8  character,         fies the end of a line. In UTF-8 mode, the  matched  character  may  be
3357         which might be more than one byte long, except (by default) newline. If         more than one byte long.
3358         the PCRE_DOTALL option is set, dots match newlines as  well.  The  han-  
3359         dling  of dot is entirely independent of the handling of circumflex and         When  a line ending is defined as a single character, dot never matches
3360         dollar, the only relationship being  that  they  both  involve  newline         that character; when the two-character sequence CRLF is used, dot  does
3361         characters. Dot has no special meaning in a character class.         not  match  CR  if  it  is immediately followed by LF, but otherwise it
3362           matches all characters (including isolated CRs and LFs). When any  Uni-
3363           code  line endings are being recognized, dot does not match CR or LF or
3364           any of the other line ending characters.
3365    
3366           The behaviour of dot with regard to newlines can  be  changed.  If  the
3367           PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3368           exception. If the two-character sequence CRLF is present in the subject
3369           string, it takes two dots to match it.
3370    
3371           The  handling of dot is entirely independent of the handling of circum-
3372           flex and dollar, the only relationship being  that  they  both  involve
3373           newlines. Dot has no special meaning in a character class.
3374    
3375    
3376  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3377    
3378         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3379         both in and out of UTF-8 mode. Unlike a dot, it can  match  a  newline.         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
3380         The  feature  is provided in Perl in order to match individual bytes in         line-ending  characters.  The  feature  is provided in Perl in order to
3381         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-
3382         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-
3383         this reason, the \C escape sequence is best avoided.         formed UTF-8 string. For this reason, the \C escape  sequence  is  best
3384           avoided.
3385    
3386         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3387         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-
3388         late the length of the lookbehind.         late the length of the lookbehind.
3389    
3390    
# Line 2780  SQUARE BRACKETS AND CHARACTER CLASSES Line 3393  SQUARE BRACKETS AND CHARACTER CLASSES
3393         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3394         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
3395         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
3396         it  should  be  the first data character in the class (after an initial         it should be the first data character in the class  (after  an  initial
3397         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3398    
3399         A character class matches a single character in the subject.  In  UTF-8         A  character  class matches a single character in the subject. In UTF-8
3400         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3401         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
3402         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3403         subject character must not be in the set defined by  the  class.  If  a         subject  character  must  not  be in the set defined by the class. If a
3404         circumflex  is actually required as a member of the class, ensure it is         circumflex is actually required as a member of the class, ensure it  is
3405         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3406    
3407         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3408         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3409         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3410         characters  that  are in the class by enumerating those that are not. A         characters that are in the class by enumerating those that are  not.  A
3411         class that starts with a circumflex is not an assertion: it still  con-         class  that starts with a circumflex is not an assertion: it still con-
3412         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3413         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3414    
3415         In UTF-8 mode, characters with values greater than 255 can be  included         In  UTF-8 mode, characters with values greater than 255 can be included
3416         in  a  class as a literal string of bytes, or by using the \x{ escaping         in a class as a literal string of bytes, or by using the  \x{  escaping
3417         mechanism.         mechanism.
3418    
3419         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3420         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3421         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
3422         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always
3423         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3424         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3425         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3426         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3427         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3428         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
3429         support.         support.
3430    
3431         The newline character is never treated in any special way in  character         Characters  that  might  indicate  line breaks are never treated in any
3432         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE         special way  when  matching  character  classes,  whatever  line-ending
3433         options is. A class such as [^a] will always match a newline.         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3434           PCRE_MULTILINE options is used. A class such as [^a] always matches one
3435         The minus (hyphen) character can be used to specify a range of  charac-         of these characters.
3436         ters  in  a  character  class.  For  example,  [d-m] matches any letter  
3437         between d and m, inclusive. If a  minus  character  is  required  in  a         The  minus (hyphen) character can be used to specify a range of charac-
3438         class,  it  must  be  escaped  with a backslash or appear in a position         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3439         where it cannot be interpreted as indicating a range, typically as  the         between  d  and  m,  inclusive.  If  a minus character is required in a
3440           class, it must be escaped with a backslash  or  appear  in  a  position
3441           where  it cannot be interpreted as indicating a range, typically as the
3442         first or last character in the class.         first or last character in the class.
3443    
3444         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
3445         ter of a range. A pattern such as [W-]46] is interpreted as a class  of         ter  of a range. A pattern such as [W-]46] is interpreted as a class of
3446         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3447         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3448         backslash  it is interpreted as the end of range, so [W-\]46] is inter-         backslash it is interpreted as the end of range, so [W-\]46] is  inter-
3449         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3450         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3451         a range.         a range.
3452    
3453         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3454         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3455         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3456         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3457    
3458         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,
3459         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
3460         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3461         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
3462         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
3463         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3464         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3465    
3466         The  character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear         The character types \d, \D, \p, \P, \s, \S, \w, and \W may also  appear
3467         in a character class, and add the characters that  they  match  to  the         in  a  character  class,  and add the characters that they match to the
3468         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3469         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3470         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3471         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3472         but not underscore.         but not underscore.
3473    
3474         The  only  metacharacters  that are recognized in character classes are         The only metacharacters that are recognized in  character  classes  are
3475         backslash, hyphen (only where it can be  interpreted  as  specifying  a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
3476         range),  circumflex  (only  at the start), opening square bracket (only         range), circumflex (only at the start), opening  square  bracket  (only
3477         when it can be interpreted as introducing a POSIX class name - see  the         when  it can be interpreted as introducing a POSIX class name - see the
3478         next  section),  and  the  terminating closing square bracket. However,         next section), and the terminating  closing  square  bracket.  However,
3479         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3480    
3481    
3482  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3483    
3484         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3485         enclosed  by  [: and :] within the enclosing square brackets. PCRE also         enclosed by [: and :] within the enclosing square brackets.  PCRE  also
3486         supports this notation. For example,         supports this notation. For example,
3487    
3488           [01[:alpha:]%]           [01[:alpha:]%]
# Line 2890  POSIX CHARACTER CLASSES Line 3505  POSIX CHARACTER CLASSES
3505           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3506           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3507    
3508         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),
3509         and space (32). Notice that this list includes the VT  character  (code         and  space  (32). Notice that this list includes the VT character (code
3510         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
3511         Perl compatibility).         Perl compatibility).
3512    
3513         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension
3514         from  Perl  5.8. Another Perl extension is negation, which is indicated         from Perl 5.8. Another Perl extension is negation, which  is  indicated
3515         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3516    
3517           [12[:^digit:]]           [12[:^digit:]]
3518    
3519         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the
3520         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3521         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
3522    
# Line 2911  POSIX CHARACTER CLASSES Line 3526  POSIX CHARACTER CLASSES
3526    
3527  VERTICAL BAR  VERTICAL BAR
3528    
3529         Vertical bar characters are used to separate alternative patterns.  For         Vertical  bar characters are used to separate alternative patterns. For
3530         example, the pattern         example, the pattern
3531    
3532           gilbert|sullivan           gilbert|sullivan
3533    
3534         matches  either "gilbert" or "sullivan". Any number of alternatives may         matches either "gilbert" or "sullivan". Any number of alternatives  may
3535         appear, and an empty  alternative  is  permitted  (matching  the  empty         appear,  and  an  empty  alternative  is  permitted (matching the empty
3536         string).   The  matching  process  tries each alternative in turn, from         string). The matching process tries each alternative in turn, from left
3537         left to right, and the first one that succeeds is used. If the alterna-         to  right, and the first one that succeeds is used. If the alternatives
3538         tives  are within a subpattern (defined below), "succeeds" means match-         are within a subpattern (defined below), "succeeds" means matching  the
3539         ing the rest of the main pattern as well as the alternative in the sub-         rest  of the main pattern as well as the alternative in the subpattern.
        pattern.  
3540    
3541    
3542  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3543    
3544         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3545         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED  options  can  be  changed  from  within the pattern by a
3546         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         sequence of Perl option letters enclosed  between  "(?"  and  ")".  The
3547         option letters are         option letters are
3548    
3549           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 2939  INTERNAL OPTION SETTING Line 3553  INTERNAL OPTION SETTING
3553    
3554         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3555         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
3556         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
3557         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
3558         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
3559         hyphen, the option is unset.         hyphen, the option is unset.
3560    
3561         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-
3562         tern parentheses), the change applies to the remainder of  the  pattern         tern  parentheses),  the change applies to the remainder of the pattern
3563         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,
3564         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
3565         in data extracted by the pcre_fullinfo() function).         in data extracted by the pcre_fullinfo() function).
3566    
3567         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
3568         rent pattern that follows it, so         subpatterns) affects only that part of the current pattern that follows
3569           it, so
3570    
3571           (a(?i)b)c           (a(?i)b)c
3572    
# Line 2968  INTERNAL OPTION SETTING Line 3583  INTERNAL OPTION SETTING
3583         the effects of option settings happen at compile time. There  would  be         the effects of option settings happen at compile time. There  would  be
3584         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3585    
3586         The  PCRE-specific  options PCRE_UNGREEDY and PCRE_EXTRA can be changed         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
3587         in the same way as the Perl-compatible options by using the  characters         can be changed in the same way as the Perl-compatible options by  using
3588         U  and X respectively. The (?X) flag setting is special in that it must         the characters J, U and X respectively.
        always occur earlier in the pattern than any of the additional features  
        it  turns on, even when it is at top level. It is best to put it at the  
        start.  
3589    
3590    
3591  SUBPATTERNS  SUBPATTERNS
# Line 2985  SUBPATTERNS Line 3597  SUBPATTERNS
3597    
3598           cat(aract|erpillar|)           cat(aract|erpillar|)
3599    
3600         matches  one  of the words "cat", "cataract", or "caterpillar". Without         matches one of the words "cat", "cataract", or  "caterpillar".  Without
3601         the parentheses, it would match "cataract",  "erpillar"  or  the  empty         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
3602         string.         string.
3603    
3604         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
3605         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
3606         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
3607         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
3608         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
3609         subpatterns.         subpatterns.
3610    
3611         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-
3612         tern         tern
3613    
3614           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3004  SUBPATTERNS Line 3616  SUBPATTERNS
3616         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3617         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3618    
3619         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
3620         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
3621         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
3622         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-
3623         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
3624         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
3625         matched against the pattern         matched against the pattern
3626    
3627           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
3628    
3629         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3630         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.  
3631    
3632         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
3633         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
3634         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3635    
3636           (?i:saturday|sunday)           (?i:saturday|sunday)
3637           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3638    
3639         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3640         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
3641         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
3642         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
3643         "Saturday".         "Saturday".
3644    
3645    
3646    DUPLICATE SUBPATTERN NUMBERS
3647    
3648           Perl 5.10 introduced a feature whereby each alternative in a subpattern
3649           uses  the same numbers for its capturing parentheses. Such a subpattern
3650           starts with (?| and is itself a non-capturing subpattern. For  example,
3651           consider this pattern:
3652    
3653             (?|(Sat)ur|(Sun))day
3654    
3655           Because  the two alternatives are inside a (?| group, both sets of cap-
3656           turing parentheses are numbered one. Thus, when  the  pattern  matches,
3657           you  can  look  at captured substring number one, whichever alternative
3658           matched. This construct is useful when you want to  capture  part,  but
3659           not all, of one of a number of alternatives. Inside a (?| group, paren-
3660           theses are numbered as usual, but the number is reset at the  start  of
3661           each  branch. The numbers of any capturing buffers that follow the sub-
3662           pattern start after the highest number used in any branch. The  follow-
3663           ing  example  is taken from the Perl documentation.  The numbers under-
3664           neath show in which buffer the captured content will be stored.
3665    
3666             # before  ---------------branch-reset----------- after
3667             / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3668             # 1            2         2  3        2     3     4
3669    
3670           A backreference or a recursive call to  a  numbered  subpattern  always
3671           refers to the first one in the pattern with the given number.
3672    
3673           An  alternative approach to using this "branch reset" feature is to use
3674           duplicate named subpatterns, as described in the next section.
3675    
3676    
3677  NAMED SUBPATTERNS  NAMED SUBPATTERNS
3678    
3679         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
3680         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
3681         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
3682         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
3683         patterns,  something  that  Perl  does  not  provide. The Python syntax         patterns. This feature was not added to Perl until release 5.10. Python
3684         (?P<name>...) is used. Names consist  of  alphanumeric  characters  and         had  the  feature earlier, and PCRE introduced it at release 4.0, using
3685         underscores, and must be unique within a pattern.         the Python syntax. PCRE now supports both the Perl and the Python  syn-
3686           tax.
3687         Named  capturing  parentheses  are  still  allocated numbers as well as  
3688         names. The PCRE API provides function calls for extracting the name-to-         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
3689         number  translation table from a compiled pattern. There is also a con-         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
3690         venience function for extracting a captured substring by name. For fur-         to capturing parentheses from other parts of the pattern, such as back-
3691         ther details see the pcreapi documentation.         references, recursion, and conditions, can be made by name as  well  as
3692           by number.
3693    
3694           Names  consist  of  up  to  32 alphanumeric characters and underscores.
3695           Named capturing parentheses are still  allocated  numbers  as  well  as
3696           names,  exactly as if the names were not present. The PCRE API provides
3697           function calls for extracting the name-to-number translation table from
3698           a compiled pattern. There is also a convenience function for extracting
3699           a captured substring by name.
3700    
3701           By default, a name must be unique within a pattern, but it is  possible
3702           to relax this constraint by setting the PCRE_DUPNAMES option at compile
3703           time. This can be useful for patterns where only one  instance  of  the
3704           named  parentheses  can  match. Suppose you want to match the name of a
3705           weekday, either as a 3-letter abbreviation or as the full name, and  in
3706           both cases you want to extract the abbreviation. This pattern (ignoring
3707           the line breaks) does the job:
3708    
3709             (?<DN>Mon|Fri|Sun)(?:day)?|
3710             (?<DN>Tue)(?:sday)?|
3711             (?<DN>Wed)(?:nesday)?|
3712             (?<DN>Thu)(?:rsday)?|
3713             (?<DN>Sat)(?:urday)?
3714    
3715           There are five capturing substrings, but only one is ever set  after  a
3716           match.  (An alternative way of solving this problem is to use a "branch
3717           reset" subpattern, as described in the previous section.)
3718    
3719           The convenience function for extracting the data by  name  returns  the
3720           substring  for  the first (and in this example, the only) subpattern of
3721           that name that matched. This saves searching  to  find  which  numbered
3722           subpattern  it  was. If you make a reference to a non-unique named sub-
3723           pattern from elsewhere in the pattern, the one that corresponds to  the
3724           lowest  number  is used. For further details of the interfaces for han-
3725           dling named subpatterns, see the pcreapi documentation.
3726    
3727    
3728  REPETITION  REPETITION
3729    
3730         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
3731         following items:         fol