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# Line 45  INTRODUCTION Line 45  INTRODUCTION
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
53         client to discover which features are  available.  The  features  them-         client  to  discover  which  features are available. The features them-
54         selves  are described in the pcrebuild page. Documentation about build-         selves are described in the pcrebuild page. Documentation about  build-
55         ing PCRE for various operating systems can be found in the README  file         ing  PCRE for various operating systems can be found in the README file
56         in the source distribution.         in the source distribution.
57    
58         The  library  contains  a number of undocumented internal functions and         The library contains a number of undocumented  internal  functions  and
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. In some environments, it is possible to control which         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         external  symbols  are  exported when a shared library is built, and in
64         these cases the undocumented symbols are not exported.         these cases the undocumented symbols are not exported.
65    
66    
67  USER DOCUMENTATION  USER DOCUMENTATION
68    
69         The  user  documentation  for PCRE comprises a number of different sec-         The user documentation for PCRE comprises a number  of  different  sec-
70         tions. In the "man" format, each of these is a separate "man page".  In         tions.  In the "man" format, each of these is a separate "man page". In
71         the  HTML  format, each is a separate page, linked from the index page.         the HTML format, each is a separate page, linked from the  index  page.
72         In the plain text format, all the sections are concatenated,  for  ease         In  the  plain text format, all the sections are concatenated, for ease
73         of searching. The sections are as follows:         of searching. The sections are as follows:
74    
75           pcre              this document           pcre              this document
# Line 83  USER DOCUMENTATION Line 84  USER DOCUMENTATION
84           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
85           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
86                               regular expressions                               regular expressions
87             pcresyntax        quick syntax reference
88           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
89           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
90           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
# Line 90  USER DOCUMENTATION Line 92  USER DOCUMENTATION
92           pcrestack         discussion of stack usage           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
96         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
97    
98    
99  LIMITATIONS  LIMITATIONS
100    
101         There  are some size limitations in PCRE but it is hoped that they will         There are some size limitations in PCRE but it is hoped that they  will
102         never in practice be relevant.         never in practice be relevant.
103    
104         The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
105         is compiled with the default internal linkage size of 2. If you want to         is compiled with the default internal linkage size of 2. If you want to
106         process regular expressions that are truly enormous,  you  can  compile         process  regular  expressions  that are truly enormous, you can compile
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 is 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  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
113    
114         There is no limit to the number of parenthesized subpatterns, but there         There is no limit to the number of parenthesized subpatterns, but there
115         can be no more than 65535 capturing subpatterns.         can be no more than 65535 capturing subpatterns.
# Line 117  LIMITATIONS Line 117  LIMITATIONS
117         The maximum length of name for a named subpattern is 32 characters, and         The maximum length of name for a named subpattern is 32 characters, and
118         the maximum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
119    
120         The maximum length of a subject string is the largest  positive  number         The  maximum  length of a subject string is the largest positive number
121         that  an integer variable can hold. However, when using the traditional         that an integer variable can hold. However, when using the  traditional
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.         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
129    
130         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
131         encoded in the UTF-8 format. For release 4.0 this was greatly  extended         encoded  in the UTF-8 format. For release 4.0 this was greatly extended
132         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
133         port for Unicode general category properties was added.         port for Unicode general category properties was added.
134    
135         In order process UTF-8 strings, you must build PCRE  to  include  UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
136         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
137         with the PCRE_UTF8 option flag. When you do this, both the pattern  and         with  the PCRE_UTF8 option flag. When you do this, both the pattern and
138         any  subject  strings  that are matched against it are treated as UTF-8         any subject strings that are matched against it are  treated  as  UTF-8
139         strings instead of just strings of bytes.         strings instead of just strings of bytes.
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 occasionally, so should not be         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
144         very big.         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, the Unicode script names such as Arabic or Han,         for a decimal number, the Unicode script names such as Arabic  or  Han,
151         and the derived properties Any and L&. A full  list  is  given  in  the         and  the  derived  properties  Any  and L&. A full list is given in the
152         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
153         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
154         ter},  is  not  supported.   Furthermore,  in Perl, many properties may         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
155         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
156         does not support this.         does not support this.
157    
158         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
159    
160           When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
161           subjects are (by default) checked for validity on entry to the relevant
162           functions. From release 7.3 of PCRE, the check is according  the  rules
163           of  RFC  3629, which are themselves derived from the Unicode specifica-
164           tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
165           allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
166           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
167           to U+DFFF.
168    
169           The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
170           which the Unicode Standard says this: "The Low Surrogate Area does  not
171           contain  any  character  assignments,  consequently  no  character code
172           charts or namelists are provided for this area. Surrogates are reserved
173           for  use  with  UTF-16 and then must be used in pairs." The code points
174           that are encoded by UTF-16 pairs  are  available  as  independent  code
175           points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
176           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
177    
178           If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
179           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
180           that your strings are valid, and therefore want to skip these checks in
181           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
182           compile time or at run time, PCRE assumes that the pattern  or  subject
183           it  is  given  (respectively)  contains only valid UTF-8 codes. In this
184           case, it does not diagnose an invalid UTF-8 string.
185    
186           If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
187           what  happens  depends on why the string is invalid. If the string con-
188           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
189           string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
190           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
191           strings  according  to  the more liberal rules of RFC 2279. However, if
192           the string does not even conform to RFC 2279, the result is  undefined.
193           Your program may crash.
194    
195           If  you  want  to  process  strings  of  values  in the full range 0 to
196           0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
197           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
198           this situation, you will have to apply your own validity check.
199    
200         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and     General comments about UTF-8 mode
        subjects are checked for validity on entry to the  relevant  functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations, you may already know  that  your  strings  are  valid,  and  
        therefore want to skip these checks in order to improve performance. If  
        you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,  
        PCRE  assumes  that  the  pattern or subject it is given (respectively)  
        contains only valid UTF-8 codes. In this case, it does not diagnose  an  
        invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when  
        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may  
        crash.  
201    
202         2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
203         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
204    
205         3. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
206         characters for values greater than \177.         characters for values greater than \177.
207    
208         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
209         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
210    
211         5. The dot metacharacter matches one UTF-8 character instead of a  sin-         4.  The dot metacharacter matches one UTF-8 character instead of a sin-
212         gle byte.         gle byte.
213    
214         6.  The  escape sequence \C can be used to match a single byte in UTF-8         5. The escape sequence \C can be used to match a single byte  in  UTF-8
215         mode, but its use can lead to some strange effects.  This  facility  is         mode,  but  its  use can lead to some strange effects. This facility is
216         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
217    
218         7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly         6. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
219         test characters of any code value, but the characters that PCRE  recog-         test  characters of any code value, but the characters that PCRE recog-
220         nizes  as  digits,  spaces,  or  word characters remain the same set as         nizes as digits, spaces, or word characters  remain  the  same  set  as
221         before, all with values less than 256. This remains true even when PCRE         before, all with values less than 256. This remains true even when PCRE
222         includes  Unicode  property support, because to do otherwise would slow         includes Unicode property support, because to do otherwise  would  slow
223         down PCRE in many common cases. If you really want to test for a  wider         down  PCRE in many common cases. If you really want to test for a wider
224         sense  of,  say,  "digit",  you must use Unicode property tests such as         sense of, say, "digit", you must use Unicode  property  tests  such  as
225         \p{Nd}.         \p{Nd}.
226    
227         8. Similarly, characters that match the POSIX named  character  classes         7.  Similarly,  characters that match the POSIX named character classes
228         are all low-valued characters.         are all low-valued characters.
229    
230         9.  Case-insensitive  matching  applies only to characters whose values         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
231         are less than 128, unless PCRE is built with Unicode property  support.         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
232         Even  when  Unicode  property support is available, PCRE still uses its         acters.
233         own character tables when checking the case of  low-valued  characters,  
234         so  as not to degrade performance.  The Unicode property information is         9. Case-insensitive matching applies only to  characters  whose  values
235           are  less than 128, unless PCRE is built with Unicode property support.
236           Even when Unicode property support is available, PCRE  still  uses  its
237           own  character  tables when checking the case of low-valued characters,
238           so as not to degrade performance.  The Unicode property information  is
239         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Even when Unicode property
240         support is available, PCRE supports case-insensitive matching only when         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         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-         small number of many-to-one mappings in Unicode;  these  are  not  sup-
243         ported by PCRE.         ported by PCRE.
244    
245    
# Line 215  AUTHOR Line 249  AUTHOR
249         University Computing Service         University Computing Service
250         Cambridge CB2 3QH, 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 two initials,         so I've taken it away. If you want to email me, use  my  two  initials,
254         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
255    
256    
257  REVISION  REVISION
258    
259         Last updated: 18 April 2007         Last updated: 09 August 2007
260         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
261  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
262    
# Line 390  AVOIDING EXCESSIVE STACK USAGE Line 424  AVOIDING EXCESSIVE STACK USAGE
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  LIMITING PCRE RESOURCE USAGE
# Line 451  USING EBCDIC CODE Line 489  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. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
498         bles.         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    
501    
502  SEE ALSO  SEE ALSO
# Line 474  AUTHOR Line 513  AUTHOR
513    
514  REVISION  REVISION
515    
516         Last updated: 16 April 2007         Last updated: 30 July 2007
517         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
518  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
519    
# Line 618  THE ALTERNATIVE MATCHING ALGORITHM Line 657  THE ALTERNATIVE MATCHING ALGORITHM
657         6.  Callouts  are  supported, but the value of the capture_top field is         6.  Callouts  are  supported, but the value of the capture_top field is
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         7.  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 alterna-         single  byte, even in UTF-8 mode, is not supported because the alterna-
662         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
663         time, for all 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 ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
670    
671         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
672         tages:         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 alternative algorithm.         rithm for partial matching do not apply to the  alternative  algorithm.
682         For non-anchored patterns, the starting position of a partial match  is         For  non-anchored patterns, the starting position of a partial match is
683         available.         available.
684    
685         3.  Because  the  alternative  algorithm  scans the subject string just         3. Because the alternative algorithm  scans  the  subject  string  just
686         once, and never needs to backtrack, it is possible to  pass  very  long         once,  and  never  needs to backtrack, it is possible to pass very long
687         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
688         for partial matching each time.         for partial matching each time.
689    
690    
# Line 650  DISADVANTAGES OF THE ALTERNATIVE ALGORIT Line 692  DISADVANTAGES OF THE ALTERNATIVE ALGORIT
692    
693         The alternative 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.
# Line 669  AUTHOR Line 711  AUTHOR
711    
712  REVISION  REVISION
713    
714         Last updated: 29 May 2007         Last updated: 08 August 2007
715         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
716  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
717    
# Line 1213  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. As PCRE has developed, some error codes  have         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.         fallen out of use. To avoid confusion, they have not been re-used.
1275    
1276            0  no error            0  no error
# Line 1259  COMPILATION ERROR CODES Line 1302  COMPILATION ERROR CODES
1302           26  malformed number or name 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
# Line 1280  COMPILATION ERROR CODES Line 1323  COMPILATION ERROR CODES
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)           48  subpattern name is too long (maximum 32 characters)
1325           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10,000)
1326           50  repeated subpattern is too long           50  [this code is not in use]
1327           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1328           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1329           53   internal  error:  previously-checked  referenced  subpattern not           53  internal  error:  previously-checked  referenced  subpattern  not
1330         found         found
1331           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1332           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1333           56  inconsistent NEWLINE options"           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 1295  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 is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1368         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1369         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1370         after calling pcre_study(), to be sure that it has run successfully.         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():
# Line 1332  STUDYING A PATTERN Line 1378  STUDYING A PATTERN
1378             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1379    
1380         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1381         that  do not have a single fixed starting character. A bitmap of possi-         that do not have a single fixed starting character. A bitmap of  possi-
1382         ble starting bytes is created.         ble starting bytes is created.
1383    
1384    
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. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1393         code is discouraged. If you are handling characters with codes  greater         code  is discouraged. If you are handling characters with codes greater
1394         than  128, you should either use UTF-8 and Unicode, or use locales, but         than 128, you should either use UTF-8 and Unicode, or use locales,  but
1395         not try to mix the two.         not try to mix the two.
1396    
1397         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1398         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1399         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1400         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1401         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1402         which may cause them to be different.         which may cause them to be different.
1403    
1404         The  internal tables can always be overridden by tables supplied by the         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         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-         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.         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
1411         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1412         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1413         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1414         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1415    
1416           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1417           tables = pcre_maketables();           tables = pcre_maketables();
1418           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1419    
1420         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1421         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1422    
1423         When pcre_maketables() runs, the tables are built  in  memory  that  is         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         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         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 1397  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 1413  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;
# Line 1426  INFORMATION ABOUT A PATTERN Line 1472  INFORMATION ABOUT A PATTERN
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. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1501         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1502         is still recognized for backwards 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), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. 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
1509    
1510         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1511         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1512    
1513         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1514         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1515         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1516    
1517           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1518    
1519         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1520         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1521         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
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           PCRE_INFO_JCHANGED
1526    
1527         Return  1  if the (?J) option setting is used in the pattern, otherwise         Return 1 if the (?J) option setting is used in the  pattern,  otherwise
1528         0. The fourth argument should point to an int variable. The (?J) inter-         0. The fourth argument should point to an int variable. The (?J) inter-
1529         nal option setting changes the local PCRE_DUPNAMES value.         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
1534         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1535         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1536         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1537         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1538         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1539         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1540    
# Line 1496  INFORMATION ABOUT A PATTERN Line 1542  INFORMATION ABOUT A PATTERN
1542           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1543           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
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. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1548         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1549         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1550         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1551         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1552         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1553         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
1557         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1558         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1559         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table  (a  pointer  to  char).  The
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         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1564         theses numbers. For example, consider  the  following  pattern  (assume         theses  numbers.  For  example,  consider the following pattern (assume
1565         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
1566         ignored):         ignored):
1567    
1568           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1569           (?<month>\d\d) - (?<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,
1573         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1574         as ??:         as ??:
1575    
# Line 1532  INFORMATION ABOUT A PATTERN Line 1578  INFORMATION ABOUT A PATTERN
1578           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
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 the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
1583         to be different for each compiled pattern.         to be different for each compiled pattern.
1584    
1585           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1586    
1587         Return  1 if the pattern can be used for partial matching, otherwise 0.         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         The  fourth  argument  should point to an int variable. The pcrepartial
1589         documentation  lists  the restrictions that apply to patterns when par-         documentation lists the restrictions that apply to patterns  when  par-
1590         tial matching is used.         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 1564  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 1572  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 1582  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 1604  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 1628  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 1658  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 pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
1715         fields (not necessarily in this order):         fields (not necessarily in this order):
1716    
1717           unsigned long int flags;           unsigned long int flags;
# Line 1671  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1721  MATCHING A PATTERN: THE TRADITIONAL FUNC
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
# Line 1680  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1730  MATCHING A PATTERN: THE TRADITIONAL FUNC
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 set by match_limit  is  imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
1747         on  the  number  of times this function is called during a match, which         on the number of times this function is called during  a  match,  which
1748         has the effect of limiting the amount of  backtracking  that  can  take         has  the  effect  of  limiting the amount of backtracking that can take
1749         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1750         for each position in the subject string.         for each position in the subject string.
1751    
1752         The default value for the limit can be set  when  PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
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 override 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,    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  match_limit_recursion field is similar to match_limit, but instead         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         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         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-         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.         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         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         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.         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         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         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         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         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         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1774         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1775    
1776         The  pcre_callout  field is used in conjunction with the "callout" fea-         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_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
1794         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1795         PCRE_PARTIAL.         PCRE_PARTIAL.
1796    
1797           PCRE_ANCHORED           PCRE_ANCHORED
1798    
1799         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1800         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
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           PCRE_NEWLINE_CR
# Line 1757  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1807  MATCHING A PATTERN: THE TRADITIONAL FUNC
1807           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1808           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1809    
1810         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
1811         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
1812         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
1813         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         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         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,         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,
1816         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt         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-         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         tion is advanced by two characters instead of one, in other  words,  to
1819         after the CRLF.         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 2039  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2090  MATCHING A PATTERN: THE TRADITIONAL FUNC
2090         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2091         description above.         description above.
2092    
          PCRE_ERROR_NULLWSLIMIT    (-22)  
   
        When a group that can match an empty  substring  is  repeated  with  an  
        unbounded  upper  limit, the subject position at the start of the group  
        must be remembered, so that a test for an empty string can be made when  
        the  end  of the group is reached. Some workspace is required for this;  
        if it runs out, this error is given.  
   
2093           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2094    
2095         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2096    
2097         Error numbers -16 to -20 are not used by pcre_exec().         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 2199  DUPLICATE SUBPATTERN NAMES Line 2242  DUPLICATE SUBPATTERN NAMES
2242         subpatterns  are  not  required  to  be unique. Normally, patterns with         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         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-         subpatterns  participates. An example is shown in the pcrepattern docu-
2245         mentation. When duplicates are present, pcre_copy_named_substring() and         mentation.
2246    
2247           When   duplicates   are   present,   pcre_copy_named_substring()    and
2248         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring()  return the first substring corresponding to
2249         the given name that is set.  If  none  are  set,  an  empty  string  is         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
2250         returned.  The pcre_get_stringnumber() function returns one of the num-         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
2251         bers that are associated with the name, but it is not defined which  it         function returns one of the numbers that are associated with the  name,
2252         is.         but it is not defined which it is.
2253    
2254         If  you want to get full details of all captured substrings for a given         If  you want to get full details of all captured substrings for a given
2255         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name, you must use  the  pcre_get_stringtable_entries()  function.  The
# Line 2406  AUTHOR Line 2451  AUTHOR
2451    
2452  REVISION  REVISION
2453    
2454         Last updated: 04 June 2007         Last updated: 09 August 2007
2455         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2456  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2457    
# Line 2593  DIFFERENCES BETWEEN PCRE AND PERL Line 2638  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  mainly         handle regular expressions. The differences described here  are  mainly
2641         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2642         tures that are expected to be in the forthcoming Perl 5.10.         some features that are expected to be in the forthcoming Perl 5.10.
2643    
2644         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2645         of  what  it does have are given in the section on UTF-8 support in the         of  what  it does have are given in the section on UTF-8 support in the
# Line 2659  DIFFERENCES BETWEEN PCRE AND PERL Line 2704  DIFFERENCES BETWEEN PCRE AND PERL
2704         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  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         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2708           (*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         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         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:         for some time. This list is with respect to Perl 5.10:
# Line 2672  DIFFERENCES BETWEEN PCRE AND PERL Line 2723  DIFFERENCES BETWEEN PCRE AND PERL
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.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2727         ignored. (Perl can be made to issue a warning.)         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 2705  AUTHOR Line 2756  AUTHOR
2756    
2757  REVISION  REVISION
2758    
2759         Last updated: 06 March 2007         Last updated: 08 August 2007
2760         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2761  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2762    
# Line 2719  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 2866  BACKSLASH Line 2919  BACKSLASH
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). Any number of hexadecimal  digits  may  appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
2921         between  \x{  and  },  but the value of the character code must be less         between  \x{  and  },  but the value of the character code must be less
2922         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
2923         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
2924         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
2925         nating  }, this form of escape is not recognized.  Instead, the initial  
2926         \x will be interpreted as a basic hexadecimal escape, with no following         If characters other than hexadecimal digits appear between \x{  and  },
2927         digits, giving a character whose 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. There is no difference in the way  they  are  han-         two  syntaxes  for  \x. There is no difference in the way they are han-
2934         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
2935    
2936         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
2937         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
2938         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
2939         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
2940         if the pattern character that follows is itself an octal digit.         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-
2944         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
2945         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
2946         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
2947         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
2948         of parenthesized subpatterns.         of parenthesized subpatterns.
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 uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
2953         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
2954         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
2955         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
2956         example:         example:
2957    
2958           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2914  BACKSLASH Line 2970  BACKSLASH
2970           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
2971                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
2972    
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 character value can be used both         All the sequences that define a single character value can be used both
2977         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
2978         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
2979         08),  and the sequences \R and \X are interpreted as the characters "R"         08), and the sequences \R and \X are interpreted as the characters  "R"
2980         and "X", respectively. Outside a character class, these sequences  have         and  "X", respectively. Outside a character class, these sequences have
2981         different meanings (see below).         different meanings (see below).
2982    
2983     Absolute and relative back references     Absolute and relative back references
2984    
2985         The  sequence  \g followed by a positive or negative number, optionally         The sequence \g followed by an unsigned or a negative  number,  option-
2986         enclosed in braces, is an absolute or relative back reference. A  named         ally  enclosed  in braces, is an absolute or relative back reference. A
2987         back  reference can be coded as \g{name}. Back references are discussed         named back reference can be coded as \g{name}. Back references are dis-
2988         later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
2989    
2990     Generic character types     Generic character types
2991    
# Line 2938  BACKSLASH Line 2994  BACKSLASH
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).  (If         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-         "use locale;" is included in a Perl script, \s may match the VT charac-
3019         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3020    
3021         A "word" character is an underscore or any character less than 256 that         In  UTF-8 mode, characters with values greater than 128 never match \d,
        is  a  letter  or  digit.  The definition of letters and digits is con-  
        trolled by PCRE's low-valued character tables, and may vary if  locale-  
        specific  matching is taking place (see "Locale support" in the pcreapi  
        page). For example, in a French locale such  as  "fr_FR"  in  Unix-like  
        systems,  or "french" in Windows, some character codes greater than 128  
        are used for accented letters, and these are matched by \w.  
   
        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-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3023         code character property support is available. The use of  locales  with         code  character  property  support is available. These sequences retain
3024         Unicode is discouraged.         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
3062           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-
3064           specific matching is taking place (see "Locale support" in the  pcreapi
3065           page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3066           systems, or "french" in Windows, some character codes greater than  128
3067           are  used for accented letters, and these are matched by \w. The use of
3068           locales with Unicode is discouraged.
3069    
3070     Newline sequences     Newline sequences
3071    
3072         Outside  a  character class, the escape sequence \R matches any Unicode         Outside a character class, the escape sequence \R matches  any  Unicode
3073         newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is         newline  sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is
3074         equivalent to the following:         equivalent to the following:
3075    
3076           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3077    
3078         This  is  an  example  of an "atomic group", details of which are given         This is an example of an "atomic group", details  of  which  are  given
3079         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3080         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,         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         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         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3083         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3084    
3085         In UTF-8 mode, two additional characters whose codepoints  are  greater         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-         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         rator,  U+2029).   Unicode character property support is not needed for
3088         these characters to be recognized.         these characters to be recognized.
3089    
3090         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
# Line 2996  BACKSLASH Line 3092  BACKSLASH
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  character  properties  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           they do work in this mode.  The extra escape sequences are:
3099    
3100           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3101           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3102           \X       an extended Unicode sequence           \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         script names, the general category properties, and "Any", which matches         script names, the general category properties, and "Any", which matches
3106         any character (including newline). Other properties such as "InMusical-         any character (including newline). Other properties such as "InMusical-
3107         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
3108         not match any characters, so always causes a match failure.         not match any characters, so always causes a match failure.
3109    
3110         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3111         A character from one of these sets can be matched using a script  name.         A  character from one of these sets can be matched using a script name.
3112         For example:         For example:
3113    
3114           \p{Greek}           \p{Greek}
3115           \P{Han}           \P{Han}
3116    
3117         Those  that are not part of an identified script are lumped together as         Those that are not part of an identified script are lumped together  as
3118         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3119    
3120         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3121         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
3122         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3123         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
3124         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
3125         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3126         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
3127         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3128         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3129    
3130         Each character has exactly one general category property, specified  by         Each  character has exactly one general category property, specified by
3131         a two-letter abbreviation. For compatibility with Perl, negation can be         a two-letter abbreviation. For compatibility with Perl, negation can be
3132         specified by including a circumflex between the opening brace  and  the         specified  by  including a circumflex between the opening brace and the
3133         property name. For example, \p{^Lu} is the same as \P{Lu}.         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-         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         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         the absence of negation, the curly brackets in the escape sequence  are
3138         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3139    
3140           \p{L}           \p{L}
# Line 3088  BACKSLASH Line 3186  BACKSLASH
3186           Zp    Paragraph separator           Zp    Paragraph separator
3187           Zs    Space separator           Zs    Space separator
3188    
3189         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3190         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3191         classified as a modifier or "other".         classified as a modifier or "other".
3192    
3193         The long synonyms for these properties  that  Perl  supports  (such  as         The  Cs  (Surrogate)  property  applies only to characters in the range
3194         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
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".         any of these properties with "Is".
3202    
3203         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3204         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3205         in the Unicode table.         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.
3209    
3210         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3211         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3212    
3213           (?>\PM\pM*)           (?>\PM\pM*)
3214    
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     Resetting the match start
3228    
3229         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         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         ously matched characters not  to  be  included  in  the  final  matched
3231         sequence. For example, the pattern:         sequence. For example, the pattern:
3232    
3233           foo\Kbar           foo\Kbar
3234    
3235         matches "foobar", but reports that it has matched "bar".  This  feature         matches  "foobar",  but reports that it has matched "bar". This feature
3236         is  similar  to  a lookbehind assertion (described below).  However, in         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         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         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,         not  interfere  with  the setting of captured substrings.  For example,
3240         when the pattern         when the pattern
3241    
3242           (foo)\Kbar           (foo)\Kbar
# Line 3139  BACKSLASH Line 3245  BACKSLASH
3245    
3246     Simple assertions     Simple assertions
3247    
3248         The  final 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
# Line 3153  BACKSLASH Line 3259  BACKSLASH
3259           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3260           \G     matches at the first matching position in the subject           \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 at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3281         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at 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
3285         of pcre_exec(). It differs from \A when the  value  of  startoffset  is         of  pcre_exec().  It  differs  from \A when the value of startoffset is
3286         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
3287         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3288         mentation where \G can be useful.         mentation where \G can be useful.
3289    
3290         Note,  however,  that  PCRE's interpretation of \G, as the start of the         Note, however, that PCRE's interpretation of \G, as the  start  of  the
3291         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3292         end  of  the  previous  match. In Perl, these can be different when the         end of the previous match. In Perl, these can  be  different  when  the
3293         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
3294         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3295    
3296         If  all  the alternatives of a pattern begin with \G, the expression is         If all the alternatives of a pattern begin with \G, the  expression  is
3297         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3298         in the compiled regular expression.         in the compiled regular expression.
3299    
# Line 3195  BACKSLASH Line 3301  BACKSLASH
3301  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3302    
3303         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3304         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
3305         point  is  at the start of the subject string. If the startoffset argu-         point is at the start of the subject string. If the  startoffset  argu-
3306         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the
3307         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
3308         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3309    
3310         Circumflex need not be the first character of the pattern if  a  number         Circumflex  need  not be the first character of the pattern if a number
3311         of  alternatives are involved, but it should be the first thing in each         of alternatives are involved, but it should be the first thing in  each
3312         alternative in which it appears if the pattern is ever  to  match  that         alternative  in  which  it appears if the pattern is ever to match that
3313         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
3314         if the pattern is constrained to match only at the start  of  the  sub-         if  the  pattern  is constrained to match only at the start of the sub-
3315         ject,  it  is  said  to be an "anchored" pattern. (There are also other         ject, it is said to be an "anchored" pattern.  (There  are  also  other
3316         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
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 at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3321         be  the  last  character of the pattern if a number of alternatives are         be the last character of the pattern if a number  of  alternatives  are
3322         involved, but it should be the last item in  any  branch  in  which  it         involved,  but  it  should  be  the last item in any branch in which it
3323         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a 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,  a  circumflex         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3331         matches  immediately after internal newlines as well as at the start of         matches immediately after internal newlines as well as at the start  of
3332         the subject string. It does not match after a  newline  that  ends  the         the  subject  string.  It  does not match after a newline that ends the
3333         string.  A dollar matches before any newlines in the string, as well as         string. A dollar matches before any newlines in the string, as well  as
3334         at the very end, when PCRE_MULTILINE is set. When newline is  specified         at  the very end, when PCRE_MULTILINE is set. When newline is specified
3335         as  the  two-character  sequence CRLF, isolated CR and LF characters do         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3336         not indicate newlines.         not indicate newlines.
3337    
3338         For example, the pattern /^abc$/ matches the subject string  "def\nabc"         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3339         (where  \n  represents a newline) in multiline mode, but not otherwise.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3340         Consequently, patterns that are anchored in single  line  mode  because         Consequently,  patterns  that  are anchored in single line mode because
3341         all  branches  start  with  ^ are not anchored in multiline mode, and a         all branches start with ^ are not anchored in  multiline  mode,  and  a
3342         match for circumflex is  possible  when  the  startoffset  argument  of         match  for  circumflex  is  possible  when  the startoffset argument of
3343         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if
3344         PCRE_MULTILINE is set.         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 or not  PCRE_MULTILINE  is         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
3349         set.         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 string except (by default) a character  that  signi-         ter  in  the subject string except (by default) a character that signi-
3356         fies  the  end  of  a line. In UTF-8 mode, the matched character may be         fies the end of a line. In UTF-8 mode, the  matched  character  may  be
3357         more than one byte long.         more than one byte long.
3358    
3359         When a line ending is defined as a single character, dot never  matches         When  a line ending is defined as a single character, dot never matches
3360         that  character; when the two-character sequence CRLF is used, dot does         that character; when the two-character sequence CRLF is used, dot  does
3361         not match CR if it is immediately followed  by  LF,  but  otherwise  it         not  match  CR  if  it  is immediately followed by LF, but otherwise it
3362         matches  all characters (including isolated CRs and LFs). When any Uni-         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         code  line endings are being recognized, dot does not match CR or LF or
3364         any of the other line ending characters.         any of the other line ending characters.
3365    
3366         The  behaviour  of  dot  with regard to newlines can be changed. If the         The behaviour of dot with regard to newlines can  be  changed.  If  the
3367         PCRE_DOTALL option is set, a dot matches  any  one  character,  without         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         exception. If the two-character sequence CRLF is present in the subject
3369         string, it takes two dots to match it.         string, it takes two dots to match it.
3370    
3371         The handling of dot is entirely independent of the handling of  circum-         The  handling of dot is entirely independent of the handling of circum-
3372         flex  and  dollar,  the  only relationship being that they both involve         flex and dollar, the only relationship being  that  they  both  involve
3373         newlines. Dot has no special meaning in a character class.         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 always matches any         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
3380         line-ending characters. The feature is provided in  Perl  in  order  to         line-ending  characters.  The  feature  is provided in Perl in order to
3381         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-
3382         acters into individual bytes, what remains in the string may be a  mal-         acters  into individual bytes, what remains in the string may be a mal-
3383         formed  UTF-8  string.  For this reason, the \C escape sequence is best         formed UTF-8 string. For this reason, the \C escape  sequence  is  best
3384         avoided.         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 3287  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         Characters that might indicate line breaks are  never  treated  in  any         Characters  that  might  indicate  line breaks are never treated in any
3432         special  way  when  matching  character  classes,  whatever line-ending         special way  when  matching  character  classes,  whatever  line-ending
3433         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and         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         PCRE_MULTILINE options is used. A class such as [^a] always matches one
3435         of these characters.         of these characters.
3436    
3437         The minus (hyphen) character can be used to specify a range of  charac-         The  minus (hyphen) character can be used to specify a range of charac-
3438         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3439         between d and m, inclusive. If a  minus  character  is  required  in  a         between  d  and  m,  inclusive.  If  a minus character is required in a
3440         class,  it  must  be  escaped  with a backslash or appear in a position         class, it must be escaped with a backslash  or  appear  in  a  position
3441         where it cannot be interpreted as indicating a range, typically as  the         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 a French 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 3399  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 3420  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 left         string). The matching process tries each alternative in turn, from left
3537         to right, and the first one that succeeds is used. If the  alternatives         to  right, and the first one that succeeds is used. If the alternatives
3538         are  within a subpattern (defined below), "succeeds" means matching the         are within a subpattern (defined below), "succeeds" means matching  the
3539         rest of the main pattern as well as the alternative in the  subpattern.         rest  of the main pattern as well as the alternative in the subpattern.
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 3447  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 (see below for a description of         An option change within a subpattern (see below for  a  description  of
3568         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3569         it, so         it, so
3570    
3571           (a(?i)b)c           (a(?i)b)c
3572    
3573         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
3574         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
3575         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
3576         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
3577         example,         example,
3578    
3579           (a(?i)b|c)           (a(?i)b|c)
3580    
3581         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
3582         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
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_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
3587         can  be changed in the same way as the Perl-compatible options by using         can be changed in the same way as the Perl-compatible options by  using
3588         the characters J, U and X respectively.         the characters J, U and X respectively.
3589    
3590    
# Line 3491  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  an  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 3510  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))
# Line 3523  SUBPATTERNS Line 3629  SUBPATTERNS
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.         1 and 2. The maximum number of capturing subpatterns is 65535.
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. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
3684         had the feature earlier, and PCRE introduced it at release  4.0,  using         had  the  feature earlier, and PCRE introduced it at release 4.0, using
3685         the  Python syntax. PCRE now supports both the Perl and the Python syn-         the Python syntax. PCRE now supports both the Perl and the Python  syn-
3686         tax.         tax.
3687    
3688         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
3689         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
3690         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
3691         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
3692         by number.         by number.
3693    
3694         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
3695         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
3696         names, exactly as if the names were not present. The PCRE API  provides         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         function calls for extracting the name-to-number translation table from
3698         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
3699         a captured substring by name.         a captured substring by name.
3700    
3701         By  default, a name must be unique within a pattern, but it is possible         By default, a name must be unique within a pattern, but it is  possible
3702         to relax this constraint by setting the PCRE_DUPNAMES option at compile         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         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         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         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         both cases you want to extract the abbreviation. This pattern (ignoring
3707         the line breaks) does the job:         the line breaks) does the job:
3708    
# Line 3575  NAMED SUBPATTERNS Line 3712  NAMED SUBPATTERNS
3712           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
3713           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
3714    
3715         There  are  five capturing substrings, but only one is ever set after a         There are five capturing substrings, but only one is ever set  after  a
3716         match.  The convenience  function  for  extracting  the  data  by  name         match.  (An alternative way of solving this problem is to use a "branch
3717         returns  the  substring  for  the first (and in this example, the only)         reset" subpattern, as described in the previous section.)
3718         subpattern of that name that matched.  This  saves  searching  to  find  
3719         which  numbered  subpattern  it  was. If you make a reference to a non-         The convenience function for extracting the data by  name  returns  the
3720         unique named subpattern from elsewhere in the  pattern,  the  one  that         substring  for  the first (and in this example, the only) subpattern of
3721         corresponds  to  the  lowest number is used. For further details of the         that name that matched. This saves searching  to  find  which  numbered
3722         interfaces for handling named subpatterns, see the  pcreapi  documenta-         subpattern  it  was. If you make a reference to a non-unique named sub-
3723         tion.         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:         following items:
3732    
3733           a literal data character           a literal data character
# Line 3601  REPETITION Line 3740  REPETITION
3740           a back reference (see next section)           a back reference (see next section)
3741           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
3742    
3743         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
3744         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
3745         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
3746         and the first must be less than or equal to the second. For example:         and the first must be less than or equal to the second. For example:
3747    
3748           z{2,4}           z{2,4}
3749    
3750         matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a         matches "zz", "zzz", or "zzzz". A closing brace on its  own  is  not  a
3751         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
3752         present,  there  is  no upper limit; if the second number and the comma         present, there is no upper limit; if the second number  and  the  comma
3753         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
3754         matches. Thus         matches. Thus
3755    
3756           [aeiou]{3,}           [aeiou]{3,}
# Line 3620  REPETITION Line 3759  REPETITION
3759    
3760           \d{8}           \d{8}
3761    
3762         matches  exactly  8  digits. An opening curly bracket that appears in a         matches exactly 8 digits. An opening curly bracket that  appears  in  a
3763         position where a quantifier is not allowed, or one that does not  match         position  where a quantifier is not allowed, or one that does not match
3764         the  syntax of a quantifier, is taken as a literal character. For exam-         the syntax of a quantifier, is taken as a literal character. For  exam-
3765         ple, {,6} is not a quantifier, but a literal string of four characters.         ple, {,6} is not a quantifier, but a literal string of four characters.
3766    
3767         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to         In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to
3768         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
3769         acters, each of which is represented by a two-byte sequence. Similarly,         acters, each of which is represented by a two-byte sequence. Similarly,
3770         when Unicode property support is available, \X{3} matches three Unicode         when Unicode property support is available, \X{3} matches three Unicode
3771         extended  sequences,  each of which may be several bytes long (and they         extended sequences, each of which may be several bytes long  (and  they
3772         may be of different lengths).         may be of different lengths).
3773    
3774         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
3775         the previous item and the quantifier were not present.         the previous item and the quantifier were not present.
3776    
3777         For  convenience, the three most common quantifiers have single-charac-         For convenience, the three most common quantifiers have  single-charac-
3778         ter abbreviations:         ter abbreviations:
3779    
3780           *    is equivalent to {0,}           *    is equivalent to {0,}
3781           +    is equivalent to {1,}           +    is equivalent to {1,}
3782           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
3783    
3784         It is possible to construct infinite loops by  following  a  subpattern         It  is  possible  to construct infinite loops by following a subpattern
3785         that can match no characters with a quantifier that has no upper limit,         that can match no characters with a quantifier that has no upper limit,
3786         for example:         for example:
3787    
3788           (a?)*           (a?)*
3789    
3790         Earlier versions of Perl and PCRE used to give an error at compile time         Earlier versions of Perl and PCRE used to give an error at compile time
3791         for  such  patterns. However, because there are cases where this can be         for such patterns. However, because there are cases where this  can  be
3792         useful, such patterns are now accepted, but if any  repetition  of  the         useful,  such  patterns  are now accepted, but if any repetition of the
3793         subpattern  does in fact match no characters, the loop is forcibly bro-         subpattern does in fact match no characters, the loop is forcibly  bro-
3794         ken.         ken.
3795    
3796         By default, the quantifiers are "greedy", that is, they match  as  much         By  default,  the quantifiers are "greedy", that is, they match as much
3797         as  possible  (up  to  the  maximum number of permitted times), without         as possible (up to the maximum  number  of  permitted  times),  without
3798         causing the rest of the pattern to fail. The classic example  of  where         causing  the  rest of the pattern to fail. The classic example of where
3799         this gives problems is in trying to match comments in C programs. These         this gives problems is in trying to match comments in C programs. These
3800         appear between /* and */ and within the comment,  individual  *  and  /         appear  between  /*  and  */ and within the comment, individual * and /
3801         characters  may  appear. An attempt to match C comments by applying the         characters may appear. An attempt to match C comments by  applying  the
3802         pattern         pattern
3803    
3804           /\*.*\*/           /\*.*\*/
# Line 3668  REPETITION Line 3807  REPETITION
3807    
3808           /* first comment */  not comment  /* second comment */           /* first comment */  not comment  /* second comment */
3809    
3810         fails, because it matches the entire string owing to the greediness  of         fails,  because it matches the entire string owing to the greediness of
3811         the .*  item.         the .*  item.
3812    
3813         However,  if  a quantifier is followed by a question mark, it ceases to         However, if a quantifier is followed by a question mark, it  ceases  to
3814         be greedy, and instead matches the minimum number of times possible, so         be greedy, and instead matches the minimum number of times possible, so
3815         the pattern         the pattern
3816    
3817           /\*.*?\*/           /\*.*?\*/
3818    
3819         does  the  right  thing with the C comments. The meaning of the various         does the right thing with the C comments. The meaning  of  the  various
3820         quantifiers is not otherwise changed,  just  the  preferred  number  of         quantifiers  is  not  otherwise  changed,  just the preferred number of
3821         matches.   Do  not  confuse this use of question mark with its use as a         matches.  Do not confuse this use of question mark with its  use  as  a
3822         quantifier in its own right. Because it has two uses, it can  sometimes         quantifier  in its own right. Because it has two uses, it can sometimes
3823         appear doubled, as in         appear doubled, as in
3824    
3825           \d??\d           \d??\d
# Line 3688  REPETITION Line 3827  REPETITION
3827         which matches one digit by preference, but can match two if that is the         which matches one digit by preference, but can match two if that is the
3828         only way the rest of the pattern matches.         only way the rest of the pattern matches.
3829    
3830         If the PCRE_UNGREEDY option is set (an option that is not available  in         If  the PCRE_UNGREEDY option is set (an option that is not available in
3831         Perl),  the  quantifiers are not greedy by default, but individual ones         Perl), the quantifiers are not greedy by default, but  individual  ones
3832         can be made greedy by following them with a  question  mark.  In  other         can  be  made  greedy  by following them with a question mark. In other
3833         words, it inverts the default behaviour.         words, it inverts the default behaviour.
3834    
3835         When  a  parenthesized  subpattern  is quantified with a minimum repeat         When a parenthesized subpattern is quantified  with  a  minimum  repeat
3836         count that is greater than 1 or with a limited maximum, more memory  is         count  that is greater than 1 or with a limited maximum, more memory is
3837         required  for  the  compiled  pattern, in proportion to the size of the         required for the compiled pattern, in proportion to  the  size  of  the
3838         minimum or maximum.         minimum or maximum.
3839    
3840         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
3841         alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,         alent to Perl's /s) is set, thus allowing the dot  to  match  newlines,
3842         the pattern is implicitly anchored, because whatever  follows  will  be         the  pattern  is  implicitly anchored, because whatever follows will be
3843         tried  against every character position in the subject string, so there         tried against every character position in the subject string, so  there
3844         is no point in retrying the overall match at  any  position  after  the         is  no  point  in  retrying the overall match at any position after the
3845         first.  PCRE  normally treats such a pattern as though it were preceded         first. PCRE normally treats such a pattern as though it  were  preceded
3846         by \A.         by \A.
3847    
3848         In cases where it is known that the subject  string  contains  no  new-         In  cases  where  it  is known that the subject string contains no new-
3849         lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-         lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
3850         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
3851    
3852         However, there is one situation where the optimization cannot be  used.         However,  there is one situation where the optimization cannot be used.
3853         When  .*   is  inside  capturing  parentheses that are the subject of a         When .*  is inside capturing parentheses that  are  the  subject  of  a
3854         backreference elsewhere in the pattern, a match at the start  may  fail         backreference  elsewhere  in the pattern, a match at the start may fail
3855         where a later one succeeds. Consider, for example:         where a later one succeeds. Consider, for example:
3856    
3857           (.*)abc\1           (.*)abc\1
3858    
3859         If  the subject is "xyz123abc123" the match point is the fourth charac-         If the subject is "xyz123abc123" the match point is the fourth  charac-
3860         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
3861    
3862         When a capturing subpattern is repeated, the value captured is the sub-         When a capturing subpattern is repeated, the value captured is the sub-
# Line 3726  REPETITION Line 3865  REPETITION
3865           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+
3866    
3867         has matched "tweedledum tweedledee" the value of the captured substring         has matched "tweedledum tweedledee" the value of the captured substring
3868         is "tweedledee". However, if there are  nested  capturing  subpatterns,         is  "tweedledee".  However,  if there are nested capturing subpatterns,
3869         the  corresponding captured values may have been set in previous itera-         the corresponding captured values may have been set in previous  itera-
3870         tions. For example, after         tions. For example, after
3871    
3872           /(a|(b))+/           /(a|(b))+/
# Line 3737  REPETITION Line 3876  REPETITION
3876    
3877  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
3878    
3879         With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")         With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
3880         repetition,  failure  of what follows normally causes the repeated item         repetition, failure of what follows normally causes the  repeated  item
3881         to be re-evaluated to see if a different number of repeats  allows  the         to  be  re-evaluated to see if a different number of repeats allows the
3882         rest  of  the pattern to match. Sometimes it is useful to prevent this,         rest of the pattern to match. Sometimes it is useful to  prevent  this,
3883         either to change the nature of the match, or to cause it  fail  earlier         either  to  change the nature of the match, or to cause it fail earlier
3884         than  it otherwise might, when the author of the pattern knows there is         than it otherwise might, when the author of the pattern knows there  is
3885         no point in carrying on.         no point in carrying on.
3886    
3887         Consider, for example, the pattern \d+foo when applied to  the  subject         Consider,  for  example, the pattern \d+foo when applied to the subject
3888         line         line
3889    
3890           123456bar           123456bar
3891    
3892         After matching all 6 digits and then failing to match "foo", the normal         After matching all 6 digits and then failing to match "foo", the normal
3893         action of the matcher is to try again with only 5 digits  matching  the         action  of  the matcher is to try again with only 5 digits matching the
3894         \d+  item,  and  then  with  4,  and  so on, before ultimately failing.         \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.
3895         "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides         "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides
3896         the  means for specifying that once a subpattern has matched, it is not         the means for specifying that once a subpattern has matched, it is  not
3897         to be re-evaluated in this way.         to be re-evaluated in this way.
3898    
3899         If we use atomic grouping for the previous example, the  matcher  gives         If  we  use atomic grouping for the previous example, the matcher gives
3900         up  immediately  on failing to match "foo" the first time. The notation         up immediately on failing to match "foo" the first time.  The  notation
3901         is a kind of special parenthesis, starting with (?> as in this example:         is a kind of special parenthesis, starting with (?> as in this example:
3902    
3903           (?>\d+)foo           (?>\d+)foo
3904    
3905         This  kind  of  parenthesis "locks up" the  part of the pattern it con-         This kind of parenthesis "locks up" the  part of the  pattern  it  con-
3906         tains once it has matched, and a failure further into  the  pattern  is         tains  once  it  has matched, and a failure further into the pattern is
3907         prevented  from  backtracking into it. Backtracking past it to previous         prevented from backtracking into it. Backtracking past it  to  previous
3908         items, however, works as normal.         items, however, works as normal.
3909    
3910         An alternative description is that a subpattern of  this  type  matches         An  alternative  description  is that a subpattern of this type matches
3911         the  string  of  characters  that an identical standalone pattern would         the string of characters that an  identical  standalone  pattern  would
3912         match, if anchored at the current point in the subject string.         match, if anchored at the current point in the subject string.
3913    
3914         Atomic grouping subpatterns are not capturing subpatterns. Simple cases         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
3915         such as the above example can be thought of as a maximizing repeat that         such as the above example can be thought of as a maximizing repeat that
3916         must swallow everything it can. So, while both \d+ and  \d+?  are  pre-         must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
3917         pared  to  adjust  the number of digits they match in order to make the         pared to adjust the number of digits they match in order  to  make  the
3918         rest of the pattern match, (?>\d+) can only match an entire sequence of         rest of the pattern match, (?>\d+) can only match an entire sequence of
3919         digits.         digits.
3920    
3921         Atomic  groups in general can of course contain arbitrarily complicated         Atomic groups in general can of course contain arbitrarily  complicated
3922         subpatterns, and can be nested. However, when  the  subpattern  for  an         subpatterns,  and  can  be  nested. However, when the subpattern for an
3923         atomic group is just a single repeated item, as in the example above, a         atomic group is just a single repeated item, as in the example above, a
3924         simpler notation, called a "possessive quantifier" can  be  used.  This         simpler  notation,  called  a "possessive quantifier" can be used. This
3925         consists  of  an  additional  + character following a quantifier. Using         consists of an additional + character  following  a  quantifier.  Using
3926         this notation, the previous example can be rewritten as         this notation, the previous example can be rewritten as
3927    
3928           \d++foo           \d++foo
3929    
3930           Note that a possessive quantifier can be used with an entire group, for
3931           example:
3932    
3933             (abc|xyz){2,3}+
3934    
3935         Possessive  quantifiers  are  always  greedy;  the   setting   of   the         Possessive  quantifiers  are  always  greedy;  the   setting   of   the
3936         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
3937         simpler forms of atomic group. However, there is no difference  in  the         simpler forms of atomic group. However, there is no difference  in  the
# Line 3860  BACK REFERENCES Line 4004  BACK REFERENCES
4004    
4005         Another way of avoiding the ambiguity inherent in  the  use  of  digits         Another way of avoiding the ambiguity inherent in  the  use  of  digits
4006         following a backslash is to use the \g escape sequence, which is a fea-         following a backslash is to use the \g escape sequence, which is a fea-
4007         ture introduced in Perl 5.10. This escape must be followed by  a  posi-         ture introduced in Perl 5.10.  This  escape  must  be  followed  by  an
4008         tive  or  a negative number, optionally enclosed in braces. These exam-         unsigned  number  or  a negative number, optionally enclosed in braces.
4009         ples are all identical:         These examples are all identical:
4010    
4011           (ring), \1           (ring), \1
4012           (ring), \g1           (ring), \g1
4013           (ring), \g{1}           (ring), \g{1}
4014    
4015         A positive number specifies an absolute reference without the ambiguity         An unsigned number specifies an absolute reference without the  ambigu-
4016         that  is  present  in  the older syntax. It is also useful when literal         ity that is present in the older syntax. It is also useful when literal
4017         digits follow the reference. A negative number is a relative reference.         digits follow the reference. A negative number is a relative reference.
4018         Consider this example:         Consider this example:
4019    
# Line 4441  CALLOUTS Line 4585  CALLOUTS
4585         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
4586    
4587    
4588    BACTRACKING CONTROL
4589    
4590           Perl  5.10 introduced a number of "Special Backtracking Control Verbs",
4591           which are described in the Perl documentation as "experimental and sub-
4592           ject  to  change or removal in a future version of Perl". It goes on to
4593           say: "Their usage in production code should be noted to avoid  problems
4594           during upgrades." The same remarks apply to the PCRE features described
4595           in this section.
4596    
4597           Since these verbs are specifically related to backtracking, they can be
4598           used  only  when  the pattern is to be matched using pcre_exec(), which
4599           uses a backtracking algorithm. They cause an error  if  encountered  by
4600           pcre_dfa_exec().
4601    
4602           The  new verbs make use of what was previously invalid syntax: an open-
4603           ing parenthesis followed by an asterisk. In Perl, they are generally of
4604           the form (*VERB:ARG) but PCRE does not support the use of arguments, so
4605           its general form is just (*VERB). Any number of these verbs  may  occur
4606           in a pattern. There are two kinds:
4607    
4608       Verbs that act immediately
4609    
4610           The following verbs act as soon as they are encountered:
4611    
4612              (*ACCEPT)
4613    
4614           This  verb causes the match to end successfully, skipping the remainder
4615           of the pattern. When inside a recursion, only the innermost pattern  is
4616           ended  immediately.  PCRE  differs  from  Perl  in  what happens if the
4617           (*ACCEPT) is inside capturing parentheses. In Perl, the data so far  is
4618           captured: in PCRE no data is captured. For example:
4619    
4620             A(A|B(*ACCEPT)|C)D
4621    
4622           This  matches  "AB", "AAD", or "ACD", but when it matches "AB", no data
4623           is captured.
4624    
4625             (*FAIL) or (*F)
4626    
4627           This verb causes the match to fail, forcing backtracking to  occur.  It
4628           is  equivalent to (?!) but easier to read. The Perl documentation notes
4629           that it is probably useful only when combined  with  (?{})  or  (??{}).
4630           Those  are,  of course, Perl features that are not present in PCRE. The
4631           nearest equivalent is the callout feature, as for example in this  pat-
4632           tern:
4633    
4634             a+(?C)(*FAIL)
4635    
4636           A  match  with the string "aaaa" always fails, but the callout is taken
4637           before each backtrack happens (in this example, 10 times).
4638    
4639       Verbs that act after backtracking
4640    
4641           The following verbs do nothing when they are encountered. Matching con-
4642           tinues  with what follows, but if there is no subsequent match, a fail-
4643           ure is forced.  The verbs  differ  in  exactly  what  kind  of  failure
4644           occurs.
4645    
4646             (*COMMIT)
4647    
4648           This  verb  causes  the whole match to fail outright if the rest of the
4649           pattern does not match. Even if the pattern is unanchored,  no  further
4650           attempts  to find a match by advancing the start point take place. Once
4651           (*COMMIT) has been passed, pcre_exec() is committed to finding a  match
4652           at the current starting point, or not at all. For example:
4653    
4654             a+(*COMMIT)b
4655    
4656           This  matches  "xxaab" but not "aacaab". It can be thought of as a kind
4657           of dynamic anchor, or "I've started, so I must finish."
4658    
4659             (*PRUNE)
4660    
4661           This verb causes the match to fail at the current position if the  rest
4662           of the pattern does not match. If the pattern is unanchored, the normal
4663           "bumpalong" advance to the next starting character then happens.  Back-
4664           tracking  can  occur as usual to the left of (*PRUNE), or when matching
4665           to the right of (*PRUNE), but if there is no match to the right,  back-
4666           tracking  cannot  cross (*PRUNE).  In simple cases, the use of (*PRUNE)
4667           is just an alternative to an atomic group or possessive quantifier, but
4668           there  are  some uses of (*PRUNE) that cannot be expressed in any other
4669           way.
4670    
4671             (*SKIP)
4672    
4673           This verb is like (*PRUNE), except that if the pattern  is  unanchored,
4674           the  "bumpalong" advance is not to the next character, but to the posi-
4675           tion in the subject where (*SKIP) was  encountered.  (*SKIP)  signifies
4676           that  whatever  text  was  matched leading up to it cannot be part of a
4677           successful match. Consider:
4678    
4679             a+(*SKIP)b
4680    
4681           If the subject is "aaaac...",  after  the  first  match  attempt  fails
4682           (starting  at  the  first  character in the string), the starting point
4683           skips on to start the next attempt at "c". Note that a possessive quan-
4684           tifer  does not have the same effect in this example; although it would
4685           suppress backtracking  during  the  first  match  attempt,  the  second
4686           attempt  would  start at the second character instead of skipping on to
4687           "c".
4688    
4689             (*THEN)
4690    
4691           This verb causes a skip to the next alternation if the rest of the pat-
4692           tern does not match. That is, it cancels pending backtracking, but only
4693           within the current alternation. Its name  comes  from  the  observation
4694           that it can be used for a pattern-based if-then-else block:
4695    
4696             ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
4697    
4698           If  the COND1 pattern matches, FOO is tried (and possibly further items
4699           after the end of the group if FOO succeeds);  on  failure  the  matcher
4700           skips  to  the second alternative and tries COND2, without backtracking
4701           into COND1. If (*THEN) is used outside  of  any  alternation,  it  acts
4702           exactly like (*PRUNE).
4703    
4704    
4705  SEE ALSO  SEE ALSO
4706    
4707         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).         pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
# Line 4455  AUTHOR Line 4716  AUTHOR
4716    
4717  REVISION  REVISION
4718    
4719         Last updated: 29 May 2007         Last updated: 09 August 2007
4720           Copyright (c) 1997-2007 University of Cambridge.
4721    ------------------------------------------------------------------------------
4722    
4723    
4724    PCRESYNTAX(3)                                                    PCRESYNTAX(3)
4725    
4726    
4727    NAME
4728           PCRE - Perl-compatible regular expressions
4729    
4730    
4731    PCRE REGULAR EXPRESSION SYNTAX SUMMARY
4732    
4733           The  full syntax and semantics of the regular expressions that are sup-
4734           ported by PCRE are described in  the  pcrepattern  documentation.  This
4735           document contains just a quick-reference summary of the syntax.
4736    
4737    
4738    QUOTING
4739    
4740             \x         where x is non-alphanumeric is a literal x
4741             \Q...\E    treat enclosed characters as literal
4742    
4743    
4744    CHARACTERS
4745    
4746             \a         alarm, that is, the BEL character (hex 07)
4747             \cx        "control-x", where x is any character
4748             \e         escape (hex 1B)
4749             \f         formfeed (hex 0C)
4750             \n         newline (hex 0A)
4751             \r         carriage return (hex 0D)
4752             \t         tab (hex 09)
4753             \ddd       character with octal code ddd, or backreference
4754             \xhh       character with hex code hh
4755             \x{hhh..}  character with hex code hhh..
4756    
4757    
4758    CHARACTER TYPES
4759    
4760             .          any character except newline;
4761                          in dotall mode, any character whatsoever
4762             \C         one byte, even in UTF-8 mode (best avoided)
4763             \d         a decimal digit
4764             \D         a character that is not a decimal digit
4765             \h         a horizontal whitespace character
4766             \H         a character that is not a horizontal whitespace character
4767             \p{xx}     a character with the xx property
4768             \P{xx}     a character without the xx property
4769             \R         a newline sequence
4770             \s         a whitespace character
4771             \S         a character that is not a whitespace character
4772             \v         a vertical whitespace character
4773             \V         a character that is not a vertical whitespace character
4774             \w         a "word" character
4775             \W         a "non-word" character
4776             \X         an extended Unicode sequence
4777    
4778           In PCRE, \d, \D, \s, \S, \w, and \W recognize only ASCII characters.
4779    
4780    
4781    GENERAL CATEGORY PROPERTY CODES FOR \p and \P
4782    
4783             C          Other
4784             Cc         Control
4785             Cf         Format
4786             Cn         Unassigned
4787             Co         Private use
4788             Cs         Surrogate
4789    
4790             L          Letter
4791             Ll         Lower case letter
4792             Lm         Modifier letter
4793             Lo         Other letter
4794             Lt         Title case letter
4795             Lu         Upper case letter
4796             L&         Ll, Lu, or Lt
4797    
4798             M          Mark
4799             Mc         Spacing mark
4800             Me         Enclosing mark
4801             Mn         Non-spacing mark
4802    
4803             N          Number
4804             Nd         Decimal number
4805             Nl         Letter number
4806             No         Other number
4807    
4808             P          Punctuation
4809             Pc         Connector punctuation
4810             Pd         Dash punctuation
4811             Pe         Close punctuation
4812             Pf         Final punctuation
4813             Pi         Initial punctuation
4814             Po         Other punctuation
4815             Ps         Open punctuation
4816    
4817             S          Symbol
4818             Sc         Currency symbol
4819             Sk         Modifier symbol
4820             Sm         Mathematical symbol
4821             So         Other symbol
4822    
4823             Z          Separator
4824             Zl         Line separator
4825             Zp         Paragraph separator
4826             Zs         Space separator
4827    
4828    
4829    SCRIPT NAMES FOR \p AND \P
4830    
4831           Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
4832           Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
4833           Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
4834           Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
4835           gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
4836           Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
4837           Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
4838           Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
4839           Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
4840    
4841    
4842    CHARACTER CLASSES
4843    
4844             [...]       positive character class
4845             [^...]      negative character class
4846             [x-y]       range (can be used for hex characters)
4847             [[:xxx:]]   positive POSIX named set
4848             [[^:xxx:]]  negative POSIX named set
4849    
4850             alnum       alphanumeric
4851             alpha       alphabetic
4852             ascii       0-127
4853             blank       space or tab
4854             cntrl       control character
4855             digit       decimal digit
4856             graph       printing, excluding space
4857             lower       lower case letter
4858             print       printing, including space
4859             punct       printing, excluding alphanumeric
4860             space       whitespace
4861             upper       upper case letter
4862             word        same as \w
4863             xdigit      hexadecimal digit
4864    
4865           In PCRE, POSIX character set names recognize only ASCII characters. You
4866           can use \Q...\E inside a character class.
4867    
4868    
4869    QUANTIFIERS
4870    
4871             ?           0 or 1, greedy
4872             ?+          0 or 1, possessive
4873             ??          0 or 1, lazy
4874             *           0 or more, greedy
4875             *+          0 or more, possessive
4876             *?          0 or more, lazy
4877             +           1 or more, greedy
4878             ++          1 or more, possessive
4879             +?          1 or more, lazy
4880             {n}         exactly n
4881             {n,m}       at least n, no more than m, greedy
4882             {n,m}+      at least n, no more than m, possessive
4883             {n,m}?      at least n, no more than m, lazy
4884             {n,}        n or more, greedy
4885             {n,}+       n or more, possessive
4886             {n,}?       n or more, lazy
4887    
4888    
4889    ANCHORS AND SIMPLE ASSERTIONS
4890    
4891             \b          word boundary
4892             \B          not a word boundary
4893             ^           start of subject
4894                          also after internal newline in multiline mode
4895             \A          start of subject
4896             $           end of subject
4897                          also before newline at end of subject
4898                          also before internal newline in multiline mode
4899             \Z          end of subject
4900                          also before newline at end of subject
4901             \z          end of subject
4902             \G          first matching position in subject
4903    
4904    
4905    MATCH POINT RESET
4906    
4907             \K          reset start of match
4908    
4909    
4910    ALTERNATION
4911    
4912             expr|expr|expr...
4913    
4914    
4915    CAPTURING
4916    
4917             (...)          capturing group
4918             (?<name>...)   named capturing group (Perl)
4919             (?'name'...)   named capturing group (Perl)
4920             (?P<name>...)  named capturing group (Python)
4921             (?:...)        non-capturing group
4922             (?|...)        non-capturing group; reset group numbers for
4923                             capturing groups in each alternative
4924    
4925    
4926    ATOMIC GROUPS
4927    
4928             (?>...)        atomic, non-capturing group
4929    
4930    
4931    COMMENT
4932    
4933             (?#....)       comment (not nestable)
4934    
4935    
4936    OPTION SETTING
4937    
4938             (?i)           caseless
4939             (?J)           allow duplicate names
4940             (?m)           multiline
4941             (?s)           single line (dotall)
4942             (?U)           default ungreedy (lazy)
4943             (?x)           extended (ignore white space)
4944             (?-...)        unset option(s)
4945    
4946    
4947    LOOKAHEAD AND LOOKBEHIND ASSERTIONS
4948    
4949             (?=...)        positive look ahead
4950             (?!...)        negative look ahead
4951             (?<=...)       positive look behind
4952             (?<!...)       negative look behind
4953    
4954           Each top-level branch of a look behind must be of a fixed length.
4955    
4956    
4957    BACKREFERENCES
4958    
4959             \n             reference by number (can be ambiguous)
4960             \gn            reference by number
4961             \g{n}          reference by number
4962             \g{-n}         relative reference by number
4963             \k<name>       reference by name (Perl)
4964             \k'name'       reference by name (Perl)
4965             \g{name}       reference by name (Perl)
4966             \k{name}       reference by name (.NET)
4967             (?P=name)      reference by name (Python)
4968    
4969    
4970    SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)
4971    
4972             (?R)           recurse whole pattern
4973             (?n)           call subpattern by absolute number
4974             (?+n)          call subpattern by relative number
4975             (?-n)          call subpattern by relative number
4976             (?&name)       call subpattern by name (Perl)
4977             (?P>name)      call subpattern by name (Python)
4978    
4979    
4980    CONDITIONAL PATTERNS
4981    
4982             (?(condition)yes-pattern)
4983             (?(condition)yes-pattern|no-pattern)
4984    
4985             (?(n)...       absolute reference condition
4986             (?(+n)...      relative reference condition
4987             (?(-n)...      relative reference condition
4988             (?(<name>)...  named reference condition (Perl)
4989             (?('name')...  named reference condition (Perl)
4990             (?(name)...    named reference condition (PCRE)
4991             (?(R)...       overall recursion condition
4992             (?(Rn)...      specific group recursion condition
4993             (?(R&name)...  specific recursion condition
4994             (?(DEFINE)...  define subpattern for reference
4995             (?(assert)...  assertion condition
4996    
4997    
4998    BACKTRACKING CONTROL
4999    
5000           The following act immediately they are reached:
5001    
5002             (*ACCEPT)      force successful match
5003             (*FAIL)        force backtrack; synonym (*F)
5004    
5005           The following act only when a subsequent match failure causes  a  back-
5006           track to reach them. They all force a match failure, but they differ in
5007           what happens afterwards. Those that advance the start-of-match point do
5008           so only if the pattern is not anchored.
5009    
5010             (*COMMIT)      overall failure, no advance of starting point
5011             (*PRUNE)       advance to next starting character
5012             (*SKIP)        advance start to current matching position
5013             (*THEN)        local failure, backtrack to next alternation
5014    
5015    
5016    CALLOUTS
5017    
5018             (?C)      callout
5019             (?Cn)     callout with data n
5020    
5021    
5022    SEE ALSO
5023    
5024           pcrepattern(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
5025    
5026    
5027    AUTHOR
5028    
5029           Philip Hazel
5030           University Computing Service
5031           Cambridge CB2 3QH, England.
5032    
5033    
5034    REVISION
5035    
5036           Last updated: 08 August 2007
5037         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
5038  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5039    
# Line 4786  RE-USING A PRECOMPILED PATTERN Line 5364  RE-USING A PRECOMPILED PATTERN
5364    
5365  COMPATIBILITY WITH DIFFERENT PCRE RELEASES  COMPATIBILITY WITH DIFFERENT PCRE RELEASES
5366    
5367         The layout of the control block that is at the start of the  data  that         In general, it is safest to  recompile  all  saved  patterns  when  you
5368         makes  up  a  compiled pattern was changed for release 5.0. If you have         update  to  a new PCRE release, though not all updates actually require
5369         any saved patterns that were compiled with  previous  releases  (not  a         this. Recompiling is definitely needed for release 7.2.
        facility  that  was  previously advertised), you will have to recompile  
        them for release 5.0 and above.  
   
        If you have any saved patterns in UTF-8 mode that use  \p  or  \P  that  
        were  compiled  with any release up to and including 6.4, you will have  
        to recompile them for release 6.5 and above.  
   
        All saved patterns from earlier releases must be recompiled for release  
        7.0  or  higher,  because  there was an internal reorganization at that  
        release.  
5370    
5371    
5372  AUTHOR  AUTHOR
# Line 4810  AUTHOR Line 5378  AUTHOR
5378    
5379  REVISION  REVISION
5380    
5381         Last updated: 24 April 2007         Last updated: 13 June 2007
5382         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
5383  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5384    
# Line 5545  PCRE SAMPLE PROGRAM Line 6113  PCRE SAMPLE PROGRAM
6113         bility  of  matching an empty string. Comments in the code explain what         bility  of  matching an empty string. Comments in the code explain what
6114         is going on.         is going on.
6115    
6116         If PCRE is installed in the standard include  and  library  directories         The demonstration program is automatically built if you use  "./config-
6117         for  your  system, you should be able to compile the demonstration pro-         ure;make"  to  build PCRE. Otherwise, if PCRE is installed in the stan-
6118         gram using this command:         dard include and library directories for your  system,  you  should  be
6119           able to compile the demonstration program using this command:
6120    
6121           gcc -o pcredemo pcredemo.c -lpcre           gcc -o pcredemo pcredemo.c -lpcre
6122    
6123         If PCRE is installed elsewhere, you may need to add additional  options         If  PCRE is installed elsewhere, you may need to add additional options
6124         to  the  command line. For example, on a Unix-like system that has PCRE         to the command line. For example, on a Unix-like system that  has  PCRE
6125         installed in /usr/local, you  can  compile  the  demonstration  program         installed  in  /usr/local,  you  can  compile the demonstration program
6126         using a command like this:         using a command like this:
6127    
6128           gcc -o pcredemo -I/usr/local/include pcredemo.c \           gcc -o pcredemo -I/usr/local/include pcredemo.c \
6129               -L/usr/local/lib -lpcre               -L/usr/local/lib -lpcre
6130    
6131         Once  you  have  compiled the demonstration program, you can run simple         Once you have compiled the demonstration program, you  can  run  simple
6132         tests like this:         tests like this:
6133    
6134           ./pcredemo 'cat|dog' 'the cat sat on the mat'           ./pcredemo 'cat|dog' 'the cat sat on the mat'
6135           ./pcredemo -g 'cat|dog' 'the dog sat on the cat'           ./pcredemo -g 'cat|dog' 'the dog sat on the cat'
6136    
6137         Note that there is a  much  more  comprehensive  test  program,  called         Note  that  there  is  a  much  more comprehensive test program, called
6138         pcretest,  which  supports  many  more  facilities  for testing regular         pcretest, which supports  many  more  facilities  for  testing  regular
6139         expressions and the PCRE library. The pcredemo program is provided as a         expressions and the PCRE library. The pcredemo program is provided as a
6140         simple coding example.         simple coding example.
6141    
# Line 5574  PCRE SAMPLE PROGRAM Line 6143  PCRE SAMPLE PROGRAM
6143         the standard library directory, you may get an error like this when you         the standard library directory, you may get an error like this when you
6144         try to run pcredemo:         try to run pcredemo:
6145    
6146           ld.so.1:  a.out:  fatal:  libpcre.so.0:  open failed: No such file or           ld.so.1: a.out: fatal: libpcre.so.0: open failed:  No  such  file  or
6147         directory         directory
6148    
6149         This is caused by the way shared library support works  on  those  sys-         This  is  caused  by the way shared library support works on those sys-
6150         tems. You need to add         tems. You need to add
6151    
6152           -R/usr/local/lib           -R/usr/local/lib
# Line 5594  AUTHOR Line 6163  AUTHOR
6163    
6164  REVISION  REVISION
6165    
6166         Last updated: 06 March 2007         Last updated: 13 June 2007
6167         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
6168  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6169  PCRESTACK(3)                                                      PCRESTACK(3)  PCRESTACK(3)                                                      PCRESTACK(3)
# Line 5664  PCRE DISCUSSION OF STACK USAGE Line 6233  PCRE DISCUSSION OF STACK USAGE
6233         In environments where stack memory is constrained, you  might  want  to         In environments where stack memory is constrained, you  might  want  to
6234         compile  PCRE to use heap memory instead of stack for remembering back-         compile  PCRE to use heap memory instead of stack for remembering back-
6235         up points. This makes it run a lot more slowly, however. Details of how         up points. This makes it run a lot more slowly, however. Details of how
6236         to do this are given in the pcrebuild documentation.         to do this are given in the pcrebuild documentation. When built in this
6237           way, instead of using the stack, PCRE obtains and frees memory by call-
6238         In  Unix-like environments, there is not often a problem with the stack         ing  the  functions  that  are  pointed to by the pcre_stack_malloc and
6239         unless very long strings are involved,  though  the  default  limit  on         pcre_stack_free variables. By default,  these  point  to  malloc()  and
6240         stack  size  varies  from system to system. Values from 8Mb to 64Mb are         free(),  but you can replace the pointers to cause PCRE to use your own
6241           functions. Since the block sizes are always the same,  and  are  always
6242           freed in reverse order, it may be possible to implement customized mem-
6243           ory handlers that are more efficient than the standard functions.
6244    
6245           In Unix-like environments, there is not often a problem with the  stack
6246           unless  very  long  strings  are  involved, though the default limit on
6247           stack size varies from system to system. Values from 8Mb  to  64Mb  are
6248         common. You can find your default limit by running the command:         common. You can find your default limit by running the command:
6249    
6250           ulimit -s           ulimit -s
6251    
6252         Unfortunately, the effect of running out of  stack  is  often  SIGSEGV,         Unfortunately,  the  effect  of  running out of stack is often SIGSEGV,
6253         though  sometimes  a more explicit error message is given. You can nor-         though sometimes a more explicit error message is given. You  can  nor-
6254         mally increase the limit on stack size by code such as this:         mally increase the limit on stack size by code such as this:
6255    
6256           struct rlimit rlim;           struct rlimit rlim;
# Line 5682  PCRE DISCUSSION OF STACK USAGE Line 6258  PCRE DISCUSSION OF STACK USAGE
6258           rlim.rlim_cur = 100*1024*1024;           rlim.rlim_cur = 100*1024*1024;
6259           setrlimit(RLIMIT_STACK, &rlim);           setrlimit(RLIMIT_STACK, &rlim);
6260    
6261         This reads the current limits (soft and hard) using  getrlimit(),  then         This  reads  the current limits (soft and hard) using getrlimit(), then
6262         attempts  to  increase  the  soft limit to 100Mb using setrlimit(). You         attempts to increase the soft limit to  100Mb  using  setrlimit().  You
6263         must do this before calling pcre_exec().         must do this before calling pcre_exec().
6264    
6265         PCRE has an internal counter that can be used to  limit  the  depth  of         PCRE  has  an  internal  counter that can be used to limit the depth of
6266         recursion,  and  thus cause pcre_exec() to give an error code before it         recursion, and thus cause pcre_exec() to give an error code  before  it
6267         runs out of stack. By default, the limit is very  large,  and  unlikely         runs  out  of  stack. By default, the limit is very large, and unlikely
6268         ever  to operate. It can be changed when PCRE is built, and it can also         ever to operate. It can be changed when PCRE is built, and it can  also
6269         be set when pcre_exec() is called. For details of these interfaces, see         be set when pcre_exec() is called. For details of these interfaces, see
6270         the pcrebuild and pcreapi documentation.         the pcrebuild and pcreapi documentation.
6271    
6272         As a very rough rule of thumb, you should reckon on about 500 bytes per         As a very rough rule of thumb, you should reckon on about 500 bytes per
6273         recursion. Thus, if you want to limit your  stack  usage  to  8Mb,  you         recursion.  Thus,  if  you  want  to limit your stack usage to 8Mb, you
6274         should  set  the  limit at 16000 recursions. A 64Mb stack, on the other         should set the limit at 16000 recursions. A 64Mb stack,  on  the  other
6275         hand, can support around 128000 recursions. The pcretest  test  program         hand,  can  support around 128000 recursions. The pcretest test program
6276         has a command line option (-S) that can be used to increase the size of         has a command line option (-S) that can be used to increase the size of
6277         its stack.         its stack.
6278    
# Line 5710  AUTHOR Line 6286  AUTHOR
6286    
6287  REVISION  REVISION
6288    
6289         Last updated: 12 March 2007         Last updated: 05 June 2007
6290         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
6291  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6292    

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