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1    -----------------------------------------------------------------------------
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
# Line 5  synopses of each function in the library Line 6  synopses of each function in the library
6  separate text files for the pcregrep and pcretest commands.  separate text files for the pcregrep and pcretest commands.
7  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
8    
 PCRE(3)                                                                PCRE(3)  
9    
10    PCRE(3)                                                                PCRE(3)
11    
12    
13  NAME  NAME
14         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
15    
16  DESCRIPTION  
17    INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few  differences.  The current implementation of PCRE (release         just  a  few differences. (Certain features that appeared in Python and
22         4.x) corresponds approximately with Perl  5.8,  including  support  for         PCRE before they appeared in Perl are also available using  the  Python
23         UTF-8  encoded  strings.   However,  this  support has to be explicitly         syntax.)
24         enabled; it is not the default.  
25           The  current  implementation of PCRE (release 7.x) corresponds approxi-
26         PCRE is written in C and released as a C library. However, a number  of         mately with Perl 5.10, including support for UTF-8 encoded strings  and
27         people  have  written  wrappers  and interfaces of various kinds. A C++         Unicode general category properties. However, UTF-8 and Unicode support
28         class is included in these contributions, which can  be  found  in  the         has to be explicitly enabled; it is not the default. The Unicode tables
29           correspond to Unicode release 5.0.0.
30    
31           In  addition to the Perl-compatible matching function, PCRE contains an
32           alternative matching function that matches the same  compiled  patterns
33           in  a different way. In certain circumstances, the alternative function
34           has some advantages. For a discussion of the two  matching  algorithms,
35           see the pcrematching page.
36    
37           PCRE  is  written  in C and released as a C library. A number of people
38           have written wrappers and interfaces of various kinds.  In  particular,
39           Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
40           included as part of the PCRE distribution. The pcrecpp page has details
41           of  this  interface.  Other  people's contributions can be found in the
42         Contrib directory at the primary FTP site, which is:         Contrib directory at the primary FTP site, which is:
43    
44         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
45    
46         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
47         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
48         tern and pcrecompat pages.         tern and pcrecompat pages.
49    
50         Some  features  of  PCRE can be included, excluded, or changed when the         Some features of PCRE can be included, excluded, or  changed  when  the
51         library is built. The pcre_config() function makes it  possible  for  a         library  is  built.  The pcre_config() function makes it possible for a
52         client  to  discover  which features are available. Documentation about         client to discover which features are  available.  The  features  them-
53         building PCRE for various operating systems can be found in the  README         selves  are described in the pcrebuild page. Documentation about build-
54         file in the source distribution.         ing PCRE for various operating systems can be found in the README  file
55           in the source distribution.
56    
57           The  library  contains  a number of undocumented internal functions and
58           data tables that are used by more than one  of  the  exported  external
59           functions,  but  which  are  not  intended for use by external callers.
60           Their names all begin with "_pcre_", which hopefully will  not  provoke
61           any name clashes. In some environments, it is possible to control which
62           external symbols are exported when a shared library is  built,  and  in
63           these cases the undocumented symbols are not exported.
64    
65    
66  USER DOCUMENTATION  USER DOCUMENTATION
67    
68         The user documentation for PCRE has been split up into a number of dif-         The  user  documentation  for PCRE comprises a number of different sec-
69         ferent sections. In the "man" format, each of these is a separate  "man         tions. In the "man" format, each of these is a separate "man page".  In
70         page".  In  the  HTML  format, each is a separate page, linked from the         the  HTML  format, each is a separate page, linked from the index page.
71         index page. In the plain text format, all  the  sections  are  concate-         In the plain text format, all the sections are concatenated,  for  ease
72         nated, for ease of searching. The sections are as follows:         of searching. The sections are as follows:
73    
74           pcre              this document           pcre              this document
75           pcreapi           details of PCRE's native API           pcre-config       show PCRE installation configuration information
76             pcreapi           details of PCRE's native C API
77           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
78           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
79           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
80             pcrecpp           details of the C++ wrapper
81           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
82             pcrematching      discussion of the two matching algorithms
83             pcrepartial       details of the partial matching facility
84           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
85                               regular expressions                               regular expressions
86           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
87           pcreposix         the POSIX-compatible API           pcreposix         the POSIX-compatible C API
88             pcreprecompile    details of saving and re-using precompiled patterns
89           pcresample        discussion of the sample program           pcresample        discussion of the sample program
90           pcretest          the pcretest testing command           pcrestack         discussion of stack usage
91             pcretest          description of the pcretest testing command
92    
93         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
94         each library function, listing its arguments and results.         each C library function, listing its arguments and results.
95    
96    
97  LIMITATIONS  LIMITATIONS
98    
99         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
100         never in practice be relevant.         never in practice be relevant.
101    
102         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
103         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
104         process  regular  expressions  that are truly enormous, you can compile         process regular expressions that are truly enormous,  you  can  compile
105         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
106         the  source  distribution and the pcrebuild documentation for details).         the source distribution and the pcrebuild documentation  for  details).
107         If these cases the limit is substantially larger.  However,  the  speed         In  these  cases the limit is substantially larger.  However, the speed
108         of execution will be slower.         of execution is slower.
109    
110         All values in repeating quantifiers must be less than 65536.  The maxi-         All values in repeating quantifiers must be less than 65536. The  maxi-
111         mum number of capturing subpatterns is 65535.         mum  compiled  length  of  subpattern  with an explicit repeat count is
112           30000 bytes. The maximum number of capturing subpatterns is 65535.
113         There is no limit to the number of non-capturing subpatterns,  but  the  
114         maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,         There is no limit to the number of parenthesized subpatterns, but there
115         including capturing subpatterns, assertions, and other types of subpat-         can be no more than 65535 capturing subpatterns.
116         tern, is 200.  
117           If  a  non-capturing subpattern with an unlimited repetition quantifier
118           can match an empty string, there is a limit of 1000 on  the  number  of
119           times  it  can  be  repeated while not matching an empty string - if it
120           does match an empty string, the loop is immediately broken.
121    
122         The  maximum  length of a subject string is the largest positive number         The maximum length of name for a named subpattern is 32 characters, and
123         that an integer variable can hold. However, PCRE uses recursion to han-         the maximum number of named subpatterns is 10000.
        dle  subpatterns  and indefinite repetition. This means that the avail-  
        able stack space may limit the size of a subject  string  that  can  be  
        processed by certain patterns.  
124    
125           The  maximum  length of a subject string is the largest positive number
126           that an integer variable can hold. However, when using the  traditional
127           matching function, PCRE uses recursion to handle subpatterns and indef-
128           inite repetition.  This means that the available stack space may  limit
129           the size of a subject string that can be processed by certain patterns.
130           For a discussion of stack issues, see the pcrestack documentation.
131    
 UTF-8 SUPPORT  
132    
133         Starting  at  release  3.3,  PCRE  has  had  some support for character  UTF-8 AND UNICODE PROPERTY SUPPORT
134         strings encoded in the UTF-8 format. For  release  4.0  this  has  been  
135         greatly extended to cover most common requirements.         From release 3.3, PCRE has  had  some  support  for  character  strings
136           encoded  in the UTF-8 format. For release 4.0 this was greatly extended
137           to cover most common requirements, and in release 5.0  additional  sup-
138           port for Unicode general category properties was added.
139    
140         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
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
# Line 106  UTF-8 SUPPORT Line 145  UTF-8 SUPPORT
145    
146         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,
147         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
148         is  limited  to testing the PCRE_UTF8 flag in several places, so should         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
149         not be very large.         very big.
150    
151           If PCRE is built with Unicode character property support (which implies
152           UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
153           ported.  The available properties that can be tested are limited to the
154           general  category  properties such as Lu for an upper case letter or Nd
155           for a decimal number, the Unicode script names such as Arabic  or  Han,
156           and  the  derived  properties  Any  and L&. A full list is given in the
157           pcrepattern documentation. Only the short names for properties are sup-
158           ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
159           ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
160           optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
161           does not support this.
162    
163         The following comments apply when PCRE is running in UTF-8 mode:         The following comments apply when PCRE is running in UTF-8 mode:
164    
# Line 123  UTF-8 SUPPORT Line 174  UTF-8 SUPPORT
174         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may
175         crash.         crash.
176    
177         2. In a pattern, the escape sequence \x{...}, where the contents of the         2. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
178         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         two-byte UTF-8 character if the value is greater than 127.
        character whose code number is the given hexadecimal number, for  exam-  
        ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,  
        the item is not recognized.  This escape sequence can be used either as  
        a literal, or within a character class.  
179    
180         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         3.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8
181         UTF-8 character if the value is greater than 127.         characters for values greater than \177.
182    
183         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
184         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
185    
186         5.  The  dot  metacharacter  matches  one  UTF-8 character instead of a         5.  The dot metacharacter matches one UTF-8 character instead of a sin-
187         single byte.         gle byte.
188    
189         6. The escape sequence \C can be used to match a single byte  in  UTF-8         6. The escape sequence \C can be used to match a single byte  in  UTF-8
190         mode, but its use can lead to some strange effects.         mode,  but  its  use can lead to some strange effects. This facility is
191           not available in the alternative matching function, pcre_dfa_exec().
        7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly  
        test characters of any code value, but the characters that PCRE  recog-  
        nizes  as  digits,  spaces,  or  word characters remain the same set as  
        before, all with values less than 256.  
   
        8. Case-insensitive matching applies only to  characters  whose  values  
        are  less  than  256.  PCRE  does  not support the notion of "case" for  
        higher-valued characters.  
192    
193         9. PCRE does not support the use of Unicode tables  and  properties  or         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
194         the Perl escapes \p, \P, and \X.         test  characters of any code value, but the characters that PCRE recog-
195           nizes as digits, spaces, or word characters  remain  the  same  set  as
196           before, all with values less than 256. This remains true even when PCRE
197           includes Unicode property support, because to do otherwise  would  slow
198           down  PCRE in many common cases. If you really want to test for a wider
199           sense of, say, "digit", you must use Unicode  property  tests  such  as
200           \p{Nd}.
201    
202           8.  Similarly,  characters that match the POSIX named character classes
203           are all low-valued characters.
204    
205           9. However, the Perl 5.10 horizontal and vertical  whitespace  matching
206           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
207           acters.
208    
209           10. Case-insensitive matching applies only to characters  whose  values
210           are  less than 128, unless PCRE is built with Unicode property support.
211           Even when Unicode property support is available, PCRE  still  uses  its
212           own  character  tables when checking the case of low-valued characters,
213           so as not to degrade performance.  The Unicode property information  is
214           used only for characters with higher values. Even when Unicode property
215           support is available, PCRE supports case-insensitive matching only when
216           there  is  a  one-to-one  mapping between a letter's cases. There are a
217           small number of many-to-one mappings in Unicode;  these  are  not  sup-
218           ported by PCRE.
219    
220    
221  AUTHOR  AUTHOR
222    
223         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
224         University Computing Service,         University Computing Service
225         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
        Phone: +44 1223 334714  
226    
227  Last updated: 20 August 2003         Putting  an actual email address here seems to have been a spam magnet,
228  Copyright (c) 1997-2003 University of Cambridge.         so I've taken it away. If you want to email me, use  my  two  initials,
229  -----------------------------------------------------------------------------         followed by the two digits 10, at the domain cam.ac.uk.
230    
231    
232    REVISION
233    
234           Last updated: 30 July 2007
235           Copyright (c) 1997-2007 University of Cambridge.
236    ------------------------------------------------------------------------------
237    
 PCRE(3)                                                                PCRE(3)  
238    
239    PCREBUILD(3)                                                      PCREBUILD(3)
240    
241    
242  NAME  NAME
243         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
244    
245    
246  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
247    
248         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
249         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. They are all selected, or  dese-
250         lected,  by  providing  options  to  the  configure script which is run         lected, by providing options to the configure script that is run before
251         before the make command. The complete list  of  options  for  configure         the make command. The complete list of  options  for  configure  (which
252         (which  includes the standard ones such as the selection of the instal-         includes  the  standard  ones such as the selection of the installation
253         lation directory) can be obtained by running         directory) can be obtained by running
254    
255           ./configure --help           ./configure --help
256    
257         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
258         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
259         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
260         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
261         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
262         not described.         is not described.
263    
264    
265    C++ SUPPORT
266    
267           By default, the configure script will search for a C++ compiler and C++
268           header files. If it finds them, it automatically builds the C++ wrapper
269           library for PCRE. You can disable this by adding
270    
271             --disable-cpp
272    
273           to the configure command.
274    
275    
276  UTF-8 SUPPORT  UTF-8 SUPPORT
# Line 204  UTF-8 SUPPORT Line 285  UTF-8 SUPPORT
285         function.         function.
286    
287    
288    UNICODE CHARACTER PROPERTY SUPPORT
289    
290           UTF-8 support allows PCRE to process character values greater than  255
291           in  the  strings that it handles. On its own, however, it does not pro-
292           vide any facilities for accessing the properties of such characters. If
293           you  want  to  be able to use the pattern escapes \P, \p, and \X, which
294           refer to Unicode character properties, you must add
295    
296             --enable-unicode-properties
297    
298           to the configure command. This implies UTF-8 support, even if you  have
299           not explicitly requested it.
300    
301           Including  Unicode  property  support  adds around 30K of tables to the
302           PCRE library. Only the general category properties such as  Lu  and  Nd
303           are supported. Details are given in the pcrepattern documentation.
304    
305    
306  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
307    
308         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating
309         ter. This is the normal newline character on Unix-like systems. You can         the end of a line. This is the normal newline  character  on  Unix-like
310         compile PCRE to use character 13 (carriage return) instead by adding         systems. You can compile PCRE to use character 13 (carriage return, CR)
311           instead, by adding
312    
313           --enable-newline-is-cr           --enable-newline-is-cr
314    
315         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
316         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
317         line character.  
318           Alternatively, you can specify that line endings are to be indicated by
319           the two character sequence CRLF. If you want this, add
320    
321             --enable-newline-is-crlf
322    
323           to the configure command. There is a fourth option, specified by
324    
325             --enable-newline-is-anycrlf
326    
327           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
328           CRLF as indicating a line ending. Finally, a fifth option, specified by
329    
330             --enable-newline-is-any
331    
332           causes PCRE to recognize any Unicode newline sequence.
333    
334           Whatever line ending convention is selected when PCRE is built  can  be
335           overridden  when  the library functions are called. At build time it is
336           conventional to use the standard for your operating system.
337    
338    
339  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
# Line 231  BUILDING SHARED AND STATIC LIBRARIES Line 350  BUILDING SHARED AND STATIC LIBRARIES
350    
351  POSIX MALLOC USAGE  POSIX MALLOC USAGE
352    
353         When PCRE is called through the  POSIX  interface  (see  the  pcreposix         When PCRE is called through the POSIX interface (see the pcreposix doc-
354         documentation),  additional working storage is required for holding the         umentation),  additional  working  storage  is required for holding the
355         pointers to capturing substrings because PCRE requires  three  integers         pointers to capturing substrings, because PCRE requires three  integers
356         per  substring,  whereas  the POSIX interface provides only two. If the         per  substring,  whereas  the POSIX interface provides only two. If the
357         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
358         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
# Line 245  POSIX MALLOC USAGE Line 364  POSIX MALLOC USAGE
364         to the configure command.         to the configure command.
365    
366    
 LIMITING PCRE RESOURCE USAGE  
   
        Internally,  PCRE  has a function called match() which it calls repeat-  
        edly (possibly recursively) when performing a  matching  operation.  By  
        limiting  the  number of times this function may be called, a limit can  
        be placed on the resources used by a single call  to  pcre_exec().  The  
        limit  can be changed at run time, as described in the pcreapi documen-  
        tation. The default is 10 million, but this can be changed by adding  a  
        setting such as  
   
          --with-match-limit=500000  
   
        to the configure command.  
   
   
367  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
368    
369         Within  a  compiled  pattern,  offset values are used to point from one         Within  a  compiled  pattern,  offset values are used to point from one
370         part to another (for example, from an opening parenthesis to an  alter-         part to another (for example, from an opening parenthesis to an  alter-
371         nation  metacharacter).  By  default two-byte values are used for these         nation  metacharacter).  By default, two-byte values are used for these
372         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets, leading to a maximum size for a  compiled  pattern  of  around
373         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K.  This  is sufficient to handle all but the most gigantic patterns.
374         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless, some people do want to process enormous patterns,  so  it
# Line 277  HANDLING VERY LARGE PATTERNS Line 381  HANDLING VERY LARGE PATTERNS
381         longer  offsets slows down the operation of PCRE because it has to load         longer  offsets slows down the operation of PCRE because it has to load
382         additional bytes when handling them.         additional bytes when handling them.
383    
        If you build PCRE with an increased link size, test 2 (and  test  5  if  
        you  are using UTF-8) will fail. Part of the output of these tests is a  
        representation of the compiled pattern, and this changes with the  link  
        size.  
   
384    
385  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
386    
387         PCRE  implements  backtracking while matching by making recursive calls         When matching with the pcre_exec() function, PCRE implements backtrack-
388         to an internal function called match(). In environments where the  size         ing  by  making recursive calls to an internal function called match().
389         of the stack is limited, this can severely limit PCRE's operation. (The         In environments where the size of the stack is limited,  this  can  se-
390         Unix environment does not usually suffer from this problem.) An  alter-         verely  limit  PCRE's operation. (The Unix environment does not usually
391         native  approach  that  uses  memory  from  the  heap to remember data,         suffer from this problem, but it may sometimes be necessary to increase
392         instead of using recursive function calls, has been implemented to work         the  maximum  stack size.  There is a discussion in the pcrestack docu-
393         round  this  problem. If you want to build a version of PCRE that works         mentation.) An alternative approach to recursion that uses memory  from
394         this way, add         the  heap  to remember data, instead of using recursive function calls,
395           has been implemented to work round the problem of limited  stack  size.
396           If you want to build a version of PCRE that works this way, add
397    
398           --disable-stack-for-recursion           --disable-stack-for-recursion
399    
400         to the configure command. With this configuration, PCRE  will  use  the         to  the  configure  command. With this configuration, PCRE will use the
401         pcre_stack_malloc   and   pcre_stack_free   variables  to  call  memory         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
402         management functions. Separate functions are provided because the usage         ment  functions. By default these point to malloc() and free(), but you
403         is very predictable: the block sizes requested are always the same, and         can replace the pointers so that your own functions are used.
404         the blocks are always freed in reverse order. A calling  program  might  
405         be  able  to implement optimized functions that perform better than the         Separate functions are  provided  rather  than  using  pcre_malloc  and
406         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
407         slowly when built in this way.         requested are always the same, and  the  blocks  are  always  freed  in
408           reverse  order.  A calling program might be able to implement optimized
409           functions that perform better  than  malloc()  and  free().  PCRE  runs
410           noticeably more slowly when built in this way. This option affects only
411           the  pcre_exec()  function;  it   is   not   relevant   for   the   the
412           pcre_dfa_exec() function.
413    
414    
415    LIMITING PCRE RESOURCE USAGE
416    
417           Internally,  PCRE has a function called match(), which it calls repeat-
418           edly  (sometimes  recursively)  when  matching  a  pattern   with   the
419           pcre_exec()  function.  By controlling the maximum number of times this
420           function may be called during a single matching operation, a limit  can
421           be  placed  on  the resources used by a single call to pcre_exec(). The
422           limit can be changed at run time, as described in the pcreapi  documen-
423           tation.  The default is 10 million, but this can be changed by adding a
424           setting such as
425    
426             --with-match-limit=500000
427    
428           to  the  configure  command.  This  setting  has  no  effect   on   the
429           pcre_dfa_exec() matching function.
430    
431           In  some  environments  it is desirable to limit the depth of recursive
432           calls of match() more strictly than the total number of calls, in order
433           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
434           for-recursion is specified) that is used. A second limit controls this;
435           it  defaults  to  the  value  that is set for --with-match-limit, which
436           imposes no additional constraints. However, you can set a  lower  limit
437           by adding, for example,
438    
439             --with-match-limit-recursion=10000
440    
441           to  the  configure  command.  This  value can also be overridden at run
442           time.
443    
444    
445    CREATING CHARACTER TABLES AT BUILD TIME
446    
447           PCRE uses fixed tables for processing characters whose code values  are
448           less  than 256. By default, PCRE is built with a set of tables that are
449           distributed in the file pcre_chartables.c.dist. These  tables  are  for
450           ASCII codes only. If you add
451    
452             --enable-rebuild-chartables
453    
454           to  the  configure  command, the distributed tables are no longer used.
455           Instead, a program called dftables is compiled and  run.  This  outputs
456           the source for new set of tables, created in the default locale of your
457           C runtime system. (This method of replacing the tables does not work if
458           you  are cross compiling, because dftables is run on the local host. If
459           you need to create alternative tables when cross  compiling,  you  will
460           have to do so "by hand".)
461    
462    
463  USING EBCDIC CODE  USING EBCDIC CODE
464    
465         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
466         character code is ASCII (or UTF-8, which is a superset of ASCII).  PCRE         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
467         can, however, be compiled to run in an EBCDIC environment by adding         This  is  the  case for most computer operating systems. PCRE can, how-
468           ever, be compiled to run in an EBCDIC environment by adding
469    
470           --enable-ebcdic           --enable-ebcdic
471    
472         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
473           bles.  You  should  only  use  it if you know that you are in an EBCDIC
474           environment (for example, an IBM mainframe operating system).
475    
 Last updated: 09 December 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
476    
477  PCRE(3)                                                                PCRE(3)  SEE ALSO
478    
479           pcreapi(3), pcre_config(3).
480    
481    
482    AUTHOR
483    
484           Philip Hazel
485           University Computing Service
486           Cambridge CB2 3QH, England.
487    
488    
489    REVISION
490    
491           Last updated: 30 July 2007
492           Copyright (c) 1997-2007 University of Cambridge.
493    ------------------------------------------------------------------------------
494    
495    
496    PCREMATCHING(3)                                                PCREMATCHING(3)
497    
498    
499  NAME  NAME
500         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
501    
502  SYNOPSIS OF PCRE API  
503    PCRE MATCHING ALGORITHMS
504    
505           This document describes the two different algorithms that are available
506           in PCRE for matching a compiled regular expression against a given sub-
507           ject  string.  The  "standard"  algorithm  is  the  one provided by the
508           pcre_exec() function.  This works in the same was  as  Perl's  matching
509           function, and provides a Perl-compatible matching operation.
510    
511           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
512           this operates in a different way, and is not  Perl-compatible.  It  has
513           advantages  and disadvantages compared with the standard algorithm, and
514           these are described below.
515    
516           When there is only one possible way in which a given subject string can
517           match  a pattern, the two algorithms give the same answer. A difference
518           arises, however, when there are multiple possibilities. For example, if
519           the pattern
520    
521             ^<.*>
522    
523           is matched against the string
524    
525             <something> <something else> <something further>
526    
527           there are three possible answers. The standard algorithm finds only one
528           of them, whereas the alternative algorithm finds all three.
529    
530    
531    REGULAR EXPRESSIONS AS TREES
532    
533           The set of strings that are matched by a regular expression can be rep-
534           resented  as  a  tree structure. An unlimited repetition in the pattern
535           makes the tree of infinite size, but it is still a tree.  Matching  the
536           pattern  to a given subject string (from a given starting point) can be
537           thought of as a search of the tree.  There are two  ways  to  search  a
538           tree:  depth-first  and  breadth-first, and these correspond to the two
539           matching algorithms provided by PCRE.
540    
541    
542    THE STANDARD MATCHING ALGORITHM
543    
544           In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
545           sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
546           depth-first search of the pattern tree. That is, it  proceeds  along  a
547           single path through the tree, checking that the subject matches what is
548           required. When there is a mismatch, the algorithm  tries  any  alterna-
549           tives  at  the  current point, and if they all fail, it backs up to the
550           previous branch point in the  tree,  and  tries  the  next  alternative
551           branch  at  that  level.  This often involves backing up (moving to the
552           left) in the subject string as well.  The  order  in  which  repetition
553           branches  are  tried  is controlled by the greedy or ungreedy nature of
554           the quantifier.
555    
556           If a leaf node is reached, a matching string has  been  found,  and  at
557           that  point the algorithm stops. Thus, if there is more than one possi-
558           ble match, this algorithm returns the first one that it finds.  Whether
559           this  is the shortest, the longest, or some intermediate length depends
560           on the way the greedy and ungreedy repetition quantifiers are specified
561           in the pattern.
562    
563           Because  it  ends  up  with a single path through the tree, it is rela-
564           tively straightforward for this algorithm to keep  track  of  the  sub-
565           strings  that  are  matched  by portions of the pattern in parentheses.
566           This provides support for capturing parentheses and back references.
567    
568    
569    THE ALTERNATIVE MATCHING ALGORITHM
570    
571           This algorithm conducts a breadth-first search of  the  tree.  Starting
572           from  the  first  matching  point  in the subject, it scans the subject
573           string from left to right, once, character by character, and as it does
574           this,  it remembers all the paths through the tree that represent valid
575           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
576           though  it is not implemented as a traditional finite state machine (it
577           keeps multiple states active simultaneously).
578    
579           The scan continues until either the end of the subject is  reached,  or
580           there  are  no more unterminated paths. At this point, terminated paths
581           represent the different matching possibilities (if there are none,  the
582           match  has  failed).   Thus,  if there is more than one possible match,
583           this algorithm finds all of them, and in particular, it finds the long-
584           est.  In PCRE, there is an option to stop the algorithm after the first
585           match (which is necessarily the shortest) has been found.
586    
587           Note that all the matches that are found start at the same point in the
588           subject. If the pattern
589    
590             cat(er(pillar)?)
591    
592           is  matched  against the string "the caterpillar catchment", the result
593           will be the three strings "cat", "cater", and "caterpillar" that  start
594           at the fourth character of the subject. The algorithm does not automat-
595           ically move on to find matches that start at later positions.
596    
597           There are a number of features of PCRE regular expressions that are not
598           supported by the alternative matching algorithm. They are as follows:
599    
600           1.  Because  the  algorithm  finds  all possible matches, the greedy or
601           ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
602           ungreedy quantifiers are treated in exactly the same way. However, pos-
603           sessive quantifiers can make a difference when what follows could  also
604           match what is quantified, for example in a pattern like this:
605    
606             ^a++\w!
607    
608           This  pattern matches "aaab!" but not "aaa!", which would be matched by
609           a non-possessive quantifier. Similarly, if an atomic group is  present,
610           it  is matched as if it were a standalone pattern at the current point,
611           and the longest match is then "locked in" for the rest of  the  overall
612           pattern.
613    
614           2. When dealing with multiple paths through the tree simultaneously, it
615           is not straightforward to keep track of  captured  substrings  for  the
616           different  matching  possibilities,  and  PCRE's implementation of this
617           algorithm does not attempt to do this. This means that no captured sub-
618           strings are available.
619    
620           3.  Because no substrings are captured, back references within the pat-
621           tern are not supported, and cause errors if encountered.
622    
623           4. For the same reason, conditional expressions that use  a  backrefer-
624           ence  as  the  condition or test for a specific group recursion are not
625           supported.
626    
627           5. Because many paths through the tree may be  active,  the  \K  escape
628           sequence, which resets the start of the match when encountered (but may
629           be on some paths and not on others), is not  supported.  It  causes  an
630           error if encountered.
631    
632           6.  Callouts  are  supported, but the value of the capture_top field is
633           always 1, and the value of the capture_last field is always -1.
634    
635           7.  The \C escape sequence, which (in the standard algorithm) matches a
636           single  byte, even in UTF-8 mode, is not supported because the alterna-
637           tive algorithm moves through the subject  string  one  character  at  a
638           time, for all active paths through the tree.
639    
640    
641    ADVANTAGES OF THE ALTERNATIVE ALGORITHM
642    
643           Using  the alternative matching algorithm provides the following advan-
644           tages:
645    
646           1. All possible matches (at a single point in the subject) are automat-
647           ically  found,  and  in particular, the longest match is found. To find
648           more than one match using the standard algorithm, you have to do kludgy
649           things with callouts.
650    
651           2.  There is much better support for partial matching. The restrictions
652           on the content of the pattern that apply when using the standard  algo-
653           rithm  for  partial matching do not apply to the alternative algorithm.
654           For non-anchored patterns, the starting position of a partial match  is
655           available.
656    
657           3.  Because  the  alternative  algorithm  scans the subject string just
658           once, and never needs to backtrack, it is possible to  pass  very  long
659           subject  strings  to  the matching function in several pieces, checking
660           for partial matching each time.
661    
662    
663    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
664    
665           The alternative algorithm suffers from a number of disadvantages:
666    
667           1. It is substantially slower than  the  standard  algorithm.  This  is
668           partly  because  it has to search for all possible matches, but is also
669           because it is less susceptible to optimization.
670    
671           2. Capturing parentheses and back references are not supported.
672    
673           3. Although atomic groups are supported, their use does not provide the
674           performance advantage that it does for the standard algorithm.
675    
676    
677    AUTHOR
678    
679           Philip Hazel
680           University Computing Service
681           Cambridge CB2 3QH, England.
682    
683    
684    REVISION
685    
686           Last updated: 29 May 2007
687           Copyright (c) 1997-2007 University of Cambridge.
688    ------------------------------------------------------------------------------
689    
690    
691    PCREAPI(3)                                                          PCREAPI(3)
692    
693    
694    NAME
695           PCRE - Perl-compatible regular expressions
696    
697    
698    PCRE NATIVE API
699    
700         #include <pcre.h>         #include <pcre.h>
701    
# Line 335  SYNOPSIS OF PCRE API Line 703  SYNOPSIS OF PCRE API
703              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
704              const unsigned char *tableptr);              const unsigned char *tableptr);
705    
706           pcre *pcre_compile2(const char *pattern, int options,
707                int *errorcodeptr,
708                const char **errptr, int *erroffset,
709                const unsigned char *tableptr);
710    
711         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
712              const char **errptr);              const char **errptr);
713    
# Line 342  SYNOPSIS OF PCRE API Line 715  SYNOPSIS OF PCRE API
715              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
716              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
717    
718           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
719                const char *subject, int length, int startoffset,
720                int options, int *ovector, int ovecsize,
721                int *workspace, int wscount);
722    
723         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
724              const char *subject, int *ovector,              const char *subject, int *ovector,
725              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 359  SYNOPSIS OF PCRE API Line 737  SYNOPSIS OF PCRE API
737         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
738              const char *name);              const char *name);
739    
740           int pcre_get_stringtable_entries(const pcre *code,
741                const char *name, char **first, char **last);
742    
743         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
744              int stringcount, int stringnumber,              int stringcount, int stringnumber,
745              const char **stringptr);              const char **stringptr);
# Line 377  SYNOPSIS OF PCRE API Line 758  SYNOPSIS OF PCRE API
758    
759         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
760    
761           int pcre_refcount(pcre *code, int adjust);
762    
763         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
764    
765         char *pcre_version(void);         char *pcre_version(void);
# Line 392  SYNOPSIS OF PCRE API Line 775  SYNOPSIS OF PCRE API
775         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
776    
777    
778  PCRE API  PCRE API OVERVIEW
779    
780         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
781         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
782         expression API.  These are described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
783           Both of these APIs define a set of C function calls. A C++  wrapper  is
784         The  native  API  function  prototypes  are  defined in the header file         distributed with PCRE. It is documented in the pcrecpp page.
785         pcre.h, and on Unix systems the library itself is called libpcre.a,  so  
786         can be accessed by adding -lpcre to the command for linking an applica-         The  native  API  C  function prototypes are defined in the header file
787         tion which calls it. The header file defines the macros PCRE_MAJOR  and         pcre.h, and on Unix systems the library itself is called  libpcre.   It
788         PCRE_MINOR  to  contain  the  major  and  minor release numbers for the         can normally be accessed by adding -lpcre to the command for linking an
789         library. Applications can use these to include  support  for  different         application  that  uses  PCRE.  The  header  file  defines  the  macros
790         releases.         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
791           bers for the library.  Applications can use these  to  include  support
792         The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used         for different releases of PCRE.
793         for compiling and matching regular expressions. A sample  program  that  
794         demonstrates  the simplest way of using them is given in the file pcre-         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
795         demo.c. The pcresample documentation describes how to run it.         pcre_exec() are used for compiling and matching regular expressions  in
796           a  Perl-compatible  manner. A sample program that demonstrates the sim-
797         There are convenience functions for extracting captured substrings from         plest way of using them is provided in the file  called  pcredemo.c  in
798         a matched subject string. They are:         the  source distribution. The pcresample documentation describes how to
799           run it.
800    
801           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
802           ble,  is  also provided. This uses a different algorithm for the match-
803           ing. The alternative algorithm finds all possible matches (at  a  given
804           point  in  the subject), and scans the subject just once. However, this
805           algorithm does not return captured substrings. A description of the two
806           matching  algorithms and their advantages and disadvantages is given in
807           the pcrematching documentation.
808    
809           In addition to the main compiling and  matching  functions,  there  are
810           convenience functions for extracting captured substrings from a subject
811           string that is matched by pcre_exec(). They are:
812    
813           pcre_copy_substring()           pcre_copy_substring()
814           pcre_copy_named_substring()           pcre_copy_named_substring()
815           pcre_get_substring()           pcre_get_substring()
816           pcre_get_named_substring()           pcre_get_named_substring()
817           pcre_get_substring_list()           pcre_get_substring_list()
818             pcre_get_stringnumber()
819             pcre_get_stringtable_entries()
820    
821         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
822         to free the memory used for extracted strings.         to free the memory used for extracted strings.
823    
824         The function pcre_maketables() is used (optionally) to build a  set  of         The  function  pcre_maketables()  is  used  to build a set of character
825         character tables in the current locale for passing to pcre_compile().         tables  in  the  current  locale   for   passing   to   pcre_compile(),
826           pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
827         The  function  pcre_fullinfo()  is used to find out information about a         provided for specialist use.  Most  commonly,  no  special  tables  are
828         compiled pattern; pcre_info() is an obsolete version which returns only         passed,  in  which case internal tables that are generated when PCRE is
829         some  of  the available information, but is retained for backwards com-         built are used.
830         patibility.  The function pcre_version() returns a pointer to a  string  
831           The function pcre_fullinfo() is used to find out  information  about  a
832           compiled  pattern; pcre_info() is an obsolete version that returns only
833           some of the available information, but is retained for  backwards  com-
834           patibility.   The function pcre_version() returns a pointer to a string
835         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
836    
837         The  global  variables  pcre_malloc and pcre_free initially contain the         The function pcre_refcount() maintains a  reference  count  in  a  data
838         entry points of the standard  malloc()  and  free()  functions  respec-         block  containing  a compiled pattern. This is provided for the benefit
839           of object-oriented applications.
840    
841           The global variables pcre_malloc and pcre_free  initially  contain  the
842           entry  points  of  the  standard malloc() and free() functions, respec-
843         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
844         so a calling program can replace them if it  wishes  to  intercept  the         so  a  calling  program  can replace them if it wishes to intercept the
845         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
846    
847         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
848         indirections to memory management functions.  These  special  functions         indirections  to  memory  management functions. These special functions
849         are  used  only  when  PCRE is compiled to use the heap for remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
850         data, instead of recursive function calls. This is a  non-standard  way         data, instead of recursive function calls, when running the pcre_exec()
851         of  building  PCRE,  for  use in environments that have limited stacks.         function. See the pcrebuild documentation for  details  of  how  to  do
852         Because of the greater use of memory management, it runs  more  slowly.         this.  It  is  a non-standard way of building PCRE, for use in environ-
853         Separate  functions  are provided so that special-purpose external code         ments that have limited stacks. Because of the greater  use  of  memory
854         can be used for this case. When used, these functions are always called         management,  it  runs  more  slowly. Separate functions are provided so
855         in  a  stack-like  manner  (last obtained, first freed), and always for         that special-purpose external code can be  used  for  this  case.  When
856         memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
857           obtained, first freed), and always for memory blocks of the same  size.
858           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
859           mentation.
860    
861         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
862         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 455  PCRE API Line 864  PCRE API
864         pcrecallout documentation.         pcrecallout documentation.
865    
866    
867    NEWLINES
868    
869           PCRE  supports five different conventions for indicating line breaks in
870           strings: a single CR (carriage return) character, a  single  LF  (line-
871           feed) character, the two-character sequence CRLF, any of the three pre-
872           ceding, or any Unicode newline sequence. The Unicode newline  sequences
873           are  the  three just mentioned, plus the single characters VT (vertical
874           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
875           separator, U+2028), and PS (paragraph separator, U+2029).
876    
877           Each  of  the first three conventions is used by at least one operating
878           system as its standard newline sequence. When PCRE is built, a  default
879           can  be  specified.  The default default is LF, which is the Unix stan-
880           dard. When PCRE is run, the default can be overridden,  either  when  a
881           pattern is compiled, or when it is matched.
882    
883           In the PCRE documentation the word "newline" is used to mean "the char-
884           acter or pair of characters that indicate a line break". The choice  of
885           newline  convention  affects  the  handling of the dot, circumflex, and
886           dollar metacharacters, the handling of #-comments in /x mode, and, when
887           CRLF  is a recognized line ending sequence, the match position advance-
888           ment for a non-anchored pattern. The choice of newline convention  does
889           not affect the interpretation of the \n or \r escape sequences.
890    
891    
892  MULTITHREADING  MULTITHREADING
893    
894         The  PCRE  functions  can be used in multi-threading applications, with         The  PCRE  functions  can be used in multi-threading applications, with
# Line 467  MULTITHREADING Line 901  MULTITHREADING
901         at once.         at once.
902    
903    
904    SAVING PRECOMPILED PATTERNS FOR LATER USE
905    
906           The compiled form of a regular expression can be saved and re-used at a
907           later time, possibly by a different program, and even on a  host  other
908           than  the  one  on  which  it  was  compiled.  Details are given in the
909           pcreprecompile documentation. However, compiling a  regular  expression
910           with  one version of PCRE for use with a different version is not guar-
911           anteed to work and may cause crashes.
912    
913    
914  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
915    
916         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
917    
918         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
919         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
920         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
921         tures.         tures.
922    
923         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
924         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
925         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
926         available:         available:
927    
928           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
929    
930         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
931         able; otherwise it is set to zero.         able; otherwise it is set to zero.
932    
933             PCRE_CONFIG_UNICODE_PROPERTIES
934    
935           The  output  is  an  integer  that is set to one if support for Unicode
936           character properties is available; otherwise it is set to zero.
937    
938           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
939    
940         The output is an integer that is set to the value of the code  that  is         The output is an integer whose value specifies  the  default  character
941         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
942         return (13), and should normally be the  standard  character  for  your         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
943         operating system.         and  -1  for  ANY. The default should normally be the standard sequence
944           for your operating system.
945    
946           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
947    
948         The  output  is  an  integer that contains the number of bytes used for         The output is an integer that contains the number  of  bytes  used  for
949         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
950         4.  Larger  values  allow larger regular expressions to be compiled, at         4. Larger values allow larger regular expressions to  be  compiled,  at
951         the expense of slower matching. The default value of  2  is  sufficient         the  expense  of  slower matching. The default value of 2 is sufficient
952         for  all  but  the  most massive patterns, since it allows the compiled         for all but the most massive patterns, since  it  allows  the  compiled
953         pattern to be up to 64K in size.         pattern to be up to 64K in size.
954    
955           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
956    
957         The output is an integer that contains the threshold  above  which  the         The  output  is  an integer that contains the threshold above which the
958         POSIX  interface  uses malloc() for output vectors. Further details are         POSIX interface uses malloc() for output vectors. Further  details  are
959         given in the pcreposix documentation.         given in the pcreposix documentation.
960    
961           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
962    
963         The output is an integer that gives the default limit for the number of         The output is an integer that gives the default limit for the number of
964         internal  matching  function  calls in a pcre_exec() execution. Further         internal matching function calls in a  pcre_exec()  execution.  Further
965         details are given with pcre_exec() below.         details are given with pcre_exec() below.
966    
967             PCRE_CONFIG_MATCH_LIMIT_RECURSION
968    
969           The  output is an integer that gives the default limit for the depth of
970           recursion when calling the internal matching function in a  pcre_exec()
971           execution. Further details are given with pcre_exec() below.
972    
973           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
974    
975         The output is an integer that is set to one if  internal  recursion  is         The  output is an integer that is set to one if internal recursion when
976         implemented  by recursive function calls that use the stack to remember         running pcre_exec() is implemented by recursive function calls that use
977         their state. This is the usual way that PCRE is compiled. The output is         the  stack  to remember their state. This is the usual way that PCRE is
978         zero  if PCRE was compiled to use blocks of data on the heap instead of         compiled. The output is zero if PCRE was compiled to use blocks of data
979         recursive  function  calls.  In  this   case,   pcre_stack_malloc   and         on  the  heap  instead  of  recursive  function  calls.  In  this case,
980         pcre_stack_free  are  called  to manage memory blocks on the heap, thus         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
981         avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
982    
983    
984  COMPILING A PATTERN  COMPILING A PATTERN
# Line 531  COMPILING A PATTERN Line 987  COMPILING A PATTERN
987              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
988              const unsigned char *tableptr);              const unsigned char *tableptr);
989    
990           pcre *pcre_compile2(const char *pattern, int options,
991                int *errorcodeptr,
992                const char **errptr, int *erroffset,
993                const unsigned char *tableptr);
994    
995         The function pcre_compile() is called to  compile  a  pattern  into  an         Either of the functions pcre_compile() or pcre_compile2() can be called
996         internal  form.  The pattern is a C string terminated by a binary zero,         to compile a pattern into an internal form. The only difference between
997         and is passed in the argument pattern. A pointer to a single  block  of         the  two interfaces is that pcre_compile2() has an additional argument,
998         memory  that is obtained via pcre_malloc is returned. This contains the         errorcodeptr, via which a numerical error code can be returned.
999         compiled code and related data.  The  pcre  type  is  defined  for  the  
1000         returned  block;  this  is a typedef for a structure whose contents are         The pattern is a C string terminated by a binary zero, and is passed in
1001         not externally defined. It is up to the caller to free the memory  when         the  pattern  argument.  A  pointer to a single block of memory that is
1002         it is no longer required.         obtained via pcre_malloc is returned. This contains the  compiled  code
1003           and related data. The pcre type is defined for the returned block; this
1004           is a typedef for a structure whose contents are not externally defined.
1005           It is up to the caller to free the memory (via pcre_free) when it is no
1006           longer required.
1007    
1008         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although the compiled code of a PCRE regex is relocatable, that is,  it
1009         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1010         fully relocatable, because it contains a copy of the tableptr argument,         fully relocatable, because it may contain a copy of the tableptr  argu-
1011         which is an address (see below).         ment, which is an address (see below).
1012    
1013         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1014         tion.  It  should  be  zero  if  no  options  are required. Some of the         pilation. It should be zero if no options are required.  The  available
1015         options, in particular, those that are compatible with Perl,  can  also         options  are  described  below. Some of them, in particular, those that
1016         be  set and unset from within the pattern (see the detailed description         are compatible with Perl, can also be set and  unset  from  within  the
1017         of regular expressions in the  pcrepattern  documentation).  For  these         pattern  (see  the  detailed  description in the pcrepattern documenta-
1018         options,  the  contents of the options argument specifies their initial         tion). For these options, the contents of the options  argument  speci-
1019         settings at the start of compilation and execution.  The  PCRE_ANCHORED         fies  their initial settings at the start of compilation and execution.
1020         option can be set at the time of matching as well as at compile time.         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time
1021           of matching as well as at compile time.
1022    
1023         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1024         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1025         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1026         sage. The offset from the start of the pattern to the  character  where         sage. This is a static string that is part of the library. You must not
1027         the  error  was  discovered  is  placed  in  the variable pointed to by         try to free it. The offset from the start of the pattern to the charac-
1028         erroffset, which must not be NULL. If it  is,  an  immediate  error  is         ter where the error was discovered is placed in the variable pointed to
1029           by  erroffset,  which must not be NULL. If it is, an immediate error is
1030         given.         given.
1031    
1032           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
1033           codeptr  argument is not NULL, a non-zero error code number is returned
1034           via this argument in the event of an error. This is in addition to  the
1035           textual error message. Error codes and messages are listed below.
1036    
1037         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
1038         character tables which are built when it is compiled, using the default         character tables that are  built  when  PCRE  is  compiled,  using  the
1039         C  locale.  Otherwise,  tableptr  must  be  the  result  of  a  call to         default  C  locale.  Otherwise, tableptr must be an address that is the
1040         pcre_maketables(). See the section on locale support below.         result of a call to pcre_maketables(). This value is  stored  with  the
1041           compiled  pattern,  and used again by pcre_exec(), unless another table
1042           pointer is passed to it. For more discussion, see the section on locale
1043           support below.
1044    
1045         This code fragment shows a typical straightforward  call  to  pcre_com-         This  code  fragment  shows a typical straightforward call to pcre_com-
1046         pile():         pile():
1047    
1048           pcre *re;           pcre *re;
# Line 581  COMPILING A PATTERN Line 1055  COMPILING A PATTERN
1055             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1056             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1057    
1058         The following option bits are defined:         The following names for option bits are defined in  the  pcre.h  header
1059           file:
1060    
1061           PCRE_ANCHORED           PCRE_ANCHORED
1062    
1063         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1064         is constrained to match only at the first matching point in the  string         is constrained to match only at the first matching point in the  string
1065         which is being searched (the "subject string"). This effect can also be         that  is being searched (the "subject string"). This effect can also be
1066         achieved by appropriate constructs in the pattern itself, which is  the         achieved by appropriate constructs in the pattern itself, which is  the
1067         only way to do it in Perl.         only way to do it in Perl.
1068    
1069             PCRE_AUTO_CALLOUT
1070    
1071           If this bit is set, pcre_compile() automatically inserts callout items,
1072           all with number 255, before each pattern item. For  discussion  of  the
1073           callout facility, see the pcrecallout documentation.
1074    
1075           PCRE_CASELESS           PCRE_CASELESS
1076    
1077         If  this  bit is set, letters in the pattern match both upper and lower         If  this  bit is set, letters in the pattern match both upper and lower
1078         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
1079         changed within a pattern by a (?i) option setting.         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
1080           always understands the concept of case for characters whose values  are
1081           less  than 128, so caseless matching is always possible. For characters
1082           with higher values, the concept of case is supported if  PCRE  is  com-
1083           piled  with Unicode property support, but not otherwise. If you want to
1084           use caseless matching for characters 128 and  above,  you  must  ensure
1085           that  PCRE  is  compiled  with Unicode property support as well as with
1086           UTF-8 support.
1087    
1088           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1089    
1090         If  this bit is set, a dollar metacharacter in the pattern matches only         If this bit is set, a dollar metacharacter in the pattern matches  only
1091         at the end of the subject string. Without this option,  a  dollar  also         at  the  end  of the subject string. Without this option, a dollar also
1092         matches  immediately before the final character if it is a newline (but         matches immediately before a newline at the end of the string (but  not
1093         not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
1094         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
1095         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1096    
1097           PCRE_DOTALL           PCRE_DOTALL
1098    
1099         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharater in the pattern matches all char-
1100         acters,  including  newlines.  Without  it, newlines are excluded. This         acters, including those that indicate newline. Without it, a  dot  does
1101         option is equivalent to Perl's /s option, and it can be changed  within         not  match  when  the  current position is at a newline. This option is
1102         a  pattern  by  a  (?s)  option  setting. A negative class such as [^a]         equivalent to Perl's /s option, and it can be changed within a  pattern
1103         always matches a newline character, independent of the setting of  this         by  a (?s) option setting. A negative class such as [^a] always matches
1104         option.         newline characters, independent of the setting of this option.
1105    
1106             PCRE_DUPNAMES
1107    
1108           If this bit is set, names used to identify capturing  subpatterns  need
1109           not be unique. This can be helpful for certain types of pattern when it
1110           is known that only one instance of the named  subpattern  can  ever  be
1111           matched.  There  are  more details of named subpatterns below; see also
1112           the pcrepattern documentation.
1113    
1114           PCRE_EXTENDED           PCRE_EXTENDED
1115    
1116         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
1117         totally ignored except  when  escaped  or  inside  a  character  class.         totally ignored except when escaped or inside a character class. White-
1118         Whitespace  does  not  include the VT character (code 11). In addition,         space does not include the VT character (code 11). In addition, charac-
1119         characters between an unescaped # outside a  character  class  and  the         ters between an unescaped # outside a character class and the next new-
1120         next newline character, inclusive, are also ignored. This is equivalent         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
1121         to Perl's /x option, and it can be changed within a pattern by  a  (?x)         option,  and  it  can be changed within a pattern by a (?x) option set-
1122         option setting.         ting.
1123    
1124         This  option  makes  it possible to include comments inside complicated         This option makes it possible to include  comments  inside  complicated
1125         patterns.  Note, however, that this applies only  to  data  characters.         patterns.   Note,  however,  that this applies only to data characters.
1126         Whitespace   characters  may  never  appear  within  special  character         Whitespace  characters  may  never  appear  within  special   character
1127         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences  in  a  pattern,  for  example  within the sequence (?( which
1128         introduces a conditional subpattern.         introduces a conditional subpattern.
1129    
1130           PCRE_EXTRA           PCRE_EXTRA
1131    
1132         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1133         of PCRE that is incompatible with Perl, but it  is  currently  of  very         of  PCRE  that  is  incompatible with Perl, but it is currently of very
1134         little  use. When set, any backslash in a pattern that is followed by a         little use. When set, any backslash in a pattern that is followed by  a
1135         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1136         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1137         backslash followed by a letter with no special meaning is treated as  a         backslash  followed by a letter with no special meaning is treated as a
1138         literal.  There  are  at  present  no other features controlled by this         literal. (Perl can, however, be persuaded to give a warning for  this.)
1139         option. It can also be set by a (?X) option setting within a pattern.         There  are  at  present no other features controlled by this option. It
1140           can also be set by a (?X) option setting within a pattern.
1141    
1142             PCRE_FIRSTLINE
1143    
1144           If this option is set, an  unanchored  pattern  is  required  to  match
1145           before  or  at  the  first  newline  in  the subject string, though the
1146           matched text may continue over the newline.
1147    
1148           PCRE_MULTILINE           PCRE_MULTILINE
1149    
1150         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
1151         "line"  of  characters (even if it actually contains several newlines).         line  of characters (even if it actually contains newlines). The "start
1152         The "start of line" metacharacter (^) matches only at the start of  the         of line" metacharacter (^) matches only at the  start  of  the  string,
1153         string,  while  the "end of line" metacharacter ($) matches only at the         while  the  "end  of line" metacharacter ($) matches only at the end of
1154         end of the string, or before a terminating  newline  (unless  PCRE_DOL-         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1155         LAR_ENDONLY is set). This is the same as Perl.         is set). This is the same as Perl.
1156    
1157         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1158         constructs match immediately following or immediately before  any  new-         constructs match immediately following or immediately  before  internal
1159         line  in the subject string, respectively, as well as at the very start         newlines  in  the  subject string, respectively, as well as at the very
1160         and end. This is equivalent to Perl's /m option, and it can be  changed         start and end. This is equivalent to Perl's /m option, and  it  can  be
1161         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
1162         ters in a subject string, or no occurrences of ^ or  $  in  a  pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1163         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1164    
1165             PCRE_NEWLINE_CR
1166             PCRE_NEWLINE_LF
1167             PCRE_NEWLINE_CRLF
1168             PCRE_NEWLINE_ANYCRLF
1169             PCRE_NEWLINE_ANY
1170    
1171           These  options  override the default newline definition that was chosen
1172           when PCRE was built. Setting the first or the second specifies  that  a
1173           newline  is  indicated  by a single character (CR or LF, respectively).
1174           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1175           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1176           that any of the three preceding sequences should be recognized. Setting
1177           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1178           recognized. The Unicode newline sequences are the three just mentioned,
1179           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1180           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1181           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1182           UTF-8 mode.
1183    
1184           The newline setting in the  options  word  uses  three  bits  that  are
1185           treated as a number, giving eight possibilities. Currently only six are
1186           used (default plus the five values above). This means that if  you  set
1187           more  than one newline option, the combination may or may not be sensi-
1188           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1189           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1190           cause an error.
1191    
1192           The only time that a line break is specially recognized when  compiling
1193           a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
1194           character class is encountered. This indicates  a  comment  that  lasts
1195           until  after the next line break sequence. In other circumstances, line
1196           break  sequences  are  treated  as  literal  data,   except   that   in
1197           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1198           and are therefore ignored.
1199    
1200           The newline option that is set at compile time becomes the default that
1201           is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1202    
1203           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1204    
1205         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1206         theses in the pattern. Any opening parenthesis that is not followed  by         theses  in the pattern. Any opening parenthesis that is not followed by
1207         ?  behaves as if it were followed by ?: but named parentheses can still         ? behaves as if it were followed by ?: but named parentheses can  still
1208         be used for capturing (and they acquire  numbers  in  the  usual  way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1209         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1210    
1211           PCRE_UNGREEDY           PCRE_UNGREEDY
1212    
1213         This  option  inverts  the "greediness" of the quantifiers so that they         This option inverts the "greediness" of the quantifiers  so  that  they
1214         are not greedy by default, but become greedy if followed by "?". It  is         are  not greedy by default, but become greedy if followed by "?". It is
1215         not  compatible  with Perl. It can also be set by a (?U) option setting         not compatible with Perl. It can also be set by a (?U)  option  setting
1216         within the pattern.         within the pattern.
1217    
1218           PCRE_UTF8           PCRE_UTF8
1219    
1220         This option causes PCRE to regard both the pattern and the  subject  as         This  option  causes PCRE to regard both the pattern and the subject as
1221         strings  of  UTF-8 characters instead of single-byte character strings.         strings of UTF-8 characters instead of single-byte  character  strings.
1222         However, it is available only if PCRE has been built to  include  UTF-8         However,  it is available only when PCRE is built to include UTF-8 sup-
1223         support.  If  not, the use of this option provokes an error. Details of         port. If not, the use of this option provokes an error. Details of  how
1224         how this option changes the behaviour of PCRE are given in the  section         this  option  changes the behaviour of PCRE are given in the section on
1225         on UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1226    
1227           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1228    
1229         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
1230         automatically checked. If an invalid UTF-8 sequence of bytes is  found,         automatically  checked. If an invalid UTF-8 sequence of bytes is found,
1231         pcre_compile()  returns an error. If you already know that your pattern         pcre_compile() returns an error. If you already know that your  pattern
1232         is valid, and you want to skip this check for performance reasons,  you         is  valid, and you want to skip this check for performance reasons, you
1233         can  set  the  PCRE_NO_UTF8_CHECK option. When it is set, the effect of         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of
1234         passing an invalid UTF-8 string as a pattern is undefined. It may cause         passing an invalid UTF-8 string as a pattern is undefined. It may cause
1235         your  program  to  crash.  Note that there is a similar option for sup-         your program to crash.  Note that this option can  also  be  passed  to
1236         pressing the checking of subject strings passed to pcre_exec().         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-
1237           ing of subject strings.
1238    
1239    
1240    COMPILATION ERROR CODES
1241    
1242           The following table lists the error  codes  than  may  be  returned  by
1243           pcre_compile2(),  along with the error messages that may be returned by
1244           both compiling functions. As PCRE has developed, some error codes  have
1245           fallen out of use. To avoid confusion, they have not been re-used.
1246    
1247              0  no error
1248              1  \ at end of pattern
1249              2  \c at end of pattern
1250              3  unrecognized character follows \
1251              4  numbers out of order in {} quantifier
1252              5  number too big in {} quantifier
1253              6  missing terminating ] for character class
1254              7  invalid escape sequence in character class
1255              8  range out of order in character class
1256              9  nothing to repeat
1257             10  [this code is not in use]
1258             11  internal error: unexpected repeat
1259             12  unrecognized character after (?
1260             13  POSIX named classes are supported only within a class
1261             14  missing )
1262             15  reference to non-existent subpattern
1263             16  erroffset passed as NULL
1264             17  unknown option bit(s) set
1265             18  missing ) after comment
1266             19  [this code is not in use]
1267             20  regular expression too large
1268             21  failed to get memory
1269             22  unmatched parentheses
1270             23  internal error: code overflow
1271             24  unrecognized character after (?<
1272             25  lookbehind assertion is not fixed length
1273             26  malformed number or name after (?(
1274             27  conditional group contains more than two branches
1275             28  assertion expected after (?(
1276             29  (?R or (?[+-]digits must be followed by )
1277             30  unknown POSIX class name
1278             31  POSIX collating elements are not supported
1279             32  this version of PCRE is not compiled with PCRE_UTF8 support
1280             33  [this code is not in use]
1281             34  character value in \x{...} sequence is too large
1282             35  invalid condition (?(0)
1283             36  \C not allowed in lookbehind assertion
1284             37  PCRE does not support \L, \l, \N, \U, or \u
1285             38  number after (?C is > 255
1286             39  closing ) for (?C expected
1287             40  recursive call could loop indefinitely
1288             41  unrecognized character after (?P
1289             42  syntax error in subpattern name (missing terminator)
1290             43  two named subpatterns have the same name
1291             44  invalid UTF-8 string
1292             45  support for \P, \p, and \X has not been compiled
1293             46  malformed \P or \p sequence
1294             47  unknown property name after \P or \p
1295             48  subpattern name is too long (maximum 32 characters)
1296             49  too many named subpatterns (maximum 10,000)
1297             50  repeated subpattern is too long
1298             51  octal value is greater than \377 (not in UTF-8 mode)
1299             52  internal error: overran compiling workspace
1300             53   internal  error:  previously-checked  referenced  subpattern not
1301           found
1302             54  DEFINE group contains more than one branch
1303             55  repeating a DEFINE group is not allowed
1304             56  inconsistent NEWLINE options"
1305             57  \g is not followed by a braced name or an optionally braced
1306                   non-zero number
1307             58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
1308    
1309    
1310  STUDYING A PATTERN  STUDYING A PATTERN
1311    
1312         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1313              const char **errptr);              const char **errptr);
1314    
1315         When a pattern is going to be used several times, it is worth  spending         If a compiled pattern is going to be used several times,  it  is  worth
1316         more  time  analyzing it in order to speed up the time taken for match-         spending more time analyzing it in order to speed up the time taken for
1317         ing. The function pcre_study() takes a pointer to a compiled pattern as         matching. The function pcre_study() takes a pointer to a compiled  pat-
1318         its first argument. If studing the pattern produces additional informa-         tern as its first argument. If studying the pattern produces additional
1319         tion that will help speed up matching, pcre_study() returns  a  pointer         information that will help speed up matching,  pcre_study()  returns  a
1320         to  a  pcre_extra  block,  in  which the study_data field points to the         pointer  to a pcre_extra block, in which the study_data field points to
1321         results of the study.         the results of the study.
1322    
1323         The returned value from  a  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1324         pcre_exec().  However,  the pcre_extra block also contains other fields         pcre_exec().  However,  a  pcre_extra  block also contains other fields
1325         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
1326         described  below.  If  studying  the pattern does not produce any addi-         described below in the section on matching a pattern.
1327         tional information, pcre_study() returns NULL. In that circumstance, if  
1328         the  calling  program  wants  to  pass  some  of  the  other  fields to         If  studying  the  pattern  does not produce any additional information
1329         pcre_exec(), it must set up its own pcre_extra block.         pcre_study() returns NULL. In that circumstance, if the calling program
1330           wants  to  pass  any of the other fields to pcre_exec(), it must set up
1331           its own pcre_extra block.
1332    
1333         The second argument contains option bits. At present,  no  options  are         The second argument of pcre_study() contains option bits.  At  present,
1334         defined for pcre_study(), and this argument should always be zero.         no options are defined, and this argument should always be zero.
1335    
1336         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.
1337         If studying succeeds (even if no data is  returned),  the  variable  it         If studying succeeds (even if no data is  returned),  the  variable  it
1338         points  to  is set to NULL. Otherwise it points to a textual error mes-         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1339         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1340         ing pcre_study(), to be sure that it has run successfully.         must  not  try  to  free it. You should test the error pointer for NULL
1341           after calling pcre_study(), to be sure that it has run successfully.
1342    
1343         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1344    
# Line 735  STUDYING A PATTERN Line 1349  STUDYING A PATTERN
1349             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1350    
1351         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1352         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-
1353         ble starting characters is created.         ble starting bytes is created.
1354    
1355    
1356  LOCALE SUPPORT  LOCALE SUPPORT
1357    
1358         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1359         letters, digits, or whatever, by reference to a  set  of  tables.  When         letters,  digits, or whatever, by reference to a set of tables, indexed
1360         running  in UTF-8 mode, this applies only to characters with codes less         by character value. When running in UTF-8 mode, this  applies  only  to
1361         than 256. The library contains a default set of tables that is  created         characters  with  codes  less than 128. Higher-valued codes never match
1362         in  the  default  C locale when PCRE is compiled. This is used when the         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built
1363         final argument of pcre_compile() is NULL, and is  sufficient  for  many         with  Unicode  character property support. The use of locales with Uni-
1364         applications.         code is discouraged. If you are handling characters with codes  greater
1365           than  128, you should either use UTF-8 and Unicode, or use locales, but
1366         An alternative set of tables can, however, be supplied. Such tables are         not try to mix the two.
1367         built by calling the pcre_maketables() function,  which  has  no  argu-  
1368         ments,  in  the  relevant  locale.  The  result  can  then be passed to         PCRE contains an internal set of tables that are used  when  the  final
1369         pcre_compile() as often as necessary. For example,  to  build  and  use         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1370         tables that are appropriate for the French locale (where accented char-         applications.  Normally, the internal tables recognize only ASCII char-
1371         acters with codes greater than 128 are treated as letters), the follow-         acters. However, when PCRE is built, it is possible to cause the inter-
1372         ing code could be used:         nal tables to be rebuilt in the default "C" locale of the local system,
1373           which may cause them to be different.
1374    
1375           The  internal tables can always be overridden by tables supplied by the
1376           application that calls PCRE. These may be created in a different locale
1377           from  the  default.  As more and more applications change to using Uni-
1378           code, the need for this locale support is expected to die away.
1379    
1380           External tables are built by calling  the  pcre_maketables()  function,
1381           which  has no arguments, in the relevant locale. The result can then be
1382           passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1383           example,  to  build  and use tables that are appropriate for the French
1384           locale (where accented characters with  values  greater  than  128  are
1385           treated as letters), the following code could be used:
1386    
1387           setlocale(LC_CTYPE, "fr");           setlocale(LC_CTYPE, "fr_FR");
1388           tables = pcre_maketables();           tables = pcre_maketables();
1389           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1390    
1391         The  tables  are  built in memory that is obtained via pcre_malloc. The         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1392         pointer that is passed to pcre_compile is saved with the compiled  pat-         if you are using Windows, the name for the French locale is "french".
1393         tern, and the same tables are used via this pointer by pcre_study() and  
1394         pcre_exec(). Thus, for any single pattern,  compilation,  studying  and         When pcre_maketables() runs, the tables are built  in  memory  that  is
1395         matching  all  happen in the same locale, but different patterns can be         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1396         compiled in different locales. It is  the  caller's  responsibility  to         that the memory containing the tables remains available for as long  as
1397         ensure  that  the memory containing the tables remains available for as         it is needed.
1398         long as it is needed.  
1399           The pointer that is passed to pcre_compile() is saved with the compiled
1400           pattern, and the same tables are used via this pointer by  pcre_study()
1401           and normally also by pcre_exec(). Thus, by default, for any single pat-
1402           tern, compilation, studying and matching all happen in the same locale,
1403           but different patterns can be compiled in different locales.
1404    
1405           It  is  possible to pass a table pointer or NULL (indicating the use of
1406           the internal tables) to pcre_exec(). Although  not  intended  for  this
1407           purpose,  this facility could be used to match a pattern in a different
1408           locale from the one in which it was compiled. Passing table pointers at
1409           run time is discussed below in the section on matching a pattern.
1410    
1411    
1412  INFORMATION ABOUT A PATTERN  INFORMATION ABOUT A PATTERN
# Line 776  INFORMATION ABOUT A PATTERN Line 1414  INFORMATION ABOUT A PATTERN
1414         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1415              int what, void *where);              int what, void *where);
1416    
1417         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1418         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1419         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1420    
1421         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1422         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
1423         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1424         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
1425         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
1426         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1427    
1428           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 792  INFORMATION ABOUT A PATTERN Line 1430  INFORMATION ABOUT A PATTERN
1430           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1431           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1432    
1433         Here  is a typical call of pcre_fullinfo(), to obtain the length of the         The "magic number" is placed at the start of each compiled  pattern  as
1434         compiled pattern:         an  simple check against passing an arbitrary memory pointer. Here is a
1435           typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1436           pattern:
1437    
1438           int rc;           int rc;
1439           unsigned long int length;           size_t length;
1440           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1441             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1442             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1443             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1444             &length);         /* where to put the data */             &length);         /* where to put the data */
1445    
1446         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
1447         are as follows:         are as follows:
1448    
1449           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1450    
1451         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1452         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1453         there are no back references.         there are no back references.
1454    
1455           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1456    
1457         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1458         argument should point to an int variable.         argument should point to an int variable.
1459    
1460             PCRE_INFO_DEFAULT_TABLES
1461    
1462           Return  a pointer to the internal default character tables within PCRE.
1463           The fourth argument should point to an unsigned char *  variable.  This
1464           information call is provided for internal use by the pcre_study() func-
1465           tion. External callers can cause PCRE to use  its  internal  tables  by
1466           passing a NULL table pointer.
1467    
1468           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1469    
1470         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1471         non-anchored    pattern.    (This    option    used    to   be   called         non-anchored pattern. The fourth argument should point to an int  vari-
1472         PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1473         compatibility.)         is still recognized for backwards compatibility.)
1474    
1475         If  there  is  a  fixed  first  byte,  e.g.  from  a  pattern  such  as         If there is a fixed first byte, for example, from  a  pattern  such  as
1476         (cat|cow|coyote), it is returned in the integer pointed  to  by  where.         (cat|cow|coyote), its value is returned. Otherwise, if either
        Otherwise, if either  
1477    
1478         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1479         branch starts with "^", or         branch starts with "^", or
# Line 846  INFORMATION ABOUT A PATTERN Line 1493  INFORMATION ABOUT A PATTERN
1493         returned. The fourth argument should point to an unsigned char *  vari-         returned. The fourth argument should point to an unsigned char *  vari-
1494         able.         able.
1495    
1496             PCRE_INFO_JCHANGED
1497    
1498           Return  1  if the (?J) option setting is used in the pattern, otherwise
1499           0. The fourth argument should point to an int variable. The (?J) inter-
1500           nal option setting changes the local PCRE_DUPNAMES option.
1501    
1502           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1503    
1504         Return  the  value of the rightmost literal byte that must exist in any         Return  the  value of the rightmost literal byte that must exist in any
# Line 862  INFORMATION ABOUT A PATTERN Line 1515  INFORMATION ABOUT A PATTERN
1515    
1516         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1517         ses. The names are just an additional way of identifying the  parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1518         ses,  which still acquire a number. A caller that wants to extract data         ses, which still acquire numbers. Several convenience functions such as
1519         from a named subpattern must convert the name to a number in  order  to         pcre_get_named_substring() are provided for  extracting  captured  sub-
1520         access  the  correct  pointers  in  the  output  vector (described with         strings  by  name. It is also possible to extract the data directly, by
1521         pcre_exec() below). In order to do this, it must first use these  three         first converting the name to a number in order to  access  the  correct
1522         values to obtain the name-to-number mapping table for the pattern.         pointers in the output vector (described with pcre_exec() below). To do
1523           the conversion, you need  to  use  the  name-to-number  map,  which  is
1524           described by these three values.
1525    
1526         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
1527         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
# Line 876  INFORMATION ABOUT A PATTERN Line 1531  INFORMATION ABOUT A PATTERN
1531         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-
1532         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-
1533         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding name, zero terminated. The names are  in  alphabetical  order.
1534         For  example,  consider  the following pattern (assume PCRE_EXTENDED is         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1535         set, so white space - including newlines - is ignored):         theses numbers. For example, consider  the  following  pattern  (assume
1536           PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is
1537           ignored):
1538    
1539           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1540           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1541    
1542         There are four named subpatterns, so the table has  four  entries,  and         There are four named subpatterns, so the table has  four  entries,  and
1543         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,
1544         with non-printing bytes shows in hex, and undefined bytes shown as ??:         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1545           as ??:
1546    
1547           00 01 d  a  t  e  00 ??           00 01 d  a  t  e  00 ??
1548           00 05 d  a  y  00 ?? ??           00 05 d  a  y  00 ?? ??
1549           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1550           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1551    
1552         When writing code to extract data from named subpatterns, remember that         When  writing  code  to  extract  data from named subpatterns using the
1553         the length of each entry may be different for each compiled pattern.         name-to-number map, remember that the length of the entries  is  likely
1554           to be different for each compiled pattern.
1555    
1556             PCRE_INFO_OKPARTIAL
1557    
1558           Return  1 if the pattern can be used for partial matching, otherwise 0.
1559           The fourth argument should point to an int  variable.  The  pcrepartial
1560           documentation  lists  the restrictions that apply to patterns when par-
1561           tial matching is used.
1562    
1563           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1564    
1565         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
1566         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1567         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1568         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1569           other words, they are the options that will be in force  when  matching
1570           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1571           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1572           and PCRE_EXTENDED.
1573    
1574         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
1575         alternatives begin with one of the following:         alternatives begin with one of the following:
1576    
1577           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 915  INFORMATION ABOUT A PATTERN Line 1585  INFORMATION ABOUT A PATTERN
1585    
1586           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1587    
1588         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
1589         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
1590         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
1591         size_t variable.         size_t variable.
1592    
1593           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1594    
1595         Returns  the  size of the data block pointed to by the study_data field         Return the size of the data block pointed to by the study_data field in
1596         in 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
1597         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
1598         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
1599         variable.         variable.
1600    
1601    
# Line 933  OBSOLETE INFO FUNCTION Line 1603  OBSOLETE INFO FUNCTION
1603    
1604         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1605    
1606         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1607         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1608         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1609         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-
1610         lowing negative numbers:         lowing negative numbers:
1611    
1612           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1613           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1614    
1615         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
1616         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
1617         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1618    
1619         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1620         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
1621         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1622    
1623    
1624  MATCHING A PATTERN  REFERENCE COUNTS
1625    
1626           int pcre_refcount(pcre *code, int adjust);
1627    
1628           The pcre_refcount() function is used to maintain a reference  count  in
1629           the data block that contains a compiled pattern. It is provided for the
1630           benefit of applications that  operate  in  an  object-oriented  manner,
1631           where different parts of the application may be using the same compiled
1632           pattern, but you want to free the block when they are all done.
1633    
1634           When a pattern is compiled, the reference count field is initialized to
1635           zero.   It is changed only by calling this function, whose action is to
1636           add the adjust value (which may be positive or  negative)  to  it.  The
1637           yield of the function is the new value. However, the value of the count
1638           is constrained to lie between 0 and 65535, inclusive. If the new  value
1639           is outside these limits, it is forced to the appropriate limit value.
1640    
1641           Except  when it is zero, the reference count is not correctly preserved
1642           if a pattern is compiled on one host and then  transferred  to  a  host
1643           whose byte-order is different. (This seems a highly unlikely scenario.)
1644    
1645    
1646    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1647    
1648         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1649              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1650              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1651    
1652         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
1653         pre-compiled pattern, which is passed in the code argument. If the pat-         compiled  pattern, which is passed in the code argument. If the pattern
1654         tern  has been studied, the result of the study should be passed in the         has been studied, the result of the study should be passed in the extra
1655         extra argument.         argument.  This  function is the main matching facility of the library,
1656           and it operates in a Perl-like manner. For specialist use there is also
1657           an  alternative matching function, which is described below in the sec-
1658           tion about the pcre_dfa_exec() function.
1659    
1660           In most applications, the pattern will have been compiled (and  option-
1661           ally  studied)  in the same process that calls pcre_exec(). However, it
1662           is possible to save compiled patterns and study data, and then use them
1663           later  in  different processes, possibly even on different hosts. For a
1664           discussion about this, see the pcreprecompile documentation.
1665    
1666         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
1667    
# Line 973  MATCHING A PATTERN Line 1674  MATCHING A PATTERN
1674             11,             /* the length of the subject string */             11,             /* the length of the subject string */
1675             0,              /* start at offset 0 in the subject */             0,              /* start at offset 0 in the subject */
1676             0,              /* default options */             0,              /* default options */
1677             ovector,        /* vector for substring information */             ovector,        /* vector of integers for substring information */
1678             30);            /* number of elements in the vector */             30);            /* number of elements (NOT size in bytes) */
1679    
1680       Extra data for pcre_exec()
1681    
1682         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
1683         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
1684         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-
1685         tional information in it. The fields in the block are as follows:         tional  information  in it. The pcre_extra block contains the following
1686           fields (not necessarily in this order):
1687    
1688           unsigned long int flags;           unsigned long int flags;
1689           void *study_data;           void *study_data;
1690           unsigned long int match_limit;           unsigned long int match_limit;
1691             unsigned long int match_limit_recursion;
1692           void *callout_data;           void *callout_data;
1693             const unsigned char *tables;
1694    
1695         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
1696         are set. The flag bits are:         are set. The flag bits are:
1697    
1698           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1699           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1700             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1701           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1702             PCRE_EXTRA_TABLES
1703    
1704         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
1705         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1706         the appropriate flag bit. You should not set this yourself, but you can         the appropriate flag bit. You should not set this yourself, but you may
1707         add to the block by setting the other fields.         add to the block by setting the other fields  and  their  corresponding
1708           flag bits.
1709    
1710         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
1711         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
1712         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
1713         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1714         repeats. Internally, PCRE uses a function called match() which it calls         repeats.
1715         repeatedly (sometimes recursively). The limit is imposed on the  number  
1716         of  times  this function is called during a match, which has the effect         Internally,  PCRE uses a function called match() which it calls repeat-
1717         of limiting the amount of recursion  and  backtracking  that  can  take         edly (sometimes recursively). The limit set by match_limit  is  imposed
1718         place.  For  patterns that are not anchored, the count starts from zero         on  the  number  of times this function is called during a match, which
1719           has the effect of limiting the amount of  backtracking  that  can  take
1720           place. For patterns that are not anchored, the count restarts from zero
1721         for each position in the subject string.         for each position in the subject string.
1722    
1723         The default limit for the library can be set when PCRE  is  built;  the         The default value for the limit can be set  when  PCRE  is  built;  the
1724         default  default  is 10 million, which handles all but the most extreme         default  default  is 10 million, which handles all but the most extreme
1725         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1726         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra     block    in    which    match_limit    is    set,    and
1727         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
1728         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1729    
1730           The  match_limit_recursion field is similar to match_limit, but instead
1731           of limiting the total number of times that match() is called, it limits
1732           the  depth  of  recursion. The recursion depth is a smaller number than
1733           the total number of calls, because not all calls to match() are  recur-
1734           sive.  This limit is of use only if it is set smaller than match_limit.
1735    
1736           Limiting the recursion depth limits the amount of  stack  that  can  be
1737           used, or, when PCRE has been compiled to use memory on the heap instead
1738           of the stack, the amount of heap memory that can be used.
1739    
1740           The default value for match_limit_recursion can be  set  when  PCRE  is
1741           built;  the  default  default  is  the  same  value  as the default for
1742           match_limit. You can override the default by suppling pcre_exec()  with
1743           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1744           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1745           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1746    
1747         The  pcre_callout  field is used in conjunction with the "callout" fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1748         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1749    
1750         The PCRE_ANCHORED option can be passed in the options  argument,  whose         The tables field  is  used  to  pass  a  character  tables  pointer  to
1751         unused  bits  must  be zero. This limits pcre_exec() to matching at the         pcre_exec();  this overrides the value that is stored with the compiled
1752         first matching position.  However,  if  a  pattern  was  compiled  with         pattern. A non-NULL value is stored with the compiled pattern  only  if
1753         PCRE_ANCHORED,  or turned out to be anchored by virtue of its contents,         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1754         it cannot be made unachored at matching time.         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
1755           PCRE's  internal  tables  to be used. This facility is helpful when re-
1756         When PCRE_UTF8 was set at compile time, the validity of the subject  as         using patterns that have been saved after compiling  with  an  external
1757         a  UTF-8  string is automatically checked, and the value of startoffset         set  of  tables,  because  the  external tables might be at a different
1758         is also checked to ensure that it points to the start of a UTF-8  char-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1759         acter.  If  an  invalid  UTF-8  sequence of bytes is found, pcre_exec()         tion for a discussion of saving compiled patterns for later use.
1760         returns  the  error  PCRE_ERROR_BADUTF8.  If  startoffset  contains  an  
1761         invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.     Option bits for pcre_exec()
1762    
1763         If  you  already  know that your subject is valid, and you want to skip         The  unused  bits of the options argument for pcre_exec() must be zero.
1764         these   checks   for   performance   reasons,   you   can    set    the         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
1765         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1766         do this for the second and subsequent calls to pcre_exec() if  you  are         PCRE_PARTIAL.
        making  repeated  calls  to  find  all  the matches in a single subject  
        string. However, you should be  sure  that  the  value  of  startoffset  
        points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is  
        set, the effect of passing an invalid UTF-8 string as a subject,  or  a  
        value  of startoffset that does not point to the start of a UTF-8 char-  
        acter, is undefined. Your program may crash.  
1767    
1768         There are also three further options that can be set only  at  matching           PCRE_ANCHORED
1769         time:  
1770           The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
1771           matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
1772           turned out to be anchored by virtue of its contents, it cannot be  made
1773           unachored at matching time.
1774    
1775             PCRE_NEWLINE_CR
1776             PCRE_NEWLINE_LF
1777             PCRE_NEWLINE_CRLF
1778             PCRE_NEWLINE_ANYCRLF
1779             PCRE_NEWLINE_ANY
1780    
1781           These  options  override  the  newline  definition  that  was chosen or
1782           defaulted when the pattern was compiled. For details, see the  descrip-
1783           tion  of  pcre_compile()  above.  During  matching,  the newline choice
1784           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1785           ters.  It may also alter the way the match position is advanced after a
1786           match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,
1787           PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt
1788           fails when the current position is at a CRLF sequence, the match  posi-
1789           tion  is  advanced by two characters instead of one, in other words, to
1790           after the CRLF.
1791    
1792           PCRE_NOTBOL           PCRE_NOTBOL
1793    
1794         The  first  character  of the string is not the beginning of a line, so         This option specifies that first character of the subject string is not
1795         the circumflex metacharacter should not match before it.  Setting  this         the  beginning  of  a  line, so the circumflex metacharacter should not
1796         without  PCRE_MULTILINE  (at  compile  time) causes circumflex never to         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1797         match.         causes  circumflex  never to match. This option affects only the behav-
1798           iour of the circumflex metacharacter. It does not affect \A.
1799    
1800           PCRE_NOTEOL           PCRE_NOTEOL
1801    
1802         The end of the string is not the end of a line, so the dollar metachar-         This option specifies that the end of the subject string is not the end
1803         acter  should  not  match  it  nor (except in multiline mode) a newline         of  a line, so the dollar metacharacter should not match it nor (except
1804         immediately before it. Setting this without PCRE_MULTILINE (at  compile         in multiline mode) a newline immediately before it. Setting this  with-
1805         time) causes dollar never to match.         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1806           option affects only the behaviour of the dollar metacharacter. It  does
1807           not affect \Z or \z.
1808    
1809           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1810    
# Line 1078  MATCHING A PATTERN Line 1824  MATCHING A PATTERN
1824         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()
1825         function,  and  when  using  the /g modifier. It is possible to emulate         function,  and  when  using  the /g modifier. It is possible to emulate
1826         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
1827         again at the same offset with PCRE_NOTEMPTY set, and then if that fails         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
1828         by advancing the starting offset (see below)  and  trying  an  ordinary         if that fails by advancing the starting offset (see below)  and  trying
1829         match again.         an ordinary match again. There is some code that demonstrates how to do
1830           this in the pcredemo.c sample program.
1831         The  subject string is passed to pcre_exec() as a pointer in subject, a  
1832         length in length, and a starting byte offset in startoffset. Unlike the           PCRE_NO_UTF8_CHECK
1833         pattern  string,  the  subject  may contain binary zero bytes. When the  
1834         starting offset is zero, the search for a match starts at the beginning         When PCRE_UTF8 is set at compile time, the validity of the subject as a
1835         of the subject, and this is by far the most common case.         UTF-8  string is automatically checked when pcre_exec() is subsequently
1836           called.  The value of startoffset is also checked  to  ensure  that  it
1837         If the pattern was compiled with the PCRE_UTF8 option, the subject must         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence
1838         be a sequence of bytes that is a valid UTF-8 string, and  the  starting         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
1839         offset  must point to the beginning of a UTF-8 character. If an invalid         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
1840         UTF-8 string or offset is passed, an error  (either  PCRE_ERROR_BADUTF8         returned.
1841         or   PCRE_ERROR_BADUTF8_OFFSET)   is   returned,   unless   the  option  
1842         PCRE_NO_UTF8_CHECK is set,  in  which  case  PCRE's  behaviour  is  not         If you already know that your subject is valid, and you  want  to  skip
1843         defined.         these    checks    for   performance   reasons,   you   can   set   the
1844           PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
1845           do  this  for the second and subsequent calls to pcre_exec() if you are
1846           making repeated calls to find all  the  matches  in  a  single  subject
1847           string.  However,  you  should  be  sure  that the value of startoffset
1848           points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
1849           set,  the  effect of passing an invalid UTF-8 string as a subject, or a
1850           value of startoffset that does not point to the start of a UTF-8  char-
1851           acter, is undefined. Your program may crash.
1852    
1853             PCRE_PARTIAL
1854    
1855           This  option  turns  on  the  partial  matching feature. If the subject
1856           string fails to match the pattern, but at some point during the  match-
1857           ing  process  the  end of the subject was reached (that is, the subject
1858           partially matches the pattern and the failure to  match  occurred  only
1859           because  there were not enough subject characters), pcre_exec() returns
1860           PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
1861           used,  there  are restrictions on what may appear in the pattern. These
1862           are discussed in the pcrepartial documentation.
1863    
1864       The string to be matched by pcre_exec()
1865    
1866           The subject string is passed to pcre_exec() as a pointer in subject,  a
1867           length  in  length, and a starting byte offset in startoffset. In UTF-8
1868           mode, the byte offset must point to the start  of  a  UTF-8  character.
1869           Unlike  the  pattern string, the subject may contain binary zero bytes.
1870           When the starting offset is zero, the search for a match starts at  the
1871           beginning of the subject, and this is by far the most common case.
1872    
1873         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
1874         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1111  MATCHING A PATTERN Line 1885  MATCHING A PATTERN
1885         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
1886         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
1887         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
1888         string again, but with startoffset  set  to  4,  it  finds  the  second         string again, but with startoffset set to 4, it finds the second occur-
1889         occurrence  of  "iss"  because  it  is able to look behind the starting         rence  of "iss" because it is able to look behind the starting point to
1890         point to discover that it is preceded by a letter.         discover that it is preceded by a letter.
1891    
1892         If a non-zero starting offset is passed when the pattern  is  anchored,         If a non-zero starting offset is passed when the pattern  is  anchored,
1893         one  attempt  to match at the given offset is tried. This can only suc-         one attempt to match at the given offset is made. This can only succeed
1894         ceed if the pattern does not require the match to be at  the  start  of         if the pattern does not require the match to be at  the  start  of  the
1895         the subject.         subject.
1896    
1897       How pcre_exec() returns captured substrings
1898    
1899         In  general, a pattern matches a certain portion of the subject, and in         In  general, a pattern matches a certain portion of the subject, and in
1900         addition, further substrings from the subject  may  be  picked  out  by         addition, further substrings from the subject  may  be  picked  out  by
# Line 1130  MATCHING A PATTERN Line 1906  MATCHING A PATTERN
1906    
1907         Captured  substrings are returned to the caller via a vector of integer         Captured  substrings are returned to the caller via a vector of integer
1908         offsets whose address is passed in ovector. The number of  elements  in         offsets whose address is passed in ovector. The number of  elements  in
1909         the vector is passed in ovecsize. The first two-thirds of the vector is         the  vector is passed in ovecsize, which must be a non-negative number.
1910         used to pass back captured substrings, each substring using a  pair  of         Note: this argument is NOT the size of ovector in bytes.
        integers.  The  remaining  third  of the vector is used as workspace by  
        pcre_exec() while matching capturing subpatterns, and is not  available  
        for  passing  back  information.  The  length passed in ovecsize should  
        always be a multiple of three. If it is not, it is rounded down.  
   
        When a match has been successful, information about captured substrings  
        is returned in pairs of integers, starting at the beginning of ovector,  
        and continuing up to two-thirds of its length at the  most.  The  first  
        element of a pair is set to the offset of the first character in a sub-  
        string, and the second is set to the  offset  of  the  first  character  
        after  the  end  of  a  substring. The first pair, ovector[0] and ovec-  
        tor[1], identify the portion of  the  subject  string  matched  by  the  
        entire  pattern.  The next pair is used for the first capturing subpat-  
        tern, and so on. The value returned by pcre_exec()  is  the  number  of  
        pairs  that  have  been set. If there are no capturing subpatterns, the  
        return value from a successful match is 1,  indicating  that  just  the  
        first pair of offsets has been set.  
1911    
1912         Some  convenience  functions  are  provided for extracting the captured         The first two-thirds of the vector is used to pass back  captured  sub-
1913         substrings as separate strings. These are described  in  the  following         strings,  each  substring using a pair of integers. The remaining third
1914         section.         of the vector is used as workspace by pcre_exec() while  matching  cap-
1915           turing  subpatterns, and is not available for passing back information.
1916         It  is  possible  for  an capturing subpattern number n+1 to match some         The length passed in ovecsize should always be a multiple of three.  If
1917         part of the subject when subpattern n has not been  used  at  all.  For         it is not, it is rounded down.
1918         example, if the string "abc" is matched against the pattern (a|(z))(bc)  
1919         subpatterns 1 and 3 are matched, but 2 is not. When this happens,  both         When  a  match  is successful, information about captured substrings is
1920         offset values corresponding to the unused subpattern are set to -1.         returned in pairs of integers, starting at the  beginning  of  ovector,
1921           and  continuing  up  to two-thirds of its length at the most. The first
1922           element of a pair is set to the offset of the first character in a sub-
1923           string,  and  the  second  is  set to the offset of the first character
1924           after the end of a substring. The  first  pair,  ovector[0]  and  ovec-
1925           tor[1],  identify  the  portion  of  the  subject string matched by the
1926           entire pattern. The next pair is used for the first  capturing  subpat-
1927           tern, and so on. The value returned by pcre_exec() is one more than the
1928           highest numbered pair that has been set. For example, if two substrings
1929           have  been captured, the returned value is 3. If there are no capturing
1930           subpatterns, the return value from a successful match is 1,  indicating
1931           that just the first pair of offsets has been set.
1932    
1933         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
1934         of the string that it matched that gets returned.         of the string that it matched that is returned.
1935    
1936         If the vector is too small to hold all the captured substrings,  it  is         If the vector is too small to hold all the captured substring  offsets,
1937         used as far as possible (up to two-thirds of its length), and the func-         it is used as far as possible (up to two-thirds of its length), and the
1938         tion returns a value of zero. In particular, if the  substring  offsets         function returns a value of zero. In particular, if the substring  off-
1939         are  not  of interest, pcre_exec() may be called with ovector passed as         sets are not of interest, pcre_exec() may be called with ovector passed
1940         NULL and ovecsize as zero. However, if the pattern contains back refer-         as NULL and ovecsize as zero. However, if  the  pattern  contains  back
1941         ences  and  the  ovector  isn't big enough to remember the related sub-         references  and  the  ovector is not big enough to remember the related
1942         strings, PCRE has to get additional memory  for  use  during  matching.         substrings, PCRE has to get additional memory for use during  matching.
1943         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
1944    
1945         Note  that  pcre_info() can be used to find out how many capturing sub-         The  pcre_info()  function  can  be used to find out how many capturing
1946         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns there are in a compiled  pattern.  The  smallest  size  for
1947         that  will  allow for n captured substrings, in addition to the offsets         ovector  that  will allow for n captured substrings, in addition to the
1948         of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
1949    
1950           It is possible for capturing subpattern number n+1 to match  some  part
1951           of the subject when subpattern n has not been used at all. For example,
1952           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
1953           return from the function is 4, and subpatterns 1 and 3 are matched, but
1954           2 is not. When this happens, both values in  the  offset  pairs  corre-
1955           sponding to unused subpatterns are set to -1.
1956    
1957           Offset  values  that correspond to unused subpatterns at the end of the
1958           expression are also set to -1. For example,  if  the  string  "abc"  is
1959           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
1960           matched. The return from the function is 2, because  the  highest  used
1961           capturing subpattern number is 1. However, you can refer to the offsets
1962           for the second and third capturing subpatterns if  you  wish  (assuming
1963           the vector is large enough, of course).
1964    
1965           Some  convenience  functions  are  provided for extracting the captured
1966           substrings as separate strings. These are described below.
1967    
1968       Error return values from pcre_exec()
1969    
1970         If pcre_exec() fails, it returns a negative number. The  following  are         If pcre_exec() fails, it returns a negative number. The  following  are
1971         defined in the header file:         defined in the header file:
# Line 1196  MATCHING A PATTERN Line 1986  MATCHING A PATTERN
1986           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
1987    
1988         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
1989         to  catch  the case when it is passed a junk pointer. This is the error         to catch the case when it is passed a junk pointer and to detect when a
1990         it gives when the magic number isn't present.         pattern that was compiled in an environment of one endianness is run in
1991           an  environment  with the other endianness. This is the error that PCRE
1992           gives when the magic number is not present.
1993    
1994           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
1995    
1996         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
1997         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
# Line 1211  MATCHING A PATTERN Line 2003  MATCHING A PATTERN
2003         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2004         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE gets a block of memory at the start of matching to  use  for  this
2005         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2006         memory is freed at the end of matching.         memory is automatically freed at the end of matching.
2007    
2008           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2009    
# Line 1221  MATCHING A PATTERN Line 2013  MATCHING A PATTERN
2013    
2014           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2015    
2016         The recursion and backtracking limit, as specified by  the  match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2017         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         pcre_extra  structure  (or  defaulted) was reached. See the description
2018         description above.         above.
2019    
2020           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2021    
# Line 1242  MATCHING A PATTERN Line 2034  MATCHING A PATTERN
2034         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2035         ter.         ter.
2036    
2037             PCRE_ERROR_PARTIAL        (-12)
2038    
2039           The  subject  string did not match, but it did match partially. See the
2040           pcrepartial documentation for details of partial matching.
2041    
2042             PCRE_ERROR_BADPARTIAL     (-13)
2043    
2044           The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
2045           items  that are not supported for partial matching. See the pcrepartial
2046           documentation for details of partial matching.
2047    
2048             PCRE_ERROR_INTERNAL       (-14)
2049    
2050           An unexpected internal error has occurred. This error could  be  caused
2051           by a bug in PCRE or by overwriting of the compiled pattern.
2052    
2053             PCRE_ERROR_BADCOUNT       (-15)
2054    
2055           This  error is given if the value of the ovecsize argument is negative.
2056    
2057             PCRE_ERROR_RECURSIONLIMIT (-21)
2058    
2059           The internal recursion limit, as specified by the match_limit_recursion
2060           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2061           description above.
2062    
2063             PCRE_ERROR_BADNEWLINE     (-23)
2064    
2065           An invalid combination of PCRE_NEWLINE_xxx options was given.
2066    
2067           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2068    
2069    
2070  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2071    
# Line 1256  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2080  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2080         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2081              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2082    
2083         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2084         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2085         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2086         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2087         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2088         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2089         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2090         extracted and has a further zero added on the end, but  the  result  is  
2091         not, of course, a C string.         A substring that contains a binary zero is correctly extracted and  has
2092           a  further zero added on the end, but the result is not, of course, a C
2093           string.  However, you can process such a string  by  referring  to  the
2094           length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2095           string().  Unfortunately, the interface to pcre_get_substring_list() is
2096           not  adequate for handling strings containing binary zeros, because the
2097           end of the final string is not independently indicated.
2098    
2099         The  first  three  arguments  are the same for all three of these func-         The first three arguments are the same for all  three  of  these  func-
2100         tions: subject is the subject string which has just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2101         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2102         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2103         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2104         entire regular expression. This is the value returned by  pcre_exec  if         entire regular expression. This is the value returned by pcre_exec() if
2105         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2106         it ran out of space in ovector, the value passed as stringcount  should         it  ran out of space in ovector, the value passed as stringcount should
2107         be the size of the vector divided by three.         be the number of elements in the vector divided by three.
2108    
2109         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2110         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2111         zero  extracts  the  substring  that  matched the entire pattern, while         zero extracts the substring that matched the  entire  pattern,  whereas
2112         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2113         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2114         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2115         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2116         The yield of the function is the length of the  string,  not  including         The  yield  of  the function is the length of the string, not including
2117         the terminating zero, or one of         the terminating zero, or one of these error codes:
2118    
2119           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2120    
2121         The  buffer  was too small for pcre_copy_substring(), or the attempt to         The buffer was too small for pcre_copy_substring(), or the  attempt  to
2122         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2123    
2124           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2125    
2126         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2127    
2128         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2129         strings  and  builds  a list of pointers to them. All this is done in a         strings and builds a list of pointers to them. All this is  done  in  a
2130         single block of memory which is obtained via pcre_malloc.  The  address         single block of memory that is obtained via pcre_malloc. The address of
2131         of the memory block is returned via listptr, which is also the start of         the memory block is returned via listptr, which is also  the  start  of
2132         the list of string pointers. The end of the list is marked  by  a  NULL         the  list  of  string pointers. The end of the list is marked by a NULL
2133         pointer. The yield of the function is zero if all went well, or         pointer. The yield of the function is zero if all  went  well,  or  the
2134           error code
2135    
2136           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2137    
# Line 1313  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2144  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2144         string  by inspecting the appropriate offset in ovector, which is nega-         string  by inspecting the appropriate offset in ovector, which is nega-
2145         tive for unset substrings.         tive for unset substrings.
2146    
2147         The    two    convenience    functions    pcre_free_substring()     and         The two convenience functions pcre_free_substring() and  pcre_free_sub-
2148         pcre_free_substring_list() can be used to free the memory returned by a         string_list()  can  be  used  to free the memory returned by a previous
2149         previous call  of  pcre_get_substring()  or  pcre_get_substring_list(),         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2150         respectively. They do nothing more than call the function pointed to by         tively.  They  do  nothing  more  than  call the function pointed to by
2151         pcre_free, which of course could be called directly from a  C  program.         pcre_free, which of course could be called directly from a  C  program.
2152         However,  PCRE is used in some situations where it is linked via a spe-         However,  PCRE is used in some situations where it is linked via a spe-
2153         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  that  cannot   use
2154         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free  directly;  it is for these cases that the functions are pro-
2155         vided.         vided.
2156    
2157    
2158  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2159    
2160           int pcre_get_stringnumber(const pcre *code,
2161                const char *name);
2162    
2163         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
2164              const char *subject, int *ovector,              const char *subject, int *ovector,
2165              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2166              char *buffer, int buffersize);              char *buffer, int buffersize);
2167    
        int pcre_get_stringnumber(const pcre *code,  
             const char *name);  
   
2168         int pcre_get_named_substring(const pcre *code,         int pcre_get_named_substring(const pcre *code,
2169              const char *subject, int *ovector,              const char *subject, int *ovector,
2170              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2171              const char **stringptr);              const char **stringptr);
2172    
2173         To extract a substring by name, you first have to find associated  num-         To extract a substring by name, you first have to find associated  num-
2174         ber.  This  can  be  done by calling pcre_get_stringnumber(). The first         ber.  For example, for this pattern
2175         argument is the compiled pattern, and the second is the name. For exam-  
2176         ple, for this pattern           (a+)b(?<xxx>\d+)...
2177    
2178           ab(?<xxx>\d+)...         the number of the subpattern called "xxx" is 2. If the name is known to
2179           be unique (PCRE_DUPNAMES was not set), you can find the number from the
2180         the  number  of the subpattern called "xxx" is 1. Given the number, you         name by calling pcre_get_stringnumber(). The first argument is the com-
2181         can then extract the substring directly, or use one  of  the  functions         piled pattern, and the second is the name. The yield of the function is
2182         described  in the previous section. For convenience, there are also two         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
2183         functions that do the whole job.         subpattern of that name.
2184    
2185           Given the number, you can extract the substring directly, or use one of
2186           the functions described in the previous section. For convenience, there
2187           are also two functions that do the whole job.
2188    
2189         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most   of   the   arguments    of    pcre_copy_named_substring()    and
2190         pcre_get_named_substring() are the same as those for the functions that         pcre_get_named_substring()  are  the  same  as  those for the similarly
2191         extract by number, and so are not re-described here. There are just two         named functions that extract by number. As these are described  in  the
2192         differences.         previous  section,  they  are not re-described here. There are just two
2193           differences:
2194    
2195         First,  instead  of a substring number, a substring name is given. Sec-         First, instead of a substring number, a substring name is  given.  Sec-
2196         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2197         to  the compiled pattern. This is needed in order to gain access to the         to the compiled pattern. This is needed in order to gain access to  the
2198         name-to-number translation table.         name-to-number translation table.
2199    
2200         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2201         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2202         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2203           behaviour may not be what you want (see the next section).
2204    
2205    
2206    DUPLICATE SUBPATTERN NAMES
2207    
2208           int pcre_get_stringtable_entries(const pcre *code,
2209                const char *name, char **first, char **last);
2210    
2211           When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
2212           subpatterns  are  not  required  to  be unique. Normally, patterns with
2213           duplicate names are such that in any one match, only one of  the  named
2214           subpatterns  participates. An example is shown in the pcrepattern docu-
2215           mentation. When duplicates are present, pcre_copy_named_substring() and
2216           pcre_get_named_substring()  return the first substring corresponding to
2217           the given name that is set.  If  none  are  set,  an  empty  string  is
2218           returned.  The pcre_get_stringnumber() function returns one of the num-
2219           bers that are associated with the name, but it is not defined which  it
2220           is.
2221    
2222           If  you want to get full details of all captured substrings for a given
2223           name, you must use  the  pcre_get_stringtable_entries()  function.  The
2224           first argument is the compiled pattern, and the second is the name. The
2225           third and fourth are pointers to variables which  are  updated  by  the
2226           function. After it has run, they point to the first and last entries in
2227           the name-to-number table  for  the  given  name.  The  function  itself
2228           returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
2229           there are none. The format of the table is described above in the  sec-
2230           tion  entitled  Information  about  a  pattern.  Given all the relevant
2231           entries for the name, you can extract each of their numbers, and  hence
2232           the captured data, if any.
2233    
2234    
2235    FINDING ALL POSSIBLE MATCHES
2236    
2237           The  traditional  matching  function  uses a similar algorithm to Perl,
2238           which stops when it finds the first match, starting at a given point in
2239           the  subject.  If you want to find all possible matches, or the longest
2240           possible match, consider using the alternative matching  function  (see
2241           below)  instead.  If you cannot use the alternative function, but still
2242           need to find all possible matches, you can kludge it up by  making  use
2243           of the callout facility, which is described in the pcrecallout documen-
2244           tation.
2245    
2246  Last updated: 09 December 2003         What you have to do is to insert a callout right at the end of the pat-
2247  Copyright (c) 1997-2003 University of Cambridge.         tern.   When your callout function is called, extract and save the cur-
2248  -----------------------------------------------------------------------------         rent matched substring. Then return  1,  which  forces  pcre_exec()  to
2249           backtrack  and  try other alternatives. Ultimately, when it runs out of
2250           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2251    
 PCRE(3)                                                                PCRE(3)  
2252    
2253    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
2254    
2255           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
2256                const char *subject, int length, int startoffset,
2257                int options, int *ovector, int ovecsize,
2258                int *workspace, int wscount);
2259    
2260           The function pcre_dfa_exec()  is  called  to  match  a  subject  string
2261           against  a  compiled pattern, using a matching algorithm that scans the
2262           subject string just once, and does not backtrack.  This  has  different
2263           characteristics  to  the  normal  algorithm, and is not compatible with
2264           Perl. Some of the features of PCRE patterns are not  supported.  Never-
2265           theless,  there are times when this kind of matching can be useful. For
2266           a discussion of the two matching algorithms, see the pcrematching docu-
2267           mentation.
2268    
2269           The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2270           pcre_exec(), plus two extras. The ovector argument is used in a differ-
2271           ent  way,  and  this is described below. The other common arguments are
2272           used in the same way as for pcre_exec(), so their  description  is  not
2273           repeated here.
2274    
2275           The  two  additional  arguments provide workspace for the function. The
2276           workspace vector should contain at least 20 elements. It  is  used  for
2277           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2278           workspace will be needed for patterns and subjects where  there  are  a
2279           lot of potential matches.
2280    
2281           Here is an example of a simple call to pcre_dfa_exec():
2282    
2283             int rc;
2284             int ovector[10];
2285             int wspace[20];
2286             rc = pcre_dfa_exec(
2287               re,             /* result of pcre_compile() */
2288               NULL,           /* we didn't study the pattern */
2289               "some string",  /* the subject string */
2290               11,             /* the length of the subject string */
2291               0,              /* start at offset 0 in the subject */
2292               0,              /* default options */
2293               ovector,        /* vector of integers for substring information */
2294               10,             /* number of elements (NOT size in bytes) */
2295               wspace,         /* working space vector */
2296               20);            /* number of elements (NOT size in bytes) */
2297    
2298       Option bits for pcre_dfa_exec()
2299    
2300           The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2301           zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2302           LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,
2303           PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
2304           three of these are the same as for pcre_exec(), so their description is
2305           not repeated here.
2306    
2307             PCRE_PARTIAL
2308    
2309           This has the same general effect as it does for  pcre_exec(),  but  the
2310           details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
2311           pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
2312           PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
2313           been no complete matches, but there is still at least one matching pos-
2314           sibility.  The portion of the string that provided the partial match is
2315           set as the first matching string.
2316    
2317             PCRE_DFA_SHORTEST
2318    
2319           Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2320           stop as soon as it has found one match. Because of the way the alterna-
2321           tive algorithm works, this is necessarily the shortest  possible  match
2322           at the first possible matching point in the subject string.
2323    
2324             PCRE_DFA_RESTART
2325    
2326           When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
2327           returns a partial match, it is possible to call it  again,  with  addi-
2328           tional  subject  characters,  and have it continue with the same match.
2329           The PCRE_DFA_RESTART option requests this action; when it is  set,  the
2330           workspace  and wscount options must reference the same vector as before
2331           because data about the match so far is left in  them  after  a  partial
2332           match.  There  is  more  discussion of this facility in the pcrepartial
2333           documentation.
2334    
2335       Successful returns from pcre_dfa_exec()
2336    
2337           When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
2338           string in the subject. Note, however, that all the matches from one run
2339           of the function start at the same point in  the  subject.  The  shorter
2340           matches  are all initial substrings of the longer matches. For example,
2341           if the pattern
2342    
2343             <.*>
2344    
2345           is matched against the string
2346    
2347             This is <something> <something else> <something further> no more
2348    
2349           the three matched strings are
2350    
2351             <something>
2352             <something> <something else>
2353             <something> <something else> <something further>
2354    
2355           On success, the yield of the function is a number  greater  than  zero,
2356           which  is  the  number of matched substrings. The substrings themselves
2357           are returned in ovector. Each string uses two elements;  the  first  is
2358           the  offset  to  the start, and the second is the offset to the end. In
2359           fact, all the strings have the same start  offset.  (Space  could  have
2360           been  saved by giving this only once, but it was decided to retain some
2361           compatibility with the way pcre_exec() returns data,  even  though  the
2362           meaning of the strings is different.)
2363    
2364           The strings are returned in reverse order of length; that is, the long-
2365           est matching string is given first. If there were too many  matches  to
2366           fit  into ovector, the yield of the function is zero, and the vector is
2367           filled with the longest matches.
2368    
2369       Error returns from pcre_dfa_exec()
2370    
2371           The pcre_dfa_exec() function returns a negative number when  it  fails.
2372           Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2373           described above.  There are in addition the following errors  that  are
2374           specific to pcre_dfa_exec():
2375    
2376             PCRE_ERROR_DFA_UITEM      (-16)
2377    
2378           This  return is given if pcre_dfa_exec() encounters an item in the pat-
2379           tern that it does not support, for instance, the use of \C  or  a  back
2380           reference.
2381    
2382             PCRE_ERROR_DFA_UCOND      (-17)
2383    
2384           This  return  is  given  if pcre_dfa_exec() encounters a condition item
2385           that uses a back reference for the condition, or a test  for  recursion
2386           in a specific group. These are not supported.
2387    
2388             PCRE_ERROR_DFA_UMLIMIT    (-18)
2389    
2390           This  return  is given if pcre_dfa_exec() is called with an extra block
2391           that contains a setting of the match_limit field. This is not supported
2392           (it is meaningless).
2393    
2394             PCRE_ERROR_DFA_WSSIZE     (-19)
2395    
2396           This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2397           workspace vector.
2398    
2399             PCRE_ERROR_DFA_RECURSE    (-20)
2400    
2401           When a recursive subpattern is processed, the matching  function  calls
2402           itself  recursively,  using  private vectors for ovector and workspace.
2403           This error is given if the output vector  is  not  large  enough.  This
2404           should be extremely rare, as a vector of size 1000 is used.
2405    
2406    
2407    SEE ALSO
2408    
2409           pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2410           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).
2411    
2412    
2413    AUTHOR
2414    
2415           Philip Hazel
2416           University Computing Service
2417           Cambridge CB2 3QH, England.
2418    
2419    
2420    REVISION
2421    
2422           Last updated: 30 July 2007
2423           Copyright (c) 1997-2007 University of Cambridge.
2424    ------------------------------------------------------------------------------
2425    
2426    
2427    PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2428    
2429    
2430  NAME  NAME
2431         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2432    
2433    
2434  PCRE CALLOUTS  PCRE CALLOUTS
2435    
2436         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
# Line 1394  PCRE CALLOUTS Line 2449  PCRE CALLOUTS
2449    
2450           (?C1)abc(?C2)def           (?C1)abc(?C2)def
2451    
2452         During matching, when PCRE reaches a callout point (and pcre_callout is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
2453         set), the external function is called. Its only argument is  a  pointer         called, PCRE automatically  inserts  callouts,  all  with  number  255,
2454         to a pcre_callout block. This contains the following variables:         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
2455           used with the pattern
2456    
2457             A(\d{2}|--)
2458    
2459           it is processed as if it were
2460    
2461           (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)
2462    
2463           Notice that there is a callout before and after  each  parenthesis  and
2464           alternation  bar.  Automatic  callouts  can  be  used  for tracking the
2465           progress of pattern matching. The pcretest command has an  option  that
2466           sets  automatic callouts; when it is used, the output indicates how the
2467           pattern is matched. This is useful information when you are  trying  to
2468           optimize the performance of a particular pattern.
2469    
2470    
2471    MISSING CALLOUTS
2472    
2473           You  should  be  aware  that,  because of optimizations in the way PCRE
2474           matches patterns, callouts sometimes do not happen. For example, if the
2475           pattern is
2476    
2477             ab(?C4)cd
2478    
2479           PCRE knows that any matching string must contain the letter "d". If the
2480           subject string is "abyz", the lack of "d" means that  matching  doesn't
2481           ever  start,  and  the  callout is never reached. However, with "abyd",
2482           though the result is still no match, the callout is obeyed.
2483    
2484    
2485    THE CALLOUT INTERFACE
2486    
2487           During matching, when PCRE reaches a callout point, the external  func-
2488           tion  defined by pcre_callout is called (if it is set). This applies to
2489           both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The
2490           only  argument  to  the callout function is a pointer to a pcre_callout
2491           block. This structure contains the following fields:
2492    
2493           int          version;           int          version;
2494           int          callout_number;           int          callout_number;
# Line 1408  PCRE CALLOUTS Line 2500  PCRE CALLOUTS
2500           int          capture_top;           int          capture_top;
2501           int          capture_last;           int          capture_last;
2502           void        *callout_data;           void        *callout_data;
2503             int          pattern_position;
2504             int          next_item_length;
2505    
2506         The  version  field  is an integer containing the version number of the         The version field is an integer containing the version  number  of  the
2507         block format. The current version  is  zero.  The  version  number  may         block  format. The initial version was 0; the current version is 1. The
2508         change  in  future if additional fields are added, but the intention is         version number will change again in future  if  additional  fields  are
2509         never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2510    
2511         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
2512         piled into the pattern (that is, the number after ?C).         piled  into  the pattern (that is, the number after ?C for manual call-
2513           outs, and 255 for automatically generated callouts).
2514    
2515         The  offset_vector field is a pointer to the vector of offsets that was         The offset_vector field is a pointer to the vector of offsets that  was
2516         passed by the caller to pcre_exec(). The contents can be  inspected  in         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2517         order  to extract substrings that have been matched so far, in the same         pcre_exec() is used, the contents can be inspected in order to  extract
2518         way as for extracting substrings after a match has completed.         substrings  that  have  been  matched  so  far,  in the same way as for
2519           extracting substrings after a match has completed. For  pcre_dfa_exec()
2520           this field is not useful.
2521    
2522         The subject and subject_length fields contain copies  the  values  that         The subject and subject_length fields contain copies of the values that
2523         were passed to pcre_exec().         were passed to pcre_exec().
2524    
2525         The  start_match  field contains the offset within the subject at which         The start_match field normally contains the offset within  the  subject
2526         the current match attempt started. If the pattern is not anchored,  the         at  which  the  current  match  attempt started. However, if the escape
2527         callout  function  may  be  called several times for different starting         sequence \K has been encountered, this value is changed to reflect  the
2528         points.         modified  starting  point.  If the pattern is not anchored, the callout
2529           function may be called several times from the same point in the pattern
2530           for different starting points in the subject.
2531    
2532         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2533         the current match pointer.         the current match pointer.
2534    
2535         The  capture_top field contains one more than the number of the highest         When the pcre_exec() function is used, the capture_top  field  contains
2536         numbered  captured  substring  so  far.  If  no  substrings  have  been         one  more than the number of the highest numbered captured substring so
2537         captured, the value of capture_top is one.         far. If no substrings have been captured, the value of  capture_top  is
2538           one.  This  is always the case when pcre_dfa_exec() is used, because it
2539         The  capture_last  field  contains the number of the most recently cap-         does not support captured substrings.
2540         tured substring.  
2541           The capture_last field contains the number of the  most  recently  cap-
2542           tured  substring. If no substrings have been captured, its value is -1.
2543           This is always the case when pcre_dfa_exec() is used.
2544    
2545         The callout_data field contains a value that is passed  to  pcre_exec()         The callout_data field contains a value that is passed  to  pcre_exec()
2546         by  the  caller specifically so that it can be passed back in callouts.         or  pcre_dfa_exec() specifically so that it can be passed back in call-
2547         It is passed in the pcre_callout field of the  pcre_extra  data  struc-         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
2548         ture.  If  no  such  data  was  passed,  the value of callout_data in a         structure.  If  no such data was passed, the value of callout_data in a
2549         pcre_callout block is NULL. There is a description  of  the  pcre_extra         pcre_callout block is NULL. There is a description  of  the  pcre_extra
2550         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2551    
2552           The  pattern_position field is present from version 1 of the pcre_call-
2553           out structure. It contains the offset to the next item to be matched in
2554           the pattern string.
2555    
2556           The  next_item_length field is present from version 1 of the pcre_call-
2557           out structure. It contains the length of the next item to be matched in
2558           the  pattern  string. When the callout immediately precedes an alterna-
2559           tion bar, a closing parenthesis, or the end of the pattern, the  length
2560           is  zero.  When the callout precedes an opening parenthesis, the length
2561           is that of the entire subpattern.
2562    
2563           The pattern_position and next_item_length fields are intended  to  help
2564           in  distinguishing between different automatic callouts, which all have
2565           the same callout number. However, they are set for all callouts.
2566    
2567    
2568  RETURN VALUES  RETURN VALUES
2569    
2570         The callout function returns an integer. If the value is zero, matching         The external callout function returns an integer to PCRE. If the  value
2571         proceeds as normal. If the value is greater than zero,  matching  fails         is  zero,  matching  proceeds  as  normal. If the value is greater than
2572         at the current point, but backtracking to test other possibilities goes         zero, matching fails at the current point, but  the  testing  of  other
2573         ahead, just as if a lookahead assertion had failed.  If  the  value  is         matching possibilities goes ahead, just as if a lookahead assertion had
2574         less  than  zero,  the  match is abandoned, and pcre_exec() returns the         failed. If the value is less than zero, the  match  is  abandoned,  and
2575         value.         pcre_exec() (or pcre_dfa_exec()) returns the negative value.
2576    
2577         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
2578         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2579         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
2580         reserved  for  use  by callout functions; it will never be used by PCRE         reserved for use by callout functions; it will never be  used  by  PCRE
2581         itself.         itself.
2582    
 Last updated: 21 January 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
2583    
2584  PCRE(3)                                                                PCRE(3)  AUTHOR
2585    
2586           Philip Hazel
2587           University Computing Service
2588           Cambridge CB2 3QH, England.
2589    
2590    
2591    REVISION
2592    
2593           Last updated: 29 May 2007
2594           Copyright (c) 1997-2007 University of Cambridge.
2595    ------------------------------------------------------------------------------
2596    
2597    
2598    PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2599    
2600    
2601  NAME  NAME
2602         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2603    
 DIFFERENCES FROM PERL  
2604    
2605         This  document describes the differences in the ways that PCRE and Perl  DIFFERENCES BETWEEN PCRE AND PERL
        handle regular expressions. The differences  described  here  are  with  
        respect to Perl 5.8.  
2606    
2607         1.  PCRE does not have full UTF-8 support. Details of what it does have         This  document describes the differences in the ways that PCRE and Perl
2608         are given in the section on UTF-8 support in the main pcre page.         handle regular expressions. The differences described here  are  mainly
2609           with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2610           some features that are expected to be in the forthcoming Perl 5.10.
2611    
2612           1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2613           of  what  it does have are given in the section on UTF-8 support in the
2614           main pcre page.
2615    
2616         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
2617         permits  them,  but they do not mean what you might think. For example,         permits  them,  but they do not mean what you might think. For example,
# Line 1498  DIFFERENCES FROM PERL Line 2627  DIFFERENCES FROM PERL
2627    
2628         4. Though binary zero characters are supported in the  subject  string,         4. Though binary zero characters are supported in the  subject  string,
2629         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
2630         mal C string, terminated by zero. The escape sequence "\0" can be  used         mal C string, terminated by zero. The escape sequence \0 can be used in
2631         in the pattern to represent a binary zero.         the pattern to represent a binary zero.
2632    
2633         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
2634         \U, \P, \p, \N, and \X. In fact these are implemented by Perl's general         \U, and \N. In fact these are implemented by Perl's general string-han-
2635         string-handling and are not part of its pattern matching engine. If any         dling  and are not part of its pattern matching engine. If any of these
2636         of these are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
2637    
2638           6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
2639           is  built  with Unicode character property support. The properties that
2640           can be tested with \p and \P are limited to the general category  prop-
2641           erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2642           derived properties Any and L&.
2643    
2644         6. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2645         ters  in  between  are  treated as literals. This is slightly different         ters  in  between  are  treated as literals. This is slightly different
2646         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
2647         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
# Line 1522  DIFFERENCES FROM PERL Line 2657  DIFFERENCES FROM PERL
2657         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
2658         classes.         classes.
2659    
2660         7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2661         constructions. However, there is some experimental support  for  recur-         constructions. However, there is support for recursive  patterns.  This
2662         sive  patterns  using the non-Perl items (?R), (?number) and (?P>name).         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE
2663         Also, the PCRE "callout" feature allows  an  external  function  to  be         "callout" feature allows an external function to be called during  pat-
2664         called during pattern matching.         tern matching. See the pcrecallout documentation for details.
2665    
2666           9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2667           always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2668           unlike Perl.
2669    
2670         8.  There  are some differences that are concerned with the settings of         10.  There are some differences that are concerned with the settings of
2671         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
2672         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2673         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2674    
2675         9. PCRE  provides  some  extensions  to  the  Perl  regular  expression         11. PCRE provides some extensions to the Perl regular expression facil-
2676         facilities:         ities.   Perl  5.10  will  include new features that are not in earlier
2677           versions, some of which (such as named parentheses) have been  in  PCRE
2678           for some time. This list is with respect to Perl 5.10:
2679    
2680         (a)  Although  lookbehind  assertions  must match fixed length strings,         (a)  Although  lookbehind  assertions  must match fixed length strings,
2681         each alternative branch of a lookbehind assertion can match a different         each alternative branch of a lookbehind assertion can match a different
# Line 1544  DIFFERENCES FROM PERL Line 2685  DIFFERENCES FROM PERL
2685         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2686    
2687         (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-
2688         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2689           ignored.  (Perl can be made to issue a warning.)
2690    
2691         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2692         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-
2693         lowed by a question mark they are.         lowed by a question mark they are.
2694    
2695         (e)  PCRE_ANCHORED  can  be used to force a pattern to be tried only at         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
2696         the first matching position in the subject string.         tried only at the first matching position in the subject string.
2697    
2698         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and  PCRE_NO_AUTO_CAP-         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
2699         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2700    
2701         (g)  The (?R), (?number), and (?P>name) constructs allows for recursive         (g) The callout facility is PCRE-specific.
        pattern matching (Perl can do  this  using  the  (?p{code})  construct,  
        which PCRE cannot support.)  
2702    
2703         (h)  PCRE supports named capturing substrings, using the Python syntax.         (h) The partial matching facility is PCRE-specific.
2704    
2705         (i) PCRE supports the possessive quantifier  "++"  syntax,  taken  from         (i) Patterns compiled by PCRE can be saved and re-used at a later time,
2706         Sun's Java package.         even on different hosts that have the other endianness.
2707    
2708         (j) The (R) condition, for testing recursion, is a PCRE extension.         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2709           different way and is not Perl-compatible.
2710    
        (k) The callout facility is PCRE-specific.  
2711    
2712  Last updated: 09 December 2003  AUTHOR
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
2713    
2714  PCRE(3)                                                                PCRE(3)         Philip Hazel
2715           University Computing Service
2716           Cambridge CB2 3QH, England.
2717    
2718    
2719    REVISION
2720    
2721           Last updated: 13 June 2007
2722           Copyright (c) 1997-2007 University of Cambridge.
2723    ------------------------------------------------------------------------------
2724    
2725    
2726    PCREPATTERN(3)                                                  PCREPATTERN(3)
2727    
2728    
2729  NAME  NAME
2730         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2731    
2732    
2733  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2734    
2735         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax  and semantics of the regular expressions supported by PCRE
2736         are described below. Regular expressions are also described in the Perl         are described below. Regular expressions are also described in the Perl
2737         documentation  and in a number of other books, some of which have copi-         documentation  and  in  a  number  of books, some of which have copious
2738         ous examples. Jeffrey Friedl's "Mastering  Regular  Expressions",  pub-         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published
2739         lished  by  O'Reilly, covers them in great detail. The description here         by  O'Reilly, covers regular expressions in great detail. This descrip-
2740         is intended as reference documentation.         tion of PCRE's regular expressions is intended as reference material.
2741    
2742         The basic operation of PCRE is on strings of bytes. However,  there  is         The original operation of PCRE was on strings of  one-byte  characters.
2743         also  support for UTF-8 character strings. To use this support you must         However,  there is now also support for UTF-8 character strings. To use
2744         build PCRE to include UTF-8 support, and then call pcre_compile()  with         this, you must build PCRE to  include  UTF-8  support,  and  then  call
2745         the  PCRE_UTF8  option.  How  this affects the pattern matching is men-         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern
2746         tioned in several places below. There is also a summary of  UTF-8  fea-         matching is mentioned in several places below. There is also a  summary
2747         tures in the section on UTF-8 support in the main pcre page.         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre
2748           page.
2749    
2750           The remainder of this document discusses the  patterns  that  are  sup-
2751           ported  by  PCRE when its main matching function, pcre_exec(), is used.
2752           From  release  6.0,   PCRE   offers   a   second   matching   function,
2753           pcre_dfa_exec(),  which matches using a different algorithm that is not
2754           Perl-compatible. Some of the features discussed below are not available
2755           when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
2756           alternative function, and how it differs from the normal function,  are
2757           discussed in the pcrematching page.
2758    
2759    
2760    CHARACTERS AND METACHARACTERS
2761    
2762         A  regular  expression  is  a pattern that is matched against a subject         A  regular  expression  is  a pattern that is matched against a subject
2763         string from left to right. Most characters stand for  themselves  in  a         string from left to right. Most characters stand for  themselves  in  a
# Line 1603  PCRE REGULAR EXPRESSION DETAILS Line 2766  PCRE REGULAR EXPRESSION DETAILS
2766    
2767           The quick brown fox           The quick brown fox
2768    
2769         matches a portion of a subject string that is identical to itself.  The         matches a portion of a subject string that is identical to itself. When
2770         power of regular expressions comes from the ability to include alterna-         caseless  matching is specified (the PCRE_CASELESS option), letters are
2771         tives and repetitions in the pattern. These are encoded in the  pattern         matched independently of case. In UTF-8 mode, PCRE  always  understands
2772         by  the  use  of meta-characters, which do not stand for themselves but         the  concept  of case for characters whose values are less than 128, so
2773         instead are interpreted in some special way.         caseless matching is always possible. For characters with  higher  val-
2774           ues,  the concept of case is supported if PCRE is compiled with Unicode
2775         There are two different sets of meta-characters: those that are  recog-         property support, but not otherwise.   If  you  want  to  use  caseless
2776         nized  anywhere in the pattern except within square brackets, and those         matching  for  characters  128  and above, you must ensure that PCRE is
2777         that are recognized in square brackets. Outside  square  brackets,  the         compiled with Unicode property support as well as with UTF-8 support.
2778         meta-characters are as follows:  
2779           The power of regular expressions comes  from  the  ability  to  include
2780           alternatives  and  repetitions in the pattern. These are encoded in the
2781           pattern by the use of metacharacters, which do not stand for themselves
2782           but instead are interpreted in some special way.
2783    
2784           There  are  two different sets of metacharacters: those that are recog-
2785           nized anywhere in the pattern except within square brackets, and  those
2786           that  are  recognized  within square brackets. Outside square brackets,
2787           the metacharacters are as follows:
2788    
2789           \      general escape character with several uses           \      general escape character with several uses
2790           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 1630  PCRE REGULAR EXPRESSION DETAILS Line 2802  PCRE REGULAR EXPRESSION DETAILS
2802                  also "possessive quantifier"                  also "possessive quantifier"
2803           {      start min/max quantifier           {      start min/max quantifier
2804    
2805         Part  of  a  pattern  that is in square brackets is called a "character         Part of a pattern that is in square brackets  is  called  a  "character
2806         class". In a character class the only meta-characters are:         class". In a character class the only metacharacters are:
2807    
2808           \      general escape character           \      general escape character
2809           ^      negate the class, but only if the first character           ^      negate the class, but only if the first character
# Line 1640  PCRE REGULAR EXPRESSION DETAILS Line 2812  PCRE REGULAR EXPRESSION DETAILS
2812                    syntax)                    syntax)
2813           ]      terminates the character class           ]      terminates the character class
2814    
2815         The following sections describe the use of each of the meta-characters.         The  following sections describe the use of each of the metacharacters.
2816    
2817    
2818  BACKSLASH  BACKSLASH
2819    
2820         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2821         a non-alphameric character, it takes  away  any  special  meaning  that         a  non-alphanumeric  character,  it takes away any special meaning that
2822         character  may  have.  This  use  of  backslash  as an escape character         character may have. This  use  of  backslash  as  an  escape  character
2823         applies both inside and outside character classes.         applies both inside and outside character classes.
2824    
2825         For example, if you want to match a * character, you write  \*  in  the         For  example,  if  you want to match a * character, you write \* in the
2826         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
2827         character would otherwise be interpreted as a meta-character, so it  is         character  would  otherwise be interpreted as a metacharacter, so it is
2828         always  safe to precede a non-alphameric with backslash to specify that         always safe to precede a non-alphanumeric  with  backslash  to  specify
2829         it stands for itself. In particular, if you want to match a  backslash,         that  it stands for itself. In particular, if you want to match a back-
2830         you write \\.         slash, you write \\.
2831    
2832         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
2833         the pattern (other than in a character class) and characters between  a         the  pattern (other than in a character class) and characters between a
2834         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
2835         An escaping backslash can be used to include a whitespace or #  charac-         ing  backslash  can  be  used to include a whitespace or # character as
2836         ter as part of the pattern.         part of the pattern.
2837    
2838         If  you  want  to remove the special meaning from a sequence of charac-         If you want to remove the special meaning from a  sequence  of  charac-
2839         ters, you can do so by putting them between \Q and \E. This is  differ-         ters,  you can do so by putting them between \Q and \E. This is differ-
2840         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
2841         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
2842         tion. Note the following examples:         tion. Note the following examples:
2843    
2844           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 1676  BACKSLASH Line 2848  BACKSLASH
2848           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
2849           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
2850    
2851         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
2852         classes.         classes.
2853    
2854       Non-printing characters
2855    
2856         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
2857         acters  in patterns in a visible manner. There is no restriction on the         acters in patterns in a visible manner. There is no restriction on  the
2858         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
2859         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
2860         editing, it is usually easier  to  use  one  of  the  following  escape         editing,  it  is  usually  easier  to  use  one of the following escape
2861         sequences than the binary character it represents:         sequences than the binary character it represents:
2862    
2863           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 1695  BACKSLASH Line 2869  BACKSLASH
2869           \t        tab (hex 09)           \t        tab (hex 09)
2870           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
2871           \xhh      character with hex code hh           \xhh      character with hex code hh
2872           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh..
2873    
2874         The  precise  effect of \cx is as follows: if x is a lower case letter,         The precise effect of \cx is as follows: if x is a lower  case  letter,
2875         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it  is converted to upper case. Then bit 6 of the character (hex 40) is
2876         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;
2877         becomes hex 7B.         becomes hex 7B.
2878    
2879         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
2880         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-         in upper or lower case). Any number of hexadecimal  digits  may  appear
2881         its may appear between \x{ and }, but the value of the  character  code         between  \x{  and  },  but the value of the character code must be less
2882         must  be  less  than  2**31  (that is, the maximum hexadecimal value is         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,
2883         7FFFFFFF). If characters other than hexadecimal digits  appear  between         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than
2884         \x{  and }, or if there is no terminating }, this form of escape is not         hexadecimal digits appear between \x{ and }, or if there is  no  termi-
2885         recognized. Instead, the initial \x will be interpreted as a basic hex-         nating  }, this form of escape is not recognized.  Instead, the initial
2886         adecimal escape, with no following digits, giving a byte whose value is         \x will be interpreted as a basic hexadecimal escape, with no following
2887         zero.         digits, giving a character whose value is zero.
2888    
2889         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
2890         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference         two syntaxes for \x. There is no difference in the way  they  are  han-
2891         in the way they are handled. For example, \xdc is exactly the  same  as         dled. For example, \xdc is exactly the same as \x{dc}.
2892         \x{dc}.  
2893           After  \0  up  to two further octal digits are read. If there are fewer
2894         After  \0  up  to  two further octal digits are read. In both cases, if         than two digits, just  those  that  are  present  are  used.  Thus  the
2895         there are fewer than two digits, just those that are present are  used.         sequence \0\x\07 specifies two binary zeros followed by a BEL character
2896         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL         (code value 7). Make sure you supply two digits after the initial  zero
2897         character (code value 7). Make sure you supply  two  digits  after  the         if the pattern character that follows is itself an octal digit.
        initial zero if the character that follows is itself an octal digit.  
2898    
2899         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-
2900         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
# Line 1733  BACKSLASH Line 2906  BACKSLASH
2906    
2907         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
2908         and there have not been that many capturing subpatterns, PCRE  re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
2909         up  to three octal digits following the backslash, and generates a sin-         up to three octal digits following the backslash, and uses them to gen-
2910         gle byte from the least significant 8 bits of the value. Any subsequent         erate a data character. Any subsequent digits stand for themselves.  In
2911         digits stand for themselves.  For example:         non-UTF-8  mode,  the  value  of a character specified in octal must be
2912           less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
2913           example:
2914    
2915           \040   is another way of writing a space           \040   is another way of writing a space
2916           \40    is the same, provided there are fewer than 40           \40    is the same, provided there are fewer than 40
# Line 1755  BACKSLASH Line 2930  BACKSLASH
2930         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
2931         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
2932    
2933         All the sequences that define a single byte value  or  a  single  UTF-8         All the sequences that define a single character value can be used both
2934         character (in UTF-8 mode) can be used both inside and outside character         inside  and  outside character classes. In addition, inside a character
2935         classes. In addition, inside a character  class,  the  sequence  \b  is         class, the sequence \b is interpreted as the backspace  character  (hex
2936         interpreted  as  the  backspace character (hex 08). Outside a character         08),  and the sequences \R and \X are interpreted as the characters "R"
2937         class it has a different meaning (see below).         and "X", respectively. Outside a character class, these sequences  have
2938           different meanings (see below).
2939    
2940       Absolute and relative back references
2941    
2942           The  sequence  \g followed by a positive or negative number, optionally
2943           enclosed in braces, is an absolute or relative back reference. A  named
2944           back  reference can be coded as \g{name}. Back references are discussed
2945           later, following the discussion of parenthesized subpatterns.
2946    
2947         The third use of backslash is for specifying generic character types:     Generic character types
2948    
2949           Another use of backslash is for specifying generic character types. The
2950           following are always recognized:
2951    
2952           \d     any decimal digit           \d     any decimal digit
2953           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
2954             \h     any horizontal whitespace character
2955             \H     any character that is not a horizontal whitespace character
2956           \s     any whitespace character           \s     any whitespace character
2957           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
2958             \v     any vertical whitespace character
2959             \V     any character that is not a vertical whitespace character
2960           \w     any "word" character           \w     any "word" character
2961           \W     any "non-word" character           \W     any "non-word" character
2962    
2963         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
2964         into  two disjoint sets. Any given character matches one, and only one,         into two disjoint sets. Any given character matches one, and only  one,
2965         of each pair.         of each pair.
2966    
        In UTF-8 mode, characters with values greater than 255 never match  \d,  
        \s, or \w, and always match \D, \S, and \W.  
   
        For  compatibility  with Perl, \s does not match the VT character (code  
        11).  This makes it different from the the POSIX "space" class. The  \s  
        characters are HT (9), LF (10), FF (12), CR (13), and space (32).  
   
        A  "word" character is any letter or digit or the underscore character,  
        that is, any character which can be part of a Perl "word". The  defini-  
        tion  of  letters  and digits is controlled by PCRE's character tables,  
        and may vary if locale- specific matching is taking place (see  "Locale  
        support"  in  the  pcreapi  page).  For  example,  in the "fr" (French)  
        locale, some character codes greater than 128  are  used  for  accented  
        letters, and these are matched by \w.  
   
2967         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
2968         acter classes. They each match one character of the  appropriate  type.         acter classes. They each match one character of the  appropriate  type.
2969         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
2970         of them fail, since there is no character to match.         of them fail, since there is no character to match.
2971    
2972         The fourth use of backslash is for certain simple assertions. An asser-         For compatibility with Perl, \s does not match the VT  character  (code
2973         tion  specifies a condition that has to be met at a particular point in         11).   This makes it different from the the POSIX "space" class. The \s
2974         a match, without consuming any characters from the subject string.  The         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
2975         use  of subpatterns for more complicated assertions is described below.         "use locale;" is included in a Perl script, \s may match the VT charac-
2976         The backslashed assertions are         ter. In PCRE, it never does.
2977    
2978           In UTF-8 mode, characters with values greater than 128 never match  \d,
2979           \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
2980           code character property support is available.  These  sequences  retain
2981           their original meanings from before UTF-8 support was available, mainly
2982           for efficiency reasons.
2983    
2984           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
2985           the  other  sequences, these do match certain high-valued codepoints in
2986           UTF-8 mode.  The horizontal space characters are:
2987    
2988             U+0009     Horizontal tab
2989             U+0020     Space
2990             U+00A0     Non-break space
2991             U+1680     Ogham space mark
2992             U+180E     Mongolian vowel separator
2993             U+2000     En quad
2994             U+2001     Em quad
2995             U+2002     En space
2996             U+2003     Em space
2997             U+2004     Three-per-em space
2998             U+2005     Four-per-em space
2999             U+2006     Six-per-em space
3000             U+2007     Figure space
3001             U+2008     Punctuation space
3002             U+2009     Thin space
3003             U+200A     Hair space
3004             U+202F     Narrow no-break space
3005             U+205F     Medium mathematical space
3006             U+3000     Ideographic space
3007    
3008           The vertical space characters are:
3009    
3010             U+000A     Linefeed
3011             U+000B     Vertical tab
3012             U+000C     Formfeed
3013             U+000D     Carriage return
3014             U+0085     Next line
3015             U+2028     Line separator
3016             U+2029     Paragraph separator
3017    
3018           A "word" character is an underscore or any character less than 256 that
3019           is  a  letter  or  digit.  The definition of letters and digits is con-
3020           trolled by PCRE's low-valued character tables, and may vary if  locale-
3021           specific  matching is taking place (see "Locale support" in the pcreapi
3022           page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3023           systems,  or "french" in Windows, some character codes greater than 128
3024           are used for accented letters, and these are matched by \w. The use  of
3025           locales with Unicode is discouraged.
3026    
3027       Newline sequences
3028    
3029           Outside  a  character class, the escape sequence \R matches any Unicode
3030           newline sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R  is
3031           equivalent to the following:
3032    
3033             (?>\r\n|\n|\x0b|\f|\r|\x85)
3034    
3035           This  is  an  example  of an "atomic group", details of which are given
3036           below.  This particular group matches either the two-character sequence
3037           CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3038           U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3039           return, U+000D), or NEL (next line, U+0085). The two-character sequence
3040           is treated as a single unit that cannot be split.
3041    
3042           In UTF-8 mode, two additional characters whose codepoints  are  greater
3043           than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3044           rator, U+2029).  Unicode character property support is not  needed  for
3045           these characters to be recognized.
3046    
3047           Inside a character class, \R matches the letter "R".
3048    
3049       Unicode character properties
3050    
3051           When PCRE is built with Unicode character property support, three addi-
3052           tional escape sequences that match characters with specific  properties
3053           are  available.   When not in UTF-8 mode, these sequences are of course
3054           limited to testing characters whose codepoints are less than  256,  but
3055           they do work in this mode.  The extra escape sequences are:
3056    
3057             \p{xx}   a character with the xx property
3058             \P{xx}   a character without the xx property
3059             \X       an extended Unicode sequence
3060    
3061           The  property  names represented by xx above are limited to the Unicode
3062           script names, the general category properties, and "Any", which matches
3063           any character (including newline). Other properties such as "InMusical-
3064           Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does
3065           not match any characters, so always causes a match failure.
3066    
3067           Sets of Unicode characters are defined as belonging to certain scripts.
3068           A character from one of these sets can be matched using a script  name.
3069           For example:
3070    
3071             \p{Greek}
3072             \P{Han}
3073    
3074           Those  that are not part of an identified script are lumped together as
3075           "Common". The current list of scripts is:
3076    
3077           Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3078           Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,
3079           Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3080           Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-
3081           gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,
3082           Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3083           Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,
3084           Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3085           Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3086    
3087           Each character has exactly one general category property, specified  by
3088           a two-letter abbreviation. For compatibility with Perl, negation can be
3089           specified by including a circumflex between the opening brace  and  the
3090           property name. For example, \p{^Lu} is the same as \P{Lu}.
3091    
3092           If only one letter is specified with \p or \P, it includes all the gen-
3093           eral category properties that start with that letter. In this case,  in
3094           the  absence of negation, the curly brackets in the escape sequence are
3095           optional; these two examples have the same effect:
3096    
3097             \p{L}
3098             \pL
3099    
3100           The following general category property codes are supported:
3101    
3102             C     Other
3103             Cc    Control
3104             Cf    Format
3105             Cn    Unassigned
3106             Co    Private use
3107             Cs    Surrogate
3108    
3109             L     Letter
3110             Ll    Lower case letter
3111             Lm    Modifier letter
3112             Lo    Other letter
3113             Lt    Title case letter
3114             Lu    Upper case letter
3115    
3116             M     Mark
3117             Mc    Spacing mark
3118             Me    Enclosing mark
3119             Mn    Non-spacing mark
3120    
3121             N     Number
3122             Nd    Decimal number
3123             Nl    Letter number
3124             No    Other number
3125    
3126             P     Punctuation
3127             Pc    Connector punctuation
3128             Pd    Dash punctuation
3129             Pe    Close punctuation
3130             Pf    Final punctuation
3131             Pi    Initial punctuation
3132             Po    Other punctuation
3133             Ps    Open punctuation
3134    
3135             S     Symbol
3136             Sc    Currency symbol
3137             Sk    Modifier symbol
3138             Sm    Mathematical symbol
3139             So    Other symbol
3140    
3141             Z     Separator
3142             Zl    Line separator
3143             Zp    Paragraph separator
3144             Zs    Space separator
3145    
3146           The special property L& is also supported: it matches a character  that
3147           has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
3148           classified as a modifier or "other".
3149    
3150           The long synonyms for these properties  that  Perl  supports  (such  as
3151           \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3152           any of these properties with "Is".
3153    
3154           No character that is in the Unicode table has the Cn (unassigned) prop-
3155           erty.  Instead, this property is assumed for any code point that is not
3156           in the Unicode table.
3157    
3158           Specifying caseless matching does not affect  these  escape  sequences.
3159           For example, \p{Lu} always matches only upper case letters.
3160    
3161           The  \X  escape  matches  any number of Unicode characters that form an
3162           extended Unicode sequence. \X is equivalent to
3163    
3164             (?>\PM\pM*)
3165    
3166           That is, it matches a character without the "mark"  property,  followed
3167           by  zero  or  more  characters with the "mark" property, and treats the
3168           sequence as an atomic group (see below).  Characters  with  the  "mark"
3169           property  are  typically  accents  that affect the preceding character.
3170           None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
3171           matches any one character.
3172    
3173           Matching  characters  by Unicode property is not fast, because PCRE has
3174           to search a structure that contains  data  for  over  fifteen  thousand
3175           characters. That is why the traditional escape sequences such as \d and
3176           \w do not use Unicode properties in PCRE.
3177    
3178       Resetting the match start
3179    
3180           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3181           ously  matched  characters  not  to  be  included  in the final matched