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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
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
 NAME  
      PCRE - Perl-compatible regular expressions  
10    
11    PCRE(3)                                                                PCRE(3)
12    
 DESCRIPTION  
13    
14       The PCRE library is a set of functions that implement  regu-  NAME
15       lar  expression  pattern  matching using the same syntax and         PCRE - Perl-compatible regular expressions
      semantics as Perl, with just a few differences. The  current  
      implementation  of  PCRE  (release 4.x) corresponds approxi-  
      mately with Perl 5.8, including support  for  UTF-8  encoded  
      strings.    However,  this  support  has  to  be  explicitly  
      enabled; it is not the default.  
   
      PCRE is written in C and released as a C library. However, a  
      number  of  people  have  written wrappers and interfaces of  
      various kinds. A C++ class is included  in  these  contribu-  
      tions,  which  can  be found in the Contrib directory at the  
      primary FTP site, which is:  
   
      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre  
   
      Details of exactly which Perl  regular  expression  features  
      are  and  are  not  supported  by PCRE are given in separate  
      documents. See the pcrepattern and pcrecompat pages.  
   
      Some features of PCRE can be included, excluded, or  changed  
      when  the library is built. The pcre_config() function makes  
      it possible for a client  to  discover  which  features  are  
      available.  Documentation  about  building  PCRE for various  
      operating systems can be found in the  README  file  in  the  
      source distribution.  
16    
17    
18  USER DOCUMENTATION  INTRODUCTION
19    
20       The user documentation for PCRE has been  split  up  into  a         The  PCRE  library is a set of functions that implement regular expres-
21       number  of  different sections. In the "man" format, each of         sion pattern matching using the same syntax and semantics as Perl, with
22       these is a separate "man page". In the HTML format, each  is         just  a few differences. Some features that appeared in Python and PCRE
23       a  separate  page,  linked from the index page. In the plain         before they appeared in Perl are also available using the  Python  syn-
24       text format, all the sections are concatenated, for ease  of         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25       searching. The sections are as follows:         items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27         pcre              this document  
28         pcreapi           details of PCRE's native API         The  current implementation of PCRE corresponds approximately with Perl
29         pcrebuild         options for building PCRE         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         pcrecallout       details of the callout feature         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         pcrecompat        discussion of Perl compatibility         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32         pcregrep          description of the pcregrep command         spond to Unicode release 6.0.0.
33         pcrepattern       syntax and semantics of supported  
34                             regular expressions         In  addition to the Perl-compatible matching function, PCRE contains an
35         pcreperform       discussion of performance issues         alternative function that matches the same compiled patterns in a  dif-
36         pcreposix         the POSIX-compatible API         ferent way. In certain circumstances, the alternative function has some
37         pcresample        discussion of the sample program         advantages.  For a discussion of the two matching algorithms,  see  the
38         pcretest          the pcretest testing command         pcrematching page.
39    
40       In addition, in the "man" and HTML formats, there is a short         PCRE  is  written  in C and released as a C library. A number of people
41       page  for  each  library function, listing its arguments and         have written wrappers and interfaces of various kinds.  In  particular,
42       results.         Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
43           included as part of the PCRE distribution. The pcrecpp page has details
44           of  this  interface.  Other  people's contributions can be found in the
45           Contrib directory at the primary FTP site, which is:
46    
47           ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
48    
49           Details of exactly which Perl regular expression features are  and  are
50           not supported by PCRE are given in separate documents. See the pcrepat-
51           tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
52           page.
53    
54           Some  features  of  PCRE can be included, excluded, or changed when the
55           library is built. The pcre_config() function makes it  possible  for  a
56           client  to  discover  which  features are available. The features them-
57           selves are described in the pcrebuild page. Documentation about  build-
58           ing  PCRE  for various operating systems can be found in the README and
59           NON-UNIX-USE files in the source distribution.
60    
61           The library contains a number of undocumented  internal  functions  and
62           data  tables  that  are  used by more than one of the exported external
63           functions, but which are not intended  for  use  by  external  callers.
64           Their  names  all begin with "_pcre_", which hopefully will not provoke
65           any name clashes. In some environments, it is possible to control which
66           external  symbols  are  exported when a shared library is built, and in
67           these cases the undocumented symbols are not exported.
68    
69    
70  LIMITATIONS  USER DOCUMENTATION
71    
72       There are some size limitations in PCRE but it is hoped that         The user documentation for PCRE comprises a number  of  different  sec-
73       they will never in practice be relevant.         tions.  In the "man" format, each of these is a separate "man page". In
74           the HTML format, each is a separate page, linked from the  index  page.
75           In  the  plain  text format, all the sections, except the pcredemo sec-
76           tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79             pcre              this document
80             pcre-config       show PCRE installation configuration information
81             pcreapi           details of PCRE's native C API
82             pcrebuild         options for building PCRE
83             pcrecallout       details of the callout feature
84             pcrecompat        discussion of Perl compatibility
85             pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87             pcregrep          description of the pcregrep command
88             pcrematching      discussion of the two matching algorithms
89             pcrepartial       details of the partial matching facility
90             pcrepattern       syntax and semantics of supported
91                                 regular expressions
92             pcreperform       discussion of performance issues
93             pcreposix         the POSIX-compatible C API
94             pcreprecompile    details of saving and re-using precompiled patterns
95             pcresample        discussion of the pcredemo program
96             pcrestack         discussion of stack usage
97             pcresyntax        quick syntax reference
98             pcretest          description of the pcretest testing command
99    
100       The maximum length of a  compiled  pattern  is  65539  (sic)         In  addition,  in the "man" and HTML formats, there is a short page for
101       bytes  if PCRE is compiled with the default internal linkage         each C library function, listing its arguments and results.
      size of 2. If you want to process regular  expressions  that  
      are  truly  enormous,  you can compile PCRE with an internal  
      linkage size of 3 or 4 (see the README file  in  the  source  
      distribution  and  the pcrebuild documentation for details).  
      If these cases the limit is substantially larger.   However,  
      the speed of execution will be slower.  
   
      All values in repeating quantifiers must be less than 65536.  
      The maximum number of capturing subpatterns is 65535.  
   
      There is no limit to the  number  of  non-capturing  subpat-  
      terns,  but  the  maximum  depth  of nesting of all kinds of  
      parenthesized subpattern, including  capturing  subpatterns,  
      assertions, and other types of subpattern, is 200.  
   
      The maximum length of a subject string is the largest  posi-  
      tive number that an integer variable can hold. However, PCRE  
      uses recursion to handle subpatterns and indefinite  repeti-  
      tion.  This  means  that the available stack space may limit  
      the size of a subject string that can be processed  by  cer-  
      tain patterns.  
102    
103    
104  UTF-8 SUPPORT  LIMITATIONS
105    
106       Starting at release 3.3, PCRE has had some support for char-         There are some size limitations in PCRE but it is hoped that they  will
107       acter  strings  encoded in the UTF-8 format. For release 4.0         never in practice be relevant.
      this has been greatly extended to cover most common require-  
      ments.  
   
      In order process UTF-8  strings,  you  must  build  PCRE  to  
      include  UTF-8  support  in  the code, and, in addition, you  
      must call pcre_compile() with  the  PCRE_UTF8  option  flag.  
      When  you  do this, both the pattern and any subject strings  
      that are matched against it are  treated  as  UTF-8  strings  
      instead of just strings of bytes.  
   
      If you compile PCRE with UTF-8 support, but do not use it at  
      run  time,  the  library will be a bit bigger, but the addi-  
      tional run time overhead is limited to testing the PCRE_UTF8  
      flag in several places, so should not be very large.  
   
      The following comments apply when PCRE is running  in  UTF-8  
      mode:  
   
      1. PCRE assumes that the strings it is given  contain  valid  
      UTF-8  codes. It does not diagnose invalid UTF-8 strings. If  
      you pass invalid UTF-8 strings  to  PCRE,  the  results  are  
      undefined.  
   
      2. In a pattern, the escape sequence \x{...}, where the con-  
      tents  of  the  braces is a string of hexadecimal digits, is  
      interpreted as a UTF-8 character whose code  number  is  the  
      given  hexadecimal  number, for example: \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.  
   
      3. The original hexadecimal escape sequence, \xhh, matches a  
      two-byte UTF-8 character if the value is greater than 127.  
   
      4. Repeat quantifiers apply to  complete  UTF-8  characters,  
      not to individual bytes, for example: \x{100}{3}.  
   
      5. The dot metacharacter matches one UTF-8 character instead  
      of a single byte.  
   
      6. The escape sequence \C can be used to match a single byte  
      in UTF-8 mode, but its use can lead to some strange effects.  
   
      7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  
      correctly test characters of any code value, but the charac-  
      ters that PCRE recognizes as digits, spaces, or word charac-  
      ters  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.  
108    
109       9. PCRE does not support the use of Unicode tables and  pro-         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
110       perties or the Perl escapes \p, \P, and \X.         is compiled with the default internal linkage size of 2. If you want to
111           process  regular  expressions  that are truly enormous, you can compile
112           PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
113           the  source  distribution and the pcrebuild documentation for details).
114           In these cases the limit is substantially larger.  However,  the  speed
115           of execution is slower.
116    
117           All values in repeating quantifiers must be less than 65536.
118    
119           There is no limit to the number of parenthesized subpatterns, but there
120           can be no more than 65535 capturing subpatterns.
121    
122           The maximum length of name for a named subpattern is 32 characters, and
123           the maximum number of named subpatterns is 10000.
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    
132    
133    UTF-8 AND UNICODE PROPERTY SUPPORT
134    
135           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
141           support in the code, and, in addition,  you  must  call  pcre_compile()
142           with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143           sequence (*UTF8). When either of these is the case,  both  the  pattern
144           and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146    
147           If you compile PCRE with UTF-8 support, but do not use it at run  time,
148           the  library will be a bit bigger, but the additional run time overhead
149           is limited to testing the PCRE_UTF8 flag occasionally, so should not be
150           very big.
151    
152           If PCRE is built with Unicode character property support (which implies
153           UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154           ported.  The available properties that can be tested are limited to the
155           general category properties such as Lu for an upper case letter  or  Nd
156           for  a  decimal number, the Unicode script names such as Arabic or Han,
157           and the derived properties Any and L&. A full  list  is  given  in  the
158           pcrepattern documentation. Only the short names for properties are sup-
159           ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
160           ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161           optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162           does not support this.
163    
164       Validity of UTF-8 strings
165    
166           When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167           subjects are (by default) checked for validity on entry to the relevant
168           functions.  From  release 7.3 of PCRE, the check is according the rules
169           of RFC 3629, which are themselves derived from the  Unicode  specifica-
170           tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171           allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174    
175           The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176           which  the Unicode Standard says this: "The Low Surrogate Area does not
177           contain any  character  assignments,  consequently  no  character  code
178           charts or namelists are provided for this area. Surrogates are reserved
179           for use with UTF-16 and then must be used in pairs."  The  code  points
180           that  are  encoded  by  UTF-16  pairs are available as independent code
181           points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184           If an invalid UTF-8 string is passed to PCRE, an error return is given.
185           At compile time, the only additional information is the offset  to  the
186           first byte of the failing character. The runtime functions (pcre_exec()
187           and pcre_dfa_exec()), pass back this information  as  well  as  a  more
188           detailed  reason  code if the caller has provided memory in which to do
189           this.
190    
191           In some situations, you may already know that your strings  are  valid,
192           and  therefore  want  to  skip these checks in order to improve perfor-
193           mance. If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run
194           time,  PCRE  assumes  that  the pattern or subject it is given (respec-
195           tively) contains only valid UTF-8 codes. In  this  case,  it  does  not
196           diagnose an invalid UTF-8 string.
197    
198           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
199           what happens depends on why the string is invalid. If the  string  con-
200           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
201           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
202           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
203           strings according to the more liberal rules of RFC  2279.  However,  if
204           the  string does not even conform to RFC 2279, the result is undefined.
205           Your program may crash.
206    
207           If you want to process strings  of  values  in  the  full  range  0  to
208           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
209           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
210           this situation, you will have to apply your own validity check.
211    
212       General comments about UTF-8 mode
213    
214           1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
215           two-byte UTF-8 character if the value is greater than 127.
216    
217           2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
218           characters for values greater than \177.
219    
220           3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
221           vidual bytes, for example: \x{100}{3}.
222    
223           4. The dot metacharacter matches one UTF-8 character instead of a  sin-
224           gle byte.
225    
226           5.  The  escape sequence \C can be used to match a single byte in UTF-8
227           mode, but its use can lead to some strange effects.  This  facility  is
228           not available in the alternative matching function, pcre_dfa_exec().
229    
230           6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
231           test characters of any code value, but, by default, the characters that
232           PCRE  recognizes  as digits, spaces, or word characters remain the same
233           set as before, all with values less than 256. This  remains  true  even
234           when  PCRE  is built to include Unicode property support, because to do
235           otherwise would slow down PCRE in many common cases. Note in particular
236           that this applies to \b and \B, because they are defined in terms of \w
237           and \W. If you really want to test for a wider sense of, say,  "digit",
238           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
239           tively, if you set the PCRE_UCP option,  the  way  that  the  character
240           escapes  work  is changed so that Unicode properties are used to deter-
241           mine which characters match. There are more details in the  section  on
242           generic character types in the pcrepattern documentation.
243    
244           7.  Similarly,  characters that match the POSIX named character classes
245           are all low-valued characters, unless the PCRE_UCP option is set.
246    
247           8. However, the horizontal and  vertical  whitespace  matching  escapes
248           (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
249           whether or not PCRE_UCP is set.
250    
251           9. Case-insensitive matching applies only to  characters  whose  values
252           are  less than 128, unless PCRE is built with Unicode property support.
253           Even when Unicode property support is available, PCRE  still  uses  its
254           own  character  tables when checking the case of low-valued characters,
255           so as not to degrade performance.  The Unicode property information  is
256           used only for characters with higher values. Furthermore, PCRE supports
257           case-insensitive matching only  when  there  is  a  one-to-one  mapping
258           between  a letter's cases. There are a small number of many-to-one map-
259           pings in Unicode; these are not supported by PCRE.
260    
261    
262  AUTHOR  AUTHOR
263    
264       Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
265       University Computing Service,         University Computing Service
266       Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
267       Phone: +44 1223 334714  
268           Putting an actual email address here seems to have been a spam  magnet,
269           so  I've  taken  it away. If you want to email me, use my two initials,
270           followed by the two digits 10, at the domain cam.ac.uk.
271    
272    
273    REVISION
274    
275           Last updated: 07 May 2011
276           Copyright (c) 1997-2011 University of Cambridge.
277    ------------------------------------------------------------------------------
278    
279    
280    PCREBUILD(3)                                                      PCREBUILD(3)
281    
 Last updated: 04 February 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
282    
283  NAME  NAME
284       PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
285    
286    
287  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
288    
289       This document describes the optional features of  PCRE  that         This  document  describes  the  optional  features  of PCRE that can be
290       can  be  selected when the library is compiled. They are all         selected when the library is compiled. It assumes use of the  configure
291       selected, or deselected, by providing options to the config-         script,  where the optional features are selected or deselected by pro-
292       ure  script  which  is run before the make command. The com-         viding options to configure before running the make  command.  However,
293       plete list of options  for  configure  (which  includes  the         the  same  options  can be selected in both Unix-like and non-Unix-like
294       standard  ones  such  as  the  selection of the installation         environments using the GUI facility of cmake-gui if you are using CMake
295       directory) can be obtained by running         instead of configure to build PCRE.
296    
297         ./configure --help         There  is  a  lot more information about building PCRE in non-Unix-like
298           environments in the file called NON_UNIX_USE, which is part of the PCRE
299       The following sections describe certain options whose  names         distribution.  You  should consult this file as well as the README file
300       begin  with  --enable  or  --disable. These settings specify         if you are building in a non-Unix-like environment.
301       changes to the defaults for the configure  command.  Because  
302       of  the  way  that  configure  works, --enable and --disable         The complete list of options for configure (which includes the standard
303       always come in pairs, so  the  complementary  option  always         ones  such  as  the  selection  of  the  installation directory) can be
304       exists  as  well, but as it specifies the default, it is not         obtained by running
305       described.  
306             ./configure --help
307    
308           The following sections include  descriptions  of  options  whose  names
309           begin with --enable or --disable. These settings specify changes to the
310           defaults for the configure command. Because of the way  that  configure
311           works,  --enable  and --disable always come in pairs, so the complemen-
312           tary option always exists as well, but as it specifies the default,  it
313           is not described.
314    
315    
316    BUILDING SHARED AND STATIC LIBRARIES
317    
318           The  PCRE building process uses libtool to build both shared and static
319           Unix libraries by default. You can suppress one of these by adding  one
320           of
321    
322             --disable-shared
323             --disable-static
324    
325           to the configure command, as required.
326    
327    
328    C++ SUPPORT
329    
330           By default, the configure script will search for a C++ compiler and C++
331           header files. If it finds them, it automatically builds the C++ wrapper
332           library for PCRE. You can disable this by adding
333    
334             --disable-cpp
335    
336           to the configure command.
337    
338    
339  UTF-8 SUPPORT  UTF-8 SUPPORT
340    
341       To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
342    
343             --enable-utf8
344    
345           to  the  configure  command.  Of  itself, this does not make PCRE treat
346           strings as UTF-8. As well as compiling PCRE with this option, you  also
347           have  have to set the PCRE_UTF8 option when you call the pcre_compile()
348           or pcre_compile2() functions.
349    
350         --enable-utf8         If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
351           expects its input to be either ASCII or UTF-8 (depending on the runtime
352           option). It is not possible to support both EBCDIC and UTF-8  codes  in
353           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
354           --enable-ebcdic are mutually exclusive.
355    
356       to the configure command. Of itself, this does not make PCRE  
357       treat  strings as UTF-8. As well as compiling PCRE with this  UNICODE CHARACTER PROPERTY SUPPORT
358       option, you also have have to set the PCRE_UTF8 option  when  
359       you call the pcre_compile() function.         UTF-8 support allows PCRE to process character values greater than  255
360           in  the  strings that it handles. On its own, however, it does not pro-
361           vide any facilities for accessing the properties of such characters. If
362           you  want  to  be able to use the pattern escapes \P, \p, and \X, which
363           refer to Unicode character properties, you must add
364    
365             --enable-unicode-properties
366    
367           to the configure command. This implies UTF-8 support, even if you  have
368           not explicitly requested it.
369    
370           Including  Unicode  property  support  adds around 30K of tables to the
371           PCRE library. Only the general category properties such as  Lu  and  Nd
372           are supported. Details are given in the pcrepattern documentation.
373    
374    
375  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
376    
377       By default, PCRE treats character 10 (linefeed) as the  new-         By  default,  PCRE interprets the linefeed (LF) character as indicating
378       line  character.  This  is  the  normal newline character on         the end of a line. This is the normal newline  character  on  Unix-like
379       Unix-like systems. You can compile PCRE to use character  13         systems.  You  can compile PCRE to use carriage return (CR) instead, by
380       (carriage return) instead by adding         adding
   
        --enable-newline-is-cr  
   
      to the configure command. For completeness there is  also  a  
      --enable-newline-is-lf  option,  which  explicitly specifies  
      linefeed as the newline character.  
381    
382             --enable-newline-is-cr
383    
384  BUILDING SHARED AND STATIC LIBRARIES         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
385           option, which explicitly specifies linefeed as the newline character.
386    
387           Alternatively, you can specify that line endings are to be indicated by
388           the two character sequence CRLF. If you want this, add
389    
390       The PCRE building process uses libtool to build both  shared           --enable-newline-is-crlf
      and  static  Unix libraries by default. You can suppress one  
      of these by adding one of  
391    
392         --disable-shared         to the configure command. There is a fourth option, specified by
        --disable-static  
393    
394       to the configure command, as required.           --enable-newline-is-anycrlf
395    
396           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
397           CRLF as indicating a line ending. Finally, a fifth option, specified by
398    
399             --enable-newline-is-any
400    
401           causes PCRE to recognize any Unicode newline sequence.
402    
403           Whatever  line  ending convention is selected when PCRE is built can be
404           overridden when the library functions are called. At build time  it  is
405           conventional to use the standard for your operating system.
406    
407    
408    WHAT \R MATCHES
409    
410           By  default,  the  sequence \R in a pattern matches any Unicode newline
411           sequence, whatever has been selected as the line  ending  sequence.  If
412           you specify
413    
414             --enable-bsr-anycrlf
415    
416           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
417           ever is selected when PCRE is built can be overridden when the  library
418           functions are called.
419    
420    
421  POSIX MALLOC USAGE  POSIX MALLOC USAGE
422    
423       When PCRE is called through the  POSIX  interface  (see  the         When PCRE is called through the POSIX interface (see the pcreposix doc-
424       pcreposix  documentation),  additional  working  storage  is         umentation), additional working storage is  required  for  holding  the
425       required for holding the pointers  to  capturing  substrings         pointers  to capturing substrings, because PCRE requires three integers
426       because  PCRE requires three integers per substring, whereas         per substring, whereas the POSIX interface provides only  two.  If  the
427       the POSIX interface provides only  two.  If  the  number  of         number of expected substrings is small, the wrapper function uses space
428       expected  substrings  is  small,  the  wrapper function uses         on the stack, because this is faster than using malloc() for each call.
429       space on the stack, because this is faster than  using  mal-         The default threshold above which the stack is no longer used is 10; it
430       loc()  for  each call. The default threshold above which the         can be changed by adding a setting such as
431       stack is no longer used is 10; it can be changed by adding a  
432       setting such as           --with-posix-malloc-threshold=20
433    
434         --with-posix-malloc-threshold=20         to the configure command.
435    
436       to the configure command.  
437    HANDLING VERY LARGE PATTERNS
438    
439           Within a compiled pattern, offset values are used  to  point  from  one
440           part  to another (for example, from an opening parenthesis to an alter-
441           nation metacharacter). By default, two-byte values are used  for  these
442           offsets,  leading  to  a  maximum size for a compiled pattern of around
443           64K. This is sufficient to handle all but the most  gigantic  patterns.
444           Nevertheless,  some  people do want to process truyl enormous patterns,
445           so it is possible to compile PCRE to use three-byte or  four-byte  off-
446           sets by adding a setting such as
447    
448             --with-link-size=3
449    
450           to  the  configure  command.  The value given must be 2, 3, or 4. Using
451           longer offsets slows down the operation of PCRE because it has to  load
452           additional bytes when handling them.
453    
454    
455    AVOIDING EXCESSIVE STACK USAGE
456    
457           When matching with the pcre_exec() function, PCRE implements backtrack-
458           ing by making recursive calls to an internal function  called  match().
459           In  environments  where  the size of the stack is limited, this can se-
460           verely limit PCRE's operation. (The Unix environment does  not  usually
461           suffer from this problem, but it may sometimes be necessary to increase
462           the maximum stack size.  There is a discussion in the  pcrestack  docu-
463           mentation.)  An alternative approach to recursion that uses memory from
464           the heap to remember data, instead of using recursive  function  calls,
465           has  been  implemented to work round the problem of limited stack size.
466           If you want to build a version of PCRE that works this way, add
467    
468             --disable-stack-for-recursion
469    
470           to the configure command. With this configuration, PCRE  will  use  the
471           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
472           ment functions. By default these point to malloc() and free(), but  you
473           can replace the pointers so that your own functions are used instead.
474    
475           Separate  functions  are  provided  rather  than  using pcre_malloc and
476           pcre_free because the  usage  is  very  predictable:  the  block  sizes
477           requested  are  always  the  same,  and  the blocks are always freed in
478           reverse order. A calling program might be able to  implement  optimized
479           functions  that  perform  better  than  malloc()  and free(). PCRE runs
480           noticeably more slowly when built in this way. This option affects only
481           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
482    
483    
484  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
485    
486       Internally, PCRE has a  function  called  match()  which  it         Internally,  PCRE has a function called match(), which it calls repeat-
487       calls  repeatedly  (possibly  recursively) when performing a         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
488       matching operation. By limiting the  number  of  times  this         pcre_exec()  function.  By controlling the maximum number of times this
489       function  may  be  called,  a  limit  can  be  placed on the         function may be called during a single matching operation, a limit  can
490       resources used by a single call to  pcre_exec().  The  limit         be  placed  on  the resources used by a single call to pcre_exec(). The
491       can  be  changed  at  run  time, as described in the pcreapi         limit can be changed at run time, as described in the pcreapi  documen-
492       documentation. The default is 10 million, but  this  can  be         tation.  The default is 10 million, but this can be changed by adding a
493       changed by adding a setting such as         setting such as
494    
495         --with-match-limit=500000           --with-match-limit=500000
496    
497       to the configure command.         to  the  configure  command.  This  setting  has  no  effect   on   the
498           pcre_dfa_exec() matching function.
499    
500           In  some  environments  it is desirable to limit the depth of recursive
501           calls of match() more strictly than the total number of calls, in order
502           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
503           for-recursion is specified) that is used. A second limit controls this;
504           it  defaults  to  the  value  that is set for --with-match-limit, which
505           imposes no additional constraints. However, you can set a  lower  limit
506           by adding, for example,
507    
508  HANDLING VERY LARGE PATTERNS           --with-match-limit-recursion=10000
509    
510       Within a compiled pattern, offset values are used  to  point         to  the  configure  command.  This  value can also be overridden at run
511       from  one  part  to  another  (for  example, from an opening         time.
512       parenthesis to an  alternation  metacharacter).  By  default  
513       two-byte  values  are  used  for these offsets, leading to a  
514       maximum size for a compiled pattern of around 64K.  This  is  CREATING CHARACTER TABLES AT BUILD TIME
515       sufficient  to  handle  all  but the most gigantic patterns.  
516       Nevertheless, some people do want to process  enormous  pat-         PCRE uses fixed tables for processing characters whose code values  are
517       terns,  so  it is possible to compile PCRE to use three-byte         less  than 256. By default, PCRE is built with a set of tables that are
518       or four-byte offsets by adding a setting such as         distributed in the file pcre_chartables.c.dist. These  tables  are  for
519           ASCII codes only. If you add
520         --with-link-size=3  
521             --enable-rebuild-chartables
522       to the configure command. The value given must be 2,  3,  or  
523       4.  Using  longer  offsets  slows down the operation of PCRE         to  the  configure  command, the distributed tables are no longer used.
524       because it has to load additional bytes when handling them.         Instead, a program called dftables is compiled and  run.  This  outputs
525           the source for new set of tables, created in the default locale of your
526       If you build PCRE with an increased link size, test  2  (and         C runtime system. (This method of replacing the tables does not work if
527       test 5 if you are using UTF-8) will fail. Part of the output         you  are cross compiling, because dftables is run on the local host. If
528       of these tests is a representation of the compiled  pattern,         you need to create alternative tables when cross  compiling,  you  will
529       and this changes with the link size.         have to do so "by hand".)
530    
531    
532    USING EBCDIC CODE
533    
534           PCRE  assumes  by  default that it will run in an environment where the
535           character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
536           This  is  the  case for most computer operating systems. PCRE can, how-
537           ever, be compiled to run in an EBCDIC environment by adding
538    
539             --enable-ebcdic
540    
541           to the configure command. This setting implies --enable-rebuild-charta-
542           bles.  You  should  only  use  it if you know that you are in an EBCDIC
543           environment (for example,  an  IBM  mainframe  operating  system).  The
544           --enable-ebcdic option is incompatible with --enable-utf8.
545    
546    
547    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
548    
549           By default, pcregrep reads all files as plain text. You can build it so
550           that it recognizes files whose names end in .gz or .bz2, and reads them
551           with libz or libbz2, respectively, by adding one or both of
552    
553             --enable-pcregrep-libz
554             --enable-pcregrep-libbz2
555    
556           to the configure command. These options naturally require that the rel-
557           evant libraries are installed on your system. Configuration  will  fail
558           if they are not.
559    
560    
561    PCREGREP BUFFER SIZE
562    
563           pcregrep  uses  an internal buffer to hold a "window" on the file it is
564           scanning, in order to be able to output "before" and "after" lines when
565           it  finds  a match. The size of the buffer is controlled by a parameter
566           whose default value is 20K. The buffer itself is three times this size,
567           but because of the way it is used for holding "before" lines, the long-
568           est line that is guaranteed to be processable is  the  parameter  size.
569           You can change the default parameter value by adding, for example,
570    
571             --with-pcregrep-bufsize=50K
572    
573           to the configure command. The caller of pcregrep can, however, override
574           this value by specifying a run-time option.
575    
576    
577    PCRETEST OPTION FOR LIBREADLINE SUPPORT
578    
579           If you add
580    
581             --enable-pcretest-libreadline
582    
583           to the configure command,  pcretest  is  linked  with  the  libreadline
584           library,  and  when its input is from a terminal, it reads it using the
585           readline() function. This provides line-editing and history facilities.
586           Note that libreadline is GPL-licensed, so if you distribute a binary of
587           pcretest linked in this way, there may be licensing issues.
588    
589           Setting this option causes the -lreadline option to  be  added  to  the
590           pcretest  build.  In many operating environments with a sytem-installed
591           libreadline this is sufficient. However, in some environments (e.g.  if
592           an  unmodified  distribution version of readline is in use), some extra
593           configuration may be necessary. The INSTALL file for  libreadline  says
594           this:
595    
596             "Readline uses the termcap functions, but does not link with the
597             termcap or curses library itself, allowing applications which link
598             with readline the to choose an appropriate library."
599    
600           If  your environment has not been set up so that an appropriate library
601           is automatically included, you may need to add something like
602    
603             LIBS="-ncurses"
604    
605           immediately before the configure command.
606    
607    
608    SEE ALSO
609    
610           pcreapi(3), pcre_config(3).
611    
612    
613    AUTHOR
614    
615           Philip Hazel
616           University Computing Service
617           Cambridge CB2 3QH, England.
618    
619    
620    REVISION
621    
622           Last updated: 02 August 2011
623           Copyright (c) 1997-2011 University of Cambridge.
624    ------------------------------------------------------------------------------
625    
626    
627    PCREMATCHING(3)                                                PCREMATCHING(3)
628    
 Last updated: 21 January 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
629    
630  NAME  NAME
631       PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
632    
633    
634    PCRE MATCHING ALGORITHMS
635    
636           This document describes the two different algorithms that are available
637           in PCRE for matching a compiled regular expression against a given sub-
638           ject  string.  The  "standard"  algorithm  is  the  one provided by the
639           pcre_exec() function.  This works in the same was  as  Perl's  matching
640           function, and provides a Perl-compatible matching operation.
641    
642           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
643           this operates in a different way, and is not  Perl-compatible.  It  has
644           advantages  and disadvantages compared with the standard algorithm, and
645           these are described below.
646    
647           When there is only one possible way in which a given subject string can
648           match  a pattern, the two algorithms give the same answer. A difference
649           arises, however, when there are multiple possibilities. For example, if
650           the pattern
651    
652             ^<.*>
653    
654  SYNOPSIS OF PCRE API         is matched against the string
655    
656       #include <pcre.h>           <something> <something else> <something further>
657    
658       pcre *pcre_compile(const char *pattern, int options,         there are three possible answers. The standard algorithm finds only one
659            const char **errptr, int *erroffset,         of them, whereas the alternative algorithm finds all three.
           const unsigned char *tableptr);  
660    
      pcre_extra *pcre_study(const pcre *code, int options,  
           const char **errptr);  
661    
662       int pcre_exec(const pcre *code, const pcre_extra *extra,  REGULAR EXPRESSIONS AS TREES
           const char *subject, int length, int startoffset,  
           int options, int *ovector, int ovecsize);  
663    
664       int pcre_copy_named_substring(const pcre *code,         The set of strings that are matched by a regular expression can be rep-
665            const char *subject, int *ovector,         resented  as  a  tree structure. An unlimited repetition in the pattern
666            int stringcount, const char *stringname,         makes the tree of infinite size, but it is still a tree.  Matching  the
667            char *buffer, int buffersize);         pattern  to a given subject string (from a given starting point) can be
668           thought of as a search of the tree.  There are two  ways  to  search  a
669           tree:  depth-first  and  breadth-first, and these correspond to the two
670           matching algorithms provided by PCRE.
671    
      int pcre_copy_substring(const char *subject, int *ovector,  
           int stringcount, int stringnumber, char *buffer,  
           int buffersize);  
672    
673       int pcre_get_named_substring(const pcre *code,  THE STANDARD MATCHING ALGORITHM
           const char *subject, int *ovector,  
           int stringcount, const char *stringname,  
           const char **stringptr);  
674    
675       int pcre_get_stringnumber(const pcre *code,         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
676            const char *name);         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
677           depth-first search of the pattern tree. That is, it  proceeds  along  a
678           single path through the tree, checking that the subject matches what is
679           required. When there is a mismatch, the algorithm  tries  any  alterna-
680           tives  at  the  current point, and if they all fail, it backs up to the
681           previous branch point in the  tree,  and  tries  the  next  alternative
682           branch  at  that  level.  This often involves backing up (moving to the
683           left) in the subject string as well.  The  order  in  which  repetition
684           branches  are  tried  is controlled by the greedy or ungreedy nature of
685           the quantifier.
686    
687       int pcre_get_substring(const char *subject, int *ovector,         If a leaf node is reached, a matching string has  been  found,  and  at
688            int stringcount, int stringnumber,         that  point the algorithm stops. Thus, if there is more than one possi-
689            const char **stringptr);         ble match, this algorithm returns the first one that it finds.  Whether
690           this  is the shortest, the longest, or some intermediate length depends
691           on the way the greedy and ungreedy repetition quantifiers are specified
692           in the pattern.
693    
694       int pcre_get_substring_list(const char *subject,         Because  it  ends  up  with a single path through the tree, it is rela-
695            int *ovector, int stringcount, const char ***listptr);         tively straightforward for this algorithm to keep  track  of  the  sub-
696           strings  that  are  matched  by portions of the pattern in parentheses.
697           This provides support for capturing parentheses and back references.
698    
      void pcre_free_substring(const char *stringptr);  
699    
700       void pcre_free_substring_list(const char **stringptr);  THE ALTERNATIVE MATCHING ALGORITHM
701    
702       const unsigned char *pcre_maketables(void);         This algorithm conducts a breadth-first search of  the  tree.  Starting
703           from  the  first  matching  point  in the subject, it scans the subject
704           string from left to right, once, character by character, and as it does
705           this,  it remembers all the paths through the tree that represent valid
706           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
707           though  it is not implemented as a traditional finite state machine (it
708           keeps multiple states active simultaneously).
709    
710       int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         Although the general principle of this matching algorithm  is  that  it
711            int what, void *where);         scans  the subject string only once, without backtracking, there is one
712           exception: when a lookaround assertion is encountered,  the  characters
713           following  or  preceding  the  current  point  have to be independently
714           inspected.
715    
716           The scan continues until either the end of the subject is  reached,  or
717           there  are  no more unterminated paths. At this point, terminated paths
718           represent the different matching possibilities (if there are none,  the
719           match  has  failed).   Thus,  if there is more than one possible match,
720           this algorithm finds all of them, and in particular, it finds the long-
721           est.  The  matches are returned in decreasing order of length. There is
722           an option to stop the algorithm after the first match (which is  neces-
723           sarily the shortest) is found.
724    
725       int pcre_info(const pcre *code, int *optptr, *firstcharptr);         Note that all the matches that are found start at the same point in the
726           subject. If the pattern
727    
728       int pcre_config(int what, void *where);           cat(er(pillar)?)?
729    
730       char *pcre_version(void);         is matched against the string "the caterpillar catchment",  the  result
731           will  be the three strings "caterpillar", "cater", and "cat" that start
732           at the fifth character of the subject. The algorithm does not automati-
733           cally move on to find matches that start at later positions.
734    
735       void *(*pcre_malloc)(size_t);         There are a number of features of PCRE regular expressions that are not
736           supported by the alternative matching algorithm. They are as follows:
737    
738       void (*pcre_free)(void *);         1. Because the algorithm finds all  possible  matches,  the  greedy  or
739           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
740           ungreedy quantifiers are treated in exactly the same way. However, pos-
741           sessive  quantifiers can make a difference when what follows could also
742           match what is quantified, for example in a pattern like this:
743    
744       int (*pcre_callout)(pcre_callout_block *);           ^a++\w!
745    
746           This pattern matches "aaab!" but not "aaa!", which would be matched  by
747           a  non-possessive quantifier. Similarly, if an atomic group is present,
748           it is matched as if it were a standalone pattern at the current  point,
749           and  the  longest match is then "locked in" for the rest of the overall
750           pattern.
751    
752  PCRE API         2. When dealing with multiple paths through the tree simultaneously, it
753           is  not  straightforward  to  keep track of captured substrings for the
754           different matching possibilities, and  PCRE's  implementation  of  this
755           algorithm does not attempt to do this. This means that no captured sub-
756           strings are available.
757    
758       PCRE has its own native API,  which  is  described  in  this         3. Because no substrings are captured, back references within the  pat-
759       document.  There  is  also  a  set of wrapper functions that         tern are not supported, and cause errors if encountered.
      correspond to the POSIX regular expression API.   These  are  
      described in the pcreposix documentation.  
760    
761       The native API function prototypes are defined in the header         4.  For  the same reason, conditional expressions that use a backrefer-
762       file  pcre.h,  and  on  Unix  systems  the library itself is         ence as the condition or test for a specific group  recursion  are  not
763       called libpcre.a, so can be accessed by adding -lpcre to the         supported.
      command  for  linking  an  application  which  calls it. The  
      header file defines the macros PCRE_MAJOR and PCRE_MINOR  to  
      contain the major and minor release numbers for the library.  
      Applications can use these to include support for  different  
      releases.  
764    
765       The functions pcre_compile(), pcre_study(), and  pcre_exec()         5.  Because  many  paths  through the tree may be active, the \K escape
766       are  used  for compiling and matching regular expressions. A         sequence, which resets the start of the match when encountered (but may
767       sample program that demonstrates the simplest way  of  using         be  on  some  paths  and not on others), is not supported. It causes an
768       them  is  given in the file pcredemo.c. The pcresample docu-         error if encountered.
      mentation describes how to run it.  
769    
770       There are convenience functions for extracting captured sub-         6. Callouts are supported, but the value of the  capture_top  field  is
771       strings from a matched subject string. They are:         always 1, and the value of the capture_last field is always -1.
772    
773         pcre_copy_substring()         7.  The \C escape sequence, which (in the standard algorithm) matches a
774         pcre_copy_named_substring()         single byte, even in UTF-8 mode, is not supported because the  alterna-
775         pcre_get_substring()         tive  algorithm  moves  through  the  subject string one character at a
776         pcre_get_named_substring()         time, for all active paths through the tree.
        pcre_get_substring_list()  
777    
778       pcre_free_substring()  and  pcre_free_substring_list()   are         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
779       also  provided,  to  free  the  memory  used  for  extracted         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
780       strings.         negative assertion.
781    
      The function pcre_maketables() is used (optionally) to build  
      a  set of character tables in the current locale for passing  
      to pcre_compile().  
782    
783       The function pcre_fullinfo() is used to find out information  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
      about a compiled pattern; pcre_info() is an obsolete version  
      which returns only some of the available information, but is  
      retained   for   backwards   compatibility.    The  function  
      pcre_version() returns a pointer to a string containing  the  
      version of PCRE and its date of release.  
784    
785       The global variables  pcre_malloc  and  pcre_free  initially         Using the alternative matching algorithm provides the following  advan-
786       contain the entry points of the standard malloc() and free()         tages:
      functions respectively. PCRE  calls  the  memory  management  
      functions  via  these  variables,  so  a calling program can  
      replace them if it  wishes  to  intercept  the  calls.  This  
      should be done before calling any PCRE functions.  
787    
788       The global variable pcre_callout initially contains NULL. It         1. All possible matches (at a single point in the subject) are automat-
789       can be set by the caller to a "callout" function, which PCRE         ically found, and in particular, the longest match is  found.  To  find
790       will then call at specified points during a matching  opera-         more than one match using the standard algorithm, you have to do kludgy
791       tion. Details are given in the pcrecallout documentation.         things with callouts.
792    
793           2. Because the alternative algorithm  scans  the  subject  string  just
794           once,  and  never  needs to backtrack, it is possible to pass very long
795           subject strings to the matching function in  several  pieces,  checking
796           for  partial  matching  each time. Although it is possible to do multi-
797           segment matching using the standard algorithm (pcre_exec()), by retain-
798           ing  partially matched substrings, it is more complicated. The pcrepar-
799           tial documentation gives details  of  partial  matching  and  discusses
800           multi-segment matching.
801    
802    
803    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
804    
805           The alternative algorithm suffers from a number of disadvantages:
806    
807           1.  It  is  substantially  slower  than the standard algorithm. This is
808           partly because it has to search for all possible matches, but  is  also
809           because it is less susceptible to optimization.
810    
811           2. Capturing parentheses and back references are not supported.
812    
813           3. Although atomic groups are supported, their use does not provide the
814           performance advantage that it does for the standard algorithm.
815    
816    
817    AUTHOR
818    
819           Philip Hazel
820           University Computing Service
821           Cambridge CB2 3QH, England.
822    
823    
824    REVISION
825    
826           Last updated: 17 November 2010
827           Copyright (c) 1997-2010 University of Cambridge.
828    ------------------------------------------------------------------------------
829    
830    
831    PCREAPI(3)                                                          PCREAPI(3)
832    
833    
834    NAME
835           PCRE - Perl-compatible regular expressions
836    
837    
838    PCRE NATIVE API
839    
840           #include <pcre.h>
841    
842           pcre *pcre_compile(const char *pattern, int options,
843                const char **errptr, int *erroffset,
844                const unsigned char *tableptr);
845    
846           pcre *pcre_compile2(const char *pattern, int options,
847                int *errorcodeptr,
848                const char **errptr, int *erroffset,
849                const unsigned char *tableptr);
850    
851           pcre_extra *pcre_study(const pcre *code, int options,
852                const char **errptr);
853    
854           int pcre_exec(const pcre *code, const pcre_extra *extra,
855                const char *subject, int length, int startoffset,
856                int options, int *ovector, int ovecsize);
857    
858           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
859                const char *subject, int length, int startoffset,
860                int options, int *ovector, int ovecsize,
861                int *workspace, int wscount);
862    
863           int pcre_copy_named_substring(const pcre *code,
864                const char *subject, int *ovector,
865                int stringcount, const char *stringname,
866                char *buffer, int buffersize);
867    
868           int pcre_copy_substring(const char *subject, int *ovector,
869                int stringcount, int stringnumber, char *buffer,
870                int buffersize);
871    
872           int pcre_get_named_substring(const pcre *code,
873                const char *subject, int *ovector,
874                int stringcount, const char *stringname,
875                const char **stringptr);
876    
877           int pcre_get_stringnumber(const pcre *code,
878                const char *name);
879    
880           int pcre_get_stringtable_entries(const pcre *code,
881                const char *name, char **first, char **last);
882    
883           int pcre_get_substring(const char *subject, int *ovector,
884                int stringcount, int stringnumber,
885                const char **stringptr);
886    
887           int pcre_get_substring_list(const char *subject,
888                int *ovector, int stringcount, const char ***listptr);
889    
890           void pcre_free_substring(const char *stringptr);
891    
892           void pcre_free_substring_list(const char **stringptr);
893    
894           const unsigned char *pcre_maketables(void);
895    
896           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
897                int what, void *where);
898    
899           int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
900    
901           int pcre_refcount(pcre *code, int adjust);
902    
903           int pcre_config(int what, void *where);
904    
905           char *pcre_version(void);
906    
907           void *(*pcre_malloc)(size_t);
908    
909           void (*pcre_free)(void *);
910    
911           void *(*pcre_stack_malloc)(size_t);
912    
913           void (*pcre_stack_free)(void *);
914    
915           int (*pcre_callout)(pcre_callout_block *);
916    
917    
918    PCRE API OVERVIEW
919    
920           PCRE has its own native API, which is described in this document. There
921           are also some wrapper functions that correspond to  the  POSIX  regular
922           expression  API.  These  are  described in the pcreposix documentation.
923           Both of these APIs define a set of C function calls. A C++  wrapper  is
924           distributed with PCRE. It is documented in the pcrecpp page.
925    
926           The  native  API  C  function prototypes are defined in the header file
927           pcre.h, and on Unix systems the library itself is called  libpcre.   It
928           can normally be accessed by adding -lpcre to the command for linking an
929           application  that  uses  PCRE.  The  header  file  defines  the  macros
930           PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
931           bers for the library.  Applications can use these  to  include  support
932           for different releases of PCRE.
933    
934           In a Windows environment, if you want to statically link an application
935           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
936           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
937           loc()   and   pcre_free()   exported   functions   will   be   declared
938           __declspec(dllimport), with unwanted results.
939    
940           The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
941           pcre_exec() are used for compiling and matching regular expressions  in
942           a  Perl-compatible  manner. A sample program that demonstrates the sim-
943           plest way of using them is provided in the file  called  pcredemo.c  in
944           the PCRE source distribution. A listing of this program is given in the
945           pcredemo documentation, and the pcresample documentation describes  how
946           to compile and run it.
947    
948           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
949           ble, is also provided. This uses a different algorithm for  the  match-
950           ing.  The  alternative algorithm finds all possible matches (at a given
951           point in the subject), and scans the subject just  once  (unless  there
952           are  lookbehind  assertions).  However,  this algorithm does not return
953           captured substrings. A description of the two matching  algorithms  and
954           their  advantages  and disadvantages is given in the pcrematching docu-
955           mentation.
956    
957           In addition to the main compiling and  matching  functions,  there  are
958           convenience functions for extracting captured substrings from a subject
959           string that is matched by pcre_exec(). They are:
960    
961             pcre_copy_substring()
962             pcre_copy_named_substring()
963             pcre_get_substring()
964             pcre_get_named_substring()
965             pcre_get_substring_list()
966             pcre_get_stringnumber()
967             pcre_get_stringtable_entries()
968    
969           pcre_free_substring() and pcre_free_substring_list() are also provided,
970           to free the memory used for extracted strings.
971    
972           The  function  pcre_maketables()  is  used  to build a set of character
973           tables  in  the  current  locale   for   passing   to   pcre_compile(),
974           pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
975           provided for specialist use.  Most  commonly,  no  special  tables  are
976           passed,  in  which case internal tables that are generated when PCRE is
977           built are used.
978    
979           The function pcre_fullinfo() is used to find out  information  about  a
980           compiled  pattern; pcre_info() is an obsolete version that returns only
981           some of the available information, but is retained for  backwards  com-
982           patibility.   The function pcre_version() returns a pointer to a string
983           containing the version of PCRE and its date of release.
984    
985           The function pcre_refcount() maintains a  reference  count  in  a  data
986           block  containing  a compiled pattern. This is provided for the benefit
987           of object-oriented applications.
988    
989           The global variables pcre_malloc and pcre_free  initially  contain  the
990           entry  points  of  the  standard malloc() and free() functions, respec-
991           tively. PCRE calls the memory management functions via these variables,
992           so  a  calling  program  can replace them if it wishes to intercept the
993           calls. This should be done before calling any PCRE functions.
994    
995           The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
996           indirections  to  memory  management functions. These special functions
997           are used only when PCRE is compiled to use  the  heap  for  remembering
998           data, instead of recursive function calls, when running the pcre_exec()
999           function. See the pcrebuild documentation for  details  of  how  to  do
1000           this.  It  is  a non-standard way of building PCRE, for use in environ-
1001           ments that have limited stacks. Because of the greater  use  of  memory
1002           management,  it  runs  more  slowly. Separate functions are provided so
1003           that special-purpose external code can be  used  for  this  case.  When
1004           used,  these  functions  are always called in a stack-like manner (last
1005           obtained, first freed), and always for memory blocks of the same  size.
1006           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
1007           mentation.
1008    
1009           The global variable pcre_callout initially contains NULL. It can be set
1010           by  the  caller  to  a "callout" function, which PCRE will then call at
1011           specified points during a matching operation. Details are given in  the
1012           pcrecallout documentation.
1013    
1014    
1015    NEWLINES
1016    
1017           PCRE  supports five different conventions for indicating line breaks in
1018           strings: a single CR (carriage return) character, a  single  LF  (line-
1019           feed) character, the two-character sequence CRLF, any of the three pre-
1020           ceding, or any Unicode newline sequence. The Unicode newline  sequences
1021           are  the  three just mentioned, plus the single characters VT (vertical
1022           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
1023           separator, U+2028), and PS (paragraph separator, U+2029).
1024    
1025           Each  of  the first three conventions is used by at least one operating
1026           system as its standard newline sequence. When PCRE is built, a  default
1027           can  be  specified.  The default default is LF, which is the Unix stan-
1028           dard. When PCRE is run, the default can be overridden,  either  when  a
1029           pattern is compiled, or when it is matched.
1030    
1031           At compile time, the newline convention can be specified by the options
1032           argument of pcre_compile(), or it can be specified by special  text  at
1033           the start of the pattern itself; this overrides any other settings. See
1034           the pcrepattern page for details of the special character sequences.
1035    
1036           In the PCRE documentation the word "newline" is used to mean "the char-
1037           acter  or pair of characters that indicate a line break". The choice of
1038           newline convention affects the handling of  the  dot,  circumflex,  and
1039           dollar metacharacters, the handling of #-comments in /x mode, and, when
1040           CRLF is a recognized line ending sequence, the match position  advance-
1041           ment for a non-anchored pattern. There is more detail about this in the
1042           section on pcre_exec() options below.
1043    
1044           The choice of newline convention does not affect the interpretation  of
1045           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1046           which is controlled in a similar way, but by separate options.
1047    
1048    
1049  MULTITHREADING  MULTITHREADING
1050    
1051       The PCRE functions can be used in  multi-threading  applica-         The PCRE functions can be used in  multi-threading  applications,  with
1052       tions, with the proviso that the memory management functions         the  proviso  that  the  memory  management  functions  pointed  to  by
1053       pointed to by pcre_malloc and  pcre_free,  and  the  callout         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1054       function  pointed  to  by  pcre_callout,  are  shared by all         callout function pointed to by pcre_callout, are shared by all threads.
1055       threads.  
1056           The  compiled form of a regular expression is not altered during match-
1057       The compiled form of a regular  expression  is  not  altered         ing, so the same compiled pattern can safely be used by several threads
1058       during  matching, so the same compiled pattern can safely be         at once.
1059       used by several threads at once.  
1060    
1061    SAVING PRECOMPILED PATTERNS FOR LATER USE
1062    
1063           The compiled form of a regular expression can be saved and re-used at a
1064           later time, possibly by a different program, and even on a  host  other
1065           than  the  one  on  which  it  was  compiled.  Details are given in the
1066           pcreprecompile documentation. However, compiling a  regular  expression
1067           with  one version of PCRE for use with a different version is not guar-
1068           anteed to work and may cause crashes.
1069    
1070    
1071  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
1072    
1073       int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1074    
1075           The function pcre_config() makes it possible for a PCRE client to  dis-
1076           cover which optional features have been compiled into the PCRE library.
1077           The pcrebuild documentation has more details about these optional  fea-
1078           tures.
1079    
1080           The  first  argument  for pcre_config() is an integer, specifying which
1081           information is required; the second argument is a pointer to a variable
1082           into  which  the  information  is  placed. The following information is
1083           available:
1084    
1085       The function pcre_config() makes  it  possible  for  a  PCRE           PCRE_CONFIG_UTF8
      client  to  discover  which optional features have been com-  
      piled into the PCRE library. The pcrebuild documentation has  
      more details about these optional features.  
1086    
1087       The first argument for pcre_config() is an integer, specify-         The output is an integer that is set to one if UTF-8 support is  avail-
1088       ing  which information is required; the second argument is a         able; otherwise it is set to zero.
      pointer to a variable into which the information is  placed.  
      The following information is available:  
1089    
1090         PCRE_CONFIG_UTF8           PCRE_CONFIG_UNICODE_PROPERTIES
1091    
1092       The output is an integer that is set to one if UTF-8 support         The  output  is  an  integer  that is set to one if support for Unicode
1093       is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1094    
1095         PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1096    
1097       The output is an integer that is set to  the  value  of  the         The output is an integer whose value specifies  the  default  character
1098       code  that  is  used for the newline character. It is either         sequence  that is recognized as meaning "newline". The four values that
1099       linefeed (10) or carriage return (13), and  should  normally         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1100       be the standard character for your operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1101           are returned in EBCDIC environments. The default should normally corre-
1102           spond to the standard sequence for your operating system.
1103    
1104         PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_BSR
1105    
1106       The output is an integer that contains the number  of  bytes         The output is an integer whose value indicates what character sequences
1107       used  for  internal linkage in compiled regular expressions.         the \R escape sequence matches by default. A value of 0 means  that  \R
1108       The value is 2, 3, or 4. Larger values allow larger  regular         matches  any  Unicode  line ending sequence; a value of 1 means that \R
1109       expressions  to be compiled, at the expense of slower match-         matches only CR, LF, or CRLF. The default can be overridden when a pat-
1110       ing. The default value of 2 is sufficient for  all  but  the         tern is compiled or matched.
      most  massive patterns, since it allows the compiled pattern  
      to be up to 64K in size.  
1111    
1112         PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_LINK_SIZE
1113    
1114       The output is an integer that contains the  threshold  above         The  output  is  an  integer that contains the number of bytes used for
1115       which  the POSIX interface uses malloc() for output vectors.         internal linkage in compiled regular expressions. The value is 2, 3, or
1116       Further details are given in the pcreposix documentation.         4.  Larger  values  allow larger regular expressions to be compiled, at
1117           the expense of slower matching. The default value of  2  is  sufficient
1118           for  all  but  the  most massive patterns, since it allows the compiled
1119           pattern to be up to 64K in size.
1120    
1121         PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1122    
1123       The output is an integer that gives the  default  limit  for         The output is an integer that contains the threshold  above  which  the
1124       the   number  of  internal  matching  function  calls  in  a         POSIX  interface  uses malloc() for output vectors. Further details are
1125       pcre_exec()  execution.  Further  details  are  given   with         given in the pcreposix documentation.
1126       pcre_exec() below.  
1127             PCRE_CONFIG_MATCH_LIMIT
1128    
1129           The output is a long integer that gives the default limit for the  num-
1130           ber  of  internal  matching  function calls in a pcre_exec() execution.
1131           Further details are given with pcre_exec() below.
1132    
1133             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1134    
1135           The output is a long integer that gives the default limit for the depth
1136           of   recursion  when  calling  the  internal  matching  function  in  a
1137           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1138           below.
1139    
1140             PCRE_CONFIG_STACKRECURSE
1141    
1142           The  output is an integer that is set to one if internal recursion when
1143           running pcre_exec() is implemented by recursive function calls that use
1144           the  stack  to remember their state. This is the usual way that PCRE is
1145           compiled. The output is zero if PCRE was compiled to use blocks of data
1146           on  the  heap  instead  of  recursive  function  calls.  In  this case,
1147           pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1148           blocks on the heap, thus avoiding the use of the stack.
1149    
1150    
1151  COMPILING A PATTERN  COMPILING A PATTERN
1152    
1153       pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1154            const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
1155            const unsigned char *tableptr);              const unsigned char *tableptr);
1156    
1157       The function pcre_compile() is called to compile  a  pattern         pcre *pcre_compile2(const char *pattern, int options,
1158       into  an internal form. The pattern is a C string terminated              int *errorcodeptr,
1159       by a binary zero, and is passed in the argument  pattern.  A              const char **errptr, int *erroffset,
1160       pointer  to  a  single  block of memory that is obtained via              const unsigned char *tableptr);
1161       pcre_malloc is returned. This contains the compiled code and  
1162       related  data.  The  pcre  type  is defined for the returned         Either of the functions pcre_compile() or pcre_compile2() can be called
1163       block; this is a typedef for a structure whose contents  are         to compile a pattern into an internal form. The only difference between
1164       not  externally  defined. It is up to the caller to free the         the  two interfaces is that pcre_compile2() has an additional argument,
1165       memory when it is no longer required.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1166           avoid  too  much repetition, we refer just to pcre_compile() below, but
1167       Although the compiled code of a PCRE regex  is  relocatable,         the information applies equally to pcre_compile2().
1168       that is, it does not depend on memory location, the complete  
1169       pcre data block is not fully relocatable,  because  it  con-         The pattern is a C string terminated by a binary zero, and is passed in
1170       tains  a  copy of the tableptr argument, which is an address         the  pattern  argument.  A  pointer to a single block of memory that is
1171       (see below).         obtained via pcre_malloc is returned. This contains the  compiled  code
1172       The options argument contains independent bits  that  affect         and related data. The pcre type is defined for the returned block; this
1173       the  compilation.  It  should  be  zero  if  no  options are         is a typedef for a structure whose contents are not externally defined.
1174       required. Some of the options, in particular, those that are         It is up to the caller to free the memory (via pcre_free) when it is no
1175       compatible  with Perl, can also be set and unset from within         longer required.
1176       the pattern (see the detailed description of regular expres-  
1177       sions  in the pcrepattern documentation). For these options,         Although the compiled code of a PCRE regex is relocatable, that is,  it
1178       the contents of the options argument specifies their initial         does not depend on memory location, the complete pcre data block is not
1179       settings  at  the  start  of  compilation and execution. The         fully relocatable, because it may contain a copy of the tableptr  argu-
1180       PCRE_ANCHORED option can be set at the time of  matching  as         ment, which is an address (see below).
1181       well as at compile time.  
1182           The options argument contains various bit settings that affect the com-
1183       If errptr is NULL, pcre_compile() returns NULL  immediately.         pilation. It should be zero if no options are required.  The  available
1184       Otherwise, if compilation of a pattern fails, pcre_compile()         options  are  described  below. Some of them (in particular, those that
1185       returns NULL, and sets the variable pointed to by errptr  to         are compatible with Perl, but some others as well) can also be set  and
1186       point  to a textual error message. The offset from the start         unset  from  within  the  pattern  (see the detailed description in the
1187       of  the  pattern  to  the  character  where  the  error  was         pcrepattern documentation). For those options that can be different  in
1188       discovered   is   placed  in  the  variable  pointed  to  by         different  parts  of  the pattern, the contents of the options argument
1189       erroffset, which must not be NULL. If it  is,  an  immediate         specifies their settings at the start of compilation and execution. The
1190       error is given.         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1191           PCRE_NO_START_OPT options can be set at the time of matching as well as
1192       If the final  argument,  tableptr,  is  NULL,  PCRE  uses  a         at compile time.
1193       default  set  of character tables which are built when it is  
1194       compiled, using the default C  locale.  Otherwise,  tableptr         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1195       must  be  the result of a call to pcre_maketables(). See the         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1196       section on locale support below.         sets the variable pointed to by errptr to point to a textual error mes-
1197           sage. This is a static string that is part of the library. You must not
1198       This code fragment shows a typical straightforward  call  to         try  to  free it. Normally, the offset from the start of the pattern to
1199       pcre_compile():         the byte that was being processed when  the  error  was  discovered  is
1200           placed  in the variable pointed to by erroffset, which must not be NULL
1201         pcre *re;         (if it is, an immediate error is given). However, for an invalid  UTF-8
1202         const char *error;         string,  the offset is that of the first byte of the failing character.
1203         int erroffset;         Also, some errors are not detected until checks are  carried  out  when
1204         re = pcre_compile(         the  whole  pattern  has been scanned; in these cases the offset passed
1205           "^A.*Z",          /* the pattern */         back is the length of the pattern.
1206           0,                /* default options */  
1207           &error,           /* for error message */         Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1208           &erroffset,       /* for error offset */         It may sometimes point into the middle of a UTF-8 character.
1209           NULL);            /* use default character tables */  
1210           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1211       The following option bits are defined:         codeptr argument is not NULL, a non-zero error code number is  returned
1212           via  this argument in the event of an error. This is in addition to the
1213         PCRE_ANCHORED         textual error message. Error codes and messages are listed below.
1214    
1215       If this bit is set, the pattern is forced to be  "anchored",         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1216       that is, it is constrained to match only at the first match-         character  tables  that  are  built  when  PCRE  is compiled, using the
1217       ing point in the string which is being searched  (the  "sub-         default C locale. Otherwise, tableptr must be an address  that  is  the
1218       ject string"). This effect can also be achieved by appropri-         result  of  a  call to pcre_maketables(). This value is stored with the
1219       ate constructs in the pattern itself, which is the only  way         compiled pattern, and used again by pcre_exec(), unless  another  table
1220       to do it in Perl.         pointer is passed to it. For more discussion, see the section on locale
1221           support below.
1222         PCRE_CASELESS  
1223           This code fragment shows a typical straightforward  call  to  pcre_com-
1224       If this bit is set, letters in the pattern match both  upper         pile():
1225       and  lower  case  letters.  It  is  equivalent  to Perl's /i  
1226       option, and it can be changed within a  pattern  by  a  (?i)           pcre *re;
1227       option setting.           const char *error;
1228             int erroffset;
1229         PCRE_DOLLAR_ENDONLY           re = pcre_compile(
1230               "^A.*Z",          /* the pattern */
1231       If this bit is set, a dollar metacharacter  in  the  pattern             0,                /* default options */
1232       matches  only at the end of the subject string. Without this             &error,           /* for error message */
1233       option, a dollar also matches immediately before  the  final             &erroffset,       /* for error offset */
1234       character  if it is a newline (but not before any other new-             NULL);            /* use default character tables */
1235       lines).  The  PCRE_DOLLAR_ENDONLY  option  is   ignored   if  
1236       PCRE_MULTILINE is set. There is no equivalent to this option         The  following  names  for option bits are defined in the pcre.h header
1237       in Perl, and no way to set it within a pattern.         file:
1238    
1239         PCRE_DOTALL           PCRE_ANCHORED
1240    
1241       If this bit is  set,  a  dot  metacharater  in  the  pattern         If this bit is set, the pattern is forced to be "anchored", that is, it
1242       matches all characters, including newlines. Without it, new-         is  constrained to match only at the first matching point in the string
1243       lines are excluded. This option is equivalent to  Perl's  /s         that is being searched (the "subject string"). This effect can also  be
1244       option,  and  it  can  be changed within a pattern by a (?s)         achieved  by appropriate constructs in the pattern itself, which is the
1245       option setting. A negative class such as [^a] always matches         only way to do it in Perl.
1246       a  newline  character,  independent  of  the setting of this  
1247       option.           PCRE_AUTO_CALLOUT
1248    
1249         PCRE_EXTENDED         If this bit is set, pcre_compile() automatically inserts callout items,
1250           all  with  number  255, before each pattern item. For discussion of the
1251       If this bit is set, whitespace data characters in  the  pat-         callout facility, see the pcrecallout documentation.
1252       tern  are  totally  ignored  except when escaped or inside a  
1253       character class. Whitespace does not include the VT  charac-           PCRE_BSR_ANYCRLF
1254       ter  (code 11). In addition, characters between an unescaped           PCRE_BSR_UNICODE
1255       # outside a character class and the next newline  character,  
1256       inclusive, are also ignored. This is equivalent to Perl's /x         These options (which are mutually exclusive) control what the \R escape
1257       option, and it can be changed within a  pattern  by  a  (?x)         sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1258       option setting.         or to match any Unicode newline sequence. The default is specified when
1259           PCRE is built. It can be overridden from within the pattern, or by set-
1260       This option makes it possible  to  include  comments  inside         ting an option when a compiled pattern is matched.
1261       complicated patterns.  Note, however, that this applies only  
1262       to data characters. Whitespace characters may  never  appear           PCRE_CASELESS
1263       within special character sequences in a pattern, for example  
1264       within the sequence (?( which introduces a conditional  sub-         If this bit is set, letters in the pattern match both upper  and  lower
1265       pattern.         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1266           changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1267         PCRE_EXTRA         always  understands the concept of case for characters whose values are
1268           less than 128, so caseless matching is always possible. For  characters
1269       This option was invented in  order  to  turn  on  additional         with  higher  values,  the concept of case is supported if PCRE is com-
1270       functionality of PCRE that is incompatible with Perl, but it         piled with Unicode property support, but not otherwise. If you want  to
1271       is currently of very little use. When set, any backslash  in         use  caseless  matching  for  characters 128 and above, you must ensure
1272       a  pattern  that is followed by a letter that has no special         that PCRE is compiled with Unicode property support  as  well  as  with
1273       meaning causes an error, thus reserving  these  combinations         UTF-8 support.
1274       for  future  expansion.  By default, as in Perl, a backslash  
1275       followed by a letter with no special meaning is treated as a           PCRE_DOLLAR_ENDONLY
1276       literal.  There  are at present no other features controlled  
1277       by this option. It can also be set by a (?X) option  setting         If  this bit is set, a dollar metacharacter in the pattern matches only
1278       within a pattern.         at the end of the subject string. Without this option,  a  dollar  also
1279           matches  immediately before a newline at the end of the string (but not
1280         PCRE_MULTILINE         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1281           if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1282       By default, PCRE treats the subject string as consisting  of         Perl, and no way to set it within a pattern.
1283       a  single "line" of characters (even if it actually contains  
1284       several newlines). The "start  of  line"  metacharacter  (^)           PCRE_DOTALL
1285       matches  only  at the start of the string, while the "end of  
1286       line" metacharacter ($) matches  only  at  the  end  of  the         If this bit is set, a dot metacharacter in the pattern matches a  char-
1287       string,    or   before   a   terminating   newline   (unless         acter of any value, including one that indicates a newline. However, it
1288       PCRE_DOLLAR_ENDONLY is set). This is the same as Perl.         only ever matches one character, even if newlines are  coded  as  CRLF.
1289           Without  this option, a dot does not match when the current position is
1290       When PCRE_MULTILINE it is set, the "start of line" and  "end         at a newline. This option is equivalent to Perl's /s option, and it can
1291       of  line"  constructs match immediately following or immedi-         be  changed within a pattern by a (?s) option setting. A negative class
1292       ately before any newline  in  the  subject  string,  respec-         such as [^a] always matches newline characters, independent of the set-
1293       tively,  as  well  as  at  the  very  start and end. This is         ting of this option.
1294       equivalent to Perl's /m option, and it can be changed within  
1295       a  pattern  by  a  (?m) option setting. If there are no "\n"           PCRE_DUPNAMES
1296       characters in a subject string, or no occurrences of ^ or  $  
1297       in a pattern, setting PCRE_MULTILINE has no effect.         If  this  bit is set, names used to identify capturing subpatterns need
1298           not be unique. This can be helpful for certain types of pattern when it
1299         PCRE_NO_AUTO_CAPTURE         is  known  that  only  one instance of the named subpattern can ever be
1300           matched. There are more details of named subpatterns  below;  see  also
1301       If this option is set, it disables the use of numbered  cap-         the pcrepattern documentation.
1302       turing  parentheses  in the pattern. Any opening parenthesis  
1303       that is not followed by ? behaves as if it were followed  by           PCRE_EXTENDED
1304       ?:  but  named  parentheses  can still be used for capturing  
1305       (and they acquire numbers in the usual  way).  There  is  no         If  this  bit  is  set,  whitespace  data characters in the pattern are
1306       equivalent of this option in Perl.         totally ignored except when escaped or inside a character class. White-
1307           space does not include the VT character (code 11). In addition, charac-
1308         PCRE_UNGREEDY         ters between an unescaped # outside a character class and the next new-
1309           line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1310       This option inverts the "greediness" of the  quantifiers  so         option, and it can be changed within a pattern by a  (?x)  option  set-
1311       that  they  are  not greedy by default, but become greedy if         ting.
1312       followed by "?". It is not compatible with Perl. It can also  
1313       be set by a (?U) option setting within the pattern.         Which  characters  are  interpreted  as  newlines  is controlled by the
1314           options passed to pcre_compile() or by a special sequence at the  start
1315         PCRE_UTF8         of  the  pattern, as described in the section entitled "Newline conven-
1316           tions" in the pcrepattern documentation. Note that the end of this type
1317       This option causes PCRE to regard both the pattern  and  the         of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1318       subject  as  strings  of UTF-8 characters instead of single-         sequences that happen to represent a newline do not count.
1319       byte character strings. However, it  is  available  only  if  
1320       PCRE  has  been  built to include UTF-8 support. If not, the         This option makes it possible to include  comments  inside  complicated
1321       use of this option provokes an error. Details  of  how  this         patterns.   Note,  however,  that this applies only to data characters.
1322       option  changes  the behaviour of PCRE are given in the sec-         Whitespace  characters  may  never  appear  within  special   character
1323       tion on UTF-8 support in the main pcre page.         sequences in a pattern, for example within the sequence (?( that intro-
1324           duces a conditional subpattern.
1325    
1326             PCRE_EXTRA
1327    
1328           This option was invented in order to turn on  additional  functionality
1329           of  PCRE  that  is  incompatible with Perl, but it is currently of very
1330           little use. When set, any backslash in a pattern that is followed by  a
1331           letter  that  has  no  special  meaning causes an error, thus reserving
1332           these combinations for future expansion. By  default,  as  in  Perl,  a
1333           backslash  followed by a letter with no special meaning is treated as a
1334           literal. (Perl can, however, be persuaded to give an error for this, by
1335           running  it with the -w option.) There are at present no other features
1336           controlled by this option. It can also be set by a (?X) option  setting
1337           within a pattern.
1338    
1339             PCRE_FIRSTLINE
1340    
1341           If  this  option  is  set,  an  unanchored pattern is required to match
1342           before or at the first  newline  in  the  subject  string,  though  the
1343           matched text may continue over the newline.
1344    
1345             PCRE_JAVASCRIPT_COMPAT
1346    
1347           If this option is set, PCRE's behaviour is changed in some ways so that
1348           it is compatible with JavaScript rather than Perl. The changes  are  as
1349           follows:
1350    
1351           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1352           error, because this is illegal in JavaScript (by default it is  treated
1353           as a data character). Thus, the pattern AB]CD becomes illegal when this
1354           option is set.
1355    
1356           (2) At run time, a back reference to an unset subpattern group  matches
1357           an  empty  string (by default this causes the current matching alterna-
1358           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1359           set  (assuming  it can find an "a" in the subject), whereas it fails by
1360           default, for Perl compatibility.
1361    
1362             PCRE_MULTILINE
1363    
1364           By default, PCRE treats the subject string as consisting  of  a  single
1365           line  of characters (even if it actually contains newlines). The "start
1366           of line" metacharacter (^) matches only at the  start  of  the  string,
1367           while  the  "end  of line" metacharacter ($) matches only at the end of
1368           the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1369           is set). This is the same as Perl.
1370    
1371           When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1372           constructs match immediately following or immediately  before  internal
1373           newlines  in  the  subject string, respectively, as well as at the very
1374           start and end. This is equivalent to Perl's /m option, and  it  can  be
1375           changed within a pattern by a (?m) option setting. If there are no new-
1376           lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1377           setting PCRE_MULTILINE has no effect.
1378    
1379             PCRE_NEWLINE_CR
1380             PCRE_NEWLINE_LF
1381             PCRE_NEWLINE_CRLF
1382             PCRE_NEWLINE_ANYCRLF
1383             PCRE_NEWLINE_ANY
1384    
1385           These  options  override the default newline definition that was chosen
1386           when PCRE was built. Setting the first or the second specifies  that  a
1387           newline  is  indicated  by a single character (CR or LF, respectively).
1388           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1389           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1390           that any of the three preceding sequences should be recognized. Setting
1391           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1392           recognized. The Unicode newline sequences are the three just mentioned,
1393           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1394           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1395           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1396           UTF-8 mode.
1397    
1398           The newline setting in the  options  word  uses  three  bits  that  are
1399           treated as a number, giving eight possibilities. Currently only six are
1400           used (default plus the five values above). This means that if  you  set
1401           more  than one newline option, the combination may or may not be sensi-
1402           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1403           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1404           cause an error.
1405    
1406           The only time that a line break in a pattern  is  specially  recognized
1407           when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1408           characters, and so are ignored in this mode. Also, an unescaped #  out-
1409           side  a  character class indicates a comment that lasts until after the
1410           next line break sequence. In other circumstances, line break  sequences
1411           in patterns are treated as literal data.
1412    
1413           The newline option that is set at compile time becomes the default that
1414           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1415    
1416             PCRE_NO_AUTO_CAPTURE
1417    
1418           If this option is set, it disables the use of numbered capturing paren-
1419           theses  in the pattern. Any opening parenthesis that is not followed by
1420           ? behaves as if it were followed by ?: but named parentheses can  still
1421           be  used  for  capturing  (and  they acquire numbers in the usual way).
1422           There is no equivalent of this option in Perl.
1423    
1424             NO_START_OPTIMIZE
1425    
1426           This is an option that acts at matching time; that is, it is really  an
1427           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1428           time, it is remembered with the compiled pattern and assumed at  match-
1429           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1430           below.
1431    
1432             PCRE_UCP
1433    
1434           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1435           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1436           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1437           are  used instead to classify characters. More details are given in the
1438           section on generic character types in the pcrepattern page. If you  set
1439           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1440           option is available only if PCRE has been compiled with  Unicode  prop-
1441           erty support.
1442    
1443             PCRE_UNGREEDY
1444    
1445           This  option  inverts  the "greediness" of the quantifiers so that they
1446           are not greedy by default, but become greedy if followed by "?". It  is
1447           not  compatible  with Perl. It can also be set by a (?U) option setting
1448           within the pattern.
1449    
1450             PCRE_UTF8
1451    
1452           This option causes PCRE to regard both the pattern and the  subject  as
1453           strings  of  UTF-8 characters instead of single-byte character strings.
1454           However, it is available only when PCRE is built to include UTF-8  sup-
1455           port.  If not, the use of this option provokes an error. Details of how
1456           this option changes the behaviour of PCRE are given in the  section  on
1457           UTF-8 support in the main pcre page.
1458    
1459             PCRE_NO_UTF8_CHECK
1460    
1461           When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1462           automatically checked. There is a  discussion  about  the  validity  of
1463           UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1464           bytes is found, pcre_compile() returns an error. If  you  already  know
1465           that your pattern is valid, and you want to skip this check for perfor-
1466           mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1467           set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1468           undefined. It may cause your program to crash. Note  that  this  option
1469           can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1470           UTF-8 validity checking of subject strings.
1471    
1472    
1473    COMPILATION ERROR CODES
1474    
1475           The following table lists the error  codes  than  may  be  returned  by
1476           pcre_compile2(),  along with the error messages that may be returned by
1477           both compiling functions. As PCRE has developed, some error codes  have
1478           fallen out of use. To avoid confusion, they have not been re-used.
1479    
1480              0  no error
1481              1  \ at end of pattern
1482              2  \c at end of pattern
1483              3  unrecognized character follows \
1484              4  numbers out of order in {} quantifier
1485              5  number too big in {} quantifier
1486              6  missing terminating ] for character class
1487              7  invalid escape sequence in character class
1488              8  range out of order in character class
1489              9  nothing to repeat
1490             10  [this code is not in use]
1491             11  internal error: unexpected repeat
1492             12  unrecognized character after (? or (?-
1493             13  POSIX named classes are supported only within a class
1494             14  missing )
1495             15  reference to non-existent subpattern
1496             16  erroffset passed as NULL
1497             17  unknown option bit(s) set
1498             18  missing ) after comment
1499             19  [this code is not in use]
1500             20  regular expression is too large
1501             21  failed to get memory
1502             22  unmatched parentheses
1503             23  internal error: code overflow
1504             24  unrecognized character after (?<
1505             25  lookbehind assertion is not fixed length
1506             26  malformed number or name after (?(
1507             27  conditional group contains more than two branches
1508             28  assertion expected after (?(
1509             29  (?R or (?[+-]digits must be followed by )
1510             30  unknown POSIX class name
1511             31  POSIX collating elements are not supported
1512             32  this version of PCRE is not compiled with PCRE_UTF8 support
1513             33  [this code is not in use]
1514             34  character value in \x{...} sequence is too large
1515             35  invalid condition (?(0)
1516             36  \C not allowed in lookbehind assertion
1517             37  PCRE does not support \L, \l, \N{name}, \U, or \u
1518             38  number after (?C is > 255
1519             39  closing ) for (?C expected
1520             40  recursive call could loop indefinitely
1521             41  unrecognized character after (?P
1522             42  syntax error in subpattern name (missing terminator)
1523             43  two named subpatterns have the same name
1524             44  invalid UTF-8 string
1525             45  support for \P, \p, and \X has not been compiled
1526             46  malformed \P or \p sequence
1527             47  unknown property name after \P or \p
1528             48  subpattern name is too long (maximum 32 characters)
1529             49  too many named subpatterns (maximum 10000)
1530             50  [this code is not in use]
1531             51  octal value is greater than \377 (not in UTF-8 mode)
1532             52  internal error: overran compiling workspace
1533             53  internal error: previously-checked referenced subpattern
1534                   not found
1535             54  DEFINE group contains more than one branch
1536             55  repeating a DEFINE group is not allowed
1537             56  inconsistent NEWLINE options
1538             57  \g is not followed by a braced, angle-bracketed, or quoted
1539                   name/number or by a plain number
1540             58  a numbered reference must not be zero
1541             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1542             60  (*VERB) not recognized
1543             61  number is too big
1544             62  subpattern name expected
1545             63  digit expected after (?+
1546             64  ] is an invalid data character in JavaScript compatibility mode
1547             65  different names for subpatterns of the same number are
1548                   not allowed
1549             66  (*MARK) must have an argument
1550             67  this version of PCRE is not compiled with PCRE_UCP support
1551             68  \c must be followed by an ASCII character
1552             69  \k is not followed by a braced, angle-bracketed, or quoted name
1553    
1554           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1555           values may be used if the limits were changed when PCRE was built.
1556    
1557    
1558  STUDYING A PATTERN  STUDYING A PATTERN
1559    
1560       pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1561            const char **errptr);              const char **errptr);
1562    
1563       When a pattern is going to be  used  several  times,  it  is         If a compiled pattern is going to be used several times,  it  is  worth
1564       worth  spending  more time analyzing it in order to speed up         spending more time analyzing it in order to speed up the time taken for
1565       the time taken for matching. The function pcre_study() takes         matching. The function pcre_study() takes a pointer to a compiled  pat-
1566       a  pointer  to  a compiled pattern as its first argument. If         tern as its first argument. If studying the pattern produces additional
1567       studing the pattern  produces  additional  information  that         information that will help speed up matching,  pcre_study()  returns  a
1568       will  help speed up matching, pcre_study() returns a pointer         pointer  to a pcre_extra block, in which the study_data field points to
1569       to a pcre_extra block, in which the study_data field  points         the results of the study.
1570       to the results of the study.  
1571           The  returned  value  from  pcre_study()  can  be  passed  directly  to
1572       The  returned  value  from  a  pcre_study()  can  be  passed         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1573       directly  to pcre_exec(). However, the pcre_extra block also         tains other fields that can be set by the caller before  the  block  is
1574       contains other fields that can be set by the  caller  before         passed; these are described below in the section on matching a pattern.
1575       the  block is passed; these are described below. If studying  
1576       the pattern does not  produce  any  additional  information,         If  studying  the  pattern  does  not  produce  any useful information,
1577       pcre_study() returns NULL. In that circumstance, if the cal-         pcre_study() returns NULL. In that circumstance, if the calling program
1578       ling program wants to pass  some  of  the  other  fields  to         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1579       pcre_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1580    
1581       The second argument contains option  bits.  At  present,  no         The second argument of pcre_study() contains option bits.  At  present,
1582       options  are  defined  for  pcre_study(),  and this argument         no options are defined, and this argument should always be zero.
1583       should always be zero.  
1584           The  third argument for pcre_study() is a pointer for an error message.
1585       The third argument for pcre_study()  is  a  pointer  for  an         If studying succeeds (even if no data is  returned),  the  variable  it
1586       error  message.  If  studying  succeeds  (even if no data is         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1587       returned), the variable it points to is set to NULL.  Other-         error message. This is a static string that is part of the library. You
1588       wise it points to a textual error message. You should there-         must  not  try  to  free it. You should test the error pointer for NULL
1589       fore  test  the  error  pointer  for  NULL   after   calling         after calling pcre_study(), to be sure that it has run successfully.
1590       pcre_study(), to be sure that it has run successfully.  
1591           This is a typical call to pcre_study():
1592       This is a typical call to pcre_study():  
1593             pcre_extra *pe;
1594         pcre_extra *pe;           pe = pcre_study(
1595         pe = pcre_study(             re,             /* result of pcre_compile() */
1596           re,             /* result of pcre_compile() */             0,              /* no options exist */
1597           0,              /* no options exist */             &error);        /* set to NULL or points to a message */
1598           &error);        /* set to NULL or points to a message */  
1599           Studying a pattern does two things: first, a lower bound for the length
1600       At present, studying a  pattern  is  useful  only  for  non-         of subject string that is needed to match the pattern is computed. This
1601       anchored  patterns  that do not have a single fixed starting         does not mean that there are any strings of that length that match, but
1602       character. A  bitmap  of  possible  starting  characters  is         it  does  guarantee that no shorter strings match. The value is used by
1603       created.         pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1604           match  strings  that are shorter than the lower bound. You can find out
1605           the value in a calling program via the pcre_fullinfo() function.
1606    
1607           Studying a pattern is also useful for non-anchored patterns that do not
1608           have  a  single fixed starting character. A bitmap of possible starting
1609           bytes is created. This speeds up finding a position in the  subject  at
1610           which to start matching.
1611    
1612           The  two  optimizations  just  described can be disabled by setting the
1613           PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1614           pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1615           callouts or (*MARK), and you want to make use of  these  facilities  in
1616           cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1617           MIZE below.
1618    
1619    
1620  LOCALE SUPPORT  LOCALE SUPPORT
1621    
1622       PCRE handles caseless matching, and determines whether char-         PCRE handles caseless matching, and determines whether  characters  are
1623       acters  are  letters, digits, or whatever, by reference to a         letters,  digits, or whatever, by reference to a set of tables, indexed
1624       set of tables. When running in UTF-8 mode, this applies only         by character value. When running in UTF-8 mode, this  applies  only  to
1625       to characters with codes less than 256. The library contains         characters  with  codes  less than 128. By default, higher-valued codes
1626       a default set of tables that is created  in  the  default  C         never match escapes such as \w or \d, but they can be tested with \p if
1627       locale  when  PCRE  is compiled. This is used when the final         PCRE  is  built with Unicode character property support. Alternatively,
1628       argument of pcre_compile() is NULL, and  is  sufficient  for         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1629       many applications.         friends to use Unicode property support instead of built-in tables. The
1630           use of locales with Unicode is discouraged. If you are handling charac-
1631       An alternative set of tables can, however, be supplied. Such         ters  with codes greater than 128, you should either use UTF-8 and Uni-
1632       tables  are built by calling the pcre_maketables() function,         code, or use locales, but not try to mix the two.
1633       which has no arguments, in the relevant locale.  The  result  
1634       can  then be passed to pcre_compile() as often as necessary.         PCRE contains an internal set of tables that are used  when  the  final
1635       For example, to build and use tables  that  are  appropriate         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1636       for  the French locale (where accented characters with codes         applications.  Normally, the internal tables recognize only ASCII char-
1637       greater than 128 are treated as letters), the following code         acters. However, when PCRE is built, it is possible to cause the inter-
1638       could be used:         nal tables to be rebuilt in the default "C" locale of the local system,
1639           which may cause them to be different.
1640         setlocale(LC_CTYPE, "fr");  
1641         tables = pcre_maketables();         The  internal tables can always be overridden by tables supplied by the
1642         re = pcre_compile(..., tables);         application that calls PCRE. These may be created in a different locale
1643           from  the  default.  As more and more applications change to using Uni-
1644       The  tables  are  built  in  memory  that  is  obtained  via         code, the need for this locale support is expected to die away.
1645       pcre_malloc.  The  pointer that is passed to pcre_compile is  
1646       saved with the compiled pattern, and  the  same  tables  are         External tables are built by calling  the  pcre_maketables()  function,
1647       used via this pointer by pcre_study() and pcre_exec(). Thus,         which  has no arguments, in the relevant locale. The result can then be
1648       for any single pattern, compilation, studying  and  matching         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1649       all happen in the same locale, but different patterns can be         example,  to  build  and use tables that are appropriate for the French
1650       compiled in different locales. It is the caller's  responsi-         locale (where accented characters with  values  greater  than  128  are
1651       bility  to  ensure  that  the  memory  containing the tables         treated as letters), the following code could be used:
1652       remains available for as long as it is needed.  
1653             setlocale(LC_CTYPE, "fr_FR");
1654             tables = pcre_maketables();
1655             re = pcre_compile(..., tables);
1656    
1657           The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1658           if you are using Windows, the name for the French locale is "french".
1659    
1660           When pcre_maketables() runs, the tables are built  in  memory  that  is
1661           obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1662           that the memory containing the tables remains available for as long  as
1663           it is needed.
1664    
1665           The pointer that is passed to pcre_compile() is saved with the compiled
1666           pattern, and the same tables are used via this pointer by  pcre_study()
1667           and normally also by pcre_exec(). Thus, by default, for any single pat-
1668           tern, compilation, studying and matching all happen in the same locale,
1669           but different patterns can be compiled in different locales.
1670    
1671           It  is  possible to pass a table pointer or NULL (indicating the use of
1672           the internal tables) to pcre_exec(). Although  not  intended  for  this
1673           purpose,  this facility could be used to match a pattern in a different
1674           locale from the one in which it was compiled. Passing table pointers at
1675           run time is discussed below in the section on matching a pattern.
1676    
1677    
1678  INFORMATION ABOUT A PATTERN  INFORMATION ABOUT A PATTERN
1679    
1680       int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1681            int what, void *where);              int what, void *where);
1682    
1683       The pcre_fullinfo() function  returns  information  about  a         The  pcre_fullinfo() function returns information about a compiled pat-
1684       compiled pattern. It replaces the obsolete pcre_info() func-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1685       tion, which is nevertheless retained for backwards compabil-         less retained for backwards compability (and is documented below).
1686       ity (and is documented below).  
1687           The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1688       The first argument for pcre_fullinfo() is a pointer  to  the         pattern. The second argument is the result of pcre_study(), or NULL  if
1689       compiled  pattern.  The  second  argument  is  the result of         the  pattern  was not studied. The third argument specifies which piece
1690       pcre_study(), or NULL if the pattern was  not  studied.  The         of information is required, and the fourth argument is a pointer  to  a
1691       third  argument  specifies  which  piece  of  information is         variable  to  receive  the  data. The yield of the function is zero for
1692       required, and the fourth argument is a pointer to a variable         success, or one of the following negative numbers:
1693       to  receive  the data. The yield of the function is zero for  
1694       success, or one of the following negative numbers:           PCRE_ERROR_NULL       the argument code was NULL
1695                                   the argument where was NULL
1696         PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1697                               the argument where was NULL           PCRE_ERROR_BADOPTION  the value of what was invalid
1698         PCRE_ERROR_BADMAGIC   the "magic number" was not found  
1699         PCRE_ERROR_BADOPTION  the value of what was invalid         The "magic number" is placed at the start of each compiled  pattern  as
1700           an  simple check against passing an arbitrary memory pointer. Here is a
1701       Here is a typical call of  pcre_fullinfo(),  to  obtain  the         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1702       length of the compiled pattern:         pattern:
1703    
1704         int rc;           int rc;
1705         unsigned long int length;           size_t length;
1706         rc = pcre_fullinfo(           rc = pcre_fullinfo(
1707           re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1708           pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1709           PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1710           &length);         /* where to put the data */             &length);         /* where to put the data */
1711    
1712       The possible values for the third argument  are  defined  in         The  possible  values for the third argument are defined in pcre.h, and
1713       pcre.h, and are as follows:         are as follows:
1714    
1715         PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1716    
1717       Return the number of the highest back reference in the  pat-         Return the number of the highest back reference  in  the  pattern.  The
1718       tern.  The  fourth argument should point to an int variable.         fourth  argument  should  point to an int variable. Zero is returned if
1719       Zero is returned if there are no back references.         there are no back references.
1720    
1721         PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1722    
1723       Return the number of capturing subpatterns in  the  pattern.         Return the number of capturing subpatterns in the pattern.  The  fourth
1724       The fourth argument should point to an int variable.         argument should point to an int variable.
1725    
1726         PCRE_INFO_FIRSTBYTE           PCRE_INFO_DEFAULT_TABLES
1727    
1728       Return information about  the  first  byte  of  any  matched         Return  a pointer to the internal default character tables within PCRE.
1729       string,  for a non-anchored pattern. (This option used to be         The fourth argument should point to an unsigned char *  variable.  This
1730       called PCRE_INFO_FIRSTCHAR; the old name is still recognized         information call is provided for internal use by the pcre_study() func-
1731       for backwards compatibility.)         tion. External callers can cause PCRE to use  its  internal  tables  by
1732           passing a NULL table pointer.
1733       If there is a fixed first byte, e.g. from a pattern such  as  
1734       (cat|cow|coyote),  it  is returned in the integer pointed to           PCRE_INFO_FIRSTBYTE
1735       by where. Otherwise, if either  
1736           Return  information  about  the first byte of any matched string, for a
1737       (a) the pattern was compiled with the PCRE_MULTILINE option,         non-anchored pattern. The fourth argument should point to an int  vari-
1738       and every branch starts with "^", or         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1739           is still recognized for backwards compatibility.)
1740       (b) every  branch  of  the  pattern  starts  with  ".*"  and  
1741       PCRE_DOTALL is not set (if it were set, the pattern would be         If there is a fixed first byte, for example, from  a  pattern  such  as
1742       anchored),         (cat|cow|coyote), its value is returned. Otherwise, if either
1743    
1744       -1 is returned, indicating that the pattern matches only  at         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1745       the  start  of  a subject string or after any newline within         branch starts with "^", or
1746       the string. Otherwise -2 is returned. For anchored patterns,  
1747       -2 is returned.         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1748           set (if it were set, the pattern would be anchored),
1749         PCRE_INFO_FIRSTTABLE  
1750           -1  is  returned, indicating that the pattern matches only at the start
1751       If the pattern was studied, and this resulted  in  the  con-         of a subject string or after any newline within the  string.  Otherwise
1752       struction of a 256-bit table indicating a fixed set of bytes         -2 is returned. For anchored patterns, -2 is returned.
1753       for the first byte in any matching string, a pointer to  the  
1754       table  is  returned.  Otherwise NULL is returned. The fourth           PCRE_INFO_FIRSTTABLE
1755       argument should point to an unsigned char * variable.  
1756           If  the pattern was studied, and this resulted in the construction of a
1757         PCRE_INFO_LASTLITERAL         256-bit table indicating a fixed set of bytes for the first byte in any
1758           matching  string, a pointer to the table is returned. Otherwise NULL is
1759       Return the value of the rightmost  literal  byte  that  must         returned. The fourth argument should point to an unsigned char *  vari-
1760       exist  in  any  matched  string, other than at its start, if         able.
1761       such a byte has been recorded. The  fourth  argument  should  
1762       point  to  an  int variable. If there is no such byte, -1 is           PCRE_INFO_HASCRORLF
1763       returned. For anchored patterns,  a  last  literal  byte  is  
1764       recorded  only  if  it follows something of variable length.         Return  1  if  the  pattern  contains any explicit matches for CR or LF
1765       For example, for the pattern /^a\d+z\d+/ the returned  value         characters, otherwise 0. The fourth argument should  point  to  an  int
1766       is "z", but for /^a\dz\d/ the returned value is -1.         variable.  An explicit match is either a literal CR or LF character, or
1767           \r or \n.
1768         PCRE_INFO_NAMECOUNT  
1769         PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_JCHANGED
1770         PCRE_INFO_NAMETABLE  
1771           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1772       PCRE supports the use of named as well as numbered capturing         otherwise  0. The fourth argument should point to an int variable. (?J)
1773       parentheses. The names are just an additional way of identi-         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1774       fying the parentheses,  which  still  acquire  a  number.  A  
1775       caller  that  wants  to extract data from a named subpattern           PCRE_INFO_LASTLITERAL
1776       must convert the name to a number in  order  to  access  the  
1777       correct  pointers  in  the  output  vector  (described  with         Return the value of the rightmost literal byte that must exist  in  any
1778       pcre_exec() below). In order to do this, it must  first  use         matched  string,  other  than  at  its  start,  if such a byte has been
1779       these  three  values  to  obtain  the name-to-number mapping         recorded. The fourth argument should point to an int variable. If there
1780       table for the pattern.         is  no such byte, -1 is returned. For anchored patterns, a last literal
1781           byte is recorded only if it follows something of variable  length.  For
1782       The  map  consists  of  a  number  of  fixed-size   entries.         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1783       PCRE_INFO_NAMECOUNT   gives   the  number  of  entries,  and         /^a\dz\d/ the returned value is -1.
1784       PCRE_INFO_NAMEENTRYSIZE gives the size of each  entry;  both  
1785       of  these return an int value. The entry size depends on the           PCRE_INFO_MINLENGTH
1786       length of the longest name.  PCRE_INFO_NAMETABLE  returns  a  
1787       pointer to the first entry of the table (a pointer to char).         If the pattern was studied and a minimum length  for  matching  subject
1788       The first two bytes of each entry are the number of the cap-         strings  was  computed,  its  value is returned. Otherwise the returned
1789       turing parenthesis, most significant byte first. The rest of         value is -1. The value is a number of characters, not bytes  (this  may
1790       the entry is the corresponding name,  zero  terminated.  The         be  relevant in UTF-8 mode). The fourth argument should point to an int
1791       names  are  in alphabetical order. For example, consider the         variable. A non-negative value is a lower bound to the  length  of  any
1792       following pattern (assume PCRE_EXTENDED  is  set,  so  white         matching  string.  There  may not be any strings of that length that do
1793       space - including newlines - is ignored):         actually match, but every string that does match is at least that long.
1794    
1795         (?P<date> (?P<year>(\d\d)?\d\d) -           PCRE_INFO_NAMECOUNT
1796         (?P<month>\d\d) - (?P<day>\d\d) )           PCRE_INFO_NAMEENTRYSIZE
1797             PCRE_INFO_NAMETABLE
1798       There are four named subpatterns,  so  the  table  has  four  
1799       entries,  and  each  entry in the table is eight bytes long.         PCRE supports the use of named as well as numbered capturing  parenthe-
1800       The table is as follows, with non-printing  bytes  shows  in         ses.  The names are just an additional way of identifying the parenthe-
1801       hex, and undefined bytes shown as ??:         ses, which still acquire numbers. Several convenience functions such as
1802           pcre_get_named_substring()  are  provided  for extracting captured sub-
1803         00 01 d  a  t  e  00 ??         strings by name. It is also possible to extract the data  directly,  by
1804         00 05 d  a  y  00 ?? ??         first  converting  the  name to a number in order to access the correct
1805         00 04 m  o  n  t  h  00         pointers in the output vector (described with pcre_exec() below). To do
1806         00 02 y  e  a  r  00 ??         the  conversion,  you  need  to  use  the  name-to-number map, which is
1807           described by these three values.
1808       When writing code to extract data  from  named  subpatterns,  
1809       remember  that the length of each entry may be different for         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1810       each compiled pattern.         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1811           of each entry; both of these  return  an  int  value.  The  entry  size
1812         PCRE_INFO_OPTIONS         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1813           a pointer to the first entry of the table  (a  pointer  to  char).  The
1814       Return a copy of the options with which the pattern was com-         first two bytes of each entry are the number of the capturing parenthe-
1815       piled.  The fourth argument should point to an unsigned long         sis, most significant byte first. The rest of the entry is  the  corre-
1816       int variable. These option bits are those specified  in  the         sponding name, zero terminated.
1817       call  to  pcre_compile(),  modified  by any top-level option  
1818       settings within the pattern itself.         The  names are in alphabetical order. Duplicate names may appear if (?|
1819           is used to create multiple groups with the same number, as described in
1820       A pattern is automatically anchored by PCRE if  all  of  its         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1821       top-level alternatives begin with one of the following:         Duplicate names for subpatterns with different  numbers  are  permitted
1822           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1823         ^     unless PCRE_MULTILINE is set         appear in the table in the order in which they were found in  the  pat-
1824         \A    always         tern.  In  the  absence  of (?| this is the order of increasing number;
1825         \G    always         when (?| is used this is not necessarily the case because later subpat-
1826         .*    if PCRE_DOTALL is set and there are no back         terns may have lower numbers.
1827                 references to the subpattern in which .* appears  
1828           As  a  simple  example of the name/number table, consider the following
1829       For such patterns, the  PCRE_ANCHORED  bit  is  set  in  the         pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1830       options returned by pcre_fullinfo().         lines - is ignored):
1831    
1832         PCRE_INFO_SIZE           (?<date> (?<year>(\d\d)?\d\d) -
1833             (?<month>\d\d) - (?<day>\d\d) )
1834       Return the size of the compiled pattern, that is, the  value  
1835       that  was  passed as the argument to pcre_malloc() when PCRE         There  are  four  named subpatterns, so the table has four entries, and
1836       was getting memory in which to place the compiled data.  The         each entry in the table is eight bytes long. The table is  as  follows,
1837       fourth argument should point to a size_t variable.         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1838           as ??:
1839         PCRE_INFO_STUDYSIZE  
1840             00 01 d  a  t  e  00 ??
1841       Returns the size  of  the  data  block  pointed  to  by  the           00 05 d  a  y  00 ?? ??
1842       study_data  field  in a pcre_extra block. That is, it is the           00 04 m  o  n  t  h  00
1843       value that was passed to pcre_malloc() when PCRE was getting           00 02 y  e  a  r  00 ??
1844       memory into which to place the data created by pcre_study().  
1845       The fourth argument should point to a size_t variable.         When writing code to extract data  from  named  subpatterns  using  the
1846           name-to-number  map,  remember that the length of the entries is likely
1847           to be different for each compiled pattern.
1848    
1849             PCRE_INFO_OKPARTIAL
1850    
1851           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1852           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1853           variable. From  release  8.00,  this  always  returns  1,  because  the
1854           restrictions  that  previously  applied  to  partial matching have been
1855           lifted. The pcrepartial documentation gives details of  partial  match-
1856           ing.
1857    
1858             PCRE_INFO_OPTIONS
1859    
1860           Return  a  copy of the options with which the pattern was compiled. The
1861           fourth argument should point to an unsigned long  int  variable.  These
1862           option bits are those specified in the call to pcre_compile(), modified
1863           by any top-level option settings at the start of the pattern itself. In
1864           other  words,  they are the options that will be in force when matching
1865           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1866           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1867           and PCRE_EXTENDED.
1868    
1869           A pattern is automatically anchored by PCRE if  all  of  its  top-level
1870           alternatives begin with one of the following:
1871    
1872             ^     unless PCRE_MULTILINE is set
1873             \A    always
1874             \G    always
1875             .*    if PCRE_DOTALL is set and there are no back
1876                     references to the subpattern in which .* appears
1877    
1878           For such patterns, the PCRE_ANCHORED bit is set in the options returned
1879           by pcre_fullinfo().
1880    
1881             PCRE_INFO_SIZE
1882    
1883           Return the size of the compiled pattern, that is, the  value  that  was
1884           passed as the argument to pcre_malloc() when PCRE was getting memory in
1885           which to place the compiled data. The fourth argument should point to a
1886           size_t variable.
1887    
1888             PCRE_INFO_STUDYSIZE
1889    
1890           Return the size of the data block pointed to by the study_data field in
1891           a pcre_extra block. If pcre_extra is NULL, or there is no  study  data,
1892           zero  is  returned.  The fourth argument should point to a size_t vari-
1893           able.  The study_data field is set by pcre_study() to  record  informa-
1894           tion  that will speed up matching (see the section entitled "Studying a
1895           pattern" above). The format of the study_data block is private, but its
1896           length  is  made  available via this option so that it can be saved and
1897           restored (see the pcreprecompile documentation for details).
1898    
1899    
1900  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
1901    
1902       int pcre_info(const pcre *code, int *optptr, *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1903    
1904       The pcre_info() function is now obsolete because its  inter-         The pcre_info() function is now obsolete because its interface  is  too
1905       face  is  too  restrictive  to return all the available data         restrictive  to return all the available data about a compiled pattern.
1906       about  a  compiled  pattern.   New   programs   should   use         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1907       pcre_fullinfo()  instead.  The  yield  of pcre_info() is the         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1908       number of capturing subpatterns, or  one  of  the  following         lowing negative numbers:
1909       negative numbers:  
1910             PCRE_ERROR_NULL       the argument code was NULL
1911         PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1912         PCRE_ERROR_BADMAGIC   the "magic number" was not found  
1913           If the optptr argument is not NULL, a copy of the  options  with  which
1914       If the optptr argument is not NULL, a copy  of  the  options         the  pattern  was  compiled  is placed in the integer it points to (see
1915       with which the pattern was compiled is placed in the integer         PCRE_INFO_OPTIONS above).
1916       it points to (see PCRE_INFO_OPTIONS above).  
1917           If the pattern is not anchored and the  firstcharptr  argument  is  not
1918       If the pattern is not anchored and the firstcharptr argument         NULL,  it is used to pass back information about the first character of
1919       is  not  NULL, it is used to pass back information about the         any matched string (see PCRE_INFO_FIRSTBYTE above).
1920       first    character    of    any    matched    string    (see  
1921       PCRE_INFO_FIRSTBYTE above).  
1922    REFERENCE COUNTS
1923    
1924           int pcre_refcount(pcre *code, int adjust);
1925    
1926           The pcre_refcount() function is used to maintain a reference  count  in
1927           the data block that contains a compiled pattern. It is provided for the
1928           benefit of applications that  operate  in  an  object-oriented  manner,
1929           where different parts of the application may be using the same compiled
1930           pattern, but you want to free the block when they are all done.
1931    
1932           When a pattern is compiled, the reference count field is initialized to
1933           zero.   It is changed only by calling this function, whose action is to
1934           add the adjust value (which may be positive or  negative)  to  it.  The
1935           yield of the function is the new value. However, the value of the count
1936           is constrained to lie between 0 and 65535, inclusive. If the new  value
1937           is outside these limits, it is forced to the appropriate limit value.
1938    
1939           Except  when it is zero, the reference count is not correctly preserved
1940           if a pattern is compiled on one host and then  transferred  to  a  host
1941           whose byte-order is different. (This seems a highly unlikely scenario.)
1942    
1943    
1944    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1945    
1946           int pcre_exec(const pcre *code, const pcre_extra *extra,
1947                const char *subject, int length, int startoffset,
1948                int options, int *ovector, int ovecsize);
1949    
1950           The  function pcre_exec() is called to match a subject string against a
1951           compiled pattern, which is passed in the code argument. If the  pattern
1952           was  studied,  the  result  of  the study should be passed in the extra
1953           argument. This function is the main matching facility of  the  library,
1954           and it operates in a Perl-like manner. For specialist use there is also
1955           an alternative matching function, which is described below in the  sec-
1956           tion about the pcre_dfa_exec() function.
1957    
1958           In  most applications, the pattern will have been compiled (and option-
1959           ally studied) in the same process that calls pcre_exec().  However,  it
1960           is possible to save compiled patterns and study data, and then use them
1961           later in different processes, possibly even on different hosts.  For  a
1962           discussion about this, see the pcreprecompile documentation.
1963    
1964           Here is an example of a simple call to pcre_exec():
1965    
1966             int rc;
1967             int ovector[30];
1968             rc = pcre_exec(
1969               re,             /* result of pcre_compile() */
1970               NULL,           /* we didn't study the pattern */
1971               "some string",  /* the subject string */
1972               11,             /* the length of the subject string */
1973               0,              /* start at offset 0 in the subject */
1974               0,              /* default options */
1975               ovector,        /* vector of integers for substring information */
1976               30);            /* number of elements (NOT size in bytes) */
1977    
1978       Extra data for pcre_exec()
1979    
1980           If  the  extra argument is not NULL, it must point to a pcre_extra data
1981           block. The pcre_study() function returns such a block (when it  doesn't
1982           return  NULL), but you can also create one for yourself, and pass addi-
1983           tional information in it. The pcre_extra block contains  the  following
1984           fields (not necessarily in this order):
1985    
1986             unsigned long int flags;
1987             void *study_data;
1988             unsigned long int match_limit;
1989             unsigned long int match_limit_recursion;
1990             void *callout_data;
1991             const unsigned char *tables;
1992             unsigned char **mark;
1993    
1994           The  flags  field  is a bitmap that specifies which of the other fields
1995           are set. The flag bits are:
1996    
1997             PCRE_EXTRA_STUDY_DATA
1998             PCRE_EXTRA_MATCH_LIMIT
1999             PCRE_EXTRA_MATCH_LIMIT_RECURSION
2000             PCRE_EXTRA_CALLOUT_DATA
2001             PCRE_EXTRA_TABLES
2002             PCRE_EXTRA_MARK
2003    
2004           Other flag bits should be set to zero. The study_data field is  set  in
2005           the  pcre_extra  block  that is returned by pcre_study(), together with
2006           the appropriate flag bit. You should not set this yourself, but you may
2007           add  to  the  block by setting the other fields and their corresponding
2008           flag bits.
2009    
2010           The match_limit field provides a means of preventing PCRE from using up
2011           a  vast amount of resources when running patterns that are not going to
2012           match, but which have a very large number  of  possibilities  in  their
2013           search  trees. The classic example is a pattern that uses nested unlim-
2014           ited repeats.
2015    
2016           Internally, PCRE uses a function called match() which it calls  repeat-
2017           edly  (sometimes  recursively). The limit set by match_limit is imposed
2018           on the number of times this function is called during  a  match,  which
2019           has  the  effect  of  limiting the amount of backtracking that can take
2020           place. For patterns that are not anchored, the count restarts from zero
2021           for each position in the subject string.
2022    
2023           The  default  value  for  the  limit can be set when PCRE is built; the
2024           default default is 10 million, which handles all but the  most  extreme
2025           cases.  You  can  override  the  default by suppling pcre_exec() with a
2026           pcre_extra    block    in    which    match_limit    is    set,     and
2027           PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
2028           exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2029    
2030           The match_limit_recursion field is similar to match_limit, but  instead
2031           of limiting the total number of times that match() is called, it limits
2032           the depth of recursion. The recursion depth is a  smaller  number  than
2033           the  total number of calls, because not all calls to match() are recur-
2034           sive.  This limit is of use only if it is set smaller than match_limit.
2035    
2036           Limiting the recursion depth limits the amount of  stack  that  can  be
2037           used, or, when PCRE has been compiled to use memory on the heap instead
2038           of the stack, the amount of heap memory that can be used.
2039    
2040           The default value for match_limit_recursion can be  set  when  PCRE  is
2041           built;  the  default  default  is  the  same  value  as the default for
2042           match_limit. You can override the default by suppling pcre_exec()  with
2043           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2044           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2045           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2046    
2047           The  callout_data  field is used in conjunction with the "callout" fea-
2048           ture, and is described in the pcrecallout documentation.
2049    
2050           The tables field  is  used  to  pass  a  character  tables  pointer  to
2051           pcre_exec();  this overrides the value that is stored with the compiled
2052           pattern. A non-NULL value is stored with the compiled pattern  only  if
2053           custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2054           ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2055           PCRE's  internal  tables  to be used. This facility is helpful when re-
2056           using patterns that have been saved after compiling  with  an  external
2057           set  of  tables,  because  the  external tables might be at a different
2058           address when pcre_exec() is called. See the  pcreprecompile  documenta-
2059           tion for a discussion of saving compiled patterns for later use.
2060    
2061           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2062           set to point to a char * variable. If the pattern  contains  any  back-
2063           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2064           with a name to pass back, a pointer to the  name  string  (zero  termi-
2065           nated)  is  placed  in  the  variable pointed to by the mark field. The
2066           names are within the compiled pattern; if you wish  to  retain  such  a
2067           name  you must copy it before freeing the memory of a compiled pattern.
2068           If there is no name to pass back, the variable pointed to by  the  mark
2069           field  set  to NULL. For details of the backtracking control verbs, see
2070           the section entitled "Backtracking control" in the pcrepattern documen-
2071           tation.
2072    
2073       Option bits for pcre_exec()
2074    
2075           The  unused  bits of the options argument for pcre_exec() must be zero.
2076           The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
2077           PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2078           PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2079           PCRE_PARTIAL_HARD.
2080    
2081             PCRE_ANCHORED
2082    
2083           The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
2084           matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
2085           turned  out to be anchored by virtue of its contents, it cannot be made
2086           unachored at matching time.
2087    
2088             PCRE_BSR_ANYCRLF
2089             PCRE_BSR_UNICODE
2090    
2091           These options (which are mutually exclusive) control what the \R escape
2092           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2093           or to match any Unicode newline sequence. These  options  override  the
2094           choice that was made or defaulted when the pattern was compiled.
2095    
2096             PCRE_NEWLINE_CR
2097             PCRE_NEWLINE_LF
2098             PCRE_NEWLINE_CRLF
2099             PCRE_NEWLINE_ANYCRLF
2100             PCRE_NEWLINE_ANY
2101    
2102           These  options  override  the  newline  definition  that  was chosen or
2103           defaulted when the pattern was compiled. For details, see the  descrip-
2104           tion  of  pcre_compile()  above.  During  matching,  the newline choice
2105           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2106           ters.  It may also alter the way the match position is advanced after a
2107           match failure for an unanchored pattern.
2108    
2109           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
2110           set,  and a match attempt for an unanchored pattern fails when the cur-
2111           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2112           explicit  matches  for  CR  or  LF  characters,  the  match position is
2113           advanced by two characters instead of one, in other words, to after the
2114           CRLF.
2115    
2116           The above rule is a compromise that makes the most common cases work as
2117           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2118           option is not set), it does not match the string "\r\nA" because, after
2119           failing at the start, it skips both the CR and the LF before  retrying.
2120           However,  the  pattern  [\r\n]A does match that string, because it con-
2121           tains an explicit CR or LF reference, and so advances only by one char-
2122           acter after the first failure.
2123    
2124           An explicit match for CR of LF is either a literal appearance of one of
2125           those characters, or one of the \r or  \n  escape  sequences.  Implicit
2126           matches  such  as [^X] do not count, nor does \s (which includes CR and
2127           LF in the characters that it matches).
2128    
2129           Notwithstanding the above, anomalous effects may still occur when  CRLF
2130           is a valid newline sequence and explicit \r or \n escapes appear in the
2131           pattern.
2132    
2133             PCRE_NOTBOL
2134    
2135           This option specifies that first character of the subject string is not
2136           the  beginning  of  a  line, so the circumflex metacharacter should not
2137           match before it. Setting this without PCRE_MULTILINE (at compile  time)
2138           causes  circumflex  never to match. This option affects only the behav-
2139           iour of the circumflex metacharacter. It does not affect \A.
2140    
2141             PCRE_NOTEOL
2142    
2143           This option specifies that the end of the subject string is not the end
2144           of  a line, so the dollar metacharacter should not match it nor (except
2145           in multiline mode) a newline immediately before it. Setting this  with-
2146           out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2147           option affects only the behaviour of the dollar metacharacter. It  does
2148           not affect \Z or \z.
2149    
2150             PCRE_NOTEMPTY
2151    
2152           An empty string is not considered to be a valid match if this option is
2153           set. If there are alternatives in the pattern, they are tried.  If  all
2154           the  alternatives  match  the empty string, the entire match fails. For
2155           example, if the pattern
2156    
2157             a?b?
2158    
2159           is applied to a string not beginning with "a" or  "b",  it  matches  an
2160           empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
2161           match is not valid, so PCRE searches further into the string for occur-
2162           rences of "a" or "b".
2163    
2164             PCRE_NOTEMPTY_ATSTART
2165    
2166           This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2167           not at the start of  the  subject  is  permitted.  If  the  pattern  is
2168           anchored, such a match can occur only if the pattern contains \K.
2169    
2170           Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2171           PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2172           match  of  the empty string within its split() function, and when using
2173           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2174           matching a null string by first trying the match again at the same off-
2175           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2176           fails, by advancing the starting offset (see below) and trying an ordi-
2177           nary match again. There is some code that demonstrates how to  do  this
2178           in  the  pcredemo sample program. In the most general case, you have to
2179           check to see if the newline convention recognizes CRLF  as  a  newline,
2180           and  if so, and the current character is CR followed by LF, advance the
2181           starting offset by two characters instead of one.
2182    
2183             PCRE_NO_START_OPTIMIZE
2184    
2185           There are a number of optimizations that pcre_exec() uses at the  start
2186           of  a  match,  in  order to speed up the process. For example, if it is
2187           known that an unanchored match must start with a specific character, it
2188           searches  the  subject  for that character, and fails immediately if it
2189           cannot find it, without actually running the  main  matching  function.
2190           This means that a special item such as (*COMMIT) at the start of a pat-
2191           tern is not considered until after a suitable starting  point  for  the
2192           match  has been found. When callouts or (*MARK) items are in use, these
2193           "start-up" optimizations can cause them to be skipped if the pattern is
2194           never  actually  used.  The start-up optimizations are in effect a pre-
2195           scan of the subject that takes place before the pattern is run.
2196    
2197           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2198           possibly  causing  performance  to  suffer,  but ensuring that in cases
2199           where the result is "no match", the callouts do occur, and  that  items
2200           such as (*COMMIT) and (*MARK) are considered at every possible starting
2201           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2202           compile time, it cannot be unset at matching time.
2203    
2204           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2205           operation.  Consider the pattern
2206    
2207             (*COMMIT)ABC
2208    
2209           When this is compiled, PCRE records the fact that a  match  must  start
2210           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2211           start-up optimization scans along the subject, finds "A" and  runs  the
2212           first  match attempt from there. The (*COMMIT) item means that the pat-
2213           tern must match the current starting position, which in this  case,  it
2214           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2215           set, the initial scan along the subject string  does  not  happen.  The
2216           first  match  attempt  is  run  starting  from "D" and when this fails,
2217           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2218           result  is  "no  match". If the pattern is studied, more start-up opti-
2219           mizations may be used. For example, a minimum length  for  the  subject
2220           may be recorded. Consider the pattern
2221    
2222             (*MARK:A)(X|Y)
2223    
2224           The  minimum  length  for  a  match is one character. If the subject is
2225           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2226           finally  an empty string.  If the pattern is studied, the final attempt
2227           does not take place, because PCRE knows that the subject is too  short,
2228           and  so  the  (*MARK) is never encountered.  In this case, studying the
2229           pattern does not affect the overall match result, which  is  still  "no
2230           match", but it does affect the auxiliary information that is returned.
2231    
2232             PCRE_NO_UTF8_CHECK
2233    
2234           When PCRE_UTF8 is set at compile time, the validity of the subject as a
2235           UTF-8 string is automatically checked when pcre_exec() is  subsequently
2236           called.   The  value  of  startoffset is also checked to ensure that it
2237           points to the start of a UTF-8 character. There is a  discussion  about
2238           the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2239           main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2240           pcre_exec()  returns  the  error  PCRE_ERROR_BADUTF8  or,  if PCRE_PAR-
2241           TIAL_HARD is set and the problem is a truncated UTF-8 character at  the
2242           end  of  the  subject, PCRE_ERROR_SHORTUTF8. In both cases, information
2243           about the precise nature of the error may also  be  returned  (see  the
2244           descriptions  of these errors in the section entitled Error return val-
2245           ues from pcre_exec() below).  If startoffset contains a value that does
2246           not  point to the start of a UTF-8 character (or to the end of the sub-
2247           ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2248    
2249           If you already know that your subject is valid, and you  want  to  skip
2250           these    checks    for   performance   reasons,   you   can   set   the
2251           PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2252           do  this  for the second and subsequent calls to pcre_exec() if you are
2253           making repeated calls to find all  the  matches  in  a  single  subject
2254           string.  However,  you  should  be  sure  that the value of startoffset
2255           points to the start of a UTF-8 character (or the end of  the  subject).
2256           When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2257           string as a subject or an invalid value of  startoffset  is  undefined.
2258           Your program may crash.
2259    
2260             PCRE_PARTIAL_HARD
2261             PCRE_PARTIAL_SOFT
2262    
2263           These  options turn on the partial matching feature. For backwards com-
2264           patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2265           match  occurs if the end of the subject string is reached successfully,
2266           but there are not enough subject characters to complete the  match.  If
2267           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2268           matching continues by testing any remaining alternatives.  Only  if  no
2269           complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2270           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2271           caller  is  prepared to handle a partial match, but only if no complete
2272           match can be found.
2273    
2274           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2275           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2276           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2277           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2278           ered to be more important that an alternative complete match.
2279    
2280           In both cases, the portion of the string that was  inspected  when  the
2281           partial match was found is set as the first matching string. There is a
2282           more detailed discussion of partial and  multi-segment  matching,  with
2283           examples, in the pcrepartial documentation.
2284    
2285       The string to be matched by pcre_exec()
2286    
2287           The  subject string is passed to pcre_exec() as a pointer in subject, a
2288           length (in bytes) in length, and a starting byte offset in startoffset.
2289           If  this  is  negative  or  greater  than  the  length  of the subject,
2290           pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2291           zero,  the  search  for a match starts at the beginning of the subject,
2292           and this is by far the most common case. In UTF-8 mode, the byte offset
2293           must  point  to  the start of a UTF-8 character (or the end of the sub-
2294           ject). Unlike the pattern string, the subject may contain  binary  zero
2295           bytes.
2296    
2297           A  non-zero  starting offset is useful when searching for another match
2298           in the same subject by calling pcre_exec() again after a previous  suc-
2299           cess.   Setting  startoffset differs from just passing over a shortened
2300           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2301           with any kind of lookbehind. For example, consider the pattern
2302    
2303             \Biss\B
2304    
2305           which  finds  occurrences  of "iss" in the middle of words. (\B matches
2306           only if the current position in the subject is not  a  word  boundary.)
2307           When  applied  to the string "Mississipi" the first call to pcre_exec()
2308           finds the first occurrence. If pcre_exec() is called  again  with  just
2309           the  remainder  of  the  subject,  namely  "issipi", it does not match,
2310           because \B is always false at the start of the subject, which is deemed
2311           to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2312           string again, but with startoffset set to 4, it finds the second occur-
2313           rence  of "iss" because it is able to look behind the starting point to
2314           discover that it is preceded by a letter.
2315    
2316           Finding all the matches in a subject is tricky  when  the  pattern  can
2317           match an empty string. It is possible to emulate Perl's /g behaviour by
2318           first  trying  the  match  again  at  the   same   offset,   with   the
2319           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2320           fails, advancing the starting  offset  and  trying  an  ordinary  match
2321           again. There is some code that demonstrates how to do this in the pcre-
2322           demo sample program. In the most general case, you have to check to see
2323           if  the newline convention recognizes CRLF as a newline, and if so, and
2324           the current character is CR followed by LF, advance the starting offset
2325           by two characters instead of one.
2326    
2327           If  a  non-zero starting offset is passed when the pattern is anchored,
2328           one attempt to match at the given offset is made. This can only succeed
2329           if  the  pattern  does  not require the match to be at the start of the
2330           subject.
2331    
2332       How pcre_exec() returns captured substrings
2333    
2334           In general, a pattern matches a certain portion of the subject, and  in
2335           addition,  further  substrings  from  the  subject may be picked out by
2336           parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2337           this  is  called "capturing" in what follows, and the phrase "capturing
2338           subpattern" is used for a fragment of a pattern that picks out  a  sub-
2339           string.  PCRE  supports several other kinds of parenthesized subpattern
2340           that do not cause substrings to be captured.
2341    
2342           Captured substrings are returned to the caller via a vector of integers
2343           whose  address is passed in ovector. The number of elements in the vec-
2344           tor is passed in ovecsize, which must be a non-negative  number.  Note:
2345           this argument is NOT the size of ovector in bytes.
2346    
2347           The  first  two-thirds of the vector is used to pass back captured sub-
2348           strings, each substring using a pair of integers. The  remaining  third
2349           of  the  vector is used as workspace by pcre_exec() while matching cap-
2350           turing subpatterns, and is not available for passing back  information.
2351           The  number passed in ovecsize should always be a multiple of three. If
2352           it is not, it is rounded down.
2353    
2354           When a match is successful, information about  captured  substrings  is
2355           returned  in  pairs  of integers, starting at the beginning of ovector,
2356           and continuing up to two-thirds of its length at the  most.  The  first
2357           element  of  each pair is set to the byte offset of the first character
2358           in a substring, and the second is set to the byte offset of  the  first
2359           character  after  the end of a substring. Note: these values are always
2360           byte offsets, even in UTF-8 mode. They are not character counts.
2361    
2362           The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2363           portion  of  the subject string matched by the entire pattern. The next
2364           pair is used for the first capturing subpattern, and so on.  The  value
2365           returned by pcre_exec() is one more than the highest numbered pair that
2366           has been set.  For example, if two substrings have been  captured,  the
2367           returned  value is 3. If there are no capturing subpatterns, the return
2368           value from a successful match is 1, indicating that just the first pair
2369           of offsets has been set.
2370    
2371           If a capturing subpattern is matched repeatedly, it is the last portion
2372           of the string that it matched that is returned.
2373    
2374           If the vector is too small to hold all the captured substring  offsets,
2375           it is used as far as possible (up to two-thirds of its length), and the
2376           function returns a value of zero. If the substring offsets are  not  of
2377           interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2378           ovecsize as zero. However, if the pattern contains back references  and
2379           the  ovector is not big enough to remember the related substrings, PCRE
2380           has to get additional memory for use during matching. Thus it  is  usu-
2381           ally advisable to supply an ovector.
2382    
2383           The pcre_fullinfo() function can be used to find out how many capturing
2384           subpatterns there are in a compiled  pattern.  The  smallest  size  for
2385           ovector  that  will allow for n captured substrings, in addition to the
2386           offsets of the substring matched by the whole pattern, is (n+1)*3.
2387    
2388           It is possible for capturing subpattern number n+1 to match  some  part
2389           of the subject when subpattern n has not been used at all. For example,
2390           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2391           return from the function is 4, and subpatterns 1 and 3 are matched, but
2392           2 is not. When this happens, both values in  the  offset  pairs  corre-
2393           sponding to unused subpatterns are set to -1.
2394    
2395           Offset  values  that correspond to unused subpatterns at the end of the
2396           expression are also set to -1. For example,  if  the  string  "abc"  is
2397           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2398           matched. The return from the function is 2, because  the  highest  used
2399           capturing  subpattern  number  is 1, and the offsets for for the second
2400           and third capturing subpatterns (assuming the vector is  large  enough,
2401           of course) are set to -1.
2402    
2403           Note: Elements of ovector that do not correspond to capturing parenthe-
2404           ses in the pattern are never changed. That is, if a pattern contains  n
2405           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2406           by pcre_exec(). The other elements retain whatever values  they  previ-
2407           ously had.
2408    
2409           Some  convenience  functions  are  provided for extracting the captured
2410           substrings as separate strings. These are described below.
2411    
2412       Error return values from pcre_exec()
2413    
2414           If pcre_exec() fails, it returns a negative number. The  following  are
2415           defined in the header file:
2416    
2417             PCRE_ERROR_NOMATCH        (-1)
2418    
2419           The subject string did not match the pattern.
2420    
2421             PCRE_ERROR_NULL           (-2)
2422    
2423           Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2424           ovecsize was not zero.
2425    
2426             PCRE_ERROR_BADOPTION      (-3)
2427    
2428           An unrecognized bit was set in the options argument.
2429    
2430             PCRE_ERROR_BADMAGIC       (-4)
2431    
2432           PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2433           to catch the case when it is passed a junk pointer and to detect when a
2434           pattern that was compiled in an environment of one endianness is run in
2435           an  environment  with the other endianness. This is the error that PCRE
2436           gives when the magic number is not present.
2437    
2438             PCRE_ERROR_UNKNOWN_OPCODE (-5)
2439    
2440           While running the pattern match, an unknown item was encountered in the
2441           compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2442           overwriting of the compiled pattern.
2443    
2444             PCRE_ERROR_NOMEMORY       (-6)
2445    
2446           If a pattern contains back references, but the ovector that  is  passed
2447           to pcre_exec() is not big enough to remember the referenced substrings,
2448           PCRE gets a block of memory at the start of matching to  use  for  this
2449           purpose.  If the call via pcre_malloc() fails, this error is given. The
2450           memory is automatically freed at the end of matching.
2451    
2452           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2453           This  can happen only when PCRE has been compiled with --disable-stack-
2454           for-recursion.
2455    
2456             PCRE_ERROR_NOSUBSTRING    (-7)
2457    
2458           This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2459           and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2460           returned by pcre_exec().
2461    
2462             PCRE_ERROR_MATCHLIMIT     (-8)
2463    
2464           The backtracking limit, as specified by  the  match_limit  field  in  a
2465           pcre_extra  structure  (or  defaulted) was reached. See the description
2466           above.
2467    
2468             PCRE_ERROR_CALLOUT        (-9)
2469    
2470           This error is never generated by pcre_exec() itself. It is provided for
2471           use  by  callout functions that want to yield a distinctive error code.
2472           See the pcrecallout documentation for details.
2473    
2474             PCRE_ERROR_BADUTF8        (-10)
2475    
2476           A string that contains an invalid UTF-8 byte sequence was passed  as  a
2477           subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2478           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2479           start  of  the  the invalid UTF-8 character is placed in the first ele-
2480           ment, and a reason code is placed in the  second  element.  The  reason
2481           codes are listed in the following section.  For backward compatibility,
2482           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2483           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2484           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2485    
2486             PCRE_ERROR_BADUTF8_OFFSET (-11)
2487    
2488           The UTF-8 byte sequence that was passed as a subject  was  checked  and
2489           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2490           value of startoffset did not point to the beginning of a UTF-8  charac-
2491           ter or the end of the subject.
2492    
2493             PCRE_ERROR_PARTIAL        (-12)
2494    
2495           The  subject  string did not match, but it did match partially. See the
2496           pcrepartial documentation for details of partial matching.
2497    
2498             PCRE_ERROR_BADPARTIAL     (-13)
2499    
2500           This code is no longer in  use.  It  was  formerly  returned  when  the
2501           PCRE_PARTIAL  option  was used with a compiled pattern containing items
2502           that were  not  supported  for  partial  matching.  From  release  8.00
2503           onwards, there are no restrictions on partial matching.
2504    
2505             PCRE_ERROR_INTERNAL       (-14)
2506    
2507           An  unexpected  internal error has occurred. This error could be caused
2508           by a bug in PCRE or by overwriting of the compiled pattern.
2509    
2510             PCRE_ERROR_BADCOUNT       (-15)
2511    
2512           This error is given if the value of the ovecsize argument is negative.
2513    
2514             PCRE_ERROR_RECURSIONLIMIT (-21)
2515    
2516           The internal recursion limit, as specified by the match_limit_recursion
2517           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2518           description above.
2519    
2520             PCRE_ERROR_BADNEWLINE     (-23)
2521    
2522           An invalid combination of PCRE_NEWLINE_xxx options was given.
2523    
2524             PCRE_ERROR_BADOFFSET      (-24)
2525    
2526           The value of startoffset was negative or greater than the length of the
2527           subject, that is, the value in length.
2528    
2529             PCRE_ERROR_SHORTUTF8      (-25)
2530    
2531           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2532           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2533           option  is  set.   Information  about  the  failure  is returned as for
2534           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2535           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2536           tion of returned information; it is retained for backwards  compatibil-
2537           ity.
2538    
2539             PCRE_ERROR_RECURSELOOP    (-26)
2540    
2541           This error is returned when pcre_exec() detects a recursion loop within
2542           the pattern. Specifically, it means that either the whole pattern or  a
2543           subpattern  has been called recursively for the second time at the same
2544           position in the subject string. Some simple patterns that might do this
2545           are  detected  and faulted at compile time, but more complicated cases,
2546           in particular mutual recursions between two different subpatterns, can-
2547           not be detected until run time.
2548    
2549           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2550    
2551       Reason codes for invalid UTF-8 strings
2552    
2553           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2554           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2555           offset  of  the  start  of the invalid UTF-8 character is placed in the
2556           first output vector element (ovector[0]) and a reason code is placed in
2557           the  second  element  (ovector[1]). The reason codes are given names in
2558           the pcre.h header file:
2559    
2560             PCRE_UTF8_ERR1
2561             PCRE_UTF8_ERR2
2562             PCRE_UTF8_ERR3
2563             PCRE_UTF8_ERR4
2564             PCRE_UTF8_ERR5
2565    
2566           The string ends with a truncated UTF-8 character;  the  code  specifies
2567           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2568           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2569           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2570           checked first; hence the possibility of 4 or 5 missing bytes.
2571    
2572             PCRE_UTF8_ERR6
2573             PCRE_UTF8_ERR7
2574             PCRE_UTF8_ERR8
2575             PCRE_UTF8_ERR9
2576             PCRE_UTF8_ERR10
2577    
2578           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2579           the  character  do  not have the binary value 0b10 (that is, either the
2580           most significant bit is 0, or the next bit is 1).
2581    
2582             PCRE_UTF8_ERR11
2583             PCRE_UTF8_ERR12
2584    
2585           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2586           long; these code points are excluded by RFC 3629.
2587    
2588             PCRE_UTF8_ERR13
2589    
2590           A  4-byte character has a value greater than 0x10fff; these code points
2591           are excluded by RFC 3629.
2592    
2593             PCRE_UTF8_ERR14
2594    
2595           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2596           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2597           so are excluded from UTF-8.
2598    
2599             PCRE_UTF8_ERR15
2600             PCRE_UTF8_ERR16
2601             PCRE_UTF8_ERR17
2602             PCRE_UTF8_ERR18
2603             PCRE_UTF8_ERR19
2604    
2605           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2606           for  a  value that can be represented by fewer bytes, which is invalid.
2607           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2608           rect coding uses just one byte.
2609    
2610             PCRE_UTF8_ERR20
2611    
2612           The two most significant bits of the first byte of a character have the
2613           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2614           ond  is  0). Such a byte can only validly occur as the second or subse-
2615           quent byte of a multi-byte character.
2616    
2617             PCRE_UTF8_ERR21
2618    
2619  MATCHING A PATTERN         The first byte of a character has the value 0xfe or 0xff. These  values
2620           can never occur in a valid UTF-8 string.
      int pcre_exec(const pcre *code, const pcre_extra *extra,  
           const char *subject, int length, int startoffset,  
           int options, int *ovector, int ovecsize);  
   
      The function pcre_exec() is called to match a subject string  
      against  a pre-compiled pattern, which is passed in the code  
      argument. If the pattern has been studied, the result of the  
      study should be passed in the extra argument.  
   
      Here is an example of a simple call to pcre_exec():  
   
        int rc;  
        int ovector[30];  
        rc = pcre_exec(  
          re,             /* result of pcre_compile() */  
          NULL,           /* we didn't study the pattern */  
          "some string",  /* the subject string */  
          11,             /* the length of the subject string */  
          0,              /* start at offset 0 in the subject */  
          0,              /* default options */  
          ovector,        /* vector for substring information */  
          30);            /* number of elements in the vector */  
   
      If the extra argument is  not  NULL,  it  must  point  to  a  
      pcre_extra  data  block.  The  pcre_study() function returns  
      such a block (when it doesn't return NULL), but you can also  
      create  one for yourself, and pass additional information in  
      it. The fields in the block are as follows:  
   
        unsigned long int flags;  
        void *study_data;  
        unsigned long int match_limit;  
        void *callout_data;  
   
      The flags field is a bitmap  that  specifies  which  of  the  
      other fields are set. The flag bits are:  
   
        PCRE_EXTRA_STUDY_DATA  
        PCRE_EXTRA_MATCH_LIMIT  
        PCRE_EXTRA_CALLOUT_DATA  
   
      Other flag bits should be set to zero. The study_data  field  
      is   set  in  the  pcre_extra  block  that  is  returned  by  
      pcre_study(), together with the appropriate  flag  bit.  You  
      should  not  set this yourself, but you can add to the block  
      by setting the other fields.  
   
      The match_limit field provides a means  of  preventing  PCRE  
      from  using  up a vast amount of resources when running pat-  
      terns that are not going to match, but  which  have  a  very  
      large  number  of  possibilities  in their search trees. The  
      classic example is the  use  of  nested  unlimited  repeats.  
      Internally,  PCRE  uses  a  function called match() which it  
      calls  repeatedly  (sometimes  recursively).  The  limit  is  
      imposed  on the number of times this function is called dur-  
      ing a match, which has the effect of limiting the amount  of  
      recursion and backtracking that can take place. For patterns  
      that are not anchored, the count starts from zero  for  each  
      position in the subject string.  
   
      The default limit for the library can be set  when  PCRE  is  
      built;  the default default is 10 million, which handles all  
      but the most extreme cases. You can reduce  the  default  by  
      suppling  pcre_exec()  with  a  pcre_extra  block  in  which  
      match_limit   is   set   to    a    smaller    value,    and  
      PCRE_EXTRA_MATCH_LIMIT  is  set  in  the flags field. If the  
      limit      is      exceeded,       pcre_exec()       returns  
      PCRE_ERROR_MATCHLIMIT.  
   
      The pcre_callout field is used in conjunction with the "cal-  
      lout"  feature,  which is described in the pcrecallout docu-  
      mentation.  
   
      The PCRE_ANCHORED option can be passed in the options  argu-  
      ment,   whose   unused   bits  must  be  zero.  This  limits  
      pcre_exec() to matching at the first matching position. How-  
      ever,  if  a  pattern  was  compiled  with PCRE_ANCHORED, or  
      turned out to be anchored by virtue of its contents, it can-  
      not be made unachored at matching time.  
   
      There are also three further options that can be set only at  
      matching time:  
   
        PCRE_NOTBOL  
   
      The first character of the string is not the beginning of  a  
      line,  so  the  circumflex  metacharacter  should  not match  
      before it. Setting this without PCRE_MULTILINE  (at  compile  
      time) causes circumflex never to match.  
   
        PCRE_NOTEOL  
   
      The end of the string is not the end of a line, so the  dol-  
      lar  metacharacter should not match it nor (except in multi-  
      line mode) a newline immediately  before  it.  Setting  this  
      without PCRE_MULTILINE (at compile time) causes dollar never  
      to match.  
   
        PCRE_NOTEMPTY  
   
      An empty string is not considered to be  a  valid  match  if  
      this  option  is  set. If there are alternatives in the pat-  
      tern, they are tried. If  all  the  alternatives  match  the  
      empty  string,  the  entire match fails. For example, if the  
      pattern  
   
        a?b?  
   
      is applied to a string not beginning with  "a"  or  "b",  it  
      matches  the  empty string at the start of the subject. With  
      PCRE_NOTEMPTY set, this match is not valid, so PCRE searches  
      further into the string for occurrences of "a" or "b".  
   
      Perl has no direct equivalent of PCRE_NOTEMPTY, but it  does  
      make  a  special case of a pattern match of the empty string  
      within its split() function, and when using the /g modifier.  
      It  is possible to emulate Perl's behaviour after matching a  
      null string by first trying the  match  again  at  the  same  
      offset  with  PCRE_NOTEMPTY  set,  and then if that fails by  
      advancing the starting offset  (see  below)  and  trying  an  
      ordinary match again.  
   
      The subject string is passed to pcre_exec() as a pointer  in  
      subject,  a length in length, and a starting offset in star-  
      toffset. Unlike the pattern string, the subject may  contain  
      binary  zero  bytes.  When  the starting offset is zero, the  
      search for a match starts at the beginning of  the  subject,  
      and this is by far the most common case.  
   
      If the pattern was compiled with the PCRE_UTF8  option,  the  
      subject  must  be  a sequence of bytes that is a valid UTF-8  
      string.  If  an  invalid  UTF-8  string  is  passed,  PCRE's  
      behaviour is not defined.  
   
      A non-zero starting offset  is  useful  when  searching  for  
      another  match  in  the  same subject by calling pcre_exec()  
      again after a previous success.  Setting startoffset differs  
      from  just  passing  over  a  shortened  string  and setting  
      PCRE_NOTBOL in the case of a pattern that  begins  with  any  
      kind of lookbehind. For example, consider the pattern  
   
        \Biss\B  
   
      which finds occurrences of "iss" in the middle of words. (\B  
      matches only if the current position in the subject is not a  
      word boundary.) When applied to the string "Mississipi"  the  
      first  call  to  pcre_exec()  finds the first occurrence. If  
      pcre_exec() is called again with just the remainder  of  the  
      subject,  namely  "issipi", it does not match, because \B is  
      always false at the start of the subject, which is deemed to  
      be  a  word  boundary. However, if pcre_exec() is passed the  
      entire string again, but with startoffset set to 4, it finds  
      the  second  occurrence  of "iss" because it is able to look  
      behind the starting point to discover that it is preceded by  
      a letter.  
   
      If a non-zero starting offset is passed when the pattern  is  
      anchored, one attempt to match at the given offset is tried.  
      This can only succeed if the pattern does  not  require  the  
      match to be at the start of the subject.  
   
      In general, a pattern matches a certain portion of the  sub-  
      ject,  and  in addition, further substrings from the subject  
      may be picked out by parts of  the  pattern.  Following  the  
      usage  in  Jeffrey Friedl's book, this is called "capturing"  
      in what follows, and the phrase  "capturing  subpattern"  is  
      used for a fragment of a pattern that picks out a substring.  
      PCRE supports several other kinds of  parenthesized  subpat-  
      tern that do not cause substrings to be captured.  
   
      Captured substrings are returned to the caller via a  vector  
      of  integer  offsets whose address is passed in ovector. The  
      number of elements in the vector is passed in ovecsize.  The  
      first two-thirds of the vector is used to pass back captured  
      substrings, each substring using a  pair  of  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  substring,  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  subpattern,  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.  
   
      Some convenience functions are provided for  extracting  the  
      captured substrings as separate strings. These are described  
      in the following section.  
   
      It is possible for an capturing  subpattern  number  n+1  to  
      match  some  part  of  the subject when subpattern n has not  
      been used at all.  For  example,  if  the  string  "abc"  is  
      matched  against the pattern (a|(z))(bc) subpatterns 1 and 3  
      are matched, but 2 is not. When this  happens,  both  offset  
      values corresponding to the unused subpattern are set to -1.  
   
      If a capturing subpattern is matched repeatedly, it  is  the  
      last  portion  of  the  string  that  it  matched  that gets  
      returned.  
   
      If the vector is too small to hold  all  the  captured  sub-  
      strings,  it is used as far as possible (up to two-thirds of  
      its length), and the function returns a value  of  zero.  In  
      particular,  if  the  substring offsets are not of interest,  
      pcre_exec() may be called with ovector passed  as  NULL  and  
      ovecsize  as  zero.  However,  if  the pattern contains back  
      references and the ovector isn't big enough to remember  the  
      related  substrings,  PCRE  has to get additional memory for  
      use during matching. Thus it is usually advisable to  supply  
      an ovector.  
   
      Note that pcre_info() can be used to find out how many  cap-  
      turing  subpatterns  there  are  in  a compiled pattern. The  
      smallest size for ovector that will  allow  for  n  captured  
      substrings,  in  addition  to  the  offsets of the substring  
      matched by the whole pattern, is (n+1)*3.  
   
      If pcre_exec() fails, it returns a negative number. The fol-  
      lowing are defined in the header file:  
   
        PCRE_ERROR_NOMATCH        (-1)  
   
      The subject string did not match the pattern.  
   
        PCRE_ERROR_NULL           (-2)  
   
      Either code or subject was passed as NULL,  or  ovector  was  
      NULL and ovecsize was not zero.  
   
        PCRE_ERROR_BADOPTION      (-3)  
   
      An unrecognized bit was set in the options argument.  
   
        PCRE_ERROR_BADMAGIC       (-4)  
   
      PCRE stores a 4-byte "magic number" at the start of the com-  
      piled  code,  to  catch  the  case  when it is passed a junk  
      pointer. This is the error it gives when  the  magic  number  
      isn't present.  
   
        PCRE_ERROR_UNKNOWN_NODE   (-5)  
   
      While running the pattern match, an unknown item was encoun-  
      tered in the compiled pattern. This error could be caused by  
      a bug in PCRE or by overwriting of the compiled pattern.  
   
        PCRE_ERROR_NOMEMORY       (-6)  
   
      If a pattern contains back references, but the ovector  that  
      is  passed  to pcre_exec() is not big enough to remember the  
      referenced substrings, PCRE gets a block of  memory  at  the  
      start  of  matching to use for this purpose. If the call via  
      pcre_malloc() fails, this error  is  given.  The  memory  is  
      freed at the end of matching.  
   
        PCRE_ERROR_NOSUBSTRING    (-7)  
   
      This   error   is   used   by   the   pcre_copy_substring(),  
      pcre_get_substring(),  and  pcre_get_substring_list()  func-  
      tions (see below). It is never returned by pcre_exec().  
   
        PCRE_ERROR_MATCHLIMIT     (-8)  
   
      The recursion and backtracking limit, as  specified  by  the  
      match_limit  field  in a pcre_extra structure (or defaulted)  
      was reached. See the description above.  
   
        PCRE_ERROR_CALLOUT        (-9)  
   
      This error is never generated by pcre_exec() itself.  It  is  
      provided  for  use by callout functions that want to yield a  
      distinctive error code. See  the  pcrecallout  documentation  
      for details.  
2621    
2622    
2623  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2624    
2625       int pcre_copy_substring(const char *subject, int *ovector,         int pcre_copy_substring(const char *subject, int *ovector,
2626            int stringcount, int stringnumber, char *buffer,              int stringcount, int stringnumber, char *buffer,
2627            int buffersize);              int buffersize);
2628    
2629       int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
2630            int stringcount, int stringnumber,              int stringcount, int stringnumber,
2631            const char **stringptr);              const char **stringptr);
2632    
2633       int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2634            int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2635    
2636       Captured substrings can be accessed directly  by  using  the         Captured  substrings  can  be  accessed  directly  by using the offsets
2637       offsets returned by pcre_exec() in ovector. For convenience,         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2638       the functions  pcre_copy_substring(),  pcre_get_substring(),         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2639       and  pcre_get_substring_list()  are  provided for extracting         string_list() are provided for extracting captured substrings  as  new,
2640       captured  substrings  as  new,   separate,   zero-terminated         separate,  zero-terminated strings. These functions identify substrings
2641       strings.  These functions identify substrings by number. The         by number. The next section describes functions  for  extracting  named
2642       next section describes functions for extracting  named  sub-         substrings.
2643       strings.   A  substring  that  contains  a  binary  zero  is  
2644       correctly extracted and has a further zero added on the end,         A  substring that contains a binary zero is correctly extracted and has
2645       but the result is not, of course, a C string.         a further zero added on the end, but the result is not, of course, a  C
2646           string.   However,  you  can  process such a string by referring to the
2647       The first three arguments are the  same  for  all  three  of         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2648       these  functions:   subject  is the subject string which has         string().  Unfortunately, the interface to pcre_get_substring_list() is
2649       just been successfully matched, ovector is a pointer to  the         not adequate for handling strings containing binary zeros, because  the
2650       vector  of  integer  offsets that was passed to pcre_exec(),         end of the final string is not independently indicated.
2651       and stringcount is the number of substrings that  were  cap-  
2652       tured by the match, including the substring that matched the         The  first  three  arguments  are the same for all three of these func-
2653       entire regular expression. This is  the  value  returned  by         tions: subject is the subject string that has  just  been  successfully
2654       pcre_exec  if  it  is  greater  than  zero.  If  pcre_exec()         matched, ovector is a pointer to the vector of integer offsets that was
2655       returned zero, indicating that it ran out of space in  ovec-         passed to pcre_exec(), and stringcount is the number of substrings that
2656       tor,  the  value passed as stringcount should be the size of         were  captured  by  the match, including the substring that matched the
2657       the vector divided by three.         entire regular expression. This is the value returned by pcre_exec() if
2658           it  is greater than zero. If pcre_exec() returned zero, indicating that
2659       The functions pcre_copy_substring() and pcre_get_substring()         it ran out of space in ovector, the value passed as stringcount  should
2660       extract a single substring, whose number is given as string-         be the number of elements in the vector divided by three.
2661       number. A value of zero extracts the substring that  matched  
2662       the entire pattern, while higher values extract the captured         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2663       substrings. For pcre_copy_substring(), the string is  placed         single substring, whose number is given as  stringnumber.  A  value  of
2664       in  buffer,  whose  length is given by buffersize, while for         zero  extracts  the  substring that matched the entire pattern, whereas
2665       pcre_get_substring() a new block of memory is  obtained  via         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2666       pcre_malloc,  and its address is returned via stringptr. The         string(),  the  string  is  placed  in buffer, whose length is given by
2667       yield of the function is  the  length  of  the  string,  not         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2668       including the terminating zero, or one of         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2669           The yield of the function is the length of the  string,  not  including
2670         PCRE_ERROR_NOMEMORY       (-6)         the terminating zero, or one of these error codes:
2671    
2672       The buffer was too small for pcre_copy_substring(),  or  the           PCRE_ERROR_NOMEMORY       (-6)
2673       attempt to get memory failed for pcre_get_substring().  
2674           The  buffer  was too small for pcre_copy_substring(), or the attempt to
2675         PCRE_ERROR_NOSUBSTRING    (-7)         get memory failed for pcre_get_substring().
2676    
2677       There is no substring whose number is stringnumber.           PCRE_ERROR_NOSUBSTRING    (-7)
2678    
2679       The pcre_get_substring_list() function extracts  all  avail-         There is no substring whose number is stringnumber.
2680       able  substrings  and builds a list of pointers to them. All  
2681       this is done in a single block of memory which  is  obtained         The pcre_get_substring_list()  function  extracts  all  available  sub-
2682       via pcre_malloc. The address of the memory block is returned         strings  and  builds  a list of pointers to them. All this is done in a
2683       via listptr, which is also the start of the list  of  string         single block of memory that is obtained via pcre_malloc. The address of
2684       pointers.  The  end of the list is marked by a NULL pointer.         the  memory  block  is returned via listptr, which is also the start of
2685       The yield of the function is zero if all went well, or         the list of string pointers. The end of the list is marked  by  a  NULL
2686           pointer.  The  yield  of  the function is zero if all went well, or the
2687         PCRE_ERROR_NOMEMORY       (-6)         error code
2688    
2689       if the attempt to get the memory block failed.           PCRE_ERROR_NOMEMORY       (-6)
2690    
2691       When any of these functions encounter a  substring  that  is         if the attempt to get the memory block failed.
2692       unset, which can happen when capturing subpattern number n+1  
2693       matches some part of the subject, but subpattern n  has  not         When any of these functions encounter a substring that is unset,  which
2694       been  used  at all, they return an empty string. This can be         can  happen  when  capturing subpattern number n+1 matches some part of
2695       distinguished  from  a  genuine  zero-length  substring   by         the subject, but subpattern n has not been used at all, they return  an
2696       inspecting the appropriate offset in ovector, which is nega-         empty string. This can be distinguished from a genuine zero-length sub-
2697       tive for unset substrings.         string by inspecting the appropriate offset in ovector, which is  nega-
2698           tive for unset substrings.
2699       The  two  convenience  functions  pcre_free_substring()  and  
2700       pcre_free_substring_list()  can  be  used to free the memory         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2701       returned by  a  previous  call  of  pcre_get_substring()  or         string_list() can be used to free the memory  returned  by  a  previous
2702       pcre_get_substring_list(),  respectively.  They  do  nothing         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2703       more than call the function pointed to by  pcre_free,  which         tively. They do nothing more than  call  the  function  pointed  to  by
2704       of  course  could  be called directly from a C program. How-         pcre_free,  which  of course could be called directly from a C program.
2705       ever, PCRE is used in some situations where it is linked via         However, PCRE is used in some situations where it is linked via a  spe-
2706       a  special  interface  to another programming language which         cial   interface  to  another  programming  language  that  cannot  use
2707       cannot use pcre_free directly; it is for  these  cases  that         pcre_free directly; it is for these cases that the functions  are  pro-
2708       the functions are provided.         vided.
2709    
2710    
2711  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2712    
2713       int pcre_copy_named_substring(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
2714            const char *subject, int *ovector,              const char *name);
2715            int stringcount, const char *stringname,  
2716            char *buffer, int buffersize);         int pcre_copy_named_substring(const pcre *code,
2717                const char *subject, int *ovector,
2718       int pcre_get_stringnumber(const pcre *code,              int stringcount, const char *stringname,
2719            const char *name);              char *buffer, int buffersize);
2720    
2721       int pcre_get_named_substring(const pcre *code,         int pcre_get_named_substring(const pcre *code,
2722            const char *subject, int *ovector,              const char *subject, int *ovector,
2723            int stringcount, const char *stringname,              int stringcount, const char *stringname,
2724            const char **stringptr);              const char **stringptr);
2725    
2726       To extract a substring by name, you first have to find asso-         To  extract a substring by name, you first have to find associated num-
2727       ciated    number.    This    can    be   done   by   calling         ber.  For example, for this pattern
2728       pcre_get_stringnumber(). The first argument is the  compiled  
2729       pattern,  and  the second is the name. For example, for this           (a+)b(?<xxx>\d+)...
2730       pattern  
2731           the number of the subpattern called "xxx" is 2. If the name is known to
2732         ab(?<xxx>\d+)...         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2733           name by calling pcre_get_stringnumber(). The first argument is the com-
2734       the number of the subpattern called "xxx" is  1.  Given  the         piled pattern, and the second is the name. The yield of the function is
2735       number,  you can then extract the substring directly, or use         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2736       one of the functions described in the previous section.  For         subpattern of that name.
2737       convenience,  there are also two functions that do the whole  
2738       job.         Given the number, you can extract the substring directly, or use one of
2739           the functions described in the previous section. For convenience, there
2740       Most of the  arguments  of  pcre_copy_named_substring()  and         are also two functions that do the whole job.
2741       pcre_get_named_substring()  are  the  same  as those for the  
2742       functions that  extract  by  number,  and  so  are  not  re-         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2743       described here. There are just two differences.         pcre_get_named_substring() are the same  as  those  for  the  similarly
2744           named  functions  that extract by number. As these are described in the
2745       First, instead of a substring number, a  substring  name  is         previous section, they are not re-described here. There  are  just  two
2746       given.  Second,  there  is  an  extra argument, given at the         differences:
2747       start, which is a pointer to the compiled pattern.  This  is  
2748       needed  in order to gain access to the name-to-number trans-         First,  instead  of a substring number, a substring name is given. Sec-
2749       lation table.         ond, there is an extra argument, given at the start, which is a pointer
2750           to  the compiled pattern. This is needed in order to gain access to the
2751       These functions  call  pcre_get_stringnumber(),  and  if  it         name-to-number translation table.
2752       succeeds,    they   then   call   pcre_copy_substring()   or  
2753       pcre_get_substring(), as appropriate.         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2754           then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2755           ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2756           behaviour may not be what you want (see the next section).
2757    
2758           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2759           terns with the same number, as described in the  section  on  duplicate
2760           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2761           distinguish the different subpatterns, because names are  not  included
2762           in  the compiled code. The matching process uses only numbers. For this
2763           reason, the use of different names for subpatterns of the  same  number
2764           causes an error at compile time.
2765    
2766    
2767    DUPLICATE SUBPATTERN NAMES
2768    
2769           int pcre_get_stringtable_entries(const pcre *code,
2770                const char *name, char **first, char **last);
2771    
2772           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2773           subpatterns are not required to be unique. (Duplicate names are  always
2774           allowed  for subpatterns with the same number, created by using the (?|
2775           feature. Indeed, if such subpatterns are named, they  are  required  to
2776           use the same names.)
2777    
2778           Normally, patterns with duplicate names are such that in any one match,
2779           only one of the named subpatterns participates. An example is shown  in
2780           the pcrepattern documentation.
2781    
2782           When    duplicates   are   present,   pcre_copy_named_substring()   and
2783           pcre_get_named_substring() return the first substring corresponding  to
2784           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2785           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2786           function  returns one of the numbers that are associated with the name,
2787           but it is not defined which it is.
2788    
2789           If you want to get full details of all captured substrings for a  given
2790           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2791           first argument is the compiled pattern, and the second is the name. The
2792           third  and  fourth  are  pointers to variables which are updated by the
2793           function. After it has run, they point to the first and last entries in
2794           the  name-to-number  table  for  the  given  name.  The function itself
2795           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2796           there  are none. The format of the table is described above in the sec-
2797           tion entitled Information about a pattern above.  Given all  the  rele-
2798           vant  entries  for the name, you can extract each of their numbers, and
2799           hence the captured data, if any.
2800    
2801    
2802    FINDING ALL POSSIBLE MATCHES
2803    
2804           The traditional matching function uses a  similar  algorithm  to  Perl,
2805           which stops when it finds the first match, starting at a given point in
2806           the subject. If you want to find all possible matches, or  the  longest
2807           possible  match,  consider using the alternative matching function (see
2808           below) instead. If you cannot use the alternative function,  but  still
2809           need  to  find all possible matches, you can kludge it up by making use
2810           of the callout facility, which is described in the pcrecallout documen-
2811           tation.
2812    
2813           What you have to do is to insert a callout right at the end of the pat-
2814           tern.  When your callout function is called, extract and save the  cur-
2815           rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2816           backtrack and try other alternatives. Ultimately, when it runs  out  of
2817           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2818    
2819    
2820