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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         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-
30         pcrecallout       details of the callout feature         eral  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 5.2.0.
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
185           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186           that your strings are valid, and therefore want to skip these checks in
187           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188           compile  time  or at run time, PCRE assumes that the pattern or subject
189           it is given (respectively) contains only valid  UTF-8  codes.  In  this
190           case, it does not diagnose an invalid UTF-8 string.
191    
192           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193           what happens depends on why the string is invalid. If the  string  con-
194           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197           strings according to the more liberal rules of RFC  2279.  However,  if
198           the  string does not even conform to RFC 2279, the result is undefined.
199           Your program may crash.
200    
201           If you want to process strings  of  values  in  the  full  range  0  to
202           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204           this situation, you will have to apply your own validity check.
205    
206       General comments about UTF-8 mode
207    
208           1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209           two-byte UTF-8 character if the value is greater than 127.
210    
211           2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212           characters for values greater than \177.
213    
214           3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215           vidual bytes, for example: \x{100}{3}.
216    
217           4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218           gle byte.
219    
220           5.  The  escape sequence \C can be used to match a single byte in UTF-8
221           mode, but its use can lead to some strange effects.  This  facility  is
222           not available in the alternative matching function, pcre_dfa_exec().
223    
224           6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225           test characters of any code value, but, by default, the characters that
226           PCRE  recognizes  as digits, spaces, or word characters remain the same
227           set as before, all with values less than 256. This  remains  true  even
228           when  PCRE  is built to include Unicode property support, because to do
229           otherwise would slow down PCRE in many common cases. Note in particular
230           that this applies to \b and \B, because they are defined in terms of \w
231           and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233           tively, if you set the PCRE_UCP option,  the  way  that  the  character
234           escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236           generic character types in the pcrepattern documentation.
237    
238           7.  Similarly,  characters that match the POSIX named character classes
239           are all low-valued characters, unless the PCRE_UCP option is set.
240    
241           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
242           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
243           acters, whether or not PCRE_UCP is set.
244    
245           9. Case-insensitive matching applies only to  characters  whose  values
246           are  less than 128, unless PCRE is built with Unicode property support.
247           Even when Unicode property support is available, PCRE  still  uses  its
248           own  character  tables when checking the case of low-valued characters,
249           so as not to degrade performance.  The Unicode property information  is
250           used only for characters with higher values. Even when Unicode property
251           support is available, PCRE supports case-insensitive matching only when
252           there  is  a  one-to-one  mapping between a letter's cases. There are a
253           small number of many-to-one mappings in Unicode;  these  are  not  sup-
254           ported by PCRE.
255    
256    
257  AUTHOR  AUTHOR
258    
259       Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
260       University Computing Service,         University Computing Service
261       Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
262       Phone: +44 1223 334714  
263           Putting  an actual email address here seems to have been a spam magnet,
264           so I've taken it away. If you want to email me, use  my  two  initials,
265           followed by the two digits 10, at the domain cam.ac.uk.
266    
267    
268    REVISION
269    
270           Last updated: 22 October 2010
271           Copyright (c) 1997-2010 University of Cambridge.
272    ------------------------------------------------------------------------------
273    
274    
275    PCREBUILD(3)                                                      PCREBUILD(3)
276    
 Last updated: 04 February 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
277    
278  NAME  NAME
279       PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
280    
281    
282  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
283    
284       This document describes the optional features of  PCRE  that         This  document  describes  the  optional  features  of PCRE that can be
285       can  be  selected when the library is compiled. They are all         selected when the library is compiled. It assumes use of the  configure
286       selected, or deselected, by providing options to the config-         script,  where the optional features are selected or deselected by pro-
287       ure  script  which  is run before the make command. The com-         viding options to configure before running the make  command.  However,
288       plete list of options  for  configure  (which  includes  the         the  same  options  can be selected in both Unix-like and non-Unix-like
289       standard  ones  such  as  the  selection of the installation         environments using the GUI facility of cmake-gui if you are using CMake
290       directory) can be obtained by running         instead of configure to build PCRE.
291    
292         ./configure --help         There  is  a  lot more information about building PCRE in non-Unix-like
293           environments in the file called NON_UNIX_USE, which is part of the PCRE
294       The following sections describe certain options whose  names         distribution.  You  should consult this file as well as the README file
295       begin  with  --enable  or  --disable. These settings specify         if you are building in a non-Unix-like environment.
296       changes to the defaults for the configure  command.  Because  
297       of  the  way  that  configure  works, --enable and --disable         The complete list of options for configure (which includes the standard
298       always come in pairs, so  the  complementary  option  always         ones  such  as  the  selection  of  the  installation directory) can be
299       exists  as  well, but as it specifies the default, it is not         obtained by running
300       described.  
301             ./configure --help
302    
303           The following sections include  descriptions  of  options  whose  names
304           begin with --enable or --disable. These settings specify changes to the
305           defaults for the configure command. Because of the way  that  configure
306           works,  --enable  and --disable always come in pairs, so the complemen-
307           tary option always exists as well, but as it specifies the default,  it
308           is not described.
309    
310    
311    C++ SUPPORT
312    
313           By default, the configure script will search for a C++ compiler and C++
314           header files. If it finds them, it automatically builds the C++ wrapper
315           library for PCRE. You can disable this by adding
316    
317             --disable-cpp
318    
319           to the configure command.
320    
321    
322  UTF-8 SUPPORT  UTF-8 SUPPORT
323    
324       To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
325    
326             --enable-utf8
327    
328           to  the  configure  command.  Of  itself, this does not make PCRE treat
329           strings as UTF-8. As well as compiling PCRE with this option, you  also
330           have  have to set the PCRE_UTF8 option when you call the pcre_compile()
331           or pcre_compile2() functions.
332    
333           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
334           expects its input to be either ASCII or UTF-8 (depending on the runtime
335           option). It is not possible to support both EBCDIC and UTF-8  codes  in
336           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
337           --enable-ebcdic are mutually exclusive.
338    
        --enable-utf8  
339    
340       to the configure command. Of itself, this does not make PCRE  UNICODE CHARACTER PROPERTY SUPPORT
341       treat  strings as UTF-8. As well as compiling PCRE with this  
342       option, you also have have to set the PCRE_UTF8 option  when         UTF-8 support allows PCRE to process character values greater than  255
343       you call the pcre_compile() function.         in  the  strings that it handles. On its own, however, it does not pro-
344           vide any facilities for accessing the properties of such characters. If
345           you  want  to  be able to use the pattern escapes \P, \p, and \X, which
346           refer to Unicode character properties, you must add
347    
348             --enable-unicode-properties
349    
350           to the configure command. This implies UTF-8 support, even if you  have
351           not explicitly requested it.
352    
353           Including  Unicode  property  support  adds around 30K of tables to the
354           PCRE library. Only the general category properties such as  Lu  and  Nd
355           are supported. Details are given in the pcrepattern documentation.
356    
357    
358  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
359    
360       By default, PCRE treats character 10 (linefeed) as the  new-         By  default,  PCRE interprets the linefeed (LF) character as indicating
361       line  character.  This  is  the  normal newline character on         the end of a line. This is the normal newline  character  on  Unix-like
362       Unix-like systems. You can compile PCRE to use character  13         systems.  You  can compile PCRE to use carriage return (CR) instead, by
363       (carriage return) instead by adding         adding
364    
365         --enable-newline-is-cr           --enable-newline-is-cr
366    
367       to the configure command. For completeness there is  also  a         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
368       --enable-newline-is-lf  option,  which  explicitly specifies         option, which explicitly specifies linefeed as the newline character.
369       linefeed as the newline character.  
370           Alternatively, you can specify that line endings are to be indicated by
371           the two character sequence CRLF. If you want this, add
372    
373             --enable-newline-is-crlf
374    
375           to the configure command. There is a fourth option, specified by
376    
377             --enable-newline-is-anycrlf
378    
379           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
380           CRLF as indicating a line ending. Finally, a fifth option, specified by
381    
382             --enable-newline-is-any
383    
384           causes PCRE to recognize any Unicode newline sequence.
385    
386           Whatever  line  ending convention is selected when PCRE is built can be
387           overridden when the library functions are called. At build time  it  is
388           conventional to use the standard for your operating system.
389    
390    
391    WHAT \R MATCHES
392    
393           By  default,  the  sequence \R in a pattern matches any Unicode newline
394           sequence, whatever has been selected as the line  ending  sequence.  If
395           you specify
396    
397             --enable-bsr-anycrlf
398    
399           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
400           ever is selected when PCRE is built can be overridden when the  library
401           functions are called.
402    
403    
404  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
405    
406       The PCRE building process uses libtool to build both  shared         The  PCRE building process uses libtool to build both shared and static
407       and  static  Unix libraries by default. You can suppress one         Unix libraries by default. You can suppress one of these by adding  one
408       of these by adding one of         of
409    
410         --disable-shared           --disable-shared
411         --disable-static           --disable-static
412    
413       to the configure command, as required.         to the configure command, as required.
414    
415    
416  POSIX MALLOC USAGE  POSIX MALLOC USAGE
417    
418       When PCRE is called through the  POSIX  interface  (see  the         When PCRE is called through the POSIX interface (see the pcreposix doc-
419       pcreposix  documentation),  additional  working  storage  is         umentation), additional working storage is  required  for  holding  the
420       required for holding the pointers  to  capturing  substrings         pointers  to capturing substrings, because PCRE requires three integers
421       because  PCRE requires three integers per substring, whereas         per substring, whereas the POSIX interface provides only  two.  If  the
422       the POSIX interface provides only  two.  If  the  number  of         number of expected substrings is small, the wrapper function uses space
423       expected  substrings  is  small,  the  wrapper function uses         on the stack, because this is faster than using malloc() for each call.
424       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
425       loc()  for  each call. The default threshold above which the         can be changed by adding a setting such as
426       stack is no longer used is 10; it can be changed by adding a  
427       setting such as           --with-posix-malloc-threshold=20
428    
429         --with-posix-malloc-threshold=20         to the configure command.
430    
431       to the configure command.  
432    HANDLING VERY LARGE PATTERNS
433    
434           Within a compiled pattern, offset values are used  to  point  from  one
435           part  to another (for example, from an opening parenthesis to an alter-
436           nation metacharacter). By default, two-byte values are used  for  these
437           offsets,  leading  to  a  maximum size for a compiled pattern of around
438           64K. This is sufficient to handle all but the most  gigantic  patterns.
439           Nevertheless,  some  people do want to process truyl enormous patterns,
440           so it is possible to compile PCRE to use three-byte or  four-byte  off-
441           sets by adding a setting such as
442    
443             --with-link-size=3
444    
445           to  the  configure  command.  The value given must be 2, 3, or 4. Using
446           longer offsets slows down the operation of PCRE because it has to  load
447           additional bytes when handling them.
448    
449    
450    AVOIDING EXCESSIVE STACK USAGE
451    
452           When matching with the pcre_exec() function, PCRE implements backtrack-
453           ing by making recursive calls to an internal function  called  match().
454           In  environments  where  the size of the stack is limited, this can se-
455           verely limit PCRE's operation. (The Unix environment does  not  usually
456           suffer from this problem, but it may sometimes be necessary to increase
457           the maximum stack size.  There is a discussion in the  pcrestack  docu-
458           mentation.)  An alternative approach to recursion that uses memory from
459           the heap to remember data, instead of using recursive  function  calls,
460           has  been  implemented to work round the problem of limited stack size.
461           If you want to build a version of PCRE that works this way, add
462    
463             --disable-stack-for-recursion
464    
465           to the configure command. With this configuration, PCRE  will  use  the
466           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
467           ment functions. By default these point to malloc() and free(), but  you
468           can replace the pointers so that your own functions are used instead.
469    
470           Separate  functions  are  provided  rather  than  using pcre_malloc and
471           pcre_free because the  usage  is  very  predictable:  the  block  sizes
472           requested  are  always  the  same,  and  the blocks are always freed in
473           reverse order. A calling program might be able to  implement  optimized
474           functions  that  perform  better  than  malloc()  and free(). PCRE runs
475           noticeably more slowly when built in this way. This option affects only
476           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
477    
478    
479  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
480    
481       Internally, PCRE has a  function  called  match()  which  it         Internally,  PCRE has a function called match(), which it calls repeat-
482       calls  repeatedly  (possibly  recursively) when performing a         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
483       matching operation. By limiting the  number  of  times  this         pcre_exec()  function.  By controlling the maximum number of times this
484       function  may  be  called,  a  limit  can  be  placed on the         function may be called during a single matching operation, a limit  can
485       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
486       can  be  changed  at  run  time, as described in the pcreapi         limit can be changed at run time, as described in the pcreapi  documen-
487       documentation. The default is 10 million, but  this  can  be         tation.  The default is 10 million, but this can be changed by adding a
488       changed by adding a setting such as         setting such as
489    
490         --with-match-limit=500000           --with-match-limit=500000
491    
492       to the configure command.         to  the  configure  command.  This  setting  has  no  effect   on   the
493           pcre_dfa_exec() matching function.
494    
495           In  some  environments  it is desirable to limit the depth of recursive
496           calls of match() more strictly than the total number of calls, in order
497           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
498           for-recursion is specified) that is used. A second limit controls this;
499           it  defaults  to  the  value  that is set for --with-match-limit, which
500           imposes no additional constraints. However, you can set a  lower  limit
501           by adding, for example,
502    
503  HANDLING VERY LARGE PATTERNS           --with-match-limit-recursion=10000
504    
505       Within a compiled pattern, offset values are used  to  point         to  the  configure  command.  This  value can also be overridden at run
506       from  one  part  to  another  (for  example, from an opening         time.
507       parenthesis to an  alternation  metacharacter).  By  default  
508       two-byte  values  are  used  for these offsets, leading to a  
509       maximum size for a compiled pattern of around 64K.  This  is  CREATING CHARACTER TABLES AT BUILD TIME
510       sufficient  to  handle  all  but the most gigantic patterns.  
511       Nevertheless, some people do want to process  enormous  pat-         PCRE uses fixed tables for processing characters whose code values  are
512       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
513       or four-byte offsets by adding a setting such as         distributed in the file pcre_chartables.c.dist. These  tables  are  for
514           ASCII codes only. If you add
515         --with-link-size=3  
516             --enable-rebuild-chartables
517       to the configure command. The value given must be 2,  3,  or  
518       4.  Using  longer  offsets  slows down the operation of PCRE         to  the  configure  command, the distributed tables are no longer used.
519       because it has to load additional bytes when handling them.         Instead, a program called dftables is compiled and  run.  This  outputs
520           the source for new set of tables, created in the default locale of your
521       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
522       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
523       of these tests is a representation of the compiled  pattern,         you need to create alternative tables when cross  compiling,  you  will
524       and this changes with the link size.         have to do so "by hand".)
525    
526    
527    USING EBCDIC CODE
528    
529           PCRE  assumes  by  default that it will run in an environment where the
530           character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
531           This  is  the  case for most computer operating systems. PCRE can, how-
532           ever, be compiled to run in an EBCDIC environment by adding
533    
534             --enable-ebcdic
535    
536           to the configure command. This setting implies --enable-rebuild-charta-
537           bles.  You  should  only  use  it if you know that you are in an EBCDIC
538           environment (for example,  an  IBM  mainframe  operating  system).  The
539           --enable-ebcdic option is incompatible with --enable-utf8.
540    
541    
542    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
543    
544           By default, pcregrep reads all files as plain text. You can build it so
545           that it recognizes files whose names end in .gz or .bz2, and reads them
546           with libz or libbz2, respectively, by adding one or both of
547    
548             --enable-pcregrep-libz
549             --enable-pcregrep-libbz2
550    
551           to the configure command. These options naturally require that the rel-
552           evant libraries are installed on your system. Configuration  will  fail
553           if they are not.
554    
555    
556    PCRETEST OPTION FOR LIBREADLINE SUPPORT
557    
558           If you add
559    
560             --enable-pcretest-libreadline
561    
562           to  the  configure  command,  pcretest  is  linked with the libreadline
563           library, and when its input is from a terminal, it reads it  using  the
564           readline() function. This provides line-editing and history facilities.
565           Note that libreadline is GPL-licensed, so if you distribute a binary of
566           pcretest linked in this way, there may be licensing issues.
567    
568           Setting  this  option  causes  the -lreadline option to be added to the
569           pcretest build. In many operating environments with  a  sytem-installed
570           libreadline this is sufficient. However, in some environments (e.g.  if
571           an unmodified distribution version of readline is in use),  some  extra
572           configuration  may  be necessary. The INSTALL file for libreadline says
573           this:
574    
575             "Readline uses the termcap functions, but does not link with the
576             termcap or curses library itself, allowing applications which link
577             with readline the to choose an appropriate library."
578    
579           If your environment has not been set up so that an appropriate  library
580           is automatically included, you may need to add something like
581    
582             LIBS="-ncurses"
583    
584           immediately before the configure command.
585    
586    
587    SEE ALSO
588    
589           pcreapi(3), pcre_config(3).
590    
591    
592    AUTHOR
593    
594           Philip Hazel
595           University Computing Service
596           Cambridge CB2 3QH, England.
597    
598    
599    REVISION
600    
601           Last updated: 29 September 2009
602           Copyright (c) 1997-2009 University of Cambridge.
603    ------------------------------------------------------------------------------
604    
605    
606    PCREMATCHING(3)                                                PCREMATCHING(3)
607    
 Last updated: 21 January 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
608    
609  NAME  NAME
610       PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
611    
612    
613    PCRE MATCHING ALGORITHMS
614    
615           This document describes the two different algorithms that are available
616           in PCRE for matching a compiled regular expression against a given sub-
617           ject  string.  The  "standard"  algorithm  is  the  one provided by the
618           pcre_exec() function.  This works in the same was  as  Perl's  matching
619           function, and provides a Perl-compatible matching operation.
620    
621           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
622           this operates in a different way, and is not  Perl-compatible.  It  has
623           advantages  and disadvantages compared with the standard algorithm, and
624           these are described below.
625    
626           When there is only one possible way in which a given subject string can
627           match  a pattern, the two algorithms give the same answer. A difference
628           arises, however, when there are multiple possibilities. For example, if
629           the pattern
630    
631             ^<.*>
632    
633           is matched against the string
634    
635  SYNOPSIS OF PCRE API           <something> <something else> <something further>
636    
637       #include <pcre.h>         there are three possible answers. The standard algorithm finds only one
638           of them, whereas the alternative algorithm finds all three.
639    
      pcre *pcre_compile(const char *pattern, int options,  
           const char **errptr, int *erroffset,  
           const unsigned char *tableptr);  
640    
641       pcre_extra *pcre_study(const pcre *code, int options,  REGULAR EXPRESSIONS AS TREES
           const char **errptr);  
642    
643       int pcre_exec(const pcre *code, const pcre_extra *extra,         The set of strings that are matched by a regular expression can be rep-
644            const char *subject, int length, int startoffset,         resented  as  a  tree structure. An unlimited repetition in the pattern
645            int options, int *ovector, int ovecsize);         makes the tree of infinite size, but it is still a tree.  Matching  the
646           pattern  to a given subject string (from a given starting point) can be
647           thought of as a search of the tree.  There are two  ways  to  search  a
648           tree:  depth-first  and  breadth-first, and these correspond to the two
649           matching algorithms provided by PCRE.
650    
      int pcre_copy_named_substring(const pcre *code,  
           const char *subject, int *ovector,  
           int stringcount, const char *stringname,  
           char *buffer, int buffersize);  
651    
652       int pcre_copy_substring(const char *subject, int *ovector,  THE STANDARD MATCHING ALGORITHM
           int stringcount, int stringnumber, char *buffer,  
           int buffersize);  
653    
654       int pcre_get_named_substring(const pcre *code,         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
655            const char *subject, int *ovector,         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
656            int stringcount, const char *stringname,         depth-first search of the pattern tree. That is, it  proceeds  along  a
657            const char **stringptr);         single path through the tree, checking that the subject matches what is
658           required. When there is a mismatch, the algorithm  tries  any  alterna-
659           tives  at  the  current point, and if they all fail, it backs up to the
660           previous branch point in the  tree,  and  tries  the  next  alternative
661           branch  at  that  level.  This often involves backing up (moving to the
662           left) in the subject string as well.  The  order  in  which  repetition
663           branches  are  tried  is controlled by the greedy or ungreedy nature of
664           the quantifier.
665    
666       int pcre_get_stringnumber(const pcre *code,         If a leaf node is reached, a matching string has  been  found,  and  at
667            const char *name);         that  point the algorithm stops. Thus, if there is more than one possi-
668           ble match, this algorithm returns the first one that it finds.  Whether
669           this  is the shortest, the longest, or some intermediate length depends
670           on the way the greedy and ungreedy repetition quantifiers are specified
671           in the pattern.
672    
673       int pcre_get_substring(const char *subject, int *ovector,         Because  it  ends  up  with a single path through the tree, it is rela-
674            int stringcount, int stringnumber,         tively straightforward for this algorithm to keep  track  of  the  sub-
675            const char **stringptr);         strings  that  are  matched  by portions of the pattern in parentheses.
676           This provides support for capturing parentheses and back references.
677    
      int pcre_get_substring_list(const char *subject,  
           int *ovector, int stringcount, const char ***listptr);  
678    
679       void pcre_free_substring(const char *stringptr);  THE ALTERNATIVE MATCHING ALGORITHM
680    
681       void pcre_free_substring_list(const char **stringptr);         This algorithm conducts a breadth-first search of  the  tree.  Starting
682           from  the  first  matching  point  in the subject, it scans the subject
683           string from left to right, once, character by character, and as it does
684           this,  it remembers all the paths through the tree that represent valid
685           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
686           though  it is not implemented as a traditional finite state machine (it
687           keeps multiple states active simultaneously).
688    
689       const unsigned char *pcre_maketables(void);         Although the general principle of this matching algorithm  is  that  it
690           scans  the subject string only once, without backtracking, there is one
691           exception: when a lookaround assertion is encountered,  the  characters
692           following  or  preceding  the  current  point  have to be independently
693           inspected.
694    
695       int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         The scan continues until either the end of the subject is  reached,  or
696            int what, void *where);         there  are  no more unterminated paths. At this point, terminated paths
697           represent the different matching possibilities (if there are none,  the
698           match  has  failed).   Thus,  if there is more than one possible match,
699           this algorithm finds all of them, and in particular, it finds the long-
700           est.  There  is  an  option to stop the algorithm after the first match
701           (which is necessarily the shortest) is found.
702    
703           Note that all the matches that are found start at the same point in the
704           subject. If the pattern
705    
706       int pcre_info(const pcre *code, int *optptr, *firstcharptr);           cat(er(pillar)?)
707    
708       int pcre_config(int what, void *where);         is  matched  against the string "the caterpillar catchment", the result
709           will be the three strings "cat", "cater", and "caterpillar" that  start
710           at the fourth character of the subject. The algorithm does not automat-
711           ically move on to find matches that start at later positions.
712    
713       char *pcre_version(void);         There are a number of features of PCRE regular expressions that are not
714           supported by the alternative matching algorithm. They are as follows:
715    
716       void *(*pcre_malloc)(size_t);         1.  Because  the  algorithm  finds  all possible matches, the greedy or
717           ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
718           ungreedy quantifiers are treated in exactly the same way. However, pos-
719           sessive quantifiers can make a difference when what follows could  also
720           match what is quantified, for example in a pattern like this:
721    
722       void (*pcre_free)(void *);           ^a++\w!
723    
724       int (*pcre_callout)(pcre_callout_block *);         This  pattern matches "aaab!" but not "aaa!", which would be matched by
725           a non-possessive quantifier. Similarly, if an atomic group is  present,
726           it  is matched as if it were a standalone pattern at the current point,
727           and the longest match is then "locked in" for the rest of  the  overall
728           pattern.
729    
730           2. When dealing with multiple paths through the tree simultaneously, it
731           is not straightforward to keep track of  captured  substrings  for  the
732           different  matching  possibilities,  and  PCRE's implementation of this
733           algorithm does not attempt to do this. This means that no captured sub-
734           strings are available.
735    
736  PCRE API         3.  Because no substrings are captured, back references within the pat-
737           tern are not supported, and cause errors if encountered.
738    
739       PCRE has its own native API,  which  is  described  in  this         4. For the same reason, conditional expressions that use  a  backrefer-
740       document.  There  is  also  a  set of wrapper functions that         ence  as  the  condition or test for a specific group recursion are not
741       correspond to the POSIX regular expression API.   These  are         supported.
      described in the pcreposix documentation.  
742    
743       The native API function prototypes are defined in the header         5. Because many paths through the tree may be  active,  the  \K  escape
744       file  pcre.h,  and  on  Unix  systems  the library itself is         sequence, which resets the start of the match when encountered (but may
745       called libpcre.a, so can be accessed by adding -lpcre to the         be on some paths and not on others), is not  supported.  It  causes  an
746       command  for  linking  an  application  which  calls it. The         error if encountered.
      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.  
747    
748       The functions pcre_compile(), pcre_study(), and  pcre_exec()         6.  Callouts  are  supported, but the value of the capture_top field is
749       are  used  for compiling and matching regular expressions. A         always 1, and the value of the capture_last field is always -1.
      sample program that demonstrates the simplest way  of  using  
      them  is  given in the file pcredemo.c. The pcresample docu-  
      mentation describes how to run it.  
750    
751       There are convenience functions for extracting captured sub-         7. The \C escape sequence, which (in the standard algorithm) matches  a
752       strings from a matched subject string. They are:         single  byte, even in UTF-8 mode, is not supported because the alterna-
753           tive algorithm moves through the subject  string  one  character  at  a
754           time, for all active paths through the tree.
755    
756         pcre_copy_substring()         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
757         pcre_copy_named_substring()         are not supported. (*FAIL) is supported, and  behaves  like  a  failing
758         pcre_get_substring()         negative assertion.
        pcre_get_named_substring()  
        pcre_get_substring_list()  
759    
      pcre_free_substring()  and  pcre_free_substring_list()   are  
      also  provided,  to  free  the  memory  used  for  extracted  
      strings.  
760    
761       The function pcre_maketables() is used (optionally) to build  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
      a  set of character tables in the current locale for passing  
      to pcre_compile().  
762    
763       The function pcre_fullinfo() is used to find out information         Using  the alternative matching algorithm provides the following advan-
764       about a compiled pattern; pcre_info() is an obsolete version         tages:
      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.  
765    
766       The global variables  pcre_malloc  and  pcre_free  initially         1. All possible matches (at a single point in the subject) are automat-
767       contain the entry points of the standard malloc() and free()         ically  found,  and  in particular, the longest match is found. To find
768       functions respectively. PCRE  calls  the  memory  management         more than one match using the standard algorithm, you have to do kludgy
769       functions  via  these  variables,  so  a calling program can         things with callouts.
      replace them if it  wishes  to  intercept  the  calls.  This  
      should be done before calling any PCRE functions.  
770    
771       The global variable pcre_callout initially contains NULL. It         2.  Because  the  alternative  algorithm  scans the subject string just
772       can be set by the caller to a "callout" function, which PCRE         once, and never needs to backtrack, it is possible to  pass  very  long
773       will then call at specified points during a matching  opera-         subject  strings  to  the matching function in several pieces, checking
774       tion. Details are given in the pcrecallout documentation.         for partial matching each time. It  is  possible  to  do  multi-segment
775           matching using pcre_exec() (by retaining partially matched substrings),
776           but it is more complicated. The pcrepartial documentation gives details
777           of partial matching and discusses multi-segment matching.
778    
779    
780    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
781    
782           The alternative algorithm suffers from a number of disadvantages:
783    
784           1.  It  is  substantially  slower  than the standard algorithm. This is
785           partly because it has to search for all possible matches, but  is  also
786           because it is less susceptible to optimization.
787    
788           2. Capturing parentheses and back references are not supported.
789    
790           3. Although atomic groups are supported, their use does not provide the
791           performance advantage that it does for the standard algorithm.
792    
793    
794    AUTHOR
795    
796           Philip Hazel
797           University Computing Service
798           Cambridge CB2 3QH, England.
799    
800    
801    REVISION
802    
803           Last updated: 22 October 2010
804           Copyright (c) 1997-2010 University of Cambridge.
805    ------------------------------------------------------------------------------
806    
807    
808    PCREAPI(3)                                                          PCREAPI(3)
809    
810    
811    NAME
812           PCRE - Perl-compatible regular expressions
813    
814    
815    PCRE NATIVE API
816    
817           #include <pcre.h>
818    
819           pcre *pcre_compile(const char *pattern, int options,
820                const char **errptr, int *erroffset,
821                const unsigned char *tableptr);
822    
823           pcre *pcre_compile2(const char *pattern, int options,
824                int *errorcodeptr,
825                const char **errptr, int *erroffset,
826                const unsigned char *tableptr);
827    
828           pcre_extra *pcre_study(const pcre *code, int options,
829                const char **errptr);
830    
831           int pcre_exec(const pcre *code, const pcre_extra *extra,
832                const char *subject, int length, int startoffset,
833                int options, int *ovector, int ovecsize);
834    
835           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
836                const char *subject, int length, int startoffset,
837                int options, int *ovector, int ovecsize,
838                int *workspace, int wscount);
839    
840           int pcre_copy_named_substring(const pcre *code,
841                const char *subject, int *ovector,
842                int stringcount, const char *stringname,
843                char *buffer, int buffersize);
844    
845           int pcre_copy_substring(const char *subject, int *ovector,
846                int stringcount, int stringnumber, char *buffer,
847                int buffersize);
848    
849           int pcre_get_named_substring(const pcre *code,
850                const char *subject, int *ovector,
851                int stringcount, const char *stringname,
852                const char **stringptr);
853    
854           int pcre_get_stringnumber(const pcre *code,
855                const char *name);
856    
857           int pcre_get_stringtable_entries(const pcre *code,
858                const char *name, char **first, char **last);
859    
860           int pcre_get_substring(const char *subject, int *ovector,
861                int stringcount, int stringnumber,
862                const char **stringptr);
863    
864           int pcre_get_substring_list(const char *subject,
865                int *ovector, int stringcount, const char ***listptr);
866    
867           void pcre_free_substring(const char *stringptr);
868    
869           void pcre_free_substring_list(const char **stringptr);
870    
871           const unsigned char *pcre_maketables(void);
872    
873           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
874                int what, void *where);
875    
876           int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
877    
878           int pcre_refcount(pcre *code, int adjust);
879    
880           int pcre_config(int what, void *where);
881    
882           char *pcre_version(void);
883    
884           void *(*pcre_malloc)(size_t);
885    
886           void (*pcre_free)(void *);
887    
888           void *(*pcre_stack_malloc)(size_t);
889    
890           void (*pcre_stack_free)(void *);
891    
892           int (*pcre_callout)(pcre_callout_block *);
893    
894    
895    PCRE API OVERVIEW
896    
897           PCRE has its own native API, which is described in this document. There
898           are also some wrapper functions that correspond to  the  POSIX  regular
899           expression  API.  These  are  described in the pcreposix documentation.
900           Both of these APIs define a set of C function calls. A C++  wrapper  is
901           distributed with PCRE. It is documented in the pcrecpp page.
902    
903           The  native  API  C  function prototypes are defined in the header file
904           pcre.h, and on Unix systems the library itself is called  libpcre.   It
905           can normally be accessed by adding -lpcre to the command for linking an
906           application  that  uses  PCRE.  The  header  file  defines  the  macros
907           PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
908           bers for the library.  Applications can use these  to  include  support
909           for different releases of PCRE.
910    
911           In a Windows environment, if you want to statically link an application
912           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
913           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
914           loc()   and   pcre_free()   exported   functions   will   be   declared
915           __declspec(dllimport), with unwanted results.
916    
917           The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
918           pcre_exec() are used for compiling and matching regular expressions  in
919           a  Perl-compatible  manner. A sample program that demonstrates the sim-
920           plest way of using them is provided in the file  called  pcredemo.c  in
921           the PCRE source distribution. A listing of this program is given in the
922           pcredemo documentation, and the pcresample documentation describes  how
923           to compile and run it.
924    
925           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
926           ble, is also provided. This uses a different algorithm for  the  match-
927           ing.  The  alternative algorithm finds all possible matches (at a given
928           point in the subject), and scans the subject just  once  (unless  there
929           are  lookbehind  assertions).  However,  this algorithm does not return
930           captured substrings. A description of the two matching  algorithms  and
931           their  advantages  and disadvantages is given in the pcrematching docu-
932           mentation.
933    
934           In addition to the main compiling and  matching  functions,  there  are
935           convenience functions for extracting captured substrings from a subject
936           string that is matched by pcre_exec(). They are:
937    
938             pcre_copy_substring()
939             pcre_copy_named_substring()
940             pcre_get_substring()
941             pcre_get_named_substring()
942             pcre_get_substring_list()
943             pcre_get_stringnumber()
944             pcre_get_stringtable_entries()
945    
946           pcre_free_substring() and pcre_free_substring_list() are also provided,
947           to free the memory used for extracted strings.
948    
949           The  function  pcre_maketables()  is  used  to build a set of character
950           tables  in  the  current  locale   for   passing   to   pcre_compile(),
951           pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
952           provided for specialist use.  Most  commonly,  no  special  tables  are
953           passed,  in  which case internal tables that are generated when PCRE is
954           built are used.
955    
956           The function pcre_fullinfo() is used to find out  information  about  a
957           compiled  pattern; pcre_info() is an obsolete version that returns only
958           some of the available information, but is retained for  backwards  com-
959           patibility.   The function pcre_version() returns a pointer to a string
960           containing the version of PCRE and its date of release.
961    
962           The function pcre_refcount() maintains a  reference  count  in  a  data
963           block  containing  a compiled pattern. This is provided for the benefit
964           of object-oriented applications.
965    
966           The global variables pcre_malloc and pcre_free  initially  contain  the
967           entry  points  of  the  standard malloc() and free() functions, respec-
968           tively. PCRE calls the memory management functions via these variables,
969           so  a  calling  program  can replace them if it wishes to intercept the
970           calls. This should be done before calling any PCRE functions.
971    
972           The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
973           indirections  to  memory  management functions. These special functions
974           are used only when PCRE is compiled to use  the  heap  for  remembering
975           data, instead of recursive function calls, when running the pcre_exec()
976           function. See the pcrebuild documentation for  details  of  how  to  do
977           this.  It  is  a non-standard way of building PCRE, for use in environ-
978           ments that have limited stacks. Because of the greater  use  of  memory
979           management,  it  runs  more  slowly. Separate functions are provided so
980           that special-purpose external code can be  used  for  this  case.  When
981           used,  these  functions  are always called in a stack-like manner (last
982           obtained, first freed), and always for memory blocks of the same  size.
983           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
984           mentation.
985    
986           The global variable pcre_callout initially contains NULL. It can be set
987           by  the  caller  to  a "callout" function, which PCRE will then call at
988           specified points during a matching operation. Details are given in  the
989           pcrecallout documentation.
990    
991    
992    NEWLINES
993    
994           PCRE  supports five different conventions for indicating line breaks in
995           strings: a single CR (carriage return) character, a  single  LF  (line-
996           feed) character, the two-character sequence CRLF, any of the three pre-
997           ceding, or any Unicode newline sequence. The Unicode newline  sequences
998           are  the  three just mentioned, plus the single characters VT (vertical
999           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
1000           separator, U+2028), and PS (paragraph separator, U+2029).
1001    
1002           Each  of  the first three conventions is used by at least one operating
1003           system as its standard newline sequence. When PCRE is built, a  default
1004           can  be  specified.  The default default is LF, which is the Unix stan-
1005           dard. When PCRE is run, the default can be overridden,  either  when  a
1006           pattern is compiled, or when it is matched.
1007    
1008           At compile time, the newline convention can be specified by the options
1009           argument of pcre_compile(), or it can be specified by special  text  at
1010           the start of the pattern itself; this overrides any other settings. See
1011           the pcrepattern page for details of the special character sequences.
1012    
1013           In the PCRE documentation the word "newline" is used to mean "the char-
1014           acter  or pair of characters that indicate a line break". The choice of
1015           newline convention affects the handling of  the  dot,  circumflex,  and
1016           dollar metacharacters, the handling of #-comments in /x mode, and, when
1017           CRLF is a recognized line ending sequence, the match position  advance-
1018           ment for a non-anchored pattern. There is more detail about this in the
1019           section on pcre_exec() options below.
1020    
1021           The choice of newline convention does not affect the interpretation  of
1022           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1023           which is controlled in a similar way, but by separate options.
1024    
1025    
1026  MULTITHREADING  MULTITHREADING
1027    
1028       The PCRE functions can be used in  multi-threading  applica-         The PCRE functions can be used in  multi-threading  applications,  with
1029       tions, with the proviso that the memory management functions         the  proviso  that  the  memory  management  functions  pointed  to  by
1030       pointed to by pcre_malloc and  pcre_free,  and  the  callout         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1031       function  pointed  to  by  pcre_callout,  are  shared by all         callout function pointed to by pcre_callout, are shared by all threads.
1032       threads.  
1033           The  compiled form of a regular expression is not altered during match-
1034       The compiled form of a regular  expression  is  not  altered         ing, so the same compiled pattern can safely be used by several threads
1035       during  matching, so the same compiled pattern can safely be         at once.
1036       used by several threads at once.  
1037    
1038    SAVING PRECOMPILED PATTERNS FOR LATER USE
1039    
1040           The compiled form of a regular expression can be saved and re-used at a
1041           later time, possibly by a different program, and even on a  host  other
1042           than  the  one  on  which  it  was  compiled.  Details are given in the
1043           pcreprecompile documentation. However, compiling a  regular  expression
1044           with  one version of PCRE for use with a different version is not guar-
1045           anteed to work and may cause crashes.
1046    
1047    
1048  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
1049    
1050       int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1051    
1052           The function pcre_config() makes it possible for a PCRE client to  dis-
1053           cover which optional features have been compiled into the PCRE library.
1054           The pcrebuild documentation has more details about these optional  fea-
1055           tures.
1056    
1057           The  first  argument  for pcre_config() is an integer, specifying which
1058           information is required; the second argument is a pointer to a variable
1059           into  which  the  information  is  placed. The following information is
1060           available:
1061    
1062       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.  
1063    
1064       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-
1065       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:  
1066    
1067         PCRE_CONFIG_UTF8           PCRE_CONFIG_UNICODE_PROPERTIES
1068    
1069       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
1070       is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1071    
1072         PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1073    
1074       The output is an integer that is set to  the  value  of  the         The output is an integer whose value specifies  the  default  character
1075       code  that  is  used for the newline character. It is either         sequence  that is recognized as meaning "newline". The four values that
1076       linefeed (10) or carriage return (13), and  should  normally         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1077       be the standard character for your operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1078           are returned in EBCDIC environments. The default should normally corre-
1079           spond to the standard sequence for your operating system.
1080    
1081         PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_BSR
1082    
1083       The output is an integer that contains the number  of  bytes         The output is an integer whose value indicates what character sequences
1084       used  for  internal linkage in compiled regular expressions.         the \R escape sequence matches by default. A value of 0 means  that  \R
1085       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
1086       expressions  to be compiled, at the expense of slower match-         matches only CR, LF, or CRLF. The default can be overridden when a pat-
1087       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.  
1088    
1089         PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_LINK_SIZE
1090    
1091       The output is an integer that contains the  threshold  above         The  output  is  an  integer that contains the number of bytes used for
1092       which  the POSIX interface uses malloc() for output vectors.         internal linkage in compiled regular expressions. The value is 2, 3, or
1093       Further details are given in the pcreposix documentation.         4.  Larger  values  allow larger regular expressions to be compiled, at
1094           the expense of slower matching. The default value of  2  is  sufficient
1095           for  all  but  the  most massive patterns, since it allows the compiled
1096           pattern to be up to 64K in size.
1097    
1098         PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1099    
1100       The output is an integer that gives the  default  limit  for         The output is an integer that contains the threshold  above  which  the
1101       the   number  of  internal  matching  function  calls  in  a         POSIX  interface  uses malloc() for output vectors. Further details are
1102       pcre_exec()  execution.  Further  details  are  given   with         given in the pcreposix documentation.
1103       pcre_exec() below.  
1104             PCRE_CONFIG_MATCH_LIMIT
1105    
1106           The output is a long integer that gives the default limit for the  num-
1107           ber  of  internal  matching  function calls in a pcre_exec() execution.
1108           Further details are given with pcre_exec() below.
1109    
1110             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1111    
1112           The output is a long integer that gives the default limit for the depth
1113           of   recursion  when  calling  the  internal  matching  function  in  a
1114           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1115           below.
1116    
1117             PCRE_CONFIG_STACKRECURSE
1118    
1119           The  output is an integer that is set to one if internal recursion when
1120           running pcre_exec() is implemented by recursive function calls that use
1121           the  stack  to remember their state. This is the usual way that PCRE is
1122           compiled. The output is zero if PCRE was compiled to use blocks of data
1123           on  the  heap  instead  of  recursive  function  calls.  In  this case,
1124           pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1125           blocks on the heap, thus avoiding the use of the stack.
1126    
1127    
1128  COMPILING A PATTERN  COMPILING A PATTERN
1129    
1130       pcre *pcre_compile(const char *pattern, int options,         pcre *pcre_compile(const char *pattern, int options,
1131            const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
1132            const unsigned char *tableptr);              const unsigned char *tableptr);
1133    
1134       The function pcre_compile() is called to compile  a  pattern         pcre *pcre_compile2(const char *pattern, int options,
1135       into  an internal form. The pattern is a C string terminated              int *errorcodeptr,
1136       by a binary zero, and is passed in the argument  pattern.  A              const char **errptr, int *erroffset,
1137       pointer  to  a  single  block of memory that is obtained via              const unsigned char *tableptr);
1138       pcre_malloc is returned. This contains the compiled code and  
1139       related  data.  The  pcre  type  is defined for the returned         Either of the functions pcre_compile() or pcre_compile2() can be called
1140       block; this is a typedef for a structure whose contents  are         to compile a pattern into an internal form. The only difference between
1141       not  externally  defined. It is up to the caller to free the         the  two interfaces is that pcre_compile2() has an additional argument,
1142       memory when it is no longer required.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1143           avoid  too  much repetition, we refer just to pcre_compile() below, but
1144       Although the compiled code of a PCRE regex  is  relocatable,         the information applies equally to pcre_compile2().
1145       that is, it does not depend on memory location, the complete  
1146       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
1147       tains  a  copy of the tableptr argument, which is an address         the  pattern  argument.  A  pointer to a single block of memory that is
1148       (see below).         obtained via pcre_malloc is returned. This contains the  compiled  code
1149       The options argument contains independent bits  that  affect         and related data. The pcre type is defined for the returned block; this
1150       the  compilation.  It  should  be  zero  if  no  options are         is a typedef for a structure whose contents are not externally defined.
1151       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
1152       compatible  with Perl, can also be set and unset from within         longer required.
1153       the pattern (see the detailed description of regular expres-  
1154       sions  in the pcrepattern documentation). For these options,         Although the compiled code of a PCRE regex is relocatable, that is,  it
1155       the contents of the options argument specifies their initial         does not depend on memory location, the complete pcre data block is not
1156       settings  at  the  start  of  compilation and execution. The         fully relocatable, because it may contain a copy of the tableptr  argu-
1157       PCRE_ANCHORED option can be set at the time of  matching  as         ment, which is an address (see below).
1158       well as at compile time.  
1159           The options argument contains various bit settings that affect the com-
1160       If errptr is NULL, pcre_compile() returns NULL  immediately.         pilation. It should be zero if no options are required.  The  available
1161       Otherwise, if compilation of a pattern fails, pcre_compile()         options  are  described  below. Some of them (in particular, those that
1162       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
1163       point  to a textual error message. The offset from the start         unset  from  within  the  pattern  (see the detailed description in the
1164       of  the  pattern  to  the  character  where  the  error  was         pcrepattern documentation). For those options that can be different  in
1165       discovered   is   placed  in  the  variable  pointed  to  by         different  parts  of  the pattern, the contents of the options argument
1166       erroffset, which must not be NULL. If it  is,  an  immediate         specifies their settings at the start of compilation and execution. The
1167       error is given.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1168           the time of matching as well as at compile time.
1169       If the final  argument,  tableptr,  is  NULL,  PCRE  uses  a  
1170       default  set  of character tables which are built when it is         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1171       compiled, using the default C  locale.  Otherwise,  tableptr         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1172       must  be  the result of a call to pcre_maketables(). See the         sets the variable pointed to by errptr to point to a textual error mes-
1173       section on locale support below.         sage. This is a static string that is part of the library. You must not
1174           try to free it. The byte offset from the start of the  pattern  to  the
1175       This code fragment shows a typical straightforward  call  to         character  that  was  being  processed when the error was discovered is
1176       pcre_compile():         placed in the variable pointed to by erroffset, which must not be NULL.
1177           If  it  is,  an  immediate error is given. Some errors are not detected
1178         pcre *re;         until checks are carried out when the whole pattern has  been  scanned;
1179         const char *error;         in this case the offset is set to the end of the pattern.
1180         int erroffset;  
1181         re = pcre_compile(         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1182           "^A.*Z",          /* the pattern */         codeptr argument is not NULL, a non-zero error code number is  returned
1183           0,                /* default options */         via  this argument in the event of an error. This is in addition to the
1184           &error,           /* for error message */         textual error message. Error codes and messages are listed below.
1185           &erroffset,       /* for error offset */  
1186           NULL);            /* use default character tables */         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1187           character  tables  that  are  built  when  PCRE  is compiled, using the
1188       The following option bits are defined:         default C locale. Otherwise, tableptr must be an address  that  is  the
1189           result  of  a  call to pcre_maketables(). This value is stored with the
1190         PCRE_ANCHORED         compiled pattern, and used again by pcre_exec(), unless  another  table
1191           pointer is passed to it. For more discussion, see the section on locale
1192       If this bit is set, the pattern is forced to be  "anchored",         support below.
1193       that is, it is constrained to match only at the first match-  
1194       ing point in the string which is being searched  (the  "sub-         This code fragment shows a typical straightforward  call  to  pcre_com-
1195       ject string"). This effect can also be achieved by appropri-         pile():
1196       ate constructs in the pattern itself, which is the only  way  
1197       to do it in Perl.           pcre *re;
1198             const char *error;
1199         PCRE_CASELESS           int erroffset;
1200             re = pcre_compile(
1201       If this bit is set, letters in the pattern match both  upper             "^A.*Z",          /* the pattern */
1202       and  lower  case  letters.  It  is  equivalent  to Perl's /i             0,                /* default options */
1203       option, and it can be changed within a  pattern  by  a  (?i)             &error,           /* for error message */
1204       option setting.             &erroffset,       /* for error offset */
1205               NULL);            /* use default character tables */
1206         PCRE_DOLLAR_ENDONLY  
1207           The  following  names  for option bits are defined in the pcre.h header
1208       If this bit is set, a dollar metacharacter  in  the  pattern         file:
1209       matches  only at the end of the subject string. Without this  
1210       option, a dollar also matches immediately before  the  final           PCRE_ANCHORED
1211       character  if it is a newline (but not before any other new-  
1212       lines).  The  PCRE_DOLLAR_ENDONLY  option  is   ignored   if         If this bit is set, the pattern is forced to be "anchored", that is, it
1213       PCRE_MULTILINE is set. There is no equivalent to this option         is  constrained to match only at the first matching point in the string
1214       in Perl, and no way to set it within a pattern.         that is being searched (the "subject string"). This effect can also  be
1215           achieved  by appropriate constructs in the pattern itself, which is the
1216         PCRE_DOTALL         only way to do it in Perl.
1217    
1218       If this bit is  set,  a  dot  metacharater  in  the  pattern           PCRE_AUTO_CALLOUT
1219       matches all characters, including newlines. Without it, new-  
1220       lines are excluded. This option is equivalent to  Perl's  /s         If this bit is set, pcre_compile() automatically inserts callout items,
1221       option,  and  it  can  be changed within a pattern by a (?s)         all  with  number  255, before each pattern item. For discussion of the
1222       option setting. A negative class such as [^a] always matches         callout facility, see the pcrecallout documentation.
1223       a  newline  character,  independent  of  the setting of this  
1224       option.           PCRE_BSR_ANYCRLF
1225             PCRE_BSR_UNICODE
1226         PCRE_EXTENDED  
1227           These options (which are mutually exclusive) control what the \R escape
1228       If this bit is set, whitespace data characters in  the  pat-         sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1229       tern  are  totally  ignored  except when escaped or inside a         or to match any Unicode newline sequence. The default is specified when
1230       character class. Whitespace does not include the VT  charac-         PCRE is built. It can be overridden from within the pattern, or by set-
1231       ter  (code 11). In addition, characters between an unescaped         ting an option when a compiled pattern is matched.
1232       # outside a character class and the next newline  character,  
1233       inclusive, are also ignored. This is equivalent to Perl's /x           PCRE_CASELESS
1234       option, and it can be changed within a  pattern  by  a  (?x)  
1235       option setting.         If this bit is set, letters in the pattern match both upper  and  lower
1236           case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1237       This option makes it possible  to  include  comments  inside         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1238       complicated patterns.  Note, however, that this applies only         always  understands the concept of case for characters whose values are
1239       to data characters. Whitespace characters may  never  appear         less than 128, so caseless matching is always possible. For  characters
1240       within special character sequences in a pattern, for example         with  higher  values,  the concept of case is supported if PCRE is com-
1241       within the sequence (?( which introduces a conditional  sub-         piled with Unicode property support, but not otherwise. If you want  to
1242       pattern.         use  caseless  matching  for  characters 128 and above, you must ensure
1243           that PCRE is compiled with Unicode property support  as  well  as  with
1244         PCRE_EXTRA         UTF-8 support.
1245    
1246       This option was invented in  order  to  turn  on  additional           PCRE_DOLLAR_ENDONLY
1247       functionality of PCRE that is incompatible with Perl, but it  
1248       is currently of very little use. When set, any backslash  in         If  this bit is set, a dollar metacharacter in the pattern matches only
1249       a  pattern  that is followed by a letter that has no special         at the end of the subject string. Without this option,  a  dollar  also
1250       meaning causes an error, thus reserving  these  combinations         matches  immediately before a newline at the end of the string (but not
1251       for  future  expansion.  By default, as in Perl, a backslash         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1252       followed by a letter with no special meaning is treated as a         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1253       literal.  There  are at present no other features controlled         Perl, and no way to set it within a pattern.
1254       by this option. It can also be set by a (?X) option  setting  
1255       within a pattern.           PCRE_DOTALL
1256    
1257         PCRE_MULTILINE         If this bit is set, a dot metacharater in the pattern matches all char-
1258           acters,  including  those that indicate newline. Without it, a dot does
1259       By default, PCRE treats the subject string as consisting  of         not match when the current position is at a  newline.  This  option  is
1260       a  single "line" of characters (even if it actually contains         equivalent  to Perl's /s option, and it can be changed within a pattern
1261       several newlines). The "start  of  line"  metacharacter  (^)         by a (?s) option setting. A negative class such as [^a] always  matches
1262       matches  only  at the start of the string, while the "end of         newline characters, independent of the setting of this option.
1263       line" metacharacter ($) matches  only  at  the  end  of  the  
1264       string,    or   before   a   terminating   newline   (unless           PCRE_DUPNAMES
1265       PCRE_DOLLAR_ENDONLY is set). This is the same as Perl.  
1266           If  this  bit is set, names used to identify capturing subpatterns need
1267       When PCRE_MULTILINE it is set, the "start of line" and  "end         not be unique. This can be helpful for certain types of pattern when it
1268       of  line"  constructs match immediately following or immedi-         is  known  that  only  one instance of the named subpattern can ever be
1269       ately before any newline  in  the  subject  string,  respec-         matched. There are more details of named subpatterns  below;  see  also
1270       tively,  as  well  as  at  the  very  start and end. This is         the pcrepattern documentation.
1271       equivalent to Perl's /m option, and it can be changed within  
1272       a  pattern  by  a  (?m) option setting. If there are no "\n"           PCRE_EXTENDED
1273       characters in a subject string, or no occurrences of ^ or  $  
1274       in a pattern, setting PCRE_MULTILINE has no effect.         If  this  bit  is  set,  whitespace  data characters in the pattern are
1275           totally ignored except when escaped or inside a character class. White-
1276         PCRE_NO_AUTO_CAPTURE         space does not include the VT character (code 11). In addition, charac-
1277           ters between an unescaped # outside a character class and the next new-
1278       If this option is set, it disables the use of numbered  cap-         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1279       turing  parentheses  in the pattern. Any opening parenthesis         option, and it can be changed within a pattern by a  (?x)  option  set-
1280       that is not followed by ? behaves as if it were followed  by         ting.
1281       ?:  but  named  parentheses  can still be used for capturing  
1282       (and they acquire numbers in the usual  way).  There  is  no         This  option  makes  it possible to include comments inside complicated
1283       equivalent of this option in Perl.         patterns.  Note, however, that this applies only  to  data  characters.
1284           Whitespace   characters  may  never  appear  within  special  character
1285         PCRE_UNGREEDY         sequences in a pattern, for  example  within  the  sequence  (?(  which
1286           introduces a conditional subpattern.
1287       This option inverts the "greediness" of the  quantifiers  so  
1288       that  they  are  not greedy by default, but become greedy if           PCRE_EXTRA
1289       followed by "?". It is not compatible with Perl. It can also  
1290       be set by a (?U) option setting within the pattern.         This  option  was invented in order to turn on additional functionality
1291           of PCRE that is incompatible with Perl, but it  is  currently  of  very
1292         PCRE_UTF8         little  use. When set, any backslash in a pattern that is followed by a
1293           letter that has no special meaning  causes  an  error,  thus  reserving
1294       This option causes PCRE to regard both the pattern  and  the         these  combinations  for  future  expansion.  By default, as in Perl, a
1295       subject  as  strings  of UTF-8 characters instead of single-         backslash followed by a letter with no special meaning is treated as  a
1296       byte character strings. However, it  is  available  only  if         literal. (Perl can, however, be persuaded to give an error for this, by
1297       PCRE  has  been  built to include UTF-8 support. If not, the         running it with the -w option.) There are at present no other  features
1298       use of this option provokes an error. Details  of  how  this         controlled  by this option. It can also be set by a (?X) option setting
1299       option  changes  the behaviour of PCRE are given in the sec-         within a pattern.
1300       tion on UTF-8 support in the main pcre page.  
1301             PCRE_FIRSTLINE
1302    
1303           If this option is set, an  unanchored  pattern  is  required  to  match
1304           before  or  at  the  first  newline  in  the subject string, though the
1305           matched text may continue over the newline.
1306    
1307             PCRE_JAVASCRIPT_COMPAT
1308    
1309           If this option is set, PCRE's behaviour is changed in some ways so that
1310           it  is  compatible with JavaScript rather than Perl. The changes are as
1311           follows:
1312    
1313           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1314           error,  because this is illegal in JavaScript (by default it is treated
1315           as a data character). Thus, the pattern AB]CD becomes illegal when this
1316           option is set.
1317    
1318           (2)  At run time, a back reference to an unset subpattern group matches
1319           an empty string (by default this causes the current  matching  alterna-
1320           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1321           set (assuming it can find an "a" in the subject), whereas it  fails  by
1322           default, for Perl compatibility.
1323    
1324             PCRE_MULTILINE
1325    
1326           By  default,  PCRE  treats the subject string as consisting of a single
1327           line of characters (even if it actually contains newlines). The  "start
1328           of  line"  metacharacter  (^)  matches only at the start of the string,
1329           while the "end of line" metacharacter ($) matches only at  the  end  of
1330           the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1331           is set). This is the same as Perl.
1332    
1333           When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1334           constructs  match  immediately following or immediately before internal
1335           newlines in the subject string, respectively, as well as  at  the  very
1336           start  and  end.  This is equivalent to Perl's /m option, and it can be
1337           changed within a pattern by a (?m) option setting. If there are no new-
1338           lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1339           setting PCRE_MULTILINE has no effect.
1340    
1341             PCRE_NEWLINE_CR
1342             PCRE_NEWLINE_LF
1343             PCRE_NEWLINE_CRLF
1344             PCRE_NEWLINE_ANYCRLF
1345             PCRE_NEWLINE_ANY
1346    
1347           These options override the default newline definition that  was  chosen
1348           when  PCRE  was built. Setting the first or the second specifies that a
1349           newline is indicated by a single character (CR  or  LF,  respectively).
1350           Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1351           two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1352           that any of the three preceding sequences should be recognized. Setting
1353           PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1354           recognized. The Unicode newline sequences are the three just mentioned,
1355           plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1356           U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1357           (paragraph separator, U+2029). The last  two  are  recognized  only  in
1358           UTF-8 mode.
1359    
1360           The  newline  setting  in  the  options  word  uses three bits that are
1361           treated as a number, giving eight possibilities. Currently only six are
1362           used  (default  plus the five values above). This means that if you set
1363           more than one newline option, the combination may or may not be  sensi-
1364           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1365           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1366           cause an error.
1367    
1368           The  only time that a line break is specially recognized when compiling
1369           a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1370           character  class  is  encountered.  This indicates a comment that lasts
1371           until after the next line break sequence. In other circumstances,  line
1372           break   sequences   are   treated  as  literal  data,  except  that  in
1373           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1374           and are therefore ignored.
1375    
1376           The newline option that is set at compile time becomes the default that
1377           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1378    
1379             PCRE_NO_AUTO_CAPTURE
1380    
1381           If this option is set, it disables the use of numbered capturing paren-
1382           theses  in the pattern. Any opening parenthesis that is not followed by
1383           ? behaves as if it were followed by ?: but named parentheses can  still
1384           be  used  for  capturing  (and  they acquire numbers in the usual way).
1385           There is no equivalent of this option in Perl.
1386    
1387             PCRE_UCP
1388    
1389           This option changes the way PCRE processes \b, \d, \s, \w, and some  of
1390           the POSIX character classes. By default, only ASCII characters are rec-
1391           ognized, but if PCRE_UCP is set, Unicode properties are used instead to
1392           classify  characters.  More details are given in the section on generic
1393           character types in the pcrepattern page. If you set PCRE_UCP,  matching
1394           one  of the items it affects takes much longer. The option is available
1395           only if PCRE has been compiled with Unicode property support.
1396    
1397             PCRE_UNGREEDY
1398    
1399           This option inverts the "greediness" of the quantifiers  so  that  they
1400           are  not greedy by default, but become greedy if followed by "?". It is
1401           not compatible with Perl. It can also be set by a (?U)  option  setting
1402           within the pattern.
1403    
1404             PCRE_UTF8
1405    
1406           This  option  causes PCRE to regard both the pattern and the subject as
1407           strings of UTF-8 characters instead of single-byte  character  strings.
1408           However,  it is available only when PCRE is built to include UTF-8 sup-
1409           port. If not, the use of this option provokes an error. Details of  how
1410           this  option  changes the behaviour of PCRE are given in the section on
1411           UTF-8 support in the main pcre page.
1412    
1413             PCRE_NO_UTF8_CHECK
1414    
1415           When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1416           automatically  checked.  There  is  a  discussion about the validity of
1417           UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
1418           bytes  is  found,  pcre_compile() returns an error. If you already know
1419           that your pattern is valid, and you want to skip this check for perfor-
1420           mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
1421           set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1422           undefined.  It  may  cause your program to crash. Note that this option
1423           can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1424           UTF-8 validity checking of subject strings.
1425    
1426    
1427    COMPILATION ERROR CODES
1428    
1429           The  following  table  lists  the  error  codes than may be returned by
1430           pcre_compile2(), along with the error messages that may be returned  by
1431           both  compiling functions. As PCRE has developed, some error codes have
1432           fallen out of use. To avoid confusion, they have not been re-used.
1433    
1434              0  no error
1435              1  \ at end of pattern
1436              2  \c at end of pattern
1437              3  unrecognized character follows \
1438              4  numbers out of order in {} quantifier
1439              5  number too big in {} quantifier
1440              6  missing terminating ] for character class
1441              7  invalid escape sequence in character class
1442              8  range out of order in character class
1443              9  nothing to repeat
1444             10  [this code is not in use]
1445             11  internal error: unexpected repeat
1446             12  unrecognized character after (? or (?-
1447             13  POSIX named classes are supported only within a class
1448             14  missing )
1449             15  reference to non-existent subpattern
1450             16  erroffset passed as NULL
1451             17  unknown option bit(s) set
1452             18  missing ) after comment
1453             19  [this code is not in use]
1454             20  regular expression is too large
1455             21  failed to get memory
1456             22  unmatched parentheses
1457             23  internal error: code overflow
1458             24  unrecognized character after (?<
1459             25  lookbehind assertion is not fixed length
1460             26  malformed number or name after (?(
1461             27  conditional group contains more than two branches
1462             28  assertion expected after (?(
1463             29  (?R or (?[+-]digits must be followed by )
1464             30  unknown POSIX class name
1465             31  POSIX collating elements are not supported
1466             32  this version of PCRE is not compiled with PCRE_UTF8 support
1467             33  [this code is not in use]
1468             34  character value in \x{...} sequence is too large
1469             35  invalid condition (?(0)
1470             36  \C not allowed in lookbehind assertion
1471             37  PCRE does not support \L, \l, \N, \U, or \u
1472             38  number after (?C is > 255
1473             39  closing ) for (?C expected
1474             40  recursive call could loop indefinitely
1475             41  unrecognized character after (?P
1476             42  syntax error in subpattern name (missing terminator)
1477             43  two named subpatterns have the same name
1478             44  invalid UTF-8 string
1479             45  support for \P, \p, and \X has not been compiled
1480             46  malformed \P or \p sequence
1481             47  unknown property name after \P or \p
1482             48  subpattern name is too long (maximum 32 characters)
1483             49  too many named subpatterns (maximum 10000)
1484             50  [this code is not in use]
1485             51  octal value is greater than \377 (not in UTF-8 mode)
1486             52  internal error: overran compiling workspace
1487             53  internal error: previously-checked referenced subpattern
1488                   not found
1489             54  DEFINE group contains more than one branch
1490             55  repeating a DEFINE group is not allowed
1491             56  inconsistent NEWLINE options
1492             57  \g is not followed by a braced, angle-bracketed, or quoted
1493                   name/number or by a plain number
1494             58  a numbered reference must not be zero
1495             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1496             60  (*VERB) not recognized
1497             61  number is too big
1498             62  subpattern name expected
1499             63  digit expected after (?+
1500             64  ] is an invalid data character in JavaScript compatibility mode
1501             65  different names for subpatterns of the same number are
1502                   not allowed
1503             66  (*MARK) must have an argument
1504             67  this version of PCRE is not compiled with PCRE_UCP support
1505    
1506           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1507           values may be used if the limits were changed when PCRE was built.
1508    
1509    
1510  STUDYING A PATTERN  STUDYING A PATTERN
1511    
1512       pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1513            const char **errptr);              const char **errptr);
1514    
1515       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
1516       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
1517       the time taken for matching. The function pcre_study() takes         matching.  The function pcre_study() takes a pointer to a compiled pat-
1518       a  pointer  to  a compiled pattern as its first argument. If         tern as its first argument. If studying the pattern produces additional
1519       studing the pattern  produces  additional  information  that         information  that  will  help speed up matching, pcre_study() returns a
1520       will  help speed up matching, pcre_study() returns a pointer         pointer to a pcre_extra block, in which the study_data field points  to
1521       to a pcre_extra block, in which the study_data field  points         the results of the study.
1522       to the results of the study.  
1523           The  returned  value  from  pcre_study()  can  be  passed  directly  to
1524       The  returned  value  from  a  pcre_study()  can  be  passed         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1525       directly  to pcre_exec(). However, the pcre_extra block also         tains  other  fields  that can be set by the caller before the block is
1526       contains other fields that can be set by the  caller  before         passed; these are described below in the section on matching a pattern.
1527       the  block is passed; these are described below. If studying  
1528       the pattern does not  produce  any  additional  information,         If studying the  pattern  does  not  produce  any  useful  information,
1529       pcre_study() returns NULL. In that circumstance, if the cal-         pcre_study() returns NULL. In that circumstance, if the calling program
1530       ling program wants to pass  some  of  the  other  fields  to         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1531       pcre_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1532    
1533       The second argument contains option  bits.  At  present,  no         The  second  argument of pcre_study() contains option bits. At present,
1534       options  are  defined  for  pcre_study(),  and this argument         no options are defined, and this argument should always be zero.
1535       should always be zero.  
1536           The third argument for pcre_study() is a pointer for an error  message.
1537       The third argument for pcre_study()  is  a  pointer  for  an         If  studying  succeeds  (even  if no data is returned), the variable it
1538       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
1539       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
1540       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
1541       fore  test  the  error  pointer  for  NULL   after   calling         after calling pcre_study(), to be sure that it has run successfully.
1542       pcre_study(), to be sure that it has run successfully.  
1543           This is a typical call to pcre_study():
1544       This is a typical call to pcre_study():  
1545             pcre_extra *pe;
1546         pcre_extra *pe;           pe = pcre_study(
1547         pe = pcre_study(             re,             /* result of pcre_compile() */
1548           re,             /* result of pcre_compile() */             0,              /* no options exist */
1549           0,              /* no options exist */             &error);        /* set to NULL or points to a message */
1550           &error);        /* set to NULL or points to a message */  
1551           Studying a pattern does two things: first, a lower bound for the length
1552       At present, studying a  pattern  is  useful  only  for  non-         of subject string that is needed to match the pattern is computed. This
1553       anchored  patterns  that do not have a single fixed starting         does not mean that there are any strings of that length that match, but
1554       character. A  bitmap  of  possible  starting  characters  is         it does guarantee that no shorter strings match. The value is  used  by
1555       created.         pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1556           match strings that are shorter than the lower bound. You can  find  out
1557           the value in a calling program via the pcre_fullinfo() function.
1558    
1559           Studying a pattern is also useful for non-anchored patterns that do not
1560           have a single fixed starting character. A bitmap of  possible  starting
1561           bytes  is  created. This speeds up finding a position in the subject at
1562           which to start matching.
1563    
1564           The two optimizations just described can be  disabled  by  setting  the
1565           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1566           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1567           callouts,  or  make  use of (*MARK), and you make use of these in cases
1568           where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE
1569           below.
1570    
1571    
1572  LOCALE SUPPORT  LOCALE SUPPORT
1573    
1574       PCRE handles caseless matching, and determines whether char-         PCRE  handles  caseless matching, and determines whether characters are
1575       acters  are  letters, digits, or whatever, by reference to a         letters, digits, or whatever, by reference to a set of tables,  indexed
1576       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
1577       to characters with codes less than 256. The library contains         characters with codes less than 128. By  default,  higher-valued  codes
1578       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
1579       locale  when  PCRE  is compiled. This is used when the final         PCRE is built with Unicode character property  support.  Alternatively,
1580       argument of pcre_compile() is NULL, and  is  sufficient  for         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1581       many applications.         friends to use Unicode property support instead of built-in tables. The
1582           use of locales with Unicode is discouraged. If you are handling charac-
1583       An alternative set of tables can, however, be supplied. Such         ters with codes greater than 128, you should either use UTF-8 and  Uni-
1584       tables  are built by calling the pcre_maketables() function,         code, or use locales, but not try to mix the two.
1585       which has no arguments, in the relevant locale.  The  result  
1586       can  then be passed to pcre_compile() as often as necessary.         PCRE  contains  an  internal set of tables that are used when the final
1587       For example, to build and use tables  that  are  appropriate         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1588       for  the French locale (where accented characters with codes         applications.  Normally, the internal tables recognize only ASCII char-
1589       greater than 128 are treated as letters), the following code         acters. However, when PCRE is built, it is possible to cause the inter-
1590       could be used:         nal tables to be rebuilt in the default "C" locale of the local system,
1591           which may cause them to be different.
1592         setlocale(LC_CTYPE, "fr");  
1593         tables = pcre_maketables();         The internal tables can always be overridden by tables supplied by  the
1594         re = pcre_compile(..., tables);         application that calls PCRE. These may be created in a different locale
1595           from the default. As more and more applications change  to  using  Uni-
1596       The  tables  are  built  in  memory  that  is  obtained  via         code, the need for this locale support is expected to die away.
1597       pcre_malloc.  The  pointer that is passed to pcre_compile is  
1598       saved with the compiled pattern, and  the  same  tables  are         External  tables  are  built by calling the pcre_maketables() function,
1599       used via this pointer by pcre_study() and pcre_exec(). Thus,         which has no arguments, in the relevant locale. The result can then  be
1600       for any single pattern, compilation, studying  and  matching         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1601       all happen in the same locale, but different patterns can be         example, to build and use tables that are appropriate  for  the  French
1602       compiled in different locales. It is the caller's  responsi-         locale  (where  accented  characters  with  values greater than 128 are
1603       bility  to  ensure  that  the  memory  containing the tables         treated as letters), the following code could be used:
1604       remains available for as long as it is needed.  
1605             setlocale(LC_CTYPE, "fr_FR");
1606             tables = pcre_maketables();
1607             re = pcre_compile(..., tables);
1608    
1609           The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1610           if you are using Windows, the name for the French locale is "french".
1611    
1612           When  pcre_maketables()  runs,  the  tables are built in memory that is
1613           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1614           that  the memory containing the tables remains available for as long as
1615           it is needed.
1616    
1617           The pointer that is passed to pcre_compile() is saved with the compiled
1618           pattern,  and the same tables are used via this pointer by pcre_study()
1619           and normally also by pcre_exec(). Thus, by default, for any single pat-
1620           tern, compilation, studying and matching all happen in the same locale,
1621           but different patterns can be compiled in different locales.
1622    
1623           It is possible to pass a table pointer or NULL (indicating the  use  of
1624           the  internal  tables)  to  pcre_exec(). Although not intended for this
1625           purpose, this facility could be used to match a pattern in a  different
1626           locale from the one in which it was compiled. Passing table pointers at
1627           run time is discussed below in the section on matching a pattern.
1628    
1629    
1630  INFORMATION ABOUT A PATTERN  INFORMATION ABOUT A PATTERN
1631    
1632       int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1633            int what, void *where);              int what, void *where);
1634    
1635       The pcre_fullinfo() function  returns  information  about  a         The pcre_fullinfo() function returns information about a compiled  pat-
1636       compiled pattern. It replaces the obsolete pcre_info() func-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1637       tion, which is nevertheless retained for backwards compabil-         less retained for backwards compability (and is documented below).
1638       ity (and is documented below).  
1639           The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1640       The first argument for pcre_fullinfo() is a pointer  to  the         pattern.  The second argument is the result of pcre_study(), or NULL if
1641       compiled  pattern.  The  second  argument  is  the result of         the pattern was not studied. The third argument specifies  which  piece
1642       pcre_study(), or NULL if the pattern was  not  studied.  The         of  information  is required, and the fourth argument is a pointer to a
1643       third  argument  specifies  which  piece  of  information is         variable to receive the data. The yield of the  function  is  zero  for
1644       required, and the fourth argument is a pointer to a variable         success, or one of the following negative numbers:
1645       to  receive  the data. The yield of the function is zero for  
1646       success, or one of the following negative numbers:           PCRE_ERROR_NULL       the argument code was NULL
1647                                   the argument where was NULL
1648         PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1649                               the argument where was NULL           PCRE_ERROR_BADOPTION  the value of what was invalid
1650         PCRE_ERROR_BADMAGIC   the "magic number" was not found  
1651         PCRE_ERROR_BADOPTION  the value of what was invalid         The  "magic  number" is placed at the start of each compiled pattern as
1652           an simple check against passing an arbitrary memory pointer. Here is  a
1653       Here is a typical call of  pcre_fullinfo(),  to  obtain  the         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1654       length of the compiled pattern:         pattern:
1655    
1656         int rc;           int rc;
1657         unsigned long int length;           size_t length;
1658         rc = pcre_fullinfo(           rc = pcre_fullinfo(
1659           re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1660           pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1661           PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1662           &length);         /* where to put the data */             &length);         /* where to put the data */
1663    
1664       The possible values for the third argument  are  defined  in         The possible values for the third argument are defined in  pcre.h,  and
1665       pcre.h, and are as follows:         are as follows:
1666    
1667         PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1668    
1669       Return the number of the highest back reference in the  pat-         Return  the  number  of  the highest back reference in the pattern. The
1670       tern.  The  fourth argument should point to an int variable.         fourth argument should point to an int variable. Zero  is  returned  if
1671       Zero is returned if there are no back references.         there are no back references.
1672    
1673         PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1674    
1675       Return the number of capturing subpatterns in  the  pattern.         Return  the  number of capturing subpatterns in the pattern. The fourth
1676       The fourth argument should point to an int variable.         argument should point to an int variable.
1677    
1678         PCRE_INFO_FIRSTBYTE           PCRE_INFO_DEFAULT_TABLES
1679    
1680       Return information about  the  first  byte  of  any  matched         Return a pointer to the internal default character tables within  PCRE.
1681       string,  for a non-anchored pattern. (This option used to be         The  fourth  argument should point to an unsigned char * variable. This
1682       called PCRE_INFO_FIRSTCHAR; the old name is still recognized         information call is provided for internal use by the pcre_study() func-
1683       for backwards compatibility.)         tion.  External  callers  can  cause PCRE to use its internal tables by
1684           passing a NULL table pointer.
1685       If there is a fixed first byte, e.g. from a pattern such  as  
1686       (cat|cow|coyote),  it  is returned in the integer pointed to           PCRE_INFO_FIRSTBYTE
1687       by where. Otherwise, if either  
1688           Return information about the first byte of any matched  string,  for  a
1689       (a) the pattern was compiled with the PCRE_MULTILINE option,         non-anchored  pattern. The fourth argument should point to an int vari-
1690       and every branch starts with "^", or         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1691           is still recognized for backwards compatibility.)
1692       (b) every  branch  of  the  pattern  starts  with  ".*"  and  
1693       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
1694       anchored),         (cat|cow|coyote), its value is returned. Otherwise, if either
1695    
1696       -1 is returned, indicating that the pattern matches only  at         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1697       the  start  of  a subject string or after any newline within         branch starts with "^", or
1698       the string. Otherwise -2 is returned. For anchored patterns,  
1699       -2 is returned.         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1700           set (if it were set, the pattern would be anchored),
1701         PCRE_INFO_FIRSTTABLE  
1702           -1 is returned, indicating that the pattern matches only at  the  start
1703       If the pattern was studied, and this resulted  in  the  con-         of  a  subject string or after any newline within the string. Otherwise
1704       struction of a 256-bit table indicating a fixed set of bytes         -2 is returned. For anchored patterns, -2 is returned.
1705       for the first byte in any matching string, a pointer to  the  
1706       table  is  returned.  Otherwise NULL is returned. The fourth           PCRE_INFO_FIRSTTABLE
1707       argument should point to an unsigned char * variable.  
1708           If the pattern was studied, and this resulted in the construction of  a
1709         PCRE_INFO_LASTLITERAL         256-bit table indicating a fixed set of bytes for the first byte in any
1710           matching string, a pointer to the table is returned. Otherwise NULL  is
1711       Return the value of the rightmost  literal  byte  that  must         returned.  The fourth argument should point to an unsigned char * vari-
1712       exist  in  any  matched  string, other than at its start, if         able.
1713       such a byte has been recorded. The  fourth  argument  should  
1714       point  to  an  int variable. If there is no such byte, -1 is           PCRE_INFO_HASCRORLF
1715       returned. For anchored patterns,  a  last  literal  byte  is  
1716       recorded  only  if  it follows something of variable length.         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1717       For example, for the pattern /^a\d+z\d+/ the returned  value         characters,  otherwise  0.  The  fourth argument should point to an int
1718       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
1719           \r or \n.
1720         PCRE_INFO_NAMECOUNT  
1721         PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_JCHANGED
1722         PCRE_INFO_NAMETABLE  
1723           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1724       PCRE supports the use of named as well as numbered capturing         otherwise 0. The fourth argument should point to an int variable.  (?J)
1725       parentheses. The names are just an additional way of identi-         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1726       fying the parentheses,  which  still  acquire  a  number.  A  
1727       caller  that  wants  to extract data from a named subpattern           PCRE_INFO_LASTLITERAL
1728       must convert the name to a number in  order  to  access  the  
1729       correct  pointers  in  the  output  vector  (described  with         Return  the  value of the rightmost literal byte that must exist in any
1730       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
1731       these  three  values  to  obtain  the name-to-number mapping         recorded. The fourth argument should point to an int variable. If there
1732       table for the pattern.         is no such byte, -1 is returned. For anchored patterns, a last  literal
1733           byte  is  recorded only if it follows something of variable length. For
1734       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
1735       PCRE_INFO_NAMECOUNT   gives   the  number  of  entries,  and         /^a\dz\d/ the returned value is -1.
1736       PCRE_INFO_NAMEENTRYSIZE gives the size of each  entry;  both  
1737       of  these return an int value. The entry size depends on the           PCRE_INFO_MINLENGTH
1738       length of the longest name.  PCRE_INFO_NAMETABLE  returns  a  
1739       pointer to the first entry of the table (a pointer to char).         If  the  pattern  was studied and a minimum length for matching subject
1740       The first two bytes of each entry are the number of the cap-         strings was computed, its value is  returned.  Otherwise  the  returned
1741       turing parenthesis, most significant byte first. The rest of         value  is  -1. The value is a number of characters, not bytes (this may
1742       the entry is the corresponding name,  zero  terminated.  The         be relevant in UTF-8 mode). The fourth argument should point to an  int
1743       names  are  in alphabetical order. For example, consider the         variable.  A  non-negative  value is a lower bound to the length of any
1744       following pattern (assume PCRE_EXTENDED  is  set,  so  white         matching string. There may not be any strings of that  length  that  do
1745       space - including newlines - is ignored):         actually match, but every string that does match is at least that long.
1746    
1747         (?P<date> (?P<year>(\d\d)?\d\d) -           PCRE_INFO_NAMECOUNT
1748         (?P<month>\d\d) - (?P<day>\d\d) )           PCRE_INFO_NAMEENTRYSIZE
1749             PCRE_INFO_NAMETABLE
1750       There are four named subpatterns,  so  the  table  has  four  
1751       entries,  and  each  entry in the table is eight bytes long.         PCRE  supports the use of named as well as numbered capturing parenthe-
1752       The table is as follows, with non-printing  bytes  shows  in         ses. The names are just an additional way of identifying the  parenthe-
1753       hex, and undefined bytes shown as ??:         ses, which still acquire numbers. Several convenience functions such as
1754           pcre_get_named_substring() are provided for  extracting  captured  sub-
1755         00 01 d  a  t  e  00 ??         strings  by  name. It is also possible to extract the data directly, by
1756         00 05 d  a  y  00 ?? ??         first converting the name to a number in order to  access  the  correct
1757         00 04 m  o  n  t  h  00         pointers in the output vector (described with pcre_exec() below). To do
1758         00 02 y  e  a  r  00 ??         the conversion, you need  to  use  the  name-to-number  map,  which  is
1759           described by these three values.
1760       When writing code to extract data  from  named  subpatterns,  
1761       remember  that the length of each entry may be different for         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1762       each compiled pattern.         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1763           of  each  entry;  both  of  these  return  an int value. The entry size
1764         PCRE_INFO_OPTIONS         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1765           a  pointer  to  the  first  entry of the table (a pointer to char). The
1766       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-
1767       piled.  The fourth argument should point to an unsigned long         sis,  most  significant byte first. The rest of the entry is the corre-
1768       int variable. These option bits are those specified  in  the         sponding name, zero terminated.
1769       call  to  pcre_compile(),  modified  by any top-level option  
1770       settings within the pattern itself.         The names are in alphabetical order. Duplicate names may appear if  (?|
1771           is used to create multiple groups with the same number, as described in
1772       A pattern is automatically anchored by PCRE if  all  of  its         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1773       top-level alternatives begin with one of the following:         Duplicate  names  for  subpatterns with different numbers are permitted
1774           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1775         ^     unless PCRE_MULTILINE is set         appear  in  the table in the order in which they were found in the pat-
1776         \A    always         tern. In the absence of (?| this is the  order  of  increasing  number;
1777         \G    always         when (?| is used this is not necessarily the case because later subpat-
1778         .*    if PCRE_DOTALL is set and there are no back         terns may have lower numbers.
1779                 references to the subpattern in which .* appears  
1780           As a simple example of the name/number table,  consider  the  following
1781       For such patterns, the  PCRE_ANCHORED  bit  is  set  in  the         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1782       options returned by pcre_fullinfo().         lines - is ignored):
1783    
1784         PCRE_INFO_SIZE           (?<date> (?<year>(\d\d)?\d\d) -
1785             (?<month>\d\d) - (?<day>\d\d) )
1786       Return the size of the compiled pattern, that is, the  value  
1787       that  was  passed as the argument to pcre_malloc() when PCRE         There are four named subpatterns, so the table has  four  entries,  and
1788       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,
1789       fourth argument should point to a size_t variable.         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1790           as ??:
1791         PCRE_INFO_STUDYSIZE  
1792             00 01 d  a  t  e  00 ??
1793       Returns the size  of  the  data  block  pointed  to  by  the           00 05 d  a  y  00 ?? ??
1794       study_data  field  in a pcre_extra block. That is, it is the           00 04 m  o  n  t  h  00
1795       value that was passed to pcre_malloc() when PCRE was getting           00 02 y  e  a  r  00 ??
1796       memory into which to place the data created by pcre_study().  
1797       The fourth argument should point to a size_t variable.         When  writing  code  to  extract  data from named subpatterns using the
1798           name-to-number map, remember that the length of the entries  is  likely
1799           to be different for each compiled pattern.
1800    
1801             PCRE_INFO_OKPARTIAL
1802    
1803           Return  1  if  the  pattern  can  be  used  for  partial  matching with
1804           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1805           variable.  From  release  8.00,  this  always  returns  1,  because the
1806           restrictions that previously applied  to  partial  matching  have  been
1807           lifted.  The  pcrepartial documentation gives details of partial match-
1808           ing.
1809    
1810             PCRE_INFO_OPTIONS
1811    
1812           Return a copy of the options with which the pattern was  compiled.  The
1813           fourth  argument  should  point to an unsigned long int variable. These
1814           option bits are those specified in the call to pcre_compile(), modified
1815           by any top-level option settings at the start of the pattern itself. In
1816           other words, they are the options that will be in force  when  matching
1817           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1818           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1819           and PCRE_EXTENDED.
1820    
1821           A  pattern  is  automatically  anchored by PCRE if all of its top-level
1822           alternatives begin with one of the following:
1823    
1824             ^     unless PCRE_MULTILINE is set
1825             \A    always
1826             \G    always
1827             .*    if PCRE_DOTALL is set and there are no back
1828                     references to the subpattern in which .* appears
1829    
1830           For such patterns, the PCRE_ANCHORED bit is set in the options returned
1831           by pcre_fullinfo().
1832    
1833             PCRE_INFO_SIZE
1834    
1835           Return  the  size  of the compiled pattern, that is, the value that was
1836           passed as the argument to pcre_malloc() when PCRE was getting memory in
1837           which to place the compiled data. The fourth argument should point to a
1838           size_t variable.
1839    
1840             PCRE_INFO_STUDYSIZE
1841    
1842           Return the size of the data block pointed to by the study_data field in
1843           a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1844           pcre_malloc() when PCRE was getting memory into which to place the data
1845           created  by  pcre_study().  If pcre_extra is NULL, or there is no study
1846           data, zero is returned. The fourth argument should point  to  a  size_t
1847           variable.
1848    
1849    
1850  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
1851    
1852       int pcre_info(const pcre *code, int *optptr, *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1853    
1854       The pcre_info() function is now obsolete because its  inter-         The  pcre_info()  function is now obsolete because its interface is too
1855       face  is  too  restrictive  to return all the available data         restrictive to return all the available data about a compiled  pattern.
1856       about  a  compiled  pattern.   New   programs   should   use         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1857       pcre_fullinfo()  instead.  The  yield  of pcre_info() is the         pcre_info() is the number of capturing subpatterns, or one of the  fol-
1858       number of capturing subpatterns, or  one  of  the  following         lowing negative numbers:
1859       negative numbers:  
1860             PCRE_ERROR_NULL       the argument code was NULL
1861         PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1862         PCRE_ERROR_BADMAGIC   the "magic number" was not found  
1863           If  the  optptr  argument is not NULL, a copy of the options with which
1864       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
1865       with which the pattern was compiled is placed in the integer         PCRE_INFO_OPTIONS above).
1866       it points to (see PCRE_INFO_OPTIONS above).  
1867           If  the  pattern  is  not anchored and the firstcharptr argument is not
1868       If the pattern is not anchored and the firstcharptr argument         NULL, it is used to pass back information about the first character  of
1869       is  not  NULL, it is used to pass back information about the         any matched string (see PCRE_INFO_FIRSTBYTE above).
1870       first    character    of    any    matched    string    (see  
1871       PCRE_INFO_FIRSTBYTE above).  
1872    REFERENCE COUNTS
1873    
1874           int pcre_refcount(pcre *code, int adjust);
1875    
1876           The  pcre_refcount()  function is used to maintain a reference count in
1877           the data block that contains a compiled pattern. It is provided for the
1878           benefit  of  applications  that  operate  in an object-oriented manner,
1879           where different parts of the application may be using the same compiled
1880           pattern, but you want to free the block when they are all done.
1881    
1882           When a pattern is compiled, the reference count field is initialized to
1883           zero.  It is changed only by calling this function, whose action is  to
1884           add  the  adjust  value  (which may be positive or negative) to it. The
1885           yield of the function is the new value. However, the value of the count
1886           is  constrained to lie between 0 and 65535, inclusive. If the new value
1887           is outside these limits, it is forced to the appropriate limit value.
1888    
1889           Except when it is zero, the reference count is not correctly  preserved
1890           if  a  pattern  is  compiled on one host and then transferred to a host
1891           whose byte-order is different. (This seems a highly unlikely scenario.)
1892    
1893    
1894    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1895    
1896           int pcre_exec(const pcre *code, const pcre_extra *extra,
1897                const char *subject, int length, int startoffset,
1898                int options, int *ovector, int ovecsize);
1899    
1900           The function pcre_exec() is called to match a subject string against  a
1901           compiled  pattern, which is passed in the code argument. If the pattern
1902           was studied, the result of the study should  be  passed  in  the  extra
1903           argument.  This  function is the main matching facility of the library,
1904           and it operates in a Perl-like manner. For specialist use there is also
1905           an  alternative matching function, which is described below in the sec-
1906           tion about the pcre_dfa_exec() function.
1907    
1908           In most applications, the pattern will have been compiled (and  option-
1909           ally  studied)  in the same process that calls pcre_exec(). However, it
1910           is possible to save compiled patterns and study data, and then use them
1911           later  in  different processes, possibly even on different hosts. For a
1912           discussion about this, see the pcreprecompile documentation.
1913    
1914           Here is an example of a simple call to pcre_exec():
1915    
1916             int rc;
1917             int ovector[30];
1918             rc = pcre_exec(
1919               re,             /* result of pcre_compile() */
1920               NULL,           /* we didn't study the pattern */
1921               "some string",  /* the subject string */
1922               11,             /* the length of the subject string */
1923               0,              /* start at offset 0 in the subject */
1924               0,              /* default options */
1925               ovector,        /* vector of integers for substring information */
1926               30);            /* number of elements (NOT size in bytes) */
1927    
1928       Extra data for pcre_exec()
1929    
1930           If the extra argument is not NULL, it must point to a  pcre_extra  data
1931           block.  The pcre_study() function returns such a block (when it doesn't
1932           return NULL), but you can also create one for yourself, and pass  addi-
1933           tional  information  in it. The pcre_extra block contains the following
1934           fields (not necessarily in this order):
1935    
1936             unsigned long int flags;
1937             void *study_data;
1938             unsigned long int match_limit;
1939             unsigned long int match_limit_recursion;
1940             void *callout_data;
1941             const unsigned char *tables;
1942             unsigned char **mark;
1943    
1944           The flags field is a bitmap that specifies which of  the  other  fields
1945           are set. The flag bits are:
1946    
1947             PCRE_EXTRA_STUDY_DATA
1948             PCRE_EXTRA_MATCH_LIMIT
1949             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1950             PCRE_EXTRA_CALLOUT_DATA
1951             PCRE_EXTRA_TABLES
1952             PCRE_EXTRA_MARK
1953    
1954           Other  flag  bits should be set to zero. The study_data field is set in
1955           the pcre_extra block that is returned by  pcre_study(),  together  with
1956           the appropriate flag bit. You should not set this yourself, but you may
1957           add to the block by setting the other fields  and  their  corresponding
1958           flag bits.
1959    
1960           The match_limit field provides a means of preventing PCRE from using up
1961           a vast amount of resources when running patterns that are not going  to
1962           match,  but  which  have  a very large number of possibilities in their
1963           search trees. The classic example is a pattern that uses nested  unlim-
1964           ited repeats.
1965    
1966           Internally,  PCRE uses a function called match() which it calls repeat-
1967           edly (sometimes recursively). The limit set by match_limit  is  imposed
1968           on  the  number  of times this function is called during a match, which
1969           has the effect of limiting the amount of  backtracking  that  can  take
1970           place. For patterns that are not anchored, the count restarts from zero
1971           for each position in the subject string.
1972    
1973           The default value for the limit can be set  when  PCRE  is  built;  the
1974           default  default  is 10 million, which handles all but the most extreme
1975           cases. You can override the default  by  suppling  pcre_exec()  with  a
1976           pcre_extra     block    in    which    match_limit    is    set,    and
1977           PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
1978           exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1979    
1980           The  match_limit_recursion field is similar to match_limit, but instead
1981           of limiting the total number of times that match() is called, it limits
1982           the  depth  of  recursion. The recursion depth is a smaller number than
1983           the total number of calls, because not all calls to match() are  recur-
1984           sive.  This limit is of use only if it is set smaller than match_limit.
1985    
1986           Limiting  the  recursion  depth  limits the amount of stack that can be
1987           used, or, when PCRE has been compiled to use memory on the heap instead
1988           of the stack, the amount of heap memory that can be used.
1989    
1990           The  default  value  for  match_limit_recursion can be set when PCRE is
1991           built; the default default  is  the  same  value  as  the  default  for
1992           match_limit.  You can override the default by suppling pcre_exec() with
1993           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1994           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1995           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1996    
1997           The callout_data field is used in conjunction with the  "callout"  fea-
1998           ture, and is described in the pcrecallout documentation.
1999    
2000           The  tables  field  is  used  to  pass  a  character  tables pointer to
2001           pcre_exec(); this overrides the value that is stored with the  compiled
2002           pattern.  A  non-NULL value is stored with the compiled pattern only if
2003           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2004           ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2005           PCRE's internal tables to be used. This facility is  helpful  when  re-
2006           using  patterns  that  have been saved after compiling with an external
2007           set of tables, because the external tables  might  be  at  a  different
2008           address  when  pcre_exec() is called. See the pcreprecompile documenta-
2009           tion for a discussion of saving compiled patterns for later use.
2010    
2011           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2012           set  to  point  to a char * variable. If the pattern contains any back-
2013           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2014           with  a  name  to  pass back, a pointer to the name string (zero termi-
2015           nated) is placed in the variable pointed to  by  the  mark  field.  The
2016           names  are  within  the  compiled pattern; if you wish to retain such a
2017           name you must copy it before freeing the memory of a compiled  pattern.
2018           If  there  is no name to pass back, the variable pointed to by the mark
2019           field set to NULL. For details of the backtracking control  verbs,  see
2020           the section entitled "Backtracking control" in the pcrepattern documen-
2021           tation.
2022    
2023       Option bits for pcre_exec()
2024    
2025           The unused bits of the options argument for pcre_exec() must  be  zero.
2026           The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2027           PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2028           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2029           PCRE_PARTIAL_HARD.
2030    
2031             PCRE_ANCHORED
2032    
2033           The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2034           matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2035           turned out to be anchored by virtue of its contents, it cannot be  made
2036           unachored at matching time.
2037    
2038             PCRE_BSR_ANYCRLF
2039             PCRE_BSR_UNICODE
2040    
2041           These options (which are mutually exclusive) control what the \R escape
2042           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2043           or  to  match  any Unicode newline sequence. These options override the
2044           choice that was made or defaulted when the pattern was compiled.
2045    
2046             PCRE_NEWLINE_CR
2047             PCRE_NEWLINE_LF
2048             PCRE_NEWLINE_CRLF
2049             PCRE_NEWLINE_ANYCRLF
2050             PCRE_NEWLINE_ANY
2051    
2052           These options override  the  newline  definition  that  was  chosen  or
2053           defaulted  when the pattern was compiled. For details, see the descrip-
2054           tion of pcre_compile()  above.  During  matching,  the  newline  choice
2055           affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2056           ters. It may also alter the way the match position is advanced after  a
2057           match failure for an unanchored pattern.
2058    
2059           When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2060           set, and a match attempt for an unanchored pattern fails when the  cur-
2061           rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2062           explicit matches for  CR  or  LF  characters,  the  match  position  is
2063           advanced by two characters instead of one, in other words, to after the
2064           CRLF.
2065    
2066           The above rule is a compromise that makes the most common cases work as
2067           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2068           option is not set), it does not match the string "\r\nA" because, after
2069           failing  at the start, it skips both the CR and the LF before retrying.
2070           However, the pattern [\r\n]A does match that string,  because  it  con-
2071           tains an explicit CR or LF reference, and so advances only by one char-
2072           acter after the first failure.
2073    
2074           An explicit match for CR of LF is either a literal appearance of one of
2075           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2076           matches such as [^X] do not count, nor does \s (which includes  CR  and
2077           LF in the characters that it matches).
2078    
2079           Notwithstanding  the above, anomalous effects may still occur when CRLF
2080           is a valid newline sequence and explicit \r or \n escapes appear in the
2081           pattern.
2082    
2083             PCRE_NOTBOL
2084    
2085           This option specifies that first character of the subject string is not
2086           the beginning of a line, so the  circumflex  metacharacter  should  not
2087           match  before it. Setting this without PCRE_MULTILINE (at compile time)
2088           causes circumflex never to match. This option affects only  the  behav-
2089           iour of the circumflex metacharacter. It does not affect \A.
2090    
2091             PCRE_NOTEOL
2092    
2093           This option specifies that the end of the subject string is not the end
2094           of a line, so the dollar metacharacter should not match it nor  (except
2095           in  multiline mode) a newline immediately before it. Setting this with-
2096           out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2097           option  affects only the behaviour of the dollar metacharacter. It does
2098           not affect \Z or \z.
2099    
2100             PCRE_NOTEMPTY
2101    
2102           An empty string is not considered to be a valid match if this option is
2103           set.  If  there are alternatives in the pattern, they are tried. If all
2104           the alternatives match the empty string, the entire  match  fails.  For
2105           example, if the pattern
2106    
2107             a?b?
2108    
2109           is  applied  to  a  string not beginning with "a" or "b", it matches an
2110           empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
2111           match is not valid, so PCRE searches further into the string for occur-
2112           rences of "a" or "b".
2113    
2114             PCRE_NOTEMPTY_ATSTART
2115    
2116           This is like PCRE_NOTEMPTY, except that an empty string match  that  is
2117           not  at  the  start  of  the  subject  is  permitted. If the pattern is
2118           anchored, such a match can occur only if the pattern contains \K.
2119    
2120           Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2121           PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2122           match of the empty string within its split() function, and  when  using
2123           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2124           matching a null string by first trying the match again at the same off-
2125           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2126           fails, by advancing the starting offset (see below) and trying an ordi-
2127           nary  match  again. There is some code that demonstrates how to do this
2128           in the pcredemo sample program. In the most general case, you  have  to
2129           check  to  see  if the newline convention recognizes CRLF as a newline,
2130           and if so, and the current character is CR followed by LF, advance  the
2131           starting offset by two characters instead of one.
2132    
2133             PCRE_NO_START_OPTIMIZE
2134    
2135           There  are a number of optimizations that pcre_exec() uses at the start
2136           of a match, in order to speed up the process. For  example,  if  it  is
2137           known that an unanchored match must start with a specific character, it
2138           searches the subject for that character, and fails  immediately  if  it
2139           cannot  find  it,  without actually running the main matching function.
2140           This means that a special item such as (*COMMIT) at the start of a pat-
2141           tern  is  not  considered until after a suitable starting point for the
2142           match has been found. When callouts or (*MARK) items are in use,  these
2143           "start-up" optimizations can cause them to be skipped if the pattern is
2144           never actually used. The start-up optimizations are in  effect  a  pre-
2145           scan of the subject that takes place before the pattern is run.
2146    
2147           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2148           possibly causing performance to suffer,  but  ensuring  that  in  cases
2149           where  the  result is "no match", the callouts do occur, and that items
2150           such as (*COMMIT) and (*MARK) are considered at every possible starting
2151           position  in  the  subject  string.  Setting PCRE_NO_START_OPTIMIZE can
2152           change the outcome of a matching operation.  Consider the pattern
2153    
2154             (*COMMIT)ABC
2155    
2156           When this is compiled, PCRE records the fact that a  match  must  start
2157           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2158           start-up optimization scans along the subject, finds "A" and  runs  the
2159           first  match attempt from there. The (*COMMIT) item means that the pat-
2160           tern must match the current starting position, which in this  case,  it
2161           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2162           set, the initial scan along the subject string  does  not  happen.  The
2163           first  match  attempt  is  run  starting  from "D" and when this fails,
2164           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2165           result  is  "no  match". If the pattern is studied, more start-up opti-
2166           mizations may be used. For example, a minimum length  for  the  subject
2167           may be recorded. Consider the pattern
2168    
2169             (*MARK:A)(X|Y)
2170    
2171           The  minimum  length  for  a  match is one character. If the subject is
2172           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2173           finally  an empty string.  If the pattern is studied, the final attempt
2174           does not take place, because PCRE knows that the subject is too  short,
2175           and  so  the  (*MARK) is never encountered.  In this case, studying the
2176           pattern does not affect the overall match result, which  is  still  "no
2177           match", but it does affect the auxiliary information that is returned.
2178    
2179             PCRE_NO_UTF8_CHECK
2180    
2181           When PCRE_UTF8 is set at compile time, the validity of the subject as a
2182           UTF-8 string is automatically checked when pcre_exec() is  subsequently
2183           called.   The  value  of  startoffset is also checked to ensure that it
2184           points to the start of a UTF-8 character. There is a  discussion  about
2185           the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2186           main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2187           pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2188           tains a value that does not point to the start of a UTF-8 character (or
2189           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2190    
2191           If  you  already  know that your subject is valid, and you want to skip
2192           these   checks   for   performance   reasons,   you   can    set    the
2193           PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2194           do this for the second and subsequent calls to pcre_exec() if  you  are
2195           making  repeated  calls  to  find  all  the matches in a single subject
2196           string. However, you should be  sure  that  the  value  of  startoffset
2197           points  to  the start of a UTF-8 character (or the end of the subject).
2198           When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid  UTF-8
2199           string  as  a  subject or an invalid value of startoffset is undefined.
2200           Your program may crash.
2201    
2202             PCRE_PARTIAL_HARD
2203             PCRE_PARTIAL_SOFT
2204    
2205           These options turn on the partial matching feature. For backwards  com-
2206           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2207           match occurs if the end of the subject string is reached  successfully,
2208           but  there  are not enough subject characters to complete the match. If
2209           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2210           matching  continues  by  testing any remaining alternatives. Only if no
2211           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2212           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2213           caller is prepared to handle a partial match, but only if  no  complete
2214           match can be found.
2215    
2216           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2217           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2218           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2219           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2220           ered to be more important that an alternative complete match.
2221    
2222           In  both  cases,  the portion of the string that was inspected when the
2223           partial match was found is set as the first matching string. There is a
2224           more  detailed  discussion  of partial and multi-segment matching, with
2225           examples, in the pcrepartial documentation.
2226    
2227       The string to be matched by pcre_exec()
2228    
2229           The subject string is passed to pcre_exec() as a pointer in subject,  a
2230           length (in bytes) in length, and a starting byte offset in startoffset.
2231           If this is  negative  or  greater  than  the  length  of  the  subject,
2232           pcre_exec() returns PCRE_ERROR_BADOFFSET.
2233    
2234           In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2235           acter (or the end of the subject). Unlike the pattern string, the  sub-
2236           ject  may  contain binary zero bytes. When the starting offset is zero,
2237           the search for a match starts at the beginning of the subject, and this
2238           is by far the most common case.
2239    
2240           A  non-zero  starting offset is useful when searching for another match
2241           in the same subject by calling pcre_exec() again after a previous  suc-
2242           cess.   Setting  startoffset differs from just passing over a shortened
2243           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2244           with any kind of lookbehind. For example, consider the pattern
2245    
2246             \Biss\B
2247    
2248           which  finds  occurrences  of "iss" in the middle of words. (\B matches
2249           only if the current position in the subject is not  a  word  boundary.)
2250           When  applied  to the string "Mississipi" the first call to pcre_exec()
2251           finds the first occurrence. If pcre_exec() is called  again  with  just
2252           the  remainder  of  the  subject,  namely  "issipi", it does not match,
2253           because \B is always false at the start of the subject, which is deemed
2254           to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2255           string again, but with startoffset set to 4, it finds the second occur-
2256           rence  of "iss" because it is able to look behind the starting point to
2257           discover that it is preceded by a letter.
2258    
2259           Finding all the matches in a subject is tricky  when  the  pattern  can
2260           match an empty string. It is possible to emulate Perl's /g behaviour by
2261           first  trying  the  match  again  at  the   same   offset,   with   the
2262           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2263           fails, advancing the starting  offset  and  trying  an  ordinary  match
2264           again. There is some code that demonstrates how to do this in the pcre-
2265           demo sample program. In the most general case, you have to check to see
2266           if  the newline convention recognizes CRLF as a newline, and if so, and
2267           the current character is CR followed by LF, advance the starting offset
2268           by two characters instead of one.
2269    
2270           If  a  non-zero starting offset is passed when the pattern is anchored,
2271           one attempt to match at the given offset is made. This can only succeed
2272           if  the  pattern  does  not require the match to be at the start of the
2273           subject.
2274    
2275       How pcre_exec() returns captured substrings
2276    
2277           In general, a pattern matches a certain portion of the subject, and  in
2278           addition,  further  substrings  from  the  subject may be picked out by
2279           parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2280           this  is  called "capturing" in what follows, and the phrase "capturing
2281           subpattern" is used for a fragment of a pattern that picks out  a  sub-
2282           string.  PCRE  supports several other kinds of parenthesized subpattern
2283           that do not cause substrings to be captured.
2284    
2285           Captured substrings are returned to the caller via a vector of integers
2286           whose  address is passed in ovector. The number of elements in the vec-
2287           tor is passed in ovecsize, which must be a non-negative  number.  Note:
2288           this argument is NOT the size of ovector in bytes.
2289    
2290           The  first  two-thirds of the vector is used to pass back captured sub-
2291           strings, each substring using a pair of integers. The  remaining  third
2292           of  the  vector is used as workspace by pcre_exec() while matching cap-
2293           turing subpatterns, and is not available for passing back  information.
2294           The  number passed in ovecsize should always be a multiple of three. If
2295           it is not, it is rounded down.
2296    
2297           When a match is successful, information about  captured  substrings  is
2298           returned  in  pairs  of integers, starting at the beginning of ovector,
2299           and continuing up to two-thirds of its length at the  most.  The  first
2300           element  of  each pair is set to the byte offset of the first character
2301           in a substring, and the second is set to the byte offset of  the  first
2302           character  after  the end of a substring. Note: these values are always
2303           byte offsets, even in UTF-8 mode. They are not character counts.
2304    
2305           The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2306           portion  of  the subject string matched by the entire pattern. The next
2307           pair is used for the first capturing subpattern, and so on.  The  value
2308           returned by pcre_exec() is one more than the highest numbered pair that
2309           has been set.  For example, if two substrings have been  captured,  the
2310           returned  value is 3. If there are no capturing subpatterns, the return
2311           value from a successful match is 1, indicating that just the first pair
2312           of offsets has been set.
2313    
2314           If a capturing subpattern is matched repeatedly, it is the last portion
2315           of the string that it matched that is returned.
2316    
2317           If the vector is too small to hold all the captured substring  offsets,
2318           it is used as far as possible (up to two-thirds of its length), and the
2319           function returns a value of zero. If the substring offsets are  not  of
2320           interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2321           ovecsize as zero. However, if the pattern contains back references  and
2322           the  ovector is not big enough to remember the related substrings, PCRE
2323           has to get additional memory for use during matching. Thus it  is  usu-
2324           ally advisable to supply an ovector.
2325    
2326           The pcre_fullinfo() function can be used to find out how many capturing
2327           subpatterns there are in a compiled  pattern.  The  smallest  size  for
2328           ovector  that  will allow for n captured substrings, in addition to the
2329           offsets of the substring matched by the whole pattern, is (n+1)*3.
2330    
2331           It is possible for capturing subpattern number n+1 to match  some  part
2332           of the subject when subpattern n has not been used at all. For example,
2333           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2334           return from the function is 4, and subpatterns 1 and 3 are matched, but
2335           2 is not. When this happens, both values in  the  offset  pairs  corre-
2336           sponding to unused subpatterns are set to -1.
2337    
2338           Offset  values  that correspond to unused subpatterns at the end of the
2339           expression are also set to -1. For example,  if  the  string  "abc"  is
2340           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2341           matched. The return from the function is 2, because  the  highest  used
2342           capturing subpattern number is 1. However, you can refer to the offsets
2343           for the second and third capturing subpatterns if  you  wish  (assuming
2344           the vector is large enough, of course).
2345    
2346           Some  convenience  functions  are  provided for extracting the captured
2347           substrings as separate strings. These are described below.
2348    
2349       Error return values from pcre_exec()
2350    
2351           If pcre_exec() fails, it returns a negative number. The  following  are
2352           defined in the header file:
2353    
2354             PCRE_ERROR_NOMATCH        (-1)
2355    
2356           The subject string did not match the pattern.
2357    
2358             PCRE_ERROR_NULL           (-2)
2359    
2360           Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2361           ovecsize was not zero.
2362    
2363             PCRE_ERROR_BADOPTION      (-3)
2364    
2365           An unrecognized bit was set in the options argument.
2366    
2367             PCRE_ERROR_BADMAGIC       (-4)
2368    
2369           PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2370           to catch the case when it is passed a junk pointer and to detect when a
2371           pattern that was compiled in an environment of one endianness is run in
2372           an  environment  with the other endianness. This is the error that PCRE
2373           gives when the magic number is not present.
2374    
2375             PCRE_ERROR_UNKNOWN_OPCODE (-5)
2376    
2377           While running the pattern match, an unknown item was encountered in the
2378           compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2379           overwriting of the compiled pattern.
2380    
2381             PCRE_ERROR_NOMEMORY       (-6)
2382    
2383           If a pattern contains back references, but the ovector that  is  passed
2384           to pcre_exec() is not big enough to remember the referenced substrings,
2385           PCRE gets a block of memory at the start of matching to  use  for  this
2386           purpose.  If the call via pcre_malloc() fails, this error is given. The
2387           memory is automatically freed at the end of matching.
2388    
2389           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2390           This  can happen only when PCRE has been compiled with --disable-stack-
2391           for-recursion.
2392    
2393             PCRE_ERROR_NOSUBSTRING    (-7)
2394    
2395           This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2396           and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2397           returned by pcre_exec().
2398    
2399             PCRE_ERROR_MATCHLIMIT     (-8)
2400    
2401           The backtracking limit, as specified by  the  match_limit  field  in  a
2402           pcre_extra  structure  (or  defaulted) was reached. See the description
2403           above.
2404    
2405             PCRE_ERROR_CALLOUT        (-9)
2406    
2407           This error is never generated by pcre_exec() itself. It is provided for
2408           use  by  callout functions that want to yield a distinctive error code.
2409           See the pcrecallout documentation for details.
2410    
2411             PCRE_ERROR_BADUTF8        (-10)
2412    
2413           A string that contains an invalid UTF-8 byte sequence was passed  as  a
2414           subject.
2415    
2416             PCRE_ERROR_BADUTF8_OFFSET (-11)
2417    
2418           The UTF-8 byte sequence that was passed as a subject was valid, but the
2419           value of startoffset did not point to the beginning of a UTF-8  charac-
2420           ter.
2421    
2422             PCRE_ERROR_PARTIAL        (-12)
2423    
2424           The  subject  string did not match, but it did match partially. See the
2425           pcrepartial documentation for details of partial matching.
2426    
2427             PCRE_ERROR_BADPARTIAL     (-13)
2428    
2429           This code is no longer in  use.  It  was  formerly  returned  when  the
2430           PCRE_PARTIAL  option  was used with a compiled pattern containing items
2431           that were  not  supported  for  partial  matching.  From  release  8.00
2432           onwards, there are no restrictions on partial matching.
2433    
2434             PCRE_ERROR_INTERNAL       (-14)
2435    
2436           An  unexpected  internal error has occurred. This error could be caused
2437           by a bug in PCRE or by overwriting of the compiled pattern.
2438    
2439             PCRE_ERROR_BADCOUNT       (-15)
2440    
2441           This error is given if the value of the ovecsize argument is negative.
2442    
2443             PCRE_ERROR_RECURSIONLIMIT (-21)
2444    
2445           The internal recursion limit, as specified by the match_limit_recursion
2446           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2447           description above.
2448    
2449             PCRE_ERROR_BADNEWLINE     (-23)
2450    
2451           An invalid combination of PCRE_NEWLINE_xxx options was given.
2452    
2453  MATCHING A PATTERN           PCRE_ERROR_BADOFFSET      (-24)
2454    
2455           The value of startoffset was negative or greater than the length of the
2456           subject, that is, the value in length.
2457    
2458       int pcre_exec(const pcre *code, const pcre_extra *extra,         Error numbers -16 to -20 and -22 are not used by pcre_exec().
           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.  
2459    
2460    
2461  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2462    
2463       int pcre_copy_substring(const char *subject, int *ovector,         int pcre_copy_substring(const char *subject, int *ovector,
2464            int stringcount, int stringnumber, char *buffer,              int stringcount, int stringnumber, char *buffer,
2465            int buffersize);              int buffersize);
2466    
2467       int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
2468            int stringcount, int stringnumber,              int stringcount, int stringnumber,
2469            const char **stringptr);              const char **stringptr);
2470    
2471       int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2472            int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2473    
2474       Captured substrings can be accessed directly  by  using  the         Captured  substrings  can  be  accessed  directly  by using the offsets
2475       offsets returned by pcre_exec() in ovector. For convenience,         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2476       the functions  pcre_copy_substring(),  pcre_get_substring(),         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2477       and  pcre_get_substring_list()  are  provided for extracting         string_list() are provided for extracting captured substrings  as  new,
2478       captured  substrings  as  new,   separate,   zero-terminated         separate,  zero-terminated strings. These functions identify substrings
2479       strings.  These functions identify substrings by number. The         by number. The next section describes functions  for  extracting  named
2480       next section describes functions for extracting  named  sub-         substrings.
2481       strings.   A  substring  that  contains  a  binary  zero  is  
2482       correctly extracted and has a further zero added on the end,         A  substring that contains a binary zero is correctly extracted and has
2483       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
2484           string.   However,  you  can  process such a string by referring to the
2485       The first three arguments are the  same  for  all  three  of         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2486       these  functions:   subject  is the subject string which has         string().  Unfortunately, the interface to pcre_get_substring_list() is
2487       just been successfully matched, ovector is a pointer to  the         not adequate for handling strings containing binary zeros, because  the
2488       vector  of  integer  offsets that was passed to pcre_exec(),         end of the final string is not independently indicated.
2489       and stringcount is the number of substrings that  were  cap-  
2490       tured by the match, including the substring that matched the         The  first  three  arguments  are the same for all three of these func-
2491       entire regular expression. This is  the  value  returned  by         tions: subject is the subject string that has  just  been  successfully
2492       pcre_exec  if  it  is  greater  than  zero.  If  pcre_exec()         matched, ovector is a pointer to the vector of integer offsets that was
2493       returned zero, indicating that it ran out of space in  ovec-         passed to pcre_exec(), and stringcount is the number of substrings that
2494       tor,  the  value passed as stringcount should be the size of         were  captured  by  the match, including the substring that matched the
2495       the vector divided by three.         entire regular expression. This is the value returned by pcre_exec() if
2496           it  is greater than zero. If pcre_exec() returned zero, indicating that
2497       The functions pcre_copy_substring() and pcre_get_substring()         it ran out of space in ovector, the value passed as stringcount  should
2498       extract a single substring, whose number is given as string-         be the number of elements in the vector divided by three.
2499       number. A value of zero extracts the substring that  matched  
2500       the entire pattern, while higher values extract the captured         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2501       substrings. For pcre_copy_substring(), the string is  placed         single substring, whose number is given as  stringnumber.  A  value  of
2502       in  buffer,  whose  length is given by buffersize, while for         zero  extracts  the  substring that matched the entire pattern, whereas
2503       pcre_get_substring() a new block of memory is  obtained  via         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2504       pcre_malloc,  and its address is returned via stringptr. The         string(),  the  string  is  placed  in buffer, whose length is given by
2505       yield of the function is  the  length  of  the  string,  not         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2506       including the terminating zero, or one of         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2507           The yield of the function is the length of the  string,  not  including
2508         PCRE_ERROR_NOMEMORY       (-6)         the terminating zero, or one of these error codes:
2509    
2510       The buffer was too small for pcre_copy_substring(),  or  the           PCRE_ERROR_NOMEMORY       (-6)
2511       attempt to get memory failed for pcre_get_substring().  
2512           The  buffer  was too small for pcre_copy_substring(), or the attempt to
2513         PCRE_ERROR_NOSUBSTRING    (-7)         get memory failed for pcre_get_substring().
2514    
2515       There is no substring whose number is stringnumber.           PCRE_ERROR_NOSUBSTRING    (-7)
2516    
2517       The pcre_get_substring_list() function extracts  all  avail-         There is no substring whose number is stringnumber.
2518       able  substrings  and builds a list of pointers to them. All  
2519       this is done in a single block of memory which  is  obtained         The pcre_get_substring_list()  function  extracts  all  available  sub-
2520       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
2521       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
2522       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
2523       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
2524           pointer.  The  yield  of  the function is zero if all went well, or the
2525         PCRE_ERROR_NOMEMORY       (-6)         error code
2526    
2527       if the attempt to get the memory block failed.           PCRE_ERROR_NOMEMORY       (-6)
2528    
2529       When any of these functions encounter a  substring  that  is         if the attempt to get the memory block failed.
2530       unset, which can happen when capturing subpattern number n+1  
2531       matches some part of the subject, but subpattern n  has  not         When any of these functions encounter a substring that is unset,  which
2532       been  used  at all, they return an empty string. This can be         can  happen  when  capturing subpattern number n+1 matches some part of
2533       distinguished  from  a  genuine  zero-length  substring   by         the subject, but subpattern n has not been used at all, they return  an
2534       inspecting the appropriate offset in ovector, which is nega-         empty string. This can be distinguished from a genuine zero-length sub-
2535       tive for unset substrings.         string by inspecting the appropriate offset in ovector, which is  nega-
2536           tive for unset substrings.
2537       The  two  convenience  functions  pcre_free_substring()  and  
2538       pcre_free_substring_list()  can  be  used to free the memory         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2539       returned by  a  previous  call  of  pcre_get_substring()  or         string_list() can be used to free the memory  returned  by  a  previous
2540       pcre_get_substring_list(),  respectively.  They  do  nothing         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2541       more than call the function pointed to by  pcre_free,  which         tively. They do nothing more than  call  the  function  pointed  to  by
2542       of  course  could  be called directly from a C program. How-         pcre_free,  which  of course could be called directly from a C program.
2543       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-
2544       a  special  interface  to another programming language which         cial   interface  to  another  programming  language  that  cannot  use
2545       cannot use pcre_free directly; it is for  these  cases  that         pcre_free directly; it is for these cases that the functions  are  pro-
2546       the functions are provided.         vided.
2547    
2548    
2549  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2550    
2551       int pcre_copy_named_substring(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
2552            const char *subject, int *ovector,              const char *name);
2553            int stringcount, const char *stringname,  
2554            char *buffer, int buffersize);         int pcre_copy_named_substring(const pcre *code,
2555                const char *subject, int *ovector,
2556       int pcre_get_stringnumber(const pcre *code,              int stringcount, const char *stringname,
2557            const char *name);              char *buffer, int buffersize);
2558    
2559       int pcre_get_named_substring(const pcre *code,         int pcre_get_named_substring(const pcre *code,
2560            const char *subject, int *ovector,              const char *subject, int *ovector,
2561            int stringcount, const char *stringname,              int stringcount, const char *stringname,
2562            const char **stringptr);              const char **stringptr);
2563    
2564       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-
2565       ciated    number.    This    can    be   done   by   calling         ber.  For example, for this pattern
2566       pcre_get_stringnumber(). The first argument is the  compiled  
2567       pattern,  and  the second is the name. For example, for this           (a+)b(?<xxx>\d+)...
2568       pattern  
2569           the number of the subpattern called "xxx" is 2. If the name is known to
2570         ab(?<xxx>\d+)...         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2571           name by calling pcre_get_stringnumber(). The first argument is the com-
2572       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
2573       number,  you can then extract the substring directly, or use         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2574       one of the functions described in the previous section.  For         subpattern of that name.
2575       convenience,  there are also two functions that do the whole  
2576       job.         Given the number, you can extract the substring directly, or use one of
2577           the functions described in the previous section. For convenience, there
2578       Most of the  arguments  of  pcre_copy_named_substring()  and         are also two functions that do the whole job.
2579       pcre_get_named_substring()  are  the  same  as those for the  
2580       functions that  extract  by  number,  and  so  are  not  re-         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2581       described here. There are just two differences.         pcre_get_named_substring() are the same  as  those  for  the  similarly
2582           named  functions  that extract by number. As these are described in the
2583       First, instead of a substring number, a  substring  name  is         previous section, they are not re-described here. There  are  just  two
2584       given.  Second,  there  is  an  extra argument, given at the         differences:
2585       start, which is a pointer to the compiled pattern.  This  is  
2586       needed  in order to gain access to the name-to-number trans-         First,  instead  of a substring number, a substring name is given. Sec-
2587       lation table.         ond, there is an extra argument, given at the start, which is a pointer
2588           to  the compiled pattern. This is needed in order to gain access to the
2589       These functions  call  pcre_get_stringnumber(),  and  if  it         name-to-number translation table.
2590       succeeds,    they   then   call   pcre_copy_substring()   or  
2591       pcre_get_substring(), as appropriate.         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2592           then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2593           ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2594           behaviour may not be what you want (see the next section).
2595    
2596           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2597           terns with the same number, as described in the  section  on  duplicate
2598           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2599           distinguish the different subpatterns, because names are  not  included
2600           in  the compiled code. The matching process uses only numbers. For this
2601           reason, the use of different names for subpatterns of the  same  number
2602           causes an error at compile time.
2603    
2604    
2605    DUPLICATE SUBPATTERN NAMES
2606    
2607           int pcre_get_stringtable_entries(const pcre *code,
2608                const char *name, char **first, char **last);
2609    
2610           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2611           subpatterns are not required to be unique. (Duplicate names are  always
2612           allowed  for subpatterns with the same number, created by using the (?|
2613           feature. Indeed, if such subpatterns are named, they  are  required  to
2614           use the same names.)
2615    
2616           Normally, patterns with duplicate names are such that in any one match,
2617           only one of the named subpatterns participates. An example is shown  in
2618           the pcrepattern documentation.
2619    
2620           When    duplicates   are   present,   pcre_copy_named_substring()   and
2621           pcre_get_named_substring() return the first substring corresponding  to
2622           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2623           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2624           function  returns one of the numbers that are associated with the name,
2625           but it is not defined which it is.
2626    
2627           If you want to get full details of all captured substrings for a  given
2628           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2629           first argument is the compiled pattern, and the second is the name. The
2630           third  and  fourth  are  pointers to variables which are updated by the
2631           function. After it has run, they point to the first and last entries in
2632           the  name-to-number  table  for  the  given  name.  The function itself
2633           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2634           there  are none. The format of the table is described above in the sec-
2635           tion entitled Information about a  pattern.   Given  all  the  relevant
2636           entries  for the name, you can extract each of their numbers, and hence
2637           the captured data, if any.
2638    
2639    
2640    FINDING ALL POSSIBLE MATCHES
2641    
2642           The traditional matching function uses a  similar  algorithm  to  Perl,
2643           which stops when it finds the first match, starting at a given point in
2644           the subject. If you want to find all possible matches, or  the  longest
2645           possible  match,  consider using the alternative matching function (see
2646           below) instead. If you cannot use the alternative function,  but  still
2647           need  to  find all possible matches, you can kludge it up by making use
2648           of the callout facility, which is described in the pcrecallout documen-
2649           tation.
2650    
2651           What you have to do is to insert a callout right at the end of the pat-
2652           tern.  When your callout function is called, extract and save the  cur-
2653           rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2654           backtrack and try other alternatives. Ultimately, when it runs  out  of
2655           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2656    
2657    
2658    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
2659    
2660           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
2661                const char *subject, int length, int startoffset,
2662                int options, int *ovector, int ovecsize,
2663                int *workspace, int wscount);
2664    
2665           The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2666           against a compiled pattern, using a matching algorithm that  scans  the
2667           subject  string  just  once, and does not backtrack. This has different
2668           characteristics to the normal algorithm, and  is  not  compatible  with
2669           Perl.  Some  of the features of PCRE patterns are not supported. Never-
2670           theless, there are times when this kind of matching can be useful.  For
2671           a  discussion  of  the  two matching algorithms, and a list of features
2672           that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2673           tion.
2674    
2675           The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2676           pcre_exec(), plus two extras. The ovector argument is used in a differ-
2677           ent  way,  and  this is described below. The other common arguments are
2678           used in the same way as for pcre_exec(), so their  description  is  not
2679           repeated here.
2680    
2681           The  two  additional  arguments provide workspace for the function. The
2682           workspace vector should contain at least 20 elements. It  is  used  for
2683           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2684           workspace will be needed for patterns and subjects where  there  are  a
2685           lot of potential matches.
2686    
2687           Here is an example of a simple call to pcre_dfa_exec():
2688    
2689             int rc;
2690             int ovector[10];
2691             int wspace[20];
2692             rc = pcre_dfa_exec(
2693               re,             /* result of pcre_compile() */
2694               NULL,           /* we didn't study the pattern */
2695               "some string",  /* the subject string */
2696               11,             /* the length of the subject string */
2697               0,              /* start at offset 0 in the subject */
2698               0,              /* default options */
2699               ovector,        /* vector of integers for substring information */
2700               10,             /* number of elements (NOT size in bytes) */
2701               wspace,         /* working space vector */
2702               20);            /* number of elements (NOT size in bytes) */
2703    
2704       Option bits for pcre_dfa_exec()
2705    
2706           The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2707           zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2708           LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2709           PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2710           PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2711           TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2712           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2713           description is not repeated here.
2714    
2715             PCRE_PARTIAL_HARD
2716             PCRE_PARTIAL_SOFT
2717    
2718           These have the same general effect as they do for pcre_exec(), but  the
2719           details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2720           pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2721           ject  is  reached  and there is still at least one matching possibility
2722           that requires additional characters. This happens even if some complete
2723           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2724           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2725           of  the  subject  is  reached, there have been no complete matches, but
2726           there is still at least one matching possibility. The  portion  of  the
2727           string  that  was inspected when the longest partial match was found is
2728           set as the first matching string  in  both  cases.   There  is  a  more
2729           detailed  discussion  of partial and multi-segment matching, with exam-
2730           ples, in the pcrepartial documentation.
2731    
2732             PCRE_DFA_SHORTEST
2733    
2734           Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2735           stop as soon as it has found one match. Because of the way the alterna-
2736           tive algorithm works, this is necessarily the shortest  possible  match
2737           at the first possible matching point in the subject string.
2738    
2739             PCRE_DFA_RESTART
2740    
2741           When pcre_dfa_exec() returns a partial match, it is possible to call it
2742           again, with additional subject characters, and have  it  continue  with
2743           the  same match. The PCRE_DFA_RESTART option requests this action; when
2744           it is set, the workspace and wscount options must  reference  the  same
2745           vector  as  before  because data about the match so far is left in them
2746           after a partial match. There is more discussion of this facility in the
2747           pcrepartial documentation.
2748    
2749       Successful returns from pcre_dfa_exec()
2750    
2751           When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2752           string in the subject. Note, however, that all the matches from one run
2753           of  the  function  start  at the same point in the subject. The shorter
2754           matches are all initial substrings of the longer matches. For  example,
2755           if the pattern
2756    
2757             <.*>
2758    
2759           is matched against the string
2760    
2761             This is <something> <something else> <something further> no more
2762    
2763           the three matched strings are
2764    
2765             <something>
2766             <something> <something else>
2767             <something> <something else> <something further>
2768    
2769           On  success,  the  yield of the function is a number greater than zero,
2770           which is the number of matched substrings.  The  substrings  themselves
2771           are  returned  in  ovector. Each string uses two elements; the first is
2772           the offset to the start, and the second is the offset to  the  end.  In
2773           fact,  all  the  strings  have the same start offset. (Space could have
2774           been saved by giving this only once, but it was decided to retain  some
2775           compatibility  with  the  way pcre_exec() returns data, even though the
2776           meaning of the strings is different.)
2777    
2778           The strings are returned in reverse order of length; that is, the long-
2779           est  matching  string is given first. If there were too many matches to
2780           fit into ovector, the yield of the function is zero, and the vector  is
2781           filled with the longest matches.
2782    
2783       Error returns from pcre_dfa_exec()
2784    
2785           The  pcre_dfa_exec()  function returns a negative number when it fails.
2786           Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2787           described  above.   There are in addition the following errors that are
2788           specific to pcre_dfa_exec():
2789    
2790             PCRE_ERROR_DFA_UITEM      (-16)
2791    
2792           This return is given if pcre_dfa_exec() encounters an item in the  pat-
2793           tern  that  it  does not support, for instance, the use of \C or a back
2794           reference.
2795    
2796             PCRE_ERROR_DFA_UCOND      (-17)
2797    
2798           This return is given if pcre_dfa_exec()  encounters  a  condition  item
2799           that  uses  a back reference for the condition, or a test for recursion
2800           in a specific group. These are not supported.
2801    
2802             PCRE_ERROR_DFA_UMLIMIT    (-18)
2803    
2804           This return is given if pcre_dfa_exec() is called with an  extra  block
2805           that contains a setting of the match_limit field. This is not supported
2806           (it is meaningless).
2807    
2808             PCRE_ERROR_DFA_WSSIZE     (-19)
2809    
2810           This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2811           workspace vector.
2812    
2813             PCRE_ERROR_DFA_RECURSE    (-20)
2814    
2815           When  a  recursive subpattern is processed, the matching function calls
2816           itself recursively, using private vectors for  ovector  and  workspace.
2817           This  error  is  given  if  the output vector is not large enough. This
2818           should be extremely rare, as a vector of size 1000 is used.
2819    
2820    
2821    SEE ALSO
2822  <