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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    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few  differences.  The current implementation of PCRE (release         just  a few differences. Some features that appeared in Python and PCRE
23         6.x) corresponds approximately with Perl  5.8,  including  support  for         before they appeared in Perl are also available using the  Python  syn-
24         UTF-8 encoded strings and Unicode general category properties. However,         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         this support has to be explicitly enabled; it is not the default.         items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27         In addition to the Perl-compatible matching function,  PCRE  also  con-  
28         tains  an  alternative matching function that matches the same compiled         The  current implementation of PCRE corresponds approximately with Perl
29         patterns in a different way. In certain circumstances, the  alternative         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-
30         function  has  some  advantages.  For  a discussion of the two matching         eral  category properties. However, UTF-8 and Unicode support has to be
31         algorithms, see the pcrematching page.         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 5.2.0.
33         PCRE is written in C and released as a C library. A  number  of  people  
34         have  written  wrappers and interfaces of various kinds. In particular,         In  addition to the Perl-compatible matching function, PCRE contains an
35         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         alternative function that matches the same compiled patterns in a  dif-
36           ferent way. In certain circumstances, the alternative function has some
37           advantages.  For a discussion of the two matching algorithms,  see  the
38           pcrematching page.
39    
40           PCRE  is  written  in C and released as a C library. A number of people
41           have written wrappers and interfaces of various kinds.  In  particular,
42           Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
43         included as part of the PCRE distribution. The pcrecpp page has details         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         of  this  interface.  Other  people's contributions can be found in the
45         Contrib directory at the primary FTP site, which is:         Contrib directory at the primary FTP site, which is:
46    
47         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
48    
49         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
50         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
51         tern and pcrecompat pages.         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         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         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
63         functions, but which are not intended  for  use  by  external  callers.         functions, but which are not intended  for  use  by  external  callers.
64         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
65         any name clashes.         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  USER DOCUMENTATION  USER DOCUMENTATION
# Line 61  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80             pcre-config       show PCRE installation configuration information
81           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
82           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
# Line 78  USER DOCUMENTATION Line 92  USER DOCUMENTATION
92           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
93           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
94           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
95           pcresample        discussion of the sample program           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           pcretest          description of the pcretest testing command
99    
100         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 96  LIMITATIONS Line 112  LIMITATIONS
112         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
113         the  source  distribution and the pcrebuild documentation for details).         the  source  distribution and the pcrebuild documentation for details).
114         In these cases the limit is substantially larger.  However,  the  speed         In these cases the limit is substantially larger.  However,  the  speed
115         of execution will be slower.         of execution is slower.
116    
117         All values in repeating quantifiers must be less than 65536.  The maxi-         All values in repeating quantifiers must be less than 65536.
        mum number of capturing subpatterns is 65535.  
118    
119         There is no limit to the number of non-capturing subpatterns,  but  the         There is no limit to the number of parenthesized subpatterns, but there
120         maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,         can be no more than 65535 capturing subpatterns.
121         including capturing subpatterns, assertions, and other types of subpat-  
122         tern, is 200.         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         The  maximum  length of a subject string is the largest positive number
126         that an integer variable can hold. However, when using the  traditional         that an integer variable can hold. However, when using the  traditional
127         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
128         inite repetition.  This means that the available stack space may  limit         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.         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  UTF-8 AND UNICODE PROPERTY SUPPORT
# Line 122  UTF-8 AND UNICODE PROPERTY SUPPORT Line 139  UTF-8 AND UNICODE PROPERTY SUPPORT
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any subject strings that are matched against it are  treated  as  UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146         If  you compile PCRE with UTF-8 support, but do not use it at run time,  
147         the library will be a bit bigger, but the additional run time  overhead         If you compile PCRE with UTF-8 support, but do not use it at run  time,
148         is  limited  to testing the PCRE_UTF8 flag in several places, so should         the  library will be a bit bigger, but the additional run time overhead
149         not be very large.         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         If PCRE is built with Unicode character property support (which implies
153         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         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         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         general category properties such as Lu for an upper case letter  or  Nd
156         for a decimal number. A full list is given in the pcrepattern  documen-         for  a  decimal number, the Unicode script names such as Arabic or Han,
157         tation. The PCRE library is increased in size by about 90K when Unicode         and the derived properties Any and L&. A full  list  is  given  in  the
158         property support is included.         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         The following comments apply when PCRE is running in UTF-8 mode:         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161           optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         does not support this.
163         subjects  are  checked for validity on entry to the relevant functions.  
164         If an invalid UTF-8 string is passed, an error return is given. In some     Validity of UTF-8 strings
165         situations,  you  may  already  know  that  your strings are valid, and  
166         therefore want to skip these checks in order to improve performance. If         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         subjects are (by default) checked for validity on entry to the relevant
168         PCRE assumes that the pattern or subject  it  is  given  (respectively)         functions.  From  release 7.3 of PCRE, the check is according the rules
169         contains  only valid UTF-8 codes. In this case, it does not diagnose an         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172         crash.         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174         2. In a pattern, the escape sequence \x{...}, where the contents of the  
175         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176         character whose code number is the given hexadecimal number, for  exam-         which  the Unicode Standard says this: "The Low Surrogate Area does not
177         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,         contain any  character  assignments,  consequently  no  character  code
178         the item is not recognized.  This escape sequence can be used either as         charts or namelists are provided for this area. Surrogates are reserved
179         a literal, or within a character class.         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         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212         UTF-8 character if the value is greater than 127.         characters for values greater than \177.
213    
214         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         gle byte.         gle byte.
219    
220         6. The escape sequence \C can be used to match a single byte  in  UTF-8         5.  The  escape sequence \C can be used to match a single byte in UTF-8
221         mode,  but  its  use can lead to some strange effects. This facility is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but, by default, the characters that
226         nizes as digits, spaces, or word characters  remain  the  same  set  as         PCRE  recognizes  as digits, spaces, or word characters remain the same
227         before, all with values less than 256. This remains true even when PCRE         set as before, all with values less than 256. This  remains  true  even
228         includes Unicode property support, because to do otherwise  would  slow         when  PCRE  is built to include Unicode property support, because to do
229         down  PCRE in many common cases. If you really want to test for a wider         otherwise would slow down PCRE in many common  cases.  Note  that  this
230         sense of, say, "digit", you must use Unicode  property  tests  such  as         also applies to \b, because it is defined in terms of \w and \W. If you
231         \p{Nd}.         really want to test for a wider sense of, say,  "digit",  you  can  use
232           explicit  Unicode property tests such as \p{Nd}.  Alternatively, if you
233         8.  Similarly,  characters that match the POSIX named character classes         set the PCRE_UCP option, the way that the  character  escapes  work  is
234         are all low-valued characters.         changed  so that Unicode properties are used to determine which charac-
235           ters match. There are more details in the section on generic  character
236           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         9. Case-insensitive matching applies only to  characters  whose  values
246         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
247         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
248         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
249         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
250         used only for characters with higher values.         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         Philip Hazel
260         University Computing Service,         University Computing Service
261         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
262    
263         Putting  an actual email address here seems to have been a spam magnet,         Putting  an actual email address here seems to have been a spam magnet,
264         so I've taken it away. If you want to email me, use my initial and sur-         so I've taken it away. If you want to email me, use  my  two  initials,
265         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
266    
267    
268  Last updated: 07 March 2005  REVISION
269  Copyright (c) 1997-2005 University of Cambridge.  
270           Last updated: 12 May 2010
271           Copyright (c) 1997-2010 University of Cambridge.
272  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
273    
274    
# Line 218  NAME Line 282  NAME
282  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
283    
284         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
285         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
286         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
287         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
288         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
289         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
290           instead of configure to build PCRE.
291    
292           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           distribution.  You  should consult this file as well as the README file
295           if you are building in a non-Unix-like environment.
296    
297           The complete list of options for configure (which includes the standard
298           ones  such  as  the  selection  of  the  installation directory) can be
299           obtained by running
300    
301           ./configure --help           ./configure --help
302    
303         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
304         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
305         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
306         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
307         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
308         not described.         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           --enable-utf8
327    
328         to  the  configure  command.  Of  itself, this does not make PCRE treat         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         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()         have  have to set the PCRE_UTF8 option when you call the pcre_compile()
331         function.         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    
339    
340  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 259  UNICODE CHARACTER PROPERTY SUPPORT Line 350  UNICODE CHARACTER PROPERTY SUPPORT
350         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF-8 support, even if you  have
351         not explicitly requested it.         not explicitly requested it.
352    
353         Including  Unicode  property  support  adds around 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
354         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
355         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
356    
357    
358  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
359    
360         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets the linefeed (LF) character as indicating
361         ter. This is the normal newline character on Unix-like systems. You can         the end of a line. This is the normal newline  character  on  Unix-like
362         compile PCRE to use character 13 (carriage return) instead by adding         systems.  You  can compile PCRE to use carriage return (CR) instead, by
363           adding
364    
365           --enable-newline-is-cr           --enable-newline-is-cr
366    
367         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
368         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
369         line 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 and  static         The  PCRE building process uses libtool to build both shared and static
407         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
408         of         of
409    
410           --disable-shared           --disable-shared
# Line 293  BUILDING SHARED AND STATIC LIBRARIES Line 416  BUILDING SHARED AND STATIC LIBRARIES
416  POSIX MALLOC USAGE  POSIX MALLOC USAGE
417    
418         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
419         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
420         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
421         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
422         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
423         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
424         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 306  POSIX MALLOC USAGE Line 429  POSIX MALLOC USAGE
429         to the configure command.         to the configure command.
430    
431    
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 calls repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
482         edly  (possibly  recursively)  when  matching  a   pattern   with   the         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
483         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec()  function.  By controlling the maximum number of times this
484         function may be called during a single matching operation, a limit  can         function may be called during a single matching operation, a limit  can
485         be  placed  on  the resources used by a single call to pcre_exec(). The         be  placed  on  the resources used by a single call to pcre_exec(). The
# Line 322  LIMITING PCRE RESOURCE USAGE Line 492  LIMITING PCRE RESOURCE USAGE
492         to  the  configure  command.  This  setting  has  no  effect   on   the         to  the  configure  command.  This  setting  has  no  effect   on   the
493         pcre_dfa_exec() matching function.         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             --with-match-limit-recursion=10000
504    
505           to  the  configure  command.  This  value can also be overridden at run
506           time.
507    
508    
509    CREATING CHARACTER TABLES AT BUILD TIME
510    
511           PCRE uses fixed tables for processing characters whose code values  are
512           less  than 256. By default, PCRE is built with a set of tables that are
513           distributed in the file pcre_chartables.c.dist. These  tables  are  for
514           ASCII codes only. If you add
515    
516             --enable-rebuild-chartables
517    
518           to  the  configure  command, the distributed tables are no longer used.
519           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           C runtime system. (This method of replacing the tables does not work if
522           you  are cross compiling, because dftables is run on the local host. If
523           you need to create alternative tables when cross  compiling,  you  will
524           have to do so "by hand".)
525    
 HANDLING VERY LARGE PATTERNS  
526    
527         Within  a  compiled  pattern,  offset values are used to point from one  USING EBCDIC CODE
        part to another (for example, from an opening parenthesis to an  alter-  
        nation  metacharacter).  By default, two-byte values are used for these  
        offsets, leading to a maximum size for a  compiled  pattern  of  around  
        64K.  This  is sufficient to handle all but the most gigantic patterns.  
        Nevertheless, some people do want to process enormous patterns,  so  it  
        is  possible  to compile PCRE to use three-byte or four-byte offsets by  
        adding a setting such as  
528    
529           --with-link-size=3         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         to the configure command. The value given must be 2,  3,  or  4.  Using           --enable-ebcdic
        longer  offsets slows down the operation of PCRE because it has to load  
        additional bytes when handling them.  
535    
536         If you build PCRE with an increased link size, test 2 (and  test  5  if         to the configure command. This setting implies --enable-rebuild-charta-
537         you  are using UTF-8) will fail. Part of the output of these tests is a         bles.  You  should  only  use  it if you know that you are in an EBCDIC
538         representation of the compiled pattern, and this changes with the  link         environment (for example,  an  IBM  mainframe  operating  system).  The
539         size.         --enable-ebcdic option is incompatible with --enable-utf8.
540    
541    
542  AVOIDING EXCESSIVE STACK USAGE  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
543    
544         When matching with the pcre_exec() function, PCRE implements backtrack-         By default, pcregrep reads all files as plain text. You can build it so
545         ing by making recursive calls to an internal function  called  match().         that it recognizes files whose names end in .gz or .bz2, and reads them
546         In  environments  where  the size of the stack is limited, this can se-         with libz or libbz2, respectively, by adding one or both of
        verely limit PCRE's operation. (The Unix environment does  not  usually  
        suffer  from  this  problem.)  An alternative approach that uses memory  
        from the heap to remember data, instead  of  using  recursive  function  
        calls,  has been implemented to work round this problem. If you want to  
        build a version of PCRE that works this way, add  
547    
548           --disable-stack-for-recursion           --enable-pcregrep-libz
549             --enable-pcregrep-libbz2
550    
551         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. These options naturally require that the rel-
552         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         evant libraries are installed on your system. Configuration  will  fail
553         ment functions. Separate functions are provided because  the  usage  is         if they are not.
        very  predictable:  the  block sizes requested are always the same, and  
        the blocks are always freed in reverse order. A calling  program  might  
        be  able  to implement optimized functions that perform better than the  
        standard malloc() and  free()  functions.  PCRE  runs  noticeably  more  
        slowly when built in this way. This option affects only the pcre_exec()  
        function; it is not relevant for the the pcre_dfa_exec() function.  
554    
555    
556  USING EBCDIC CODE  PCRETEST OPTION FOR LIBREADLINE SUPPORT
557    
558         PCRE assumes by default that it will run in an  environment  where  the         If you add
        character  code  is  ASCII  (or Unicode, which is a superset of ASCII).  
        PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by  
        adding  
559    
560           --enable-ebcdic           --enable-pcretest-libreadline
561    
562         to the configure command.         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  Last updated: 28 February 2005  
592  Copyright (c) 1997-2005 University of Cambridge.  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    
# Line 418  PCRE MATCHING ALGORITHMS Line 635  PCRE MATCHING ALGORITHMS
635           <something> <something else> <something further>           <something> <something else> <something further>
636    
637         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
638         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
639    
640    
641  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 427  REGULAR EXPRESSIONS AS TREES Line 644  REGULAR EXPRESSIONS AS TREES
644         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
645         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
646         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
647         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
648         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
649         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
650    
651    
652  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
653    
654         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
655         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
656         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
657         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
658         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 459  THE STANDARD MATCHING ALGORITHM Line 676  THE STANDARD MATCHING ALGORITHM
676         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
677    
678    
679  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
680    
681         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
682         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
683         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
684         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
685         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
686         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
687           keeps multiple states active simultaneously).
688         The  scan  continues until either the end of the subject is reached, or  
689         there are no more unterminated paths. At this point,  terminated  paths         Although the general principle of this matching algorithm  is  that  it
690         represent  the different matching possibilities (if there are none, the         scans  the subject string only once, without backtracking, there is one
691         match has failed).  Thus, if there is more  than  one  possible  match,         exception: when a lookaround assertion is encountered,  the  characters
692           following  or  preceding  the  current  point  have to be independently
693           inspected.
694    
695           The scan continues until either the end of the subject is  reached,  or
696           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-         this algorithm finds all of them, and in particular, it finds the long-
700         est. In PCRE, there is an option to stop the algorithm after the  first         est.  There  is  an  option to stop the algorithm after the first match
701         match (which is necessarily the shortest) has been found.         (which is necessarily the shortest) is found.
702    
703         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
704         subject. If the pattern         subject. If the pattern
705    
706           cat(er(pillar)?)           cat(er(pillar)?)
707    
708         is matched against the string "the caterpillar catchment",  the  result         is  matched  against the string "the caterpillar catchment", the result
709         will  be the three strings "cat", "cater", and "caterpillar" that start         will be the three strings "cat", "cater", and "caterpillar" that  start
710         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
711         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
712    
713         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
714         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
715    
716         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1.  Because  the  algorithm  finds  all possible matches, the greedy or
717         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
718         ungreedy quantifiers are treated in exactly the same way.         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             ^a++\w!
723    
724           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         2. When dealing with multiple paths through the tree simultaneously, it
731         is  not  straightforward  to  keep track of captured substrings for the         is not straightforward to keep track of  captured  substrings  for  the
732         different matching possibilities, and  PCRE's  implementation  of  this         different  matching  possibilities,  and  PCRE's implementation of this
733         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
734         strings are available.         strings are available.
735    
736         3. Because no substrings are captured, back references within the  pat-         3.  Because no substrings are captured, back references within the pat-
737         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
738    
739         4.  For  the same reason, conditional expressions that use a backrefer-         4. For the same reason, conditional expressions that use  a  backrefer-
740         ence as the condition are not supported.         ence  as  the  condition or test for a specific group recursion are not
741           supported.
742    
743           5. Because many paths through the tree may be  active,  the  \K  escape
744           sequence, which resets the start of the match when encountered (but may
745           be on some paths and not on others), is not  supported.  It  causes  an
746           error if encountered.
747    
748         5. Callouts are supported, but the value of the  capture_top  field  is         6.  Callouts  are  supported, but the value of the capture_top field is
749         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
750    
751         6.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
752         single byte, even in UTF-8 mode, is not supported because the DFA algo-         single  byte, even in UTF-8 mode, is not supported because the alterna-
753         rithm moves through the subject string one character at a time, for all         tive algorithm moves through the subject  string  one  character  at  a
754         active paths through the tree.         time, for all active paths through the tree.
755    
756           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
757           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
758           negative assertion.
759    
 ADVANTAGES OF THE DFA ALGORITHM  
760    
761         Using the DFA matching algorithm provides the following advantages:  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
762    
763           Using  the alternative matching algorithm provides the following advan-
764           tages:
765    
766         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
767         ically  found,  and  in particular, the longest match is found. To find         ically  found,  and  in particular, the longest match is found. To find
768         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
769         things with callouts.         things with callouts.
770    
771         2.  There is much better support for partial matching. The restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
772         on the content of the pattern that apply when using the standard  algo-         once, and never needs to backtrack, it is possible to  pass  very  long
773         rithm  for partial matching do not apply to the DFA algorithm. For non-         subject  strings  to  the matching function in several pieces, checking
774         anchored patterns, the starting position of a partial match  is  avail-         for partial matching each time.  The  pcrepartial  documentation  gives
775         able.         details of partial matching.
   
        3.  Because  the  DFA algorithm scans the subject string just once, and  
        never needs to backtrack, it is possible  to  pass  very  long  subject  
        strings  to  the matching function in several pieces, checking for par-  
        tial matching each time.  
776    
777    
778  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
779    
780         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
781    
782         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
783         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
784         because it is less susceptible to optimization.         because it is less susceptible to optimization.
785    
786         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
787    
788         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
789         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
        rithm.  
790    
791  Last updated: 28 February 2005  
792  Copyright (c) 1997-2005 University of Cambridge.  AUTHOR
793    
794           Philip Hazel
795           University Computing Service
796           Cambridge CB2 3QH, England.
797    
798    
799    REVISION
800    
801           Last updated: 29 September 2009
802           Copyright (c) 1997-2009 University of Cambridge.
803  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
804    
805    
# Line 603  PCRE NATIVE API Line 852  PCRE NATIVE API
852         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
853              const char *name);              const char *name);
854    
855           int pcre_get_stringtable_entries(const pcre *code,
856                const char *name, char **first, char **last);
857    
858         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
859              int stringcount, int stringnumber,              int stringcount, int stringnumber,
860              const char **stringptr);              const char **stringptr);
# Line 641  PCRE NATIVE API Line 893  PCRE NATIVE API
893  PCRE API OVERVIEW  PCRE API OVERVIEW
894    
895         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
896         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
897         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
898         Both of these APIs define a set of C function calls. A C++  wrapper  is         Both of these APIs define a set of C function calls. A C++  wrapper  is
899         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 654  PCRE API OVERVIEW Line 906  PCRE API OVERVIEW
906         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
907         for different releases of PCRE.         for different releases of PCRE.
908    
909           In a Windows environment, if you want to statically link an application
910           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
911           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
912           loc()   and   pcre_free()   exported   functions   will   be   declared
913           __declspec(dllimport), with unwanted results.
914    
915         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
916         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
917         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
918         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
919         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
920         run it.         pcredemo documentation, and the pcresample documentation describes  how
921           to compile and run it.
922    
923         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
924         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
925         ing. This allows it to find all possible matches (at a given  point  in         ing.  The  alternative algorithm finds all possible matches (at a given
926         the  subject),  not  just  one. However, this algorithm does not return         point in the subject), and scans the subject just  once  (unless  there
927           are  lookbehind  assertions).  However,  this algorithm does not return
928         captured substrings. A description of the two matching  algorithms  and         captured substrings. A description of the two matching  algorithms  and
929         their  advantages  and disadvantages is given in the pcrematching docu-         their  advantages  and disadvantages is given in the pcrematching docu-
930         mentation.         mentation.
# Line 679  PCRE API OVERVIEW Line 939  PCRE API OVERVIEW
939           pcre_get_named_substring()           pcre_get_named_substring()
940           pcre_get_substring_list()           pcre_get_substring_list()
941           pcre_get_stringnumber()           pcre_get_stringnumber()
942             pcre_get_stringtable_entries()
943    
944         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
945         to free the memory used for extracted strings.         to free the memory used for extracted strings.
# Line 710  PCRE API OVERVIEW Line 971  PCRE API OVERVIEW
971         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
972         are used only when PCRE is compiled to use  the  heap  for  remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
973         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
974         function. This is a non-standard way of building PCRE, for use in envi-         function. See the pcrebuild documentation for  details  of  how  to  do
975         ronments that have limited stacks. Because of the greater use of memory         this.  It  is  a non-standard way of building PCRE, for use in environ-
976         management, it runs more slowly.  Separate functions  are  provided  so         ments that have limited stacks. Because of the greater  use  of  memory
977         that  special-purpose  external  code  can  be used for this case. When         management,  it  runs  more  slowly. Separate functions are provided so
978         used, these functions are always called in a  stack-like  manner  (last         that special-purpose external code can be  used  for  this  case.  When
979         obtained,  first freed), and always for memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
980           obtained, first freed), and always for memory blocks of the same  size.
981           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
982           mentation.
983    
984         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
985         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 723  PCRE API OVERVIEW Line 987  PCRE API OVERVIEW
987         pcrecallout documentation.         pcrecallout documentation.
988    
989    
990    NEWLINES
991    
992           PCRE  supports five different conventions for indicating line breaks in
993           strings: a single CR (carriage return) character, a  single  LF  (line-
994           feed) character, the two-character sequence CRLF, any of the three pre-
995           ceding, or any Unicode newline sequence. The Unicode newline  sequences
996           are  the  three just mentioned, plus the single characters VT (vertical
997           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
998           separator, U+2028), and PS (paragraph separator, U+2029).
999    
1000           Each  of  the first three conventions is used by at least one operating
1001           system as its standard newline sequence. When PCRE is built, a  default
1002           can  be  specified.  The default default is LF, which is the Unix stan-
1003           dard. When PCRE is run, the default can be overridden,  either  when  a
1004           pattern is compiled, or when it is matched.
1005    
1006           At compile time, the newline convention can be specified by the options
1007           argument of pcre_compile(), or it can be specified by special  text  at
1008           the start of the pattern itself; this overrides any other settings. See
1009           the pcrepattern page for details of the special character sequences.
1010    
1011           In the PCRE documentation the word "newline" is used to mean "the char-
1012           acter  or pair of characters that indicate a line break". The choice of
1013           newline convention affects the handling of  the  dot,  circumflex,  and
1014           dollar metacharacters, the handling of #-comments in /x mode, and, when
1015           CRLF is a recognized line ending sequence, the match position  advance-
1016           ment for a non-anchored pattern. There is more detail about this in the
1017           section on pcre_exec() options below.
1018    
1019           The choice of newline convention does not affect the interpretation  of
1020           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1021           which is controlled in a similar way, but by separate options.
1022    
1023    
1024  MULTITHREADING  MULTITHREADING
1025    
1026         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1027         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1028         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1029         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 740  SAVING PRECOMPILED PATTERNS FOR LATER US Line 1038  SAVING PRECOMPILED PATTERNS FOR LATER US
1038         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1039         later time, possibly by a different program, and even on a  host  other         later time, possibly by a different program, and even on a  host  other
1040         than  the  one  on  which  it  was  compiled.  Details are given in the         than  the  one  on  which  it  was  compiled.  Details are given in the
1041         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
1042           with  one version of PCRE for use with a different version is not guar-
1043           anteed to work and may cause crashes.
1044    
1045    
1046  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 769  CHECKING BUILD-TIME OPTIONS Line 1069  CHECKING BUILD-TIME OPTIONS
1069    
1070           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1071    
1072         The output is an integer that is set to the value of the code  that  is         The output is an integer whose value specifies  the  default  character
1073         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
1074         return (13), and should normally be the  standard  character  for  your         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1075         operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1076           are returned in EBCDIC environments. The default should normally corre-
1077           spond to the standard sequence for your operating system.
1078    
1079             PCRE_CONFIG_BSR
1080    
1081           The output is an integer whose value indicates what character sequences
1082           the \R escape sequence matches by default. A value of 0 means  that  \R
1083           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1084           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1085           tern is compiled or matched.
1086    
1087           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1088    
# Line 791  CHECKING BUILD-TIME OPTIONS Line 1101  CHECKING BUILD-TIME OPTIONS
1101    
1102           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1103    
1104         The output is an integer that gives the default limit for the number of         The output is a long integer that gives the default limit for the  num-
1105         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1106         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1107    
1108             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1109    
1110           The output is a long integer that gives the default limit for the depth
1111           of   recursion  when  calling  the  internal  matching  function  in  a
1112           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1113           below.
1114    
1115           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1116    
1117         The output is an integer that is set to one if internal recursion  when         The  output is an integer that is set to one if internal recursion when
1118         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1119         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1120         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1121         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1122         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1123         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1124    
1125    
# Line 819  COMPILING A PATTERN Line 1136  COMPILING A PATTERN
1136    
1137         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1138         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1139         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1140         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1141           avoid  too  much repetition, we refer just to pcre_compile() below, but
1142           the information applies equally to pcre_compile2().
1143    
1144         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1145         the pattern argument. A pointer to a single block  of  memory  that  is         the  pattern  argument.  A  pointer to a single block of memory that is
1146         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1147         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1148         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1149         It is up to the caller  to  free  the  memory  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1150         required.         longer required.
1151    
1152         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although the compiled code of a PCRE regex is relocatable, that is,  it
1153         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1154         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1155         ment, which is an address (see below).         ment, which is an address (see below).
1156    
1157         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1158         tion.  It  should  be  zero  if  no options are required. The available         pilation. It should be zero if no options are required.  The  available
1159         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them (in particular, those that
1160         are  compatible  with  Perl,  can also be set and unset from within the         are compatible with Perl, but some others as well) can also be set  and
1161         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset  from  within  the  pattern  (see the detailed description in the
1162         tion).  For  these options, the contents of the options argument speci-         pcrepattern documentation). For those options that can be different  in
1163         fies their initial settings at the start of compilation and  execution.         different  parts  of  the pattern, the contents of the options argument
1164         The  PCRE_ANCHORED option can be set at the time of matching as well as         specifies their settings at the start of compilation and execution. The
1165         at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1166           the time of matching as well as at compile time.
1167    
1168         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1169         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1170         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1171         sage.  The  offset from the start of the pattern to the character where         sage. This is a static string that is part of the library. You must not
1172         the error was discovered is  placed  in  the  variable  pointed  to  by         try to free it. The byte offset from the start of the  pattern  to  the
1173         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         character  that  was  being  processed when the error was discovered is
1174         given.         placed in the variable pointed to by erroffset, which must not be NULL.
1175           If  it  is,  an  immediate error is given. Some errors are not detected
1176         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         until checks are carried out when the whole pattern has  been  scanned;
1177         codeptr  argument is not NULL, a non-zero error code number is returned         in this case the offset is set to the end of the pattern.
1178         via this argument in the event of an error. This is in addition to  the  
1179           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1180           codeptr argument is not NULL, a non-zero error code number is  returned
1181           via  this argument in the event of an error. This is in addition to the
1182         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1183    
1184         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1185         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1186         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1187         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1188         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1189         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1190         support below.         support below.
1191    
1192         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1193         pile():         pile():
1194    
1195           pcre *re;           pcre *re;
# Line 879  COMPILING A PATTERN Line 1202  COMPILING A PATTERN
1202             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1203             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1204    
1205         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1206         file:         file:
1207    
1208           PCRE_ANCHORED           PCRE_ANCHORED
1209    
1210         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1211         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1212         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1213         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1214         only way to do it in Perl.         only way to do it in Perl.
1215    
1216           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1217    
1218         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1219         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1220         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1221    
1222             PCRE_BSR_ANYCRLF
1223             PCRE_BSR_UNICODE
1224    
1225           These options (which are mutually exclusive) control what the \R escape
1226           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1227           or to match any Unicode newline sequence. The default is specified when
1228           PCRE is built. It can be overridden from within the pattern, or by set-
1229           ting an option when a compiled pattern is matched.
1230    
1231           PCRE_CASELESS           PCRE_CASELESS
1232    
1233         If  this  bit is set, letters in the pattern match both upper and lower         If this bit is set, letters in the pattern match both upper  and  lower
1234         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1235         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1236         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1237         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1238         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1239         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1240         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1241         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1242         UTF-8 support.         UTF-8 support.
1243    
1244           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1245    
1246         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1247         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1248         matches immediately before the final character if it is a newline  (but         matches  immediately before a newline at the end of the string (but not
1249         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1250         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1251         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1252    
1253           PCRE_DOTALL           PCRE_DOTALL
1254    
1255         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharater in the pattern matches all char-
1256         acters, including newlines. Without it,  newlines  are  excluded.  This         acters,  including  those that indicate newline. Without it, a dot does
1257         option  is equivalent to Perl's /s option, and it can be changed within         not match when the current position is at a  newline.  This  option  is
1258         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]         equivalent  to Perl's /s option, and it can be changed within a pattern
1259         always  matches a newline character, independent of the setting of this         by a (?s) option setting. A negative class such as [^a] always  matches
1260         option.         newline characters, independent of the setting of this option.
1261    
1262             PCRE_DUPNAMES
1263    
1264           If  this  bit is set, names used to identify capturing subpatterns need
1265           not be unique. This can be helpful for certain types of pattern when it
1266           is  known  that  only  one instance of the named subpattern can ever be
1267           matched. There are more details of named subpatterns  below;  see  also
1268           the pcrepattern documentation.
1269    
1270           PCRE_EXTENDED           PCRE_EXTENDED
1271    
1272         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1273         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1274         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1275         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1276         line character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1277         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)         option, and it can be changed within a pattern by a  (?x)  option  set-
1278         option setting.         ting.
1279    
1280         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1281         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1282         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1283         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1284         introduces a conditional subpattern.         introduces a conditional subpattern.
1285    
1286           PCRE_EXTRA           PCRE_EXTRA
1287    
1288         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1289         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1290         little use. When set, any backslash in a pattern that is followed by  a         little  use. When set, any backslash in a pattern that is followed by a
1291         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1292         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1293         backslash  followed by a letter with no special meaning is treated as a         backslash followed by a letter with no special meaning is treated as  a
1294         literal. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give an error for this, by
1295         option. It can also be set by a (?X) option setting within a pattern.         running it with the -w option.) There are at present no other  features
1296           controlled  by this option. It can also be set by a (?X) option setting
1297           within a pattern.
1298    
1299           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1300    
1301         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1302         before or at the first newline character in the subject string,  though         before  or  at  the  first  newline  in  the subject string, though the
1303         the matched text may continue over the newline.         matched text may continue over the newline.
1304    
1305             PCRE_JAVASCRIPT_COMPAT
1306    
1307           If this option is set, PCRE's behaviour is changed in some ways so that
1308           it  is  compatible with JavaScript rather than Perl. The changes are as
1309           follows:
1310    
1311           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1312           error,  because this is illegal in JavaScript (by default it is treated
1313           as a data character). Thus, the pattern AB]CD becomes illegal when this
1314           option is set.
1315    
1316           (2)  At run time, a back reference to an unset subpattern group matches
1317           an empty string (by default this causes the current  matching  alterna-
1318           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1319           set (assuming it can find an "a" in the subject), whereas it  fails  by
1320           default, for Perl compatibility.
1321    
1322           PCRE_MULTILINE           PCRE_MULTILINE
1323    
# Line 970  COMPILING A PATTERN Line 1329  COMPILING A PATTERN
1329         is set). This is the same as Perl.         is set). This is the same as Perl.
1330    
1331         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1332         constructs  match  immediately following or immediately before any new-         constructs  match  immediately following or immediately before internal
1333         line in the subject string, respectively, as well as at the very  start         newlines in the subject string, respectively, as well as  at  the  very
1334         and  end. This is equivalent to Perl's /m option, and it can be changed         start  and  end.  This is equivalent to Perl's /m option, and it can be
1335         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
1336         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1337         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1338    
1339             PCRE_NEWLINE_CR
1340             PCRE_NEWLINE_LF
1341             PCRE_NEWLINE_CRLF
1342             PCRE_NEWLINE_ANYCRLF
1343             PCRE_NEWLINE_ANY
1344    
1345           These options override the default newline definition that  was  chosen
1346           when  PCRE  was built. Setting the first or the second specifies that a
1347           newline is indicated by a single character (CR  or  LF,  respectively).
1348           Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1349           two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1350           that any of the three preceding sequences should be recognized. Setting
1351           PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1352           recognized. The Unicode newline sequences are the three just mentioned,
1353           plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1354           U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1355           (paragraph separator, U+2029). The last  two  are  recognized  only  in
1356           UTF-8 mode.
1357    
1358           The  newline  setting  in  the  options  word  uses three bits that are
1359           treated as a number, giving eight possibilities. Currently only six are
1360           used  (default  plus the five values above). This means that if you set
1361           more than one newline option, the combination may or may not be  sensi-
1362           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1363           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1364           cause an error.
1365    
1366           The  only time that a line break is specially recognized when compiling
1367           a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1368           character  class  is  encountered.  This indicates a comment that lasts
1369           until after the next line break sequence. In other circumstances,  line
1370           break   sequences   are   treated  as  literal  data,  except  that  in
1371           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1372           and are therefore ignored.
1373    
1374           The newline option that is set at compile time becomes the default that
1375           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1376    
1377           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1378    
1379         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
# Line 985  COMPILING A PATTERN Line 1382  COMPILING A PATTERN
1382         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1383         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1384    
1385             PCRE_UCP
1386    
1387           This option changes the way PCRE processes \b, \d, \s, \w, and some  of
1388           the POSIX character classes. By default, only ASCII characters are rec-
1389           ognized, but if PCRE_UCP is set, Unicode properties are used instead to
1390           classify  characters.  More details are given in the section on generic
1391           character types in the pcrepattern page. If you set PCRE_UCP,  matching
1392           one  of the items it affects takes much longer. The option is available
1393           only if PCRE has been compiled with Unicode property support.
1394    
1395           PCRE_UNGREEDY           PCRE_UNGREEDY
1396    
1397         This option inverts the "greediness" of the quantifiers  so  that  they         This option inverts the "greediness" of the quantifiers  so  that  they
# Line 1004  COMPILING A PATTERN Line 1411  COMPILING A PATTERN
1411           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1412    
1413         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1414         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1415         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
1416         is  valid, and you want to skip this check for performance reasons, you         bytes  is  found,  pcre_compile() returns an error. If you already know
1417         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1418         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
1419         your program to crash.  Note that this option can  also  be  passed  to         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1420         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined.  It  may  cause your program to crash. Note that this option
1421         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1422           UTF-8 validity checking of subject strings.
1423    
1424    
1425  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1426    
1427         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1428         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1429         both compiling functions.         both  compiling functions. As PCRE has developed, some error codes have
1430           fallen out of use. To avoid confusion, they have not been re-used.
1431    
1432            0  no error            0  no error
1433            1  \ at end of pattern            1  \ at end of pattern
# Line 1030  COMPILATION ERROR CODES Line 1439  COMPILATION ERROR CODES
1439            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1440            8  range out of order in character class            8  range out of order in character class
1441            9  nothing to repeat            9  nothing to repeat
1442           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1443           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1444           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1445           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1446           14  missing )           14  missing )
1447           15  reference to non-existent subpattern           15  reference to non-existent subpattern
1448           16  erroffset passed as NULL           16  erroffset passed as NULL
1449           17  unknown option bit(s) set           17  unknown option bit(s) set
1450           18  missing ) after comment           18  missing ) after comment
1451           19  parentheses nested too deeply           19  [this code is not in use]
1452           20  regular expression too large           20  regular expression is too large
1453           21  failed to get memory           21  failed to get memory
1454           22  unmatched parentheses           22  unmatched parentheses
1455           23  internal error: code overflow           23  internal error: code overflow
1456           24  unrecognized character after (?<           24  unrecognized character after (?<
1457           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1458           26  malformed number after (?(           26  malformed number or name after (?(
1459           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1460           28  assertion expected after (?(           28  assertion expected after (?(
1461           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1462           30  unknown POSIX class name           30  unknown POSIX class name
1463           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1464           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1465           33  spare error           33  [this code is not in use]
1466           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1467           35  invalid condition (?(0)           35  invalid condition (?(0)
1468           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1062  COMPILATION ERROR CODES Line 1471  COMPILATION ERROR CODES
1471           39  closing ) for (?C expected           39  closing ) for (?C expected
1472           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1473           41  unrecognized character after (?P           41  unrecognized character after (?P
1474           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1475           43  two named groups have the same name           43  two named subpatterns have the same name
1476           44  invalid UTF-8 string           44  invalid UTF-8 string
1477           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1478           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1479           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1480             48  subpattern name is too long (maximum 32 characters)
1481             49  too many named subpatterns (maximum 10000)
1482             50  [this code is not in use]
1483             51  octal value is greater than \377 (not in UTF-8 mode)
1484             52  internal error: overran compiling workspace
1485             53  internal error: previously-checked referenced subpattern
1486                   not found
1487             54  DEFINE group contains more than one branch
1488             55  repeating a DEFINE group is not allowed
1489             56  inconsistent NEWLINE options
1490             57  \g is not followed by a braced, angle-bracketed, or quoted
1491                   name/number or by a plain number
1492             58  a numbered reference must not be zero
1493             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1494             60  (*VERB) not recognized
1495             61  number is too big
1496             62  subpattern name expected
1497             63  digit expected after (?+
1498             64  ] is an invalid data character in JavaScript compatibility mode
1499             65  different names for subpatterns of the same number are
1500                   not allowed
1501             66  (*MARK) must have an argument
1502             67  this version of PCRE is not compiled with PCRE_UCP support
1503    
1504           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1505           values may be used if the limits were changed when PCRE was built.
1506    
1507    
1508  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1075  STUDYING A PATTERN Line 1510  STUDYING A PATTERN
1510         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1511              const char **errptr);              const char **errptr);
1512    
1513         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1514         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1515         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1516         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1517         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1518         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
1519         the results of the study.         the results of the study.
1520    
1521         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1522         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1523         that can be set by the caller before the block  is  passed;  these  are         tains  other  fields  that can be set by the caller before the block is
1524         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1525    
1526         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1527         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1528         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1529         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1530    
1531         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1532         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1533    
1534         The  third argument for pcre_study() is a pointer for an error message.         The third argument for pcre_study() is a pointer for an error  message.
1535         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1536         points  to  is set to NULL. Otherwise it points to a textual error mes-         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1537         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1538         ing pcre_study(), to be sure that it has run successfully.         must not try to free it. You should test the  error  pointer  for  NULL
1539           after calling pcre_study(), to be sure that it has run successfully.
1540    
1541         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1542    
# Line 1110  STUDYING A PATTERN Line 1546  STUDYING A PATTERN
1546             0,              /* no options exist */             0,              /* no options exist */
1547             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1548    
1549         At present, studying a pattern is useful only for non-anchored patterns         Studying a pattern does two things: first, a lower bound for the length
1550         that do not have a single fixed starting character. A bitmap of  possi-         of subject string that is needed to match the pattern is computed. This
1551         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1552           it does guarantee that no shorter strings match. The value is  used  by
1553           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1554           match strings that are shorter than the lower bound. You can  find  out
1555           the value in a calling program via the pcre_fullinfo() function.
1556    
1557           Studying a pattern is also useful for non-anchored patterns that do not
1558           have a single fixed starting character. A bitmap of  possible  starting
1559           bytes  is  created. This speeds up finding a position in the subject at
1560           which to start matching.
1561    
1562           The two optimizations just described can be  disabled  by  setting  the
1563           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1564           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1565           callouts,  or  make  use of (*MARK), and you make use of these in cases
1566           where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE
1567           below.
1568    
1569    
1570  LOCALE SUPPORT  LOCALE SUPPORT
1571    
1572         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1573         letters digits, or whatever, by reference to a set of  tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1574         by  character  value.  When running in UTF-8 mode, this applies only to         by  character  value.  When running in UTF-8 mode, this applies only to
1575         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. By  default,  higher-valued  codes
1576         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built         never match escapes such as \w or \d, but they can be tested with \p if
1577         with Unicode character property support.         PCRE is built with Unicode character property  support.  Alternatively,
1578           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1579         An internal set of tables is created in the default C locale when  PCRE         friends to use Unicode property support instead of built-in tables. The
1580         is  built.  This  is  used when the final argument of pcre_compile() is         use of locales with Unicode is discouraged. If you are handling charac-
1581         NULL, and is sufficient for many applications. An  alternative  set  of         ters with codes greater than 128, you should either use UTF-8 and  Uni-
1582         tables  can,  however, be supplied. These may be created in a different         code, or use locales, but not try to mix the two.
1583         locale from the default. As more and more applications change to  using  
1584         Unicode, the need for this locale support is expected to die away.         PCRE  contains  an  internal set of tables that are used when the final
1585           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1586           applications.  Normally, the internal tables recognize only ASCII char-
1587           acters. However, when PCRE is built, it is possible to cause the inter-
1588           nal tables to be rebuilt in the default "C" locale of the local system,
1589           which may cause them to be different.
1590    
1591           The internal tables can always be overridden by tables supplied by  the
1592           application that calls PCRE. These may be created in a different locale
1593           from the default. As more and more applications change  to  using  Uni-
1594           code, the need for this locale support is expected to die away.
1595    
1596         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
1597         which has no arguments, in the relevant locale. The result can then  be         which has no arguments, in the relevant locale. The result can then  be
# Line 1142  LOCALE SUPPORT Line 1604  LOCALE SUPPORT
1604           tables = pcre_maketables();           tables = pcre_maketables();
1605           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1606    
1607         When pcre_maketables() runs, the tables are built  in  memory  that  is         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1608         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         if you are using Windows, the name for the French locale is "french".
1609         that the memory containing the tables remains available for as long  as  
1610           When  pcre_maketables()  runs,  the  tables are built in memory that is
1611           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1612           that  the memory containing the tables remains available for as long as
1613         it is needed.         it is needed.
1614    
1615         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1616         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
1617         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1618         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1619         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1620    
1621         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1622         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1623         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1624         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1625         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1626    
# Line 1165  INFORMATION ABOUT A PATTERN Line 1630  INFORMATION ABOUT A PATTERN
1630         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1631              int what, void *where);              int what, void *where);
1632    
1633         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1634         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1635         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1636    
1637         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1638         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
1639         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1640         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
1641         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
1642         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1643    
1644           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1181  INFORMATION ABOUT A PATTERN Line 1646  INFORMATION ABOUT A PATTERN
1646           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1647           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1648    
1649         The "magic number" is placed at the start of each compiled  pattern  as         The  "magic  number" is placed at the start of each compiled pattern as
1650         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1651         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1652         pattern:         pattern:
1653    
1654           int rc;           int rc;
1655           unsigned long int length;           size_t length;
1656           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1657             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1658             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1659             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1660             &length);         /* where to put the data */             &length);         /* where to put the data */
1661    
1662         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1663         are as follows:         are as follows:
1664    
1665           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1666    
1667         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1668         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1669         there are no back references.         there are no back references.
1670    
1671           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1672    
1673         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1674         argument should point to an int variable.         argument should point to an int variable.
1675    
1676           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1677    
1678         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1679         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1680         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1681         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1682         passing a NULL table pointer.         passing a NULL table pointer.
1683    
1684           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1685    
1686         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1687         non-anchored   pattern.   (This    option    used    to    be    called         non-anchored  pattern. The fourth argument should point to an int vari-
1688         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1689         compatibility.)         is still recognized for backwards compatibility.)
1690    
1691         If there is a fixed first byte, for example, from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1692         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.         (cat|cow|coyote), its value is returned. Otherwise, if either
        Otherwise, if either  
1693    
1694         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1695         branch starts with "^", or         branch starts with "^", or
# Line 1245  INFORMATION ABOUT A PATTERN Line 1709  INFORMATION ABOUT A PATTERN
1709         returned.  The fourth argument should point to an unsigned char * vari-         returned.  The fourth argument should point to an unsigned char * vari-
1710         able.         able.
1711    
1712             PCRE_INFO_HASCRORLF
1713    
1714           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1715           characters,  otherwise  0.  The  fourth argument should point to an int
1716           variable. An explicit match is either a literal CR or LF character,  or
1717           \r or \n.
1718    
1719             PCRE_INFO_JCHANGED
1720    
1721           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1722           otherwise 0. The fourth argument should point to an int variable.  (?J)
1723           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1724    
1725           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1726    
1727         Return the value of the rightmost literal byte that must exist  in  any         Return  the  value of the rightmost literal byte that must exist in any
1728         matched  string,  other  than  at  its  start,  if such a byte has been         matched string, other than at its  start,  if  such  a  byte  has  been
1729         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1730         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such byte, -1 is returned. For anchored patterns, a last  literal
1731         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1732         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1733         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1734    
1735             PCRE_INFO_MINLENGTH
1736    
1737           If  the  pattern  was studied and a minimum length for matching subject
1738           strings was computed, its value is  returned.  Otherwise  the  returned
1739           value  is  -1. The value is a number of characters, not bytes (this may
1740           be relevant in UTF-8 mode). The fourth argument should point to an  int
1741           variable.  A  non-negative  value is a lower bound to the length of any
1742           matching string. There may not be any strings of that  length  that  do
1743           actually match, but every string that does match is at least that long.
1744    
1745           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1746           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1747           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1748    
1749         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1750         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1751         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
1752         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring() are provided for  extracting  captured  sub-
1753         captured substring by name. It is also possible  to  extract  the  data         strings  by  name. It is also possible to extract the data directly, by
1754         directly,  by  first converting the name to a number in order to access         first converting the name to a number in order to  access  the  correct
1755         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
1756         below).  To  do the conversion, you need to use the name-to-number map,         the conversion, you need  to  use  the  name-to-number  map,  which  is
1757         which is described by these three values.         described by these three values.
1758    
1759         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1760         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1761         of each entry; both of these  return  an  int  value.  The  entry  size         of  each  entry;  both  of  these  return  an int value. The entry size
1762         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1763         a pointer to the first entry of the table  (a  pointer  to  char).  The         a  pointer  to  the  first  entry of the table (a pointer to char). The
1764         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1765         sis, most significant byte first. The rest of the entry is  the  corre-         sis,  most  significant byte first. The rest of the entry is the corre-
1766         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
        For example, consider the following pattern  (assume  PCRE_EXTENDED  is  
        set, so white space - including newlines - is ignored):  
1767    
1768           (?P<date> (?P<year>(\d\d)?\d\d) -         The names are in alphabetical order. Duplicate names may appear if  (?|
1769           (?P<month>\d\d) - (?P<day>\d\d) )         is used to create multiple groups with the same number, as described in
1770           the section on duplicate subpattern numbers in  the  pcrepattern  page.
1771           Duplicate  names  for  subpatterns with different numbers are permitted
1772           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1773           appear  in  the table in the order in which they were found in the pat-
1774           tern. In the absence of (?| this is the  order  of  increasing  number;
1775           when (?| is used this is not necessarily the case because later subpat-
1776           terns may have lower numbers.
1777    
1778           As a simple example of the name/number table,  consider  the  following
1779           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1780           lines - is ignored):
1781    
1782         There  are  four  named subpatterns, so the table has four entries, and           (?<date> (?<year>(\d\d)?\d\d) -
1783         each entry in the table is eight bytes long. The table is  as  follows,           (?<month>\d\d) - (?<day>\d\d) )
1784    
1785           There are four named subpatterns, so the table has  four  entries,  and
1786           each  entry  in the table is eight bytes long. The table is as follows,
1787         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1788         as ??:         as ??:
1789    
# Line 1293  INFORMATION ABOUT A PATTERN Line 1792  INFORMATION ABOUT A PATTERN
1792           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1793           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1794    
1795         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1796         name-to-number map, remember that the length of each entry is likely to         name-to-number map, remember that the length of the entries  is  likely
1797         be different for each compiled pattern.         to be different for each compiled pattern.
1798    
1799             PCRE_INFO_OKPARTIAL
1800    
1801           Return  1  if  the  pattern  can  be  used  for  partial  matching with
1802           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1803           variable.  From  release  8.00,  this  always  returns  1,  because the
1804           restrictions that previously applied  to  partial  matching  have  been
1805           lifted.  The  pcrepartial documentation gives details of partial match-
1806           ing.
1807    
1808           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1809    
1810         Return a copy of the options with which the pattern was  compiled.  The         Return a copy of the options with which the pattern was  compiled.  The
1811         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
1812         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1813         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1814           other words, they are the options that will be in force  when  matching
1815           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1816           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1817           and PCRE_EXTENDED.
1818    
1819         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1820         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1328  INFORMATION ABOUT A PATTERN Line 1840  INFORMATION ABOUT A PATTERN
1840         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1841         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1842         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1843         created  by  pcre_study(). The fourth argument should point to a size_t         created  by  pcre_study().  If pcre_extra is NULL, or there is no study
1844           data, zero is returned. The fourth argument should point  to  a  size_t
1845         variable.         variable.
1846    
1847    
# Line 1336  OBSOLETE INFO FUNCTION Line 1849  OBSOLETE INFO FUNCTION
1849    
1850         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1851    
1852         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1853         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1854         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1855         pcre_info()  is the number of capturing subpatterns, or one of the fol-         pcre_info() is the number of capturing subpatterns, or one of the  fol-
1856         lowing negative numbers:         lowing negative numbers:
1857    
1858           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1859           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1860    
1861         If the optptr argument is not NULL, a copy of the  options  with  which         If  the  optptr  argument is not NULL, a copy of the options with which
1862         the  pattern  was  compiled  is placed in the integer it points to (see         the pattern was compiled is placed in the integer  it  points  to  (see
1863         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1864    
1865         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1866         NULL,  it is used to pass back information about the first character of         NULL, it is used to pass back information about the first character  of
1867         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1868    
1869    
# Line 1358  REFERENCE COUNTS Line 1871  REFERENCE COUNTS
1871    
1872         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1873    
1874         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1875         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1876         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1877         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1878         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1879    
1880         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1881         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1882         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1883         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1884         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1885         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1886    
1887         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1888         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1889         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1890    
1891    
# Line 1384  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1897  MATCHING A PATTERN: THE TRADITIONAL FUNC
1897    
1898         The function pcre_exec() is called to match a subject string against  a         The function pcre_exec() is called to match a subject string against  a
1899         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
1900         has been studied, the result of the study should be passed in the extra         was studied, the result of the study should  be  passed  in  the  extra
1901         argument.  This  function is the main matching facility of the library,         argument.  This  function is the main matching facility of the library,
1902         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1903         an  alternative matching function, which is described below in the sec-         an  alternative matching function, which is described below in the sec-
# Line 1415  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1928  MATCHING A PATTERN: THE TRADITIONAL FUNC
1928         If the extra argument is not NULL, it must point to a  pcre_extra  data         If the extra argument is not NULL, it must point to a  pcre_extra  data
1929         block.  The pcre_study() function returns such a block (when it doesn't         block.  The pcre_study() function returns such a block (when it doesn't
1930         return NULL), but you can also create one for yourself, and pass  addi-         return NULL), but you can also create one for yourself, and pass  addi-
1931         tional  information in it. The fields in a pcre_extra block are as fol-         tional  information  in it. The pcre_extra block contains the following
1932         lows:         fields (not necessarily in this order):
1933    
1934           unsigned long int flags;           unsigned long int flags;
1935           void *study_data;           void *study_data;
1936           unsigned long int match_limit;           unsigned long int match_limit;
1937             unsigned long int match_limit_recursion;
1938           void *callout_data;           void *callout_data;
1939           const unsigned char *tables;           const unsigned char *tables;
1940             unsigned char **mark;
1941    
1942         The flags field is a bitmap that specifies which of  the  other  fields         The flags field is a bitmap that specifies which of  the  other  fields
1943         are set. The flag bits are:         are set. The flag bits are:
1944    
1945           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1946           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1947             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1948           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1949           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1950             PCRE_EXTRA_MARK
1951    
1952         Other  flag  bits should be set to zero. The study_data field is set in         Other  flag  bits should be set to zero. The study_data field is set in
1953         the pcre_extra block that is returned by  pcre_study(),  together  with         the pcre_extra block that is returned by  pcre_study(),  together  with
# Line 1441  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1958  MATCHING A PATTERN: THE TRADITIONAL FUNC
1958         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1959         a vast amount of resources when running patterns that are not going  to         a vast amount of resources when running patterns that are not going  to
1960         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
1961         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1962         repeats.         ited repeats.
1963    
1964         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1965         edly (sometimes recursively). The limit is imposed  on  the  number  of         edly (sometimes recursively). The limit set by match_limit  is  imposed
1966         times  this  function is called during a match, which has the effect of         on  the  number  of times this function is called during a match, which
1967         limiting the amount of recursion and backtracking that can take  place.         has the effect of limiting the amount of  backtracking  that  can  take
1968         For patterns that are not anchored, the count starts from zero for each         place. For patterns that are not anchored, the count restarts from zero
1969         position in the subject string.         for each position in the subject string.
1970    
1971         The default limit for the library can be set when PCRE  is  built;  the         The default value for the limit can be set  when  PCRE  is  built;  the
1972         default  default  is 10 million, which handles all but the most extreme         default  default  is 10 million, which handles all but the most extreme
1973         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1974         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra     block    in    which    match_limit    is    set,    and
1975         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
1976         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1977    
1978         The  pcre_callout  field is used in conjunction with the "callout" fea-         The  match_limit_recursion field is similar to match_limit, but instead
1979         ture, which is described in the pcrecallout documentation.         of limiting the total number of times that match() is called, it limits
1980           the  depth  of  recursion. The recursion depth is a smaller number than
1981         The tables field  is  used  to  pass  a  character  tables  pointer  to         the total number of calls, because not all calls to match() are  recur-
1982         pcre_exec();  this overrides the value that is stored with the compiled         sive.  This limit is of use only if it is set smaller than match_limit.
1983         pattern. A non-NULL value is stored with the compiled pattern  only  if  
1984         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         Limiting  the  recursion  depth  limits the amount of stack that can be
1985           used, or, when PCRE has been compiled to use memory on the heap instead
1986           of the stack, the amount of heap memory that can be used.
1987    
1988           The  default  value  for  match_limit_recursion can be set when PCRE is
1989           built; the default default  is  the  same  value  as  the  default  for
1990           match_limit.  You can override the default by suppling pcre_exec() with
1991           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1992           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1993           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1994    
1995           The callout_data field is used in conjunction with the  "callout"  fea-
1996           ture, and is described in the pcrecallout documentation.
1997    
1998           The  tables  field  is  used  to  pass  a  character  tables pointer to
1999           pcre_exec(); this overrides the value that is stored with the  compiled
2000           pattern.  A  non-NULL value is stored with the compiled pattern only if
2001           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2002         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2003         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
2004         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2005         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2006         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2007         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2008    
2009           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2010           set  to  point  to a char * variable. If the pattern contains any back-
2011           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2012           with  a  name  to  pass back, a pointer to the name string (zero termi-
2013           nated) is placed in the variable pointed to  by  the  mark  field.  The
2014           names  are  within  the  compiled pattern; if you wish to retain such a
2015           name you must copy it before freeing the memory of a compiled  pattern.
2016           If  there  is no name to pass back, the variable pointed to by the mark
2017           field set to NULL. For details of the backtracking control  verbs,  see
2018           the section entitled "Backtracking control" in the pcrepattern documen-
2019           tation.
2020    
2021     Option bits for pcre_exec()     Option bits for pcre_exec()
2022    
2023         The  unused  bits of the options argument for pcre_exec() must be zero.         The unused bits of the options argument for pcre_exec() must  be  zero.
2024         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2025         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2026           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2027           PCRE_PARTIAL_HARD.
2028    
2029           PCRE_ANCHORED           PCRE_ANCHORED
2030    
2031         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2032         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2033         turned  out to be anchored by virtue of its contents, it cannot be made         turned out to be anchored by virtue of its contents, it cannot be  made
2034         unachored at matching time.         unachored at matching time.
2035    
2036             PCRE_BSR_ANYCRLF
2037             PCRE_BSR_UNICODE
2038    
2039           These options (which are mutually exclusive) control what the \R escape
2040           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2041           or  to  match  any Unicode newline sequence. These options override the
2042           choice that was made or defaulted when the pattern was compiled.
2043    
2044             PCRE_NEWLINE_CR
2045             PCRE_NEWLINE_LF
2046             PCRE_NEWLINE_CRLF
2047             PCRE_NEWLINE_ANYCRLF
2048             PCRE_NEWLINE_ANY
2049    
2050           These options override  the  newline  definition  that  was  chosen  or
2051           defaulted  when the pattern was compiled. For details, see the descrip-
2052           tion of pcre_compile()  above.  During  matching,  the  newline  choice
2053           affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2054           ters. It may also alter the way the match position is advanced after  a
2055           match failure for an unanchored pattern.
2056    
2057           When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2058           set, and a match attempt for an unanchored pattern fails when the  cur-
2059           rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2060           explicit matches for  CR  or  LF  characters,  the  match  position  is
2061           advanced by two characters instead of one, in other words, to after the
2062           CRLF.
2063    
2064           The above rule is a compromise that makes the most common cases work as
2065           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2066           option is not set), it does not match the string "\r\nA" because, after
2067           failing  at the start, it skips both the CR and the LF before retrying.
2068           However, the pattern [\r\n]A does match that string,  because  it  con-
2069           tains an explicit CR or LF reference, and so advances only by one char-
2070           acter after the first failure.
2071    
2072           An explicit match for CR of LF is either a literal appearance of one of
2073           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2074           matches such as [^X] do not count, nor does \s (which includes  CR  and
2075           LF in the characters that it matches).
2076    
2077           Notwithstanding  the above, anomalous effects may still occur when CRLF
2078           is a valid newline sequence and explicit \r or \n escapes appear in the
2079           pattern.
2080    
2081           PCRE_NOTBOL           PCRE_NOTBOL
2082    
2083         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2084         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2085         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2086         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2087         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2088    
2089           PCRE_NOTEOL           PCRE_NOTEOL
2090    
2091         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2092         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2093         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2094         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2095         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2096         not affect \Z or \z.         not affect \Z or \z.
2097    
2098           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2099    
2100         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2101         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2102         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2103         example, if the pattern         example, if the pattern
2104    
2105           a?b?           a?b?
2106    
2107         is applied to a string not beginning with "a" or "b",  it  matches  the         is  applied  to  a  string not beginning with "a" or "b", it matches an
2108         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
2109         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2110         rences of "a" or "b".         rences of "a" or "b".
2111    
2112         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2113         cial case of a pattern match of the empty  string  within  its  split()  
2114         function,  and  when  using  the /g modifier. It is possible to emulate         This is like PCRE_NOTEMPTY, except that an empty string match  that  is
2115         Perl's behaviour after matching a null string by first trying the match         not  at  the  start  of  the  subject  is  permitted. If the pattern is
2116         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2117         if that fails by advancing the starting offset (see below)  and  trying  
2118         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2119         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2120           match of the empty string within its split() function, and  when  using
2121           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2122           matching a null string by first trying the match again at the same off-
2123           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2124           fails, by advancing the starting offset (see below) and trying an ordi-
2125           nary  match  again. There is some code that demonstrates how to do this
2126           in the pcredemo sample program.
2127    
2128             PCRE_NO_START_OPTIMIZE
2129    
2130           There are a number of optimizations that pcre_exec() uses at the  start
2131           of  a  match,  in  order to speed up the process. For example, if it is
2132           known that an unanchored match must start with a specific character, it
2133           searches  the  subject  for that character, and fails immediately if it
2134           cannot find it, without actually running the  main  matching  function.
2135           This means that a special item such as (*COMMIT) at the start of a pat-
2136           tern is not considered until after a suitable starting  point  for  the
2137           match  has been found. When callouts or (*MARK) items are in use, these
2138           "start-up" optimizations can cause them to be skipped if the pattern is
2139           never  actually  used.  The start-up optimizations are in effect a pre-
2140           scan of the subject that takes place before the pattern is run.
2141    
2142           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2143           possibly  causing  performance  to  suffer,  but ensuring that in cases
2144           where the result is "no match", the callouts do occur, and  that  items
2145           such as (*COMMIT) and (*MARK) are considered at every possible starting
2146           position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can
2147           change the outcome of a matching operation.  Consider the pattern
2148    
2149             (*COMMIT)ABC
2150    
2151           When  this  is  compiled, PCRE records the fact that a match must start
2152           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2153           start-up  optimization  scans along the subject, finds "A" and runs the
2154           first match attempt from there. The (*COMMIT) item means that the  pat-
2155           tern  must  match the current starting position, which in this case, it
2156           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2157           set,  the  initial  scan  along the subject string does not happen. The
2158           first match attempt is run starting  from  "D"  and  when  this  fails,
2159           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2160           result is "no match". If the pattern is studied,  more  start-up  opti-
2161           mizations  may  be  used. For example, a minimum length for the subject
2162           may be recorded. Consider the pattern
2163    
2164             (*MARK:A)(X|Y)
2165    
2166           The minimum length for a match is one  character.  If  the  subject  is
2167           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2168           finally an empty string.  If the pattern is studied, the final  attempt
2169           does  not take place, because PCRE knows that the subject is too short,
2170           and so the (*MARK) is never encountered.  In this  case,  studying  the
2171           pattern  does  not  affect the overall match result, which is still "no
2172           match", but it does affect the auxiliary information that is returned.
2173    
2174           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2175    
2176         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2177         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2178         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2179         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2180         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2181         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2182         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2183           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2184         If you already know that your subject is valid, and you  want  to  skip  
2185         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
2186         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
2187         do  this  for the second and subsequent calls to pcre_exec() if you are         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2188         making repeated calls to find all  the  matches  in  a  single  subject         do this for the second and subsequent calls to pcre_exec() if  you  are
2189         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
2190         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         string. However, you should be  sure  that  the  value  of  startoffset
2191         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
2192         value of startoffset that does not point to the start of a UTF-8  char-         set, the effect of passing an invalid UTF-8 string as a subject,  or  a
2193           value  of startoffset that does not point to the start of a UTF-8 char-
2194         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2195    
2196           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2197             PCRE_PARTIAL_SOFT
2198    
2199         This  option  turns  on  the  partial  matching feature. If the subject         These options turn on the partial matching feature. For backwards  com-
2200         string fails to match the pattern, but at some point during the  match-         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2201         ing  process  the  end of the subject was reached (that is, the subject         match occurs if the end of the subject string is reached  successfully,
2202         partially matches the pattern and the failure to  match  occurred  only         but  there  are not enough subject characters to complete the match. If
2203         because  there were not enough subject characters), pcre_exec() returns         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
2204         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
2205         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any other alternatives. Only if they  all
2206         are discussed in the pcrepartial documentation.         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
2207           The portion of the string that was inspected when the partial match was
2208           found  is  set  as  the first matching string. There is a more detailed
2209           discussion in the pcrepartial documentation.
2210    
2211     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2212    
2213         The subject string is passed to pcre_exec() as a pointer in subject,  a         The subject string is passed to pcre_exec() as a pointer in subject,  a
2214         length  in  length, and a starting byte offset in startoffset. In UTF-8         length (in bytes) in length, and a starting byte offset in startoffset.
2215         mode, the byte offset must point to the start  of  a  UTF-8  character.         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2216         Unlike  the  pattern string, the subject may contain binary zero bytes.         acter.  Unlike  the pattern string, the subject may contain binary zero
2217         When the starting offset is zero, the search for a match starts at  the         bytes. When the starting offset is zero, the search for a match  starts
2218         beginning of the subject, and this is by far the most common case.         at  the  beginning  of  the subject, and this is by far the most common
2219           case.
2220         A  non-zero  starting offset is useful when searching for another match  
2221         in the same subject by calling pcre_exec() again after a previous  suc-         A non-zero starting offset is useful when searching for  another  match
2222         cess.   Setting  startoffset differs from just passing over a shortened         in  the same subject by calling pcre_exec() again after a previous suc-
2223         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         cess.  Setting startoffset differs from just passing over  a  shortened
2224           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2225         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2226    
2227           \Biss\B           \Biss\B
2228    
2229         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2230         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
2231         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2232         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2233         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2234         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2235         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
2236         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2237         rence  of "iss" because it is able to look behind the starting point to         rence of "iss" because it is able to look behind the starting point  to
2238         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2239    
2240         If a non-zero starting offset is passed when the pattern  is  anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2241         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2242         if the pattern does not require the match to be at  the  start  of  the         if  the  pattern  does  not require the match to be at the start of the
2243         subject.         subject.
2244    
2245     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2246    
2247         In  general, a pattern matches a certain portion of the subject, and in         In general, a pattern matches a certain portion of the subject, and  in
2248         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2249         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2250         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2251         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2252         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2253         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2254    
2255         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2256         offsets whose address is passed in ovector. The number of  elements  in         whose  address is passed in ovector. The number of elements in the vec-
2257         the  vector is passed in ovecsize, which must be a non-negative number.         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2258         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2259    
2260         The first two-thirds of the vector is used to pass back  captured  sub-         The  first  two-thirds of the vector is used to pass back captured sub-
2261         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2262         of the vector is used as workspace by pcre_exec() while  matching  cap-         of  the  vector is used as workspace by pcre_exec() while matching cap-
2263         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2264         The length passed in ovecsize should always be a multiple of three.  If         The  number passed in ovecsize should always be a multiple of three. If
2265         it is not, it is rounded down.         it is not, it is rounded down.
2266    
2267         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2268         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2269         and  continuing  up  to two-thirds of its length at the most. The first         and continuing up to two-thirds of its length at the  most.  The  first
2270         element of a pair is set to the offset of the first character in a sub-         element  of  each pair is set to the byte offset of the first character
2271         string,  and  the  second  is  set to the offset of the first character         in a substring, and the second is set to the byte offset of  the  first
2272         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         character  after  the end of a substring. Note: these values are always
2273         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2274         entire pattern. The next pair is used for the first  capturing  subpat-  
2275         tern,  and  so  on.  The value returned by pcre_exec() is the number of         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2276         pairs that have been set. If there are no  capturing  subpatterns,  the         portion  of  the subject string matched by the entire pattern. The next
2277         return  value  from  a  successful match is 1, indicating that just the         pair is used for the first capturing subpattern, and so on.  The  value
2278         first pair of offsets has been set.         returned by pcre_exec() is one more than the highest numbered pair that
2279           has been set.  For example, if two substrings have been  captured,  the
2280         Some convenience functions are provided  for  extracting  the  captured         returned  value is 3. If there are no capturing subpatterns, the return
2281         substrings  as  separate  strings. These are described in the following         value from a successful match is 1, indicating that just the first pair
2282         section.         of offsets has been set.
   
        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.  
2283    
2284         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2285         of the string that it matched that is returned.         of the string that it matched that is returned.
2286    
2287         If  the vector is too small to hold all the captured substring offsets,         If the vector is too small to hold all the captured substring  offsets,
2288         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2289         function  returns a value of zero. In particular, if the substring off-         function returns a value of zero. If the substring offsets are  not  of
2290         sets are not of interest, pcre_exec() may be called with ovector passed         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2291         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         ovecsize as zero. However, if the pattern contains back references  and
2292         references and the ovector is not big enough to  remember  the  related         the  ovector is not big enough to remember the related substrings, PCRE
2293         substrings,  PCRE has to get additional memory for use during matching.         has to get additional memory for use during matching. Thus it  is  usu-
2294         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2295    
2296         Note that pcre_info() can be used to find out how many  capturing  sub-         The pcre_fullinfo() function can be used to find out how many capturing
2297         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2298         that will allow for n captured substrings, in addition to  the  offsets         ovector  that  will allow for n captured substrings, in addition to the
2299         of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2300    
2301           It is possible for capturing subpattern number n+1 to match  some  part
2302           of the subject when subpattern n has not been used at all. For example,
2303           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2304           return from the function is 4, and subpatterns 1 and 3 are matched, but
2305           2 is not. When this happens, both values in  the  offset  pairs  corre-
2306           sponding to unused subpatterns are set to -1.
2307    
2308           Offset  values  that correspond to unused subpatterns at the end of the
2309           expression are also set to -1. For example,  if  the  string  "abc"  is
2310           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2311           matched. The return from the function is 2, because  the  highest  used
2312           capturing subpattern number is 1. However, you can refer to the offsets
2313           for the second and third capturing subpatterns if  you  wish  (assuming
2314           the vector is large enough, of course).
2315    
2316     Return values from pcre_exec()         Some  convenience  functions  are  provided for extracting the captured
2317           substrings as separate strings. These are described below.
2318    
2319         If  pcre_exec()  fails, it returns a negative number. The following are     Error return values from pcre_exec()
2320    
2321           If pcre_exec() fails, it returns a negative number. The  following  are
2322         defined in the header file:         defined in the header file:
2323    
2324           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1663  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2327  MATCHING A PATTERN: THE TRADITIONAL FUNC
2327    
2328           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2329    
2330         Either code or subject was passed as NULL,  or  ovector  was  NULL  and         Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2331         ovecsize was not zero.         ovecsize was not zero.
2332    
2333           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1672  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2336  MATCHING A PATTERN: THE TRADITIONAL FUNC
2336    
2337           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2338    
2339         PCRE  stores a 4-byte "magic number" at the start of the compiled code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2340         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2341         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2342         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2343         gives when the magic number is not present.         gives when the magic number is not present.
2344    
2345           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2346    
2347         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2348         compiled pattern. This error could be caused by a bug  in  PCRE  or  by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2349         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2350    
2351           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2352    
2353         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2354         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2355         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
2356         purpose. If the call via pcre_malloc() fails, this error is given.  The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2357         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2358    
2359           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2360           This  can happen only when PCRE has been compiled with --disable-stack-
2361           for-recursion.
2362    
2363           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2364    
2365         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2366         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2367         returned by pcre_exec().         returned by pcre_exec().
2368    
2369           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2370    
2371         The  recursion  and backtracking limit, as specified by the match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2372         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra  structure  (or  defaulted) was reached. See the description
2373         description above.         above.
2374    
2375           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2376    
2377         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2378         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2379         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2380    
2381           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2382    
2383         A  string  that contains an invalid UTF-8 byte sequence was passed as a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2384         subject.         subject.
2385    
2386           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2387    
2388         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2389         value  of startoffset did not point to the beginning of a UTF-8 charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2390         ter.         ter.
2391    
2392           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2393    
2394         The subject string did not match, but it did match partially.  See  the         The  subject  string did not match, but it did match partially. See the
2395         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2396    
2397           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2398    
2399         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2400         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2401         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2402           onwards, there are no restrictions on partial matching.
2403    
2404           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2405    
# Line 1739  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2408  MATCHING A PATTERN: THE TRADITIONAL FUNC
2408    
2409           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2410    
2411         This error is given if the value of the ovecsize argument is  negative.         This error is given if the value of the ovecsize argument is negative.
2412    
2413             PCRE_ERROR_RECURSIONLIMIT (-21)
2414    
2415           The internal recursion limit, as specified by the match_limit_recursion
2416           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2417           description above.
2418    
2419             PCRE_ERROR_BADNEWLINE     (-23)
2420    
2421           An invalid combination of PCRE_NEWLINE_xxx options was given.
2422    
2423           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2424    
2425    
2426  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1755  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2436  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2436         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2437              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2438    
2439         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2440         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2441         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2442         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2443         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2444         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2445         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2446         extracted and has a further zero added on the end, but  the  result  is  
2447         not, of course, a C string.         A substring that contains a binary zero is correctly extracted and  has
2448           a  further zero added on the end, but the result is not, of course, a C
2449           string.  However, you can process such a string  by  referring  to  the
2450           length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2451           string().  Unfortunately, the interface to pcre_get_substring_list() is
2452           not  adequate for handling strings containing binary zeros, because the
2453           end of the final string is not independently indicated.
2454    
2455         The  first  three  arguments  are the same for all three of these func-         The first three arguments are the same for all  three  of  these  func-
2456         tions: subject is the subject string that has  just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2457         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2458         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2459         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2460         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2461         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2462         it ran out of space in ovector, the value passed as stringcount  should         it  ran out of space in ovector, the value passed as stringcount should
2463         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2464    
2465         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2466         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2467         zero  extracts  the  substring that matched the entire pattern, whereas         zero extracts the substring that matched the  entire  pattern,  whereas
2468         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2469         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2470         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2471         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2472         The yield of the function is the length of the  string,  not  including         The  yield  of  the function is the length of the string, not including
2473         the terminating zero, or one of         the terminating zero, or one of these error codes:
2474    
2475           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2476    
2477         The  buffer  was too small for pcre_copy_substring(), or the attempt to         The buffer was too small for pcre_copy_substring(), or the  attempt  to
2478         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2479    
2480           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2481    
2482         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2483    
2484         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2485         strings  and  builds  a list of pointers to them. All this is done in a         strings and builds a list of pointers to them. All this is  done  in  a
2486         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2487         the  memory  block  is returned via listptr, which is also the start of         the memory block is returned via listptr, which is also  the  start  of
2488         the list of string pointers. The end of the list is marked  by  a  NULL         the  list  of  string pointers. The end of the list is marked by a NULL
2489         pointer. The yield of the function is zero if all went well, or         pointer. The yield of the function is zero if all  went  well,  or  the
2490           error code
2491    
2492           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2493    
# Line 1818  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2506  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2506         tively.  They  do  nothing  more  than  call the function pointed to by         tively.  They  do  nothing  more  than  call the function pointed to by
2507         pcre_free, which of course could be called directly from a  C  program.         pcre_free, which of course could be called directly from a  C  program.
2508         However,  PCRE is used in some situations where it is linked via a spe-         However,  PCRE is used in some situations where it is linked via a spe-
2509         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  that  cannot   use
2510         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free  directly;  it is for these cases that the functions are pro-
2511         vided.         vided.
2512    
# Line 1841  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2529  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2529         To extract a substring by name, you first have to find associated  num-         To extract a substring by name, you first have to find associated  num-
2530         ber.  For example, for this pattern         ber.  For example, for this pattern
2531    
2532           (a+)b(?P<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2533    
2534         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. If the name is known to
2535         from the name by calling pcre_get_stringnumber(). The first argument is         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2536         the  compiled  pattern,  and  the  second is the name. The yield of the         name by calling pcre_get_stringnumber(). The first argument is the com-
2537         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if         piled pattern, and the second is the name. The yield of the function is
2538         there is no subpattern of that name.         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
2539           subpattern of that name.
2540    
2541         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2542         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2543         are also two functions that do the whole job.         are also two functions that do the whole job.
2544    
2545         Most    of    the    arguments   of   pcre_copy_named_substring()   and         Most   of   the   arguments    of    pcre_copy_named_substring()    and
2546         pcre_get_named_substring() are the same  as  those  for  the  similarly         pcre_get_named_substring()  are  the  same  as  those for the similarly
2547         named  functions  that extract by number. As these are described in the         named functions that extract by number. As these are described  in  the
2548         previous section, they are not re-described here. There  are  just  two         previous  section,  they  are not re-described here. There are just two
2549         differences:         differences:
2550    
2551         First,  instead  of a substring number, a substring name is given. Sec-         First, instead of a substring number, a substring name is  given.  Sec-
2552         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2553         to  the compiled pattern. This is needed in order to gain access to the         to the compiled pattern. This is needed in order to gain access to  the
2554         name-to-number translation table.         name-to-number translation table.
2555    
2556         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2557         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2558         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2559           behaviour may not be what you want (see the next section).
2560    
2561           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2562           terns  with  the  same number, as described in the section on duplicate
2563           subpattern numbers in the pcrepattern page, you  cannot  use  names  to
2564           distinguish  the  different subpatterns, because names are not included
2565           in the compiled code. The matching process uses only numbers. For  this
2566           reason,  the  use of different names for subpatterns of the same number
2567           causes an error at compile time.
2568    
2569    
2570    DUPLICATE SUBPATTERN NAMES
2571    
2572           int pcre_get_stringtable_entries(const pcre *code,
2573                const char *name, char **first, char **last);
2574    
2575           When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
2576           subpatterns  are not required to be unique. (Duplicate names are always
2577           allowed for subpatterns with the same number, created by using the  (?|
2578           feature.  Indeed,  if  such subpatterns are named, they are required to
2579           use the same names.)
2580    
2581           Normally, patterns with duplicate names are such that in any one match,
2582           only  one of the named subpatterns participates. An example is shown in
2583           the pcrepattern documentation.
2584    
2585           When   duplicates   are   present,   pcre_copy_named_substring()    and
2586           pcre_get_named_substring()  return the first substring corresponding to
2587           the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
2588           (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
2589           function returns one of the numbers that are associated with the  name,
2590           but it is not defined which it is.
2591    
2592           If  you want to get full details of all captured substrings for a given
2593           name, you must use  the  pcre_get_stringtable_entries()  function.  The
2594           first argument is the compiled pattern, and the second is the name. The
2595           third and fourth are pointers to variables which  are  updated  by  the
2596           function. After it has run, they point to the first and last entries in
2597           the name-to-number table  for  the  given  name.  The  function  itself
2598           returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
2599           there are none. The format of the table is described above in the  sec-
2600           tion  entitled  Information  about  a  pattern.  Given all the relevant
2601           entries for the name, you can extract each of their numbers, and  hence
2602           the captured data, if any.
2603    
2604    
2605  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2606    
2607         The traditional matching function uses a  similar  algorithm  to  Perl,         The  traditional  matching  function  uses a similar algorithm to Perl,
2608         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2609         the subject. If you want to find all possible matches, or  the  longest         the  subject.  If you want to find all possible matches, or the longest
2610         possible  match,  consider using the alternative matching function (see         possible match, consider using the alternative matching  function  (see
2611         below) instead. If you cannot use the alternative function,  but  still         below)  instead.  If you cannot use the alternative function, but still
2612         need  to  find all possible matches, you can kludge it up by making use         need to find all possible matches, you can kludge it up by  making  use
2613         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2614         tation.         tation.
2615    
2616         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2617         tern.  When your callout function is called, extract and save the  cur-         tern.   When your callout function is called, extract and save the cur-
2618         rent  matched  substring.  Then  return  1, which forces pcre_exec() to         rent matched substring. Then return  1,  which  forces  pcre_exec()  to
2619         backtrack and try other alternatives. Ultimately, when it runs  out  of         backtrack  and  try other alternatives. Ultimately, when it runs out of
2620         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2621    
2622    
# Line 1894  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2627  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2627              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2628              int *workspace, int wscount);              int *workspace, int wscount);
2629    
2630         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The function pcre_dfa_exec()  is  called  to  match  a  subject  string
2631         against a compiled pattern, using a "DFA" matching algorithm. This  has         against  a  compiled pattern, using a matching algorithm that scans the
2632         different  characteristics to the normal algorithm, and is not compati-         subject string just once, and does not backtrack.  This  has  different
2633         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics  to  the  normal  algorithm, and is not compatible with
2634         Nevertheless, there are times when this kind of matching can be useful.         Perl. Some of the features of PCRE patterns are not  supported.  Never-
2635         For a discussion of the two matching algorithms, see  the  pcrematching         theless,  there are times when this kind of matching can be useful. For
2636         documentation.         a discussion of the two matching algorithms, and  a  list  of  features
2637           that  pcre_dfa_exec() does not support, see the pcrematching documenta-
2638           tion.
2639    
2640         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The arguments for the pcre_dfa_exec() function  are  the  same  as  for
2641         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2642         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
2643         used in the same way as for pcre_exec(), so their  description  is  not         used  in  the  same way as for pcre_exec(), so their description is not
2644         repeated here.         repeated here.
2645    
2646         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
2647         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
2648         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2649         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
2650         lot of possible matches.         lot of potential matches.
2651    
2652         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_dfa_exec():
2653    
2654           int rc;           int rc;
2655           int ovector[10];           int ovector[10];
2656           int wspace[20];           int wspace[20];
2657           rc = pcre_exec(           rc = pcre_dfa_exec(
2658             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2659             NULL,           /* we didn't study the pattern */             NULL,           /* we didn't study the pattern */
2660             "some string",  /* the subject string */             "some string",  /* the subject string */
# Line 1933  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2668  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2668    
2669     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2670    
2671         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The unused bits of the options argument  for  pcre_dfa_exec()  must  be
2672         zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
2673         PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2674         PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,
2675         these  are  the  same  as  for pcre_exec(), so their description is not         PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD,  PCRE_PAR-
2676         repeated here.         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and PCRE_DFA_RESTART.  All but the last
2677           four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
2678           PCRE_PARTIAL         description is not repeated here.
2679    
2680         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2681         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2682         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2683         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These  have the same general effect as they do for pcre_exec(), but the
2684         been no complete matches, but there is still at least one matching pos-         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2685         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2686         set as the first matching string.         ject is reached and there is still at least  one  matching  possibility
2687           that requires additional characters. This happens even if some complete
2688           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2689           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2690           of the subject is reached, there have been  no  complete  matches,  but
2691           there  is  still  at least one matching possibility. The portion of the
2692           string that was inspected when the longest partial match was  found  is
2693           set as the first matching string in both cases.
2694    
2695           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2696    
2697         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2698         stop  as  soon  as  it  has found one match. Because of the way the DFA         stop as soon as it has found one match. Because of the way the alterna-
2699         algorithm works, this is necessarily the shortest possible match at the         tive  algorithm  works, this is necessarily the shortest possible match
2700         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2701    
2702           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2703    
2704         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2705         returns a partial match, it is possible to call it  again,  with  addi-         again,  with  additional  subject characters, and have it continue with
2706         tional  subject  characters,  and have it continue with the same match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
2707         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it  is  set,  the workspace and wscount options must reference the same
2708         workspace  and wscount options must reference the same vector as before         vector as before because data about the match so far is  left  in  them
2709         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
2710         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2711    
2712     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2713    
# Line 1991  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2732  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2732         On success, the yield of the function is a number  greater  than  zero,         On success, the yield of the function is a number  greater  than  zero,
2733         which  is  the  number of matched substrings. The substrings themselves         which  is  the  number of matched substrings. The substrings themselves
2734         are returned in ovector. Each string uses two elements;  the  first  is         are returned in ovector. Each string uses two elements;  the  first  is
2735         the  offset  to the start, and the second is the offset to the end. All         the  offset  to  the start, and the second is the offset to the end. In
2736         the strings have the same start offset. (Space could have been saved by         fact, all the strings have the same start  offset.  (Space  could  have
2737         giving  this only once, but it was decided to retain some compatibility         been  saved by giving this only once, but it was decided to retain some
2738         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility with the way pcre_exec() returns data,  even  though  the
2739         strings is different.)         meaning of the strings is different.)
2740    
2741         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2742         est matching string is given first. If there were too many  matches  to         est matching string is given first. If there were too many  matches  to
# Line 2017  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2758  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2758    
2759           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2760    
2761         This  return is given if pcre_dfa_exec() encounters a condition item in         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2762         a pattern that uses a back reference for the  condition.  This  is  not         that uses a back reference for the condition, or a test  for  recursion
2763         supported.         in a specific group. These are not supported.
2764    
2765           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2766    
# Line 2039  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2780  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2780         This error is given if the output vector  is  not  large  enough.  This         This error is given if the output vector  is  not  large  enough.  This
2781         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2782    
2783  Last updated: 16 May 2005  
2784  Copyright (c) 1997-2005 University of Cambridge.  SEE ALSO
2785    
2786           pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2787           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2788    
2789    
2790    AUTHOR
2791    
2792           Philip Hazel
2793           University Computing Service
2794           Cambridge CB2 3QH, England.
2795    
2796    
2797    REVISION
2798    
2799           Last updated: 21 June 2010
2800           Copyright (c) 1997-2010 University of Cambridge.
2801  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2802    
2803    
# Line 2067  PCRE CALLOUTS Line 2824  PCRE CALLOUTS
2824         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2825         points:         points:
2826    
2827           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2828    
2829         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
2830         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2831         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is         with  number  255,  before  each  item  in the pattern. For example, if
2832         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2833    
2834           A(\d{2}|--)           A(\d{2}|--)
2835    
# Line 2091  PCRE CALLOUTS Line 2848  PCRE CALLOUTS
2848  MISSING CALLOUTS  MISSING CALLOUTS
2849    
2850         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2851         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2852         pattern is         example, if the pattern is
2853    
2854           ab(?C4)cd           ab(?C4)cd
2855    
# Line 2101  MISSING CALLOUTS Line 2858  MISSING CALLOUTS
2858         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2859         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2860    
2861           If the pattern is studied, PCRE knows the minimum length of a  matching
2862           string,  and will immediately give a "no match" return without actually
2863           running a match if the subject is not long enough, or,  for  unanchored
2864           patterns, if it has been scanned far enough.
2865    
2866           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2867           MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
2868           matching  process,  but  does  ensure that callouts such as the example
2869           above are obeyed.
2870    
2871    
2872  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2873    
# Line 2128  THE CALLOUT INTERFACE Line 2895  THE CALLOUT INTERFACE
2895         version number will change again in future  if  additional  fields  are         version number will change again in future  if  additional  fields  are
2896         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2897    
2898         The callout_number field contains the number of the  callout,  as  com-         The  callout_number  field  contains the number of the callout, as com-
2899         piled  into  the pattern (that is, the number after ?C for manual call-         piled into the pattern (that is, the number after ?C for  manual  call-
2900         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2901    
2902         The offset_vector field is a pointer to the vector of offsets that  was         The  offset_vector field is a pointer to the vector of offsets that was
2903         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
2904         pcre_exec() is used, the contents can be inspected in order to  extract         pcre_exec()  is used, the contents can be inspected in order to extract
2905         substrings  that  have  been  matched  so  far,  in the same way as for         substrings that have been matched so  far,  in  the  same  way  as  for
2906         extracting substrings after a match has completed. For  pcre_dfa_exec()         extracting  substrings after a match has completed. For pcre_dfa_exec()
2907         this field is not useful.         this field is not useful.
2908    
2909         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2910         were passed to pcre_exec().         were passed to pcre_exec().
2911    
2912         The start_match field contains the offset within the subject  at  which         The  start_match  field normally contains the offset within the subject
2913         the  current match attempt started. If the pattern is not anchored, the         at which the current match attempt  started.  However,  if  the  escape
2914         callout function may be called several times from the same point in the         sequence  \K has been encountered, this value is changed to reflect the
2915         pattern for different starting points in the subject.         modified starting point. If the pattern is not  anchored,  the  callout
2916           function may be called several times from the same point in the pattern
2917           for different starting points in the subject.
2918    
2919         The  current_position  field  contains the offset within the subject of         The current_position field contains the offset within  the  subject  of
2920         the current match pointer.         the current match pointer.
2921    
2922         When the pcre_exec() function is used, the capture_top  field  contains         When  the  pcre_exec() function is used, the capture_top field contains
2923         one  more than the number of the highest numbered captured substring so         one more than the number of the highest numbered captured substring  so
2924         far. If no substrings have been captured, the value of  capture_top  is         far.  If  no substrings have been captured, the value of capture_top is
2925         one.  This  is always the case when pcre_dfa_exec() is used, because it         one. This is always the case when pcre_dfa_exec() is used,  because  it
2926         does not support captured substrings.         does not support captured substrings.
2927    
2928         The capture_last field contains the number of the  most  recently  cap-         The  capture_last  field  contains the number of the most recently cap-
2929         tured  substring. If no substrings have been captured, its value is -1.         tured substring. If no substrings have been captured, its value is  -1.
2930         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2931    
2932         The callout_data field contains a value that is passed  to  pcre_exec()         The  callout_data  field contains a value that is passed to pcre_exec()
2933         or  pcre_dfa_exec() specifically so that it can be passed back in call-         or pcre_dfa_exec() specifically so that it can be passed back in  call-
2934         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
2935         structure.  If  no such data was passed, the value of callout_data in a         structure. If no such data was passed, the value of callout_data  in  a
2936         pcre_callout block is NULL. There is a description  of  the  pcre_extra         pcre_callout  block  is  NULL. There is a description of the pcre_extra
2937         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2938    
2939         The  pattern_position field is present from version 1 of the pcre_call-         The pattern_position field is present from version 1 of the  pcre_call-
2940         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
2941         the pattern string.         the pattern string.
2942    
2943         The  next_item_length field is present from version 1 of the pcre_call-         The next_item_length field is present from version 1 of the  pcre_call-
2944         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
2945         the  pattern  string. When the callout immediately precedes an alterna-         the pattern string. When the callout immediately precedes  an  alterna-
2946         tion bar, a closing parenthesis, or the end of the pattern, the  length         tion  bar, a closing parenthesis, or the end of the pattern, the length
2947         is  zero.  When the callout precedes an opening parenthesis, the length         is zero. When the callout precedes an opening parenthesis,  the  length
2948         is that of the entire subpattern.         is that of the entire subpattern.
2949    
2950         The pattern_position and next_item_length fields are intended  to  help         The  pattern_position  and next_item_length fields are intended to help
2951         in  distinguishing between different automatic callouts, which all have         in distinguishing between different automatic callouts, which all  have
2952         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2953    
2954    
2955  RETURN VALUES  RETURN VALUES
2956    
2957         The external callout function returns an integer to PCRE. If the  value         The  external callout function returns an integer to PCRE. If the value
2958         is  zero,  matching  proceeds  as  normal. If the value is greater than         is zero, matching proceeds as normal. If  the  value  is  greater  than
2959         zero, matching fails at the current point, but  the  testing  of  other         zero,  matching  fails  at  the current point, but the testing of other
2960         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
2961         failed. If the value is less than zero, the  match  is  abandoned,  and         failed.  If  the  value  is less than zero, the match is abandoned, and
2962         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
2963    
2964         Negative   values   should   normally   be   chosen  from  the  set  of         Negative  values  should  normally  be   chosen   from   the   set   of
2965         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2966         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
2967         reserved for use by callout functions; it will never be  used  by  PCRE         reserved  for  use  by callout functions; it will never be used by PCRE
2968         itself.         itself.
2969    
2970  Last updated: 28 February 2005  
2971  Copyright (c) 1997-2005 University of Cambridge.  AUTHOR
2972    
2973           Philip Hazel
2974           University Computing Service
2975           Cambridge CB2 3QH, England.
2976    
2977    
2978    REVISION
2979    
2980           Last updated: 29 September 2009
2981           Copyright (c) 1997-2009 University of Cambridge.
2982  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2983    
2984    
# Line 2214  DIFFERENCES BETWEEN PCRE AND PERL Line 2993  DIFFERENCES BETWEEN PCRE AND PERL
2993    
2994         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2995         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
2996         respect to Perl 5.8.         respect to Perl 5.10/5.11.
2997    
2998         1.  PCRE does not have full UTF-8 support. Details of what it does have         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
2999         are given in the section on UTF-8 support in the main pcre page.         of what it does have are given in the section on UTF-8 support  in  the
3000           main pcre page.
3001    
3002         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3003         permits  them,  but they do not mean what you might think. For example,         permits them, but they do not mean what you might think.  For  example,
3004         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
3005         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3006    
3007         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3008         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3009         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3010         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3011         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3012         branch.         branch.
3013    
3014         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3015         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3016         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3017         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3018    
3019         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3020         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
3021         dling  and are not part of its pattern matching engine. If any of these         dling and are not part of its pattern matching engine. If any of  these
3022         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3023    
3024         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3025         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3026         can be tested with \p and \P are limited to the general category  prop-         can  be tested with \p and \P are limited to the general category prop-
3027         erties such as Lu and Nd.         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3028           derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3029           property, which Perl does not; the  Perl  documentation  says  "Because
3030           Perl hides the need for the user to understand the internal representa-
3031           tion of Unicode characters, there is no need to implement the  somewhat
3032           messy concept of surrogates."
3033    
3034         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3035         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
# Line 2262  DIFFERENCES BETWEEN PCRE AND PERL Line 3047  DIFFERENCES BETWEEN PCRE AND PERL
3047         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3048         classes.         classes.
3049    
3050         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3051         constructions.  However,  there is support for recursive patterns using         constructions.  However,  there is support for recursive patterns. This
3052         the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3053         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3054         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3055    
3056         9. There are some differences that are concerned with the  settings  of         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3057           always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3058           unlike Perl. There is a discussion of an example that explains this  in
3059           more  detail  in  the section on recursion differences from Perl in the
3060           pcrepattern page.
3061    
3062           10. There are some differences that are concerned with the settings  of
3063         captured  strings  when  part  of  a  pattern is repeated. For example,         captured  strings  when  part  of  a  pattern is repeated. For example,
3064         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3065         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3066    
3067         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3068         ities:         pattern names is not as general as Perl's. This is a consequence of the
3069           fact the PCRE works internally just with numbers, using an external ta-
3070         (a) Although lookbehind assertions must  match  fixed  length  strings,         ble to translate between numbers and names. In  particular,  a  pattern
3071         each alternative branch of a lookbehind assertion can match a different         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3072         length of string. Perl requires them all to have the same length.         the same number but different names, is not supported,  and  causes  an
3073           error  at compile time. If it were allowed, it would not be possible to
3074           distinguish which parentheses matched, because both names map  to  cap-
3075           turing subpattern number 1. To avoid this confusing situation, an error
3076           is given at compile time.
3077    
3078           12. PCRE provides some extensions to the Perl regular expression facil-
3079           ities.   Perl  5.10  includes new features that are not in earlier ver-
3080           sions of Perl, some of which (such as named parentheses) have  been  in
3081           PCRE for some time. This list is with respect to Perl 5.10:
3082    
3083           (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
3084           strings, each alternative branch of a lookbehind assertion can match  a
3085           different  length  of  string.  Perl requires them all to have the same
3086           length.
3087    
3088         (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $         (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $
3089         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3090    
3091         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
3092         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3093           ignored.  (Perl can be made to issue a warning.)
3094    
3095         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-
3096         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
3097         lowed by a question mark they are.         lowed by a question mark they are.
3098    
3099         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
3100         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3101    
3102         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3103         TURE options for pcre_exec() have no Perl equivalents.         and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-
3104           lents.
3105    
3106         (g) The (?R), (?number), and (?P>name) constructs allows for  recursive         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
3107         pattern  matching  (Perl  can  do  this using the (?p{code}) construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
3108    
3109         (h) PCRE supports named capturing substrings, using the Python  syntax.         (h) The callout facility is PCRE-specific.
3110    
3111         (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
3112    
3113         (j) The (R) condition, for testing recursion, is a PCRE extension.         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3114           even on different hosts that have the other endianness.
3115    
3116         (k) The callout facility is PCRE-specific.         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
3117           different way and is not Perl-compatible.
3118    
3119         (l) The partial matching facility is PCRE-specific.         (l)  PCRE  recognizes some special sequences such as (*CR) at the start
3120           of a pattern that set overall options that cannot be changed within the
3121           pattern.
3122    
        (m) Patterns compiled by PCRE can be saved and re-used at a later time,  
        even on different hosts that have the other endianness.  
3123    
3124         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a  AUTHOR
3125         different way and is not Perl-compatible.  
3126           Philip Hazel
3127           University Computing Service
3128           Cambridge CB2 3QH, England.
3129    
3130    
3131    REVISION
3132    
3133  Last updated: 28 February 2005         Last updated: 12 May 2010
3134  Copyright (c) 1997-2005 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3135  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3136    
3137    
# Line 2331  NAME Line 3144  NAME
3144    
3145  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3146    
3147         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3148         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3149         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3150         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3151         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3152         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3153           Python, .NET, and Oniguruma.
3154    
3155           Perl's  regular expressions are described in its own documentation, and
3156           regular expressions in general are covered in a number of  books,  some
3157           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3158           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3159           great  detail.  This  description  of  PCRE's  regular  expressions  is
3160           intended as reference material.
3161    
3162         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3163         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
3164         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, PCRE must be built to include UTF-8 support, and  you  must  call
3165         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3166         matching is mentioned in several places below. There is also a  summary         also a special sequence that can be given at the start of a pattern:
3167         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3168         page.           (*UTF8)
3169    
3170           Starting a pattern with this sequence  is  equivalent  to  setting  the
3171           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3172           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3173           below.  There  is  also  a  summary of UTF-8 features in the section on
3174           UTF-8 support in the main pcre page.
3175    
3176           Another special sequence that may appear at the start of a  pattern  or
3177           in combination with (*UTF8) is:
3178    
3179             (*UCP)
3180    
3181           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3182           sequences such as \d and \w to  use  Unicode  properties  to  determine
3183           character types, instead of recognizing only characters with codes less
3184           than 128 via a lookup table.
3185    
3186         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3187         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
3188         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
3189         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
3190         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
3191         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3192         the pcrematching page.         alternative function, and how it differs from the normal function,  are
3193           discussed in the pcrematching page.
3194         A regular expression is a pattern that is  matched  against  a  subject  
3195         string  from  left  to right. Most characters stand for themselves in a  
3196         pattern, and match the corresponding characters in the  subject.  As  a  NEWLINE CONVENTIONS
3197    
3198           PCRE  supports five different conventions for indicating line breaks in
3199           strings: a single CR (carriage return) character, a  single  LF  (line-
3200           feed) character, the two-character sequence CRLF, any of the three pre-
3201           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3202           discussion  about newlines, and shows how to set the newline convention
3203           in the options arguments for the compiling and matching functions.
3204    
3205           It is also possible to specify a newline convention by starting a  pat-
3206           tern string with one of the following five sequences:
3207    
3208             (*CR)        carriage return
3209             (*LF)        linefeed
3210             (*CRLF)      carriage return, followed by linefeed
3211             (*ANYCRLF)   any of the three above
3212             (*ANY)       all Unicode newline sequences
3213    
3214           These  override  the default and the options given to pcre_compile() or
3215           pcre_compile2(). For example, on a Unix system where LF is the  default
3216           newline sequence, the pattern
3217    
3218             (*CR)a.b
3219    
3220           changes the convention to CR. That pattern matches "a\nb" because LF is
3221           no longer a newline. Note that these special settings,  which  are  not
3222           Perl-compatible,  are  recognized  only at the very start of a pattern,
3223           and that they must be in upper case.  If  more  than  one  of  them  is
3224           present, the last one is used.
3225    
3226           The  newline convention affects the interpretation of the dot metachar-
3227           acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
3228           ever,  it  does  not  affect  what  the  \R escape sequence matches. By
3229           default, this is any Unicode newline sequence, for Perl  compatibility.
3230           However,  this can be changed; see the description of \R in the section
3231           entitled "Newline sequences" below. A change of \R setting can be  com-
3232           bined with a change of newline convention.
3233    
3234    
3235    CHARACTERS AND METACHARACTERS
3236    
3237           A  regular  expression  is  a pattern that is matched against a subject
3238           string from left to right. Most characters stand for  themselves  in  a
3239           pattern,  and  match  the corresponding characters in the subject. As a
3240         trivial example, the pattern         trivial example, the pattern
3241    
3242           The quick brown fox           The quick brown fox
3243    
3244         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3245         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3246         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3247         the concept of case for characters whose values are less than  128,  so         the  concept  of case for characters whose values are less than 128, so
3248         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3249         ues, the concept of case is supported if PCRE is compiled with  Unicode         ues,  the concept of case is supported if PCRE is compiled with Unicode
3250         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3251         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3252         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3253    
3254         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3255         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3256         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3257         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3258    
3259         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3260         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3261         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
3262         metacharacters are as follows:         the metacharacters are as follows:
3263    
3264           \      general escape character with several uses           \      general escape character with several uses
3265           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2397  PCRE REGULAR EXPRESSION DETAILS Line 3277  PCRE REGULAR EXPRESSION DETAILS
3277                  also "possessive quantifier"                  also "possessive quantifier"
3278           {      start min/max quantifier           {      start min/max quantifier
3279    
3280         Part  of  a  pattern  that is in square brackets is called a "character         Part of a pattern that is in square brackets  is  called  a  "character
3281         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3282    
3283           \      general escape character           \      general escape character
# Line 2407  PCRE REGULAR EXPRESSION DETAILS Line 3287  PCRE REGULAR EXPRESSION DETAILS
3287                    syntax)                    syntax)
3288           ]      terminates the character class           ]      terminates the character class
3289    
3290         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3291    
3292    
3293  BACKSLASH  BACKSLASH
# Line 2426  BACKSLASH Line 3306  BACKSLASH
3306    
3307         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3308         the pattern (other than in a character class) and characters between  a         the pattern (other than in a character class) and characters between  a
3309         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
3310         An escaping backslash can be used to include a whitespace or #  charac-         ing backslash can be used to include a whitespace  or  #  character  as
3311         ter as part of the pattern.         part of the pattern.
3312    
3313         If  you  want  to remove the special meaning from a sequence of charac-         If  you  want  to remove the special meaning from a sequence of charac-
3314         ters, you can do so by putting them between \Q and \E. This is  differ-         ters, you can do so by putting them between \Q and \E. This is  differ-
# Line 2452  BACKSLASH Line 3332  BACKSLASH
3332         acters  in patterns in a visible manner. There is no restriction on the         acters  in patterns in a visible manner. There is no restriction on the
3333         appearance of non-printing characters, apart from the binary zero  that         appearance of non-printing characters, apart from the binary zero  that
3334         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3335         editing, it is usually easier  to  use  one  of  the  following  escape         editing, it is  often  easier  to  use  one  of  the  following  escape
3336         sequences than the binary character it represents:         sequences than the binary character it represents:
3337    
3338           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3339           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3340           \e        escape (hex 1B)           \e        escape (hex 1B)
3341           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3342           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3343           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3344           \t        tab (hex 09)           \t        tab (hex 09)
3345           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3346           \xhh      character with hex code hh           \xhh      character with hex code hh
3347           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh..
3348    
3349         The  precise  effect of \cx is as follows: if x is a lower case letter,         The  precise  effect of \cx is as follows: if x is a lower case letter,
3350         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it is converted to upper case. Then bit 6 of the character (hex 40)  is
# Line 2472  BACKSLASH Line 3352  BACKSLASH
3352         becomes hex 7B.         becomes hex 7B.
3353    
3354         After \x, from zero to two hexadecimal digits are read (letters can  be         After \x, from zero to two hexadecimal digits are read (letters can  be
3355         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-         in  upper  or  lower case). Any number of hexadecimal digits may appear
3356         its may appear between \x{ and }, but the value of the  character  code         between \x{ and }, but the value of the character  code  must  be  less
3357         must  be  less  than  2**31  (that is, the maximum hexadecimal value is         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3358         7FFFFFFF). If characters other than hexadecimal digits  appear  between         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3359         \x{  and }, or if there is no terminating }, this form of escape is not         than the largest Unicode code point, which is 10FFFF.
3360         recognized. Instead, the initial \x will  be  interpreted  as  a  basic  
3361         hexadecimal  escape, with no following digits, giving a character whose         If  characters  other than hexadecimal digits appear between \x{ and },
3362         value is zero.         or if there is no terminating }, this form of escape is not recognized.
3363           Instead,  the  initial