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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
# Line 63  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 80  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 98  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 124  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 in particular
230         sense of, say, "digit", you must use Unicode  property  tests  such  as         that this applies to \b and \B, because they are defined in terms of \w
231         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233         8.  Similarly,  characters that match the POSIX named character classes         tively, if you set the PCRE_UCP option,  the  way  that  the  character
234         are all low-valued characters.         escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236           generic character types in the pcrepattern documentation.
237    
238           7.  Similarly,  characters that match the POSIX named character classes
239           are all low-valued characters, unless the PCRE_UCP option is set.
240    
241           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
242           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
243           acters, whether or not PCRE_UCP is set.
244    
245         9. Case-insensitive matching applies only to  characters  whose  values         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    
 Last updated: 07 March 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
267    
268    REVISION
269    
270           Last updated: 22 October 2010
271           Copyright (c) 1997-2010 University of Cambridge.
272    ------------------------------------------------------------------------------
273    
274    
275  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
276    
277    
# Line 220  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  C++ SUPPORT
# Line 249  C++ SUPPORT Line 321  C++ SUPPORT
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 272  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 306  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 319  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 335  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    
592    AUTHOR
593    
594           Philip Hazel
595           University Computing Service
596           Cambridge CB2 3QH, England.
597    
 Last updated: 15 August 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
598    
599    REVISION
600    
601           Last updated: 29 September 2009
602           Copyright (c) 1997-2009 University of Cambridge.
603    ------------------------------------------------------------------------------
604    
605    
606  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
607    
608    
# Line 431  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 440  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 472  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. It  is  possible  to  do  multi-segment
775         able.         matching using pcre_exec() (by retaining partially matched substrings),
776           but it is more complicated. The pcrepartial documentation gives details
777         3.  Because  the  DFA algorithm scans the subject string just once, and         of partial matching and discusses multi-segment matching.
        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.  
778    
779    
780  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
781    
782         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
783    
784         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
785         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
786         because it is less susceptible to optimization.         because it is less susceptible to optimization.
787    
788         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
789    
790         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
791         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
792         rithm.  
793    
794    AUTHOR
795    
796           Philip Hazel
797           University Computing Service
798           Cambridge CB2 3QH, England.
799    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
800    
801    REVISION
802    
803           Last updated: 22 October 2010
804           Copyright (c) 1997-2010 University of Cambridge.
805    ------------------------------------------------------------------------------
806    
807    
808  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
809    
810    
# Line 616  PCRE NATIVE API Line 854  PCRE NATIVE API
854         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
855              const char *name);              const char *name);
856    
857           int pcre_get_stringtable_entries(const pcre *code,
858                const char *name, char **first, char **last);
859    
860         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
861              int stringcount, int stringnumber,              int stringcount, int stringnumber,
862              const char **stringptr);              const char **stringptr);
# Line 654  PCRE NATIVE API Line 895  PCRE NATIVE API
895  PCRE API OVERVIEW  PCRE API OVERVIEW
896    
897         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
898         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
899         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
900         Both of these APIs define a set of C function calls. A C++  wrapper  is         Both of these APIs define a set of C function calls. A C++  wrapper  is
901         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 667  PCRE API OVERVIEW Line 908  PCRE API OVERVIEW
908         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
909         for different releases of PCRE.         for different releases of PCRE.
910    
911           In a Windows environment, if you want to statically link an application
912           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
913           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
914           loc()   and   pcre_free()   exported   functions   will   be   declared
915           __declspec(dllimport), with unwanted results.
916    
917         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
918         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
919         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
920         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
921         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
922         run it.         pcredemo documentation, and the pcresample documentation describes  how
923           to compile and run it.
924    
925         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
926         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
927         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
928         the  subject),  not  just  one. However, this algorithm does not return         point in the subject), and scans the subject just  once  (unless  there
929           are  lookbehind  assertions).  However,  this algorithm does not return
930         captured substrings. A description of the two matching  algorithms  and         captured substrings. A description of the two matching  algorithms  and
931         their  advantages  and disadvantages is given in the pcrematching docu-         their  advantages  and disadvantages is given in the pcrematching docu-
932         mentation.         mentation.
# Line 692  PCRE API OVERVIEW Line 941  PCRE API OVERVIEW
941           pcre_get_named_substring()           pcre_get_named_substring()
942           pcre_get_substring_list()           pcre_get_substring_list()
943           pcre_get_stringnumber()           pcre_get_stringnumber()
944             pcre_get_stringtable_entries()
945    
946         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
947         to free the memory used for extracted strings.         to free the memory used for extracted strings.
# Line 723  PCRE API OVERVIEW Line 973  PCRE API OVERVIEW
973         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
974         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
975         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
976         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
977         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-
978         management, it runs more slowly.  Separate functions  are  provided  so         ments that have limited stacks. Because of the greater  use  of  memory
979         that  special-purpose  external  code  can  be used for this case. When         management,  it  runs  more  slowly. Separate functions are provided so
980         used, these functions are always called in a  stack-like  manner  (last         that special-purpose external code can be  used  for  this  case.  When
981         obtained,  first freed), and always for memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
982           obtained, first freed), and always for memory blocks of the same  size.
983           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
984           mentation.
985    
986         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
987         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 736  PCRE API OVERVIEW Line 989  PCRE API OVERVIEW
989         pcrecallout documentation.         pcrecallout documentation.
990    
991    
992    NEWLINES
993    
994           PCRE  supports five different conventions for indicating line breaks in
995           strings: a single CR (carriage return) character, a  single  LF  (line-
996           feed) character, the two-character sequence CRLF, any of the three pre-
997           ceding, or any Unicode newline sequence. The Unicode newline  sequences
998           are  the  three just mentioned, plus the single characters VT (vertical
999           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
1000           separator, U+2028), and PS (paragraph separator, U+2029).
1001    
1002           Each  of  the first three conventions is used by at least one operating
1003           system as its standard newline sequence. When PCRE is built, a  default
1004           can  be  specified.  The default default is LF, which is the Unix stan-
1005           dard. When PCRE is run, the default can be overridden,  either  when  a
1006           pattern is compiled, or when it is matched.
1007    
1008           At compile time, the newline convention can be specified by the options
1009           argument of pcre_compile(), or it can be specified by special  text  at
1010           the start of the pattern itself; this overrides any other settings. See
1011           the pcrepattern page for details of the special character sequences.
1012    
1013           In the PCRE documentation the word "newline" is used to mean "the char-
1014           acter  or pair of characters that indicate a line break". The choice of
1015           newline convention affects the handling of  the  dot,  circumflex,  and
1016           dollar metacharacters, the handling of #-comments in /x mode, and, when
1017           CRLF is a recognized line ending sequence, the match position  advance-
1018           ment for a non-anchored pattern. There is more detail about this in the
1019           section on pcre_exec() options below.
1020    
1021           The choice of newline convention does not affect the interpretation  of
1022           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1023           which is controlled in a similar way, but by separate options.
1024    
1025    
1026  MULTITHREADING  MULTITHREADING
1027    
1028         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1029         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1030         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
1031         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 753  SAVING PRECOMPILED PATTERNS FOR LATER US Line 1040  SAVING PRECOMPILED PATTERNS FOR LATER US
1040         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
1041         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
1042         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
1043         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
1044           with  one version of PCRE for use with a different version is not guar-
1045           anteed to work and may cause crashes.
1046    
1047    
1048  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 782  CHECKING BUILD-TIME OPTIONS Line 1071  CHECKING BUILD-TIME OPTIONS
1071    
1072           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1073    
1074         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
1075         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
1076         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,
1077         operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1078           are returned in EBCDIC environments. The default should normally corre-
1079           spond to the standard sequence for your operating system.
1080    
1081             PCRE_CONFIG_BSR
1082    
1083           The output is an integer whose value indicates what character sequences
1084           the \R escape sequence matches by default. A value of 0 means  that  \R
1085           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1086           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1087           tern is compiled or matched.
1088    
1089           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1090    
# Line 804  CHECKING BUILD-TIME OPTIONS Line 1103  CHECKING BUILD-TIME OPTIONS
1103    
1104           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1105    
1106         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-
1107         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1108         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1109    
1110             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1111    
1112           The output is a long integer that gives the default limit for the depth
1113           of   recursion  when  calling  the  internal  matching  function  in  a
1114           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1115           below.
1116    
1117           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1118    
1119         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
1120         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1121         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1122         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1123         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1124         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1125         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1126    
1127    
# Line 832  COMPILING A PATTERN Line 1138  COMPILING A PATTERN
1138    
1139         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1140         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1141         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1142         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1143           avoid  too  much repetition, we refer just to pcre_compile() below, but
1144           the information applies equally to pcre_compile2().
1145    
1146         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
1147         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
1148         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1149         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
1150         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1151         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
1152         required.         longer required.
1153    
1154         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
1155         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
1156         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1157         ment, which is an address (see below).         ment, which is an address (see below).
1158    
1159         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1160         tion.  It  should  be  zero  if  no options are required. The available         pilation. It should be zero if no options are required.  The  available
1161         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them (in particular, those that
1162         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
1163         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset  from  within  the  pattern  (see the detailed description in the
1164         tion).  For  these options, the contents of the options argument speci-         pcrepattern documentation). For those options that can be different  in
1165         fies their initial settings at the start of compilation and  execution.         different  parts  of  the pattern, the contents of the options argument
1166         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
1167         at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1168           the time of matching as well as at compile time.
1169    
1170         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1171         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1172         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-
1173         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
1174         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
1175         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         character  that  was  being  processed when the error was discovered is
1176         given.         placed in the variable pointed to by erroffset, which must not be NULL.
1177           If  it  is,  an  immediate error is given. Some errors are not detected
1178         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         until checks are carried out when the whole pattern has  been  scanned;
1179         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.
1180         via this argument in the event of an error. This is in addition to  the  
1181           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1182           codeptr argument is not NULL, a non-zero error code number is  returned
1183           via  this argument in the event of an error. This is in addition to the
1184         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1185    
1186         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
1187         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1188         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1189         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1190         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1191         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1192         support below.         support below.
1193    
1194         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1195         pile():         pile():
1196    
1197           pcre *re;           pcre *re;
# Line 892  COMPILING A PATTERN Line 1204  COMPILING A PATTERN
1204             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1205             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1206    
1207         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
1208         file:         file:
1209    
1210           PCRE_ANCHORED           PCRE_ANCHORED
1211    
1212         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
1213         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
1214         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1215         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1216         only way to do it in Perl.         only way to do it in Perl.
1217    
1218           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1219    
1220         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1221         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1222         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1223    
1224             PCRE_BSR_ANYCRLF
1225             PCRE_BSR_UNICODE
1226    
1227           These options (which are mutually exclusive) control what the \R escape
1228           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1229           or to match any Unicode newline sequence. The default is specified when
1230           PCRE is built. It can be overridden from within the pattern, or by set-
1231           ting an option when a compiled pattern is matched.
1232    
1233           PCRE_CASELESS           PCRE_CASELESS
1234    
1235         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
1236         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
1237         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
1238         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1239         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1240         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-
1241         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1242         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1243         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1244         UTF-8 support.         UTF-8 support.
1245    
1246           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1247    
1248         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
1249         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
1250         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
1251         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1252         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
1253         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1254    
1255           PCRE_DOTALL           PCRE_DOTALL
1256    
1257         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-
1258         acters, including newlines. Without it,  newlines  are  excluded.  This         acters,  including  those that indicate newline. Without it, a dot does
1259         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
1260         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
1261         always  matches a newline character, independent of the setting of this         by a (?s) option setting. A negative class such as [^a] always  matches
1262         option.         newline characters, independent of the setting of this option.
1263    
1264             PCRE_DUPNAMES
1265    
1266           If  this  bit is set, names used to identify capturing subpatterns need
1267           not be unique. This can be helpful for certain types of pattern when it
1268           is  known  that  only  one instance of the named subpattern can ever be
1269           matched. There are more details of named subpatterns  below;  see  also
1270           the pcrepattern documentation.
1271    
1272           PCRE_EXTENDED           PCRE_EXTENDED
1273    
1274         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1275         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1276         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1277         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1278         line character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1279         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-
1280         option setting.         ting.
1281    
1282         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1283         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1284         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1285         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1286         introduces a conditional subpattern.         introduces a conditional subpattern.
1287    
1288           PCRE_EXTRA           PCRE_EXTRA
1289    
1290         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1291         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1292         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
1293         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1294         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1295         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
1296         literal. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give an error for this, by
1297         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
1298           controlled  by this option. It can also be set by a (?X) option setting
1299           within a pattern.
1300    
1301           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1302    
1303         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1304         before or at the first newline character in the subject string,  though         before  or  at  the  first  newline  in  the subject string, though the
1305         the matched text may continue over the newline.         matched text may continue over the newline.
1306    
1307             PCRE_JAVASCRIPT_COMPAT
1308    
1309           If this option is set, PCRE's behaviour is changed in some ways so that
1310           it  is  compatible with JavaScript rather than Perl. The changes are as
1311           follows:
1312    
1313           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1314           error,  because this is illegal in JavaScript (by default it is treated
1315           as a data character). Thus, the pattern AB]CD becomes illegal when this
1316           option is set.
1317    
1318           (2)  At run time, a back reference to an unset subpattern group matches
1319           an empty string (by default this causes the current  matching  alterna-
1320           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1321           set (assuming it can find an "a" in the subject), whereas it  fails  by
1322           default, for Perl compatibility.
1323    
1324           PCRE_MULTILINE           PCRE_MULTILINE
1325    
# Line 983  COMPILING A PATTERN Line 1331  COMPILING A PATTERN
1331         is set). This is the same as Perl.         is set). This is the same as Perl.
1332    
1333         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"
1334         constructs  match  immediately following or immediately before any new-         constructs  match  immediately following or immediately before internal
1335         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
1336         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
1337         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-
1338         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,
1339         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1340    
1341             PCRE_NEWLINE_CR
1342             PCRE_NEWLINE_LF
1343             PCRE_NEWLINE_CRLF
1344             PCRE_NEWLINE_ANYCRLF
1345             PCRE_NEWLINE_ANY
1346    
1347           These options override the default newline definition that  was  chosen
1348           when  PCRE  was built. Setting the first or the second specifies that a
1349           newline is indicated by a single character (CR  or  LF,  respectively).
1350           Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1351           two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1352           that any of the three preceding sequences should be recognized. Setting
1353           PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1354           recognized. The Unicode newline sequences are the three just mentioned,
1355           plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1356           U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1357           (paragraph separator, U+2029). The last  two  are  recognized  only  in
1358           UTF-8 mode.
1359    
1360           The  newline  setting  in  the  options  word  uses three bits that are
1361           treated as a number, giving eight possibilities. Currently only six are
1362           used  (default  plus the five values above). This means that if you set
1363           more than one newline option, the combination may or may not be  sensi-
1364           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1365           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1366           cause an error.
1367    
1368           The  only time that a line break is specially recognized when compiling
1369           a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1370           character  class  is  encountered.  This indicates a comment that lasts
1371           until after the next line break sequence. In other circumstances,  line
1372           break   sequences   are   treated  as  literal  data,  except  that  in
1373           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1374           and are therefore ignored.
1375    
1376           The newline option that is set at compile time becomes the default that
1377           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1378    
1379           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1380    
1381         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 998  COMPILING A PATTERN Line 1384  COMPILING A PATTERN
1384         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1385         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1386    
1387             PCRE_UCP
1388    
1389           This option changes the way PCRE processes \b, \d, \s, \w, and some  of
1390           the POSIX character classes. By default, only ASCII characters are rec-
1391           ognized, but if PCRE_UCP is set, Unicode properties are used instead to
1392           classify  characters.  More details are given in the section on generic
1393           character types in the pcrepattern page. If you set PCRE_UCP,  matching
1394           one  of the items it affects takes much longer. The option is available
1395           only if PCRE has been compiled with Unicode property support.
1396    
1397           PCRE_UNGREEDY           PCRE_UNGREEDY
1398    
1399         This option inverts the "greediness" of the quantifiers  so  that  they         This option inverts the "greediness" of the quantifiers  so  that  they
# Line 1017  COMPILING A PATTERN Line 1413  COMPILING A PATTERN
1413           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1414    
1415         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
1416         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1417         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
1418         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
1419         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-
1420         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
1421         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
1422         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
1423         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1424           UTF-8 validity checking of subject strings.
1425    
1426    
1427  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1428    
1429         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1430         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1431         both compiling functions.         both  compiling functions. As PCRE has developed, some error codes have
1432           fallen out of use. To avoid confusion, they have not been re-used.
1433    
1434            0  no error            0  no error
1435            1  \ at end of pattern            1  \ at end of pattern
# Line 1043  COMPILATION ERROR CODES Line 1441  COMPILATION ERROR CODES
1441            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1442            8  range out of order in character class            8  range out of order in character class
1443            9  nothing to repeat            9  nothing to repeat
1444           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1445           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1446           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1447           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1448           14  missing )           14  missing )
1449           15  reference to non-existent subpattern           15  reference to non-existent subpattern
1450           16  erroffset passed as NULL           16  erroffset passed as NULL
1451           17  unknown option bit(s) set           17  unknown option bit(s) set
1452           18  missing ) after comment           18  missing ) after comment
1453           19  parentheses nested too deeply           19  [this code is not in use]
1454           20  regular expression too large           20  regular expression is too large
1455           21  failed to get memory           21  failed to get memory
1456           22  unmatched parentheses           22  unmatched parentheses
1457           23  internal error: code overflow           23  internal error: code overflow
1458           24  unrecognized character after (?<           24  unrecognized character after (?<
1459           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1460           26  malformed number after (?(           26  malformed number or name after (?(
1461           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1462           28  assertion expected after (?(           28  assertion expected after (?(
1463           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1464           30  unknown POSIX class name           30  unknown POSIX class name
1465           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1466           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1467           33  spare error           33  [this code is not in use]
1468           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1469           35  invalid condition (?(0)           35  invalid condition (?(0)
1470           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1075  COMPILATION ERROR CODES Line 1473  COMPILATION ERROR CODES
1473           39  closing ) for (?C expected           39  closing ) for (?C expected
1474           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1475           41  unrecognized character after (?P           41  unrecognized character after (?P
1476           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1477           43  two named groups have the same name           43  two named subpatterns have the same name
1478           44  invalid UTF-8 string           44  invalid UTF-8 string
1479           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1480           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1481           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1482             48  subpattern name is too long (maximum 32 characters)
1483             49  too many named subpatterns (maximum 10000)
1484             50  [this code is not in use]
1485             51  octal value is greater than \377 (not in UTF-8 mode)
1486             52  internal error: overran compiling workspace
1487             53  internal error: previously-checked referenced subpattern
1488                   not found
1489             54  DEFINE group contains more than one branch
1490             55  repeating a DEFINE group is not allowed
1491             56  inconsistent NEWLINE options
1492             57  \g is not followed by a braced, angle-bracketed, or quoted
1493                   name/number or by a plain number
1494             58  a numbered reference must not be zero
1495             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1496             60  (*VERB) not recognized
1497             61  number is too big
1498             62  subpattern name expected
1499             63  digit expected after (?+
1500             64  ] is an invalid data character in JavaScript compatibility mode
1501             65  different names for subpatterns of the same number are
1502                   not allowed
1503             66  (*MARK) must have an argument
1504             67  this version of PCRE is not compiled with PCRE_UCP support
1505    
1506           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1507           values may be used if the limits were changed when PCRE was built.
1508    
1509    
1510  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1088  STUDYING A PATTERN Line 1512  STUDYING A PATTERN
1512         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1513              const char **errptr);              const char **errptr);
1514    
1515         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
1516         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
1517         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1518         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1519         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1520         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
1521         the results of the study.         the results of the study.
1522    
1523         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1524         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1525         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
1526         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1527    
1528         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1529         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1530         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
1531         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1532    
1533         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1534         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1535    
1536         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.
1537         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1538         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
1539         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
1540         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
1541           after calling pcre_study(), to be sure that it has run successfully.
1542    
1543         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1544    
# Line 1123  STUDYING A PATTERN Line 1548  STUDYING A PATTERN
1548             0,              /* no options exist */             0,              /* no options exist */
1549             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1550    
1551         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
1552         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
1553         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1554           it does guarantee that no shorter strings match. The value is  used  by
1555           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1556           match strings that are shorter than the lower bound. You can  find  out
1557           the value in a calling program via the pcre_fullinfo() function.
1558    
1559           Studying a pattern is also useful for non-anchored patterns that do not
1560           have a single fixed starting character. A bitmap of  possible  starting
1561           bytes  is  created. This speeds up finding a position in the subject at
1562           which to start matching.
1563    
1564           The two optimizations just described can be  disabled  by  setting  the
1565           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1566           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1567           callouts,  or  make  use of (*MARK), and you make use of these in cases
1568           where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE
1569           below.
1570    
1571    
1572  LOCALE SUPPORT  LOCALE SUPPORT
1573    
1574         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1575         letters digits, or whatever, by reference to a set of  tables,  indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1576         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
1577         characters with codes less than 128. Higher-valued  codes  never  match         characters with codes less than 128. By  default,  higher-valued  codes
1578         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
1579         with Unicode character property support.         PCRE is built with Unicode character property  support.  Alternatively,
1580           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1581         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
1582         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-
1583         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-
1584         tables  can,  however, be supplied. These may be created in a different         code, or use locales, but not try to mix the two.
1585         locale from the default. As more and more applications change to  using  
1586         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
1587           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1588           applications.  Normally, the internal tables recognize only ASCII char-
1589           acters. However, when PCRE is built, it is possible to cause the inter-
1590           nal tables to be rebuilt in the default "C" locale of the local system,
1591           which may cause them to be different.
1592    
1593           The internal tables can always be overridden by tables supplied by  the
1594           application that calls PCRE. These may be created in a different locale
1595           from the default. As more and more applications change  to  using  Uni-
1596           code, the need for this locale support is expected to die away.
1597    
1598         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
1599         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 1155  LOCALE SUPPORT Line 1606  LOCALE SUPPORT
1606           tables = pcre_maketables();           tables = pcre_maketables();
1607           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1608    
1609         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;
1610         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".
1611         that the memory containing the tables remains available for as long  as  
1612           When  pcre_maketables()  runs,  the  tables are built in memory that is
1613           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1614           that  the memory containing the tables remains available for as long as
1615         it is needed.         it is needed.
1616    
1617         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
1618         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()
1619         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-
1620         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1621         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1622    
1623         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1624         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1625         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1626         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1627         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1628    
# Line 1178  INFORMATION ABOUT A PATTERN Line 1632  INFORMATION ABOUT A PATTERN
1632         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1633              int what, void *where);              int what, void *where);
1634    
1635         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1636         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1637         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1638    
1639         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1640         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
1641         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1642         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
1643         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
1644         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1645    
1646           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1194  INFORMATION ABOUT A PATTERN Line 1648  INFORMATION ABOUT A PATTERN
1648           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1649           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1650    
1651         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
1652         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1653         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1654         pattern:         pattern:
1655    
1656           int rc;           int rc;
1657           unsigned long int length;           size_t length;
1658           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1659             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1660             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
1661             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1662             &length);         /* where to put the data */             &length);         /* where to put the data */
1663    
1664         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1665         are as follows:         are as follows:
1666    
1667           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1668    
1669         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1670         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1671         there are no back references.         there are no back references.
1672    
1673           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1674    
1675         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1676         argument should point to an int variable.         argument should point to an int variable.
1677    
1678           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1679    
1680         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1681         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1682         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1683         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1684         passing a NULL table pointer.         passing a NULL table pointer.
1685    
1686           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1687    
1688         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1689         non-anchored   pattern.   (This    option    used    to    be    called         non-anchored  pattern. The fourth argument should point to an int vari-
1690         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1691         compatibility.)         is still recognized for backwards compatibility.)
1692    
1693         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
1694         (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  
1695    
1696         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1697         branch starts with "^", or         branch starts with "^", or
# Line 1258  INFORMATION ABOUT A PATTERN Line 1711  INFORMATION ABOUT A PATTERN
1711         returned.  The fourth argument should point to an unsigned char * vari-         returned.  The fourth argument should point to an unsigned char * vari-
1712         able.         able.
1713    
1714             PCRE_INFO_HASCRORLF
1715    
1716           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1717           characters,  otherwise  0.  The  fourth argument should point to an int
1718           variable. An explicit match is either a literal CR or LF character,  or
1719           \r or \n.
1720    
1721             PCRE_INFO_JCHANGED
1722    
1723           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1724           otherwise 0. The fourth argument should point to an int variable.  (?J)
1725           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1726    
1727           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1728    
1729         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
1730         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
1731         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1732         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
1733         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1734         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
1735         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1736    
1737             PCRE_INFO_MINLENGTH
1738    
1739           If  the  pattern  was studied and a minimum length for matching subject
1740           strings was computed, its value is  returned.  Otherwise  the  returned
1741           value  is  -1. The value is a number of characters, not bytes (this may
1742           be relevant in UTF-8 mode). The fourth argument should point to an  int
1743           variable.  A  non-negative  value is a lower bound to the length of any
1744           matching string. There may not be any strings of that  length  that  do
1745           actually match, but every string that does match is at least that long.
1746    
1747           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1748           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1749           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1750    
1751         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1752         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1753         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
1754         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring() are provided for  extracting  captured  sub-
1755         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
1756         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
1757         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
1758         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
1759         which is described by these three values.         described by these three values.
1760    
1761         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
1762         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1763         of each entry; both of these  return  an  int  value.  The  entry  size         of  each  entry;  both  of  these  return  an int value. The entry size
1764         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1765         a pointer to the first entry of the table  (a  pointer  to  char).  The         a  pointer  to  the  first  entry of the table (a pointer to char). The
1766         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-
1767         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-
1768         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1769         For example, consider the following pattern  (assume  PCRE_EXTENDED  is  
1770         set, so white space - including newlines - is ignored):         The names are in alphabetical order. Duplicate names may appear if  (?|
1771           is used to create multiple groups with the same number, as described in
1772           the section on duplicate subpattern numbers in  the  pcrepattern  page.
1773           Duplicate  names  for  subpatterns with different numbers are permitted
1774           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1775           appear  in  the table in the order in which they were found in the pat-
1776           tern. In the absence of (?| this is the  order  of  increasing  number;
1777           when (?| is used this is not necessarily the case because later subpat-
1778           terns may have lower numbers.
1779    
1780           As a simple example of the name/number table,  consider  the  following
1781           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1782           lines - is ignored):
1783    
1784           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1785           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1786    
1787         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1788         each entry in the table is eight bytes long. The table is  as  follows,         each  entry  in the table is eight bytes long. The table is as follows,
1789         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1790         as ??:         as ??:
1791    
# Line 1306  INFORMATION ABOUT A PATTERN Line 1794  INFORMATION ABOUT A PATTERN
1794           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1795           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1796    
1797         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1798         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
1799         be different for each compiled pattern.         to be different for each compiled pattern.
1800    
1801             PCRE_INFO_OKPARTIAL
1802    
1803           Return  1  if  the  pattern  can  be  used  for  partial  matching with
1804           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1805           variable.  From  release  8.00,  this  always  returns  1,  because the
1806           restrictions that previously applied  to  partial  matching  have  been
1807           lifted.  The  pcrepartial documentation gives details of partial match-
1808           ing.
1809    
1810           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1811    
1812         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
1813         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
1814         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1815         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1816           other words, they are the options that will be in force  when  matching
1817           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1818           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1819           and PCRE_EXTENDED.
1820    
1821         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1822         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1341  INFORMATION ABOUT A PATTERN Line 1842  INFORMATION ABOUT A PATTERN
1842         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
1843         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
1844         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
1845         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
1846           data, zero is returned. The fourth argument should point  to  a  size_t
1847         variable.         variable.
1848    
1849    
# Line 1349  OBSOLETE INFO FUNCTION Line 1851  OBSOLETE INFO FUNCTION
1851    
1852         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1853    
1854         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1855         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1856         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1857         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-
1858         lowing negative numbers:         lowing negative numbers:
1859    
1860           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1861           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1862    
1863         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
1864         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
1865         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1866    
1867         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1868         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
1869         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1870    
1871    
# Line 1371  REFERENCE COUNTS Line 1873  REFERENCE COUNTS
1873    
1874         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1875    
1876         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1877         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1878         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1879         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1880         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1881    
1882         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1883         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1884         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1885         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1886         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1887         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1888    
1889         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1890         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1891         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1892    
1893    
# Line 1397  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1899  MATCHING A PATTERN: THE TRADITIONAL FUNC
1899    
1900         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
1901         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
1902         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
1903         argument.  This  function is the main matching facility of the library,         argument.  This  function is the main matching facility of the library,
1904         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1905         an  alternative matching function, which is described below in the sec-         an  alternative matching function, which is described below in the sec-
# Line 1428  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1930  MATCHING A PATTERN: THE TRADITIONAL FUNC
1930         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
1931         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
1932         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-
1933         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
1934         lows:         fields (not necessarily in this order):
1935    
1936           unsigned long int flags;           unsigned long int flags;
1937           void *study_data;           void *study_data;
1938           unsigned long int match_limit;           unsigned long int match_limit;
1939             unsigned long int match_limit_recursion;
1940           void *callout_data;           void *callout_data;
1941           const unsigned char *tables;           const unsigned char *tables;
1942             unsigned char **mark;
1943    
1944         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
1945         are set. The flag bits are:         are set. The flag bits are:
1946    
1947           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1948           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1949             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1950           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1951           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1952             PCRE_EXTRA_MARK
1953    
1954         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
1955         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 1454  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1960  MATCHING A PATTERN: THE TRADITIONAL FUNC
1960         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
1961         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
1962         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
1963         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1964         repeats.         ited repeats.
1965    
1966         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1967         edly (sometimes recursively). The limit is imposed  on  the  number  of         edly (sometimes recursively). The limit set by match_limit  is  imposed
1968         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
1969         limiting the amount of recursion and backtracking that can take  place.         has the effect of limiting the amount of  backtracking  that  can  take
1970         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
1971         position in the subject string.         for each position in the subject string.
1972    
1973         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
1974         default  default  is 10 million, which handles all but the most extreme         default  default  is 10 million, which handles all but the most extreme
1975         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1976         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra     block    in    which    match_limit    is    set,    and
1977         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
1978         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1979    
1980         The  pcre_callout  field is used in conjunction with the "callout" fea-         The  match_limit_recursion field is similar to match_limit, but instead
1981         ture, which is described in the pcrecallout documentation.         of limiting the total number of times that match() is called, it limits
1982           the  depth  of  recursion. The recursion depth is a smaller number than
1983         The tables field  is  used  to  pass  a  character  tables  pointer  to         the total number of calls, because not all calls to match() are  recur-
1984         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.
1985         pattern. A non-NULL value is stored with the compiled pattern  only  if  
1986         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         Limiting  the  recursion  depth  limits the amount of stack that can be
1987           used, or, when PCRE has been compiled to use memory on the heap instead
1988           of the stack, the amount of heap memory that can be used.
1989    
1990           The  default  value  for  match_limit_recursion can be set when PCRE is
1991           built; the default default  is  the  same  value  as  the  default  for
1992           match_limit.  You can override the default by suppling pcre_exec() with
1993           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1994           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1995           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1996    
1997           The callout_data field is used in conjunction with the  "callout"  fea-
1998           ture, and is described in the pcrecallout documentation.
1999    
2000           The  tables  field  is  used  to  pass  a  character  tables pointer to
2001           pcre_exec(); this overrides the value that is stored with the  compiled
2002           pattern.  A  non-NULL value is stored with the compiled pattern only if
2003           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2004         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2005         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
2006         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2007         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2008         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2009         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2010    
2011           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2012           set  to  point  to a char * variable. If the pattern contains any back-
2013           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2014           with  a  name  to  pass back, a pointer to the name string (zero termi-
2015           nated) is placed in the variable pointed to  by  the  mark  field.  The
2016           names  are  within  the  compiled pattern; if you wish to retain such a
2017           name you must copy it before freeing the memory of a compiled  pattern.
2018           If  there  is no name to pass back, the variable pointed to by the mark
2019           field set to NULL. For details of the backtracking control  verbs,  see
2020           the section entitled "Backtracking control" in the pcrepattern documen-
2021           tation.
2022    
2023     Option bits for pcre_exec()     Option bits for pcre_exec()
2024    
2025         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.
2026         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,
2027         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2028           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2029           PCRE_PARTIAL_HARD.
2030    
2031           PCRE_ANCHORED           PCRE_ANCHORED
2032    
2033         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2034         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2035         turned  out to be anchored by virtue of its contents, it cannot be made         turned out to be anchored by virtue of its contents, it cannot be  made
2036         unachored at matching time.         unachored at matching time.
2037    
2038             PCRE_BSR_ANYCRLF
2039             PCRE_BSR_UNICODE
2040    
2041           These options (which are mutually exclusive) control what the \R escape
2042           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2043           or  to  match  any Unicode newline sequence. These options override the
2044           choice that was made or defaulted when the pattern was compiled.
2045    
2046             PCRE_NEWLINE_CR
2047             PCRE_NEWLINE_LF
2048             PCRE_NEWLINE_CRLF
2049             PCRE_NEWLINE_ANYCRLF
2050             PCRE_NEWLINE_ANY
2051    
2052           These options override  the  newline  definition  that  was  chosen  or
2053           defaulted  when the pattern was compiled. For details, see the descrip-
2054           tion of pcre_compile()  above.  During  matching,  the  newline  choice
2055           affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2056           ters. It may also alter the way the match position is advanced after  a
2057           match failure for an unanchored pattern.
2058    
2059           When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2060           set, and a match attempt for an unanchored pattern fails when the  cur-
2061           rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2062           explicit matches for  CR  or  LF  characters,  the  match  position  is
2063           advanced by two characters instead of one, in other words, to after the
2064           CRLF.
2065    
2066           The above rule is a compromise that makes the most common cases work as
2067           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2068           option is not set), it does not match the string "\r\nA" because, after
2069           failing  at the start, it skips both the CR and the LF before retrying.
2070           However, the pattern [\r\n]A does match that string,  because  it  con-
2071           tains an explicit CR or LF reference, and so advances only by one char-
2072           acter after the first failure.
2073    
2074           An explicit match for CR of LF is either a literal appearance of one of
2075           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2076           matches such as [^X] do not count, nor does \s (which includes  CR  and
2077           LF in the characters that it matches).
2078    
2079           Notwithstanding  the above, anomalous effects may still occur when CRLF
2080           is a valid newline sequence and explicit \r or \n escapes appear in the
2081           pattern.
2082    
2083           PCRE_NOTBOL           PCRE_NOTBOL
2084    
2085         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2086         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2087         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2088         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2089         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2090    
2091           PCRE_NOTEOL           PCRE_NOTEOL
2092    
2093         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
2094         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
2095         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2096         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2097         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2098         not affect \Z or \z.         not affect \Z or \z.
2099    
2100           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2101    
2102         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
2103         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
2104         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2105         example, if the pattern         example, if the pattern
2106    
2107           a?b?           a?b?
2108    
2109         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
2110         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
2111         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-
2112         rences of "a" or "b".         rences of "a" or "b".
2113    
2114         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2115         cial case of a pattern match of the empty  string  within  its  split()  
2116         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
2117         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
2118         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.
2119         if that fails by advancing the starting offset (see below)  and  trying  
2120         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2121         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2122           match of the empty string within its split() function, and  when  using
2123           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2124           matching a null string by first trying the match again at the same off-
2125           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2126           fails, by advancing the starting offset (see below) and trying an ordi-
2127           nary  match  again. There is some code that demonstrates how to do this
2128           in the pcredemo sample program. In the most general case, you  have  to
2129           check  to  see  if the newline convention recognizes CRLF as a newline,
2130           and if so, and the current character is CR followed by LF, advance  the
2131           starting offset by two characters instead of one.
2132    
2133             PCRE_NO_START_OPTIMIZE
2134    
2135           There  are a number of optimizations that pcre_exec() uses at the start
2136           of a match, in order to speed up the process. For  example,  if  it  is
2137           known that an unanchored match must start with a specific character, it
2138           searches the subject for that character, and fails  immediately  if  it
2139           cannot  find  it,  without actually running the main matching function.
2140           This means that a special item such as (*COMMIT) at the start of a pat-
2141           tern  is  not  considered until after a suitable starting point for the
2142           match has been found. When callouts or (*MARK) items are in use,  these
2143           "start-up" optimizations can cause them to be skipped if the pattern is
2144           never actually used. The start-up optimizations are in  effect  a  pre-
2145           scan of the subject that takes place before the pattern is run.
2146    
2147           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2148           possibly causing performance to suffer,  but  ensuring  that  in  cases
2149           where  the  result is "no match", the callouts do occur, and that items
2150           such as (*COMMIT) and (*MARK) are considered at every possible starting
2151           position  in  the  subject  string.  Setting PCRE_NO_START_OPTIMIZE can
2152           change the outcome of a matching operation.  Consider the pattern
2153    
2154             (*COMMIT)ABC
2155    
2156           When this is compiled, PCRE records the fact that a  match  must  start
2157           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2158           start-up optimization scans along the subject, finds "A" and  runs  the
2159           first  match attempt from there. The (*COMMIT) item means that the pat-
2160           tern must match the current starting position, which in this  case,  it
2161           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2162           set, the initial scan along the subject string  does  not  happen.  The
2163           first  match  attempt  is  run  starting  from "D" and when this fails,
2164           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2165           result  is  "no  match". If the pattern is studied, more start-up opti-
2166           mizations may be used. For example, a minimum length  for  the  subject
2167           may be recorded. Consider the pattern
2168    
2169             (*MARK:A)(X|Y)
2170    
2171           The  minimum  length  for  a  match is one character. If the subject is
2172           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2173           finally  an empty string.  If the pattern is studied, the final attempt
2174           does not take place, because PCRE knows that the subject is too  short,
2175           and  so  the  (*MARK) is never encountered.  In this case, studying the
2176           pattern does not affect the overall match result, which  is  still  "no
2177           match", but it does affect the auxiliary information that is returned.
2178    
2179           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2180    
2181         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
2182         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2183         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2184         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
2185         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
2186         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2187         returned.         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2188           tains a value that does not point to the start of a UTF-8 character (or
2189         If you already know that your subject is valid, and you  want  to  skip         to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2190         these    checks    for   performance   reasons,   you   can   set   the  
2191         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         If  you  already  know that your subject is valid, and you want to skip
2192         do  this  for the second and subsequent calls to pcre_exec() if you are         these   checks   for   performance   reasons,   you   can    set    the
2193         making repeated calls to find all  the  matches  in  a  single  subject         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2194         string.  However,  you  should  be  sure  that the value of startoffset         do this for the second and subsequent calls to pcre_exec() if  you  are
2195         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         making  repeated  calls  to  find  all  the matches in a single subject
2196         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         string. However, you should be  sure  that  the  value  of  startoffset
2197         value of startoffset that does not point to the start of a UTF-8  char-         points  to  the start of a UTF-8 character (or the end of the subject).
2198         acter, is undefined. Your program may crash.         When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid  UTF-8
2199           string  as  a  subject or an invalid value of startoffset is undefined.
2200           PCRE_PARTIAL         Your program may crash.
2201    
2202         This  option  turns  on  the  partial  matching feature. If the subject           PCRE_PARTIAL_HARD
2203         string fails to match the pattern, but at some point during the  match-           PCRE_PARTIAL_SOFT
2204         ing  process  the  end of the subject was reached (that is, the subject  
2205         partially matches the pattern and the failure to  match  occurred  only         These options turn on the partial matching feature. For backwards  com-
2206         because  there were not enough subject characters), pcre_exec() returns         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2207         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         match occurs if the end of the subject string is reached  successfully,
2208         used,  there  are restrictions on what may appear in the pattern. These         but  there  are not enough subject characters to complete the match. If
2209         are discussed in the pcrepartial documentation.         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2210           matching  continues  by  testing any remaining alternatives. Only if no
2211           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2212           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2213           caller is prepared to handle a partial match, but only if  no  complete
2214           match can be found.
2215    
2216           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2217           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2218           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2219           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2220           ered to be more important that an alternative complete match.
2221    
2222           In  both  cases,  the portion of the string that was inspected when the
2223           partial match was found is set as the first matching string. There is a
2224           more  detailed  discussion  of partial and multi-segment matching, with
2225           examples, in the pcrepartial documentation.
2226    
2227     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2228    
2229         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
2230         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.
2231         mode, the byte offset must point to the start  of  a  UTF-8  character.         If this is  negative  or  greater  than  the  length  of  the  subject,
2232         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET.
2233         When the starting offset is zero, the search for a match starts at  the  
2234         beginning of the subject, and this is by far the most common case.         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2235           acter (or the end of the subject). Unlike the pattern string, the  sub-
2236           ject  may  contain binary zero bytes. When the starting offset is zero,
2237           the search for a match starts at the beginning of the subject, and this
2238           is by far the most common case.
2239    
2240         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2241         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1598  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2256  MATCHING A PATTERN: THE TRADITIONAL FUNC
2256         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
2257         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2258    
2259         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2260           match an empty string. It is possible to emulate Perl's /g behaviour by
2261           first  trying  the  match  again  at  the   same   offset,   with   the
2262           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2263           fails, advancing the starting  offset  and  trying  an  ordinary  match
2264           again. There is some code that demonstrates how to do this in the pcre-
2265           demo sample program. In the most general case, you have to check to see
2266           if  the newline convention recognizes CRLF as a newline, and if so, and
2267           the current character is CR followed by LF, advance the starting offset
2268           by two characters instead of one.
2269    
2270           If  a  non-zero starting offset is passed when the pattern is anchored,
2271         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2272         if the pattern does not require the match to be at  the  start  of  the         if  the  pattern  does  not require the match to be at the start of the
2273         subject.         subject.
2274    
2275     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2276    
2277         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
2278         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2279         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2280         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2281         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2282         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2283         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2284    
2285         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2286         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-
2287         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:
2288         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2289    
2290         The first two-thirds of the vector is used to pass back  captured  sub-         The  first  two-thirds of the vector is used to pass back captured sub-
2291         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2292         of the vector is used as workspace by pcre_exec() while  matching  cap-         of  the  vector is used as workspace by pcre_exec() while matching cap-
2293         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2294         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
2295         it is not, it is rounded down.         it is not, it is rounded down.
2296    
2297         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2298         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2299         and  continuing  up  to two-thirds of its length at the most. The first         and continuing up to two-thirds of its length at the  most.  The  first
2300         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
2301         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
2302         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
2303         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2304         entire pattern. The next pair is used for the first  capturing  subpat-  
2305         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
2306         pairs that have been set. If there are no  capturing  subpatterns,  the         portion  of  the subject string matched by the entire pattern. The next
2307         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
2308         first pair of offsets has been set.         returned by pcre_exec() is one more than the highest numbered pair that
2309           has been set.  For example, if two substrings have been  captured,  the
2310         Some convenience functions are provided  for  extracting  the  captured         returned  value is 3. If there are no capturing subpatterns, the return
2311         substrings  as  separate  strings. These are described in the following         value from a successful match is 1, indicating that just the first pair
2312         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.  
2313    
2314         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2315         of the string that it matched that is returned.         of the string that it matched that is returned.
2316    
2317         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,
2318         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
2319         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
2320         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
2321         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         ovecsize as zero. However, if the pattern contains back references  and
2322         references and the ovector is not big enough to  remember  the  related         the  ovector is not big enough to remember the related substrings, PCRE
2323         substrings,  PCRE has to get additional memory for use during matching.         has to get additional memory for use during matching. Thus it  is  usu-
2324         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2325    
2326         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
2327         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2328         that will allow for n captured substrings, in addition to  the  offsets         ovector  that  will allow for n captured substrings, in addition to the
2329         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.
2330    
2331           It is possible for capturing subpattern number n+1 to match  some  part
2332           of the subject when subpattern n has not been used at all. For example,
2333           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2334           return from the function is 4, and subpatterns 1 and 3 are matched, but
2335           2 is not. When this happens, both values in  the  offset  pairs  corre-
2336           sponding to unused subpatterns are set to -1.
2337    
2338           Offset  values  that correspond to unused subpatterns at the end of the
2339           expression are also set to -1. For example,  if  the  string  "abc"  is
2340           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2341           matched. The return from the function is 2, because  the  highest  used
2342           capturing subpattern number is 1. However, you can refer to the offsets
2343           for the second and third capturing subpatterns if  you  wish  (assuming
2344           the vector is large enough, of course).
2345    
2346     Return values from pcre_exec()         Some  convenience  functions  are  provided for extracting the captured
2347           substrings as separate strings. These are described below.
2348    
2349         If  pcre_exec()  fails, it returns a negative number. The following are     Error return values from pcre_exec()
2350    
2351           If pcre_exec() fails, it returns a negative number. The  following  are
2352         defined in the header file:         defined in the header file:
2353    
2354           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1676  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2357  MATCHING A PATTERN: THE TRADITIONAL FUNC
2357    
2358           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2359    
2360         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
2361         ovecsize was not zero.         ovecsize was not zero.
2362    
2363           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1685  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2366  MATCHING A PATTERN: THE TRADITIONAL FUNC
2366    
2367           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2368    
2369         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,
2370         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
2371         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
2372         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2373         gives when the magic number is not present.         gives when the magic number is not present.
2374    
2375           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2376    
2377         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2378         compiled pattern. This error could be caused by a bug  in  PCRE  or  by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2379         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2380    
2381           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2382    
2383         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2384         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2385         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
2386         purpose. If the call via pcre_malloc() fails, this error is given.  The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2387         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2388    
2389           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2390           This  can happen only when PCRE has been compiled with --disable-stack-
2391           for-recursion.
2392    
2393           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2394    
2395         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2396         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2397         returned by pcre_exec().         returned by pcre_exec().
2398    
2399           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2400    
2401         The  recursion  and backtracking limit, as specified by the match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2402         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra  structure  (or  defaulted) was reached. See the description
2403         description above.         above.
2404    
2405           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2406    
2407         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
2408         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2409         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2410    
2411           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2412    
2413         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
2414         subject.         subject.
2415    
2416           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2417    
2418         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
2419         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-
2420         ter.         ter.
2421    
2422           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2423    
2424         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
2425         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2426    
2427           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2428    
2429         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2430         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2431         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2432           onwards, there are no restrictions on partial matching.
2433    
2434           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2435    
# Line 1752  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2438  MATCHING A PATTERN: THE TRADITIONAL FUNC
2438    
2439           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2440    
2441         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.
2442    
2443             PCRE_ERROR_RECURSIONLIMIT (-21)
2444    
2445           The internal recursion limit, as specified by the match_limit_recursion
2446           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2447           description above.
2448    
2449             PCRE_ERROR_BADNEWLINE     (-23)
2450    
2451           An invalid combination of PCRE_NEWLINE_xxx options was given.
2452    
2453             PCRE_ERROR_BADOFFSET      (-24)
2454    
2455           The value of startoffset was negative or greater than the length of the
2456           subject, that is, the value in length.
2457    
2458           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2459    
2460    
2461  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1774  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2477  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2477         string_list() are provided for extracting captured substrings  as  new,         string_list() are provided for extracting captured substrings  as  new,
2478         separate,  zero-terminated strings. These functions identify substrings         separate,  zero-terminated strings. These functions identify substrings
2479         by number. The next section describes functions  for  extracting  named         by number. The next section describes functions  for  extracting  named
2480         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2481         extracted and has a further zero added on the end, but  the  result  is  
2482         not, of course, a C string.         A  substring that contains a binary zero is correctly extracted and has
2483           a further zero added on the end, but the result is not, of course, a  C
2484           string.   However,  you  can  process such a string by referring to the
2485           length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2486           string().  Unfortunately, the interface to pcre_get_substring_list() is
2487           not adequate for handling strings containing binary zeros, because  the
2488           end of the final string is not independently indicated.
2489    
2490         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-
2491         tions: subject is the subject string that has  just  been  successfully         tions: subject is the subject string that has  just  been  successfully
# Line 1796  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2505  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2505         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2506         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2507         The yield of the function is the length of the  string,  not  including         The yield of the function is the length of the  string,  not  including
2508         the terminating zero, or one of         the terminating zero, or one of these error codes:
2509    
2510           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2511    
# Line 1812  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2521  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2521         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
2522         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
2523         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
2524         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
2525           error code
2526    
2527           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2528    
2529         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2530    
2531         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2532         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2533         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2534         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2535         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2536         tive for unset substrings.         tive for unset substrings.
2537    
2538         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2539         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2540         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2541         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2542         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.
2543         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-
2544         cial  interface  to  another  programming  language  which  cannot  use         cial   interface  to  another  programming  language  that  cannot  use
2545         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-
2546         vided.         vided.
2547    
2548    
# Line 1851  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2561  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2561              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2562              const char **stringptr);              const char **stringptr);
2563    
2564         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2565         ber.  For example, for this pattern         ber.  For example, for this pattern
2566    
2567           (a+)b(?P<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2568    
2569         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
2570         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
2571         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-
2572         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
2573         there is no subpattern of that name.         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2574           subpattern of that name.
2575    
2576         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
2577         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
# Line 1879  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2590  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2590    
2591         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2592         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2593         ate.         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2594           behaviour may not be what you want (see the next section).
2595    
2596           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2597           terns with the same number, as described in the  section  on  duplicate
2598           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2599           distinguish the different subpatterns, because names are  not  included
2600           in  the compiled code. The matching process uses only numbers. For this
2601           reason, the use of different names for subpatterns of the  same  number
2602           causes an error at compile time.
2603    
2604    
2605    DUPLICATE SUBPATTERN NAMES
2606    
2607           int pcre_get_stringtable_entries(const pcre *code,
2608                const char *name, char **first, char **last);
2609    
2610           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2611           subpatterns are not required to be unique. (Duplicate names are  always
2612           allowed  for subpatterns with the same number, created by using the (?|
2613           feature. Indeed, if such subpatterns are named, they  are  required  to
2614           use the same names.)
2615    
2616           Normally, patterns with duplicate names are such that in any one match,
2617           only one of the named subpatterns participates. An example is shown  in
2618           the pcrepattern documentation.
2619    
2620           When    duplicates   are   present,   pcre_copy_named_substring()   and
2621           pcre_get_named_substring() return the first substring corresponding  to
2622           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2623           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2624           function  returns one of the numbers that are associated with the name,
2625           but it is not defined which it is.
2626    
2627           If you want to get full details of all captured substrings for a  given
2628           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2629           first argument is the compiled pattern, and the second is the name. The
2630           third  and  fourth  are  pointers to variables which are updated by the
2631           function. After it has run, they point to the first and last entries in
2632           the  name-to-number  table  for  the  given  name.  The function itself
2633           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2634           there  are none. The format of the table is described above in the sec-
2635           tion entitled Information about a  pattern.   Given  all  the  relevant
2636           entries  for the name, you can extract each of their numbers, and hence
2637           the captured data, if any.
2638    
2639    
2640  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 1908  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2663  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2663              int *workspace, int wscount);              int *workspace, int wscount);
2664    
2665         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2666         against a compiled pattern, using a "DFA" matching algorithm. This  has         against a compiled pattern, using a matching algorithm that  scans  the
2667         different  characteristics to the normal algorithm, and is not compati-         subject  string  just  once, and does not backtrack. This has different
2668         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics to the normal algorithm, and  is  not  compatible  with
2669         Nevertheless, there are times when this kind of matching can be useful.         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2670         For a discussion of the two matching algorithms, see  the  pcrematching         theless, there are times when this kind of matching can be useful.  For
2671         documentation.         a  discussion  of  the  two matching algorithms, and a list of features
2672           that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2673           tion.
2674    
2675         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2676         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 1925  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2682  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2682         workspace vector should contain at least 20 elements. It  is  used  for         workspace vector should contain at least 20 elements. It  is  used  for
2683         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2684         workspace will be needed for patterns and subjects where  there  are  a         workspace will be needed for patterns and subjects where  there  are  a
2685         lot of possible matches.         lot of potential matches.
2686    
2687         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_dfa_exec():
2688    
2689           int rc;           int rc;
2690           int ovector[10];           int ovector[10];
2691           int wspace[20];           int wspace[20];
2692           rc = pcre_exec(           rc = pcre_dfa_exec(
2693             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2694             NULL,           /* we didn't study the pattern */             NULL,           /* we didn't study the pattern */
2695             "some string",  /* the subject string */             "some string",  /* the subject string */
# Line 1947  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2704  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2704     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2705    
2706         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
2707         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-
2708         PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2709         PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2710         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-
2711         repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2712           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2713           PCRE_PARTIAL         description is not repeated here.
2714    
2715         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2716         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2717         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2718         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
2719         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2720         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-
2721         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2722           that requires additional characters. This happens even if some complete
2723           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2724           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2725           of  the  subject  is  reached, there have been no complete matches, but
2726           there is still at least one matching possibility. The  portion  of  the
2727           string  that  was inspected when the longest partial match was found is
2728           set as the first matching string  in  both  cases.   There  is  a  more
2729           detailed  discussion  of partial and multi-segment matching, with exam-
2730           ples, in the pcrepartial documentation.
2731    
2732           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2733    
2734         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2735         stop  as  soon  as  it  has found one match. Because of the way the DFA         stop as soon as it has found one match. Because of the way the alterna-
2736         algorithm works, this is necessarily the shortest possible match at the         tive algorithm works, this is necessarily the shortest  possible  match
2737         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2738    
2739           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2740    
2741         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
2742         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2743         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2744         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
2745         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
2746         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
2747         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2748    
2749     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2750    
2751         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2752         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2753         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2754         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2755         if the pattern         if the pattern
2756    
2757           <.*>           <.*>
# Line 2001  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2766  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2766           <something> <something else>           <something> <something else>
2767           <something> <something else> <something further>           <something> <something else> <something further>
2768    
2769         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,
2770         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2771         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2772         the  offset  to the start, and the second is the offset to the end. All         the offset to the start, and the second is the offset to  the  end.  In
2773         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
2774         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
2775         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility  with  the  way pcre_exec() returns data, even though the
2776         strings is different.)         meaning of the strings is different.)
2777    
2778         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-
2779         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
2780         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2781         filled with the longest matches.         filled with the longest matches.
2782    
2783     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2784    
2785         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2786         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2787         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2788         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2789    
2790           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2791    
2792         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2793         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2794         reference.         reference.
2795    
2796           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2797    
2798         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
2799         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
2800         supported.         in a specific group. These are not supported.
2801    
2802           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2803    
2804         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2805         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2806         (it is meaningless).         (it is meaningless).
2807    
2808           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2809    
2810         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2811         workspace vector.         workspace vector.
2812    
2813           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2814    
2815         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2816         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2817         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
2818         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2819    
2820  Last updated: 16 May 2005  
2821  Copyright (c) 1997-2005 University of Cambridge.  SEE ALSO
2822  ------------------------------------------------------------------------------  
2823           pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2824           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2825    
2826    
2827    AUTHOR
2828    
2829           Philip Hazel
2830           University Computing Service
2831           Cambridge CB2 3QH, England.
2832    
2833    
2834    REVISION
2835    
2836           Last updated: 06 November 2010
2837           Copyright (c) 1997-2010 University of Cambridge.
2838    ------------------------------------------------------------------------------
2839    
2840    
2841  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2842    
2843    
# Line 2080  PCRE CALLOUTS Line 2861  PCRE CALLOUTS
2861         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2862         points:         points:
2863    
2864           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2865    
2866         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
2867         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2868         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
2869         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2870    
2871           A(\d{2}|--)           A(\d{2}|--)
2872    
# Line 2104  PCRE CALLOUTS Line 2885  PCRE CALLOUTS
2885  MISSING CALLOUTS  MISSING CALLOUTS
2886    
2887         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2888         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2889         pattern is         example, if the pattern is
2890    
2891           ab(?C4)cd           ab(?C4)cd
2892    
# Line 2114  MISSING CALLOUTS Line 2895  MISSING CALLOUTS
2895         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2896         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2897    
2898           If the pattern is studied, PCRE knows the minimum length of a  matching
2899           string,  and will immediately give a "no match" return without actually
2900           running a match if the subject is not long enough, or,  for  unanchored
2901           patterns, if it has been scanned far enough.
2902    
2903           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2904           MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
2905           matching  process,  but  does  ensure that callouts such as the example
2906           above are obeyed.
2907    
2908    
2909  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2910    
# Line 2141  THE CALLOUT INTERFACE Line 2932  THE CALLOUT INTERFACE
2932         version number will change again in future  if  additional  fields  are         version number will change again in future  if  additional  fields  are
2933         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.
2934    
2935         The callout_number field contains the number of the  callout,  as  com-         The  callout_number  field  contains the number of the callout, as com-
2936         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-
2937         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2938    
2939         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
2940         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
2941         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
2942         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
2943         extracting substrings after a match has completed. For  pcre_dfa_exec()         extracting  substrings after a match has completed. For pcre_dfa_exec()
2944         this field is not useful.         this field is not useful.
2945    
2946         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2947         were passed to pcre_exec().         were passed to pcre_exec().
2948    
2949         The start_match field contains the offset within the subject  at  which         The  start_match  field normally contains the offset within the subject
2950         the  current match attempt started. If the pattern is not anchored, the         at which the current match attempt  started.  However,  if  the  escape
2951         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
2952         pattern for different starting points in the subject.         modified starting point. If the pattern is not  anchored,  the  callout
2953           function may be called several times from the same point in the pattern
2954           for different starting points in the subject.
2955    
2956         The  current_position  field  contains the offset within the subject of         The current_position field contains the offset within  the  subject  of
2957         the current match pointer.         the current match pointer.
2958    
2959         When the pcre_exec() function is used, the capture_top  field  contains         When  the  pcre_exec() function is used, the capture_top field contains
2960         one  more than the number of the highest numbered captured substring so         one more than the number of the highest numbered captured substring  so
2961         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
2962         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
2963         does not support captured substrings.         does not support captured substrings.
2964    
2965         The capture_last field contains the number of the  most  recently  cap-         The  capture_last  field  contains the number of the most recently cap-
2966         tured  substring. If no substrings have been captured, its value is -1.         tured substring. If no substrings have been captured, its value is  -1.
2967         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2968    
2969         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()
2970         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-
2971         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
2972         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
2973         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
2974         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2975    
2976         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-
2977         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
2978         the pattern string.         the pattern string.
2979    
2980         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-
2981         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
2982         the  pattern  string. When the callout immediately precedes an alterna-         the pattern string. When the callout immediately precedes  an  alterna-
2983         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
2984         is  zero.  When the callout precedes an opening parenthesis, the length         is zero. When the callout precedes an opening parenthesis,  the  length
2985         is that of the entire subpattern.         is that of the entire subpattern.
2986    
2987         The pattern_position and next_item_length fields are intended  to  help         The  pattern_position  and next_item_length fields are intended to help
2988         in  distinguishing between different automatic callouts, which all have         in distinguishing between different automatic callouts, which all  have
2989         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2990    
2991    
2992  RETURN VALUES  RETURN VALUES
2993    
2994         The external callout function returns an integer to PCRE. If the  value         The  external callout function returns an integer to PCRE. If the value
2995         is  zero,  matching  proceeds  as  normal. If the value is greater than         is zero, matching proceeds as normal. If  the  value  is  greater  than
2996         zero, matching fails at the current point, but  the  testing  of  other         zero,  matching  fails  at  the current point, but the testing of other
2997         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
2998         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
2999         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3000    
3001         Negative   values   should   normally   be   chosen  from  the  set  of         Negative  values  should  normally  be   chosen   from   the   set   of
3002         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3003         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
3004         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
3005         itself.         itself.
3006    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
3007    
3008    AUTHOR
3009    
3010           Philip Hazel
3011           University Computing Service
3012           Cambridge CB2 3QH, England.
3013    
3014    
3015    REVISION
3016    
3017           Last updated: 29 September 2009
3018           Copyright (c) 1997-2009 University of Cambridge.
3019    ------------------------------------------------------------------------------
3020    
3021    
3022  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3023    
3024    
# Line 2227  DIFFERENCES BETWEEN PCRE AND PERL Line 3030  DIFFERENCES BETWEEN PCRE AND PERL
3030    
3031         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3032         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3033         respect to Perl 5.8.         respect to Perl versions 5.10 and above.
3034    
3035         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
3036         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
3037           main pcre page.
3038    
3039         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3040         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,
3041         (?!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
3042         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3043    
3044         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3045         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3046         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3047         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3048         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3049         branch.         branch.
3050    
3051         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3052         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-
3053         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
3054         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3055    
3056         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3057         \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-
3058         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
3059         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3060    
3061         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
3062         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3063         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-
3064         erties such as Lu and Nd.         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3065           derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3066           property, which Perl does not; the  Perl  documentation  says  "Because
3067           Perl hides the need for the user to understand the internal representa-
3068           tion of Unicode characters, there is no need to implement the  somewhat
3069           messy concept of surrogates."
3070    
3071         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3072         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
# Line 2275  DIFFERENCES BETWEEN PCRE AND PERL Line 3084  DIFFERENCES BETWEEN PCRE AND PERL
3084         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3085         classes.         classes.
3086    
3087         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3088         constructions.  However,  there is support for recursive patterns using         constructions.  However,  there is support for recursive patterns. This
3089         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
3090         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3091         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3092    
3093         9. There are some differences that are concerned with the  settings  of         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3094           always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3095           unlike Perl. There is a discussion of an example that explains this  in
3096           more  detail  in  the section on recursion differences from Perl in the
3097           pcrepattern page.
3098    
3099           10. There are some differences that are concerned with the settings  of
3100         captured  strings  when  part  of  a  pattern is repeated. For example,         captured  strings  when  part  of  a  pattern is repeated. For example,
3101         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3102         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3103    
3104         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3105         ities:         pattern names is not as general as Perl's. This is a consequence of the
3106           fact the PCRE works internally just with numbers, using an external ta-
3107         (a) Although lookbehind assertions must  match  fixed  length  strings,         ble to translate between numbers and names. In  particular,  a  pattern
3108         each alternative branch of a lookbehind assertion can match a different         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3109         length of string. Perl requires them all to have the same length.         the same number but different names, is not supported,  and  causes  an
3110           error  at compile time. If it were allowed, it would not be possible to
3111           distinguish which parentheses matched, because both names map  to  cap-
3112           turing subpattern number 1. To avoid this confusing situation, an error
3113           is given at compile time.
3114    
3115           12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3116           example, between the ( and ? at the start of a subpattern.
3117    
3118           13. PCRE provides some extensions to the Perl regular expression facil-
3119           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3120           sions  of  Perl, some of which (such as named parentheses) have been in
3121           PCRE for some time. This list is with respect to Perl 5.10:
3122    
3123           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3124           strings,  each alternative branch of a lookbehind assertion can match a
3125           different length of string. Perl requires them all  to  have  the  same
3126           length.
3127    
3128         (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 $
3129         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3130    
3131         (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-
3132         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3133           ignored.  (Perl can be made to issue a warning.)
3134    
3135         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3136         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2306  DIFFERENCES BETWEEN PCRE AND PERL Line 3139  DIFFERENCES BETWEEN PCRE AND PERL
3139         (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
3140         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3141    
3142         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3143         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3144           lents.
3145    
3146         (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
3147         pattern  matching  (Perl  can  do  this using the (?p{code}) construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
3148    
3149         (h) PCRE supports named capturing substrings, using the Python  syntax.         (h) The callout facility is PCRE-specific.
3150    
3151         (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
3152    
3153         (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,
3154           even on different hosts that have the other endianness.
3155    
3156         (k) The callout facility is PCRE-specific.         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3157           different way and is not Perl-compatible.
3158    
3159         (l) The partial matching facility is PCRE-specific.         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3160           of a pattern that set overall options that cannot be changed within the
3161           pattern.
3162    
        (m) Patterns compiled by PCRE can be saved and re-used at a later time,  
        even on different hosts that have the other endianness.  
3163    
3164         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a  AUTHOR
        different way and is not Perl-compatible.  
3165    
3166  Last updated: 28 February 2005         Philip Hazel
3167  Copyright (c) 1997-2005 University of Cambridge.         University Computing Service
3168  ------------------------------------------------------------------------------         Cambridge CB2 3QH, England.
3169    
3170    
3171    REVISION
3172    
3173           Last updated: 31 October 2010
3174           Copyright (c) 1997-2010 University of Cambridge.
3175    ------------------------------------------------------------------------------
3176    
3177    
3178  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3179    
3180    
# Line 2344  NAME Line 3184  NAME
3184    
3185  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3186    
3187         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3188         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3189         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
3190         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3191         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3192         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3193           Python, .NET, and Oniguruma.
3194    
3195           Perl's  regular expressions are described in its own documentation, and
3196           regular expressions in general are covered in a number of  books,  some
3197           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3198           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3199           great  detail.  This  description  of  PCRE's  regular  expressions  is
3200           intended as reference material.
3201    
3202         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3203         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
3204         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
3205         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3206         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:
3207         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3208         page.           (*UTF8)
3209    
3210           Starting a pattern with this sequence  is  equivalent  to  setting  the
3211           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3212           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3213           below.  There  is  also  a  summary of UTF-8 features in the section on
3214           UTF-8 support in the main pcre page.
3215    
3216           Another special sequence that may appear at the start of a  pattern  or
3217           in combination with (*UTF8) is:
3218    
3219             (*UCP)
3220    
3221           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3222           sequences such as \d and \w to  use  Unicode  properties  to  determine
3223           character types, instead of recognizing only characters with codes less
3224           than 128 via a lookup table.
3225    
3226         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3227         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
3228         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
3229         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
3230         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
3231         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3232         the pcrematching page.         alternative function, and how it differs from the normal function,  are
3233           discussed in the pcrematching page.
3234         A regular expression is a pattern that is  matched  against  a  subject  
3235         string  from  left  to right. Most characters stand for themselves in a  
3236         pattern, and match the corresponding characters in the  subject.  As  a  NEWLINE CONVENTIONS
3237    
3238           PCRE  supports five different conventions for indicating line breaks in
3239           strings: a single CR (carriage return) character, a  single  LF  (line-
3240           feed) character, the two-character sequence CRLF, any of the three pre-
3241           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3242           discussion  about newlines, and shows how to set the newline convention
3243           in the options arguments for the compiling and matching functions.
3244    
3245           It is also possible to specify a newline convention by starting a  pat-
3246           tern string with one of the following five sequences:
3247    
3248             (*CR)        carriage return
3249             (*LF)        linefeed
3250             (*CRLF)      carriage return, followed by linefeed
3251             (*ANYCRLF)   any of the three above
3252             (*ANY)       all Unicode newline sequences
3253    
3254           These  override  the default and the options given to pcre_compile() or
3255           pcre_compile2(). For example, on a Unix system where LF is the  default
3256           newline sequence, the pattern
3257    
3258             (*CR)a.b
3259    
3260           changes the convention to CR. That pattern matches "a\nb" because LF is
3261           no longer a newline. Note that these special settings,  which  are  not
3262           Perl-compatible,  are  recognized  only at the very start of a pattern,
3263           and that they must be in upper case.  If  more  than  one  of  them  is
3264           present, the last one is used.
3265    
3266           The  newline convention affects the interpretation of the dot metachar-
3267           acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
3268           ever,  it  does  not  affect  what  the  \R escape sequence matches. By
3269           default, this is any Unicode newline sequence, for Perl  compatibility.
3270           However,  this can be changed; see the description of \R in the section
3271           entitled "Newline sequences" below. A change of \R setting can be  com-
3272           bined with a change of newline convention.
3273    
3274    
3275    CHARACTERS AND METACHARACTERS
3276    
3277           A  regular  expression  is  a pattern that is matched against a subject
3278           string from left to right. Most characters stand for  themselves  in  a
3279           pattern,  and  match  the corresponding characters in the subject. As a
3280         trivial example, the pattern         trivial example, the pattern
3281    
3282           The quick brown fox           The quick brown fox
3283    
3284         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
3285         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3286         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3287         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
3288         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3289         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
3290         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3291         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3292         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3293    
3294         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3295         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3296         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3297         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3298    
3299         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3300         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3301         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
3302         metacharacters are as follows:         the metacharacters are as follows:
3303    
3304           \      general escape character with several uses           \      general escape character with several uses
3305           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2410  PCRE REGULAR EXPRESSION DETAILS Line 3317  PCRE REGULAR EXPRESSION DETAILS
3317                  also "possessive quantifier"                  also "possessive quantifier"
3318           {      start min/max quantifier           {      start min/max quantifier
3319    
3320         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
3321         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3322    
3323           \      general escape character           \      general escape character
# Line 2420  PCRE REGULAR EXPRESSION DETAILS Line 3327  PCRE REGULAR EXPRESSION DETAILS
3327                    syntax)                    syntax)
3328           ]      terminates the character class           ]      terminates the character class
3329    
3330         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3331    
3332    
3333  BACKSLASH  BACKSLASH
# Line 2439  BACKSLASH Line 3346  BACKSLASH
3346    
3347         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3348         the pattern (other than in a character class) and characters between  a         the pattern (other than in a character class) and characters between  a
3349         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
3350         An escaping backslash can be used to include a whitespace or #  charac-         ing backslash can be used to include a whitespace  or  #  character  as
3351         ter as part of the pattern.         part of the pattern.
3352    
3353         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-
3354         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 2457  BACKSLASH Line 3364  BACKSLASH
3364           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3365    
3366         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3367         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3368    
3369     Non-printing characters     Non-printing characters
3370    
# Line 2465  BACKSLASH Line 3372  BACKSLASH
3372         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
3373         appearance of non-printing characters, apart from the binary zero  that         appearance of non-printing characters, apart from the binary zero  that
3374         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3375         editing, it is usually easier  to  use  one  of  the  following  escape         editing, it is  often  easier  to  use  one  of  the  following  escape
3376         sequences than the binary character it represents:         sequences than the binary character it represents:
3377    
3378           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3379           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3380           \e        escape (hex 1B)           \e        escape (hex 1B)
3381           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3382           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3383           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3384           \t        tab (hex 09)           \t        tab (hex 09)
3385           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference