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1    -----------------------------------------------------------------------------
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
 PCRE(3)                                                                PCRE(3)  
10    
11    PCRE(3)                                                                PCRE(3)
12    
13    
14  NAME  NAME
15         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
16    
17  DESCRIPTION  
18    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. Certain features that appeared in Python and
23         4.x) corresponds approximately with Perl  5.8,  including  support  for         PCRE before they appeared in Perl are also available using  the  Python
24         UTF-8  encoded  strings.   However,  this  support has to be explicitly         syntax.  There is also some support for certain .NET and Oniguruma syn-
25         enabled; it is not the default.         tax items, and there is an option for  requesting  some  minor  changes
26           that give better JavaScript compatibility.
27         PCRE is written in C and released as a C library. However, a number  of  
28         people  have  written  wrappers  and interfaces of various kinds. A C++         The  current implementation of PCRE (release 8.xx) corresponds approxi-
29         class is included in these contributions, which can  be  found  in  the         mately with Perl 5.10, including support for UTF-8 encoded strings  and
30           Unicode general category properties. However, UTF-8 and Unicode support
31           has to be explicitly enabled; it is not the default. The Unicode tables
32           correspond to Unicode release 5.1.
33    
34           In  addition to the Perl-compatible matching function, PCRE contains an
35           alternative matching function that matches the same  compiled  patterns
36           in  a different way. In certain circumstances, the alternative function
37           has some advantages. For a discussion of the two  matching  algorithms,
38           see the 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
44           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. Documentation about         client  to  discover  which  features are available. The features them-
57         building PCRE for various operating systems can be found in the  README         selves are described in the pcrebuild page. Documentation about  build-
58         file in the source distribution.         ing  PCRE for various operating systems can be found in the README file
59           in the source distribution.
60    
61           The library contains a number of undocumented  internal  functions  and
62           data  tables  that  are  used by more than one of the exported external
63           functions, but which are not intended  for  use  by  external  callers.
64           Their  names  all begin with "_pcre_", which hopefully will not provoke
65           any name clashes. In some environments, it is possible to control which
66           external  symbols  are  exported when a shared library is built, and in
67           these cases the undocumented symbols are not exported.
68    
69    
70  USER DOCUMENTATION  USER DOCUMENTATION
71    
72         The user documentation for PCRE has been split up into a number of dif-         The user documentation for PCRE comprises a number  of  different  sec-
73         ferent sections. In the "man" format, each of these is a separate  "man         tions.  In the "man" format, each of these is a separate "man page". In
74         page".  In  the  HTML  format, each is a separate page, linked from the         the HTML format, each is a separate page, linked from the  index  page.
75         index page. In the plain text format, all  the  sections  are  concate-         In  the  plain  text format, all the sections, except the pcredemo sec-
76         nated, for ease 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           pcreapi           details of PCRE's native API           pcre-config       show PCRE installation configuration information
81             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
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
89             pcrepartial       details of the partial matching facility
90           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
91                               regular expressions                               regular expressions
92             pcresyntax        quick syntax reference
93           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
94           pcreposix         the POSIX-compatible API           pcreposix         the POSIX-compatible C API
95           pcresample        discussion of the sample program           pcreprecompile    details of saving and re-using precompiled patterns
96           pcretest          the pcretest testing command           pcresample        discussion of the pcredemo program
97             pcrestack         discussion of stack usage
98             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
101         each library function, listing its arguments and results.         each C library function, listing its arguments and results.
102    
103    
104  LIMITATIONS  LIMITATIONS
# Line 74  LIMITATIONS Line 111  LIMITATIONS
111         process  regular  expressions  that are truly enormous, you can compile         process  regular  expressions  that are truly enormous, you can compile
112         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in         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         If 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.
        including capturing subpatterns, assertions, and other types of subpat-  
        tern, is 200.  
121    
122         The  maximum  length of a subject string is the largest positive number         The maximum length of name for a named subpattern is 32 characters, and
123         that an integer variable can hold. However, PCRE uses recursion to han-         the maximum number of named subpatterns is 10000.
        dle  subpatterns  and indefinite repetition. This means that the avail-  
        able stack space may limit the size of a subject  string  that  can  be  
        processed by certain patterns.  
124    
125           The  maximum  length of a subject string is the largest positive number
126           that an integer variable can hold. However, when using the  traditional
127           matching function, PCRE uses recursion to handle subpatterns and indef-
128           inite repetition.  This means that the available stack space may  limit
129           the size of a subject string that can be processed by certain patterns.
130           For a discussion of stack issues, see the pcrestack documentation.
131    
 UTF-8 SUPPORT  
132    
133         Starting  at  release  3.3,  PCRE  has  had  some support for character  UTF-8 AND UNICODE PROPERTY SUPPORT
134         strings encoded in the UTF-8 format. For  release  4.0  this  has  been  
135         greatly extended to cover most common requirements.         From release 3.3, PCRE has  had  some  support  for  character  strings
136           encoded  in the UTF-8 format. For release 4.0 this was greatly extended
137           to cover most common requirements, and in release 5.0  additional  sup-
138           port for Unicode general category properties was added.
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
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 just strings of bytes.
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         The following comments apply when PCRE is running in UTF-8 mode:  
152           If PCRE is built with Unicode character property support (which implies
153         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154         subjects  are  checked for validity on entry to the relevant functions.         ported.  The available properties that can be tested are limited to the
155         If an invalid UTF-8 string is passed, an error return is given. In some         general category properties such as Lu for an upper case letter  or  Nd
156         situations,  you  may  already  know  that  your strings are valid, and         for  a  decimal number, the Unicode script names such as Arabic or Han,
157         therefore want to skip these checks in order to improve performance. If         and the derived properties Any and L&. A full  list  is  given  in  the
158         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         pcrepattern documentation. Only the short names for properties are sup-
159         PCRE assumes that the pattern or subject  it  is  given  (respectively)         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
160         contains  only valid UTF-8 codes. In this case, it does not diagnose an         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         does not support this.
163         crash.  
164       Validity of UTF-8 strings
165         2. In a pattern, the escape sequence \x{...}, where the contents of the  
166         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167         character whose code number is the given hexadecimal number, for  exam-         subjects are (by default) checked for validity on entry to the relevant
168         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,         functions.  From  release 7.3 of PCRE, the check is according the rules
169         the item is not recognized.  This escape sequence can be used either as         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         a literal, or within a character class.         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171           allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174    
175           The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176           which  the Unicode Standard says this: "The Low Surrogate Area does not
177           contain any  character  assignments,  consequently  no  character  code
178           charts or namelists are provided for this area. Surrogates are reserved
179           for use with UTF-16 and then must be used in pairs."  The  code  points
180           that  are  encoded  by  UTF-16  pairs are available as independent code
181           points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184           If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186           that your strings are valid, and therefore want to skip these checks in
187           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188           compile  time  or at run time, PCRE assumes that the pattern or subject
189           it is given (respectively) contains only valid  UTF-8  codes.  In  this
190           case, it does not diagnose an invalid UTF-8 string.
191    
192           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193           what happens depends on why the string is invalid. If the  string  con-
194           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197           strings according to the more liberal rules of RFC  2279.  However,  if
198           the  string does not even conform to RFC 2279, the result is undefined.
199           Your program may crash.
200    
201           If you want to process strings  of  values  in  the  full  range  0  to
202           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204           this situation, you will have to apply your own validity check.
205    
206       General comments about UTF-8 mode
207    
208         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209         UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
210    
211         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212           characters for values greater than \177.
213    
214           3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         5.  The  dot  metacharacter  matches  one  UTF-8 character instead of a         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         single 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.         mode, but its use can lead to some strange effects.  This  facility  is
222           not available in the alternative matching function, pcre_dfa_exec().
223    
224         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 the characters that PCRE  recog-
226         nizes  as  digits,  spaces,  or  word characters remain the same set as         nizes  as  digits,  spaces,  or  word characters remain the same set as
227         before, all with values less than 256.         before, all with values less than 256. This remains true even when PCRE
228           includes  Unicode  property support, because to do otherwise would slow
229         8. Case-insensitive matching applies only to  characters  whose  values         down PCRE in many common cases. If you really want to test for a  wider
230         are  less  than  256.  PCRE  does  not support the notion of "case" for         sense  of,  say,  "digit",  you must use Unicode property tests such as
231         higher-valued characters.         \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
232           terms of \w and \W.
233         9. PCRE does not support the use of Unicode tables  and  properties  or  
234         the Perl escapes \p, \P, and \X.         7.  Similarly,  characters that match the POSIX named character classes
235           are all low-valued characters.
236    
237           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
238           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
239           acters.
240    
241           9. Case-insensitive matching applies only to  characters  whose  values
242           are  less than 128, unless PCRE is built with Unicode property support.
243           Even when Unicode property support is available, PCRE  still  uses  its
244           own  character  tables when checking the case of low-valued characters,
245           so as not to degrade performance.  The Unicode property information  is
246           used only for characters with higher values. Even when Unicode property
247           support is available, PCRE supports case-insensitive matching only when
248           there  is  a  one-to-one  mapping between a letter's cases. There are a
249           small number of many-to-one mappings in Unicode;  these  are  not  sup-
250           ported by PCRE.
251    
252    
253  AUTHOR  AUTHOR
254    
255         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
256         University Computing Service,         University Computing Service
257         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
258         Phone: +44 1223 334714  
259           Putting  an actual email address here seems to have been a spam magnet,
260  Last updated: 20 August 2003         so I've taken it away. If you want to email me, use  my  two  initials,
261  Copyright (c) 1997-2003 University of Cambridge.         followed by the two digits 10, at the domain cam.ac.uk.
262  -----------------------------------------------------------------------------  
263    
264  PCRE(3)                                                                PCRE(3)  REVISION
265    
266           Last updated: 01 September 2009
267           Copyright (c) 1997-2009 University of Cambridge.
268    ------------------------------------------------------------------------------
269    
270    
271    PCREBUILD(3)                                                      PCREBUILD(3)
272    
273    
274  NAME  NAME
275         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
276    
277    
278  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
279    
280         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
281         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
282         lected,  by  providing  options  to  the  configure script which is run         script,  where the optional features are selected or deselected by pro-
283         before the make command. The complete list  of  options  for  configure         viding options to configure before running the make  command.  However,
284         (which  includes the standard ones such as the selection of the instal-         the  same  options  can be selected in both Unix-like and non-Unix-like
285         lation directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
286           instead of configure to build PCRE.
287    
288           There  is  a  lot more information about building PCRE in non-Unix-like
289           environments in the file called NON_UNIX_USE, which is part of the PCRE
290           distribution.  You  should consult this file as well as the README file
291           if you are building in a non-Unix-like environment.
292    
293           The complete list of options for configure (which includes the standard
294           ones  such  as  the  selection  of  the  installation directory) can be
295           obtained by running
296    
297           ./configure --help           ./configure --help
298    
299         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
300         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
301         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
302         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
303         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
304         not described.         is not described.
305    
306    
307    C++ SUPPORT
308    
309           By default, the configure script will search for a C++ compiler and C++
310           header files. If it finds them, it automatically builds the C++ wrapper
311           library for PCRE. You can disable this by adding
312    
313             --disable-cpp
314    
315           to the configure command.
316    
317    
318  UTF-8 SUPPORT  UTF-8 SUPPORT
319    
320         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
321    
322           --enable-utf8           --enable-utf8
323    
# Line 203  UTF-8 SUPPORT Line 326  UTF-8 SUPPORT
326         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()
327         function.         function.
328    
329           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
330           expects its input to be either ASCII or UTF-8 (depending on the runtime
331           option). It is not possible to support both EBCDIC and UTF-8  codes  in
332           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
333           --enable-ebcdic are mutually exclusive.
334    
335    
336    UNICODE CHARACTER PROPERTY SUPPORT
337    
338           UTF-8 support allows PCRE to process character values greater than  255
339           in  the  strings that it handles. On its own, however, it does not pro-
340           vide any facilities for accessing the properties of such characters. If
341           you  want  to  be able to use the pattern escapes \P, \p, and \X, which
342           refer to Unicode character properties, you must add
343    
344             --enable-unicode-properties
345    
346           to the configure command. This implies UTF-8 support, even if you  have
347           not explicitly requested it.
348    
349           Including  Unicode  property  support  adds around 30K of tables to the
350           PCRE library. Only the general category properties such as  Lu  and  Nd
351           are supported. Details are given in the pcrepattern documentation.
352    
353    
354  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
355    
356         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets the linefeed (LF) character as indicating
357         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
358         compile PCRE to use character 13 (carriage return) instead by adding         systems.  You  can compile PCRE to use carriage return (CR) instead, by
359           adding
360    
361           --enable-newline-is-cr           --enable-newline-is-cr
362    
363         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
364         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
365         line character.  
366           Alternatively, you can specify that line endings are to be indicated by
367           the two character sequence CRLF. If you want this, add
368    
369             --enable-newline-is-crlf
370    
371           to the configure command. There is a fourth option, specified by
372    
373             --enable-newline-is-anycrlf
374    
375           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
376           CRLF as indicating a line ending. Finally, a fifth option, specified by
377    
378             --enable-newline-is-any
379    
380           causes PCRE to recognize any Unicode newline sequence.
381    
382           Whatever  line  ending convention is selected when PCRE is built can be
383           overridden when the library functions are called. At build time  it  is
384           conventional to use the standard for your operating system.
385    
386    
387    WHAT \R MATCHES
388    
389           By  default,  the  sequence \R in a pattern matches any Unicode newline
390           sequence, whatever has been selected as the line  ending  sequence.  If
391           you specify
392    
393             --enable-bsr-anycrlf
394    
395           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
396           ever is selected when PCRE is built can be overridden when the  library
397           functions are called.
398    
399    
400  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
401    
402         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
403         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
404         of         of
405    
406           --disable-shared           --disable-shared
# Line 231  BUILDING SHARED AND STATIC LIBRARIES Line 411  BUILDING SHARED AND STATIC LIBRARIES
411    
412  POSIX MALLOC USAGE  POSIX MALLOC USAGE
413    
414         When PCRE is called through the  POSIX  interface  (see  the  pcreposix         When PCRE is called through the POSIX interface (see the pcreposix doc-
415         documentation),  additional working storage is required for holding the         umentation), additional working storage is  required  for  holding  the
416         pointers to capturing substrings because PCRE requires  three  integers         pointers  to capturing substrings, because PCRE requires three integers
417         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
418         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
419         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.
420         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 245  POSIX MALLOC USAGE Line 425  POSIX MALLOC USAGE
425         to the configure command.         to the configure command.
426    
427    
428    HANDLING VERY LARGE PATTERNS
429    
430           Within a compiled pattern, offset values are used  to  point  from  one
431           part  to another (for example, from an opening parenthesis to an alter-
432           nation metacharacter). By default, two-byte values are used  for  these
433           offsets,  leading  to  a  maximum size for a compiled pattern of around
434           64K. This is sufficient to handle all but the most  gigantic  patterns.
435           Nevertheless,  some  people do want to process enormous patterns, so it
436           is possible to compile PCRE to use three-byte or four-byte  offsets  by
437           adding a setting such as
438    
439             --with-link-size=3
440    
441           to  the  configure  command.  The value given must be 2, 3, or 4. Using
442           longer offsets slows down the operation of PCRE because it has to  load
443           additional bytes when handling them.
444    
445    
446    AVOIDING EXCESSIVE STACK USAGE
447    
448           When matching with the pcre_exec() function, PCRE implements backtrack-
449           ing by making recursive calls to an internal function  called  match().
450           In  environments  where  the size of the stack is limited, this can se-
451           verely limit PCRE's operation. (The Unix environment does  not  usually
452           suffer from this problem, but it may sometimes be necessary to increase
453           the maximum stack size.  There is a discussion in the  pcrestack  docu-
454           mentation.)  An alternative approach to recursion that uses memory from
455           the heap to remember data, instead of using recursive  function  calls,
456           has  been  implemented to work round the problem of limited stack size.
457           If you want to build a version of PCRE that works this way, add
458    
459             --disable-stack-for-recursion
460    
461           to the configure command. With this configuration, PCRE  will  use  the
462           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
463           ment functions. By default these point to malloc() and free(), but  you
464           can replace the pointers so that your own functions are used.
465    
466           Separate  functions  are  provided  rather  than  using pcre_malloc and
467           pcre_free because the  usage  is  very  predictable:  the  block  sizes
468           requested  are  always  the  same,  and  the blocks are always freed in
469           reverse order. A calling program might be able to  implement  optimized
470           functions  that  perform  better  than  malloc()  and free(). PCRE runs
471           noticeably more slowly when built in this way. This option affects only
472           the   pcre_exec()   function;   it   is   not   relevant  for  the  the
473           pcre_dfa_exec() function.
474    
475    
476  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
477    
478         Internally,  PCRE  has a function called match() which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
479         edly (possibly recursively) when performing a  matching  operation.  By         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
480         limiting  the  number of times this function may be called, a limit can         pcre_exec() function. By controlling the maximum number of  times  this
481           function  may be called during a single matching operation, a limit can
482         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
483         limit  can be changed at run time, as described in the pcreapi documen-         limit  can be changed at run time, as described in the pcreapi documen-
484         tation. The default is 10 million, but this can be changed by adding  a         tation. The default is 10 million, but this can be changed by adding  a
# Line 257  LIMITING PCRE RESOURCE USAGE Line 486  LIMITING PCRE RESOURCE USAGE
486    
487           --with-match-limit=500000           --with-match-limit=500000
488    
489         to the configure command.         to   the   configure  command.  This  setting  has  no  effect  on  the
490           pcre_dfa_exec() matching function.
491    
492           In some environments it is desirable to limit the  depth  of  recursive
493           calls of match() more strictly than the total number of calls, in order
494           to restrict the maximum amount of stack (or heap,  if  --disable-stack-
495           for-recursion is specified) that is used. A second limit controls this;
496           it defaults to the value that  is  set  for  --with-match-limit,  which
497           imposes  no  additional constraints. However, you can set a lower limit
498           by adding, for example,
499    
500             --with-match-limit-recursion=10000
501    
502           to the configure command. This value can  also  be  overridden  at  run
503           time.
504    
505    
506    CREATING CHARACTER TABLES AT BUILD TIME
507    
508           PCRE  uses fixed tables for processing characters whose code values are
509           less than 256. By default, PCRE is built with a set of tables that  are
510           distributed  in  the  file pcre_chartables.c.dist. These tables are for
511           ASCII codes only. If you add
512    
513             --enable-rebuild-chartables
514    
515           to the configure command, the distributed tables are  no  longer  used.
516           Instead,  a  program  called dftables is compiled and run. This outputs
517           the source for new set of tables, created in the default locale of your
518           C runtime system. (This method of replacing the tables does not work if
519           you are cross compiling, because dftables is run on the local host.  If
520           you  need  to  create alternative tables when cross compiling, you will
521           have to do so "by hand".)
522    
 HANDLING VERY LARGE PATTERNS  
523    
524         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  
525    
526           --with-link-size=3         PCRE assumes by default that it will run in an  environment  where  the
527           character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
528           This is the case for most computer operating systems.  PCRE  can,  how-
529           ever, be compiled to run in an EBCDIC environment by adding
530    
531         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.  
532    
533         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-
534         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
535         representation of the compiled pattern, and this changes with the  link         environment  (for  example,  an  IBM  mainframe  operating system). The
536         size.         --enable-ebcdic option is incompatible with --enable-utf8.
537    
538    
539  AVOIDING EXCESSIVE STACK USAGE  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
540    
541         PCRE  implements  backtracking while matching by making recursive calls         By default, pcregrep reads all files as plain text. You can build it so
542         to an internal function called match(). In environments where the  size         that it recognizes files whose names end in .gz or .bz2, and reads them
543         of the stack is limited, this can severely limit PCRE's operation. (The         with libz or libbz2, respectively, by adding one or both of
        Unix environment does not usually suffer from this problem.) An  alter-  
        native  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  
544    
545           --disable-stack-for-recursion           --enable-pcregrep-libz
546             --enable-pcregrep-libbz2
547    
548         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. These options naturally require that the rel-
549         pcre_stack_malloc   and   pcre_stack_free   variables  to  call  memory         evant  libraries  are installed on your system. Configuration will fail
550         management functions. Separate functions are provided because the usage         if they are not.
        is 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.  
551    
552    
553  USING EBCDIC CODE  PCRETEST OPTION FOR LIBREADLINE SUPPORT
554    
555         PCRE  assumes  by  default that it will run in an environment where the         If you add
        character code is ASCII (or UTF-8, which is a superset of ASCII).  PCRE  
        can, however, be compiled to run in an EBCDIC environment by adding  
556    
557           --enable-ebcdic           --enable-pcretest-libreadline
558    
559         to the configure command.         to the configure command,  pcretest  is  linked  with  the  libreadline
560           library,  and  when its input is from a terminal, it reads it using the
561           readline() function. This provides line-editing and history facilities.
562           Note that libreadline is GPL-licenced, so if you distribute a binary of
563           pcretest linked in this way, there may be licensing issues.
564    
565  Last updated: 09 December 2003         Setting this option causes the -lreadline option to  be  added  to  the
566  Copyright (c) 1997-2003 University of Cambridge.         pcretest  build.  In many operating environments with a sytem-installed
567  -----------------------------------------------------------------------------         libreadline this is sufficient. However, in some environments (e.g.  if
568           an  unmodified  distribution version of readline is in use), some extra
569           configuration may be necessary. The INSTALL file for  libreadline  says
570           this:
571    
572  PCRE(3)                                                                PCRE(3)           "Readline uses the termcap functions, but does not link with the
573             termcap or curses library itself, allowing applications which link
574             with readline the to choose an appropriate library."
575    
576           If  your environment has not been set up so that an appropriate library
577           is automatically included, you may need to add something like
578    
579             LIBS="-ncurses"
580    
581           immediately before the configure command.
582    
583    
584    SEE ALSO
585    
586           pcreapi(3), pcre_config(3).
587    
588    
589    AUTHOR
590    
591           Philip Hazel
592           University Computing Service
593           Cambridge CB2 3QH, England.
594    
595    
596    REVISION
597    
598           Last updated: 06 September 2009
599           Copyright (c) 1997-2009 University of Cambridge.
600    ------------------------------------------------------------------------------
601    
602    
603    PCREMATCHING(3)                                                PCREMATCHING(3)
604    
605    
606    NAME
607           PCRE - Perl-compatible regular expressions
608    
609    
610    PCRE MATCHING ALGORITHMS
611    
612           This document describes the two different algorithms that are available
613           in PCRE for matching a compiled regular expression against a given sub-
614           ject  string.  The  "standard"  algorithm  is  the  one provided by the
615           pcre_exec() function.  This works in the same was  as  Perl's  matching
616           function, and provides a Perl-compatible matching operation.
617    
618           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
619           this operates in a different way, and is not  Perl-compatible.  It  has
620           advantages  and disadvantages compared with the standard algorithm, and
621           these are described below.
622    
623           When there is only one possible way in which a given subject string can
624           match  a pattern, the two algorithms give the same answer. A difference
625           arises, however, when there are multiple possibilities. For example, if
626           the pattern
627    
628             ^<.*>
629    
630           is matched against the string
631    
632             <something> <something else> <something further>
633    
634           there are three possible answers. The standard algorithm finds only one
635           of them, whereas the alternative algorithm finds all three.
636    
637    
638    REGULAR EXPRESSIONS AS TREES
639    
640           The set of strings that are matched by a regular expression can be rep-
641           resented  as  a  tree structure. An unlimited repetition in the pattern
642           makes the tree of infinite size, but it is still a tree.  Matching  the
643           pattern  to a given subject string (from a given starting point) can be
644           thought of as a search of the tree.  There are two  ways  to  search  a
645           tree:  depth-first  and  breadth-first, and these correspond to the two
646           matching algorithms provided by PCRE.
647    
648    
649    THE STANDARD MATCHING ALGORITHM
650    
651           In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
652           sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
653           depth-first search of the pattern tree. That is, it  proceeds  along  a
654           single path through the tree, checking that the subject matches what is
655           required. When there is a mismatch, the algorithm  tries  any  alterna-
656           tives  at  the  current point, and if they all fail, it backs up to the
657           previous branch point in the  tree,  and  tries  the  next  alternative
658           branch  at  that  level.  This often involves backing up (moving to the
659           left) in the subject string as well.  The  order  in  which  repetition
660           branches  are  tried  is controlled by the greedy or ungreedy nature of
661           the quantifier.
662    
663           If a leaf node is reached, a matching string has  been  found,  and  at
664           that  point the algorithm stops. Thus, if there is more than one possi-
665           ble match, this algorithm returns the first one that it finds.  Whether
666           this  is the shortest, the longest, or some intermediate length depends
667           on the way the greedy and ungreedy repetition quantifiers are specified
668           in the pattern.
669    
670           Because  it  ends  up  with a single path through the tree, it is rela-
671           tively straightforward for this algorithm to keep  track  of  the  sub-
672           strings  that  are  matched  by portions of the pattern in parentheses.
673           This provides support for capturing parentheses and back references.
674    
675    
676    THE ALTERNATIVE MATCHING ALGORITHM
677    
678           This algorithm conducts a breadth-first search of  the  tree.  Starting
679           from  the  first  matching  point  in the subject, it scans the subject
680           string from left to right, once, character by character, and as it does
681           this,  it remembers all the paths through the tree that represent valid
682           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
683           though  it is not implemented as a traditional finite state machine (it
684           keeps multiple states active simultaneously).
685    
686           The scan continues until either the end of the subject is  reached,  or
687           there  are  no more unterminated paths. At this point, terminated paths
688           represent the different matching possibilities (if there are none,  the
689           match  has  failed).   Thus,  if there is more than one possible match,
690           this algorithm finds all of them, and in particular, it finds the long-
691           est.  In PCRE, there is an option to stop the algorithm after the first
692           match (which is necessarily the shortest) has been found.
693    
694           Note that all the matches that are found start at the same point in the
695           subject. If the pattern
696    
697             cat(er(pillar)?)
698    
699           is  matched  against the string "the caterpillar catchment", the result
700           will be the three strings "cat", "cater", and "caterpillar" that  start
701           at the fourth character of the subject. The algorithm does not automat-
702           ically move on to find matches that start at later positions.
703    
704           Although the general principle of this matching algorithm  is  that  it
705           scans  the subject string only once, without backtracking, there is one
706           exception: when a lookbehind assertion is  encountered,  the  preceding
707           characters have to be re-inspected.
708    
709           There are a number of features of PCRE regular expressions that are not
710           supported by the alternative matching algorithm. They are as follows:
711    
712           1. Because the algorithm finds all  possible  matches,  the  greedy  or
713           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
714           ungreedy quantifiers are treated in exactly the same way. However, pos-
715           sessive  quantifiers can make a difference when what follows could also
716           match what is quantified, for example in a pattern like this:
717    
718             ^a++\w!
719    
720           This pattern matches "aaab!" but not "aaa!", which would be matched  by
721           a  non-possessive quantifier. Similarly, if an atomic group is present,
722           it is matched as if it were a standalone pattern at the current  point,
723           and  the  longest match is then "locked in" for the rest of the overall
724           pattern.
725    
726           2. When dealing with multiple paths through the tree simultaneously, it
727           is  not  straightforward  to  keep track of captured substrings for the
728           different matching possibilities, and  PCRE's  implementation  of  this
729           algorithm does not attempt to do this. This means that no captured sub-
730           strings are available.
731    
732           3. Because no substrings are captured, back references within the  pat-
733           tern are not supported, and cause errors if encountered.
734    
735           4.  For  the same reason, conditional expressions that use a backrefer-
736           ence as the condition or test for a specific group  recursion  are  not
737           supported.
738    
739           5.  Because  many  paths  through the tree may be active, the \K escape
740           sequence, which resets the start of the match when encountered (but may
741           be  on  some  paths  and not on others), is not supported. It causes an
742           error if encountered.
743    
744           6. Callouts are supported, but the value of the  capture_top  field  is
745           always 1, and the value of the capture_last field is always -1.
746    
747           7.  The \C escape sequence, which (in the standard algorithm) matches a
748           single byte, even in UTF-8 mode, is not supported because the  alterna-
749           tive  algorithm  moves  through  the  subject string one character at a
750           time, for all active paths through the tree.
751    
752           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
753           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
754           negative assertion.
755    
756    
757    ADVANTAGES OF THE ALTERNATIVE ALGORITHM
758    
759           Using the alternative matching algorithm provides the following  advan-
760           tages:
761    
762           1. All possible matches (at a single point in the subject) are automat-
763           ically found, and in particular, the longest match is  found.  To  find
764           more than one match using the standard algorithm, you have to do kludgy
765           things with callouts.
766    
767           2. Because the alternative algorithm  scans  the  subject  string  just
768           once,  and  never  needs to backtrack, it is possible to pass very long
769           subject strings to the matching function in  several  pieces,  checking
770           for partial matching each time.
771    
772    
773    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
774    
775           The alternative algorithm suffers from a number of disadvantages:
776    
777           1.  It  is  substantially  slower  than the standard algorithm. This is
778           partly because it has to search for all possible matches, but  is  also
779           because it is less susceptible to optimization.
780    
781           2. Capturing parentheses and back references are not supported.
782    
783           3. Although atomic groups are supported, their use does not provide the
784           performance advantage that it does for the standard algorithm.
785    
786    
787    AUTHOR
788    
789           Philip Hazel
790           University Computing Service
791           Cambridge CB2 3QH, England.
792    
793    
794    REVISION
795    
796           Last updated: 05 September 2009
797           Copyright (c) 1997-2009 University of Cambridge.
798    ------------------------------------------------------------------------------
799    
800    
801    PCREAPI(3)                                                          PCREAPI(3)
802    
803    
804  NAME  NAME
805         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
806    
807  SYNOPSIS OF PCRE API  
808    PCRE NATIVE API
809    
810         #include <pcre.h>         #include <pcre.h>
811    
# Line 335  SYNOPSIS OF PCRE API Line 813  SYNOPSIS OF PCRE API
813              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
814              const unsigned char *tableptr);              const unsigned char *tableptr);
815    
816           pcre *pcre_compile2(const char *pattern, int options,
817                int *errorcodeptr,
818                const char **errptr, int *erroffset,
819                const unsigned char *tableptr);
820    
821         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
822              const char **errptr);              const char **errptr);
823    
# Line 342  SYNOPSIS OF PCRE API Line 825  SYNOPSIS OF PCRE API
825              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
826              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
827    
828           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
829                const char *subject, int length, int startoffset,
830                int options, int *ovector, int ovecsize,
831                int *workspace, int wscount);
832    
833         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
834              const char *subject, int *ovector,              const char *subject, int *ovector,
835              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 359  SYNOPSIS OF PCRE API Line 847  SYNOPSIS OF PCRE API
847         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
848              const char *name);              const char *name);
849    
850           int pcre_get_stringtable_entries(const pcre *code,
851                const char *name, char **first, char **last);
852    
853         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
854              int stringcount, int stringnumber,              int stringcount, int stringnumber,
855              const char **stringptr);              const char **stringptr);
# Line 377  SYNOPSIS OF PCRE API Line 868  SYNOPSIS OF PCRE API
868    
869         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
870    
871           int pcre_refcount(pcre *code, int adjust);
872    
873         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
874    
875         char *pcre_version(void);         char *pcre_version(void);
# Line 392  SYNOPSIS OF PCRE API Line 885  SYNOPSIS OF PCRE API
885         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
886    
887    
888  PCRE API  PCRE API OVERVIEW
889    
890         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
891         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
892         expression API.  These are described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
893           Both of these APIs define a set of C function calls. A C++  wrapper  is
894         The  native  API  function  prototypes  are  defined in the header file         distributed with PCRE. It is documented in the pcrecpp page.
895         pcre.h, and on Unix systems the library itself is called libpcre.a,  so  
896         can be accessed by adding -lpcre to the command for linking an applica-         The  native  API  C  function prototypes are defined in the header file
897         tion which calls it. The header file defines the macros PCRE_MAJOR  and         pcre.h, and on Unix systems the library itself is called  libpcre.   It
898         PCRE_MINOR  to  contain  the  major  and  minor release numbers for the         can normally be accessed by adding -lpcre to the command for linking an
899         library. Applications can use these to include  support  for  different         application  that  uses  PCRE.  The  header  file  defines  the  macros
900         releases.         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
901           bers for the library.  Applications can use these  to  include  support
902         The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used         for different releases of PCRE.
903         for compiling and matching regular expressions. A sample  program  that  
904         demonstrates  the simplest way of using them is given in the file pcre-         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
905         demo.c. The pcresample documentation describes how to run it.         pcre_exec() are used for compiling and matching regular expressions  in
906           a  Perl-compatible  manner. A sample program that demonstrates the sim-
907         There are convenience functions for extracting captured substrings from         plest way of using them is provided in the file  called  pcredemo.c  in
908         a matched subject string. They are:         the PCRE source distribution. A listing of this program is given in the
909           pcredemo documentation, and the pcresample documentation describes  how
910           to compile and run it.
911    
912           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
913           ble, is also provided. This uses a different algorithm for  the  match-
914           ing.  The  alternative algorithm finds all possible matches (at a given
915           point in the subject), and scans the subject just  once  (unless  there
916           are  lookbehind  assertions).  However,  this algorithm does not return
917           captured substrings. A description of the two matching  algorithms  and
918           their  advantages  and disadvantages is given in the pcrematching docu-
919           mentation.
920    
921           In addition to the main compiling and  matching  functions,  there  are
922           convenience functions for extracting captured substrings from a subject
923           string that is matched by pcre_exec(). They are:
924    
925           pcre_copy_substring()           pcre_copy_substring()
926           pcre_copy_named_substring()           pcre_copy_named_substring()
927           pcre_get_substring()           pcre_get_substring()
928           pcre_get_named_substring()           pcre_get_named_substring()
929           pcre_get_substring_list()           pcre_get_substring_list()
930             pcre_get_stringnumber()
931             pcre_get_stringtable_entries()
932    
933         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
934         to free the memory used for extracted strings.         to free the memory used for extracted strings.
935    
936         The function pcre_maketables() is used (optionally) to build a  set  of         The  function  pcre_maketables()  is  used  to build a set of character
937         character tables in the current locale for passing to pcre_compile().         tables  in  the  current  locale   for   passing   to   pcre_compile(),
938           pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
939         The  function  pcre_fullinfo()  is used to find out information about a         provided for specialist use.  Most  commonly,  no  special  tables  are
940         compiled pattern; pcre_info() is an obsolete version which returns only         passed,  in  which case internal tables that are generated when PCRE is
941         some  of  the available information, but is retained for backwards com-         built are used.
942         patibility.  The function pcre_version() returns a pointer to a  string  
943           The function pcre_fullinfo() is used to find out  information  about  a
944           compiled  pattern; pcre_info() is an obsolete version that returns only
945           some of the available information, but is retained for  backwards  com-
946           patibility.   The function pcre_version() returns a pointer to a string
947         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
948    
949         The  global  variables  pcre_malloc and pcre_free initially contain the         The function pcre_refcount() maintains a  reference  count  in  a  data
950         entry points of the standard  malloc()  and  free()  functions  respec-         block  containing  a compiled pattern. This is provided for the benefit
951           of object-oriented applications.
952    
953           The global variables pcre_malloc and pcre_free  initially  contain  the
954           entry  points  of  the  standard malloc() and free() functions, respec-
955         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
956         so a calling program can replace them if it  wishes  to  intercept  the         so  a  calling  program  can replace them if it wishes to intercept the
957         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
958    
959         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
960         indirections to memory management functions.  These  special  functions         indirections  to  memory  management functions. These special functions
961         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
962         data, instead of recursive function calls. This is a  non-standard  way         data, instead of recursive function calls, when running the pcre_exec()
963         of  building  PCRE,  for  use in environments that have limited stacks.         function. See the pcrebuild documentation for  details  of  how  to  do
964         Because of the greater use of memory management, it runs  more  slowly.         this.  It  is  a non-standard way of building PCRE, for use in environ-
965         Separate  functions  are provided so that special-purpose external code         ments that have limited stacks. Because of the greater  use  of  memory
966         can be used for this case. When used, these functions are always called         management,  it  runs  more  slowly. Separate functions are provided so
967         in  a  stack-like  manner  (last obtained, first freed), and always for         that special-purpose external code can be  used  for  this  case.  When
968         memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
969           obtained, first freed), and always for memory blocks of the same  size.
970           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
971           mentation.
972    
973         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
974         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 455  PCRE API Line 976  PCRE API
976         pcrecallout documentation.         pcrecallout documentation.
977    
978    
979    NEWLINES
980    
981           PCRE  supports five different conventions for indicating line breaks in
982           strings: a single CR (carriage return) character, a  single  LF  (line-
983           feed) character, the two-character sequence CRLF, any of the three pre-
984           ceding, or any Unicode newline sequence. The Unicode newline  sequences
985           are  the  three just mentioned, plus the single characters VT (vertical
986           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
987           separator, U+2028), and PS (paragraph separator, U+2029).
988    
989           Each  of  the first three conventions is used by at least one operating
990           system as its standard newline sequence. When PCRE is built, a  default
991           can  be  specified.  The default default is LF, which is the Unix stan-
992           dard. When PCRE is run, the default can be overridden,  either  when  a
993           pattern is compiled, or when it is matched.
994    
995           At compile time, the newline convention can be specified by the options
996           argument of pcre_compile(), or it can be specified by special  text  at
997           the start of the pattern itself; this overrides any other settings. See
998           the pcrepattern page for details of the special character sequences.
999    
1000           In the PCRE documentation the word "newline" is used to mean "the char-
1001           acter  or pair of characters that indicate a line break". The choice of
1002           newline convention affects the handling of  the  dot,  circumflex,  and
1003           dollar metacharacters, the handling of #-comments in /x mode, and, when
1004           CRLF is a recognized line ending sequence, the match position  advance-
1005           ment for a non-anchored pattern. There is more detail about this in the
1006           section on pcre_exec() options below.
1007    
1008           The choice of newline convention does not affect the interpretation  of
1009           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1010           which is controlled in a similar way, but by separate options.
1011    
1012    
1013  MULTITHREADING  MULTITHREADING
1014    
1015         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1016         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1017         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
1018         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 467  MULTITHREADING Line 1022  MULTITHREADING
1022         at once.         at once.
1023    
1024    
1025    SAVING PRECOMPILED PATTERNS FOR LATER USE
1026    
1027           The compiled form of a regular expression can be saved and re-used at a
1028           later time, possibly by a different program, and even on a  host  other
1029           than  the  one  on  which  it  was  compiled.  Details are given in the
1030           pcreprecompile documentation. However, compiling a  regular  expression
1031           with  one version of PCRE for use with a different version is not guar-
1032           anteed to work and may cause crashes.
1033    
1034    
1035  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
1036    
1037         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1038    
1039         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
1040         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1041         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
1042         tures.         tures.
1043    
1044         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
1045         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1046         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
1047         available:         available:
1048    
1049           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1050    
1051         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
1052         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1053    
1054             PCRE_CONFIG_UNICODE_PROPERTIES
1055    
1056           The  output  is  an  integer  that is set to one if support for Unicode
1057           character properties is available; otherwise it is set to zero.
1058    
1059           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1060    
1061         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
1062         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
1063         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,
1064         operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1065           are returned in EBCDIC environments. The default should normally corre-
1066           spond to the standard sequence for your operating system.
1067    
1068             PCRE_CONFIG_BSR
1069    
1070           The output is an integer whose value indicates what character sequences
1071           the \R escape sequence matches by default. A value of 0 means  that  \R
1072           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1073           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1074           tern is compiled or matched.
1075    
1076           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1077    
# Line 510  CHECKING BUILD-TIME OPTIONS Line 1090  CHECKING BUILD-TIME OPTIONS
1090    
1091           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1092    
1093         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-
1094         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1095         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1096    
1097             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1098    
1099           The output is a long integer that gives the default limit for the depth
1100           of   recursion  when  calling  the  internal  matching  function  in  a
1101           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1102           below.
1103    
1104           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1105    
1106         The output is an integer that is set to one if  internal  recursion  is         The  output is an integer that is set to one if internal recursion when
1107         implemented  by recursive function calls that use the stack to remember         running pcre_exec() is implemented by recursive function calls that use
1108         their state. This is the usual way that PCRE is compiled. The output is         the  stack  to remember their state. This is the usual way that PCRE is
1109         zero  if PCRE was compiled to use blocks of data on the heap instead of         compiled. The output is zero if PCRE was compiled to use blocks of data
1110         recursive  function  calls.  In  this   case,   pcre_stack_malloc   and         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1111         pcre_stack_free  are  called  to manage memory blocks on the heap, thus         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1112         avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1113    
1114    
1115  COMPILING A PATTERN  COMPILING A PATTERN
# Line 531  COMPILING A PATTERN Line 1118  COMPILING A PATTERN
1118              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
1119              const unsigned char *tableptr);              const unsigned char *tableptr);
1120    
1121           pcre *pcre_compile2(const char *pattern, int options,
1122                int *errorcodeptr,
1123                const char **errptr, int *erroffset,
1124                const unsigned char *tableptr);
1125    
1126         The function pcre_compile() is called to  compile  a  pattern  into  an         Either of the functions pcre_compile() or pcre_compile2() can be called
1127         internal  form.  The pattern is a C string terminated by a binary zero,         to compile a pattern into an internal form. The only difference between
1128         and is passed in the argument pattern. A pointer to a single  block  of         the  two interfaces is that pcre_compile2() has an additional argument,
1129         memory  that is obtained via pcre_malloc is returned. This contains the         errorcodeptr, via which a numerical error code can be returned.
1130         compiled code and related data.  The  pcre  type  is  defined  for  the  
1131         returned  block;  this  is a typedef for a structure whose contents are         The pattern is a C string terminated by a binary zero, and is passed in
1132         not externally defined. It is up to the caller to free the memory  when         the  pattern  argument.  A  pointer to a single block of memory that is
1133         it is no longer required.         obtained via pcre_malloc is returned. This contains the  compiled  code
1134           and related data. The pcre type is defined for the returned block; this
1135           is a typedef for a structure whose contents are not externally defined.
1136           It is up to the caller to free the memory (via pcre_free) when it is no
1137           longer required.
1138    
1139         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
1140         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
1141         fully relocatable, because it contains a copy of the tableptr argument,         fully relocatable, because it may contain a copy of the tableptr  argu-
1142         which is an address (see below).         ment, which is an address (see below).
1143    
1144         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1145         tion.  It  should  be  zero  if  no  options  are required. Some of the         pilation. It should be zero if no options are required.  The  available
1146         options, in particular, those that are compatible with Perl,  can  also         options  are  described  below. Some of them (in particular, those that
1147         be  set and unset from within the pattern (see the detailed description         are compatible with Perl, but also some others) can  also  be  set  and
1148         of regular expressions in the  pcrepattern  documentation).  For  these         unset  from  within  the  pattern  (see the detailed description in the
1149         options,  the  contents of the options argument specifies their initial         pcrepattern documentation). For those options that can be different  in
1150         settings at the start of compilation and execution.  The  PCRE_ANCHORED         different  parts  of  the pattern, the contents of the options argument
1151         option can be set at the time of matching as well as at compile time.         specifies their initial settings at the start of compilation and execu-
1152           tion.  The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the
1153           time of matching as well as at compile time.
1154    
1155         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1156         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1157         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-
1158         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
1159         the  error  was  discovered  is  placed  in  the variable pointed to by         try to free it. The offset from the start of the pattern to the charac-
1160         erroffset, which must not be NULL. If it  is,  an  immediate  error  is         ter where the error was discovered is placed in the variable pointed to
1161           by erroffset, which must not be NULL. If it is, an immediate  error  is
1162         given.         given.
1163    
1164         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1165         character tables which are built when it is compiled, using the default         codeptr argument is not NULL, a non-zero error code number is  returned
1166         C  locale.  Otherwise,  tableptr  must  be  the  result  of  a  call to         via  this argument in the event of an error. This is in addition to the
1167         pcre_maketables(). See the section on locale support below.         textual error message. Error codes and messages are listed below.
1168    
1169           If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1170           character  tables  that  are  built  when  PCRE  is compiled, using the
1171           default C locale. Otherwise, tableptr must be an address  that  is  the
1172           result  of  a  call to pcre_maketables(). This value is stored with the
1173           compiled pattern, and used again by pcre_exec(), unless  another  table
1174           pointer is passed to it. For more discussion, see the section on locale
1175           support below.
1176    
1177         This code fragment shows a typical straightforward  call  to  pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1178         pile():         pile():
# Line 581  COMPILING A PATTERN Line 1187  COMPILING A PATTERN
1187             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1188             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1189    
1190         The following option bits are defined:         The  following  names  for option bits are defined in the pcre.h header
1191           file:
1192    
1193           PCRE_ANCHORED           PCRE_ANCHORED
1194    
1195         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
1196         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
1197         which is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1198         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1199         only way to do it in Perl.         only way to do it in Perl.
1200    
1201             PCRE_AUTO_CALLOUT
1202    
1203           If this bit is set, pcre_compile() automatically inserts callout items,
1204           all  with  number  255, before each pattern item. For discussion of the
1205           callout facility, see the pcrecallout documentation.
1206    
1207             PCRE_BSR_ANYCRLF
1208             PCRE_BSR_UNICODE
1209    
1210           These options (which are mutually exclusive) control what the \R escape
1211           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1212           or to match any Unicode newline sequence. The default is specified when
1213           PCRE is built. It can be overridden from within the pattern, or by set-
1214           ting an option when a compiled pattern is matched.
1215    
1216           PCRE_CASELESS           PCRE_CASELESS
1217    
1218         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
1219         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
1220         changed within a pattern by a (?i) option setting.         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1221           always  understands the concept of case for characters whose values are
1222           less than 128, so caseless matching is always possible. For  characters
1223           with  higher  values,  the concept of case is supported if PCRE is com-
1224           piled with Unicode property support, but not otherwise. If you want  to
1225           use  caseless  matching  for  characters 128 and above, you must ensure
1226           that PCRE is compiled with Unicode property support  as  well  as  with
1227           UTF-8 support.
1228    
1229           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1230    
1231         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
1232         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
1233         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
1234         not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1235         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
1236         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1237    
1238           PCRE_DOTALL           PCRE_DOTALL
1239    
1240         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-
1241         acters,  including  newlines.  Without  it, newlines are excluded. This         acters,  including  those that indicate newline. Without it, a dot does
1242         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
1243         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
1244         always matches a newline character, independent of the setting of  this         by a (?s) option setting. A negative class such as [^a] always  matches
1245         option.         newline characters, independent of the setting of this option.
1246    
1247             PCRE_DUPNAMES
1248    
1249           If  this  bit is set, names used to identify capturing subpatterns need
1250           not be unique. This can be helpful for certain types of pattern when it
1251           is  known  that  only  one instance of the named subpattern can ever be
1252           matched. There are more details of named subpatterns  below;  see  also
1253           the pcrepattern documentation.
1254    
1255           PCRE_EXTENDED           PCRE_EXTENDED
1256    
1257         If  this  bit  is  set,  whitespace  data characters in the pattern are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1258         totally ignored except  when  escaped  or  inside  a  character  class.         totally ignored except when escaped or inside a character class. White-
1259         Whitespace  does  not  include the VT character (code 11). In addition,         space does not include the VT character (code 11). In addition, charac-
1260         characters between an unescaped # outside a  character  class  and  the         ters between an unescaped # outside a character class and the next new-
1261         next newline character, inclusive, are also ignored. This is equivalent         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1262         to Perl's /x option, and it can be changed within a pattern by  a  (?x)         option, and it can be changed within a pattern by a  (?x)  option  set-
1263         option setting.         ting.
1264    
1265         This  option  makes  it possible to include comments inside complicated         This  option  makes  it possible to include comments inside complicated
1266         patterns.  Note, however, that this applies only  to  data  characters.         patterns.  Note, however, that this applies only  to  data  characters.
# Line 639  COMPILING A PATTERN Line 1276  COMPILING A PATTERN
1276         letter that has no special meaning  causes  an  error,  thus  reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1277         these  combinations  for  future  expansion.  By default, as in Perl, a         these  combinations  for  future  expansion.  By default, as in Perl, a
1278         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
1279         literal.  There  are  at  present  no other features controlled by this         literal.  (Perl can, however, be persuaded to give a warning for this.)
1280         option. It can also be set by a (?X) option setting within a pattern.         There are at present no other features controlled by  this  option.  It
1281           can also be set by a (?X) option setting within a pattern.
1282    
1283             PCRE_FIRSTLINE
1284    
1285           If  this  option  is  set,  an  unanchored pattern is required to match
1286           before or at the first  newline  in  the  subject  string,  though  the
1287           matched text may continue over the newline.
1288    
1289             PCRE_JAVASCRIPT_COMPAT
1290    
1291           If this option is set, PCRE's behaviour is changed in some ways so that
1292           it is compatible with JavaScript rather than Perl. The changes  are  as
1293           follows:
1294    
1295           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1296           error, because this is illegal in JavaScript (by default it is  treated
1297           as a data character). Thus, the pattern AB]CD becomes illegal when this
1298           option is set.
1299    
1300           (2) At run time, a back reference to an unset subpattern group  matches
1301           an  empty  string (by default this causes the current matching alterna-
1302           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1303           set  (assuming  it can find an "a" in the subject), whereas it fails by
1304           default, for Perl compatibility.
1305    
1306           PCRE_MULTILINE           PCRE_MULTILINE
1307    
1308         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
1309         "line"  of  characters (even if it actually contains several newlines).         line  of characters (even if it actually contains newlines). The "start
1310         The "start of line" metacharacter (^) matches only at the start of  the         of line" metacharacter (^) matches only at the  start  of  the  string,
1311         string,  while  the "end of line" metacharacter ($) matches only at the         while  the  "end  of line" metacharacter ($) matches only at the end of
1312         end of the string, or before a terminating  newline  (unless  PCRE_DOL-         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1313         LAR_ENDONLY is set). This is the same as Perl.         is set). This is the same as Perl.
1314    
1315         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"
1316         constructs match immediately following or immediately before  any  new-         constructs match immediately following or immediately  before  internal
1317         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
1318         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
1319         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-
1320         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,
1321         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1322    
1323             PCRE_NEWLINE_CR
1324             PCRE_NEWLINE_LF
1325             PCRE_NEWLINE_CRLF
1326             PCRE_NEWLINE_ANYCRLF
1327             PCRE_NEWLINE_ANY
1328    
1329           These  options  override the default newline definition that was chosen
1330           when PCRE was built. Setting the first or the second specifies  that  a
1331           newline  is  indicated  by a single character (CR or LF, respectively).
1332           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1333           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1334           that any of the three preceding sequences should be recognized. Setting
1335           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1336           recognized. The Unicode newline sequences are the three just mentioned,
1337           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1338           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1339           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1340           UTF-8 mode.
1341    
1342           The newline setting in the  options  word  uses  three  bits  that  are
1343           treated as a number, giving eight possibilities. Currently only six are
1344           used (default plus the five values above). This means that if  you  set
1345           more  than one newline option, the combination may or may not be sensi-
1346           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1347           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1348           cause an error.
1349    
1350           The only time that a line break is specially recognized when  compiling
1351           a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
1352           character class is encountered. This indicates  a  comment  that  lasts
1353           until  after the next line break sequence. In other circumstances, line
1354           break  sequences  are  treated  as  literal  data,   except   that   in
1355           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1356           and are therefore ignored.
1357    
1358           The newline option that is set at compile time becomes the default that
1359           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1360    
1361           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1362    
1363         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 678  COMPILING A PATTERN Line 1377  COMPILING A PATTERN
1377    
1378         This option causes PCRE to regard both the pattern and the  subject  as         This option causes PCRE to regard both the pattern and the  subject  as
1379         strings  of  UTF-8 characters instead of single-byte character strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1380         However, it is available only if PCRE has been built to  include  UTF-8         However, it is available only when PCRE is built to include UTF-8  sup-
1381         support.  If  not, the use of this option provokes an error. Details of         port.  If not, the use of this option provokes an error. Details of how
1382         how this option changes the behaviour of PCRE are given in the  section         this option changes the behaviour of PCRE are given in the  section  on
1383         on UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1384    
1385           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1386    
1387         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
1388         automatically checked. If an invalid UTF-8 sequence of bytes is  found,         automatically checked. There is a  discussion  about  the  validity  of
1389         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
1390         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
1391         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-
1392         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
1393         your  program  to  crash.  Note that there is a similar option for sup-         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1394         pressing the checking of subject strings passed to pcre_exec().         undefined. It may cause your program to crash. Note  that  this  option
1395           can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1396           UTF-8 validity checking of subject strings.
1397    
1398    
1399    COMPILATION ERROR CODES
1400    
1401           The following table lists the error  codes  than  may  be  returned  by
1402           pcre_compile2(),  along with the error messages that may be returned by
1403           both compiling functions. As PCRE has developed, some error codes  have
1404           fallen out of use. To avoid confusion, they have not been re-used.
1405    
1406              0  no error
1407              1  \ at end of pattern
1408              2  \c at end of pattern
1409              3  unrecognized character follows \
1410              4  numbers out of order in {} quantifier
1411              5  number too big in {} quantifier
1412              6  missing terminating ] for character class
1413              7  invalid escape sequence in character class
1414              8  range out of order in character class
1415              9  nothing to repeat
1416             10  [this code is not in use]
1417             11  internal error: unexpected repeat
1418             12  unrecognized character after (? or (?-
1419             13  POSIX named classes are supported only within a class
1420             14  missing )
1421             15  reference to non-existent subpattern
1422             16  erroffset passed as NULL
1423             17  unknown option bit(s) set
1424             18  missing ) after comment
1425             19  [this code is not in use]
1426             20  regular expression is too large
1427             21  failed to get memory
1428             22  unmatched parentheses
1429             23  internal error: code overflow
1430             24  unrecognized character after (?<
1431             25  lookbehind assertion is not fixed length
1432             26  malformed number or name after (?(
1433             27  conditional group contains more than two branches
1434             28  assertion expected after (?(
1435             29  (?R or (?[+-]digits must be followed by )
1436             30  unknown POSIX class name
1437             31  POSIX collating elements are not supported
1438             32  this version of PCRE is not compiled with PCRE_UTF8 support
1439             33  [this code is not in use]
1440             34  character value in \x{...} sequence is too large
1441             35  invalid condition (?(0)
1442             36  \C not allowed in lookbehind assertion
1443             37  PCRE does not support \L, \l, \N, \U, or \u
1444             38  number after (?C is > 255
1445             39  closing ) for (?C expected
1446             40  recursive call could loop indefinitely
1447             41  unrecognized character after (?P
1448             42  syntax error in subpattern name (missing terminator)
1449             43  two named subpatterns have the same name
1450             44  invalid UTF-8 string
1451             45  support for \P, \p, and \X has not been compiled
1452             46  malformed \P or \p sequence
1453             47  unknown property name after \P or \p
1454             48  subpattern name is too long (maximum 32 characters)
1455             49  too many named subpatterns (maximum 10000)
1456             50  [this code is not in use]
1457             51  octal value is greater than \377 (not in UTF-8 mode)
1458             52  internal error: overran compiling workspace
1459             53   internal  error:  previously-checked  referenced  subpattern not
1460           found
1461             54  DEFINE group contains more than one branch
1462             55  repeating a DEFINE group is not allowed
1463             56  inconsistent NEWLINE options
1464             57  \g is not followed by a braced, angle-bracketed, or quoted
1465                   name/number or by a plain number
1466             58  a numbered reference must not be zero
1467             59  (*VERB) with an argument is not supported
1468             60  (*VERB) not recognized
1469             61  number is too big
1470             62  subpattern name expected
1471             63  digit expected after (?+
1472             64  ] is an invalid data character in JavaScript compatibility mode
1473    
1474           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1475           values may be used if the limits were changed when PCRE was built.
1476    
1477    
1478  STUDYING A PATTERN  STUDYING A PATTERN
1479    
1480         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1481              const char **errptr);              const char **errptr);
1482    
1483         When a pattern is going to be used several times, it is worth  spending         If  a  compiled  pattern is going to be used several times, it is worth
1484         more  time  analyzing it in order to speed up the time taken for match-         spending more time analyzing it in order to speed up the time taken for
1485         ing. The function pcre_study() takes a pointer to a compiled pattern as         matching.  The function pcre_study() takes a pointer to a compiled pat-
1486         its first argument. If studing the pattern produces additional informa-         tern as its first argument. If studying the pattern produces additional
1487         tion that will help speed up matching, pcre_study() returns  a  pointer         information  that  will  help speed up matching, pcre_study() returns a
1488         to  a  pcre_extra  block,  in  which the study_data field points to the         pointer to a pcre_extra block, in which the study_data field points  to
1489         results of the study.         the results of the study.
1490    
1491         The returned value from  a  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1492         pcre_exec().  However,  the pcre_extra block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1493         that can be set by the caller before the block  is  passed;  these  are         that  can  be  set  by the caller before the block is passed; these are
1494         described  below.  If  studying  the pattern does not produce any addi-         described below in the section on matching a pattern.
1495         tional information, pcre_study() returns NULL. In that circumstance, if  
1496         the  calling  program  wants  to  pass  some  of  the  other  fields to         If studying the pattern does not  produce  any  additional  information
1497         pcre_exec(), it must set up its own pcre_extra block.         pcre_study() returns NULL. In that circumstance, if the calling program
1498           wants to pass any of the other fields to pcre_exec(), it  must  set  up
1499         The second argument contains option bits. At present,  no  options  are         its own pcre_extra block.
1500         defined for pcre_study(), and this argument should always be zero.  
1501           The  second  argument of pcre_study() contains option bits. At present,
1502         The  third argument for pcre_study() is a pointer for an error message.         no options are defined, and this argument should always be zero.
1503         If studying succeeds (even if no data is  returned),  the  variable  it  
1504         points  to  is set to NULL. Otherwise it points to a textual error mes-         The third argument for pcre_study() is a pointer for an error  message.
1505         sage. You should therefore test the error pointer for NULL after  call-         If  studying  succeeds  (even  if no data is returned), the variable it
1506         ing pcre_study(), to be sure that it has run successfully.         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1507           error message. This is a static string that is part of the library. You
1508           must not try to free it. You should test the  error  pointer  for  NULL
1509           after calling pcre_study(), to be sure that it has run successfully.
1510    
1511         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1512    
# Line 736  STUDYING A PATTERN Line 1518  STUDYING A PATTERN
1518    
1519         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1520         that do not have a single fixed starting character. A bitmap of  possi-         that do not have a single fixed starting character. A bitmap of  possi-
1521         ble starting characters is created.         ble starting bytes is created.
1522    
1523    
1524  LOCALE SUPPORT  LOCALE SUPPORT
1525    
1526         PCRE  handles  caseless matching, and determines whether characters are         PCRE  handles  caseless matching, and determines whether characters are
1527         letters, digits, or whatever, by reference to a  set  of  tables.  When         letters, digits, or whatever, by reference to a set of tables,  indexed
1528         running  in UTF-8 mode, this applies only to characters with codes less         by  character  value.  When running in UTF-8 mode, this applies only to
1529         than 256. The library contains a default set of tables that is  created         characters with codes less than 128. Higher-valued  codes  never  match
1530         in  the  default  C locale when PCRE is compiled. This is used when the         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1531         final argument of pcre_compile() is NULL, and is  sufficient  for  many         with Unicode character property support. The use of locales  with  Uni-
1532         applications.         code  is discouraged. If you are handling characters with codes greater
1533           than 128, you should either use UTF-8 and Unicode, or use locales,  but
1534         An alternative set of tables can, however, be supplied. Such tables are         not try to mix the two.
1535         built by calling the pcre_maketables() function,  which  has  no  argu-  
1536         ments,  in  the  relevant  locale.  The  result  can  then be passed to         PCRE  contains  an  internal set of tables that are used when the final
1537         pcre_compile() as often as necessary. For example,  to  build  and  use         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1538         tables that are appropriate for the French locale (where accented char-         applications.  Normally, the internal tables recognize only ASCII char-
1539         acters with codes greater than 128 are treated as letters), the follow-         acters. However, when PCRE is built, it is possible to cause the inter-
1540         ing code could be used:         nal tables to be rebuilt in the default "C" locale of the local system,
1541           which may cause them to be different.
1542    
1543           The internal tables can always be overridden by tables supplied by  the
1544           application that calls PCRE. These may be created in a different locale
1545           from the default. As more and more applications change  to  using  Uni-
1546           code, the need for this locale support is expected to die away.
1547    
1548           External  tables  are  built by calling the pcre_maketables() function,
1549           which has no arguments, in the relevant locale. The result can then  be
1550           passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1551           example, to build and use tables that are appropriate  for  the  French
1552           locale  (where  accented  characters  with  values greater than 128 are
1553           treated as letters), the following code could be used:
1554    
1555           setlocale(LC_CTYPE, "fr");           setlocale(LC_CTYPE, "fr_FR");
1556           tables = pcre_maketables();           tables = pcre_maketables();
1557           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1558    
1559         The  tables  are  built in memory that is obtained via pcre_malloc. The         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1560         pointer that is passed to pcre_compile is saved with the compiled  pat-         if you are using Windows, the name for the French locale is "french".
1561         tern, and the same tables are used via this pointer by pcre_study() and  
1562         pcre_exec(). Thus, for any single pattern,  compilation,  studying  and         When  pcre_maketables()  runs,  the  tables are built in memory that is
1563         matching  all  happen in the same locale, but different patterns can be         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1564         compiled in different locales. It is  the  caller's  responsibility  to         that  the memory containing the tables remains available for as long as
1565         ensure  that  the memory containing the tables remains available for as         it is needed.
1566         long as it is needed.  
1567           The pointer that is passed to pcre_compile() is saved with the compiled
1568           pattern,  and the same tables are used via this pointer by pcre_study()
1569           and normally also by pcre_exec(). Thus, by default, for any single pat-
1570           tern, compilation, studying and matching all happen in the same locale,
1571           but different patterns can be compiled in different locales.
1572    
1573           It is possible to pass a table pointer or NULL (indicating the  use  of
1574           the  internal  tables)  to  pcre_exec(). Although not intended for this
1575           purpose, this facility could be used to match a pattern in a  different
1576           locale from the one in which it was compiled. Passing table pointers at
1577           run time is discussed below in the section on matching a pattern.
1578    
1579    
1580  INFORMATION ABOUT A PATTERN  INFORMATION ABOUT A PATTERN
# Line 792  INFORMATION ABOUT A PATTERN Line 1598  INFORMATION ABOUT A PATTERN
1598           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1599           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1600    
1601         Here  is a typical call of pcre_fullinfo(), to obtain the length of the         The  "magic  number" is placed at the start of each compiled pattern as
1602         compiled pattern:         an simple check against passing an arbitrary memory pointer. Here is  a
1603           typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1604           pattern:
1605    
1606           int rc;           int rc;
1607           unsigned long int length;           size_t length;
1608           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1609             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1610             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
# Line 817  INFORMATION ABOUT A PATTERN Line 1625  INFORMATION ABOUT A PATTERN
1625         Return  the  number of capturing subpatterns in the pattern. The fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1626         argument should point to an int variable.         argument should point to an int variable.
1627    
1628             PCRE_INFO_DEFAULT_TABLES
1629    
1630           Return a pointer to the internal default character tables within  PCRE.
1631           The  fourth  argument should point to an unsigned char * variable. This
1632           information call is provided for internal use by the pcre_study() func-
1633           tion.  External  callers  can  cause PCRE to use its internal tables by
1634           passing a NULL table pointer.
1635    
1636           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1637    
1638         Return information about the first byte of any matched  string,  for  a         Return information about the first byte of any matched  string,  for  a
1639         non-anchored    pattern.    (This    option    used    to   be   called         non-anchored  pattern. The fourth argument should point to an int vari-
1640         PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1641         compatibility.)         is still recognized for backwards compatibility.)
1642    
1643         If  there  is  a  fixed  first  byte,  e.g.  from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1644         (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  
1645    
1646         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1647         branch starts with "^", or         branch starts with "^", or
1648    
1649         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1650         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1651    
1652         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1653         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1654         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1655    
1656           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1657    
1658         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1659         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1660         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1661         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1662         able.         able.
1663    
1664             PCRE_INFO_HASCRORLF
1665    
1666           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1667           characters,  otherwise  0.  The  fourth argument should point to an int
1668           variable. An explicit match is either a literal CR or LF character,  or
1669           \r or \n.
1670    
1671             PCRE_INFO_JCHANGED
1672    
1673           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1674           otherwise 0. The fourth argument should point to an int variable.  (?J)
1675           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1676    
1677           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1678    
1679         Return  the  value of the rightmost literal byte that must exist in any         Return  the  value of the rightmost literal byte that must exist in any
# Line 862  INFORMATION ABOUT A PATTERN Line 1690  INFORMATION ABOUT A PATTERN
1690    
1691         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1692         ses. The names are just an additional way of identifying the  parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1693         ses,  which still acquire a number. A caller that wants to extract data         ses, which still acquire numbers. Several convenience functions such as
1694         from a named subpattern must convert the name to a number in  order  to         pcre_get_named_substring() are provided for  extracting  captured  sub-
1695         access  the  correct  pointers  in  the  output  vector (described with         strings  by  name. It is also possible to extract the data directly, by
1696         pcre_exec() below). In order to do this, it must first use these  three         first converting the name to a number in order to  access  the  correct
1697         values to obtain the name-to-number mapping table for the pattern.         pointers in the output vector (described with pcre_exec() below). To do
1698           the conversion, you need  to  use  the  name-to-number  map,  which  is
1699           described by these three values.
1700    
1701         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
1702         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
# Line 876  INFORMATION ABOUT A PATTERN Line 1706  INFORMATION ABOUT A PATTERN
1706         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-
1707         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-
1708         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding name, zero terminated. The names are  in  alphabetical  order.
1709         For  example,  consider  the following pattern (assume PCRE_EXTENDED is         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1710         set, so white space - including newlines - is ignored):         theses numbers. For example, consider  the  following  pattern  (assume
1711           PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is
1712           ignored):
1713    
1714           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1715           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1716    
1717         There are four named subpatterns, so the table has  four  entries,  and         There are four named subpatterns, so the table has  four  entries,  and
1718         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,
1719         with non-printing bytes shows in hex, and undefined bytes shown as ??:         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1720           as ??:
1721    
1722           00 01 d  a  t  e  00 ??           00 01 d  a  t  e  00 ??
1723           00 05 d  a  y  00 ?? ??           00 05 d  a  y  00 ?? ??
1724           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1725           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1726    
1727         When writing code to extract data from named subpatterns, remember that         When  writing  code  to  extract  data from named subpatterns using the
1728         the length of each entry may be different for each compiled pattern.         name-to-number map, remember that the length of the entries  is  likely
1729           to be different for each compiled pattern.
1730    
1731             PCRE_INFO_OKPARTIAL
1732    
1733           Return  1  if  the  pattern  can  be  used  for  partial  matching with
1734           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1735           variable.  From  release  8.00,  this  always  returns  1,  because the
1736           restrictions that previously applied  to  partial  matching  have  been
1737           lifted.  The  pcrepartial documentation gives details of partial match-
1738           ing.
1739    
1740           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1741    
1742         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
1743         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1744         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1745         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1746           other words, they are the options that will be in force  when  matching
1747           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1748           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1749           and PCRE_EXTENDED.
1750    
1751         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
1752         alternatives begin with one of the following:         alternatives begin with one of the following:
1753    
1754           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 915  INFORMATION ABOUT A PATTERN Line 1762  INFORMATION ABOUT A PATTERN
1762    
1763           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1764    
1765         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1766         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1767         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1768         size_t variable.         size_t variable.
1769    
1770           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1771    
1772         Returns  the  size of the data block pointed to by the study_data field         Return the size of the data block pointed to by the study_data field in
1773         in a pcre_extra block. That is, it is the  value  that  was  passed  to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1774         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
1775         created by pcre_study(). The fourth argument should point to  a  size_t         created  by  pcre_study(). The fourth argument should point to a size_t
1776         variable.         variable.
1777    
1778    
# Line 933  OBSOLETE INFO FUNCTION Line 1780  OBSOLETE INFO FUNCTION
1780    
1781         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1782    
1783         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1784         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1785         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1786         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-
1787         lowing negative numbers:         lowing negative numbers:
1788    
1789           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1790           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1791    
1792         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
1793         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
1794         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1795    
1796         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1797         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
1798         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1799    
1800    
1801  MATCHING A PATTERN  REFERENCE COUNTS
1802    
1803           int pcre_refcount(pcre *code, int adjust);
1804    
1805           The pcre_refcount() function is used to maintain a reference  count  in
1806           the data block that contains a compiled pattern. It is provided for the
1807           benefit of applications that  operate  in  an  object-oriented  manner,
1808           where different parts of the application may be using the same compiled
1809           pattern, but you want to free the block when they are all done.
1810    
1811           When a pattern is compiled, the reference count field is initialized to
1812           zero.   It is changed only by calling this function, whose action is to
1813           add the adjust value (which may be positive or  negative)  to  it.  The
1814           yield of the function is the new value. However, the value of the count
1815           is constrained to lie between 0 and 65535, inclusive. If the new  value
1816           is outside these limits, it is forced to the appropriate limit value.
1817    
1818           Except  when it is zero, the reference count is not correctly preserved
1819           if a pattern is compiled on one host and then  transferred  to  a  host
1820           whose byte-order is different. (This seems a highly unlikely scenario.)
1821    
1822    
1823    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1824    
1825         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1826              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1827              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1828    
1829         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
1830         pre-compiled pattern, which is passed in the code argument. If the pat-         compiled pattern, which is passed in the code argument. If the  pattern
1831         tern  has been studied, the result of the study should be passed in the         has been studied, the result of the study should be passed in the extra
1832         extra argument.         argument. This function is the main matching facility of  the  library,
1833           and it operates in a Perl-like manner. For specialist use there is also
1834           an alternative matching function, which is described below in the  sec-
1835           tion about the pcre_dfa_exec() function.
1836    
1837           In  most applications, the pattern will have been compiled (and option-
1838           ally studied) in the same process that calls pcre_exec().  However,  it
1839           is possible to save compiled patterns and study data, and then use them
1840           later in different processes, possibly even on different hosts.  For  a
1841           discussion about this, see the pcreprecompile documentation.
1842    
1843         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
1844    
# Line 973  MATCHING A PATTERN Line 1851  MATCHING A PATTERN
1851             11,             /* the length of the subject string */             11,             /* the length of the subject string */
1852             0,              /* start at offset 0 in the subject */             0,              /* start at offset 0 in the subject */
1853             0,              /* default options */             0,              /* default options */
1854             ovector,        /* vector for substring information */             ovector,        /* vector of integers for substring information */
1855             30);            /* number of elements in the vector */             30);            /* number of elements (NOT size in bytes) */
1856    
1857         If the extra argument is not NULL, it must point to a  pcre_extra  data     Extra data for pcre_exec()
1858         block.  The pcre_study() function returns such a block (when it doesn't  
1859         return NULL), but you can also create one for yourself, and pass  addi-         If  the  extra argument is not NULL, it must point to a pcre_extra data
1860         tional information in it. The fields in the block are as follows:         block. The pcre_study() function returns such a block (when it  doesn't
1861           return  NULL), but you can also create one for yourself, and pass addi-
1862           tional information in it. The pcre_extra block contains  the  following
1863           fields (not necessarily in this order):
1864    
1865           unsigned long int flags;           unsigned long int flags;
1866           void *study_data;           void *study_data;
1867           unsigned long int match_limit;           unsigned long int match_limit;
1868             unsigned long int match_limit_recursion;
1869           void *callout_data;           void *callout_data;
1870             const unsigned char *tables;
1871    
1872         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
1873         are set. The flag bits are:         are set. The flag bits are:
1874    
1875           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1876           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1877             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1878           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1879             PCRE_EXTRA_TABLES
1880    
1881         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
1882         the  pcre_extra  block  that is returned by pcre_study(), together with         the  pcre_extra  block  that is returned by pcre_study(), together with
1883         the appropriate flag bit. You should not set this yourself, but you can         the appropriate flag bit. You should not set this yourself, but you may
1884         add to the block by setting the other fields.         add  to  the  block by setting the other fields and their corresponding
1885           flag bits.
1886    
1887         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
1888         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
1889         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1890         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees.  The  classic  example  is  the  use of nested unlimited
1891         repeats. Internally, PCRE uses a function called match() which it calls         repeats.
1892         repeatedly (sometimes recursively). The limit is imposed on the  number  
1893         of  times  this function is called during a match, which has the effect         Internally, PCRE uses a function called match() which it calls  repeat-
1894         of limiting the amount of recursion  and  backtracking  that  can  take         edly  (sometimes  recursively). The limit set by match_limit is imposed
1895         place.  For  patterns that are not anchored, the count starts from zero         on the number of times this function is called during  a  match,  which
1896           has  the  effect  of  limiting the amount of backtracking that can take
1897           place. For patterns that are not anchored, the count restarts from zero
1898         for each position in the subject string.         for each position in the subject string.
1899    
1900         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
1901         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1902         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1903         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra    block    in    which    match_limit    is    set,     and
1904         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
1905         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1906    
1907         The  pcre_callout  field is used in conjunction with the "callout" fea-         The match_limit_recursion field is similar to match_limit, but  instead
1908         ture, which is described in the pcrecallout documentation.         of limiting the total number of times that match() is called, it limits
1909           the depth of recursion. The recursion depth is a  smaller  number  than
1910           the  total number of calls, because not all calls to match() are recur-
1911           sive.  This limit is of use only if it is set smaller than match_limit.
1912    
1913           Limiting the recursion depth limits the amount of  stack  that  can  be
1914           used, or, when PCRE has been compiled to use memory on the heap instead
1915           of the stack, the amount of heap memory that can be used.
1916    
1917           The default value for match_limit_recursion can be  set  when  PCRE  is
1918           built;  the  default  default  is  the  same  value  as the default for
1919           match_limit. You can override the default by suppling pcre_exec()  with
1920           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1921           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1922           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1923    
1924           The  callout_data  field is used in conjunction with the "callout" fea-
1925           ture, and is described in the pcrecallout documentation.
1926    
1927           The tables field  is  used  to  pass  a  character  tables  pointer  to
1928           pcre_exec();  this overrides the value that is stored with the compiled
1929           pattern. A non-NULL value is stored with the compiled pattern  only  if
1930           custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1931           ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
1932           PCRE's  internal  tables  to be used. This facility is helpful when re-
1933           using patterns that have been saved after compiling  with  an  external
1934           set  of  tables,  because  the  external tables might be at a different
1935           address when pcre_exec() is called. See the  pcreprecompile  documenta-
1936           tion for a discussion of saving compiled patterns for later use.
1937    
1938       Option bits for pcre_exec()
1939    
1940           The  unused  bits of the options argument for pcre_exec() must be zero.
1941           The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
1942           PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
1943           PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
1944           PCRE_PARTIAL_HARD.
1945    
1946         The PCRE_ANCHORED option can be passed in the options  argument,  whose           PCRE_ANCHORED
        unused  bits  must  be zero. This limits pcre_exec() to matching at the  
        first matching position.  However,  if  a  pattern  was  compiled  with  
        PCRE_ANCHORED,  or turned out to be anchored by virtue of its contents,  
        it cannot be made unachored at matching time.  
   
        When PCRE_UTF8 was set at compile time, the validity of the subject  as  
        a  UTF-8  string is automatically checked, and the value of startoffset  
        is also checked to ensure that it points to the start of a UTF-8  char-  
        acter.  If  an  invalid  UTF-8  sequence of bytes is found, pcre_exec()  
        returns  the  error  PCRE_ERROR_BADUTF8.  If  startoffset  contains  an  
        invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.  
1947    
1948         If  you  already  know that your subject is valid, and you want to skip         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1949         these   checks   for   performance   reasons,   you   can    set    the         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1950         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         turned  out to be anchored by virtue of its contents, it cannot be made
1951         do this for the second and subsequent calls to pcre_exec() if  you  are         unachored at matching time.
1952         making  repeated  calls  to  find  all  the matches in a single subject  
1953         string. However, you should be  sure  that  the  value  of  startoffset           PCRE_BSR_ANYCRLF
1954         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is           PCRE_BSR_UNICODE
1955         set, the effect of passing an invalid UTF-8 string as a subject,  or  a  
1956         value  of startoffset that does not point to the start of a UTF-8 char-         These options (which are mutually exclusive) control what the \R escape
1957         acter, is undefined. Your program may crash.         sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1958           or to match any Unicode newline sequence. These  options  override  the
1959           choice that was made or defaulted when the pattern was compiled.
1960    
1961             PCRE_NEWLINE_CR
1962             PCRE_NEWLINE_LF
1963             PCRE_NEWLINE_CRLF
1964             PCRE_NEWLINE_ANYCRLF
1965             PCRE_NEWLINE_ANY
1966    
1967           These  options  override  the  newline  definition  that  was chosen or
1968           defaulted when the pattern was compiled. For details, see the  descrip-
1969           tion  of  pcre_compile()  above.  During  matching,  the newline choice
1970           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1971           ters.  It may also alter the way the match position is advanced after a
1972           match failure for an unanchored pattern.
1973    
1974           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1975           set,  and a match attempt for an unanchored pattern fails when the cur-
1976           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1977           explicit  matches  for  CR  or  LF  characters,  the  match position is
1978           advanced by two characters instead of one, in other words, to after the
1979           CRLF.
1980    
1981           The above rule is a compromise that makes the most common cases work as
1982           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1983           option is not set), it does not match the string "\r\nA" because, after
1984           failing at the start, it skips both the CR and the LF before  retrying.
1985           However,  the  pattern  [\r\n]A does match that string, because it con-
1986           tains an explicit CR or LF reference, and so advances only by one char-
1987           acter after the first failure.
1988    
1989           An explicit match for CR of LF is either a literal appearance of one of
1990           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1991           matches  such  as [^X] do not count, nor does \s (which includes CR and
1992           LF in the characters that it matches).
1993    
1994         There are also three further options that can be set only  at  matching         Notwithstanding the above, anomalous effects may still occur when  CRLF
1995         time:         is a valid newline sequence and explicit \r or \n escapes appear in the
1996           pattern.
1997    
1998           PCRE_NOTBOL           PCRE_NOTBOL
1999    
2000         The  first  character  of the string is not the beginning of a line, so         This option specifies that first character of the subject string is not
2001         the circumflex metacharacter should not match before it.  Setting  this         the  beginning  of  a  line, so the circumflex metacharacter should not
2002         without  PCRE_MULTILINE  (at  compile  time) causes circumflex never to         match before it. Setting this without PCRE_MULTILINE (at compile  time)
2003         match.         causes  circumflex  never to match. This option affects only the behav-
2004           iour of the circumflex metacharacter. It does not affect \A.
2005    
2006           PCRE_NOTEOL           PCRE_NOTEOL
2007    
2008         The end of the string is not the end of a line, so the dollar metachar-         This option specifies that the end of the subject string is not the end
2009         acter  should  not  match  it  nor (except in multiline mode) a newline         of  a line, so the dollar metacharacter should not match it nor (except
2010         immediately before it. Setting this without PCRE_MULTILINE (at  compile         in multiline mode) a newline immediately before it. Setting this  with-
2011         time) causes dollar never to match.         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2012           option affects only the behaviour of the dollar metacharacter. It  does
2013           not affect \Z or \z.
2014    
2015           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2016    
# Line 1069  MATCHING A PATTERN Line 2021  MATCHING A PATTERN
2021    
2022           a?b?           a?b?
2023    
2024         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
2025         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
2026         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-
2027         rences of "a" or "b".         rences of "a" or "b".
2028    
2029         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2030         cial case of a pattern match of the empty  string  within  its  split()  
2031         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
2032         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
2033         again at the same offset with PCRE_NOTEMPTY set, and then if that fails         anchored, such a match can occur only if the pattern contains \K.
2034         by advancing the starting offset (see below)  and  trying  an  ordinary  
2035         match again.         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2036           PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2037         The  subject string is passed to pcre_exec() as a pointer in subject, a         match  of  the empty string within its split() function, and when using
2038         length in length, and a starting byte offset in startoffset. Unlike the         the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2039         pattern  string,  the  subject  may contain binary zero bytes. When the         matching a null string by first trying the match again at the same off-
2040         starting offset is zero, the search for a match starts at the beginning         set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2041         of the subject, and this is by far the most common case.         fails, by advancing the starting offset (see below) and trying an ordi-
2042           nary match again. There is some code that demonstrates how to  do  this
2043         If the pattern was compiled with the PCRE_UTF8 option, the subject must         in the pcredemo sample program.
2044         be a sequence of bytes that is a valid UTF-8 string, and  the  starting  
2045         offset  must point to the beginning of a UTF-8 character. If an invalid           PCRE_NO_START_OPTIMIZE
2046         UTF-8 string or offset is passed, an error  (either  PCRE_ERROR_BADUTF8  
2047         or   PCRE_ERROR_BADUTF8_OFFSET)   is   returned,   unless   the  option         There  are a number of optimizations that pcre_exec() uses at the start
2048         PCRE_NO_UTF8_CHECK is set,  in  which  case  PCRE's  behaviour  is  not         of a match, in order to speed up the process. For  example,  if  it  is
2049         defined.         known  that  a  match must start with a specific character, it searches
2050           the subject for that character, and fails immediately if it cannot find
2051         A  non-zero  starting offset is useful when searching for another match         it,  without actually running the main matching function. When callouts
2052         in the same subject by calling pcre_exec() again after a previous  suc-         are in use, these optimizations can cause  them  to  be  skipped.  This
2053         cess.   Setting  startoffset differs from just passing over a shortened         option  disables  the  "start-up" optimizations, causing performance to
2054         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         suffer, but ensuring that the callouts do occur.
2055    
2056             PCRE_NO_UTF8_CHECK
2057    
2058           When PCRE_UTF8 is set at compile time, the validity of the subject as a
2059           UTF-8  string is automatically checked when pcre_exec() is subsequently
2060           called.  The value of startoffset is also checked  to  ensure  that  it
2061           points  to  the start of a UTF-8 character. There is a discussion about
2062           the validity of UTF-8 strings in the section on UTF-8  support  in  the
2063           main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2064           pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2065           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2066    
2067           If  you  already  know that your subject is valid, and you want to skip
2068           these   checks   for   performance   reasons,   you   can    set    the
2069           PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2070           do this for the second and subsequent calls to pcre_exec() if  you  are
2071           making  repeated  calls  to  find  all  the matches in a single subject
2072           string. However, you should be  sure  that  the  value  of  startoffset
2073           points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
2074           set, the effect of passing an invalid UTF-8 string as a subject,  or  a
2075           value  of startoffset that does not point to the start of a UTF-8 char-
2076           acter, is undefined. Your program may crash.
2077    
2078             PCRE_PARTIAL_HARD
2079             PCRE_PARTIAL_SOFT
2080    
2081           These options turn on the partial matching feature. For backwards  com-
2082           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2083           match occurs if the end of the subject string is reached  successfully,
2084           but  there  are not enough subject characters to complete the match. If
2085           this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
2086           returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
2087           matching continues by testing any other alternatives. Only if they  all
2088           fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
2089           The portion of the string that was inspected when the partial match was
2090           found  is  set  as  the first matching string. There is a more detailed
2091           discussion in the pcrepartial documentation.
2092    
2093       The string to be matched by pcre_exec()
2094    
2095           The subject string is passed to pcre_exec() as a pointer in subject,  a
2096           length (in bytes) in length, and a starting byte offset in startoffset.
2097           In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2098           acter.  Unlike  the pattern string, the subject may contain binary zero
2099           bytes. When the starting offset is zero, the search for a match  starts
2100           at  the  beginning  of  the subject, and this is by far the most common
2101           case.
2102    
2103           A non-zero starting offset is useful when searching for  another  match
2104           in  the same subject by calling pcre_exec() again after a previous suc-
2105           cess.  Setting startoffset differs from just passing over  a  shortened
2106           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2107         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2108    
2109           \Biss\B           \Biss\B
2110    
2111         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2112         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
2113         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2114         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2115         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2116         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2117         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
2118         string again, but with startoffset  set  to  4,  it  finds  the  second         string again, but with startoffset set to 4, it finds the second occur-
2119         occurrence  of  "iss"  because  it  is able to look behind the starting         rence of "iss" because it is able to look behind the starting point  to
2120         point to discover that it is preceded by a letter.         discover that it is preceded by a letter.
2121    
2122         If a non-zero starting offset is passed when the pattern  is  anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2123         one  attempt  to match at the given offset is tried. This can only suc-         one attempt to match at the given offset is made. This can only succeed
2124         ceed if the pattern does not require the match to be at  the  start  of         if  the  pattern  does  not require the match to be at the start of the
2125         the subject.         subject.
2126    
2127         In  general, a pattern matches a certain portion of the subject, and in     How pcre_exec() returns captured substrings
2128         addition, further substrings from the subject  may  be  picked  out  by  
2129         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         In general, a pattern matches a certain portion of the subject, and  in
2130         this is called "capturing" in what follows, and the  phrase  "capturing         addition,  further  substrings  from  the  subject may be picked out by
2131         subpattern"  is  used for a fragment of a pattern that picks out a sub-         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2132         string. PCRE supports several other kinds of  parenthesized  subpattern         this  is  called "capturing" in what follows, and the phrase "capturing
2133           subpattern" is used for a fragment of a pattern that picks out  a  sub-
2134           string.  PCRE  supports several other kinds of parenthesized subpattern
2135         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2136    
2137         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2138         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-
2139         the vector is passed in ovecsize. The first two-thirds of the vector is         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2140         used to pass back captured substrings, each substring using a  pair  of         this argument is NOT the size of ovector in bytes.
2141         integers.  The  remaining  third  of the vector is used as workspace by  
2142         pcre_exec() while matching capturing subpatterns, and is not  available         The  first  two-thirds of the vector is used to pass back captured sub-
2143         for  passing  back  information.  The  length passed in ovecsize should         strings, each substring using a pair of integers. The  remaining  third
2144         always be a multiple of three. If it is not, it is rounded down.         of  the  vector is used as workspace by pcre_exec() while matching cap-
2145           turing subpatterns, and is not available for passing back  information.
2146           The  number passed in ovecsize should always be a multiple of three. If
2147           it is not, it is rounded down.
2148    
2149         When a match has been successful, information about captured substrings         When a match is successful, information about  captured  substrings  is
2150         is returned in pairs of integers, starting at the beginning of ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2151         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
2152         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
2153         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
2154         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
2155         tor[1], identify the portion of  the  subject  string  matched  by  the         byte offsets, even in UTF-8 mode. They are not character counts.
2156         entire  pattern.  The next pair is used for the first capturing subpat-  
2157         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
2158         pairs  that  have  been set. If there are no capturing subpatterns, the         portion  of  the subject string matched by the entire pattern. The next
2159         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
2160         first pair of offsets has been set.         returned by pcre_exec() is one more than the highest numbered pair that
2161           has been set.  For example, if two substrings have been  captured,  the
2162           returned  value is 3. If there are no capturing subpatterns, the return
2163           value from a successful match is 1, indicating that just the first pair
2164           of offsets has been set.
2165    
2166         Some  convenience  functions  are  provided for extracting the captured         If a capturing subpattern is matched repeatedly, it is the last portion
2167         substrings as separate strings. These are described  in  the  following         of the string that it matched that is returned.
        section.  
2168    
2169         It  is  possible  for  an capturing subpattern number n+1 to match some         If the vector is too small to hold all the captured substring  offsets,
2170         part of the subject when subpattern n has not been  used  at  all.  For         it is used as far as possible (up to two-thirds of its length), and the
2171         example, if the string "abc" is matched against the pattern (a|(z))(bc)         function returns a value of zero. If the substring offsets are  not  of
2172         subpatterns 1 and 3 are matched, but 2 is not. When this happens,  both         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2173         offset values corresponding to the unused subpattern are set to -1.         ovecsize as zero. However, if the pattern contains back references  and
2174           the  ovector is not big enough to remember the related substrings, PCRE
2175           has to get additional memory for use during matching. Thus it  is  usu-
2176           ally advisable to supply an ovector.
2177    
2178           The  pcre_info()  function  can  be used to find out how many capturing
2179           subpatterns there are in a compiled  pattern.  The  smallest  size  for
2180           ovector  that  will allow for n captured substrings, in addition to the
2181           offsets of the substring matched by the whole pattern, is (n+1)*3.
2182    
2183           It is possible for capturing subpattern number n+1 to match  some  part
2184           of the subject when subpattern n has not been used at all. For example,
2185           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2186           return from the function is 4, and subpatterns 1 and 3 are matched, but
2187           2 is not. When this happens, both values in  the  offset  pairs  corre-
2188           sponding to unused subpatterns are set to -1.
2189    
2190           Offset  values  that correspond to unused subpatterns at the end of the
2191           expression are also set to -1. For example,  if  the  string  "abc"  is
2192           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2193           matched. The return from the function is 2, because  the  highest  used
2194           capturing subpattern number is 1. However, you can refer to the offsets
2195           for the second and third capturing subpatterns if  you  wish  (assuming
2196           the vector is large enough, of course).
2197    
2198         If a capturing subpattern is matched repeatedly, it is the last portion         Some  convenience  functions  are  provided for extracting the captured
2199         of the string that it matched that gets returned.         substrings as separate strings. These are described below.
2200    
2201         If the vector is too small to hold all the captured substrings,  it  is     Error return values from pcre_exec()
        used as far as possible (up to two-thirds of its length), and the func-  
        tion returns a value of zero. In particular, if the  substring  offsets  
        are  not  of interest, pcre_exec() may be called with ovector passed as  
        NULL and ovecsize as zero. However, if the pattern contains back refer-  
        ences  and  the  ovector  isn't big enough to remember the related sub-  
        strings, PCRE has to get additional memory  for  use  during  matching.  
        Thus it is usually advisable to supply an ovector.  
   
        Note  that  pcre_info() can be used to find out how many capturing sub-  
        patterns there are in a compiled pattern. The smallest size for ovector  
        that  will  allow for n captured substrings, in addition to the offsets  
        of the substring matched by the whole pattern, is (n+1)*3.  
2202    
2203         If pcre_exec() fails, it returns a negative number. The  following  are         If pcre_exec() fails, it returns a negative number. The  following  are
2204         defined in the header file:         defined in the header file:
# Line 1196  MATCHING A PATTERN Line 2219  MATCHING A PATTERN
2219           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2220    
2221         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,
2222         to  catch  the case when it is passed a junk pointer. This is the error         to catch the case when it is passed a junk pointer and to detect when a
2223         it gives when the magic number isn't present.         pattern that was compiled in an environment of one endianness is run in
2224           an  environment  with the other endianness. This is the error that PCRE
2225           gives when the magic number is not present.
2226    
2227           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2228    
2229         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2230         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
# Line 1211  MATCHING A PATTERN Line 2236  MATCHING A PATTERN
2236         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2237         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
2238         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
2239         memory is freed at the end of matching.         memory is automatically freed at the end of matching.
2240    
2241           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2242    
# Line 1221  MATCHING A PATTERN Line 2246  MATCHING A PATTERN
2246    
2247           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2248    
2249         The recursion and backtracking limit, as specified by  the  match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2250         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         pcre_extra  structure  (or  defaulted) was reached. See the description
2251         description above.         above.
2252    
2253           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2254    
# Line 1242  MATCHING A PATTERN Line 2267  MATCHING A PATTERN
2267         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-
2268         ter.         ter.
2269    
2270             PCRE_ERROR_PARTIAL        (-12)
2271    
2272           The  subject  string did not match, but it did match partially. See the
2273           pcrepartial documentation for details of partial matching.
2274    
2275             PCRE_ERROR_BADPARTIAL     (-13)
2276    
2277           This code is no longer in  use.  It  was  formerly  returned  when  the
2278           PCRE_PARTIAL  option  was used with a compiled pattern containing items
2279           that were  not  supported  for  partial  matching.  From  release  8.00
2280           onwards, there are no restrictions on partial matching.
2281    
2282             PCRE_ERROR_INTERNAL       (-14)
2283    
2284           An  unexpected  internal error has occurred. This error could be caused
2285           by a bug in PCRE or by overwriting of the compiled pattern.
2286    
2287             PCRE_ERROR_BADCOUNT       (-15)
2288    
2289           This error is given if the value of the ovecsize argument is negative.
2290    
2291             PCRE_ERROR_RECURSIONLIMIT (-21)
2292    
2293           The internal recursion limit, as specified by the match_limit_recursion
2294           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2295           description above.
2296    
2297             PCRE_ERROR_BADNEWLINE     (-23)
2298    
2299           An invalid combination of PCRE_NEWLINE_xxx options was given.
2300    
2301           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2302    
2303    
2304  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2305    
# Line 1256  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2314  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2314         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2315              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2316    
2317         Captured  substrings  can  be  accessed  directly  by using the offsets         Captured substrings can be  accessed  directly  by  using  the  offsets
2318         returned by pcre_exec() in  ovector.  For  convenience,  the  functions         returned  by  pcre_exec()  in  ovector.  For convenience, the functions
2319         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2320         string_list() are provided for extracting captured substrings  as  new,         string_list()  are  provided for extracting captured substrings as new,
2321         separate,  zero-terminated strings. These functions identify substrings         separate, zero-terminated strings. These functions identify  substrings
2322         by number. The next section describes functions  for  extracting  named         by  number.  The  next section describes functions for extracting named
2323         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2324         extracted and has a further zero added on the end, but  the  result  is  
2325         not, of course, a C string.         A substring that contains a binary zero is correctly extracted and  has
2326           a  further zero added on the end, but the result is not, of course, a C
2327           string.  However, you can process such a string  by  referring  to  the
2328           length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
2329           string().  Unfortunately, the interface to pcre_get_substring_list() is
2330           not  adequate for handling strings containing binary zeros, because the
2331           end of the final string is not independently indicated.
2332    
2333         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-
2334         tions: subject is the subject string which has just  been  successfully         tions:  subject  is  the subject string that has just been successfully
2335         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2336         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2337         were  captured  by  the match, including the substring that matched the         were captured by the match, including the substring  that  matched  the
2338         entire regular expression. This is the value returned by  pcre_exec  if         entire regular expression. This is the value returned by pcre_exec() if
2339         it  is greater than zero. If pcre_exec() returned zero, indicating that         it is greater than zero. If pcre_exec() returned zero, indicating  that
2340         it ran out of space in ovector, the value passed as stringcount  should         it  ran out of space in ovector, the value passed as stringcount should
2341         be the size of the vector divided by three.         be the number of elements in the vector divided by three.
2342    
2343         The  functions pcre_copy_substring() and pcre_get_substring() extract a         The functions pcre_copy_substring() and pcre_get_substring() extract  a
2344         single substring, whose number is given as  stringnumber.  A  value  of         single  substring,  whose  number  is given as stringnumber. A value of
2345         zero  extracts  the  substring  that  matched the entire pattern, while         zero extracts the substring that matched the  entire  pattern,  whereas
2346         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
2347         string(),  the  string  is  placed  in buffer, whose length is given by         string(), the string is placed in buffer,  whose  length  is  given  by
2348         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize,  while  for  pcre_get_substring()  a new block of memory is
2349         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained via pcre_malloc, and its address is  returned  via  stringptr.
2350         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
2351         the terminating zero, or one of         the terminating zero, or one of these error codes:
2352    
2353           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2354    
2355         The  buffer  was too small for pcre_copy_substring(), or the attempt to         The buffer was too small for pcre_copy_substring(), or the  attempt  to
2356         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2357    
2358           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2359    
2360         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2361    
2362         The pcre_get_substring_list()  function  extracts  all  available  sub-         The  pcre_get_substring_list()  function  extracts  all  available sub-
2363         strings  and  builds  a list of pointers to them. All this is done in a         strings and builds a list of pointers to them. All this is  done  in  a
2364         single block of memory which is obtained via pcre_malloc.  The  address         single block of memory that is obtained via pcre_malloc. The address of
2365         of the memory block is returned via listptr, which is also the start of         the memory block is returned via listptr, which is also  the  start  of
2366         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
2367         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
2368           error code
2369    
2370           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2371    
# Line 1313  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2378  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2378         string  by inspecting the appropriate offset in ovector, which is nega-         string  by inspecting the appropriate offset in ovector, which is nega-
2379         tive for unset substrings.         tive for unset substrings.
2380    
2381         The    two    convenience    functions    pcre_free_substring()     and         The two convenience functions pcre_free_substring() and  pcre_free_sub-
2382         pcre_free_substring_list() can be used to free the memory returned by a         string_list()  can  be  used  to free the memory returned by a previous
2383         previous call  of  pcre_get_substring()  or  pcre_get_substring_list(),         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2384         respectively. They do nothing more than call the function pointed to by         tively.  They  do  nothing  more  than  call the function pointed to by
2385         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.
2386         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-
2387         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  that  cannot   use
2388         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-
2389         vided.         vided.
2390    
2391    
2392  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2393    
2394           int pcre_get_stringnumber(const pcre *code,
2395                const char *name);
2396    
2397         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
2398              const char *subject, int *ovector,              const char *subject, int *ovector,
2399              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2400              char *buffer, int buffersize);              char *buffer, int buffersize);
2401    
        int pcre_get_stringnumber(const pcre *code,  
             const char *name);  
   
2402         int pcre_get_named_substring(const pcre *code,         int pcre_get_named_substring(const pcre *code,
2403              const char *subject, int *ovector,              const char *subject, int *ovector,
2404              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2405              const char **stringptr);              const char **stringptr);
2406    
2407         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-
2408         ber.  This  can  be  done by calling pcre_get_stringnumber(). The first         ber.  For example, for this pattern
2409         argument is the compiled pattern, and the second is the name. For exam-  
2410         ple, for this pattern           (a+)b(?<xxx>\d+)...
2411    
2412           ab(?<xxx>\d+)...         the number of the subpattern called "xxx" is 2. If the name is known to
2413           be unique (PCRE_DUPNAMES was not set), you can find the number from the
2414         the  number  of the subpattern called "xxx" is 1. Given the number, you         name by calling pcre_get_stringnumber(). The first argument is the com-
2415         can then extract the substring directly, or use one  of  the  functions         piled pattern, and the second is the name. The yield of the function is
2416         described  in the previous section. For convenience, there are also two         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no
2417         functions that do the whole job.         subpattern of that name.
2418    
2419           Given the number, you can extract the substring directly, or use one of
2420           the functions described in the previous section. For convenience, there
2421           are also two functions that do the whole job.
2422    
2423         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most   of   the   arguments    of    pcre_copy_named_substring()    and
2424         pcre_get_named_substring() are the same as those for the functions that         pcre_get_named_substring()  are  the  same  as  those for the similarly
2425         extract by number, and so are not re-described here. There are just two         named functions that extract by number. As these are described  in  the
2426         differences.         previous  section,  they  are not re-described here. There are just two
2427           differences:
2428    
2429         First,  instead  of a substring number, a substring name is given. Sec-         First, instead of a substring number, a substring name is  given.  Sec-
2430         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2431         to  the compiled pattern. This is needed in order to gain access to the         to the compiled pattern. This is needed in order to gain access to  the
2432         name-to-number translation table.         name-to-number translation table.
2433    
2434         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2435         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2436         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2437           behaviour may not be what you want (see the next section).
2438    
2439           Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
2440           patterns  with  the  same  number,  you cannot use names to distinguish
2441           them, because names are not included in the compiled code. The matching
2442           process uses only numbers.
2443    
2444    
2445    DUPLICATE SUBPATTERN NAMES
2446    
2447           int pcre_get_stringtable_entries(const pcre *code,
2448                const char *name, char **first, char **last);
2449    
2450           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2451           subpatterns are not required to  be  unique.  Normally,  patterns  with
2452           duplicate  names  are such that in any one match, only one of the named
2453           subpatterns participates. An example is shown in the pcrepattern  docu-
2454           mentation.
2455    
2456           When    duplicates   are   present,   pcre_copy_named_substring()   and
2457           pcre_get_named_substring() return the first substring corresponding  to
2458           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2459           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2460           function  returns one of the numbers that are associated with the name,
2461           but it is not defined which it is.
2462    
2463           If you want to get full details of all captured substrings for a  given
2464           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2465           first argument is the compiled pattern, and the second is the name. The
2466           third  and  fourth  are  pointers to variables which are updated by the
2467           function. After it has run, they point to the first and last entries in
2468           the  name-to-number  table  for  the  given  name.  The function itself
2469           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2470           there  are none. The format of the table is described above in the sec-
2471           tion entitled Information about a  pattern.   Given  all  the  relevant
2472           entries  for the name, you can extract each of their numbers, and hence
2473           the captured data, if any.
2474    
2475    
2476    FINDING ALL POSSIBLE MATCHES
2477    
2478           The traditional matching function uses a  similar  algorithm  to  Perl,
2479           which stops when it finds the first match, starting at a given point in
2480           the subject. If you want to find all possible matches, or  the  longest
2481           possible  match,  consider using the alternative matching function (see
2482           below) instead. If you cannot use the alternative function,  but  still
2483           need  to  find all possible matches, you can kludge it up by making use
2484           of the callout facility, which is described in the pcrecallout documen-
2485           tation.
2486    
2487  Last updated: 09 December 2003         What you have to do is to insert a callout right at the end of the pat-
2488  Copyright (c) 1997-2003 University of Cambridge.         tern.  When your callout function is called, extract and save the  cur-
2489  -----------------------------------------------------------------------------         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2490           backtrack and try other alternatives. Ultimately, when it runs  out  of
2491           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2492    
 PCRE(3)                                                                PCRE(3)  
2493    
2494    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
2495    
2496           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
2497                const char *subject, int length, int startoffset,
2498                int options, int *ovector, int ovecsize,
2499                int *workspace, int wscount);
2500    
2501  NAME         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2502         PCRE - Perl-compatible regular expressions         against a compiled pattern, using a matching algorithm that  scans  the
2503           subject  string  just  once, and does not backtrack. This has different
2504           characteristics to the normal algorithm, and  is  not  compatible  with
2505           Perl.  Some  of the features of PCRE patterns are not supported. Never-
2506           theless, there are times when this kind of matching can be useful.  For
2507           a  discussion  of  the  two matching algorithms, and a list of features
2508           that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2509           tion.
2510    
2511  PCRE CALLOUTS         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2512           pcre_exec(), plus two extras. The ovector argument is used in a differ-
2513           ent  way,  and  this is described below. The other common arguments are
2514           used in the same way as for pcre_exec(), so their  description  is  not
2515           repeated here.
2516    
2517           The  two  additional  arguments provide workspace for the function. The
2518           workspace vector should contain at least 20 elements. It  is  used  for
2519           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2520           workspace will be needed for patterns and subjects where  there  are  a
2521           lot of potential matches.
2522    
2523         int (*pcre_callout)(pcre_callout_block *);         Here is an example of a simple call to pcre_dfa_exec():
2524    
2525         PCRE provides a feature called "callout", which is a means of temporar-           int rc;
2526         ily passing control to the caller of PCRE  in  the  middle  of  pattern           int ovector[10];
2527         matching.  The  caller of PCRE provides an external function by putting           int wspace[20];
2528         its entry point in the global variable pcre_callout. By  default,  this           rc = pcre_dfa_exec(
2529         variable contains NULL, which disables all calling out.             re,             /* result of pcre_compile() */
2530               NULL,           /* we didn't study the pattern */
2531               "some string",  /* the subject string */
2532               11,             /* the length of the subject string */
2533               0,              /* start at offset 0 in the subject */
2534               0,              /* default options */
2535               ovector,        /* vector of integers for substring information */
2536               10,             /* number of elements (NOT size in bytes) */
2537               wspace,         /* working space vector */
2538               20);            /* number of elements (NOT size in bytes) */
2539    
2540         Within  a  regular  expression,  (?C) indicates the points at which the     Option bits for pcre_dfa_exec()
        external function is to be called.  Different  callout  points  can  be  
        identified  by  putting  a number less than 256 after the letter C. The  
        default value is zero.  For  example,  this  pattern  has  two  callout  
        points:  
2541    
2542           (?C1)abc(?C2)def         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2543           zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2544           LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2545           PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
2546           TIAL_SOFT,  PCRE_DFA_SHORTEST,  and  PCRE_DFA_RESTART. All but the last
2547           four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
2548           description is not repeated here.
2549    
2550         During matching, when PCRE reaches a callout point (and pcre_callout is           PCRE_PARTIAL_HARD
2551         set), the external function is called. Its only argument is  a  pointer           PCRE_PARTIAL_SOFT
2552         to a pcre_callout block. This contains the following variables:  
2553           These  have the same general effect as they do for pcre_exec(), but the
2554           details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2555           pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2556           ject is reached and there is still at least  one  matching  possibility
2557           that requires additional characters. This happens even if some complete
2558           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2559           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2560           of the subject is reached, there have been  no  complete  matches,  but
2561           there  is  still  at least one matching possibility. The portion of the
2562           string that was inspected when the longest partial match was  found  is
2563           set as the first matching string in both cases.
2564    
2565             PCRE_DFA_SHORTEST
2566    
2567           Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2568           stop as soon as it has found one match. Because of the way the alterna-
2569           tive  algorithm  works, this is necessarily the shortest possible match
2570           at the first possible matching point in the subject string.
2571    
2572             PCRE_DFA_RESTART
2573    
2574           When pcre_dfa_exec() returns a partial match, it is possible to call it
2575           again,  with  additional  subject characters, and have it continue with
2576           the same match. The PCRE_DFA_RESTART option requests this action;  when
2577           it  is  set,  the workspace and wscount options must reference the same
2578           vector as before because data about the match so far is  left  in  them
2579           after a partial match. There is more discussion of this facility in the
2580           pcrepartial documentation.
2581    
2582       Successful returns from pcre_dfa_exec()
2583    
2584           When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
2585           string in the subject. Note, however, that all the matches from one run
2586           of the function start at the same point in  the  subject.  The  shorter
2587           matches  are all initial substrings of the longer matches. For example,
2588           if the pattern
2589    
2590             <.*>
2591    
2592           is matched against the string
2593    
2594             This is <something> <something else> <something further> no more
2595    
2596           the three matched strings are
2597    
2598             <something>
2599             <something> <something else>
2600             <something> <something else> <something further>
2601    
2602           On success, the yield of the function is a number  greater  than  zero,
2603           which  is  the  number of matched substrings. The substrings themselves
2604           are returned in ovector. Each string uses two elements;  the  first  is
2605           the  offset  to  the start, and the second is the offset to the end. In
2606           fact, all the strings have the same start  offset.  (Space  could  have
2607           been  saved by giving this only once, but it was decided to retain some
2608           compatibility with the way pcre_exec() returns data,  even  though  the
2609           meaning of the strings is different.)
2610    
2611           The strings are returned in reverse order of length; that is, the long-
2612           est matching string is given first. If there were too many  matches  to
2613           fit  into ovector, the yield of the function is zero, and the vector is
2614           filled with the longest matches.
2615    
2616       Error returns from pcre_dfa_exec()
2617    
2618           The pcre_dfa_exec() function returns a negative number when  it  fails.
2619           Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2620           described above.  There are in addition the following errors  that  are
2621           specific to pcre_dfa_exec():
2622    
2623             PCRE_ERROR_DFA_UITEM      (-16)
2624    
2625           This  return is given if pcre_dfa_exec() encounters an item in the pat-
2626           tern that it does not support, for instance, the use of \C  or  a  back
2627           reference.
2628    
2629             PCRE_ERROR_DFA_UCOND      (-17)
2630    
2631           This  return  is  given  if pcre_dfa_exec() encounters a condition item
2632           that uses a back reference for the condition, or a test  for  recursion
2633           in a specific group. These are not supported.
2634    
2635             PCRE_ERROR_DFA_UMLIMIT    (-18)
2636    
2637           This  return  is given if pcre_dfa_exec() is called with an extra block
2638           that contains a setting of the match_limit field. This is not supported
2639           (it is meaningless).
2640    
2641             PCRE_ERROR_DFA_WSSIZE     (-19)
2642    
2643           This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2644           workspace vector.
2645    
2646             PCRE_ERROR_DFA_RECURSE    (-20)
2647    
2648           When a recursive subpattern is processed, the matching  function  calls
2649           itself  recursively,  using  private vectors for ovector and workspace.
2650           This error is given if the output vector  is  not  large  enough.  This
2651           should be extremely rare, as a vector of size 1000 is used.
2652    
2653    
2654    SEE ALSO
2655    
2656           pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2657           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2658    
2659    
2660    AUTHOR
2661    
2662           Philip Hazel
2663           University Computing Service
2664           Cambridge CB2 3QH, England.
2665    
2666    
2667    REVISION
2668    
2669           Last updated: 11 September 2009
2670           Copyright (c) 1997-2009 University of Cambridge.
2671    ------------------------------------------------------------------------------
2672    
2673    
2674    PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2675    
2676    
2677    NAME
2678           PCRE - Perl-compatible regular expressions
2679    
2680    
2681    PCRE CALLOUTS
2682    
2683           int (*pcre_callout)(pcre_callout_block *);
2684    
2685           PCRE provides a feature called "callout", which is a means of temporar-
2686           ily passing control to the caller of PCRE  in  the  middle  of  pattern
2687           matching.  The  caller of PCRE provides an external function by putting
2688           its entry point in the global variable pcre_callout. By  default,  this
2689           variable contains NULL, which disables all calling out.
2690    
2691           Within  a  regular  expression,  (?C) indicates the points at which the
2692           external function is to be called.  Different  callout  points  can  be
2693           identified  by  putting  a number less than 256 after the letter C. The
2694           default value is zero.  For  example,  this  pattern  has  two  callout
2695           points:
2696    
2697             (?C1)abc(?C2)def
2698    
2699           If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
2700           called, PCRE automatically  inserts  callouts,  all  with  number  255,
2701           before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
2702           used with the pattern
2703    
2704             A(\d{2}|--)
2705    
2706           it is processed as if it were
2707    
2708           (?C255)A(?C255)((?C255)\d{2}(?C255)|(?C255)-(?C255)-(?C255))(?C255)
2709    
2710           Notice that there is a callout before and after  each  parenthesis  and
2711           alternation  bar.  Automatic  callouts  can  be  used  for tracking the
2712           progress of pattern matching. The pcretest command has an  option  that
2713           sets  automatic callouts; when it is used, the output indicates how the
2714           pattern is matched. This is useful information when you are  trying  to
2715           optimize the performance of a particular pattern.
2716    
2717    
2718    MISSING CALLOUTS
2719    
2720           You  should  be  aware  that,  because of optimizations in the way PCRE
2721           matches patterns by default, callouts  sometimes  do  not  happen.  For
2722           example, if the pattern is
2723    
2724             ab(?C4)cd
2725    
2726           PCRE knows that any matching string must contain the letter "d". If the
2727           subject string is "abyz", the lack of "d" means that  matching  doesn't
2728           ever  start,  and  the  callout is never reached. However, with "abyd",
2729           though the result is still no match, the callout is obeyed.
2730    
2731           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2732           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2733           matching process, but does ensure that callouts  such  as  the  example
2734           above are obeyed.
2735    
2736    
2737    THE CALLOUT INTERFACE
2738    
2739           During  matching, when PCRE reaches a callout point, the external func-
2740           tion defined by pcre_callout is called (if it is set). This applies  to
2741           both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2742           only argument to the callout function is a pointer  to  a  pcre_callout
2743           block. This structure contains the following fields:
2744    
2745           int          version;           int          version;
2746           int          callout_number;           int          callout_number;
# Line 1408  PCRE CALLOUTS Line 2752  PCRE CALLOUTS
2752           int          capture_top;           int          capture_top;
2753           int          capture_last;           int          capture_last;
2754           void        *callout_data;           void        *callout_data;
2755             int          pattern_position;
2756             int          next_item_length;
2757    
2758         The  version  field  is an integer containing the version number of the         The  version  field  is an integer containing the version number of the
2759         block format. The current version  is  zero.  The  version  number  may         block format. The initial version was 0; the current version is 1.  The
2760         change  in  future if additional fields are added, but the intention is         version  number  will  change  again in future if additional fields are
2761         never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2762    
2763         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
2764         piled into the pattern (that is, the number after ?C).         piled  into  the pattern (that is, the number after ?C for manual call-
2765           outs, and 255 for automatically generated callouts).
2766    
2767         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
2768         passed by the caller to pcre_exec(). The contents can be  inspected  in         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2769         order  to extract substrings that have been matched so far, in the same         pcre_exec() is used, the contents can be inspected in order to  extract
2770         way as for extracting substrings after a match has completed.         substrings  that  have  been  matched  so  far,  in the same way as for
2771           extracting substrings after a match has completed. For  pcre_dfa_exec()
2772           this field is not useful.
2773    
2774         The subject and subject_length fields contain copies  the  values  that         The subject and subject_length fields contain copies of the values that
2775         were passed to pcre_exec().         were passed to pcre_exec().
2776    
2777         The  start_match  field contains the offset within the subject at which         The start_match field normally contains the offset within  the  subject
2778         the current match attempt started. If the pattern is not anchored,  the         at  which  the  current  match  attempt started. However, if the escape
2779         callout  function  may  be  called several times for different starting         sequence \K has been encountered, this value is changed to reflect  the
2780         points.         modified  starting  point.  If the pattern is not anchored, the callout
2781           function may be called several times from the same point in the pattern
2782           for different starting points in the subject.
2783    
2784         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2785         the current match pointer.         the current match pointer.
2786    
2787         The  capture_top field contains one more than the number of the highest         When the pcre_exec() function is used, the capture_top  field  contains
2788         numbered  captured  substring  so  far.  If  no  substrings  have  been         one  more than the number of the highest numbered captured substring so
2789         captured, the value of capture_top is one.         far. If no substrings have been captured, the value of  capture_top  is
2790           one.  This  is always the case when pcre_dfa_exec() is used, because it
2791         The  capture_last  field  contains the number of the most recently cap-         does not support captured substrings.
2792         tured substring.  
2793           The capture_last field contains the number of the  most  recently  cap-
2794           tured  substring. If no substrings have been captured, its value is -1.
2795           This is always the case when pcre_dfa_exec() is used.
2796    
2797         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()
2798         by  the  caller specifically so that it can be passed back in callouts.         or  pcre_dfa_exec() specifically so that it can be passed back in call-
2799         It is passed in the pcre_callout field of the  pcre_extra  data  struc-         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
2800         ture.  If  no  such  data  was  passed,  the value of callout_data in a         structure.  If  no such data was passed, the value of callout_data in a
2801         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
2802         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2803    
2804           The  pattern_position field is present from version 1 of the pcre_call-
2805           out structure. It contains the offset to the next item to be matched in
2806           the pattern string.
2807    
2808           The  next_item_length field is present from version 1 of the pcre_call-
2809           out structure. It contains the length of the next item to be matched in
2810           the  pattern  string. When the callout immediately precedes an alterna-
2811           tion bar, a closing parenthesis, or the end of the pattern, the  length
2812           is  zero.  When the callout precedes an opening parenthesis, the length
2813           is that of the entire subpattern.
2814    
2815           The pattern_position and next_item_length fields are intended  to  help
2816           in  distinguishing between different automatic callouts, which all have
2817           the same callout number. However, they are set for all callouts.
2818    
2819    
2820  RETURN VALUES  RETURN VALUES
2821    
2822         The callout function returns an integer. If the value is zero, matching         The external callout function returns an integer to PCRE. If the  value
2823         proceeds as normal. If the value is greater than zero,  matching  fails         is  zero,  matching  proceeds  as  normal. If the value is greater than
2824         at the current point, but backtracking to test other possibilities goes         zero, matching fails at the current point, but  the  testing  of  other
2825         ahead, just as if a lookahead assertion had failed.  If  the  value  is         matching possibilities goes ahead, just as if a lookahead assertion had
2826         less  than  zero,  the  match is abandoned, and pcre_exec() returns the         failed. If the value is less than zero, the  match  is  abandoned,  and
2827         value.         pcre_exec() (or pcre_dfa_exec()) returns the negative value.
2828    
2829         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
2830         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2831         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
2832         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
2833         itself.         itself.
2834    
 Last updated: 21 January 2003  
 Copyright (c) 1997-2003 University of Cambridge.  
 -----------------------------------------------------------------------------  
2835    
2836  PCRE(3)                                                                PCRE(3)  AUTHOR
2837    
2838           Philip Hazel
2839           University Computing Service
2840           Cambridge CB2 3QH, England.
2841    
2842    
2843    REVISION
2844    
2845           Last updated: 15 March 2009
2846           Copyright (c) 1997-2009 University of Cambridge.
2847    ------------------------------------------------------------------------------
2848    
2849    
2850    PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2851    
2852    
2853  NAME  NAME
2854         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2855    
 DIFFERENCES FROM PERL  
2856    
2857         This  document describes the differences in the ways that PCRE and Perl  DIFFERENCES BETWEEN PCRE AND PERL
        handle regular expressions. The differences  described  here  are  with  
        respect to Perl 5.8.  
2858    
2859         1.  PCRE does not have full UTF-8 support. Details of what it does have         This  document describes the differences in the ways that PCRE and Perl
2860         are given in the section on UTF-8 support in the main pcre page.         handle regular expressions. The differences described here  are  mainly
2861           with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2862           some features that are in Perl 5.10.
2863    
2864           1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2865           of  what  it does have are given in the section on UTF-8 support in the
2866           main pcre page.
2867    
2868         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
2869         permits  them,  but they do not mean what you might think. For example,         permits  them,  but they do not mean what you might think. For example,
# Line 1498  DIFFERENCES FROM PERL Line 2879  DIFFERENCES FROM PERL
2879    
2880         4. Though binary zero characters are supported in the  subject  string,         4. Though binary zero characters are supported in the  subject  string,
2881         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-
2882         mal C string, terminated by zero. The escape sequence "\0" can be  used         mal C string, terminated by zero. The escape sequence \0 can be used in
2883         in the pattern to represent a binary zero.         the pattern to represent a binary zero.
2884    
2885         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
2886         \U, \P, \p, \N, and \X. In fact these are implemented by Perl's general         \U, and \N. In fact these are implemented by Perl's general string-han-
2887         string-handling and are not part of its pattern matching engine. If any         dling  and are not part of its pattern matching engine. If any of these
2888         of these are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
2889    
2890           6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
2891           is  built  with Unicode character property support. The properties that
2892           can be tested with \p and \P are limited to the general category  prop-
2893           erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2894           derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
2895           property,  which  Perl  does  not; the Perl documentation says "Because
2896           Perl hides the need for the user to understand the internal representa-
2897           tion  of Unicode characters, there is no need to implement the somewhat
2898           messy concept of surrogates."
2899    
2900         6. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2901         ters  in  between  are  treated as literals. This is slightly different         ters  in  between  are  treated as literals. This is slightly different
2902         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
2903         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
# Line 1522  DIFFERENCES FROM PERL Line 2913  DIFFERENCES FROM PERL
2913         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
2914         classes.         classes.
2915    
2916         7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2917         constructions. However, there is some experimental support  for  recur-         constructions. However, there is support for recursive  patterns.  This
2918         sive  patterns  using the non-Perl items (?R), (?number) and (?P>name).         is  not  available  in Perl 5.8, but it is in Perl 5.10. Also, the PCRE
2919         Also, the PCRE "callout" feature allows  an  external  function  to  be         "callout" feature allows an external function to be called during  pat-
2920         called during pattern matching.         tern matching. See the pcrecallout documentation for details.
2921    
2922           9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2923           always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2924           unlike  Perl. There is a discussion of an example that explains this in
2925           more detail in the section on recursion differences from  Perl  in  the
2926           pcrecompat page.
2927    
2928         8.  There  are some differences that are concerned with the settings of         10.  There are some differences that are concerned with the settings of
2929         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
2930         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2931         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2932    
2933         9. PCRE  provides  some  extensions  to  the  Perl  regular  expression         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2934         facilities:         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2935           the forms without an argument. PCRE does not support (*MARK).
2936    
2937           12. PCRE provides some extensions to the Perl regular expression facil-
2938           ities.   Perl  5.10  will  include new features that are not in earlier
2939           versions, some of which (such as named parentheses) have been  in  PCRE
2940           for some time. This list is with respect to Perl 5.10:
2941    
2942         (a)  Although  lookbehind  assertions  must match fixed length strings,         (a)  Although  lookbehind  assertions  must match fixed length strings,
2943         each alternative branch of a lookbehind assertion can match a different         each alternative branch of a lookbehind assertion can match a different
# Line 1544  DIFFERENCES FROM PERL Line 2947  DIFFERENCES FROM PERL
2947         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2948    
2949         (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-
2950         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2951           ignored.  (Perl can be made to issue a warning.)
2952    
2953         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2954         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-
2955         lowed by a question mark they are.         lowed by a question mark they are.
2956    
2957         (e)  PCRE_ANCHORED  can  be used to force a pattern to be tried only at         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
2958         the first matching position in the subject string.         tried only at the first matching position in the subject string.
2959    
2960         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and  PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2961         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
2962           lents.
2963    
2964         (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
2965         pattern matching (Perl can do  this  using  the  (?p{code})  construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
2966    
2967         (h)  PCRE supports named capturing substrings, using the Python syntax.         (h) The callout facility is PCRE-specific.
2968    
2969         (i) PCRE supports the possessive quantifier  "++"  syntax,  taken  from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
2970    
2971         (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,
2972           even on different hosts that have the other endianness.
2973    
2974         (k) The callout facility is PCRE-specific.         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2975           different way and is not Perl-compatible.
2976    
2977  Last updated: 09 December 2003         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
2978  Copyright (c) 1997-2003 University of Cambridge.         of a pattern that set overall options that cannot be changed within the
2979  -----------------------------------------------------------------------------         pattern.
2980    
 PCRE(3)                                                                PCRE(3)  
2981    
2982    AUTHOR
2983    
2984           Philip Hazel
2985           University Computing Service
2986           Cambridge CB2 3QH, England.
2987    
2988    
2989    REVISION
2990    
2991           Last updated: 18 September 2009
2992           Copyright (c) 1997-2009 University of Cambridge.
2993    ------------------------------------------------------------------------------
2994    
2995    
2996    PCREPATTERN(3)                                                  PCREPATTERN(3)
2997    
2998    
2999  NAME  NAME
3000         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3001    
3002    
3003  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3004    
3005         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3006         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3007         documentation  and in a number of other books, some of which have copi-         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3008         ous examples. Jeffrey Friedl's "Mastering  Regular  Expressions",  pub-         semantics as closely as it can. PCRE  also  supports  some  alternative
3009         lished  by  O'Reilly, covers them in great detail. The description here         regular  expression  syntax (which does not conflict with the Perl syn-
3010         is intended as reference documentation.         tax) in order to provide some compatibility with regular expressions in
3011           Python, .NET, and Oniguruma.
3012         The basic operation of PCRE is on strings of bytes. However,  there  is  
3013         also  support for UTF-8 character strings. To use this support you must         Perl's  regular expressions are described in its own documentation, and
3014         build PCRE to include UTF-8 support, and then call pcre_compile()  with         regular expressions in general are covered in a number of  books,  some
3015         the  PCRE_UTF8  option.  How  this affects the pattern matching is men-         of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3016         tioned in several places below. There is also a summary of  UTF-8  fea-         Expressions", published by  O'Reilly,  covers  regular  expressions  in
3017         tures in the section on UTF-8 support in the main pcre page.         great  detail.  This  description  of  PCRE's  regular  expressions  is
3018           intended as reference material.
3019    
3020           The original operation of PCRE was on strings of  one-byte  characters.
3021           However,  there is now also support for UTF-8 character strings. To use
3022           this, you must build PCRE to  include  UTF-8  support,  and  then  call
3023           pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
3024           sequence that can be given at the start of a pattern:
3025    
3026             (*UTF8)
3027    
3028           Starting a pattern with this sequence  is  equivalent  to  setting  the
3029           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3030           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3031           below.  There  is  also  a  summary of UTF-8 features in the section on
3032           UTF-8 support in the main pcre page.
3033    
3034           The remainder of this document discusses the  patterns  that  are  sup-
3035           ported  by  PCRE when its main matching function, pcre_exec(), is used.
3036           From  release  6.0,   PCRE   offers   a   second   matching   function,
3037           pcre_dfa_exec(),  which matches using a different algorithm that is not
3038           Perl-compatible. Some of the features discussed below are not available
3039           when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3040           alternative function, and how it differs from the normal function,  are
3041           discussed in the pcrematching page.
3042    
3043    
3044    NEWLINE CONVENTIONS
3045    
3046           PCRE  supports five different conventions for indicating line breaks in
3047           strings: a single CR (carriage return) character, a  single  LF  (line-
3048           feed) character, the two-character sequence CRLF, any of the three pre-
3049           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3050           discussion  about newlines, and shows how to set the newline convention
3051           in the options arguments for the compiling and matching functions.
3052    
3053           It is also possible to specify a newline convention by starting a  pat-
3054           tern string with one of the following five sequences:
3055    
3056             (*CR)        carriage return
3057             (*LF)        linefeed
3058             (*CRLF)      carriage return, followed by linefeed
3059             (*ANYCRLF)   any of the three above
3060             (*ANY)       all Unicode newline sequences
3061    
3062           These override the default and the options given to pcre_compile(). For
3063           example, on a Unix system where LF is the default newline sequence, the
3064           pattern
3065    
3066             (*CR)a.b
3067    
3068           changes the convention to CR. That pattern matches "a\nb" because LF is
3069           no longer a newline. Note that these special settings,  which  are  not
3070           Perl-compatible,  are  recognized  only at the very start of a pattern,
3071           and that they must be in upper case.  If  more  than  one  of  them  is
3072           present, the last one is used.
3073    
3074           The  newline  convention  does  not  affect what the \R escape sequence
3075           matches. By default, this is any Unicode  newline  sequence,  for  Perl
3076           compatibility.  However, this can be changed; see the description of \R
3077           in the section entitled "Newline sequences" below. A change of \R  set-
3078           ting can be combined with a change of newline convention.
3079    
3080    
3081    CHARACTERS AND METACHARACTERS
3082    
3083         A  regular  expression  is  a pattern that is matched against a subject         A  regular  expression  is  a pattern that is matched against a subject
3084         string from left to right. Most characters stand for  themselves  in  a         string from left to right. Most characters stand for  themselves  in  a
# Line 1603  PCRE REGULAR EXPRESSION DETAILS Line 3087  PCRE REGULAR EXPRESSION DETAILS
3087    
3088           The quick brown fox           The quick brown fox
3089    
3090         matches a portion of a subject string that is identical to itself.  The         matches a portion of a subject string that is identical to itself. When
3091         power of regular expressions comes from the ability to include alterna-         caseless  matching is specified (the PCRE_CASELESS option), letters are
3092         tives and repetitions in the pattern. These are encoded in the  pattern         matched independently of case. In UTF-8 mode, PCRE  always  understands
3093         by  the  use  of meta-characters, which do not stand for themselves but         the  concept  of case for characters whose values are less than 128, so
3094         instead are interpreted in some special way.         caseless matching is always possible. For characters with  higher  val-
3095           ues,  the concept of case is supported if PCRE is compiled with Unicode
3096         There are two different sets of meta-characters: those that are  recog-         property support, but not otherwise.   If  you  want  to  use  caseless
3097         nized  anywhere in the pattern except within square brackets, and those         matching  for  characters  128  and above, you must ensure that PCRE is
3098         that are recognized in square brackets. Outside  square  brackets,  the         compiled with Unicode property support as well as with UTF-8 support.
3099         meta-characters are as follows:  
3100           The power of regular expressions comes  from  the  ability  to  include
3101           alternatives  and  repetitions in the pattern. These are encoded in the
3102           pattern by the use of metacharacters, which do not stand for themselves
3103           but instead are interpreted in some special way.
3104    
3105           There  are  two different sets of metacharacters: those that are recog-
3106           nized anywhere in the pattern except within square brackets, and  those
3107           that  are  recognized  within square brackets. Outside square brackets,
3108           the metacharacters are as follows:
3109    
3110           \      general escape character with several uses           \      general escape character with several uses
3111           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 1630  PCRE REGULAR EXPRESSION DETAILS Line 3123  PCRE REGULAR EXPRESSION DETAILS
3123                  also "possessive quantifier"                  also "possessive quantifier"
3124           {      start min/max quantifier           {      start min/max quantifier
3125    
3126         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
3127         class". In a character class the only meta-characters are:         class". In a character class the only metacharacters are:
3128    
3129           \      general escape character           \      general escape character
3130           ^      negate the class, but only if the first character           ^      negate the class, but only if the first character
# Line 1640  PCRE REGULAR EXPRESSION DETAILS Line 3133  PCRE REGULAR EXPRESSION DETAILS
3133                    syntax)                    syntax)
3134           ]      terminates the character class           ]      terminates the character class
3135    
3136         The following sections describe the use of each of the meta-characters.         The following sections describe the use of each of the metacharacters.
3137    
3138    
3139  BACKSLASH  BACKSLASH
3140    
3141         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3142         a non-alphameric character, it takes  away  any  special  meaning  that         a non-alphanumeric character, it takes away any  special  meaning  that
3143         character  may  have.  This  use  of  backslash  as an escape character         character  may  have.  This  use  of  backslash  as an escape character
3144         applies both inside and outside character classes.         applies both inside and outside character classes.
3145    
3146         For example, if you want to match a * character, you write  \*  in  the         For example, if you want to match a * character, you write  \*  in  the
3147         pattern.   This  escaping  action  applies whether or not the following         pattern.   This  escaping  action  applies whether or not the following
3148         character would otherwise be interpreted as a meta-character, so it  is         character would otherwise be interpreted as a metacharacter, so  it  is
3149         always  safe to precede a non-alphameric with backslash to specify that         always  safe  to  precede  a non-alphanumeric with backslash to specify
3150         it stands for itself. In particular, if you want to match a  backslash,         that it stands for itself. In particular, if you want to match a  back-
3151         you write \\.         slash, you write \\.
3152    
3153         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3154         the pattern (other than in a character class) and characters between  a         the pattern (other than in a character class) and characters between  a
3155         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
3156         An escaping backslash can be used to include a whitespace or #  charac-         ing backslash can be used to include a whitespace  or  #  character  as
3157         ter as part of the pattern.         part of the pattern.
3158    
3159         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-
3160         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 1679  BACKSLASH Line 3172  BACKSLASH
3172         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3173         classes.         classes.
3174    
3175       Non-printing characters
3176    
3177         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3178         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
3179         appearance of non-printing characters, apart from the binary zero  that         appearance of non-printing characters, apart from the binary zero  that
# Line 1690  BACKSLASH Line 3185  BACKSLASH
3185           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3186           \e        escape (hex 1B)           \e        escape (hex 1B)
3187           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3188           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3189           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3190<