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# Line 18  INTRODUCTION Line 18  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few  differences.  The current implementation of PCRE (release         just  a  few  differences. Certain features that appeared in Python and
22         6.x) corresponds approximately with Perl  5.8,  including  support  for         PCRE before they appeared in Perl are also available using  the  Python
23         UTF-8 encoded strings and Unicode general category properties. However,         syntax.  There is also some support for certain .NET and Oniguruma syn-
24         this support has to be explicitly enabled; it is not the default.         tax items, and there is an option for  requesting  some  minor  changes
25           that give better JavaScript compatibility.
26         In addition to the Perl-compatible matching function,  PCRE  also  con-  
27         tains  an  alternative matching function that matches the same compiled         The  current  implementation of PCRE (release 7.x) corresponds approxi-
28         patterns in a different way. In certain circumstances, the  alternative         mately with Perl 5.10, including support for UTF-8 encoded strings  and
29         function  has  some  advantages.  For  a discussion of the two matching         Unicode general category properties. However, UTF-8 and Unicode support
30         algorithms, see the pcrematching page.         has to be explicitly enabled; it is not the default. The Unicode tables
31           correspond to Unicode release 5.0.0.
32         PCRE is written in C and released as a C library. A  number  of  people  
33         have  written  wrappers and interfaces of various kinds. In particular,         In  addition to the Perl-compatible matching function, PCRE contains an
34         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         alternative matching function that matches the same  compiled  patterns
35           in  a different way. In certain circumstances, the alternative function
36           has some advantages. For a discussion of the two  matching  algorithms,
37           see the pcrematching page.
38    
39           PCRE  is  written  in C and released as a C library. A number of people
40           have written wrappers and interfaces of various kinds.  In  particular,
41           Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
42         included as part of the PCRE distribution. The pcrecpp page has details         included as part of the PCRE distribution. The pcrecpp page has details
43         of this interface. Other people's contributions can  be  found  in  the         of  this  interface.  Other  people's contributions can be found in the
44         Contrib directory at the primary FTP site, which is:         Contrib directory at the primary FTP site, which is:
45    
46         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
47    
48         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
49         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
50         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
51           page.
52    
53         Some  features  of  PCRE can be included, excluded, or changed when the         Some  features  of  PCRE can be included, excluded, or changed when the
54         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
# Line 53  INTRODUCTION Line 61  INTRODUCTION
61         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
62         functions, but which are not intended  for  use  by  external  callers.         functions, but which are not intended  for  use  by  external  callers.
63         Their  names  all begin with "_pcre_", which hopefully will not provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
64         any name clashes.         any name clashes. In some environments, it is possible to control which
65           external  symbols  are  exported when a shared library is built, and in
66           these cases the undocumented symbols are not exported.
67    
68    
69  USER DOCUMENTATION  USER DOCUMENTATION
# Line 65  USER DOCUMENTATION Line 75  USER DOCUMENTATION
75         of searching. The sections are as follows:         of searching. The sections are as follows:
76    
77           pcre              this document           pcre              this document
78             pcre-config       show PCRE installation configuration information
79           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
80           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
81           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
# Line 75  USER DOCUMENTATION Line 86  USER DOCUMENTATION
86           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
87           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
88                               regular expressions                               regular expressions
89             pcresyntax        quick syntax reference
90           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
91           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
92           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
93           pcresample        discussion of the sample program           pcresample        discussion of the sample program
94             pcrestack         discussion of stack usage
95           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
96    
97         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 96  LIMITATIONS Line 109  LIMITATIONS
109         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
110         the  source  distribution and the pcrebuild documentation for details).         the  source  distribution and the pcrebuild documentation for details).
111         In these cases the limit is substantially larger.  However,  the  speed         In these cases the limit is substantially larger.  However,  the  speed
112         of execution will be slower.         of execution is slower.
113    
114           All values in repeating quantifiers must be less than 65536.
115    
116         All values in repeating quantifiers must be less than 65536.  The maxi-         There is no limit to the number of parenthesized subpatterns, but there
117         mum number of capturing subpatterns is 65535.         can be no more than 65535 capturing subpatterns.
118    
119         There is no limit to the number of non-capturing subpatterns,  but  the         The maximum length of name for a named subpattern is 32 characters, and
120         maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,         the maximum number of named subpatterns is 10000.
        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 a subject string is the largest positive number
123         that an integer variable can hold. However, when using the  traditional         that an integer variable can hold. However, when using the  traditional
124         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
125         inite repetition.  This means that the available stack space may  limit         inite repetition.  This means that the available stack space may  limit
126         the size of a subject string that can be processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
127           For a discussion of stack issues, see the pcrestack documentation.
128    
129    
130  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
# Line 128  UTF-8 AND UNICODE PROPERTY SUPPORT Line 142  UTF-8 AND UNICODE PROPERTY SUPPORT
142    
143         If  you compile PCRE with UTF-8 support, but do not use it at run time,         If  you compile PCRE with UTF-8 support, but do not use it at run time,
144         the library will be a bit bigger, but the additional run time  overhead         the library will be a bit bigger, but the additional run time  overhead
145         is  limited  to testing the PCRE_UTF8 flag in several places, so should         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
146         not be very large.         very big.
147    
148         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
149         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
150         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
151         general  category  properties such as Lu for an upper case letter or Nd         general  category  properties such as Lu for an upper case letter or Nd
152         for a decimal number. A full list is given in the pcrepattern  documen-         for a decimal number, the Unicode script names such as Arabic  or  Han,
153         tation. The PCRE library is increased in size by about 90K when Unicode         and  the  derived  properties  Any  and L&. A full list is given in the
154         property support is included.         pcrepattern documentation. Only the short names for properties are sup-
155           ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
156         The following comments apply when PCRE is running in UTF-8 mode:         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
157           optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
158         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         does not support this.
159         subjects  are  checked for validity on entry to the relevant functions.  
160         If an invalid UTF-8 string is passed, an error return is given. In some     Validity of UTF-8 strings
161         situations,  you  may  already  know  that  your strings are valid, and  
162         therefore want to skip these checks in order to improve performance. If         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and
163         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         subjects are (by default) checked for validity on entry to the relevant
164         PCRE assumes that the pattern or subject  it  is  given  (respectively)         functions. From release 7.3 of PCRE, the check is according  the  rules
165         contains  only valid UTF-8 codes. In this case, it does not diagnose an         of  RFC  3629, which are themselves derived from the Unicode specifica-
166         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which
167         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current
168         crash.         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
169           to U+DFFF.
170         2. In a pattern, the escape sequence \x{...}, where the contents of the  
171         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of
172         character whose code number is the given hexadecimal number, for  exam-         which the Unicode Standard says this: "The Low Surrogate Area does  not
173         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,         contain  any  character  assignments,  consequently  no  character code
174         the item is not recognized.  This escape sequence can be used either as         charts or namelists are provided for this area. Surrogates are reserved
175         a literal, or within a character class.         for  use  with  UTF-16 and then must be used in pairs." The code points
176           that are encoded by UTF-16 pairs  are  available  as  independent  code
177           points  in  the  UTF-8  encoding.  (In other words, the whole surrogate
178           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
179    
180           If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return
181           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
182           that your strings are valid, and therefore want to skip these checks in
183           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
184           compile time or at run time, PCRE assumes that the pattern  or  subject
185           it  is  given  (respectively)  contains only valid UTF-8 codes. In this
186           case, it does not diagnose an invalid UTF-8 string.
187    
188           If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,
189           what  happens  depends on why the string is invalid. If the string con-
190           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
191           string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,
192           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
193           strings  according  to  the more liberal rules of RFC 2279. However, if
194           the string does not even conform to RFC 2279, the result is  undefined.
195           Your program may crash.
196    
197           If  you  want  to  process  strings  of  values  in the full range 0 to
198           0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can
199           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
200           this situation, you will have to apply your own validity check.
201    
202       General comments about UTF-8 mode
203    
204         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
205         UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
206    
207         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
208           characters for values greater than \177.
209    
210           3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
211         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
212    
213         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         4.  The dot metacharacter matches one UTF-8 character instead of a sin-
214         gle byte.         gle byte.
215    
216         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
217         mode,  but  its  use can lead to some strange effects. This facility is         mode,  but  its  use can lead to some strange effects. This facility is
218         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
219    
220         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
221         test  characters of any code value, but the characters that PCRE recog-         test  characters of any code value, but the characters that PCRE recog-
222         nizes as digits, spaces, or word characters  remain  the  same  set  as         nizes as digits, spaces, or word characters  remain  the  same  set  as
223         before, all with values less than 256. This remains true even when PCRE         before, all with values less than 256. This remains true even when PCRE
# Line 182  UTF-8 AND UNICODE PROPERTY SUPPORT Line 226  UTF-8 AND UNICODE PROPERTY SUPPORT
226         sense of, say, "digit", you must use Unicode  property  tests  such  as         sense of, say, "digit", you must use Unicode  property  tests  such  as
227         \p{Nd}.         \p{Nd}.
228    
229         8.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
230         are all low-valued characters.         are all low-valued characters.
231    
232           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
233           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
234           acters.
235    
236         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
237         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
238         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
239         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
240         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
241         used only for characters with higher values.         used only for characters with higher values. Even when Unicode property
242           support is available, PCRE supports case-insensitive matching only when
243           there  is  a  one-to-one  mapping between a letter's cases. There are a
244           small number of many-to-one mappings in Unicode;  these  are  not  sup-
245           ported by PCRE.
246    
247    
248  AUTHOR  AUTHOR
249    
250         Philip Hazel         Philip Hazel
251         University Computing Service,         University Computing Service
252         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
253    
254         Putting  an actual email address here seems to have been a spam magnet,         Putting  an actual email address here seems to have been a spam magnet,
255         so I've taken it away. If you want to email me, use my initial and sur-         so I've taken it away. If you want to email me, use  my  two  initials,
256         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
257    
258    
259    REVISION
260    
261  Last updated: 07 March 2005         Last updated: 12 April 2008
262  Copyright (c) 1997-2005 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
263  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
264    
265    
# Line 218  NAME Line 273  NAME
273  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
274    
275         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
276         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
277         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
278         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
279         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
280         directory) can be obtained by running         environments using the GUI facility of  CMakeSetup  if  you  are  using
281           CMake instead of configure to build PCRE.
282    
283           The complete list of options for configure (which includes the standard
284           ones such as the  selection  of  the  installation  directory)  can  be
285           obtained by running
286    
287           ./configure --help           ./configure --help
288    
289         The following sections describe certain options whose names begin  with         The  following  sections  include  descriptions  of options whose names
290         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
291         for the configure command. Because of the  way  that  configure  works,         defaults  for  the configure command. Because of the way that configure
292         --enable  and  --disable  always  come  in  pairs, so the complementary         works, --enable and --disable always come in pairs, so  the  complemen-
293         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
294         not described.         is not described.
295    
296    
297    C++ SUPPORT
298    
299           By default, the configure script will search for a C++ compiler and C++
300           header files. If it finds them, it automatically builds the C++ wrapper
301           library for PCRE. You can disable this by adding
302    
303             --disable-cpp
304    
305           to the configure command.
306    
307    
308  UTF-8 SUPPORT  UTF-8 SUPPORT
# Line 240  UTF-8 SUPPORT Line 311  UTF-8 SUPPORT
311    
312           --enable-utf8           --enable-utf8
313    
314         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
315         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings  as UTF-8. As well as compiling PCRE with this option, you also
316         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()
317         function.         function.
318    
319    
320  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
321    
322         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
323         in  the  strings that it handles. On its own, however, it does not pro-         in the strings that it handles. On its own, however, it does  not  pro-
324         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
325         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         you want to be able to use the pattern escapes \P, \p,  and  \X,  which
326         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
327    
328           --enable-unicode-properties           --enable-unicode-properties
329    
330         to the configure command. This implies UTF-8 support, even if you  have         to  the configure command. This implies UTF-8 support, even if you have
331         not explicitly requested it.         not explicitly requested it.
332    
333         Including  Unicode  property  support  adds around 90K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
334         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE  library.  Only  the general category properties such as Lu and Nd
335         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
336    
337    
338  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
339    
340         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating
341         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
342         compile PCRE to use character 13 (carriage return) instead by adding         systems. You can compile PCRE to use character 13 (carriage return, CR)
343           instead, by adding
344    
345           --enable-newline-is-cr           --enable-newline-is-cr
346    
347         to the configure command. For completeness there is  also  a  --enable-         to  the  configure  command.  There  is  also  a --enable-newline-is-lf
348         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
349         line character.  
350           Alternatively, you can specify that line endings are to be indicated by
351           the two character sequence CRLF. If you want this, add
352    
353             --enable-newline-is-crlf
354    
355           to the configure command. There is a fourth option, specified by
356    
357             --enable-newline-is-anycrlf
358    
359           which  causes  PCRE  to recognize any of the three sequences CR, LF, or
360           CRLF as indicating a line ending. Finally, a fifth option, specified by
361    
362             --enable-newline-is-any
363    
364           causes PCRE to recognize any Unicode newline sequence.
365    
366           Whatever  line  ending convention is selected when PCRE is built can be
367           overridden when the library functions are called. At build time  it  is
368           conventional to use the standard for your operating system.
369    
370    
371    WHAT \R MATCHES
372    
373           By  default,  the  sequence \R in a pattern matches any Unicode newline
374           sequence, whatever has been selected as the line  ending  sequence.  If
375           you specify
376    
377             --enable-bsr-anycrlf
378    
379           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
380           ever is selected when PCRE is built can be overridden when the  library
381           functions are called.
382    
383    
384  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
385    
386         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
387         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
388         of         of
389    
390           --disable-shared           --disable-shared
# Line 293  BUILDING SHARED AND STATIC LIBRARIES Line 396  BUILDING SHARED AND STATIC LIBRARIES
396  POSIX MALLOC USAGE  POSIX MALLOC USAGE
397    
398         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
399         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
400         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
401         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
402         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
403         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.
404         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 306  POSIX MALLOC USAGE Line 409  POSIX MALLOC USAGE
409         to the configure command.         to the configure command.
410    
411    
 LIMITING PCRE RESOURCE USAGE  
   
        Internally,  PCRE has a function called match(), which it calls repeat-  
        edly  (possibly  recursively)  when  matching  a   pattern   with   the  
        pcre_exec()  function.  By controlling the maximum number of times this  
        function may be called during a single matching operation, a limit  can  
        be  placed  on  the resources used by a single call to pcre_exec(). The  
        limit can be changed at run time, as described in the pcreapi  documen-  
        tation.  The default is 10 million, but this can be changed by adding a  
        setting such as  
   
          --with-match-limit=500000  
   
        to  the  configure  command.  This  setting  has  no  effect   on   the  
        pcre_dfa_exec() matching function.  
   
   
412  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
413    
414         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
415         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
416         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
417         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
418         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
419         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process enormous patterns, so it
420         is  possible  to compile PCRE to use three-byte or four-byte offsets by         is possible to compile PCRE to use three-byte or four-byte  offsets  by
421         adding a setting such as         adding a setting such as
422    
423           --with-link-size=3           --with-link-size=3
424    
425         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
426         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
427         additional bytes when handling them.         additional bytes when handling them.
428    
        If you build PCRE with an increased link size, test 2 (and  test  5  if  
        you  are using UTF-8) will fail. Part of the output of these tests is a  
        representation of the compiled pattern, and this changes with the  link  
        size.  
   
429    
430  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
431    
# Line 352  AVOIDING EXCESSIVE STACK USAGE Line 433  AVOIDING EXCESSIVE STACK USAGE
433         ing by making recursive calls to an internal function  called  match().         ing by making recursive calls to an internal function  called  match().
434         In  environments  where  the size of the stack is limited, this can se-         In  environments  where  the size of the stack is limited, this can se-
435         verely limit PCRE's operation. (The Unix environment does  not  usually         verely limit PCRE's operation. (The Unix environment does  not  usually
436         suffer  from  this  problem.)  An alternative approach that uses memory         suffer from this problem, but it may sometimes be necessary to increase
437         from the heap to remember data, instead  of  using  recursive  function         the maximum stack size.  There is a discussion in the  pcrestack  docu-
438         calls,  has been implemented to work round this problem. If you want to         mentation.)  An alternative approach to recursion that uses memory from
439         build a version of PCRE that works this way, add         the heap to remember data, instead of using recursive  function  calls,
440           has  been  implemented to work round the problem of limited stack size.
441           If you want to build a version of PCRE that works this way, add
442    
443           --disable-stack-for-recursion           --disable-stack-for-recursion
444    
445         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. With this configuration, PCRE  will  use  the
446         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
447         ment functions. Separate functions are provided because  the  usage  is         ment functions. By default these point to malloc() and free(), but  you
448         very  predictable:  the  block sizes requested are always the same, and         can replace the pointers so that your own functions are used.
449         the blocks are always freed in reverse order. A calling  program  might  
450         be  able  to implement optimized functions that perform better than the         Separate  functions  are  provided  rather  than  using pcre_malloc and
451         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
452         slowly when built in this way. This option affects only the pcre_exec()         requested  are  always  the  same,  and  the blocks are always freed in
453         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
454           functions  that  perform  better  than  malloc()  and free(). PCRE runs
455           noticeably more slowly when built in this way. This option affects only
456           the   pcre_exec()   function;   it   is   not   relevant  for  the  the
457           pcre_dfa_exec() function.
458    
459    
460    LIMITING PCRE RESOURCE USAGE
461    
462           Internally, PCRE has a function called match(), which it calls  repeat-
463           edly   (sometimes   recursively)  when  matching  a  pattern  with  the
464           pcre_exec() function. By controlling the maximum number of  times  this
465           function  may be called during a single matching operation, a limit can
466           be placed on the resources used by a single call  to  pcre_exec().  The
467           limit  can be changed at run time, as described in the pcreapi documen-
468           tation. The default is 10 million, but this can be changed by adding  a
469           setting such as
470    
471             --with-match-limit=500000
472    
473           to   the   configure  command.  This  setting  has  no  effect  on  the
474           pcre_dfa_exec() matching function.
475    
476           In some environments it is desirable to limit the  depth  of  recursive
477           calls of match() more strictly than the total number of calls, in order
478           to restrict the maximum amount of stack (or heap,  if  --disable-stack-
479           for-recursion is specified) that is used. A second limit controls this;
480           it defaults to the value that  is  set  for  --with-match-limit,  which
481           imposes  no  additional constraints. However, you can set a lower limit
482           by adding, for example,
483    
484             --with-match-limit-recursion=10000
485    
486           to the configure command. This value can  also  be  overridden  at  run
487           time.
488    
489    
490    CREATING CHARACTER TABLES AT BUILD TIME
491    
492           PCRE  uses fixed tables for processing characters whose code values are
493           less than 256. By default, PCRE is built with a set of tables that  are
494           distributed  in  the  file pcre_chartables.c.dist. These tables are for
495           ASCII codes only. If you add
496    
497             --enable-rebuild-chartables
498    
499           to the configure command, the distributed tables are  no  longer  used.
500           Instead,  a  program  called dftables is compiled and run. This outputs
501           the source for new set of tables, created in the default locale of your
502           C runtime system. (This method of replacing the tables does not work if
503           you are cross compiling, because dftables is run on the local host.  If
504           you  need  to  create alternative tables when cross compiling, you will
505           have to do so "by hand".)
506    
507    
508  USING EBCDIC CODE  USING EBCDIC CODE
509    
510         PCRE assumes by default that it will run in an  environment  where  the         PCRE assumes by default that it will run in an  environment  where  the
511         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
512         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This is the case for most computer operating systems.  PCRE  can,  how-
513         adding         ever, be compiled to run in an EBCDIC environment by adding
514    
515           --enable-ebcdic           --enable-ebcdic
516    
517         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
518           bles. You should only use it if you know that  you  are  in  an  EBCDIC
519           environment (for example, an IBM mainframe operating system).
520    
521    
522    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
523    
524  Last updated: 28 February 2005         By default, pcregrep reads all files as plain text. You can build it so
525  Copyright (c) 1997-2005 University of Cambridge.         that it recognizes files whose names end in .gz or .bz2, and reads them
526           with libz or libbz2, respectively, by adding one or both of
527    
528             --enable-pcregrep-libz
529             --enable-pcregrep-libbz2
530    
531           to the configure command. These options naturally require that the rel-
532           evant libraries are installed on your system. Configuration  will  fail
533           if they are not.
534    
535    
536    PCRETEST OPTION FOR LIBREADLINE SUPPORT
537    
538           If you add
539    
540             --enable-pcretest-libreadline
541    
542           to  the  configure  command,  pcretest  is  linked with the libreadline
543           library, and when its input is from a terminal, it reads it  using  the
544           readline() function. This provides line-editing and history facilities.
545           Note that libreadline is GPL-licenced, so if you distribute a binary of
546           pcretest linked in this way, there may be licensing issues.
547    
548           Setting  this  option  causes  the -lreadline option to be added to the
549           pcretest build. In many operating environments with  a  sytem-installed
550           libreadline this is sufficient. However, in some environments (e.g.  if
551           an unmodified distribution version of readline is in use),  some  extra
552           configuration  may  be necessary. The INSTALL file for libreadline says
553           this:
554    
555             "Readline uses the termcap functions, but does not link with the
556             termcap or curses library itself, allowing applications which link
557             with readline the to choose an appropriate library."
558    
559           If your environment has not been set up so that an appropriate  library
560           is automatically included, you may need to add something like
561    
562             LIBS="-ncurses"
563    
564           immediately before the configure command.
565    
566    
567    SEE ALSO
568    
569           pcreapi(3), pcre_config(3).
570    
571    
572    AUTHOR
573    
574           Philip Hazel
575           University Computing Service
576           Cambridge CB2 3QH, England.
577    
578    
579    REVISION
580    
581           Last updated: 13 April 2008
582           Copyright (c) 1997-2008 University of Cambridge.
583  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
584    
585    
# Line 418  PCRE MATCHING ALGORITHMS Line 615  PCRE MATCHING ALGORITHMS
615           <something> <something else> <something further>           <something> <something else> <something further>
616    
617         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
618         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
619    
620    
621  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 427  REGULAR EXPRESSIONS AS TREES Line 624  REGULAR EXPRESSIONS AS TREES
624         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
625         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
626         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
627         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
628         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
629         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
630    
631    
632  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
633    
634         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
635         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
636         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
637         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
638         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 459  THE STANDARD MATCHING ALGORITHM Line 656  THE STANDARD MATCHING ALGORITHM
656         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
657    
658    
659  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
660    
661         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
662         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
663         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
664         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
665         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
666         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
667           keeps multiple states active simultaneously).
668         The  scan  continues until either the end of the subject is reached, or  
669         there are no more unterminated paths. At this point,  terminated  paths         The scan continues until either the end of the subject is  reached,  or
670         represent  the different matching possibilities (if there are none, the         there  are  no more unterminated paths. At this point, terminated paths
671         match has failed).  Thus, if there is more  than  one  possible  match,         represent the different matching possibilities (if there are none,  the
672           match  has  failed).   Thus,  if there is more than one possible match,
673         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
674         est. In PCRE, there is an option to stop the algorithm after the  first         est.  In PCRE, there is an option to stop the algorithm after the first
675         match (which is necessarily the shortest) has been found.         match (which is necessarily the shortest) has been found.
676    
677         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
# Line 481  THE DFA MATCHING ALGORITHM Line 679  THE DFA MATCHING ALGORITHM
679    
680           cat(er(pillar)?)           cat(er(pillar)?)
681    
682         is matched against the string "the caterpillar catchment",  the  result         is  matched  against the string "the caterpillar catchment", the result
683         will  be the three strings "cat", "cater", and "caterpillar" that start         will be the three strings "cat", "cater", and "caterpillar" that  start
684         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
685         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
686    
687         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
688         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
689    
690         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1.  Because  the  algorithm  finds  all possible matches, the greedy or
691         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
692         ungreedy quantifiers are treated in exactly the same way.         ungreedy quantifiers are treated in exactly the same way. However, pos-
693           sessive quantifiers can make a difference when what follows could  also
694           match what is quantified, for example in a pattern like this:
695    
696             ^a++\w!
697    
698           This  pattern matches "aaab!" but not "aaa!", which would be matched by
699           a non-possessive quantifier. Similarly, if an atomic group is  present,
700           it  is matched as if it were a standalone pattern at the current point,
701           and the longest match is then "locked in" for the rest of  the  overall
702           pattern.
703    
704         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
705         is  not  straightforward  to  keep track of captured substrings for the         is not straightforward to keep track of  captured  substrings  for  the
706         different matching possibilities, and  PCRE's  implementation  of  this         different  matching  possibilities,  and  PCRE's implementation of this
707         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
708         strings are available.         strings are available.
709    
710         3. Because no substrings are captured, back references within the  pat-         3.  Because no substrings are captured, back references within the pat-
711         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
712    
713         4.  For  the same reason, conditional expressions that use a backrefer-         4. For the same reason, conditional expressions that use  a  backrefer-
714         ence as the condition are not supported.         ence  as  the  condition or test for a specific group recursion are not
715           supported.
716    
717           5. Because many paths through the tree may be  active,  the  \K  escape
718           sequence, which resets the start of the match when encountered (but may
719           be on some paths and not on others), is not  supported.  It  causes  an
720           error if encountered.
721    
722         5. Callouts are supported, but the value of the  capture_top  field  is         6.  Callouts  are  supported, but the value of the capture_top field is
723         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
724    
725         6.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
726         single byte, even in UTF-8 mode, is not supported because the DFA algo-         single  byte, even in UTF-8 mode, is not supported because the alterna-
727         rithm moves through the subject string one character at a time, for all         tive algorithm moves through the subject  string  one  character  at  a
728         active paths through the tree.         time, for all active paths through the tree.
729    
730           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
731           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
732           negative assertion.
733    
 ADVANTAGES OF THE DFA ALGORITHM  
734    
735         Using the DFA matching algorithm provides the following advantages:  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
736    
737           Using  the alternative matching algorithm provides the following advan-
738           tages:
739    
740         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
741         ically  found,  and  in particular, the longest match is found. To find         ically  found,  and  in particular, the longest match is found. To find
# Line 525  ADVANTAGES OF THE DFA ALGORITHM Line 744  ADVANTAGES OF THE DFA ALGORITHM
744    
745         2.  There is much better support for partial matching. The restrictions         2.  There is much better support for partial matching. The restrictions
746         on the content of the pattern that apply when using the standard  algo-         on the content of the pattern that apply when using the standard  algo-
747         rithm  for partial matching do not apply to the DFA algorithm. For non-         rithm  for  partial matching do not apply to the alternative algorithm.
748         anchored patterns, the starting position of a partial match  is  avail-         For non-anchored patterns, the starting position of a partial match  is
749         able.         available.
750    
751         3.  Because  the  DFA algorithm scans the subject string just once, and         3.  Because  the  alternative  algorithm  scans the subject string just
752         never needs to backtrack, it is possible  to  pass  very  long  subject         once, and never needs to backtrack, it is possible to  pass  very  long
753         strings  to  the matching function in several pieces, checking for par-         subject  strings  to  the matching function in several pieces, checking
754         tial matching each time.         for partial matching each time.
755    
756    
757  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
758    
759         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
760    
761         1. It is substantially slower than  the  standard  algorithm.  This  is         1. It is substantially slower than  the  standard  algorithm.  This  is
762         partly  because  it has to search for all possible matches, but is also         partly  because  it has to search for all possible matches, but is also
# Line 545  DISADVANTAGES OF THE DFA ALGORITHM Line 764  DISADVANTAGES OF THE DFA ALGORITHM
764    
765         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
766    
767         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
768         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
769         rithm.  
770    
771    AUTHOR
772    
773           Philip Hazel
774           University Computing Service
775           Cambridge CB2 3QH, England.
776    
777  Last updated: 28 February 2005  
778  Copyright (c) 1997-2005 University of Cambridge.  REVISION
779    
780           Last updated: 19 April 2008
781           Copyright (c) 1997-2008 University of Cambridge.
782  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
783    
784    
# Line 603  PCRE NATIVE API Line 831  PCRE NATIVE API
831         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
832              const char *name);              const char *name);
833    
834           int pcre_get_stringtable_entries(const pcre *code,
835                const char *name, char **first, char **last);
836    
837         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
838              int stringcount, int stringnumber,              int stringcount, int stringnumber,
839              const char **stringptr);              const char **stringptr);
# Line 641  PCRE NATIVE API Line 872  PCRE NATIVE API
872  PCRE API OVERVIEW  PCRE API OVERVIEW
873    
874         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
875         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
876         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
877         Both of these APIs define a set of C function calls. A C++  wrapper  is         Both of these APIs define a set of C function calls. A C++  wrapper  is
878         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 659  PCRE API OVERVIEW Line 890  PCRE API OVERVIEW
890         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
891         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
892         the  source distribution. The pcresample documentation describes how to         the  source distribution. The pcresample documentation describes how to
893         run it.         compile and run it.
894    
895         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
896         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
897         ing. This allows it to find all possible matches (at a given  point  in         ing. The alternative algorithm finds all possible matches (at  a  given
898         the  subject),  not  just  one. However, this algorithm does not return         point  in  the subject), and scans the subject just once. However, this
899         captured substrings. A description of the two matching  algorithms  and         algorithm does not return captured substrings. A description of the two
900         their  advantages  and disadvantages is given in the pcrematching docu-         matching  algorithms and their advantages and disadvantages is given in
901         mentation.         the pcrematching documentation.
902    
903         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
904         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 679  PCRE API OVERVIEW Line 910  PCRE API OVERVIEW
910           pcre_get_named_substring()           pcre_get_named_substring()
911           pcre_get_substring_list()           pcre_get_substring_list()
912           pcre_get_stringnumber()           pcre_get_stringnumber()
913             pcre_get_stringtable_entries()
914    
915         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
916         to free the memory used for extracted strings.         to free the memory used for extracted strings.
# Line 710  PCRE API OVERVIEW Line 942  PCRE API OVERVIEW
942         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
943         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
944         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
945         function. This is a non-standard way of building PCRE, for use in envi-         function. See the pcrebuild documentation for  details  of  how  to  do
946         ronments that have limited stacks. Because of the greater use of memory         this.  It  is  a non-standard way of building PCRE, for use in environ-
947         management, it runs more slowly.  Separate functions  are  provided  so         ments that have limited stacks. Because of the greater  use  of  memory
948         that  special-purpose  external  code  can  be used for this case. When         management,  it  runs  more  slowly. Separate functions are provided so
949         used, these functions are always called in a  stack-like  manner  (last         that special-purpose external code can be  used  for  this  case.  When
950         obtained,  first freed), and always for memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
951           obtained, first freed), and always for memory blocks of the same  size.
952           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
953           mentation.
954    
955         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
956         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 723  PCRE API OVERVIEW Line 958  PCRE API OVERVIEW
958         pcrecallout documentation.         pcrecallout documentation.
959    
960    
961    NEWLINES
962    
963           PCRE  supports five different conventions for indicating line breaks in
964           strings: a single CR (carriage return) character, a  single  LF  (line-
965           feed) character, the two-character sequence CRLF, any of the three pre-
966           ceding, or any Unicode newline sequence. The Unicode newline  sequences
967           are  the  three just mentioned, plus the single characters VT (vertical
968           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
969           separator, U+2028), and PS (paragraph separator, U+2029).
970    
971           Each  of  the first three conventions is used by at least one operating
972           system as its standard newline sequence. When PCRE is built, a  default
973           can  be  specified.  The default default is LF, which is the Unix stan-
974           dard. When PCRE is run, the default can be overridden,  either  when  a
975           pattern is compiled, or when it is matched.
976    
977           At compile time, the newline convention can be specified by the options
978           argument of pcre_compile(), or it can be specified by special  text  at
979           the start of the pattern itself; this overrides any other settings. See
980           the pcrepattern page for details of the special character sequences.
981    
982           In the PCRE documentation the word "newline" is used to mean "the char-
983           acter  or pair of characters that indicate a line break". The choice of
984           newline convention affects the handling of  the  dot,  circumflex,  and
985           dollar metacharacters, the handling of #-comments in /x mode, and, when
986           CRLF is a recognized line ending sequence, the match position  advance-
987           ment for a non-anchored pattern. There is more detail about this in the
988           section on pcre_exec() options below.
989    
990           The choice of newline convention does not affect the interpretation  of
991           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
992           which is controlled in a similar way, but by separate options.
993    
994    
995  MULTITHREADING  MULTITHREADING
996    
997         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
998         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
999         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
1000         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1001    
1002         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1003         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1004         at once.         at once.
1005    
# Line 738  MULTITHREADING Line 1007  MULTITHREADING
1007  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1008    
1009         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1010         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
1011         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
1012         pcreprecompile documentation.         pcreprecompile  documentation.  However, compiling a regular expression
1013           with one version of PCRE for use with a different version is not  guar-
1014           anteed to work and may cause crashes.
1015    
1016    
1017  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
1018    
1019         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1020    
1021         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-
1022         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1023         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
1024         tures.         tures.
1025    
1026         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
1027         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1028         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
1029         available:         available:
1030    
1031           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1032    
1033         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-
1034         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1035    
1036           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1037    
1038         The  output  is  an  integer  that is set to one if support for Unicode         The output is an integer that is set to  one  if  support  for  Unicode
1039         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1040    
1041           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1042    
1043         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
1044         used  for the newline character. It is either linefeed (10) or carriage         sequence that is recognized as meaning "newline". The four values  that
1045         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,
1046         operating system.         and -1 for ANY. The default should normally be  the  standard  sequence
1047           for your operating system.
1048    
1049             PCRE_CONFIG_BSR
1050    
1051           The output is an integer whose value indicates what character sequences
1052           the \R escape sequence matches by default. A value of 0 means  that  \R
1053           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1054           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1055           tern is compiled or matched.
1056    
1057           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1058    
# Line 795  CHECKING BUILD-TIME OPTIONS Line 1075  CHECKING BUILD-TIME OPTIONS
1075         internal  matching  function  calls in a pcre_exec() execution. Further         internal  matching  function  calls in a pcre_exec() execution. Further
1076         details are given with pcre_exec() below.         details are given with pcre_exec() below.
1077    
1078             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1079    
1080           The output is an integer that gives the default limit for the depth  of
1081           recursion  when calling the internal matching function in a pcre_exec()
1082           execution. Further details are given with pcre_exec() below.
1083    
1084           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1085    
1086         The output is an integer that is set to one if internal recursion  when         The output is an integer that is set to one if internal recursion  when
# Line 827  COMPILING A PATTERN Line 1113  COMPILING A PATTERN
1113         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained  via  pcre_malloc is returned. This contains the compiled code
1114         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1115         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1116         It is up to the caller  to  free  the  memory  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1117         required.         longer required.
1118    
1119         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
1120         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
1121         fully  relocatable, because it may contain a copy of the tableptr argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1122         ment, which is an address (see below).         ment, which is an address (see below).
1123    
1124         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1125         tion.  It  should  be  zero  if  no options are required. The available         pilation.  It  should be zero if no options are required. The available
1126         options are described below. Some of them, in  particular,  those  that         options are described below. Some of them, in  particular,  those  that
1127         are  compatible  with  Perl,  can also be set and unset from within the         are  compatible  with  Perl,  can also be set and unset from within the
1128         pattern (see the detailed description  in  the  pcrepattern  documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
1129         tion).  For  these options, the contents of the options argument speci-         tion).  For  these options, the contents of the options argument speci-
1130         fies their initial settings at the start of compilation and  execution.         fies their initial settings at the start of compilation and  execution.
1131         The  PCRE_ANCHORED option can be set at the time of matching as well as         The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time
1132         at compile time.         of matching as well as at compile time.
1133    
1134         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1135         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1136         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-
1137         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
1138         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-
1139         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
1140           by erroffset, which must not be NULL. If it is, an immediate  error  is
1141         given.         given.
1142    
1143         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1144         codeptr  argument is not NULL, a non-zero error code number is returned         codeptr argument is not NULL, a non-zero error code number is  returned
1145         via this argument in the event of an error. This is in addition to  the         via  this argument in the event of an error. This is in addition to the
1146         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1147    
1148         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1149         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1150         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1151         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1152         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1153         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1154         support below.         support below.
1155    
1156         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1157         pile():         pile():
1158    
1159           pcre *re;           pcre *re;
# Line 879  COMPILING A PATTERN Line 1166  COMPILING A PATTERN
1166             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1167             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1168    
1169         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1170         file:         file:
1171    
1172           PCRE_ANCHORED           PCRE_ANCHORED
1173    
1174         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
1175         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
1176         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1177         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1178         only way to do it in Perl.         only way to do it in Perl.
1179    
1180           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1181    
1182         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1183         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1184         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1185    
1186             PCRE_BSR_ANYCRLF
1187             PCRE_BSR_UNICODE
1188    
1189           These options (which are mutually exclusive) control what the \R escape
1190           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1191           or to match any Unicode newline sequence. The default is specified when
1192           PCRE is built. It can be overridden from within the pattern, or by set-
1193           ting an option when a compiled pattern is matched.
1194    
1195           PCRE_CASELESS           PCRE_CASELESS
1196    
1197         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
1198         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
1199         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1200         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1201         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1202         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1203         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1204         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1205         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1206         UTF-8 support.         UTF-8 support.
1207    
1208           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1209    
1210         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
1211         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
1212         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
1213         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1214         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
1215         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1216    
1217           PCRE_DOTALL           PCRE_DOTALL
1218    
1219         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-
1220         acters, including newlines. Without it,  newlines  are  excluded.  This         acters,  including  those that indicate newline. Without it, a dot does
1221         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
1222         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
1223         always  matches a newline character, independent of the setting of this         by a (?s) option setting. A negative class such as [^a] always  matches
1224         option.         newline characters, independent of the setting of this option.
1225    
1226             PCRE_DUPNAMES
1227    
1228           If  this  bit is set, names used to identify capturing subpatterns need
1229           not be unique. This can be helpful for certain types of pattern when it
1230           is  known  that  only  one instance of the named subpattern can ever be
1231           matched. There are more details of named subpatterns  below;  see  also
1232           the pcrepattern documentation.
1233    
1234           PCRE_EXTENDED           PCRE_EXTENDED
1235    
1236         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1237         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1238         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1239         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1240         line character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1241         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-
1242         option setting.         ting.
1243    
1244         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1245         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1246         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1247         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1248         introduces a conditional subpattern.         introduces a conditional subpattern.
1249    
1250           PCRE_EXTRA           PCRE_EXTRA
1251    
1252         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1253         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1254         little use. When set, any backslash in a pattern that is followed by  a         little  use. When set, any backslash in a pattern that is followed by a
1255         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1256         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1257         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
1258         literal. There are at present no  other  features  controlled  by  this         literal.  (Perl can, however, be persuaded to give a warning for this.)
1259         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
1260           can also be set by a (?X) option setting within a pattern.
1261    
1262           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1263    
1264         If  this  option  is  set,  an  unanchored pattern is required to match         If  this  option  is  set,  an  unanchored pattern is required to match
1265         before or at the first newline character in the subject string,  though         before or at the first  newline  in  the  subject  string,  though  the
1266         the matched text may continue over the newline.         matched text may continue over the newline.
1267    
1268             PCRE_JAVASCRIPT_COMPAT
1269    
1270           If this option is set, PCRE's behaviour is changed in some ways so that
1271           it is compatible with JavaScript rather than Perl. The changes  are  as
1272           follows:
1273    
1274           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1275           error, because this is illegal in JavaScript (by default it is  treated
1276           as a data character). Thus, the pattern AB]CD becomes illegal when this
1277           option is set.
1278    
1279           (2) At run time, a back reference to an unset subpattern group  matches
1280           an  empty  string (by default this causes the current matching alterna-
1281           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1282           set  (assuming  it can find an "a" in the subject), whereas it fails by
1283           default, for Perl compatibility.
1284    
1285           PCRE_MULTILINE           PCRE_MULTILINE
1286    
1287         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1288         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1289         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1290         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1291         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1292         is set). This is the same as Perl.         is set). This is the same as Perl.
1293    
1294         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"
1295         constructs  match  immediately following or immediately before any new-         constructs match immediately following or immediately  before  internal
1296         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
1297         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
1298         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-
1299         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,
1300         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1301    
1302             PCRE_NEWLINE_CR
1303             PCRE_NEWLINE_LF
1304             PCRE_NEWLINE_CRLF
1305             PCRE_NEWLINE_ANYCRLF
1306             PCRE_NEWLINE_ANY
1307    
1308           These  options  override the default newline definition that was chosen
1309           when PCRE was built. Setting the first or the second specifies  that  a
1310           newline  is  indicated  by a single character (CR or LF, respectively).
1311           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1312           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1313           that any of the three preceding sequences should be recognized. Setting
1314           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1315           recognized. The Unicode newline sequences are the three just mentioned,
1316           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1317           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1318           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1319           UTF-8 mode.
1320    
1321           The newline setting in the  options  word  uses  three  bits  that  are
1322           treated as a number, giving eight possibilities. Currently only six are
1323           used (default plus the five values above). This means that if  you  set
1324           more  than one newline option, the combination may or may not be sensi-
1325           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1326           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1327           cause an error.
1328    
1329           The only time that a line break is specially recognized when  compiling
1330           a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
1331           character class is encountered. This indicates  a  comment  that  lasts
1332           until  after the next line break sequence. In other circumstances, line
1333           break  sequences  are  treated  as  literal  data,   except   that   in
1334           PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1335           and are therefore ignored.
1336    
1337           The newline option that is set at compile time becomes the default that
1338           is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1339    
1340           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1341    
1342         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 1004  COMPILING A PATTERN Line 1364  COMPILING A PATTERN
1364           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1365    
1366         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
1367         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1368         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
1369         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
1370         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-
1371         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
1372         your program to crash.  Note that this option can  also  be  passed  to         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1373         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined.  It  may  cause your program to crash. Note that this option
1374         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1375           UTF-8 validity checking of subject strings.
1376    
1377    
1378  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1379    
1380         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1381         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1382         both compiling functions.         both  compiling functions. As PCRE has developed, some error codes have
1383           fallen out of use. To avoid confusion, they have not been re-used.
1384    
1385            0  no error            0  no error
1386            1  \ at end of pattern            1  \ at end of pattern
# Line 1030  COMPILATION ERROR CODES Line 1392  COMPILATION ERROR CODES
1392            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1393            8  range out of order in character class            8  range out of order in character class
1394            9  nothing to repeat            9  nothing to repeat
1395           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1396           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1397           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1398           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1399           14  missing )           14  missing )
1400           15  reference to non-existent subpattern           15  reference to non-existent subpattern
1401           16  erroffset passed as NULL           16  erroffset passed as NULL
1402           17  unknown option bit(s) set           17  unknown option bit(s) set
1403           18  missing ) after comment           18  missing ) after comment
1404           19  parentheses nested too deeply           19  [this code is not in use]
1405           20  regular expression too large           20  regular expression is too large
1406           21  failed to get memory           21  failed to get memory
1407           22  unmatched parentheses           22  unmatched parentheses
1408           23  internal error: code overflow           23  internal error: code overflow
1409           24  unrecognized character after (?<           24  unrecognized character after (?<
1410           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1411           26  malformed number after (?(           26  malformed number or name after (?(
1412           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1413           28  assertion expected after (?(           28  assertion expected after (?(
1414           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1415           30  unknown POSIX class name           30  unknown POSIX class name
1416           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1417           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1418           33  spare error           33  [this code is not in use]
1419           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1420           35  invalid condition (?(0)           35  invalid condition (?(0)
1421           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1062  COMPILATION ERROR CODES Line 1424  COMPILATION ERROR CODES
1424           39  closing ) for (?C expected           39  closing ) for (?C expected
1425           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1426           41  unrecognized character after (?P           41  unrecognized character after (?P
1427           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1428           43  two named groups have the same name           43  two named subpatterns have the same name
1429           44  invalid UTF-8 string           44  invalid UTF-8 string
1430           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1431           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1432           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1433             48  subpattern name is too long (maximum 32 characters)
1434             49  too many named subpatterns (maximum 10000)
1435             50  [this code is not in use]
1436             51  octal value is greater than \377 (not in UTF-8 mode)
1437             52  internal error: overran compiling workspace
1438             53  internal  error:  previously-checked  referenced  subpattern  not
1439           found
1440             54  DEFINE group contains more than one branch
1441             55  repeating a DEFINE group is not allowed
1442             56  inconsistent NEWLINE options
1443             57  \g is not followed by a braced, angle-bracketed, or quoted
1444                   name/number or by a plain number
1445             58  a numbered reference must not be zero
1446             59  (*VERB) with an argument is not supported
1447             60  (*VERB) not recognized
1448             61  number is too big
1449             62  subpattern name expected
1450             63  digit expected after (?+
1451             64  ] is an invalid data character in JavaScript compatibility mode
1452    
1453           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1454           values may be used if the limits were changed when PCRE was built.
1455    
1456    
1457  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1098  STUDYING A PATTERN Line 1482  STUDYING A PATTERN
1482    
1483         The  third argument for pcre_study() is a pointer for an error message.         The  third argument for pcre_study() is a pointer for an error message.
1484         If studying succeeds (even if no data is  returned),  the  variable  it         If studying succeeds (even if no data is  returned),  the  variable  it
1485         points  to  is set to NULL. Otherwise it points to a textual error mes-         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1486         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1487         ing pcre_study(), to be sure that it has run successfully.         must  not  try  to  free it. You should test the error pointer for NULL
1488           after calling pcre_study(), to be sure that it has run successfully.
1489    
1490         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1491    
# Line 1111  STUDYING A PATTERN Line 1496  STUDYING A PATTERN
1496             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1497    
1498         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1499         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-
1500         ble starting bytes is created.         ble starting bytes is created.
1501    
1502    
1503  LOCALE SUPPORT  LOCALE SUPPORT
1504    
1505         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1506         letters digits, or whatever, by reference to a set of  tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1507         by  character  value.  When running in UTF-8 mode, this applies only to         by character value. When running in UTF-8 mode, this  applies  only  to
1508         characters with codes less than 128. Higher-valued  codes  never  match         characters  with  codes  less than 128. Higher-valued codes never match
1509         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built
1510         with Unicode character property support.         with  Unicode  character property support. The use of locales with Uni-
1511           code is discouraged. If you are handling characters with codes  greater
1512         An internal set of tables is created in the default C locale when  PCRE         than  128, you should either use UTF-8 and Unicode, or use locales, but
1513         is  built.  This  is  used when the final argument of pcre_compile() is         not try to mix the two.
1514         NULL, and is sufficient for many applications. An  alternative  set  of  
1515         tables  can,  however, be supplied. These may be created in a different         PCRE contains an internal set of tables that are used  when  the  final
1516         locale from the default. As more and more applications change to  using         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1517         Unicode, the need for this locale support is expected to die away.         applications.  Normally, the internal tables recognize only ASCII char-
1518           acters. However, when PCRE is built, it is possible to cause the inter-
1519         External  tables  are  built by calling the pcre_maketables() function,         nal tables to be rebuilt in the default "C" locale of the local system,
1520         which has no arguments, in the relevant locale. The result can then  be         which may cause them to be different.
1521         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For  
1522         example, to build and use tables that are appropriate  for  the  French         The  internal tables can always be overridden by tables supplied by the
1523         locale  (where  accented  characters  with  values greater than 128 are         application that calls PCRE. These may be created in a different locale
1524           from  the  default.  As more and more applications change to using Uni-
1525           code, the need for this locale support is expected to die away.
1526    
1527           External tables are built by calling  the  pcre_maketables()  function,
1528           which  has no arguments, in the relevant locale. The result can then be
1529           passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1530           example,  to  build  and use tables that are appropriate for the French
1531           locale (where accented characters with  values  greater  than  128  are
1532         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1533    
1534           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1535           tables = pcre_maketables();           tables = pcre_maketables();
1536           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1537    
1538           The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1539           if you are using Windows, the name for the French locale is "french".
1540    
1541         When pcre_maketables() runs, the tables are built  in  memory  that  is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1542         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1543         that the memory containing the tables remains available for as long  as         that the memory containing the tables remains available for as long  as
# Line 1187  INFORMATION ABOUT A PATTERN Line 1583  INFORMATION ABOUT A PATTERN
1583         pattern:         pattern:
1584    
1585           int rc;           int rc;
1586           unsigned long int length;           size_t length;
1587           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1588             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1589             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
# Line 1219  INFORMATION ABOUT A PATTERN Line 1615  INFORMATION ABOUT A PATTERN
1615           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1616    
1617         Return  information  about  the first byte of any matched string, for a         Return  information  about  the first byte of any matched string, for a
1618         non-anchored   pattern.   (This    option    used    to    be    called         non-anchored pattern. The fourth argument should point to an int  vari-
1619         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1620         compatibility.)         is still recognized for backwards compatibility.)
1621    
1622         If there is a fixed first byte, for example, from  a  pattern  such  as         If there is a fixed first byte, for example, from  a  pattern  such  as
1623         (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  
1624    
1625         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1626         branch starts with "^", or         branch starts with "^", or
1627    
1628         (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
1629         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1630    
1631         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1632         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1633         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1634    
1635           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1636    
1637         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
1638         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
1639         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1640         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1641         able.         able.
1642    
1643             PCRE_INFO_HASCRORLF
1644    
1645           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1646           characters, otherwise 0. The fourth argument should  point  to  an  int
1647           variable.  An explicit match is either a literal CR or LF character, or
1648           \r or \n.
1649    
1650             PCRE_INFO_JCHANGED
1651    
1652           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1653           otherwise  0. The fourth argument should point to an int variable. (?J)
1654           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1655    
1656           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1657    
1658         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 1261  INFORMATION ABOUT A PATTERN Line 1669  INFORMATION ABOUT A PATTERN
1669    
1670         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1671         ses.  The names are just an additional way of identifying the parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1672         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
1673         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring()  are  provided  for extracting captured sub-
1674         captured substring by name. It is also possible  to  extract  the  data         strings by name. It is also possible to extract the data  directly,  by
1675         directly,  by  first converting the name to a number in order to access         first  converting  the  name to a number in order to access the correct
1676         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
1677         below).  To  do the conversion, you need to use the name-to-number map,         the  conversion,  you  need  to  use  the  name-to-number map, which is
1678         which is described by these three values.         described by these three values.
1679    
1680         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
1681         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 1277  INFORMATION ABOUT A PATTERN Line 1685  INFORMATION ABOUT A PATTERN
1685         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-
1686         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-
1687         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1688         For example, consider the following pattern  (assume  PCRE_EXTENDED  is         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1689         set, so white space - including newlines - is ignored):         theses  numbers.  For  example,  consider the following pattern (assume
1690           PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
1691           ignored):
1692    
1693           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1694           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1695    
1696         There  are  four  named subpatterns, so the table has four entries, and         There  are  four  named subpatterns, so the table has four entries, and
1697         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,
# Line 1294  INFORMATION ABOUT A PATTERN Line 1704  INFORMATION ABOUT A PATTERN
1704           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1705    
1706         When writing code to extract data  from  named  subpatterns  using  the         When writing code to extract data  from  named  subpatterns  using  the
1707         name-to-number map, remember that the length of each entry is likely to         name-to-number  map,  remember that the length of the entries is likely
1708         be different for each compiled pattern.         to be different for each compiled pattern.
1709    
1710             PCRE_INFO_OKPARTIAL
1711    
1712           Return 1 if the pattern can be used for partial matching, otherwise  0.
1713           The  fourth  argument  should point to an int variable. The pcrepartial
1714           documentation lists the restrictions that apply to patterns  when  par-
1715           tial matching is used.
1716    
1717           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1718    
1719         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
1720         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1721         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1722         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1723           other  words,  they are the options that will be in force when matching
1724           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1725           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1726           and PCRE_EXTENDED.
1727    
1728         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
1729         alternatives begin with one of the following:         alternatives begin with one of the following:
1730    
1731           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1318  INFORMATION ABOUT A PATTERN Line 1739  INFORMATION ABOUT A PATTERN
1739    
1740           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1741    
1742         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
1743         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
1744         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
1745         size_t variable.         size_t variable.
# Line 1326  INFORMATION ABOUT A PATTERN Line 1747  INFORMATION ABOUT A PATTERN
1747           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1748    
1749         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1750         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
1751         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
1752         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
1753         variable.         variable.
1754    
1755    
# Line 1336  OBSOLETE INFO FUNCTION Line 1757  OBSOLETE INFO FUNCTION
1757    
1758         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1759    
1760         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1761         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1762         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1763         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-
1764         lowing negative numbers:         lowing negative numbers:
1765    
1766           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1767           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1768    
1769         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
1770         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
1771         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1772    
1773         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1774         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
1775         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1776    
1777    
# Line 1358  REFERENCE COUNTS Line 1779  REFERENCE COUNTS
1779    
1780         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1781    
1782         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1783         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1784         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1785         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1786         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1787    
1788         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1789         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1790         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1791         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1792         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1793         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1794    
1795         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1796         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1797         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1798    
1799    
# Line 1382  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1803  MATCHING A PATTERN: THE TRADITIONAL FUNC
1803              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1804              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1805    
1806         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
1807         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1808         has been studied, the result of the study should be passed in the extra         has been studied, the result of the study should be passed in the extra
1809         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1810         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1811         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1812         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1813    
1814         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1815         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1816         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1817         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1818         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1819    
1820         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1412  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1833  MATCHING A PATTERN: THE TRADITIONAL FUNC
1833    
1834     Extra data for pcre_exec()     Extra data for pcre_exec()
1835    
1836         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
1837         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
1838         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
1839         tional  information in it. The fields in a pcre_extra block are as fol-         tional information in it. The pcre_extra block contains  the  following
1840         lows:         fields (not necessarily in this order):
1841    
1842           unsigned long int flags;           unsigned long int flags;
1843           void *study_data;           void *study_data;
1844           unsigned long int match_limit;           unsigned long int match_limit;
1845             unsigned long int match_limit_recursion;
1846           void *callout_data;           void *callout_data;
1847           const unsigned char *tables;           const unsigned char *tables;
1848    
1849         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
1850         are set. The flag bits are:         are set. The flag bits are:
1851    
1852           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1853           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1854             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1855           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1856           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1857    
1858         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
1859         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1860         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1861         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1862         flag bits.         flag bits.
1863    
1864         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
1865         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
1866         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1867         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees.  The  classic  example  is  the  use of nested unlimited
1868         repeats.         repeats.
1869    
1870         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1871         edly (sometimes recursively). The limit is imposed  on  the  number  of         edly  (sometimes  recursively). The limit set by match_limit is imposed
1872         times  this  function is called during a match, which has the effect of         on the number of times this function is called during  a  match,  which
1873         limiting the amount of recursion and backtracking that can take  place.         has  the  effect  of  limiting the amount of backtracking that can take
1874         For patterns that are not anchored, the count starts from zero for each         place. For patterns that are not anchored, the count restarts from zero
1875         position in the subject string.         for each position in the subject string.
1876    
1877         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
1878         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1879         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1880         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra    block    in    which    match_limit    is    set,     and
1881         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
1882         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1883    
1884         The  pcre_callout  field is used in conjunction with the "callout" fea-         The match_limit_recursion field is similar to match_limit, but  instead
1885           of limiting the total number of times that match() is called, it limits
1886           the depth of recursion. The recursion depth is a  smaller  number  than
1887           the  total number of calls, because not all calls to match() are recur-
1888           sive.  This limit is of use only if it is set smaller than match_limit.
1889    
1890           Limiting  the  recursion  depth  limits the amount of stack that can be
1891           used, or, when PCRE has been compiled to use memory on the heap instead
1892           of the stack, the amount of heap memory that can be used.
1893    
1894           The  default  value  for  match_limit_recursion can be set when PCRE is
1895           built; the default default  is  the  same  value  as  the  default  for
1896           match_limit.  You can override the default by suppling pcre_exec() with
1897           a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1898           PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1899           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1900    
1901           The pcre_callout field is used in conjunction with the  "callout"  fea-
1902         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1903    
1904         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
1905         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
1906         pattern. A non-NULL value is stored with the compiled pattern  only  if         pattern.  A  non-NULL value is stored with the compiled pattern only if
1907         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
1908         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
1909         PCRE's  internal  tables  to be used. This facility is helpful when re-         PCRE's internal tables to be used. This facility is  helpful  when  re-
1910         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
1911         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
1912         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
1913         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1914    
1915     Option bits for pcre_exec()     Option bits for pcre_exec()
1916    
1917         The  unused  bits of the options argument for pcre_exec() must be zero.         The unused bits of the options argument for pcre_exec() must  be  zero.
1918         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
1919         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and
1920           PCRE_PARTIAL.
1921    
1922           PCRE_ANCHORED           PCRE_ANCHORED
1923    
# Line 1485  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1926  MATCHING A PATTERN: THE TRADITIONAL FUNC
1926         turned  out to be anchored by virtue of its contents, it cannot be made         turned  out to be anchored by virtue of its contents, it cannot be made
1927         unachored at matching time.         unachored at matching time.
1928    
1929             PCRE_BSR_ANYCRLF
1930             PCRE_BSR_UNICODE
1931    
1932           These options (which are mutually exclusive) control what the \R escape
1933           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1934           or to match any Unicode newline sequence. These  options  override  the
1935           choice that was made or defaulted when the pattern was compiled.
1936    
1937             PCRE_NEWLINE_CR
1938             PCRE_NEWLINE_LF
1939             PCRE_NEWLINE_CRLF
1940             PCRE_NEWLINE_ANYCRLF
1941             PCRE_NEWLINE_ANY
1942    
1943           These  options  override  the  newline  definition  that  was chosen or
1944           defaulted when the pattern was compiled. For details, see the  descrip-
1945           tion  of  pcre_compile()  above.  During  matching,  the newline choice
1946           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1947           ters.  It may also alter the way the match position is advanced after a
1948           match failure for an unanchored pattern.
1949    
1950           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1951           set,  and a match attempt for an unanchored pattern fails when the cur-
1952           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1953           explicit  matches  for  CR  or  LF  characters,  the  match position is
1954           advanced by two characters instead of one, in other words, to after the
1955           CRLF.
1956    
1957           The above rule is a compromise that makes the most common cases work as
1958           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1959           option is not set), it does not match the string "\r\nA" because, after
1960           failing at the start, it skips both the CR and the LF before  retrying.
1961           However,  the  pattern  [\r\n]A does match that string, because it con-
1962           tains an explicit CR or LF reference, and so advances only by one char-
1963           acter after the first failure.
1964    
1965           An explicit match for CR of LF is either a literal appearance of one of
1966           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1967           matches  such  as [^X] do not count, nor does \s (which includes CR and
1968           LF in the characters that it matches).
1969    
1970           Notwithstanding the above, anomalous effects may still occur when  CRLF
1971           is a valid newline sequence and explicit \r or \n escapes appear in the
1972           pattern.
1973    
1974           PCRE_NOTBOL           PCRE_NOTBOL
1975    
1976         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
# Line 1530  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2016  MATCHING A PATTERN: THE TRADITIONAL FUNC
2016         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2017         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2018         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2019         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2020         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2021         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2022         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2023           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2024         If you already know that your subject is valid, and you  want  to  skip  
2025         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
2026         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
2027         do  this  for the second and subsequent calls to pcre_exec() if you are         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2028         making repeated calls to find all  the  matches  in  a  single  subject         do this for the second and subsequent calls to pcre_exec() if  you  are
2029         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
2030         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         string. However, you should be  sure  that  the  value  of  startoffset
2031         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
2032         value of startoffset that does not point to the start of a UTF-8  char-         set, the effect of passing an invalid UTF-8 string as a subject,  or  a
2033           value  of startoffset that does not point to the start of a UTF-8 char-
2034         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2035    
2036           PCRE_PARTIAL           PCRE_PARTIAL
2037    
2038         This  option  turns  on  the  partial  matching feature. If the subject         This option turns on the  partial  matching  feature.  If  the  subject
2039         string fails to match the pattern, but at some point during the  match-         string  fails to match the pattern, but at some point during the match-
2040         ing  process  the  end of the subject was reached (that is, the subject         ing process the end of the subject was reached (that  is,  the  subject
2041         partially matches the pattern and the failure to  match  occurred  only         partially  matches  the  pattern and the failure to match occurred only
2042         because  there were not enough subject characters), pcre_exec() returns         because there were not enough subject characters), pcre_exec()  returns
2043         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
2044         used,  there  are restrictions on what may appear in the pattern. These         used, there are restrictions on what may appear in the  pattern.  These
2045         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
2046    
2047     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2048    
2049         The subject string is passed to pcre_exec() as a pointer in subject,  a         The  subject string is passed to pcre_exec() as a pointer in subject, a
2050         length  in  length, and a starting byte offset in startoffset. In UTF-8         length in length, and a starting byte offset in startoffset.  In  UTF-8
2051         mode, the byte offset must point to the start  of  a  UTF-8  character.         mode,  the  byte  offset  must point to the start of a UTF-8 character.
2052         Unlike  the  pattern string, the subject may contain binary zero bytes.         Unlike the pattern string, the subject may contain binary  zero  bytes.
2053         When the starting offset is zero, the search for a match starts at  the         When  the starting offset is zero, the search for a match starts at the
2054         beginning of the subject, and this is by far the most common case.         beginning of the subject, and this is by far the most common case.
2055    
2056         A  non-zero  starting offset is useful when searching for another match         A non-zero starting offset is useful when searching for  another  match
2057         in the same subject by calling pcre_exec() again after a previous  suc-         in  the same subject by calling pcre_exec() again after a previous suc-
2058         cess.   Setting  startoffset differs from just passing over a shortened         cess.  Setting startoffset differs from just passing over  a  shortened
2059         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2060         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2061    
2062           \Biss\B           \Biss\B
2063    
2064         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2065         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.)
2066         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2067         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2068         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2069         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
2070         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
2071         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2072         rence  of "iss" because it is able to look behind the starting point to         rence of "iss" because it is able to look behind the starting point  to
2073         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2074    
2075         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,
2076         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2077         if the pattern does not require the match to be at  the  start  of  the         if  the  pattern  does  not require the match to be at the start of the
2078         subject.         subject.
2079    
2080     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2081    
2082         In  general, a pattern matches a certain portion of the subject, and in         In general, a pattern matches a certain portion of the subject, and  in
2083         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2084         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2085         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2086         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2087         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2088         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2089    
2090         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of  integer
2091         offsets whose address is passed in ovector. The number of  elements  in         offsets  whose  address is passed in ovector. The number of elements in
2092         the  vector is passed in ovecsize, which must be a non-negative number.         the vector is passed in ovecsize, which must be a non-negative  number.
2093         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
2094    
2095         The first two-thirds of the vector is used to pass back  captured  sub-         The  first  two-thirds of the vector is used to pass back captured sub-
2096         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2097         of the vector is used as workspace by pcre_exec() while  matching  cap-         of  the  vector is used as workspace by pcre_exec() while matching cap-
2098         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2099         The length passed in ovecsize should always be a multiple of three.  If         The  length passed in ovecsize should always be a multiple of three. If
2100         it is not, it is rounded down.         it is not, it is rounded down.
2101    
2102         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2103         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2104         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
2105         element of a pair is set to the offset of the first character in a sub-         element of a pair is set to the offset of the first character in a sub-
2106         string,  and  the  second  is  set to the offset of the first character         string, and the second is set to the  offset  of  the  first  character
2107         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
2108         tor[1],  identify  the  portion  of  the  subject string matched by the         tor[1], identify the portion of  the  subject  string  matched  by  the
2109         entire pattern. The next pair is used for the first  capturing  subpat-         entire  pattern.  The next pair is used for the first capturing subpat-
2110         tern,  and  so  on.  The value returned by pcre_exec() is the number of         tern, and so on. The value returned by pcre_exec() is one more than the
2111         pairs that have been set. If there are no  capturing  subpatterns,  the         highest numbered pair that has been set. For example, if two substrings
2112         return  value  from  a  successful match is 1, indicating that just the         have been captured, the returned value is 3. If there are no  capturing
2113         first pair of offsets has been set.         subpatterns,  the return value from a successful match is 1, indicating
2114           that just the first pair of offsets has been set.
        Some convenience functions are provided  for  extracting  the  captured  
        substrings  as  separate  strings. These are described in the following  
        section.  
   
        It is possible for an capturing subpattern number  n+1  to  match  some  
        part  of  the  subject  when subpattern n has not been used at all. For  
        example, if the string "abc" is matched against the pattern (a|(z))(bc)  
        subpatterns  1 and 3 are matched, but 2 is not. When this happens, both  
        offset values corresponding to the unused subpattern are set to -1.  
2115    
2116         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2117         of the string that it matched that is returned.         of the string that it matched that is returned.
# Line 1647  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2125  MATCHING A PATTERN: THE TRADITIONAL FUNC
2125         substrings,  PCRE has to get additional memory for use during matching.         substrings,  PCRE has to get additional memory for use during matching.
2126         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
2127    
2128         Note that pcre_info() can be used to find out how many  capturing  sub-         The pcre_info() function can be used to find  out  how  many  capturing
2129         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2130         that will allow for n captured substrings, in addition to  the  offsets         ovector that will allow for n captured substrings, in addition  to  the
2131         of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2132    
2133           It  is  possible for capturing subpattern number n+1 to match some part
2134           of the subject when subpattern n has not been used at all. For example,
2135           if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2136           return from the function is 4, and subpatterns 1 and 3 are matched, but
2137           2  is  not.  When  this happens, both values in the offset pairs corre-
2138           sponding to unused subpatterns are set to -1.
2139    
2140           Offset values that correspond to unused subpatterns at the end  of  the
2141           expression  are  also  set  to  -1. For example, if the string "abc" is
2142           matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
2143           matched.  The  return  from the function is 2, because the highest used
2144           capturing subpattern number is 1. However, you can refer to the offsets
2145           for  the  second  and third capturing subpatterns if you wish (assuming
2146           the vector is large enough, of course).
2147    
2148           Some convenience functions are provided  for  extracting  the  captured
2149           substrings as separate strings. These are described below.
2150    
2151     Return values from pcre_exec()     Error return values from pcre_exec()
2152    
2153         If  pcre_exec()  fails, it returns a negative number. The following are         If  pcre_exec()  fails, it returns a negative number. The following are
2154         defined in the header file:         defined in the header file:
# Line 1678  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2174  MATCHING A PATTERN: THE TRADITIONAL FUNC
2174         an environment with the other endianness. This is the error  that  PCRE         an environment with the other endianness. This is the error  that  PCRE
2175         gives when the magic number is not present.         gives when the magic number is not present.
2176    
2177           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2178    
2179         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2180         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 1700  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2196  MATCHING A PATTERN: THE TRADITIONAL FUNC
2196    
2197           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2198    
2199         The  recursion  and backtracking limit, as specified by the match_limit         The  backtracking  limit,  as  specified  by the match_limit field in a
2200         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra structure (or defaulted) was reached.  See  the  description
2201         description above.         above.
2202    
2203           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2204    
# Line 1741  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2237  MATCHING A PATTERN: THE TRADITIONAL FUNC
2237    
2238         This error is given if the value of the ovecsize argument is  negative.         This error is given if the value of the ovecsize argument is  negative.
2239    
2240             PCRE_ERROR_RECURSIONLIMIT (-21)
2241    
2242           The internal recursion limit, as specified by the match_limit_recursion
2243           field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2244           description above.
2245    
2246             PCRE_ERROR_BADNEWLINE     (-23)
2247    
2248           An invalid combination of PCRE_NEWLINE_xxx options was given.
2249    
2250           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2251    
2252    
2253  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2254    
# Line 1761  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2269  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2269         string_list() are provided for extracting captured substrings  as  new,         string_list() are provided for extracting captured substrings  as  new,
2270         separate,  zero-terminated strings. These functions identify substrings         separate,  zero-terminated strings. These functions identify substrings
2271         by number. The next section describes functions  for  extracting  named         by number. The next section describes functions  for  extracting  named
2272         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2273         extracted and has a further zero added on the end, but  the  result  is  
2274         not, of course, a C string.         A  substring that contains a binary zero is correctly extracted and has
2275           a further zero added on the end, but the result is not, of course, a  C
2276           string.   However,  you  can  process such a string by referring to the
2277           length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2278           string().  Unfortunately, the interface to pcre_get_substring_list() is
2279           not adequate for handling strings containing binary zeros, because  the
2280           end of the final string is not independently indicated.
2281    
2282         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-
2283         tions: subject is the subject string that has  just  been  successfully         tions: subject is the subject string that has  just  been  successfully
# Line 1783  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2297  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2297         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2298         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2299         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
2300         the terminating zero, or one of         the terminating zero, or one of these error codes:
2301    
2302           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2303    
# Line 1799  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2313  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2313         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2314         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
2315         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
2316         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
2317           error code
2318    
2319           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2320    
2321         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2322    
2323         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2324         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2325         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2326         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2327         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2328         tive for unset substrings.         tive for unset substrings.
2329    
2330         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2331         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2332         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2333         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2334         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.
2335         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-
2336         cial  interface  to  another  programming  language  which  cannot  use         cial   interface  to  another  programming  language  that  cannot  use
2337         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-
2338         vided.         vided.
2339    
2340    
# Line 1838  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2353  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2353              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2354              const char **stringptr);              const char **stringptr);
2355    
2356         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-
2357         ber.  For example, for this pattern         ber.  For example, for this pattern
2358    
2359           (a+)b(?P<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2360    
2361         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. If the name is known to
2362         from the name by calling pcre_get_stringnumber(). The first argument is         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2363         the  compiled  pattern,  and  the  second is the name. The yield of the         name by calling pcre_get_stringnumber(). The first argument is the com-
2364         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if         piled pattern, and the second is the name. The yield of the function is
2365         there is no subpattern of that name.         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2366           subpattern of that name.
2367    
2368         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2369         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
# Line 1866  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2382  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2382    
2383         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2384         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2385         ate.         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2386           behaviour may not be what you want (see the next section).
2387    
2388    
2389    DUPLICATE SUBPATTERN NAMES
2390    
2391           int pcre_get_stringtable_entries(const pcre *code,
2392                const char *name, char **first, char **last);
2393    
2394           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2395           subpatterns are not required to  be  unique.  Normally,  patterns  with
2396           duplicate  names  are such that in any one match, only one of the named
2397           subpatterns participates. An example is shown in the pcrepattern  docu-
2398           mentation.
2399    
2400           When    duplicates   are   present,   pcre_copy_named_substring()   and
2401           pcre_get_named_substring() return the first substring corresponding  to
2402           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2403           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2404           function  returns one of the numbers that are associated with the name,
2405           but it is not defined which it is.
2406    
2407           If you want to get full details of all captured substrings for a  given
2408           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2409           first argument is the compiled pattern, and the second is the name. The
2410           third  and  fourth  are  pointers to variables which are updated by the
2411           function. After it has run, they point to the first and last entries in
2412           the  name-to-number  table  for  the  given  name.  The function itself
2413           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2414           there  are none. The format of the table is described above in the sec-
2415           tion entitled Information about a  pattern.   Given  all  the  relevant
2416           entries  for the name, you can extract each of their numbers, and hence
2417           the captured data, if any.
2418    
2419    
2420  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 1895  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2443  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2443              int *workspace, int wscount);              int *workspace, int wscount);
2444    
2445         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2446         against a compiled pattern, using a "DFA" matching algorithm. This  has         against a compiled pattern, using a matching algorithm that  scans  the
2447         different  characteristics to the normal algorithm, and is not compati-         subject  string  just  once, and does not backtrack. This has different
2448         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics to the normal algorithm, and  is  not  compatible  with
2449         Nevertheless, there are times when this kind of matching can be useful.         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2450         For a discussion of the two matching algorithms, see  the  pcrematching         theless, there are times when this kind of matching can be useful.  For
2451         documentation.         a discussion of the two matching algorithms, see the pcrematching docu-
2452           mentation.
2453    
2454         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The arguments for the pcre_dfa_exec() function  are  the  same  as  for
2455         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2456         ent  way,  and  this is described below. The other common arguments are         ent way, and this is described below. The other  common  arguments  are
2457         used in the same way as for pcre_exec(), so their  description  is  not         used  in  the  same way as for pcre_exec(), so their description is not
2458         repeated here.         repeated here.
2459    
2460         The  two  additional  arguments provide workspace for the function. The         The two additional arguments provide workspace for  the  function.  The
2461         workspace vector should contain at least 20 elements. It  is  used  for         workspace  vector  should  contain at least 20 elements. It is used for
2462         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2463         workspace will be needed for patterns and subjects where  there  are  a         workspace  will  be  needed for patterns and subjects where there are a
2464         lot of possible matches.         lot of potential matches.
2465    
2466         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_dfa_exec():
2467    
2468           int rc;           int rc;
2469           int ovector[10];           int ovector[10];
2470           int wspace[20];           int wspace[20];
2471           rc = pcre_exec(           rc = pcre_dfa_exec(
2472             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2473             NULL,           /* we didn't study the pattern */             NULL,           /* we didn't study the pattern */
2474             "some string",  /* the subject string */             "some string",  /* the subject string */
# Line 1933  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2482  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2482    
2483     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2484    
2485         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The unused bits of the options argument  for  pcre_dfa_exec()  must  be
2486         zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
2487         PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
2488         PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
2489         these  are  the  same  as  for pcre_exec(), so their description is not         three of these are the same as for pcre_exec(), so their description is
2490         repeated here.         not repeated here.
2491    
2492           PCRE_PARTIAL           PCRE_PARTIAL
2493    
2494         This has the same general effect as it does for  pcre_exec(),  but  the         This  has  the  same general effect as it does for pcre_exec(), but the
2495         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
2496         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
2497         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have
2498         been no complete matches, but there is still at least one matching pos-         been no complete matches, but there is still at least one matching pos-
2499         sibility.  The portion of the string that provided the partial match is         sibility. The portion of the string that provided the partial match  is
2500         set as the first matching string.         set as the first matching string.
2501    
2502           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2503    
2504         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
2505         stop  as  soon  as  it  has found one match. Because of the way the DFA         stop as soon as it has found one match. Because of the way the alterna-
2506         algorithm works, this is necessarily the shortest possible match at the         tive  algorithm  works, this is necessarily the shortest possible match
2507         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2508    
2509           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2510    
2511         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
2512         returns a partial match, it is possible to call it  again,  with  addi-         returns  a  partial  match, it is possible to call it again, with addi-
2513         tional  subject  characters,  and have it continue with the same match.         tional subject characters, and have it continue with  the  same  match.
2514         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         The  PCRE_DFA_RESTART  option requests this action; when it is set, the
2515         workspace  and wscount options must reference the same vector as before         workspace and wscount options must reference the same vector as  before
2516         because data about the match so far is left in  them  after  a  partial         because  data  about  the  match so far is left in them after a partial
2517         match.  There  is  more  discussion of this facility in the pcrepartial         match. There is more discussion of this  facility  in  the  pcrepartial
2518         documentation.         documentation.
2519    
2520     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2521    
2522         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2523         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2524         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2525         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2526         if the pattern         if the pattern
2527    
2528           <.*>           <.*>
# Line 1988  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2537  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2537           <something> <something else>           <something> <something else>
2538           <something> <something else> <something further>           <something> <something else> <something further>
2539    
2540         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2541         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2542         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2543         the  offset  to the start, and the second is the offset to the end. All         the offset to the start, and the second is the offset to  the  end.  In
2544         the strings have the same start offset. (Space could have been saved by         fact,  all  the  strings  have the same start offset. (Space could have
2545         giving  this only once, but it was decided to retain some compatibility         been saved by giving this only once, but it was decided to retain  some
2546         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility  with  the  way pcre_exec() returns data, even though the
2547         strings is different.)         meaning of the strings is different.)
2548    
2549         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2550         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2551         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2552         filled with the longest matches.         filled with the longest matches.
2553    
2554     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2555    
2556         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2557         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2558         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2559         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2560    
2561           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2562    
2563         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2564         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2565         reference.         reference.
2566    
2567           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2568    
2569         This  return is given if pcre_dfa_exec() encounters a condition item in         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2570         a pattern that uses a back reference for the  condition.  This  is  not         that  uses  a back reference for the condition, or a test for recursion
2571         supported.         in a specific group. These are not supported.
2572    
2573           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2574    
2575         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2576         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2577         (it is meaningless).         (it is meaningless).
2578    
2579           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2580    
2581         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2582         workspace vector.         workspace vector.
2583    
2584           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2585    
2586         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2587         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2588         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2589         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2590    
2591  Last updated: 16 May 2005  
2592  Copyright (c) 1997-2005 University of Cambridge.  SEE ALSO
2593    
2594           pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2595           tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2596    
2597    
2598    AUTHOR
2599    
2600           Philip Hazel
2601           University Computing Service
2602           Cambridge CB2 3QH, England.
2603    
2604    
2605    REVISION
2606    
2607           Last updated: 12 April 2008
2608           Copyright (c) 1997-2008 University of Cambridge.
2609  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2610    
2611    
# Line 2067  PCRE CALLOUTS Line 2632  PCRE CALLOUTS
2632         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2633         points:         points:
2634    
2635           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2636    
2637         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
2638         called, PCRE automatically  inserts  callouts,  all  with  number  255,         called, PCRE automatically  inserts  callouts,  all  with  number  255,
# Line 2142  THE CALLOUT INTERFACE Line 2707  THE CALLOUT INTERFACE
2707         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2708         were passed to pcre_exec().         were passed to pcre_exec().
2709    
2710         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2711         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2712         callout function may be called several times from the same point in the         sequence \K has been encountered, this value is changed to reflect  the
2713         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2714           function may be called several times from the same point in the pattern
2715           for different starting points in the subject.
2716    
2717         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2718         the current match pointer.         the current match pointer.
# Line 2198  RETURN VALUES Line 2765  RETURN VALUES
2765         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
2766         itself.         itself.
2767    
2768  Last updated: 28 February 2005  
2769  Copyright (c) 1997-2005 University of Cambridge.  AUTHOR
2770    
2771           Philip Hazel
2772           University Computing Service
2773           Cambridge CB2 3QH, England.
2774    
2775    
2776    REVISION
2777    
2778           Last updated: 29 May 2007
2779           Copyright (c) 1997-2007 University of Cambridge.
2780  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2781    
2782    
# Line 2213  NAME Line 2790  NAME
2790  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2791    
2792         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2793         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences described here  are  mainly
2794         respect to Perl 5.8.         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2795           some features that are expected to be in the forthcoming Perl 5.10.
2796         1.  PCRE does not have full UTF-8 support. Details of what it does have  
2797         are given in the section on UTF-8 support in the main pcre page.         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
2798           of  what  it does have are given in the section on UTF-8 support in the
2799           main pcre page.
2800    
2801         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
2802         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 2244  DIFFERENCES BETWEEN PCRE AND PERL Line 2823  DIFFERENCES BETWEEN PCRE AND PERL
2823         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
2824         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
2825         can be tested with \p and \P are limited to the general category  prop-         can be tested with \p and \P are limited to the general category  prop-
2826         erties such as Lu and Nd.         erties  such  as  Lu and Nd, script names such as Greek or Han, and the
2827           derived properties Any and L&.
2828    
2829         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2830         ters in between are treated as literals.  This  is  slightly  different         ters  in  between  are  treated as literals. This is slightly different
2831         from  Perl  in  that  $  and  @ are also handled as literals inside the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
2832         quotes. In Perl, they cause variable interpolation (but of course  PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
2833         does not have variables). Note the following examples:         does not have variables). Note the following examples:
2834    
2835             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2259  DIFFERENCES BETWEEN PCRE AND PERL Line 2839  DIFFERENCES BETWEEN PCRE AND PERL
2839             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
2840             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
2841    
2842         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
2843         classes.         classes.
2844    
2845         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2846         constructions.  However,  there is support for recursive patterns using         constructions. However, there is support for recursive  patterns.  This
2847         the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE
2848         "callout"  feature allows an external function to be called during pat-         "callout" feature allows an external function to be called during  pat-
2849         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
2850    
2851         9. There are some differences that are concerned with the  settings  of         9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2852         captured  strings  when  part  of  a  pattern is repeated. For example,         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2853         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         unlike Perl.
2854    
2855           10.  There are some differences that are concerned with the settings of
2856           captured strings when part of  a  pattern  is  repeated.  For  example,
2857           matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2858         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2859    
2860         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2861         ities:         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2862           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2863           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2864           ture group; this is different to Perl.
2865    
2866           12. PCRE provides some extensions to the Perl regular expression facil-
2867           ities.   Perl  5.10  will  include new features that are not in earlier
2868           versions, some of which (such as named parentheses) have been  in  PCRE
2869           for some time. This list is with respect to Perl 5.10:
2870    
2871         (a) Although lookbehind assertions must  match  fixed  length  strings,         (a)  Although  lookbehind  assertions  must match fixed length strings,
2872         each alternative branch of a lookbehind assertion can match a different         each alternative branch of a lookbehind assertion can match a different
2873         length of string. Perl requires them all to have the same length.         length of string. Perl requires them all to have the same length.
2874    
2875         (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
2876         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2877    
2878         (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-
2879         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2880           ignored.  (Perl can be made to issue a warning.)
2881    
2882         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2883         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2296  DIFFERENCES BETWEEN PCRE AND PERL Line 2889  DIFFERENCES BETWEEN PCRE AND PERL
2889         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
2890         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2891    
2892         (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
2893         pattern  matching  (Perl  can  do  this using the (?p{code}) construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
2894    
2895         (h) PCRE supports named capturing substrings, using the Python  syntax.         (h) The callout facility is PCRE-specific.
2896    
2897         (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
2898    
2899         (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,
2900           even on different hosts that have the other endianness.
2901    
2902         (k) The callout facility is PCRE-specific.         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2903           different way and is not Perl-compatible.
2904    
2905         (l) The partial matching facility is PCRE-specific.         (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2906           of a pattern that set overall options that cannot be changed within the
2907           pattern.
2908    
        (m) Patterns compiled by PCRE can be saved and re-used at a later time,  
        even on different hosts that have the other endianness.  
2909    
2910         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a  AUTHOR
        different way and is not Perl-compatible.  
2911    
2912  Last updated: 28 February 2005         Philip Hazel
2913  Copyright (c) 1997-2005 University of Cambridge.         University Computing Service
2914           Cambridge CB2 3QH, England.
2915    
2916    
2917    REVISION
2918    
2919           Last updated: 11 September 2007
2920           Copyright (c) 1997-2007 University of Cambridge.
2921  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2922    
2923    
# Line 2331  NAME Line 2930  NAME
2930    
2931  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2932    
2933         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
2934         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
2935         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
2936         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
2937         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
2938         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
2939           Python, .NET, and Oniguruma.
2940    
2941           Perl's  regular expressions are described in its own documentation, and
2942           regular expressions in general are covered in a number of  books,  some
2943           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
2944           Expressions", published by  O'Reilly,  covers  regular  expressions  in
2945           great  detail.  This  description  of  PCRE's  regular  expressions  is
2946           intended as reference material.
2947    
2948         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2949         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
# Line 2350  PCRE REGULAR EXPRESSION DETAILS Line 2957  PCRE REGULAR EXPRESSION DETAILS
2957         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
2958         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
2959         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
2960         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
2961         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
2962         the pcrematching page.         alternative function, and how it differs from the normal function,  are
2963           discussed in the pcrematching page.
2964         A regular expression is a pattern that is  matched  against  a  subject  
2965         string  from  left  to right. Most characters stand for themselves in a  
2966         pattern, and match the corresponding characters in the  subject.  As  a  NEWLINE CONVENTIONS
2967    
2968           PCRE  supports five different conventions for indicating line breaks in
2969           strings: a single CR (carriage return) character, a  single  LF  (line-
2970           feed) character, the two-character sequence CRLF, any of the three pre-
2971           ceding, or any Unicode newline sequence. The pcreapi page  has  further
2972           discussion  about newlines, and shows how to set the newline convention
2973           in the options arguments for the compiling and matching functions.
2974    
2975           It is also possible to specify a newline convention by starting a  pat-
2976           tern string with one of the following five sequences:
2977    
2978             (*CR)        carriage return
2979             (*LF)        linefeed
2980             (*CRLF)      carriage return, followed by linefeed
2981             (*ANYCRLF)   any of the three above
2982             (*ANY)       all Unicode newline sequences
2983    
2984           These override the default and the options given to pcre_compile(). For
2985           example, on a Unix system where LF is the default newline sequence, the
2986           pattern
2987    
2988             (*CR)a.b
2989    
2990           changes the convention to CR. That pattern matches "a\nb" because LF is
2991           no longer a newline. Note that these special settings,  which  are  not
2992           Perl-compatible,  are  recognized  only at the very start of a pattern,
2993           and that they must be in upper case.  If  more  than  one  of  them  is
2994           present, the last one is used.
2995    
2996           The  newline  convention  does  not  affect what the \R escape sequence
2997           matches. By default, this is any Unicode  newline  sequence,  for  Perl
2998           compatibility.  However, this can be changed; see the description of \R
2999           in the section entitled "Newline sequences" below. A change of \R  set-
3000           ting can be combined with a change of newline convention.
3001    
3002    
3003    CHARACTERS AND METACHARACTERS
3004    
3005           A  regular  expression  is  a pattern that is matched against a subject
3006           string from left to right. Most characters stand for  themselves  in  a
3007           pattern,  and  match  the corresponding characters in the subject. As a
3008         trivial example, the pattern         trivial example, the pattern
3009    
3010           The quick brown fox           The quick brown fox
3011    
3012         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3013         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3014         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3015         the concept of case for characters whose values are less than  128,  so         the  concept  of case for characters whose values are less than 128, so
3016         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3017         ues, the concept of case is supported if PCRE is compiled with  Unicode         ues,  the concept of case is supported if PCRE is compiled with Unicode
3018         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3019         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3020         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3021    
3022         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3023         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3024         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3025         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3026    
3027         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3028         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3029         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
3030         metacharacters are as follows:         the metacharacters are as follows:
3031    
3032           \      general escape character with several uses           \      general escape character with several uses
3033           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2397  PCRE REGULAR EXPRESSION DETAILS Line 3045  PCRE REGULAR EXPRESSION DETAILS
3045                  also "possessive quantifier"                  also "possessive quantifier"
3046           {      start min/max quantifier           {      start min/max quantifier
3047    
3048         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
3049         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3050    
3051           \      general escape character           \      general escape character
# Line 2407  PCRE REGULAR EXPRESSION DETAILS Line 3055  PCRE REGULAR EXPRESSION DETAILS
3055                    syntax)                    syntax)
3056           ]      terminates the character class           ]      terminates the character class
3057    
3058         The following sections describe the use of each of the  metacharacters.         The  following sections describe the use of each of the metacharacters.
3059    
3060    
3061  BACKSLASH  BACKSLASH
3062    
3063         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3064         a non-alphanumeric character, it takes away any  special  meaning  that         a  non-alphanumeric  character,  it takes away any special meaning that
3065         character  may  have.  This  use  of  backslash  as an escape character         character may have. This  use  of  backslash  as  an  escape  character
3066         applies both inside and outside character classes.         applies both inside and outside character classes.
3067    
3068         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
3069         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3070         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3071         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3072         that it stands for itself. In particular, if you want to match a  back-         that  it stands for itself. In particular, if you want to match a back-
3073         slash, you write \\.         slash, you write \\.
3074    
3075         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3076         the pattern (other than in a character class) and characters between  a         the  pattern (other than in a character class) and characters between a
3077         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
3078         An escaping backslash can be used to include a whitespace or #  charac-         ing  backslash  can  be  used to include a whitespace or # character as
3079         ter as part of the pattern.         part of the pattern.
3080    
3081         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-
3082         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-
3083         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
3084         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3085         tion. Note the following examples:         tion. Note the following examples:
3086    
3087           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2443  BACKSLASH Line 3091  BACKSLASH
3091           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3092           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3093    
3094         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3095         classes.         classes.
3096    
3097     Non-printing characters     Non-printing characters
3098    
3099         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-
3100         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
3101         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3102         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3103         editing, it is usually easier  to  use  one  of  the  following  escape         editing,  it  is  usually  easier  to  use  one of the following escape
3104         sequences than the binary character it represents:         sequences than the binary character it represents:
3105    
3106           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3107           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3108           \e        escape (hex 1B)           \e        escape (hex 1B)
3109           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3110           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3111           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3112           \t        tab (hex 09)           \t        tab (hex 09)
3113           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
3114           \xhh      character with hex code hh           \xhh      character with hex code hh
3115           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh..
3116    
3117         The  precise  effect of \cx is as follows: if x is a lower case letter,         The precise effect of \cx is as follows: if x is a lower  case  letter,
3118         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it  is converted to upper case. Then bit 6 of the character (hex 40) is
3119         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;
3120         becomes hex 7B.         becomes hex 7B.
3121    
3122         After \x, from zero to two hexadecimal digits are read (letters can  be         After  \x, from zero to two hexadecimal digits are read (letters can be
3123         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-         in upper or lower case). Any number of hexadecimal  digits  may  appear
3124         its may appear between \x{ and }, but the value of the  character  code         between  \x{  and  },  but the value of the character code must be less
3125         must  be  less  than  2**31  (that is, the maximum hexadecimal value is         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3126         7FFFFFFF). If characters other than hexadecimal digits  appear  between         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3127         \x{  and }, or if there is no terminating }, this form of escape is not         than the largest Unicode code point, which is 10FFFF.
3128         recognized. Instead, the initial \x will  be  interpreted  as  a  basic  
3129         hexadecimal  escape, with no following digits, giving a character whose         If characters other than hexadecimal digits appear between \x{  and  },
3130         value is zero.         or if there is no terminating }, this form of escape is not recognized.
3131           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3132           escape,  with  no  following  digits, giving a character whose value is
3133           zero.
3134    
3135         Characters whose value is less than 256 can be defined by either of the         Characters whose value is less than 256 can be defined by either of the
3136         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference         two  syntaxes  for  \x. There is no difference in the way they are han-
3137         in the way they are handled. For example, \xdc is exactly the  same  as         dled. For example, \xdc is exactly the same as \x{dc}.
3138         \x{dc}.  
3139           After \0 up to two further octal digits are read. If  there  are  fewer
3140         After  \0  up  to  two further octal digits are read. In both cases, if         than  two  digits,  just  those  that  are  present  are used. Thus the
3141         there are fewer than two digits, just those that are present are  used.         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3142         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL         (code  value 7). Make sure you supply two digits after the initial zero
3143         character (code value 7). Make sure you supply  two  digits  after  the         if the pattern character that follows is itself an octal digit.
        initial  zero  if the pattern character that follows is itself an octal  
        digit.  
3144    
3145         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3146         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
# Line 2503  BACKSLASH Line 3152  BACKSLASH
3152    
3153         Inside a character class, or if the decimal number is  greater  than  9         Inside a character class, or if the decimal number is  greater  than  9
3154         and  there have not been that many capturing subpatterns, PCRE re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3155         up to three octal digits following the backslash, and generates a  sin-         up to three octal digits following the backslash, and uses them to gen-
3156         gle byte from the least significant 8 bits of the value. Any subsequent         erate  a data character. Any subsequent digits stand for themselves. In
3157         digits stand for themselves.  For example:         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3158           less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3159           example:
3160    
3161           \040   is another way of writing a space           \040   is another way of writing a space
3162           \40    is the same, provided there are fewer than 40           \40    is the same, provided there are fewer than 40
# Line 2525  BACKSLASH Line 3176  BACKSLASH
3176         Note that octal values of 100 or greater must not be  introduced  by  a         Note that octal values of 100 or greater must not be  introduced  by  a
3177         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3178    
3179         All  the  sequences  that  define a single byte value or a single UTF-8         All the sequences that define a single character value can be used both
3180         character (in UTF-8 mode) can be used both inside and outside character         inside and outside character classes. In addition, inside  a  character
3181         classes.  In  addition,  inside  a  character class, the sequence \b is         class,  the  sequence \b is interpreted as the backspace character (hex
3182         interpreted as the backspace character (hex 08), and the sequence \X is         08), and the sequences \R and \X are interpreted as the characters  "R"
3183         interpreted  as  the  character  "X".  Outside a character class, these         and  "X", respectively. Outside a character class, these sequences have
3184         sequences have different meanings (see below).         different meanings (see below).
3185    
3186       Absolute and relative back references
3187    
3188           The sequence \g followed by an unsigned or a negative  number,  option-
3189           ally  enclosed  in braces, is an absolute or relative back reference. A
3190           named back reference can be coded as \g{name}. Back references are dis-
3191           cussed later, following the discussion of parenthesized subpatterns.
3192    
3193       Absolute and relative subroutine calls
3194    
3195           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3196           name or a number enclosed either in angle brackets or single quotes, is
3197           an  alternative  syntax for referencing a subpattern as a "subroutine".
3198           Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3199           \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3200           reference; the latter is a subroutine call.
3201    
3202     Generic character types     Generic character types
3203    
3204         The third use of backslash is for specifying generic  character  types.         Another use of backslash is for specifying generic character types. The
3205         The following are always recognized:         following are always recognized:
3206    
3207           \d     any decimal digit           \d     any decimal digit
3208           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3209             \h     any horizontal whitespace character
3210             \H     any character that is not a horizontal whitespace character
3211           \s     any whitespace character           \s     any whitespace character
3212           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3213             \v     any vertical whitespace character
3214             \V     any character that is not a vertical whitespace character
3215           \w     any "word" character           \w     any "word" character
3216           \W     any "non-word" character           \W     any "non-word" character
3217    
# Line 2555  BACKSLASH Line 3226  BACKSLASH
3226    
3227         For compatibility with Perl, \s does not match the VT  character  (code         For compatibility with Perl, \s does not match the VT  character  (code
3228         11).   This makes it different from the the POSIX "space" class. The \s         11).   This makes it different from the the POSIX "space" class. The \s
3229         characters are HT (9), LF (10), FF (12), CR (13), and space (32).         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3230           "use locale;" is included in a Perl script, \s may match the VT charac-
3231           ter. In PCRE, it never does.
3232    
3233           In UTF-8 mode, characters with values greater than 128 never match  \d,
3234           \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3235           code character property support is available.  These  sequences  retain
3236           their original meanings from before UTF-8 support was available, mainly
3237           for efficiency reasons.
3238    
3239           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3240           the  other  sequences, these do match certain high-valued codepoints in
3241           UTF-8 mode.  The horizontal space characters are:
3242    
3243             U+0009     Horizontal tab
3244             U+0020     Space
3245             U+00A0     Non-break space
3246             U+1680     Ogham space mark
3247             U+180E     Mongolian vowel separator
3248             U+2000     En quad
3249             U+2001     Em quad
3250             U+2002     En space
3251             U+2003     Em space
3252             U+2004     Three-per-em space
3253             U+2005     Four-per-em space
3254             U+2006     Six-per-em space
3255             U+2007     Figure space
3256             U+2008     Punctuation space
3257             U+2009     Thin space
3258             U+200A     Hair space
3259             U+202F     Narrow no-break space
3260             U+205F     Medium mathematical space
3261             U+3000     Ideographic space
3262    
3263           The vertical space characters are:
3264    
3265             U+000A     Linefeed
3266             U+000B     Vertical tab
3267             U+000C     Formfeed
3268             U+000D     Carriage return
3269             U+0085     Next line
3270             U+2028     Line separator
3271             U+2029     Paragraph separator
3272    
3273         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character less than 256 that
3274         is  a  letter  or  digit.  The definition of letters and digits is con-         is  a  letter  or  digit.  The definition of letters and digits is con-
3275         trolled by PCRE's low-valued character tables, and may vary if  locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3276         specific  matching is taking place (see "Locale support" in the pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3277         page). For example, in the  "fr_FR"  (French)  locale,  some  character         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3278         codes  greater  than  128  are used for accented letters, and these are         systems,  or "french" in Windows, some character codes greater than 128
3279         matched by \w.         are used for accented letters, and these are matched by \w. The use  of
3280           locales with Unicode is discouraged.
3281    
3282       Newline sequences
3283    
3284           Outside  a  character class, by default, the escape sequence \R matches
3285           any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3286           mode \R is equivalent to the following:
3287    
3288             (?>\r\n|\n|\x0b|\f|\r|\x85)
3289    
3290           This  is  an  example  of an "atomic group", details of which are given
3291           below.  This particular group matches either the two-character sequence
3292           CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3293           U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3294           return, U+000D), or NEL (next line, U+0085). The two-character sequence
3295           is treated as a single unit that cannot be split.
3296    
3297           In UTF-8 mode, two additional characters whose codepoints  are  greater
3298           than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3299           rator, U+2029).  Unicode character property support is not  needed  for
3300           these characters to be recognized.
3301    
3302           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3303           the complete set  of  Unicode  line  endings)  by  setting  the  option
3304           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3305           (BSR is an abbrevation for "backslash R".) This can be made the default
3306           when  PCRE  is  built;  if this is the case, the other behaviour can be
3307           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3308           specify  these  settings  by  starting a pattern string with one of the
3309           following sequences:
3310    
3311             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3312             (*BSR_UNICODE)   any Unicode newline sequence
3313    
3314           These override the default and the options given to pcre_compile(), but
3315           they can be overridden by options given to pcre_exec(). Note that these
3316           special settings, which are not Perl-compatible, are recognized only at
3317           the  very  start  of a pattern, and that they must be in upper case. If
3318           more than one of them is present, the last one is  used.  They  can  be
3319           combined  with  a  change of newline convention, for example, a pattern
3320           can start with:
3321    
3322         In UTF-8 mode, characters with values greater than 128 never match  \d,           (*ANY)(*BSR_ANYCRLF)
3323         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-  
3324         code character property support is available.         Inside a character class, \R matches the letter "R".
3325    
3326     Unicode character properties     Unicode character properties
3327    
3328         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3329         tional  escape sequences to match generic character types are available         tional  escape sequences that match characters with specific properties
3330         when UTF-8 mode is selected. They are:         are available.  When not in UTF-8 mode, these sequences are  of  course
3331           limited  to  testing characters whose codepoints are less than 256, but
3332          \p{xx}   a character with the xx property         they do work in this mode.  The extra escape sequences are:
3333          \P{xx}   a character without the xx property  
3334          \X       an extended Unicode sequence           \p{xx}   a character with the xx property
3335             \P{xx}   a character without the xx property
3336             \X       an extended Unicode sequence
3337    
3338         The property names represented by xx above are limited to  the  Unicode         The property names represented by xx above are limited to  the  Unicode
3339         general  category properties. Each character has exactly one such prop-         script names, the general category properties, and "Any", which matches
3340         erty, specified by a two-letter abbreviation.  For  compatibility  with         any character (including newline). Other properties such as "InMusical-
3341         Perl,  negation  can be specified by including a circumflex between the         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
3342         opening brace and the property name. For example, \p{^Lu} is  the  same         not match any characters, so always causes a match failure.
3343         as \P{Lu}.  
3344           Sets of Unicode characters are defined as belonging to certain scripts.
3345         If  only  one  letter  is  specified with \p or \P, it includes all the         A  character from one of these sets can be matched using a script name.
3346         properties that start with that letter. In this case, in the absence of         For example:
3347         negation, the curly brackets in the escape sequence are optional; these  
3348         two examples have the same effect:           \p{Greek}
3349             \P{Han}
3350    
3351           Those that are not part of an identified script are lumped together  as
3352           "Common". The current list of scripts is:
3353    
3354           Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3355           Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
3356           Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3357           Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
3358           gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
3359           Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3360           Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
3361           Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3362           Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3363    
3364           Each  character has exactly one general category property, specified by
3365           a two-letter abbreviation. For compatibility with Perl, negation can be
3366           specified  by  including a circumflex between the opening brace and the
3367           property name. For example, \p{^Lu} is the same as \P{Lu}.
3368    
3369           If only one letter is specified with \p or \P, it includes all the gen-
3370           eral  category properties that start with that letter. In this case, in
3371           the absence of negation, the curly brackets in the escape sequence  are
3372           optional; these two examples have the same effect:
3373    
3374           \p{L}           \p{L}
3375           \pL           \pL
3376    
3377         The following property codes are supported:         The following general category property codes are supported:
3378    
3379           C     Other           C     Other
3380           Cc    Control           Cc    Control
# Line 2640  BACKSLASH Line 3420  BACKSLASH
3420           Zp    Paragraph separator           Zp    Paragraph separator
3421           Zs    Space separator           Zs    Space separator
3422    
3423         Extended properties such as "Greek" or "InMusicalSymbols" are not  sup-         The  special property L& is also supported: it matches a character that
3424         ported by PCRE.         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3425           classified as a modifier or "other".
3426    
3427           The  Cs  (Surrogate)  property  applies only to characters in the range
3428           U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3429           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3430           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3431           the pcreapi page).
3432    
3433           The  long  synonyms  for  these  properties that Perl supports (such as
3434           \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3435           any of these properties with "Is".
3436    
3437           No character that is in the Unicode table has the Cn (unassigned) prop-
3438           erty.  Instead, this property is assumed for any code point that is not
3439           in the Unicode table.
3440    
3441         Specifying  caseless  matching  does not affect these escape sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3442         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
# Line 2654  BACKSLASH Line 3449  BACKSLASH
3449         That  is,  it matches a character without the "mark" property, followed         That  is,  it matches a character without the "mark" property, followed
3450         by zero or more characters with the "mark"  property,  and  treats  the         by zero or more characters with the "mark"  property,  and  treats  the
3451         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3452         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3453           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3454           matches any one character.
3455    
3456         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3457         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3458         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3459         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3460    
3461       Resetting the match start
3462    
3463           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3464           ously matched characters not  to  be  included  in  the  final  matched
3465           sequence. For example, the pattern:
3466    
3467             foo\Kbar
3468    
3469           matches  "foobar",  but reports that it has matched "bar". This feature
3470           is similar to a lookbehind assertion (described  below).   However,  in
3471           this  case, the part of the subject before the real match does not have
3472           to be of fixed length, as lookbehind assertions do. The use of \K  does
3473           not  interfere  with  the setting of captured substrings.  For example,
3474           when the pattern
3475    
3476             (foo)\Kbar
3477    
3478           matches "foobar", the first substring is still set to "foo".
3479    
3480     Simple assertions     Simple assertions
3481    
3482         The fourth use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3483         tion specifies a condition that has to be met at a particular point  in         tion  specifies a condition that has to be met at a particular point in
3484         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3485         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3486         The backslashed assertions are:         The backslashed assertions are:
3487    
3488           \b     matches at a word boundary           \b     matches at a word boundary
3489           \B     matches when not at a word boundary           \B     matches when not at a word boundary
3490           \A     matches at start of subject           \A     matches at the start of the subject
3491           \Z     matches at end of subject or before newline at end           \Z     matches at the end of the subject
3492           \z     matches at end of subject                   also matches before a newline at the end of the subject
3493           \G     matches at first matching position in subject           \z     matches only at the end of the subject
3494             \G     matches at the first matching position in the subject
3495    
3496         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3497         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3498         acter class).         acter class).
3499    
3500         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3501         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3502         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3503         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3504    
3505         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3506         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3507         at the very start and end of the subject string, whatever  options  are         at  the  very start and end of the subject string, whatever options are
3508         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3509         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3510         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3511         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3512         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3513         the subject, \A can never match. The difference between \Z  and  \z  is         the  subject,  \A  can never match. The difference between \Z and \z is
3514         that  \Z  matches  before  a  newline that is the last character of the         that \Z matches before a newline at the end of the string as well as at
3515         string as well as at the end of the string, whereas \z matches only  at         the very end, whereas \z matches only at the end.
        the end.  
3516    
3517         The  \G assertion is true only when the current matching position is at         The  \G assertion is true only when the current matching position is at
3518         the start point of the match, as specified by the startoffset  argument         the start point of the match, as specified by the startoffset  argument
# Line 2735  CIRCUMFLEX AND DOLLAR Line 3551  CIRCUMFLEX AND DOLLAR
3551    
3552         A  dollar  character  is  an assertion that is true only if the current         A  dollar  character  is  an assertion that is true only if the current
3553         matching point is at the end of  the  subject  string,  or  immediately         matching point is at the end of  the  subject  string,  or  immediately
3554         before a newline character that is the last character in the string (by         before a newline at the end of the string (by default). Dollar need not
3555         default). Dollar need not be the last character of  the  pattern  if  a         be the last character of the pattern if a number  of  alternatives  are
3556         number  of alternatives are involved, but it should be the last item in         involved,  but  it  should  be  the last item in any branch in which it
3557         any branch in which it appears.  Dollar has no  special  meaning  in  a         appears. Dollar has no special meaning in a character class.
        character class.  
3558    
3559         The  meaning  of  dollar  can be changed so that it matches only at the         The meaning of dollar can be changed so that it  matches  only  at  the
3560         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at
3561         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3562    
3563         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3564         PCRE_MULTILINE option is set. When this is the case, they match immedi-         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3565         ately  after  and  immediately  before  an  internal newline character,         matches immediately after internal newlines as well as at the start  of
3566         respectively, in addition to matching at the start and end of the  sub-         the  subject  string.  It  does not match after a newline that ends the
3567         ject  string.  For  example,  the  pattern  /^abc$/ matches the subject         string. A dollar matches before any newlines in the string, as well  as
3568         string "def\nabc" (where \n represents a newline character)  in  multi-         at  the very end, when PCRE_MULTILINE is set. When newline is specified
3569         line mode, but not otherwise.  Consequently, patterns that are anchored         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3570         in single line mode because all branches start with ^ are not  anchored         not indicate newlines.
3571         in  multiline  mode,  and  a  match for circumflex is possible when the  
3572         startoffset  argument  of  pcre_exec()  is  non-zero.   The   PCRE_DOL-         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3573         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3574           Consequently,  patterns  that  are anchored in single line mode because
3575           all branches start with ^ are not anchored in  multiline  mode,  and  a
3576           match  for  circumflex  is  possible  when  the startoffset argument of
3577           pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if
3578           PCRE_MULTILINE is set.
3579    
3580         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note  that  the sequences \A, \Z, and \z can be used to match the start
3581         and end of the subject in both modes, and if all branches of a  pattern         and end of the subject in both modes, and if all branches of a  pattern
3582         start  with  \A it is always anchored, whether PCRE_MULTILINE is set or         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
3583         not.         set.
3584    
3585    
3586  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3587    
3588         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3589         ter  in  the  subject,  including a non-printing character, but not (by         ter  in  the subject string except (by default) a character that signi-
3590         default) newline.  In UTF-8 mode, a dot matches  any  UTF-8  character,         fies the end of a line. In UTF-8 mode, the  matched  character  may  be
3591         which might be more than one byte long, except (by default) newline. If         more than one byte long.
3592         the PCRE_DOTALL option is set, dots match newlines as  well.  The  han-  
3593         dling  of dot is entirely independent of the handling of circumflex and         When  a line ending is defined as a single character, dot never matches
3594         dollar, the only relationship being  that  they  both  involve  newline         that character; when the two-character sequence CRLF is used, dot  does
3595         characters. Dot has no special meaning in a character class.         not  match  CR  if  it  is immediately followed by LF, but otherwise it
3596           matches all characters (including isolated CRs and LFs). When any  Uni-
3597           code  line endings are being recognized, dot does not match CR or LF or
3598           any of the other line ending characters.
3599    
3600           The behaviour of dot with regard to newlines can  be  changed.  If  the
3601           PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3602           exception. If the two-character sequence CRLF is present in the subject
3603           string, it takes two dots to match it.
3604    
3605           The  handling of dot is entirely independent of the handling of circum-
3606           flex and dollar, the only relationship being  that  they  both  involve
3607           newlines. Dot has no special meaning in a character class.
3608    
3609    
3610  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3611    
3612         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3613         both in and out of UTF-8 mode. Unlike a dot, it can  match  a  newline.         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
3614         The  feature  is provided in Perl in order to match individual bytes in         line-ending  characters.  The  feature  is provided in Perl in order to
3615         UTF-8 mode. Because it  breaks  up  UTF-8  characters  into  individual         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-
3616         bytes,  what remains in the string may be a malformed UTF-8 string. For         acters  into individual bytes, what remains in the string may be a mal-
3617         this reason, the \C escape sequence is best avoided.         formed UTF-8 string. For this reason, the \C escape  sequence  is  best
3618           avoided.
3619    
3620         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3621         below),  because  in UTF-8 mode this would make it impossible to calcu-         below), because in UTF-8 mode this would make it impossible  to  calcu-
3622         late the length of the lookbehind.         late the length of the lookbehind.
3623    
3624    
# Line 2794  SQUARE BRACKETS AND CHARACTER CLASSES Line 3627  SQUARE BRACKETS AND CHARACTER CLASSES
3627         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3628         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
3629         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
3630         it  should  be  the first data character in the class (after an initial         it should be the first data character in the class  (after  an  initial
3631         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3632    
3633         A character class matches a single character in the subject.  In  UTF-8         A  character  class matches a single character in the subject. In UTF-8
3634         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3635         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
3636         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3637         subject character must not be in the set defined by  the  class.  If  a         subject  character  must  not  be in the set defined by the class. If a
3638         circumflex  is actually required as a member of the class, ensure it is         circumflex is actually required as a member of the class, ensure it  is
3639         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3640    
3641         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3642         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3643         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3644         characters  that  are in the class by enumerating those that are not. A         characters that are in the class by enumerating those that are  not.  A
3645         class that starts with a circumflex is not an assertion: it still  con-         class  that starts with a circumflex is not an assertion: it still con-
3646         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3647         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3648    
3649         In UTF-8 mode, characters with values greater than 255 can be  included         In  UTF-8 mode, characters with values greater than 255 can be included
3650         in  a  class as a literal string of bytes, or by using the \x{ escaping         in a class as a literal string of bytes, or by using the  \x{  escaping
3651         mechanism.         mechanism.
3652    
3653         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3654         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3655         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
3656         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always
3657         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3658         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3659         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3660         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3661         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3662         PCRE  is  compiled  with Unicode property support as well as with UTF-8         PCRE is compiled with Unicode property support as well  as  with  UTF-8
3663         support.         support.
3664    
3665         The newline character is never treated in any special way in  character         Characters  that  might  indicate  line breaks are never treated in any
3666         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE         special way  when  matching  character  classes,  whatever  line-ending
3667         options is. A class such as [^a] will always match a newline.         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3668           PCRE_MULTILINE options is used. A class such as [^a] always matches one
3669         The minus (hyphen) character can be used to specify a range of  charac-         of these characters.
3670         ters  in  a  character  class.  For  example,  [d-m] matches any letter  
3671         between d and m, inclusive. If a  minus  character  is  required  in  a         The  minus (hyphen) character can be used to specify a range of charac-
3672         class,  it  must  be  escaped  with a backslash or appear in a position         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3673         where it cannot be interpreted as indicating a range, typically as  the         between  d  and  m,  inclusive.  If  a minus character is required in a
3674           class, it must be escaped with a backslash  or  appear  in  a  position
3675           where  it cannot be interpreted as indicating a range, typically as the
3676         first or last character in the class.         first or last character in the class.
3677    
3678         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
3679         ter of a range. A pattern such as [W-]46] is interpreted as a class  of         ter  of a range. A pattern such as [W-]46] is interpreted as a class of
3680         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3681         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3682         backslash  it is interpreted as the end of range, so [W-\]46] is inter-         backslash it is interpreted as the end of range, so [W-\]46] is  inter-
3683         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3684         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3685         a range.         a range.
3686    
3687         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3688         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3689         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3690         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3691    
3692         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
3693         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
3694         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3695         character tables for the "fr_FR" locale are in use, [\xc8-\xcb] matches         character  tables  for  a French locale are in use, [\xc8-\xcb] matches
3696         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the
3697         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3698         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3699    
3700         The  character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear         The character types \d, \D, \p, \P, \s, \S, \w, and \W may also  appear
3701         in a character class, and add the characters that  they  match  to  the         in  a  character  class,  and add the characters that they match to the
3702         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3703         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3704         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3705         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3706         but not underscore.         but not underscore.
3707