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revision 371 by ph10, Mon Aug 25 18:28:05 2008 UTC revision 392 by ph10, Tue Mar 17 21:30:30 2009 UTC
# Line 94  USER DOCUMENTATION Line 94  USER DOCUMENTATION
94           pcrestack         discussion of stack usage           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
98         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
99    
100    
101  LIMITATIONS  LIMITATIONS
102    
103         There are some size limitations in PCRE but it is hoped that they  will         There  are some size limitations in PCRE but it is hoped that they will
104         never in practice be relevant.         never in practice be relevant.
105    
106         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE         The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE
107         is compiled with the default internal linkage size of 2. If you want to         is compiled with the default internal linkage size of 2. If you want to
108         process  regular  expressions  that are truly enormous, you can compile         process regular expressions that are truly enormous,  you  can  compile
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 is slower.         of execution is slower.
113    
114         All values in repeating quantifiers must be less than 65536.         All values in repeating quantifiers must be less than 65536.
# Line 119  LIMITATIONS Line 119  LIMITATIONS
119         The maximum length of name for a named subpattern is 32 characters, and         The maximum length of name for a named subpattern is 32 characters, and
120         the maximum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
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.         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
131    
132         From release 3.3, PCRE has  had  some  support  for  character  strings         From  release  3.3,  PCRE  has  had  some support for character strings
133         encoded  in the UTF-8 format. For release 4.0 this was greatly extended         encoded in the UTF-8 format. For release 4.0 this was greatly  extended
134         to cover most common requirements, and in release 5.0  additional  sup-         to  cover  most common requirements, and in release 5.0 additional sup-
135         port for Unicode general category properties was added.         port for Unicode general category properties was added.
136    
137         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In order process UTF-8 strings, you must build PCRE  to  include  UTF-8
138         support in the code, and, in addition,  you  must  call  pcre_compile()         support  in  the  code,  and, in addition, you must call pcre_compile()
139         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with the PCRE_UTF8 option flag. When you do this, both the pattern  and
140         any subject strings that are matched against it are  treated  as  UTF-8         any  subject  strings  that are matched against it are treated as UTF-8
141         strings instead of just strings of bytes.         strings instead of just strings of bytes.
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 occasionally, so should not be         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
146         very big.         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, the Unicode script names such as Arabic  or  Han,         for  a  decimal number, the Unicode script names such as Arabic or Han,
153         and  the  derived  properties  Any  and L&. A full list is given in the         and the derived properties Any and L&. A full  list  is  given  in  the
154         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
155         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
156         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
157         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
158         does not support this.         does not support this.
159    
160     Validity of UTF-8 strings     Validity of UTF-8 strings
161    
162         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
163         subjects are (by default) checked for validity on entry to the relevant         subjects are (by default) checked for validity on entry to the relevant
164         functions. From release 7.3 of PCRE, the check is according  the  rules         functions.  From  release 7.3 of PCRE, the check is according the rules
165         of  RFC  3629, which are themselves derived from the Unicode specifica-         of RFC 3629, which are themselves derived from the  Unicode  specifica-
166         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
167         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
168         check allows only values in the range U+0 to U+10FFFF, excluding U+D800         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
169         to U+DFFF.         to U+DFFF.
170    
171         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
172         which the Unicode Standard says this: "The Low Surrogate Area does  not         which  the Unicode Standard says this: "The Low Surrogate Area does not
173         contain  any  character  assignments,  consequently  no  character code         contain any  character  assignments,  consequently  no  character  code
174         charts or namelists are provided for this area. Surrogates are reserved         charts or namelists are provided for this area. Surrogates are reserved
175         for  use  with  UTF-16 and then must be used in pairs." The code points         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         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         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.)         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         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         (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         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         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         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         it is given (respectively) contains only valid  UTF-8  codes.  In  this
186         case, it does not diagnose an invalid UTF-8 string.         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,         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-         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         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,         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         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         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.         the  string does not even conform to RFC 2279, the result is undefined.
195         Your program may crash.         Your program may crash.
196    
197         If  you  want  to  process  strings  of  values  in the full range 0 to         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         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         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.         this situation, you will have to apply your own validity check.
201    
202     General comments about UTF-8 mode     General comments about UTF-8 mode
203    
204         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
205         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
206    
207         2.  Octal  numbers  up to \777 are recognized, and match two-byte UTF-8         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
208         characters for values greater than \177.         characters for values greater than \177.
209    
210         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         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         4.  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         5. 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         6. 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
224         includes Unicode property support, because to do otherwise  would  slow         includes  Unicode  property support, because to do otherwise would slow
225         down  PCRE in many common cases. If you really want to test for a wider         down PCRE in many common cases. If you really want to test for a  wider
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         7.  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         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-         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
234         acters.         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. Even when Unicode property         used only for characters with higher values. Even when Unicode property
242         support is available, PCRE supports case-insensitive matching only when         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         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-         small  number  of  many-to-one  mappings in Unicode; these are not sup-
245         ported by PCRE.         ported by PCRE.
246    
247    
# Line 251  AUTHOR Line 251  AUTHOR
251         University Computing Service         University Computing Service
252         Cambridge CB2 3QH, 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  two  initials,         so  I've  taken  it away. If you want to email me, use my two initials,
256         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
257    
258    
# Line 307  C++ SUPPORT Line 307  C++ SUPPORT
307    
308  UTF-8 SUPPORT  UTF-8 SUPPORT
309    
310         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
311    
312           --enable-utf8           --enable-utf8
313    
# Line 316  UTF-8 SUPPORT Line 316  UTF-8 SUPPORT
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           If  you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
320           expects its input to be either ASCII or UTF-8 (depending on the runtime
321           option).  It  is not possible to support both EBCDIC and UTF-8 codes in
322           the same  version  of  the  library.  Consequently,  --enable-utf8  and
323           --enable-ebcdic are mutually exclusive.
324    
325    
326  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
327    
# Line 337  UNICODE CHARACTER PROPERTY SUPPORT Line 343  UNICODE CHARACTER PROPERTY SUPPORT
343    
344  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
345    
346         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By default, PCRE interprets the linefeed (LF) character  as  indicating
347         the  end  of  a line. This is the normal newline character on Unix-like         the  end  of  a line. This is the normal newline character on Unix-like
348         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems. You can compile PCRE to use carriage return (CR)  instead,  by
349         instead, by adding         adding
350    
351           --enable-newline-is-cr           --enable-newline-is-cr
352    
# Line 363  CODE VALUE OF NEWLINE Line 369  CODE VALUE OF NEWLINE
369    
370         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
371    
372         Whatever  line  ending convention is selected when PCRE is built can be         Whatever line ending convention is selected when PCRE is built  can  be
373         overridden when the library functions are called. At build time  it  is         overridden  when  the library functions are called. At build time it is
374         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
375    
376    
377  WHAT \R MATCHES  WHAT \R MATCHES
378    
379         By  default,  the  sequence \R in a pattern matches any Unicode newline         By default, the sequence \R in a pattern matches  any  Unicode  newline
380         sequence, whatever has been selected as the line  ending  sequence.  If         sequence,  whatever  has  been selected as the line ending sequence. If
381         you specify         you specify
382    
383           --enable-bsr-anycrlf           --enable-bsr-anycrlf
384    
385         the  default  is changed so that \R matches only CR, LF, or CRLF. What-         the default is changed so that \R matches only CR, LF, or  CRLF.  What-
386         ever is selected when PCRE is built can be overridden when the  library         ever  is selected when PCRE is built can be overridden when the library
387         functions are called.         functions are called.
388    
389    
390  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
391    
392         The  PCRE building process uses libtool to build both shared and static         The PCRE building process uses libtool to build both shared and  static
393         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
394         of         of
395    
396           --disable-shared           --disable-shared
# Line 396  BUILDING SHARED AND STATIC LIBRARIES Line 402  BUILDING SHARED AND STATIC LIBRARIES
402  POSIX MALLOC USAGE  POSIX MALLOC USAGE
403    
404         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
405         umentation), additional working storage is  required  for  holding  the         umentation),  additional  working  storage  is required for holding the
406         pointers  to capturing substrings, because PCRE requires three integers         pointers to capturing substrings, because PCRE requires three  integers
407         per substring, whereas the POSIX interface provides only  two.  If  the         per  substring,  whereas  the POSIX interface provides only two. If the
408         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
409         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.
410         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 411  POSIX MALLOC USAGE Line 417  POSIX MALLOC USAGE
417    
418  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
419    
420         Within a compiled pattern, offset values are used  to  point  from  one         Within  a  compiled  pattern,  offset values are used to point from one
421         part  to another (for example, from an opening parenthesis to an alter-         part to another (for example, from an opening parenthesis to an  alter-
422         nation metacharacter). By default, two-byte values are used  for  these         nation  metacharacter).  By default, two-byte values are used for these
423         offsets,  leading  to  a  maximum size for a compiled pattern of around         offsets, leading to a maximum size for a  compiled  pattern  of  around
424         64K. This is sufficient to handle all but the most  gigantic  patterns.         64K.  This  is sufficient to handle all but the most gigantic patterns.
425         Nevertheless,  some  people do want to process enormous patterns, so it         Nevertheless, some people do want to process enormous patterns,  so  it
426         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
427         adding a setting such as         adding a setting such as
428    
429           --with-link-size=3           --with-link-size=3
430    
431         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
432         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
433         additional bytes when handling them.         additional bytes when handling them.
434    
435    
436  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
437    
438         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
439         ing by making recursive calls to an internal function  called  match().         ing  by  making recursive calls to an internal function called match().
440         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-
441         verely limit PCRE's operation. (The Unix environment does  not  usually         verely  limit  PCRE's operation. (The Unix environment does not usually
442         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
443         the maximum stack size.  There is a discussion in the  pcrestack  docu-         the  maximum  stack size.  There is a discussion in the pcrestack docu-
444         mentation.)  An alternative approach to recursion that uses memory from         mentation.) An alternative approach to recursion that uses memory  from
445         the heap to remember data, instead of using recursive  function  calls,         the  heap  to remember data, instead of using recursive function calls,
446         has  been  implemented to work round the problem of limited stack size.         has been implemented to work round the problem of limited  stack  size.
447         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
448    
449           --disable-stack-for-recursion           --disable-stack-for-recursion
450    
451         to the configure command. With this configuration, PCRE  will  use  the         to  the  configure  command. With this configuration, PCRE will use the
452         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
453         ment functions. By default these point to malloc() and free(), but  you         ment  functions. By default these point to malloc() and free(), but you
454         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used.
455    
456         Separate  functions  are  provided  rather  than  using pcre_malloc and         Separate functions are  provided  rather  than  using  pcre_malloc  and
457         pcre_free because the  usage  is  very  predictable:  the  block  sizes         pcre_free  because  the  usage  is  very  predictable:  the block sizes
458         requested  are  always  the  same,  and  the blocks are always freed in         requested are always the same, and  the  blocks  are  always  freed  in
459         reverse order. A calling program might be able to  implement  optimized         reverse  order.  A calling program might be able to implement optimized
460         functions  that  perform  better  than  malloc()  and free(). PCRE runs         functions that perform better  than  malloc()  and  free().  PCRE  runs
461         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
462         the   pcre_exec()   function;   it   is   not   relevant  for  the  the         the  pcre_exec()  function;  it   is   not   relevant   for   the   the
463         pcre_dfa_exec() function.         pcre_dfa_exec() function.
464    
465    
466  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
467    
468         Internally, PCRE has a function called match(), which it calls  repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
469         edly   (sometimes   recursively)  when  matching  a  pattern  with  the         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
470         pcre_exec() function. By controlling the maximum number of  times  this         pcre_exec()  function.  By controlling the maximum number of times this
471         function  may be called during a single matching operation, a limit can         function may be called during a single matching operation, a limit  can
472         be placed on the resources used by a single call  to  pcre_exec().  The         be  placed  on  the resources used by a single call to pcre_exec(). The
473         limit  can be changed at run time, as described in the pcreapi documen-         limit can be changed at run time, as described in the pcreapi  documen-
474         tation. The default is 10 million, but this can be changed by adding  a         tation.  The default is 10 million, but this can be changed by adding a
475         setting such as         setting such as
476    
477           --with-match-limit=500000           --with-match-limit=500000
478    
479         to   the   configure  command.  This  setting  has  no  effect  on  the         to  the  configure  command.  This  setting  has  no  effect   on   the
480         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
481    
482         In some environments it is desirable to limit the  depth  of  recursive         In  some  environments  it is desirable to limit the depth of recursive
483         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
484         to restrict the maximum amount of stack (or heap,  if  --disable-stack-         to  restrict  the maximum amount of stack (or heap, if --disable-stack-
485         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
486         it defaults to the value that  is  set  for  --with-match-limit,  which         it  defaults  to  the  value  that is set for --with-match-limit, which
487         imposes  no  additional constraints. However, you can set a lower limit         imposes no additional constraints. However, you can set a  lower  limit
488         by adding, for example,         by adding, for example,
489    
490           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
491    
492         to the configure command. This value can  also  be  overridden  at  run         to  the  configure  command.  This  value can also be overridden at run
493         time.         time.
494    
495    
496  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
497    
498         PCRE  uses fixed tables for processing characters whose code values are         PCRE uses fixed tables for processing characters whose code values  are
499         less than 256. By default, PCRE is built with a set of tables that  are         less  than 256. By default, PCRE is built with a set of tables that are
500         distributed  in  the  file pcre_chartables.c.dist. These tables are for         distributed in the file pcre_chartables.c.dist. These  tables  are  for
501         ASCII codes only. If you add         ASCII codes only. If you add
502    
503           --enable-rebuild-chartables           --enable-rebuild-chartables
504    
505         to the configure command, the distributed tables are  no  longer  used.         to  the  configure  command, the distributed tables are no longer used.
506         Instead,  a  program  called dftables is compiled and run. This outputs         Instead, a program called dftables is compiled and  run.  This  outputs
507         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
508         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
509         you are cross compiling, because dftables is run on the local host.  If         you  are cross compiling, because dftables is run on the local host. If
510         you  need  to  create alternative tables when cross compiling, you will         you need to create alternative tables when cross  compiling,  you  will
511         have to do so "by hand".)         have to do so "by hand".)
512    
513    
514  USING EBCDIC CODE  USING EBCDIC CODE
515    
516         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
517         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
518         This is the case for most computer operating systems.  PCRE  can,  how-         This  is  the  case for most computer operating systems. PCRE can, how-
519         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
520    
521           --enable-ebcdic           --enable-ebcdic
522    
523         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
524         bles. You should only use it if you know that  you  are  in  an  EBCDIC         bles.  You  should  only  use  it if you know that you are in an EBCDIC
525         environment (for example, an IBM mainframe operating system).         environment (for example,  an  IBM  mainframe  operating  system).  The
526           --enable-ebcdic option is incompatible with --enable-utf8.
527    
528    
529  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
# Line 578  AUTHOR Line 585  AUTHOR
585    
586  REVISION  REVISION
587    
588         Last updated: 13 April 2008         Last updated: 17 March 2009
589         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
590  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
591    
592    
# Line 999  MULTITHREADING Line 1006  MULTITHREADING
1006         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
1007         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1008    
1009         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
1010         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
1011         at once.         at once.
1012    
# Line 1007  MULTITHREADING Line 1014  MULTITHREADING
1014  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1015    
1016         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
1017         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
1018         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
1019         pcreprecompile  documentation.  However, compiling a regular expression         pcreprecompile documentation. However, compiling a  regular  expression
1020         with one version of PCRE for use with a different version is not  guar-         with  one version of PCRE for use with a different version is not guar-
1021         anteed to work and may cause crashes.         anteed to work and may cause crashes.
1022    
1023    
# Line 1018  CHECKING BUILD-TIME OPTIONS Line 1025  CHECKING BUILD-TIME OPTIONS
1025    
1026         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1027    
1028         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-
1029         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1030         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
1031         tures.         tures.
1032    
1033         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
1034         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1035         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
1036         available:         available:
1037    
1038           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1039    
1040         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-
1041         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1042    
1043           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1044    
1045         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
1046         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1047    
1048           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1049    
1050         The  output  is  an integer whose value specifies the default character         The output is an integer whose value specifies  the  default  character
1051         sequence that is recognized as meaning "newline". The four values  that         sequence  that is recognized as meaning "newline". The four values that
1052         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1053         and -1 for ANY. The default should normally be  the  standard  sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1054         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1055           spond to the standard sequence for your operating system.
1056    
1057           PCRE_CONFIG_BSR           PCRE_CONFIG_BSR
1058    
# Line 1071  CHECKING BUILD-TIME OPTIONS Line 1079  CHECKING BUILD-TIME OPTIONS
1079    
1080           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1081    
1082         The output is an integer that gives the default limit for the number of         The output is a long integer that gives the default limit for the  num-
1083         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1084         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1085    
1086           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1087    
1088         The output is an integer that gives the default limit for the depth  of         The output is a long integer that gives the default limit for the depth
1089         recursion  when calling the internal matching function in a pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1090         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1091           below.
1092    
1093           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1094    
1095         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
1096         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1097         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1098         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1099         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1100         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1101         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1102    
1103    
# Line 1105  COMPILING A PATTERN Line 1114  COMPILING A PATTERN
1114    
1115         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1116         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1117         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1118         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1119    
1120         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1121         the pattern argument. A pointer to a single block  of  memory  that  is         the  pattern  argument.  A  pointer to a single block of memory that is
1122         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1123         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
1124         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1125         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1126         longer required.         longer required.
1127    
1128         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
1129         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
1130         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1131         ment, which is an address (see below).         ment, which is an address (see below).
1132    
1133         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1134         pilation.  It  should be zero if no options are required. The available         pilation. It should be zero if no options are required.  The  available
1135         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them, in particular, those that
1136         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
1137         pattern (see the detailed description  in  the  pcrepattern  documenta-         pattern  (see  the  detailed  description in the pcrepattern documenta-
1138         tion).  For  these options, the contents of the options argument speci-         tion). For these options, the contents of the options  argument  speci-
1139         fies their initial settings at the start of compilation and  execution.         fies  their initial settings at the start of compilation and execution.
1140         The  PCRE_ANCHORED  and PCRE_NEWLINE_xxx options can be set at the time         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time
1141         of matching as well as at compile time.         of matching as well as at compile time.
1142    
1143         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1144         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1145         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-
1146         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1147         try to free it. The offset from the start of the pattern to the charac-         try to free it. The offset from the start of the pattern to the charac-
1148         ter where the error was discovered is placed in the variable pointed to         ter where the error was discovered is placed in the variable pointed to
1149         by erroffset, which must not be NULL. If it is, an immediate  error  is         by  erroffset,  which must not be NULL. If it is, an immediate error is
1150         given.         given.
1151    
1152         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
1153         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
1154         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
1155         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1156    
1157         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
1158         character  tables  that  are  built  when  PCRE  is compiled, using the         character tables that are  built  when  PCRE  is  compiled,  using  the
1159         default C locale. Otherwise, tableptr must be an address  that  is  the         default  C  locale.  Otherwise, tableptr must be an address that is the
1160         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
1161         compiled pattern, and used again by pcre_exec(), unless  another  table         compiled  pattern,  and used again by pcre_exec(), unless another table
1162         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
1163         support below.         support below.
1164    
1165         This code fragment shows a typical straightforward  call  to  pcre_com-         This  code  fragment  shows a typical straightforward call to pcre_com-
1166         pile():         pile():
1167    
1168           pcre *re;           pcre *re;
# Line 1166  COMPILING A PATTERN Line 1175  COMPILING A PATTERN
1175             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1176             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1177    
1178         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
1179         file:         file:
1180    
1181           PCRE_ANCHORED           PCRE_ANCHORED
1182    
1183         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
1184         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
1185         that is being searched (the "subject string"). This effect can also  be         that  is being searched (the "subject string"). This effect can also be
1186         achieved  by appropriate constructs in the pattern itself, which is the         achieved by appropriate constructs in the pattern itself, which is  the
1187         only way to do it in Perl.         only way to do it in Perl.
1188    
1189           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1190    
1191         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1192         all  with  number  255, before each pattern item. For discussion of the         all with number 255, before each pattern item. For  discussion  of  the
1193         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1194    
1195           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
1196           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
1197    
1198         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
1199         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1200         or to match any Unicode newline sequence. The default is specified when         or to match any Unicode newline sequence. The default is specified when
1201         PCRE is built. It can be overridden from within the pattern, or by set-         PCRE is built. It can be overridden from within the pattern, or by set-
1202         ting an option when a compiled pattern is matched.         ting an option when a compiled pattern is matched.
1203    
1204           PCRE_CASELESS           PCRE_CASELESS
1205    
1206         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
1207         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
1208         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
1209         always  understands the concept of case for characters whose values are         always understands the concept of case for characters whose values  are
1210         less than 128, so caseless matching is always possible. For  characters         less  than 128, so caseless matching is always possible. For characters
1211         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-
1212         piled with Unicode property support, but not otherwise. If you want  to         piled  with Unicode property support, but not otherwise. If you want to
1213         use  caseless  matching  for  characters 128 and above, you must ensure         use caseless matching for characters 128 and  above,  you  must  ensure
1214         that PCRE is compiled with Unicode property support  as  well  as  with         that  PCRE  is  compiled  with Unicode property support as well as with
1215         UTF-8 support.         UTF-8 support.
1216    
1217           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1218    
1219         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
1220         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
1221         matches  immediately before a newline at the end of the string (but not         matches immediately before a newline at the end of the string (but  not
1222         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
1223         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
1224         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1225    
1226           PCRE_DOTALL           PCRE_DOTALL
1227    
1228         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-
1229         acters,  including  those that indicate newline. Without it, a dot does         acters, including those that indicate newline. Without it, a  dot  does
1230         not match when the current position is at a  newline.  This  option  is         not  match  when  the  current position is at a newline. This option is
1231         equivalent  to Perl's /s option, and it can be changed within a pattern         equivalent to Perl's /s option, and it can be changed within a  pattern
1232         by a (?s) option setting. A negative class such as [^a] always  matches         by  a (?s) option setting. A negative class such as [^a] always matches
1233         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1234    
1235           PCRE_DUPNAMES           PCRE_DUPNAMES
1236    
1237         If  this  bit is set, names used to identify capturing subpatterns need         If this bit is set, names used to identify capturing  subpatterns  need
1238         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1239         is  known  that  only  one instance of the named subpattern can ever be         is known that only one instance of the named  subpattern  can  ever  be
1240         matched. There are more details of named subpatterns  below;  see  also         matched.  There  are  more details of named subpatterns below; see also
1241         the pcrepattern documentation.         the pcrepattern documentation.
1242    
1243           PCRE_EXTENDED           PCRE_EXTENDED
1244    
1245         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
1246         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1247         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1248         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1249         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
1250         option, and it can be changed within a pattern by a  (?x)  option  set-         option,  and  it  can be changed within a pattern by a (?x) option set-
1251         ting.         ting.
1252    
1253         This  option  makes  it possible to include comments inside complicated         This option makes it possible to include  comments  inside  complicated
1254         patterns.  Note, however, that this applies only  to  data  characters.         patterns.   Note,  however,  that this applies only to data characters.
1255         Whitespace   characters  may  never  appear  within  special  character         Whitespace  characters  may  never  appear  within  special   character
1256         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences  in  a  pattern,  for  example  within the sequence (?( which
1257         introduces a conditional subpattern.         introduces a conditional subpattern.
1258    
1259           PCRE_EXTRA           PCRE_EXTRA
1260    
1261         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1262         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
1263         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
1264         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1265         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1266         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
1267         literal.  (Perl can, however, be persuaded to give a warning for this.)         literal. (Perl can, however, be persuaded to give a warning for  this.)
1268         There are at present no other features controlled by  this  option.  It         There  are  at  present no other features controlled by this option. It
1269         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1270    
1271           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1272    
1273         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1274         before or at the first  newline  in  the  subject  string,  though  the         before  or  at  the  first  newline  in  the subject string, though the
1275         matched text may continue over the newline.         matched text may continue over the newline.
1276    
1277           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1278    
1279         If this option is set, PCRE's behaviour is changed in some ways so that         If this option is set, PCRE's behaviour is changed in some ways so that
1280         it is compatible with JavaScript rather than Perl. The changes  are  as         it  is  compatible with JavaScript rather than Perl. The changes are as
1281         follows:         follows:
1282    
1283         (1)  A  lone  closing square bracket in a pattern causes a compile-time         (1) A lone closing square bracket in a pattern  causes  a  compile-time
1284         error, because this is illegal in JavaScript (by default it is  treated         error,  because this is illegal in JavaScript (by default it is treated
1285         as a data character). Thus, the pattern AB]CD becomes illegal when this         as a data character). Thus, the pattern AB]CD becomes illegal when this
1286         option is set.         option is set.
1287    
1288         (2) At run time, a back reference to an unset subpattern group  matches         (2)  At run time, a back reference to an unset subpattern group matches
1289         an  empty  string (by default this causes the current matching alterna-         an empty string (by default this causes the current  matching  alterna-
1290         tive to fail). A pattern such as (\1)(a) succeeds when this  option  is         tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1291         set  (assuming  it can find an "a" in the subject), whereas it fails by         set (assuming it can find an "a" in the subject), whereas it  fails  by
1292         default, for Perl compatibility.         default, for Perl compatibility.
1293    
1294           PCRE_MULTILINE           PCRE_MULTILINE
1295    
1296         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1297         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1298         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1299         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1300         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1301         is set). This is the same as Perl.         is set). This is the same as Perl.
1302    
1303         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"
1304         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1305         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1306         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1307         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1308         lines 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,
1309         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1310    
1311           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1305  COMPILING A PATTERN Line 1314  COMPILING A PATTERN
1314           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1315           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1316    
1317         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1318         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1319         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1320         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1321         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1322         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1323         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1324         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1325         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1326         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1327         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1328         UTF-8 mode.         UTF-8 mode.
1329    
1330         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1331         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1332         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1333         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1334         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1335         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1336         cause an error.         cause an error.
1337    
1338         The only time that a line break is specially recognized when  compiling         The  only time that a line break is specially recognized when compiling
1339         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1340         character class is encountered. This indicates  a  comment  that  lasts         character  class  is  encountered.  This indicates a comment that lasts
1341         until  after the next line break sequence. In other circumstances, line         until after the next line break sequence. In other circumstances,  line
1342         break  sequences  are  treated  as  literal  data,   except   that   in         break   sequences   are   treated  as  literal  data,  except  that  in
1343         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1344         and are therefore ignored.         and are therefore ignored.
1345    
1346         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1347         is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1348    
1349           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1350    
# Line 1803  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1812  MATCHING A PATTERN: THE TRADITIONAL FUNC
1812              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1813              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1814    
1815         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
1816         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1817         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
1818         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1819         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
1820         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1821         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1822    
1823         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1824         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1825         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
1826         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1827         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1828    
1829         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1833  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1842  MATCHING A PATTERN: THE TRADITIONAL FUNC
1842    
1843     Extra data for pcre_exec()     Extra data for pcre_exec()
1844    
1845         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
1846         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
1847         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-
1848         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1849         fields (not necessarily in this order):         fields (not necessarily in this order):
1850    
1851           unsigned long int flags;           unsigned long int flags;
# Line 1846  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1855  MATCHING A PATTERN: THE TRADITIONAL FUNC
1855           void *callout_data;           void *callout_data;
1856           const unsigned char *tables;           const unsigned char *tables;
1857    
1858         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
1859         are set. The flag bits are:         are set. The flag bits are:
1860    
1861           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1855  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1864  MATCHING A PATTERN: THE TRADITIONAL FUNC
1864           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1865           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1866    
1867         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
1868         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1869         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
1870         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1871         flag bits.         flag bits.
1872    
1873         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
1874         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
1875         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1876         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1877         repeats.         repeats.
1878    
1879         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1880         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1881         on the number of times this function is called during  a  match,  which         on  the  number  of times this function is called during a match, which
1882         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1883         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1884         for each position in the subject string.         for each position in the subject string.
1885    
1886         The  default  value  for  the  limit can be set when PCRE is built; the         The default value for the limit can be set  when  PCRE  is  built;  the
1887         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1888         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1889         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
1890         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
1891         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1892    
1893         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
1894         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
1895         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
1896         the  total number of calls, because not all calls to match() are recur-         the total number of calls, because not all calls to match() are  recur-
1897         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
1898    
1899         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting  the  recursion  depth  limits the amount of stack that can be
# Line 1916  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1925  MATCHING A PATTERN: THE TRADITIONAL FUNC
1925    
1926         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.
1927         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
1928         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,    PCRE_NO_START_OPTIMIZE,
1929         PCRE_PARTIAL.         PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1930    
1931           PCRE_ANCHORED           PCRE_ANCHORED
1932    
# Line 2011  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2020  MATCHING A PATTERN: THE TRADITIONAL FUNC
2020         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
2021         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
2022    
2023             PCRE_NO_START_OPTIMIZE
2024    
2025           There are a number of optimizations that pcre_exec() uses at the  start
2026           of  a  match,  in  order to speed up the process. For example, if it is
2027           known that a match must start with a specific  character,  it  searches
2028           the subject for that character, and fails immediately if it cannot find
2029           it, without actually running the main matching function. When  callouts
2030           are  in  use,  these  optimizations  can cause them to be skipped. This
2031           option disables the "start-up" optimizations,  causing  performance  to
2032           suffer, but ensuring that the callouts do occur.
2033    
2034           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2035    
2036         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
2037         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2038         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2039         points  to  the start of a UTF-8 character. There is a discussion about         points to the start of a UTF-8 character. There is a  discussion  about
2040         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2041         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2042         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2043         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2044    
2045         If  you  already  know that your subject is valid, and you want to skip         If you already know that your subject is valid, and you  want  to  skip
2046         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
2047         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2048         do this for the second and subsequent calls to pcre_exec() if  you  are         do  this  for the second and subsequent calls to pcre_exec() if you are
2049         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
2050         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2051         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
2052         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
2053         value  of startoffset that does not point to the start of a UTF-8 char-         value of startoffset that does not point to the start of a UTF-8  char-
2054         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2055    
2056           PCRE_PARTIAL           PCRE_PARTIAL
2057    
2058         This option turns on the  partial  matching  feature.  If  the  subject         This  option  turns  on  the  partial  matching feature. If the subject
2059         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-
2060         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
2061         partially  matches  the  pattern and the failure to match occurred only         partially matches the pattern and the failure to  match  occurred  only
2062         because there were not enough subject characters), pcre_exec()  returns         because  there were not enough subject characters), pcre_exec() returns
2063         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
2064         used, there are restrictions on what may appear in the  pattern.  These         used,  there  are restrictions on what may appear in the pattern. These
2065         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
2066    
2067     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2068    
2069         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
2070         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2071         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2072         acter. Unlike the pattern string, the subject may contain  binary  zero         acter.  Unlike  the pattern string, the subject may contain binary zero
2073         bytes.  When the starting offset is zero, the search for a match starts         bytes. When the starting offset is zero, the search for a match  starts
2074         at the beginning of the subject, and this is by  far  the  most  common         at  the  beginning  of  the subject, and this is by far the most common
2075         case.         case.
2076    
2077         A  non-zero  starting offset is useful when searching for another match         A non-zero starting offset is useful when searching for  another  match
2078         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-
2079         cess.   Setting  startoffset differs from just passing over a shortened         cess.  Setting startoffset differs from just passing over  a  shortened
2080         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
2081         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2082    
2083           \Biss\B           \Biss\B
2084    
2085         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2086         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.)
2087         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2088         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2089         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2090         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
2091         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
2092         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-
2093         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
2094         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2095    
2096         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,
2097         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
2098         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
2099         subject.         subject.
2100    
2101     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2102    
2103         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
2104         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2105         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2106         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2107         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-
2108         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2109         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2110    
2111         Captured substrings are returned to the caller via a vector of integers         Captured substrings are returned to the caller via a vector of integers
2112         whose address is passed in ovector. The number of elements in the  vec-         whose  address is passed in ovector. The number of elements in the vec-
2113         tor  is  passed in ovecsize, which must be a non-negative number. Note:         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2114         this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2115    
2116         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-
2117         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2118         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-
2119         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2120         The number passed in ovecsize should always be a multiple of three.  If         The  number passed in ovecsize should always be a multiple of three. If
2121         it is not, it is rounded down.         it is not, it is rounded down.
2122    
2123         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2124         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2125         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
2126         element of each pair is set to the byte offset of the  first  character         element  of  each pair is set to the byte offset of the first character
2127         in  a  substring, and the second is set to the byte offset of the first         in a substring, and the second is set to the byte offset of  the  first
2128         character after the end of a substring. Note: these values  are  always         character  after  the end of a substring. Note: these values are always
2129         byte offsets, even in UTF-8 mode. They are not character counts.         byte offsets, even in UTF-8 mode. They are not character counts.
2130    
2131         The  first  pair  of  integers, ovector[0] and ovector[1], identify the         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2132         portion of the subject string matched by the entire pattern.  The  next         portion  of  the subject string matched by the entire pattern. The next
2133         pair  is  used for the first capturing subpattern, and so on. The value         pair is used for the first capturing subpattern, and so on.  The  value
2134         returned by pcre_exec() is one more than the highest numbered pair that         returned by pcre_exec() is one more than the highest numbered pair that
2135         has  been  set.  For example, if two substrings have been captured, the         has been set.  For example, if two substrings have been  captured,  the
2136         returned value is 3. If there are no capturing subpatterns, the  return         returned  value is 3. If there are no capturing subpatterns, the return
2137         value from a successful match is 1, indicating that just the first pair         value from a successful match is 1, indicating that just the first pair
2138         of offsets has been set.         of offsets has been set.
2139    
2140         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2141         of the string that it matched that is returned.         of the string that it matched that is returned.
2142    
2143         If  the vector is too small to hold all the captured substring offsets,         If the vector is too small to hold all the captured substring  offsets,
2144         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2145         function  returns  a value of zero. If the substring offsets are not of         function returns a value of zero. If the substring offsets are  not  of
2146         interest, pcre_exec() may be called with ovector  passed  as  NULL  and         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2147         ovecsize  as zero. However, if the pattern contains back references and         ovecsize as zero. However, if the pattern contains back references  and
2148         the ovector is not big enough to remember the related substrings,  PCRE         the  ovector is not big enough to remember the related substrings, PCRE
2149         has  to  get additional memory for use during matching. Thus it is usu-         has to get additional memory for use during matching. Thus it  is  usu-
2150         ally advisable to supply an ovector.         ally advisable to supply an ovector.
2151    
2152         The pcre_info() function can be used to find  out  how  many  capturing         The  pcre_info()  function  can  be used to find out how many capturing
2153         subpatterns  there  are  in  a  compiled pattern. The smallest size for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2154         ovector that will allow for n captured substrings, in addition  to  the         ovector  that  will allow for n captured substrings, in addition to the
2155         offsets 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.
2156    
2157         It  is  possible for capturing subpattern number n+1 to match some part         It is possible for capturing subpattern number n+1 to match  some  part
2158         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2159         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2160         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2161         2  is  not.  When  this happens, both values in the offset pairs corre-         2 is not. When this happens, both values in  the  offset  pairs  corre-
2162         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2163    
2164         Offset values that correspond to unused subpatterns at the end  of  the         Offset  values  that correspond to unused subpatterns at the end of the
2165         expression  are  also  set  to  -1. For example, if the string "abc" is         expression are also set to -1. For example,  if  the  string  "abc"  is
2166         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2167         matched.  The  return  from the function is 2, because the highest used         matched. The return from the function is 2, because  the  highest  used
2168         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2169         for  the  second  and third capturing subpatterns if you wish (assuming         for the second and third capturing subpatterns if  you  wish  (assuming
2170         the vector is large enough, of course).         the vector is large enough, of course).
2171    
2172         Some convenience functions are provided  for  extracting  the  captured         Some  convenience  functions  are  provided for extracting the captured
2173         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2174    
2175     Error return values from pcre_exec()     Error return values from pcre_exec()
2176    
2177         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2178         defined in the header file:         defined in the header file:
2179    
2180           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2163  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2183  MATCHING A PATTERN: THE TRADITIONAL FUNC
2183    
2184           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2185    
2186         Either code or subject was passed as NULL,  or  ovector  was  NULL  and         Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2187         ovecsize was not zero.         ovecsize was not zero.
2188    
2189           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2172  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2192  MATCHING A PATTERN: THE TRADITIONAL FUNC
2192    
2193           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2194    
2195         PCRE  stores a 4-byte "magic number" at the start of the compiled code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2196         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2197         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2198         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2199         gives when the magic number is not present.         gives when the magic number is not present.
2200    
2201           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2202    
2203         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2204         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
2205         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2206    
2207           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2208    
2209         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2210         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2211         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
2212         purpose. If the call via pcre_malloc() fails, this error is given.  The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2213         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2214    
2215           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2216    
2217         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2218         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2219         returned by pcre_exec().         returned by pcre_exec().
2220    
2221           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2222    
2223         The  backtracking  limit,  as  specified  by the match_limit field in a         The backtracking limit, as specified by  the  match_limit  field  in  a
2224         pcre_extra structure (or defaulted) was reached.  See  the  description         pcre_extra  structure  (or  defaulted) was reached. See the description
2225         above.         above.
2226    
2227           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2228    
2229         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2230         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2231         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2232    
2233           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2234    
2235         A  string  that contains an invalid UTF-8 byte sequence was passed as a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2236         subject.         subject.
2237    
2238           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2239    
2240         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2241         value  of startoffset did not point to the beginning of a UTF-8 charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2242         ter.         ter.
2243    
2244           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2245    
2246         The subject string did not match, but it did match partially.  See  the         The  subject  string did not match, but it did match partially. See the
2247         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2248    
2249           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2250    
2251         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
2252         items that are not supported for partial matching. See the  pcrepartial         items  that are not supported for partial matching. See the pcrepartial
2253         documentation for details of partial matching.         documentation for details of partial matching.
2254    
2255           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2256    
2257         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2258         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2259    
2260           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2261    
2262         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.
2263    
2264           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2265    
# Line 2389  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2409  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2409         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2410         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2411    
2412           Warning:  If the pattern uses the "(?|" feature to set up multiple sub-
2413           patterns with the same number, you  cannot  use  names  to  distinguish
2414           them, because names are not included in the compiled code. The matching
2415           process uses only numbers.
2416    
2417    
2418  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2419    
2420         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2421              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2422    
2423         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
2424         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns  are  not  required  to  be unique. Normally, patterns with
2425         duplicate  names  are such that in any one match, only one of the named         duplicate names are such that in any one match, only one of  the  named
2426         subpatterns participates. An example is shown in the pcrepattern  docu-         subpatterns  participates. An example is shown in the pcrepattern docu-
2427         mentation.         mentation.
2428    
2429         When    duplicates   are   present,   pcre_copy_named_substring()   and         When   duplicates   are   present,   pcre_copy_named_substring()    and
2430         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring()  return the first substring corresponding to
2431         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
2432         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
2433         function  returns one of the numbers that are associated with the name,         function returns one of the numbers that are associated with the  name,
2434         but it is not defined which it is.         but it is not defined which it is.
2435    
2436         If you want to get full details of all captured substrings for a  given         If  you want to get full details of all captured substrings for a given
2437         name,  you  must  use  the pcre_get_stringtable_entries() function. The         name, you must use  the  pcre_get_stringtable_entries()  function.  The
2438         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2439         third  and  fourth  are  pointers to variables which are updated by the         third and fourth are pointers to variables which  are  updated  by  the
2440         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2441         the  name-to-number  table  for  the  given  name.  The function itself         the name-to-number table  for  the  given  name.  The  function  itself
2442         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
2443         there  are none. The format of the table is described above in the sec-         there are none. The format of the table is described above in the  sec-
2444         tion entitled Information about a  pattern.   Given  all  the  relevant         tion  entitled  Information  about  a  pattern.  Given all the relevant
2445         entries  for the name, you can extract each of their numbers, and hence         entries for the name, you can extract each of their numbers, and  hence
2446         the captured data, if any.         the captured data, if any.
2447    
2448    
2449  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2450    
2451         The traditional matching function uses a  similar  algorithm  to  Perl,         The  traditional  matching  function  uses a similar algorithm to Perl,
2452         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2453         the subject. If you want to find all possible matches, or  the  longest         the  subject.  If you want to find all possible matches, or the longest
2454         possible  match,  consider using the alternative matching function (see         possible match, consider using the alternative matching  function  (see
2455         below) instead. If you cannot use the alternative function,  but  still         below)  instead.  If you cannot use the alternative function, but still
2456         need  to  find all possible matches, you can kludge it up by making use         need to find all possible matches, you can kludge it up by  making  use
2457         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2458         tation.         tation.
2459    
2460         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2461         tern.  When your callout function is called, extract and save the  cur-         tern.   When your callout function is called, extract and save the cur-
2462         rent  matched  substring.  Then  return  1, which forces pcre_exec() to         rent matched substring. Then return  1,  which  forces  pcre_exec()  to
2463         backtrack and try other alternatives. Ultimately, when it runs  out  of         backtrack  and  try other alternatives. Ultimately, when it runs out of
2464         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2465    
2466    
# Line 2446  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2471  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2471              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2472              int *workspace, int wscount);              int *workspace, int wscount);
2473    
2474         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The function pcre_dfa_exec()  is  called  to  match  a  subject  string
2475         against a compiled pattern, using a matching algorithm that  scans  the         against  a  compiled pattern, using a matching algorithm that scans the
2476         subject  string  just  once, and does not backtrack. This has different         subject string just once, and does not backtrack.  This  has  different
2477         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics  to  the  normal  algorithm, and is not compatible with
2478         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl. Some of the features of PCRE patterns are not  supported.  Never-
2479         theless, there are times when this kind of matching can be useful.  For         theless,  there are times when this kind of matching can be useful. For
2480         a discussion of the two matching algorithms, see the pcrematching docu-         a discussion of the two matching algorithms, see the pcrematching docu-
2481         mentation.         mentation.
2482    
2483         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
2484         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-
2485         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2486         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
2487         repeated here.         repeated here.
2488    
2489         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2490         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2491         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2492         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2493         lot of potential matches.         lot of potential matches.
2494    
2495         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2486  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2511  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2511    
2512     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2513    
2514         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
2515         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2516         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,
2517         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
2518         three of these are the same as for pcre_exec(), so their description is         three of these are the same as for pcre_exec(), so their description is
2519         not repeated here.         not repeated here.
2520    
2521           PCRE_PARTIAL           PCRE_PARTIAL
2522    
2523         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
2524         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
2525         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
2526         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
2527         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-
2528         sibility. The portion of the string that provided the partial match  is         sibility.  The portion of the string that provided the partial match is
2529         set as the first matching string.         set as the first matching string.
2530    
2531           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2532    
2533         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2534         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2535         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2536         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2537    
2538           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2539    
2540         When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
2541         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-
2542         tional subject characters, and have it continue with  the  same  match.         tional  subject  characters,  and have it continue with the same match.
2543         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
2544         workspace and wscount options must reference the same vector as  before         workspace  and wscount options must reference the same vector as before
2545         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
2546         match. There is more discussion of this  facility  in  the  pcrepartial         match.  There  is  more  discussion of this facility in the pcrepartial
2547         documentation.         documentation.
2548    
2549     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2550    
2551         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-
2552         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
2553         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
2554         matches are all initial substrings of the longer matches. For  example,         matches  are all initial substrings of the longer matches. For example,
2555         if the pattern         if the pattern
2556    
2557           <.*>           <.*>
# Line 2541  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2566  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2566           <something> <something else>           <something> <something else>
2567           <something> <something else> <something further>           <something> <something else> <something further>
2568    
2569         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,
2570         which is the number of matched substrings.  The  substrings  themselves         which  is  the  number of matched substrings. The substrings themselves
2571         are  returned  in  ovector. Each string uses two elements; the first is         are returned in ovector. Each string uses two elements;  the  first  is
2572         the offset to the start, and the second is the offset to  the  end.  In         the  offset  to  the start, and the second is the offset to the end. In
2573         fact,  all  the  strings  have the same start offset. (Space could have         fact, all the strings have the same start  offset.  (Space  could  have
2574         been saved by giving this only once, but it was decided to retain  some         been  saved by giving this only once, but it was decided to retain some
2575         compatibility  with  the  way pcre_exec() returns data, even though the         compatibility with the way pcre_exec() returns data,  even  though  the
2576         meaning of the strings is different.)         meaning of the strings is different.)
2577    
2578         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-
2579         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
2580         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
2581         filled with the longest matches.         filled with the longest matches.
2582    
2583     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2584    
2585         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2586         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
2587         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2588         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2589    
2590           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2591    
2592         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-
2593         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
2594         reference.         reference.
2595    
2596           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2597    
2598         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2599         that  uses  a back reference for the condition, or a test for recursion         that uses a back reference for the condition, or a test  for  recursion
2600         in a specific group. These are not supported.         in a specific group. These are not supported.
2601    
2602           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2603    
2604         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
2605         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
2606         (it is meaningless).         (it is meaningless).
2607    
2608           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2609    
2610         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
2611         workspace vector.         workspace vector.
2612    
2613           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2614    
2615         When  a  recursive subpattern is processed, the matching function calls         When a recursive subpattern is processed, the matching  function  calls
2616         itself recursively, using private vectors for  ovector  and  workspace.         itself  recursively,  using  private vectors for ovector and workspace.
2617         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
2618         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2619    
2620    
2621  SEE ALSO  SEE ALSO
2622    
2623         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2624         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2625    
2626    
2627  AUTHOR  AUTHOR
# Line 2608  AUTHOR Line 2633  AUTHOR
2633    
2634  REVISION  REVISION
2635    
2636         Last updated: 24 August 2008         Last updated: 17 March 2009
2637         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2638  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2639    
2640    
# Line 2660  PCRE CALLOUTS Line 2685  PCRE CALLOUTS
2685  MISSING CALLOUTS  MISSING CALLOUTS
2686    
2687         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2688         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2689         pattern is         example, if the pattern is
2690    
2691           ab(?C4)cd           ab(?C4)cd
2692    
# Line 2670  MISSING CALLOUTS Line 2695  MISSING CALLOUTS
2695         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2696         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2697    
2698           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2699           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2700           matching process, but does ensure that callouts  such  as  the  example
2701           above are obeyed.
2702    
2703    
2704  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2705    
2706         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2707         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2708         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2709         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2710         block. This structure contains the following fields:         block. This structure contains the following fields:
2711    
2712           int          version;           int          version;
# Line 2692  THE CALLOUT INTERFACE Line 2722  THE CALLOUT INTERFACE
2722           int          pattern_position;           int          pattern_position;
2723           int          next_item_length;           int          next_item_length;
2724    
2725         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2726         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2727         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2728         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2729    
2730         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2779  AUTHOR Line 2809  AUTHOR
2809    
2810  REVISION  REVISION
2811    
2812         Last updated: 29 May 2007         Last updated: 15 March 2009
2813         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2814  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2815    
2816    
# Line 3059  CHARACTERS AND METACHARACTERS Line 3089  CHARACTERS AND METACHARACTERS
3089                    syntax)                    syntax)
3090           ]      terminates the character class           ]      terminates the character class
3091    
3092         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3093    
3094    
3095  BACKSLASH  BACKSLASH
3096    
3097         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3098         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3099         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3100         applies both inside and outside character classes.         applies both inside and outside character classes.
3101    
3102         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
3103         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3104         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3105         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3106         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-
3107         slash, you write \\.         slash, you write \\.
3108    
3109         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3110         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3111         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3112         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3113         part of the pattern.         part of the pattern.
3114    
3115         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-
3116         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-
3117         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
3118         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3119         tion. Note the following examples:         tion. Note the following examples:
3120    
3121           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3095  BACKSLASH Line 3125  BACKSLASH
3125           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3126           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3127    
3128         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3129         classes.         classes.
3130    
3131     Non-printing characters     Non-printing characters
3132    
3133         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-
3134         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
3135         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3136         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3137         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
3138         sequences than the binary character it represents:         sequences than the binary character it represents:
3139    
3140           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 3118  BACKSLASH Line 3148  BACKSLASH
3148           \xhh      character with hex code hh           \xhh      character with hex code hh
3149           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3150    
3151         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,
3152         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
3153         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;
3154         becomes hex 7B.         becomes hex 7B.
3155    
3156         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
3157         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3158         between  \x{  and  },  but the value of the character code must be less         between \x{ and }, but the value of the character  code  must  be  less
3159         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3160         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3161         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3162    
3163         If characters other than hexadecimal digits appear between \x{  and  },         If  characters  other than hexadecimal digits appear between \x{ and },
3164         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3165         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3166         escape,  with  no  following  digits, giving a character whose value is         escape, with no following digits, giving a  character  whose  value  is
3167         zero.         zero.
3168    
3169         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
3170         two  syntaxes  for  \x. There is no difference in the way they are han-         two syntaxes for \x. There is no difference in the way  they  are  han-
3171         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3172    
3173         After \0 up to two further octal digits are read. If  there  are  fewer         After  \0  up  to two further octal digits are read. If there are fewer
3174         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3175         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3176         (code  value 7). Make sure you supply two digits after the initial zero         (code value 7). Make sure you supply two digits after the initial  zero
3177         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3178    
3179         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-
3180         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3181         its as a decimal number. If the number is less than  10,  or  if  there         its  as  a  decimal  number. If the number is less than 10, or if there
3182         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3183         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3184         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3185         of parenthesized subpatterns.         of parenthesized subpatterns.
3186    
3187         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
3188         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3189         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3190         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3191         non-UTF-8 mode, the value of a character specified  in  octal  must  be         non-UTF-8  mode,  the  value  of a character specified in octal must be
3192         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
3193         example:         example:
3194    
3195           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3177  BACKSLASH Line 3207  BACKSLASH
3207           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3208                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3209    
3210         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
3211         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3212    
3213         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3214         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3215         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3216         08), and the sequences \R and \X are interpreted as the characters  "R"         08),  and the sequences \R and \X are interpreted as the characters "R"
3217         and  "X", respectively. Outside a character class, these sequences have         and "X", respectively. Outside a character class, these sequences  have
3218         different meanings (see below).         different meanings (see below).
3219    
3220     Absolute and relative back references     Absolute and relative back references
3221    
3222         The sequence \g followed by an unsigned or a negative  number,  option-         The  sequence  \g followed by an unsigned or a negative number, option-
3223         ally  enclosed  in braces, is an absolute or relative back reference. A         ally enclosed in braces, is an absolute or relative back  reference.  A
3224         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3225         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3226    
3227     Absolute and relative subroutine calls     Absolute and relative subroutine calls
3228    
3229         For  compatibility with Oniguruma, the non-Perl syntax \g followed by a         For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3230         name or a number enclosed either in angle brackets or single quotes, is         name or a number enclosed either in angle brackets or single quotes, is
3231         an  alternative  syntax for referencing a subpattern as a "subroutine".         an alternative syntax for referencing a subpattern as  a  "subroutine".
3232         Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and         Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3233         \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back         \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3234         reference; the latter is a subroutine call.         reference; the latter is a subroutine call.
3235    
3236     Generic character types     Generic character types
# Line 3220  BACKSLASH Line 3250  BACKSLASH
3250           \W     any "non-word" character           \W     any "non-word" character
3251    
3252         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
3253         into two disjoint sets. Any given character matches one, and only  one,         into  two disjoint sets. Any given character matches one, and only one,
3254         of each pair.         of each pair.
3255    
3256         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
3257         acter classes. They each match one character of the  appropriate  type.         acter  classes.  They each match one character of the appropriate type.
3258         If  the current matching point is at the end of the subject string, all         If the current matching point is at the end of the subject string,  all
3259         of them fail, since there is no character to match.         of them fail, since there is no character to match.
3260    
3261         For compatibility with Perl, \s does not match the VT  character  (code         For  compatibility  with Perl, \s does not match the VT character (code
3262         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
3263         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3264         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3265         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3266    
3267         In UTF-8 mode, characters with values greater than 128 never match  \d,         In  UTF-8 mode, characters with values greater than 128 never match \d,
3268         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3269         code character property support is available.  These  sequences  retain         code  character  property  support is available. These sequences retain
3270         their original meanings from before UTF-8 support was available, mainly         their original meanings from before UTF-8 support was available, mainly
3271         for efficiency reasons.         for efficiency reasons.
3272    
3273         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3274         the  other  sequences, these do match certain high-valued codepoints in         the other sequences, these do match certain high-valued  codepoints  in
3275         UTF-8 mode.  The horizontal space characters are:         UTF-8 mode.  The horizontal space characters are:
3276    
3277           U+0009     Horizontal tab           U+0009     Horizontal tab
# Line 3275  BACKSLASH Line 3305  BACKSLASH
3305           U+2029     Paragraph separator           U+2029     Paragraph separator
3306    
3307         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
3308         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-
3309         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-
3310         specific  matching is taking place (see "Locale support" in the pcreapi         specific matching is taking place (see "Locale support" in the  pcreapi
3311         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3312         systems,  or "french" in Windows, some character codes greater than 128         systems, or "french" in Windows, some character codes greater than  128
3313         are used for accented letters, and these are matched by \w. The use  of         are  used for accented letters, and these are matched by \w. The use of
3314         locales with Unicode is discouraged.         locales with Unicode is discouraged.
3315    
3316     Newline sequences     Newline sequences
3317    
3318         Outside  a  character class, by default, the escape sequence \R matches         Outside a character class, by default, the escape sequence  \R  matches
3319         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3320         mode \R is equivalent to the following:         mode \R is equivalent to the following:
3321    
3322           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3323    
3324         This  is  an  example  of an "atomic group", details of which are given         This is an example of an "atomic group", details  of  which  are  given
3325         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3326         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3327         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3328         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3329         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3330    
3331         In UTF-8 mode, two additional characters whose codepoints  are  greater         In  UTF-8  mode, two additional characters whose codepoints are greater
3332         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3333         rator, U+2029).  Unicode character property support is not  needed  for         rator,  U+2029).   Unicode character property support is not needed for
3334         these characters to be recognized.         these characters to be recognized.
3335    
3336         It is possible to restrict \R to match only CR, LF, or CRLF (instead of         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3337         the complete set  of  Unicode  line  endings)  by  setting  the  option         the  complete  set  of  Unicode  line  endings)  by  setting the option
3338         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3339         (BSR is an abbrevation for "backslash R".) This can be made the default         (BSR is an abbrevation for "backslash R".) This can be made the default
3340         when  PCRE  is  built;  if this is the case, the other behaviour can be         when PCRE is built; if this is the case, the  other  behaviour  can  be
3341         requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to         requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3342         specify  these  settings  by  starting a pattern string with one of the         specify these settings by starting a pattern string  with  one  of  the
3343         following sequences:         following sequences:
3344    
3345           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
# Line 3318  BACKSLASH Line 3348  BACKSLASH
3348         These override the default and the options given to pcre_compile(), but         These override the default and the options given to pcre_compile(), but
3349         they can be overridden by options given to pcre_exec(). Note that these         they can be overridden by options given to pcre_exec(). Note that these
3350         special settings, which are not Perl-compatible, are recognized only at         special settings, which are not Perl-compatible, are recognized only at
3351         the  very  start  of a pattern, and that they must be in upper case. If         the very start of a pattern, and that they must be in  upper  case.  If
3352         more than one of them is present, the last one is  used.  They  can  be         more  than  one  of  them is present, the last one is used. They can be
3353         combined  with  a  change of newline convention, for example, a pattern         combined with a change of newline convention, for  example,  a  pattern
3354         can start with:         can start with:
3355    
3356           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
# Line 3330  BACKSLASH Line 3360  BACKSLASH
3360     Unicode character properties     Unicode character properties
3361    
3362         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3363         tional  escape sequences that match characters with specific properties         tional escape sequences that match characters with specific  properties
3364         are available.  When not in UTF-8 mode, these sequences are  of  course         are  available.   When not in UTF-8 mode, these sequences are of course
3365         limited  to  testing characters whose codepoints are less than 256, but         limited to testing characters whose codepoints are less than  256,  but
3366         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3367    
3368           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3369           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3370           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3371    
3372         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3373         script names, the general category properties, and "Any", which matches         script names, the general category properties, and "Any", which matches
3374         any character (including newline). Other properties such as "InMusical-         any character (including newline). Other properties such as "InMusical-
3375         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does
3376         not match any characters, so always causes a match failure.         not match any characters, so always causes a match failure.
3377    
3378         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3379         A  character from one of these sets can be matched using a script name.         A character from one of these sets can be matched using a script  name.
3380         For example:         For example:
3381    
3382           \p{Greek}           \p{Greek}
3383           \P{Han}           \P{Han}
3384    
3385         Those that are not part of an identified script are lumped together  as         Those  that are not part of an identified script are lumped together as
3386         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3387    
3388         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
3389         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,
3390         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
3391         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-
3392         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,
3393         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
3394         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,
3395         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
3396         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
3397    
3398         Each  character has exactly one general category property, specified by         Each character has exactly one general category property, specified  by
3399         a two-letter abbreviation. For compatibility with Perl, negation can be         a two-letter abbreviation. For compatibility with Perl, negation can be
3400         specified  by  including a circumflex between the opening brace and the         specified by including a circumflex between the opening brace  and  the
3401         property name. For example, \p{^Lu} is the same as \P{Lu}.         property name. For example, \p{^Lu} is the same as \P{Lu}.
3402    
3403         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3404         eral  category properties that start with that letter. In this case, in         eral category properties that start with that letter. In this case,  in
3405         the absence of negation, the curly brackets in the escape sequence  are         the  absence of negation, the curly brackets in the escape sequence are
3406         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3407    
3408           \p{L}           \p{L}
# Line 3424  BACKSLASH Line 3454  BACKSLASH
3454           Zp    Paragraph separator           Zp    Paragraph separator
3455           Zs    Space separator           Zs    Space separator
3456    
3457         The  special property L& is also supported: it matches a character that         The special property L& is also supported: it matches a character  that
3458         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
3459         classified as a modifier or "other".         classified as a modifier or "other".
3460    
3461         The  Cs  (Surrogate)  property  applies only to characters in the range         The Cs (Surrogate) property applies only to  characters  in  the  range
3462         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3463         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3464         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in         ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3465         the pcreapi page).         the pcreapi page).
3466    
3467         The  long  synonyms  for  these  properties that Perl supports (such as         The long synonyms for these properties  that  Perl  supports  (such  as
3468         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3469         any of these properties with "Is".         any of these properties with "Is".
3470    
3471         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3472         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3473         in the Unicode table.         in the Unicode table.
3474    
3475         Specifying  caseless  matching  does not affect these escape sequences.         Specifying caseless matching does not affect  these  escape  sequences.
3476         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3477    
3478         The \X escape matches any number of Unicode  characters  that  form  an         The  \X  escape  matches  any number of Unicode characters that form an
3479         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3480    
3481           (?>\PM\pM*)           (?>\PM\pM*)
3482    
3483         That  is,  it matches a character without the "mark" property, followed         That is, it matches a character without the "mark"  property,  followed
3484         by zero or more characters with the "mark"  property,  and  treats  the         by  zero  or  more  characters with the "mark" property, and treats the
3485         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence as an atomic group (see below).  Characters  with  the  "mark"
3486         property are typically accents that  affect  the  preceding  character.         property  are  typically  accents  that affect the preceding character.
3487         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X         None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
3488         matches any one character.         matches any one character.
3489    
3490         Matching characters by Unicode property is not fast, because  PCRE  has         Matching  characters  by Unicode property is not fast, because PCRE has
3491         to  search  a  structure  that  contains data for over fifteen thousand         to search a structure that contains  data  for  over  fifteen  thousand
3492         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3493         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3494    
3495     Resetting the match start     Resetting the match start
3496    
3497         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3498         ously matched characters not  to  be  included  in  the  final  matched         ously  matched  characters  not  to  be  included  in the final matched
3499         sequence. For example, the pattern:         sequence. For example, the pattern:
3500    
3501           foo\Kbar           foo\Kbar
3502    
3503         matches  "foobar",  but reports that it has matched "bar". This feature         matches "foobar", but reports that it has matched "bar".  This  feature
3504         is similar to a lookbehind assertion (described  below).   However,  in         is  similar  to  a lookbehind assertion (described below).  However, in
3505         this  case, the part of the subject before the real match does not have         this case, the part of the subject before the real match does not  have
3506         to be of fixed length, as lookbehind assertions do. The use of \K  does         to  be of fixed length, as lookbehind assertions do. The use of \K does
3507         not  interfere  with  the setting of captured substrings.  For example,         not interfere with the setting of captured  substrings.   For  example,
3508         when the pattern         when the pattern
3509    
3510           (foo)\Kbar           (foo)\Kbar
# Line 3483  BACKSLASH Line 3513  BACKSLASH
3513    
3514     Simple assertions     Simple assertions
3515    
3516         The final use of backslash is for certain simple assertions. An  asser-         The  final use of backslash is for certain simple assertions. An asser-
3517         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
3518         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
3519         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
3520         The backslashed assertions are:         The backslashed assertions are:
3521    
3522           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3497  BACKSLASH Line 3527  BACKSLASH
3527           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3528           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3529    
3530         These assertions may not appear in character classes (but note that  \b         These  assertions may not appear in character classes (but note that \b
3531         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3532         acter class).         acter class).
3533    
3534         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
3535         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.
3536         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
3537         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3538    
3539         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
3540         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
3541         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
3542         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
3543         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
3544         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
3545         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
3546         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
3547         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
3548         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3549         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3550    
3551         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
3552         the start point of the match, as specified by the startoffset  argument         the  start point of the match, as specified by the startoffset argument
3553         of  pcre_exec().  It  differs  from \A when the value of startoffset is         of pcre_exec(). It differs from \A when the  value  of  startoffset  is
3554         non-zero. By calling pcre_exec() multiple times with appropriate  argu-         non-zero.  By calling pcre_exec() multiple times with appropriate argu-
3555         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3556         mentation where \G can be useful.         mentation where \G can be useful.
3557    
3558         Note, however, that PCRE's interpretation of \G, as the  start  of  the         Note,  however,  that  PCRE's interpretation of \G, as the start of the
3559         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3560         end of the previous match. In Perl, these can  be  different  when  the         end  of  the  previous  match. In Perl, these can be different when the
3561         previously  matched  string was empty. Because PCRE does just one match         previously matched string was empty. Because PCRE does just  one  match
3562         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3563    
3564         If all the alternatives of a pattern begin with \G, the  expression  is         If  all  the alternatives of a pattern begin with \G, the expression is
3565         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3566         in the compiled regular expression.         in the compiled regular expression.
3567    
# Line 3539  BACKSLASH Line 3569  BACKSLASH
3569  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3570    
3571         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3572         character  is  an  assertion  that is true only if the current matching         character is an assertion that is true only  if  the  current  matching
3573         point is at the start of the subject string. If the  startoffset  argu-         point  is  at the start of the subject string. If the startoffset argu-
3574         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
3575         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
3576         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3577    
3578         Circumflex  need  not be the first character of the pattern if a number         Circumflex need not be the first character of the pattern if  a  number
3579         of alternatives are involved, but it should be the first thing in  each         of  alternatives are involved, but it should be the first thing in each
3580         alternative  in  which  it appears if the pattern is ever to match that         alternative in which it appears if the pattern is ever  to  match  that
3581         branch. If all possible alternatives start with a circumflex, that  is,         branch.  If all possible alternatives start with a circumflex, that is,
3582         if  the  pattern  is constrained to match only at the start of the sub-         if the pattern is constrained to match only at the start  of  the  sub-
3583         ject, it is said to be an "anchored" pattern.  (There  are  also  other         ject,  it  is  said  to be an "anchored" pattern. (There are also other
3584         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3585    
3586         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
3587         matching point is at the end of  the  subject  string,  or  immediately         matching  point  is  at  the  end of the subject string, or immediately
3588         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3589         be the last character of the pattern if a number  of  alternatives  are         be  the  last  character of the pattern if a number of alternatives are
3590         involved,  but  it  should  be  the last item in any branch in which it         involved, but it should be the last item in  any  branch  in  which  it
3591         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3592    
3593         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
3594         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
3595         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3596    
3597         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3598         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex
3599         matches immediately after internal newlines as well as at the start  of         matches  immediately after internal newlines as well as at the start of
3600         the  subject  string.  It  does not match after a newline that ends the         the subject string. It does not match after a  newline  that  ends  the
3601         string. A dollar matches before any newlines in the string, as well  as         string.  A dollar matches before any newlines in the string, as well as
3602         at  the very end, when PCRE_MULTILINE is set. When newline is specified         at the very end, when PCRE_MULTILINE is set. When newline is  specified
3603         as the two-character sequence CRLF, isolated CR and  LF  characters  do         as  the  two-character  sequence CRLF, isolated CR and LF characters do
3604         not indicate newlines.         not indicate newlines.
3605    
3606         For  example, the pattern /^abc$/ matches the subject string "def\nabc"         For example, the pattern /^abc$/ matches the subject string  "def\nabc"
3607         (where \n represents a newline) in multiline mode, but  not  otherwise.         (where  \n  represents a newline) in multiline mode, but not otherwise.
3608         Consequently,  patterns  that  are anchored in single line mode because         Consequently, patterns that are anchored in single  line  mode  because
3609         all branches start with ^ are not anchored in  multiline  mode,  and  a         all  branches  start  with  ^ are not anchored in multiline mode, and a
3610         match  for  circumflex  is  possible  when  the startoffset argument of         match for circumflex is  possible  when  the  startoffset  argument  of
3611         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
3612         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3613    
3614         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
3615         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
3616         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
3617         set.         set.
3618    
3619    
3620  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3621    
3622         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-
3623         ter  in  the subject string except (by default) a character that signi-         ter in the subject string except (by default) a character  that  signi-
3624         fies the end of a line. In UTF-8 mode, the  matched  character  may  be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
3625         more than one byte long.         more than one byte long.
3626    
3627         When  a line ending is defined as a single character, dot never matches         When a line ending is defined as a single character, dot never  matches
3628         that character; when the two-character sequence CRLF is used, dot  does         that  character; when the two-character sequence CRLF is used, dot does
3629         not  match  CR  if  it  is immediately followed by LF, but otherwise it         not match CR if it is immediately followed  by  LF,  but  otherwise  it
3630         matches all characters (including isolated CRs and LFs). When any  Uni-         matches  all characters (including isolated CRs and LFs). When any Uni-
3631         code  line endings are being recognized, dot does not match CR or LF or         code line endings are being recognized, dot does not match CR or LF  or
3632         any of the other line ending characters.         any of the other line ending characters.
3633    
3634         The behaviour of dot with regard to newlines can  be  changed.  If  the         The  behaviour  of  dot  with regard to newlines can be changed. If the
3635         PCRE_DOTALL  option  is  set,  a dot matches any one character, without         PCRE_DOTALL option is set, a dot matches  any  one  character,  without
3636         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3637         string, it takes two dots to match it.         string, it takes two dots to match it.
3638    
3639         The  handling of dot is entirely independent of the handling of circum-         The handling of dot is entirely independent of the handling of  circum-
3640         flex and dollar, the only relationship being  that  they  both  involve         flex  and  dollar,  the  only relationship being that they both involve
3641         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3642    
3643    
3644  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3645    
3646         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3647         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
3648         line-ending  characters.  The  feature  is provided in Perl in order to         line-ending characters. The feature is provided in  Perl  in  order  to
3649         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
3650         acters  into individual bytes, what remains in the string may be a mal-         acters into individual bytes, what remains in the string may be a  mal-
3651         formed UTF-8 string. For this reason, the \C escape  sequence  is  best         formed  UTF-8  string.  For this reason, the \C escape sequence is best
3652         avoided.         avoided.
3653    
3654         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
3655         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-
3656         late the length of the lookbehind.         late the length of the lookbehind.
3657    
3658    
# Line 3631  SQUARE BRACKETS AND CHARACTER CLASSES Line 3661  SQUARE BRACKETS AND CHARACTER CLASSES
3661         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3662         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-
3663         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,
3664         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
3665         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3666    
3667         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
3668         mode, the character may occupy more than one byte. A matched  character         mode,  the character may occupy more than one byte. A matched character
3669         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
3670         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
3671         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
3672         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
3673         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3674    
3675         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
3676         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
3677         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3678         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
3679         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-
3680         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
3681         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3682    
3683         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
3684         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
3685         mechanism.         mechanism.
3686    
3687         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
3688         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
3689         [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
3690         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
3691         understands  the  concept  of case for characters whose values are less         understands the concept of case for characters whose  values  are  less
3692         than 128, so caseless matching is always possible. For characters  with         than  128, so caseless matching is always possible. For characters with
3693         higher  values,  the  concept  of case is supported if PCRE is compiled         higher values, the concept of case is supported  if  PCRE  is  compiled
3694         with Unicode property support, but not otherwise.  If you want  to  use         with  Unicode  property support, but not otherwise.  If you want to use
3695         caseless  matching  for  characters 128 and above, you must ensure that         caseless matching for characters 128 and above, you  must  ensure  that
3696         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
3697         support.         support.
3698    
3699         Characters  that  might  indicate  line breaks are never treated in any         Characters that might indicate line breaks are  never  treated  in  any
3700         special way  when  matching  character  classes,  whatever  line-ending         special  way  when  matching  character  classes,  whatever line-ending
3701         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
3702         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
3703         of these characters.         of these characters.
3704    
3705         The  minus (hyphen) character can be used to specify a range of charac-         The minus (hyphen) character can be used to specify a range of  charac-
3706         ters in a character  class.  For  example,  [d-m]  matches  any  letter         ters  in  a  character  class.  For  example,  [d-m] matches any letter
3707         between  d  and  m,  inclusive.  If  a minus character is required in a         between d and m, inclusive. If a  minus  character  is  required  in  a
3708         class, it must be escaped with a backslash  or  appear  in  a  position         class,  it  must  be  escaped  with a backslash or appear in a position
3709         where  it cannot be interpreted as indicating a range, typically as the         where it cannot be interpreted as indicating a range, typically as  the
3710         first or last character in the class.         first or last character in the class.
3711    
3712         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-
3713         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
3714         two characters ("W" and "-") followed by a literal string "46]", so  it         two  characters ("W" and "-") followed by a literal string "46]", so it
3715         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
3716         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-
3717         preted  as a class containing a range followed by two other characters.         preted as a class containing a range followed by two other  characters.
3718         The octal or hexadecimal representation of "]" can also be used to  end         The  octal or hexadecimal representation of "]" can also be used to end
3719         a range.         a range.
3720    
3721         Ranges  operate in the collating sequence of character values. They can         Ranges operate in the collating sequence of character values. They  can
3722         also  be  used  for  characters  specified  numerically,  for   example         also   be  used  for  characters  specified  numerically,  for  example
3723         [\000-\037].  In UTF-8 mode, ranges can include characters whose values         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
3724         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3725    
3726         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,
3727         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
3728         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
3729         character  tables  for  a French locale are in use, [\xc8-\xcb] matches         character tables for a French locale are in  use,  [\xc8-\xcb]  matches
3730         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
3731         concept  of  case for characters with values greater than 128 only when         concept of case for characters with values greater than 128  only  when
3732         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3733    
3734         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
3735         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
3736         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3737         flex  can  conveniently  be used with the upper case character types to         flex can conveniently be used with the upper case  character  types  to
3738         specify a more restricted set of characters  than  the  matching  lower         specify  a  more  restricted  set of characters than the matching lower
3739         case  type.  For example, the class [^\W_] matches any letter or digit,         case type. For example, the class [^\W_] matches any letter  or  digit,
3740         but not underscore.         but not underscore.
3741    
3742         The only metacharacters that are recognized in  character  classes  are         The  only  metacharacters  that are recognized in character classes are
3743         backslash,  hyphen  (only  where  it can be interpreted as specifying a         backslash, hyphen (only where it can be  interpreted  as  specifying  a
3744         range), circumflex (only at the start), opening  square  bracket  (only         range),  circumflex  (only  at the start), opening square bracket (only
3745         when  it can be interpreted as introducing a POSIX class name - see the         when it can be interpreted as introducing a POSIX class name - see  the
3746         next section), and the terminating  closing  square  bracket.  However,         next  section),  and  the  terminating closing square bracket. However,
3747         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3748    
3749    
3750  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3751    
3752         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3753         enclosed by [: and :] within the enclosing square brackets.  PCRE  also         enclosed  by  [: and :] within the enclosing square brackets. PCRE also
3754         supports this notation. For example,         supports this notation. For example,
3755    
3756           [01[:alpha:]%]           [01[:alpha:]%]
# Line 3743  POSIX CHARACTER CLASSES Line 3773  POSIX CHARACTER CLASSES
3773           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3774           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3775    
3776         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
3777         and  space  (32). Notice that this list includes the VT character (code         and space (32). Notice that this list includes the VT  character  (code
3778         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
3779         Perl compatibility).         Perl compatibility).
3780    
3781         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension
3782         from Perl 5.8. Another Perl extension is negation, which  is  indicated         from  Perl  5.8. Another Perl extension is negation, which is indicated
3783         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3784    
3785           [12[:^digit:]]           [12[:^digit:]]
3786    
3787         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the
3788         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3789         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
3790    
# Line 3774  VERTICAL BAR Line 3804  VERTICAL BAR
3804         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3805         to  right, and the first one that succeeds is used. If the alternatives         to  right, and the first one that succeeds is used. If the alternatives
3806         are within a subpattern (defined below), "succeeds" means matching  the         are within a subpattern (defined below), "succeeds" means matching  the
3807         rest  of the main pattern as well as the alternative in the subpattern.         rest of the main pattern as well as the alternative in the subpattern.
3808    
3809    
3810  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3811    
3812         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
3813         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
3814         within the pattern by  a  sequence  of  Perl  option  letters  enclosed         within  the  pattern  by  a  sequence  of  Perl option letters enclosed
3815         between "(?" and ")".  The option letters are         between "(?" and ")".  The option letters are
3816    
3817           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 3791  INTERNAL OPTION SETTING Line 3821  INTERNAL OPTION SETTING
3821    
3822         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3823         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
3824         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-
3825         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,
3826         is  also  permitted.  If  a  letter  appears  both before and after the         is also permitted. If a  letter  appears  both  before  and  after  the
3827         hyphen, the option is unset.         hyphen, the option is unset.
3828    
3829         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
3830         can  be changed in the same way as the Perl-compatible options by using         can be changed in the same way as the Perl-compatible options by  using
3831         the characters J, U and X respectively.         the characters J, U and X respectively.
3832    
3833         When an option change occurs at top level (that is, not inside  subpat-         When  an option change occurs at top level (that is, not inside subpat-
3834         tern  parentheses),  the change applies to the remainder of the pattern         tern parentheses), the change applies to the remainder of  the  pattern
3835         that follows.  If the change is placed right at the start of a pattern,         that follows.  If the change is placed right at the start of a pattern,
3836         PCRE extracts it into the global options (and it will therefore show up         PCRE extracts it into the global options (and it will therefore show up
3837         in data extracted by the pcre_fullinfo() function).         in data extracted by the pcre_fullinfo() function).
3838    
3839         An option change within a subpattern (see below for  a  description  of         An  option  change  within a subpattern (see below for a description of
3840         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3841         it, so         it, so
3842    
3843           (a(?i)b)c           (a(?i)b)c
3844    
3845         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
3846         used).   By  this means, options can be made to have different settings         used).  By this means, options can be made to have  different  settings
3847         in different parts of the pattern. Any changes made in one  alternative         in  different parts of the pattern. Any changes made in one alternative
3848         do  carry  on  into subsequent branches within the same subpattern. For         do carry on into subsequent branches within the  same  subpattern.  For
3849         example,         example,
3850    
3851           (a(?i)b|c)           (a(?i)b|c)
3852    
3853         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the
3854         first  branch  is  abandoned before the option setting. This is because         first branch is abandoned before the option setting.  This  is  because
3855         the effects of option settings happen at compile time. There  would  be         the  effects  of option settings happen at compile time. There would be
3856         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3857    
3858         Note:  There  are  other  PCRE-specific  options that can be set by the         Note: There are other PCRE-specific options that  can  be  set  by  the
3859         application when the compile or match functions  are  called.  In  some         application  when  the  compile  or match functions are called. In some
3860         cases  the  pattern  can  contain special leading sequences to override         cases the pattern can contain special  leading  sequences  to  override
3861         what the application has set or what has been  defaulted.  Details  are         what  the  application  has set or what has been defaulted. Details are
3862         given in the section entitled "Newline sequences" above.         given in the section entitled "Newline sequences" above.
3863    
3864    
# Line 3841  SUBPATTERNS Line 3871  SUBPATTERNS
3871    
3872           cat(aract|erpillar|)           cat(aract|erpillar|)
3873    
3874         matches one of the words "cat", "cataract", or  "caterpillar".  Without         matches  one  of the words "cat", "cataract", or "caterpillar". Without
3875         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty
3876         string.         string.
3877    
3878         2. It sets up the subpattern as  a  capturing  subpattern.  This  means         2.  It  sets  up  the  subpattern as a capturing subpattern. This means
3879         that,  when  the  whole  pattern  matches,  that portion of the subject         that, when the whole pattern  matches,  that  portion  of  the  subject
3880         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
3881         ovector  argument  of pcre_exec(). Opening parentheses are counted from         ovector argument of pcre_exec(). Opening parentheses are  counted  from
3882         left to right (starting from 1) to obtain  numbers  for  the  capturing         left  to  right  (starting  from 1) to obtain numbers for the capturing
3883         subpatterns.         subpatterns.
3884    
3885         For  example,  if the string "the red king" is matched against the pat-         For example, if the string "the red king" is matched against  the  pat-
3886         tern         tern
3887    
3888           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3860  SUBPATTERNS Line 3890  SUBPATTERNS
3890         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3891         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3892    
3893         The  fact  that  plain  parentheses  fulfil two functions is not always         The fact that plain parentheses fulfil  two  functions  is  not  always
3894         helpful.  There are often times when a grouping subpattern is  required         helpful.   There are often times when a grouping subpattern is required
3895         without  a capturing requirement. If an opening parenthesis is followed         without a capturing requirement. If an opening parenthesis is  followed
3896         by a question mark and a colon, the subpattern does not do any  captur-         by  a question mark and a colon, the subpattern does not do any captur-
3897         ing,  and  is  not  counted when computing the number of any subsequent         ing, and is not counted when computing the  number  of  any  subsequent
3898         capturing subpatterns. For example, if the string "the white queen"  is         capturing  subpatterns. For example, if the string "the white queen" is
3899         matched against the pattern         matched against the pattern
3900    
3901           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 3873  SUBPATTERNS Line 3903  SUBPATTERNS
3903         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3904         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
3905    
3906         As a convenient shorthand, if any option settings are required  at  the         As  a  convenient shorthand, if any option settings are required at the
3907         start  of  a  non-capturing  subpattern,  the option letters may appear         start of a non-capturing subpattern,  the  option  letters  may  appear
3908         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3909    
3910           (?i:saturday|sunday)           (?i:saturday|sunday)
3911           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3912    
3913         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3914         tried  from  left  to right, and options are not reset until the end of         tried from left to right, and options are not reset until  the  end  of
3915         the subpattern is reached, an option setting in one branch does  affect         the  subpattern is reached, an option setting in one branch does affect
3916         subsequent  branches,  so  the above patterns match "SUNDAY" as well as         subsequent branches, so the above patterns match "SUNDAY"  as  well  as
3917         "Saturday".         "Saturday".
3918    
3919    
3920  DUPLICATE SUBPATTERN NUMBERS  DUPLICATE SUBPATTERN NUMBERS
3921    
3922         Perl 5.10 introduced a feature whereby each alternative in a subpattern         Perl 5.10 introduced a feature whereby each alternative in a subpattern
3923         uses  the same numbers for its capturing parentheses. Such a subpattern         uses the same numbers for its capturing parentheses. Such a  subpattern
3924         starts with (?| and is itself a non-capturing subpattern. For  example,         starts  with (?| and is itself a non-capturing subpattern. For example,
3925         consider this pattern:         consider this pattern:
3926    
3927           (?|(Sat)ur|(Sun))day           (?|(Sat)ur|(Sun))day
3928    
3929         Because  the two alternatives are inside a (?| group, both sets of cap-         Because the two alternatives are inside a (?| group, both sets of  cap-
3930         turing parentheses are numbered one. Thus, when  the  pattern  matches,         turing  parentheses  are  numbered one. Thus, when the pattern matches,
3931         you  can  look  at captured substring number one, whichever alternative         you can look at captured substring number  one,  whichever  alternative
3932         matched. This construct is useful when you want to  capture  part,  but         matched.  This  construct  is useful when you want to capture part, but
3933         not all, of one of a number of alternatives. Inside a (?| group, paren-         not all, of one of a number of alternatives. Inside a (?| group, paren-
3934         theses are numbered as usual, but the number is reset at the  start  of         theses  are  numbered as usual, but the number is reset at the start of
3935         each  branch. The numbers of any capturing buffers that follow the sub-         each branch. The numbers of any capturing buffers that follow the  sub-
3936         pattern start after the highest number used in any branch. The  follow-         pattern  start after the highest number used in any branch. The follow-
3937         ing  example  is taken from the Perl documentation.  The numbers under-         ing example is taken from the Perl documentation.  The  numbers  under-
3938         neath show in which buffer the captured content will be stored.         neath show in which buffer the captured content will be stored.
3939    
3940           # before  ---------------branch-reset----------- after           # before  ---------------branch-reset----------- after
3941           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3942           # 1            2         2  3        2     3     4           # 1            2         2  3        2     3     4
3943    
3944         A backreference or a recursive call to  a  numbered  subpattern  always         A  backreference  or  a  recursive call to a numbered subpattern always
3945         refers to the first one in the pattern with the given number.         refers to the first one in the pattern with the given number.
3946    
3947         An  alternative approach to using this "branch reset" feature is to use         An alternative approach to using this "branch reset" feature is to  use
3948         duplicate named subpatterns, as described in the next section.         duplicate named subpatterns, as described in the next section.
3949    
3950    
3951  NAMED SUBPATTERNS  NAMED SUBPATTERNS
3952    
3953         Identifying capturing parentheses by number is simple, but  it  can  be         Identifying  capturing  parentheses  by number is simple, but it can be
3954         very  hard  to keep track of the numbers in complicated regular expres-         very hard to keep track of the numbers in complicated  regular  expres-
3955         sions. Furthermore, if an  expression  is  modified,  the  numbers  may         sions.  Furthermore,  if  an  expression  is  modified, the numbers may
3956         change.  To help with this difficulty, PCRE supports the naming of sub-         change. To help with this difficulty, PCRE supports the naming of  sub-
3957         patterns. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
3958         had  the  feature earlier, and PCRE introduced it at release 4.0, using         had the feature earlier, and PCRE introduced it at release  4.0,  using
3959         the Python syntax. PCRE now supports both the Perl and the Python  syn-         the  Python syntax. PCRE now supports both the Perl and the Python syn-
3960         tax.         tax.
3961    
3962         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
3963         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References
3964         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
3965         references, recursion, and conditions, can be made by name as  well  as         references,  recursion,  and conditions, can be made by name as well as
3966         by number.         by number.
3967    
3968         Names  consist  of  up  to  32 alphanumeric characters and underscores.         Names consist of up to  32  alphanumeric  characters  and  underscores.
3969         Named capturing parentheses are still  allocated  numbers  as  well  as         Named  capturing  parentheses  are  still  allocated numbers as well as
3970         names,  exactly as if the names were not present. The PCRE API provides         names, exactly as if the names were not present. The PCRE API  provides
3971         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
3972         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
3973         a captured substring by name.         a captured substring by name.
3974    
3975         By default, a name must be unique within a pattern, but it is  possible         By  default, a name must be unique within a pattern, but it is possible
3976         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
3977         time. This can be useful for patterns where only one  instance  of  the         time.  This  can  be useful for patterns where only one instance of the
3978         named  parentheses  can  match. Suppose you want to match the name of a         named parentheses can match. Suppose you want to match the  name  of  a
3979         weekday, either as a 3-letter abbreviation or as the full name, and  in         weekday,  either as a 3-letter abbreviation or as the full name, and in
3980         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
3981         the line breaks) does the job:         the line breaks) does the job:
3982    
# Line 3956  NAMED SUBPATTERNS Line 3986  NAMED SUBPATTERNS
3986           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
3987           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
3988    
3989         There are five capturing substrings, but only one is ever set  after  a         There  are  five capturing substrings, but only one is ever set after a
3990         match.  (An alternative way of solving this problem is to use a "branch         match.  (An alternative way of solving this problem is to use a "branch
3991         reset" subpattern, as described in the previous section.)         reset" subpattern, as described in the previous section.)
3992    
3993         The convenience function for extracting the data by  name  returns  the         The  convenience  function  for extracting the data by name returns the
3994         substring  for  the first (and in this example, the only) subpattern of         substring for the first (and in this example, the only)  subpattern  of
3995         that name that matched. This saves searching  to  find  which  numbered         that  name  that  matched.  This saves searching to find which numbered
3996         subpattern  it  was. If you make a reference to a non-unique named sub-         subpattern it was. If you make a reference to a non-unique  named  sub-
3997         pattern from elsewhere in the pattern, the one that corresponds to  the         pattern  from elsewhere in the pattern, the one that corresponds to the
3998         lowest  number  is used. For further details of the interfaces for han-         lowest number is used. For further details of the interfaces  for  han-
3999         dling named subpatterns, see the pcreapi documentation.         dling named subpatterns, see the pcreapi documentation.
4000    
4001           Warning: You cannot use different names to distinguish between two sub-
4002           patterns with the same number (see the previous section)  because  PCRE
4003           uses only the numbers when matching.
4004    
4005    
4006  REPETITION  REPETITION
4007    
4008         Repetition is specified by quantifiers, which can  follow  any  of  the         Repetition  is  specified  by  quantifiers, which can follow any of the
4009         following items:         following items:
4010    
4011           a literal data character           a literal data character
# Line 3984  REPETITION Line 4018  REPETITION
4018           a back reference (see next section)           a back reference (see next section)
4019           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4020    
4021         The  general repetition quantifier specifies a minimum and maximum num-         The general repetition quantifier specifies a minimum and maximum  num-
4022         ber of permitted matches, by giving the two numbers in  curly  brackets         ber  of  permitted matches, by giving the two numbers in curly brackets
4023         (braces),  separated  by  a comma. The numbers must be less than 65536,         (braces), separated by a comma. The numbers must be  less  than  65536,
4024         and the first must be less than or equal to the second. For example:         and the first must be less than or equal to the second. For example:
4025    
4026           z{2,4}           z{2,4}
4027    
4028         matches "zz", "zzz", or "zzzz". A closing brace on its  own  is  not  a         matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a
4029         special  character.  If  the second number is omitted, but the comma is         special character. If the second number is omitted, but  the  comma  is
4030         present, there is no upper limit; if the second number  and  the  comma         present,  there  is  no upper limit; if the second number and the comma
4031         are  both omitted, the quantifier specifies an exact number of required         are both omitted, the quantifier specifies an exact number of  required
4032         matches. Thus         matches. Thus
4033    
4034           [aeiou]{3,}           [aeiou]{3,}
# Line 4003  REPETITION Line 4037  REPETITION
4037    
4038           \d{8}           \d{8}
4039    
4040         matches exactly 8 digits. An opening curly bracket that  appears  in  a         matches  exactly  8  digits. An opening curly bracket that appears in a
4041         position  where a quantifier is not allowed, or one that does not match         position where a quantifier is not allowed, or one that does not  match
4042         the syntax of a quantifier, is taken as a literal character. For  exam-         the  syntax of a quantifier, is taken as a literal character. For exam-
4043         ple, {,6} is not a quantifier, but a literal string of four characters.         ple, {,6} is not a quantifier, but a literal string of four characters.
4044    
4045         In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to         In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to
# Line 4149  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4183  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4183    
4184           (?>\d+)foo           (?>\d+)foo
4185    
4186         This  kind  of  parenthesis "locks up" the  part of the pattern it con-         This kind of parenthesis "locks up" the  part of the  pattern  it  con-
4187         tains once it has matched, and a failure further into  the  pattern  is         tains  once  it  has matched, and a failure further into the pattern is
4188         prevented  from  backtracking into it. Backtracking past it to previous         prevented from backtracking into it. Backtracking past it  to  previous
4189         items, however, works as normal.         items, however, works as normal.
4190    
4191         An alternative description is that a subpattern of  this  type  matches         An  alternative  description  is that a subpattern of this type matches
4192         the  string  of  characters  that an identical standalone pattern would         the string of characters that an  identical  standalone  pattern  would
4193         match, if anchored at the current point in the subject string.         match, if anchored at the current point in the subject string.
4194    
4195         Atomic grouping subpatterns are not capturing subpatterns. Simple cases         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
4196         such as the above example can be thought of as a maximizing repeat that         such as the above example can be thought of as a maximizing repeat that
4197         must swallow everything it can. So, while both \d+ and  \d+?  are  pre-         must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
4198         pared  to  adjust  the number of digits they match in order to make the         pared to adjust the number of digits they match in order  to  make  the
4199         rest of the pattern match, (?>\d+) can only match an entire sequence of         rest of the pattern match, (?>\d+) can only match an entire sequence of
4200         digits.         digits.
4201    
4202         Atomic  groups in general can of course contain arbitrarily complicated         Atomic groups in general can of course contain arbitrarily  complicated
4203         subpatterns, and can be nested. However, when  the  subpattern  for  an         subpatterns,  and  can  be  nested. However, when the subpattern for an
4204         atomic group is just a single repeated item, as in the example above, a         atomic group is just a single repeated item, as in the example above, a
4205         simpler notation, called a "possessive quantifier" can  be  used.  This         simpler  notation,  called  a "possessive quantifier" can be used. This
4206         consists  of  an  additional  + character following a quantifier. Using         consists of an additional + character  following  a  quantifier.  Using
4207         this notation, the previous example can be rewritten as         this notation, the previous example can be rewritten as
4208    
4209           \d++foo           \d++foo
# Line 4179  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4213  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4213    
4214           (abc|xyz){2,3}+           (abc|xyz){2,3}+
4215    
4216         Possessive   quantifiers   are   always  greedy;  the  setting  of  the         Possessive  quantifiers  are  always  greedy;  the   setting   of   the
4217         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
4218         simpler  forms  of atomic group. However, there is no difference in the         simpler forms of atomic group. However, there is no difference  in  the
4219         meaning of a possessive quantifier and  the  equivalent  atomic  group,         meaning  of  a  possessive  quantifier and the equivalent atomic group,
4220         though  there  may  be a performance difference; possessive quantifiers         though there may be a performance  difference;  possessive  quantifiers
4221         should be slightly faster.         should be slightly faster.
4222    
4223         The possessive quantifier syntax is an extension to the Perl  5.8  syn-         The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-
4224         tax.   Jeffrey  Friedl  originated the idea (and the name) in the first         tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first
4225         edition of his book. Mike McCloskey liked it, so implemented it when he         edition of his book. Mike McCloskey liked it, so implemented it when he
4226         built  Sun's Java package, and PCRE copied it from there. It ultimately         built Sun's Java package, and PCRE copied it from there. It  ultimately
4227         found its way into Perl at release 5.10.         found its way into Perl at release 5.10.
4228    
4229         PCRE has an optimization that automatically "possessifies" certain sim-         PCRE has an optimization that automatically "possessifies" certain sim-
4230         ple  pattern  constructs.  For  example, the sequence A+B is treated as         ple pattern constructs. For example, the sequence  A+B  is  treated  as
4231         A++B because there is no point in backtracking into a sequence  of  A's         A++B  because  there is no point in backtracking into a sequence of A's
4232         when B must follow.         when B must follow.
4233    
4234         When  a  pattern  contains an unlimited repeat inside a subpattern that         When a pattern contains an unlimited repeat inside  a  subpattern  that
4235         can itself be repeated an unlimited number of  times,  the  use  of  an         can  itself  be  repeated  an  unlimited number of times, the use of an
4236         atomic  group  is  the  only way to avoid some failing matches taking a         atomic group is the only way to avoid some  failing  matches  taking  a
4237         very long time indeed. The pattern         very long time indeed. The pattern
4238    
4239           (\D+|<\d+>)*[!?]           (\D+|<\d+>)*[!?]
4240    
4241         matches an unlimited number of substrings that either consist  of  non-         matches  an  unlimited number of substrings that either consist of non-
4242         digits,  or  digits  enclosed in <>, followed by either ! or ?. When it         digits, or digits enclosed in <>, followed by either ! or  ?.  When  it
4243         matches, it runs quickly. However, if it is applied to         matches, it runs quickly. However, if it is applied to
4244    
4245           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
4246    
4247         it takes a long time before reporting  failure.  This  is  because  the         it  takes  a  long  time  before reporting failure. This is because the
4248         string  can be divided between the internal \D+ repeat and the external         string can be divided between the internal \D+ repeat and the  external
4249         * repeat in a large number of ways, and all  have  to  be  tried.  (The         *  repeat  in  a  large  number of ways, and all have to be tried. (The
4250         example  uses  [!?]  rather than a single character at the end, because         example uses [!?] rather than a single character at  the  end,  because
4251         both PCRE and Perl have an optimization that allows  for  fast  failure         both  PCRE  and  Perl have an optimization that allows for fast failure
4252         when  a single character is used. They remember the last single charac-         when a single character is used. They remember the last single  charac-
4253         ter that is required for a match, and fail early if it is  not  present         ter  that  is required for a match, and fail early if it is not present
4254         in  the  string.)  If  the pattern is changed so that it uses an atomic         in the string.) If the pattern is changed so that  it  uses  an  atomic
4255         group, like this:         group, like this:
4256    
4257           ((?>\D+)|<\d+>)*[!?]           ((?>\D+)|<\d+>)*[!?]
4258    
4259         sequences of non-digits cannot be broken, and failure happens  quickly.         sequences of non-digits cannot be broken, and failure happens quickly.
4260    
4261    
4262  BACK REFERENCES  BACK REFERENCES
# Line 4985  AUTHOR Line 5019  AUTHOR
5019    
5020  REVISION  REVISION
5021    
5022         Last updated: 19 April 2008         Last updated: 08 March 2009
5023         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
5024  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5025    
5026    
# Line 5514  MULTI-SEGMENT MATCHING WITH pcre_dfa_exe Line 5548  MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
5548            0: dogsbody            0: dogsbody
5549            1: dog            1: dog
5550    
5551         The  pattern matches the words "dog" or "dogsbody". When the subject is         The pattern matches the words "dog" or "dogsbody". When the subject  is
5552         presented in several parts ("do" and "gsb" being  the  first  two)  the         presented  in  several  parts  ("do" and "gsb" being the first two) the
5553         match  stops  when "dog" has been found, and it is not possible to con-         match stops when "dog" has been found, and it is not possible  to  con-
5554         tinue. On the other hand,  if  "dogsbody"  is  presented  as  a  single         tinue.  On  the  other  hand,  if  "dogsbody"  is presented as a single
5555         string, both matches are found.         string, both matches are found.
5556    
5557         Because  of  this  phenomenon,  it does not usually make sense to end a         Because of this phenomenon, it does not usually make  sense  to  end  a
5558         pattern that is going to be matched in this way with a variable repeat.         pattern that is going to be matched in this way with a variable repeat.
5559    
5560         4. Patterns that contain alternatives at the top level which do not all         4. Patterns that contain alternatives at the top level which do not all
# Line 5867  DESCRIPTION Line 5901  DESCRIPTION
5901         command  for  linking  an application that uses them. Because the POSIX         command  for  linking  an application that uses them. Because the POSIX
5902         functions call the native ones, it is also necessary to add -lpcre.         functions call the native ones, it is also necessary to add -lpcre.
5903    
5904         I have implemented only those option bits that can be reasonably mapped         I have implemented only those POSIX option bits that can be  reasonably
5905         to PCRE native options. In addition, the option REG_EXTENDED is defined         mapped  to PCRE native options. In addition, the option REG_EXTENDED is
5906         with the value zero. This has no effect, but since  programs  that  are         defined with the value zero. This has no  effect,  but  since  programs
5907         written  to  the  POSIX interface often use it, this makes it easier to         that  are  written  to  the POSIX interface often use it, this makes it
5908         slot in PCRE as a replacement library. Other POSIX options are not even         easier to slot in PCRE as a replacement library.  Other  POSIX  options
5909         defined.         are not even defined.
5910    
5911         When  PCRE  is  called  via these functions, it is only the API that is         When  PCRE  is  called  via these functions, it is only the API that is
5912         POSIX-like in style. The syntax and semantics of  the  regular  expres-         POSIX-like in style. The syntax and semantics of  the  regular  expres-
# Line 5952  COMPILING A PATTERN Line 5986  COMPILING A PATTERN
5986  MATCHING NEWLINE CHARACTERS  MATCHING NEWLINE CHARACTERS
5987    
5988         This area is not simple, because POSIX and Perl take different views of         This area is not simple, because POSIX and Perl take different views of
5989         things.  It is not possible to get PCRE to obey  POSIX  semantics,  but         things.   It  is  not possible to get PCRE to obey POSIX semantics, but
5990         then  PCRE was never intended to be a POSIX engine. The following table         then PCRE was never intended to be a POSIX engine. The following  table
5991         lists the different possibilities for matching  newline  characters  in         lists  the  different  possibilities for matching newline characters in
5992         PCRE:         PCRE:
5993    
5994                                   Default   Change with                                   Default   Change with
# Line 5976  MATCHING NEWLINE CHARACTERS Line 6010  MATCHING NEWLINE CHARACTERS
6010           ^ matches \n in middle     no     REG_NEWLINE           ^ matches \n in middle     no     REG_NEWLINE
6011    
6012         PCRE's behaviour is the same as Perl's, except that there is no equiva-         PCRE's behaviour is the same as Perl's, except that there is no equiva-
6013         lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl,  there  is         lent  for  PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is
6014         no way to stop newline from matching [^a].         no way to stop newline from matching [^a].
6015    
6016         The   default  POSIX  newline  handling  can  be  obtained  by  setting         The  default  POSIX  newline  handling  can  be  obtained  by   setting
6017         PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to  make  PCRE         PCRE_DOTALL  and  PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE
6018         behave exactly as for the REG_NEWLINE action.         behave exactly as for the REG_NEWLINE action.
6019    
6020    
6021  MATCHING A PATTERN  MATCHING A PATTERN
6022    
6023         The  function  regexec()  is  called  to  match a compiled pattern preg         The function regexec() is called  to  match  a  compiled  pattern  preg
6024         against a given string, which is by default terminated by a  zero  byte         against  a  given string, which is by default terminated by a zero byte
6025         (but  see  REG_STARTEND below), subject to the options in eflags. These         (but see REG_STARTEND below), subject to the options in  eflags.  These
6026         can be:         can be:
6027    
6028           REG_NOTBOL           REG_NOTBOL
# Line 5996  MATCHING A PATTERN Line 6030  MATCHING A PATTERN
6030         The PCRE_NOTBOL option is set when calling the underlying PCRE matching         The PCRE_NOTBOL option is set when calling the underlying PCRE matching
6031         function.         function.
6032    
6033             REG_NOTEMPTY
6034    
6035           The PCRE_NOTEMPTY option is set when calling the underlying PCRE match-
6036           ing function. Note that REG_NOTEMPTY is not part of the POSIX standard.
6037           However, setting this option can give more POSIX-like behaviour in some
6038           situations.
6039    
6040           REG_NOTEOL           REG_NOTEOL
6041    
6042         The PCRE_NOTEOL option is set when calling the underlying PCRE matching         The PCRE_NOTEOL option is set when calling the underlying PCRE matching
# Line 6058  AUTHOR Line 6099  AUTHOR
6099    
6100  REVISION  REVISION
6101    
6102         Last updated: 05 April 2008         Last updated: 11 March 2009
6103         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
6104  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6105    
6106    
# Line 6163  MATCHING INTERFACE Line 6204  MATCHING INTERFACE
6204         need    more,    consider    using    the    more   general   interface         need    more,    consider    using    the    more   general   interface
6205         pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.         pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
6206    
6207           NOTE: Do not use no_arg, which is used internally to mark the end of  a
6208           list  of optional arguments, as a placeholder for missing arguments, as
6209           this can lead to segfaults.
6210    
6211    
6212  QUOTING METACHARACTERS  QUOTING METACHARACTERS
6213    
# Line 6396  AUTHOR Line 6441  AUTHOR
6441    
6442  REVISION  REVISION
6443    
6444         Last updated: 12 November 2007         Last updated: 17 March 2009
6445  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6446    
6447    

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