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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few  differences.  The current implementation of PCRE (release         just  a few differences. Some features that appeared in Python and PCRE
23         6.x) corresponds approximately with Perl  5.8,  including  support  for         before they appeared in Perl are also available using the  Python  syn-
24         UTF-8 encoded strings and Unicode general category properties. However,         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         this support has to be explicitly enabled; it is not the default.         items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27         In addition to the Perl-compatible matching function,  PCRE  also  con-  
28         tains  an  alternative matching function that matches the same compiled         The  current implementation of PCRE corresponds approximately with Perl
29         patterns in a different way. In certain circumstances, the  alternative         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         function  has  some  advantages.  For  a discussion of the two matching         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         algorithms, see the pcrematching page.         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 5.2.0.
33         PCRE is written in C and released as a C library. A  number  of  people  
34         have  written  wrappers and interfaces of various kinds. In particular,         In  addition to the Perl-compatible matching function, PCRE contains an
35         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now         alternative function that matches the same compiled patterns in a  dif-
36           ferent way. In certain circumstances, the alternative function has some
37           advantages.  For a discussion of the two matching algorithms,  see  the
38           pcrematching page.
39    
40           PCRE  is  written  in C and released as a C library. A number of people
41           have written wrappers and interfaces of various kinds.  In  particular,
42           Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
43         included as part of the PCRE distribution. The pcrecpp page has details         included as part of the PCRE distribution. The pcrecpp page has details
44         of this interface. Other people's contributions can  be  found  in  the         of  this  interface.  Other  people's contributions can be found in the
45         Contrib directory at the primary FTP site, which is:         Contrib directory at the primary FTP site, which is:
46    
47         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
48    
49         Details  of  exactly which Perl regular expression features are and are         Details of exactly which Perl regular expression features are  and  are
50         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
51         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
52           page.
53    
54         Some  features  of  PCRE can be included, excluded, or changed when the         Some  features  of  PCRE can be included, excluded, or changed when the
55         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
# Line 63  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80             pcre-config       show PCRE installation configuration information
81           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
82           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
# Line 80  USER DOCUMENTATION Line 92  USER DOCUMENTATION
92           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
93           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
94           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
95           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
96             pcrestack         discussion of stack usage
97             pcresyntax        quick syntax reference
98           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
99    
100         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 98  LIMITATIONS Line 112  LIMITATIONS
112         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
113         the  source  distribution and the pcrebuild documentation for details).         the  source  distribution and the pcrebuild documentation for details).
114         In these cases the limit is substantially larger.  However,  the  speed         In these cases the limit is substantially larger.  However,  the  speed
115         of execution will be slower.         of execution is slower.
116    
117         All values in repeating quantifiers must be less than 65536.  The maxi-         All values in repeating quantifiers must be less than 65536.
        mum number of capturing subpatterns is 65535.  
118    
119         There is no limit to the number of non-capturing subpatterns,  but  the         There is no limit to the number of parenthesized subpatterns, but there
120         maximum  depth  of  nesting  of  all kinds of parenthesized subpattern,         can be no more than 65535 capturing subpatterns.
121         including capturing subpatterns, assertions, and other types of subpat-  
122         tern, is 200.         The maximum length of name for a named subpattern is 32 characters, and
123           the maximum number of named subpatterns is 10000.
124    
125         The  maximum  length of a subject string is the largest positive number         The  maximum  length of a subject string is the largest positive number
126         that an integer variable can hold. However, when using the  traditional         that an integer variable can hold. However, when using the  traditional
127         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
128         inite repetition.  This means that the available stack space may  limit         inite repetition.  This means that the available stack space may  limit
129         the size of a subject string that can be processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
130           For a discussion of stack issues, see the pcrestack documentation.
131    
132    
133  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
# Line 124  UTF-8 AND UNICODE PROPERTY SUPPORT Line 139  UTF-8 AND UNICODE PROPERTY SUPPORT
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any subject strings that are matched against it are  treated  as  UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146         If  you compile PCRE with UTF-8 support, but do not use it at run time,  
147         the library will be a bit bigger, but the additional run time  overhead         If you compile PCRE with UTF-8 support, but do not use it at run  time,
148         is  limited  to testing the PCRE_UTF8 flag in several places, so should         the  library will be a bit bigger, but the additional run time overhead
149         not be very large.         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
150           very big.
151    
152         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
153         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
155         general  category  properties such as Lu for an upper case letter or Nd         general category properties such as Lu for an upper case letter  or  Nd
156         for a decimal number. A full list is given in the pcrepattern  documen-         for  a  decimal number, the Unicode script names such as Arabic or Han,
157         tation. The PCRE library is increased in size by about 90K when Unicode         and the derived properties Any and L&. A full  list  is  given  in  the
158         property support is included.         pcrepattern documentation. Only the short names for properties are sup-
159           ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
160         The following comments apply when PCRE is running in UTF-8 mode:         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161           optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and         does not support this.
163         subjects  are  checked for validity on entry to the relevant functions.  
164         If an invalid UTF-8 string is passed, an error return is given. In some     Validity of UTF-8 strings
165         situations,  you  may  already  know  that  your strings are valid, and  
166         therefore want to skip these checks in order to improve performance. If         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,         subjects are (by default) checked for validity on entry to the relevant
168         PCRE assumes that the pattern or subject  it  is  given  (respectively)         functions.  From  release 7.3 of PCRE, the check is according the rules
169         contains  only valid UTF-8 codes. In this case, it does not diagnose an         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172         crash.         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174         2. In a pattern, the escape sequence \x{...}, where the contents of the  
175         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176         character whose code number is the given hexadecimal number, for  exam-         which  the Unicode Standard says this: "The Low Surrogate Area does not
177         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,         contain any  character  assignments,  consequently  no  character  code
178         the item is not recognized.  This escape sequence can be used either as         charts or namelists are provided for this area. Surrogates are reserved
179         a literal, or within a character class.         for use with UTF-16 and then must be used in pairs."  The  code  points
180           that  are  encoded  by  UTF-16  pairs are available as independent code
181           points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184           If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186           that your strings are valid, and therefore want to skip these checks in
187           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188           compile  time  or at run time, PCRE assumes that the pattern or subject
189           it is given (respectively) contains only valid  UTF-8  codes.  In  this
190           case, it does not diagnose an invalid UTF-8 string.
191    
192           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193           what happens depends on why the string is invalid. If the  string  con-
194           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197           strings according to the more liberal rules of RFC  2279.  However,  if
198           the  string does not even conform to RFC 2279, the result is undefined.
199           Your program may crash.
200    
201           If you want to process strings  of  values  in  the  full  range  0  to
202           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204           this situation, you will have to apply your own validity check.
205    
206       General comments about UTF-8 mode
207    
208           1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209           two-byte UTF-8 character if the value is greater than 127.
210    
211         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212         UTF-8 character if the value is greater than 127.         characters for values greater than \177.
213    
214         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         5.  The dot metacharacter matches one UTF-8 character instead of a sin-         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         gle byte.         gle byte.
219    
220         6. The escape sequence \C can be used to match a single byte  in  UTF-8         5.  The  escape sequence \C can be used to match a single byte in UTF-8
221         mode,  but  its  use can lead to some strange effects. This facility is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but, by default, the characters that
226         nizes as digits, spaces, or word characters  remain  the  same  set  as         PCRE  recognizes  as digits, spaces, or word characters remain the same
227         before, all with values less than 256. This remains true even when PCRE         set as before, all with values less than 256. This  remains  true  even
228         includes Unicode property support, because to do otherwise  would  slow         when  PCRE  is built to include Unicode property support, because to do
229         down  PCRE in many common cases. If you really want to test for a wider         otherwise would slow down PCRE in many common cases. Note in particular
230         sense of, say, "digit", you must use Unicode  property  tests  such  as         that this applies to \b and \B, because they are defined in terms of \w
231         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233         8.  Similarly,  characters that match the POSIX named character classes         tively, if you set the PCRE_UCP option,  the  way  that  the  character
234         are all low-valued characters.         escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236           generic character types in the pcrepattern documentation.
237    
238           7.  Similarly,  characters that match the POSIX named character classes
239           are all low-valued characters, unless the PCRE_UCP option is set.
240    
241           8. However, the horizontal and  vertical  whitespace  matching  escapes
242           (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
243           whether or not PCRE_UCP is set.
244    
245         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
246         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
247         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
248         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
249         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
250         used only for characters with higher values.         used only for characters with higher values. Furthermore, PCRE supports
251           case-insensitive matching only  when  there  is  a  one-to-one  mapping
252           between  a letter's cases. There are a small number of many-to-one map-
253           pings in Unicode; these are not supported by PCRE.
254    
255    
256  AUTHOR  AUTHOR
257    
258         Philip Hazel         Philip Hazel
259         University Computing Service,         University Computing Service
260         Cambridge CB2 3QG, England.         Cambridge CB2 3QH, England.
261    
262         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,
263         so I've taken it away. If you want to email me, use my initial and sur-         so  I've  taken  it away. If you want to email me, use my two initials,
264         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
265    
 Last updated: 07 March 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
266    
267    REVISION
268    
269           Last updated: 13 November 2010
270           Copyright (c) 1997-2010 University of Cambridge.
271    ------------------------------------------------------------------------------
272    
273    
274  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
275    
276    
# Line 220  NAME Line 281  NAME
281  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
282    
283         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
284         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
285         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
286         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
287         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
288         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
289           instead of configure to build PCRE.
290    
291           There  is  a  lot more information about building PCRE in non-Unix-like
292           environments in the file called NON_UNIX_USE, which is part of the PCRE
293           distribution.  You  should consult this file as well as the README file
294           if you are building in a non-Unix-like environment.
295    
296           The complete list of options for configure (which includes the standard
297           ones  such  as  the  selection  of  the  installation directory) can be
298           obtained by running
299    
300           ./configure --help           ./configure --help
301    
302         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
303         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
304         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
305         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
306         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
307         not described.         is not described.
308    
309    
310  C++ SUPPORT  C++ SUPPORT
# Line 249  C++ SUPPORT Line 320  C++ SUPPORT
320    
321  UTF-8 SUPPORT  UTF-8 SUPPORT
322    
323         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
324    
325           --enable-utf8           --enable-utf8
326    
327         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
328         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings as UTF-8. As well as compiling PCRE with this option, you  also
329         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()
330         function.         or pcre_compile2() functions.
331    
332           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
333           expects its input to be either ASCII or UTF-8 (depending on the runtime
334           option). It is not possible to support both EBCDIC and UTF-8  codes  in
335           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
336           --enable-ebcdic are mutually exclusive.
337    
338    
339  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 272  UNICODE CHARACTER PROPERTY SUPPORT Line 349  UNICODE CHARACTER PROPERTY SUPPORT
349         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF-8 support, even if you  have
350         not explicitly requested it.         not explicitly requested it.
351    
352         Including  Unicode  property  support  adds around 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
353         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
354         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
355    
356    
357  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
358    
359         By default, PCRE treats character 10 (linefeed) as the newline  charac-         By  default,  PCRE interprets the linefeed (LF) character as indicating
360         ter. This is the normal newline character on Unix-like systems. You can         the end of a line. This is the normal newline  character  on  Unix-like
361         compile PCRE to use character 13 (carriage return) instead by adding         systems.  You  can compile PCRE to use carriage return (CR) instead, by
362           adding
363    
364           --enable-newline-is-cr           --enable-newline-is-cr
365    
366         to the configure command. For completeness there is  also  a  --enable-         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
367         newline-is-lf  option,  which explicitly specifies linefeed as the new-         option, which explicitly specifies linefeed as the newline character.
368         line character.  
369           Alternatively, you can specify that line endings are to be indicated by
370           the two character sequence CRLF. If you want this, add
371    
372             --enable-newline-is-crlf
373    
374           to the configure command. There is a fourth option, specified by
375    
376             --enable-newline-is-anycrlf
377    
378           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
379           CRLF as indicating a line ending. Finally, a fifth option, specified by
380    
381             --enable-newline-is-any
382    
383           causes PCRE to recognize any Unicode newline sequence.
384    
385           Whatever  line  ending convention is selected when PCRE is built can be
386           overridden when the library functions are called. At build time  it  is
387           conventional to use the standard for your operating system.
388    
389    
390    WHAT \R MATCHES
391    
392           By  default,  the  sequence \R in a pattern matches any Unicode newline
393           sequence, whatever has been selected as the line  ending  sequence.  If
394           you specify
395    
396             --enable-bsr-anycrlf
397    
398           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
399           ever is selected when PCRE is built can be overridden when the  library
400           functions are called.
401    
402    
403  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
404    
405         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
406         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
407         of         of
408    
409           --disable-shared           --disable-shared
# Line 306  BUILDING SHARED AND STATIC LIBRARIES Line 415  BUILDING SHARED AND STATIC LIBRARIES
415  POSIX MALLOC USAGE  POSIX MALLOC USAGE
416    
417         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
418         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
419         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
420         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
421         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
422         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.
423         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 319  POSIX MALLOC USAGE Line 428  POSIX MALLOC USAGE
428         to the configure command.         to the configure command.
429    
430    
431    HANDLING VERY LARGE PATTERNS
432    
433           Within a compiled pattern, offset values are used  to  point  from  one
434           part  to another (for example, from an opening parenthesis to an alter-
435           nation metacharacter). By default, two-byte values are used  for  these
436           offsets,  leading  to  a  maximum size for a compiled pattern of around
437           64K. This is sufficient to handle all but the most  gigantic  patterns.
438           Nevertheless,  some  people do want to process truyl enormous patterns,
439           so it is possible to compile PCRE to use three-byte or  four-byte  off-
440           sets by adding a setting such as
441    
442             --with-link-size=3
443    
444           to  the  configure  command.  The value given must be 2, 3, or 4. Using
445           longer offsets slows down the operation of PCRE because it has to  load
446           additional bytes when handling them.
447    
448    
449    AVOIDING EXCESSIVE STACK USAGE
450    
451           When matching with the pcre_exec() function, PCRE implements backtrack-
452           ing by making recursive calls to an internal function  called  match().
453           In  environments  where  the size of the stack is limited, this can se-
454           verely limit PCRE's operation. (The Unix environment does  not  usually
455           suffer from this problem, but it may sometimes be necessary to increase
456           the maximum stack size.  There is a discussion in the  pcrestack  docu-
457           mentation.)  An alternative approach to recursion that uses memory from
458           the heap to remember data, instead of using recursive  function  calls,
459           has  been  implemented to work round the problem of limited stack size.
460           If you want to build a version of PCRE that works this way, add
461    
462             --disable-stack-for-recursion
463    
464           to the configure command. With this configuration, PCRE  will  use  the
465           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
466           ment functions. By default these point to malloc() and free(), but  you
467           can replace the pointers so that your own functions are used instead.
468    
469           Separate  functions  are  provided  rather  than  using pcre_malloc and
470           pcre_free because the  usage  is  very  predictable:  the  block  sizes
471           requested  are  always  the  same,  and  the blocks are always freed in
472           reverse order. A calling program might be able to  implement  optimized
473           functions  that  perform  better  than  malloc()  and free(). PCRE runs
474           noticeably more slowly when built in this way. This option affects only
475           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
476    
477    
478  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
479    
480         Internally,  PCRE has a function called match(), which it calls repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
481         edly  (possibly  recursively)  when  matching  a   pattern   with   the         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
482         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec()  function.  By controlling the maximum number of times this
483         function may be called during a single matching operation, a limit  can         function may be called during a single matching operation, a limit  can
484         be  placed  on  the resources used by a single call to pcre_exec(). The         be  placed  on  the resources used by a single call to pcre_exec(). The
# Line 335  LIMITING PCRE RESOURCE USAGE Line 491  LIMITING PCRE RESOURCE USAGE
491         to  the  configure  command.  This  setting  has  no  effect   on   the         to  the  configure  command.  This  setting  has  no  effect   on   the
492         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
493    
494           In  some  environments  it is desirable to limit the depth of recursive
495           calls of match() more strictly than the total number of calls, in order
496           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
497           for-recursion is specified) that is used. A second limit controls this;
498           it  defaults  to  the  value  that is set for --with-match-limit, which
499           imposes no additional constraints. However, you can set a  lower  limit
500           by adding, for example,
501    
502             --with-match-limit-recursion=10000
503    
504           to  the  configure  command.  This  value can also be overridden at run
505           time.
506    
507    
508    CREATING CHARACTER TABLES AT BUILD TIME
509    
510           PCRE uses fixed tables for processing characters whose code values  are
511           less  than 256. By default, PCRE is built with a set of tables that are
512           distributed in the file pcre_chartables.c.dist. These  tables  are  for
513           ASCII codes only. If you add
514    
515             --enable-rebuild-chartables
516    
517           to  the  configure  command, the distributed tables are no longer used.
518           Instead, a program called dftables is compiled and  run.  This  outputs
519           the source for new set of tables, created in the default locale of your
520           C runtime system. (This method of replacing the tables does not work if
521           you  are cross compiling, because dftables is run on the local host. If
522           you need to create alternative tables when cross  compiling,  you  will
523           have to do so "by hand".)
524    
 HANDLING VERY LARGE PATTERNS  
525    
526         Within  a  compiled  pattern,  offset values are used to point from one  USING EBCDIC CODE
        part to another (for example, from an opening parenthesis to an  alter-  
        nation  metacharacter).  By default, two-byte values are used for these  
        offsets, leading to a maximum size for a  compiled  pattern  of  around  
        64K.  This  is sufficient to handle all but the most gigantic patterns.  
        Nevertheless, some people do want to process enormous patterns,  so  it  
        is  possible  to compile PCRE to use three-byte or four-byte offsets by  
        adding a setting such as  
527    
528           --with-link-size=3         PCRE  assumes  by  default that it will run in an environment where the
529           character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
530           This  is  the  case for most computer operating systems. PCRE can, how-
531           ever, be compiled to run in an EBCDIC environment by adding
532    
533         to the configure command. The value given must be 2,  3,  or  4.  Using           --enable-ebcdic
        longer  offsets slows down the operation of PCRE because it has to load  
        additional bytes when handling them.  
534    
535         If you build PCRE with an increased link size, test 2 (and  test  5  if         to the configure command. This setting implies --enable-rebuild-charta-
536         you  are using UTF-8) will fail. Part of the output of these tests is a         bles.  You  should  only  use  it if you know that you are in an EBCDIC
537         representation of the compiled pattern, and this changes with the  link         environment (for example,  an  IBM  mainframe  operating  system).  The
538         size.         --enable-ebcdic option is incompatible with --enable-utf8.
539    
540    
541  AVOIDING EXCESSIVE STACK USAGE  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
542    
543         When matching with the pcre_exec() function, PCRE implements backtrack-         By default, pcregrep reads all files as plain text. You can build it so
544         ing by making recursive calls to an internal function  called  match().         that it recognizes files whose names end in .gz or .bz2, and reads them
545         In  environments  where  the size of the stack is limited, this can se-         with libz or libbz2, respectively, by adding one or both of
        verely limit PCRE's operation. (The Unix environment does  not  usually  
        suffer  from  this  problem.)  An alternative approach that uses memory  
        from the heap to remember data, instead  of  using  recursive  function  
        calls,  has been implemented to work round this problem. If you want to  
        build a version of PCRE that works this way, add  
546    
547           --disable-stack-for-recursion           --enable-pcregrep-libz
548             --enable-pcregrep-libbz2
549    
550         to the configure command. With this configuration, PCRE  will  use  the         to the configure command. These options naturally require that the rel-
551         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-         evant libraries are installed on your system. Configuration  will  fail
552         ment functions. Separate functions are provided because  the  usage  is         if they are not.
        very  predictable:  the  block sizes requested are always the same, and  
        the blocks are always freed in reverse order. A calling  program  might  
        be  able  to implement optimized functions that perform better than the  
        standard malloc() and  free()  functions.  PCRE  runs  noticeably  more  
        slowly when built in this way. This option affects only the pcre_exec()  
        function; it is not relevant for the the pcre_dfa_exec() function.  
553    
554    
555  USING EBCDIC CODE  PCRETEST OPTION FOR LIBREADLINE SUPPORT
556    
557         PCRE assumes by default that it will run in an  environment  where  the         If you add
        character  code  is  ASCII  (or Unicode, which is a superset of ASCII).  
        PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by  
        adding  
558    
559           --enable-ebcdic           --enable-pcretest-libreadline
560    
561         to the configure command.         to  the  configure  command,  pcretest  is  linked with the libreadline
562           library, and when its input is from a terminal, it reads it  using  the
563           readline() function. This provides line-editing and history facilities.
564           Note that libreadline is GPL-licensed, so if you distribute a binary of
565           pcretest linked in this way, there may be licensing issues.
566    
567  Last updated: 15 August 2005         Setting  this  option  causes  the -lreadline option to be added to the
568  Copyright (c) 1997-2005 University of Cambridge.         pcretest build. In many operating environments with  a  sytem-installed
569  ------------------------------------------------------------------------------         libreadline this is sufficient. However, in some environments (e.g.  if
570           an unmodified distribution version of readline is in use),  some  extra
571           configuration  may  be necessary. The INSTALL file for libreadline says
572           this:
573    
574             "Readline uses the termcap functions, but does not link with the
575             termcap or curses library itself, allowing applications which link
576             with readline the to choose an appropriate library."
577    
578           If your environment has not been set up so that an appropriate  library
579           is automatically included, you may need to add something like
580    
581             LIBS="-ncurses"
582    
583           immediately before the configure command.
584    
585    
586    SEE ALSO
587    
588           pcreapi(3), pcre_config(3).
589    
590    
591    AUTHOR
592    
593           Philip Hazel
594           University Computing Service
595           Cambridge CB2 3QH, England.
596    
597    
598    REVISION
599    
600           Last updated: 29 September 2009
601           Copyright (c) 1997-2009 University of Cambridge.
602    ------------------------------------------------------------------------------
603    
604    
605  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
606    
607    
# Line 431  PCRE MATCHING ALGORITHMS Line 634  PCRE MATCHING ALGORITHMS
634           <something> <something else> <something further>           <something> <something else> <something further>
635    
636         there are three possible answers. The standard algorithm finds only one         there are three possible answers. The standard algorithm finds only one
637         of them, whereas the DFA algorithm finds all three.         of them, whereas the alternative algorithm finds all three.
638    
639    
640  REGULAR EXPRESSIONS AS TREES  REGULAR EXPRESSIONS AS TREES
# Line 440  REGULAR EXPRESSIONS AS TREES Line 643  REGULAR EXPRESSIONS AS TREES
643         resented  as  a  tree structure. An unlimited repetition in the pattern         resented  as  a  tree structure. An unlimited repetition in the pattern
644         makes the tree of infinite size, but it is still a tree.  Matching  the         makes the tree of infinite size, but it is still a tree.  Matching  the
645         pattern  to a given subject string (from a given starting point) can be         pattern  to a given subject string (from a given starting point) can be
646         thought of as a search of the tree.  There are  two  standard  ways  to         thought of as a search of the tree.  There are two  ways  to  search  a
647         search  a  tree: depth-first and breadth-first, and these correspond to         tree:  depth-first  and  breadth-first, and these correspond to the two
648         the two matching algorithms provided by PCRE.         matching algorithms provided by PCRE.
649    
650    
651  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
652    
653         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
654         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
655         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
656         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
657         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 472  THE STANDARD MATCHING ALGORITHM Line 675  THE STANDARD MATCHING ALGORITHM
675         This provides support for capturing parentheses and back references.         This provides support for capturing parentheses and back references.
676    
677    
678  THE DFA MATCHING ALGORITHM  THE ALTERNATIVE MATCHING ALGORITHM
679    
680         DFA stands for "deterministic finite automaton", but you do not need to         This algorithm conducts a breadth-first search of  the  tree.  Starting
681         understand the origins of that name. This algorithm conducts a breadth-         from  the  first  matching  point  in the subject, it scans the subject
682         first search of the tree. Starting from the first matching point in the         string from left to right, once, character by character, and as it does
683         subject,  it scans the subject string from left to right, once, charac-         this,  it remembers all the paths through the tree that represent valid
684         ter by character, and as it does  this,  it  remembers  all  the  paths         matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
685         through the tree that represent valid matches.         though  it is not implemented as a traditional finite state machine (it
686           keeps multiple states active simultaneously).
687         The  scan  continues until either the end of the subject is reached, or  
688         there are no more unterminated paths. At this point,  terminated  paths         Although the general principle of this matching algorithm  is  that  it
689         represent  the different matching possibilities (if there are none, the         scans  the subject string only once, without backtracking, there is one
690         match has failed).  Thus, if there is more  than  one  possible  match,         exception: when a lookaround assertion is encountered,  the  characters
691           following  or  preceding  the  current  point  have to be independently
692           inspected.
693    
694           The scan continues until either the end of the subject is  reached,  or
695           there  are  no more unterminated paths. At this point, terminated paths
696           represent the different matching possibilities (if there are none,  the
697           match  has  failed).   Thus,  if there is more than one possible match,
698         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
699         est. In PCRE, there is an option to stop the algorithm after the  first         est.  The  matches are returned in decreasing order of length. There is
700         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
701           sarily the shortest) is found.
702    
703         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
704         subject. If the pattern         subject. If the pattern
705    
706           cat(er(pillar)?)           cat(er(pillar)?)?
707    
708         is matched against the string "the caterpillar catchment",  the  result         is matched against the string "the caterpillar catchment",  the  result
709         will  be the three strings "cat", "cater", and "caterpillar" that start         will  be the three strings "caterpillar", "cater", and "cat" that start
710         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
711         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
712    
713         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
714         supported by the DFA matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
715    
716         1. Because the algorithm finds all  possible  matches,  the  greedy  or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
717         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
718         ungreedy quantifiers are treated in exactly the same way.         ungreedy quantifiers are treated in exactly the same way. However, pos-
719           sessive  quantifiers can make a difference when what follows could also
720           match what is quantified, for example in a pattern like this:
721    
722             ^a++\w!
723    
724           This pattern matches "aaab!" but not "aaa!", which would be matched  by
725           a  non-possessive quantifier. Similarly, if an atomic group is present,
726           it is matched as if it were a standalone pattern at the current  point,
727           and  the  longest match is then "locked in" for the rest of the overall
728           pattern.
729    
730         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
731         is  not  straightforward  to  keep track of captured substrings for the         is  not  straightforward  to  keep track of captured substrings for the
# Line 516  THE DFA MATCHING ALGORITHM Line 737  THE DFA MATCHING ALGORITHM
737         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
738    
739         4.  For  the same reason, conditional expressions that use a backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
740         ence as the condition are not supported.         ence as the condition or test for a specific group  recursion  are  not
741           supported.
742    
743         5. Callouts are supported, but the value of the  capture_top  field  is         5.  Because  many  paths  through the tree may be active, the \K escape
744           sequence, which resets the start of the match when encountered (but may
745           be  on  some  paths  and not on others), is not supported. It causes an
746           error if encountered.
747    
748           6. Callouts are supported, but the value of the  capture_top  field  is
749         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
750    
751         6.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The \C escape sequence, which (in the standard algorithm) matches a
752         single byte, even in UTF-8 mode, is not supported because the DFA algo-         single byte, even in UTF-8 mode, is not supported because the  alterna-
753         rithm moves through the subject string one character at a time, for all         tive  algorithm  moves  through  the  subject string one character at a
754         active paths through the tree.         time, for all active paths through the tree.
755    
756           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
757           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
758           negative assertion.
759    
760    
761  ADVANTAGES OF THE DFA ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
762    
763         Using the DFA matching algorithm provides the following advantages:         Using the alternative matching algorithm provides the following  advan-
764           tages:
765    
766         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
767         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
768         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
769         things with callouts.         things with callouts.
770    
771         2.  There is much better support for partial matching. The restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
772         on the content of the pattern that apply when using the standard  algo-         once,  and  never  needs to backtrack, it is possible to pass very long
773         rithm  for partial matching do not apply to the DFA algorithm. For non-         subject strings to the matching function in  several  pieces,  checking
774         anchored patterns, the starting position of a partial match  is  avail-         for  partial  matching  each time. Although it is possible to do multi-
775         able.         segment matching using the standard algorithm (pcre_exec()), by retain-
776           ing  partially matched substrings, it is more complicated. The pcrepar-
777         3.  Because  the  DFA algorithm scans the subject string just once, and         tial documentation gives details  of  partial  matching  and  discusses
778         never needs to backtrack, it is possible  to  pass  very  long  subject         multi-segment matching.
        strings  to  the matching function in several pieces, checking for par-  
        tial matching each time.  
779    
780    
781  DISADVANTAGES OF THE DFA ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
782    
783         The DFA algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
784    
785         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
786         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
787         because it is less susceptible to optimization.         because it is less susceptible to optimization.
788    
789         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
790    
791         3. The "atomic group" feature of PCRE regular expressions is supported,         3. Although atomic groups are supported, their use does not provide the
792         but  does not provide the advantage that it does for the standard algo-         performance advantage that it does for the standard algorithm.
        rithm.  
793    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
794    
795    AUTHOR
796    
797           Philip Hazel
798           University Computing Service
799           Cambridge CB2 3QH, England.
800    
801    
802    REVISION
803    
804           Last updated: 17 November 2010
805           Copyright (c) 1997-2010 University of Cambridge.
806    ------------------------------------------------------------------------------
807    
808    
809  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
810    
811    
# Line 616  PCRE NATIVE API Line 855  PCRE NATIVE API
855         int pcre_get_stringnumber(const pcre *code,         int pcre_get_stringnumber(const pcre *code,
856              const char *name);              const char *name);
857    
858           int pcre_get_stringtable_entries(const pcre *code,
859                const char *name, char **first, char **last);
860    
861         int pcre_get_substring(const char *subject, int *ovector,         int pcre_get_substring(const char *subject, int *ovector,
862              int stringcount, int stringnumber,              int stringcount, int stringnumber,
863              const char **stringptr);              const char **stringptr);
# Line 654  PCRE NATIVE API Line 896  PCRE NATIVE API
896  PCRE API OVERVIEW  PCRE API OVERVIEW
897    
898         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
899         is also a set of wrapper functions that correspond to the POSIX regular         are also some wrapper functions that correspond to  the  POSIX  regular
900         expression  API.  These  are  described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
901         Both of these APIs define a set of C function calls. A C++  wrapper  is         Both of these APIs define a set of C function calls. A C++  wrapper  is
902         distributed with PCRE. It is documented in the pcrecpp page.         distributed with PCRE. It is documented in the pcrecpp page.
# Line 667  PCRE API OVERVIEW Line 909  PCRE API OVERVIEW
909         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
910         for different releases of PCRE.         for different releases of PCRE.
911    
912           In a Windows environment, if you want to statically link an application
913           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
914           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
915           loc()   and   pcre_free()   exported   functions   will   be   declared
916           __declspec(dllimport), with unwanted results.
917    
918         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
919         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
920         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
921         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
922         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
923         run it.         pcredemo documentation, and the pcresample documentation describes  how
924           to compile and run it.
925    
926         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
927         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
928         ing. This allows it to find all possible matches (at a given  point  in         ing.  The  alternative algorithm finds all possible matches (at a given
929         the  subject),  not  just  one. However, this algorithm does not return         point in the subject), and scans the subject just  once  (unless  there
930           are  lookbehind  assertions).  However,  this algorithm does not return
931         captured substrings. A description of the two matching  algorithms  and         captured substrings. A description of the two matching  algorithms  and
932         their  advantages  and disadvantages is given in the pcrematching docu-         their  advantages  and disadvantages is given in the pcrematching docu-
933         mentation.         mentation.
# Line 692  PCRE API OVERVIEW Line 942  PCRE API OVERVIEW
942           pcre_get_named_substring()           pcre_get_named_substring()
943           pcre_get_substring_list()           pcre_get_substring_list()
944           pcre_get_stringnumber()           pcre_get_stringnumber()
945             pcre_get_stringtable_entries()
946    
947         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
948         to free the memory used for extracted strings.         to free the memory used for extracted strings.
# Line 723  PCRE API OVERVIEW Line 974  PCRE API OVERVIEW
974         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
975         are used only when PCRE is compiled to use  the  heap  for  remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
976         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
977         function. This is a non-standard way of building PCRE, for use in envi-         function. See the pcrebuild documentation for  details  of  how  to  do
978         ronments that have limited stacks. Because of the greater use of memory         this.  It  is  a non-standard way of building PCRE, for use in environ-
979         management, it runs more slowly.  Separate functions  are  provided  so         ments that have limited stacks. Because of the greater  use  of  memory
980         that  special-purpose  external  code  can  be used for this case. When         management,  it  runs  more  slowly. Separate functions are provided so
981         used, these functions are always called in a  stack-like  manner  (last         that special-purpose external code can be  used  for  this  case.  When
982         obtained,  first freed), and always for memory blocks of the same size.         used,  these  functions  are always called in a stack-like manner (last
983           obtained, first freed), and always for memory blocks of the same  size.
984           There  is  a discussion about PCRE's stack usage in the pcrestack docu-
985           mentation.
986    
987         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
988         by  the  caller  to  a "callout" function, which PCRE will then call at         by  the  caller  to  a "callout" function, which PCRE will then call at
# Line 736  PCRE API OVERVIEW Line 990  PCRE API OVERVIEW
990         pcrecallout documentation.         pcrecallout documentation.
991    
992    
993    NEWLINES
994    
995           PCRE  supports five different conventions for indicating line breaks in
996           strings: a single CR (carriage return) character, a  single  LF  (line-
997           feed) character, the two-character sequence CRLF, any of the three pre-
998           ceding, or any Unicode newline sequence. The Unicode newline  sequences
999           are  the  three just mentioned, plus the single characters VT (vertical
1000           tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
1001           separator, U+2028), and PS (paragraph separator, U+2029).
1002    
1003           Each  of  the first three conventions is used by at least one operating
1004           system as its standard newline sequence. When PCRE is built, a  default
1005           can  be  specified.  The default default is LF, which is the Unix stan-
1006           dard. When PCRE is run, the default can be overridden,  either  when  a
1007           pattern is compiled, or when it is matched.
1008    
1009           At compile time, the newline convention can be specified by the options
1010           argument of pcre_compile(), or it can be specified by special  text  at
1011           the start of the pattern itself; this overrides any other settings. See
1012           the pcrepattern page for details of the special character sequences.
1013    
1014           In the PCRE documentation the word "newline" is used to mean "the char-
1015           acter  or pair of characters that indicate a line break". The choice of
1016           newline convention affects the handling of  the  dot,  circumflex,  and
1017           dollar metacharacters, the handling of #-comments in /x mode, and, when
1018           CRLF is a recognized line ending sequence, the match position  advance-
1019           ment for a non-anchored pattern. There is more detail about this in the
1020           section on pcre_exec() options below.
1021    
1022           The choice of newline convention does not affect the interpretation  of
1023           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1024           which is controlled in a similar way, but by separate options.
1025    
1026    
1027  MULTITHREADING  MULTITHREADING
1028    
1029         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1030         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1031         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
1032         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 753  SAVING PRECOMPILED PATTERNS FOR LATER US Line 1041  SAVING PRECOMPILED PATTERNS FOR LATER US
1041         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
1042         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
1043         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
1044         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
1045           with  one version of PCRE for use with a different version is not guar-
1046           anteed to work and may cause crashes.
1047    
1048    
1049  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 782  CHECKING BUILD-TIME OPTIONS Line 1072  CHECKING BUILD-TIME OPTIONS
1072    
1073           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1074    
1075         The output is an integer that is set to the value of the code  that  is         The output is an integer whose value specifies  the  default  character
1076         used  for the newline character. It is either linefeed (10) or carriage         sequence  that is recognized as meaning "newline". The four values that
1077         return (13), and should normally be the  standard  character  for  your         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1078         operating system.         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1079           are returned in EBCDIC environments. The default should normally corre-
1080           spond to the standard sequence for your operating system.
1081    
1082             PCRE_CONFIG_BSR
1083    
1084           The output is an integer whose value indicates what character sequences
1085           the \R escape sequence matches by default. A value of 0 means  that  \R
1086           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1087           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1088           tern is compiled or matched.
1089    
1090           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1091    
# Line 804  CHECKING BUILD-TIME OPTIONS Line 1104  CHECKING BUILD-TIME OPTIONS
1104    
1105           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1106    
1107         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-
1108         internal  matching  function  calls in a pcre_exec() execution. Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1109         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1110    
1111             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1112    
1113           The output is a long integer that gives the default limit for the depth
1114           of   recursion  when  calling  the  internal  matching  function  in  a
1115           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1116           below.
1117    
1118           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1119    
1120         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
1121         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1122         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
1123         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
1124         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1125         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1126         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1127    
1128    
# Line 832  COMPILING A PATTERN Line 1139  COMPILING A PATTERN
1139    
1140         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1141         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1142         the two interfaces is that pcre_compile2() has an additional  argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1143         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1144           avoid  too  much repetition, we refer just to pcre_compile() below, but
1145           the information applies equally to pcre_compile2().
1146    
1147         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
1148         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
1149         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1150         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
1151         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1152         It is up to the caller  to  free  the  memory  when  it  is  no  longer         It is up to the caller to free the memory (via pcre_free) when it is no
1153         required.         longer required.
1154    
1155         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
1156         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
1157         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1158         ment, which is an address (see below).         ment, which is an address (see below).
1159    
1160         The options argument contains independent bits that affect the compila-         The options argument contains various bit settings that affect the com-
1161         tion.  It  should  be  zero  if  no options are required. The available         pilation. It should be zero if no options are required.  The  available
1162         options are described below. Some of them, in  particular,  those  that         options  are  described  below. Some of them (in particular, those that
1163         are  compatible  with  Perl,  can also be set and unset from within the         are compatible with Perl, but some others as well) can also be set  and
1164         pattern (see the detailed description  in  the  pcrepattern  documenta-         unset  from  within  the  pattern  (see the detailed description in the
1165         tion).  For  these options, the contents of the options argument speci-         pcrepattern documentation). For those options that can be different  in
1166         fies their initial settings at the start of compilation and  execution.         different  parts  of  the pattern, the contents of the options argument
1167         The  PCRE_ANCHORED option can be set at the time of matching as well as         specifies their settings at the start of compilation and execution. The
1168         at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1169           the time of matching as well as at compile time.
1170    
1171         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1172         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1173         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-
1174         sage.  The  offset from the start of the pattern to the character where         sage. This is a static string that is part of the library. You must not
1175         the error was discovered is  placed  in  the  variable  pointed  to  by         try to free it. The offset from the start of the pattern  to  the  byte
1176         erroffset,  which  must  not  be  NULL. If it is, an immediate error is         that was being processed when the error was discovered is placed in the
1177         given.         variable pointed to by erroffset, which must not be NULL. If it is,  an
1178           immediate error is given. Some errors are not detected until checks are
1179         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         carried out when the whole pattern has been scanned; in this  case  the
1180         codeptr  argument is not NULL, a non-zero error code number is returned         offset is set to the end of the pattern.
1181         via this argument in the event of an error. This is in addition to  the  
1182           Note  that  the offset is in bytes, not characters, even in UTF-8 mode.
1183           It may point into the middle of a UTF-8 character  (for  example,  when
1184           PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
1185    
1186           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1187           codeptr argument is not NULL, a non-zero error code number is  returned
1188           via  this argument in the event of an error. This is in addition to the
1189         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1190    
1191         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
1192         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1193         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1194         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
1195         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1196         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
1197         support below.         support below.
1198    
1199         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1200         pile():         pile():
1201    
1202           pcre *re;           pcre *re;
# Line 892  COMPILING A PATTERN Line 1209  COMPILING A PATTERN
1209             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1210             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1211    
1212         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
1213         file:         file:
1214    
1215           PCRE_ANCHORED           PCRE_ANCHORED
1216    
1217         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
1218         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
1219         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1220         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1221         only way to do it in Perl.         only way to do it in Perl.
1222    
1223           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1224    
1225         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1226         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1227         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1228    
1229             PCRE_BSR_ANYCRLF
1230             PCRE_BSR_UNICODE
1231    
1232           These options (which are mutually exclusive) control what the \R escape
1233           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1234           or to match any Unicode newline sequence. The default is specified when
1235           PCRE is built. It can be overridden from within the pattern, or by set-
1236           ting an option when a compiled pattern is matched.
1237    
1238           PCRE_CASELESS           PCRE_CASELESS
1239    
1240         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
1241         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
1242         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
1243         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1244         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1245         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-
1246         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1247         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1248         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1249         UTF-8 support.         UTF-8 support.
1250    
1251           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1252    
1253         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
1254         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
1255         matches immediately before the final character if it is a newline  (but         matches  immediately before a newline at the end of the string (but not
1256         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1257         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1258         in Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1259    
1260           PCRE_DOTALL           PCRE_DOTALL
1261    
1262         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
1263         acters, including newlines. Without it,  newlines  are  excluded.  This         acter of any value, including one that indicates a newline. However, it
1264         option  is equivalent to Perl's /s option, and it can be changed within         only ever matches one character, even if newlines are  coded  as  CRLF.
1265         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]         Without  this option, a dot does not match when the current position is
1266         always  matches a newline character, independent of the setting of this         at a newline. This option is equivalent to Perl's /s option, and it can
1267         option.         be  changed within a pattern by a (?s) option setting. A negative class
1268           such as [^a] always matches newline characters, independent of the set-
1269           ting of this option.
1270    
1271             PCRE_DUPNAMES
1272    
1273           If  this  bit is set, names used to identify capturing subpatterns need
1274           not be unique. This can be helpful for certain types of pattern when it
1275           is  known  that  only  one instance of the named subpattern can ever be
1276           matched. There are more details of named subpatterns  below;  see  also
1277           the pcrepattern documentation.
1278    
1279           PCRE_EXTENDED           PCRE_EXTENDED
1280    
1281         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1282         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1283         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1284         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1285         line character, inclusive, are also  ignored.  This  is  equivalent  to         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1286         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)         option, and it can be changed within a pattern by a  (?x)  option  set-
1287         option setting.         ting.
1288    
1289           Which  characters  are  interpreted  as  newlines  is controlled by the
1290           options passed to pcre_compile() or by a special sequence at the  start
1291           of  the  pattern, as described in the section entitled "Newline conven-
1292           tions" in the pcrepattern documentation. Note that the end of this type
1293           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1294           sequences that happen to represent a newline do not count.
1295    
1296         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1297         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1298         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1299         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1300         introduces a conditional subpattern.         duces a conditional subpattern.
1301    
1302           PCRE_EXTRA           PCRE_EXTRA
1303    
# Line 964  COMPILING A PATTERN Line 1307  COMPILING A PATTERN
1307         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1308         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1309         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
1310         literal. There are at present no  other  features  controlled  by  this         literal. (Perl can, however, be persuaded to give an error for this, by
1311         option. It can also be set by a (?X) option setting within a pattern.         running  it with the -w option.) There are at present no other features
1312           controlled by this option. It can also be set by a (?X) option  setting
1313           within a pattern.
1314    
1315           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1316    
1317         If  this  option  is  set,  an  unanchored pattern is required to match         If  this  option  is  set,  an  unanchored pattern is required to match
1318         before or at the first newline character in the subject string,  though         before or at the first  newline  in  the  subject  string,  though  the
1319         the matched text may continue over the newline.         matched text may continue over the newline.
1320    
1321             PCRE_JAVASCRIPT_COMPAT
1322    
1323           If this option is set, PCRE's behaviour is changed in some ways so that
1324           it is compatible with JavaScript rather than Perl. The changes  are  as
1325           follows:
1326    
1327           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1328           error, because this is illegal in JavaScript (by default it is  treated
1329           as a data character). Thus, the pattern AB]CD becomes illegal when this
1330           option is set.
1331    
1332           (2) At run time, a back reference to an unset subpattern group  matches
1333           an  empty  string (by default this causes the current matching alterna-
1334           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1335           set  (assuming  it can find an "a" in the subject), whereas it fails by
1336           default, for Perl compatibility.
1337    
1338           PCRE_MULTILINE           PCRE_MULTILINE
1339    
1340         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1341         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1342         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1343         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1344         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1345         is set). This is the same as Perl.         is set). This is the same as Perl.
1346    
1347         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"
1348         constructs  match  immediately following or immediately before any new-         constructs match immediately following or immediately  before  internal
1349         line in the subject string, respectively, as well as at the very  start         newlines  in  the  subject string, respectively, as well as at the very
1350         and  end. This is equivalent to Perl's /m option, and it can be changed         start and end. This is equivalent to Perl's /m option, and  it  can  be
1351         within a pattern by a (?m) option setting. If there are no "\n" charac-         changed within a pattern by a (?m) option setting. If there are no new-
1352         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1353         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1354    
1355             PCRE_NEWLINE_CR
1356             PCRE_NEWLINE_LF
1357             PCRE_NEWLINE_CRLF
1358             PCRE_NEWLINE_ANYCRLF
1359             PCRE_NEWLINE_ANY
1360    
1361           These  options  override the default newline definition that was chosen
1362           when PCRE was built. Setting the first or the second specifies  that  a
1363           newline  is  indicated  by a single character (CR or LF, respectively).
1364           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1365           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1366           that any of the three preceding sequences should be recognized. Setting
1367           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1368           recognized. The Unicode newline sequences are the three just mentioned,
1369           plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1370           U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1371           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1372           UTF-8 mode.
1373    
1374           The newline setting in the  options  word  uses  three  bits  that  are
1375           treated as a number, giving eight possibilities. Currently only six are
1376           used (default plus the five values above). This means that if  you  set
1377           more  than one newline option, the combination may or may not be sensi-
1378           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1379           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1380           cause an error.
1381    
1382           The only time that a line break in a pattern  is  specially  recognized
1383           when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1384           characters, and so are ignored in this mode. Also, an unescaped #  out-
1385           side  a  character class indicates a comment that lasts until after the
1386           next line break sequence. In other circumstances, line break  sequences
1387           in patterns are treated as literal data.
1388    
1389           The newline option that is set at compile time becomes the default that
1390           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1391    
1392           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1393    
1394         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
# Line 998  COMPILING A PATTERN Line 1397  COMPILING A PATTERN
1397         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1398         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1399    
1400             PCRE_UCP
1401    
1402           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1403           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1404           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1405           are  used instead to classify characters. More details are given in the
1406           section on generic character types in the pcrepattern page. If you  set
1407           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1408           option is available only if PCRE has been compiled with  Unicode  prop-
1409           erty support.
1410    
1411           PCRE_UNGREEDY           PCRE_UNGREEDY
1412    
1413         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1414         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1415         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1416         within the pattern.         within the pattern.
1417    
1418           PCRE_UTF8           PCRE_UTF8
1419    
1420         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1421         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1422         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1423         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1424         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  section  on
1425         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1426    
1427           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1428    
1429         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1430         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1431         pcre_compile() returns an error. If you already know that your  pattern         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1432         is  valid, and you want to skip this check for performance reasons, you         bytes is found, pcre_compile() returns an error. If  you  already  know
1433         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1434         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1435         your program to crash.  Note that this option can  also  be  passed  to         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1436         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined. It may cause your program to crash. Note  that  this  option
1437         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1438           UTF-8 validity checking of subject strings.
1439    
1440    
1441  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1442    
1443         The following table lists the error  codes  than  may  be  returned  by         The following table lists the error  codes  than  may  be  returned  by
1444         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(),  along with the error messages that may be returned by
1445         both compiling functions.         both compiling functions. As PCRE has developed, some error codes  have
1446           fallen out of use. To avoid confusion, they have not been re-used.
1447    
1448            0  no error            0  no error
1449            1  \ at end of pattern            1  \ at end of pattern
# Line 1043  COMPILATION ERROR CODES Line 1455  COMPILATION ERROR CODES
1455            7  invalid escape sequence in character class            7  invalid escape sequence in character class
1456            8  range out of order in character class            8  range out of order in character class
1457            9  nothing to repeat            9  nothing to repeat
1458           10  operand of unlimited repeat could match the empty string           10  [this code is not in use]
1459           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1460           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1461           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1462           14  missing )           14  missing )
1463           15  reference to non-existent subpattern           15  reference to non-existent subpattern
1464           16  erroffset passed as NULL           16  erroffset passed as NULL
1465           17  unknown option bit(s) set           17  unknown option bit(s) set
1466           18  missing ) after comment           18  missing ) after comment
1467           19  parentheses nested too deeply           19  [this code is not in use]
1468           20  regular expression too large           20  regular expression is too large
1469           21  failed to get memory           21  failed to get memory
1470           22  unmatched parentheses           22  unmatched parentheses
1471           23  internal error: code overflow           23  internal error: code overflow
1472           24  unrecognized character after (?<           24  unrecognized character after (?<
1473           25  lookbehind assertion is not fixed length           25  lookbehind assertion is not fixed length
1474           26  malformed number after (?(           26  malformed number or name after (?(
1475           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1476           28  assertion expected after (?(           28  assertion expected after (?(
1477           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1478           30  unknown POSIX class name           30  unknown POSIX class name
1479           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1480           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
1481           33  spare error           33  [this code is not in use]
1482           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1483           35  invalid condition (?(0)           35  invalid condition (?(0)
1484           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
# Line 1075  COMPILATION ERROR CODES Line 1487  COMPILATION ERROR CODES
1487           39  closing ) for (?C expected           39  closing ) for (?C expected
1488           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
1489           41  unrecognized character after (?P           41  unrecognized character after (?P
1490           42  syntax error after (?P           42  syntax error in subpattern name (missing terminator)
1491           43  two named groups have the same name           43  two named subpatterns have the same name
1492           44  invalid UTF-8 string           44  invalid UTF-8 string
1493           45  support for \P, \p, and \X has not been compiled           45  support for \P, \p, and \X has not been compiled
1494           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1495           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1496             48  subpattern name is too long (maximum 32 characters)
1497             49  too many named subpatterns (maximum 10000)
1498             50  [this code is not in use]
1499             51  octal value is greater than \377 (not in UTF-8 mode)
1500             52  internal error: overran compiling workspace
1501             53  internal error: previously-checked referenced subpattern
1502                   not found
1503             54  DEFINE group contains more than one branch
1504             55  repeating a DEFINE group is not allowed
1505             56  inconsistent NEWLINE options
1506             57  \g is not followed by a braced, angle-bracketed, or quoted
1507                   name/number or by a plain number
1508             58  a numbered reference must not be zero
1509             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1510             60  (*VERB) not recognized
1511             61  number is too big
1512             62  subpattern name expected
1513             63  digit expected after (?+
1514             64  ] is an invalid data character in JavaScript compatibility mode
1515             65  different names for subpatterns of the same number are
1516                   not allowed
1517             66  (*MARK) must have an argument
1518             67  this version of PCRE is not compiled with PCRE_UCP support
1519    
1520           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1521           values may be used if the limits were changed when PCRE was built.
1522    
1523    
1524  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1097  STUDYING A PATTERN Line 1535  STUDYING A PATTERN
1535         the results of the study.         the results of the study.
1536    
1537         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1538         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1539         that can be set by the caller before the block  is  passed;  these  are         tains other fields that can be set by the caller before  the  block  is
1540         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1541    
1542         If  studying  the  pattern  does not produce any additional information         If  studying  the  pattern  does  not  produce  any useful information,
1543         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1544         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1545         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1546    
1547         The second argument of pcre_study() contains option bits.  At  present,         The second argument of pcre_study() contains option bits.  At  present,
1548         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1549    
1550         The  third argument for pcre_study() is a pointer for an error message.         The  third argument for pcre_study() is a pointer for an error message.
1551         If studying succeeds (even if no data is  returned),  the  variable  it         If studying succeeds (even if no data is  returned),  the  variable  it
1552         points  to  is set to NULL. Otherwise it points to a textual error mes-         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1553         sage. You should therefore test the error pointer for NULL after  call-         error message. This is a static string that is part of the library. You
1554         ing pcre_study(), to be sure that it has run successfully.         must  not  try  to  free it. You should test the error pointer for NULL
1555           after calling pcre_study(), to be sure that it has run successfully.
1556    
1557         This is a typical call to pcre_study():         This is a typical call to pcre_study():
1558    
# Line 1123  STUDYING A PATTERN Line 1562  STUDYING A PATTERN
1562             0,              /* no options exist */             0,              /* no options exist */
1563             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1564    
1565         At present, studying a pattern is useful only for non-anchored patterns         Studying a pattern does two things: first, a lower bound for the length
1566         that do not have a single fixed starting character. A bitmap of  possi-         of subject string that is needed to match the pattern is computed. This
1567         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1568           it  does  guarantee that no shorter strings match. The value is used by
1569           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1570           match  strings  that are shorter than the lower bound. You can find out
1571           the value in a calling program via the pcre_fullinfo() function.
1572    
1573           Studying a pattern is also useful for non-anchored patterns that do not
1574           have  a  single fixed starting character. A bitmap of possible starting
1575           bytes is created. This speeds up finding a position in the  subject  at
1576           which to start matching.
1577    
1578           The  two  optimizations  just  described can be disabled by setting the
1579           PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1580           pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1581           callouts or (*MARK), and you want to make use of  these  facilities  in
1582           cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1583           MIZE below.
1584    
1585    
1586  LOCALE SUPPORT  LOCALE SUPPORT
1587    
1588         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1589         letters digits, or whatever, by reference to a set of  tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1590         by  character  value.  When running in UTF-8 mode, this applies only to         by character value. When running in UTF-8 mode, this  applies  only  to
1591         characters with codes less than 128. Higher-valued  codes  never  match         characters  with  codes  less than 128. By default, higher-valued codes
1592         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built         never match escapes such as \w or \d, but they can be tested with \p if
1593         with Unicode character property support.         PCRE  is  built with Unicode character property support. Alternatively,
1594           the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1595         An internal set of tables is created in the default C locale when  PCRE         friends to use Unicode property support instead of built-in tables. The
1596         is  built.  This  is  used when the final argument of pcre_compile() is         use of locales with Unicode is discouraged. If you are handling charac-
1597         NULL, and is sufficient for many applications. An  alternative  set  of         ters  with codes greater than 128, you should either use UTF-8 and Uni-
1598         tables  can,  however, be supplied. These may be created in a different         code, or use locales, but not try to mix the two.
1599         locale from the default. As more and more applications change to  using  
1600         Unicode, the need for this locale support is expected to die away.         PCRE contains an internal set of tables that are used  when  the  final
1601           argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1602         External  tables  are  built by calling the pcre_maketables() function,         applications.  Normally, the internal tables recognize only ASCII char-
1603         which has no arguments, in the relevant locale. The result can then  be         acters. However, when PCRE is built, it is possible to cause the inter-
1604         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         nal tables to be rebuilt in the default "C" locale of the local system,
1605         example, to build and use tables that are appropriate  for  the  French         which may cause them to be different.
1606         locale  (where  accented  characters  with  values greater than 128 are  
1607           The  internal tables can always be overridden by tables supplied by the
1608           application that calls PCRE. These may be created in a different locale
1609           from  the  default.  As more and more applications change to using Uni-
1610           code, the need for this locale support is expected to die away.
1611    
1612           External tables are built by calling  the  pcre_maketables()  function,
1613           which  has no arguments, in the relevant locale. The result can then be
1614           passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1615           example,  to  build  and use tables that are appropriate for the French
1616           locale (where accented characters with  values  greater  than  128  are
1617         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1618    
1619           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1620           tables = pcre_maketables();           tables = pcre_maketables();
1621           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1622    
1623           The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1624           if you are using Windows, the name for the French locale is "french".
1625    
1626         When pcre_maketables() runs, the tables are built  in  memory  that  is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1627         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1628         that the memory containing the tables remains available for as long  as         that the memory containing the tables remains available for as long  as
# Line 1200  INFORMATION ABOUT A PATTERN Line 1668  INFORMATION ABOUT A PATTERN
1668         pattern:         pattern:
1669    
1670           int rc;           int rc;
1671           unsigned long int length;           size_t length;
1672           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1673             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1674             pe,               /* result of pcre_study(), or NULL */             pe,               /* result of pcre_study(), or NULL */
# Line 1232  INFORMATION ABOUT A PATTERN Line 1700  INFORMATION ABOUT A PATTERN
1700           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1701    
1702         Return  information  about  the first byte of any matched string, for a         Return  information  about  the first byte of any matched string, for a
1703         non-anchored   pattern.   (This    option    used    to    be    called         non-anchored pattern. The fourth argument should point to an int  vari-
1704         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1705         compatibility.)         is still recognized for backwards compatibility.)
1706    
1707         If there is a fixed first byte, for example, from  a  pattern  such  as         If there is a fixed first byte, for example, from  a  pattern  such  as
1708         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.         (cat|cow|coyote), its value is returned. Otherwise, if either
        Otherwise, if either  
1709    
1710         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1711         branch starts with "^", or         branch starts with "^", or
1712    
1713         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1714         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1715    
1716         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1717         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1718         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1719    
1720           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1721    
1722         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
1723         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1724         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1725         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1726         able.         able.
1727    
1728             PCRE_INFO_HASCRORLF
1729    
1730           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1731           characters, otherwise 0. The fourth argument should  point  to  an  int
1732           variable.  An explicit match is either a literal CR or LF character, or
1733           \r or \n.
1734    
1735             PCRE_INFO_JCHANGED
1736    
1737           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1738           otherwise  0. The fourth argument should point to an int variable. (?J)
1739           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1740    
1741           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1742    
1743         Return the value of the rightmost literal byte that must exist  in  any         Return the value of the rightmost literal byte that must exist  in  any
# Line 1268  INFORMATION ABOUT A PATTERN Line 1748  INFORMATION ABOUT A PATTERN
1748         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1749         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1750    
1751             PCRE_INFO_MINLENGTH
1752    
1753           If the pattern was studied and a minimum length  for  matching  subject
1754           strings  was  computed,  its  value is returned. Otherwise the returned
1755           value is -1. The value is a number of characters, not bytes  (this  may
1756           be  relevant in UTF-8 mode). The fourth argument should point to an int
1757           variable. A non-negative value is a lower bound to the  length  of  any
1758           matching  string.  There  may not be any strings of that length that do
1759           actually match, but every string that does match is at least that long.
1760    
1761           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1762           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1763           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1764    
1765         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1766         ses.  The names are just an additional way of identifying the parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1767         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses, which still acquire numbers. Several convenience functions such as
1768         pcre_get_named_substring()  is  provided  for  extracting an individual         pcre_get_named_substring()  are  provided  for extracting captured sub-
1769         captured substring by name. It is also possible  to  extract  the  data         strings by name. It is also possible to extract the data  directly,  by
1770         directly,  by  first converting the name to a number in order to access         first  converting  the  name to a number in order to access the correct
1771         the correct pointers in the output vector (described  with  pcre_exec()         pointers in the output vector (described with pcre_exec() below). To do
1772         below).  To  do the conversion, you need to use the name-to-number map,         the  conversion,  you  need  to  use  the  name-to-number map, which is
1773         which is described by these three values.         described by these three values.
1774    
1775         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1776         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
# Line 1289  INFORMATION ABOUT A PATTERN Line 1779  INFORMATION ABOUT A PATTERN
1779         a pointer to the first entry of the table  (a  pointer  to  char).  The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1780         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1781         sis, most significant byte first. The rest of the entry is  the  corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1782         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1783         For example, consider the following pattern  (assume  PCRE_EXTENDED  is  
1784         set, so white space - including newlines - is ignored):         The  names are in alphabetical order. Duplicate names may appear if (?|
1785           is used to create multiple groups with the same number, as described in
1786           the  section  on  duplicate subpattern numbers in the pcrepattern page.
1787           Duplicate names for subpatterns with different  numbers  are  permitted
1788           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1789           appear in the table in the order in which they were found in  the  pat-
1790           tern.  In  the  absence  of (?| this is the order of increasing number;
1791           when (?| is used this is not necessarily the case because later subpat-
1792           terns may have lower numbers.
1793    
1794           As  a  simple  example of the name/number table, consider the following
1795           pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1796           lines - is ignored):
1797    
1798           (?P<date> (?P<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1799           (?P<month>\d\d) - (?P<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1800    
1801         There  are  four  named subpatterns, so the table has four entries, and         There  are  four  named subpatterns, so the table has four entries, and
1802         each entry in the table is eight bytes long. The table is  as  follows,         each entry in the table is eight bytes long. The table is  as  follows,
# Line 1307  INFORMATION ABOUT A PATTERN Line 1809  INFORMATION ABOUT A PATTERN
1809           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1810    
1811         When writing code to extract data  from  named  subpatterns  using  the         When writing code to extract data  from  named  subpatterns  using  the
1812         name-to-number map, remember that the length of each entry is likely to         name-to-number  map,  remember that the length of the entries is likely
1813         be different for each compiled pattern.         to be different for each compiled pattern.
1814    
1815             PCRE_INFO_OKPARTIAL
1816    
1817           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1818           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1819           variable. From  release  8.00,  this  always  returns  1,  because  the
1820           restrictions  that  previously  applied  to  partial matching have been
1821           lifted. The pcrepartial documentation gives details of  partial  match-
1822           ing.
1823    
1824           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1825    
1826         Return a copy of the options with which the pattern was  compiled.  The         Return  a  copy of the options with which the pattern was compiled. The
1827         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1828         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1829         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1830           other  words,  they are the options that will be in force when matching
1831           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1832           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1833           and PCRE_EXTENDED.
1834    
1835         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A pattern is automatically anchored by PCRE if  all  of  its  top-level
1836         alternatives begin with one of the following:         alternatives begin with one of the following:
1837    
1838           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1331  INFORMATION ABOUT A PATTERN Line 1846  INFORMATION ABOUT A PATTERN
1846    
1847           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1848    
1849         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of the compiled pattern, that is, the  value  that  was
1850         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1851         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1852         size_t variable.         size_t variable.
# Line 1339  INFORMATION ABOUT A PATTERN Line 1854  INFORMATION ABOUT A PATTERN
1854           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1855    
1856         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1857         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
1858         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1859         created  by  pcre_study(). The fourth argument should point to a size_t         created by pcre_study(). If pcre_extra is NULL, or there  is  no  study
1860           data,  zero  is  returned. The fourth argument should point to a size_t
1861         variable.         variable.
1862    
1863    
# Line 1395  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1911  MATCHING A PATTERN: THE TRADITIONAL FUNC
1911              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1912              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1913    
1914         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
1915         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1916         has been studied, the result of the study should be passed in the extra         was  studied,  the  result  of  the study should be passed in the extra
1917         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1918         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
1919         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1920         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1921    
1922         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1923         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1924         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
1925         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1926         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1927    
1928         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1425  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1941  MATCHING A PATTERN: THE TRADITIONAL FUNC
1941    
1942     Extra data for pcre_exec()     Extra data for pcre_exec()
1943    
1944         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
1945         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
1946         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-
1947         tional  information in it. The fields in a pcre_extra block are as fol-         tional information in it. The pcre_extra block contains  the  following
1948         lows:         fields (not necessarily in this order):
1949    
1950           unsigned long int flags;           unsigned long int flags;
1951           void *study_data;           void *study_data;
1952           unsigned long int match_limit;           unsigned long int match_limit;
1953             unsigned long int match_limit_recursion;
1954           void *callout_data;           void *callout_data;
1955           const unsigned char *tables;           const unsigned char *tables;
1956             unsigned char **mark;
1957    
1958         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
1959         are set. The flag bits are:         are set. The flag bits are:
1960    
1961           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1962           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1963             PCRE_EXTRA_MATCH_LIMIT_RECURSION
1964           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1965           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1966             PCRE_EXTRA_MARK
1967    
1968         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
1969         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1970         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
1971         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1972         flag bits.         flag bits.
1973    
1974         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
1975         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
1976         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1977         search trees. The classic  example  is  the  use  of  nested  unlimited         search  trees. The classic example is a pattern that uses nested unlim-
1978         repeats.         ited repeats.
1979    
1980         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1981         edly (sometimes recursively). The limit is imposed  on  the  number  of         edly  (sometimes  recursively). The limit set by match_limit is imposed
1982         times  this  function is called during a match, which has the effect of         on the number of times this function is called during  a  match,  which
1983         limiting the amount of recursion and backtracking that can take  place.         has  the  effect  of  limiting the amount of backtracking that can take
1984         For patterns that are not anchored, the count starts from zero for each         place. For patterns that are not anchored, the count restarts from zero
1985         position in the subject string.         for each position in the subject string.
1986    
1987         The default limit for the library can be set when PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
1988         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1989         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1990         pcre_extra  block  in  which match_limit is set to a smaller value, and         pcre_extra    block    in    which    match_limit    is    set,     and
1991         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
1992         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1993    
1994         The  pcre_callout  field is used in conjunction with the "callout" fea-         The match_limit_recursion field is similar to match_limit, but  instead
1995         ture, which is described in the pcrecallout documentation.         of limiting the total number of times that match() is called, it limits
1996           the depth of recursion. The recursion depth is a  smaller  number  than
1997           the  total number of calls, because not all calls to match() are recur-
1998           sive.  This limit is of use only if it is set smaller than match_limit.
1999    
2000           Limiting the recursion depth limits the amount of  stack  that  can  be
2001           used, or, when PCRE has been compiled to use memory on the heap instead
2002           of the stack, the amount of heap memory that can be used.
2003    
2004           The default value for match_limit_recursion can be  set  when  PCRE  is
2005           built;  the  default  default  is  the  same  value  as the default for
2006           match_limit. You can override the default by suppling pcre_exec()  with
2007           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2008           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2009           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2010    
2011           The  callout_data  field is used in conjunction with the "callout" fea-
2012           ture, and is described in the pcrecallout documentation.
2013    
2014         The tables field  is  used  to  pass  a  character  tables  pointer  to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2015         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec();  this overrides the value that is stored with the compiled
# Line 1485  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2022  MATCHING A PATTERN: THE TRADITIONAL FUNC
2022         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2023         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2024    
2025           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2026           set to point to a char * variable. If the pattern  contains  any  back-
2027           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2028           with a name to pass back, a pointer to the  name  string  (zero  termi-
2029           nated)  is  placed  in  the  variable pointed to by the mark field. The
2030           names are within the compiled pattern; if you wish  to  retain  such  a
2031           name  you must copy it before freeing the memory of a compiled pattern.
2032           If there is no name to pass back, the variable pointed to by  the  mark
2033           field  set  to NULL. For details of the backtracking control verbs, see
2034           the section entitled "Backtracking control" in the pcrepattern documen-
2035           tation.
2036    
2037     Option bits for pcre_exec()     Option bits for pcre_exec()
2038    
2039         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.
2040         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
2041         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2042           PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2043           PCRE_PARTIAL_HARD.
2044    
2045           PCRE_ANCHORED           PCRE_ANCHORED
2046    
# Line 1498  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2049  MATCHING A PATTERN: THE TRADITIONAL FUNC
2049         turned  out to be anchored by virtue of its contents, it cannot be made         turned  out to be anchored by virtue of its contents, it cannot be made
2050         unachored at matching time.         unachored at matching time.
2051    
2052             PCRE_BSR_ANYCRLF
2053             PCRE_BSR_UNICODE
2054    
2055           These options (which are mutually exclusive) control what the \R escape
2056           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2057           or to match any Unicode newline sequence. These  options  override  the
2058           choice that was made or defaulted when the pattern was compiled.
2059    
2060             PCRE_NEWLINE_CR
2061             PCRE_NEWLINE_LF
2062             PCRE_NEWLINE_CRLF
2063             PCRE_NEWLINE_ANYCRLF
2064             PCRE_NEWLINE_ANY
2065    
2066           These  options  override  the  newline  definition  that  was chosen or
2067           defaulted when the pattern was compiled. For details, see the  descrip-
2068           tion  of  pcre_compile()  above.  During  matching,  the newline choice
2069           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2070           ters.  It may also alter the way the match position is advanced after a
2071           match failure for an unanchored pattern.
2072    
2073           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
2074           set,  and a match attempt for an unanchored pattern fails when the cur-
2075           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2076           explicit  matches  for  CR  or  LF  characters,  the  match position is
2077           advanced by two characters instead of one, in other words, to after the
2078           CRLF.
2079    
2080           The above rule is a compromise that makes the most common cases work as
2081           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2082           option is not set), it does not match the string "\r\nA" because, after
2083           failing at the start, it skips both the CR and the LF before  retrying.
2084           However,  the  pattern  [\r\n]A does match that string, because it con-
2085           tains an explicit CR or LF reference, and so advances only by one char-
2086           acter after the first failure.
2087    
2088           An explicit match for CR of LF is either a literal appearance of one of
2089           those characters, or one of the \r or  \n  escape  sequences.  Implicit
2090           matches  such  as [^X] do not count, nor does \s (which includes CR and
2091           LF in the characters that it matches).
2092    
2093           Notwithstanding the above, anomalous effects may still occur when  CRLF
2094           is a valid newline sequence and explicit \r or \n escapes appear in the
2095           pattern.
2096    
2097           PCRE_NOTBOL           PCRE_NOTBOL
2098    
2099         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
# Line 1524  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2120  MATCHING A PATTERN: THE TRADITIONAL FUNC
2120    
2121           a?b?           a?b?
2122    
2123         is applied to a string not beginning with "a" or "b",  it  matches  the         is applied to a string not beginning with "a" or  "b",  it  matches  an
2124         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
2125         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2126         rences of "a" or "b".         rences of "a" or "b".
2127    
2128         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2129         cial case of a pattern match of the empty  string  within  its  split()  
2130         function,  and  when  using  the /g modifier. It is possible to emulate         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2131         Perl's behaviour after matching a null string by first trying the match         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2132         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2133         if that fails by advancing the starting offset (see below)  and  trying  
2134         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2135         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2136           match  of  the empty string within its split() function, and when using
2137           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2138           matching a null string by first trying the match again at the same off-
2139           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2140           fails, by advancing the starting offset (see below) and trying an ordi-
2141           nary match again. There is some code that demonstrates how to  do  this
2142           in  the  pcredemo sample program. In the most general case, you have to
2143           check to see if the newline convention recognizes CRLF  as  a  newline,
2144           and  if so, and the current character is CR followed by LF, advance the
2145           starting offset by two characters instead of one.
2146    
2147             PCRE_NO_START_OPTIMIZE
2148    
2149           There are a number of optimizations that pcre_exec() uses at the  start
2150           of  a  match,  in  order to speed up the process. For example, if it is
2151           known that an unanchored match must start with a specific character, it
2152           searches  the  subject  for that character, and fails immediately if it
2153           cannot find it, without actually running the  main  matching  function.
2154           This means that a special item such as (*COMMIT) at the start of a pat-
2155           tern is not considered until after a suitable starting  point  for  the
2156           match  has been found. When callouts or (*MARK) items are in use, these
2157           "start-up" optimizations can cause them to be skipped if the pattern is
2158           never  actually  used.  The start-up optimizations are in effect a pre-
2159           scan of the subject that takes place before the pattern is run.
2160    
2161           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2162           possibly  causing  performance  to  suffer,  but ensuring that in cases
2163           where the result is "no match", the callouts do occur, and  that  items
2164           such as (*COMMIT) and (*MARK) are considered at every possible starting
2165           position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can
2166           change the outcome of a matching operation.  Consider the pattern
2167    
2168             (*COMMIT)ABC
2169    
2170           When  this  is  compiled, PCRE records the fact that a match must start
2171           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2172           start-up  optimization  scans along the subject, finds "A" and runs the
2173           first match attempt from there. The (*COMMIT) item means that the  pat-
2174           tern  must  match the current starting position, which in this case, it
2175           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2176           set,  the  initial  scan  along the subject string does not happen. The
2177           first match attempt is run starting  from  "D"  and  when  this  fails,
2178           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2179           result is "no match". If the pattern is studied,  more  start-up  opti-
2180           mizations  may  be  used. For example, a minimum length for the subject
2181           may be recorded. Consider the pattern
2182    
2183             (*MARK:A)(X|Y)
2184    
2185           The minimum length for a match is one  character.  If  the  subject  is
2186           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2187           finally an empty string.  If the pattern is studied, the final  attempt
2188           does  not take place, because PCRE knows that the subject is too short,
2189           and so the (*MARK) is never encountered.  In this  case,  studying  the
2190           pattern  does  not  affect the overall match result, which is still "no
2191           match", but it does affect the auxiliary information that is returned.
2192    
2193           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2194    
2195         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
2196         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2197         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2198         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2199         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2200         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2201         returned.         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2202           TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
2203           end of the subject, PCRE_ERROR_SHORTUTF8.  If  startoffset  contains  a
2204           value  that does not point to the start of a UTF-8 character (or to the
2205           end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2206    
2207         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
2208         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1554  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2210  MATCHING A PATTERN: THE TRADITIONAL FUNC
2210         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
2211         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2212         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2213         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         points to the start of a UTF-8 character (or the end of  the  subject).
2214         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2215         value of startoffset that does not point to the start of a UTF-8  char-         string as a subject or an invalid value of  startoffset  is  undefined.
2216         acter, is undefined. Your program may crash.         Your program may crash.
2217    
2218           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2219             PCRE_PARTIAL_SOFT
2220         This  option  turns  on  the  partial  matching feature. If the subject  
2221         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2222         ing  process  the  end of the subject was reached (that is, the subject         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2223         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2224         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2225         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2226         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2227         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2228           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2229           caller  is  prepared to handle a partial match, but only if no complete
2230           match can be found.
2231    
2232           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2233           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2234           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2235           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2236           ered to be more important that an alternative complete match.
2237    
2238           In both cases, the portion of the string that was  inspected  when  the
2239           partial match was found is set as the first matching string. There is a
2240           more detailed discussion of partial and  multi-segment  matching,  with
2241           examples, in the pcrepartial documentation.
2242    
2243     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2244    
2245         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
2246         length  in  length, and a starting byte offset in startoffset. In UTF-8         length (in bytes) in length, and a starting byte offset in startoffset.
2247         mode, the byte offset must point to the start  of  a  UTF-8  character.         If  this  is  negative  or  greater  than  the  length  of the subject,
2248         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2249         When the starting offset is zero, the search for a match starts at  the         zero,  the  search  for a match starts at the beginning of the subject,
2250         beginning of the subject, and this is by far the most common case.         and this is by far the most common case. In UTF-8 mode, the byte offset
2251           must  point  to  the start of a UTF-8 character (or the end of the sub-
2252           ject). Unlike the pattern string, the subject may contain  binary  zero
2253           bytes.
2254    
2255         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2256         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1598  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2271  MATCHING A PATTERN: THE TRADITIONAL FUNC
2271         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
2272         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2273    
2274         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2275           match an empty string. It is possible to emulate Perl's /g behaviour by
2276           first  trying  the  match  again  at  the   same   offset,   with   the
2277           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2278           fails, advancing the starting  offset  and  trying  an  ordinary  match
2279           again. There is some code that demonstrates how to do this in the pcre-
2280           demo sample program. In the most general case, you have to check to see
2281           if  the newline convention recognizes CRLF as a newline, and if so, and
2282           the current character is CR followed by LF, advance the starting offset
2283           by two characters instead of one.
2284    
2285           If  a  non-zero starting offset is passed when the pattern is anchored,
2286         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
2287         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
2288         subject.         subject.
2289    
2290     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2291    
2292         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
2293         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2294         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2295         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2296         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-
2297         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2298         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2299    
2300         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2301         offsets whose address is passed in ovector. The number of  elements  in         whose  address is passed in ovector. The number of elements in the vec-
2302         the  vector is passed in ovecsize, which must be a non-negative number.         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2303         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2304    
2305         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-
2306         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2307         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-
2308         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2309         The length passed in ovecsize should always be a multiple of three.  If         The  number passed in ovecsize should always be a multiple of three. If
2310         it is not, it is rounded down.         it is not, it is rounded down.
2311    
2312         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2313         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2314         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
2315         element of a pair is set to the offset of the first character in a sub-         element  of  each pair is set to the byte offset of the first character
2316         string,  and  the  second  is  set to the offset of the first character         in a substring, and the second is set to the byte offset of  the  first
2317         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         character  after  the end of a substring. Note: these values are always
2318         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2319         entire pattern. The next pair is used for the first  capturing  subpat-  
2320         tern,  and  so  on.  The value returned by pcre_exec() is the number of         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2321         pairs that have been set. If there are no  capturing  subpatterns,  the         portion  of  the subject string matched by the entire pattern. The next
2322         return  value  from  a  successful match is 1, indicating that just the         pair is used for the first capturing subpattern, and so on.  The  value
2323         first pair of offsets has been set.         returned by pcre_exec() is one more than the highest numbered pair that
2324           has been set.  For example, if two substrings have been  captured,  the
2325         Some convenience functions are provided  for  extracting  the  captured         returned  value is 3. If there are no capturing subpatterns, the return
2326         substrings  as  separate  strings. These are described in the following         value from a successful match is 1, indicating that just the first pair
2327         section.         of offsets has been set.
   
        It is possible for an capturing subpattern number  n+1  to  match  some  
        part  of  the  subject  when subpattern n has not been used at all. For  
        example, if the string "abc" is matched against the pattern (a|(z))(bc)  
        subpatterns  1 and 3 are matched, but 2 is not. When this happens, both  
        offset values corresponding to the unused subpattern are set to -1.  
2328    
2329         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2330         of the string that it matched that is returned.         of the string that it matched that is returned.
2331    
2332         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,
2333         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
2334         function  returns a value of zero. In particular, if the substring off-         function returns a value of zero. If the substring offsets are  not  of
2335         sets are not of interest, pcre_exec() may be called with ovector passed         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2336         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         ovecsize as zero. However, if the pattern contains back references  and
2337         references and the ovector is not big enough to  remember  the  related         the  ovector is not big enough to remember the related substrings, PCRE
2338         substrings,  PCRE has to get additional memory for use during matching.         has to get additional memory for use during matching. Thus it  is  usu-
2339         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2340    
2341         Note that pcre_info() can be used to find out how many  capturing  sub-         The pcre_fullinfo() function can be used to find out how many capturing
2342         patterns there are in a compiled pattern. The smallest size for ovector         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2343         that will allow for n captured substrings, in addition to  the  offsets         ovector  that  will allow for n captured substrings, in addition to the
2344         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.
2345    
2346           It is possible for capturing subpattern number n+1 to match  some  part
2347           of the subject when subpattern n has not been used at all. For example,
2348           if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2349           return from the function is 4, and subpatterns 1 and 3 are matched, but
2350           2 is not. When this happens, both values in  the  offset  pairs  corre-
2351           sponding to unused subpatterns are set to -1.
2352    
2353           Offset  values  that correspond to unused subpatterns at the end of the
2354           expression are also set to -1. For example,  if  the  string  "abc"  is
2355           matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2356           matched. The return from the function is 2, because  the  highest  used
2357           capturing  subpattern  number  is 1, and the offsets for for the second
2358           and third capturing subpatterns (assuming the vector is  large  enough,
2359           of course) are set to -1.
2360    
2361           Note: Elements of ovector that do not correspond to capturing parenthe-
2362           ses in the pattern are never changed. That is, if a pattern contains  n
2363           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2364           by pcre_exec(). The other elements retain whatever values  they  previ-
2365           ously had.
2366    
2367           Some  convenience  functions  are  provided for extracting the captured
2368           substrings as separate strings. These are described below.
2369    
2370     Return values from pcre_exec()     Error return values from pcre_exec()
2371    
2372         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2373         defined in the header file:         defined in the header file:
2374    
2375           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1676  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2378  MATCHING A PATTERN: THE TRADITIONAL FUNC
2378    
2379           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2380    
2381         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
2382         ovecsize was not zero.         ovecsize was not zero.
2383    
2384           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1685  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2387  MATCHING A PATTERN: THE TRADITIONAL FUNC
2387    
2388           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2389    
2390         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,
2391         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
2392         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
2393         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2394         gives when the magic number is not present.         gives when the magic number is not present.
2395    
2396           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2397    
2398         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2399         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
2400         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2401    
2402           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2403    
2404         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2405         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2406         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
2407         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
2408         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2409    
2410           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2411           This  can happen only when PCRE has been compiled with --disable-stack-
2412           for-recursion.
2413    
2414           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2415    
2416         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2417         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2418         returned by pcre_exec().         returned by pcre_exec().
2419    
2420           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2421    
2422         The  recursion  and backtracking limit, as specified by the match_limit         The backtracking limit, as specified by  the  match_limit  field  in  a
2423         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         pcre_extra  structure  (or  defaulted) was reached. See the description
2424         description above.         above.
2425    
2426           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2427    
2428         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
2429         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2430         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2431    
2432           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2433    
2434         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
2435         subject.         subject.   However,  if  PCRE_PARTIAL_HARD  is set and the problem is a
2436           truncated UTF-8 character at the end of the subject,  PCRE_ERROR_SHORT-
2437           UTF8 is used instead.
2438    
2439           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2440    
2441         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
2442         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-
2443         ter.         ter or the end of the subject.
2444    
2445           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2446    
2447         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
2448         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2449    
2450           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2451    
2452         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2453         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2454         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2455           onwards, there are no restrictions on partial matching.
2456    
2457           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2458    
# Line 1752  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2461  MATCHING A PATTERN: THE TRADITIONAL FUNC
2461    
2462           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2463    
2464         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.
2465    
2466             PCRE_ERROR_RECURSIONLIMIT (-21)
2467    
2468           The internal recursion limit, as specified by the match_limit_recursion
2469           field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2470           description above.
2471    
2472             PCRE_ERROR_BADNEWLINE     (-23)
2473    
2474           An invalid combination of PCRE_NEWLINE_xxx options was given.
2475    
2476             PCRE_ERROR_BADOFFSET      (-24)
2477    
2478           The value of startoffset was negative or greater than the length of the
2479           subject, that is, the value in length.
2480    
2481             PCRE_ERROR_SHORTUTF8      (-25)
2482    
2483           The  subject  string ended with an incomplete (truncated) UTF-8 charac-
2484           ter, and the PCRE_PARTIAL_HARD option was  set.  Without  this  option,
2485           PCRE_ERROR_BADUTF8 is returned in this situation.
2486    
2487           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2488    
2489    
2490  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1774  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2506  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2506         string_list() are provided for extracting captured substrings  as  new,         string_list() are provided for extracting captured substrings  as  new,
2507         separate,  zero-terminated strings. These functions identify substrings         separate,  zero-terminated strings. These functions identify substrings
2508         by number. The next section describes functions  for  extracting  named         by number. The next section describes functions  for  extracting  named
2509         substrings.  A  substring  that  contains  a  binary  zero is correctly         substrings.
2510         extracted and has a further zero added on the end, but  the  result  is  
2511         not, of course, a C string.         A  substring that contains a binary zero is correctly extracted and has
2512           a further zero added on the end, but the result is not, of course, a  C
2513           string.   However,  you  can  process such a string by referring to the
2514           length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2515           string().  Unfortunately, the interface to pcre_get_substring_list() is
2516           not adequate for handling strings containing binary zeros, because  the
2517           end of the final string is not independently indicated.
2518    
2519         The  first  three  arguments  are the same for all three of these func-         The  first  three  arguments  are the same for all three of these func-
2520         tions: subject is the subject string that has  just  been  successfully         tions: subject is the subject string that has  just  been  successfully
# Line 1796  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2534  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2534         buffersize, while for pcre_get_substring() a new  block  of  memory  is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2535         obtained  via  pcre_malloc,  and its address is returned via stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2536         The yield of the function is the length of the  string,  not  including         The yield of the function is the length of the  string,  not  including
2537         the terminating zero, or one of         the terminating zero, or one of these error codes:
2538    
2539           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2540    
# Line 1812  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2550  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2550         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2551         the  memory  block  is returned via listptr, which is also the start of         the  memory  block  is returned via listptr, which is also the start of
2552         the list of string pointers. The end of the list is marked  by  a  NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2553         pointer. The yield of the function is zero if all went well, or         pointer.  The  yield  of  the function is zero if all went well, or the
2554           error code
2555    
2556           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2557    
2558         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2559    
2560         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2561         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2562         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2563         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2564         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2565         tive for unset substrings.         tive for unset substrings.
2566    
2567         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2568         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2569         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2570         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2571         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2572         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2573         cial  interface  to  another  programming  language  which  cannot  use         cial   interface  to  another  programming  language  that  cannot  use
2574         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2575         vided.         vided.
2576    
2577    
# Line 1851  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2590  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2590              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2591              const char **stringptr);              const char **stringptr);
2592    
2593         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2594         ber.  For example, for this pattern         ber.  For example, for this pattern
2595    
2596           (a+)b(?P<xxx>\d+)...           (a+)b(?<xxx>\d+)...
2597    
2598         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. If the name is known to
2599         from the name by calling pcre_get_stringnumber(). The first argument is         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2600         the  compiled  pattern,  and  the  second is the name. The yield of the         name by calling pcre_get_stringnumber(). The first argument is the com-
2601         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if         piled pattern, and the second is the name. The yield of the function is
2602         there is no subpattern of that name.         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2603           subpattern of that name.
2604    
2605         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2606         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
# Line 1879  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2619  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2619    
2620         These functions call pcre_get_stringnumber(), and if it succeeds,  they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2621         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2622         ate.         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2623           behaviour may not be what you want (see the next section).
2624    
2625           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2626           terns with the same number, as described in the  section  on  duplicate
2627           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2628           distinguish the different subpatterns, because names are  not  included
2629           in  the compiled code. The matching process uses only numbers. For this
2630           reason, the use of different names for subpatterns of the  same  number
2631           causes an error at compile time.
2632    
2633    
2634    DUPLICATE SUBPATTERN NAMES
2635    
2636           int pcre_get_stringtable_entries(const pcre *code,
2637                const char *name, char **first, char **last);
2638    
2639           When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2640           subpatterns are not required to be unique. (Duplicate names are  always
2641           allowed  for subpatterns with the same number, created by using the (?|
2642           feature. Indeed, if such subpatterns are named, they  are  required  to
2643           use the same names.)
2644    
2645           Normally, patterns with duplicate names are such that in any one match,
2646           only one of the named subpatterns participates. An example is shown  in
2647           the pcrepattern documentation.
2648    
2649           When    duplicates   are   present,   pcre_copy_named_substring()   and
2650           pcre_get_named_substring() return the first substring corresponding  to
2651           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2652           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2653           function  returns one of the numbers that are associated with the name,
2654           but it is not defined which it is.
2655    
2656           If you want to get full details of all captured substrings for a  given
2657           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2658           first argument is the compiled pattern, and the second is the name. The
2659           third  and  fourth  are  pointers to variables which are updated by the
2660           function. After it has run, they point to the first and last entries in
2661           the  name-to-number  table  for  the  given  name.  The function itself
2662           returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2663           there  are none. The format of the table is described above in the sec-
2664           tion entitled Information about a  pattern.   Given  all  the  relevant
2665           entries  for the name, you can extract each of their numbers, and hence
2666           the captured data, if any.
2667    
2668    
2669  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 1908  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2692  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2692              int *workspace, int wscount);              int *workspace, int wscount);
2693    
2694         The  function  pcre_dfa_exec()  is  called  to  match  a subject string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2695         against a compiled pattern, using a "DFA" matching algorithm. This  has         against a compiled pattern, using a matching algorithm that  scans  the
2696         different  characteristics to the normal algorithm, and is not compati-         subject  string  just  once, and does not backtrack. This has different
2697         ble with Perl. Some of the features of PCRE patterns are not supported.         characteristics to the normal algorithm, and  is  not  compatible  with
2698         Nevertheless, there are times when this kind of matching can be useful.         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2699         For a discussion of the two matching algorithms, see  the  pcrematching         theless, there are times when this kind of matching can be useful.  For
2700         documentation.         a  discussion  of  the  two matching algorithms, and a list of features
2701           that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2702           tion.
2703    
2704         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
2705         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 1925  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2711  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2711         workspace vector should contain at least 20 elements. It  is  used  for         workspace vector should contain at least 20 elements. It  is  used  for
2712         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2713         workspace will be needed for patterns and subjects where  there  are  a         workspace will be needed for patterns and subjects where  there  are  a
2714         lot of possible matches.         lot of potential matches.
2715    
2716         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_dfa_exec():
2717    
2718           int rc;           int rc;
2719           int ovector[10];           int ovector[10];
2720           int wspace[20];           int wspace[20];
2721           rc = pcre_exec(           rc = pcre_dfa_exec(
2722             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
2723             NULL,           /* we didn't study the pattern */             NULL,           /* we didn't study the pattern */
2724             "some string",  /* the subject string */             "some string",  /* the subject string */
# Line 1947  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2733  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2733     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2734    
2735         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
2736         zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2737         PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2738         PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2739         these  are  the  same  as  for pcre_exec(), so their description is not         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2740         repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2741           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2742           PCRE_PARTIAL         description is not repeated here.
2743    
2744         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2745         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2746         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2747         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These have the same general effect as they do for pcre_exec(), but  the
2748         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2749         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2750         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2751           that requires additional characters. This happens even if some complete
2752           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2753           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2754           of  the  subject  is  reached, there have been no complete matches, but
2755           there is still at least one matching possibility. The  portion  of  the
2756           string  that  was inspected when the longest partial match was found is
2757           set as the first matching string  in  both  cases.   There  is  a  more
2758           detailed  discussion  of partial and multi-segment matching, with exam-
2759           ples, in the pcrepartial documentation.
2760    
2761           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2762    
2763         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2764         stop  as  soon  as  it  has found one match. Because of the way the DFA         stop as soon as it has found one match. Because of the way the alterna-
2765         algorithm works, this is necessarily the shortest possible match at the         tive algorithm works, this is necessarily the shortest  possible  match
2766         first possible matching point in the subject string.         at the first possible matching point in the subject string.
2767    
2768           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2769    
2770         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2771         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2772         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2773         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it is set, the workspace and wscount options must  reference  the  same
2774         workspace  and wscount options must reference the same vector as before         vector  as  before  because data about the match so far is left in them
2775         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
2776         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2777    
2778     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2779    
2780         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-
2781         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
2782         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
2783         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2784         if the pattern         if the pattern
2785    
2786           <.*>           <.*>
# Line 2001  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2795  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2795           <something> <something else>           <something> <something else>
2796           <something> <something else> <something further>           <something> <something else> <something further>
2797    
2798         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,
2799         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2800         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2801         the  offset  to the start, and the second is the offset to the end. All         the offset to the start, and the second is the offset to  the  end.  In
2802         the strings have the same start offset. (Space could have been saved by         fact,  all  the  strings  have the same start offset. (Space could have
2803         giving  this only once, but it was decided to retain some compatibility         been saved by giving this only once, but it was decided to retain  some
2804         with the way pcre_exec() returns data, even though the meaning  of  the         compatibility  with  the  way pcre_exec() returns data, even though the
2805         strings is different.)         meaning of the strings is different.)
2806    
2807         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-
2808         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
2809         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
2810         filled with the longest matches.         filled with the longest matches.
2811    
2812     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2813    
2814         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2815         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
2816         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2817         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2818    
2819           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2820    
2821         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-
2822         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
2823         reference.         reference.
2824    
2825           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2826    
2827         This  return is given if pcre_dfa_exec() encounters a condition item in         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2828         a pattern that uses a back reference for the  condition.  This  is  not         that  uses  a back reference for the condition, or a test for recursion
2829         supported.         in a specific group. These are not supported.
2830    
2831           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2832    
2833         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
2834         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
2835         (it is meaningless).         (it is meaningless).
2836    
2837           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2838    
2839         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
2840         workspace vector.         workspace vector.
2841    
2842           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2843    
2844         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2845         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2846         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
2847         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2848    
 Last updated: 16 May 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
2849    
2850    SEE ALSO
2851    
2852           pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2853           tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2854    
2855    
2856    AUTHOR
2857    
2858           Philip Hazel
2859           University Computing Service
2860           Cambridge CB2 3QH, England.
2861    
2862    
2863    REVISION
2864    
2865           Last updated: 13 November 2010
2866           Copyright (c) 1997-2010 University of Cambridge.
2867    ------------------------------------------------------------------------------
2868    
2869    
2870  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2871    
2872    
# Line 2080  PCRE CALLOUTS Line 2890  PCRE CALLOUTS
2890         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2891         points:         points:
2892    
2893           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2894    
2895         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
2896         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2897         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is         with  number  255,  before  each  item  in the pattern. For example, if
2898         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2899    
2900           A(\d{2}|--)           A(\d{2}|--)
2901    
# Line 2104  PCRE CALLOUTS Line 2914  PCRE CALLOUTS
2914  MISSING CALLOUTS  MISSING CALLOUTS
2915    
2916         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2917         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2918         pattern is         example, if the pattern is
2919    
2920           ab(?C4)cd           ab(?C4)cd
2921    
# Line 2114  MISSING CALLOUTS Line 2924  MISSING CALLOUTS
2924         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2925         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2926    
2927           If the pattern is studied, PCRE knows the minimum length of a  matching
2928           string,  and will immediately give a "no match" return without actually
2929           running a match if the subject is not long enough, or,  for  unanchored
2930           patterns, if it has been scanned far enough.
2931    
2932           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2933           MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
2934           matching  process,  but  does  ensure that callouts such as the example
2935           above are obeyed.
2936    
2937    
2938  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2939    
# Line 2141  THE CALLOUT INTERFACE Line 2961  THE CALLOUT INTERFACE
2961         version number will change again in future  if  additional  fields  are         version number will change again in future  if  additional  fields  are
2962         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.
2963    
2964         The callout_number field contains the number of the  callout,  as  com-         The  callout_number  field  contains the number of the callout, as com-
2965         piled  into  the pattern (that is, the number after ?C for manual call-         piled into the pattern (that is, the number after ?C for  manual  call-
2966         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2967    
2968         The offset_vector field is a pointer to the vector of offsets that  was         The  offset_vector field is a pointer to the vector of offsets that was
2969         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
2970         pcre_exec() is used, the contents can be inspected in order to  extract         pcre_exec()  is used, the contents can be inspected in order to extract
2971         substrings  that  have  been  matched  so  far,  in the same way as for         substrings that have been matched so  far,  in  the  same  way  as  for
2972         extracting substrings after a match has completed. For  pcre_dfa_exec()         extracting  substrings after a match has completed. For pcre_dfa_exec()
2973         this field is not useful.         this field is not useful.
2974    
2975         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2976         were passed to pcre_exec().         were passed to pcre_exec().
2977    
2978         The start_match field contains the offset within the subject  at  which         The  start_match  field normally contains the offset within the subject
2979         the  current match attempt started. If the pattern is not anchored, the         at which the current match attempt  started.  However,  if  the  escape
2980         callout function may be called several times from the same point in the         sequence  \K has been encountered, this value is changed to reflect the
2981         pattern for different starting points in the subject.         modified starting point. If the pattern is not  anchored,  the  callout
2982           function may be called several times from the same point in the pattern
2983           for different starting points in the subject.
2984    
2985         The  current_position  field  contains the offset within the subject of         The current_position field contains the offset within  the  subject  of
2986         the current match pointer.         the current match pointer.
2987    
2988         When the pcre_exec() function is used, the capture_top  field  contains         When  the  pcre_exec() function is used, the capture_top field contains
2989         one  more than the number of the highest numbered captured substring so         one more than the number of the highest numbered captured substring  so
2990         far. If no substrings have been captured, the value of  capture_top  is         far.  If  no substrings have been captured, the value of capture_top is
2991         one.  This  is always the case when pcre_dfa_exec() is used, because it         one. This is always the case when pcre_dfa_exec() is used,  because  it
2992         does not support captured substrings.         does not support captured substrings.
2993    
2994         The capture_last field contains the number of the  most  recently  cap-         The  capture_last  field  contains the number of the most recently cap-
2995         tured  substring. If no substrings have been captured, its value is -1.         tured substring. If no substrings have been captured, its value is  -1.
2996         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2997    
2998         The callout_data field contains a value that is passed  to  pcre_exec()         The  callout_data  field contains a value that is passed to pcre_exec()
2999         or  pcre_dfa_exec() specifically so that it can be passed back in call-         or pcre_dfa_exec() specifically so that it can be passed back in  call-
3000         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
3001         structure.  If  no such data was passed, the value of callout_data in a         structure. If no such data was passed, the value of callout_data  in  a
3002         pcre_callout block is NULL. There is a description  of  the  pcre_extra         pcre_callout  block  is  NULL. There is a description of the pcre_extra
3003         structure in the pcreapi documentation.         structure in the pcreapi documentation.
3004    
3005         The  pattern_position field is present from version 1 of the pcre_call-         The pattern_position field is present from version 1 of the  pcre_call-
3006         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
3007         the pattern string.         the pattern string.
3008    
3009         The  next_item_length field is present from version 1 of the pcre_call-         The next_item_length field is present from version 1 of the  pcre_call-
3010         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
3011         the  pattern  string. When the callout immediately precedes an alterna-         the pattern string. When the callout immediately precedes  an  alterna-
3012         tion bar, a closing parenthesis, or the end of the pattern, the  length         tion  bar, a closing parenthesis, or the end of the pattern, the length
3013         is  zero.  When the callout precedes an opening parenthesis, the length         is zero. When the callout precedes an opening parenthesis,  the  length
3014         is that of the entire subpattern.         is that of the entire subpattern.
3015    
3016         The pattern_position and next_item_length fields are intended  to  help         The  pattern_position  and next_item_length fields are intended to help
3017         in  distinguishing between different automatic callouts, which all have         in distinguishing between different automatic callouts, which all  have
3018         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3019    
3020    
3021  RETURN VALUES  RETURN VALUES
3022    
3023         The external callout function returns an integer to PCRE. If the  value         The  external callout function returns an integer to PCRE. If the value
3024         is  zero,  matching  proceeds  as  normal. If the value is greater than         is zero, matching proceeds as normal. If  the  value  is  greater  than
3025         zero, matching fails at the current point, but  the  testing  of  other         zero,  matching  fails  at  the current point, but the testing of other
3026         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3027         failed. If the value is less than zero, the  match  is  abandoned,  and         failed.  If  the  value  is less than zero, the match is abandoned, and
3028         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3029    
3030         Negative   values   should   normally   be   chosen  from  the  set  of         Negative  values  should  normally  be   chosen   from   the   set   of
3031         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3032         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
3033         reserved for use by callout functions; it will never be  used  by  PCRE         reserved  for  use  by callout functions; it will never be used by PCRE
3034         itself.         itself.
3035    
3036  Last updated: 28 February 2005  
3037  Copyright (c) 1997-2005 University of Cambridge.  AUTHOR
3038  ------------------------------------------------------------------------------  
3039           Philip Hazel
3040           University Computing Service
3041           Cambridge CB2 3QH, England.
3042    
3043    
3044    REVISION
3045    
3046           Last updated: 29 September 2009
3047           Copyright (c) 1997-2009 University of Cambridge.
3048    ------------------------------------------------------------------------------
3049    
3050    
3051  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3052    
3053    
# Line 2227  DIFFERENCES BETWEEN PCRE AND PERL Line 3059  DIFFERENCES BETWEEN PCRE AND PERL
3059    
3060         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3061         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3062         respect to Perl 5.8.         respect to Perl versions 5.10 and above.
3063    
3064         1.  PCRE does not have full UTF-8 support. Details of what it does have         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3065         are given in the section on UTF-8 support in the main pcre page.         of what it does have are given in the section on UTF-8 support  in  the
3066           main pcre page.
3067    
3068         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3069         permits  them,  but they do not mean what you might think. For example,         permits them, but they do not mean what you might think.  For  example,
3070         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
3071         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3072    
3073         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3074         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3075         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3076         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3077         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3078         branch.         branch.
3079    
3080         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3081         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3082         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3083         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3084    
3085         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3086         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
3087         dling  and are not part of its pattern matching engine. If any of these         dling and are not part of its pattern matching engine. If any of  these
3088         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3089    
3090         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3091         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3092         can be tested with \p and \P are limited to the general category  prop-         can  be tested with \p and \P are limited to the general category prop-
3093         erties such as Lu and Nd.         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3094           derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3095           property, which Perl does not; the  Perl  documentation  says  "Because
3096           Perl hides the need for the user to understand the internal representa-
3097           tion of Unicode characters, there is no need to implement the  somewhat
3098           messy concept of surrogates."
3099    
3100         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3101         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
# Line 2275  DIFFERENCES BETWEEN PCRE AND PERL Line 3113  DIFFERENCES BETWEEN PCRE AND PERL
3113         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3114         classes.         classes.
3115    
3116         8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3117         constructions.  However,  there is support for recursive patterns using         constructions.  However,  there is support for recursive patterns. This
3118         the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3119         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3120         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3121    
3122         9. There are some differences that are concerned with the  settings  of         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3123           always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3124           unlike Perl. There is a discussion of an example that explains this  in
3125           more  detail  in  the section on recursion differences from Perl in the
3126           pcrepattern page.
3127    
3128           10. There are some differences that are concerned with the settings  of
3129         captured  strings  when  part  of  a  pattern is repeated. For example,         captured  strings  when  part  of  a  pattern is repeated. For example,
3130         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3131         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3132    
3133         10. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3134         ities:         pattern names is not as general as Perl's. This is a consequence of the
3135           fact the PCRE works internally just with numbers, using an external ta-
3136           ble to translate between numbers and names. In  particular,  a  pattern
3137           such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3138           the same number but different names, is not supported,  and  causes  an
3139           error  at compile time. If it were allowed, it would not be possible to
3140           distinguish which parentheses matched, because both names map  to  cap-
3141           turing subpattern number 1. To avoid this confusing situation, an error
3142           is given at compile time.
3143    
3144           12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3145           example, between the ( and ? at the start of a subpattern.
3146    
3147           13. PCRE provides some extensions to the Perl regular expression facil-
3148           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3149           sions  of  Perl, some of which (such as named parentheses) have been in
3150           PCRE for some time. This list is with respect to Perl 5.10:
3151    
3152           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3153           strings,  each alternative branch of a lookbehind assertion can match a
3154           different length of string. Perl requires them all  to  have  the  same
3155           length.
3156    
3157         (a) Although lookbehind assertions must  match  fixed  length  strings,         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
        each alternative branch of a lookbehind assertion can match a different  
        length of string. Perl requires them all to have the same length.  
   
        (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $  
3158         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3159    
3160         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
3161         cial meaning is faulted.         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3162           ignored.  (Perl can be made to issue a warning.)
3163    
3164         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3165         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2306  DIFFERENCES BETWEEN PCRE AND PERL Line 3168  DIFFERENCES BETWEEN PCRE AND PERL
3168         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
3169         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3170    
3171         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3172         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3173           lents.
3174    
3175         (g) The (?R), (?number), and (?P>name) constructs allows for  recursive         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3176         pattern  matching  (Perl  can  do  this using the (?p{code}) construct,         CRLF by the PCRE_BSR_ANYCRLF option.
        which PCRE cannot support.)  
3177    
3178         (h) PCRE supports named capturing substrings, using the Python  syntax.         (h) The callout facility is PCRE-specific.
3179    
3180         (i)  PCRE  supports  the  possessive quantifier "++" syntax, taken from         (i) The partial matching facility is PCRE-specific.
        Sun's Java package.  
3181    
3182         (j) The (R) condition, for testing recursion, is a PCRE extension.         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3183           even on different hosts that have the other endianness.
3184    
3185         (k) The callout facility is PCRE-specific.         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3186           different way and is not Perl-compatible.
3187    
3188         (l) The partial matching facility is PCRE-specific.         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3189           of a pattern that set overall options that cannot be changed within the
3190           pattern.
3191    
        (m) Patterns compiled by PCRE can be saved and re-used at a later time,  
        even on different hosts that have the other endianness.  
3192    
3193         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a  AUTHOR
3194         different way and is not Perl-compatible.  
3195           Philip Hazel
3196           University Computing Service
3197           Cambridge CB2 3QH, England.
3198    
 Last updated: 28 February 2005  
 Copyright (c) 1997-2005 University of Cambridge.  
 ------------------------------------------------------------------------------  
3199    
3200    REVISION
3201    
3202           Last updated: 31 October 2010
3203           Copyright (c) 1997-2010 University of Cambridge.
3204    ------------------------------------------------------------------------------
3205    
3206    
3207  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3208    
3209    
# Line 2344  NAME Line 3213  NAME
3213    
3214  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3215    
3216         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3217         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3218         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3219         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3220         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3221         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3222           Python, .NET, and Oniguruma.
3223    
3224           Perl's  regular expressions are described in its own documentation, and
3225           regular expressions in general are covered in a number of  books,  some
3226           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3227           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3228           great  detail.  This  description  of  PCRE's  regular  expressions  is
3229           intended as reference material.
3230    
3231         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3232         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
3233         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, PCRE must be built to include UTF-8 support, and  you  must  call
3234         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3235         matching is mentioned in several places below. There is also a  summary         also a special sequence that can be given at the start of a pattern:
3236         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3237         page.           (*UTF8)
3238    
3239           Starting a pattern with this sequence  is  equivalent  to  setting  the
3240           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3241           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3242           below.  There  is  also  a  summary of UTF-8 features in the section on
3243           UTF-8 support in the main pcre page.
3244    
3245           Another special sequence that may appear at the start of a  pattern  or
3246           in combination with (*UTF8) is:
3247    
3248             (*UCP)
3249    
3250           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3251           sequences such as \d and \w to  use  Unicode  properties  to  determine
3252           character types, instead of recognizing only characters with codes less
3253           than 128 via a lookup table.
3254    
3255         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3256         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
3257         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
3258         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
3259         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
3260         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3261         the pcrematching page.         alternative function, and how it differs from the normal function,  are
3262           discussed in the pcrematching page.
3263         A regular expression is a pattern that is  matched  against  a  subject  
3264         string  from  left  to right. Most characters stand for themselves in a  
3265         pattern, and match the corresponding characters in the  subject.  As  a  NEWLINE CONVENTIONS
3266    
3267           PCRE  supports five different conventions for indicating line breaks in
3268           strings: a single CR (carriage return) character, a  single  LF  (line-
3269           feed) character, the two-character sequence CRLF, any of the three pre-
3270           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3271           discussion  about newlines, and shows how to set the newline convention
3272           in the options arguments for the compiling and matching functions.
3273    
3274           It is also possible to specify a newline convention by starting a  pat-
3275           tern string with one of the following five sequences:
3276    
3277             (*CR)        carriage return
3278             (*LF)        linefeed
3279             (*CRLF)      carriage return, followed by linefeed
3280             (*ANYCRLF)   any of the three above
3281             (*ANY)       all Unicode newline sequences
3282    
3283           These  override  the default and the options given to pcre_compile() or
3284           pcre_compile2(). For example, on a Unix system where LF is the  default
3285           newline sequence, the pattern
3286    
3287             (*CR)a.b
3288    
3289           changes the convention to CR. That pattern matches "a\nb" because LF is
3290           no longer a newline. Note that these special settings,  which  are  not
3291           Perl-compatible,  are  recognized  only at the very start of a pattern,
3292           and that they must be in upper case.  If  more  than  one  of  them  is
3293           present, the last one is used.
3294    
3295           The  newline convention affects the interpretation of the dot metachar-
3296           acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
3297           ever,  it  does  not  affect  what  the  \R escape sequence matches. By
3298           default, this is any Unicode newline sequence, for Perl  compatibility.
3299           However,  this can be changed; see the description of \R in the section
3300           entitled "Newline sequences" below. A change of \R setting can be  com-
3301           bined with a change of newline convention.
3302    
3303    
3304    CHARACTERS AND METACHARACTERS
3305    
3306           A  regular  expression  is  a pattern that is matched against a subject
3307           string from left to right. Most characters stand for  themselves  in  a
3308           pattern,  and  match  the corresponding characters in the subject. As a
3309         trivial example, the pattern         trivial example, the pattern
3310    
3311           The quick brown fox           The quick brown fox
3312    
3313         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3314         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3315         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3316         the concept of case for characters whose values are less than  128,  so         the  concept  of case for characters whose values are less than 128, so
3317         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3318         ues, the concept of case is supported if PCRE is compiled with  Unicode         ues,  the concept of case is supported if PCRE is compiled with Unicode
3319         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3320         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3321         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3322    
3323         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3324         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3325         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3326         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3327    
3328         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3329         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3330         that are recognized in square brackets. Outside  square  brackets,  the         that  are  recognized  within square brackets. Outside square brackets,
3331         metacharacters are as follows:         the metacharacters are as follows:
3332    
3333           \      general escape character with several uses           \      general escape character with several uses
3334           ^      assert start of string (or line, in multiline mode)           ^      assert start of string (or line, in multiline mode)
# Line 2410  PCRE REGULAR EXPRESSION DETAILS Line 3346  PCRE REGULAR EXPRESSION DETAILS
3346                  also "possessive quantifier"                  also "possessive quantifier"
3347           {      start min/max quantifier           {      start min/max quantifier
3348    
3349         Part  of  a  pattern  that is in square brackets is called a "character         Part of a pattern that is in square brackets  is  called  a  "character
3350         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3351    
3352           \      general escape character           \      general escape character
# Line 2420  PCRE REGULAR EXPRESSION DETAILS Line 3356  PCRE REGULAR EXPRESSION DETAILS
3356                    syntax)                    syntax)
3357           ]      terminates the character class           ]      terminates the character class
3358    
3359         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3360    
3361    
3362  BACKSLASH  BACKSLASH
# Line 2439  BACKSLASH Line 3375  BACKSLASH
3375    
3376         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3377         the pattern (other than in a character class) and characters between  a         the pattern (other than in a character class) and characters between  a
3378         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline are ignored. An escap-
3379         An escaping backslash can be used to include a whitespace or #  charac-         ing backslash can be used to include a whitespace  or  #  character  as
3380         ter as part of the pattern.         part of the pattern.
3381    
3382         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-
3383         ters, you can do so by putting them between \Q and \E. This is  differ-         ters, you can do so by putting them between \Q and \E. This is  differ-
# Line 2457  BACKSLASH Line 3393  BACKSLASH
3393           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3394    
3395         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3396         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3397    
3398     Non-printing characters     Non-printing characters
3399    
# Line 2465  BACKSLASH Line 3401  BACKSLASH
3401         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
3402         appearance of non-printing characters, apart from the binary zero  that         appearance of non-printing characters, apart from the binary zero  that
3403         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3404         editing, it is usually easier  to  use  one  of  the  following  escape         editing, it is  often  easier  to  use  one  of  the  following  escape
3405         sequences than the binary character it represents:         sequences than the binary character it represents:
3406    
3407           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3408           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3409           \e        escape (hex 1B)           \e        escape (hex 1B)
3410           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3411           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3412           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3413           \t        tab (hex 09)           \t        tab (hex 09)
3414           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3415           \xhh      character with hex code hh           \xhh      character with hex code hh
3416           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh..
3417    
3418         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,
3419         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it is converted to upper case. Then bit 6 of the character (hex 40)  is
# Line 2485  BACKSLASH Line 3421  BACKSLASH
3421         becomes hex 7B.         becomes hex 7B.
3422    
3423         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
3424         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-         in  upper  or  lower case). Any number of hexadecimal digits may appear
3425         its may appear between \x{ and }, but the value of the  character  code         between \x{ and }, but the value of the character  code  must  be  less
3426         must  be  less  than  2**31  (that is, the maximum hexadecimal value is         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3427         7FFFFFFF). If characters other than hexadecimal digits  appear  between         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3428         \x{  and }, or if there is no terminating }, this form of escape is not         than the largest Unicode code point, which is 10FFFF.
3429         recognized. Instead, the initial \x will  be  interpreted  as  a  basic  
3430         hexadecimal  escape, with no following digits, giving a character whose         If  characters  other than hexadecimal digits appear between \x{ and },
3431         value is zero.         or if there is no terminating }, this form of escape is not recognized.
3432           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3433           escape, with no following digits, giving a  character  whose  value  is
3434           zero.
3435    
3436         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
3437         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference         two syntaxes for \x. There is no difference in the way  they  are  han-
3438         in the way they are handled. For example, \xdc is exactly the  same  as         dled. For example, \xdc is exactly the same as \x{dc}.
3439         \x{dc}.  
3440           After  \0  up  to two further octal digits are read. If there are fewer
3441         After  \0  up  to  two further octal digits are read. In both cases, if         than two digits, just  those  that  are  present  are  used.  Thus  the
3442         there are fewer than two digits, just those that are present are  used.         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3443         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL         (code value 7). Make sure you supply two digits after the initial  zero
3444         character (code value 7). Make sure you supply  two  digits  after  the         if the pattern character that follows is itself an octal digit.
        initial  zero  if the pattern character that follows is itself an octal  
        digit.  
3445    
3446         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-
3447         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3448         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
3449         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3450         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3451         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3452         of parenthesized subpatterns.         of parenthesized subpatterns.
3453    
3454         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
3455         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3456         up to three octal digits following the backslash, and generates a  sin-         up to three octal digits following the backslash, and uses them to gen-
3457         gle byte from the least significant 8 bits of the value. Any subsequent         erate a data character. Any subsequent digits stand for themselves.  In
3458         digits stand for themselves.  For example:         non-UTF-8  mode,  the  value  of a character specified in octal must be
3459           less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
3460           example:
3461    
3462           \040   is another way of writing a space           \040   is another way of writing a space
3463           \40    is the same, provided there are fewer than 40           \40    is the same, provided there are fewer than 40
# Line 2535  BACKSLASH Line 3474  BACKSLASH
3474           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3475                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3476    
3477         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
3478         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3479    
3480         All  the  sequences  that  define a single byte value or a single UTF-8         All the sequences that define a single character value can be used both
3481         character (in UTF-8 mode) can be used both inside and outside character         inside  and  outside character classes. In addition, inside a character
3482         classes.  In  addition,  inside  a  character class, the sequence \b is         class, the sequence \b is interpreted as the backspace  character  (hex
3483         interpreted as the backspace character (hex 08), and the sequence \X is         08).  The sequences \B, \N, \R, and \X are not special inside a charac-
3484         interpreted  as  the  character  "X".  Outside a character class, these         ter class. Like any  other  unrecognized  escape  sequences,  they  are
3485         sequences have different meanings (see below).         treated  as  the  literal characters "B", "N", "R", and "X" by default,
3486           but cause an error if the PCRE_EXTRA option is set. Outside a character
3487           class, these sequences have different meanings.
3488    
3489       Absolute and relative back references
3490