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1    -----------------------------------------------------------------------------
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
 NAME  
      PCRE - Perl-compatible regular expressions  
10    
11    PCRE(3)                    Library Functions Manual                    PCRE(3)
12    
13    
14    
15    NAME
16           PCRE - Perl-compatible regular expressions
17    
18    INTRODUCTION
19    
20           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
22           just  a few differences. Some features that appeared in Python and PCRE
23           before they appeared in Perl are also available using the  Python  syn-
24           tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26           give better JavaScript compatibility.
27    
28           Starting with release 8.30, it is possible to compile two separate PCRE
29           libraries:  the  original,  which  supports  8-bit  character   strings
30           (including  UTF-8  strings),  and a second library that supports 16-bit
31           character strings (including UTF-16 strings). The build process  allows
32           either  one  or both to be built. The majority of the work to make this
33           possible was done by Zoltan Herczeg.
34    
35           Starting with release 8.32 it is possible to compile a  third  separate
36           PCRE  library  that supports 32-bit character strings (including UTF-32
37           strings). The build process allows any combination of the 8-,  16-  and
38           32-bit  libraries. The work to make this possible was done by Christian
39           Persch.
40    
41           The three libraries contain identical sets of  functions,  except  that
42           the  names  in  the 16-bit library start with pcre16_ instead of pcre_,
43           and the names in the 32-bit  library  start  with  pcre32_  instead  of
44           pcre_.  To avoid over-complication and reduce the documentation mainte-
45           nance load, most of the documentation describes the 8-bit library, with
46           the  differences  for  the  16-bit and 32-bit libraries described sepa-
47           rately in the pcre16 and  pcre32  pages.  References  to  functions  or
48           structures  of  the  form  pcre[16|32]_xxx  should  be  read as meaning
49           "pcre_xxx when using the  8-bit  library,  pcre16_xxx  when  using  the
50           16-bit library, or pcre32_xxx when using the 32-bit library".
51    
52           The  current implementation of PCRE corresponds approximately with Perl
53           5.12, including support for UTF-8/16/32  encoded  strings  and  Unicode
54           general  category  properties. However, UTF-8/16/32 and Unicode support
55           has to be explicitly enabled; it is not the default. The Unicode tables
56           correspond to Unicode release 6.3.0.
57    
58           In  addition to the Perl-compatible matching function, PCRE contains an
59           alternative function that matches the same compiled patterns in a  dif-
60           ferent way. In certain circumstances, the alternative function has some
61           advantages.  For a discussion of the two matching algorithms,  see  the
62           pcrematching page.
63    
64           PCRE  is  written  in C and released as a C library. A number of people
65           have written wrappers and interfaces of various kinds.  In  particular,
66           Google  Inc.   have  provided a comprehensive C++ wrapper for the 8-bit
67           library. This is now included as part of  the  PCRE  distribution.  The
68           pcrecpp  page  has  details of this interface. Other people's contribu-
69           tions can be found in the Contrib directory at the  primary  FTP  site,
70           which is:
71    
72           ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
73    
74           Details  of  exactly which Perl regular expression features are and are
75           not supported by PCRE are given in separate documents. See the pcrepat-
76           tern  and pcrecompat pages. There is a syntax summary in the pcresyntax
77           page.
78    
79           Some features of PCRE can be included, excluded, or  changed  when  the
80           library  is  built.  The pcre_config() function makes it possible for a
81           client to discover which features are  available.  The  features  them-
82           selves  are described in the pcrebuild page. Documentation about build-
83           ing PCRE for various operating systems can be found in the  README  and
84           NON-AUTOTOOLS_BUILD files in the source distribution.
85    
86           The  libraries contains a number of undocumented internal functions and
87           data tables that are used by more than one  of  the  exported  external
88           functions,  but  which  are  not  intended for use by external callers.
89           Their names all begin with "_pcre_" or "_pcre16_" or "_pcre32_",  which
90           hopefully  will  not provoke any name clashes. In some environments, it
91           is possible to control which  external  symbols  are  exported  when  a
92           shared  library  is  built, and in these cases the undocumented symbols
93           are not exported.
94    
95    
96    SECURITY CONSIDERATIONS
97    
98           If you are using PCRE in a non-UTF application that  permits  users  to
99           supply  arbitrary  patterns  for  compilation, you should be aware of a
100           feature that allows users to turn on UTF support from within a pattern,
101           provided  that  PCRE  was built with UTF support. For example, an 8-bit
102           pattern that begins with "(*UTF8)" or "(*UTF)"  turns  on  UTF-8  mode,
103           which  interprets  patterns and subjects as strings of UTF-8 characters
104           instead of individual 8-bit characters.  This causes both  the  pattern
105           and any data against which it is matched to be checked for UTF-8 valid-
106           ity. If the data string is very long, such a  check  might  use  suffi-
107           ciently  many  resources  as  to cause your application to lose perfor-
108           mance.
109    
110           One  way  of  guarding  against  this  possibility  is   to   use   the
111           pcre_fullinfo()  function  to  check the compiled pattern's options for
112           UTF.  Alternatively, from release 8.33, you can set the  PCRE_NEVER_UTF
113           option  at compile time. This causes an compile time error if a pattern
114           contains a UTF-setting sequence.
115    
116           If your application is one that supports UTF, be  aware  that  validity
117           checking  can  take time. If the same data string is to be matched many
118           times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second
119           and subsequent matches to save redundant checks.
120    
121           Another  way  that  performance can be hit is by running a pattern that
122           has a very large search tree against a string that  will  never  match.
123           Nested  unlimited  repeats in a pattern are a common example. PCRE pro-
124           vides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT fea-
125           ture in the pcreapi page.
126    
127    
128    USER DOCUMENTATION
129    
130           The  user  documentation  for PCRE comprises a number of different sec-
131           tions. In the "man" format, each of these is a separate "man page".  In
132           the  HTML  format, each is a separate page, linked from the index page.
133           In the plain text format, all the sections, except  the  pcredemo  sec-
134           tion, are concatenated, for ease of searching. The sections are as fol-
135           lows:
136    
137             pcre              this document
138             pcre-config       show PCRE installation configuration information
139             pcre16            details of the 16-bit library
140             pcre32            details of the 32-bit library
141             pcreapi           details of PCRE's native C API
142             pcrebuild         building PCRE
143             pcrecallout       details of the callout feature
144             pcrecompat        discussion of Perl compatibility
145             pcrecpp           details of the C++ wrapper for the 8-bit library
146             pcredemo          a demonstration C program that uses PCRE
147             pcregrep          description of the pcregrep command (8-bit only)
148             pcrejit           discussion of the just-in-time optimization support
149             pcrelimits        details of size and other limits
150             pcrematching      discussion of the two matching algorithms
151             pcrepartial       details of the partial matching facility
152             pcrepattern       syntax and semantics of supported
153                                 regular expressions
154             pcreperform       discussion of performance issues
155             pcreposix         the POSIX-compatible C API for the 8-bit library
156             pcreprecompile    details of saving and re-using precompiled patterns
157             pcresample        discussion of the pcredemo program
158             pcrestack         discussion of stack usage
159             pcresyntax        quick syntax reference
160             pcretest          description of the pcretest testing command
161             pcreunicode       discussion of Unicode and UTF-8/16/32 support
162    
163           In addition, in the "man" and HTML formats, there is a short  page  for
164           each C library function, listing its arguments and results.
165    
166    
167    AUTHOR
168    
169           Philip Hazel
170           University Computing Service
171           Cambridge CB2 3QH, England.
172    
173           Putting  an actual email address here seems to have been a spam magnet,
174           so I've taken it away. If you want to email me, use  my  two  initials,
175           followed by the two digits 10, at the domain cam.ac.uk.
176    
177    
178    REVISION
179    
180           Last updated: 13 May 2013
181           Copyright (c) 1997-2013 University of Cambridge.
182    ------------------------------------------------------------------------------
183    
184    
185    PCRE(3)                    Library Functions Manual                    PCRE(3)
186    
187    
188    
189    NAME
190           PCRE - Perl-compatible regular expressions
191    
192           #include <pcre.h>
193    
194    
195    PCRE 16-BIT API BASIC FUNCTIONS
196    
197           pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
198                const char **errptr, int *erroffset,
199                const unsigned char *tableptr);
200    
201           pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
202                int *errorcodeptr,
203                const char **errptr, int *erroffset,
204                const unsigned char *tableptr);
205    
206           pcre16_extra *pcre16_study(const pcre16 *code, int options,
207                const char **errptr);
208    
209           void pcre16_free_study(pcre16_extra *extra);
210    
211           int pcre16_exec(const pcre16 *code, const pcre16_extra *extra,
212                PCRE_SPTR16 subject, int length, int startoffset,
213                int options, int *ovector, int ovecsize);
214    
215           int pcre16_dfa_exec(const pcre16 *code, const pcre16_extra *extra,
216                PCRE_SPTR16 subject, int length, int startoffset,
217                int options, int *ovector, int ovecsize,
218                int *workspace, int wscount);
219    
220    
221    PCRE 16-BIT API STRING EXTRACTION FUNCTIONS
222    
223           int pcre16_copy_named_substring(const pcre16 *code,
224                PCRE_SPTR16 subject, int *ovector,
225                int stringcount, PCRE_SPTR16 stringname,
226                PCRE_UCHAR16 *buffer, int buffersize);
227    
228           int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
229                int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
230                int buffersize);
231    
232           int pcre16_get_named_substring(const pcre16 *code,
233                PCRE_SPTR16 subject, int *ovector,
234                int stringcount, PCRE_SPTR16 stringname,
235                PCRE_SPTR16 *stringptr);
236    
237           int pcre16_get_stringnumber(const pcre16 *code,
238                PCRE_SPTR16 name);
239    
240           int pcre16_get_stringtable_entries(const pcre16 *code,
241                PCRE_SPTR16 name, PCRE_UCHAR16 **first, PCRE_UCHAR16 **last);
242    
243           int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
244                int stringcount, int stringnumber,
245                PCRE_SPTR16 *stringptr);
246    
247           int pcre16_get_substring_list(PCRE_SPTR16 subject,
248                int *ovector, int stringcount, PCRE_SPTR16 **listptr);
249    
250           void pcre16_free_substring(PCRE_SPTR16 stringptr);
251    
252           void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);
253    
254    
255    PCRE 16-BIT API AUXILIARY FUNCTIONS
256    
257           pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);
258    
259           void pcre16_jit_stack_free(pcre16_jit_stack *stack);
260    
261           void pcre16_assign_jit_stack(pcre16_extra *extra,
262                pcre16_jit_callback callback, void *data);
263    
264           const unsigned char *pcre16_maketables(void);
265    
266           int pcre16_fullinfo(const pcre16 *code, const pcre16_extra *extra,
267                int what, void *where);
268    
269           int pcre16_refcount(pcre16 *code, int adjust);
270    
271           int pcre16_config(int what, void *where);
272    
273           const char *pcre16_version(void);
274    
275           int pcre16_pattern_to_host_byte_order(pcre16 *code,
276                pcre16_extra *extra, const unsigned char *tables);
277    
278    
279    PCRE 16-BIT API INDIRECTED FUNCTIONS
280    
281           void *(*pcre16_malloc)(size_t);
282    
283           void (*pcre16_free)(void *);
284    
285           void *(*pcre16_stack_malloc)(size_t);
286    
287           void (*pcre16_stack_free)(void *);
288    
289           int (*pcre16_callout)(pcre16_callout_block *);
290    
291    
292    PCRE 16-BIT API 16-BIT-ONLY FUNCTION
293    
294           int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
295                PCRE_SPTR16 input, int length, int *byte_order,
296                int keep_boms);
297    
298    
299    THE PCRE 16-BIT LIBRARY
300    
301           Starting  with  release  8.30, it is possible to compile a PCRE library
302           that supports 16-bit character strings, including  UTF-16  strings,  as
303           well  as  or instead of the original 8-bit library. The majority of the
304           work to make  this  possible  was  done  by  Zoltan  Herczeg.  The  two
305           libraries contain identical sets of functions, used in exactly the same
306           way. Only the names of the functions and the data types of their  argu-
307           ments  and results are different. To avoid over-complication and reduce
308           the documentation maintenance load,  most  of  the  PCRE  documentation
309           describes  the  8-bit  library,  with only occasional references to the
310           16-bit library. This page describes what is different when you use  the
311           16-bit library.
312    
313           WARNING:  A  single  application can be linked with both libraries, but
314           you must take care when processing any particular pattern to use  func-
315           tions  from  just one library. For example, if you want to study a pat-
316           tern that was compiled with  pcre16_compile(),  you  must  do  so  with
317           pcre16_study(), not pcre_study(), and you must free the study data with
318           pcre16_free_study().
319    
320    
321    THE HEADER FILE
322    
323           There is only one header file, pcre.h. It contains prototypes  for  all
324           the functions in all libraries, as well as definitions of flags, struc-
325           tures, error codes, etc.
326    
327    
328    THE LIBRARY NAME
329    
330           In Unix-like systems, the 16-bit library is called libpcre16,  and  can
331           normally  be  accesss  by adding -lpcre16 to the command for linking an
332           application that uses PCRE.
333    
334    
335    STRING TYPES
336    
337           In the 8-bit library, strings are passed to PCRE library  functions  as
338           vectors  of  bytes  with  the  C  type "char *". In the 16-bit library,
339           strings are passed as vectors of unsigned 16-bit quantities. The  macro
340           PCRE_UCHAR16  specifies  an  appropriate  data type, and PCRE_SPTR16 is
341           defined as "const PCRE_UCHAR16 *". In very  many  environments,  "short
342           int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
343           as "unsigned short int", but checks that it really  is  a  16-bit  data
344           type.  If  it is not, the build fails with an error message telling the
345           maintainer to modify the definition appropriately.
346    
347    
348    STRUCTURE TYPES
349    
350           The types of the opaque structures that are used  for  compiled  16-bit
351           patterns  and  JIT stacks are pcre16 and pcre16_jit_stack respectively.
352           The  type  of  the  user-accessible  structure  that  is  returned   by
353           pcre16_study()  is  pcre16_extra, and the type of the structure that is
354           used for passing data to a callout  function  is  pcre16_callout_block.
355           These structures contain the same fields, with the same names, as their
356           8-bit counterparts. The only difference is that pointers  to  character
357           strings are 16-bit instead of 8-bit types.
358    
359    
360    16-BIT FUNCTIONS
361    
362           For  every function in the 8-bit library there is a corresponding func-
363           tion in the 16-bit library with a name that starts with pcre16_ instead
364           of  pcre_.  The  prototypes are listed above. In addition, there is one
365           extra function, pcre16_utf16_to_host_byte_order(). This  is  a  utility
366           function  that converts a UTF-16 character string to host byte order if
367           necessary. The other 16-bit  functions  expect  the  strings  they  are
368           passed to be in host byte order.
369    
370           The input and output arguments of pcre16_utf16_to_host_byte_order() may
371           point to the same address, that is, conversion in place  is  supported.
372           The output buffer must be at least as long as the input.
373    
374           The  length  argument  specifies the number of 16-bit data units in the
375           input string; a negative value specifies a zero-terminated string.
376    
377           If byte_order is NULL, it is assumed that the string starts off in host
378           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
379           the string (commonly as the first character).
380    
381           If byte_order is not NULL, a non-zero value of the integer to which  it
382           points  means  that  the input starts off in host byte order, otherwise
383           the opposite order is assumed. Again, BOMs in  the  string  can  change
384           this. The final byte order is passed back at the end of processing.
385    
386           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
387           copied into the output string. Otherwise they are discarded.
388    
389           The result of the function is the number of 16-bit  units  placed  into
390           the  output  buffer,  including  the  zero terminator if the string was
391           zero-terminated.
392    
393    
394    SUBJECT STRING OFFSETS
395    
396           The lengths and starting offsets of subject strings must  be  specified
397           in  16-bit  data units, and the offsets within subject strings that are
398           returned by the matching functions are in also 16-bit units rather than
399           bytes.
400    
401    
402    NAMED SUBPATTERNS
403    
404           The  name-to-number translation table that is maintained for named sub-
405           patterns uses 16-bit characters.  The  pcre16_get_stringtable_entries()
406           function returns the length of each entry in the table as the number of
407           16-bit data units.
408    
409    
410    OPTION NAMES
411    
412           There   are   two   new   general   option   names,   PCRE_UTF16    and
413           PCRE_NO_UTF16_CHECK,     which     correspond    to    PCRE_UTF8    and
414           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
415           define  the  same bits in the options word. There is a discussion about
416           the validity of UTF-16 strings in the pcreunicode page.
417    
418           For the pcre16_config() function there is an  option  PCRE_CONFIG_UTF16
419           that  returns  1  if UTF-16 support is configured, otherwise 0. If this
420           option  is  given  to  pcre_config()  or  pcre32_config(),  or  if  the
421           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF32  option is given to pcre16_con-
422           fig(), the result is the PCRE_ERROR_BADOPTION error.
423    
424    
425    CHARACTER CODES
426    
427           In 16-bit mode, when  PCRE_UTF16  is  not  set,  character  values  are
428           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
429           that they can range from 0 to 0xffff instead of 0  to  0xff.  Character
430           types  for characters less than 0xff can therefore be influenced by the
431           locale in the same way as before.  Characters greater  than  0xff  have
432           only one case, and no "type" (such as letter or digit).
433    
434           In  UTF-16  mode,  the  character  code  is  Unicode, in the range 0 to
435           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
436           because  those  are "surrogate" values that are used in pairs to encode
437           values greater than 0xffff.
438    
439           A UTF-16 string can indicate its endianness by special code knows as  a
440           byte-order mark (BOM). The PCRE functions do not handle this, expecting
441           strings  to  be  in  host  byte  order.  A  utility   function   called
442           pcre16_utf16_to_host_byte_order()  is  provided  to help with this (see
443           above).
444    
445    
446    ERROR NAMES
447    
448           The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16  corre-
449           spond  to  their  8-bit  counterparts.  The error PCRE_ERROR_BADMODE is
450           given when a compiled pattern is passed to a  function  that  processes
451           patterns  in  the  other  mode, for example, if a pattern compiled with
452           pcre_compile() is passed to pcre16_exec().
453    
454           There are new error codes whose names  begin  with  PCRE_UTF16_ERR  for
455           invalid  UTF-16  strings,  corresponding to the PCRE_UTF8_ERR codes for
456           UTF-8 strings that are described in the section entitled "Reason  codes
457           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
458           are:
459    
460             PCRE_UTF16_ERR1  Missing low surrogate at end of string
461             PCRE_UTF16_ERR2  Invalid low surrogate follows high surrogate
462             PCRE_UTF16_ERR3  Isolated low surrogate
463             PCRE_UTF16_ERR4  Non-character
464    
465    
466    ERROR TEXTS
467    
468           If there is an error while compiling a pattern, the error text that  is
469           passed  back by pcre16_compile() or pcre16_compile2() is still an 8-bit
470           character string, zero-terminated.
471    
472    
473    CALLOUTS
474    
475           The subject and mark fields in the callout block that is  passed  to  a
476           callout function point to 16-bit vectors.
477    
478    
479    TESTING
480    
481           The  pcretest  program continues to operate with 8-bit input and output
482           files, but it can be used for testing the 16-bit library. If it is  run
483           with the command line option -16, patterns and subject strings are con-
484           verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
485           library  functions  are used instead of the 8-bit ones. Returned 16-bit
486           strings are converted to 8-bit for output. If both the  8-bit  and  the
487           32-bit libraries were not compiled, pcretest defaults to 16-bit and the
488           -16 option is ignored.
489    
490           When PCRE is being built, the RunTest script that is  called  by  "make
491           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
492           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
493           priately.
494    
495    
496    NOT SUPPORTED IN 16-BIT MODE
497    
498           Not all the features of the 8-bit library are available with the 16-bit
499           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
500           library, and the pcregrep program is at present 8-bit only.
501    
502    
503    AUTHOR
504    
505           Philip Hazel
506           University Computing Service
507           Cambridge CB2 3QH, England.
508    
509    
510    REVISION
511    
512           Last updated: 12 May 2013
513           Copyright (c) 1997-2013 University of Cambridge.
514    ------------------------------------------------------------------------------
515    
516    
517    PCRE(3)                    Library Functions Manual                    PCRE(3)
518    
519    
520    
521    NAME
522           PCRE - Perl-compatible regular expressions
523    
524           #include <pcre.h>
525    
526    
527    PCRE 32-BIT API BASIC FUNCTIONS
528    
529           pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options,
530                const char **errptr, int *erroffset,
531                const unsigned char *tableptr);
532    
533           pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options,
534                int *errorcodeptr,
535                const unsigned char *tableptr);
536    
537           pcre32_extra *pcre32_study(const pcre32 *code, int options,
538                const char **errptr);
539    
540           void pcre32_free_study(pcre32_extra *extra);
541    
542           int pcre32_exec(const pcre32 *code, const pcre32_extra *extra,
543                PCRE_SPTR32 subject, int length, int startoffset,
544                int options, int *ovector, int ovecsize);
545    
546           int pcre32_dfa_exec(const pcre32 *code, const pcre32_extra *extra,
547                PCRE_SPTR32 subject, int length, int startoffset,
548                int options, int *ovector, int ovecsize,
549                int *workspace, int wscount);
550    
551    
552    PCRE 32-BIT API STRING EXTRACTION FUNCTIONS
553    
554           int pcre32_copy_named_substring(const pcre32 *code,
555                PCRE_SPTR32 subject, int *ovector,
556                int stringcount, PCRE_SPTR32 stringname,
557                PCRE_UCHAR32 *buffer, int buffersize);
558    
559           int pcre32_copy_substring(PCRE_SPTR32 subject, int *ovector,
560                int stringcount, int stringnumber, PCRE_UCHAR32 *buffer,
561                int buffersize);
562    
563           int pcre32_get_named_substring(const pcre32 *code,
564                PCRE_SPTR32 subject, int *ovector,
565                int stringcount, PCRE_SPTR32 stringname,
566                PCRE_SPTR32 *stringptr);
567    
568           int pcre32_get_stringnumber(const pcre32 *code,
569                PCRE_SPTR32 name);
570    
571           int pcre32_get_stringtable_entries(const pcre32 *code,
572                PCRE_SPTR32 name, PCRE_UCHAR32 **first, PCRE_UCHAR32 **last);
573    
574           int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector,
575                int stringcount, int stringnumber,
576                PCRE_SPTR32 *stringptr);
577    
578           int pcre32_get_substring_list(PCRE_SPTR32 subject,
579                int *ovector, int stringcount, PCRE_SPTR32 **listptr);
580    
581           void pcre32_free_substring(PCRE_SPTR32 stringptr);
582    
583           void pcre32_free_substring_list(PCRE_SPTR32 *stringptr);
584    
585    
586    PCRE 32-BIT API AUXILIARY FUNCTIONS
587    
588           pcre32_jit_stack *pcre32_jit_stack_alloc(int startsize, int maxsize);
589    
590           void pcre32_jit_stack_free(pcre32_jit_stack *stack);
591    
592           void pcre32_assign_jit_stack(pcre32_extra *extra,
593                pcre32_jit_callback callback, void *data);
594    
595           const unsigned char *pcre32_maketables(void);
596    
597           int pcre32_fullinfo(const pcre32 *code, const pcre32_extra *extra,
598                int what, void *where);
599    
600           int pcre32_refcount(pcre32 *code, int adjust);
601    
602           int pcre32_config(int what, void *where);
603    
604           const char *pcre32_version(void);
605    
606           int pcre32_pattern_to_host_byte_order(pcre32 *code,
607                pcre32_extra *extra, const unsigned char *tables);
608    
609    
610    PCRE 32-BIT API INDIRECTED FUNCTIONS
611    
612           void *(*pcre32_malloc)(size_t);
613    
614           void (*pcre32_free)(void *);
615    
616           void *(*pcre32_stack_malloc)(size_t);
617    
618           void (*pcre32_stack_free)(void *);
619    
620           int (*pcre32_callout)(pcre32_callout_block *);
621    
622    
623    PCRE 32-BIT API 32-BIT-ONLY FUNCTION
624    
625           int pcre32_utf32_to_host_byte_order(PCRE_UCHAR32 *output,
626                PCRE_SPTR32 input, int length, int *byte_order,
627                int keep_boms);
628    
629    
630    THE PCRE 32-BIT LIBRARY
631    
632           Starting  with  release  8.32, it is possible to compile a PCRE library
633           that supports 32-bit character strings, including  UTF-32  strings,  as
634           well as or instead of the original 8-bit library. This work was done by
635           Christian Persch, based on the work done  by  Zoltan  Herczeg  for  the
636           16-bit  library.  All  three  libraries contain identical sets of func-
637           tions, used in exactly the same way.  Only the names of  the  functions
638           and  the  data  types  of their arguments and results are different. To
639           avoid over-complication and reduce the documentation maintenance  load,
640           most  of  the PCRE documentation describes the 8-bit library, with only
641           occasional references to the 16-bit and  32-bit  libraries.  This  page
642           describes what is different when you use the 32-bit library.
643    
644           WARNING:  A  single  application  can  be linked with all or any of the
645           three libraries, but you must take care when processing any  particular
646           pattern  to  use  functions  from just one library. For example, if you
647           want to study a pattern that was compiled  with  pcre32_compile(),  you
648           must do so with pcre32_study(), not pcre_study(), and you must free the
649           study data with pcre32_free_study().
650    
651    
652    THE HEADER FILE
653    
654           There is only one header file, pcre.h. It contains prototypes  for  all
655           the functions in all libraries, as well as definitions of flags, struc-
656           tures, error codes, etc.
657    
658    
659    THE LIBRARY NAME
660    
661           In Unix-like systems, the 32-bit library is called libpcre32,  and  can
662           normally  be  accesss  by adding -lpcre32 to the command for linking an
663           application that uses PCRE.
664    
665    
666    STRING TYPES
667    
668           In the 8-bit library, strings are passed to PCRE library  functions  as
669           vectors  of  bytes  with  the  C  type "char *". In the 32-bit library,
670           strings are passed as vectors of unsigned 32-bit quantities. The  macro
671           PCRE_UCHAR32  specifies  an  appropriate  data type, and PCRE_SPTR32 is
672           defined as "const PCRE_UCHAR32 *". In very many environments, "unsigned
673           int" is a 32-bit data type. When PCRE is built, it defines PCRE_UCHAR32
674           as "unsigned int", but checks that it really is a 32-bit data type.  If
675           it is not, the build fails with an error message telling the maintainer
676           to modify the definition appropriately.
677    
678    
679    STRUCTURE TYPES
680    
681           The types of the opaque structures that are used  for  compiled  32-bit
682           patterns  and  JIT stacks are pcre32 and pcre32_jit_stack respectively.
683           The  type  of  the  user-accessible  structure  that  is  returned   by
684           pcre32_study()  is  pcre32_extra, and the type of the structure that is
685           used for passing data to a callout  function  is  pcre32_callout_block.
686           These structures contain the same fields, with the same names, as their
687           8-bit counterparts. The only difference is that pointers  to  character
688           strings are 32-bit instead of 8-bit types.
689    
690    
691    32-BIT FUNCTIONS
692    
693           For  every function in the 8-bit library there is a corresponding func-
694           tion in the 32-bit library with a name that starts with pcre32_ instead
695           of  pcre_.  The  prototypes are listed above. In addition, there is one
696           extra function, pcre32_utf32_to_host_byte_order(). This  is  a  utility
697           function  that converts a UTF-32 character string to host byte order if
698           necessary. The other 32-bit  functions  expect  the  strings  they  are
699           passed to be in host byte order.
700    
701           The input and output arguments of pcre32_utf32_to_host_byte_order() may
702           point to the same address, that is, conversion in place  is  supported.
703           The output buffer must be at least as long as the input.
704    
705           The  length  argument  specifies the number of 32-bit data units in the
706           input string; a negative value specifies a zero-terminated string.
707    
708           If byte_order is NULL, it is assumed that the string starts off in host
709           byte  order. This may be changed by byte-order marks (BOMs) anywhere in
710           the string (commonly as the first character).
711    
712           If byte_order is not NULL, a non-zero value of the integer to which  it
713           points  means  that  the input starts off in host byte order, otherwise
714           the opposite order is assumed. Again, BOMs in  the  string  can  change
715           this. The final byte order is passed back at the end of processing.
716    
717           If  keep_boms  is  not  zero,  byte-order  mark characters (0xfeff) are
718           copied into the output string. Otherwise they are discarded.
719    
720           The result of the function is the number of 32-bit  units  placed  into
721           the  output  buffer,  including  the  zero terminator if the string was
722           zero-terminated.
723    
724    
725    SUBJECT STRING OFFSETS
726    
727           The lengths and starting offsets of subject strings must  be  specified
728           in  32-bit  data units, and the offsets within subject strings that are
729           returned by the matching functions are in also 32-bit units rather than
730           bytes.
731    
732    
733    NAMED SUBPATTERNS
734    
735           The  name-to-number translation table that is maintained for named sub-
736           patterns uses 32-bit characters.  The  pcre32_get_stringtable_entries()
737           function returns the length of each entry in the table as the number of
738           32-bit data units.
739    
740    
741    OPTION NAMES
742    
743           There   are   two   new   general   option   names,   PCRE_UTF32    and
744           PCRE_NO_UTF32_CHECK,     which     correspond    to    PCRE_UTF8    and
745           PCRE_NO_UTF8_CHECK in the 8-bit library. In  fact,  these  new  options
746           define  the  same bits in the options word. There is a discussion about
747           the validity of UTF-32 strings in the pcreunicode page.
748    
749           For the pcre32_config() function there is an  option  PCRE_CONFIG_UTF32
750           that  returns  1  if UTF-32 support is configured, otherwise 0. If this
751           option  is  given  to  pcre_config()  or  pcre16_config(),  or  if  the
752           PCRE_CONFIG_UTF8  or  PCRE_CONFIG_UTF16  option is given to pcre32_con-
753           fig(), the result is the PCRE_ERROR_BADOPTION error.
754    
755    
756    CHARACTER CODES
757    
758           In 32-bit mode, when  PCRE_UTF32  is  not  set,  character  values  are
759           treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
760           that they can range from 0 to 0x7fffffff instead of 0 to 0xff.  Charac-
761           ter  types for characters less than 0xff can therefore be influenced by
762           the locale in the same way as before.   Characters  greater  than  0xff
763           have only one case, and no "type" (such as letter or digit).
764    
765           In  UTF-32  mode,  the  character  code  is  Unicode, in the range 0 to
766           0x10ffff, with the exception of values in the range  0xd800  to  0xdfff
767           because those are "surrogate" values that are ill-formed in UTF-32.
768    
769           A  UTF-32 string can indicate its endianness by special code knows as a
770           byte-order mark (BOM). The PCRE functions do not handle this, expecting
771           strings   to   be  in  host  byte  order.  A  utility  function  called
772           pcre32_utf32_to_host_byte_order() is provided to help  with  this  (see
773           above).
774    
775    
776    ERROR NAMES
777    
778           The  error  PCRE_ERROR_BADUTF32  corresponds  to its 8-bit counterpart.
779           The error PCRE_ERROR_BADMODE is given when a compiled pattern is passed
780           to  a  function that processes patterns in the other mode, for example,
781           if a pattern compiled with pcre_compile() is passed to pcre32_exec().
782    
783           There are new error codes whose names  begin  with  PCRE_UTF32_ERR  for
784           invalid  UTF-32  strings,  corresponding to the PCRE_UTF8_ERR codes for
785           UTF-8 strings that are described in the section entitled "Reason  codes
786           for  invalid UTF-8 strings" in the main pcreapi page. The UTF-32 errors
787           are:
788    
789             PCRE_UTF32_ERR1  Surrogate character (range from 0xd800 to 0xdfff)
790             PCRE_UTF32_ERR2  Non-character
791             PCRE_UTF32_ERR3  Character > 0x10ffff
792    
793    
794    ERROR TEXTS
795    
796           If there is an error while compiling a pattern, the error text that  is
797           passed  back by pcre32_compile() or pcre32_compile2() is still an 8-bit
798           character string, zero-terminated.
799    
800    
801    CALLOUTS
802    
803           The subject and mark fields in the callout block that is  passed  to  a
804           callout function point to 32-bit vectors.
805    
806    
807    TESTING
808    
809           The  pcretest  program continues to operate with 8-bit input and output
810           files, but it can be used for testing the 32-bit library. If it is  run
811           with the command line option -32, patterns and subject strings are con-
812           verted from 8-bit to 32-bit before being passed to PCRE, and the 32-bit
813           library  functions  are used instead of the 8-bit ones. Returned 32-bit
814           strings are converted to 8-bit for output. If both the  8-bit  and  the
815           16-bit libraries were not compiled, pcretest defaults to 32-bit and the
816           -32 option is ignored.
817    
818           When PCRE is being built, the RunTest script that is  called  by  "make
819           check"  uses  the  pcretest  -C  option to discover which of the 8-bit,
820           16-bit and 32-bit libraries has been built, and runs the  tests  appro-
821           priately.
822    
823    
824    NOT SUPPORTED IN 32-BIT MODE
825    
826           Not all the features of the 8-bit library are available with the 32-bit
827           library. The C++ and POSIX wrapper functions  support  only  the  8-bit
828           library, and the pcregrep program is at present 8-bit only.
829    
830    
831    AUTHOR
832    
833           Philip Hazel
834           University Computing Service
835           Cambridge CB2 3QH, England.
836    
837    
838    REVISION
839    
840           Last updated: 12 May 2013
841           Copyright (c) 1997-2013 University of Cambridge.
842    ------------------------------------------------------------------------------
843    
844    
845    PCREBUILD(3)               Library Functions Manual               PCREBUILD(3)
846    
847    
848    
849    NAME
850           PCRE - Perl-compatible regular expressions
851    
852    BUILDING PCRE
853    
854           PCRE  is  distributed with a configure script that can be used to build
855           the library in Unix-like environments using the applications  known  as
856           Autotools.   Also  in  the  distribution  are files to support building
857           using CMake instead of configure. The text file README contains general
858           information  about  building  with Autotools (some of which is repeated
859           below), and also has some comments about building on various  operating
860           systems.  There  is  a lot more information about building PCRE without
861           using Autotools (including information about using CMake  and  building
862           "by  hand")  in  the  text file called NON-AUTOTOOLS-BUILD.  You should
863           consult this file as well as the README file if you are building  in  a
864           non-Unix-like environment.
865    
866    
867    PCRE BUILD-TIME OPTIONS
868    
869           The  rest of this document describes the optional features of PCRE that
870           can be selected when the library is compiled. It  assumes  use  of  the
871           configure  script,  where  the  optional features are selected or dese-
872           lected by providing options to configure before running the  make  com-
873           mand.  However,  the same options can be selected in both Unix-like and
874           non-Unix-like environments using the GUI facility of cmake-gui  if  you
875           are using CMake instead of configure to build PCRE.
876    
877           If  you  are not using Autotools or CMake, option selection can be done
878           by editing the config.h file, or by passing parameter settings  to  the
879           compiler, as described in NON-AUTOTOOLS-BUILD.
880    
881           The complete list of options for configure (which includes the standard
882           ones such as the  selection  of  the  installation  directory)  can  be
883           obtained by running
884    
885             ./configure --help
886    
887           The  following  sections  include  descriptions  of options whose names
888           begin with --enable or --disable. These settings specify changes to the
889           defaults  for  the configure command. Because of the way that configure
890           works, --enable and --disable always come in pairs, so  the  complemen-
891           tary  option always exists as well, but as it specifies the default, it
892           is not described.
893    
894    
895    BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES
896    
897           By default, a library called libpcre  is  built,  containing  functions
898           that  take  string  arguments  contained in vectors of bytes, either as
899           single-byte characters, or interpreted as UTF-8 strings. You  can  also
900           build  a  separate library, called libpcre16, in which strings are con-
901           tained in vectors of 16-bit data units and interpreted either  as  sin-
902           gle-unit characters or UTF-16 strings, by adding
903    
904             --enable-pcre16
905    
906           to  the  configure  command.  You  can  also build yet another separate
907           library, called libpcre32, in which strings are contained in vectors of
908           32-bit  data  units and interpreted either as single-unit characters or
909           UTF-32 strings, by adding
910    
911             --enable-pcre32
912    
913           to the configure command. If you do not want the 8-bit library, add
914    
915             --disable-pcre8
916    
917           as well. At least one of the three libraries must be built.  Note  that
918           the  C++  and  POSIX  wrappers are for the 8-bit library only, and that
919           pcregrep is an 8-bit program. None of these are  built  if  you  select
920           only the 16-bit or 32-bit libraries.
921    
922    
923    BUILDING SHARED AND STATIC LIBRARIES
924    
925           The  Autotools  PCRE building process uses libtool to build both shared
926           and static libraries by default. You  can  suppress  one  of  these  by
927           adding one of
928    
929             --disable-shared
930             --disable-static
931    
932           to the configure command, as required.
933    
934    
935    C++ SUPPORT
936    
937           By  default,  if the 8-bit library is being built, the configure script
938           will search for a C++ compiler and C++ header files. If it finds  them,
939           it  automatically  builds  the C++ wrapper library (which supports only
940           8-bit strings). You can disable this by adding
941    
942             --disable-cpp
943    
944           to the configure command.
945    
946    
947    UTF-8, UTF-16 AND UTF-32 SUPPORT
948    
949           To build PCRE with support for UTF Unicode character strings, add
950    
951             --enable-utf
952    
953           to the configure command. This setting applies to all three  libraries,
954           adding  support  for  UTF-8 to the 8-bit library, support for UTF-16 to
955           the 16-bit library, and  support  for  UTF-32  to  the  to  the  32-bit
956           library.  There  are no separate options for enabling UTF-8, UTF-16 and
957           UTF-32 independently because that would allow ridiculous settings  such
958           as  requesting UTF-16 support while building only the 8-bit library. It
959           is not possible to build one library with UTF support and another with-
960           out  in the same configuration. (For backwards compatibility, --enable-
961           utf8 is a synonym of --enable-utf.)
962    
963           Of itself, this setting does not make  PCRE  treat  strings  as  UTF-8,
964           UTF-16  or UTF-32. As well as compiling PCRE with this option, you also
965           have have to set the PCRE_UTF8, PCRE_UTF16  or  PCRE_UTF32  option  (as
966           appropriate) when you call one of the pattern compiling functions.
967    
968           If  you  set --enable-utf when compiling in an EBCDIC environment, PCRE
969           expects its input to be either ASCII or UTF-8 (depending  on  the  run-
970           time option). It is not possible to support both EBCDIC and UTF-8 codes
971           in the same version of  the  library.  Consequently,  --enable-utf  and
972           --enable-ebcdic are mutually exclusive.
973    
974    
975    UNICODE CHARACTER PROPERTY SUPPORT
976    
977           UTF  support allows the libraries to process character codepoints up to
978           0x10ffff in the strings that they handle. On its own, however, it  does
979           not provide any facilities for accessing the properties of such charac-
980           ters. If you want to be able to use the pattern escapes \P, \p, and \X,
981           which refer to Unicode character properties, you must add
982    
983             --enable-unicode-properties
984    
985           to  the  configure  command. This implies UTF support, even if you have
986           not explicitly requested it.
987    
988           Including Unicode property support adds around 30K  of  tables  to  the
989           PCRE  library.  Only  the general category properties such as Lu and Nd
990           are supported. Details are given in the pcrepattern documentation.
991    
992    
993    JUST-IN-TIME COMPILER SUPPORT
994    
995           Just-in-time compiler support is included in the build by specifying
996    
997             --enable-jit
998    
999           This support is available only for certain hardware  architectures.  If
1000           this  option  is  set  for  an unsupported architecture, a compile time
1001           error occurs.  See the pcrejit documentation for a  discussion  of  JIT
1002           usage. When JIT support is enabled, pcregrep automatically makes use of
1003           it, unless you add
1004    
1005             --disable-pcregrep-jit
1006    
1007           to the "configure" command.
1008    
1009    
1010    CODE VALUE OF NEWLINE
1011    
1012           By default, PCRE interprets the linefeed (LF) character  as  indicating
1013           the  end  of  a line. This is the normal newline character on Unix-like
1014           systems. You can compile PCRE to use carriage return (CR)  instead,  by
1015           adding
1016    
1017             --enable-newline-is-cr
1018    
1019           to  the  configure  command.  There  is  also  a --enable-newline-is-lf
1020           option, which explicitly specifies linefeed as the newline character.
1021    
1022           Alternatively, you can specify that line endings are to be indicated by
1023           the two character sequence CRLF. If you want this, add
1024    
1025             --enable-newline-is-crlf
1026    
1027           to the configure command. There is a fourth option, specified by
1028    
1029             --enable-newline-is-anycrlf
1030    
1031           which  causes  PCRE  to recognize any of the three sequences CR, LF, or
1032           CRLF as indicating a line ending. Finally, a fifth option, specified by
1033    
1034             --enable-newline-is-any
1035    
1036           causes PCRE to recognize any Unicode newline sequence.
1037    
1038           Whatever line ending convention is selected when PCRE is built  can  be
1039           overridden  when  the library functions are called. At build time it is
1040           conventional to use the standard for your operating system.
1041    
1042    
1043    WHAT \R MATCHES
1044    
1045           By default, the sequence \R in a pattern matches  any  Unicode  newline
1046           sequence,  whatever  has  been selected as the line ending sequence. If
1047           you specify
1048    
1049             --enable-bsr-anycrlf
1050    
1051           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
1052           ever  is selected when PCRE is built can be overridden when the library
1053           functions are called.
1054    
1055    
1056    POSIX MALLOC USAGE
1057    
1058           When the 8-bit library is called through the POSIX interface  (see  the
1059           pcreposix  documentation),  additional  working storage is required for
1060           holding the pointers to capturing  substrings,  because  PCRE  requires
1061           three integers per substring, whereas the POSIX interface provides only
1062           two. If the number of expected substrings is small, the  wrapper  func-
1063           tion  uses  space  on the stack, because this is faster than using mal-
1064           loc() for each call. The default threshold above which the stack is  no
1065           longer used is 10; it can be changed by adding a setting such as
1066    
1067             --with-posix-malloc-threshold=20
1068    
1069           to the configure command.
1070    
1071    
1072    HANDLING VERY LARGE PATTERNS
1073    
1074           Within  a  compiled  pattern,  offset values are used to point from one
1075           part to another (for example, from an opening parenthesis to an  alter-
1076           nation  metacharacter).  By default, in the 8-bit and 16-bit libraries,
1077           two-byte values are used for these offsets, leading to a  maximum  size
1078           for  a compiled pattern of around 64K. This is sufficient to handle all
1079           but the most gigantic patterns.  Nevertheless, some people do  want  to
1080           process  truly  enormous patterns, so it is possible to compile PCRE to
1081           use three-byte or four-byte offsets by adding a setting such as
1082    
1083             --with-link-size=3
1084    
1085           to the configure command. The value given must be 2, 3, or 4.  For  the
1086           16-bit  library,  a  value of 3 is rounded up to 4. In these libraries,
1087           using longer offsets slows down the operation of PCRE because it has to
1088           load  additional  data  when  handling them. For the 32-bit library the
1089           value is always 4 and cannot be overridden; the value  of  --with-link-
1090           size is ignored.
1091    
1092    
1093    AVOIDING EXCESSIVE STACK USAGE
1094    
1095           When matching with the pcre_exec() function, PCRE implements backtrack-
1096           ing by making recursive calls to an internal function  called  match().
1097           In  environments  where  the size of the stack is limited, this can se-
1098           verely limit PCRE's operation. (The Unix environment does  not  usually
1099           suffer from this problem, but it may sometimes be necessary to increase
1100           the maximum stack size.  There is a discussion in the  pcrestack  docu-
1101           mentation.)  An alternative approach to recursion that uses memory from
1102           the heap to remember data, instead of using recursive  function  calls,
1103           has  been  implemented to work round the problem of limited stack size.
1104           If you want to build a version of PCRE that works this way, add
1105    
1106             --disable-stack-for-recursion
1107    
1108           to the configure command. With this configuration, PCRE  will  use  the
1109           pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
1110           ment functions. By default these point to malloc() and free(), but  you
1111           can replace the pointers so that your own functions are used instead.
1112    
1113           Separate  functions  are  provided  rather  than  using pcre_malloc and
1114           pcre_free because the  usage  is  very  predictable:  the  block  sizes
1115           requested  are  always  the  same,  and  the blocks are always freed in
1116           reverse order. A calling program might be able to  implement  optimized
1117           functions  that  perform  better  than  malloc()  and free(). PCRE runs
1118           noticeably more slowly when built in this way. This option affects only
1119           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
1120    
1121    
1122    LIMITING PCRE RESOURCE USAGE
1123    
1124           Internally,  PCRE has a function called match(), which it calls repeat-
1125           edly  (sometimes  recursively)  when  matching  a  pattern   with   the
1126           pcre_exec()  function.  By controlling the maximum number of times this
1127           function may be called during a single matching operation, a limit  can
1128           be  placed  on  the resources used by a single call to pcre_exec(). The
1129           limit can be changed at run time, as described in the pcreapi  documen-
1130           tation.  The default is 10 million, but this can be changed by adding a
1131           setting such as
1132    
1133             --with-match-limit=500000
1134    
1135           to  the  configure  command.  This  setting  has  no  effect   on   the
1136           pcre_dfa_exec() matching function.
1137    
1138           In  some  environments  it is desirable to limit the depth of recursive
1139           calls of match() more strictly than the total number of calls, in order
1140           to  restrict  the maximum amount of stack (or heap, if --disable-stack-
1141           for-recursion is specified) that is used. A second limit controls this;
1142           it  defaults  to  the  value  that is set for --with-match-limit, which
1143           imposes no additional constraints. However, you can set a  lower  limit
1144           by adding, for example,
1145    
1146             --with-match-limit-recursion=10000
1147    
1148           to  the  configure  command.  This  value can also be overridden at run
1149           time.
1150    
1151    
1152    CREATING CHARACTER TABLES AT BUILD TIME
1153    
1154           PCRE uses fixed tables for processing characters whose code values  are
1155           less  than 256. By default, PCRE is built with a set of tables that are
1156           distributed in the file pcre_chartables.c.dist. These  tables  are  for
1157           ASCII codes only. If you add
1158    
1159             --enable-rebuild-chartables
1160    
1161           to  the  configure  command, the distributed tables are no longer used.
1162           Instead, a program called dftables is compiled and  run.  This  outputs
1163           the source for new set of tables, created in the default locale of your
1164           C run-time system. (This method of replacing the tables does  not  work
1165           if  you are cross compiling, because dftables is run on the local host.
1166           If you need to create alternative tables when cross compiling, you will
1167           have to do so "by hand".)
1168    
1169    
1170    USING EBCDIC CODE
1171    
1172           PCRE  assumes  by  default that it will run in an environment where the
1173           character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
1174           This  is  the  case for most computer operating systems. PCRE can, how-
1175           ever, be compiled to run in an EBCDIC environment by adding
1176    
1177             --enable-ebcdic
1178    
1179           to the configure command. This setting implies --enable-rebuild-charta-
1180           bles.  You  should  only  use  it if you know that you are in an EBCDIC
1181           environment (for example,  an  IBM  mainframe  operating  system).  The
1182           --enable-ebcdic option is incompatible with --enable-utf.
1183    
1184           The EBCDIC character that corresponds to an ASCII LF is assumed to have
1185           the value 0x15 by default. However, in some EBCDIC  environments,  0x25
1186           is used. In such an environment you should use
1187    
1188             --enable-ebcdic-nl25
1189    
1190           as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR
1191           has the same value as in ASCII, namely, 0x0d.  Whichever  of  0x15  and
1192           0x25 is not chosen as LF is made to correspond to the Unicode NEL char-
1193           acter (which, in Unicode, is 0x85).
1194    
1195           The options that select newline behaviour, such as --enable-newline-is-
1196           cr, and equivalent run-time options, refer to these character values in
1197           an EBCDIC environment.
1198    
1199    
1200    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
1201    
1202           By default, pcregrep reads all files as plain text. You can build it so
1203           that it recognizes files whose names end in .gz or .bz2, and reads them
1204           with libz or libbz2, respectively, by adding one or both of
1205    
1206             --enable-pcregrep-libz
1207             --enable-pcregrep-libbz2
1208    
1209           to the configure command. These options naturally require that the rel-
1210           evant  libraries  are installed on your system. Configuration will fail
1211           if they are not.
1212    
1213    
1214    PCREGREP BUFFER SIZE
1215    
1216           pcregrep uses an internal buffer to hold a "window" on the file  it  is
1217           scanning, in order to be able to output "before" and "after" lines when
1218           it finds a match. The size of the buffer is controlled by  a  parameter
1219           whose default value is 20K. The buffer itself is three times this size,
1220           but because of the way it is used for holding "before" lines, the long-
1221           est  line  that  is guaranteed to be processable is the parameter size.
1222           You can change the default parameter value by adding, for example,
1223    
1224             --with-pcregrep-bufsize=50K
1225    
1226           to the configure command. The caller of pcregrep can, however, override
1227           this value by specifying a run-time option.
1228    
1229    
1230    PCRETEST OPTION FOR LIBREADLINE SUPPORT
1231    
1232           If you add
1233    
1234             --enable-pcretest-libreadline
1235    
1236           to  the  configure  command,  pcretest  is  linked with the libreadline
1237           library, and when its input is from a terminal, it reads it  using  the
1238           readline() function. This provides line-editing and history facilities.
1239           Note that libreadline is GPL-licensed, so if you distribute a binary of
1240           pcretest linked in this way, there may be licensing issues.
1241    
1242           Setting  this  option  causes  the -lreadline option to be added to the
1243           pcretest build. In many operating environments with  a  sytem-installed
1244           libreadline this is sufficient. However, in some environments (e.g.  if
1245           an unmodified distribution version of readline is in use),  some  extra
1246           configuration  may  be necessary. The INSTALL file for libreadline says
1247           this:
1248    
1249             "Readline uses the termcap functions, but does not link with the
1250             termcap or curses library itself, allowing applications which link
1251             with readline the to choose an appropriate library."
1252    
1253           If your environment has not been set up so that an appropriate  library
1254           is automatically included, you may need to add something like
1255    
1256             LIBS="-ncurses"
1257    
1258           immediately before the configure command.
1259    
1260    
1261    DEBUGGING WITH VALGRIND SUPPORT
1262    
1263           By adding the
1264    
1265             --enable-valgrind
1266    
1267           option  to to the configure command, PCRE will use valgrind annotations
1268           to mark certain memory regions as  unaddressable.  This  allows  it  to
1269           detect invalid memory accesses, and is mostly useful for debugging PCRE
1270           itself.
1271    
1272    
1273    CODE COVERAGE REPORTING
1274    
1275           If your C compiler is gcc, you can build a version  of  PCRE  that  can
1276           generate a code coverage report for its test suite. To enable this, you
1277           must install lcov version 1.6 or above. Then specify
1278    
1279             --enable-coverage
1280    
1281           to the configure command and build PCRE in the usual way.
1282    
1283           Note that using ccache (a caching C compiler) is incompatible with code
1284           coverage  reporting. If you have configured ccache to run automatically
1285           on your system, you must set the environment variable
1286    
1287             CCACHE_DISABLE=1
1288    
1289           before running make to build PCRE, so that ccache is not used.
1290    
1291           When --enable-coverage is used,  the  following  addition  targets  are
1292           added to the Makefile:
1293    
1294             make coverage
1295    
1296           This  creates  a  fresh  coverage report for the PCRE test suite. It is
1297           equivalent to running "make coverage-reset", "make  coverage-baseline",
1298           "make check", and then "make coverage-report".
1299    
1300             make coverage-reset
1301    
1302           This zeroes the coverage counters, but does nothing else.
1303    
1304             make coverage-baseline
1305    
1306           This captures baseline coverage information.
1307    
1308             make coverage-report
1309    
1310           This creates the coverage report.
1311    
1312             make coverage-clean-report
1313    
1314           This  removes the generated coverage report without cleaning the cover-
1315           age data itself.
1316    
1317             make coverage-clean-data
1318    
1319           This removes the captured coverage data without removing  the  coverage
1320           files created at compile time (*.gcno).
1321    
1322             make coverage-clean
1323    
1324           This  cleans all coverage data including the generated coverage report.
1325           For more information about code coverage, see the gcov and  lcov  docu-
1326           mentation.
1327    
1328    
1329    SEE ALSO
1330    
1331           pcreapi(3), pcre16, pcre32, pcre_config(3).
1332    
1333    
1334    AUTHOR
1335    
1336           Philip Hazel
1337           University Computing Service
1338           Cambridge CB2 3QH, England.
1339    
1340    
1341    REVISION
1342    
1343           Last updated: 12 May 2013
1344           Copyright (c) 1997-2013 University of Cambridge.
1345    ------------------------------------------------------------------------------
1346    
1347    
1348    PCREMATCHING(3)            Library Functions Manual            PCREMATCHING(3)
1349    
1350    
1351    
1352    NAME
1353           PCRE - Perl-compatible regular expressions
1354    
1355    PCRE MATCHING ALGORITHMS
1356    
1357           This document describes the two different algorithms that are available
1358           in PCRE for matching a compiled regular expression against a given sub-
1359           ject  string.  The  "standard"  algorithm  is  the  one provided by the
1360           pcre_exec(), pcre16_exec() and pcre32_exec() functions. These  work  in
1361           the  same as as Perl's matching function, and provide a Perl-compatible
1362           matching  operation.   The  just-in-time  (JIT)  optimization  that  is
1363           described  in  the pcrejit documentation is compatible with these func-
1364           tions.
1365    
1366           An  alternative  algorithm  is   provided   by   the   pcre_dfa_exec(),
1367           pcre16_dfa_exec()  and  pcre32_dfa_exec()  functions; they operate in a
1368           different way, and are not Perl-compatible. This alternative has advan-
1369           tages and disadvantages compared with the standard algorithm, and these
1370           are described below.
1371    
1372           When there is only one possible way in which a given subject string can
1373           match  a pattern, the two algorithms give the same answer. A difference
1374           arises, however, when there are multiple possibilities. For example, if
1375           the pattern
1376    
1377             ^<.*>
1378    
1379           is matched against the string
1380    
1381             <something> <something else> <something further>
1382    
1383           there are three possible answers. The standard algorithm finds only one
1384           of them, whereas the alternative algorithm finds all three.
1385    
1386    
1387    REGULAR EXPRESSIONS AS TREES
1388    
1389           The set of strings that are matched by a regular expression can be rep-
1390           resented  as  a  tree structure. An unlimited repetition in the pattern
1391           makes the tree of infinite size, but it is still a tree.  Matching  the
1392           pattern  to a given subject string (from a given starting point) can be
1393           thought of as a search of the tree.  There are two  ways  to  search  a
1394           tree:  depth-first  and  breadth-first, and these correspond to the two
1395           matching algorithms provided by PCRE.
1396    
1397    
1398    THE STANDARD MATCHING ALGORITHM
1399    
1400           In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
1401           sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
1402           depth-first search of the pattern tree. That is, it  proceeds  along  a
1403           single path through the tree, checking that the subject matches what is
1404           required. When there is a mismatch, the algorithm  tries  any  alterna-
1405           tives  at  the  current point, and if they all fail, it backs up to the
1406           previous branch point in the  tree,  and  tries  the  next  alternative
1407           branch  at  that  level.  This often involves backing up (moving to the
1408           left) in the subject string as well.  The  order  in  which  repetition
1409           branches  are  tried  is controlled by the greedy or ungreedy nature of
1410           the quantifier.
1411    
1412           If a leaf node is reached, a matching string has  been  found,  and  at
1413           that  point the algorithm stops. Thus, if there is more than one possi-
1414           ble match, this algorithm returns the first one that it finds.  Whether
1415           this  is the shortest, the longest, or some intermediate length depends
1416           on the way the greedy and ungreedy repetition quantifiers are specified
1417           in the pattern.
1418    
1419           Because  it  ends  up  with a single path through the tree, it is rela-
1420           tively straightforward for this algorithm to keep  track  of  the  sub-
1421           strings  that  are  matched  by portions of the pattern in parentheses.
1422           This provides support for capturing parentheses and back references.
1423    
1424    
1425    THE ALTERNATIVE MATCHING ALGORITHM
1426    
1427           This algorithm conducts a breadth-first search of  the  tree.  Starting
1428           from  the  first  matching  point  in the subject, it scans the subject
1429           string from left to right, once, character by character, and as it does
1430           this,  it remembers all the paths through the tree that represent valid
1431           matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
1432           though  it is not implemented as a traditional finite state machine (it
1433           keeps multiple states active simultaneously).
1434    
1435           Although the general principle of this matching algorithm  is  that  it
1436           scans  the subject string only once, without backtracking, there is one
1437           exception: when a lookaround assertion is encountered,  the  characters
1438           following  or  preceding  the  current  point  have to be independently
1439           inspected.
1440    
1441           The scan continues until either the end of the subject is  reached,  or
1442           there  are  no more unterminated paths. At this point, terminated paths
1443           represent the different matching possibilities (if there are none,  the
1444           match  has  failed).   Thus,  if there is more than one possible match,
1445           this algorithm finds all of them, and in particular, it finds the long-
1446           est.  The  matches are returned in decreasing order of length. There is
1447           an option to stop the algorithm after the first match (which is  neces-
1448           sarily the shortest) is found.
1449    
1450           Note that all the matches that are found start at the same point in the
1451           subject. If the pattern
1452    
1453             cat(er(pillar)?)?
1454    
1455           is matched against the string "the caterpillar catchment",  the  result
1456           will  be the three strings "caterpillar", "cater", and "cat" that start
1457           at the fifth character of the subject. The algorithm does not automati-
1458           cally move on to find matches that start at later positions.
1459    
1460           PCRE's  "auto-possessification" optimization usually applies to charac-
1461           ter repeats at the end of a pattern (as well as internally). For  exam-
1462           ple, the pattern "a\d+" is compiled as if it were "a\d++" because there
1463           is no point even considering the possibility of backtracking  into  the
1464           repeated  digits.  For  DFA matching, this means that only one possible
1465           match is found. If you really do want multiple matches in  such  cases,
1466           either use an ungreedy repeat ("a\d+?") or set the PCRE_NO_AUTO_POSSESS
1467           option when compiling.
1468    
1469           There are a number of features of PCRE regular expressions that are not
1470           supported by the alternative matching algorithm. They are as follows:
1471    
1472           1.  Because  the  algorithm  finds  all possible matches, the greedy or
1473           ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
1474           ungreedy quantifiers are treated in exactly the same way. However, pos-
1475           sessive quantifiers can make a difference when what follows could  also
1476           match what is quantified, for example in a pattern like this:
1477    
1478             ^a++\w!
1479    
1480           This  pattern matches "aaab!" but not "aaa!", which would be matched by
1481           a non-possessive quantifier. Similarly, if an atomic group is  present,
1482           it  is matched as if it were a standalone pattern at the current point,
1483           and the longest match is then "locked in" for the rest of  the  overall
1484           pattern.
1485    
1486           2. When dealing with multiple paths through the tree simultaneously, it
1487           is not straightforward to keep track of  captured  substrings  for  the
1488           different  matching  possibilities,  and  PCRE's implementation of this
1489           algorithm does not attempt to do this. This means that no captured sub-
1490           strings are available.
1491    
1492           3.  Because no substrings are captured, back references within the pat-
1493           tern are not supported, and cause errors if encountered.
1494    
1495           4. For the same reason, conditional expressions that use  a  backrefer-
1496           ence  as  the  condition or test for a specific group recursion are not
1497           supported.
1498    
1499           5. Because many paths through the tree may be  active,  the  \K  escape
1500           sequence, which resets the start of the match when encountered (but may
1501           be on some paths and not on others), is not  supported.  It  causes  an
1502           error if encountered.
1503    
1504           6.  Callouts  are  supported, but the value of the capture_top field is
1505           always 1, and the value of the capture_last field is always -1.
1506    
1507           7. The \C escape sequence, which (in  the  standard  algorithm)  always
1508           matches  a  single data unit, even in UTF-8, UTF-16 or UTF-32 modes, is
1509           not supported in these modes, because the alternative  algorithm  moves
1510           through the subject string one character (not data unit) at a time, for
1511           all active paths through the tree.
1512    
1513           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
1514           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
1515           negative assertion.
1516    
1517    
1518    ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1519    
1520           Using the alternative matching algorithm provides the following  advan-
1521           tages:
1522    
1523           1. All possible matches (at a single point in the subject) are automat-
1524           ically found, and in particular, the longest match is  found.  To  find
1525           more than one match using the standard algorithm, you have to do kludgy
1526           things with callouts.
1527    
1528           2. Because the alternative algorithm  scans  the  subject  string  just
1529           once, and never needs to backtrack (except for lookbehinds), it is pos-
1530           sible to pass very long subject strings to  the  matching  function  in
1531           several pieces, checking for partial matching each time. Although it is
1532           possible to do multi-segment matching using the standard  algorithm  by
1533           retaining  partially  matched  substrings,  it is more complicated. The
1534           pcrepartial documentation gives details of partial  matching  and  dis-
1535           cusses multi-segment matching.
1536    
1537    
1538    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1539    
1540           The alternative algorithm suffers from a number of disadvantages:
1541    
1542           1.  It  is  substantially  slower  than the standard algorithm. This is
1543           partly because it has to search for all possible matches, but  is  also
1544           because it is less susceptible to optimization.
1545    
1546           2. Capturing parentheses and back references are not supported.
1547    
1548           3. Although atomic groups are supported, their use does not provide the
1549           performance advantage that it does for the standard algorithm.
1550    
1551    
1552    AUTHOR
1553    
1554           Philip Hazel
1555           University Computing Service
1556           Cambridge CB2 3QH, England.
1557    
1558    
1559    REVISION
1560    
1561           Last updated: 12 November 2013
1562           Copyright (c) 1997-2012 University of Cambridge.
1563    ------------------------------------------------------------------------------
1564    
1565    
1566    PCREAPI(3)                 Library Functions Manual                 PCREAPI(3)
1567    
1568    
1569    
1570    NAME
1571           PCRE - Perl-compatible regular expressions
1572    
1573           #include <pcre.h>
1574    
1575    
1576    PCRE NATIVE API BASIC FUNCTIONS
1577    
1578           pcre *pcre_compile(const char *pattern, int options,
1579                const char **errptr, int *erroffset,
1580                const unsigned char *tableptr);
1581    
1582           pcre *pcre_compile2(const char *pattern, int options,
1583                int *errorcodeptr,
1584                const char **errptr, int *erroffset,
1585                const unsigned char *tableptr);
1586    
1587           pcre_extra *pcre_study(const pcre *code, int options,
1588                const char **errptr);
1589    
1590           void pcre_free_study(pcre_extra *extra);
1591    
1592           int pcre_exec(const pcre *code, const pcre_extra *extra,
1593                const char *subject, int length, int startoffset,
1594                int options, int *ovector, int ovecsize);
1595    
1596           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1597                const char *subject, int length, int startoffset,
1598                int options, int *ovector, int ovecsize,
1599                int *workspace, int wscount);
1600    
1601    
1602    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1603    
1604           int pcre_copy_named_substring(const pcre *code,
1605                const char *subject, int *ovector,
1606                int stringcount, const char *stringname,
1607                char *buffer, int buffersize);
1608    
1609           int pcre_copy_substring(const char *subject, int *ovector,
1610                int stringcount, int stringnumber, char *buffer,
1611                int buffersize);
1612    
1613           int pcre_get_named_substring(const pcre *code,
1614                const char *subject, int *ovector,
1615                int stringcount, const char *stringname,
1616                const char **stringptr);
1617    
1618           int pcre_get_stringnumber(const pcre *code,
1619                const char *name);
1620    
1621           int pcre_get_stringtable_entries(const pcre *code,
1622                const char *name, char **first, char **last);
1623    
1624           int pcre_get_substring(const char *subject, int *ovector,
1625                int stringcount, int stringnumber,
1626                const char **stringptr);
1627    
1628           int pcre_get_substring_list(const char *subject,
1629                int *ovector, int stringcount, const char ***listptr);
1630    
1631           void pcre_free_substring(const char *stringptr);
1632    
1633           void pcre_free_substring_list(const char **stringptr);
1634    
1635    
1636    PCRE NATIVE API AUXILIARY FUNCTIONS
1637    
1638           int pcre_jit_exec(const pcre *code, const pcre_extra *extra,
1639                const char *subject, int length, int startoffset,
1640                int options, int *ovector, int ovecsize,
1641                pcre_jit_stack *jstack);
1642    
1643           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1644    
1645           void pcre_jit_stack_free(pcre_jit_stack *stack);
1646    
1647           void pcre_assign_jit_stack(pcre_extra *extra,
1648                pcre_jit_callback callback, void *data);
1649    
1650           const unsigned char *pcre_maketables(void);
1651    
1652           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1653                int what, void *where);
1654    
1655           int pcre_refcount(pcre *code, int adjust);
1656    
1657           int pcre_config(int what, void *where);
1658    
1659           const char *pcre_version(void);
1660    
1661           int pcre_pattern_to_host_byte_order(pcre *code,
1662                pcre_extra *extra, const unsigned char *tables);
1663    
1664    
1665    PCRE NATIVE API INDIRECTED FUNCTIONS
1666    
1667           void *(*pcre_malloc)(size_t);
1668    
1669           void (*pcre_free)(void *);
1670    
1671           void *(*pcre_stack_malloc)(size_t);
1672    
1673           void (*pcre_stack_free)(void *);
1674    
1675           int (*pcre_callout)(pcre_callout_block *);
1676    
1677    
1678    PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES
1679    
1680           As  well  as  support  for  8-bit character strings, PCRE also supports
1681           16-bit strings (from release 8.30) and  32-bit  strings  (from  release
1682           8.32),  by means of two additional libraries. They can be built as well
1683           as, or instead of, the 8-bit library. To avoid too  much  complication,
1684           this  document describes the 8-bit versions of the functions, with only
1685           occasional references to the 16-bit and 32-bit libraries.
1686    
1687           The 16-bit and 32-bit functions operate in the same way as their  8-bit
1688           counterparts;  they  just  use different data types for their arguments
1689           and results, and their names start with pcre16_ or pcre32_  instead  of
1690           pcre_.  For  every  option  that  has  UTF8  in  its name (for example,
1691           PCRE_UTF8), there are corresponding 16-bit and 32-bit names  with  UTF8
1692           replaced by UTF16 or UTF32, respectively. This facility is in fact just
1693           cosmetic; the 16-bit and 32-bit option names define the same  bit  val-
1694           ues.
1695    
1696           References to bytes and UTF-8 in this document should be read as refer-
1697           ences to 16-bit data units and UTF-16 when using the 16-bit library, or
1698           32-bit  data  units  and  UTF-32  when using the 32-bit library, unless
1699           specified otherwise.  More details of the specific differences for  the
1700           16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages.
1701    
1702    
1703    PCRE API OVERVIEW
1704    
1705           PCRE has its own native API, which is described in this document. There
1706           are also some wrapper functions (for the 8-bit library only) that  cor-
1707           respond  to  the  POSIX  regular  expression  API, but they do not give
1708           access to all the functionality. They are described  in  the  pcreposix
1709           documentation.  Both  of these APIs define a set of C function calls. A
1710           C++ wrapper (again for the 8-bit library only) is also distributed with
1711           PCRE. It is documented in the pcrecpp page.
1712    
1713           The  native  API  C  function prototypes are defined in the header file
1714           pcre.h, and on Unix-like systems the (8-bit) library itself  is  called
1715           libpcre.  It  can  normally be accessed by adding -lpcre to the command
1716           for linking an application that uses PCRE. The header file defines  the
1717           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1718           numbers for the library. Applications can use these to include  support
1719           for different releases of PCRE.
1720    
1721           In a Windows environment, if you want to statically link an application
1722           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
1723           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
1724           loc()   and   pcre_free()   exported   functions   will   be   declared
1725           __declspec(dllimport), with unwanted results.
1726    
1727           The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
1728           pcre_exec() are used for compiling and matching regular expressions  in
1729           a  Perl-compatible  manner. A sample program that demonstrates the sim-
1730           plest way of using them is provided in the file  called  pcredemo.c  in
1731           the PCRE source distribution. A listing of this program is given in the
1732           pcredemo documentation, and the pcresample documentation describes  how
1733           to compile and run it.
1734    
1735           Just-in-time  compiler  support is an optional feature of PCRE that can
1736           be built in appropriate hardware environments. It greatly speeds up the
1737           matching  performance  of  many  patterns.  Simple  programs can easily
1738           request that it be used if available, by  setting  an  option  that  is
1739           ignored  when  it is not relevant. More complicated programs might need
1740           to    make    use    of    the    functions     pcre_jit_stack_alloc(),
1741           pcre_jit_stack_free(),  and pcre_assign_jit_stack() in order to control
1742           the JIT code's memory usage.
1743    
1744           From release 8.32 there is also a direct interface for  JIT  execution,
1745           which  gives  improved performance. The JIT-specific functions are dis-
1746           cussed in the pcrejit documentation.
1747    
1748           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1749           ble,  is  also provided. This uses a different algorithm for the match-
1750           ing. The alternative algorithm finds all possible matches (at  a  given
1751           point  in  the  subject), and scans the subject just once (unless there
1752           are lookbehind assertions). However, this  algorithm  does  not  return
1753           captured  substrings.  A description of the two matching algorithms and
1754           their advantages and disadvantages is given in the  pcrematching  docu-
1755           mentation.
1756    
1757           In  addition  to  the  main compiling and matching functions, there are
1758           convenience functions for extracting captured substrings from a subject
1759           string that is matched by pcre_exec(). They are:
1760    
1761             pcre_copy_substring()
1762             pcre_copy_named_substring()
1763             pcre_get_substring()
1764             pcre_get_named_substring()
1765             pcre_get_substring_list()
1766             pcre_get_stringnumber()
1767             pcre_get_stringtable_entries()
1768    
1769           pcre_free_substring() and pcre_free_substring_list() are also provided,
1770           to free the memory used for extracted strings.
1771    
1772           The function pcre_maketables() is used to  build  a  set  of  character
1773           tables   in   the   current   locale  for  passing  to  pcre_compile(),
1774           pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
1775           provided  for  specialist  use.  Most  commonly,  no special tables are
1776           passed, in which case internal tables that are generated when  PCRE  is
1777           built are used.
1778    
1779           The  function  pcre_fullinfo()  is used to find out information about a
1780           compiled pattern. The function pcre_version() returns a  pointer  to  a
1781           string containing the version of PCRE and its date of release.
1782    
1783           The  function  pcre_refcount()  maintains  a  reference count in a data
1784           block containing a compiled pattern. This is provided for  the  benefit
1785           of object-oriented applications.
1786    
1787           The  global  variables  pcre_malloc and pcre_free initially contain the
1788           entry points of the standard malloc()  and  free()  functions,  respec-
1789           tively. PCRE calls the memory management functions via these variables,
1790           so a calling program can replace them if it  wishes  to  intercept  the
1791           calls. This should be done before calling any PCRE functions.
1792    
1793           The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1794           indirections to memory management functions.  These  special  functions
1795           are  used  only  when  PCRE is compiled to use the heap for remembering
1796           data, instead of recursive function calls, when running the pcre_exec()
1797           function.  See  the  pcrebuild  documentation  for details of how to do
1798           this. It is a non-standard way of building PCRE, for  use  in  environ-
1799           ments  that  have  limited stacks. Because of the greater use of memory
1800           management, it runs more slowly. Separate  functions  are  provided  so
1801           that  special-purpose  external  code  can  be used for this case. When
1802           used, these functions are always called in a  stack-like  manner  (last
1803           obtained,  first freed), and always for memory blocks of the same size.
1804           There is a discussion about PCRE's stack usage in the  pcrestack  docu-
1805           mentation.
1806    
1807           The global variable pcre_callout initially contains NULL. It can be set
1808           by the caller to a "callout" function, which PCRE  will  then  call  at
1809           specified  points during a matching operation. Details are given in the
1810           pcrecallout documentation.
1811    
1812    
1813    NEWLINES
1814    
1815           PCRE supports five different conventions for indicating line breaks  in
1816           strings:  a  single  CR (carriage return) character, a single LF (line-
1817           feed) character, the two-character sequence CRLF, any of the three pre-
1818           ceding,  or any Unicode newline sequence. The Unicode newline sequences
1819           are the three just mentioned, plus the single characters  VT  (vertical
1820           tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
1821           separator, U+2028), and PS (paragraph separator, U+2029).
1822    
1823           Each of the first three conventions is used by at least  one  operating
1824           system  as its standard newline sequence. When PCRE is built, a default
1825           can be specified.  The default default is LF, which is the  Unix  stan-
1826           dard.  When  PCRE  is run, the default can be overridden, either when a
1827           pattern is compiled, or when it is matched.
1828    
1829           At compile time, the newline convention can be specified by the options
1830           argument  of  pcre_compile(), or it can be specified by special text at
1831           the start of the pattern itself; this overrides any other settings. See
1832           the pcrepattern page for details of the special character sequences.
1833    
1834           In the PCRE documentation the word "newline" is used to mean "the char-
1835           acter or pair of characters that indicate a line break". The choice  of
1836           newline  convention  affects  the  handling of the dot, circumflex, and
1837           dollar metacharacters, the handling of #-comments in /x mode, and, when
1838           CRLF  is a recognized line ending sequence, the match position advance-
1839           ment for a non-anchored pattern. There is more detail about this in the
1840           section on pcre_exec() options below.
1841    
1842           The  choice of newline convention does not affect the interpretation of
1843           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1844           which is controlled in a similar way, but by separate options.
1845    
1846    
1847    MULTITHREADING
1848    
1849           The  PCRE  functions  can be used in multi-threading applications, with
1850           the  proviso  that  the  memory  management  functions  pointed  to  by
1851           pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1852           callout function pointed to by pcre_callout, are shared by all threads.
1853    
1854           The compiled form of a regular expression is not altered during  match-
1855           ing, so the same compiled pattern can safely be used by several threads
1856           at once.
1857    
1858           If the just-in-time optimization feature is being used, it needs  sepa-
1859           rate  memory stack areas for each thread. See the pcrejit documentation
1860           for more details.
1861    
1862    
1863    SAVING PRECOMPILED PATTERNS FOR LATER USE
1864    
1865           The compiled form of a regular expression can be saved and re-used at a
1866           later  time,  possibly by a different program, and even on a host other
1867           than the one on which  it  was  compiled.  Details  are  given  in  the
1868           pcreprecompile  documentation,  which  includes  a  description  of the
1869           pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1870           lar  expression  with one version of PCRE for use with a different ver-
1871           sion is not guaranteed to work and may cause crashes.
1872    
1873    
1874    CHECKING BUILD-TIME OPTIONS
1875    
1876           int pcre_config(int what, void *where);
1877    
1878           The function pcre_config() makes it possible for a PCRE client to  dis-
1879           cover which optional features have been compiled into the PCRE library.
1880           The pcrebuild documentation has more details about these optional  fea-
1881           tures.
1882    
1883           The  first  argument  for pcre_config() is an integer, specifying which
1884           information is required; the second argument is a pointer to a variable
1885           into  which  the  information  is placed. The returned value is zero on
1886           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1887           in  the  first argument is not recognized. The following information is
1888           available:
1889    
1890             PCRE_CONFIG_UTF8
1891    
1892           The output is an integer that is set to one if UTF-8 support is  avail-
1893           able;  otherwise it is set to zero. This value should normally be given
1894           to the 8-bit version of this function, pcre_config(). If it is given to
1895           the   16-bit  or  32-bit  version  of  this  function,  the  result  is
1896           PCRE_ERROR_BADOPTION.
1897    
1898             PCRE_CONFIG_UTF16
1899    
1900           The output is an integer that is set to one if UTF-16 support is avail-
1901           able;  otherwise it is set to zero. This value should normally be given
1902           to the 16-bit version of this function, pcre16_config(). If it is given
1903           to  the  8-bit  or  32-bit  version  of  this  function,  the result is
1904           PCRE_ERROR_BADOPTION.
1905    
1906             PCRE_CONFIG_UTF32
1907    
1908           The output is an integer that is set to one if UTF-32 support is avail-
1909           able;  otherwise it is set to zero. This value should normally be given
1910           to the 32-bit version of this function, pcre32_config(). If it is given
1911           to  the  8-bit  or  16-bit  version  of  this  function,  the result is
1912           PCRE_ERROR_BADOPTION.
1913    
1914             PCRE_CONFIG_UNICODE_PROPERTIES
1915    
1916           The output is an integer that is set to  one  if  support  for  Unicode
1917           character properties is available; otherwise it is set to zero.
1918    
1919             PCRE_CONFIG_JIT
1920    
1921           The output is an integer that is set to one if support for just-in-time
1922           compiling is available; otherwise it is set to zero.
1923    
1924             PCRE_CONFIG_JITTARGET
1925    
1926           The output is a pointer to a zero-terminated "const char *" string.  If
1927           JIT support is available, the string contains the name of the architec-
1928           ture for which the JIT compiler is configured, for example  "x86  32bit
1929           (little  endian  +  unaligned)".  If  JIT support is not available, the
1930           result is NULL.
1931    
1932             PCRE_CONFIG_NEWLINE
1933    
1934           The output is an integer whose value specifies  the  default  character
1935           sequence  that  is recognized as meaning "newline". The values that are
1936           supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338
1937           for  CRLF,  -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR,
1938           ANYCRLF, and ANY yield the same values. However, the value  for  LF  is
1939           normally  21, though some EBCDIC environments use 37. The corresponding
1940           values for CRLF are 3349 and 3365. The default should  normally  corre-
1941           spond to the standard sequence for your operating system.
1942    
1943             PCRE_CONFIG_BSR
1944    
1945           The output is an integer whose value indicates what character sequences
1946           the \R escape sequence matches by default. A value of 0 means  that  \R
1947           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1948           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1949           tern is compiled or matched.
1950    
1951             PCRE_CONFIG_LINK_SIZE
1952    
1953           The  output  is  an  integer that contains the number of bytes used for
1954           internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1955           library, the value can be 2, 3, or 4. For the 16-bit library, the value
1956           is either 2 or 4 and is  still  a  number  of  bytes.  For  the  32-bit
1957           library, the value is either 2 or 4 and is still a number of bytes. The
1958           default value of 2 is sufficient for all but the most massive patterns,
1959           since  it  allows  the compiled pattern to be up to 64K in size. Larger
1960           values allow larger regular expressions to be compiled, at the  expense
1961           of slower matching.
1962    
1963             PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1964    
1965           The  output  is  an integer that contains the threshold above which the
1966           POSIX interface uses malloc() for output vectors. Further  details  are
1967           given in the pcreposix documentation.
1968    
1969             PCRE_CONFIG_PARENS_LIMIT
1970    
1971           The output is a long integer that gives the maximum depth of nesting of
1972           parentheses (of any kind) in a pattern. This limit is  imposed  to  cap
1973           the amount of system stack used when a pattern is compiled. It is spec-
1974           ified when PCRE is built; the default is 250.
1975    
1976             PCRE_CONFIG_MATCH_LIMIT
1977    
1978           The output is a long integer that gives the default limit for the  num-
1979           ber  of  internal  matching  function calls in a pcre_exec() execution.
1980           Further details are given with pcre_exec() below.
1981    
1982             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1983    
1984           The output is a long integer that gives the default limit for the depth
1985           of   recursion  when  calling  the  internal  matching  function  in  a
1986           pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1987           below.
1988    
1989             PCRE_CONFIG_STACKRECURSE
1990    
1991           The  output is an integer that is set to one if internal recursion when
1992           running pcre_exec() is implemented by recursive function calls that use
1993           the  stack  to remember their state. This is the usual way that PCRE is
1994           compiled. The output is zero if PCRE was compiled to use blocks of data
1995           on  the  heap  instead  of  recursive  function  calls.  In  this case,
1996           pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1997           blocks on the heap, thus avoiding the use of the stack.
1998    
1999    
2000    COMPILING A PATTERN
2001    
2002           pcre *pcre_compile(const char *pattern, int options,
2003                const char **errptr, int *erroffset,
2004                const unsigned char *tableptr);
2005    
2006           pcre *pcre_compile2(const char *pattern, int options,
2007                int *errorcodeptr,
2008                const char **errptr, int *erroffset,
2009                const unsigned char *tableptr);
2010    
2011           Either of the functions pcre_compile() or pcre_compile2() can be called
2012           to compile a pattern into an internal form. The only difference between
2013           the  two interfaces is that pcre_compile2() has an additional argument,
2014           errorcodeptr, via which a numerical error  code  can  be  returned.  To
2015           avoid  too  much repetition, we refer just to pcre_compile() below, but
2016           the information applies equally to pcre_compile2().
2017    
2018           The pattern is a C string terminated by a binary zero, and is passed in
2019           the  pattern  argument.  A  pointer to a single block of memory that is
2020           obtained via pcre_malloc is returned. This contains the  compiled  code
2021           and related data. The pcre type is defined for the returned block; this
2022           is a typedef for a structure whose contents are not externally defined.
2023           It is up to the caller to free the memory (via pcre_free) when it is no
2024           longer required.
2025    
2026           Although the compiled code of a PCRE regex is relocatable, that is,  it
2027           does not depend on memory location, the complete pcre data block is not
2028           fully relocatable, because it may contain a copy of the tableptr  argu-
2029           ment, which is an address (see below).
2030    
2031           The options argument contains various bit settings that affect the com-
2032           pilation. It should be zero if no options are required.  The  available
2033           options  are  described  below. Some of them (in particular, those that
2034           are compatible with Perl, but some others as well) can also be set  and
2035           unset  from  within  the  pattern  (see the detailed description in the
2036           pcrepattern documentation). For those options that can be different  in
2037           different  parts  of  the pattern, the contents of the options argument
2038           specifies their settings at the start of compilation and execution. The
2039           PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
2040           PCRE_NO_START_OPTIMIZE options can be set at the time  of  matching  as
2041           well as at compile time.
2042    
2043           If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
2044           if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
2045           sets the variable pointed to by errptr to point to a textual error mes-
2046           sage. This is a static string that is part of the library. You must not
2047           try  to  free it. Normally, the offset from the start of the pattern to
2048           the data unit that was being processed when the error was discovered is
2049           placed  in the variable pointed to by erroffset, which must not be NULL
2050           (if it is, an immediate error is given). However, for an invalid  UTF-8
2051           or  UTF-16  string,  the  offset  is that of the first data unit of the
2052           failing character.
2053    
2054           Some errors are not detected until the whole pattern has been  scanned;
2055           in  these  cases,  the offset passed back is the length of the pattern.
2056           Note that the offset is in data units, not characters, even  in  a  UTF
2057           mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char-
2058           acter.
2059    
2060           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
2061           codeptr  argument is not NULL, a non-zero error code number is returned
2062           via this argument in the event of an error. This is in addition to  the
2063           textual error message. Error codes and messages are listed below.
2064    
2065           If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
2066           character tables that are  built  when  PCRE  is  compiled,  using  the
2067           default  C  locale.  Otherwise, tableptr must be an address that is the
2068           result of a call to pcre_maketables(). This value is  stored  with  the
2069           compiled  pattern,  and  used  again by pcre_exec() and pcre_dfa_exec()
2070           when the pattern is matched. For more discussion, see  the  section  on
2071           locale support below.
2072    
2073           This  code  fragment  shows a typical straightforward call to pcre_com-
2074           pile():
2075    
2076             pcre *re;
2077             const char *error;
2078             int erroffset;
2079             re = pcre_compile(
2080               "^A.*Z",          /* the pattern */
2081               0,                /* default options */
2082               &error,           /* for error message */
2083               &erroffset,       /* for error offset */
2084               NULL);            /* use default character tables */
2085    
2086           The following names for option bits are defined in  the  pcre.h  header
2087           file:
2088    
2089             PCRE_ANCHORED
2090    
2091           If this bit is set, the pattern is forced to be "anchored", that is, it
2092           is constrained to match only at the first matching point in the  string
2093           that  is being searched (the "subject string"). This effect can also be
2094           achieved by appropriate constructs in the pattern itself, which is  the
2095           only way to do it in Perl.
2096    
2097             PCRE_AUTO_CALLOUT
2098    
2099           If this bit is set, pcre_compile() automatically inserts callout items,
2100           all with number 255, before each pattern item. For  discussion  of  the
2101           callout facility, see the pcrecallout documentation.
2102    
2103             PCRE_BSR_ANYCRLF
2104             PCRE_BSR_UNICODE
2105    
2106           These options (which are mutually exclusive) control what the \R escape
2107           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2108           or to match any Unicode newline sequence. The default is specified when
2109           PCRE is built. It can be overridden from within the pattern, or by set-
2110           ting an option when a compiled pattern is matched.
2111    
2112             PCRE_CASELESS
2113    
2114           If  this  bit is set, letters in the pattern match both upper and lower
2115           case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
2116           changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
2117           always understands the concept of case for characters whose values  are
2118           less  than 128, so caseless matching is always possible. For characters
2119           with higher values, the concept of case is supported if  PCRE  is  com-
2120           piled  with Unicode property support, but not otherwise. If you want to
2121           use caseless matching for characters 128 and  above,  you  must  ensure
2122           that  PCRE  is  compiled  with Unicode property support as well as with
2123           UTF-8 support.
2124    
2125             PCRE_DOLLAR_ENDONLY
2126    
2127           If this bit is set, a dollar metacharacter in the pattern matches  only
2128           at  the  end  of the subject string. Without this option, a dollar also
2129           matches immediately before a newline at the end of the string (but  not
2130           before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
2131           if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
2132           Perl, and no way to set it within a pattern.
2133    
2134             PCRE_DOTALL
2135    
2136           If  this bit is set, a dot metacharacter in the pattern matches a char-
2137           acter of any value, including one that indicates a newline. However, it
2138           only  ever  matches  one character, even if newlines are coded as CRLF.
2139           Without this option, a dot does not match when the current position  is
2140           at a newline. This option is equivalent to Perl's /s option, and it can
2141           be changed within a pattern by a (?s) option setting. A negative  class
2142           such as [^a] always matches newline characters, independent of the set-
2143           ting of this option.
2144    
2145             PCRE_DUPNAMES
2146    
2147           If this bit is set, names used to identify capturing  subpatterns  need
2148           not be unique. This can be helpful for certain types of pattern when it
2149           is known that only one instance of the named  subpattern  can  ever  be
2150           matched.  There  are  more details of named subpatterns below; see also
2151           the pcrepattern documentation.
2152    
2153             PCRE_EXTENDED
2154    
2155           If this bit is set, most white space  characters  in  the  pattern  are
2156           totally  ignored  except when escaped or inside a character class. How-
2157           ever, white space is not allowed within  sequences  such  as  (?>  that
2158           introduce  various  parenthesized  subpatterns,  nor within a numerical
2159           quantifier such as {1,3}.  However, ignorable white space is  permitted
2160           between an item and a following quantifier and between a quantifier and
2161           a following + that indicates possessiveness.
2162    
2163           White space did not used to include the VT character (code 11), because
2164           Perl did not treat this character as white space. However, Perl changed
2165           at release 5.18, so PCRE followed  at  release  8.34,  and  VT  is  now
2166           treated as white space.
2167    
2168           PCRE_EXTENDED  also  causes characters between an unescaped # outside a
2169           character class  and  the  next  newline,  inclusive,  to  be  ignored.
2170           PCRE_EXTENDED  is equivalent to Perl's /x option, and it can be changed
2171           within a pattern by a (?x) option setting.
2172    
2173           Which characters are interpreted  as  newlines  is  controlled  by  the
2174           options  passed to pcre_compile() or by a special sequence at the start
2175           of the pattern, as described in the section entitled  "Newline  conven-
2176           tions" in the pcrepattern documentation. Note that the end of this type
2177           of comment is  a  literal  newline  sequence  in  the  pattern;  escape
2178           sequences that happen to represent a newline do not count.
2179    
2180           This  option  makes  it possible to include comments inside complicated
2181           patterns.  Note, however, that this applies only  to  data  characters.
2182           White  space  characters  may  never  appear  within  special character
2183           sequences in a pattern, for example within the sequence (?( that intro-
2184           duces a conditional subpattern.
2185    
2186             PCRE_EXTRA
2187    
2188           This  option  was invented in order to turn on additional functionality
2189           of PCRE that is incompatible with Perl, but it  is  currently  of  very
2190           little  use. When set, any backslash in a pattern that is followed by a
2191           letter that has no special meaning  causes  an  error,  thus  reserving
2192           these  combinations  for  future  expansion.  By default, as in Perl, a
2193           backslash followed by a letter with no special meaning is treated as  a
2194           literal. (Perl can, however, be persuaded to give an error for this, by
2195           running it with the -w option.) There are at present no other  features
2196           controlled  by this option. It can also be set by a (?X) option setting
2197           within a pattern.
2198    
2199             PCRE_FIRSTLINE
2200    
2201           If this option is set, an  unanchored  pattern  is  required  to  match
2202           before  or  at  the  first  newline  in  the subject string, though the
2203           matched text may continue over the newline.
2204    
2205             PCRE_JAVASCRIPT_COMPAT
2206    
2207           If this option is set, PCRE's behaviour is changed in some ways so that
2208           it  is  compatible with JavaScript rather than Perl. The changes are as
2209           follows:
2210    
2211           (1) A lone closing square bracket in a pattern  causes  a  compile-time
2212           error,  because this is illegal in JavaScript (by default it is treated
2213           as a data character). Thus, the pattern AB]CD becomes illegal when this
2214           option is set.
2215    
2216           (2)  At run time, a back reference to an unset subpattern group matches
2217           an empty string (by default this causes the current  matching  alterna-
2218           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
2219           set (assuming it can find an "a" in the subject), whereas it  fails  by
2220           default, for Perl compatibility.
2221    
2222           (3) \U matches an upper case "U" character; by default \U causes a com-
2223           pile time error (Perl uses \U to upper case subsequent characters).
2224    
2225           (4) \u matches a lower case "u" character unless it is followed by four
2226           hexadecimal  digits,  in  which case the hexadecimal number defines the
2227           code point to match. By default, \u causes a compile time  error  (Perl
2228           uses it to upper case the following character).
2229    
2230           (5)  \x matches a lower case "x" character unless it is followed by two
2231           hexadecimal digits, in which case the hexadecimal  number  defines  the
2232           code  point  to  match. By default, as in Perl, a hexadecimal number is
2233           always expected after \x, but it may have zero, one, or two digits (so,
2234           for example, \xz matches a binary zero character followed by z).
2235    
2236             PCRE_MULTILINE
2237    
2238           By  default,  for  the purposes of matching "start of line" and "end of
2239           line", PCRE treats the subject string as consisting of a single line of
2240           characters,  even if it actually contains newlines. The "start of line"
2241           metacharacter (^) matches only at the start of the string, and the "end
2242           of  line"  metacharacter  ($) matches only at the end of the string, or
2243           before a terminating newline (except when PCRE_DOLLAR_ENDONLY is  set).
2244           Note,  however,  that  unless  PCRE_DOTALL  is set, the "any character"
2245           metacharacter (.) does not match at a newline. This behaviour  (for  ^,
2246           $, and dot) is the same as Perl.
2247    
2248           When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
2249           constructs match immediately following or immediately  before  internal
2250           newlines  in  the  subject string, respectively, as well as at the very
2251           start and end. This is equivalent to Perl's /m option, and  it  can  be
2252           changed within a pattern by a (?m) option setting. If there are no new-
2253           lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
2254           setting PCRE_MULTILINE has no effect.
2255    
2256             PCRE_NEVER_UTF
2257    
2258           This option locks out interpretation of the pattern as UTF-8 (or UTF-16
2259           or UTF-32 in the 16-bit and 32-bit libraries). In particular,  it  pre-
2260           vents  the  creator of the pattern from switching to UTF interpretation
2261           by starting the pattern with (*UTF). This may be useful in applications
2262           that  process  patterns  from  external  sources.  The  combination  of
2263           PCRE_UTF8 and PCRE_NEVER_UTF also causes an error.
2264    
2265             PCRE_NEWLINE_CR
2266             PCRE_NEWLINE_LF
2267             PCRE_NEWLINE_CRLF
2268             PCRE_NEWLINE_ANYCRLF
2269             PCRE_NEWLINE_ANY
2270    
2271           These options override the default newline definition that  was  chosen
2272           when  PCRE  was built. Setting the first or the second specifies that a
2273           newline is indicated by a single character (CR  or  LF,  respectively).
2274           Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
2275           two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
2276           that any of the three preceding sequences should be recognized. Setting
2277           PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
2278           recognized.
2279    
2280           In  an ASCII/Unicode environment, the Unicode newline sequences are the
2281           three just mentioned, plus the  single  characters  VT  (vertical  tab,
2282           U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep-
2283           arator, U+2028), and PS (paragraph separator, U+2029).  For  the  8-bit
2284           library, the last two are recognized only in UTF-8 mode.
2285    
2286           When  PCRE is compiled to run in an EBCDIC (mainframe) environment, the
2287           code for CR is 0x0d, the same as ASCII. However, the character code for
2288           LF  is  normally 0x15, though in some EBCDIC environments 0x25 is used.
2289           Whichever of these is not LF is made to  correspond  to  Unicode's  NEL
2290           character.  EBCDIC  codes  are all less than 256. For more details, see
2291           the pcrebuild documentation.
2292    
2293           The newline setting in the  options  word  uses  three  bits  that  are
2294           treated as a number, giving eight possibilities. Currently only six are
2295           used (default plus the five values above). This means that if  you  set
2296           more  than one newline option, the combination may or may not be sensi-
2297           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
2298           PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
2299           cause an error.
2300    
2301           The only time that a line break in a pattern  is  specially  recognized
2302           when  compiling is when PCRE_EXTENDED is set. CR and LF are white space
2303           characters, and so are ignored in this mode. Also, an unescaped #  out-
2304           side  a  character class indicates a comment that lasts until after the
2305           next line break sequence. In other circumstances, line break  sequences
2306           in patterns are treated as literal data.
2307    
2308           The newline option that is set at compile time becomes the default that
2309           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
2310    
2311             PCRE_NO_AUTO_CAPTURE
2312    
2313           If this option is set, it disables the use of numbered capturing paren-
2314           theses  in the pattern. Any opening parenthesis that is not followed by
2315           ? behaves as if it were followed by ?: but named parentheses can  still
2316           be  used  for  capturing  (and  they acquire numbers in the usual way).
2317           There is no equivalent of this option in Perl.
2318    
2319             PCRE_NO_AUTO_POSSESS
2320    
2321           If this option is set, it disables "auto-possessification". This is  an
2322           optimization  that,  for example, turns a+b into a++b in order to avoid
2323           backtracks into a+ that can never be successful. However,  if  callouts
2324           are  in  use,  auto-possessification  means that some of them are never
2325           taken. You can set this option if you want the matching functions to do
2326           a  full  unoptimized  search and run all the callouts, but it is mainly
2327           provided for testing purposes.
2328    
2329             PCRE_NO_START_OPTIMIZE
2330    
2331           This is an option that acts at matching time; that is, it is really  an
2332           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
2333           time, it is remembered with the compiled pattern and assumed at  match-
2334           ing  time.  This is necessary if you want to use JIT execution, because
2335           the JIT compiler needs to know whether or not this option is  set.  For
2336           details see the discussion of PCRE_NO_START_OPTIMIZE below.
2337    
2338             PCRE_UCP
2339    
2340           This  option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
2341           \w, and some of the POSIX character classes.  By  default,  only  ASCII
2342           characters  are  recognized, but if PCRE_UCP is set, Unicode properties
2343           are used instead to classify characters. More details are given in  the
2344           section  on generic character types in the pcrepattern page. If you set
2345           PCRE_UCP, matching one of the items it affects takes much  longer.  The
2346           option  is  available only if PCRE has been compiled with Unicode prop-
2347           erty support.
2348    
2349             PCRE_UNGREEDY
2350    
2351           This option inverts the "greediness" of the quantifiers  so  that  they
2352           are  not greedy by default, but become greedy if followed by "?". It is
2353           not compatible with Perl. It can also be set by a (?U)  option  setting
2354           within the pattern.
2355    
2356             PCRE_UTF8
2357    
2358           This  option  causes PCRE to regard both the pattern and the subject as
2359           strings of UTF-8 characters instead of single-byte strings. However, it
2360           is  available  only  when PCRE is built to include UTF support. If not,
2361           the use of this option provokes an error. Details of  how  this  option
2362           changes the behaviour of PCRE are given in the pcreunicode page.
2363    
2364             PCRE_NO_UTF8_CHECK
2365    
2366           When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
2367           automatically checked. There is a  discussion  about  the  validity  of
2368           UTF-8  strings in the pcreunicode page. If an invalid UTF-8 sequence is
2369           found, pcre_compile() returns an error. If you already know  that  your
2370           pattern  is valid, and you want to skip this check for performance rea-
2371           sons, you can set the PCRE_NO_UTF8_CHECK option.  When it is  set,  the
2372           effect of passing an invalid UTF-8 string as a pattern is undefined. It
2373           may cause your program to crash or loop. Note that this option can also
2374           be  passed to pcre_exec() and pcre_dfa_exec(), to suppress the validity
2375           checking of subject strings only. If the same string is  being  matched
2376           many  times, the option can be safely set for the second and subsequent
2377           matchings to improve performance.
2378    
2379    
2380    COMPILATION ERROR CODES
2381    
2382           The following table lists the error  codes  than  may  be  returned  by
2383           pcre_compile2(),  along with the error messages that may be returned by
2384           both compiling functions. Note that error  messages  are  always  8-bit
2385           ASCII  strings,  even  in 16-bit or 32-bit mode. As PCRE has developed,
2386           some error codes have fallen out of use. To avoid confusion, they  have
2387           not been re-used.
2388    
2389              0  no error
2390              1  \ at end of pattern
2391              2  \c at end of pattern
2392              3  unrecognized character follows \
2393              4  numbers out of order in {} quantifier
2394              5  number too big in {} quantifier
2395              6  missing terminating ] for character class
2396              7  invalid escape sequence in character class
2397              8  range out of order in character class
2398              9  nothing to repeat
2399             10  [this code is not in use]
2400             11  internal error: unexpected repeat
2401             12  unrecognized character after (? or (?-
2402             13  POSIX named classes are supported only within a class
2403             14  missing )
2404             15  reference to non-existent subpattern
2405             16  erroffset passed as NULL
2406             17  unknown option bit(s) set
2407             18  missing ) after comment
2408             19  [this code is not in use]
2409             20  regular expression is too large
2410             21  failed to get memory
2411             22  unmatched parentheses
2412             23  internal error: code overflow
2413             24  unrecognized character after (?<
2414             25  lookbehind assertion is not fixed length
2415             26  malformed number or name after (?(
2416             27  conditional group contains more than two branches
2417             28  assertion expected after (?(
2418             29  (?R or (?[+-]digits must be followed by )
2419             30  unknown POSIX class name
2420             31  POSIX collating elements are not supported
2421             32  this version of PCRE is compiled without UTF support
2422             33  [this code is not in use]
2423             34  character value in \x{} or \o{} is too large
2424             35  invalid condition (?(0)
2425             36  \C not allowed in lookbehind assertion
2426             37  PCRE does not support \L, \l, \N{name}, \U, or \u
2427             38  number after (?C is > 255
2428             39  closing ) for (?C expected
2429             40  recursive call could loop indefinitely
2430             41  unrecognized character after (?P
2431             42  syntax error in subpattern name (missing terminator)
2432             43  two named subpatterns have the same name
2433             44  invalid UTF-8 string (specifically UTF-8)
2434             45  support for \P, \p, and \X has not been compiled
2435             46  malformed \P or \p sequence
2436             47  unknown property name after \P or \p
2437             48  subpattern name is too long (maximum 32 characters)
2438             49  too many named subpatterns (maximum 10000)
2439             50  [this code is not in use]
2440             51  octal value is greater than \377 in 8-bit non-UTF-8 mode
2441             52  internal error: overran compiling workspace
2442             53  internal error: previously-checked referenced subpattern
2443                   not found
2444             54  DEFINE group contains more than one branch
2445             55  repeating a DEFINE group is not allowed
2446             56  inconsistent NEWLINE options
2447             57  \g is not followed by a braced, angle-bracketed, or quoted
2448                   name/number or by a plain number
2449             58  a numbered reference must not be zero
2450             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
2451             60  (*VERB) not recognized or malformed
2452             61  number is too big
2453             62  subpattern name expected
2454             63  digit expected after (?+
2455             64  ] is an invalid data character in JavaScript compatibility mode
2456             65  different names for subpatterns of the same number are
2457                   not allowed
2458             66  (*MARK) must have an argument
2459             67  this version of PCRE is not compiled with Unicode property
2460                   support
2461             68  \c must be followed by an ASCII character
2462             69  \k is not followed by a braced, angle-bracketed, or quoted name
2463             70  internal error: unknown opcode in find_fixedlength()
2464             71  \N is not supported in a class
2465             72  too many forward references
2466             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
2467             74  invalid UTF-16 string (specifically UTF-16)
2468             75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
2469             76  character value in \u.... sequence is too large
2470             77  invalid UTF-32 string (specifically UTF-32)
2471             78  setting UTF is disabled by the application
2472             79  non-hex character in \x{} (closing brace missing?)
2473             80  non-octal character in \o{} (closing brace missing?)
2474             81  missing opening brace after \o
2475             82  parentheses are too deeply nested
2476             83  invalid range in character class
2477    
2478           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
2479           values may be used if the limits were changed when PCRE was built.
2480    
2481    
2482    STUDYING A PATTERN
2483    
2484           pcre_extra *pcre_study(const pcre *code, int options,
2485                const char **errptr);
2486    
2487           If a compiled pattern is going to be used several times,  it  is  worth
2488           spending more time analyzing it in order to speed up the time taken for
2489           matching. The function pcre_study() takes a pointer to a compiled  pat-
2490           tern as its first argument. If studying the pattern produces additional
2491           information that will help speed up matching,  pcre_study()  returns  a
2492           pointer  to a pcre_extra block, in which the study_data field points to
2493           the results of the study.
2494    
2495           The  returned  value  from  pcre_study()  can  be  passed  directly  to
2496           pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
2497           tains other fields that can be set by the caller before  the  block  is
2498           passed; these are described below in the section on matching a pattern.
2499    
2500           If  studying  the  pattern  does  not  produce  any useful information,
2501           pcre_study() returns NULL by default.  In  that  circumstance,  if  the
2502           calling program wants to pass any of the other fields to pcre_exec() or
2503           pcre_dfa_exec(), it must set up its own pcre_extra block.  However,  if
2504           pcre_study()  is  called  with  the  PCRE_STUDY_EXTRA_NEEDED option, it
2505           returns a pcre_extra block even if studying did not find any additional
2506           information.  It  may still return NULL, however, if an error occurs in
2507           pcre_study().
2508    
2509           The second argument of pcre_study() contains  option  bits.  There  are
2510           three further options in addition to PCRE_STUDY_EXTRA_NEEDED:
2511    
2512             PCRE_STUDY_JIT_COMPILE
2513             PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
2514             PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
2515    
2516           If  any  of  these are set, and the just-in-time compiler is available,
2517           the pattern is further compiled into machine code  that  executes  much
2518           faster  than  the  pcre_exec()  interpretive  matching function. If the
2519           just-in-time compiler is not available, these options are ignored.  All
2520           undefined bits in the options argument must be zero.
2521    
2522           JIT  compilation  is  a heavyweight optimization. It can take some time
2523           for patterns to be analyzed, and for one-off matches  and  simple  pat-
2524           terns  the benefit of faster execution might be offset by a much slower
2525           study time.  Not all patterns can be optimized by the JIT compiler. For
2526           those  that cannot be handled, matching automatically falls back to the
2527           pcre_exec() interpreter. For more details, see the  pcrejit  documenta-
2528           tion.
2529    
2530           The  third argument for pcre_study() is a pointer for an error message.
2531           If studying succeeds (even if no data is  returned),  the  variable  it
2532           points  to  is  set  to NULL. Otherwise it is set to point to a textual
2533           error message. This is a static string that is part of the library. You
2534           must  not  try  to  free it. You should test the error pointer for NULL
2535           after calling pcre_study(), to be sure that it has run successfully.
2536    
2537           When you are finished with a pattern, you can free the memory used  for
2538           the study data by calling pcre_free_study(). This function was added to
2539           the API for release 8.20. For earlier versions,  the  memory  could  be
2540           freed  with  pcre_free(), just like the pattern itself. This will still
2541           work in cases where JIT optimization is not used, but it  is  advisable
2542           to change to the new function when convenient.
2543    
2544           This  is  a typical way in which pcre_study() is used (except that in a
2545           real application there should be tests for errors):
2546    
2547             int rc;
2548             pcre *re;
2549             pcre_extra *sd;
2550             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
2551             sd = pcre_study(
2552               re,             /* result of pcre_compile() */
2553               0,              /* no options */
2554               &error);        /* set to NULL or points to a message */
2555             rc = pcre_exec(   /* see below for details of pcre_exec() options */
2556               re, sd, "subject", 7, 0, 0, ovector, 30);
2557             ...
2558             pcre_free_study(sd);
2559             pcre_free(re);
2560    
2561           Studying a pattern does two things: first, a lower bound for the length
2562           of subject string that is needed to match the pattern is computed. This
2563           does not mean that there are any strings of that length that match, but
2564           it  does  guarantee that no shorter strings match. The value is used to
2565           avoid wasting time by trying to match strings that are shorter than the
2566           lower  bound.  You  can find out the value in a calling program via the
2567           pcre_fullinfo() function.
2568    
2569           Studying a pattern is also useful for non-anchored patterns that do not
2570           have  a  single fixed starting character. A bitmap of possible starting
2571           bytes is created. This speeds up finding a position in the  subject  at
2572           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
2573           values less than 256.  In 32-bit mode, the bitmap is  used  for  32-bit
2574           values less than 256.)
2575    
2576           These  two optimizations apply to both pcre_exec() and pcre_dfa_exec(),
2577           and the information is also used by the JIT  compiler.   The  optimiza-
2578           tions  can  be  disabled  by setting the PCRE_NO_START_OPTIMIZE option.
2579           You might want to do this if your pattern contains callouts or  (*MARK)
2580           and  you  want  to make use of these facilities in cases where matching
2581           fails.
2582    
2583           PCRE_NO_START_OPTIMIZE can be specified at either compile time or  exe-
2584           cution   time.   However,   if   PCRE_NO_START_OPTIMIZE  is  passed  to
2585           pcre_exec(), (that is, after any JIT compilation has happened) JIT exe-
2586           cution  is disabled. For JIT execution to work with PCRE_NO_START_OPTI-
2587           MIZE, the option must be set at compile time.
2588    
2589           There is a longer discussion of PCRE_NO_START_OPTIMIZE below.
2590    
2591    
2592    LOCALE SUPPORT
2593    
2594           PCRE handles caseless matching, and determines whether  characters  are
2595           letters,  digits, or whatever, by reference to a set of tables, indexed
2596           by character code point. When running in UTF-8 mode, or in the  16-  or
2597           32-bit libraries, this applies only to characters with code points less
2598           than 256. By default, higher-valued code  points  never  match  escapes
2599           such  as \w or \d. However, if PCRE is built with Unicode property sup-
2600           port, all characters can be tested with \p and \P,  or,  alternatively,
2601           the  PCRE_UCP option can be set when a pattern is compiled; this causes
2602           \w and friends to use Unicode property support instead of the  built-in
2603           tables.
2604    
2605           The  use  of  locales  with Unicode is discouraged. If you are handling
2606           characters with code points greater than 128,  you  should  either  use
2607           Unicode support, or use locales, but not try to mix the two.
2608    
2609           PCRE  contains  an  internal set of tables that are used when the final
2610           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
2611           applications.  Normally, the internal tables recognize only ASCII char-
2612           acters. However, when PCRE is built, it is possible to cause the inter-
2613           nal tables to be rebuilt in the default "C" locale of the local system,
2614           which may cause them to be different.
2615    
2616           The internal tables can always be overridden by tables supplied by  the
2617           application that calls PCRE. These may be created in a different locale
2618           from the default. As more and more applications change  to  using  Uni-
2619           code, the need for this locale support is expected to die away.
2620    
2621           External  tables  are  built by calling the pcre_maketables() function,
2622           which has no arguments, in the relevant locale. The result can then  be
2623           passed  to  pcre_compile() as often as necessary. For example, to build
2624           and use tables that  are  appropriate  for  the  French  locale  (where
2625           accented  characters  with  values greater than 128 are treated as let-
2626           ters), the following code could be used:
2627    
2628             setlocale(LC_CTYPE, "fr_FR");
2629             tables = pcre_maketables();
2630             re = pcre_compile(..., tables);
2631    
2632           The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
2633           if you are using Windows, the name for the French locale is "french".
2634    
2635           When  pcre_maketables()  runs,  the  tables are built in memory that is
2636           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
2637           that  the memory containing the tables remains available for as long as
2638           it is needed.
2639    
2640           The pointer that is passed to pcre_compile() is saved with the compiled
2641           pattern,  and the same tables are used via this pointer by pcre_study()
2642           and also by pcre_exec() and pcre_dfa_exec(). Thus, for any single  pat-
2643           tern, compilation, studying and matching all happen in the same locale,
2644           but different patterns can be processed in different locales.
2645    
2646           It is possible to pass a table pointer or NULL (indicating the  use  of
2647           the internal tables) to pcre_exec() or pcre_dfa_exec() (see the discus-
2648           sion below in the section on matching a pattern). This facility is pro-
2649           vided  for  use  with  pre-compiled  patterns  that have been saved and
2650           reloaded.  Character tables are not saved with patterns, so if  a  non-
2651           standard table was used at compile time, it must be provided again when
2652           the reloaded pattern is matched. Attempting to  use  this  facility  to
2653           match a pattern in a different locale from the one in which it was com-
2654           piled is likely to lead to anomalous (usually incorrect) results.
2655    
2656    
2657    INFORMATION ABOUT A PATTERN
2658    
2659           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
2660                int what, void *where);
2661    
2662           The pcre_fullinfo() function returns information about a compiled  pat-
2663           tern.  It replaces the pcre_info() function, which was removed from the
2664           library at version 8.30, after more than 10 years of obsolescence.
2665    
2666           The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
2667           pattern.  The second argument is the result of pcre_study(), or NULL if
2668           the pattern was not studied. The third argument specifies  which  piece
2669           of  information  is required, and the fourth argument is a pointer to a
2670           variable to receive the data. The yield of the  function  is  zero  for
2671           success, or one of the following negative numbers:
2672    
2673             PCRE_ERROR_NULL           the argument code was NULL
2674                                       the argument where was NULL
2675             PCRE_ERROR_BADMAGIC       the "magic number" was not found
2676             PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2677                                       endianness
2678             PCRE_ERROR_BADOPTION      the value of what was invalid
2679             PCRE_ERROR_UNSET          the requested field is not set
2680    
2681           The  "magic  number" is placed at the start of each compiled pattern as
2682           an simple check against passing an arbitrary memory pointer. The  endi-
2683           anness error can occur if a compiled pattern is saved and reloaded on a
2684           different host. Here is a typical call of  pcre_fullinfo(),  to  obtain
2685           the length of the compiled pattern:
2686    
2687             int rc;
2688             size_t length;
2689             rc = pcre_fullinfo(
2690               re,               /* result of pcre_compile() */
2691               sd,               /* result of pcre_study(), or NULL */
2692               PCRE_INFO_SIZE,   /* what is required */
2693               &length);         /* where to put the data */
2694    
2695           The  possible  values for the third argument are defined in pcre.h, and
2696           are as follows:
2697    
2698             PCRE_INFO_BACKREFMAX
2699    
2700           Return the number of the highest back reference  in  the  pattern.  The
2701           fourth  argument  should  point to an int variable. Zero is returned if
2702           there are no back references.
2703    
2704             PCRE_INFO_CAPTURECOUNT
2705    
2706           Return the number of capturing subpatterns in the pattern.  The  fourth
2707           argument should point to an int variable.
2708    
2709             PCRE_INFO_DEFAULT_TABLES
2710    
2711           Return  a pointer to the internal default character tables within PCRE.
2712           The fourth argument should point to an unsigned char *  variable.  This
2713           information call is provided for internal use by the pcre_study() func-
2714           tion. External callers can cause PCRE to use  its  internal  tables  by
2715           passing a NULL table pointer.
2716    
2717             PCRE_INFO_FIRSTBYTE
2718    
2719           Return information about the first data unit of any matched string, for
2720           a non-anchored pattern. (The name of this option refers  to  the  8-bit
2721           library,  where data units are bytes.) The fourth argument should point
2722           to an int variable.
2723    
2724           If there is a fixed first value, for example, the  letter  "c"  from  a
2725           pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2726           library, the value is always less than 256. In the 16-bit  library  the
2727           value can be up to 0xffff. In the 32-bit library the value can be up to
2728           0x10ffff.
2729    
2730           If there is no fixed first value, and if either
2731    
2732           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2733           branch starts with "^", or
2734    
2735           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2736           set (if it were set, the pattern would be anchored),
2737    
2738           -1 is returned, indicating that the pattern matches only at  the  start
2739           of  a  subject string or after any newline within the string. Otherwise
2740           -2 is returned. For anchored patterns, -2 is returned.
2741    
2742           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2743           is  unable to return the full 32-bit range of the character, this value
2744           is   deprecated;   instead   the   PCRE_INFO_FIRSTCHARACTERFLAGS    and
2745           PCRE_INFO_FIRSTCHARACTER values should be used.
2746    
2747             PCRE_INFO_FIRSTTABLE
2748    
2749           If  the pattern was studied, and this resulted in the construction of a
2750           256-bit table indicating a fixed set of values for the first data  unit
2751           in  any  matching string, a pointer to the table is returned. Otherwise
2752           NULL is returned. The fourth argument should point to an unsigned  char
2753           * variable.
2754    
2755             PCRE_INFO_HASCRORLF
2756    
2757           Return  1  if  the  pattern  contains any explicit matches for CR or LF
2758           characters, otherwise 0. The fourth argument should  point  to  an  int
2759           variable.  An explicit match is either a literal CR or LF character, or
2760           \r or \n.
2761    
2762             PCRE_INFO_JCHANGED
2763    
2764           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
2765           otherwise  0. The fourth argument should point to an int variable. (?J)
2766           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2767    
2768             PCRE_INFO_JIT
2769    
2770           Return 1 if the pattern was studied with one of the  JIT  options,  and
2771           just-in-time compiling was successful. The fourth argument should point
2772           to an int variable. A return value of 0 means that JIT support  is  not
2773           available  in this version of PCRE, or that the pattern was not studied
2774           with a JIT option, or that the JIT compiler could not handle this  par-
2775           ticular  pattern. See the pcrejit documentation for details of what can
2776           and cannot be handled.
2777    
2778             PCRE_INFO_JITSIZE
2779    
2780           If the pattern was successfully studied with a JIT option,  return  the
2781           size  of the JIT compiled code, otherwise return zero. The fourth argu-
2782           ment should point to a size_t variable.
2783    
2784             PCRE_INFO_LASTLITERAL
2785    
2786           Return the value of the rightmost literal data unit that must exist  in
2787           any  matched  string, other than at its start, if such a value has been
2788           recorded. The fourth argument should point to an int variable. If there
2789           is no such value, -1 is returned. For anchored patterns, a last literal
2790           value is recorded only if it follows something of variable length.  For
2791           example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
2792           /^a\dz\d/ the returned value is -1.
2793    
2794           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2795           is  unable to return the full 32-bit range of characters, this value is
2796           deprecated;     instead     the     PCRE_INFO_REQUIREDCHARFLAGS     and
2797           PCRE_INFO_REQUIREDCHAR values should be used.
2798    
2799             PCRE_INFO_MATCH_EMPTY
2800    
2801           Return  1  if  the  pattern can match an empty string, otherwise 0. The
2802           fourth argument should point to an int variable.
2803    
2804             PCRE_INFO_MATCHLIMIT
2805    
2806           If the pattern set a match limit by  including  an  item  of  the  form
2807           (*LIMIT_MATCH=nnnn)  at  the  start,  the value is returned. The fourth
2808           argument should point to an unsigned 32-bit integer. If no  such  value
2809           has   been   set,   the  call  to  pcre_fullinfo()  returns  the  error
2810           PCRE_ERROR_UNSET.
2811    
2812             PCRE_INFO_MAXLOOKBEHIND
2813    
2814           Return the number of characters (NB not  data  units)  in  the  longest
2815           lookbehind  assertion  in  the pattern. This information is useful when
2816           doing multi-segment matching using  the  partial  matching  facilities.
2817           Note that the simple assertions \b and \B require a one-character look-
2818           behind. \A also registers a one-character lookbehind,  though  it  does
2819           not  actually inspect the previous character. This is to ensure that at
2820           least one character from the old segment is retained when a new segment
2821           is processed. Otherwise, if there are no lookbehinds in the pattern, \A
2822           might match incorrectly at the start of a new segment.
2823    
2824             PCRE_INFO_MINLENGTH
2825    
2826           If the pattern was studied and a minimum length  for  matching  subject
2827           strings  was  computed,  its  value is returned. Otherwise the returned
2828           value is -1. The value is a number of characters, which in UTF mode may
2829           be  different from the number of data units. The fourth argument should
2830           point to an int variable. A non-negative value is a lower bound to  the
2831           length  of  any  matching  string. There may not be any strings of that
2832           length that do actually match, but every string that does match  is  at
2833           least that long.
2834    
2835             PCRE_INFO_NAMECOUNT
2836             PCRE_INFO_NAMEENTRYSIZE
2837             PCRE_INFO_NAMETABLE
2838    
2839           PCRE  supports the use of named as well as numbered capturing parenthe-
2840           ses. The names are just an additional way of identifying the  parenthe-
2841           ses, which still acquire numbers. Several convenience functions such as
2842           pcre_get_named_substring() are provided for  extracting  captured  sub-
2843           strings  by  name. It is also possible to extract the data directly, by
2844           first converting the name to a number in order to  access  the  correct
2845           pointers in the output vector (described with pcre_exec() below). To do
2846           the conversion, you need  to  use  the  name-to-number  map,  which  is
2847           described by these three values.
2848    
2849           The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
2850           gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2851           of  each  entry;  both  of  these  return  an int value. The entry size
2852           depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
2853           a pointer to the first entry of the table. This is a pointer to char in
2854           the 8-bit library, where the first two bytes of each entry are the num-
2855           ber  of  the capturing parenthesis, most significant byte first. In the
2856           16-bit library, the pointer points to 16-bit data units, the  first  of
2857           which  contains  the  parenthesis  number.  In  the 32-bit library, the
2858           pointer points to 32-bit data units, the first of  which  contains  the
2859           parenthesis  number.  The  rest of the entry is the corresponding name,
2860           zero terminated.
2861    
2862           The names are in alphabetical order. If (?| is used to create  multiple
2863           groups  with  the same number, as described in the section on duplicate
2864           subpattern numbers in the pcrepattern page, the groups may be given the
2865           same  name,  but  there is only one entry in the table. Different names
2866           for groups of the same number are not permitted.  Duplicate  names  for
2867           subpatterns with different numbers are permitted, but only if PCRE_DUP-
2868           NAMES is set. They appear in the table in the order in which they  were
2869           found  in  the  pattern.  In  the  absence  of (?| this is the order of
2870           increasing number; when (?| is used this is not  necessarily  the  case
2871           because later subpatterns may have lower numbers.
2872    
2873           As  a  simple  example of the name/number table, consider the following
2874           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2875           set, so white space - including newlines - is ignored):
2876    
2877             (?<date> (?<year>(\d\d)?\d\d) -
2878             (?<month>\d\d) - (?<day>\d\d) )
2879    
2880           There  are  four  named subpatterns, so the table has four entries, and
2881           each entry in the table is eight bytes long. The table is  as  follows,
2882           with non-printing bytes shows in hexadecimal, and undefined bytes shown
2883           as ??:
2884    
2885             00 01 d  a  t  e  00 ??
2886             00 05 d  a  y  00 ?? ??
2887             00 04 m  o  n  t  h  00
2888             00 02 y  e  a  r  00 ??
2889    
2890           When writing code to extract data  from  named  subpatterns  using  the
2891           name-to-number  map,  remember that the length of the entries is likely
2892           to be different for each compiled pattern.
2893    
2894             PCRE_INFO_OKPARTIAL
2895    
2896           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
2897           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
2898           variable. From  release  8.00,  this  always  returns  1,  because  the
2899           restrictions  that  previously  applied  to  partial matching have been
2900           lifted. The pcrepartial documentation gives details of  partial  match-
2901           ing.
2902    
2903             PCRE_INFO_OPTIONS
2904    
2905           Return  a  copy of the options with which the pattern was compiled. The
2906           fourth argument should point to an unsigned long  int  variable.  These
2907           option bits are those specified in the call to pcre_compile(), modified
2908           by any top-level option settings at the start of the pattern itself. In
2909           other  words,  they are the options that will be in force when matching
2910           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
2911           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
2912           and PCRE_EXTENDED.
2913    
2914           A pattern is automatically anchored by PCRE if  all  of  its  top-level
2915           alternatives begin with one of the following:
2916    
2917             ^     unless PCRE_MULTILINE is set
2918             \A    always
2919             \G    always
2920             .*    if PCRE_DOTALL is set and there are no back
2921                     references to the subpattern in which .* appears
2922    
2923           For such patterns, the PCRE_ANCHORED bit is set in the options returned
2924           by pcre_fullinfo().
2925    
2926             PCRE_INFO_RECURSIONLIMIT
2927    
2928           If the pattern set a recursion limit by including an item of  the  form
2929           (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth
2930           argument should point to an unsigned 32-bit integer. If no  such  value
2931           has   been   set,   the  call  to  pcre_fullinfo()  returns  the  error
2932           PCRE_ERROR_UNSET.
2933    
2934             PCRE_INFO_SIZE
2935    
2936           Return the size of  the  compiled  pattern  in  bytes  (for  all  three
2937           libraries). The fourth argument should point to a size_t variable. This
2938           value does not include the size of the pcre structure that is  returned
2939           by  pcre_compile().  The  value  that  is  passed  as  the  argument to
2940           pcre_malloc() when pcre_compile() is getting memory in which  to  place
2941           the compiled data is the value returned by this option plus the size of
2942           the pcre structure. Studying a compiled pattern, with or  without  JIT,
2943           does not alter the value returned by this option.
2944    
2945             PCRE_INFO_STUDYSIZE
2946    
2947           Return  the  size  in bytes (for all three libraries) of the data block
2948           pointed to by the study_data field in a pcre_extra block. If pcre_extra
2949           is  NULL, or there is no study data, zero is returned. The fourth argu-
2950           ment should point to a size_t variable. The study_data field is set  by
2951           pcre_study() to record information that will speed up matching (see the
2952           section entitled  "Studying  a  pattern"  above).  The  format  of  the
2953           study_data  block is private, but its length is made available via this
2954           option so that it can be saved and  restored  (see  the  pcreprecompile
2955           documentation for details).
2956    
2957             PCRE_INFO_FIRSTCHARACTERFLAGS
2958    
2959           Return information about the first data unit of any matched string, for
2960           a non-anchored pattern. The fourth argument  should  point  to  an  int
2961           variable.
2962    
2963           If  there  is  a  fixed first value, for example, the letter "c" from a
2964           pattern such as (cat|cow|coyote), 1  is  returned,  and  the  character
2965           value can be retrieved using PCRE_INFO_FIRSTCHARACTER.
2966    
2967           If there is no fixed first value, and if either
2968    
2969           (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
2970           branch starts with "^", or
2971    
2972           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2973           set (if it were set, the pattern would be anchored),
2974    
2975           2 is returned, indicating that the pattern matches only at the start of
2976           a subject string or after any newline within the string. Otherwise 0 is
2977           returned. For anchored patterns, 0 is returned.
2978    
2979             PCRE_INFO_FIRSTCHARACTER
2980    
2981           Return   the  fixed  first  character  value  in  the  situation  where
2982           PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; otherwise return 0. The fourth
2983           argument should point to an uint_t variable.
2984    
2985           In  the 8-bit library, the value is always less than 256. In the 16-bit
2986           library the value can be up to 0xffff. In the 32-bit library in  UTF-32
2987           mode  the  value  can  be up to 0x10ffff, and up to 0xffffffff when not
2988           using UTF-32 mode.
2989    
2990             PCRE_INFO_REQUIREDCHARFLAGS
2991    
2992           Returns 1 if there is a rightmost literal data unit that must exist  in
2993           any matched string, other than at its start. The fourth argument should
2994           point to an int variable. If there is no such value, 0 is returned.  If
2995           returning  1,  the  character  value  itself  can  be  retrieved  using
2996           PCRE_INFO_REQUIREDCHAR.
2997    
2998           For anchored patterns, a last literal value is recorded only if it fol-
2999           lows  something  of  variable  length.  For  example,  for  the pattern
3000           /^a\d+z\d+/  the   returned   value   1   (with   "z"   returned   from
3001           PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0.
3002    
3003             PCRE_INFO_REQUIREDCHAR
3004    
3005           Return  the value of the rightmost literal data unit that must exist in
3006           any matched string, other than at its start, if such a value  has  been
3007           recorded.  The fourth argument should point to an uint32_t variable. If
3008           there is no such value, 0 is returned.
3009    
3010    
3011    REFERENCE COUNTS
3012    
3013           int pcre_refcount(pcre *code, int adjust);
3014    
3015           The pcre_refcount() function is used to maintain a reference  count  in
3016           the data block that contains a compiled pattern. It is provided for the
3017           benefit of applications that  operate  in  an  object-oriented  manner,
3018           where different parts of the application may be using the same compiled
3019           pattern, but you want to free the block when they are all done.
3020    
3021           When a pattern is compiled, the reference count field is initialized to
3022           zero.   It is changed only by calling this function, whose action is to
3023           add the adjust value (which may be positive or  negative)  to  it.  The
3024           yield of the function is the new value. However, the value of the count
3025           is constrained to lie between 0 and 65535, inclusive. If the new  value
3026           is outside these limits, it is forced to the appropriate limit value.
3027    
3028           Except  when it is zero, the reference count is not correctly preserved
3029           if a pattern is compiled on one host and then  transferred  to  a  host
3030           whose byte-order is different. (This seems a highly unlikely scenario.)
3031    
3032    
3033    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
3034    
3035           int pcre_exec(const pcre *code, const pcre_extra *extra,
3036                const char *subject, int length, int startoffset,
3037                int options, int *ovector, int ovecsize);
3038    
3039           The  function pcre_exec() is called to match a subject string against a
3040           compiled pattern, which is passed in the code argument. If the  pattern
3041           was  studied,  the  result  of  the study should be passed in the extra
3042           argument. You can call pcre_exec() with the same code and  extra  argu-
3043           ments  as  many  times as you like, in order to match different subject
3044           strings with the same pattern.
3045    
3046           This function is the main matching facility  of  the  library,  and  it
3047           operates  in  a  Perl-like  manner. For specialist use there is also an
3048           alternative matching function, which is described below in the  section
3049           about the pcre_dfa_exec() function.
3050    
3051           In  most applications, the pattern will have been compiled (and option-
3052           ally studied) in the same process that calls pcre_exec().  However,  it
3053           is possible to save compiled patterns and study data, and then use them
3054           later in different processes, possibly even on different hosts.  For  a
3055           discussion about this, see the pcreprecompile documentation.
3056    
3057           Here is an example of a simple call to pcre_exec():
3058    
3059             int rc;
3060             int ovector[30];
3061             rc = pcre_exec(
3062               re,             /* result of pcre_compile() */
3063               NULL,           /* we didn't study the pattern */
3064               "some string",  /* the subject string */
3065               11,             /* the length of the subject string */
3066               0,              /* start at offset 0 in the subject */
3067               0,              /* default options */
3068               ovector,        /* vector of integers for substring information */
3069               30);            /* number of elements (NOT size in bytes) */
3070    
3071       Extra data for pcre_exec()
3072    
3073           If  the  extra argument is not NULL, it must point to a pcre_extra data
3074           block. The pcre_study() function returns such a block (when it  doesn't
3075           return  NULL), but you can also create one for yourself, and pass addi-
3076           tional information in it. The pcre_extra block contains  the  following
3077           fields (not necessarily in this order):
3078    
3079             unsigned long int flags;
3080             void *study_data;
3081             void *executable_jit;
3082             unsigned long int match_limit;
3083             unsigned long int match_limit_recursion;
3084             void *callout_data;
3085             const unsigned char *tables;
3086             unsigned char **mark;
3087    
3088           In  the  16-bit  version  of  this  structure,  the mark field has type
3089           "PCRE_UCHAR16 **".
3090    
3091           In the 32-bit version of  this  structure,  the  mark  field  has  type
3092           "PCRE_UCHAR32 **".
3093    
3094           The  flags  field is used to specify which of the other fields are set.
3095           The flag bits are:
3096    
3097             PCRE_EXTRA_CALLOUT_DATA
3098             PCRE_EXTRA_EXECUTABLE_JIT
3099             PCRE_EXTRA_MARK
3100             PCRE_EXTRA_MATCH_LIMIT
3101             PCRE_EXTRA_MATCH_LIMIT_RECURSION
3102             PCRE_EXTRA_STUDY_DATA
3103             PCRE_EXTRA_TABLES
3104    
3105           Other flag bits should be set to zero. The study_data field  and  some-
3106           times  the executable_jit field are set in the pcre_extra block that is
3107           returned by pcre_study(), together with the appropriate flag bits.  You
3108           should  not set these yourself, but you may add to the block by setting
3109           other fields and their corresponding flag bits.
3110    
3111           The match_limit field provides a means of preventing PCRE from using up
3112           a  vast amount of resources when running patterns that are not going to
3113           match, but which have a very large number  of  possibilities  in  their
3114           search  trees. The classic example is a pattern that uses nested unlim-
3115           ited repeats.
3116    
3117           Internally, pcre_exec() uses a function called match(), which it  calls
3118           repeatedly  (sometimes  recursively).  The  limit set by match_limit is
3119           imposed on the number of times this function is called during a  match,
3120           which  has  the  effect of limiting the amount of backtracking that can
3121           take place. For patterns that are not anchored, the count restarts from
3122           zero for each position in the subject string.
3123    
3124           When pcre_exec() is called with a pattern that was successfully studied
3125           with a JIT option, the way that the matching is  executed  is  entirely
3126           different.  However, there is still the possibility of runaway matching
3127           that goes on for a very long time, and so the match_limit value is also
3128           used in this case (but in a different way) to limit how long the match-
3129           ing can continue.
3130    
3131           The default value for the limit can be set  when  PCRE  is  built;  the
3132           default  default  is 10 million, which handles all but the most extreme
3133           cases. You can override the default  by  suppling  pcre_exec()  with  a
3134           pcre_extra     block    in    which    match_limit    is    set,    and
3135           PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
3136           exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
3137    
3138           A  value  for  the  match  limit may also be supplied by an item at the
3139           start of a pattern of the form
3140    
3141             (*LIMIT_MATCH=d)
3142    
3143           where d is a decimal number. However, such a setting is ignored  unless
3144           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3145           such limit is set, less than the default.
3146    
3147           The match_limit_recursion field is similar to match_limit, but  instead
3148           of limiting the total number of times that match() is called, it limits
3149           the depth of recursion. The recursion depth is a  smaller  number  than
3150           the  total number of calls, because not all calls to match() are recur-
3151           sive.  This limit is of use only if it is set smaller than match_limit.
3152    
3153           Limiting the recursion depth limits the amount of  machine  stack  that
3154           can  be used, or, when PCRE has been compiled to use memory on the heap
3155           instead of the stack, the amount of heap memory that can be used.  This
3156           limit  is not relevant, and is ignored, when matching is done using JIT
3157           compiled code.
3158    
3159           The default value for match_limit_recursion can be  set  when  PCRE  is
3160           built;  the  default  default  is  the  same  value  as the default for
3161           match_limit. You can override the default by suppling pcre_exec()  with
3162           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
3163           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
3164           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
3165    
3166           A  value for the recursion limit may also be supplied by an item at the
3167           start of a pattern of the form
3168    
3169             (*LIMIT_RECURSION=d)
3170    
3171           where d is a decimal number. However, such a setting is ignored  unless
3172           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3173           such limit is set, less than the default.
3174    
3175           The callout_data field is used in conjunction with the  "callout"  fea-
3176           ture, and is described in the pcrecallout documentation.
3177    
3178           The  tables field is provided for use with patterns that have been pre-
3179           compiled using custom character tables, saved to disc or elsewhere, and
3180           then  reloaded,  because the tables that were used to compile a pattern
3181           are not saved with it. See the pcreprecompile documentation for a  dis-
3182           cussion  of  saving  compiled patterns for later use. If NULL is passed
3183           using this mechanism, it forces PCRE's internal tables to be used.
3184    
3185           Warning: The tables that pcre_exec() uses must be  the  same  as  those
3186           that  were used when the pattern was compiled. If this is not the case,
3187           the behaviour of pcre_exec() is undefined. Therefore, when a pattern is
3188           compiled  and  matched  in the same process, this field should never be
3189           set. In this (the most common) case, the correct table pointer is auto-
3190           matically  passed  with  the  compiled  pattern  from pcre_compile() to
3191           pcre_exec().
3192    
3193           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
3194           set  to point to a suitable variable. If the pattern contains any back-
3195           tracking control verbs such as (*MARK:NAME), and the execution ends  up
3196           with  a  name  to  pass back, a pointer to the name string (zero termi-
3197           nated) is placed in the variable pointed to  by  the  mark  field.  The
3198           names  are  within  the  compiled pattern; if you wish to retain such a
3199           name you must copy it before freeing the memory of a compiled  pattern.
3200           If  there  is no name to pass back, the variable pointed to by the mark
3201           field is set to NULL. For details of the  backtracking  control  verbs,
3202           see the section entitled "Backtracking control" in the pcrepattern doc-
3203           umentation.
3204    
3205       Option bits for pcre_exec()
3206    
3207           The unused bits of the options argument for pcre_exec() must  be  zero.
3208           The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
3209           PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
3210           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,  and
3211           PCRE_PARTIAL_SOFT.
3212    
3213           If the pattern was successfully studied with one  of  the  just-in-time
3214           (JIT) compile options, the only supported options for JIT execution are
3215           PCRE_NO_UTF8_CHECK,    PCRE_NOTBOL,     PCRE_NOTEOL,     PCRE_NOTEMPTY,
3216           PCRE_NOTEMPTY_ATSTART,  PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
3217           unsupported option is used, JIT execution is disabled  and  the  normal
3218           interpretive code in pcre_exec() is run.
3219    
3220             PCRE_ANCHORED
3221    
3222           The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
3223           matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
3224           turned  out to be anchored by virtue of its contents, it cannot be made
3225           unachored at matching time.
3226    
3227             PCRE_BSR_ANYCRLF
3228             PCRE_BSR_UNICODE
3229    
3230           These options (which are mutually exclusive) control what the \R escape
3231           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
3232           or to match any Unicode newline sequence. These  options  override  the
3233           choice that was made or defaulted when the pattern was compiled.
3234    
3235             PCRE_NEWLINE_CR
3236             PCRE_NEWLINE_LF
3237             PCRE_NEWLINE_CRLF
3238             PCRE_NEWLINE_ANYCRLF
3239             PCRE_NEWLINE_ANY
3240    
3241           These  options  override  the  newline  definition  that  was chosen or
3242           defaulted when the pattern was compiled. For details, see the  descrip-
3243           tion  of  pcre_compile()  above.  During  matching,  the newline choice
3244           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
3245           ters.  It may also alter the way the match position is advanced after a
3246           match failure for an unanchored pattern.
3247    
3248           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
3249           set,  and a match attempt for an unanchored pattern fails when the cur-
3250           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
3251           explicit  matches  for  CR  or  LF  characters,  the  match position is
3252           advanced by two characters instead of one, in other words, to after the
3253           CRLF.
3254    
3255           The above rule is a compromise that makes the most common cases work as
3256           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
3257           option is not set), it does not match the string "\r\nA" because, after
3258           failing at the start, it skips both the CR and the LF before  retrying.
3259           However,  the  pattern  [\r\n]A does match that string, because it con-
3260           tains an explicit CR or LF reference, and so advances only by one char-
3261           acter after the first failure.
3262    
3263           An explicit match for CR of LF is either a literal appearance of one of
3264           those characters, or one of the \r or  \n  escape  sequences.  Implicit
3265           matches  such  as [^X] do not count, nor does \s (which includes CR and
3266           LF in the characters that it matches).
3267    
3268           Notwithstanding the above, anomalous effects may still occur when  CRLF
3269           is a valid newline sequence and explicit \r or \n escapes appear in the
3270           pattern.
3271    
3272             PCRE_NOTBOL
3273    
3274           This option specifies that first character of the subject string is not
3275           the  beginning  of  a  line, so the circumflex metacharacter should not
3276           match before it. Setting this without PCRE_MULTILINE (at compile  time)
3277           causes  circumflex  never to match. This option affects only the behav-
3278           iour of the circumflex metacharacter. It does not affect \A.
3279    
3280             PCRE_NOTEOL
3281    
3282           This option specifies that the end of the subject string is not the end
3283           of  a line, so the dollar metacharacter should not match it nor (except
3284           in multiline mode) a newline immediately before it. Setting this  with-
3285           out PCRE_MULTILINE (at compile time) causes dollar never to match. This
3286           option affects only the behaviour of the dollar metacharacter. It  does
3287           not affect \Z or \z.
3288    
3289             PCRE_NOTEMPTY
3290    
3291           An empty string is not considered to be a valid match if this option is
3292           set. If there are alternatives in the pattern, they are tried.  If  all
3293           the  alternatives  match  the empty string, the entire match fails. For
3294           example, if the pattern
3295    
3296             a?b?
3297    
3298           is applied to a string not beginning with "a" or  "b",  it  matches  an
3299           empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
3300           match is not valid, so PCRE searches further into the string for occur-
3301           rences of "a" or "b".
3302    
3303             PCRE_NOTEMPTY_ATSTART
3304    
3305           This  is  like PCRE_NOTEMPTY, except that an empty string match that is
3306           not at the start of  the  subject  is  permitted.  If  the  pattern  is
3307           anchored, such a match can occur only if the pattern contains \K.
3308    
3309           Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
3310           PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
3311           match  of  the empty string within its split() function, and when using
3312           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
3313           matching a null string by first trying the match again at the same off-
3314           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
3315           fails, by advancing the starting offset (see below) and trying an ordi-
3316           nary match again. There is some code that demonstrates how to  do  this
3317           in  the  pcredemo sample program. In the most general case, you have to
3318           check to see if the newline convention recognizes CRLF  as  a  newline,
3319           and  if so, and the current character is CR followed by LF, advance the
3320           starting offset by two characters instead of one.
3321    
3322             PCRE_NO_START_OPTIMIZE
3323    
3324           There are a number of optimizations that pcre_exec() uses at the  start
3325           of  a  match,  in  order to speed up the process. For example, if it is
3326           known that an unanchored match must start with a specific character, it
3327           searches  the  subject  for that character, and fails immediately if it
3328           cannot find it, without actually running the  main  matching  function.
3329           This means that a special item such as (*COMMIT) at the start of a pat-
3330           tern is not considered until after a suitable starting  point  for  the
3331           match  has been found. Also, when callouts or (*MARK) items are in use,
3332           these "start-up" optimizations can cause them to be skipped if the pat-
3333           tern is never actually used. The start-up optimizations are in effect a
3334           pre-scan of the subject that takes place before the pattern is run.
3335    
3336           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
3337           possibly  causing  performance  to  suffer,  but ensuring that in cases
3338           where the result is "no match", the callouts do occur, and  that  items
3339           such as (*COMMIT) and (*MARK) are considered at every possible starting
3340           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
3341           compile  time,  it  cannot  be  unset  at  matching  time.  The  use of
3342           PCRE_NO_START_OPTIMIZE  at  matching  time  (that  is,  passing  it  to
3343           pcre_exec())  disables  JIT  execution;  in this situation, matching is
3344           always done using interpretively.
3345    
3346           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
3347           operation.  Consider the pattern
3348    
3349             (*COMMIT)ABC
3350    
3351           When  this  is  compiled, PCRE records the fact that a match must start
3352           with the character "A". Suppose the subject  string  is  "DEFABC".  The
3353           start-up  optimization  scans along the subject, finds "A" and runs the
3354           first match attempt from there. The (*COMMIT) item means that the  pat-
3355           tern  must  match the current starting position, which in this case, it
3356           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
3357           set,  the  initial  scan  along the subject string does not happen. The
3358           first match attempt is run starting  from  "D"  and  when  this  fails,
3359           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
3360           result is "no match". If the pattern is studied,  more  start-up  opti-
3361           mizations  may  be  used. For example, a minimum length for the subject
3362           may be recorded. Consider the pattern
3363    
3364             (*MARK:A)(X|Y)
3365    
3366           The minimum length for a match is one  character.  If  the  subject  is
3367           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
3368           finally an empty string.  If the pattern is studied, the final  attempt
3369           does  not take place, because PCRE knows that the subject is too short,
3370           and so the (*MARK) is never encountered.  In this  case,  studying  the
3371           pattern  does  not  affect the overall match result, which is still "no
3372           match", but it does affect the auxiliary information that is returned.
3373    
3374             PCRE_NO_UTF8_CHECK
3375    
3376           When PCRE_UTF8 is set at compile time, the validity of the subject as a
3377           UTF-8  string is automatically checked when pcre_exec() is subsequently
3378           called.  The entire string is checked before any other processing takes
3379           place.  The  value  of  startoffset  is  also checked to ensure that it
3380           points to the start of a UTF-8 character. There is a  discussion  about
3381           the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
3382           sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
3383           PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
3384           truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
3385           both  cases, information about the precise nature of the error may also
3386           be returned (see the descriptions of these errors in the section  enti-
3387           tled  Error return values from pcre_exec() below).  If startoffset con-
3388           tains a value that does not point to the start of a UTF-8 character (or
3389           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
3390    
3391           If  you  already  know that your subject is valid, and you want to skip
3392           these   checks   for   performance   reasons,   you   can    set    the
3393           PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
3394           do this for the second and subsequent calls to pcre_exec() if  you  are
3395           making  repeated  calls  to  find  all  the matches in a single subject
3396           string. However, you should be  sure  that  the  value  of  startoffset
3397           points  to  the  start of a character (or the end of the subject). When
3398           PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
3399           subject  or  an invalid value of startoffset is undefined. Your program
3400           may crash or loop.
3401    
3402             PCRE_PARTIAL_HARD
3403             PCRE_PARTIAL_SOFT
3404    
3405           These options turn on the partial matching feature. For backwards  com-
3406           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
3407           match occurs if the end of the subject string is reached  successfully,
3408           but  there  are not enough subject characters to complete the match. If
3409           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
3410           matching  continues  by  testing any remaining alternatives. Only if no
3411           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
3412           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
3413           caller is prepared to handle a partial match, but only if  no  complete
3414           match can be found.
3415    
3416           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this