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1    -----------------------------------------------------------------------------
2    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
4    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. Neither has
6    the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8    -----------------------------------------------------------------------------
9    
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 6.2.0.
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           There are a number of features of PCRE regular expressions that are not
1461           supported by the alternative matching algorithm. They are as follows:
1462    
1463           1. Because the algorithm finds all  possible  matches,  the  greedy  or
1464           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
1465           ungreedy quantifiers are treated in exactly the same way. However, pos-
1466           sessive  quantifiers can make a difference when what follows could also
1467           match what is quantified, for example in a pattern like this:
1468    
1469             ^a++\w!
1470    
1471           This pattern matches "aaab!" but not "aaa!", which would be matched  by
1472           a  non-possessive quantifier. Similarly, if an atomic group is present,
1473           it is matched as if it were a standalone pattern at the current  point,
1474           and  the  longest match is then "locked in" for the rest of the overall
1475           pattern.
1476    
1477           2. When dealing with multiple paths through the tree simultaneously, it
1478           is  not  straightforward  to  keep track of captured substrings for the
1479           different matching possibilities, and  PCRE's  implementation  of  this
1480           algorithm does not attempt to do this. This means that no captured sub-
1481           strings are available.
1482    
1483           3. Because no substrings are captured, back references within the  pat-
1484           tern are not supported, and cause errors if encountered.
1485    
1486           4.  For  the same reason, conditional expressions that use a backrefer-
1487           ence as the condition or test for a specific group  recursion  are  not
1488           supported.
1489    
1490           5.  Because  many  paths  through the tree may be active, the \K escape
1491           sequence, which resets the start of the match when encountered (but may
1492           be  on  some  paths  and not on others), is not supported. It causes an
1493           error if encountered.
1494    
1495           6. Callouts are supported, but the value of the  capture_top  field  is
1496           always 1, and the value of the capture_last field is always -1.
1497    
1498           7.  The  \C  escape  sequence, which (in the standard algorithm) always
1499           matches a single data unit, even in UTF-8, UTF-16 or UTF-32  modes,  is
1500           not  supported  in these modes, because the alternative algorithm moves
1501           through the subject string one character (not data unit) at a time, for
1502           all active paths through the tree.
1503    
1504           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
1505           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
1506           negative assertion.
1507    
1508    
1509    ADVANTAGES OF THE ALTERNATIVE ALGORITHM
1510    
1511           Using  the alternative matching algorithm provides the following advan-
1512           tages:
1513    
1514           1. All possible matches (at a single point in the subject) are automat-
1515           ically  found,  and  in particular, the longest match is found. To find
1516           more than one match using the standard algorithm, you have to do kludgy
1517           things with callouts.
1518    
1519           2.  Because  the  alternative  algorithm  scans the subject string just
1520           once, and never needs to backtrack (except for lookbehinds), it is pos-
1521           sible  to  pass  very  long subject strings to the matching function in
1522           several pieces, checking for partial matching each time. Although it is
1523           possible  to  do multi-segment matching using the standard algorithm by
1524           retaining partially matched substrings, it  is  more  complicated.  The
1525           pcrepartial  documentation  gives  details of partial matching and dis-
1526           cusses multi-segment matching.
1527    
1528    
1529    DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
1530    
1531           The alternative algorithm suffers from a number of disadvantages:
1532    
1533           1. It is substantially slower than  the  standard  algorithm.  This  is
1534           partly  because  it has to search for all possible matches, but is also
1535           because it is less susceptible to optimization.
1536    
1537           2. Capturing parentheses and back references are not supported.
1538    
1539           3. Although atomic groups are supported, their use does not provide the
1540           performance advantage that it does for the standard algorithm.
1541    
1542    
1543    AUTHOR
1544    
1545           Philip Hazel
1546           University Computing Service
1547           Cambridge CB2 3QH, England.
1548    
1549    
1550    REVISION
1551    
1552           Last updated: 08 January 2012
1553           Copyright (c) 1997-2012 University of Cambridge.
1554    ------------------------------------------------------------------------------
1555    
1556    
1557    PCREAPI(3)                 Library Functions Manual                 PCREAPI(3)
1558    
1559    
1560    
1561    NAME
1562           PCRE - Perl-compatible regular expressions
1563    
1564           #include <pcre.h>
1565    
1566    
1567    PCRE NATIVE API BASIC FUNCTIONS
1568    
1569           pcre *pcre_compile(const char *pattern, int options,
1570                const char **errptr, int *erroffset,
1571                const unsigned char *tableptr);
1572    
1573           pcre *pcre_compile2(const char *pattern, int options,
1574                int *errorcodeptr,
1575                const char **errptr, int *erroffset,
1576                const unsigned char *tableptr);
1577    
1578           pcre_extra *pcre_study(const pcre *code, int options,
1579                const char **errptr);
1580    
1581           void pcre_free_study(pcre_extra *extra);
1582    
1583           int pcre_exec(const pcre *code, const pcre_extra *extra,
1584                const char *subject, int length, int startoffset,
1585                int options, int *ovector, int ovecsize);
1586    
1587           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1588                const char *subject, int length, int startoffset,
1589                int options, int *ovector, int ovecsize,
1590                int *workspace, int wscount);
1591    
1592    
1593    PCRE NATIVE API STRING EXTRACTION FUNCTIONS
1594    
1595           int pcre_copy_named_substring(const pcre *code,
1596                const char *subject, int *ovector,
1597                int stringcount, const char *stringname,
1598                char *buffer, int buffersize);
1599    
1600           int pcre_copy_substring(const char *subject, int *ovector,
1601                int stringcount, int stringnumber, char *buffer,
1602                int buffersize);
1603    
1604           int pcre_get_named_substring(const pcre *code,
1605                const char *subject, int *ovector,
1606                int stringcount, const char *stringname,
1607                const char **stringptr);
1608    
1609           int pcre_get_stringnumber(const pcre *code,
1610                const char *name);
1611    
1612           int pcre_get_stringtable_entries(const pcre *code,
1613                const char *name, char **first, char **last);
1614    
1615           int pcre_get_substring(const char *subject, int *ovector,
1616                int stringcount, int stringnumber,
1617                const char **stringptr);
1618    
1619           int pcre_get_substring_list(const char *subject,
1620                int *ovector, int stringcount, const char ***listptr);
1621    
1622           void pcre_free_substring(const char *stringptr);
1623    
1624           void pcre_free_substring_list(const char **stringptr);
1625    
1626    
1627    PCRE NATIVE API AUXILIARY FUNCTIONS
1628    
1629           int pcre_jit_exec(const pcre *code, const pcre_extra *extra,
1630                const char *subject, int length, int startoffset,
1631                int options, int *ovector, int ovecsize,
1632                pcre_jit_stack *jstack);
1633    
1634           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
1635    
1636           void pcre_jit_stack_free(pcre_jit_stack *stack);
1637    
1638           void pcre_assign_jit_stack(pcre_extra *extra,
1639                pcre_jit_callback callback, void *data);
1640    
1641           const unsigned char *pcre_maketables(void);
1642    
1643           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1644                int what, void *where);
1645    
1646           int pcre_refcount(pcre *code, int adjust);
1647    
1648           int pcre_config(int what, void *where);
1649    
1650           const char *pcre_version(void);
1651    
1652           int pcre_pattern_to_host_byte_order(pcre *code,
1653                pcre_extra *extra, const unsigned char *tables);
1654    
1655    
1656    PCRE NATIVE API INDIRECTED FUNCTIONS
1657    
1658           void *(*pcre_malloc)(size_t);
1659    
1660           void (*pcre_free)(void *);
1661    
1662           void *(*pcre_stack_malloc)(size_t);
1663    
1664           void (*pcre_stack_free)(void *);
1665    
1666           int (*pcre_callout)(pcre_callout_block *);
1667    
1668    
1669    PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES
1670    
1671           As  well  as  support  for  8-bit character strings, PCRE also supports
1672           16-bit strings (from release 8.30) and  32-bit  strings  (from  release
1673           8.32),  by means of two additional libraries. They can be built as well
1674           as, or instead of, the 8-bit library. To avoid too  much  complication,
1675           this  document describes the 8-bit versions of the functions, with only
1676           occasional references to the 16-bit and 32-bit libraries.
1677    
1678           The 16-bit and 32-bit functions operate in the same way as their  8-bit
1679           counterparts;  they  just  use different data types for their arguments
1680           and results, and their names start with pcre16_ or pcre32_  instead  of
1681           pcre_.  For  every  option  that  has  UTF8  in  its name (for example,
1682           PCRE_UTF8), there are corresponding 16-bit and 32-bit names  with  UTF8
1683           replaced by UTF16 or UTF32, respectively. This facility is in fact just
1684           cosmetic; the 16-bit and 32-bit option names define the same  bit  val-
1685           ues.
1686    
1687           References to bytes and UTF-8 in this document should be read as refer-
1688           ences to 16-bit data units and UTF-16 when using the 16-bit library, or
1689           32-bit  data  units  and  UTF-32  when using the 32-bit library, unless
1690           specified otherwise.  More details of the specific differences for  the
1691           16-bit and 32-bit libraries are given in the pcre16 and pcre32 pages.
1692    
1693    
1694    PCRE API OVERVIEW
1695    
1696           PCRE has its own native API, which is described in this document. There
1697           are also some wrapper functions (for the 8-bit library only) that  cor-
1698           respond  to  the  POSIX  regular  expression  API, but they do not give
1699           access to all the functionality. They are described  in  the  pcreposix
1700           documentation.  Both  of these APIs define a set of C function calls. A
1701           C++ wrapper (again for the 8-bit library only) is also distributed with
1702           PCRE. It is documented in the pcrecpp page.
1703    
1704           The  native  API  C  function prototypes are defined in the header file
1705           pcre.h, and on Unix-like systems the (8-bit) library itself  is  called
1706           libpcre.  It  can  normally be accessed by adding -lpcre to the command
1707           for linking an application that uses PCRE. The header file defines  the
1708           macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
1709           numbers for the library. Applications can use these to include  support
1710           for different releases of PCRE.
1711    
1712           In a Windows environment, if you want to statically link an application
1713           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
1714           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
1715           loc()   and   pcre_free()   exported   functions   will   be   declared
1716           __declspec(dllimport), with unwanted results.
1717    
1718           The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
1719           pcre_exec() are used for compiling and matching regular expressions  in
1720           a  Perl-compatible  manner. A sample program that demonstrates the sim-
1721           plest way of using them is provided in the file  called  pcredemo.c  in
1722           the PCRE source distribution. A listing of this program is given in the
1723           pcredemo documentation, and the pcresample documentation describes  how
1724           to compile and run it.
1725    
1726           Just-in-time  compiler  support is an optional feature of PCRE that can
1727           be built in appropriate hardware environments. It greatly speeds up the
1728           matching  performance  of  many  patterns.  Simple  programs can easily
1729           request that it be used if available, by  setting  an  option  that  is
1730           ignored  when  it is not relevant. More complicated programs might need
1731           to    make    use    of    the    functions     pcre_jit_stack_alloc(),
1732           pcre_jit_stack_free(),  and pcre_assign_jit_stack() in order to control
1733           the JIT code's memory usage.
1734    
1735           From release 8.32 there is also a direct interface for  JIT  execution,
1736           which  gives  improved performance. The JIT-specific functions are dis-
1737           cussed in the pcrejit documentation.
1738    
1739           A second matching function, pcre_dfa_exec(), which is not Perl-compati-
1740           ble,  is  also provided. This uses a different algorithm for the match-
1741           ing. The alternative algorithm finds all possible matches (at  a  given
1742           point  in  the  subject), and scans the subject just once (unless there
1743           are lookbehind assertions). However, this  algorithm  does  not  return
1744           captured  substrings.  A description of the two matching algorithms and
1745           their advantages and disadvantages is given in the  pcrematching  docu-
1746           mentation.
1747    
1748           In  addition  to  the  main compiling and matching functions, there are
1749           convenience functions for extracting captured substrings from a subject
1750           string that is matched by pcre_exec(). They are:
1751    
1752             pcre_copy_substring()
1753             pcre_copy_named_substring()
1754             pcre_get_substring()
1755             pcre_get_named_substring()
1756             pcre_get_substring_list()
1757             pcre_get_stringnumber()
1758             pcre_get_stringtable_entries()
1759    
1760           pcre_free_substring() and pcre_free_substring_list() are also provided,
1761           to free the memory used for extracted strings.
1762    
1763           The function pcre_maketables() is used to  build  a  set  of  character
1764           tables   in   the   current   locale  for  passing  to  pcre_compile(),
1765           pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
1766           provided  for  specialist  use.  Most  commonly,  no special tables are
1767           passed, in which case internal tables that are generated when  PCRE  is
1768           built are used.
1769    
1770           The  function  pcre_fullinfo()  is used to find out information about a
1771           compiled pattern. The function pcre_version() returns a  pointer  to  a
1772           string containing the version of PCRE and its date of release.
1773    
1774           The  function  pcre_refcount()  maintains  a  reference count in a data
1775           block containing a compiled pattern. This is provided for  the  benefit
1776           of object-oriented applications.
1777    
1778           The  global  variables  pcre_malloc and pcre_free initially contain the
1779           entry points of the standard malloc()  and  free()  functions,  respec-
1780           tively. PCRE calls the memory management functions via these variables,
1781           so a calling program can replace them if it  wishes  to  intercept  the
1782           calls. This should be done before calling any PCRE functions.
1783    
1784           The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
1785           indirections to memory management functions.  These  special  functions
1786           are  used  only  when  PCRE is compiled to use the heap for remembering
1787           data, instead of recursive function calls, when running the pcre_exec()
1788           function.  See  the  pcrebuild  documentation  for details of how to do
1789           this. It is a non-standard way of building PCRE, for  use  in  environ-
1790           ments  that  have  limited stacks. Because of the greater use of memory
1791           management, it runs more slowly. Separate  functions  are  provided  so
1792           that  special-purpose  external  code  can  be used for this case. When
1793           used, these functions are always called in a  stack-like  manner  (last
1794           obtained,  first freed), and always for memory blocks of the same size.
1795           There is a discussion about PCRE's stack usage in the  pcrestack  docu-
1796           mentation.
1797    
1798           The global variable pcre_callout initially contains NULL. It can be set
1799           by the caller to a "callout" function, which PCRE  will  then  call  at
1800           specified  points during a matching operation. Details are given in the
1801           pcrecallout documentation.
1802    
1803    
1804    NEWLINES
1805    
1806           PCRE supports five different conventions for indicating line breaks  in
1807           strings:  a  single  CR (carriage return) character, a single LF (line-
1808           feed) character, the two-character sequence CRLF, any of the three pre-
1809           ceding,  or any Unicode newline sequence. The Unicode newline sequences
1810           are the three just mentioned, plus the single characters  VT  (vertical
1811           tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line
1812           separator, U+2028), and PS (paragraph separator, U+2029).
1813    
1814           Each of the first three conventions is used by at least  one  operating
1815           system  as its standard newline sequence. When PCRE is built, a default
1816           can be specified.  The default default is LF, which is the  Unix  stan-
1817           dard.  When  PCRE  is run, the default can be overridden, either when a
1818           pattern is compiled, or when it is matched.
1819    
1820           At compile time, the newline convention can be specified by the options
1821           argument  of  pcre_compile(), or it can be specified by special text at
1822           the start of the pattern itself; this overrides any other settings. See
1823           the pcrepattern page for details of the special character sequences.
1824    
1825           In the PCRE documentation the word "newline" is used to mean "the char-
1826           acter or pair of characters that indicate a line break". The choice  of
1827           newline  convention  affects  the  handling of the dot, circumflex, and
1828           dollar metacharacters, the handling of #-comments in /x mode, and, when
1829           CRLF  is a recognized line ending sequence, the match position advance-
1830           ment for a non-anchored pattern. There is more detail about this in the
1831           section on pcre_exec() options below.
1832    
1833           The  choice of newline convention does not affect the interpretation of
1834           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
1835           which is controlled in a similar way, but by separate options.
1836    
1837    
1838    MULTITHREADING
1839    
1840           The  PCRE  functions  can be used in multi-threading applications, with
1841           the  proviso  that  the  memory  management  functions  pointed  to  by
1842           pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1843           callout function pointed to by pcre_callout, are shared by all threads.
1844    
1845           The compiled form of a regular expression is not altered during  match-
1846           ing, so the same compiled pattern can safely be used by several threads
1847           at once.
1848    
1849           If the just-in-time optimization feature is being used, it needs  sepa-
1850           rate  memory stack areas for each thread. See the pcrejit documentation
1851           for more details.
1852    
1853    
1854    SAVING PRECOMPILED PATTERNS FOR LATER USE
1855    
1856           The compiled form of a regular expression can be saved and re-used at a
1857           later  time,  possibly by a different program, and even on a host other
1858           than the one on which  it  was  compiled.  Details  are  given  in  the
1859           pcreprecompile  documentation,  which  includes  a  description  of the
1860           pcre_pattern_to_host_byte_order() function. However, compiling a  regu-
1861           lar  expression  with one version of PCRE for use with a different ver-
1862           sion is not guaranteed to work and may cause crashes.
1863    
1864    
1865    CHECKING BUILD-TIME OPTIONS
1866    
1867           int pcre_config(int what, void *where);
1868    
1869           The function pcre_config() makes it possible for a PCRE client to  dis-
1870           cover which optional features have been compiled into the PCRE library.
1871           The pcrebuild documentation has more details about these optional  fea-
1872           tures.
1873    
1874           The  first  argument  for pcre_config() is an integer, specifying which
1875           information is required; the second argument is a pointer to a variable
1876           into  which  the  information  is placed. The returned value is zero on
1877           success, or the negative error code PCRE_ERROR_BADOPTION if  the  value
1878           in  the  first argument is not recognized. The following information is
1879           available:
1880    
1881             PCRE_CONFIG_UTF8
1882    
1883           The output is an integer that is set to one if UTF-8 support is  avail-
1884           able;  otherwise it is set to zero. This value should normally be given
1885           to the 8-bit version of this function, pcre_config(). If it is given to
1886           the   16-bit  or  32-bit  version  of  this  function,  the  result  is
1887           PCRE_ERROR_BADOPTION.
1888    
1889             PCRE_CONFIG_UTF16
1890    
1891           The output is an integer that is set to one if UTF-16 support is avail-
1892           able;  otherwise it is set to zero. This value should normally be given
1893           to the 16-bit version of this function, pcre16_config(). If it is given
1894           to  the  8-bit  or  32-bit  version  of  this  function,  the result is
1895           PCRE_ERROR_BADOPTION.
1896    
1897             PCRE_CONFIG_UTF32
1898    
1899           The output is an integer that is set to one if UTF-32 support is avail-
1900           able;  otherwise it is set to zero. This value should normally be given
1901           to the 32-bit version of this function, pcre32_config(). If it is given
1902           to  the  8-bit  or  16-bit  version  of  this  function,  the result is
1903           PCRE_ERROR_BADOPTION.
1904    
1905             PCRE_CONFIG_UNICODE_PROPERTIES
1906    
1907           The output is an integer that is set to  one  if  support  for  Unicode
1908           character properties is available; otherwise it is set to zero.
1909    
1910             PCRE_CONFIG_JIT
1911    
1912           The output is an integer that is set to one if support for just-in-time
1913           compiling is available; otherwise it is set to zero.
1914    
1915             PCRE_CONFIG_JITTARGET
1916    
1917           The output is a pointer to a zero-terminated "const char *" string.  If
1918           JIT support is available, the string contains the name of the architec-
1919           ture for which the JIT compiler is configured, for example  "x86  32bit
1920           (little  endian  +  unaligned)".  If  JIT support is not available, the
1921           result is NULL.
1922    
1923             PCRE_CONFIG_NEWLINE
1924    
1925           The output is an integer whose value specifies  the  default  character
1926           sequence  that  is recognized as meaning "newline". The values that are
1927           supported in ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338
1928           for  CRLF,  -2 for ANYCRLF, and -1 for ANY. In EBCDIC environments, CR,
1929           ANYCRLF, and ANY yield the same values. However, the value  for  LF  is
1930           normally  21, though some EBCDIC environments use 37. The corresponding
1931           values for CRLF are 3349 and 3365. The default should  normally  corre-
1932           spond to the standard sequence for your operating system.
1933    
1934             PCRE_CONFIG_BSR
1935    
1936           The output is an integer whose value indicates what character sequences
1937           the \R escape sequence matches by default. A value of 0 means  that  \R
1938           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1939           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1940           tern is compiled or matched.
1941    
1942             PCRE_CONFIG_LINK_SIZE
1943    
1944           The  output  is  an  integer that contains the number of bytes used for
1945           internal  linkage  in  compiled  regular  expressions.  For  the  8-bit
1946           library, the value can be 2, 3, or 4. For the 16-bit library, the value
1947           is either 2 or 4 and is  still  a  number  of  bytes.  For  the  32-bit
1948           library, the value is either 2 or 4 and is still a number of bytes. The
1949           default value of 2 is sufficient for all but the most massive patterns,
1950           since  it  allows  the compiled pattern to be up to 64K in size. Larger
1951           values allow larger regular expressions to be compiled, at the  expense
1952           of slower matching.
1953    
1954             PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1955    
1956           The  output  is  an integer that contains the threshold above which the
1957           POSIX interface uses malloc() for output vectors. Further  details  are
1958           given in the pcreposix documentation.
1959    
1960             PCRE_CONFIG_MATCH_LIMIT
1961    
1962           The  output is a long integer that gives the default limit for the num-
1963           ber of internal matching function calls  in  a  pcre_exec()  execution.
1964           Further details are given with pcre_exec() below.
1965    
1966             PCRE_CONFIG_MATCH_LIMIT_RECURSION
1967    
1968           The output is a long integer that gives the default limit for the depth
1969           of  recursion  when  calling  the  internal  matching  function  in   a
1970           pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1971           below.
1972    
1973             PCRE_CONFIG_STACKRECURSE
1974    
1975           The output is an integer that is set to one if internal recursion  when
1976           running pcre_exec() is implemented by recursive function calls that use
1977           the stack to remember their state. This is the usual way that  PCRE  is
1978           compiled. The output is zero if PCRE was compiled to use blocks of data
1979           on the  heap  instead  of  recursive  function  calls.  In  this  case,
1980           pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1981           blocks on the heap, thus avoiding the use of the stack.
1982    
1983    
1984    COMPILING A PATTERN
1985    
1986           pcre *pcre_compile(const char *pattern, int options,
1987                const char **errptr, int *erroffset,
1988                const unsigned char *tableptr);
1989    
1990           pcre *pcre_compile2(const char *pattern, int options,
1991                int *errorcodeptr,
1992                const char **errptr, int *erroffset,
1993                const unsigned char *tableptr);
1994    
1995           Either of the functions pcre_compile() or pcre_compile2() can be called
1996           to compile a pattern into an internal form. The only difference between
1997           the two interfaces is that pcre_compile2() has an additional  argument,
1998           errorcodeptr,  via  which  a  numerical  error code can be returned. To
1999           avoid too much repetition, we refer just to pcre_compile()  below,  but
2000           the information applies equally to pcre_compile2().
2001    
2002           The pattern is a C string terminated by a binary zero, and is passed in
2003           the pattern argument. A pointer to a single block  of  memory  that  is
2004           obtained  via  pcre_malloc is returned. This contains the compiled code
2005           and related data. The pcre type is defined for the returned block; this
2006           is a typedef for a structure whose contents are not externally defined.
2007           It is up to the caller to free the memory (via pcre_free) when it is no
2008           longer required.
2009    
2010           Although  the compiled code of a PCRE regex is relocatable, that is, it
2011           does not depend on memory location, the complete pcre data block is not
2012           fully  relocatable, because it may contain a copy of the tableptr argu-
2013           ment, which is an address (see below).
2014    
2015           The options argument contains various bit settings that affect the com-
2016           pilation.  It  should be zero if no options are required. The available
2017           options are described below. Some of them (in  particular,  those  that
2018           are  compatible with Perl, but some others as well) can also be set and
2019           unset from within the pattern (see  the  detailed  description  in  the
2020           pcrepattern  documentation). For those options that can be different in
2021           different parts of the pattern, the contents of  the  options  argument
2022           specifies their settings at the start of compilation and execution. The
2023           PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK,  and
2024           PCRE_NO_START_OPTIMIZE  options  can  be set at the time of matching as
2025           well as at compile time.
2026    
2027           If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
2028           if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
2029           sets the variable pointed to by errptr to point to a textual error mes-
2030           sage. This is a static string that is part of the library. You must not
2031           try to free it. Normally, the offset from the start of the  pattern  to
2032           the data unit that was being processed when the error was discovered is
2033           placed in the variable pointed to by erroffset, which must not be  NULL
2034           (if  it is, an immediate error is given). However, for an invalid UTF-8
2035           or UTF-16 string, the offset is that of the  first  data  unit  of  the
2036           failing character.
2037    
2038           Some  errors are not detected until the whole pattern has been scanned;
2039           in these cases, the offset passed back is the length  of  the  pattern.
2040           Note  that  the  offset is in data units, not characters, even in a UTF
2041           mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char-
2042           acter.
2043    
2044           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
2045           codeptr argument is not NULL, a non-zero error code number is  returned
2046           via  this argument in the event of an error. This is in addition to the
2047           textual error message. Error codes and messages are listed below.
2048    
2049           If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
2050           character  tables  that  are  built  when  PCRE  is compiled, using the
2051           default C locale. Otherwise, tableptr must be an address  that  is  the
2052           result  of  a  call to pcre_maketables(). This value is stored with the
2053           compiled pattern, and used again by pcre_exec(), unless  another  table
2054           pointer is passed to it. For more discussion, see the section on locale
2055           support below.
2056    
2057           This code fragment shows a typical straightforward  call  to  pcre_com-
2058           pile():
2059    
2060             pcre *re;
2061             const char *error;
2062             int erroffset;
2063             re = pcre_compile(
2064               "^A.*Z",          /* the pattern */
2065               0,                /* default options */
2066               &error,           /* for error message */
2067               &erroffset,       /* for error offset */
2068               NULL);            /* use default character tables */
2069    
2070           The  following  names  for option bits are defined in the pcre.h header
2071           file:
2072    
2073             PCRE_ANCHORED
2074    
2075           If this bit is set, the pattern is forced to be "anchored", that is, it
2076           is  constrained to match only at the first matching point in the string
2077           that is being searched (the "subject string"). This effect can also  be
2078           achieved  by appropriate constructs in the pattern itself, which is the
2079           only way to do it in Perl.
2080    
2081             PCRE_AUTO_CALLOUT
2082    
2083           If this bit is set, pcre_compile() automatically inserts callout items,
2084           all  with  number  255, before each pattern item. For discussion of the
2085           callout facility, see the pcrecallout documentation.
2086    
2087             PCRE_BSR_ANYCRLF
2088             PCRE_BSR_UNICODE
2089    
2090           These options (which are mutually exclusive) control what the \R escape
2091           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2092           or to match any Unicode newline sequence. The default is specified when
2093           PCRE is built. It can be overridden from within the pattern, or by set-
2094           ting an option when a compiled pattern is matched.
2095    
2096             PCRE_CASELESS
2097    
2098           If this bit is set, letters in the pattern match both upper  and  lower
2099           case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
2100           changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
2101           always  understands the concept of case for characters whose values are
2102           less than 128, so caseless matching is always possible. For  characters
2103           with  higher  values,  the concept of case is supported if PCRE is com-
2104           piled with Unicode property support, but not otherwise. If you want  to
2105           use  caseless  matching  for  characters 128 and above, you must ensure
2106           that PCRE is compiled with Unicode property support  as  well  as  with
2107           UTF-8 support.
2108    
2109             PCRE_DOLLAR_ENDONLY
2110    
2111           If  this bit is set, a dollar metacharacter in the pattern matches only
2112           at the end of the subject string. Without this option,  a  dollar  also
2113           matches  immediately before a newline at the end of the string (but not
2114           before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
2115           if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
2116           Perl, and no way to set it within a pattern.
2117    
2118             PCRE_DOTALL
2119    
2120           If this bit is set, a dot metacharacter in the pattern matches a  char-
2121           acter of any value, including one that indicates a newline. However, it
2122           only ever matches one character, even if newlines are  coded  as  CRLF.
2123           Without  this option, a dot does not match when the current position is
2124           at a newline. This option is equivalent to Perl's /s option, and it can
2125           be  changed within a pattern by a (?s) option setting. A negative class
2126           such as [^a] always matches newline characters, independent of the set-
2127           ting of this option.
2128    
2129             PCRE_DUPNAMES
2130    
2131           If  this  bit is set, names used to identify capturing subpatterns need
2132           not be unique. This can be helpful for certain types of pattern when it
2133           is  known  that  only  one instance of the named subpattern can ever be
2134           matched. There are more details of named subpatterns  below;  see  also
2135           the pcrepattern documentation.
2136    
2137             PCRE_EXTENDED
2138    
2139           If  this  bit  is  set,  white space data characters in the pattern are
2140           totally ignored except when escaped or inside a character class.  White
2141           space does not include the VT character (code 11). In addition, charac-
2142           ters between an unescaped # outside a character class and the next new-
2143           line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
2144           option, and it can be changed within a pattern by a  (?x)  option  set-
2145           ting.
2146    
2147           Which  characters  are  interpreted  as  newlines  is controlled by the
2148           options passed to pcre_compile() or by a special sequence at the  start
2149           of  the  pattern, as described in the section entitled "Newline conven-
2150           tions" in the pcrepattern documentation. Note that the end of this type
2151           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
2152           sequences that happen to represent a newline do not count.
2153    
2154           This option makes it possible to include  comments  inside  complicated
2155           patterns.   Note,  however,  that this applies only to data characters.
2156           White space  characters  may  never  appear  within  special  character
2157           sequences in a pattern, for example within the sequence (?( that intro-
2158           duces a conditional subpattern.
2159    
2160             PCRE_EXTRA
2161    
2162           This option was invented in order to turn on  additional  functionality
2163           of  PCRE  that  is  incompatible with Perl, but it is currently of very
2164           little use. When set, any backslash in a pattern that is followed by  a
2165           letter  that  has  no  special  meaning causes an error, thus reserving
2166           these combinations for future expansion. By  default,  as  in  Perl,  a
2167           backslash  followed by a letter with no special meaning is treated as a
2168           literal. (Perl can, however, be persuaded to give an error for this, by
2169           running  it with the -w option.) There are at present no other features
2170           controlled by this option. It can also be set by a (?X) option  setting
2171           within a pattern.
2172    
2173             PCRE_FIRSTLINE
2174    
2175           If  this  option  is  set,  an  unanchored pattern is required to match
2176           before or at the first  newline  in  the  subject  string,  though  the
2177           matched text may continue over the newline.
2178    
2179             PCRE_JAVASCRIPT_COMPAT
2180    
2181           If this option is set, PCRE's behaviour is changed in some ways so that
2182           it is compatible with JavaScript rather than Perl. The changes  are  as
2183           follows:
2184    
2185           (1)  A  lone  closing square bracket in a pattern causes a compile-time
2186           error, because this is illegal in JavaScript (by default it is  treated
2187           as a data character). Thus, the pattern AB]CD becomes illegal when this
2188           option is set.
2189    
2190           (2) At run time, a back reference to an unset subpattern group  matches
2191           an  empty  string (by default this causes the current matching alterna-
2192           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
2193           set  (assuming  it can find an "a" in the subject), whereas it fails by
2194           default, for Perl compatibility.
2195    
2196           (3) \U matches an upper case "U" character; by default \U causes a com-
2197           pile time error (Perl uses \U to upper case subsequent characters).
2198    
2199           (4) \u matches a lower case "u" character unless it is followed by four
2200           hexadecimal digits, in which case the hexadecimal  number  defines  the
2201           code  point  to match. By default, \u causes a compile time error (Perl
2202           uses it to upper case the following character).
2203    
2204           (5) \x matches a lower case "x" character unless it is followed by  two
2205           hexadecimal  digits,  in  which case the hexadecimal number defines the
2206           code point to match. By default, as in Perl, a  hexadecimal  number  is
2207           always expected after \x, but it may have zero, one, or two digits (so,
2208           for example, \xz matches a binary zero character followed by z).
2209    
2210             PCRE_MULTILINE
2211    
2212           By default, for the purposes of matching "start of line"  and  "end  of
2213           line", PCRE treats the subject string as consisting of a single line of
2214           characters, even if it actually contains newlines. The "start of  line"
2215           metacharacter (^) matches only at the start of the string, and the "end
2216           of line" metacharacter ($) matches only at the end of  the  string,  or
2217           before  a terminating newline (except when PCRE_DOLLAR_ENDONLY is set).
2218           Note, however, that unless PCRE_DOTALL  is  set,  the  "any  character"
2219           metacharacter  (.)  does not match at a newline. This behaviour (for ^,
2220           $, and dot) is the same as Perl.
2221    
2222           When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
2223           constructs  match  immediately following or immediately before internal
2224           newlines in the subject string, respectively, as well as  at  the  very
2225           start  and  end.  This is equivalent to Perl's /m option, and it can be
2226           changed within a pattern by a (?m) option setting. If there are no new-
2227           lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
2228           setting PCRE_MULTILINE has no effect.
2229    
2230             PCRE_NEVER_UTF
2231    
2232           This option locks out interpretation of the pattern as UTF-8 (or UTF-16
2233           or  UTF-32  in the 16-bit and 32-bit libraries). In particular, it pre-
2234           vents the creator of the pattern from switching to  UTF  interpretation
2235           by starting the pattern with (*UTF). This may be useful in applications
2236           that  process  patterns  from  external  sources.  The  combination  of
2237           PCRE_UTF8 and PCRE_NEVER_UTF also causes an error.
2238    
2239             PCRE_NEWLINE_CR
2240             PCRE_NEWLINE_LF
2241             PCRE_NEWLINE_CRLF
2242             PCRE_NEWLINE_ANYCRLF
2243             PCRE_NEWLINE_ANY
2244    
2245           These  options  override the default newline definition that was chosen
2246           when PCRE was built. Setting the first or the second specifies  that  a
2247           newline  is  indicated  by a single character (CR or LF, respectively).
2248           Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
2249           two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
2250           that any of the three preceding sequences should be recognized. Setting
2251           PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
2252           recognized.
2253    
2254           In an ASCII/Unicode environment, the Unicode newline sequences are  the
2255           three  just  mentioned,  plus  the  single characters VT (vertical tab,
2256           U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line sep-
2257           arator,  U+2028),  and  PS (paragraph separator, U+2029). For the 8-bit
2258           library, the last two are recognized only in UTF-8 mode.
2259    
2260           When PCRE is compiled to run in an EBCDIC (mainframe) environment,  the
2261           code for CR is 0x0d, the same as ASCII. However, the character code for
2262           LF is normally 0x15, though in some EBCDIC environments 0x25  is  used.
2263           Whichever  of  these  is  not LF is made to correspond to Unicode's NEL
2264           character. EBCDIC codes are all less than 256. For  more  details,  see
2265           the pcrebuild documentation.
2266    
2267           The  newline  setting  in  the  options  word  uses three bits that are
2268           treated as a number, giving eight possibilities. Currently only six are
2269           used  (default  plus the five values above). This means that if you set
2270           more than one newline option, the combination may or may not be  sensi-
2271           ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
2272           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
2273           cause an error.
2274    
2275           The  only  time  that a line break in a pattern is specially recognized
2276           when compiling is when PCRE_EXTENDED is set. CR and LF are white  space
2277           characters,  and so are ignored in this mode. Also, an unescaped # out-
2278           side a character class indicates a comment that lasts until  after  the
2279           next  line break sequence. In other circumstances, line break sequences
2280           in patterns are treated as literal data.
2281    
2282           The newline option that is set at compile time becomes the default that
2283           is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
2284    
2285             PCRE_NO_AUTO_CAPTURE
2286    
2287           If this option is set, it disables the use of numbered capturing paren-
2288           theses in the pattern. Any opening parenthesis that is not followed  by
2289           ?  behaves as if it were followed by ?: but named parentheses can still
2290           be used for capturing (and they acquire  numbers  in  the  usual  way).
2291           There is no equivalent of this option in Perl.
2292    
2293             PCRE_NO_START_OPTIMIZE
2294    
2295           This  is an option that acts at matching time; that is, it is really an
2296           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
2297           time,  it is remembered with the compiled pattern and assumed at match-
2298           ing time. This is necessary if you want to use JIT  execution,  because
2299           the  JIT  compiler needs to know whether or not this option is set. For
2300           details see the discussion of PCRE_NO_START_OPTIMIZE below.
2301    
2302             PCRE_UCP
2303    
2304           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
2305           \w,  and  some  of  the POSIX character classes. By default, only ASCII
2306           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
2307           are  used instead to classify characters. More details are given in the
2308           section on generic character types in the pcrepattern page. If you  set
2309           PCRE_UCP,  matching  one of the items it affects takes much longer. The
2310           option is available only if PCRE has been compiled with  Unicode  prop-
2311           erty support.
2312    
2313             PCRE_UNGREEDY
2314    
2315           This  option  inverts  the "greediness" of the quantifiers so that they
2316           are not greedy by default, but become greedy if followed by "?". It  is
2317           not  compatible  with Perl. It can also be set by a (?U) option setting
2318           within the pattern.
2319    
2320             PCRE_UTF8
2321    
2322           This option causes PCRE to regard both the pattern and the  subject  as
2323           strings of UTF-8 characters instead of single-byte strings. However, it
2324           is available only when PCRE is built to include UTF  support.  If  not,
2325           the  use  of  this option provokes an error. Details of how this option
2326           changes the behaviour of PCRE are given in the pcreunicode page.
2327    
2328             PCRE_NO_UTF8_CHECK
2329    
2330           When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
2331           automatically  checked.  There  is  a  discussion about the validity of
2332           UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence  is
2333           found,  pcre_compile()  returns an error. If you already know that your
2334           pattern is valid, and you want to skip this check for performance  rea-
2335           sons,  you  can set the PCRE_NO_UTF8_CHECK option.  When it is set, the
2336           effect of passing an invalid UTF-8 string as a pattern is undefined. It
2337           may  cause  your  program  to  crash. Note that this option can also be
2338           passed to pcre_exec() and pcre_dfa_exec(),  to  suppress  the  validity
2339           checking  of  subject strings only. If the same string is being matched
2340           many times, the option can be safely set for the second and  subsequent
2341           matchings to improve performance.
2342    
2343    
2344    COMPILATION ERROR CODES
2345    
2346           The  following  table  lists  the  error  codes than may be returned by
2347           pcre_compile2(), along with the error messages that may be returned  by
2348           both  compiling  functions.  Note  that error messages are always 8-bit
2349           ASCII strings, even in 16-bit or 32-bit mode. As  PCRE  has  developed,
2350           some  error codes have fallen out of use. To avoid confusion, they have
2351           not been re-used.
2352    
2353              0  no error
2354              1  \ at end of pattern
2355              2  \c at end of pattern
2356              3  unrecognized character follows \
2357              4  numbers out of order in {} quantifier
2358              5  number too big in {} quantifier
2359              6  missing terminating ] for character class
2360              7  invalid escape sequence in character class
2361              8  range out of order in character class
2362              9  nothing to repeat
2363             10  [this code is not in use]
2364             11  internal error: unexpected repeat
2365             12  unrecognized character after (? or (?-
2366             13  POSIX named classes are supported only within a class
2367             14  missing )
2368             15  reference to non-existent subpattern
2369             16  erroffset passed as NULL
2370             17  unknown option bit(s) set
2371             18  missing ) after comment
2372             19  [this code is not in use]
2373             20  regular expression is too large
2374             21  failed to get memory
2375             22  unmatched parentheses
2376             23  internal error: code overflow
2377             24  unrecognized character after (?<
2378             25  lookbehind assertion is not fixed length
2379             26  malformed number or name after (?(
2380             27  conditional group contains more than two branches
2381             28  assertion expected after (?(
2382             29  (?R or (?[+-]digits must be followed by )
2383             30  unknown POSIX class name
2384             31  POSIX collating elements are not supported
2385             32  this version of PCRE is compiled without UTF support
2386             33  [this code is not in use]
2387             34  character value in \x{...} sequence is too large
2388             35  invalid condition (?(0)
2389             36  \C not allowed in lookbehind assertion
2390             37  PCRE does not support \L, \l, \N{name}, \U, or \u
2391             38  number after (?C is > 255
2392             39  closing ) for (?C expected
2393             40  recursive call could loop indefinitely
2394             41  unrecognized character after (?P
2395             42  syntax error in subpattern name (missing terminator)
2396             43  two named subpatterns have the same name
2397             44  invalid UTF-8 string (specifically UTF-8)
2398             45  support for \P, \p, and \X has not been compiled
2399             46  malformed \P or \p sequence
2400             47  unknown property name after \P or \p
2401             48  subpattern name is too long (maximum 32 characters)
2402             49  too many named subpatterns (maximum 10000)
2403             50  [this code is not in use]
2404             51  octal value is greater than \377 in 8-bit non-UTF-8 mode
2405             52  internal error: overran compiling workspace
2406             53  internal error: previously-checked referenced subpattern
2407                   not found
2408             54  DEFINE group contains more than one branch
2409             55  repeating a DEFINE group is not allowed
2410             56  inconsistent NEWLINE options
2411             57  \g is not followed by a braced, angle-bracketed, or quoted
2412                   name/number or by a plain number
2413             58  a numbered reference must not be zero
2414             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
2415             60  (*VERB) not recognized or malformed
2416             61  number is too big
2417             62  subpattern name expected
2418             63  digit expected after (?+
2419             64  ] is an invalid data character in JavaScript compatibility mode
2420             65  different names for subpatterns of the same number are
2421                   not allowed
2422             66  (*MARK) must have an argument
2423             67  this version of PCRE is not compiled with Unicode property
2424                   support
2425             68  \c must be followed by an ASCII character
2426             69  \k is not followed by a braced, angle-bracketed, or quoted name
2427             70  internal error: unknown opcode in find_fixedlength()
2428             71  \N is not supported in a class
2429             72  too many forward references
2430             73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
2431             74  invalid UTF-16 string (specifically UTF-16)
2432             75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
2433             76  character value in \u.... sequence is too large
2434             77  invalid UTF-32 string (specifically UTF-32)
2435    
2436           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
2437           values may be used if the limits were changed when PCRE was built.
2438    
2439    
2440    STUDYING A PATTERN
2441    
2442           pcre_extra *pcre_study(const pcre *code, int options,
2443                const char **errptr);
2444    
2445           If  a  compiled  pattern is going to be used several times, it is worth
2446           spending more time analyzing it in order to speed up the time taken for
2447           matching.  The function pcre_study() takes a pointer to a compiled pat-
2448           tern as its first argument. If studying the pattern produces additional
2449           information  that  will  help speed up matching, pcre_study() returns a
2450           pointer to a pcre_extra block, in which the study_data field points  to
2451           the results of the study.
2452    
2453           The  returned  value  from  pcre_study()  can  be  passed  directly  to
2454           pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
2455           tains  other  fields  that can be set by the caller before the block is
2456           passed; these are described below in the section on matching a pattern.
2457    
2458           If studying the  pattern  does  not  produce  any  useful  information,
2459           pcre_study()  returns  NULL  by  default.  In that circumstance, if the
2460           calling program wants to pass any of the other fields to pcre_exec() or
2461           pcre_dfa_exec(),  it  must set up its own pcre_extra block. However, if
2462           pcre_study() is called  with  the  PCRE_STUDY_EXTRA_NEEDED  option,  it
2463           returns a pcre_extra block even if studying did not find any additional
2464           information. It may still return NULL, however, if an error  occurs  in
2465           pcre_study().
2466    
2467           The  second  argument  of  pcre_study() contains option bits. There are
2468           three further options in addition to PCRE_STUDY_EXTRA_NEEDED:
2469    
2470             PCRE_STUDY_JIT_COMPILE
2471             PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
2472             PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
2473    
2474           If any of these are set, and the just-in-time  compiler  is  available,
2475           the  pattern  is  further compiled into machine code that executes much
2476           faster than the pcre_exec()  interpretive  matching  function.  If  the
2477           just-in-time  compiler is not available, these options are ignored. All
2478           undefined bits in the options argument must be zero.
2479    
2480           JIT compilation is a heavyweight optimization. It can  take  some  time
2481           for  patterns  to  be analyzed, and for one-off matches and simple pat-
2482           terns the benefit of faster execution might be offset by a much  slower
2483           study time.  Not all patterns can be optimized by the JIT compiler. For
2484           those that cannot be handled, matching automatically falls back to  the
2485           pcre_exec()  interpreter.  For more details, see the pcrejit documenta-
2486           tion.
2487    
2488           The third argument for pcre_study() is a pointer for an error  message.
2489           If  studying  succeeds  (even  if no data is returned), the variable it
2490           points to is set to NULL. Otherwise it is set to  point  to  a  textual
2491           error message. This is a static string that is part of the library. You
2492           must not try to free it. You should test the  error  pointer  for  NULL
2493           after calling pcre_study(), to be sure that it has run successfully.
2494    
2495           When  you are finished with a pattern, you can free the memory used for
2496           the study data by calling pcre_free_study(). This function was added to
2497           the  API  for  release  8.20. For earlier versions, the memory could be
2498           freed with pcre_free(), just like the pattern itself. This  will  still
2499           work  in  cases where JIT optimization is not used, but it is advisable
2500           to change to the new function when convenient.
2501    
2502           This is a typical way in which pcre_study() is used (except that  in  a
2503           real application there should be tests for errors):
2504    
2505             int rc;
2506             pcre *re;
2507             pcre_extra *sd;
2508             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
2509             sd = pcre_study(
2510               re,             /* result of pcre_compile() */
2511               0,              /* no options */
2512               &error);        /* set to NULL or points to a message */
2513             rc = pcre_exec(   /* see below for details of pcre_exec() options */
2514               re, sd, "subject", 7, 0, 0, ovector, 30);
2515             ...
2516             pcre_free_study(sd);
2517             pcre_free(re);
2518    
2519           Studying a pattern does two things: first, a lower bound for the length
2520           of subject string that is needed to match the pattern is computed. This
2521           does not mean that there are any strings of that length that match, but
2522           it does guarantee that no shorter strings match. The value is  used  to
2523           avoid wasting time by trying to match strings that are shorter than the
2524           lower bound. You can find out the value in a calling  program  via  the
2525           pcre_fullinfo() function.
2526    
2527           Studying a pattern is also useful for non-anchored patterns that do not
2528           have a single fixed starting character. A bitmap of  possible  starting
2529           bytes  is  created. This speeds up finding a position in the subject at
2530           which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
2531           values  less  than  256.  In 32-bit mode, the bitmap is used for 32-bit
2532           values less than 256.)
2533    
2534           These two optimizations apply to both pcre_exec() and  pcre_dfa_exec(),
2535           and  the  information  is also used by the JIT compiler.  The optimiza-
2536           tions can be disabled by  setting  the  PCRE_NO_START_OPTIMIZE  option.
2537           You  might want to do this if your pattern contains callouts or (*MARK)
2538           and you want to make use of these facilities in  cases  where  matching
2539           fails.
2540    
2541           PCRE_NO_START_OPTIMIZE  can be specified at either compile time or exe-
2542           cution  time.  However,  if   PCRE_NO_START_OPTIMIZE   is   passed   to
2543           pcre_exec(), (that is, after any JIT compilation has happened) JIT exe-
2544           cution is disabled. For JIT execution to work with  PCRE_NO_START_OPTI-
2545           MIZE, the option must be set at compile time.
2546    
2547           There is a longer discussion of PCRE_NO_START_OPTIMIZE below.
2548    
2549    
2550    LOCALE SUPPORT
2551    
2552           PCRE  handles  caseless matching, and determines whether characters are
2553           letters, digits, or whatever, by reference to a set of tables,  indexed
2554           by  character  value.  When running in UTF-8 mode, this applies only to
2555           characters with codes less than 128. By  default,  higher-valued  codes
2556           never match escapes such as \w or \d, but they can be tested with \p if
2557           PCRE is built with Unicode character property  support.  Alternatively,
2558           the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
2559           friends to use Unicode property support instead of built-in tables. The
2560           use of locales with Unicode is discouraged. If you are handling charac-
2561           ters with codes greater than 128, you should either use UTF-8 and  Uni-
2562           code, or use locales, but not try to mix the two.
2563    
2564           PCRE  contains  an  internal set of tables that are used when the final
2565           argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
2566           applications.  Normally, the internal tables recognize only ASCII char-
2567           acters. However, when PCRE is built, it is possible to cause the inter-
2568           nal tables to be rebuilt in the default "C" locale of the local system,
2569           which may cause them to be different.
2570    
2571           The internal tables can always be overridden by tables supplied by  the
2572           application that calls PCRE. These may be created in a different locale
2573           from the default. As more and more applications change  to  using  Uni-
2574           code, the need for this locale support is expected to die away.
2575    
2576           External  tables  are  built by calling the pcre_maketables() function,
2577           which has no arguments, in the relevant locale. The result can then  be
2578           passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
2579           example, to build and use tables that are appropriate  for  the  French
2580           locale  (where  accented  characters  with  values greater than 128 are
2581           treated as letters), the following code could be used:
2582    
2583             setlocale(LC_CTYPE, "fr_FR");
2584             tables = pcre_maketables();
2585             re = pcre_compile(..., tables);
2586    
2587           The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
2588           if you are using Windows, the name for the French locale is "french".
2589    
2590           When  pcre_maketables()  runs,  the  tables are built in memory that is
2591           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
2592           that  the memory containing the tables remains available for as long as
2593           it is needed.
2594    
2595           The pointer that is passed to pcre_compile() is saved with the compiled
2596           pattern,  and the same tables are used via this pointer by pcre_study()
2597           and normally also by pcre_exec(). Thus, by default, for any single pat-
2598           tern, compilation, studying and matching all happen in the same locale,
2599           but different patterns can be compiled in different locales.
2600    
2601           It is possible to pass a table pointer or NULL (indicating the  use  of
2602           the  internal  tables)  to  pcre_exec(). Although not intended for this
2603           purpose, this facility could be used to match a pattern in a  different
2604           locale from the one in which it was compiled. Passing table pointers at
2605           run time is discussed below in the section on matching a pattern.
2606    
2607    
2608    INFORMATION ABOUT A PATTERN
2609    
2610           int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
2611                int what, void *where);
2612    
2613           The pcre_fullinfo() function returns information about a compiled  pat-
2614           tern.  It replaces the pcre_info() function, which was removed from the
2615           library at version 8.30, after more than 10 years of obsolescence.
2616    
2617           The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
2618           pattern.  The second argument is the result of pcre_study(), or NULL if
2619           the pattern was not studied. The third argument specifies  which  piece
2620           of  information  is required, and the fourth argument is a pointer to a
2621           variable to receive the data. The yield of the  function  is  zero  for
2622           success, or one of the following negative numbers:
2623    
2624             PCRE_ERROR_NULL           the argument code was NULL
2625                                       the argument where was NULL
2626             PCRE_ERROR_BADMAGIC       the "magic number" was not found
2627             PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
2628                                       endianness
2629             PCRE_ERROR_BADOPTION      the value of what was invalid
2630             PCRE_ERROR_UNSET          the requested field is not set
2631    
2632           The  "magic  number" is placed at the start of each compiled pattern as
2633           an simple check against passing an arbitrary memory pointer. The  endi-
2634           anness error can occur if a compiled pattern is saved and reloaded on a
2635           different host. Here is a typical call of  pcre_fullinfo(),  to  obtain
2636           the length of the compiled pattern:
2637    
2638             int rc;
2639             size_t length;
2640             rc = pcre_fullinfo(
2641               re,               /* result of pcre_compile() */
2642               sd,               /* result of pcre_study(), or NULL */
2643               PCRE_INFO_SIZE,   /* what is required */
2644               &length);         /* where to put the data */
2645    
2646           The  possible  values for the third argument are defined in pcre.h, and
2647           are as follows:
2648    
2649             PCRE_INFO_BACKREFMAX
2650    
2651           Return the number of the highest back reference  in  the  pattern.  The
2652           fourth  argument  should  point to an int variable. Zero is returned if
2653           there are no back references.
2654    
2655             PCRE_INFO_CAPTURECOUNT
2656    
2657           Return the number of capturing subpatterns in the pattern.  The  fourth
2658           argument should point to an int variable.
2659    
2660             PCRE_INFO_DEFAULT_TABLES
2661    
2662           Return  a pointer to the internal default character tables within PCRE.
2663           The fourth argument should point to an unsigned char *  variable.  This
2664           information call is provided for internal use by the pcre_study() func-
2665           tion. External callers can cause PCRE to use  its  internal  tables  by
2666           passing a NULL table pointer.
2667    
2668             PCRE_INFO_FIRSTBYTE
2669    
2670           Return information about the first data unit of any matched string, for
2671           a non-anchored pattern. (The name of this option refers  to  the  8-bit
2672           library,  where data units are bytes.) The fourth argument should point
2673           to an int variable.
2674    
2675           If there is a fixed first value, for example, the  letter  "c"  from  a
2676           pattern  such  as (cat|cow|coyote), its value is returned. In the 8-bit
2677           library, the value is always less than 256. In the 16-bit  library  the
2678           value can be up to 0xffff. In the 32-bit library the value can be up to
2679           0x10ffff.
2680    
2681           If there is no fixed first value, and if either
2682    
2683           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2684           branch starts with "^", or
2685    
2686           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2687           set (if it were set, the pattern would be anchored),
2688    
2689           -1 is returned, indicating that the pattern matches only at  the  start
2690           of  a  subject string or after any newline within the string. Otherwise
2691           -2 is returned. For anchored patterns, -2 is returned.
2692    
2693           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2694           is  unable to return the full 32-bit range of the character, this value
2695           is   deprecated;   instead   the   PCRE_INFO_FIRSTCHARACTERFLAGS    and
2696           PCRE_INFO_FIRSTCHARACTER values should be used.
2697    
2698             PCRE_INFO_FIRSTTABLE
2699    
2700           If  the pattern was studied, and this resulted in the construction of a
2701           256-bit table indicating a fixed set of values for the first data  unit
2702           in  any  matching string, a pointer to the table is returned. Otherwise
2703           NULL is returned. The fourth argument should point to an unsigned  char
2704           * variable.
2705    
2706             PCRE_INFO_HASCRORLF
2707    
2708           Return  1  if  the  pattern  contains any explicit matches for CR or LF
2709           characters, otherwise 0. The fourth argument should  point  to  an  int
2710           variable.  An explicit match is either a literal CR or LF character, or
2711           \r or \n.
2712    
2713             PCRE_INFO_JCHANGED
2714    
2715           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
2716           otherwise  0. The fourth argument should point to an int variable. (?J)
2717           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
2718    
2719             PCRE_INFO_JIT
2720    
2721           Return 1 if the pattern was studied with one of the  JIT  options,  and
2722           just-in-time compiling was successful. The fourth argument should point
2723           to an int variable. A return value of 0 means that JIT support  is  not
2724           available  in this version of PCRE, or that the pattern was not studied
2725           with a JIT option, or that the JIT compiler could not handle this  par-
2726           ticular  pattern. See the pcrejit documentation for details of what can
2727           and cannot be handled.
2728    
2729             PCRE_INFO_JITSIZE
2730    
2731           If the pattern was successfully studied with a JIT option,  return  the
2732           size  of the JIT compiled code, otherwise return zero. The fourth argu-
2733           ment should point to a size_t variable.
2734    
2735             PCRE_INFO_LASTLITERAL
2736    
2737           Return the value of the rightmost literal data unit that must exist  in
2738           any  matched  string, other than at its start, if such a value has been
2739           recorded. The fourth argument should point to an int variable. If there
2740           is no such value, -1 is returned. For anchored patterns, a last literal
2741           value is recorded only if it follows something of variable length.  For
2742           example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
2743           /^a\dz\d/ the returned value is -1.
2744    
2745           Since for the 32-bit library using the non-UTF-32 mode,  this  function
2746           is  unable to return the full 32-bit range of the character, this value
2747           is   deprecated;   instead    the    PCRE_INFO_REQUIREDCHARFLAGS    and
2748           PCRE_INFO_REQUIREDCHAR values should be used.
2749    
2750             PCRE_INFO_MATCHLIMIT
2751    
2752           If  the  pattern  set  a  match  limit by including an item of the form
2753           (*LIMIT_MATCH=nnnn) at the start, the value  is  returned.  The  fourth
2754           argument  should  point to an unsigned 32-bit integer. If no such value
2755           has  been  set,  the  call  to  pcre_fullinfo()   returns   the   error
2756           PCRE_ERROR_UNSET.
2757    
2758             PCRE_INFO_MAXLOOKBEHIND
2759    
2760           Return  the  number  of  characters  (NB not data units) in the longest
2761           lookbehind assertion in the pattern. This information  is  useful  when
2762           doing  multi-segment  matching  using  the partial matching facilities.
2763           Note that the simple assertions \b and \B require a one-character look-
2764           behind.  \A  also  registers a one-character lookbehind, though it does
2765           not actually inspect the previous character. This is to ensure that  at
2766           least one character from the old segment is retained when a new segment
2767           is processed. Otherwise, if there are no lookbehinds in the pattern, \A
2768           might match incorrectly at the start of a new segment.
2769    
2770             PCRE_INFO_MINLENGTH
2771    
2772           If  the  pattern  was studied and a minimum length for matching subject
2773           strings was computed, its value is  returned.  Otherwise  the  returned
2774           value is -1. The value is a number of characters, which in UTF mode may
2775           be different from the number of data units. The fourth argument  should
2776           point  to an int variable. A non-negative value is a lower bound to the
2777           length of any matching string. There may not be  any  strings  of  that
2778           length  that  do actually match, but every string that does match is at
2779           least that long.
2780    
2781             PCRE_INFO_NAMECOUNT
2782             PCRE_INFO_NAMEENTRYSIZE
2783             PCRE_INFO_NAMETABLE
2784    
2785           PCRE supports the use of named as well as numbered capturing  parenthe-
2786           ses.  The names are just an additional way of identifying the parenthe-
2787           ses, which still acquire numbers. Several convenience functions such as
2788           pcre_get_named_substring()  are  provided  for extracting captured sub-
2789           strings by name. It is also possible to extract the data  directly,  by
2790           first  converting  the  name to a number in order to access the correct
2791           pointers in the output vector (described with pcre_exec() below). To do
2792           the  conversion,  you  need  to  use  the  name-to-number map, which is
2793           described by these three values.
2794    
2795           The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
2796           gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
2797           of each entry; both of these  return  an  int  value.  The  entry  size
2798           depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
2799           a pointer to the first entry of the table. This is a pointer to char in
2800           the 8-bit library, where the first two bytes of each entry are the num-
2801           ber of the capturing parenthesis, most significant byte first.  In  the
2802           16-bit  library,  the pointer points to 16-bit data units, the first of
2803           which contains the parenthesis  number.  In  the  32-bit  library,  the
2804           pointer  points  to  32-bit data units, the first of which contains the
2805           parenthesis number. The rest of the entry is  the  corresponding  name,
2806           zero terminated.
2807    
2808           The  names are in alphabetical order. Duplicate names may appear if (?|
2809           is used to create multiple groups with the same number, as described in
2810           the  section  on  duplicate subpattern numbers in the pcrepattern page.
2811           Duplicate names for subpatterns with different  numbers  are  permitted
2812           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
2813           appear in the table in the order in which they were found in  the  pat-
2814           tern.  In  the  absence  of (?| this is the order of increasing number;
2815           when (?| is used this is not necessarily the case because later subpat-
2816           terns may have lower numbers.
2817    
2818           As  a  simple  example of the name/number table, consider the following
2819           pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
2820           set, so white space - including newlines - is ignored):
2821    
2822             (?<date> (?<year>(\d\d)?\d\d) -
2823             (?<month>\d\d) - (?<day>\d\d) )
2824    
2825           There  are  four  named subpatterns, so the table has four entries, and
2826           each entry in the table is eight bytes long. The table is  as  follows,
2827           with non-printing bytes shows in hexadecimal, and undefined bytes shown
2828           as ??:
2829    
2830             00 01 d  a  t  e  00 ??
2831             00 05 d  a  y  00 ?? ??
2832             00 04 m  o  n  t  h  00
2833             00 02 y  e  a  r  00 ??
2834    
2835           When writing code to extract data  from  named  subpatterns  using  the
2836           name-to-number  map,  remember that the length of the entries is likely
2837           to be different for each compiled pattern.
2838    
2839             PCRE_INFO_OKPARTIAL
2840    
2841           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
2842           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
2843           variable. From  release  8.00,  this  always  returns  1,  because  the
2844           restrictions  that  previously  applied  to  partial matching have been
2845           lifted. The pcrepartial documentation gives details of  partial  match-
2846           ing.
2847    
2848             PCRE_INFO_OPTIONS
2849    
2850           Return  a  copy of the options with which the pattern was compiled. The
2851           fourth argument should point to an unsigned long  int  variable.  These
2852           option bits are those specified in the call to pcre_compile(), modified
2853           by any top-level option settings at the start of the pattern itself. In
2854           other  words,  they are the options that will be in force when matching
2855           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
2856           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
2857           and PCRE_EXTENDED.
2858    
2859           A pattern is automatically anchored by PCRE if  all  of  its  top-level
2860           alternatives begin with one of the following:
2861    
2862             ^     unless PCRE_MULTILINE is set
2863             \A    always
2864             \G    always
2865             .*    if PCRE_DOTALL is set and there are no back
2866                     references to the subpattern in which .* appears
2867    
2868           For such patterns, the PCRE_ANCHORED bit is set in the options returned
2869           by pcre_fullinfo().
2870    
2871             PCRE_INFO_RECURSIONLIMIT
2872    
2873           If the pattern set a recursion limit by including an item of  the  form
2874           (*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth
2875           argument should point to an unsigned 32-bit integer. If no  such  value
2876           has   been   set,   the  call  to  pcre_fullinfo()  returns  the  error
2877           PCRE_ERROR_UNSET.
2878    
2879             PCRE_INFO_SIZE
2880    
2881           Return the size of  the  compiled  pattern  in  bytes  (for  all  three
2882           libraries). The fourth argument should point to a size_t variable. This
2883           value does not include the size of the pcre structure that is  returned
2884           by  pcre_compile().  The  value  that  is  passed  as  the  argument to
2885           pcre_malloc() when pcre_compile() is getting memory in which  to  place
2886           the compiled data is the value returned by this option plus the size of
2887           the pcre structure. Studying a compiled pattern, with or  without  JIT,
2888           does not alter the value returned by this option.
2889    
2890             PCRE_INFO_STUDYSIZE
2891    
2892           Return  the  size  in bytes (for all three libraries) of the data block
2893           pointed to by the study_data field in a pcre_extra block. If pcre_extra
2894           is  NULL, or there is no study data, zero is returned. The fourth argu-
2895           ment should point to a size_t variable. The study_data field is set  by
2896           pcre_study() to record information that will speed up matching (see the
2897           section entitled  "Studying  a  pattern"  above).  The  format  of  the
2898           study_data  block is private, but its length is made available via this
2899           option so that it can be saved and  restored  (see  the  pcreprecompile
2900           documentation for details).
2901    
2902             PCRE_INFO_FIRSTCHARACTERFLAGS
2903    
2904           Return information about the first data unit of any matched string, for
2905           a non-anchored pattern. The fourth argument  should  point  to  an  int
2906           variable.
2907    
2908           If  there  is  a  fixed first value, for example, the letter "c" from a
2909           pattern such as (cat|cow|coyote), 1  is  returned,  and  the  character
2910           value can be retrieved using PCRE_INFO_FIRSTCHARACTER.
2911    
2912           If there is no fixed first value, and if either
2913    
2914           (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
2915           branch starts with "^", or
2916    
2917           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2918           set (if it were set, the pattern would be anchored),
2919    
2920           2 is returned, indicating that the pattern matches only at the start of
2921           a subject string or after any newline within the string. Otherwise 0 is
2922           returned. For anchored patterns, 0 is returned.
2923    
2924             PCRE_INFO_FIRSTCHARACTER
2925    
2926           Return  the  fixed  first character value, if PCRE_INFO_FIRSTCHARACTER-
2927           FLAGS returned 1; otherwise returns 0. The fourth argument should point
2928           to an uint_t variable.
2929    
2930           In  the 8-bit library, the value is always less than 256. In the 16-bit
2931           library the value can be up to 0xffff. In the 32-bit library in  UTF-32
2932           mode  the  value  can  be up to 0x10ffff, and up to 0xffffffff when not
2933           using UTF-32 mode.
2934    
2935           If there is no fixed first value, and if either
2936    
2937           (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
2938           branch starts with "^", or
2939    
2940           (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
2941           set (if it were set, the pattern would be anchored),
2942    
2943           -1 is returned, indicating that the pattern matches only at  the  start
2944           of  a  subject string or after any newline within the string. Otherwise
2945           -2 is returned. For anchored patterns, -2 is returned.
2946    
2947             PCRE_INFO_REQUIREDCHARFLAGS
2948    
2949           Returns 1 if there is a rightmost literal data unit that must exist  in
2950           any matched string, other than at its start. The fourth argument should
2951           point to an int variable. If there is no such value, 0 is returned.  If
2952           returning  1,  the  character  value  itself  can  be  retrieved  using
2953           PCRE_INFO_REQUIREDCHAR.
2954    
2955           For anchored patterns, a last literal value is recorded only if it fol-
2956           lows  something  of  variable  length.  For  example,  for  the pattern
2957           /^a\d+z\d+/  the   returned   value   1   (with   "z"   returned   from
2958           PCRE_INFO_REQUIREDCHAR), but for /^a\dz\d/ the returned value is 0.
2959    
2960             PCRE_INFO_REQUIREDCHAR
2961    
2962           Return  the value of the rightmost literal data unit that must exist in
2963           any matched string, other than at its start, if such a value  has  been
2964           recorded.  The fourth argument should point to an uint32_t variable. If
2965           there is no such value, 0 is returned.
2966    
2967    
2968    REFERENCE COUNTS
2969    
2970           int pcre_refcount(pcre *code, int adjust);
2971    
2972           The pcre_refcount() function is used to maintain a reference  count  in
2973           the data block that contains a compiled pattern. It is provided for the
2974           benefit of applications that  operate  in  an  object-oriented  manner,
2975           where different parts of the application may be using the same compiled
2976           pattern, but you want to free the block when they are all done.
2977    
2978           When a pattern is compiled, the reference count field is initialized to
2979           zero.   It is changed only by calling this function, whose action is to
2980           add the adjust value (which may be positive or  negative)  to  it.  The
2981           yield of the function is the new value. However, the value of the count
2982           is constrained to lie between 0 and 65535, inclusive. If the new  value
2983           is outside these limits, it is forced to the appropriate limit value.
2984    
2985           Except  when it is zero, the reference count is not correctly preserved
2986           if a pattern is compiled on one host and then  transferred  to  a  host
2987           whose byte-order is different. (This seems a highly unlikely scenario.)
2988    
2989    
2990    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
2991    
2992           int pcre_exec(const pcre *code, const pcre_extra *extra,
2993                const char *subject, int length, int startoffset,
2994                int options, int *ovector, int ovecsize);
2995    
2996           The  function pcre_exec() is called to match a subject string against a
2997           compiled pattern, which is passed in the code argument. If the  pattern
2998           was  studied,  the  result  of  the study should be passed in the extra
2999           argument. You can call pcre_exec() with the same code and  extra  argu-
3000           ments  as  many  times as you like, in order to match different subject
3001           strings with the same pattern.
3002    
3003           This function is the main matching facility  of  the  library,  and  it
3004           operates  in  a  Perl-like  manner. For specialist use there is also an
3005           alternative matching function, which is described below in the  section
3006           about the pcre_dfa_exec() function.
3007    
3008           In  most applications, the pattern will have been compiled (and option-
3009           ally studied) in the same process that calls pcre_exec().  However,  it
3010           is possible to save compiled patterns and study data, and then use them
3011           later in different processes, possibly even on different hosts.  For  a
3012           discussion about this, see the pcreprecompile documentation.
3013    
3014           Here is an example of a simple call to pcre_exec():
3015    
3016             int rc;
3017             int ovector[30];
3018             rc = pcre_exec(
3019               re,             /* result of pcre_compile() */
3020               NULL,           /* we didn't study the pattern */
3021               "some string",  /* the subject string */
3022               11,             /* the length of the subject string */
3023               0,              /* start at offset 0 in the subject */
3024               0,              /* default options */
3025               ovector,        /* vector of integers for substring information */
3026               30);            /* number of elements (NOT size in bytes) */
3027    
3028       Extra data for pcre_exec()
3029    
3030           If  the  extra argument is not NULL, it must point to a pcre_extra data
3031           block. The pcre_study() function returns such a block (when it  doesn't
3032           return  NULL), but you can also create one for yourself, and pass addi-
3033           tional information in it. The pcre_extra block contains  the  following
3034           fields (not necessarily in this order):
3035    
3036             unsigned long int flags;
3037             void *study_data;
3038             void *executable_jit;
3039             unsigned long int match_limit;
3040             unsigned long int match_limit_recursion;
3041             void *callout_data;
3042             const unsigned char *tables;
3043             unsigned char **mark;
3044    
3045           In  the  16-bit  version  of  this  structure,  the mark field has type
3046           "PCRE_UCHAR16 **".
3047    
3048           In the 32-bit version of  this  structure,  the  mark  field  has  type
3049           "PCRE_UCHAR32 **".
3050    
3051           The  flags  field is used to specify which of the other fields are set.
3052           The flag bits are:
3053    
3054             PCRE_EXTRA_CALLOUT_DATA
3055             PCRE_EXTRA_EXECUTABLE_JIT
3056             PCRE_EXTRA_MARK
3057             PCRE_EXTRA_MATCH_LIMIT
3058             PCRE_EXTRA_MATCH_LIMIT_RECURSION
3059             PCRE_EXTRA_STUDY_DATA
3060             PCRE_EXTRA_TABLES
3061    
3062           Other flag bits should be set to zero. The study_data field  and  some-
3063           times  the executable_jit field are set in the pcre_extra block that is
3064           returned by pcre_study(), together with the appropriate flag bits.  You
3065           should  not set these yourself, but you may add to the block by setting
3066           other fields and their corresponding flag bits.
3067    
3068           The match_limit field provides a means of preventing PCRE from using up
3069           a  vast amount of resources when running patterns that are not going to
3070           match, but which have a very large number  of  possibilities  in  their
3071           search  trees. The classic example is a pattern that uses nested unlim-
3072           ited repeats.
3073    
3074           Internally, pcre_exec() uses a function called match(), which it  calls
3075           repeatedly  (sometimes  recursively).  The  limit set by match_limit is
3076           imposed on the number of times this function is called during a  match,
3077           which  has  the  effect of limiting the amount of backtracking that can
3078           take place. For patterns that are not anchored, the count restarts from
3079           zero for each position in the subject string.
3080    
3081           When pcre_exec() is called with a pattern that was successfully studied
3082           with a JIT option, the way that the matching is  executed  is  entirely
3083           different.  However, there is still the possibility of runaway matching
3084           that goes on for a very long time, and so the match_limit value is also
3085           used in this case (but in a different way) to limit how long the match-
3086           ing can continue.
3087    
3088           The default value for the limit can be set  when  PCRE  is  built;  the
3089           default  default  is 10 million, which handles all but the most extreme
3090           cases. You can override the default  by  suppling  pcre_exec()  with  a
3091           pcre_extra     block    in    which    match_limit    is    set,    and
3092           PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
3093           exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
3094    
3095           A  value  for  the  match  limit may also be supplied by an item at the
3096           start of a pattern of the form
3097    
3098             (*LIMIT_MATCH=d)
3099    
3100           where d is a decimal number. However, such a setting is ignored  unless
3101           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3102           such limit is set, less than the default.
3103    
3104           The match_limit_recursion field is similar to match_limit, but  instead
3105           of limiting the total number of times that match() is called, it limits
3106           the depth of recursion. The recursion depth is a  smaller  number  than
3107           the  total number of calls, because not all calls to match() are recur-
3108           sive.  This limit is of use only if it is set smaller than match_limit.
3109    
3110           Limiting the recursion depth limits the amount of  machine  stack  that
3111           can  be used, or, when PCRE has been compiled to use memory on the heap
3112           instead of the stack, the amount of heap memory that can be used.  This
3113           limit  is not relevant, and is ignored, when matching is done using JIT
3114           compiled code.
3115    
3116           The default value for match_limit_recursion can be  set  when  PCRE  is
3117           built;  the  default  default  is  the  same  value  as the default for
3118           match_limit. You can override the default by suppling pcre_exec()  with
3119           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
3120           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
3121           limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
3122    
3123           A  value for the recursion limit may also be supplied by an item at the
3124           start of a pattern of the form
3125    
3126             (*LIMIT_RECURSION=d)
3127    
3128           where d is a decimal number. However, such a setting is ignored  unless
3129           d  is  less  than  the limit set by the caller of pcre_exec() or, if no
3130           such limit is set, less than the default.
3131    
3132           The callout_data field is used in conjunction with the  "callout"  fea-
3133           ture, and is described in the pcrecallout documentation.
3134    
3135           The  tables  field  is  used  to  pass  a  character  tables pointer to
3136           pcre_exec(); this overrides the value that is stored with the  compiled
3137           pattern.  A  non-NULL value is stored with the compiled pattern only if
3138           custom tables were supplied to pcre_compile() via  its  tableptr  argu-
3139           ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
3140           PCRE's internal tables to be used. This facility is  helpful  when  re-
3141           using  patterns  that  have been saved after compiling with an external
3142           set of tables, because the external tables  might  be  at  a  different
3143           address  when  pcre_exec() is called. See the pcreprecompile documenta-
3144           tion for a discussion of saving compiled patterns for later use.
3145    
3146           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
3147           set  to point to a suitable variable. If the pattern contains any back-
3148           tracking control verbs such as (*MARK:NAME), and the execution ends  up
3149           with  a  name  to  pass back, a pointer to the name string (zero termi-
3150           nated) is placed in the variable pointed to  by  the  mark  field.  The
3151           names  are  within  the  compiled pattern; if you wish to retain such a
3152           name you must copy it before freeing the memory of a compiled  pattern.
3153           If  there  is no name to pass back, the variable pointed to by the mark
3154           field is set to NULL. For details of the  backtracking  control  verbs,
3155           see the section entitled "Backtracking control" in the pcrepattern doc-
3156           umentation.
3157    
3158       Option bits for pcre_exec()
3159    
3160           The unused bits of the options argument for pcre_exec() must  be  zero.
3161           The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
3162           PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
3163           PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_HARD,  and
3164           PCRE_PARTIAL_SOFT.
3165    
3166           If the pattern was successfully studied with one  of  the  just-in-time
3167           (JIT) compile options, the only supported options for JIT execution are
3168           PCRE_NO_UTF8_CHECK,    PCRE_NOTBOL,     PCRE_NOTEOL,     PCRE_NOTEMPTY,
3169           PCRE_NOTEMPTY_ATSTART,  PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
3170           unsupported option is used, JIT execution is disabled  and  the  normal
3171           interpretive code in pcre_exec() is run.
3172    
3173             PCRE_ANCHORED
3174    
3175           The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
3176           matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
3177           turned  out to be anchored by virtue of its contents, it cannot be made
3178           unachored at matching time.
3179    
3180             PCRE_BSR_ANYCRLF
3181             PCRE_BSR_UNICODE
3182    
3183           These options (which are mutually exclusive) control what the \R escape
3184           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
3185           or to match any Unicode newline sequence. These  options  override  the
3186           choice that was made or defaulted when the pattern was compiled.
3187    
3188             PCRE_NEWLINE_CR
3189             PCRE_NEWLINE_LF
3190             PCRE_NEWLINE_CRLF
3191             PCRE_NEWLINE_ANYCRLF
3192             PCRE_NEWLINE_ANY
3193    
3194           These  options  override  the  newline  definition  that  was chosen or
3195           defaulted when the pattern was compiled. For details, see the  descrip-
3196           tion  of  pcre_compile()  above.  During  matching,  the newline choice
3197           affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
3198           ters.  It may also alter the way the match position is advanced after a
3199           match failure for an unanchored pattern.
3200    
3201           When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
3202           set,  and a match attempt for an unanchored pattern fails when the cur-
3203           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
3204           explicit  matches  for  CR  or  LF  characters,  the  match position is
3205           advanced by two characters instead of one, in other words, to after the
3206           CRLF.
3207    
3208           The above rule is a compromise that makes the most common cases work as
3209           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
3210           option is not set), it does not match the string "\r\nA" because, after
3211           failing at the start, it skips both the CR and the LF before  retrying.
3212           However,  the  pattern  [\r\n]A does match that string, because it con-
3213           tains an explicit CR or LF reference, and so advances only by one char-
3214           acter after the first failure.
3215    
3216           An explicit match for CR of LF is either a literal appearance of one of
3217           those characters, or one of the \r or  \n  escape  sequences.  Implicit
3218           matches  such  as [^X] do not count, nor does \s (which includes CR and
3219           LF in the characters that it matches).
3220    
3221           Notwithstanding the above, anomalous effects may still occur when  CRLF
3222           is a valid newline sequence and explicit \r or \n escapes appear in the
3223           pattern.
3224    
3225             PCRE_NOTBOL
3226    
3227           This option specifies that first character of the subject string is not
3228           the  beginning  of  a  line, so the circumflex metacharacter should not
3229           match before it. Setting this without PCRE_MULTILINE (at compile  time)
3230           causes  circumflex  never to match. This option affects only the behav-
3231           iour of the circumflex metacharacter. It does not affect \A.
3232    
3233             PCRE_NOTEOL
3234    
3235           This option specifies that the end of the subject string is not the end
3236           of  a line, so the dollar metacharacter should not match it nor (except
3237           in multiline mode) a newline immediately before it. Setting this  with-
3238           out PCRE_MULTILINE (at compile time) causes dollar never to match. This
3239           option affects only the behaviour of the dollar metacharacter. It  does
3240           not affect \Z or \z.
3241    
3242             PCRE_NOTEMPTY
3243    
3244           An empty string is not considered to be a valid match if this option is
3245           set. If there are alternatives in the pattern, they are tried.  If  all
3246           the  alternatives  match  the empty string, the entire match fails. For
3247           example, if the pattern
3248    
3249             a?b?
3250    
3251           is applied to a string not beginning with "a" or  "b",  it  matches  an
3252           empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
3253           match is not valid, so PCRE searches further into the string for occur-
3254           rences of "a" or "b".
3255    
3256             PCRE_NOTEMPTY_ATSTART
3257    
3258           This  is  like PCRE_NOTEMPTY, except that an empty string match that is
3259           not at the start of  the  subject  is  permitted.  If  the  pattern  is
3260           anchored, such a match can occur only if the pattern contains \K.
3261    
3262           Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
3263           PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
3264           match  of  the empty string within its split() function, and when using
3265           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
3266           matching a null string by first trying the match again at the same off-
3267           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
3268           fails, by advancing the starting offset (see below) and trying an ordi-
3269           nary match again. There is some code that demonstrates how to  do  this
3270           in  the  pcredemo sample program. In the most general case, you have to
3271           check to see if the newline convention recognizes CRLF  as  a  newline,
3272           and  if so, and the current character is CR followed by LF, advance the
3273           starting offset by two characters instead of one.
3274    
3275             PCRE_NO_START_OPTIMIZE
3276    
3277           There are a number of optimizations that pcre_exec() uses at the  start
3278           of  a  match,  in  order to speed up the process. For example, if it is
3279           known that an unanchored match must start with a specific character, it
3280           searches  the  subject  for that character, and fails immediately if it
3281           cannot find it, without actually running the  main  matching  function.
3282           This means that a special item such as (*COMMIT) at the start of a pat-
3283           tern is not considered until after a suitable starting  point  for  the
3284           match  has been found. Also, when callouts or (*MARK) items are in use,
3285           these "start-up" optimizations can cause them to be skipped if the pat-
3286           tern is never actually used. The start-up optimizations are in effect a
3287           pre-scan of the subject that takes place before the pattern is run.
3288    
3289           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
3290           possibly  causing  performance  to  suffer,  but ensuring that in cases
3291           where the result is "no match", the callouts do occur, and  that  items
3292           such as (*COMMIT) and (*MARK) are considered at every possible starting
3293           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
3294           compile  time,  it  cannot  be  unset  at  matching  time.  The  use of
3295           PCRE_NO_START_OPTIMIZE  at  matching  time  (that  is,  passing  it  to
3296           pcre_exec())  disables  JIT  execution;  in this situation, matching is
3297           always done using interpretively.
3298    
3299           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
3300           operation.  Consider the pattern
3301    
3302             (*COMMIT)ABC
3303    
3304           When  this  is  compiled, PCRE records the fact that a match must start
3305           with the character "A". Suppose the subject  string  is  "DEFABC".  The
3306           start-up  optimization  scans along the subject, finds "A" and runs the
3307           first match attempt from there. The (*COMMIT) item means that the  pat-
3308           tern  must  match the current starting position, which in this case, it
3309           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
3310           set,  the  initial  scan  along the subject string does not happen. The
3311           first match attempt is run starting  from  "D"  and  when  this  fails,
3312           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
3313           result is "no match". If the pattern is studied,  more  start-up  opti-
3314           mizations  may  be  used. For example, a minimum length for the subject
3315           may be recorded. Consider the pattern
3316    
3317             (*MARK:A)(X|Y)
3318    
3319           The minimum length for a match is one  character.  If  the  subject  is
3320           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
3321           finally an empty string.  If the pattern is studied, the final  attempt
3322           does  not take place, because PCRE knows that the subject is too short,
3323           and so the (*MARK) is never encountered.  In this  case,  studying  the
3324           pattern  does  not  affect the overall match result, which is still "no
3325           match", but it does affect the auxiliary information that is returned.
3326    
3327             PCRE_NO_UTF8_CHECK
3328    
3329           When PCRE_UTF8 is set at compile time, the validity of the subject as a
3330           UTF-8  string is automatically checked when pcre_exec() is subsequently
3331           called.  The entire string is checked before any other processing takes
3332           place.  The  value  of  startoffset  is  also checked to ensure that it
3333           points to the start of a UTF-8 character. There is a  discussion  about
3334           the  validity  of  UTF-8 strings in the pcreunicode page. If an invalid
3335           sequence  of  bytes   is   found,   pcre_exec()   returns   the   error
3336           PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
3337           truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
3338           both  cases, information about the precise nature of the error may also
3339           be returned (see the descriptions of these errors in the section  enti-
3340           tled  Error return values from pcre_exec() below).  If startoffset con-
3341           tains a value that does not point to the start of a UTF-8 character (or
3342           to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
3343    
3344           If  you  already  know that your subject is valid, and you want to skip
3345           these   checks   for   performance   reasons,   you   can    set    the
3346           PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
3347           do this for the second and subsequent calls to pcre_exec() if  you  are
3348           making  repeated  calls  to  find  all  the matches in a single subject
3349           string. However, you should be  sure  that  the  value  of  startoffset
3350           points  to  the  start of a character (or the end of the subject). When
3351           PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
3352           subject  or  an invalid value of startoffset is undefined. Your program
3353           may crash.
3354    
3355             PCRE_PARTIAL_HARD
3356             PCRE_PARTIAL_SOFT
3357    
3358           These options turn on the partial matching feature. For backwards  com-
3359           patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
3360           match occurs if the end of the subject string is reached  successfully,
3361           but  there  are not enough subject characters to complete the match. If
3362           this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
3363           matching  continues  by  testing any remaining alternatives. Only if no
3364           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
3365           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
3366           caller is prepared to handle a partial match, but only if  no  complete
3367           match can be found.
3368    
3369           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
3370           case, if a partial match  is  found,  pcre_exec()  immediately  returns
3371           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
3372           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
3373           ered to be more important that an alternative complete match.
3374    
3375           In  both  cases,  the portion of the string that was inspected when the
3376           partial match was found is set as the first matching string. There is a
3377           more  detailed  discussion  of partial and multi-segment matching, with
3378           examples, in the pcrepartial documentation.
3379    
3380       The string to be matched by pcre_exec()
3381    
3382           The subject string is passed to pcre_exec() as a pointer in subject,  a
3383           length  in  length, and a starting offset in startoffset. The units for
3384           length and startoffset are bytes for the  8-bit  library,  16-bit  data
3385           items  for  the  16-bit  library,  and 32-bit data items for the 32-bit
3386           library.
3387    
3388           If startoffset is negative or greater than the length of  the  subject,
3389           pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
3390           zero, the search for a match starts at the beginning  of  the  subject,
3391           and  this  is by far the most common case. In UTF-8 or UTF-16 mode, the
3392           offset must point to the start of a character, or the end of  the  sub-
3393           ject  (in  UTF-32 mode, one data unit equals one character, so all off-
3394           sets are valid). Unlike the pattern string,  the  subject  may  contain
3395           binary zeroes.
3396    
3397           A  non-zero  starting offset is useful when searching for another match
3398           in the same subject by calling pcre_exec() again after a previous  suc-
3399           cess.   Setting  startoffset differs from just passing over a shortened
3400           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
3401           with any kind of lookbehind. For example, consider the pattern
3402    
3403             \Biss\B
3404    
3405           which  finds  occurrences  of "iss" in the middle of words. (\B matches
3406           only if the current position in the subject is not  a  word  boundary.)
3407           When  applied  to the string "Mississipi" the first call to pcre_exec()
3408           finds the first occurrence. If pcre_exec() is called  again  with  just
3409           the  remainder  of  the  subject,  namely  "issipi", it does not match,
3410           because \B is always false at the start of the subject, which is deemed
3411           to  be  a  word  boundary. However, if pcre_exec() is passed the entire
3412           string again, but with startoffset set to 4, it finds the second occur-
3413           rence  of "iss" because it is able to look behind the starting point to
3414           discover that it is preceded by a letter.
3415    
3416           Finding all the matches in a subject is tricky  when  the  pattern  can
3417           match an empty string. It is possible to emulate Perl's /g behaviour by
3418           first  trying  the  match  again  at  the   same   offset,   with   the