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Load pcre-5.0 into code/trunk.
1 .TH PCRE 3
3 PCRE - Perl-compatible regular expressions
5 .rs
6 .sp
7 .B #include <pcre.h>
8 .PP
9 .SM
10 .br
11 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
12 .ti +5n
13 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
14 .ti +5n
15 .B const unsigned char *\fItableptr\fP);
16 .PP
17 .br
18 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
19 .ti +5n
20 .B const char **\fIerrptr\fP);
21 .PP
22 .br
23 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
24 .ti +5n
25 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
26 .ti +5n
27 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
28 .PP
29 .br
30 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
31 .ti +5n
32 .B const char *\fIsubject\fP, int *\fIovector\fP,
33 .ti +5n
34 .B int \fIstringcount\fP, const char *\fIstringname\fP,
35 .ti +5n
36 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
37 .PP
38 .br
39 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
40 .ti +5n
41 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
42 .ti +5n
43 .B int \fIbuffersize\fP);
44 .PP
45 .br
46 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
47 .ti +5n
48 .B const char *\fIsubject\fP, int *\fIovector\fP,
49 .ti +5n
50 .B int \fIstringcount\fP, const char *\fIstringname\fP,
51 .ti +5n
52 .B const char **\fIstringptr\fP);
53 .PP
54 .br
55 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
56 .ti +5n
57 .B const char *\fIname\fP);
58 .PP
59 .br
60 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
61 .ti +5n
62 .B int \fIstringcount\fP, int \fIstringnumber\fP,
63 .ti +5n
64 .B const char **\fIstringptr\fP);
65 .PP
66 .br
67 .B int pcre_get_substring_list(const char *\fIsubject\fP,
68 .ti +5n
69 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
70 .PP
71 .br
72 .B void pcre_free_substring(const char *\fIstringptr\fP);
73 .PP
74 .br
75 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
76 .PP
77 .br
78 .B const unsigned char *pcre_maketables(void);
79 .PP
80 .br
81 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
82 .ti +5n
83 .B int \fIwhat\fP, void *\fIwhere\fP);
84 .PP
85 .br
86 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
87 .B *\fIfirstcharptr\fP);
88 .PP
89 .br
90 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
91 .PP
92 .br
93 .B char *pcre_version(void);
94 .PP
95 .br
96 .B void *(*pcre_malloc)(size_t);
97 .PP
98 .br
99 .B void (*pcre_free)(void *);
100 .PP
101 .br
102 .B void *(*pcre_stack_malloc)(size_t);
103 .PP
104 .br
105 .B void (*pcre_stack_free)(void *);
106 .PP
107 .br
108 .B int (*pcre_callout)(pcre_callout_block *);
109 .
110 .
112 .rs
113 .sp
114 PCRE has its own native API, which is described in this document. There is also
115 a set of wrapper functions that correspond to the POSIX regular expression API.
116 These are described in the
117 .\" HREF
118 \fBpcreposix\fP
119 .\"
120 documentation.
121 .P
122 The native API function prototypes are defined in the header file \fBpcre.h\fP,
123 and on Unix systems the library itself is called \fBlibpcre\fP. It can
124 normally be accessed by adding \fB-lpcre\fP to the command for linking an
125 application that uses PCRE. The header file defines the macros PCRE_MAJOR and
126 PCRE_MINOR to contain the major and minor release numbers for the library.
127 Applications can use these to include support for different releases of PCRE.
128 .P
129 The functions \fBpcre_compile()\fP, \fBpcre_study()\fP, and \fBpcre_exec()\fP
130 are used for compiling and matching regular expressions. A sample program that
131 demonstrates the simplest way of using them is provided in the file called
132 \fIpcredemo.c\fP in the source distribution. The
133 .\" HREF
134 \fBpcresample\fP
135 .\"
136 documentation describes how to run it.
137 .P
138 In addition to the main compiling and matching functions, there are convenience
139 functions for extracting captured substrings from a matched subject string.
140 They are:
141 .sp
142 \fBpcre_copy_substring()\fP
143 \fBpcre_copy_named_substring()\fP
144 \fBpcre_get_substring()\fP
145 \fBpcre_get_named_substring()\fP
146 \fBpcre_get_substring_list()\fP
147 \fBpcre_get_stringnumber()\fP
148 .sp
149 \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
150 provided, to free the memory used for extracted strings.
151 .P
152 The function \fBpcre_maketables()\fP is used to build a set of character tables
153 in the current locale for passing to \fBpcre_compile()\fP or \fBpcre_exec()\fP.
154 This is an optional facility that is provided for specialist use. Most
155 commonly, no special tables are passed, in which case internal tables that are
156 generated when PCRE is built are used.
157 .P
158 The function \fBpcre_fullinfo()\fP is used to find out information about a
159 compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
160 some of the available information, but is retained for backwards compatibility.
161 The function \fBpcre_version()\fP returns a pointer to a string containing the
162 version of PCRE and its date of release.
163 .P
164 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
165 the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
166 respectively. PCRE calls the memory management functions via these variables,
167 so a calling program can replace them if it wishes to intercept the calls. This
168 should be done before calling any PCRE functions.
169 .P
170 The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
171 indirections to memory management functions. These special functions are used
172 only when PCRE is compiled to use the heap for remembering data, instead of
173 recursive function calls. This is a non-standard way of building PCRE, for use
174 in environments that have limited stacks. Because of the greater use of memory
175 management, it runs more slowly. Separate functions are provided so that
176 special-purpose external code can be used for this case. When used, these
177 functions are always called in a stack-like manner (last obtained, first
178 freed), and always for memory blocks of the same size.
179 .P
180 The global variable \fBpcre_callout\fP initially contains NULL. It can be set
181 by the caller to a "callout" function, which PCRE will then call at specified
182 points during a matching operation. Details are given in the
183 .\" HREF
184 \fBpcrecallout\fP
185 .\"
186 documentation.
187 .
188 .
190 .rs
191 .sp
192 The PCRE functions can be used in multi-threading applications, with the
193 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
194 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
195 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
196 .P
197 The compiled form of a regular expression is not altered during matching, so
198 the same compiled pattern can safely be used by several threads at once.
199 .
200 .
202 .rs
203 .sp
204 The compiled form of a regular expression can be saved and re-used at a later
205 time, possibly by a different program, and even on a host other than the one on
206 which it was compiled. Details are given in the
207 .\" HREF
208 \fBpcreprecompile\fP
209 .\"
210 documentation.
211 .
212 .
214 .rs
215 .sp
216 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
217 .PP
218 The function \fBpcre_config()\fP makes it possible for a PCRE client to
219 discover which optional features have been compiled into the PCRE library. The
220 .\" HREF
221 \fBpcrebuild\fP
222 .\"
223 documentation has more details about these optional features.
224 .P
225 The first argument for \fBpcre_config()\fP is an integer, specifying which
226 information is required; the second argument is a pointer to a variable into
227 which the information is placed. The following information is available:
228 .sp
230 .sp
231 The output is an integer that is set to one if UTF-8 support is available;
232 otherwise it is set to zero.
233 .sp
235 .sp
236 The output is an integer that is set to one if support for Unicode character
237 properties is available; otherwise it is set to zero.
238 .sp
240 .sp
241 The output is an integer that is set to the value of the code that is used for
242 the newline character. It is either linefeed (10) or carriage return (13), and
243 should normally be the standard character for your operating system.
244 .sp
246 .sp
247 The output is an integer that contains the number of bytes used for internal
248 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
249 allow larger regular expressions to be compiled, at the expense of slower
250 matching. The default value of 2 is sufficient for all but the most massive
251 patterns, since it allows the compiled pattern to be up to 64K in size.
252 .sp
254 .sp
255 The output is an integer that contains the threshold above which the POSIX
256 interface uses \fBmalloc()\fP for output vectors. Further details are given in
257 the
258 .\" HREF
259 \fBpcreposix\fP
260 .\"
261 documentation.
262 .sp
264 .sp
265 The output is an integer that gives the default limit for the number of
266 internal matching function calls in a \fBpcre_exec()\fP execution. Further
267 details are given with \fBpcre_exec()\fP below.
268 .sp
270 .sp
271 The output is an integer that is set to one if internal recursion is
272 implemented by recursive function calls that use the stack to remember their
273 state. This is the usual way that PCRE is compiled. The output is zero if PCRE
274 was compiled to use blocks of data on the heap instead of recursive function
275 calls. In this case, \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are
276 called to manage memory blocks on the heap, thus avoiding the use of the stack.
277 .
278 .
280 .rs
281 .sp
282 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
283 .ti +5n
284 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
285 .ti +5n
286 .B const unsigned char *\fItableptr\fP);
287 .P
288 The function \fBpcre_compile()\fP is called to compile a pattern into an
289 internal form. The pattern is a C string terminated by a binary zero, and
290 is passed in the \fIpattern\fP argument. A pointer to a single block of memory
291 that is obtained via \fBpcre_malloc\fP is returned. This contains the compiled
292 code and related data. The \fBpcre\fP type is defined for the returned block;
293 this is a typedef for a structure whose contents are not externally defined. It
294 is up to the caller to free the memory when it is no longer required.
295 .P
296 Although the compiled code of a PCRE regex is relocatable, that is, it does not
297 depend on memory location, the complete \fBpcre\fP data block is not
298 fully relocatable, because it may contain a copy of the \fItableptr\fP
299 argument, which is an address (see below).
300 .P
301 The \fIoptions\fP argument contains independent bits that affect the
302 compilation. It should be zero if no options are required. The available
303 options are described below. Some of them, in particular, those that are
304 compatible with Perl, can also be set and unset from within the pattern (see
305 the detailed description in the
306 .\" HREF
307 \fBpcrepattern\fP
308 .\"
309 documentation). For these options, the contents of the \fIoptions\fP argument
310 specifies their initial settings at the start of compilation and execution. The
311 PCRE_ANCHORED option can be set at the time of matching as well as at compile
312 time.
313 .P
314 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
315 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
316 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
317 error message. The offset from the start of the pattern to the character where
318 the error was discovered is placed in the variable pointed to by
319 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
320 .P
321 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
322 character tables that are built when PCRE is compiled, using the default C
323 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
324 call to \fBpcre_maketables()\fP. This value is stored with the compiled
325 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
326 passed to it. For more discussion, see the section on locale support below.
327 .P
328 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
329 .sp
330 pcre *re;
331 const char *error;
332 int erroffset;
333 re = pcre_compile(
334 "^A.*Z", /* the pattern */
335 0, /* default options */
336 &error, /* for error message */
337 &erroffset, /* for error offset */
338 NULL); /* use default character tables */
339 .sp
340 The following names for option bits are defined in the \fBpcre.h\fP header
341 file:
342 .sp
344 .sp
345 If this bit is set, the pattern is forced to be "anchored", that is, it is
346 constrained to match only at the first matching point in the string that is
347 being searched (the "subject string"). This effect can also be achieved by
348 appropriate constructs in the pattern itself, which is the only way to do it in
349 Perl.
350 .sp
352 .sp
353 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
354 all with number 255, before each pattern item. For discussion of the callout
355 facility, see the
356 .\" HREF
357 \fBpcrecallout\fP
358 .\"
359 documentation.
360 .sp
362 .sp
363 If this bit is set, letters in the pattern match both upper and lower case
364 letters. It is equivalent to Perl's /i option, and it can be changed within a
365 pattern by a (?i) option setting. When running in UTF-8 mode, case support for
366 high-valued characters is available only when PCRE is built with Unicode
367 character property support.
368 .sp
370 .sp
371 If this bit is set, a dollar metacharacter in the pattern matches only at the
372 end of the subject string. Without this option, a dollar also matches
373 immediately before the final character if it is a newline (but not before any
374 other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is
375 set. There is no equivalent to this option in Perl, and no way to set it within
376 a pattern.
377 .sp
379 .sp
380 If this bit is set, a dot metacharater in the pattern matches all characters,
381 including newlines. Without it, newlines are excluded. This option is
382 equivalent to Perl's /s option, and it can be changed within a pattern by a
383 (?s) option setting. A negative class such as [^a] always matches a newline
384 character, independent of the setting of this option.
385 .sp
387 .sp
388 If this bit is set, whitespace data characters in the pattern are totally
389 ignored except when escaped or inside a character class. Whitespace does not
390 include the VT character (code 11). In addition, characters between an
391 unescaped # outside a character class and the next newline character,
392 inclusive, are also ignored. This is equivalent to Perl's /x option, and it can
393 be changed within a pattern by a (?x) option setting.
394 .P
395 This option makes it possible to include comments inside complicated patterns.
396 Note, however, that this applies only to data characters. Whitespace characters
397 may never appear within special character sequences in a pattern, for example
398 within the sequence (?( which introduces a conditional subpattern.
399 .sp
401 .sp
402 This option was invented in order to turn on additional functionality of PCRE
403 that is incompatible with Perl, but it is currently of very little use. When
404 set, any backslash in a pattern that is followed by a letter that has no
405 special meaning causes an error, thus reserving these combinations for future
406 expansion. By default, as in Perl, a backslash followed by a letter with no
407 special meaning is treated as a literal. There are at present no other features
408 controlled by this option. It can also be set by a (?X) option setting within a
409 pattern.
410 .sp
412 .sp
413 By default, PCRE treats the subject string as consisting of a single line of
414 characters (even if it actually contains newlines). The "start of line"
415 metacharacter (^) matches only at the start of the string, while the "end of
416 line" metacharacter ($) matches only at the end of the string, or before a
417 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
418 Perl.
419 .P
420 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
421 match immediately following or immediately before any newline in the subject
422 string, respectively, as well as at the very start and end. This is equivalent
423 to Perl's /m option, and it can be changed within a pattern by a (?m) option
424 setting. If there are no "\en" characters in a subject string, or no
425 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
426 .sp
428 .sp
429 If this option is set, it disables the use of numbered capturing parentheses in
430 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
431 were followed by ?: but named parentheses can still be used for capturing (and
432 they acquire numbers in the usual way). There is no equivalent of this option
433 in Perl.
434 .sp
436 .sp
437 This option inverts the "greediness" of the quantifiers so that they are not
438 greedy by default, but become greedy if followed by "?". It is not compatible
439 with Perl. It can also be set by a (?U) option setting within the pattern.
440 .sp
442 .sp
443 This option causes PCRE to regard both the pattern and the subject as strings
444 of UTF-8 characters instead of single-byte character strings. However, it is
445 available only when PCRE is built to include UTF-8 support. If not, the use
446 of this option provokes an error. Details of how this option changes the
447 behaviour of PCRE are given in the
448 .\" HTML <a href="pcre.html#utf8support">
449 .\" </a>
450 section on UTF-8 support
451 .\"
452 in the main
453 .\" HREF
454 \fBpcre\fP
455 .\"
456 page.
457 .sp
459 .sp
460 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
461 automatically checked. If an invalid UTF-8 sequence of bytes is found,
462 \fBpcre_compile()\fP returns an error. If you already know that your pattern is
463 valid, and you want to skip this check for performance reasons, you can set the
464 PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
465 UTF-8 string as a pattern is undefined. It may cause your program to crash.
466 Note that this option can also be passed to \fBpcre_exec()\fP, to suppress the
467 UTF-8 validity checking of subject strings.
468 .
469 .
471 .rs
472 .sp
473 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
474 .ti +5n
475 .B const char **\fIerrptr\fP);
476 .PP
477 If a compiled pattern is going to be used several times, it is worth spending
478 more time analyzing it in order to speed up the time taken for matching. The
479 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
480 argument. If studying the pattern produces additional information that will
481 help speed up matching, \fBpcre_study()\fP returns a pointer to a
482 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
483 results of the study.
484 .P
485 The returned value from \fBpcre_study()\fP can be passed directly to
486 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
487 fields that can be set by the caller before the block is passed; these are
488 described
489 .\" HTML <a href="#extradata">
490 .\" </a>
491 below
492 .\"
493 in the section on matching a pattern.
494 .P
495 If studying the pattern does not produce any additional information,
496 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
497 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
498 own \fBpcre_extra\fP block.
499 .P
500 The second argument of \fBpcre_study()\fP contains option bits. At present, no
501 options are defined, and this argument should always be zero.
502 .P
503 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
504 studying succeeds (even if no data is returned), the variable it points to is
505 set to NULL. Otherwise it points to a textual error message. You should
506 therefore test the error pointer for NULL after calling \fBpcre_study()\fP, to
507 be sure that it has run successfully.
508 .P
509 This is a typical call to \fBpcre_study\fP():
510 .sp
511 pcre_extra *pe;
512 pe = pcre_study(
513 re, /* result of pcre_compile() */
514 0, /* no options exist */
515 &error); /* set to NULL or points to a message */
516 .sp
517 At present, studying a pattern is useful only for non-anchored patterns that do
518 not have a single fixed starting character. A bitmap of possible starting
519 bytes is created.
520 .
521 .
522 .\" HTML <a name="localesupport"></a>
524 .rs
525 .sp
526 PCRE handles caseless matching, and determines whether characters are letters,
527 digits, or whatever, by reference to a set of tables, indexed by character
528 value. (When running in UTF-8 mode, this applies only to characters with codes
529 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
530 can be tested with \ep if PCRE is built with Unicode character property
531 support.)
532 .P
533 An internal set of tables is created in the default C locale when PCRE is
534 built. This is used when the final argument of \fBpcre_compile()\fP is NULL,
535 and is sufficient for many applications. An alternative set of tables can,
536 however, be supplied. These may be created in a different locale from the
537 default. As more and more applications change to using Unicode, the need for
538 this locale support is expected to die away.
539 .P
540 External tables are built by calling the \fBpcre_maketables()\fP function,
541 which has no arguments, in the relevant locale. The result can then be passed
542 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
543 example, to build and use tables that are appropriate for the French locale
544 (where accented characters with values greater than 128 are treated as letters),
545 the following code could be used:
546 .sp
547 setlocale(LC_CTYPE, "fr_FR");
548 tables = pcre_maketables();
549 re = pcre_compile(..., tables);
550 .sp
551 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
552 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
553 that the memory containing the tables remains available for as long as it is
554 needed.
555 .P
556 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
557 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
558 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
559 pattern, compilation, studying and matching all happen in the same locale, but
560 different patterns can be compiled in different locales.
561 .P
562 It is possible to pass a table pointer or NULL (indicating the use of the
563 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
564 this facility could be used to match a pattern in a different locale from the
565 one in which it was compiled. Passing table pointers at run time is discussed
566 below in the section on matching a pattern.
567 .
568 .
570 .rs
571 .sp
572 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
573 .ti +5n
574 .B int \fIwhat\fP, void *\fIwhere\fP);
575 .PP
576 The \fBpcre_fullinfo()\fP function returns information about a compiled
577 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
578 nevertheless retained for backwards compability (and is documented below).
579 .P
580 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
581 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
582 the pattern was not studied. The third argument specifies which piece of
583 information is required, and the fourth argument is a pointer to a variable
584 to receive the data. The yield of the function is zero for success, or one of
585 the following negative numbers:
586 .sp
587 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
588 the argument \fIwhere\fP was NULL
589 PCRE_ERROR_BADMAGIC the "magic number" was not found
590 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
591 .sp
592 The "magic number" is placed at the start of each compiled pattern as an simple
593 check against passing an arbitrary memory pointer. Here is a typical call of
594 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
595 .sp
596 int rc;
597 unsigned long int length;
598 rc = pcre_fullinfo(
599 re, /* result of pcre_compile() */
600 pe, /* result of pcre_study(), or NULL */
601 PCRE_INFO_SIZE, /* what is required */
602 &length); /* where to put the data */
603 .sp
604 The possible values for the third argument are defined in \fBpcre.h\fP, and are
605 as follows:
606 .sp
608 .sp
609 Return the number of the highest back reference in the pattern. The fourth
610 argument should point to an \fBint\fP variable. Zero is returned if there are
611 no back references.
612 .sp
614 .sp
615 Return the number of capturing subpatterns in the pattern. The fourth argument
616 should point to an \fBint\fP variable.
617 .sp
619 .sp
620 Return a pointer to the internal default character tables within PCRE. The
621 fourth argument should point to an \fBunsigned char *\fP variable. This
622 information call is provided for internal use by the \fBpcre_study()\fP
623 function. External callers can cause PCRE to use its internal tables by passing
624 a NULL table pointer.
625 .sp
627 .sp
628 Return information about the first byte of any matched string, for a
629 non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the
630 old name is still recognized for backwards compatibility.)
631 .P
632 If there is a fixed first byte, for example, from a pattern such as
633 (cat|cow|coyote), it is returned in the integer pointed to by \fIwhere\fP.
634 Otherwise, if either
635 .sp
636 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
637 starts with "^", or
638 .sp
639 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
640 (if it were set, the pattern would be anchored),
641 .sp
642 -1 is returned, indicating that the pattern matches only at the start of a
643 subject string or after any newline within the string. Otherwise -2 is
644 returned. For anchored patterns, -2 is returned.
645 .sp
647 .sp
648 If the pattern was studied, and this resulted in the construction of a 256-bit
649 table indicating a fixed set of bytes for the first byte in any matching
650 string, a pointer to the table is returned. Otherwise NULL is returned. The
651 fourth argument should point to an \fBunsigned char *\fP variable.
652 .sp
654 .sp
655 Return the value of the rightmost literal byte that must exist in any matched
656 string, other than at its start, if such a byte has been recorded. The fourth
657 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
658 returned. For anchored patterns, a last literal byte is recorded only if it
659 follows something of variable length. For example, for the pattern
660 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
661 is -1.
662 .sp
666 .sp
667 PCRE supports the use of named as well as numbered capturing parentheses. The
668 names are just an additional way of identifying the parentheses, which still
669 acquire numbers. A convenience function called \fBpcre_get_named_substring()\fP
670 is provided for extracting an individual captured substring by name. It is also
671 possible to extract the data directly, by first converting the name to a number
672 in order to access the correct pointers in the output vector (described with
673 \fBpcre_exec()\fP below). To do the conversion, you need to use the
674 name-to-number map, which is described by these three values.
675 .P
676 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
677 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
678 entry; both of these return an \fBint\fP value. The entry size depends on the
679 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
680 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
681 are the number of the capturing parenthesis, most significant byte first. The
682 rest of the entry is the corresponding name, zero terminated. The names are in
683 alphabetical order. For example, consider the following pattern (assume
684 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
685 .sp
686 .\" JOIN
687 (?P<date> (?P<year>(\ed\ed)?\ed\ed) -
688 (?P<month>\ed\ed) - (?P<day>\ed\ed) )
689 .sp
690 There are four named subpatterns, so the table has four entries, and each entry
691 in the table is eight bytes long. The table is as follows, with non-printing
692 bytes shows in hexadecimal, and undefined bytes shown as ??:
693 .sp
694 00 01 d a t e 00 ??
695 00 05 d a y 00 ?? ??
696 00 04 m o n t h 00
697 00 02 y e a r 00 ??
698 .sp
699 When writing code to extract data from named subpatterns using the
700 name-to-number map, remember that the length of each entry is likely to be
701 different for each compiled pattern.
702 .sp
704 .sp
705 Return a copy of the options with which the pattern was compiled. The fourth
706 argument should point to an \fBunsigned long int\fP variable. These option bits
707 are those specified in the call to \fBpcre_compile()\fP, modified by any
708 top-level option settings within the pattern itself.
709 .P
710 A pattern is automatically anchored by PCRE if all of its top-level
711 alternatives begin with one of the following:
712 .sp
713 ^ unless PCRE_MULTILINE is set
714 \eA always
715 \eG always
716 .\" JOIN
717 .* if PCRE_DOTALL is set and there are no back
718 references to the subpattern in which .* appears
719 .sp
720 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
721 \fBpcre_fullinfo()\fP.
722 .sp
724 .sp
725 Return the size of the compiled pattern, that is, the value that was passed as
726 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
727 place the compiled data. The fourth argument should point to a \fBsize_t\fP
728 variable.
729 .sp
731 .sp
732 Return the size of the data block pointed to by the \fIstudy_data\fP field in
733 a \fBpcre_extra\fP block. That is, it is the value that was passed to
734 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
735 created by \fBpcre_study()\fP. The fourth argument should point to a
736 \fBsize_t\fP variable.
737 .
738 .
740 .rs
741 .sp
742 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
743 .B *\fIfirstcharptr\fP);
744 .PP
745 The \fBpcre_info()\fP function is now obsolete because its interface is too
746 restrictive to return all the available data about a compiled pattern. New
747 programs should use \fBpcre_fullinfo()\fP instead. The yield of
748 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
749 following negative numbers:
750 .sp
751 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
752 PCRE_ERROR_BADMAGIC the "magic number" was not found
753 .sp
754 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
755 pattern was compiled is placed in the integer it points to (see
757 .P
758 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
759 it is used to pass back information about the first character of any matched
760 string (see PCRE_INFO_FIRSTBYTE above).
761 .
762 .
764 .rs
765 .sp
766 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
767 .ti +5n
768 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
769 .ti +5n
770 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
771 .P
772 The function \fBpcre_exec()\fP is called to match a subject string against a
773 compiled pattern, which is passed in the \fIcode\fP argument. If the
774 pattern has been studied, the result of the study should be passed in the
775 \fIextra\fP argument.
776 .P
777 In most applications, the pattern will have been compiled (and optionally
778 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
779 possible to save compiled patterns and study data, and then use them later
780 in different processes, possibly even on different hosts. For a discussion
781 about this, see the
782 .\" HREF
783 \fBpcreprecompile\fP
784 .\"
785 documentation.
786 .P
787 Here is an example of a simple call to \fBpcre_exec()\fP:
788 .sp
789 int rc;
790 int ovector[30];
791 rc = pcre_exec(
792 re, /* result of pcre_compile() */
793 NULL, /* we didn't study the pattern */
794 "some string", /* the subject string */
795 11, /* the length of the subject string */
796 0, /* start at offset 0 in the subject */
797 0, /* default options */
798 ovector, /* vector of integers for substring information */
799 30); /* number of elements in the vector (NOT size in bytes) */
800 .
801 .\" HTML <a name="extradata"></a>
802 .SS "Extra data for \fBpcre_exec()\fR"
803 .rs
804 .sp
805 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
806 data block. The \fBpcre_study()\fP function returns such a block (when it
807 doesn't return NULL), but you can also create one for yourself, and pass
808 additional information in it. The fields in a \fBpcre_extra\fP block are as
809 follows:
810 .sp
811 unsigned long int \fIflags\fP;
812 void *\fIstudy_data\fP;
813 unsigned long int \fImatch_limit\fP;
814 void *\fIcallout_data\fP;
815 const unsigned char *\fItables\fP;
816 .sp
817 The \fIflags\fP field is a bitmap that specifies which of the other fields
818 are set. The flag bits are:
819 .sp
824 .sp
825 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
826 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
827 the appropriate flag bit. You should not set this yourself, but you may add to
828 the block by setting the other fields and their corresponding flag bits.
829 .P
830 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
831 vast amount of resources when running patterns that are not going to match,
832 but which have a very large number of possibilities in their search trees. The
833 classic example is the use of nested unlimited repeats.
834 .P
835 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
836 (sometimes recursively). The limit is imposed on the number of times this
837 function is called during a match, which has the effect of limiting the amount
838 of recursion and backtracking that can take place. For patterns that are not
839 anchored, the count starts from zero for each position in the subject string.
840 .P
841 The default limit for the library can be set when PCRE is built; the default
842 default is 10 million, which handles all but the most extreme cases. You can
843 reduce the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP block
844 in which \fImatch_limit\fP is set to a smaller value, and
845 PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fP field. If the limit is
846 exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_MATCHLIMIT.
847 .P
848 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
849 which is described in the
850 .\" HREF
851 \fBpcrecallout\fP
852 .\"
853 documentation.
854 .P
855 The \fItables\fP field is used to pass a character tables pointer to
856 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
857 pattern. A non-NULL value is stored with the compiled pattern only if custom
858 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
859 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
860 internal tables to be used. This facility is helpful when re-using patterns
861 that have been saved after compiling with an external set of tables, because
862 the external tables might be at a different address when \fBpcre_exec()\fP is
863 called. See the
864 .\" HREF
865 \fBpcreprecompile\fP
866 .\"
867 documentation for a discussion of saving compiled patterns for later use.
868 .
869 .SS "Option bits for \fBpcre_exec()\fP"
870 .rs
871 .sp
872 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
873 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NOTBOL,
875 .sp
877 .sp
878 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
879 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
880 to be anchored by virtue of its contents, it cannot be made unachored at
881 matching time.
882 .sp
884 .sp
885 This option specifies that first character of the subject string is not the
886 beginning of a line, so the circumflex metacharacter should not match before
887 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
888 never to match. This option affects only the behaviour of the circumflex
889 metacharacter. It does not affect \eA.
890 .sp
892 .sp
893 This option specifies that the end of the subject string is not the end of a
894 line, so the dollar metacharacter should not match it nor (except in multiline
895 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
896 compile time) causes dollar never to match. This option affects only the
897 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
898 .sp
900 .sp
901 An empty string is not considered to be a valid match if this option is set. If
902 there are alternatives in the pattern, they are tried. If all the alternatives
903 match the empty string, the entire match fails. For example, if the pattern
904 .sp
905 a?b?
906 .sp
907 is applied to a string not beginning with "a" or "b", it matches the empty
908 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
909 valid, so PCRE searches further into the string for occurrences of "a" or "b".
910 .P
911 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
912 of a pattern match of the empty string within its \fBsplit()\fP function, and
913 when using the /g modifier. It is possible to emulate Perl's behaviour after
914 matching a null string by first trying the match again at the same offset with
915 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
916 starting offset (see below) and trying an ordinary match again. There is some
917 code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
918 .sp
920 .sp
921 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
922 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
923 The value of \fIstartoffset\fP is also checked to ensure that it points to the
924 start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
925 \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP
926 contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
927 .P
928 If you already know that your subject is valid, and you want to skip these
929 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
930 calling \fBpcre_exec()\fP. You might want to do this for the second and
931 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
932 all the matches in a single subject string. However, you should be sure that
933 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
934 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
935 subject, or a value of \fIstartoffset\fP that does not point to the start of a
936 UTF-8 character, is undefined. Your program may crash.
937 .sp
939 .sp
940 This option turns on the partial matching feature. If the subject string fails
941 to match the pattern, but at some point during the matching process the end of
942 the subject was reached (that is, the subject partially matches the pattern and
943 the failure to match occurred only because there were not enough subject
944 characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
945 PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
946 may appear in the pattern. These are discussed in the
947 .\" HREF
948 \fBpcrepartial\fP
949 .\"
950 documentation.
951 .
952 .SS "The string to be matched by \fBpcre_exec()\fP"
953 .rs
954 .sp
955 The subject string is passed to \fBpcre_exec()\fP as a pointer in
956 \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
957 \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
958 UTF-8 character. Unlike the pattern string, the subject may contain binary zero
959 bytes. When the starting offset is zero, the search for a match starts at the
960 beginning of the subject, and this is by far the most common case.
961 .P
962 A non-zero starting offset is useful when searching for another match in the
963 same subject by calling \fBpcre_exec()\fP again after a previous success.
964 Setting \fIstartoffset\fP differs from just passing over a shortened string and
965 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
966 lookbehind. For example, consider the pattern
967 .sp
968 \eBiss\eB
969 .sp
970 which finds occurrences of "iss" in the middle of words. (\eB matches only if
971 the current position in the subject is not a word boundary.) When applied to
972 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
973 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
974 subject, namely "issipi", it does not match, because \eB is always false at the
975 start of the subject, which is deemed to be a word boundary. However, if
976 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
977 set to 4, it finds the second occurrence of "iss" because it is able to look
978 behind the starting point to discover that it is preceded by a letter.
979 .P
980 If a non-zero starting offset is passed when the pattern is anchored, one
981 attempt to match at the given offset is made. This can only succeed if the
982 pattern does not require the match to be at the start of the subject.
983 .
984 .SS "How \fBpcre_exec()\fP returns captured substrings"
985 .rs
986 .sp
987 In general, a pattern matches a certain portion of the subject, and in
988 addition, further substrings from the subject may be picked out by parts of the
989 pattern. Following the usage in Jeffrey Friedl's book, this is called
990 "capturing" in what follows, and the phrase "capturing subpattern" is used for
991 a fragment of a pattern that picks out a substring. PCRE supports several other
992 kinds of parenthesized subpattern that do not cause substrings to be captured.
993 .P
994 Captured substrings are returned to the caller via a vector of integer offsets
995 whose address is passed in \fIovector\fP. The number of elements in the vector
996 is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
997 this argument is NOT the size of \fIovector\fP in bytes.
998 .P
999 The first two-thirds of the vector is used to pass back captured substrings,
1000 each substring using a pair of integers. The remaining third of the vector is
1001 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1002 and is not available for passing back information. The length passed in
1003 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1004 rounded down.
1005 .P
1006 When a match is successful, information about captured substrings is returned
1007 in pairs of integers, starting at the beginning of \fIovector\fP, and
1008 continuing up to two-thirds of its length at the most. The first element of a
1009 pair is set to the offset of the first character in a substring, and the second
1010 is set to the offset of the first character after the end of a substring. The
1011 first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
1012 subject string matched by the entire pattern. The next pair is used for the
1013 first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
1014 is the number of pairs that have been set. If there are no capturing
1015 subpatterns, the return value from a successful match is 1, indicating that
1016 just the first pair of offsets has been set.
1017 .P
1018 Some convenience functions are provided for extracting the captured substrings
1019 as separate strings. These are described in the following section.
1020 .P
1021 It is possible for an capturing subpattern number \fIn+1\fP to match some
1022 part of the subject when subpattern \fIn\fP has not been used at all. For
1023 example, if the string "abc" is matched against the pattern (a|(z))(bc)
1024 subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset
1025 values corresponding to the unused subpattern are set to -1.
1026 .P
1027 If a capturing subpattern is matched repeatedly, it is the last portion of the
1028 string that it matched that is returned.
1029 .P
1030 If the vector is too small to hold all the captured substring offsets, it is
1031 used as far as possible (up to two-thirds of its length), and the function
1032 returns a value of zero. In particular, if the substring offsets are not of
1033 interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1034 \fIovecsize\fP as zero. However, if the pattern contains back references and
1035 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1036 has to get additional memory for use during matching. Thus it is usually
1037 advisable to supply an \fIovector\fP.
1038 .P
1039 Note that \fBpcre_info()\fP can be used to find out how many capturing
1040 subpatterns there are in a compiled pattern. The smallest size for
1041 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1042 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1043 .
1044 .SS "Return values from \fBpcre_exec()\fP"
1045 .rs
1046 .sp
1047 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1048 defined in the header file:
1049 .sp
1051 .sp
1052 The subject string did not match the pattern.
1053 .sp
1055 .sp
1056 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1057 NULL and \fIovecsize\fP was not zero.
1058 .sp
1060 .sp
1061 An unrecognized bit was set in the \fIoptions\fP argument.
1062 .sp
1064 .sp
1065 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1066 the case when it is passed a junk pointer and to detect when a pattern that was
1067 compiled in an environment of one endianness is run in an environment with the
1068 other endianness. This is the error that PCRE gives when the magic number is
1069 not present.
1070 .sp
1072 .sp
1073 While running the pattern match, an unknown item was encountered in the
1074 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1075 of the compiled pattern.
1076 .sp
1078 .sp
1079 If a pattern contains back references, but the \fIovector\fP that is passed to
1080 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1081 gets a block of memory at the start of matching to use for this purpose. If the
1082 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1083 automatically freed at the end of matching.
1084 .sp
1086 .sp
1087 This error is used by the \fBpcre_copy_substring()\fP,
1088 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1089 below). It is never returned by \fBpcre_exec()\fP.
1090 .sp
1092 .sp
1093 The recursion and backtracking limit, as specified by the \fImatch_limit\fP
1094 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1095 description above.
1096 .sp
1098 .sp
1099 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1100 use by callout functions that want to yield a distinctive error code. See the
1101 .\" HREF
1102 \fBpcrecallout\fP
1103 .\"
1104 documentation for details.
1105 .sp
1107 .sp
1108 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1109 .sp
1111 .sp
1112 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1113 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1114 .sp
1116 .sp
1117 The subject string did not match, but it did match partially. See the
1118 .\" HREF
1119 \fBpcrepartial\fP
1120 .\"
1121 documentation for details of partial matching.
1122 .sp
1124 .sp
1125 The PCRE_PARTIAL option was used with a compiled pattern containing items that
1126 are not supported for partial matching. See the
1127 .\" HREF
1128 \fBpcrepartial\fP
1129 .\"
1130 documentation for details of partial matching.
1131 .sp
1133 .sp
1134 An unexpected internal error has occurred. This error could be caused by a bug
1135 in PCRE or by overwriting of the compiled pattern.
1136 .sp
1138 .sp
1139 This error is given if the value of the \fIovecsize\fP argument is negative.
1140 .
1141 .
1143 .rs
1144 .sp
1145 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1146 .ti +5n
1147 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1148 .ti +5n
1149 .B int \fIbuffersize\fP);
1150 .PP
1151 .br
1152 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1153 .ti +5n
1154 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1155 .ti +5n
1156 .B const char **\fIstringptr\fP);
1157 .PP
1158 .br
1159 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1160 .ti +5n
1161 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1162 .PP
1163 Captured substrings can be accessed directly by using the offsets returned by
1164 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1165 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1166 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1167 as new, separate, zero-terminated strings. These functions identify substrings
1168 by number. The next section describes functions for extracting named
1169 substrings. A substring that contains a binary zero is correctly extracted and
1170 has a further zero added on the end, but the result is not, of course,
1171 a C string.
1172 .P
1173 The first three arguments are the same for all three of these functions:
1174 \fIsubject\fP is the subject string that has just been successfully matched,
1175 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1176 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1177 captured by the match, including the substring that matched the entire regular
1178 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1179 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1180 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1181 number of elements in the vector divided by three.
1182 .P
1183 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1184 extract a single substring, whose number is given as \fIstringnumber\fP. A
1185 value of zero extracts the substring that matched the entire pattern, whereas
1186 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1187 the string is placed in \fIbuffer\fP, whose length is given by
1188 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1189 obtained via \fBpcre_malloc\fP, and its address is returned via
1190 \fIstringptr\fP. The yield of the function is the length of the string, not
1191 including the terminating zero, or one of
1192 .sp
1194 .sp
1195 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1196 memory failed for \fBpcre_get_substring()\fP.
1197 .sp
1199 .sp
1200 There is no substring whose number is \fIstringnumber\fP.
1201 .P
1202 The \fBpcre_get_substring_list()\fP function extracts all available substrings
1203 and builds a list of pointers to them. All this is done in a single block of
1204 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1205 is returned via \fIlistptr\fP, which is also the start of the list of string
1206 pointers. The end of the list is marked by a NULL pointer. The yield of the
1207 function is zero if all went well, or
1208 .sp
1210 .sp
1211 if the attempt to get the memory block failed.
1212 .P
1213 When any of these functions encounter a substring that is unset, which can
1214 happen when capturing subpattern number \fIn+1\fP matches some part of the
1215 subject, but subpattern \fIn\fP has not been used at all, they return an empty
1216 string. This can be distinguished from a genuine zero-length substring by
1217 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1218 substrings.
1219 .P
1220 The two convenience functions \fBpcre_free_substring()\fP and
1221 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1222 a previous call of \fBpcre_get_substring()\fP or
1223 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1224 the function pointed to by \fBpcre_free\fP, which of course could be called
1225 directly from a C program. However, PCRE is used in some situations where it is
1226 linked via a special interface to another programming language which cannot use
1227 \fBpcre_free\fP directly; it is for these cases that the functions are
1228 provided.
1229 .
1230 .
1232 .rs
1233 .sp
1234 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1235 .ti +5n
1236 .B const char *\fIname\fP);
1237 .PP
1238 .br
1239 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1240 .ti +5n
1241 .B const char *\fIsubject\fP, int *\fIovector\fP,
1242 .ti +5n
1243 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1244 .ti +5n
1245 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1246 .PP
1247 .br
1248 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1249 .ti +5n
1250 .B const char *\fIsubject\fP, int *\fIovector\fP,
1251 .ti +5n
1252 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1253 .ti +5n
1254 .B const char **\fIstringptr\fP);
1255 .PP
1256 To extract a substring by name, you first have to find associated number.
1257 For example, for this pattern
1258 .sp
1259 (a+)b(?<xxx>\ed+)...
1260 .sp
1261 the number of the subpattern called "xxx" is 2. You can find the number from
1262 the name by calling \fBpcre_get_stringnumber()\fP. The first argument is the
1263 compiled pattern, and the second is the name. The yield of the function is the
1264 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1265 that name.
1266 .P
1267 Given the number, you can extract the substring directly, or use one of the
1268 functions described in the previous section. For convenience, there are also
1269 two functions that do the whole job.
1270 .P
1271 Most of the arguments of \fIpcre_copy_named_substring()\fP and
1272 \fIpcre_get_named_substring()\fP are the same as those for the similarly named
1273 functions that extract by number. As these are described in the previous
1274 section, they are not re-described here. There are just two differences:
1275 .P
1276 First, instead of a substring number, a substring name is given. Second, there
1277 is an extra argument, given at the start, which is a pointer to the compiled
1278 pattern. This is needed in order to gain access to the name-to-number
1279 translation table.
1280 .P
1281 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1282 then call \fIpcre_copy_substring()\fP or \fIpcre_get_substring()\fP, as
1283 appropriate.
1284 .P
1285 .in 0
1286 Last updated: 09 September 2004
1287 .br
1288 Copyright (c) 1997-2004 University of Cambridge.

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