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Allow fixed-length subroutine calls in lookbehinds.
3 PCRE - Perl-compatible regular expressions
5 .rs
6 .sp
7 .B #include <pcre.h>
8 .PP
9 .SM
10 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
11 .ti +5n
12 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
13 .ti +5n
14 .B const unsigned char *\fItableptr\fP);
15 .PP
16 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
17 .ti +5n
18 .B int *\fIerrorcodeptr\fP,
19 .ti +5n
20 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
21 .ti +5n
22 .B const unsigned char *\fItableptr\fP);
23 .PP
24 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
25 .ti +5n
26 .B const char **\fIerrptr\fP);
27 .PP
28 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
29 .ti +5n
30 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
31 .ti +5n
32 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
33 .PP
34 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
35 .ti +5n
36 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
37 .ti +5n
38 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
39 .ti +5n
40 .B int *\fIworkspace\fP, int \fIwscount\fP);
41 .PP
42 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
43 .ti +5n
44 .B const char *\fIsubject\fP, int *\fIovector\fP,
45 .ti +5n
46 .B int \fIstringcount\fP, const char *\fIstringname\fP,
47 .ti +5n
48 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
49 .PP
50 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
51 .ti +5n
52 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53 .ti +5n
54 .B int \fIbuffersize\fP);
55 .PP
56 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
57 .ti +5n
58 .B const char *\fIsubject\fP, int *\fIovector\fP,
59 .ti +5n
60 .B int \fIstringcount\fP, const char *\fIstringname\fP,
61 .ti +5n
62 .B const char **\fIstringptr\fP);
63 .PP
64 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
65 .ti +5n
66 .B const char *\fIname\fP);
67 .PP
68 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
69 .ti +5n
70 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71 .PP
72 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
73 .ti +5n
74 .B int \fIstringcount\fP, int \fIstringnumber\fP,
75 .ti +5n
76 .B const char **\fIstringptr\fP);
77 .PP
78 .B int pcre_get_substring_list(const char *\fIsubject\fP,
79 .ti +5n
80 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
81 .PP
82 .B void pcre_free_substring(const char *\fIstringptr\fP);
83 .PP
84 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
85 .PP
86 .B const unsigned char *pcre_maketables(void);
87 .PP
88 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
89 .ti +5n
90 .B int \fIwhat\fP, void *\fIwhere\fP);
91 .PP
92 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
93 .B *\fIfirstcharptr\fP);
94 .PP
95 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
96 .PP
97 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
98 .PP
99 .B char *pcre_version(void);
100 .PP
101 .B void *(*pcre_malloc)(size_t);
102 .PP
103 .B void (*pcre_free)(void *);
104 .PP
105 .B void *(*pcre_stack_malloc)(size_t);
106 .PP
107 .B void (*pcre_stack_free)(void *);
108 .PP
109 .B int (*pcre_callout)(pcre_callout_block *);
110 .
111 .
113 .rs
114 .sp
115 PCRE has its own native API, which is described in this document. There are
116 also some wrapper functions that correspond to the POSIX regular expression
117 API. These are described in the
118 .\" HREF
119 \fBpcreposix\fP
120 .\"
121 documentation. Both of these APIs define a set of C function calls. A C++
122 wrapper is distributed with PCRE. It is documented in the
123 .\" HREF
124 \fBpcrecpp\fP
125 .\"
126 page.
127 .P
128 The native API C function prototypes are defined in the header file
129 \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
130 It can normally be accessed by adding \fB-lpcre\fP to the command for linking
131 an application that uses PCRE. The header file defines the macros PCRE_MAJOR
132 and PCRE_MINOR to contain the major and minor release numbers for the library.
133 Applications can use these to include support for different releases of PCRE.
134 .P
135 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
136 and \fBpcre_exec()\fP are used for compiling and matching regular expressions
137 in a Perl-compatible manner. A sample program that demonstrates the simplest
138 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
139 source distribution. A listing of this program is given in the
140 .\" HREF
141 \fBpcredemo\fP
142 .\"
143 documentation, and the
144 .\" HREF
145 \fBpcresample\fP
146 .\"
147 documentation describes how to compile and run it.
148 .P
149 A second matching function, \fBpcre_dfa_exec()\fP, which is not
150 Perl-compatible, is also provided. This uses a different algorithm for the
151 matching. The alternative algorithm finds all possible matches (at a given
152 point in the subject), and scans the subject just once (unless there are
153 lookbehind assertions). However, this algorithm does not return captured
154 substrings. A description of the two matching algorithms and their advantages
155 and disadvantages is given in the
156 .\" HREF
157 \fBpcrematching\fP
158 .\"
159 documentation.
160 .P
161 In addition to the main compiling and matching functions, there are convenience
162 functions for extracting captured substrings from a subject string that is
163 matched by \fBpcre_exec()\fP. They are:
164 .sp
165 \fBpcre_copy_substring()\fP
166 \fBpcre_copy_named_substring()\fP
167 \fBpcre_get_substring()\fP
168 \fBpcre_get_named_substring()\fP
169 \fBpcre_get_substring_list()\fP
170 \fBpcre_get_stringnumber()\fP
171 \fBpcre_get_stringtable_entries()\fP
172 .sp
173 \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
174 provided, to free the memory used for extracted strings.
175 .P
176 The function \fBpcre_maketables()\fP is used to build a set of character tables
177 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
178 or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
179 specialist use. Most commonly, no special tables are passed, in which case
180 internal tables that are generated when PCRE is built are used.
181 .P
182 The function \fBpcre_fullinfo()\fP is used to find out information about a
183 compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
184 some of the available information, but is retained for backwards compatibility.
185 The function \fBpcre_version()\fP returns a pointer to a string containing the
186 version of PCRE and its date of release.
187 .P
188 The function \fBpcre_refcount()\fP maintains a reference count in a data block
189 containing a compiled pattern. This is provided for the benefit of
190 object-oriented applications.
191 .P
192 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
193 the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
194 respectively. PCRE calls the memory management functions via these variables,
195 so a calling program can replace them if it wishes to intercept the calls. This
196 should be done before calling any PCRE functions.
197 .P
198 The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
199 indirections to memory management functions. These special functions are used
200 only when PCRE is compiled to use the heap for remembering data, instead of
201 recursive function calls, when running the \fBpcre_exec()\fP function. See the
202 .\" HREF
203 \fBpcrebuild\fP
204 .\"
205 documentation for details of how to do this. It is a non-standard way of
206 building PCRE, for use in environments that have limited stacks. Because of the
207 greater use of memory management, it runs more slowly. Separate functions are
208 provided so that special-purpose external code can be used for this case. When
209 used, these functions are always called in a stack-like manner (last obtained,
210 first freed), and always for memory blocks of the same size. There is a
211 discussion about PCRE's stack usage in the
212 .\" HREF
213 \fBpcrestack\fP
214 .\"
215 documentation.
216 .P
217 The global variable \fBpcre_callout\fP initially contains NULL. It can be set
218 by the caller to a "callout" function, which PCRE will then call at specified
219 points during a matching operation. Details are given in the
220 .\" HREF
221 \fBpcrecallout\fP
222 .\"
223 documentation.
224 .
225 .
226 .\" HTML <a name="newlines"></a>
228 .rs
229 .sp
230 PCRE supports five different conventions for indicating line breaks in
231 strings: a single CR (carriage return) character, a single LF (linefeed)
232 character, the two-character sequence CRLF, any of the three preceding, or any
233 Unicode newline sequence. The Unicode newline sequences are the three just
234 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
235 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
236 (paragraph separator, U+2029).
237 .P
238 Each of the first three conventions is used by at least one operating system as
239 its standard newline sequence. When PCRE is built, a default can be specified.
240 The default default is LF, which is the Unix standard. When PCRE is run, the
241 default can be overridden, either when a pattern is compiled, or when it is
242 matched.
243 .P
244 At compile time, the newline convention can be specified by the \fIoptions\fP
245 argument of \fBpcre_compile()\fP, or it can be specified by special text at the
246 start of the pattern itself; this overrides any other settings. See the
247 .\" HREF
248 \fBpcrepattern\fP
249 .\"
250 page for details of the special character sequences.
251 .P
252 In the PCRE documentation the word "newline" is used to mean "the character or
253 pair of characters that indicate a line break". The choice of newline
254 convention affects the handling of the dot, circumflex, and dollar
255 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
256 recognized line ending sequence, the match position advancement for a
257 non-anchored pattern. There is more detail about this in the
258 .\" HTML <a href="#execoptions">
259 .\" </a>
260 section on \fBpcre_exec()\fP options
261 .\"
262 below.
263 .P
264 The choice of newline convention does not affect the interpretation of
265 the \en or \er escape sequences, nor does it affect what \eR matches, which is
266 controlled in a similar way, but by separate options.
267 .
268 .
270 .rs
271 .sp
272 The PCRE functions can be used in multi-threading applications, with the
273 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
274 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
275 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
276 .P
277 The compiled form of a regular expression is not altered during matching, so
278 the same compiled pattern can safely be used by several threads at once.
279 .
280 .
282 .rs
283 .sp
284 The compiled form of a regular expression can be saved and re-used at a later
285 time, possibly by a different program, and even on a host other than the one on
286 which it was compiled. Details are given in the
287 .\" HREF
288 \fBpcreprecompile\fP
289 .\"
290 documentation. However, compiling a regular expression with one version of PCRE
291 for use with a different version is not guaranteed to work and may cause
292 crashes.
293 .
294 .
296 .rs
297 .sp
298 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
299 .PP
300 The function \fBpcre_config()\fP makes it possible for a PCRE client to
301 discover which optional features have been compiled into the PCRE library. The
302 .\" HREF
303 \fBpcrebuild\fP
304 .\"
305 documentation has more details about these optional features.
306 .P
307 The first argument for \fBpcre_config()\fP is an integer, specifying which
308 information is required; the second argument is a pointer to a variable into
309 which the information is placed. The following information is available:
310 .sp
312 .sp
313 The output is an integer that is set to one if UTF-8 support is available;
314 otherwise it is set to zero.
315 .sp
317 .sp
318 The output is an integer that is set to one if support for Unicode character
319 properties is available; otherwise it is set to zero.
320 .sp
322 .sp
323 The output is an integer whose value specifies the default character sequence
324 that is recognized as meaning "newline". The four values that are supported
325 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
326 Though they are derived from ASCII, the same values are returned in EBCDIC
327 environments. The default should normally correspond to the standard sequence
328 for your operating system.
329 .sp
331 .sp
332 The output is an integer whose value indicates what character sequences the \eR
333 escape sequence matches by default. A value of 0 means that \eR matches any
334 Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
335 or CRLF. The default can be overridden when a pattern is compiled or matched.
336 .sp
338 .sp
339 The output is an integer that contains the number of bytes used for internal
340 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
341 allow larger regular expressions to be compiled, at the expense of slower
342 matching. The default value of 2 is sufficient for all but the most massive
343 patterns, since it allows the compiled pattern to be up to 64K in size.
344 .sp
346 .sp
347 The output is an integer that contains the threshold above which the POSIX
348 interface uses \fBmalloc()\fP for output vectors. Further details are given in
349 the
350 .\" HREF
351 \fBpcreposix\fP
352 .\"
353 documentation.
354 .sp
356 .sp
357 The output is a long integer that gives the default limit for the number of
358 internal matching function calls in a \fBpcre_exec()\fP execution. Further
359 details are given with \fBpcre_exec()\fP below.
360 .sp
362 .sp
363 The output is a long integer that gives the default limit for the depth of
364 recursion when calling the internal matching function in a \fBpcre_exec()\fP
365 execution. Further details are given with \fBpcre_exec()\fP below.
366 .sp
368 .sp
369 The output is an integer that is set to one if internal recursion when running
370 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
371 to remember their state. This is the usual way that PCRE is compiled. The
372 output is zero if PCRE was compiled to use blocks of data on the heap instead
373 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
374 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
375 avoiding the use of the stack.
376 .
377 .
379 .rs
380 .sp
381 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
382 .ti +5n
383 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
384 .ti +5n
385 .B const unsigned char *\fItableptr\fP);
386 .sp
387 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
388 .ti +5n
389 .B int *\fIerrorcodeptr\fP,
390 .ti +5n
391 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
392 .ti +5n
393 .B const unsigned char *\fItableptr\fP);
394 .P
395 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
396 called to compile a pattern into an internal form. The only difference between
397 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
398 \fIerrorcodeptr\fP, via which a numerical error code can be returned.
399 .P
400 The pattern is a C string terminated by a binary zero, and is passed in the
401 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
402 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
403 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
404 for a structure whose contents are not externally defined. It is up to the
405 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
406 .P
407 Although the compiled code of a PCRE regex is relocatable, that is, it does not
408 depend on memory location, the complete \fBpcre\fP data block is not
409 fully relocatable, because it may contain a copy of the \fItableptr\fP
410 argument, which is an address (see below).
411 .P
412 The \fIoptions\fP argument contains various bit settings that affect the
413 compilation. It should be zero if no options are required. The available
414 options are described below. Some of them (in particular, those that are
415 compatible with Perl, but also some others) can also be set and unset from
416 within the pattern (see the detailed description in the
417 .\" HREF
418 \fBpcrepattern\fP
419 .\"
420 documentation). For those options that can be different in different parts of
421 the pattern, the contents of the \fIoptions\fP argument specifies their initial
422 settings at the start of compilation and execution. The PCRE_ANCHORED and
423 PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
424 compile time.
425 .P
426 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
427 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
428 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
429 error message. This is a static string that is part of the library. You must
430 not try to free it. The byte offset from the start of the pattern to the
431 character that was being processes when the error was discovered is placed in
432 the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
433 an immediate error is given. Some errors are not detected until checks are
434 carried out when the whole pattern has been scanned; in this case the offset is
435 set to the end of the pattern.
436 .P
437 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
438 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
439 returned via this argument in the event of an error. This is in addition to the
440 textual error message. Error codes and messages are listed below.
441 .P
442 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
443 character tables that are built when PCRE is compiled, using the default C
444 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
445 call to \fBpcre_maketables()\fP. This value is stored with the compiled
446 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
447 passed to it. For more discussion, see the section on locale support below.
448 .P
449 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
450 .sp
451 pcre *re;
452 const char *error;
453 int erroffset;
454 re = pcre_compile(
455 "^A.*Z", /* the pattern */
456 0, /* default options */
457 &error, /* for error message */
458 &erroffset, /* for error offset */
459 NULL); /* use default character tables */
460 .sp
461 The following names for option bits are defined in the \fBpcre.h\fP header
462 file:
463 .sp
465 .sp
466 If this bit is set, the pattern is forced to be "anchored", that is, it is
467 constrained to match only at the first matching point in the string that is
468 being searched (the "subject string"). This effect can also be achieved by
469 appropriate constructs in the pattern itself, which is the only way to do it in
470 Perl.
471 .sp
473 .sp
474 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
475 all with number 255, before each pattern item. For discussion of the callout
476 facility, see the
477 .\" HREF
478 \fBpcrecallout\fP
479 .\"
480 documentation.
481 .sp
484 .sp
485 These options (which are mutually exclusive) control what the \eR escape
486 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
487 match any Unicode newline sequence. The default is specified when PCRE is
488 built. It can be overridden from within the pattern, or by setting an option
489 when a compiled pattern is matched.
490 .sp
492 .sp
493 If this bit is set, letters in the pattern match both upper and lower case
494 letters. It is equivalent to Perl's /i option, and it can be changed within a
495 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
496 concept of case for characters whose values are less than 128, so caseless
497 matching is always possible. For characters with higher values, the concept of
498 case is supported if PCRE is compiled with Unicode property support, but not
499 otherwise. If you want to use caseless matching for characters 128 and above,
500 you must ensure that PCRE is compiled with Unicode property support as well as
501 with UTF-8 support.
502 .sp
504 .sp
505 If this bit is set, a dollar metacharacter in the pattern matches only at the
506 end of the subject string. Without this option, a dollar also matches
507 immediately before a newline at the end of the string (but not before any other
508 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
509 There is no equivalent to this option in Perl, and no way to set it within a
510 pattern.
511 .sp
513 .sp
514 If this bit is set, a dot metacharater in the pattern matches all characters,
515 including those that indicate newline. Without it, a dot does not match when
516 the current position is at a newline. This option is equivalent to Perl's /s
517 option, and it can be changed within a pattern by a (?s) option setting. A
518 negative class such as [^a] always matches newline characters, independent of
519 the setting of this option.
520 .sp
522 .sp
523 If this bit is set, names used to identify capturing subpatterns need not be
524 unique. This can be helpful for certain types of pattern when it is known that
525 only one instance of the named subpattern can ever be matched. There are more
526 details of named subpatterns below; see also the
527 .\" HREF
528 \fBpcrepattern\fP
529 .\"
530 documentation.
531 .sp
533 .sp
534 If this bit is set, whitespace data characters in the pattern are totally
535 ignored except when escaped or inside a character class. Whitespace does not
536 include the VT character (code 11). In addition, characters between an
537 unescaped # outside a character class and the next newline, inclusive, are also
538 ignored. This is equivalent to Perl's /x option, and it can be changed within a
539 pattern by a (?x) option setting.
540 .P
541 This option makes it possible to include comments inside complicated patterns.
542 Note, however, that this applies only to data characters. Whitespace characters
543 may never appear within special character sequences in a pattern, for example
544 within the sequence (?( which introduces a conditional subpattern.
545 .sp
547 .sp
548 This option was invented in order to turn on additional functionality of PCRE
549 that is incompatible with Perl, but it is currently of very little use. When
550 set, any backslash in a pattern that is followed by a letter that has no
551 special meaning causes an error, thus reserving these combinations for future
552 expansion. By default, as in Perl, a backslash followed by a letter with no
553 special meaning is treated as a literal. (Perl can, however, be persuaded to
554 give a warning for this.) There are at present no other features controlled by
555 this option. It can also be set by a (?X) option setting within a pattern.
556 .sp
558 .sp
559 If this option is set, an unanchored pattern is required to match before or at
560 the first newline in the subject string, though the matched text may continue
561 over the newline.
562 .sp
564 .sp
565 If this option is set, PCRE's behaviour is changed in some ways so that it is
566 compatible with JavaScript rather than Perl. The changes are as follows:
567 .P
568 (1) A lone closing square bracket in a pattern causes a compile-time error,
569 because this is illegal in JavaScript (by default it is treated as a data
570 character). Thus, the pattern AB]CD becomes illegal when this option is set.
571 .P
572 (2) At run time, a back reference to an unset subpattern group matches an empty
573 string (by default this causes the current matching alternative to fail). A
574 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
575 an "a" in the subject), whereas it fails by default, for Perl compatibility.
576 .sp
578 .sp
579 By default, PCRE treats the subject string as consisting of a single line of
580 characters (even if it actually contains newlines). The "start of line"
581 metacharacter (^) matches only at the start of the string, while the "end of
582 line" metacharacter ($) matches only at the end of the string, or before a
583 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
584 Perl.
585 .P
586 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
587 match immediately following or immediately before internal newlines in the
588 subject string, respectively, as well as at the very start and end. This is
589 equivalent to Perl's /m option, and it can be changed within a pattern by a
590 (?m) option setting. If there are no newlines in a subject string, or no
591 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
592 .sp
598 .sp
599 These options override the default newline definition that was chosen when PCRE
600 was built. Setting the first or the second specifies that a newline is
601 indicated by a single character (CR or LF, respectively). Setting
602 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
603 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
604 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
605 that any Unicode newline sequence should be recognized. The Unicode newline
606 sequences are the three just mentioned, plus the single characters VT (vertical
607 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
608 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
609 recognized only in UTF-8 mode.
610 .P
611 The newline setting in the options word uses three bits that are treated
612 as a number, giving eight possibilities. Currently only six are used (default
613 plus the five values above). This means that if you set more than one newline
614 option, the combination may or may not be sensible. For example,
616 other combinations may yield unused numbers and cause an error.
617 .P
618 The only time that a line break is specially recognized when compiling a
619 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
620 class is encountered. This indicates a comment that lasts until after the next
621 line break sequence. In other circumstances, line break sequences are treated
622 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
623 as whitespace characters and are therefore ignored.
624 .P
625 The newline option that is set at compile time becomes the default that is used
626 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
627 .sp
629 .sp
630 If this option is set, it disables the use of numbered capturing parentheses in
631 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
632 were followed by ?: but named parentheses can still be used for capturing (and
633 they acquire numbers in the usual way). There is no equivalent of this option
634 in Perl.
635 .sp
637 .sp
638 This option inverts the "greediness" of the quantifiers so that they are not
639 greedy by default, but become greedy if followed by "?". It is not compatible
640 with Perl. It can also be set by a (?U) option setting within the pattern.
641 .sp
643 .sp
644 This option causes PCRE to regard both the pattern and the subject as strings
645 of UTF-8 characters instead of single-byte character strings. However, it is
646 available only when PCRE is built to include UTF-8 support. If not, the use
647 of this option provokes an error. Details of how this option changes the
648 behaviour of PCRE are given in the
649 .\" HTML <a href="pcre.html#utf8support">
650 .\" </a>
651 section on UTF-8 support
652 .\"
653 in the main
654 .\" HREF
655 \fBpcre\fP
656 .\"
657 page.
658 .sp
660 .sp
661 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
662 automatically checked. There is a discussion about the
663 .\" HTML <a href="pcre.html#utf8strings">
664 .\" </a>
665 validity of UTF-8 strings
666 .\"
667 in the main
668 .\" HREF
669 \fBpcre\fP
670 .\"
671 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
672 returns an error. If you already know that your pattern is valid, and you want
673 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
674 option. When it is set, the effect of passing an invalid UTF-8 string as a
675 pattern is undefined. It may cause your program to crash. Note that this option
676 can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
677 the UTF-8 validity checking of subject strings.
678 .
679 .
681 .rs
682 .sp
683 The following table lists the error codes than may be returned by
684 \fBpcre_compile2()\fP, along with the error messages that may be returned by
685 both compiling functions. As PCRE has developed, some error codes have fallen
686 out of use. To avoid confusion, they have not been re-used.
687 .sp
688 0 no error
689 1 \e at end of pattern
690 2 \ec at end of pattern
691 3 unrecognized character follows \e
692 4 numbers out of order in {} quantifier
693 5 number too big in {} quantifier
694 6 missing terminating ] for character class
695 7 invalid escape sequence in character class
696 8 range out of order in character class
697 9 nothing to repeat
698 10 [this code is not in use]
699 11 internal error: unexpected repeat
700 12 unrecognized character after (? or (?-
701 13 POSIX named classes are supported only within a class
702 14 missing )
703 15 reference to non-existent subpattern
704 16 erroffset passed as NULL
705 17 unknown option bit(s) set
706 18 missing ) after comment
707 19 [this code is not in use]
708 20 regular expression is too large
709 21 failed to get memory
710 22 unmatched parentheses
711 23 internal error: code overflow
712 24 unrecognized character after (?<
713 25 lookbehind assertion is not fixed length
714 26 malformed number or name after (?(
715 27 conditional group contains more than two branches
716 28 assertion expected after (?(
717 29 (?R or (?[+-]digits must be followed by )
718 30 unknown POSIX class name
719 31 POSIX collating elements are not supported
720 32 this version of PCRE is not compiled with PCRE_UTF8 support
721 33 [this code is not in use]
722 34 character value in \ex{...} sequence is too large
723 35 invalid condition (?(0)
724 36 \eC not allowed in lookbehind assertion
725 37 PCRE does not support \eL, \el, \eN, \eU, or \eu
726 38 number after (?C is > 255
727 39 closing ) for (?C expected
728 40 recursive call could loop indefinitely
729 41 unrecognized character after (?P
730 42 syntax error in subpattern name (missing terminator)
731 43 two named subpatterns have the same name
732 44 invalid UTF-8 string
733 45 support for \eP, \ep, and \eX has not been compiled
734 46 malformed \eP or \ep sequence
735 47 unknown property name after \eP or \ep
736 48 subpattern name is too long (maximum 32 characters)
737 49 too many named subpatterns (maximum 10000)
738 50 [this code is not in use]
739 51 octal value is greater than \e377 (not in UTF-8 mode)
740 52 internal error: overran compiling workspace
741 53 internal error: previously-checked referenced subpattern not found
742 54 DEFINE group contains more than one branch
743 55 repeating a DEFINE group is not allowed
744 56 inconsistent NEWLINE options
745 57 \eg is not followed by a braced, angle-bracketed, or quoted
746 name/number or by a plain number
747 58 a numbered reference must not be zero
748 59 (*VERB) with an argument is not supported
749 60 (*VERB) not recognized
750 61 number is too big
751 62 subpattern name expected
752 63 digit expected after (?+
753 64 ] is an invalid data character in JavaScript compatibility mode
754 .sp
755 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
756 be used if the limits were changed when PCRE was built.
757 .
758 .
760 .rs
761 .sp
762 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
763 .ti +5n
764 .B const char **\fIerrptr\fP);
765 .PP
766 If a compiled pattern is going to be used several times, it is worth spending
767 more time analyzing it in order to speed up the time taken for matching. The
768 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
769 argument. If studying the pattern produces additional information that will
770 help speed up matching, \fBpcre_study()\fP returns a pointer to a
771 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
772 results of the study.
773 .P
774 The returned value from \fBpcre_study()\fP can be passed directly to
775 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
776 fields that can be set by the caller before the block is passed; these are
777 described
778 .\" HTML <a href="#extradata">
779 .\" </a>
780 below
781 .\"
782 in the section on matching a pattern.
783 .P
784 If studying the pattern does not produce any additional information
785 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
786 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
787 own \fBpcre_extra\fP block.
788 .P
789 The second argument of \fBpcre_study()\fP contains option bits. At present, no
790 options are defined, and this argument should always be zero.
791 .P
792 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
793 studying succeeds (even if no data is returned), the variable it points to is
794 set to NULL. Otherwise it is set to point to a textual error message. This is a
795 static string that is part of the library. You must not try to free it. You
796 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
797 sure that it has run successfully.
798 .P
799 This is a typical call to \fBpcre_study\fP():
800 .sp
801 pcre_extra *pe;
802 pe = pcre_study(
803 re, /* result of pcre_compile() */
804 0, /* no options exist */
805 &error); /* set to NULL or points to a message */
806 .sp
807 At present, studying a pattern is useful only for non-anchored patterns that do
808 not have a single fixed starting character. A bitmap of possible starting
809 bytes is created.
810 .
811 .
812 .\" HTML <a name="localesupport"></a>
814 .rs
815 .sp
816 PCRE handles caseless matching, and determines whether characters are letters,
817 digits, or whatever, by reference to a set of tables, indexed by character
818 value. When running in UTF-8 mode, this applies only to characters with codes
819 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
820 can be tested with \ep if PCRE is built with Unicode character property
821 support. The use of locales with Unicode is discouraged. If you are handling
822 characters with codes greater than 128, you should either use UTF-8 and
823 Unicode, or use locales, but not try to mix the two.
824 .P
825 PCRE contains an internal set of tables that are used when the final argument
826 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
827 Normally, the internal tables recognize only ASCII characters. However, when
828 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
829 default "C" locale of the local system, which may cause them to be different.
830 .P
831 The internal tables can always be overridden by tables supplied by the
832 application that calls PCRE. These may be created in a different locale from
833 the default. As more and more applications change to using Unicode, the need
834 for this locale support is expected to die away.
835 .P
836 External tables are built by calling the \fBpcre_maketables()\fP function,
837 which has no arguments, in the relevant locale. The result can then be passed
838 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
839 example, to build and use tables that are appropriate for the French locale
840 (where accented characters with values greater than 128 are treated as letters),
841 the following code could be used:
842 .sp
843 setlocale(LC_CTYPE, "fr_FR");
844 tables = pcre_maketables();
845 re = pcre_compile(..., tables);
846 .sp
847 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
848 are using Windows, the name for the French locale is "french".
849 .P
850 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
851 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
852 that the memory containing the tables remains available for as long as it is
853 needed.
854 .P
855 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
856 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
857 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
858 pattern, compilation, studying and matching all happen in the same locale, but
859 different patterns can be compiled in different locales.
860 .P
861 It is possible to pass a table pointer or NULL (indicating the use of the
862 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
863 this facility could be used to match a pattern in a different locale from the
864 one in which it was compiled. Passing table pointers at run time is discussed
865 below in the section on matching a pattern.
866 .
867 .
869 .rs
870 .sp
871 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
872 .ti +5n
873 .B int \fIwhat\fP, void *\fIwhere\fP);
874 .PP
875 The \fBpcre_fullinfo()\fP function returns information about a compiled
876 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
877 nevertheless retained for backwards compability (and is documented below).
878 .P
879 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
880 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
881 the pattern was not studied. The third argument specifies which piece of
882 information is required, and the fourth argument is a pointer to a variable
883 to receive the data. The yield of the function is zero for success, or one of
884 the following negative numbers:
885 .sp
886 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
887 the argument \fIwhere\fP was NULL
888 PCRE_ERROR_BADMAGIC the "magic number" was not found
889 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
890 .sp
891 The "magic number" is placed at the start of each compiled pattern as an simple
892 check against passing an arbitrary memory pointer. Here is a typical call of
893 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
894 .sp
895 int rc;
896 size_t length;
897 rc = pcre_fullinfo(
898 re, /* result of pcre_compile() */
899 pe, /* result of pcre_study(), or NULL */
900 PCRE_INFO_SIZE, /* what is required */
901 &length); /* where to put the data */
902 .sp
903 The possible values for the third argument are defined in \fBpcre.h\fP, and are
904 as follows:
905 .sp
907 .sp
908 Return the number of the highest back reference in the pattern. The fourth
909 argument should point to an \fBint\fP variable. Zero is returned if there are
910 no back references.
911 .sp
913 .sp
914 Return the number of capturing subpatterns in the pattern. The fourth argument
915 should point to an \fBint\fP variable.
916 .sp
918 .sp
919 Return a pointer to the internal default character tables within PCRE. The
920 fourth argument should point to an \fBunsigned char *\fP variable. This
921 information call is provided for internal use by the \fBpcre_study()\fP
922 function. External callers can cause PCRE to use its internal tables by passing
923 a NULL table pointer.
924 .sp
926 .sp
927 Return information about the first byte of any matched string, for a
928 non-anchored pattern. The fourth argument should point to an \fBint\fP
929 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
930 still recognized for backwards compatibility.)
931 .P
932 If there is a fixed first byte, for example, from a pattern such as
933 (cat|cow|coyote), its value is returned. Otherwise, if either
934 .sp
935 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
936 starts with "^", or
937 .sp
938 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
939 (if it were set, the pattern would be anchored),
940 .sp
941 -1 is returned, indicating that the pattern matches only at the start of a
942 subject string or after any newline within the string. Otherwise -2 is
943 returned. For anchored patterns, -2 is returned.
944 .sp
946 .sp
947 If the pattern was studied, and this resulted in the construction of a 256-bit
948 table indicating a fixed set of bytes for the first byte in any matching
949 string, a pointer to the table is returned. Otherwise NULL is returned. The
950 fourth argument should point to an \fBunsigned char *\fP variable.
951 .sp
953 .sp
954 Return 1 if the pattern contains any explicit matches for CR or LF characters,
955 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
956 explicit match is either a literal CR or LF character, or \er or \en.
957 .sp
959 .sp
960 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
961 0. The fourth argument should point to an \fBint\fP variable. (?J) and
962 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
963 .sp
965 .sp
966 Return the value of the rightmost literal byte that must exist in any matched
967 string, other than at its start, if such a byte has been recorded. The fourth
968 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
969 returned. For anchored patterns, a last literal byte is recorded only if it
970 follows something of variable length. For example, for the pattern
971 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
972 is -1.
973 .sp
977 .sp
978 PCRE supports the use of named as well as numbered capturing parentheses. The
979 names are just an additional way of identifying the parentheses, which still
980 acquire numbers. Several convenience functions such as
981 \fBpcre_get_named_substring()\fP are provided for extracting captured
982 substrings by name. It is also possible to extract the data directly, by first
983 converting the name to a number in order to access the correct pointers in the
984 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
985 you need to use the name-to-number map, which is described by these three
986 values.
987 .P
988 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
989 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
990 entry; both of these return an \fBint\fP value. The entry size depends on the
991 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
992 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
993 are the number of the capturing parenthesis, most significant byte first. The
994 rest of the entry is the corresponding name, zero terminated. The names are in
995 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
996 their parentheses numbers. For example, consider the following pattern (assume
997 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
998 .sp
999 .\" JOIN
1000 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1001 (?<month>\ed\ed) - (?<day>\ed\ed) )
1002 .sp
1003 There are four named subpatterns, so the table has four entries, and each entry
1004 in the table is eight bytes long. The table is as follows, with non-printing
1005 bytes shows in hexadecimal, and undefined bytes shown as ??:
1006 .sp
1007 00 01 d a t e 00 ??
1008 00 05 d a y 00 ?? ??
1009 00 04 m o n t h 00
1010 00 02 y e a r 00 ??
1011 .sp
1012 When writing code to extract data from named subpatterns using the
1013 name-to-number map, remember that the length of the entries is likely to be
1014 different for each compiled pattern.
1015 .sp
1017 .sp
1018 Return 1 if the pattern can be used for partial matching with
1019 \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1020 \fBint\fP variable. From release 8.00, this always returns 1, because the
1021 restrictions that previously applied to partial matching have been lifted. The
1022 .\" HREF
1023 \fBpcrepartial\fP
1024 .\"
1025 documentation gives details of partial matching.
1026 .sp
1028 .sp
1029 Return a copy of the options with which the pattern was compiled. The fourth
1030 argument should point to an \fBunsigned long int\fP variable. These option bits
1031 are those specified in the call to \fBpcre_compile()\fP, modified by any
1032 top-level option settings at the start of the pattern itself. In other words,
1033 they are the options that will be in force when matching starts. For example,
1034 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1036 .P
1037 A pattern is automatically anchored by PCRE if all of its top-level
1038 alternatives begin with one of the following:
1039 .sp
1040 ^ unless PCRE_MULTILINE is set
1041 \eA always
1042 \eG always
1043 .\" JOIN
1044 .* if PCRE_DOTALL is set and there are no back
1045 references to the subpattern in which .* appears
1046 .sp
1047 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1048 \fBpcre_fullinfo()\fP.
1049 .sp
1051 .sp
1052 Return the size of the compiled pattern, that is, the value that was passed as
1053 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1054 place the compiled data. The fourth argument should point to a \fBsize_t\fP
1055 variable.
1056 .sp
1058 .sp
1059 Return the size of the data block pointed to by the \fIstudy_data\fP field in
1060 a \fBpcre_extra\fP block. That is, it is the value that was passed to
1061 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1062 created by \fBpcre_study()\fP. The fourth argument should point to a
1063 \fBsize_t\fP variable.
1064 .
1065 .
1067 .rs
1068 .sp
1069 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1070 .B *\fIfirstcharptr\fP);
1071 .PP
1072 The \fBpcre_info()\fP function is now obsolete because its interface is too
1073 restrictive to return all the available data about a compiled pattern. New
1074 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1075 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1076 following negative numbers:
1077 .sp
1078 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1079 PCRE_ERROR_BADMAGIC the "magic number" was not found
1080 .sp
1081 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1082 pattern was compiled is placed in the integer it points to (see
1083 PCRE_INFO_OPTIONS above).
1084 .P
1085 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1086 it is used to pass back information about the first character of any matched
1087 string (see PCRE_INFO_FIRSTBYTE above).
1088 .
1089 .
1091 .rs
1092 .sp
1093 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1094 .PP
1095 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1096 data block that contains a compiled pattern. It is provided for the benefit of
1097 applications that operate in an object-oriented manner, where different parts
1098 of the application may be using the same compiled pattern, but you want to free
1099 the block when they are all done.
1100 .P
1101 When a pattern is compiled, the reference count field is initialized to zero.
1102 It is changed only by calling this function, whose action is to add the
1103 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1104 function is the new value. However, the value of the count is constrained to
1105 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1106 it is forced to the appropriate limit value.
1107 .P
1108 Except when it is zero, the reference count is not correctly preserved if a
1109 pattern is compiled on one host and then transferred to a host whose byte-order
1110 is different. (This seems a highly unlikely scenario.)
1111 .
1112 .
1114 .rs
1115 .sp
1116 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1117 .ti +5n
1118 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1119 .ti +5n
1120 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1121 .P
1122 The function \fBpcre_exec()\fP is called to match a subject string against a
1123 compiled pattern, which is passed in the \fIcode\fP argument. If the
1124 pattern has been studied, the result of the study should be passed in the
1125 \fIextra\fP argument. This function is the main matching facility of the
1126 library, and it operates in a Perl-like manner. For specialist use there is
1127 also an alternative matching function, which is described
1128 .\" HTML <a href="#dfamatch">
1129 .\" </a>
1130 below
1131 .\"
1132 in the section about the \fBpcre_dfa_exec()\fP function.
1133 .P
1134 In most applications, the pattern will have been compiled (and optionally
1135 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1136 possible to save compiled patterns and study data, and then use them later
1137 in different processes, possibly even on different hosts. For a discussion
1138 about this, see the
1139 .\" HREF
1140 \fBpcreprecompile\fP
1141 .\"
1142 documentation.
1143 .P
1144 Here is an example of a simple call to \fBpcre_exec()\fP:
1145 .sp
1146 int rc;
1147 int ovector[30];
1148 rc = pcre_exec(
1149 re, /* result of pcre_compile() */
1150 NULL, /* we didn't study the pattern */
1151 "some string", /* the subject string */
1152 11, /* the length of the subject string */
1153 0, /* start at offset 0 in the subject */
1154 0, /* default options */
1155 ovector, /* vector of integers for substring information */
1156 30); /* number of elements (NOT size in bytes) */
1157 .
1158 .\" HTML <a name="extradata"></a>
1159 .SS "Extra data for \fBpcre_exec()\fR"
1160 .rs
1161 .sp
1162 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1163 data block. The \fBpcre_study()\fP function returns such a block (when it
1164 doesn't return NULL), but you can also create one for yourself, and pass
1165 additional information in it. The \fBpcre_extra\fP block contains the following
1166 fields (not necessarily in this order):
1167 .sp
1168 unsigned long int \fIflags\fP;
1169 void *\fIstudy_data\fP;
1170 unsigned long int \fImatch_limit\fP;
1171 unsigned long int \fImatch_limit_recursion\fP;
1172 void *\fIcallout_data\fP;
1173 const unsigned char *\fItables\fP;
1174 .sp
1175 The \fIflags\fP field is a bitmap that specifies which of the other fields
1176 are set. The flag bits are:
1177 .sp
1183 .sp
1184 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1185 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1186 the appropriate flag bit. You should not set this yourself, but you may add to
1187 the block by setting the other fields and their corresponding flag bits.
1188 .P
1189 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1190 vast amount of resources when running patterns that are not going to match,
1191 but which have a very large number of possibilities in their search trees. The
1192 classic example is the use of nested unlimited repeats.
1193 .P
1194 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1195 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1196 number of times this function is called during a match, which has the effect of
1197 limiting the amount of backtracking that can take place. For patterns that are
1198 not anchored, the count restarts from zero for each position in the subject
1199 string.
1200 .P
1201 The default value for the limit can be set when PCRE is built; the default
1202 default is 10 million, which handles all but the most extreme cases. You can
1203 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1204 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1205 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1207 .P
1208 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1209 instead of limiting the total number of times that \fBmatch()\fP is called, it
1210 limits the depth of recursion. The recursion depth is a smaller number than the
1211 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1212 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1213 .P
1214 Limiting the recursion depth limits the amount of stack that can be used, or,
1215 when PCRE has been compiled to use memory on the heap instead of the stack, the
1216 amount of heap memory that can be used.
1217 .P
1218 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1219 built; the default default is the same value as the default for
1220 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1221 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1222 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1223 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1224 .P
1225 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1226 and is described in the
1227 .\" HREF
1228 \fBpcrecallout\fP
1229 .\"
1230 documentation.
1231 .P
1232 The \fItables\fP field is used to pass a character tables pointer to
1233 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1234 pattern. A non-NULL value is stored with the compiled pattern only if custom
1235 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1236 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1237 internal tables to be used. This facility is helpful when re-using patterns
1238 that have been saved after compiling with an external set of tables, because
1239 the external tables might be at a different address when \fBpcre_exec()\fP is
1240 called. See the
1241 .\" HREF
1242 \fBpcreprecompile\fP
1243 .\"
1244 documentation for a discussion of saving compiled patterns for later use.
1245 .
1246 .\" HTML <a name="execoptions"></a>
1247 .SS "Option bits for \fBpcre_exec()\fP"
1248 .rs
1249 .sp
1250 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1251 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1255 .sp
1257 .sp
1258 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1259 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1260 to be anchored by virtue of its contents, it cannot be made unachored at
1261 matching time.
1262 .sp
1265 .sp
1266 These options (which are mutually exclusive) control what the \eR escape
1267 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1268 match any Unicode newline sequence. These options override the choice that was
1269 made or defaulted when the pattern was compiled.
1270 .sp
1276 .sp
1277 These options override the newline definition that was chosen or defaulted when
1278 the pattern was compiled. For details, see the description of
1279 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1280 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1281 the way the match position is advanced after a match failure for an unanchored
1282 pattern.
1283 .P
1285 match attempt for an unanchored pattern fails when the current position is at a
1286 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1287 characters, the match position is advanced by two characters instead of one, in
1288 other words, to after the CRLF.
1289 .P
1290 The above rule is a compromise that makes the most common cases work as
1291 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1292 set), it does not match the string "\er\enA" because, after failing at the
1293 start, it skips both the CR and the LF before retrying. However, the pattern
1294 [\er\en]A does match that string, because it contains an explicit CR or LF
1295 reference, and so advances only by one character after the first failure.
1296 .P
1297 An explicit match for CR of LF is either a literal appearance of one of those
1298 characters, or one of the \er or \en escape sequences. Implicit matches such as
1299 [^X] do not count, nor does \es (which includes CR and LF in the characters
1300 that it matches).
1301 .P
1302 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1303 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1304 .sp
1306 .sp
1307 This option specifies that first character of the subject string is not the
1308 beginning of a line, so the circumflex metacharacter should not match before
1309 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1310 never to match. This option affects only the behaviour of the circumflex
1311 metacharacter. It does not affect \eA.
1312 .sp
1314 .sp
1315 This option specifies that the end of the subject string is not the end of a
1316 line, so the dollar metacharacter should not match it nor (except in multiline
1317 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1318 compile time) causes dollar never to match. This option affects only the
1319 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1320 .sp
1322 .sp
1323 An empty string is not considered to be a valid match if this option is set. If
1324 there are alternatives in the pattern, they are tried. If all the alternatives
1325 match the empty string, the entire match fails. For example, if the pattern
1326 .sp
1327 a?b?
1328 .sp
1329 is applied to a string not beginning with "a" or "b", it matches an empty
1330 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1331 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1332 .sp
1334 .sp
1335 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1336 the start of the subject is permitted. If the pattern is anchored, such a match
1337 can occur only if the pattern contains \eK.
1338 .P
1339 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1340 does make a special case of a pattern match of the empty string within its
1341 \fBsplit()\fP function, and when using the /g modifier. It is possible to
1342 emulate Perl's behaviour after matching a null string by first trying the match
1343 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1344 if that fails, by advancing the starting offset (see below) and trying an
1345 ordinary match again. There is some code that demonstrates how to do this in
1346 the
1347 .\" HREF
1348 \fBpcredemo\fP
1349 .\"
1350 sample program.
1351 .sp
1353 .sp
1354 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1355 a match, in order to speed up the process. For example, if it is known that a
1356 match must start with a specific character, it searches the subject for that
1357 character, and fails immediately if it cannot find it, without actually running
1358 the main matching function. When callouts are in use, these optimizations can
1359 cause them to be skipped. This option disables the "start-up" optimizations,
1360 causing performance to suffer, but ensuring that the callouts do occur.
1361 .sp
1363 .sp
1364 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1365 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1366 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1367 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1368 strings in the
1369 .\" HTML <a href="pcre.html#utf8strings">
1370 .\" </a>
1371 section on UTF-8 support
1372 .\"
1373 in the main
1374 .\" HREF
1375 \fBpcre\fP
1376 .\"
1377 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1378 the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1379 PCRE_ERROR_BADUTF8_OFFSET is returned.
1380 .P
1381 If you already know that your subject is valid, and you want to skip these
1382 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1383 calling \fBpcre_exec()\fP. You might want to do this for the second and
1384 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1385 all the matches in a single subject string. However, you should be sure that
1386 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1387 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1388 subject, or a value of \fIstartoffset\fP that does not point to the start of a
1389 UTF-8 character, is undefined. Your program may crash.
1390 .sp
1393 .sp
1394 These options turn on the partial matching feature. For backwards
1395 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1396 occurs if the end of the subject string is reached successfully, but there are
1397 not enough subject characters to complete the match. If this happens when
1398 PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1399 PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1400 by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1401 returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1402 was inspected when the partial match was found is set as the first matching
1403 string. There is a more detailed discussion in the
1404 .\" HREF
1405 \fBpcrepartial\fP
1406 .\"
1407 documentation.
1408 .
1409 .SS "The string to be matched by \fBpcre_exec()\fP"
1410 .rs
1411 .sp
1412 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1413 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1414 in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1415 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1416 zero bytes. When the starting offset is zero, the search for a match starts at
1417 the beginning of the subject, and this is by far the most common case.
1418 .P
1419 A non-zero starting offset is useful when searching for another match in the
1420 same subject by calling \fBpcre_exec()\fP again after a previous success.
1421 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1422 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1423 lookbehind. For example, consider the pattern
1424 .sp
1425 \eBiss\eB
1426 .sp
1427 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1428 the current position in the subject is not a word boundary.) When applied to
1429 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1430 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1431 subject, namely "issipi", it does not match, because \eB is always false at the
1432 start of the subject, which is deemed to be a word boundary. However, if
1433 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1434 set to 4, it finds the second occurrence of "iss" because it is able to look
1435 behind the starting point to discover that it is preceded by a letter.
1436 .P
1437 If a non-zero starting offset is passed when the pattern is anchored, one
1438 attempt to match at the given offset is made. This can only succeed if the
1439 pattern does not require the match to be at the start of the subject.
1440 .
1441 .SS "How \fBpcre_exec()\fP returns captured substrings"
1442 .rs
1443 .sp
1444 In general, a pattern matches a certain portion of the subject, and in
1445 addition, further substrings from the subject may be picked out by parts of the
1446 pattern. Following the usage in Jeffrey Friedl's book, this is called
1447 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1448 a fragment of a pattern that picks out a substring. PCRE supports several other
1449 kinds of parenthesized subpattern that do not cause substrings to be captured.
1450 .P
1451 Captured substrings are returned to the caller via a vector of integers whose
1452 address is passed in \fIovector\fP. The number of elements in the vector is
1453 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1454 argument is NOT the size of \fIovector\fP in bytes.
1455 .P
1456 The first two-thirds of the vector is used to pass back captured substrings,
1457 each substring using a pair of integers. The remaining third of the vector is
1458 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1459 and is not available for passing back information. The number passed in
1460 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1461 rounded down.
1462 .P
1463 When a match is successful, information about captured substrings is returned
1464 in pairs of integers, starting at the beginning of \fIovector\fP, and
1465 continuing up to two-thirds of its length at the most. The first element of
1466 each pair is set to the byte offset of the first character in a substring, and
1467 the second is set to the byte offset of the first character after the end of a
1468 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1469 mode. They are not character counts.
1470 .P
1471 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1472 portion of the subject string matched by the entire pattern. The next pair is
1473 used for the first capturing subpattern, and so on. The value returned by
1474 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1475 For example, if two substrings have been captured, the returned value is 3. If
1476 there are no capturing subpatterns, the return value from a successful match is
1477 1, indicating that just the first pair of offsets has been set.
1478 .P
1479 If a capturing subpattern is matched repeatedly, it is the last portion of the
1480 string that it matched that is returned.
1481 .P
1482 If the vector is too small to hold all the captured substring offsets, it is
1483 used as far as possible (up to two-thirds of its length), and the function
1484 returns a value of zero. If the substring offsets are not of interest,
1485 \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1486 \fIovecsize\fP as zero. However, if the pattern contains back references and
1487 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1488 has to get additional memory for use during matching. Thus it is usually
1489 advisable to supply an \fIovector\fP.
1490 .P
1491 The \fBpcre_info()\fP function can be used to find out how many capturing
1492 subpatterns there are in a compiled pattern. The smallest size for
1493 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1494 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1495 .P
1496 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1497 the subject when subpattern \fIn\fP has not been used at all. For example, if
1498 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1499 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1500 happens, both values in the offset pairs corresponding to unused subpatterns
1501 are set to -1.
1502 .P
1503 Offset values that correspond to unused subpatterns at the end of the
1504 expression are also set to -1. For example, if the string "abc" is matched
1505 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1506 return from the function is 2, because the highest used capturing subpattern
1507 number is 1. However, you can refer to the offsets for the second and third
1508 capturing subpatterns if you wish (assuming the vector is large enough, of
1509 course).
1510 .P
1511 Some convenience functions are provided for extracting the captured substrings
1512 as separate strings. These are described below.
1513 .
1514 .\" HTML <a name="errorlist"></a>
1515 .SS "Error return values from \fBpcre_exec()\fP"
1516 .rs
1517 .sp
1518 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1519 defined in the header file:
1520 .sp
1522 .sp
1523 The subject string did not match the pattern.
1524 .sp
1526 .sp
1527 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1528 NULL and \fIovecsize\fP was not zero.
1529 .sp
1531 .sp
1532 An unrecognized bit was set in the \fIoptions\fP argument.
1533 .sp
1535 .sp
1536 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1537 the case when it is passed a junk pointer and to detect when a pattern that was
1538 compiled in an environment of one endianness is run in an environment with the
1539 other endianness. This is the error that PCRE gives when the magic number is
1540 not present.
1541 .sp
1543 .sp
1544 While running the pattern match, an unknown item was encountered in the
1545 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1546 of the compiled pattern.
1547 .sp
1549 .sp
1550 If a pattern contains back references, but the \fIovector\fP that is passed to
1551 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1552 gets a block of memory at the start of matching to use for this purpose. If the
1553 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1554 automatically freed at the end of matching.
1555 .sp
1557 .sp
1558 This error is used by the \fBpcre_copy_substring()\fP,
1559 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1560 below). It is never returned by \fBpcre_exec()\fP.
1561 .sp
1563 .sp
1564 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1565 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1566 above.
1567 .sp
1569 .sp
1570 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1571 use by callout functions that want to yield a distinctive error code. See the
1572 .\" HREF
1573 \fBpcrecallout\fP
1574 .\"
1575 documentation for details.
1576 .sp
1578 .sp
1579 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1580 .sp
1582 .sp
1583 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1584 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1585 .sp
1587 .sp
1588 The subject string did not match, but it did match partially. See the
1589 .\" HREF
1590 \fBpcrepartial\fP
1591 .\"
1592 documentation for details of partial matching.
1593 .sp
1595 .sp
1596 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1597 option was used with a compiled pattern containing items that were not
1598 supported for partial matching. From release 8.00 onwards, there are no
1599 restrictions on partial matching.
1600 .sp
1602 .sp
1603 An unexpected internal error has occurred. This error could be caused by a bug
1604 in PCRE or by overwriting of the compiled pattern.
1605 .sp
1607 .sp
1608 This error is given if the value of the \fIovecsize\fP argument is negative.
1609 .sp
1611 .sp
1612 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1613 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1614 description above.
1615 .sp
1617 .sp
1618 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1619 .P
1620 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1621 .
1622 .
1624 .rs
1625 .sp
1626 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1627 .ti +5n
1628 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1629 .ti +5n
1630 .B int \fIbuffersize\fP);
1631 .PP
1632 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1633 .ti +5n
1634 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1635 .ti +5n
1636 .B const char **\fIstringptr\fP);
1637 .PP
1638 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1639 .ti +5n
1640 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1641 .PP
1642 Captured substrings can be accessed directly by using the offsets returned by
1643 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1644 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1645 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1646 as new, separate, zero-terminated strings. These functions identify substrings
1647 by number. The next section describes functions for extracting named
1648 substrings.
1649 .P
1650 A substring that contains a binary zero is correctly extracted and has a
1651 further zero added on the end, but the result is not, of course, a C string.
1652 However, you can process such a string by referring to the length that is
1653 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1654 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1655 for handling strings containing binary zeros, because the end of the final
1656 string is not independently indicated.
1657 .P
1658 The first three arguments are the same for all three of these functions:
1659 \fIsubject\fP is the subject string that has just been successfully matched,
1660 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1661 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1662 captured by the match, including the substring that matched the entire regular
1663 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1664 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1665 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1666 number of elements in the vector divided by three.
1667 .P
1668 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1669 extract a single substring, whose number is given as \fIstringnumber\fP. A
1670 value of zero extracts the substring that matched the entire pattern, whereas
1671 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1672 the string is placed in \fIbuffer\fP, whose length is given by
1673 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1674 obtained via \fBpcre_malloc\fP, and its address is returned via
1675 \fIstringptr\fP. The yield of the function is the length of the string, not
1676 including the terminating zero, or one of these error codes:
1677 .sp
1679 .sp
1680 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1681 memory failed for \fBpcre_get_substring()\fP.
1682 .sp
1684 .sp
1685 There is no substring whose number is \fIstringnumber\fP.
1686 .P
1687 The \fBpcre_get_substring_list()\fP function extracts all available substrings
1688 and builds a list of pointers to them. All this is done in a single block of
1689 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1690 is returned via \fIlistptr\fP, which is also the start of the list of string
1691 pointers. The end of the list is marked by a NULL pointer. The yield of the
1692 function is zero if all went well, or the error code
1693 .sp
1695 .sp
1696 if the attempt to get the memory block failed.
1697 .P
1698 When any of these functions encounter a substring that is unset, which can
1699 happen when capturing subpattern number \fIn+1\fP matches some part of the
1700 subject, but subpattern \fIn\fP has not been used at all, they return an empty
1701 string. This can be distinguished from a genuine zero-length substring by
1702 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1703 substrings.
1704 .P
1705 The two convenience functions \fBpcre_free_substring()\fP and
1706 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1707 a previous call of \fBpcre_get_substring()\fP or
1708 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1709 the function pointed to by \fBpcre_free\fP, which of course could be called
1710 directly from a C program. However, PCRE is used in some situations where it is
1711 linked via a special interface to another programming language that cannot use
1712 \fBpcre_free\fP directly; it is for these cases that the functions are
1713 provided.
1714 .
1715 .
1717 .rs
1718 .sp
1719 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1720 .ti +5n
1721 .B const char *\fIname\fP);
1722 .PP
1723 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1724 .ti +5n
1725 .B const char *\fIsubject\fP, int *\fIovector\fP,
1726 .ti +5n
1727 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1728 .ti +5n
1729 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1730 .PP
1731 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1732 .ti +5n
1733 .B const char *\fIsubject\fP, int *\fIovector\fP,
1734 .ti +5n
1735 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1736 .ti +5n
1737 .B const char **\fIstringptr\fP);
1738 .PP
1739 To extract a substring by name, you first have to find associated number.
1740 For example, for this pattern
1741 .sp
1742 (a+)b(?<xxx>\ed+)...
1743 .sp
1744 the number of the subpattern called "xxx" is 2. If the name is known to be
1745 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1746 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1747 pattern, and the second is the name. The yield of the function is the
1748 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1749 that name.
1750 .P
1751 Given the number, you can extract the substring directly, or use one of the
1752 functions described in the previous section. For convenience, there are also
1753 two functions that do the whole job.
1754 .P
1755 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1756 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1757 functions that extract by number. As these are described in the previous
1758 section, they are not re-described here. There are just two differences:
1759 .P
1760 First, instead of a substring number, a substring name is given. Second, there
1761 is an extra argument, given at the start, which is a pointer to the compiled
1762 pattern. This is needed in order to gain access to the name-to-number
1763 translation table.
1764 .P
1765 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1766 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1767 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1768 the behaviour may not be what you want (see the next section).
1769 .P
1770 \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
1771 subpatterns with the same number, you cannot use names to distinguish them,
1772 because names are not included in the compiled code. The matching process uses
1773 only numbers.
1774 .
1776 .rs
1777 .sp
1778 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1779 .ti +5n
1780 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1781 .PP
1782 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1783 are not required to be unique. Normally, patterns with duplicate names are such
1784 that in any one match, only one of the named subpatterns participates. An
1785 example is shown in the
1786 .\" HREF
1787 \fBpcrepattern\fP
1788 .\"
1789 documentation.
1790 .P
1791 When duplicates are present, \fBpcre_copy_named_substring()\fP and
1792 \fBpcre_get_named_substring()\fP return the first substring corresponding to
1793 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1794 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1795 returns one of the numbers that are associated with the name, but it is not
1796 defined which it is.
1797 .P
1798 If you want to get full details of all captured substrings for a given name,
1799 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1800 argument is the compiled pattern, and the second is the name. The third and
1801 fourth are pointers to variables which are updated by the function. After it
1802 has run, they point to the first and last entries in the name-to-number table
1803 for the given name. The function itself returns the length of each entry, or
1804 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1805 described above in the section entitled \fIInformation about a pattern\fP.
1806 Given all the relevant entries for the name, you can extract each of their
1807 numbers, and hence the captured data, if any.
1808 .
1809 .
1811 .rs
1812 .sp
1813 The traditional matching function uses a similar algorithm to Perl, which stops
1814 when it finds the first match, starting at a given point in the subject. If you
1815 want to find all possible matches, or the longest possible match, consider
1816 using the alternative matching function (see below) instead. If you cannot use
1817 the alternative function, but still need to find all possible matches, you
1818 can kludge it up by making use of the callout facility, which is described in
1819 the
1820 .\" HREF
1821 \fBpcrecallout\fP
1822 .\"
1823 documentation.
1824 .P
1825 What you have to do is to insert a callout right at the end of the pattern.
1826 When your callout function is called, extract and save the current matched
1827 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1828 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1829 will yield PCRE_ERROR_NOMATCH.
1830 .
1831 .
1832 .\" HTML <a name="dfamatch"></a>
1834 .rs
1835 .sp
1836 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1837 .ti +5n
1838 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1839 .ti +5n
1840 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1841 .ti +5n
1842 .B int *\fIworkspace\fP, int \fIwscount\fP);
1843 .P
1844 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1845 a compiled pattern, using a matching algorithm that scans the subject string
1846 just once, and does not backtrack. This has different characteristics to the
1847 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1848 patterns are not supported. Nevertheless, there are times when this kind of
1849 matching can be useful. For a discussion of the two matching algorithms, and a
1850 list of features that \fBpcre_dfa_exec()\fP does not support, see the
1851 .\" HREF
1852 \fBpcrematching\fP
1853 .\"
1854 documentation.
1855 .P
1856 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1857 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1858 different way, and this is described below. The other common arguments are used
1859 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1860 here.
1861 .P
1862 The two additional arguments provide workspace for the function. The workspace
1863 vector should contain at least 20 elements. It is used for keeping track of
1864 multiple paths through the pattern tree. More workspace will be needed for
1865 patterns and subjects where there are a lot of potential matches.
1866 .P
1867 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1868 .sp
1869 int rc;
1870 int ovector[10];
1871 int wspace[20];
1872 rc = pcre_dfa_exec(
1873 re, /* result of pcre_compile() */
1874 NULL, /* we didn't study the pattern */
1875 "some string", /* the subject string */
1876 11, /* the length of the subject string */
1877 0, /* start at offset 0 in the subject */
1878 0, /* default options */
1879 ovector, /* vector of integers for substring information */
1880 10, /* number of elements (NOT size in bytes) */
1881 wspace, /* working space vector */
1882 20); /* number of elements (NOT size in bytes) */
1883 .
1884 .SS "Option bits for \fBpcre_dfa_exec()\fP"
1885 .rs
1886 .sp
1887 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1888 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1891 and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1892 for \fBpcre_exec()\fP, so their description is not repeated here.
1893 .sp
1896 .sp
1897 These have the same general effect as they do for \fBpcre_exec()\fP, but the
1898 details are slightly different. When PCRE_PARTIAL_HARD is set for
1899 \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
1900 is reached and there is still at least one matching possibility that requires
1901 additional characters. This happens even if some complete matches have also
1902 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1903 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1904 there have been no complete matches, but there is still at least one matching
1905 possibility. The portion of the string that was inspected when the longest
1906 partial match was found is set as the first matching string in both cases.
1907 .sp
1909 .sp
1910 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1911 soon as it has found one match. Because of the way the alternative algorithm
1912 works, this is necessarily the shortest possible match at the first possible
1913 matching point in the subject string.
1914 .sp
1916 .sp
1917 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
1918 again, with additional subject characters, and have it continue with the same
1919 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1920 \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
1921 before because data about the match so far is left in them after a partial
1922 match. There is more discussion of this facility in the
1923 .\" HREF
1924 \fBpcrepartial\fP
1925 .\"
1926 documentation.
1927 .
1928 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1929 .rs
1930 .sp
1931 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1932 substring in the subject. Note, however, that all the matches from one run of
1933 the function start at the same point in the subject. The shorter matches are
1934 all initial substrings of the longer matches. For example, if the pattern
1935 .sp
1936 <.*>
1937 .sp
1938 is matched against the string
1939 .sp
1940 This is <something> <something else> <something further> no more
1941 .sp
1942 the three matched strings are
1943 .sp
1944 <something>
1945 <something> <something else>
1946 <something> <something else> <something further>
1947 .sp
1948 On success, the yield of the function is a number greater than zero, which is
1949 the number of matched substrings. The substrings themselves are returned in
1950 \fIovector\fP. Each string uses two elements; the first is the offset to the
1951 start, and the second is the offset to the end. In fact, all the strings have
1952 the same start offset. (Space could have been saved by giving this only once,
1953 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1954 returns data, even though the meaning of the strings is different.)
1955 .P
1956 The strings are returned in reverse order of length; that is, the longest
1957 matching string is given first. If there were too many matches to fit into
1958 \fIovector\fP, the yield of the function is zero, and the vector is filled with
1959 the longest matches.
1960 .
1961 .SS "Error returns from \fBpcre_dfa_exec()\fP"
1962 .rs
1963 .sp
1964 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1965 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1966 described
1967 .\" HTML <a href="#errorlist">
1968 .\" </a>
1969 above.
1970 .\"
1971 There are in addition the following errors that are specific to
1972 \fBpcre_dfa_exec()\fP:
1973 .sp
1975 .sp
1976 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1977 that it does not support, for instance, the use of \eC or a back reference.
1978 .sp
1980 .sp
1981 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1982 uses a back reference for the condition, or a test for recursion in a specific
1983 group. These are not supported.
1984 .sp
1986 .sp
1987 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1988 block that contains a setting of the \fImatch_limit\fP field. This is not
1989 supported (it is meaningless).
1990 .sp
1992 .sp
1993 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1994 \fIworkspace\fP vector.
1995 .sp
1997 .sp
1998 When a recursive subpattern is processed, the matching function calls itself
1999 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2000 error is given if the output vector is not large enough. This should be
2001 extremely rare, as a vector of size 1000 is used.
2002 .
2003 .
2004 .SH "SEE ALSO"
2005 .rs
2006 .sp
2007 \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2008 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2009 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2010 .
2011 .
2013 .rs
2014 .sp
2015 .nf
2016 Philip Hazel
2017 University Computing Service
2018 Cambridge CB2 3QH, England.
2019 .fi
2020 .
2021 .
2023 .rs
2024 .sp
2025 .nf
2026 Last updated: 22 September 2009
2027 Copyright (c) 1997-2009 University of Cambridge.
2028 .fi


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