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Don't advance by 2 if explicit \r or \n in the pattern. Add 
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 source
139 distribution. The
140 .\" HREF
141 \fBpcresample\fP
142 .\"
143 documentation describes how to run it.
144 .P
145 A second matching function, \fBpcre_dfa_exec()\fP, which is not
146 Perl-compatible, is also provided. This uses a different algorithm for the
147 matching. The alternative algorithm finds all possible matches (at a given
148 point in the subject), and scans the subject just once. However, this algorithm
149 does not return captured substrings. A description of the two matching
150 algorithms and their advantages and disadvantages is given in the
151 .\" HREF
152 \fBpcrematching\fP
153 .\"
154 documentation.
155 .P
156 In addition to the main compiling and matching functions, there are convenience
157 functions for extracting captured substrings from a subject string that is
158 matched by \fBpcre_exec()\fP. They are:
159 .sp
160 \fBpcre_copy_substring()\fP
161 \fBpcre_copy_named_substring()\fP
162 \fBpcre_get_substring()\fP
163 \fBpcre_get_named_substring()\fP
164 \fBpcre_get_substring_list()\fP
165 \fBpcre_get_stringnumber()\fP
166 \fBpcre_get_stringtable_entries()\fP
167 .sp
168 \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
169 provided, to free the memory used for extracted strings.
170 .P
171 The function \fBpcre_maketables()\fP is used to build a set of character tables
172 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
173 or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
174 specialist use. Most commonly, no special tables are passed, in which case
175 internal tables that are generated when PCRE is built are used.
176 .P
177 The function \fBpcre_fullinfo()\fP is used to find out information about a
178 compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
179 some of the available information, but is retained for backwards compatibility.
180 The function \fBpcre_version()\fP returns a pointer to a string containing the
181 version of PCRE and its date of release.
182 .P
183 The function \fBpcre_refcount()\fP maintains a reference count in a data block
184 containing a compiled pattern. This is provided for the benefit of
185 object-oriented applications.
186 .P
187 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
188 the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
189 respectively. PCRE calls the memory management functions via these variables,
190 so a calling program can replace them if it wishes to intercept the calls. This
191 should be done before calling any PCRE functions.
192 .P
193 The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
194 indirections to memory management functions. These special functions are used
195 only when PCRE is compiled to use the heap for remembering data, instead of
196 recursive function calls, when running the \fBpcre_exec()\fP function. See the
197 .\" HREF
198 \fBpcrebuild\fP
199 .\"
200 documentation for details of how to do this. It is a non-standard way of
201 building PCRE, for use in environments that have limited stacks. Because of the
202 greater use of memory management, it runs more slowly. Separate functions are
203 provided so that special-purpose external code can be used for this case. When
204 used, these functions are always called in a stack-like manner (last obtained,
205 first freed), and always for memory blocks of the same size. There is a
206 discussion about PCRE's stack usage in the
207 .\" HREF
208 \fBpcrestack\fP
209 .\"
210 documentation.
211 .P
212 The global variable \fBpcre_callout\fP initially contains NULL. It can be set
213 by the caller to a "callout" function, which PCRE will then call at specified
214 points during a matching operation. Details are given in the
215 .\" HREF
216 \fBpcrecallout\fP
217 .\"
218 documentation.
219 .
220 .
222 .rs
223 .sp
224 PCRE supports five different conventions for indicating line breaks in
225 strings: a single CR (carriage return) character, a single LF (linefeed)
226 character, the two-character sequence CRLF, any of the three preceding, or any
227 Unicode newline sequence. The Unicode newline sequences are the three just
228 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
229 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
230 (paragraph separator, U+2029).
231 .P
232 Each of the first three conventions is used by at least one operating system as
233 its standard newline sequence. When PCRE is built, a default can be specified.
234 The default default is LF, which is the Unix standard. When PCRE is run, the
235 default can be overridden, either when a pattern is compiled, or when it is
236 matched.
237 .P
238 In the PCRE documentation the word "newline" is used to mean "the character or
239 pair of characters that indicate a line break". The choice of newline
240 convention affects the handling of the dot, circumflex, and dollar
241 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
242 recognized line ending sequence, the match position advancement for a
243 non-anchored pattern. There is more detail about this in the
244 .\" HTML <a href="#execoptions">
245 .\" </a>
246 section on \fBpcre_exec()\fP options
247 .\"
248 below. The choice of newline convention does not affect the interpretation of
249 the \en or \er escape sequences.
250 .
251 .
253 .rs
254 .sp
255 The PCRE functions can be used in multi-threading applications, with the
256 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
257 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
258 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
259 .P
260 The compiled form of a regular expression is not altered during matching, so
261 the same compiled pattern can safely be used by several threads at once.
262 .
263 .
265 .rs
266 .sp
267 The compiled form of a regular expression can be saved and re-used at a later
268 time, possibly by a different program, and even on a host other than the one on
269 which it was compiled. Details are given in the
270 .\" HREF
271 \fBpcreprecompile\fP
272 .\"
273 documentation. However, compiling a regular expression with one version of PCRE
274 for use with a different version is not guaranteed to work and may cause
275 crashes.
276 .
277 .
279 .rs
280 .sp
281 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
282 .PP
283 The function \fBpcre_config()\fP makes it possible for a PCRE client to
284 discover which optional features have been compiled into the PCRE library. The
285 .\" HREF
286 \fBpcrebuild\fP
287 .\"
288 documentation has more details about these optional features.
289 .P
290 The first argument for \fBpcre_config()\fP is an integer, specifying which
291 information is required; the second argument is a pointer to a variable into
292 which the information is placed. The following information is available:
293 .sp
295 .sp
296 The output is an integer that is set to one if UTF-8 support is available;
297 otherwise it is set to zero.
298 .sp
300 .sp
301 The output is an integer that is set to one if support for Unicode character
302 properties is available; otherwise it is set to zero.
303 .sp
305 .sp
306 The output is an integer whose value specifies the default character sequence
307 that is recognized as meaning "newline". The four values that are supported
308 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The
309 default should normally be the standard sequence for your operating system.
310 .sp
312 .sp
313 The output is an integer that contains the number of bytes used for internal
314 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
315 allow larger regular expressions to be compiled, at the expense of slower
316 matching. The default value of 2 is sufficient for all but the most massive
317 patterns, since it allows the compiled pattern to be up to 64K in size.
318 .sp
320 .sp
321 The output is an integer that contains the threshold above which the POSIX
322 interface uses \fBmalloc()\fP for output vectors. Further details are given in
323 the
324 .\" HREF
325 \fBpcreposix\fP
326 .\"
327 documentation.
328 .sp
330 .sp
331 The output is an integer that gives the default limit for the number of
332 internal matching function calls in a \fBpcre_exec()\fP execution. Further
333 details are given with \fBpcre_exec()\fP below.
334 .sp
336 .sp
337 The output is an integer that gives the default limit for the depth of
338 recursion when calling the internal matching function in a \fBpcre_exec()\fP
339 execution. Further details are given with \fBpcre_exec()\fP below.
340 .sp
342 .sp
343 The output is an integer that is set to one if internal recursion when running
344 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
345 to remember their state. This is the usual way that PCRE is compiled. The
346 output is zero if PCRE was compiled to use blocks of data on the heap instead
347 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
348 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
349 avoiding the use of the stack.
350 .
351 .
353 .rs
354 .sp
355 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
356 .ti +5n
357 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
358 .ti +5n
359 .B const unsigned char *\fItableptr\fP);
360 .sp
361 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
362 .ti +5n
363 .B int *\fIerrorcodeptr\fP,
364 .ti +5n
365 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
366 .ti +5n
367 .B const unsigned char *\fItableptr\fP);
368 .P
369 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
370 called to compile a pattern into an internal form. The only difference between
371 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
372 \fIerrorcodeptr\fP, via which a numerical error code can be returned.
373 .P
374 The pattern is a C string terminated by a binary zero, and is passed in the
375 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
376 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
377 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
378 for a structure whose contents are not externally defined. It is up to the
379 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
380 .P
381 Although the compiled code of a PCRE regex is relocatable, that is, it does not
382 depend on memory location, the complete \fBpcre\fP data block is not
383 fully relocatable, because it may contain a copy of the \fItableptr\fP
384 argument, which is an address (see below).
385 .P
386 The \fIoptions\fP argument contains various bit settings that affect the
387 compilation. It should be zero if no options are required. The available
388 options are described below. Some of them, in particular, those that are
389 compatible with Perl, can also be set and unset from within the pattern (see
390 the detailed description in the
391 .\" HREF
392 \fBpcrepattern\fP
393 .\"
394 documentation). For these options, the contents of the \fIoptions\fP argument
395 specifies their initial settings at the start of compilation and execution. The
396 PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
397 matching as well as at compile time.
398 .P
399 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
400 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
401 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
402 error message. This is a static string that is part of the library. You must
403 not try to free it. The offset from the start of the pattern to the character
404 where the error was discovered is placed in the variable pointed to by
405 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
406 .P
407 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
408 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
409 returned via this argument in the event of an error. This is in addition to the
410 textual error message. Error codes and messages are listed below.
411 .P
412 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
413 character tables that are built when PCRE is compiled, using the default C
414 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
415 call to \fBpcre_maketables()\fP. This value is stored with the compiled
416 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
417 passed to it. For more discussion, see the section on locale support below.
418 .P
419 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
420 .sp
421 pcre *re;
422 const char *error;
423 int erroffset;
424 re = pcre_compile(
425 "^A.*Z", /* the pattern */
426 0, /* default options */
427 &error, /* for error message */
428 &erroffset, /* for error offset */
429 NULL); /* use default character tables */
430 .sp
431 The following names for option bits are defined in the \fBpcre.h\fP header
432 file:
433 .sp
435 .sp
436 If this bit is set, the pattern is forced to be "anchored", that is, it is
437 constrained to match only at the first matching point in the string that is
438 being searched (the "subject string"). This effect can also be achieved by
439 appropriate constructs in the pattern itself, which is the only way to do it in
440 Perl.
441 .sp
443 .sp
444 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
445 all with number 255, before each pattern item. For discussion of the callout
446 facility, see the
447 .\" HREF
448 \fBpcrecallout\fP
449 .\"
450 documentation.
451 .sp
453 .sp
454 If this bit is set, letters in the pattern match both upper and lower case
455 letters. It is equivalent to Perl's /i option, and it can be changed within a
456 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
457 concept of case for characters whose values are less than 128, so caseless
458 matching is always possible. For characters with higher values, the concept of
459 case is supported if PCRE is compiled with Unicode property support, but not
460 otherwise. If you want to use caseless matching for characters 128 and above,
461 you must ensure that PCRE is compiled with Unicode property support as well as
462 with UTF-8 support.
463 .sp
465 .sp
466 If this bit is set, a dollar metacharacter in the pattern matches only at the
467 end of the subject string. Without this option, a dollar also matches
468 immediately before a newline at the end of the string (but not before any other
469 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
470 There is no equivalent to this option in Perl, and no way to set it within a
471 pattern.
472 .sp
474 .sp
475 If this bit is set, a dot metacharater in the pattern matches all characters,
476 including those that indicate newline. Without it, a dot does not match when
477 the current position is at a newline. This option is equivalent to Perl's /s
478 option, and it can be changed within a pattern by a (?s) option setting. A
479 negative class such as [^a] always matches newline characters, independent of
480 the setting of this option.
481 .sp
483 .sp
484 If this bit is set, names used to identify capturing subpatterns need not be
485 unique. This can be helpful for certain types of pattern when it is known that
486 only one instance of the named subpattern can ever be matched. There are more
487 details of named subpatterns below; see also the
488 .\" HREF
489 \fBpcrepattern\fP
490 .\"
491 documentation.
492 .sp
494 .sp
495 If this bit is set, whitespace data characters in the pattern are totally
496 ignored except when escaped or inside a character class. Whitespace does not
497 include the VT character (code 11). In addition, characters between an
498 unescaped # outside a character class and the next newline, inclusive, are also
499 ignored. This is equivalent to Perl's /x option, and it can be changed within a
500 pattern by a (?x) option setting.
501 .P
502 This option makes it possible to include comments inside complicated patterns.
503 Note, however, that this applies only to data characters. Whitespace characters
504 may never appear within special character sequences in a pattern, for example
505 within the sequence (?( which introduces a conditional subpattern.
506 .sp
508 .sp
509 This option was invented in order to turn on additional functionality of PCRE
510 that is incompatible with Perl, but it is currently of very little use. When
511 set, any backslash in a pattern that is followed by a letter that has no
512 special meaning causes an error, thus reserving these combinations for future
513 expansion. By default, as in Perl, a backslash followed by a letter with no
514 special meaning is treated as a literal. (Perl can, however, be persuaded to
515 give a warning for this.) There are at present no other features controlled by
516 this option. It can also be set by a (?X) option setting within a pattern.
517 .sp
519 .sp
520 If this option is set, an unanchored pattern is required to match before or at
521 the first newline in the subject string, though the matched text may continue
522 over the newline.
523 .sp
525 .sp
526 By default, PCRE treats the subject string as consisting of a single line of
527 characters (even if it actually contains newlines). The "start of line"
528 metacharacter (^) matches only at the start of the string, while the "end of
529 line" metacharacter ($) matches only at the end of the string, or before a
530 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
531 Perl.
532 .P
533 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
534 match immediately following or immediately before internal newlines in the
535 subject string, respectively, as well as at the very start and end. This is
536 equivalent to Perl's /m option, and it can be changed within a pattern by a
537 (?m) option setting. If there are no newlines in a subject string, or no
538 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
539 .sp
545 .sp
546 These options override the default newline definition that was chosen when PCRE
547 was built. Setting the first or the second specifies that a newline is
548 indicated by a single character (CR or LF, respectively). Setting
549 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
550 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
551 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
552 that any Unicode newline sequence should be recognized. The Unicode newline
553 sequences are the three just mentioned, plus the single characters VT (vertical
554 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
555 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
556 recognized only in UTF-8 mode.
557 .P
558 The newline setting in the options word uses three bits that are treated
559 as a number, giving eight possibilities. Currently only six are used (default
560 plus the five values above). This means that if you set more than one newline
561 option, the combination may or may not be sensible. For example,
563 other combinations may yield unused numbers and cause an error.
564 .P
565 The only time that a line break is specially recognized when compiling a
566 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
567 class is encountered. This indicates a comment that lasts until after the next
568 line break sequence. In other circumstances, line break sequences are treated
569 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
570 as whitespace characters and are therefore ignored.
571 .P
572 The newline option that is set at compile time becomes the default that is used
573 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
574 .sp
576 .sp
577 If this option is set, it disables the use of numbered capturing parentheses in
578 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
579 were followed by ?: but named parentheses can still be used for capturing (and
580 they acquire numbers in the usual way). There is no equivalent of this option
581 in Perl.
582 .sp
584 .sp
585 This option inverts the "greediness" of the quantifiers so that they are not
586 greedy by default, but become greedy if followed by "?". It is not compatible
587 with Perl. It can also be set by a (?U) option setting within the pattern.
588 .sp
590 .sp
591 This option causes PCRE to regard both the pattern and the subject as strings
592 of UTF-8 characters instead of single-byte character strings. However, it is
593 available only when PCRE is built to include UTF-8 support. If not, the use
594 of this option provokes an error. Details of how this option changes the
595 behaviour of PCRE are given in the
596 .\" HTML <a href="pcre.html#utf8support">
597 .\" </a>
598 section on UTF-8 support
599 .\"
600 in the main
601 .\" HREF
602 \fBpcre\fP
603 .\"
604 page.
605 .sp
607 .sp
608 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
609 automatically checked. There is a discussion about the
610 .\" HTML <a href="pcre.html#utf8strings">
611 .\" </a>
612 validity of UTF-8 strings
613 .\"
614 in the main
615 .\" HREF
616 \fBpcre\fP
617 .\"
618 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
619 returns an error. If you already know that your pattern is valid, and you want
620 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
621 option. When it is set, the effect of passing an invalid UTF-8 string as a
622 pattern is undefined. It may cause your program to crash. Note that this option
623 can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
624 the UTF-8 validity checking of subject strings.
625 .
626 .
628 .rs
629 .sp
630 The following table lists the error codes than may be returned by
631 \fBpcre_compile2()\fP, along with the error messages that may be returned by
632 both compiling functions. As PCRE has developed, some error codes have fallen
633 out of use. To avoid confusion, they have not been re-used.
634 .sp
635 0 no error
636 1 \e at end of pattern
637 2 \ec at end of pattern
638 3 unrecognized character follows \e
639 4 numbers out of order in {} quantifier
640 5 number too big in {} quantifier
641 6 missing terminating ] for character class
642 7 invalid escape sequence in character class
643 8 range out of order in character class
644 9 nothing to repeat
645 10 [this code is not in use]
646 11 internal error: unexpected repeat
647 12 unrecognized character after (?
648 13 POSIX named classes are supported only within a class
649 14 missing )
650 15 reference to non-existent subpattern
651 16 erroffset passed as NULL
652 17 unknown option bit(s) set
653 18 missing ) after comment
654 19 [this code is not in use]
655 20 regular expression too large
656 21 failed to get memory
657 22 unmatched parentheses
658 23 internal error: code overflow
659 24 unrecognized character after (?<
660 25 lookbehind assertion is not fixed length
661 26 malformed number or name after (?(
662 27 conditional group contains more than two branches
663 28 assertion expected after (?(
664 29 (?R or (?[+-]digits must be followed by )
665 30 unknown POSIX class name
666 31 POSIX collating elements are not supported
667 32 this version of PCRE is not compiled with PCRE_UTF8 support
668 33 [this code is not in use]
669 34 character value in \ex{...} sequence is too large
670 35 invalid condition (?(0)
671 36 \eC not allowed in lookbehind assertion
672 37 PCRE does not support \eL, \el, \eN, \eU, or \eu
673 38 number after (?C is > 255
674 39 closing ) for (?C expected
675 40 recursive call could loop indefinitely
676 41 unrecognized character after (?P
677 42 syntax error in subpattern name (missing terminator)
678 43 two named subpatterns have the same name
679 44 invalid UTF-8 string
680 45 support for \eP, \ep, and \eX has not been compiled
681 46 malformed \eP or \ep sequence
682 47 unknown property name after \eP or \ep
683 48 subpattern name is too long (maximum 32 characters)
684 49 too many named subpatterns (maximum 10,000)
685 50 [this code is not in use]
686 51 octal value is greater than \e377 (not in UTF-8 mode)
687 52 internal error: overran compiling workspace
688 53 internal error: previously-checked referenced subpattern not found
689 54 DEFINE group contains more than one branch
690 55 repeating a DEFINE group is not allowed
691 56 inconsistent NEWLINE options"
692 57 \eg is not followed by a braced name or an optionally braced
693 non-zero number
694 58 (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
695 .
696 .
698 .rs
699 .sp
700 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
701 .ti +5n
702 .B const char **\fIerrptr\fP);
703 .PP
704 If a compiled pattern is going to be used several times, it is worth spending
705 more time analyzing it in order to speed up the time taken for matching. The
706 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
707 argument. If studying the pattern produces additional information that will
708 help speed up matching, \fBpcre_study()\fP returns a pointer to a
709 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
710 results of the study.
711 .P
712 The returned value from \fBpcre_study()\fP can be passed directly to
713 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
714 fields that can be set by the caller before the block is passed; these are
715 described
716 .\" HTML <a href="#extradata">
717 .\" </a>
718 below
719 .\"
720 in the section on matching a pattern.
721 .P
722 If studying the pattern does not produce any additional information
723 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
724 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
725 own \fBpcre_extra\fP block.
726 .P
727 The second argument of \fBpcre_study()\fP contains option bits. At present, no
728 options are defined, and this argument should always be zero.
729 .P
730 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
731 studying succeeds (even if no data is returned), the variable it points to is
732 set to NULL. Otherwise it is set to point to a textual error message. This is a
733 static string that is part of the library. You must not try to free it. You
734 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
735 sure that it has run successfully.
736 .P
737 This is a typical call to \fBpcre_study\fP():
738 .sp
739 pcre_extra *pe;
740 pe = pcre_study(
741 re, /* result of pcre_compile() */
742 0, /* no options exist */
743 &error); /* set to NULL or points to a message */
744 .sp
745 At present, studying a pattern is useful only for non-anchored patterns that do
746 not have a single fixed starting character. A bitmap of possible starting
747 bytes is created.
748 .
749 .
750 .\" HTML <a name="localesupport"></a>
752 .rs
753 .sp
754 PCRE handles caseless matching, and determines whether characters are letters,
755 digits, or whatever, by reference to a set of tables, indexed by character
756 value. When running in UTF-8 mode, this applies only to characters with codes
757 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
758 can be tested with \ep if PCRE is built with Unicode character property
759 support. The use of locales with Unicode is discouraged. If you are handling
760 characters with codes greater than 128, you should either use UTF-8 and
761 Unicode, or use locales, but not try to mix the two.
762 .P
763 PCRE contains an internal set of tables that are used when the final argument
764 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
765 Normally, the internal tables recognize only ASCII characters. However, when
766 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
767 default "C" locale of the local system, which may cause them to be different.
768 .P
769 The internal tables can always be overridden by tables supplied by the
770 application that calls PCRE. These may be created in a different locale from
771 the default. As more and more applications change to using Unicode, the need
772 for this locale support is expected to die away.
773 .P
774 External tables are built by calling the \fBpcre_maketables()\fP function,
775 which has no arguments, in the relevant locale. The result can then be passed
776 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
777 example, to build and use tables that are appropriate for the French locale
778 (where accented characters with values greater than 128 are treated as letters),
779 the following code could be used:
780 .sp
781 setlocale(LC_CTYPE, "fr_FR");
782 tables = pcre_maketables();
783 re = pcre_compile(..., tables);
784 .sp
785 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
786 are using Windows, the name for the French locale is "french".
787 .P
788 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
789 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
790 that the memory containing the tables remains available for as long as it is
791 needed.
792 .P
793 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
794 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
795 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
796 pattern, compilation, studying and matching all happen in the same locale, but
797 different patterns can be compiled in different locales.
798 .P
799 It is possible to pass a table pointer or NULL (indicating the use of the
800 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
801 this facility could be used to match a pattern in a different locale from the
802 one in which it was compiled. Passing table pointers at run time is discussed
803 below in the section on matching a pattern.
804 .
805 .
807 .rs
808 .sp
809 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
810 .ti +5n
811 .B int \fIwhat\fP, void *\fIwhere\fP);
812 .PP
813 The \fBpcre_fullinfo()\fP function returns information about a compiled
814 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
815 nevertheless retained for backwards compability (and is documented below).
816 .P
817 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
818 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
819 the pattern was not studied. The third argument specifies which piece of
820 information is required, and the fourth argument is a pointer to a variable
821 to receive the data. The yield of the function is zero for success, or one of
822 the following negative numbers:
823 .sp
824 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
825 the argument \fIwhere\fP was NULL
826 PCRE_ERROR_BADMAGIC the "magic number" was not found
827 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
828 .sp
829 The "magic number" is placed at the start of each compiled pattern as an simple
830 check against passing an arbitrary memory pointer. Here is a typical call of
831 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
832 .sp
833 int rc;
834 size_t length;
835 rc = pcre_fullinfo(
836 re, /* result of pcre_compile() */
837 pe, /* result of pcre_study(), or NULL */
838 PCRE_INFO_SIZE, /* what is required */
839 &length); /* where to put the data */
840 .sp
841 The possible values for the third argument are defined in \fBpcre.h\fP, and are
842 as follows:
843 .sp
845 .sp
846 Return the number of the highest back reference in the pattern. The fourth
847 argument should point to an \fBint\fP variable. Zero is returned if there are
848 no back references.
849 .sp
851 .sp
852 Return the number of capturing subpatterns in the pattern. The fourth argument
853 should point to an \fBint\fP variable.
854 .sp
856 .sp
857 Return a pointer to the internal default character tables within PCRE. The
858 fourth argument should point to an \fBunsigned char *\fP variable. This
859 information call is provided for internal use by the \fBpcre_study()\fP
860 function. External callers can cause PCRE to use its internal tables by passing
861 a NULL table pointer.
862 .sp
864 .sp
865 Return information about the first byte of any matched string, for a
866 non-anchored pattern. The fourth argument should point to an \fBint\fP
867 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
868 still recognized for backwards compatibility.)
869 .P
870 If there is a fixed first byte, for example, from a pattern such as
871 (cat|cow|coyote), its value is returned. Otherwise, if either
872 .sp
873 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
874 starts with "^", or
875 .sp
876 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
877 (if it were set, the pattern would be anchored),
878 .sp
879 -1 is returned, indicating that the pattern matches only at the start of a
880 subject string or after any newline within the string. Otherwise -2 is
881 returned. For anchored patterns, -2 is returned.
882 .sp
884 .sp
885 If the pattern was studied, and this resulted in the construction of a 256-bit
886 table indicating a fixed set of bytes for the first byte in any matching
887 string, a pointer to the table is returned. Otherwise NULL is returned. The
888 fourth argument should point to an \fBunsigned char *\fP variable.
889 .sp
891 .sp
892 Return 1 if the pattern contains any explicit matches for CR or LF characters,
893 otherwise 0. The fourth argument should point to an \fBint\fP variable.
894 .sp
896 .sp
897 Return 1 if the (?J) option setting is used in the pattern, otherwise 0. The
898 fourth argument should point to an \fBint\fP variable. The (?J) internal option
899 setting changes the local PCRE_DUPNAMES option.
900 .sp
902 .sp
903 Return the value of the rightmost literal byte that must exist in any matched
904 string, other than at its start, if such a byte has been recorded. The fourth
905 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
906 returned. For anchored patterns, a last literal byte is recorded only if it
907 follows something of variable length. For example, for the pattern
908 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
909 is -1.
910 .sp
914 .sp
915 PCRE supports the use of named as well as numbered capturing parentheses. The
916 names are just an additional way of identifying the parentheses, which still
917 acquire numbers. Several convenience functions such as
918 \fBpcre_get_named_substring()\fP are provided for extracting captured
919 substrings by name. It is also possible to extract the data directly, by first
920 converting the name to a number in order to access the correct pointers in the
921 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
922 you need to use the name-to-number map, which is described by these three
923 values.
924 .P
925 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
926 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
927 entry; both of these return an \fBint\fP value. The entry size depends on the
928 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
929 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
930 are the number of the capturing parenthesis, most significant byte first. The
931 rest of the entry is the corresponding name, zero terminated. The names are in
932 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
933 their parentheses numbers. For example, consider the following pattern (assume
934 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
935 .sp
936 .\" JOIN
937 (?<date> (?<year>(\ed\ed)?\ed\ed) -
938 (?<month>\ed\ed) - (?<day>\ed\ed) )
939 .sp
940 There are four named subpatterns, so the table has four entries, and each entry
941 in the table is eight bytes long. The table is as follows, with non-printing
942 bytes shows in hexadecimal, and undefined bytes shown as ??:
943 .sp
944 00 01 d a t e 00 ??
945 00 05 d a y 00 ?? ??
946 00 04 m o n t h 00
947 00 02 y e a r 00 ??
948 .sp
949 When writing code to extract data from named subpatterns using the
950 name-to-number map, remember that the length of the entries is likely to be
951 different for each compiled pattern.
952 .sp
954 .sp
955 Return 1 if the pattern can be used for partial matching, otherwise 0. The
956 fourth argument should point to an \fBint\fP variable. The
957 .\" HREF
958 \fBpcrepartial\fP
959 .\"
960 documentation lists the restrictions that apply to patterns when partial
961 matching is used.
962 .sp
964 .sp
965 Return a copy of the options with which the pattern was compiled. The fourth
966 argument should point to an \fBunsigned long int\fP variable. These option bits
967 are those specified in the call to \fBpcre_compile()\fP, modified by any
968 top-level option settings at the start of the pattern itself. In other words,
969 they are the options that will be in force when matching starts. For example,
970 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
972 .P
973 A pattern is automatically anchored by PCRE if all of its top-level
974 alternatives begin with one of the following:
975 .sp
976 ^ unless PCRE_MULTILINE is set
977 \eA always
978 \eG always
979 .\" JOIN
980 .* if PCRE_DOTALL is set and there are no back
981 references to the subpattern in which .* appears
982 .sp
983 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
984 \fBpcre_fullinfo()\fP.
985 .sp
987 .sp
988 Return the size of the compiled pattern, that is, the value that was passed as
989 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
990 place the compiled data. The fourth argument should point to a \fBsize_t\fP
991 variable.
992 .sp
994 .sp
995 Return the size of the data block pointed to by the \fIstudy_data\fP field in
996 a \fBpcre_extra\fP block. That is, it is the value that was passed to
997 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
998 created by \fBpcre_study()\fP. The fourth argument should point to a
999 \fBsize_t\fP variable.
1000 .
1001 .
1003 .rs
1004 .sp
1005 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1006 .B *\fIfirstcharptr\fP);
1007 .PP
1008 The \fBpcre_info()\fP function is now obsolete because its interface is too
1009 restrictive to return all the available data about a compiled pattern. New
1010 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1011 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1012 following negative numbers:
1013 .sp
1014 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1015 PCRE_ERROR_BADMAGIC the "magic number" was not found
1016 .sp
1017 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1018 pattern was compiled is placed in the integer it points to (see
1019 PCRE_INFO_OPTIONS above).
1020 .P
1021 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1022 it is used to pass back information about the first character of any matched
1023 string (see PCRE_INFO_FIRSTBYTE above).
1024 .
1025 .
1027 .rs
1028 .sp
1029 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1030 .PP
1031 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1032 data block that contains a compiled pattern. It is provided for the benefit of
1033 applications that operate in an object-oriented manner, where different parts
1034 of the application may be using the same compiled pattern, but you want to free
1035 the block when they are all done.
1036 .P
1037 When a pattern is compiled, the reference count field is initialized to zero.
1038 It is changed only by calling this function, whose action is to add the
1039 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1040 function is the new value. However, the value of the count is constrained to
1041 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1042 it is forced to the appropriate limit value.
1043 .P
1044 Except when it is zero, the reference count is not correctly preserved if a
1045 pattern is compiled on one host and then transferred to a host whose byte-order
1046 is different. (This seems a highly unlikely scenario.)
1047 .
1048 .
1050 .rs
1051 .sp
1052 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1053 .ti +5n
1054 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1055 .ti +5n
1056 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1057 .P
1058 The function \fBpcre_exec()\fP is called to match a subject string against a
1059 compiled pattern, which is passed in the \fIcode\fP argument. If the
1060 pattern has been studied, the result of the study should be passed in the
1061 \fIextra\fP argument. This function is the main matching facility of the
1062 library, and it operates in a Perl-like manner. For specialist use there is
1063 also an alternative matching function, which is described
1064 .\" HTML <a href="#dfamatch">
1065 .\" </a>
1066 below
1067 .\"
1068 in the section about the \fBpcre_dfa_exec()\fP function.
1069 .P
1070 In most applications, the pattern will have been compiled (and optionally
1071 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1072 possible to save compiled patterns and study data, and then use them later
1073 in different processes, possibly even on different hosts. For a discussion
1074 about this, see the
1075 .\" HREF
1076 \fBpcreprecompile\fP
1077 .\"
1078 documentation.
1079 .P
1080 Here is an example of a simple call to \fBpcre_exec()\fP:
1081 .sp
1082 int rc;
1083 int ovector[30];
1084 rc = pcre_exec(
1085 re, /* result of pcre_compile() */
1086 NULL, /* we didn't study the pattern */
1087 "some string", /* the subject string */
1088 11, /* the length of the subject string */
1089 0, /* start at offset 0 in the subject */
1090 0, /* default options */
1091 ovector, /* vector of integers for substring information */
1092 30); /* number of elements (NOT size in bytes) */
1093 .
1094 .\" HTML <a name="extradata"></a>
1095 .SS "Extra data for \fBpcre_exec()\fR"
1096 .rs
1097 .sp
1098 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1099 data block. The \fBpcre_study()\fP function returns such a block (when it
1100 doesn't return NULL), but you can also create one for yourself, and pass
1101 additional information in it. The \fBpcre_extra\fP block contains the following
1102 fields (not necessarily in this order):
1103 .sp
1104 unsigned long int \fIflags\fP;
1105 void *\fIstudy_data\fP;
1106 unsigned long int \fImatch_limit\fP;
1107 unsigned long int \fImatch_limit_recursion\fP;
1108 void *\fIcallout_data\fP;
1109 const unsigned char *\fItables\fP;
1110 .sp
1111 The \fIflags\fP field is a bitmap that specifies which of the other fields
1112 are set. The flag bits are:
1113 .sp
1119 .sp
1120 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1121 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1122 the appropriate flag bit. You should not set this yourself, but you may add to
1123 the block by setting the other fields and their corresponding flag bits.
1124 .P
1125 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1126 vast amount of resources when running patterns that are not going to match,
1127 but which have a very large number of possibilities in their search trees. The
1128 classic example is the use of nested unlimited repeats.
1129 .P
1130 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1131 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1132 number of times this function is called during a match, which has the effect of
1133 limiting the amount of backtracking that can take place. For patterns that are
1134 not anchored, the count restarts from zero for each position in the subject
1135 string.
1136 .P
1137 The default value for the limit can be set when PCRE is built; the default
1138 default is 10 million, which handles all but the most extreme cases. You can
1139 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1140 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1141 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1143 .P
1144 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1145 instead of limiting the total number of times that \fBmatch()\fP is called, it
1146 limits the depth of recursion. The recursion depth is a smaller number than the
1147 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1148 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1149 .P
1150 Limiting the recursion depth limits the amount of stack that can be used, or,
1151 when PCRE has been compiled to use memory on the heap instead of the stack, the
1152 amount of heap memory that can be used.
1153 .P
1154 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1155 built; the default default is the same value as the default for
1156 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1157 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1158 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1159 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1160 .P
1161 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1162 which is described in the
1163 .\" HREF
1164 \fBpcrecallout\fP
1165 .\"
1166 documentation.
1167 .P
1168 The \fItables\fP field is used to pass a character tables pointer to
1169 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1170 pattern. A non-NULL value is stored with the compiled pattern only if custom
1171 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1172 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1173 internal tables to be used. This facility is helpful when re-using patterns
1174 that have been saved after compiling with an external set of tables, because
1175 the external tables might be at a different address when \fBpcre_exec()\fP is
1176 called. See the
1177 .\" HREF
1178 \fBpcreprecompile\fP
1179 .\"
1180 documentation for a discussion of saving compiled patterns for later use.
1181 .
1182 .\" HTML <a name="execoptions"></a>
1183 .SS "Option bits for \fBpcre_exec()\fP"
1184 .rs
1185 .sp
1186 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1187 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1189 .sp
1191 .sp
1192 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1193 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1194 to be anchored by virtue of its contents, it cannot be made unachored at
1195 matching time.
1196 .sp
1202 .sp
1203 These options override the newline definition that was chosen or defaulted when
1204 the pattern was compiled. For details, see the description of
1205 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1206 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1207 the way the match position is advanced after a match failure for an unanchored
1208 pattern.
1209 .P
1211 match attempt for an unanchored pattern fails when the current position is at a
1212 CRLF sequence, and the pattern contains no explicit matches for CR or NL
1213 characters, the match position is advanced by two characters instead of one, in
1214 other words, to after the CRLF.
1215 .P
1216 The above rule is a compromise that makes the most common cases work as
1217 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1218 set), it does not match the string "\er\enA" because, after failing at the
1219 start, it skips both the CR and the LF before retrying. However, the pattern
1220 [\er\en]A does match that string, because it contains an explicit CR or LF
1221 reference, and so advances only by one character after the first failure.
1222 Note than an explicit CR or LF reference occurs for negated character classes
1223 such as [^X] because they can match CR or LF characters.
1224 .P
1225 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1226 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1227 .sp
1229 .sp
1230 This option specifies that first character of the subject string is not the
1231 beginning of a line, so the circumflex metacharacter should not match before
1232 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1233 never to match. This option affects only the behaviour of the circumflex
1234 metacharacter. It does not affect \eA.
1235 .sp
1237 .sp
1238 This option specifies that the end of the subject string is not the end of a
1239 line, so the dollar metacharacter should not match it nor (except in multiline
1240 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1241 compile time) causes dollar never to match. This option affects only the
1242 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1243 .sp
1245 .sp
1246 An empty string is not considered to be a valid match if this option is set. If
1247 there are alternatives in the pattern, they are tried. If all the alternatives
1248 match the empty string, the entire match fails. For example, if the pattern
1249 .sp
1250 a?b?
1251 .sp
1252 is applied to a string not beginning with "a" or "b", it matches the empty
1253 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1254 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1255 .P
1256 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1257 of a pattern match of the empty string within its \fBsplit()\fP function, and
1258 when using the /g modifier. It is possible to emulate Perl's behaviour after
1259 matching a null string by first trying the match again at the same offset with
1260 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1261 starting offset (see below) and trying an ordinary match again. There is some
1262 code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1263 .sp
1265 .sp
1266 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1267 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1268 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1269 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1270 strings in the
1271 .\" HTML <a href="pcre.html#utf8strings">
1272 .\" </a>
1273 section on UTF-8 support
1274 .\"
1275 in the main
1276 .\" HREF
1277 \fBpcre\fP
1278 .\"
1279 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1280 the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1281 PCRE_ERROR_BADUTF8_OFFSET is returned.
1282 .P
1283 If you already know that your subject is valid, and you want to skip these
1284 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1285 calling \fBpcre_exec()\fP. You might want to do this for the second and
1286 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1287 all the matches in a single subject string. However, you should be sure that
1288 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1289 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1290 subject, or a value of \fIstartoffset\fP that does not point to the start of a
1291 UTF-8 character, is undefined. Your program may crash.
1292 .sp
1294 .sp
1295 This option turns on the partial matching feature. If the subject string fails
1296 to match the pattern, but at some point during the matching process the end of
1297 the subject was reached (that is, the subject partially matches the pattern and
1298 the failure to match occurred only because there were not enough subject
1299 characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1300 PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1301 may appear in the pattern. These are discussed in the
1302 .\" HREF
1303 \fBpcrepartial\fP
1304 .\"
1305 documentation.
1306 .
1307 .SS "The string to be matched by \fBpcre_exec()\fP"
1308 .rs
1309 .sp
1310 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1311 \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
1312 \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
1313 UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1314 bytes. When the starting offset is zero, the search for a match starts at the
1315 beginning of the subject, and this is by far the most common case.
1316 .P
1317 A non-zero starting offset is useful when searching for another match in the
1318 same subject by calling \fBpcre_exec()\fP again after a previous success.
1319 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1320 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1321 lookbehind. For example, consider the pattern
1322 .sp
1323 \eBiss\eB
1324 .sp
1325 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1326 the current position in the subject is not a word boundary.) When applied to
1327 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1328 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1329 subject, namely "issipi", it does not match, because \eB is always false at the
1330 start of the subject, which is deemed to be a word boundary. However, if
1331 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1332 set to 4, it finds the second occurrence of "iss" because it is able to look
1333 behind the starting point to discover that it is preceded by a letter.
1334 .P
1335 If a non-zero starting offset is passed when the pattern is anchored, one
1336 attempt to match at the given offset is made. This can only succeed if the
1337 pattern does not require the match to be at the start of the subject.
1338 .
1339 .SS "How \fBpcre_exec()\fP returns captured substrings"
1340 .rs
1341 .sp
1342 In general, a pattern matches a certain portion of the subject, and in
1343 addition, further substrings from the subject may be picked out by parts of the
1344 pattern. Following the usage in Jeffrey Friedl's book, this is called
1345 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1346 a fragment of a pattern that picks out a substring. PCRE supports several other
1347 kinds of parenthesized subpattern that do not cause substrings to be captured.
1348 .P
1349 Captured substrings are returned to the caller via a vector of integer offsets
1350 whose address is passed in \fIovector\fP. The number of elements in the vector
1351 is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
1352 this argument is NOT the size of \fIovector\fP in bytes.
1353 .P
1354 The first two-thirds of the vector is used to pass back captured substrings,
1355 each substring using a pair of integers. The remaining third of the vector is
1356 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1357 and is not available for passing back information. The length passed in
1358 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1359 rounded down.
1360 .P
1361 When a match is successful, information about captured substrings is returned
1362 in pairs of integers, starting at the beginning of \fIovector\fP, and
1363 continuing up to two-thirds of its length at the most. The first element of a
1364 pair is set to the offset of the first character in a substring, and the second
1365 is set to the offset of the first character after the end of a substring. The
1366 first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
1367 subject string matched by the entire pattern. The next pair is used for the
1368 first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
1369 is one more than the highest numbered pair that has been set. For example, if
1370 two substrings have been captured, the returned value is 3. If there are no
1371 capturing subpatterns, the return value from a successful match is 1,
1372 indicating that just the first pair of offsets has been set.
1373 .P
1374 If a capturing subpattern is matched repeatedly, it is the last portion of the
1375 string that it matched that is returned.
1376 .P
1377 If the vector is too small to hold all the captured substring offsets, it is
1378 used as far as possible (up to two-thirds of its length), and the function
1379 returns a value of zero. In particular, if the substring offsets are not of
1380 interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1381 \fIovecsize\fP as zero. However, if the pattern contains back references and
1382 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1383 has to get additional memory for use during matching. Thus it is usually
1384 advisable to supply an \fIovector\fP.
1385 .P
1386 The \fBpcre_info()\fP function can be used to find out how many capturing
1387 subpatterns there are in a compiled pattern. The smallest size for
1388 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1389 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1390 .P
1391 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1392 the subject when subpattern \fIn\fP has not been used at all. For example, if
1393 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1394 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1395 happens, both values in the offset pairs corresponding to unused subpatterns
1396 are set to -1.
1397 .P
1398 Offset values that correspond to unused subpatterns at the end of the
1399 expression are also set to -1. For example, if the string "abc" is matched
1400 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1401 return from the function is 2, because the highest used capturing subpattern
1402 number is 1. However, you can refer to the offsets for the second and third
1403 capturing subpatterns if you wish (assuming the vector is large enough, of
1404 course).
1405 .P
1406 Some convenience functions are provided for extracting the captured substrings
1407 as separate strings. These are described below.
1408 .
1409 .\" HTML <a name="errorlist"></a>
1410 .SS "Error return values from \fBpcre_exec()\fP"
1411 .rs
1412 .sp
1413 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1414 defined in the header file:
1415 .sp
1417 .sp
1418 The subject string did not match the pattern.
1419 .sp
1421 .sp
1422 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1423 NULL and \fIovecsize\fP was not zero.
1424 .sp
1426 .sp
1427 An unrecognized bit was set in the \fIoptions\fP argument.
1428 .sp
1430 .sp
1431 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1432 the case when it is passed a junk pointer and to detect when a pattern that was
1433 compiled in an environment of one endianness is run in an environment with the
1434 other endianness. This is the error that PCRE gives when the magic number is
1435 not present.
1436 .sp
1438 .sp
1439 While running the pattern match, an unknown item was encountered in the
1440 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1441 of the compiled pattern.
1442 .sp
1444 .sp
1445 If a pattern contains back references, but the \fIovector\fP that is passed to
1446 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1447 gets a block of memory at the start of matching to use for this purpose. If the
1448 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1449 automatically freed at the end of matching.
1450 .sp
1452 .sp
1453 This error is used by the \fBpcre_copy_substring()\fP,
1454 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1455 below). It is never returned by \fBpcre_exec()\fP.
1456 .sp
1458 .sp
1459 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1460 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1461 above.
1462 .sp
1464 .sp
1465 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1466 use by callout functions that want to yield a distinctive error code. See the
1467 .\" HREF
1468 \fBpcrecallout\fP
1469 .\"
1470 documentation for details.
1471 .sp
1473 .sp
1474 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1475 .sp
1477 .sp
1478 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1479 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1480 .sp
1482 .sp
1483 The subject string did not match, but it did match partially. See the
1484 .\" HREF
1485 \fBpcrepartial\fP
1486 .\"
1487 documentation for details of partial matching.
1488 .sp
1490 .sp
1491 The PCRE_PARTIAL option was used with a compiled pattern containing items that
1492 are not supported for partial matching. See the
1493 .\" HREF
1494 \fBpcrepartial\fP
1495 .\"
1496 documentation for details of partial matching.
1497 .sp
1499 .sp
1500 An unexpected internal error has occurred. This error could be caused by a bug
1501 in PCRE or by overwriting of the compiled pattern.
1502 .sp
1504 .sp
1505 This error is given if the value of the \fIovecsize\fP argument is negative.
1506 .sp
1508 .sp
1509 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1510 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1511 description above.
1512 .sp
1514 .sp
1515 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1516 .P
1517 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1518 .
1519 .
1521 .rs
1522 .sp
1523 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1524 .ti +5n
1525 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1526 .ti +5n
1527 .B int \fIbuffersize\fP);
1528 .PP
1529 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1530 .ti +5n
1531 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1532 .ti +5n
1533 .B const char **\fIstringptr\fP);
1534 .PP
1535 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1536 .ti +5n
1537 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1538 .PP
1539 Captured substrings can be accessed directly by using the offsets returned by
1540 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1541 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1542 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1543 as new, separate, zero-terminated strings. These functions identify substrings
1544 by number. The next section describes functions for extracting named
1545 substrings.
1546 .P
1547 A substring that contains a binary zero is correctly extracted and has a
1548 further zero added on the end, but the result is not, of course, a C string.
1549 However, you can process such a string by referring to the length that is
1550 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1551 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1552 for handling strings containing binary zeros, because the end of the final
1553 string is not independently indicated.
1554 .P
1555 The first three arguments are the same for all three of these functions:
1556 \fIsubject\fP is the subject string that has just been successfully matched,
1557 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1558 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1559 captured by the match, including the substring that matched the entire regular
1560 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1561 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1562 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1563 number of elements in the vector divided by three.
1564 .P
1565 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1566 extract a single substring, whose number is given as \fIstringnumber\fP. A
1567 value of zero extracts the substring that matched the entire pattern, whereas
1568 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1569 the string is placed in \fIbuffer\fP, whose length is given by
1570 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1571 obtained via \fBpcre_malloc\fP, and its address is returned via
1572 \fIstringptr\fP. The yield of the function is the length of the string, not
1573 including the terminating zero, or one of these error codes:
1574 .sp
1576 .sp
1577 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1578 memory failed for \fBpcre_get_substring()\fP.
1579 .sp
1581 .sp
1582 There is no substring whose number is \fIstringnumber\fP.
1583 .P
1584 The \fBpcre_get_substring_list()\fP function extracts all available substrings
1585 and builds a list of pointers to them. All this is done in a single block of
1586 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1587 is returned via \fIlistptr\fP, which is also the start of the list of string
1588 pointers. The end of the list is marked by a NULL pointer. The yield of the
1589 function is zero if all went well, or the error code
1590 .sp
1592 .sp
1593 if the attempt to get the memory block failed.
1594 .P
1595 When any of these functions encounter a substring that is unset, which can
1596 happen when capturing subpattern number \fIn+1\fP matches some part of the
1597 subject, but subpattern \fIn\fP has not been used at all, they return an empty
1598 string. This can be distinguished from a genuine zero-length substring by
1599 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1600 substrings.
1601 .P
1602 The two convenience functions \fBpcre_free_substring()\fP and
1603 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1604 a previous call of \fBpcre_get_substring()\fP or
1605 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1606 the function pointed to by \fBpcre_free\fP, which of course could be called
1607 directly from a C program. However, PCRE is used in some situations where it is
1608 linked via a special interface to another programming language that cannot use
1609 \fBpcre_free\fP directly; it is for these cases that the functions are
1610 provided.
1611 .
1612 .
1614 .rs
1615 .sp
1616 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1617 .ti +5n
1618 .B const char *\fIname\fP);
1619 .PP
1620 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1621 .ti +5n
1622 .B const char *\fIsubject\fP, int *\fIovector\fP,
1623 .ti +5n
1624 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1625 .ti +5n
1626 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1627 .PP
1628 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1629 .ti +5n
1630 .B const char *\fIsubject\fP, int *\fIovector\fP,
1631 .ti +5n
1632 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1633 .ti +5n
1634 .B const char **\fIstringptr\fP);
1635 .PP
1636 To extract a substring by name, you first have to find associated number.
1637 For example, for this pattern
1638 .sp
1639 (a+)b(?<xxx>\ed+)...
1640 .sp
1641 the number of the subpattern called "xxx" is 2. If the name is known to be
1642 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1643 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1644 pattern, and the second is the name. The yield of the function is the
1645 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1646 that name.
1647 .P
1648 Given the number, you can extract the substring directly, or use one of the
1649 functions described in the previous section. For convenience, there are also
1650 two functions that do the whole job.
1651 .P
1652 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1653 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1654 functions that extract by number. As these are described in the previous
1655 section, they are not re-described here. There are just two differences:
1656 .P
1657 First, instead of a substring number, a substring name is given. Second, there
1658 is an extra argument, given at the start, which is a pointer to the compiled
1659 pattern. This is needed in order to gain access to the name-to-number
1660 translation table.
1661 .P
1662 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1663 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1664 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1665 the behaviour may not be what you want (see the next section).
1666 .
1667 .
1669 .rs
1670 .sp
1671 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1672 .ti +5n
1673 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1674 .PP
1675 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1676 are not required to be unique. Normally, patterns with duplicate names are such
1677 that in any one match, only one of the named subpatterns participates. An
1678 example is shown in the
1679 .\" HREF
1680 \fBpcrepattern\fP
1681 .\"
1682 documentation.
1683 .P
1684 When duplicates are present, \fBpcre_copy_named_substring()\fP and
1685 \fBpcre_get_named_substring()\fP return the first substring corresponding to
1686 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1687 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1688 returns one of the numbers that are associated with the name, but it is not
1689 defined which it is.
1690 .P
1691 If you want to get full details of all captured substrings for a given name,
1692 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1693 argument is the compiled pattern, and the second is the name. The third and
1694 fourth are pointers to variables which are updated by the function. After it
1695 has run, they point to the first and last entries in the name-to-number table
1696 for the given name. The function itself returns the length of each entry, or
1697 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1698 described above in the section entitled \fIInformation about a pattern\fP.
1699 Given all the relevant entries for the name, you can extract each of their
1700 numbers, and hence the captured data, if any.
1701 .
1702 .
1704 .rs
1705 .sp
1706 The traditional matching function uses a similar algorithm to Perl, which stops
1707 when it finds the first match, starting at a given point in the subject. If you
1708 want to find all possible matches, or the longest possible match, consider
1709 using the alternative matching function (see below) instead. If you cannot use
1710 the alternative function, but still need to find all possible matches, you
1711 can kludge it up by making use of the callout facility, which is described in
1712 the
1713 .\" HREF
1714 \fBpcrecallout\fP
1715 .\"
1716 documentation.
1717 .P
1718 What you have to do is to insert a callout right at the end of the pattern.
1719 When your callout function is called, extract and save the current matched
1720 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1721 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1722 will yield PCRE_ERROR_NOMATCH.
1723 .
1724 .
1725 .\" HTML <a name="dfamatch"></a>
1727 .rs
1728 .sp
1729 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1730 .ti +5n
1731 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1732 .ti +5n
1733 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1734 .ti +5n
1735 .B int *\fIworkspace\fP, int \fIwscount\fP);
1736 .P
1737 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1738 a compiled pattern, using a matching algorithm that scans the subject string
1739 just once, and does not backtrack. This has different characteristics to the
1740 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1741 patterns are not supported. Nevertheless, there are times when this kind of
1742 matching can be useful. For a discussion of the two matching algorithms, see
1743 the
1744 .\" HREF
1745 \fBpcrematching\fP
1746 .\"
1747 documentation.
1748 .P
1749 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1750 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1751 different way, and this is described below. The other common arguments are used
1752 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1753 here.
1754 .P
1755 The two additional arguments provide workspace for the function. The workspace
1756 vector should contain at least 20 elements. It is used for keeping track of
1757 multiple paths through the pattern tree. More workspace will be needed for
1758 patterns and subjects where there are a lot of potential matches.
1759 .P
1760 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1761 .sp
1762 int rc;
1763 int ovector[10];
1764 int wspace[20];
1765 rc = pcre_dfa_exec(
1766 re, /* result of pcre_compile() */
1767 NULL, /* we didn't study the pattern */
1768 "some string", /* the subject string */
1769 11, /* the length of the subject string */
1770 0, /* start at offset 0 in the subject */
1771 0, /* default options */
1772 ovector, /* vector of integers for substring information */
1773 10, /* number of elements (NOT size in bytes) */
1774 wspace, /* working space vector */
1775 20); /* number of elements (NOT size in bytes) */
1776 .
1777 .SS "Option bits for \fBpcre_dfa_exec()\fP"
1778 .rs
1779 .sp
1780 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1781 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1783 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1784 the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1785 .sp
1787 .sp
1788 This has the same general effect as it does for \fBpcre_exec()\fP, but the
1789 details are slightly different. When PCRE_PARTIAL is set for
1790 \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1791 PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1792 complete matches, but there is still at least one matching possibility. The
1793 portion of the string that provided the partial match is set as the first
1794 matching string.
1795 .sp
1797 .sp
1798 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1799 soon as it has found one match. Because of the way the alternative algorithm
1800 works, this is necessarily the shortest possible match at the first possible
1801 matching point in the subject string.
1802 .sp
1804 .sp
1805 When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1806 a partial match, it is possible to call it again, with additional subject
1807 characters, and have it continue with the same match. The PCRE_DFA_RESTART
1808 option requests this action; when it is set, the \fIworkspace\fP and
1809 \fIwscount\fP options must reference the same vector as before because data
1810 about the match so far is left in them after a partial match. There is more
1811 discussion of this facility in the
1812 .\" HREF
1813 \fBpcrepartial\fP
1814 .\"
1815 documentation.
1816 .
1817 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1818 .rs
1819 .sp
1820 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1821 substring in the subject. Note, however, that all the matches from one run of
1822 the function start at the same point in the subject. The shorter matches are
1823 all initial substrings of the longer matches. For example, if the pattern
1824 .sp
1825 <.*>
1826 .sp
1827 is matched against the string
1828 .sp
1829 This is <something> <something else> <something further> no more
1830 .sp
1831 the three matched strings are
1832 .sp
1833 <something>
1834 <something> <something else>
1835 <something> <something else> <something further>
1836 .sp
1837 On success, the yield of the function is a number greater than zero, which is
1838 the number of matched substrings. The substrings themselves are returned in
1839 \fIovector\fP. Each string uses two elements; the first is the offset to the
1840 start, and the second is the offset to the end. In fact, all the strings have
1841 the same start offset. (Space could have been saved by giving this only once,
1842 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1843 returns data, even though the meaning of the strings is different.)
1844 .P
1845 The strings are returned in reverse order of length; that is, the longest
1846 matching string is given first. If there were too many matches to fit into
1847 \fIovector\fP, the yield of the function is zero, and the vector is filled with
1848 the longest matches.
1849 .
1850 .SS "Error returns from \fBpcre_dfa_exec()\fP"
1851 .rs
1852 .sp
1853 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1854 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1855 described
1856 .\" HTML <a href="#errorlist">
1857 .\" </a>
1858 above.
1859 .\"
1860 There are in addition the following errors that are specific to
1861 \fBpcre_dfa_exec()\fP:
1862 .sp
1864 .sp
1865 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1866 that it does not support, for instance, the use of \eC or a back reference.
1867 .sp
1869 .sp
1870 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1871 uses a back reference for the condition, or a test for recursion in a specific
1872 group. These are not supported.
1873 .sp
1875 .sp
1876 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1877 block that contains a setting of the \fImatch_limit\fP field. This is not
1878 supported (it is meaningless).
1879 .sp
1881 .sp
1882 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1883 \fIworkspace\fP vector.
1884 .sp
1886 .sp
1887 When a recursive subpattern is processed, the matching function calls itself
1888 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1889 error is given if the output vector is not large enough. This should be
1890 extremely rare, as a vector of size 1000 is used.
1891 .
1892 .
1893 .SH "SEE ALSO"
1894 .rs
1895 .sp
1896 \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1897 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1898 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1899 .
1900 .
1902 .rs
1903 .sp
1904 .nf
1905 Philip Hazel
1906 University Computing Service
1907 Cambridge CB2 3QH, England.
1908 .fi
1909 .
1910 .
1912 .rs
1913 .sp
1914 .nf
1915 Last updated: 21 August 2007
1916 Copyright (c) 1997-2007 University of Cambridge.
1917 .fi


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