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1 .TH PCREAPI 3
2 .SH NAME
3 PCRE - Perl-compatible regular expressions
4 .SH "PCRE NATIVE API"
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 .
112 .SH "PCRE API OVERVIEW"
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 compile and 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 .
221 .\" HTML <a name="newlines"></a>
222 .SH NEWLINES
223 .rs
224 .sp
225 PCRE supports five different conventions for indicating line breaks in
226 strings: a single CR (carriage return) character, a single LF (linefeed)
227 character, the two-character sequence CRLF, any of the three preceding, or any
228 Unicode newline sequence. The Unicode newline sequences are the three just
229 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
230 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
231 (paragraph separator, U+2029).
232 .P
233 Each of the first three conventions is used by at least one operating system as
234 its standard newline sequence. When PCRE is built, a default can be specified.
235 The default default is LF, which is the Unix standard. When PCRE is run, the
236 default can be overridden, either when a pattern is compiled, or when it is
237 matched.
238 .P
239 At compile time, the newline convention can be specified by the \fIoptions\fP
240 argument of \fBpcre_compile()\fP, or it can be specified by special text at the
241 start of the pattern itself; this overrides any other settings. See the
242 .\" HREF
243 \fBpcrepattern\fP
244 .\"
245 page for details of the special character sequences.
246 .P
247 In the PCRE documentation the word "newline" is used to mean "the character or
248 pair of characters that indicate a line break". The choice of newline
249 convention affects the handling of the dot, circumflex, and dollar
250 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
251 recognized line ending sequence, the match position advancement for a
252 non-anchored pattern. There is more detail about this in the
253 .\" HTML <a href="#execoptions">
254 .\" </a>
255 section on \fBpcre_exec()\fP options
256 .\"
257 below.
258 .P
259 The choice of newline convention does not affect the interpretation of
260 the \en or \er escape sequences, nor does it affect what \eR matches, which is
261 controlled in a similar way, but by separate options.
262 .
263 .
264 .SH MULTITHREADING
265 .rs
266 .sp
267 The PCRE functions can be used in multi-threading applications, with the
268 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
269 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
270 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
271 .P
272 The compiled form of a regular expression is not altered during matching, so
273 the same compiled pattern can safely be used by several threads at once.
274 .
275 .
276 .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
277 .rs
278 .sp
279 The compiled form of a regular expression can be saved and re-used at a later
280 time, possibly by a different program, and even on a host other than the one on
281 which it was compiled. Details are given in the
282 .\" HREF
283 \fBpcreprecompile\fP
284 .\"
285 documentation. However, compiling a regular expression with one version of PCRE
286 for use with a different version is not guaranteed to work and may cause
287 crashes.
288 .
289 .
290 .SH "CHECKING BUILD-TIME OPTIONS"
291 .rs
292 .sp
293 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
294 .PP
295 The function \fBpcre_config()\fP makes it possible for a PCRE client to
296 discover which optional features have been compiled into the PCRE library. The
297 .\" HREF
298 \fBpcrebuild\fP
299 .\"
300 documentation has more details about these optional features.
301 .P
302 The first argument for \fBpcre_config()\fP is an integer, specifying which
303 information is required; the second argument is a pointer to a variable into
304 which the information is placed. The following information is available:
305 .sp
306 PCRE_CONFIG_UTF8
307 .sp
308 The output is an integer that is set to one if UTF-8 support is available;
309 otherwise it is set to zero.
310 .sp
311 PCRE_CONFIG_UNICODE_PROPERTIES
312 .sp
313 The output is an integer that is set to one if support for Unicode character
314 properties is available; otherwise it is set to zero.
315 .sp
316 PCRE_CONFIG_NEWLINE
317 .sp
318 The output is an integer whose value specifies the default character sequence
319 that is recognized as meaning "newline". The four values that are supported
320 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY. The
321 default should normally be the standard sequence for your operating system.
322 .sp
323 PCRE_CONFIG_BSR
324 .sp
325 The output is an integer whose value indicates what character sequences the \eR
326 escape sequence matches by default. A value of 0 means that \eR matches any
327 Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
328 or CRLF. The default can be overridden when a pattern is compiled or matched.
329 .sp
330 PCRE_CONFIG_LINK_SIZE
331 .sp
332 The output is an integer that contains the number of bytes used for internal
333 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
334 allow larger regular expressions to be compiled, at the expense of slower
335 matching. The default value of 2 is sufficient for all but the most massive
336 patterns, since it allows the compiled pattern to be up to 64K in size.
337 .sp
338 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
339 .sp
340 The output is an integer that contains the threshold above which the POSIX
341 interface uses \fBmalloc()\fP for output vectors. Further details are given in
342 the
343 .\" HREF
344 \fBpcreposix\fP
345 .\"
346 documentation.
347 .sp
348 PCRE_CONFIG_MATCH_LIMIT
349 .sp
350 The output is a long integer that gives the default limit for the number of
351 internal matching function calls in a \fBpcre_exec()\fP execution. Further
352 details are given with \fBpcre_exec()\fP below.
353 .sp
354 PCRE_CONFIG_MATCH_LIMIT_RECURSION
355 .sp
356 The output is a long integer that gives the default limit for the depth of
357 recursion when calling the internal matching function in a \fBpcre_exec()\fP
358 execution. Further details are given with \fBpcre_exec()\fP below.
359 .sp
360 PCRE_CONFIG_STACKRECURSE
361 .sp
362 The output is an integer that is set to one if internal recursion when running
363 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
364 to remember their state. This is the usual way that PCRE is compiled. The
365 output is zero if PCRE was compiled to use blocks of data on the heap instead
366 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
367 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
368 avoiding the use of the stack.
369 .
370 .
371 .SH "COMPILING A PATTERN"
372 .rs
373 .sp
374 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
375 .ti +5n
376 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
377 .ti +5n
378 .B const unsigned char *\fItableptr\fP);
379 .sp
380 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
381 .ti +5n
382 .B int *\fIerrorcodeptr\fP,
383 .ti +5n
384 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
385 .ti +5n
386 .B const unsigned char *\fItableptr\fP);
387 .P
388 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
389 called to compile a pattern into an internal form. The only difference between
390 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
391 \fIerrorcodeptr\fP, via which a numerical error code can be returned.
392 .P
393 The pattern is a C string terminated by a binary zero, and is passed in the
394 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
395 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
396 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
397 for a structure whose contents are not externally defined. It is up to the
398 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
399 .P
400 Although the compiled code of a PCRE regex is relocatable, that is, it does not
401 depend on memory location, the complete \fBpcre\fP data block is not
402 fully relocatable, because it may contain a copy of the \fItableptr\fP
403 argument, which is an address (see below).
404 .P
405 The \fIoptions\fP argument contains various bit settings that affect the
406 compilation. It should be zero if no options are required. The available
407 options are described below. Some of them, in particular, those that are
408 compatible with Perl, can also be set and unset from within the pattern (see
409 the detailed description in the
410 .\" HREF
411 \fBpcrepattern\fP
412 .\"
413 documentation). For these options, the contents of the \fIoptions\fP argument
414 specifies their initial settings at the start of compilation and execution. The
415 PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
416 matching as well as at compile time.
417 .P
418 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
419 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
420 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
421 error message. This is a static string that is part of the library. You must
422 not try to free it. The offset from the start of the pattern to the character
423 where the error was discovered is placed in the variable pointed to by
424 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
425 .P
426 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
427 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
428 returned via this argument in the event of an error. This is in addition to the
429 textual error message. Error codes and messages are listed below.
430 .P
431 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
432 character tables that are built when PCRE is compiled, using the default C
433 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
434 call to \fBpcre_maketables()\fP. This value is stored with the compiled
435 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
436 passed to it. For more discussion, see the section on locale support below.
437 .P
438 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
439 .sp
440 pcre *re;
441 const char *error;
442 int erroffset;
443 re = pcre_compile(
444 "^A.*Z", /* the pattern */
445 0, /* default options */
446 &error, /* for error message */
447 &erroffset, /* for error offset */
448 NULL); /* use default character tables */
449 .sp
450 The following names for option bits are defined in the \fBpcre.h\fP header
451 file:
452 .sp
453 PCRE_ANCHORED
454 .sp
455 If this bit is set, the pattern is forced to be "anchored", that is, it is
456 constrained to match only at the first matching point in the string that is
457 being searched (the "subject string"). This effect can also be achieved by
458 appropriate constructs in the pattern itself, which is the only way to do it in
459 Perl.
460 .sp
461 PCRE_AUTO_CALLOUT
462 .sp
463 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
464 all with number 255, before each pattern item. For discussion of the callout
465 facility, see the
466 .\" HREF
467 \fBpcrecallout\fP
468 .\"
469 documentation.
470 .sp
471 PCRE_BSR_ANYCRLF
472 PCRE_BSR_UNICODE
473 .sp
474 These options (which are mutually exclusive) control what the \eR escape
475 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
476 match any Unicode newline sequence. The default is specified when PCRE is
477 built. It can be overridden from within the pattern, or by setting an option
478 when a compiled pattern is matched.
479 .sp
480 PCRE_CASELESS
481 .sp
482 If this bit is set, letters in the pattern match both upper and lower case
483 letters. It is equivalent to Perl's /i option, and it can be changed within a
484 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
485 concept of case for characters whose values are less than 128, so caseless
486 matching is always possible. For characters with higher values, the concept of
487 case is supported if PCRE is compiled with Unicode property support, but not
488 otherwise. If you want to use caseless matching for characters 128 and above,
489 you must ensure that PCRE is compiled with Unicode property support as well as
490 with UTF-8 support.
491 .sp
492 PCRE_DOLLAR_ENDONLY
493 .sp
494 If this bit is set, a dollar metacharacter in the pattern matches only at the
495 end of the subject string. Without this option, a dollar also matches
496 immediately before a newline at the end of the string (but not before any other
497 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
498 There is no equivalent to this option in Perl, and no way to set it within a
499 pattern.
500 .sp
501 PCRE_DOTALL
502 .sp
503 If this bit is set, a dot metacharater in the pattern matches all characters,
504 including those that indicate newline. Without it, a dot does not match when
505 the current position is at a newline. This option is equivalent to Perl's /s
506 option, and it can be changed within a pattern by a (?s) option setting. A
507 negative class such as [^a] always matches newline characters, independent of
508 the setting of this option.
509 .sp
510 PCRE_DUPNAMES
511 .sp
512 If this bit is set, names used to identify capturing subpatterns need not be
513 unique. This can be helpful for certain types of pattern when it is known that
514 only one instance of the named subpattern can ever be matched. There are more
515 details of named subpatterns below; see also the
516 .\" HREF
517 \fBpcrepattern\fP
518 .\"
519 documentation.
520 .sp
521 PCRE_EXTENDED
522 .sp
523 If this bit is set, whitespace data characters in the pattern are totally
524 ignored except when escaped or inside a character class. Whitespace does not
525 include the VT character (code 11). In addition, characters between an
526 unescaped # outside a character class and the next newline, inclusive, are also
527 ignored. This is equivalent to Perl's /x option, and it can be changed within a
528 pattern by a (?x) option setting.
529 .P
530 This option makes it possible to include comments inside complicated patterns.
531 Note, however, that this applies only to data characters. Whitespace characters
532 may never appear within special character sequences in a pattern, for example
533 within the sequence (?( which introduces a conditional subpattern.
534 .sp
535 PCRE_EXTRA
536 .sp
537 This option was invented in order to turn on additional functionality of PCRE
538 that is incompatible with Perl, but it is currently of very little use. When
539 set, any backslash in a pattern that is followed by a letter that has no
540 special meaning causes an error, thus reserving these combinations for future
541 expansion. By default, as in Perl, a backslash followed by a letter with no
542 special meaning is treated as a literal. (Perl can, however, be persuaded to
543 give a warning for this.) There are at present no other features controlled by
544 this option. It can also be set by a (?X) option setting within a pattern.
545 .sp
546 PCRE_FIRSTLINE
547 .sp
548 If this option is set, an unanchored pattern is required to match before or at
549 the first newline in the subject string, though the matched text may continue
550 over the newline.
551 .sp
552 PCRE_JAVASCRIPT_COMPAT
553 .sp
554 If this option is set, PCRE's behaviour is changed in some ways so that it is
555 compatible with JavaScript rather than Perl. The changes are as follows:
556 .P
557 (1) A lone closing square bracket in a pattern causes a compile-time error,
558 because this is illegal in JavaScript (by default it is treated as a data
559 character). Thus, the pattern AB]CD becomes illegal when this option is set.
560 .P
561 (2) At run time, a back reference to an unset subpattern group matches an empty
562 string (by default this causes the current matching alternative to fail). A
563 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
564 an "a" in the subject), whereas it fails by default, for Perl compatibility.
565 .sp
566 PCRE_MULTILINE
567 .sp
568 By default, PCRE treats the subject string as consisting of a single line of
569 characters (even if it actually contains newlines). The "start of line"
570 metacharacter (^) matches only at the start of the string, while the "end of
571 line" metacharacter ($) matches only at the end of the string, or before a
572 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
573 Perl.
574 .P
575 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
576 match immediately following or immediately before internal newlines in the
577 subject string, respectively, as well as at the very start and end. This is
578 equivalent to Perl's /m option, and it can be changed within a pattern by a
579 (?m) option setting. If there are no newlines in a subject string, or no
580 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
581 .sp
582 PCRE_NEWLINE_CR
583 PCRE_NEWLINE_LF
584 PCRE_NEWLINE_CRLF
585 PCRE_NEWLINE_ANYCRLF
586 PCRE_NEWLINE_ANY
587 .sp
588 These options override the default newline definition that was chosen when PCRE
589 was built. Setting the first or the second specifies that a newline is
590 indicated by a single character (CR or LF, respectively). Setting
591 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
592 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
593 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
594 that any Unicode newline sequence should be recognized. The Unicode newline
595 sequences are the three just mentioned, plus the single characters VT (vertical
596 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
597 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
598 recognized only in UTF-8 mode.
599 .P
600 The newline setting in the options word uses three bits that are treated
601 as a number, giving eight possibilities. Currently only six are used (default
602 plus the five values above). This means that if you set more than one newline
603 option, the combination may or may not be sensible. For example,
604 PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
605 other combinations may yield unused numbers and cause an error.
606 .P
607 The only time that a line break is specially recognized when compiling a
608 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
609 class is encountered. This indicates a comment that lasts until after the next
610 line break sequence. In other circumstances, line break sequences are treated
611 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
612 as whitespace characters and are therefore ignored.
613 .P
614 The newline option that is set at compile time becomes the default that is used
615 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
616 .sp
617 PCRE_NO_AUTO_CAPTURE
618 .sp
619 If this option is set, it disables the use of numbered capturing parentheses in
620 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
621 were followed by ?: but named parentheses can still be used for capturing (and
622 they acquire numbers in the usual way). There is no equivalent of this option
623 in Perl.
624 .sp
625 PCRE_UNGREEDY
626 .sp
627 This option inverts the "greediness" of the quantifiers so that they are not
628 greedy by default, but become greedy if followed by "?". It is not compatible
629 with Perl. It can also be set by a (?U) option setting within the pattern.
630 .sp
631 PCRE_UTF8
632 .sp
633 This option causes PCRE to regard both the pattern and the subject as strings
634 of UTF-8 characters instead of single-byte character strings. However, it is
635 available only when PCRE is built to include UTF-8 support. If not, the use
636 of this option provokes an error. Details of how this option changes the
637 behaviour of PCRE are given in the
638 .\" HTML <a href="pcre.html#utf8support">
639 .\" </a>
640 section on UTF-8 support
641 .\"
642 in the main
643 .\" HREF
644 \fBpcre\fP
645 .\"
646 page.
647 .sp
648 PCRE_NO_UTF8_CHECK
649 .sp
650 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
651 automatically checked. There is a discussion about the
652 .\" HTML <a href="pcre.html#utf8strings">
653 .\" </a>
654 validity of UTF-8 strings
655 .\"
656 in the main
657 .\" HREF
658 \fBpcre\fP
659 .\"
660 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
661 returns an error. If you already know that your pattern is valid, and you want
662 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
663 option. When it is set, the effect of passing an invalid UTF-8 string as a
664 pattern is undefined. It may cause your program to crash. Note that this option
665 can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
666 the UTF-8 validity checking of subject strings.
667 .
668 .
669 .SH "COMPILATION ERROR CODES"
670 .rs
671 .sp
672 The following table lists the error codes than may be returned by
673 \fBpcre_compile2()\fP, along with the error messages that may be returned by
674 both compiling functions. As PCRE has developed, some error codes have fallen
675 out of use. To avoid confusion, they have not been re-used.
676 .sp
677 0 no error
678 1 \e at end of pattern
679 2 \ec at end of pattern
680 3 unrecognized character follows \e
681 4 numbers out of order in {} quantifier
682 5 number too big in {} quantifier
683 6 missing terminating ] for character class
684 7 invalid escape sequence in character class
685 8 range out of order in character class
686 9 nothing to repeat
687 10 [this code is not in use]
688 11 internal error: unexpected repeat
689 12 unrecognized character after (? or (?-
690 13 POSIX named classes are supported only within a class
691 14 missing )
692 15 reference to non-existent subpattern
693 16 erroffset passed as NULL
694 17 unknown option bit(s) set
695 18 missing ) after comment
696 19 [this code is not in use]
697 20 regular expression is too large
698 21 failed to get memory
699 22 unmatched parentheses
700 23 internal error: code overflow
701 24 unrecognized character after (?<
702 25 lookbehind assertion is not fixed length
703 26 malformed number or name after (?(
704 27 conditional group contains more than two branches
705 28 assertion expected after (?(
706 29 (?R or (?[+-]digits must be followed by )
707 30 unknown POSIX class name
708 31 POSIX collating elements are not supported
709 32 this version of PCRE is not compiled with PCRE_UTF8 support
710 33 [this code is not in use]
711 34 character value in \ex{...} sequence is too large
712 35 invalid condition (?(0)
713 36 \eC not allowed in lookbehind assertion
714 37 PCRE does not support \eL, \el, \eN, \eU, or \eu
715 38 number after (?C is > 255
716 39 closing ) for (?C expected
717 40 recursive call could loop indefinitely
718 41 unrecognized character after (?P
719 42 syntax error in subpattern name (missing terminator)
720 43 two named subpatterns have the same name
721 44 invalid UTF-8 string
722 45 support for \eP, \ep, and \eX has not been compiled
723 46 malformed \eP or \ep sequence
724 47 unknown property name after \eP or \ep
725 48 subpattern name is too long (maximum 32 characters)
726 49 too many named subpatterns (maximum 10000)
727 50 [this code is not in use]
728 51 octal value is greater than \e377 (not in UTF-8 mode)
729 52 internal error: overran compiling workspace
730 53 internal error: previously-checked referenced subpattern not found
731 54 DEFINE group contains more than one branch
732 55 repeating a DEFINE group is not allowed
733 56 inconsistent NEWLINE options
734 57 \eg is not followed by a braced, angle-bracketed, or quoted
735 name/number or by a plain number
736 58 a numbered reference must not be zero
737 59 (*VERB) with an argument is not supported
738 60 (*VERB) not recognized
739 61 number is too big
740 62 subpattern name expected
741 63 digit expected after (?+
742 64 ] is an invalid data character in JavaScript compatibility mode
743 .sp
744 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
745 be used if the limits were changed when PCRE was built.
746 .
747 .
748 .SH "STUDYING A PATTERN"
749 .rs
750 .sp
751 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
752 .ti +5n
753 .B const char **\fIerrptr\fP);
754 .PP
755 If a compiled pattern is going to be used several times, it is worth spending
756 more time analyzing it in order to speed up the time taken for matching. The
757 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
758 argument. If studying the pattern produces additional information that will
759 help speed up matching, \fBpcre_study()\fP returns a pointer to a
760 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
761 results of the study.
762 .P
763 The returned value from \fBpcre_study()\fP can be passed directly to
764 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
765 fields that can be set by the caller before the block is passed; these are
766 described
767 .\" HTML <a href="#extradata">
768 .\" </a>
769 below
770 .\"
771 in the section on matching a pattern.
772 .P
773 If studying the pattern does not produce any additional information
774 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
775 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
776 own \fBpcre_extra\fP block.
777 .P
778 The second argument of \fBpcre_study()\fP contains option bits. At present, no
779 options are defined, and this argument should always be zero.
780 .P
781 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
782 studying succeeds (even if no data is returned), the variable it points to is
783 set to NULL. Otherwise it is set to point to a textual error message. This is a
784 static string that is part of the library. You must not try to free it. You
785 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
786 sure that it has run successfully.
787 .P
788 This is a typical call to \fBpcre_study\fP():
789 .sp
790 pcre_extra *pe;
791 pe = pcre_study(
792 re, /* result of pcre_compile() */
793 0, /* no options exist */
794 &error); /* set to NULL or points to a message */
795 .sp
796 At present, studying a pattern is useful only for non-anchored patterns that do
797 not have a single fixed starting character. A bitmap of possible starting
798 bytes is created.
799 .
800 .
801 .\" HTML <a name="localesupport"></a>
802 .SH "LOCALE SUPPORT"
803 .rs
804 .sp
805 PCRE handles caseless matching, and determines whether characters are letters,
806 digits, or whatever, by reference to a set of tables, indexed by character
807 value. When running in UTF-8 mode, this applies only to characters with codes
808 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
809 can be tested with \ep if PCRE is built with Unicode character property
810 support. The use of locales with Unicode is discouraged. If you are handling
811 characters with codes greater than 128, you should either use UTF-8 and
812 Unicode, or use locales, but not try to mix the two.
813 .P
814 PCRE contains an internal set of tables that are used when the final argument
815 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
816 Normally, the internal tables recognize only ASCII characters. However, when
817 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
818 default "C" locale of the local system, which may cause them to be different.
819 .P
820 The internal tables can always be overridden by tables supplied by the
821 application that calls PCRE. These may be created in a different locale from
822 the default. As more and more applications change to using Unicode, the need
823 for this locale support is expected to die away.
824 .P
825 External tables are built by calling the \fBpcre_maketables()\fP function,
826 which has no arguments, in the relevant locale. The result can then be passed
827 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
828 example, to build and use tables that are appropriate for the French locale
829 (where accented characters with values greater than 128 are treated as letters),
830 the following code could be used:
831 .sp
832 setlocale(LC_CTYPE, "fr_FR");
833 tables = pcre_maketables();
834 re = pcre_compile(..., tables);
835 .sp
836 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
837 are using Windows, the name for the French locale is "french".
838 .P
839 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
840 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
841 that the memory containing the tables remains available for as long as it is
842 needed.
843 .P
844 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
845 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
846 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
847 pattern, compilation, studying and matching all happen in the same locale, but
848 different patterns can be compiled in different locales.
849 .P
850 It is possible to pass a table pointer or NULL (indicating the use of the
851 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
852 this facility could be used to match a pattern in a different locale from the
853 one in which it was compiled. Passing table pointers at run time is discussed
854 below in the section on matching a pattern.
855 .
856 .
857 .SH "INFORMATION ABOUT A PATTERN"
858 .rs
859 .sp
860 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
861 .ti +5n
862 .B int \fIwhat\fP, void *\fIwhere\fP);
863 .PP
864 The \fBpcre_fullinfo()\fP function returns information about a compiled
865 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
866 nevertheless retained for backwards compability (and is documented below).
867 .P
868 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
869 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
870 the pattern was not studied. The third argument specifies which piece of
871 information is required, and the fourth argument is a pointer to a variable
872 to receive the data. The yield of the function is zero for success, or one of
873 the following negative numbers:
874 .sp
875 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
876 the argument \fIwhere\fP was NULL
877 PCRE_ERROR_BADMAGIC the "magic number" was not found
878 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
879 .sp
880 The "magic number" is placed at the start of each compiled pattern as an simple
881 check against passing an arbitrary memory pointer. Here is a typical call of
882 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
883 .sp
884 int rc;
885 size_t length;
886 rc = pcre_fullinfo(
887 re, /* result of pcre_compile() */
888 pe, /* result of pcre_study(), or NULL */
889 PCRE_INFO_SIZE, /* what is required */
890 &length); /* where to put the data */
891 .sp
892 The possible values for the third argument are defined in \fBpcre.h\fP, and are
893 as follows:
894 .sp
895 PCRE_INFO_BACKREFMAX
896 .sp
897 Return the number of the highest back reference in the pattern. The fourth
898 argument should point to an \fBint\fP variable. Zero is returned if there are
899 no back references.
900 .sp
901 PCRE_INFO_CAPTURECOUNT
902 .sp
903 Return the number of capturing subpatterns in the pattern. The fourth argument
904 should point to an \fBint\fP variable.
905 .sp
906 PCRE_INFO_DEFAULT_TABLES
907 .sp
908 Return a pointer to the internal default character tables within PCRE. The
909 fourth argument should point to an \fBunsigned char *\fP variable. This
910 information call is provided for internal use by the \fBpcre_study()\fP
911 function. External callers can cause PCRE to use its internal tables by passing
912 a NULL table pointer.
913 .sp
914 PCRE_INFO_FIRSTBYTE
915 .sp
916 Return information about the first byte of any matched string, for a
917 non-anchored pattern. The fourth argument should point to an \fBint\fP
918 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
919 still recognized for backwards compatibility.)
920 .P
921 If there is a fixed first byte, for example, from a pattern such as
922 (cat|cow|coyote), its value is returned. Otherwise, if either
923 .sp
924 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
925 starts with "^", or
926 .sp
927 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
928 (if it were set, the pattern would be anchored),
929 .sp
930 -1 is returned, indicating that the pattern matches only at the start of a
931 subject string or after any newline within the string. Otherwise -2 is
932 returned. For anchored patterns, -2 is returned.
933 .sp
934 PCRE_INFO_FIRSTTABLE
935 .sp
936 If the pattern was studied, and this resulted in the construction of a 256-bit
937 table indicating a fixed set of bytes for the first byte in any matching
938 string, a pointer to the table is returned. Otherwise NULL is returned. The
939 fourth argument should point to an \fBunsigned char *\fP variable.
940 .sp
941 PCRE_INFO_HASCRORLF
942 .sp
943 Return 1 if the pattern contains any explicit matches for CR or LF characters,
944 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
945 explicit match is either a literal CR or LF character, or \er or \en.
946 .sp
947 PCRE_INFO_JCHANGED
948 .sp
949 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
950 0. The fourth argument should point to an \fBint\fP variable. (?J) and
951 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
952 .sp
953 PCRE_INFO_LASTLITERAL
954 .sp
955 Return the value of the rightmost literal byte that must exist in any matched
956 string, other than at its start, if such a byte has been recorded. The fourth
957 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
958 returned. For anchored patterns, a last literal byte is recorded only if it
959 follows something of variable length. For example, for the pattern
960 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
961 is -1.
962 .sp
963 PCRE_INFO_NAMECOUNT
964 PCRE_INFO_NAMEENTRYSIZE
965 PCRE_INFO_NAMETABLE
966 .sp
967 PCRE supports the use of named as well as numbered capturing parentheses. The
968 names are just an additional way of identifying the parentheses, which still
969 acquire numbers. Several convenience functions such as
970 \fBpcre_get_named_substring()\fP are provided for extracting captured
971 substrings by name. It is also possible to extract the data directly, by first
972 converting the name to a number in order to access the correct pointers in the
973 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
974 you need to use the name-to-number map, which is described by these three
975 values.
976 .P
977 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
978 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
979 entry; both of these return an \fBint\fP value. The entry size depends on the
980 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
981 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
982 are the number of the capturing parenthesis, most significant byte first. The
983 rest of the entry is the corresponding name, zero terminated. The names are in
984 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
985 their parentheses numbers. For example, consider the following pattern (assume
986 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
987 .sp
988 .\" JOIN
989 (?<date> (?<year>(\ed\ed)?\ed\ed) -
990 (?<month>\ed\ed) - (?<day>\ed\ed) )
991 .sp
992 There are four named subpatterns, so the table has four entries, and each entry
993 in the table is eight bytes long. The table is as follows, with non-printing
994 bytes shows in hexadecimal, and undefined bytes shown as ??:
995 .sp
996 00 01 d a t e 00 ??
997 00 05 d a y 00 ?? ??
998 00 04 m o n t h 00
999 00 02 y e a r 00 ??
1000 .sp
1001 When writing code to extract data from named subpatterns using the
1002 name-to-number map, remember that the length of the entries is likely to be
1003 different for each compiled pattern.
1004 .sp
1005 PCRE_INFO_OKPARTIAL
1006 .sp
1007 Return 1 if the pattern can be used for partial matching, otherwise 0. The
1008 fourth argument should point to an \fBint\fP variable. The
1009 .\" HREF
1010 \fBpcrepartial\fP
1011 .\"
1012 documentation lists the restrictions that apply to patterns when partial
1013 matching is used.
1014 .sp
1015 PCRE_INFO_OPTIONS
1016 .sp
1017 Return a copy of the options with which the pattern was compiled. The fourth
1018 argument should point to an \fBunsigned long int\fP variable. These option bits
1019 are those specified in the call to \fBpcre_compile()\fP, modified by any
1020 top-level option settings at the start of the pattern itself. In other words,
1021 they are the options that will be in force when matching starts. For example,
1022 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1023 result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1024 .P
1025 A pattern is automatically anchored by PCRE if all of its top-level
1026 alternatives begin with one of the following:
1027 .sp
1028 ^ unless PCRE_MULTILINE is set
1029 \eA always
1030 \eG always
1031 .\" JOIN
1032 .* if PCRE_DOTALL is set and there are no back
1033 references to the subpattern in which .* appears
1034 .sp
1035 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1036 \fBpcre_fullinfo()\fP.
1037 .sp
1038 PCRE_INFO_SIZE
1039 .sp
1040 Return the size of the compiled pattern, that is, the value that was passed as
1041 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1042 place the compiled data. The fourth argument should point to a \fBsize_t\fP
1043 variable.
1044 .sp
1045 PCRE_INFO_STUDYSIZE
1046 .sp
1047 Return the size of the data block pointed to by the \fIstudy_data\fP field in
1048 a \fBpcre_extra\fP block. That is, it is the value that was passed to
1049 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1050 created by \fBpcre_study()\fP. The fourth argument should point to a
1051 \fBsize_t\fP variable.
1052 .
1053 .
1054 .SH "OBSOLETE INFO FUNCTION"
1055 .rs
1056 .sp
1057 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1058 .B *\fIfirstcharptr\fP);
1059 .PP
1060 The \fBpcre_info()\fP function is now obsolete because its interface is too
1061 restrictive to return all the available data about a compiled pattern. New
1062 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1063 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1064 following negative numbers:
1065 .sp
1066 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1067 PCRE_ERROR_BADMAGIC the "magic number" was not found
1068 .sp
1069 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1070 pattern was compiled is placed in the integer it points to (see
1071 PCRE_INFO_OPTIONS above).
1072 .P
1073 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1074 it is used to pass back information about the first character of any matched
1075 string (see PCRE_INFO_FIRSTBYTE above).
1076 .
1077 .
1078 .SH "REFERENCE COUNTS"
1079 .rs
1080 .sp
1081 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1082 .PP
1083 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1084 data block that contains a compiled pattern. It is provided for the benefit of
1085 applications that operate in an object-oriented manner, where different parts
1086 of the application may be using the same compiled pattern, but you want to free
1087 the block when they are all done.
1088 .P
1089 When a pattern is compiled, the reference count field is initialized to zero.
1090 It is changed only by calling this function, whose action is to add the
1091 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1092 function is the new value. However, the value of the count is constrained to
1093 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1094 it is forced to the appropriate limit value.
1095 .P
1096 Except when it is zero, the reference count is not correctly preserved if a
1097 pattern is compiled on one host and then transferred to a host whose byte-order
1098 is different. (This seems a highly unlikely scenario.)
1099 .
1100 .
1101 .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1102 .rs
1103 .sp
1104 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1105 .ti +5n
1106 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1107 .ti +5n
1108 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1109 .P
1110 The function \fBpcre_exec()\fP is called to match a subject string against a
1111 compiled pattern, which is passed in the \fIcode\fP argument. If the
1112 pattern has been studied, the result of the study should be passed in the
1113 \fIextra\fP argument. This function is the main matching facility of the
1114 library, and it operates in a Perl-like manner. For specialist use there is
1115 also an alternative matching function, which is described
1116 .\" HTML <a href="#dfamatch">
1117 .\" </a>
1118 below
1119 .\"
1120 in the section about the \fBpcre_dfa_exec()\fP function.
1121 .P
1122 In most applications, the pattern will have been compiled (and optionally
1123 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1124 possible to save compiled patterns and study data, and then use them later
1125 in different processes, possibly even on different hosts. For a discussion
1126 about this, see the
1127 .\" HREF
1128 \fBpcreprecompile\fP
1129 .\"
1130 documentation.
1131 .P
1132 Here is an example of a simple call to \fBpcre_exec()\fP:
1133 .sp
1134 int rc;
1135 int ovector[30];
1136 rc = pcre_exec(
1137 re, /* result of pcre_compile() */
1138 NULL, /* we didn't study the pattern */
1139 "some string", /* the subject string */
1140 11, /* the length of the subject string */
1141 0, /* start at offset 0 in the subject */
1142 0, /* default options */
1143 ovector, /* vector of integers for substring information */
1144 30); /* number of elements (NOT size in bytes) */
1145 .
1146 .\" HTML <a name="extradata"></a>
1147 .SS "Extra data for \fBpcre_exec()\fR"
1148 .rs
1149 .sp
1150 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1151 data block. The \fBpcre_study()\fP function returns such a block (when it
1152 doesn't return NULL), but you can also create one for yourself, and pass
1153 additional information in it. The \fBpcre_extra\fP block contains the following
1154 fields (not necessarily in this order):
1155 .sp
1156 unsigned long int \fIflags\fP;
1157 void *\fIstudy_data\fP;
1158 unsigned long int \fImatch_limit\fP;
1159 unsigned long int \fImatch_limit_recursion\fP;
1160 void *\fIcallout_data\fP;
1161 const unsigned char *\fItables\fP;
1162 .sp
1163 The \fIflags\fP field is a bitmap that specifies which of the other fields
1164 are set. The flag bits are:
1165 .sp
1166 PCRE_EXTRA_STUDY_DATA
1167 PCRE_EXTRA_MATCH_LIMIT
1168 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1169 PCRE_EXTRA_CALLOUT_DATA
1170 PCRE_EXTRA_TABLES
1171 .sp
1172 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1173 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1174 the appropriate flag bit. You should not set this yourself, but you may add to
1175 the block by setting the other fields and their corresponding flag bits.
1176 .P
1177 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1178 vast amount of resources when running patterns that are not going to match,
1179 but which have a very large number of possibilities in their search trees. The
1180 classic example is the use of nested unlimited repeats.
1181 .P
1182 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1183 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1184 number of times this function is called during a match, which has the effect of
1185 limiting the amount of backtracking that can take place. For patterns that are
1186 not anchored, the count restarts from zero for each position in the subject
1187 string.
1188 .P
1189 The default value for the limit can be set when PCRE is built; the default
1190 default is 10 million, which handles all but the most extreme cases. You can
1191 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1192 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1193 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1194 PCRE_ERROR_MATCHLIMIT.
1195 .P
1196 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1197 instead of limiting the total number of times that \fBmatch()\fP is called, it
1198 limits the depth of recursion. The recursion depth is a smaller number than the
1199 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1200 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1201 .P
1202 Limiting the recursion depth limits the amount of stack that can be used, or,
1203 when PCRE has been compiled to use memory on the heap instead of the stack, the
1204 amount of heap memory that can be used.
1205 .P
1206 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1207 built; the default default is the same value as the default for
1208 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1209 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1210 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1211 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1212 .P
1213 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1214 which is described in the
1215 .\" HREF
1216 \fBpcrecallout\fP
1217 .\"
1218 documentation.
1219 .P
1220 The \fItables\fP field is used to pass a character tables pointer to
1221 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1222 pattern. A non-NULL value is stored with the compiled pattern only if custom
1223 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1224 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1225 internal tables to be used. This facility is helpful when re-using patterns
1226 that have been saved after compiling with an external set of tables, because
1227 the external tables might be at a different address when \fBpcre_exec()\fP is
1228 called. See the
1229 .\" HREF
1230 \fBpcreprecompile\fP
1231 .\"
1232 documentation for a discussion of saving compiled patterns for later use.
1233 .
1234 .\" HTML <a name="execoptions"></a>
1235 .SS "Option bits for \fBpcre_exec()\fP"
1236 .rs
1237 .sp
1238 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1239 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1240 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,
1241 PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1242 .sp
1243 PCRE_ANCHORED
1244 .sp
1245 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1246 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1247 to be anchored by virtue of its contents, it cannot be made unachored at
1248 matching time.
1249 .sp
1250 PCRE_BSR_ANYCRLF
1251 PCRE_BSR_UNICODE
1252 .sp
1253 These options (which are mutually exclusive) control what the \eR escape
1254 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1255 match any Unicode newline sequence. These options override the choice that was
1256 made or defaulted when the pattern was compiled.
1257 .sp
1258 PCRE_NEWLINE_CR
1259 PCRE_NEWLINE_LF
1260 PCRE_NEWLINE_CRLF
1261 PCRE_NEWLINE_ANYCRLF
1262 PCRE_NEWLINE_ANY
1263 .sp
1264 These options override the newline definition that was chosen or defaulted when
1265 the pattern was compiled. For details, see the description of
1266 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1267 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1268 the way the match position is advanced after a match failure for an unanchored
1269 pattern.
1270 .P
1271 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1272 match attempt for an unanchored pattern fails when the current position is at a
1273 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1274 characters, the match position is advanced by two characters instead of one, in
1275 other words, to after the CRLF.
1276 .P
1277 The above rule is a compromise that makes the most common cases work as
1278 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1279 set), it does not match the string "\er\enA" because, after failing at the
1280 start, it skips both the CR and the LF before retrying. However, the pattern
1281 [\er\en]A does match that string, because it contains an explicit CR or LF
1282 reference, and so advances only by one character after the first failure.
1283 .P
1284 An explicit match for CR of LF is either a literal appearance of one of those
1285 characters, or one of the \er or \en escape sequences. Implicit matches such as
1286 [^X] do not count, nor does \es (which includes CR and LF in the characters
1287 that it matches).
1288 .P
1289 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1290 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1291 .sp
1292 PCRE_NOTBOL
1293 .sp
1294 This option specifies that first character of the subject string is not the
1295 beginning of a line, so the circumflex metacharacter should not match before
1296 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1297 never to match. This option affects only the behaviour of the circumflex
1298 metacharacter. It does not affect \eA.
1299 .sp
1300 PCRE_NOTEOL
1301 .sp
1302 This option specifies that the end of the subject string is not the end of a
1303 line, so the dollar metacharacter should not match it nor (except in multiline
1304 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1305 compile time) causes dollar never to match. This option affects only the
1306 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1307 .sp
1308 PCRE_NOTEMPTY
1309 .sp
1310 An empty string is not considered to be a valid match if this option is set. If
1311 there are alternatives in the pattern, they are tried. If all the alternatives
1312 match the empty string, the entire match fails. For example, if the pattern
1313 .sp
1314 a?b?
1315 .sp
1316 is applied to a string not beginning with "a" or "b", it matches the empty
1317 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1318 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1319 .P
1320 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1321 of a pattern match of the empty string within its \fBsplit()\fP function, and
1322 when using the /g modifier. It is possible to emulate Perl's behaviour after
1323 matching a null string by first trying the match again at the same offset with
1324 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1325 starting offset (see below) and trying an ordinary match again. There is some
1326 code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1327 .sp
1328 PCRE_NO_START_OPTIMIZE
1329 .sp
1330 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1331 a match, in order to speed up the process. For example, if it is known that a
1332 match must start with a specific character, it searches the subject for that
1333 character, and fails immediately if it cannot find it, without actually running
1334 the main matching function. When callouts are in use, these optimizations can
1335 cause them to be skipped. This option disables the "start-up" optimizations,
1336 causing performance to suffer, but ensuring that the callouts do occur.
1337 .sp
1338 PCRE_NO_UTF8_CHECK
1339 .sp
1340 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1341 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1342 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1343 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1344 strings in the
1345 .\" HTML <a href="pcre.html#utf8strings">
1346 .\" </a>
1347 section on UTF-8 support
1348 .\"
1349 in the main
1350 .\" HREF
1351 \fBpcre\fP
1352 .\"
1353 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1354 the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1355 PCRE_ERROR_BADUTF8_OFFSET is returned.
1356 .P
1357 If you already know that your subject is valid, and you want to skip these
1358 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1359 calling \fBpcre_exec()\fP. You might want to do this for the second and
1360 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1361 all the matches in a single subject string. However, you should be sure that
1362 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1363 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1364 subject, or a value of \fIstartoffset\fP that does not point to the start of a
1365 UTF-8 character, is undefined. Your program may crash.
1366 .sp
1367 PCRE_PARTIAL
1368 .sp
1369 This option turns on the partial matching feature. If the subject string fails
1370 to match the pattern, but at some point during the matching process the end of
1371 the subject was reached (that is, the subject partially matches the pattern and
1372 the failure to match occurred only because there were not enough subject
1373 characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1374 PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1375 may appear in the pattern. These are discussed in the
1376 .\" HREF
1377 \fBpcrepartial\fP
1378 .\"
1379 documentation.
1380 .
1381 .SS "The string to be matched by \fBpcre_exec()\fP"
1382 .rs
1383 .sp
1384 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1385 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1386 in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1387 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1388 zero bytes. When the starting offset is zero, the search for a match starts at
1389 the beginning of the subject, and this is by far the most common case.
1390 .P
1391 A non-zero starting offset is useful when searching for another match in the
1392 same subject by calling \fBpcre_exec()\fP again after a previous success.
1393 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1394 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1395 lookbehind. For example, consider the pattern
1396 .sp
1397 \eBiss\eB
1398 .sp
1399 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1400 the current position in the subject is not a word boundary.) When applied to
1401 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1402 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1403 subject, namely "issipi", it does not match, because \eB is always false at the
1404 start of the subject, which is deemed to be a word boundary. However, if
1405 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1406 set to 4, it finds the second occurrence of "iss" because it is able to look
1407 behind the starting point to discover that it is preceded by a letter.
1408 .P
1409 If a non-zero starting offset is passed when the pattern is anchored, one
1410 attempt to match at the given offset is made. This can only succeed if the
1411 pattern does not require the match to be at the start of the subject.
1412 .
1413 .SS "How \fBpcre_exec()\fP returns captured substrings"
1414 .rs
1415 .sp
1416 In general, a pattern matches a certain portion of the subject, and in
1417 addition, further substrings from the subject may be picked out by parts of the
1418 pattern. Following the usage in Jeffrey Friedl's book, this is called
1419 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1420 a fragment of a pattern that picks out a substring. PCRE supports several other
1421 kinds of parenthesized subpattern that do not cause substrings to be captured.
1422 .P
1423 Captured substrings are returned to the caller via a vector of integers whose
1424 address is passed in \fIovector\fP. The number of elements in the vector is
1425 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1426 argument is NOT the size of \fIovector\fP in bytes.
1427 .P
1428 The first two-thirds of the vector is used to pass back captured substrings,
1429 each substring using a pair of integers. The remaining third of the vector is
1430 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1431 and is not available for passing back information. The number passed in
1432 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1433 rounded down.
1434 .P
1435 When a match is successful, information about captured substrings is returned
1436 in pairs of integers, starting at the beginning of \fIovector\fP, and
1437 continuing up to two-thirds of its length at the most. The first element of
1438 each pair is set to the byte offset of the first character in a substring, and
1439 the second is set to the byte offset of the first character after the end of a
1440 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1441 mode. They are not character counts.
1442 .P
1443 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1444 portion of the subject string matched by the entire pattern. The next pair is
1445 used for the first capturing subpattern, and so on. The value returned by
1446 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1447 For example, if two substrings have been captured, the returned value is 3. If
1448 there are no capturing subpatterns, the return value from a successful match is
1449 1, indicating that just the first pair of offsets has been set.
1450 .P
1451 If a capturing subpattern is matched repeatedly, it is the last portion of the
1452 string that it matched that is returned.
1453 .P
1454 If the vector is too small to hold all the captured substring offsets, it is
1455 used as far as possible (up to two-thirds of its length), and the function
1456 returns a value of zero. If the substring offsets are not of interest,
1457 \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1458 \fIovecsize\fP as zero. However, if the pattern contains back references and
1459 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1460 has to get additional memory for use during matching. Thus it is usually
1461 advisable to supply an \fIovector\fP.
1462 .P
1463 The \fBpcre_info()\fP function can be used to find out how many capturing
1464 subpatterns there are in a compiled pattern. The smallest size for
1465 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1466 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1467 .P
1468 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1469 the subject when subpattern \fIn\fP has not been used at all. For example, if
1470 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1471 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1472 happens, both values in the offset pairs corresponding to unused subpatterns
1473 are set to -1.
1474 .P
1475 Offset values that correspond to unused subpatterns at the end of the
1476 expression are also set to -1. For example, if the string "abc" is matched
1477 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1478 return from the function is 2, because the highest used capturing subpattern
1479 number is 1. However, you can refer to the offsets for the second and third
1480 capturing subpatterns if you wish (assuming the vector is large enough, of
1481 course).
1482 .P
1483 Some convenience functions are provided for extracting the captured substrings
1484 as separate strings. These are described below.
1485 .
1486 .\" HTML <a name="errorlist"></a>
1487 .SS "Error return values from \fBpcre_exec()\fP"
1488 .rs
1489 .sp
1490 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1491 defined in the header file:
1492 .sp
1493 PCRE_ERROR_NOMATCH (-1)
1494 .sp
1495 The subject string did not match the pattern.
1496 .sp
1497 PCRE_ERROR_NULL (-2)
1498 .sp
1499 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1500 NULL and \fIovecsize\fP was not zero.
1501 .sp
1502 PCRE_ERROR_BADOPTION (-3)
1503 .sp
1504 An unrecognized bit was set in the \fIoptions\fP argument.
1505 .sp
1506 PCRE_ERROR_BADMAGIC (-4)
1507 .sp
1508 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1509 the case when it is passed a junk pointer and to detect when a pattern that was
1510 compiled in an environment of one endianness is run in an environment with the
1511 other endianness. This is the error that PCRE gives when the magic number is
1512 not present.
1513 .sp
1514 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1515 .sp
1516 While running the pattern match, an unknown item was encountered in the
1517 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1518 of the compiled pattern.
1519 .sp
1520 PCRE_ERROR_NOMEMORY (-6)
1521 .sp
1522 If a pattern contains back references, but the \fIovector\fP that is passed to
1523 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1524 gets a block of memory at the start of matching to use for this purpose. If the
1525 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1526 automatically freed at the end of matching.
1527 .sp
1528 PCRE_ERROR_NOSUBSTRING (-7)
1529 .sp
1530 This error is used by the \fBpcre_copy_substring()\fP,
1531 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1532 below). It is never returned by \fBpcre_exec()\fP.
1533 .sp
1534 PCRE_ERROR_MATCHLIMIT (-8)
1535 .sp
1536 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1537 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1538 above.
1539 .sp
1540 PCRE_ERROR_CALLOUT (-9)
1541 .sp
1542 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1543 use by callout functions that want to yield a distinctive error code. See the
1544 .\" HREF
1545 \fBpcrecallout\fP
1546 .\"
1547 documentation for details.
1548 .sp
1549 PCRE_ERROR_BADUTF8 (-10)
1550 .sp
1551 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1552 .sp
1553 PCRE_ERROR_BADUTF8_OFFSET (-11)
1554 .sp
1555 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1556 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1557 .sp
1558 PCRE_ERROR_PARTIAL (-12)
1559 .sp
1560 The subject string did not match, but it did match partially. See the
1561 .\" HREF
1562 \fBpcrepartial\fP
1563 .\"
1564 documentation for details of partial matching.
1565 .sp
1566 PCRE_ERROR_BADPARTIAL (-13)
1567 .sp
1568 The PCRE_PARTIAL option was used with a compiled pattern containing items that
1569 are not supported for partial matching. See the
1570 .\" HREF
1571 \fBpcrepartial\fP
1572 .\"
1573 documentation for details of partial matching.
1574 .sp
1575 PCRE_ERROR_INTERNAL (-14)
1576 .sp
1577 An unexpected internal error has occurred. This error could be caused by a bug
1578 in PCRE or by overwriting of the compiled pattern.
1579 .sp
1580 PCRE_ERROR_BADCOUNT (-15)
1581 .sp
1582 This error is given if the value of the \fIovecsize\fP argument is negative.
1583 .sp
1584 PCRE_ERROR_RECURSIONLIMIT (-21)
1585 .sp
1586 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1587 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1588 description above.
1589 .sp
1590 PCRE_ERROR_BADNEWLINE (-23)
1591 .sp
1592 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1593 .P
1594 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1595 .
1596 .
1597 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1598 .rs
1599 .sp
1600 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1601 .ti +5n
1602 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1603 .ti +5n
1604 .B int \fIbuffersize\fP);
1605 .PP
1606 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1607 .ti +5n
1608 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1609 .ti +5n
1610 .B const char **\fIstringptr\fP);
1611 .PP
1612 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1613 .ti +5n
1614 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1615 .PP
1616 Captured substrings can be accessed directly by using the offsets returned by
1617 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1618 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1619 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1620 as new, separate, zero-terminated strings. These functions identify substrings
1621 by number. The next section describes functions for extracting named
1622 substrings.
1623 .P
1624 A substring that contains a binary zero is correctly extracted and has a
1625 further zero added on the end, but the result is not, of course, a C string.
1626 However, you can process such a string by referring to the length that is
1627 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1628 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1629 for handling strings containing binary zeros, because the end of the final
1630 string is not independently indicated.
1631 .P
1632 The first three arguments are the same for all three of these functions:
1633 \fIsubject\fP is the subject string that has just been successfully matched,
1634 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1635 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1636 captured by the match, including the substring that matched the entire regular
1637 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1638 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1639 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1640 number of elements in the vector divided by three.
1641 .P
1642 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1643 extract a single substring, whose number is given as \fIstringnumber\fP. A
1644 value of zero extracts the substring that matched the entire pattern, whereas
1645 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1646 the string is placed in \fIbuffer\fP, whose length is given by
1647 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1648 obtained via \fBpcre_malloc\fP, and its address is returned via
1649 \fIstringptr\fP. The yield of the function is the length of the string, not
1650 including the terminating zero, or one of these error codes:
1651 .sp
1652 PCRE_ERROR_NOMEMORY (-6)
1653 .sp
1654 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1655 memory failed for \fBpcre_get_substring()\fP.
1656 .sp
1657 PCRE_ERROR_NOSUBSTRING (-7)
1658 .sp
1659 There is no substring whose number is \fIstringnumber\fP.
1660 .P
1661 The \fBpcre_get_substring_list()\fP function extracts all available substrings
1662 and builds a list of pointers to them. All this is done in a single block of
1663 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1664 is returned via \fIlistptr\fP, which is also the start of the list of string
1665 pointers. The end of the list is marked by a NULL pointer. The yield of the
1666 function is zero if all went well, or the error code
1667 .sp
1668 PCRE_ERROR_NOMEMORY (-6)
1669 .sp
1670 if the attempt to get the memory block failed.
1671 .P
1672 When any of these functions encounter a substring that is unset, which can
1673 happen when capturing subpattern number \fIn+1\fP matches some part of the
1674 subject, but subpattern \fIn\fP has not been used at all, they return an empty
1675 string. This can be distinguished from a genuine zero-length substring by
1676 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1677 substrings.
1678 .P
1679 The two convenience functions \fBpcre_free_substring()\fP and
1680 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1681 a previous call of \fBpcre_get_substring()\fP or
1682 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1683 the function pointed to by \fBpcre_free\fP, which of course could be called
1684 directly from a C program. However, PCRE is used in some situations where it is
1685 linked via a special interface to another programming language that cannot use
1686 \fBpcre_free\fP directly; it is for these cases that the functions are
1687 provided.
1688 .
1689 .
1690 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1691 .rs
1692 .sp
1693 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1694 .ti +5n
1695 .B const char *\fIname\fP);
1696 .PP
1697 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1698 .ti +5n
1699 .B const char *\fIsubject\fP, int *\fIovector\fP,
1700 .ti +5n
1701 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1702 .ti +5n
1703 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1704 .PP
1705 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1706 .ti +5n
1707 .B const char *\fIsubject\fP, int *\fIovector\fP,
1708 .ti +5n
1709 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1710 .ti +5n
1711 .B const char **\fIstringptr\fP);
1712 .PP
1713 To extract a substring by name, you first have to find associated number.
1714 For example, for this pattern
1715 .sp
1716 (a+)b(?<xxx>\ed+)...
1717 .sp
1718 the number of the subpattern called "xxx" is 2. If the name is known to be
1719 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1720 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1721 pattern, and the second is the name. The yield of the function is the
1722 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1723 that name.
1724 .P
1725 Given the number, you can extract the substring directly, or use one of the
1726 functions described in the previous section. For convenience, there are also
1727 two functions that do the whole job.
1728 .P
1729 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1730 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1731 functions that extract by number. As these are described in the previous
1732 section, they are not re-described here. There are just two differences:
1733 .P
1734 First, instead of a substring number, a substring name is given. Second, there
1735 is an extra argument, given at the start, which is a pointer to the compiled
1736 pattern. This is needed in order to gain access to the name-to-number
1737 translation table.
1738 .P
1739 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1740 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1741 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1742 the behaviour may not be what you want (see the next section).
1743 .P
1744 \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
1745 subpatterns with the same number, you cannot use names to distinguish them,
1746 because names are not included in the compiled code. The matching process uses
1747 only numbers.
1748 .
1749 .SH "DUPLICATE SUBPATTERN NAMES"
1750 .rs
1751 .sp
1752 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1753 .ti +5n
1754 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1755 .PP
1756 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1757 are not required to be unique. Normally, patterns with duplicate names are such
1758 that in any one match, only one of the named subpatterns participates. An
1759 example is shown in the
1760 .\" HREF
1761 \fBpcrepattern\fP
1762 .\"
1763 documentation.
1764 .P
1765 When duplicates are present, \fBpcre_copy_named_substring()\fP and
1766 \fBpcre_get_named_substring()\fP return the first substring corresponding to
1767 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1768 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1769 returns one of the numbers that are associated with the name, but it is not
1770 defined which it is.
1771 .P
1772 If you want to get full details of all captured substrings for a given name,
1773 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1774 argument is the compiled pattern, and the second is the name. The third and
1775 fourth are pointers to variables which are updated by the function. After it
1776 has run, they point to the first and last entries in the name-to-number table
1777 for the given name. The function itself returns the length of each entry, or
1778 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1779 described above in the section entitled \fIInformation about a pattern\fP.
1780 Given all the relevant entries for the name, you can extract each of their
1781 numbers, and hence the captured data, if any.
1782 .
1783 .
1784 .SH "FINDING ALL POSSIBLE MATCHES"
1785 .rs
1786 .sp
1787 The traditional matching function uses a similar algorithm to Perl, which stops
1788 when it finds the first match, starting at a given point in the subject. If you
1789 want to find all possible matches, or the longest possible match, consider
1790 using the alternative matching function (see below) instead. If you cannot use
1791 the alternative function, but still need to find all possible matches, you
1792 can kludge it up by making use of the callout facility, which is described in
1793 the
1794 .\" HREF
1795 \fBpcrecallout\fP
1796 .\"
1797 documentation.
1798 .P
1799 What you have to do is to insert a callout right at the end of the pattern.
1800 When your callout function is called, extract and save the current matched
1801 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1802 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1803 will yield PCRE_ERROR_NOMATCH.
1804 .
1805 .
1806 .\" HTML <a name="dfamatch"></a>
1807 .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1808 .rs
1809 .sp
1810 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1811 .ti +5n
1812 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1813 .ti +5n
1814 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1815 .ti +5n
1816 .B int *\fIworkspace\fP, int \fIwscount\fP);
1817 .P
1818 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1819 a compiled pattern, using a matching algorithm that scans the subject string
1820 just once, and does not backtrack. This has different characteristics to the
1821 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1822 patterns are not supported. Nevertheless, there are times when this kind of
1823 matching can be useful. For a discussion of the two matching algorithms, see
1824 the
1825 .\" HREF
1826 \fBpcrematching\fP
1827 .\"
1828 documentation.
1829 .P
1830 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1831 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1832 different way, and this is described below. The other common arguments are used
1833 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1834 here.
1835 .P
1836 The two additional arguments provide workspace for the function. The workspace
1837 vector should contain at least 20 elements. It is used for keeping track of
1838 multiple paths through the pattern tree. More workspace will be needed for
1839 patterns and subjects where there are a lot of potential matches.
1840 .P
1841 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1842 .sp
1843 int rc;
1844 int ovector[10];
1845 int wspace[20];
1846 rc = pcre_dfa_exec(
1847 re, /* result of pcre_compile() */
1848 NULL, /* we didn't study the pattern */
1849 "some string", /* the subject string */
1850 11, /* the length of the subject string */
1851 0, /* start at offset 0 in the subject */
1852 0, /* default options */
1853 ovector, /* vector of integers for substring information */
1854 10, /* number of elements (NOT size in bytes) */
1855 wspace, /* working space vector */
1856 20); /* number of elements (NOT size in bytes) */
1857 .
1858 .SS "Option bits for \fBpcre_dfa_exec()\fP"
1859 .rs
1860 .sp
1861 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1862 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1863 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
1864 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1865 the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1866 .sp
1867 PCRE_PARTIAL
1868 .sp
1869 This has the same general effect as it does for \fBpcre_exec()\fP, but the
1870 details are slightly different. When PCRE_PARTIAL is set for
1871 \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1872 PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1873 complete matches, but there is still at least one matching possibility. The
1874 portion of the string that provided the partial match is set as the first
1875 matching string.
1876 .sp
1877 PCRE_DFA_SHORTEST
1878 .sp
1879 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1880 soon as it has found one match. Because of the way the alternative algorithm
1881 works, this is necessarily the shortest possible match at the first possible
1882 matching point in the subject string.
1883 .sp
1884 PCRE_DFA_RESTART
1885 .sp
1886 When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1887 a partial match, it is possible to call it again, with additional subject
1888 characters, and have it continue with the same match. The PCRE_DFA_RESTART
1889 option requests this action; when it is set, the \fIworkspace\fP and
1890 \fIwscount\fP options must reference the same vector as before because data
1891 about the match so far is left in them after a partial match. There is more
1892 discussion of this facility in the
1893 .\" HREF
1894 \fBpcrepartial\fP
1895 .\"
1896 documentation.
1897 .
1898 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1899 .rs
1900 .sp
1901 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1902 substring in the subject. Note, however, that all the matches from one run of
1903 the function start at the same point in the subject. The shorter matches are
1904 all initial substrings of the longer matches. For example, if the pattern
1905 .sp
1906 <.*>
1907 .sp
1908 is matched against the string
1909 .sp
1910 This is <something> <something else> <something further> no more
1911 .sp
1912 the three matched strings are
1913 .sp
1914 <something>
1915 <something> <something else>
1916 <something> <something else> <something further>
1917 .sp
1918 On success, the yield of the function is a number greater than zero, which is
1919 the number of matched substrings. The substrings themselves are returned in
1920 \fIovector\fP. Each string uses two elements; the first is the offset to the
1921 start, and the second is the offset to the end. In fact, all the strings have
1922 the same start offset. (Space could have been saved by giving this only once,
1923 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1924 returns data, even though the meaning of the strings is different.)
1925 .P
1926 The strings are returned in reverse order of length; that is, the longest
1927 matching string is given first. If there were too many matches to fit into
1928 \fIovector\fP, the yield of the function is zero, and the vector is filled with
1929 the longest matches.
1930 .
1931 .SS "Error returns from \fBpcre_dfa_exec()\fP"
1932 .rs
1933 .sp
1934 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1935 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1936 described
1937 .\" HTML <a href="#errorlist">
1938 .\" </a>
1939 above.
1940 .\"
1941 There are in addition the following errors that are specific to
1942 \fBpcre_dfa_exec()\fP:
1943 .sp
1944 PCRE_ERROR_DFA_UITEM (-16)
1945 .sp
1946 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1947 that it does not support, for instance, the use of \eC or a back reference.
1948 .sp
1949 PCRE_ERROR_DFA_UCOND (-17)
1950 .sp
1951 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1952 uses a back reference for the condition, or a test for recursion in a specific
1953 group. These are not supported.
1954 .sp
1955 PCRE_ERROR_DFA_UMLIMIT (-18)
1956 .sp
1957 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1958 block that contains a setting of the \fImatch_limit\fP field. This is not
1959 supported (it is meaningless).
1960 .sp
1961 PCRE_ERROR_DFA_WSSIZE (-19)
1962 .sp
1963 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1964 \fIworkspace\fP vector.
1965 .sp
1966 PCRE_ERROR_DFA_RECURSE (-20)
1967 .sp
1968 When a recursive subpattern is processed, the matching function calls itself
1969 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1970 error is given if the output vector is not large enough. This should be
1971 extremely rare, as a vector of size 1000 is used.
1972 .
1973 .
1974 .SH "SEE ALSO"
1975 .rs
1976 .sp
1977 \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1978 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1979 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1980 .
1981 .
1982 .SH AUTHOR
1983 .rs
1984 .sp
1985 .nf
1986 Philip Hazel
1987 University Computing Service
1988 Cambridge CB2 3QH, England.
1989 .fi
1990 .
1991 .
1992 .SH REVISION
1993 .rs
1994 .sp
1995 .nf
1996 Last updated: 15 March 2009
1997 Copyright (c) 1997-2009 University of Cambridge.
1998 .fi

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