/[pcre]/code/trunk/doc/pcreapi.3
ViewVC logotype

Contents of /code/trunk/doc/pcreapi.3

Parent Directory Parent Directory | Revision Log Revision Log


Revision 392 - (show annotations) (download)
Tue Mar 17 21:30:30 2009 UTC (5 years, 9 months ago) by ph10
File size: 85999 byte(s)
Update after detrailing for a test release.

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.
321 Though they are derived from ASCII, the same values are returned in EBCDIC
322 environments. The default should normally correspond to the standard sequence
323 for your operating system.
324 .sp
325 PCRE_CONFIG_BSR
326 .sp
327 The output is an integer whose value indicates what character sequences the \eR
328 escape sequence matches by default. A value of 0 means that \eR matches any
329 Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
330 or CRLF. The default can be overridden when a pattern is compiled or matched.
331 .sp
332 PCRE_CONFIG_LINK_SIZE
333 .sp
334 The output is an integer that contains the number of bytes used for internal
335 linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
336 allow larger regular expressions to be compiled, at the expense of slower
337 matching. The default value of 2 is sufficient for all but the most massive
338 patterns, since it allows the compiled pattern to be up to 64K in size.
339 .sp
340 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
341 .sp
342 The output is an integer that contains the threshold above which the POSIX
343 interface uses \fBmalloc()\fP for output vectors. Further details are given in
344 the
345 .\" HREF
346 \fBpcreposix\fP
347 .\"
348 documentation.
349 .sp
350 PCRE_CONFIG_MATCH_LIMIT
351 .sp
352 The output is a long integer that gives the default limit for the number of
353 internal matching function calls in a \fBpcre_exec()\fP execution. Further
354 details are given with \fBpcre_exec()\fP below.
355 .sp
356 PCRE_CONFIG_MATCH_LIMIT_RECURSION
357 .sp
358 The output is a long integer that gives the default limit for the depth of
359 recursion when calling the internal matching function in a \fBpcre_exec()\fP
360 execution. Further details are given with \fBpcre_exec()\fP below.
361 .sp
362 PCRE_CONFIG_STACKRECURSE
363 .sp
364 The output is an integer that is set to one if internal recursion when running
365 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
366 to remember their state. This is the usual way that PCRE is compiled. The
367 output is zero if PCRE was compiled to use blocks of data on the heap instead
368 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
369 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
370 avoiding the use of the stack.
371 .
372 .
373 .SH "COMPILING A PATTERN"
374 .rs
375 .sp
376 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
377 .ti +5n
378 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
379 .ti +5n
380 .B const unsigned char *\fItableptr\fP);
381 .sp
382 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
383 .ti +5n
384 .B int *\fIerrorcodeptr\fP,
385 .ti +5n
386 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
387 .ti +5n
388 .B const unsigned char *\fItableptr\fP);
389 .P
390 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
391 called to compile a pattern into an internal form. The only difference between
392 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
393 \fIerrorcodeptr\fP, via which a numerical error code can be returned.
394 .P
395 The pattern is a C string terminated by a binary zero, and is passed in the
396 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
397 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
398 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
399 for a structure whose contents are not externally defined. It is up to the
400 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
401 .P
402 Although the compiled code of a PCRE regex is relocatable, that is, it does not
403 depend on memory location, the complete \fBpcre\fP data block is not
404 fully relocatable, because it may contain a copy of the \fItableptr\fP
405 argument, which is an address (see below).
406 .P
407 The \fIoptions\fP argument contains various bit settings that affect the
408 compilation. It should be zero if no options are required. The available
409 options are described below. Some of them, in particular, those that are
410 compatible with Perl, can also be set and unset from within the pattern (see
411 the detailed description in the
412 .\" HREF
413 \fBpcrepattern\fP
414 .\"
415 documentation). For these options, the contents of the \fIoptions\fP argument
416 specifies their initial settings at the start of compilation and execution. The
417 PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
418 matching as well as at compile time.
419 .P
420 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
421 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
422 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
423 error message. This is a static string that is part of the library. You must
424 not try to free it. The offset from the start of the pattern to the character
425 where the error was discovered is placed in the variable pointed to by
426 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
427 .P
428 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
429 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
430 returned via this argument in the event of an error. This is in addition to the
431 textual error message. Error codes and messages are listed below.
432 .P
433 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
434 character tables that are built when PCRE is compiled, using the default C
435 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
436 call to \fBpcre_maketables()\fP. This value is stored with the compiled
437 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
438 passed to it. For more discussion, see the section on locale support below.
439 .P
440 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
441 .sp
442 pcre *re;
443 const char *error;
444 int erroffset;
445 re = pcre_compile(
446 "^A.*Z", /* the pattern */
447 0, /* default options */
448 &error, /* for error message */
449 &erroffset, /* for error offset */
450 NULL); /* use default character tables */
451 .sp
452 The following names for option bits are defined in the \fBpcre.h\fP header
453 file:
454 .sp
455 PCRE_ANCHORED
456 .sp
457 If this bit is set, the pattern is forced to be "anchored", that is, it is
458 constrained to match only at the first matching point in the string that is
459 being searched (the "subject string"). This effect can also be achieved by
460 appropriate constructs in the pattern itself, which is the only way to do it in
461 Perl.
462 .sp
463 PCRE_AUTO_CALLOUT
464 .sp
465 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
466 all with number 255, before each pattern item. For discussion of the callout
467 facility, see the
468 .\" HREF
469 \fBpcrecallout\fP
470 .\"
471 documentation.
472 .sp
473 PCRE_BSR_ANYCRLF
474 PCRE_BSR_UNICODE
475 .sp
476 These options (which are mutually exclusive) control what the \eR escape
477 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
478 match any Unicode newline sequence. The default is specified when PCRE is
479 built. It can be overridden from within the pattern, or by setting an option
480 when a compiled pattern is matched.
481 .sp
482 PCRE_CASELESS
483 .sp
484 If this bit is set, letters in the pattern match both upper and lower case
485 letters. It is equivalent to Perl's /i option, and it can be changed within a
486 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
487 concept of case for characters whose values are less than 128, so caseless
488 matching is always possible. For characters with higher values, the concept of
489 case is supported if PCRE is compiled with Unicode property support, but not
490 otherwise. If you want to use caseless matching for characters 128 and above,
491 you must ensure that PCRE is compiled with Unicode property support as well as
492 with UTF-8 support.
493 .sp
494 PCRE_DOLLAR_ENDONLY
495 .sp
496 If this bit is set, a dollar metacharacter in the pattern matches only at the
497 end of the subject string. Without this option, a dollar also matches
498 immediately before a newline at the end of the string (but not before any other
499 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
500 There is no equivalent to this option in Perl, and no way to set it within a
501 pattern.
502 .sp
503 PCRE_DOTALL
504 .sp
505 If this bit is set, a dot metacharater in the pattern matches all characters,
506 including those that indicate newline. Without it, a dot does not match when
507 the current position is at a newline. This option is equivalent to Perl's /s
508 option, and it can be changed within a pattern by a (?s) option setting. A
509 negative class such as [^a] always matches newline characters, independent of
510 the setting of this option.
511 .sp
512 PCRE_DUPNAMES
513 .sp
514 If this bit is set, names used to identify capturing subpatterns need not be
515 unique. This can be helpful for certain types of pattern when it is known that
516 only one instance of the named subpattern can ever be matched. There are more
517 details of named subpatterns below; see also the
518 .\" HREF
519 \fBpcrepattern\fP
520 .\"
521 documentation.
522 .sp
523 PCRE_EXTENDED
524 .sp
525 If this bit is set, whitespace data characters in the pattern are totally
526 ignored except when escaped or inside a character class. Whitespace does not
527 include the VT character (code 11). In addition, characters between an
528 unescaped # outside a character class and the next newline, inclusive, are also
529 ignored. This is equivalent to Perl's /x option, and it can be changed within a
530 pattern by a (?x) option setting.
531 .P
532 This option makes it possible to include comments inside complicated patterns.
533 Note, however, that this applies only to data characters. Whitespace characters
534 may never appear within special character sequences in a pattern, for example
535 within the sequence (?( which introduces a conditional subpattern.
536 .sp
537 PCRE_EXTRA
538 .sp
539 This option was invented in order to turn on additional functionality of PCRE
540 that is incompatible with Perl, but it is currently of very little use. When
541 set, any backslash in a pattern that is followed by a letter that has no
542 special meaning causes an error, thus reserving these combinations for future
543 expansion. By default, as in Perl, a backslash followed by a letter with no
544 special meaning is treated as a literal. (Perl can, however, be persuaded to
545 give a warning for this.) There are at present no other features controlled by
546 this option. It can also be set by a (?X) option setting within a pattern.
547 .sp
548 PCRE_FIRSTLINE
549 .sp
550 If this option is set, an unanchored pattern is required to match before or at
551 the first newline in the subject string, though the matched text may continue
552 over the newline.
553 .sp
554 PCRE_JAVASCRIPT_COMPAT
555 .sp
556 If this option is set, PCRE's behaviour is changed in some ways so that it is
557 compatible with JavaScript rather than Perl. The changes are as follows:
558 .P
559 (1) A lone closing square bracket in a pattern causes a compile-time error,
560 because this is illegal in JavaScript (by default it is treated as a data
561 character). Thus, the pattern AB]CD becomes illegal when this option is set.
562 .P
563 (2) At run time, a back reference to an unset subpattern group matches an empty
564 string (by default this causes the current matching alternative to fail). A
565 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
566 an "a" in the subject), whereas it fails by default, for Perl compatibility.
567 .sp
568 PCRE_MULTILINE
569 .sp
570 By default, PCRE treats the subject string as consisting of a single line of
571 characters (even if it actually contains newlines). The "start of line"
572 metacharacter (^) matches only at the start of the string, while the "end of
573 line" metacharacter ($) matches only at the end of the string, or before a
574 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
575 Perl.
576 .P
577 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
578 match immediately following or immediately before internal newlines in the
579 subject string, respectively, as well as at the very start and end. This is
580 equivalent to Perl's /m option, and it can be changed within a pattern by a
581 (?m) option setting. If there are no newlines in a subject string, or no
582 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
583 .sp
584 PCRE_NEWLINE_CR
585 PCRE_NEWLINE_LF
586 PCRE_NEWLINE_CRLF
587 PCRE_NEWLINE_ANYCRLF
588 PCRE_NEWLINE_ANY
589 .sp
590 These options override the default newline definition that was chosen when PCRE
591 was built. Setting the first or the second specifies that a newline is
592 indicated by a single character (CR or LF, respectively). Setting
593 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
594 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
595 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
596 that any Unicode newline sequence should be recognized. The Unicode newline
597 sequences are the three just mentioned, plus the single characters VT (vertical
598 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
599 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
600 recognized only in UTF-8 mode.
601 .P
602 The newline setting in the options word uses three bits that are treated
603 as a number, giving eight possibilities. Currently only six are used (default
604 plus the five values above). This means that if you set more than one newline
605 option, the combination may or may not be sensible. For example,
606 PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
607 other combinations may yield unused numbers and cause an error.
608 .P
609 The only time that a line break is specially recognized when compiling a
610 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
611 class is encountered. This indicates a comment that lasts until after the next
612 line break sequence. In other circumstances, line break sequences are treated
613 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
614 as whitespace characters and are therefore ignored.
615 .P
616 The newline option that is set at compile time becomes the default that is used
617 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
618 .sp
619 PCRE_NO_AUTO_CAPTURE
620 .sp
621 If this option is set, it disables the use of numbered capturing parentheses in
622 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
623 were followed by ?: but named parentheses can still be used for capturing (and
624 they acquire numbers in the usual way). There is no equivalent of this option
625 in Perl.
626 .sp
627 PCRE_UNGREEDY
628 .sp
629 This option inverts the "greediness" of the quantifiers so that they are not
630 greedy by default, but become greedy if followed by "?". It is not compatible
631 with Perl. It can also be set by a (?U) option setting within the pattern.
632 .sp
633 PCRE_UTF8
634 .sp
635 This option causes PCRE to regard both the pattern and the subject as strings
636 of UTF-8 characters instead of single-byte character strings. However, it is
637 available only when PCRE is built to include UTF-8 support. If not, the use
638 of this option provokes an error. Details of how this option changes the
639 behaviour of PCRE are given in the
640 .\" HTML <a href="pcre.html#utf8support">
641 .\" </a>
642 section on UTF-8 support
643 .\"
644 in the main
645 .\" HREF
646 \fBpcre\fP
647 .\"
648 page.
649 .sp
650 PCRE_NO_UTF8_CHECK
651 .sp
652 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
653 automatically checked. There is a discussion about the
654 .\" HTML <a href="pcre.html#utf8strings">
655 .\" </a>
656 validity of UTF-8 strings
657 .\"
658 in the main
659 .\" HREF
660 \fBpcre\fP
661 .\"
662 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
663 returns an error. If you already know that your pattern is valid, and you want
664 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
665 option. When it is set, the effect of passing an invalid UTF-8 string as a
666 pattern is undefined. It may cause your program to crash. Note that this option
667 can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
668 the UTF-8 validity checking of subject strings.
669 .
670 .
671 .SH "COMPILATION ERROR CODES"
672 .rs
673 .sp
674 The following table lists the error codes than may be returned by
675 \fBpcre_compile2()\fP, along with the error messages that may be returned by
676 both compiling functions. As PCRE has developed, some error codes have fallen
677 out of use. To avoid confusion, they have not been re-used.
678 .sp
679 0 no error
680 1 \e at end of pattern
681 2 \ec at end of pattern
682 3 unrecognized character follows \e
683 4 numbers out of order in {} quantifier
684 5 number too big in {} quantifier
685 6 missing terminating ] for character class
686 7 invalid escape sequence in character class
687 8 range out of order in character class
688 9 nothing to repeat
689 10 [this code is not in use]
690 11 internal error: unexpected repeat
691 12 unrecognized character after (? or (?-
692 13 POSIX named classes are supported only within a class
693 14 missing )
694 15 reference to non-existent subpattern
695 16 erroffset passed as NULL
696 17 unknown option bit(s) set
697 18 missing ) after comment
698 19 [this code is not in use]
699 20 regular expression is too large
700 21 failed to get memory
701 22 unmatched parentheses
702 23 internal error: code overflow
703 24 unrecognized character after (?<
704 25 lookbehind assertion is not fixed length
705 26 malformed number or name after (?(
706 27 conditional group contains more than two branches
707 28 assertion expected after (?(
708 29 (?R or (?[+-]digits must be followed by )
709 30 unknown POSIX class name
710 31 POSIX collating elements are not supported
711 32 this version of PCRE is not compiled with PCRE_UTF8 support
712 33 [this code is not in use]
713 34 character value in \ex{...} sequence is too large
714 35 invalid condition (?(0)
715 36 \eC not allowed in lookbehind assertion
716 37 PCRE does not support \eL, \el, \eN, \eU, or \eu
717 38 number after (?C is > 255
718 39 closing ) for (?C expected
719 40 recursive call could loop indefinitely
720 41 unrecognized character after (?P
721 42 syntax error in subpattern name (missing terminator)
722 43 two named subpatterns have the same name
723 44 invalid UTF-8 string
724 45 support for \eP, \ep, and \eX has not been compiled
725 46 malformed \eP or \ep sequence
726 47 unknown property name after \eP or \ep
727 48 subpattern name is too long (maximum 32 characters)
728 49 too many named subpatterns (maximum 10000)
729 50 [this code is not in use]
730 51 octal value is greater than \e377 (not in UTF-8 mode)
731 52 internal error: overran compiling workspace
732 53 internal error: previously-checked referenced subpattern not found
733 54 DEFINE group contains more than one branch
734 55 repeating a DEFINE group is not allowed
735 56 inconsistent NEWLINE options
736 57 \eg is not followed by a braced, angle-bracketed, or quoted
737 name/number or by a plain number
738 58 a numbered reference must not be zero
739 59 (*VERB) with an argument is not supported
740 60 (*VERB) not recognized
741 61 number is too big
742 62 subpattern name expected
743 63 digit expected after (?+
744 64 ] is an invalid data character in JavaScript compatibility mode
745 .sp
746 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
747 be used if the limits were changed when PCRE was built.
748 .
749 .
750 .SH "STUDYING A PATTERN"
751 .rs
752 .sp
753 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
754 .ti +5n
755 .B const char **\fIerrptr\fP);
756 .PP
757 If a compiled pattern is going to be used several times, it is worth spending
758 more time analyzing it in order to speed up the time taken for matching. The
759 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
760 argument. If studying the pattern produces additional information that will
761 help speed up matching, \fBpcre_study()\fP returns a pointer to a
762 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
763 results of the study.
764 .P
765 The returned value from \fBpcre_study()\fP can be passed directly to
766 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
767 fields that can be set by the caller before the block is passed; these are
768 described
769 .\" HTML <a href="#extradata">
770 .\" </a>
771 below
772 .\"
773 in the section on matching a pattern.
774 .P
775 If studying the pattern does not produce any additional information
776 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
777 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
778 own \fBpcre_extra\fP block.
779 .P
780 The second argument of \fBpcre_study()\fP contains option bits. At present, no
781 options are defined, and this argument should always be zero.
782 .P
783 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
784 studying succeeds (even if no data is returned), the variable it points to is
785 set to NULL. Otherwise it is set to point to a textual error message. This is a
786 static string that is part of the library. You must not try to free it. You
787 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
788 sure that it has run successfully.
789 .P
790 This is a typical call to \fBpcre_study\fP():
791 .sp
792 pcre_extra *pe;
793 pe = pcre_study(
794 re, /* result of pcre_compile() */
795 0, /* no options exist */
796 &error); /* set to NULL or points to a message */
797 .sp
798 At present, studying a pattern is useful only for non-anchored patterns that do
799 not have a single fixed starting character. A bitmap of possible starting
800 bytes is created.
801 .
802 .
803 .\" HTML <a name="localesupport"></a>
804 .SH "LOCALE SUPPORT"
805 .rs
806 .sp
807 PCRE handles caseless matching, and determines whether characters are letters,
808 digits, or whatever, by reference to a set of tables, indexed by character
809 value. When running in UTF-8 mode, this applies only to characters with codes
810 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
811 can be tested with \ep if PCRE is built with Unicode character property
812 support. The use of locales with Unicode is discouraged. If you are handling
813 characters with codes greater than 128, you should either use UTF-8 and
814 Unicode, or use locales, but not try to mix the two.
815 .P
816 PCRE contains an internal set of tables that are used when the final argument
817 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
818 Normally, the internal tables recognize only ASCII characters. However, when
819 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
820 default "C" locale of the local system, which may cause them to be different.
821 .P
822 The internal tables can always be overridden by tables supplied by the
823 application that calls PCRE. These may be created in a different locale from
824 the default. As more and more applications change to using Unicode, the need
825 for this locale support is expected to die away.
826 .P
827 External tables are built by calling the \fBpcre_maketables()\fP function,
828 which has no arguments, in the relevant locale. The result can then be passed
829 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
830 example, to build and use tables that are appropriate for the French locale
831 (where accented characters with values greater than 128 are treated as letters),
832 the following code could be used:
833 .sp
834 setlocale(LC_CTYPE, "fr_FR");
835 tables = pcre_maketables();
836 re = pcre_compile(..., tables);
837 .sp
838 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
839 are using Windows, the name for the French locale is "french".
840 .P
841 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
842 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
843 that the memory containing the tables remains available for as long as it is
844 needed.
845 .P
846 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
847 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
848 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
849 pattern, compilation, studying and matching all happen in the same locale, but
850 different patterns can be compiled in different locales.
851 .P
852 It is possible to pass a table pointer or NULL (indicating the use of the
853 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
854 this facility could be used to match a pattern in a different locale from the
855 one in which it was compiled. Passing table pointers at run time is discussed
856 below in the section on matching a pattern.
857 .
858 .
859 .SH "INFORMATION ABOUT A PATTERN"
860 .rs
861 .sp
862 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
863 .ti +5n
864 .B int \fIwhat\fP, void *\fIwhere\fP);
865 .PP
866 The \fBpcre_fullinfo()\fP function returns information about a compiled
867 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
868 nevertheless retained for backwards compability (and is documented below).
869 .P
870 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
871 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
872 the pattern was not studied. The third argument specifies which piece of
873 information is required, and the fourth argument is a pointer to a variable
874 to receive the data. The yield of the function is zero for success, or one of
875 the following negative numbers:
876 .sp
877 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
878 the argument \fIwhere\fP was NULL
879 PCRE_ERROR_BADMAGIC the "magic number" was not found
880 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
881 .sp
882 The "magic number" is placed at the start of each compiled pattern as an simple
883 check against passing an arbitrary memory pointer. Here is a typical call of
884 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
885 .sp
886 int rc;
887 size_t length;
888 rc = pcre_fullinfo(
889 re, /* result of pcre_compile() */
890 pe, /* result of pcre_study(), or NULL */
891 PCRE_INFO_SIZE, /* what is required */
892 &length); /* where to put the data */
893 .sp
894 The possible values for the third argument are defined in \fBpcre.h\fP, and are
895 as follows:
896 .sp
897 PCRE_INFO_BACKREFMAX
898 .sp
899 Return the number of the highest back reference in the pattern. The fourth
900 argument should point to an \fBint\fP variable. Zero is returned if there are
901 no back references.
902 .sp
903 PCRE_INFO_CAPTURECOUNT
904 .sp
905 Return the number of capturing subpatterns in the pattern. The fourth argument
906 should point to an \fBint\fP variable.
907 .sp
908 PCRE_INFO_DEFAULT_TABLES
909 .sp
910 Return a pointer to the internal default character tables within PCRE. The
911 fourth argument should point to an \fBunsigned char *\fP variable. This
912 information call is provided for internal use by the \fBpcre_study()\fP
913 function. External callers can cause PCRE to use its internal tables by passing
914 a NULL table pointer.
915 .sp
916 PCRE_INFO_FIRSTBYTE
917 .sp
918 Return information about the first byte of any matched string, for a
919 non-anchored pattern. The fourth argument should point to an \fBint\fP
920 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
921 still recognized for backwards compatibility.)
922 .P
923 If there is a fixed first byte, for example, from a pattern such as
924 (cat|cow|coyote), its value is returned. Otherwise, if either
925 .sp
926 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
927 starts with "^", or
928 .sp
929 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
930 (if it were set, the pattern would be anchored),
931 .sp
932 -1 is returned, indicating that the pattern matches only at the start of a
933 subject string or after any newline within the string. Otherwise -2 is
934 returned. For anchored patterns, -2 is returned.
935 .sp
936 PCRE_INFO_FIRSTTABLE
937 .sp
938 If the pattern was studied, and this resulted in the construction of a 256-bit
939 table indicating a fixed set of bytes for the first byte in any matching
940 string, a pointer to the table is returned. Otherwise NULL is returned. The
941 fourth argument should point to an \fBunsigned char *\fP variable.
942 .sp
943 PCRE_INFO_HASCRORLF
944 .sp
945 Return 1 if the pattern contains any explicit matches for CR or LF characters,
946 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
947 explicit match is either a literal CR or LF character, or \er or \en.
948 .sp
949 PCRE_INFO_JCHANGED
950 .sp
951 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
952 0. The fourth argument should point to an \fBint\fP variable. (?J) and
953 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
954 .sp
955 PCRE_INFO_LASTLITERAL
956 .sp
957 Return the value of the rightmost literal byte that must exist in any matched
958 string, other than at its start, if such a byte has been recorded. The fourth
959 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
960 returned. For anchored patterns, a last literal byte is recorded only if it
961 follows something of variable length. For example, for the pattern
962 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
963 is -1.
964 .sp
965 PCRE_INFO_NAMECOUNT
966 PCRE_INFO_NAMEENTRYSIZE
967 PCRE_INFO_NAMETABLE
968 .sp
969 PCRE supports the use of named as well as numbered capturing parentheses. The
970 names are just an additional way of identifying the parentheses, which still
971 acquire numbers. Several convenience functions such as
972 \fBpcre_get_named_substring()\fP are provided for extracting captured
973 substrings by name. It is also possible to extract the data directly, by first
974 converting the name to a number in order to access the correct pointers in the
975 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
976 you need to use the name-to-number map, which is described by these three
977 values.
978 .P
979 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
980 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
981 entry; both of these return an \fBint\fP value. The entry size depends on the
982 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
983 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
984 are the number of the capturing parenthesis, most significant byte first. The
985 rest of the entry is the corresponding name, zero terminated. The names are in
986 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
987 their parentheses numbers. For example, consider the following pattern (assume
988 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
989 .sp
990 .\" JOIN
991 (?<date> (?<year>(\ed\ed)?\ed\ed) -
992 (?<month>\ed\ed) - (?<day>\ed\ed) )
993 .sp
994 There are four named subpatterns, so the table has four entries, and each entry
995 in the table is eight bytes long. The table is as follows, with non-printing
996 bytes shows in hexadecimal, and undefined bytes shown as ??:
997 .sp
998 00 01 d a t e 00 ??
999 00 05 d a y 00 ?? ??
1000 00 04 m o n t h 00
1001 00 02 y e a r 00 ??
1002 .sp
1003 When writing code to extract data from named subpatterns using the
1004 name-to-number map, remember that the length of the entries is likely to be
1005 different for each compiled pattern.
1006 .sp
1007 PCRE_INFO_OKPARTIAL
1008 .sp
1009 Return 1 if the pattern can be used for partial matching, otherwise 0. The
1010 fourth argument should point to an \fBint\fP variable. The
1011 .\" HREF
1012 \fBpcrepartial\fP
1013 .\"
1014 documentation lists the restrictions that apply to patterns when partial
1015 matching is used.
1016 .sp
1017 PCRE_INFO_OPTIONS
1018 .sp
1019 Return a copy of the options with which the pattern was compiled. The fourth
1020 argument should point to an \fBunsigned long int\fP variable. These option bits
1021 are those specified in the call to \fBpcre_compile()\fP, modified by any
1022 top-level option settings at the start of the pattern itself. In other words,
1023 they are the options that will be in force when matching starts. For example,
1024 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1025 result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1026 .P
1027 A pattern is automatically anchored by PCRE if all of its top-level
1028 alternatives begin with one of the following:
1029 .sp
1030 ^ unless PCRE_MULTILINE is set
1031 \eA always
1032 \eG always
1033 .\" JOIN
1034 .* if PCRE_DOTALL is set and there are no back
1035 references to the subpattern in which .* appears
1036 .sp
1037 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1038 \fBpcre_fullinfo()\fP.
1039 .sp
1040 PCRE_INFO_SIZE
1041 .sp
1042 Return the size of the compiled pattern, that is, the value that was passed as
1043 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1044 place the compiled data. The fourth argument should point to a \fBsize_t\fP
1045 variable.
1046 .sp
1047 PCRE_INFO_STUDYSIZE
1048 .sp
1049 Return the size of the data block pointed to by the \fIstudy_data\fP field in
1050 a \fBpcre_extra\fP block. That is, it is the value that was passed to
1051 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1052 created by \fBpcre_study()\fP. The fourth argument should point to a
1053 \fBsize_t\fP variable.
1054 .
1055 .
1056 .SH "OBSOLETE INFO FUNCTION"
1057 .rs
1058 .sp
1059 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1060 .B *\fIfirstcharptr\fP);
1061 .PP
1062 The \fBpcre_info()\fP function is now obsolete because its interface is too
1063 restrictive to return all the available data about a compiled pattern. New
1064 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1065 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1066 following negative numbers:
1067 .sp
1068 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1069 PCRE_ERROR_BADMAGIC the "magic number" was not found
1070 .sp
1071 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1072 pattern was compiled is placed in the integer it points to (see
1073 PCRE_INFO_OPTIONS above).
1074 .P
1075 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1076 it is used to pass back information about the first character of any matched
1077 string (see PCRE_INFO_FIRSTBYTE above).
1078 .
1079 .
1080 .SH "REFERENCE COUNTS"
1081 .rs
1082 .sp
1083 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1084 .PP
1085 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1086 data block that contains a compiled pattern. It is provided for the benefit of
1087 applications that operate in an object-oriented manner, where different parts
1088 of the application may be using the same compiled pattern, but you want to free
1089 the block when they are all done.
1090 .P
1091 When a pattern is compiled, the reference count field is initialized to zero.
1092 It is changed only by calling this function, whose action is to add the
1093 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1094 function is the new value. However, the value of the count is constrained to
1095 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1096 it is forced to the appropriate limit value.
1097 .P
1098 Except when it is zero, the reference count is not correctly preserved if a
1099 pattern is compiled on one host and then transferred to a host whose byte-order
1100 is different. (This seems a highly unlikely scenario.)
1101 .
1102 .
1103 .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1104 .rs
1105 .sp
1106 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1107 .ti +5n
1108 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1109 .ti +5n
1110 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1111 .P
1112 The function \fBpcre_exec()\fP is called to match a subject string against a
1113 compiled pattern, which is passed in the \fIcode\fP argument. If the
1114 pattern has been studied, the result of the study should be passed in the
1115 \fIextra\fP argument. This function is the main matching facility of the
1116 library, and it operates in a Perl-like manner. For specialist use there is
1117 also an alternative matching function, which is described
1118 .\" HTML <a href="#dfamatch">
1119 .\" </a>
1120 below
1121 .\"
1122 in the section about the \fBpcre_dfa_exec()\fP function.
1123 .P
1124 In most applications, the pattern will have been compiled (and optionally
1125 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1126 possible to save compiled patterns and study data, and then use them later
1127 in different processes, possibly even on different hosts. For a discussion
1128 about this, see the
1129 .\" HREF
1130 \fBpcreprecompile\fP
1131 .\"
1132 documentation.
1133 .P
1134 Here is an example of a simple call to \fBpcre_exec()\fP:
1135 .sp
1136 int rc;
1137 int ovector[30];
1138 rc = pcre_exec(
1139 re, /* result of pcre_compile() */
1140 NULL, /* we didn't study the pattern */
1141 "some string", /* the subject string */
1142 11, /* the length of the subject string */
1143 0, /* start at offset 0 in the subject */
1144 0, /* default options */
1145 ovector, /* vector of integers for substring information */
1146 30); /* number of elements (NOT size in bytes) */
1147 .
1148 .\" HTML <a name="extradata"></a>
1149 .SS "Extra data for \fBpcre_exec()\fR"
1150 .rs
1151 .sp
1152 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1153 data block. The \fBpcre_study()\fP function returns such a block (when it
1154 doesn't return NULL), but you can also create one for yourself, and pass
1155 additional information in it. The \fBpcre_extra\fP block contains the following
1156 fields (not necessarily in this order):
1157 .sp
1158 unsigned long int \fIflags\fP;
1159 void *\fIstudy_data\fP;
1160 unsigned long int \fImatch_limit\fP;
1161 unsigned long int \fImatch_limit_recursion\fP;
1162 void *\fIcallout_data\fP;
1163 const unsigned char *\fItables\fP;
1164 .sp
1165 The \fIflags\fP field is a bitmap that specifies which of the other fields
1166 are set. The flag bits are:
1167 .sp
1168 PCRE_EXTRA_STUDY_DATA
1169 PCRE_EXTRA_MATCH_LIMIT
1170 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1171 PCRE_EXTRA_CALLOUT_DATA
1172 PCRE_EXTRA_TABLES
1173 .sp
1174 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1175 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1176 the appropriate flag bit. You should not set this yourself, but you may add to
1177 the block by setting the other fields and their corresponding flag bits.
1178 .P
1179 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1180 vast amount of resources when running patterns that are not going to match,
1181 but which have a very large number of possibilities in their search trees. The
1182 classic example is the use of nested unlimited repeats.
1183 .P
1184 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1185 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1186 number of times this function is called during a match, which has the effect of
1187 limiting the amount of backtracking that can take place. For patterns that are
1188 not anchored, the count restarts from zero for each position in the subject
1189 string.
1190 .P
1191 The default value for the limit can be set when PCRE is built; the default
1192 default is 10 million, which handles all but the most extreme cases. You can
1193 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1194 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1195 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1196 PCRE_ERROR_MATCHLIMIT.
1197 .P
1198 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1199 instead of limiting the total number of times that \fBmatch()\fP is called, it
1200 limits the depth of recursion. The recursion depth is a smaller number than the
1201 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1202 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1203 .P
1204 Limiting the recursion depth limits the amount of stack that can be used, or,
1205 when PCRE has been compiled to use memory on the heap instead of the stack, the
1206 amount of heap memory that can be used.
1207 .P
1208 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1209 built; the default default is the same value as the default for
1210 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1211 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1212 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1213 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1214 .P
1215 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1216 which is described in the
1217 .\" HREF
1218 \fBpcrecallout\fP
1219 .\"
1220 documentation.
1221 .P
1222 The \fItables\fP field is used to pass a character tables pointer to
1223 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1224 pattern. A non-NULL value is stored with the compiled pattern only if custom
1225 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1226 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1227 internal tables to be used. This facility is helpful when re-using patterns
1228 that have been saved after compiling with an external set of tables, because
1229 the external tables might be at a different address when \fBpcre_exec()\fP is
1230 called. See the
1231 .\" HREF
1232 \fBpcreprecompile\fP
1233 .\"
1234 documentation for a discussion of saving compiled patterns for later use.
1235 .
1236 .\" HTML <a name="execoptions"></a>
1237 .SS "Option bits for \fBpcre_exec()\fP"
1238 .rs
1239 .sp
1240 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1241 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1242 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,
1243 PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1244 .sp
1245 PCRE_ANCHORED
1246 .sp
1247 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1248 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1249 to be anchored by virtue of its contents, it cannot be made unachored at
1250 matching time.
1251 .sp
1252 PCRE_BSR_ANYCRLF
1253 PCRE_BSR_UNICODE
1254 .sp
1255 These options (which are mutually exclusive) control what the \eR escape
1256 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1257 match any Unicode newline sequence. These options override the choice that was
1258 made or defaulted when the pattern was compiled.
1259 .sp
1260 PCRE_NEWLINE_CR
1261 PCRE_NEWLINE_LF
1262 PCRE_NEWLINE_CRLF
1263 PCRE_NEWLINE_ANYCRLF
1264 PCRE_NEWLINE_ANY
1265 .sp
1266 These options override the newline definition that was chosen or defaulted when
1267 the pattern was compiled. For details, see the description of
1268 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1269 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1270 the way the match position is advanced after a match failure for an unanchored
1271 pattern.
1272 .P
1273 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1274 match attempt for an unanchored pattern fails when the current position is at a
1275 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1276 characters, the match position is advanced by two characters instead of one, in
1277 other words, to after the CRLF.
1278 .P
1279 The above rule is a compromise that makes the most common cases work as
1280 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1281 set), it does not match the string "\er\enA" because, after failing at the
1282 start, it skips both the CR and the LF before retrying. However, the pattern
1283 [\er\en]A does match that string, because it contains an explicit CR or LF
1284 reference, and so advances only by one character after the first failure.
1285 .P
1286 An explicit match for CR of LF is either a literal appearance of one of those
1287 characters, or one of the \er or \en escape sequences. Implicit matches such as
1288 [^X] do not count, nor does \es (which includes CR and LF in the characters
1289 that it matches).
1290 .P
1291 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1292 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1293 .sp
1294 PCRE_NOTBOL
1295 .sp
1296 This option specifies that first character of the subject string is not the
1297 beginning of a line, so the circumflex metacharacter should not match before
1298 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1299 never to match. This option affects only the behaviour of the circumflex
1300 metacharacter. It does not affect \eA.
1301 .sp
1302 PCRE_NOTEOL
1303 .sp
1304 This option specifies that the end of the subject string is not the end of a
1305 line, so the dollar metacharacter should not match it nor (except in multiline
1306 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1307 compile time) causes dollar never to match. This option affects only the
1308 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1309 .sp
1310 PCRE_NOTEMPTY
1311 .sp
1312 An empty string is not considered to be a valid match if this option is set. If
1313 there are alternatives in the pattern, they are tried. If all the alternatives
1314 match the empty string, the entire match fails. For example, if the pattern
1315 .sp
1316 a?b?
1317 .sp
1318 is applied to a string not beginning with "a" or "b", it matches the empty
1319 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1320 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1321 .P
1322 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1323 of a pattern match of the empty string within its \fBsplit()\fP function, and
1324 when using the /g modifier. It is possible to emulate Perl's behaviour after
1325 matching a null string by first trying the match again at the same offset with
1326 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1327 starting offset (see below) and trying an ordinary match again. There is some
1328 code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1329 .sp
1330 PCRE_NO_START_OPTIMIZE
1331 .sp
1332 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1333 a match, in order to speed up the process. For example, if it is known that a
1334 match must start with a specific character, it searches the subject for that
1335 character, and fails immediately if it cannot find it, without actually running
1336 the main matching function. When callouts are in use, these optimizations can
1337 cause them to be skipped. This option disables the "start-up" optimizations,
1338 causing performance to suffer, but ensuring that the callouts do occur.
1339 .sp
1340 PCRE_NO_UTF8_CHECK
1341 .sp
1342 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1343 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1344 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1345 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1346 strings in the
1347 .\" HTML <a href="pcre.html#utf8strings">
1348 .\" </a>
1349 section on UTF-8 support
1350 .\"
1351 in the main
1352 .\" HREF
1353 \fBpcre\fP
1354 .\"
1355 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1356 the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1357 PCRE_ERROR_BADUTF8_OFFSET is returned.
1358 .P
1359 If you already know that your subject is valid, and you want to skip these
1360 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1361 calling \fBpcre_exec()\fP. You might want to do this for the second and
1362 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1363 all the matches in a single subject string. However, you should be sure that
1364 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1365 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1366 subject, or a value of \fIstartoffset\fP that does not point to the start of a
1367 UTF-8 character, is undefined. Your program may crash.
1368 .sp
1369 PCRE_PARTIAL
1370 .sp
1371 This option turns on the partial matching feature. If the subject string fails
1372 to match the pattern, but at some point during the matching process the end of
1373 the subject was reached (that is, the subject partially matches the pattern and
1374 the failure to match occurred only because there were not enough subject
1375 characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1376 PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1377 may appear in the pattern. These are discussed in the
1378 .\" HREF
1379 \fBpcrepartial\fP
1380 .\"
1381 documentation.
1382 .
1383 .SS "The string to be matched by \fBpcre_exec()\fP"
1384 .rs
1385 .sp
1386 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1387 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1388 in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1389 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1390 zero bytes. When the starting offset is zero, the search for a match starts at
1391 the beginning of the subject, and this is by far the most common case.
1392 .P
1393 A non-zero starting offset is useful when searching for another match in the
1394 same subject by calling \fBpcre_exec()\fP again after a previous success.
1395 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1396 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1397 lookbehind. For example, consider the pattern
1398 .sp
1399 \eBiss\eB
1400 .sp
1401 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1402 the current position in the subject is not a word boundary.) When applied to
1403 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1404 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1405 subject, namely "issipi", it does not match, because \eB is always false at the
1406 start of the subject, which is deemed to be a word boundary. However, if
1407 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1408 set to 4, it finds the second occurrence of "iss" because it is able to look
1409 behind the starting point to discover that it is preceded by a letter.
1410 .P
1411 If a non-zero starting offset is passed when the pattern is anchored, one
1412 attempt to match at the given offset is made. This can only succeed if the
1413 pattern does not require the match to be at the start of the subject.
1414 .
1415 .SS "How \fBpcre_exec()\fP returns captured substrings"
1416 .rs
1417 .sp
1418 In general, a pattern matches a certain portion of the subject, and in
1419 addition, further substrings from the subject may be picked out by parts of the
1420 pattern. Following the usage in Jeffrey Friedl's book, this is called
1421 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1422 a fragment of a pattern that picks out a substring. PCRE supports several other
1423 kinds of parenthesized subpattern that do not cause substrings to be captured.
1424 .P
1425 Captured substrings are returned to the caller via a vector of integers whose
1426 address is passed in \fIovector\fP. The number of elements in the vector is
1427 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1428 argument is NOT the size of \fIovector\fP in bytes.
1429 .P
1430 The first two-thirds of the vector is used to pass back captured substrings,
1431 each substring using a pair of integers. The remaining third of the vector is
1432 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1433 and is not available for passing back information. The number passed in
1434 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1435 rounded down.
1436 .P
1437 When a match is successful, information about captured substrings is returned
1438 in pairs of integers, starting at the beginning of \fIovector\fP, and
1439 continuing up to two-thirds of its length at the most. The first element of
1440 each pair is set to the byte offset of the first character in a substring, and
1441 the second is set to the byte offset of the first character after the end of a
1442 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1443 mode. They are not character counts.
1444 .P
1445 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1446 portion of the subject string matched by the entire pattern. The next pair is
1447 used for the first capturing subpattern, and so on. The value returned by
1448 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1449 For example, if two substrings have been captured, the returned value is 3. If
1450 there are no capturing subpatterns, the return value from a successful match is
1451 1, indicating that just the first pair of offsets has been set.
1452 .P
1453 If a capturing subpattern is matched repeatedly, it is the last portion of the
1454 string that it matched that is returned.
1455 .P
1456 If the vector is too small to hold all the captured substring offsets, it is
1457 used as far as possible (up to two-thirds of its length), and the function
1458 returns a value of zero. If the substring offsets are not of interest,
1459 \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1460 \fIovecsize\fP as zero. However, if the pattern contains back references and
1461 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1462 has to get additional memory for use during matching. Thus it is usually
1463 advisable to supply an \fIovector\fP.
1464 .P
1465 The \fBpcre_info()\fP function can be used to find out how many capturing
1466 subpatterns there are in a compiled pattern. The smallest size for
1467 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1468 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1469 .P
1470 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1471 the subject when subpattern \fIn\fP has not been used at all. For example, if
1472 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1473 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1474 happens, both values in the offset pairs corresponding to unused subpatterns
1475 are set to -1.
1476 .P
1477 Offset values that correspond to unused subpatterns at the end of the
1478 expression are also set to -1. For example, if the string "abc" is matched
1479 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1480 return from the function is 2, because the highest used capturing subpattern
1481 number is 1. However, you can refer to the offsets for the second and third
1482 capturing subpatterns if you wish (assuming the vector is large enough, of
1483 course).
1484 .P
1485 Some convenience functions are provided for extracting the captured substrings
1486 as separate strings. These are described below.
1487 .
1488 .\" HTML <a name="errorlist"></a>
1489 .SS "Error return values from \fBpcre_exec()\fP"
1490 .rs
1491 .sp
1492 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1493 defined in the header file:
1494 .sp
1495 PCRE_ERROR_NOMATCH (-1)
1496 .sp
1497 The subject string did not match the pattern.
1498 .sp
1499 PCRE_ERROR_NULL (-2)
1500 .sp
1501 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1502 NULL and \fIovecsize\fP was not zero.
1503 .sp
1504 PCRE_ERROR_BADOPTION (-3)
1505 .sp
1506 An unrecognized bit was set in the \fIoptions\fP argument.
1507 .sp
1508 PCRE_ERROR_BADMAGIC (-4)
1509 .sp
1510 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1511 the case when it is passed a junk pointer and to detect when a pattern that was
1512 compiled in an environment of one endianness is run in an environment with the
1513 other endianness. This is the error that PCRE gives when the magic number is
1514 not present.
1515 .sp
1516 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1517 .sp
1518 While running the pattern match, an unknown item was encountered in the
1519 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1520 of the compiled pattern.
1521 .sp
1522 PCRE_ERROR_NOMEMORY (-6)
1523 .sp
1524 If a pattern contains back references, but the \fIovector\fP that is passed to
1525 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1526 gets a block of memory at the start of matching to use for this purpose. If the
1527 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1528 automatically freed at the end of matching.
1529 .sp
1530 PCRE_ERROR_NOSUBSTRING (-7)
1531 .sp
1532 This error is used by the \fBpcre_copy_substring()\fP,
1533 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1534 below). It is never returned by \fBpcre_exec()\fP.
1535 .sp
1536 PCRE_ERROR_MATCHLIMIT (-8)
1537 .sp
1538 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1539 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1540 above.
1541 .sp
1542 PCRE_ERROR_CALLOUT (-9)
1543 .sp
1544 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1545 use by callout functions that want to yield a distinctive error code. See the
1546 .\" HREF
1547 \fBpcrecallout\fP
1548 .\"
1549 documentation for details.
1550 .sp
1551 PCRE_ERROR_BADUTF8 (-10)
1552 .sp
1553 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1554 .sp
1555 PCRE_ERROR_BADUTF8_OFFSET (-11)
1556 .sp
1557 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1558 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1559 .sp
1560 PCRE_ERROR_PARTIAL (-12)
1561 .sp
1562 The subject string did not match, but it did match partially. See the
1563 .\" HREF
1564 \fBpcrepartial\fP
1565 .\"
1566 documentation for details of partial matching.
1567 .sp
1568 PCRE_ERROR_BADPARTIAL (-13)
1569 .sp
1570 The PCRE_PARTIAL option was used with a compiled pattern containing items that
1571 are not supported for partial matching. See the
1572 .\" HREF
1573 \fBpcrepartial\fP
1574 .\"
1575 documentation for details of partial matching.
1576 .sp
1577 PCRE_ERROR_INTERNAL (-14)
1578 .sp
1579 An unexpected internal error has occurred. This error could be caused by a bug
1580 in PCRE or by overwriting of the compiled pattern.
1581 .sp
1582 PCRE_ERROR_BADCOUNT (-15)
1583 .sp
1584 This error is given if the value of the \fIovecsize\fP argument is negative.
1585 .sp
1586 PCRE_ERROR_RECURSIONLIMIT (-21)
1587 .sp
1588 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1589 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1590 description above.
1591 .sp
1592 PCRE_ERROR_BADNEWLINE (-23)
1593 .sp
1594 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1595 .P
1596 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1597 .
1598 .
1599 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1600 .rs
1601 .sp
1602 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1603 .ti +5n
1604 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1605 .ti +5n
1606 .B int \fIbuffersize\fP);
1607 .PP
1608 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1609 .ti +5n
1610 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1611 .ti +5n
1612 .B const char **\fIstringptr\fP);
1613 .PP
1614 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1615 .ti +5n
1616 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1617 .PP
1618 Captured substrings can be accessed directly by using the offsets returned by
1619 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1620 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1621 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1622 as new, separate, zero-terminated strings. These functions identify substrings
1623 by number. The next section describes functions for extracting named
1624 substrings.
1625 .P
1626 A substring that contains a binary zero is correctly extracted and has a
1627 further zero added on the end, but the result is not, of course, a C string.
1628 However, you can process such a string by referring to the length that is
1629 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1630 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1631 for handling strings containing binary zeros, because the end of the final
1632 string is not independently indicated.
1633 .P
1634 The first three arguments are the same for all three of these functions:
1635 \fIsubject\fP is the subject string that has just been successfully matched,
1636 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1637 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1638 captured by the match, including the substring that matched the entire regular
1639 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1640 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1641 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1642 number of elements in the vector divided by three.
1643 .P
1644 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1645 extract a single substring, whose number is given as \fIstringnumber\fP. A
1646 value of zero extracts the substring that matched the entire pattern, whereas
1647 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1648 the string is placed in \fIbuffer\fP, whose length is given by
1649 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1650 obtained via \fBpcre_malloc\fP, and its address is returned via
1651 \fIstringptr\fP. The yield of the function is the length of the string, not
1652 including the terminating zero, or one of these error codes:
1653 .sp
1654 PCRE_ERROR_NOMEMORY (-6)
1655 .sp
1656 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1657 memory failed for \fBpcre_get_substring()\fP.
1658 .sp
1659 PCRE_ERROR_NOSUBSTRING (-7)
1660 .sp
1661 There is no substring whose number is \fIstringnumber\fP.
1662 .P
1663 The \fBpcre_get_substring_list()\fP function extracts all available substrings
1664 and builds a list of pointers to them. All this is done in a single block of
1665 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1666 is returned via \fIlistptr\fP, which is also the start of the list of string
1667 pointers. The end of the list is marked by a NULL pointer. The yield of the
1668 function is zero if all went well, or the error code
1669 .sp
1670 PCRE_ERROR_NOMEMORY (-6)
1671 .sp
1672 if the attempt to get the memory block failed.
1673 .P
1674 When any of these functions encounter a substring that is unset, which can
1675 happen when capturing subpattern number \fIn+1\fP matches some part of the
1676 subject, but subpattern \fIn\fP has not been used at all, they return an empty
1677 string. This can be distinguished from a genuine zero-length substring by
1678 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1679 substrings.
1680 .P
1681 The two convenience functions \fBpcre_free_substring()\fP and
1682 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1683 a previous call of \fBpcre_get_substring()\fP or
1684 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1685 the function pointed to by \fBpcre_free\fP, which of course could be called
1686 directly from a C program. However, PCRE is used in some situations where it is
1687 linked via a special interface to another programming language that cannot use
1688 \fBpcre_free\fP directly; it is for these cases that the functions are
1689 provided.
1690 .
1691 .
1692 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1693 .rs
1694 .sp
1695 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1696 .ti +5n
1697 .B const char *\fIname\fP);
1698 .PP
1699 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1700 .ti +5n
1701 .B const char *\fIsubject\fP, int *\fIovector\fP,
1702 .ti +5n
1703 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1704 .ti +5n
1705 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1706 .PP
1707 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1708 .ti +5n
1709 .B const char *\fIsubject\fP, int *\fIovector\fP,
1710 .ti +5n
1711 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1712 .ti +5n
1713 .B const char **\fIstringptr\fP);
1714 .PP
1715 To extract a substring by name, you first have to find associated number.
1716 For example, for this pattern
1717 .sp
1718 (a+)b(?<xxx>\ed+)...
1719 .sp
1720 the number of the subpattern called "xxx" is 2. If the name is known to be
1721 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1722 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1723 pattern, and the second is the name. The yield of the function is the
1724 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1725 that name.
1726 .P
1727 Given the number, you can extract the substring directly, or use one of the
1728 functions described in the previous section. For convenience, there are also
1729 two functions that do the whole job.
1730 .P
1731 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1732 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1733 functions that extract by number. As these are described in the previous
1734 section, they are not re-described here. There are just two differences:
1735 .P
1736 First, instead of a substring number, a substring name is given. Second, there
1737 is an extra argument, given at the start, which is a pointer to the compiled
1738 pattern. This is needed in order to gain access to the name-to-number
1739 translation table.
1740 .P
1741 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1742 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1743 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1744 the behaviour may not be what you want (see the next section).
1745 .P
1746 \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
1747 subpatterns with the same number, you cannot use names to distinguish them,
1748 because names are not included in the compiled code. The matching process uses
1749 only numbers.
1750 .
1751 .SH "DUPLICATE SUBPATTERN NAMES"
1752 .rs
1753 .sp
1754 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1755 .ti +5n
1756 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1757 .PP
1758 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1759 are not required to be unique. Normally, patterns with duplicate names are such
1760 that in any one match, only one of the named subpatterns participates. An
1761 example is shown in the
1762 .\" HREF
1763 \fBpcrepattern\fP
1764 .\"
1765 documentation.
1766 .P
1767 When duplicates are present, \fBpcre_copy_named_substring()\fP and
1768 \fBpcre_get_named_substring()\fP return the first substring corresponding to
1769 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1770 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1771 returns one of the numbers that are associated with the name, but it is not
1772 defined which it is.
1773 .P
1774 If you want to get full details of all captured substrings for a given name,
1775 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1776 argument is the compiled pattern, and the second is the name. The third and
1777 fourth are pointers to variables which are updated by the function. After it
1778 has run, they point to the first and last entries in the name-to-number table
1779 for the given name. The function itself returns the length of each entry, or
1780 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1781 described above in the section entitled \fIInformation about a pattern\fP.
1782 Given all the relevant entries for the name, you can extract each of their
1783 numbers, and hence the captured data, if any.
1784 .
1785 .
1786 .SH "FINDING ALL POSSIBLE MATCHES"
1787 .rs
1788 .sp
1789 The traditional matching function uses a similar algorithm to Perl, which stops
1790 when it finds the first match, starting at a given point in the subject. If you
1791 want to find all possible matches, or the longest possible match, consider
1792 using the alternative matching function (see below) instead. If you cannot use
1793 the alternative function, but still need to find all possible matches, you
1794 can kludge it up by making use of the callout facility, which is described in
1795 the
1796 .\" HREF
1797 \fBpcrecallout\fP
1798 .\"
1799 documentation.
1800 .P
1801 What you have to do is to insert a callout right at the end of the pattern.
1802 When your callout function is called, extract and save the current matched
1803 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1804 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1805 will yield PCRE_ERROR_NOMATCH.
1806 .
1807 .
1808 .\" HTML <a name="dfamatch"></a>
1809 .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1810 .rs
1811 .sp
1812 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1813 .ti +5n
1814 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1815 .ti +5n
1816 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1817 .ti +5n
1818 .B int *\fIworkspace\fP, int \fIwscount\fP);
1819 .P
1820 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1821 a compiled pattern, using a matching algorithm that scans the subject string
1822 just once, and does not backtrack. This has different characteristics to the
1823 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1824 patterns are not supported. Nevertheless, there are times when this kind of
1825 matching can be useful. For a discussion of the two matching algorithms, see
1826 the
1827 .\" HREF
1828 \fBpcrematching\fP
1829 .\"
1830 documentation.
1831 .P
1832 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1833 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1834 different way, and this is described below. The other common arguments are used
1835 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1836 here.
1837 .P
1838 The two additional arguments provide workspace for the function. The workspace
1839 vector should contain at least 20 elements. It is used for keeping track of
1840 multiple paths through the pattern tree. More workspace will be needed for
1841 patterns and subjects where there are a lot of potential matches.
1842 .P
1843 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1844 .sp
1845 int rc;
1846 int ovector[10];
1847 int wspace[20];
1848 rc = pcre_dfa_exec(
1849 re, /* result of pcre_compile() */
1850 NULL, /* we didn't study the pattern */
1851 "some string", /* the subject string */
1852 11, /* the length of the subject string */
1853 0, /* start at offset 0 in the subject */
1854 0, /* default options */
1855 ovector, /* vector of integers for substring information */
1856 10, /* number of elements (NOT size in bytes) */
1857 wspace, /* working space vector */
1858 20); /* number of elements (NOT size in bytes) */
1859 .
1860 .SS "Option bits for \fBpcre_dfa_exec()\fP"
1861 .rs
1862 .sp
1863 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1864 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1865 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
1866 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1867 the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1868 .sp
1869 PCRE_PARTIAL
1870 .sp
1871 This has the same general effect as it does for \fBpcre_exec()\fP, but the
1872 details are slightly different. When PCRE_PARTIAL is set for
1873 \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1874 PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1875 complete matches, but there is still at least one matching possibility. The
1876 portion of the string that provided the partial match is set as the first
1877 matching string.
1878 .sp
1879 PCRE_DFA_SHORTEST
1880 .sp
1881 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1882 soon as it has found one match. Because of the way the alternative algorithm
1883 works, this is necessarily the shortest possible match at the first possible
1884 matching point in the subject string.
1885 .sp
1886 PCRE_DFA_RESTART
1887 .sp
1888 When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1889 a partial match, it is possible to call it again, with additional subject
1890 characters, and have it continue with the same match. The PCRE_DFA_RESTART
1891 option requests this action; when it is set, the \fIworkspace\fP and
1892 \fIwscount\fP options must reference the same vector as before because data
1893 about the match so far is left in them after a partial match. There is more
1894 discussion of this facility in the
1895 .\" HREF
1896 \fBpcrepartial\fP
1897 .\"
1898 documentation.
1899 .
1900 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1901 .rs
1902 .sp
1903 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1904 substring in the subject. Note, however, that all the matches from one run of
1905 the function start at the same point in the subject. The shorter matches are
1906 all initial substrings of the longer matches. For example, if the pattern
1907 .sp
1908 <.*>
1909 .sp
1910 is matched against the string
1911 .sp
1912 This is <something> <something else> <something further> no more
1913 .sp
1914 the three matched strings are
1915 .sp
1916 <something>
1917 <something> <something else>
1918 <something> <something else> <something further>
1919 .sp
1920 On success, the yield of the function is a number greater than zero, which is
1921 the number of matched substrings. The substrings themselves are returned in
1922 \fIovector\fP. Each string uses two elements; the first is the offset to the
1923 start, and the second is the offset to the end. In fact, all the strings have
1924 the same start offset. (Space could have been saved by giving this only once,
1925 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1926 returns data, even though the meaning of the strings is different.)
1927 .P
1928 The strings are returned in reverse order of length; that is, the longest
1929 matching string is given first. If there were too many matches to fit into
1930 \fIovector\fP, the yield of the function is zero, and the vector is filled with
1931 the longest matches.
1932 .
1933 .SS "Error returns from \fBpcre_dfa_exec()\fP"
1934 .rs
1935 .sp
1936 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1937 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1938 described
1939 .\" HTML <a href="#errorlist">
1940 .\" </a>
1941 above.
1942 .\"
1943 There are in addition the following errors that are specific to
1944 \fBpcre_dfa_exec()\fP:
1945 .sp
1946 PCRE_ERROR_DFA_UITEM (-16)
1947 .sp
1948 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1949 that it does not support, for instance, the use of \eC or a back reference.
1950 .sp
1951 PCRE_ERROR_DFA_UCOND (-17)
1952 .sp
1953 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1954 uses a back reference for the condition, or a test for recursion in a specific
1955 group. These are not supported.
1956 .sp
1957 PCRE_ERROR_DFA_UMLIMIT (-18)
1958 .sp
1959 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1960 block that contains a setting of the \fImatch_limit\fP field. This is not
1961 supported (it is meaningless).
1962 .sp
1963 PCRE_ERROR_DFA_WSSIZE (-19)
1964 .sp
1965 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1966 \fIworkspace\fP vector.
1967 .sp
1968 PCRE_ERROR_DFA_RECURSE (-20)
1969 .sp
1970 When a recursive subpattern is processed, the matching function calls itself
1971 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1972 error is given if the output vector is not large enough. This should be
1973 extremely rare, as a vector of size 1000 is used.
1974 .
1975 .
1976 .SH "SEE ALSO"
1977 .rs
1978 .sp
1979 \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1980 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1981 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1982 .
1983 .
1984 .SH AUTHOR
1985 .rs
1986 .sp
1987 .nf
1988 Philip Hazel
1989 University Computing Service
1990 Cambridge CB2 3QH, England.
1991 .fi
1992 .
1993 .
1994 .SH REVISION
1995 .rs
1996 .sp
1997 .nf
1998 Last updated: 17 March 2009
1999 Copyright (c) 1997-2009 University of Cambridge.
2000 .fi

Properties

Name Value
svn:eol-style native
svn:keywords "Author Date Id Revision Url"

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12