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Revision 426 - (show annotations)
Wed Aug 26 15:38:32 2009 UTC (10 years ago) by ph10
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Remove restrictions on pcre_exec() partial matching.
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, but also some others) can also be set and unset from
411 within the pattern (see the detailed description in the
412 .\" HREF
413 \fBpcrepattern\fP
414 .\"
415 documentation). For those options that can be different in different parts of
416 the pattern, the contents of the \fIoptions\fP argument specifies their initial
417 settings at the start of compilation and execution. The PCRE_ANCHORED and
418 PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
419 compile time.
420 .P
421 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
422 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
423 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
424 error message. This is a static string that is part of the library. You must
425 not try to free it. The offset from the start of the pattern to the character
426 where the error was discovered is placed in the variable pointed to by
427 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
428 .P
429 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
430 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
431 returned via this argument in the event of an error. This is in addition to the
432 textual error message. Error codes and messages are listed below.
433 .P
434 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
435 character tables that are built when PCRE is compiled, using the default C
436 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
437 call to \fBpcre_maketables()\fP. This value is stored with the compiled
438 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
439 passed to it. For more discussion, see the section on locale support below.
440 .P
441 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
442 .sp
443 pcre *re;
444 const char *error;
445 int erroffset;
446 re = pcre_compile(
447 "^A.*Z", /* the pattern */
448 0, /* default options */
449 &error, /* for error message */
450 &erroffset, /* for error offset */
451 NULL); /* use default character tables */
452 .sp
453 The following names for option bits are defined in the \fBpcre.h\fP header
454 file:
455 .sp
456 PCRE_ANCHORED
457 .sp
458 If this bit is set, the pattern is forced to be "anchored", that is, it is
459 constrained to match only at the first matching point in the string that is
460 being searched (the "subject string"). This effect can also be achieved by
461 appropriate constructs in the pattern itself, which is the only way to do it in
462 Perl.
463 .sp
464 PCRE_AUTO_CALLOUT
465 .sp
466 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
467 all with number 255, before each pattern item. For discussion of the callout
468 facility, see the
469 .\" HREF
470 \fBpcrecallout\fP
471 .\"
472 documentation.
473 .sp
474 PCRE_BSR_ANYCRLF
475 PCRE_BSR_UNICODE
476 .sp
477 These options (which are mutually exclusive) control what the \eR escape
478 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
479 match any Unicode newline sequence. The default is specified when PCRE is
480 built. It can be overridden from within the pattern, or by setting an option
481 when a compiled pattern is matched.
482 .sp
483 PCRE_CASELESS
484 .sp
485 If this bit is set, letters in the pattern match both upper and lower case
486 letters. It is equivalent to Perl's /i option, and it can be changed within a
487 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
488 concept of case for characters whose values are less than 128, so caseless
489 matching is always possible. For characters with higher values, the concept of
490 case is supported if PCRE is compiled with Unicode property support, but not
491 otherwise. If you want to use caseless matching for characters 128 and above,
492 you must ensure that PCRE is compiled with Unicode property support as well as
493 with UTF-8 support.
494 .sp
495 PCRE_DOLLAR_ENDONLY
496 .sp
497 If this bit is set, a dollar metacharacter in the pattern matches only at the
498 end of the subject string. Without this option, a dollar also matches
499 immediately before a newline at the end of the string (but not before any other
500 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
501 There is no equivalent to this option in Perl, and no way to set it within a
502 pattern.
503 .sp
504 PCRE_DOTALL
505 .sp
506 If this bit is set, a dot metacharater in the pattern matches all characters,
507 including those that indicate newline. Without it, a dot does not match when
508 the current position is at a newline. This option is equivalent to Perl's /s
509 option, and it can be changed within a pattern by a (?s) option setting. A
510 negative class such as [^a] always matches newline characters, independent of
511 the setting of this option.
512 .sp
513 PCRE_DUPNAMES
514 .sp
515 If this bit is set, names used to identify capturing subpatterns need not be
516 unique. This can be helpful for certain types of pattern when it is known that
517 only one instance of the named subpattern can ever be matched. There are more
518 details of named subpatterns below; see also the
519 .\" HREF
520 \fBpcrepattern\fP
521 .\"
522 documentation.
523 .sp
524 PCRE_EXTENDED
525 .sp
526 If this bit is set, whitespace data characters in the pattern are totally
527 ignored except when escaped or inside a character class. Whitespace does not
528 include the VT character (code 11). In addition, characters between an
529 unescaped # outside a character class and the next newline, inclusive, are also
530 ignored. This is equivalent to Perl's /x option, and it can be changed within a
531 pattern by a (?x) option setting.
532 .P
533 This option makes it possible to include comments inside complicated patterns.
534 Note, however, that this applies only to data characters. Whitespace characters
535 may never appear within special character sequences in a pattern, for example
536 within the sequence (?( which introduces a conditional subpattern.
537 .sp
538 PCRE_EXTRA
539 .sp
540 This option was invented in order to turn on additional functionality of PCRE
541 that is incompatible with Perl, but it is currently of very little use. When
542 set, any backslash in a pattern that is followed by a letter that has no
543 special meaning causes an error, thus reserving these combinations for future
544 expansion. By default, as in Perl, a backslash followed by a letter with no
545 special meaning is treated as a literal. (Perl can, however, be persuaded to
546 give a warning for this.) There are at present no other features controlled by
547 this option. It can also be set by a (?X) option setting within a pattern.
548 .sp
549 PCRE_FIRSTLINE
550 .sp
551 If this option is set, an unanchored pattern is required to match before or at
552 the first newline in the subject string, though the matched text may continue
553 over the newline.
554 .sp
555 PCRE_JAVASCRIPT_COMPAT
556 .sp
557 If this option is set, PCRE's behaviour is changed in some ways so that it is
558 compatible with JavaScript rather than Perl. The changes are as follows:
559 .P
560 (1) A lone closing square bracket in a pattern causes a compile-time error,
561 because this is illegal in JavaScript (by default it is treated as a data
562 character). Thus, the pattern AB]CD becomes illegal when this option is set.
563 .P
564 (2) At run time, a back reference to an unset subpattern group matches an empty
565 string (by default this causes the current matching alternative to fail). A
566 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
567 an "a" in the subject), whereas it fails by default, for Perl compatibility.
568 .sp
569 PCRE_MULTILINE
570 .sp
571 By default, PCRE treats the subject string as consisting of a single line of
572 characters (even if it actually contains newlines). The "start of line"
573 metacharacter (^) matches only at the start of the string, while the "end of
574 line" metacharacter ($) matches only at the end of the string, or before a
575 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
576 Perl.
577 .P
578 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
579 match immediately following or immediately before internal newlines in the
580 subject string, respectively, as well as at the very start and end. This is
581 equivalent to Perl's /m option, and it can be changed within a pattern by a
582 (?m) option setting. If there are no newlines in a subject string, or no
583 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
584 .sp
585 PCRE_NEWLINE_CR
586 PCRE_NEWLINE_LF
587 PCRE_NEWLINE_CRLF
588 PCRE_NEWLINE_ANYCRLF
589 PCRE_NEWLINE_ANY
590 .sp
591 These options override the default newline definition that was chosen when PCRE
592 was built. Setting the first or the second specifies that a newline is
593 indicated by a single character (CR or LF, respectively). Setting
594 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
595 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
596 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
597 that any Unicode newline sequence should be recognized. The Unicode newline
598 sequences are the three just mentioned, plus the single characters VT (vertical
599 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
600 separator, U+2028), and PS (paragraph separator, U+2029). The last two are
601 recognized only in UTF-8 mode.
602 .P
603 The newline setting in the options word uses three bits that are treated
604 as a number, giving eight possibilities. Currently only six are used (default
605 plus the five values above). This means that if you set more than one newline
606 option, the combination may or may not be sensible. For example,
607 PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
608 other combinations may yield unused numbers and cause an error.
609 .P
610 The only time that a line break is specially recognized when compiling a
611 pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
612 class is encountered. This indicates a comment that lasts until after the next
613 line break sequence. In other circumstances, line break sequences are treated
614 as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
615 as whitespace characters and are therefore ignored.
616 .P
617 The newline option that is set at compile time becomes the default that is used
618 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
619 .sp
620 PCRE_NO_AUTO_CAPTURE
621 .sp
622 If this option is set, it disables the use of numbered capturing parentheses in
623 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
624 were followed by ?: but named parentheses can still be used for capturing (and
625 they acquire numbers in the usual way). There is no equivalent of this option
626 in Perl.
627 .sp
628 PCRE_UNGREEDY
629 .sp
630 This option inverts the "greediness" of the quantifiers so that they are not
631 greedy by default, but become greedy if followed by "?". It is not compatible
632 with Perl. It can also be set by a (?U) option setting within the pattern.
633 .sp
634 PCRE_UTF8
635 .sp
636 This option causes PCRE to regard both the pattern and the subject as strings
637 of UTF-8 characters instead of single-byte character strings. However, it is
638 available only when PCRE is built to include UTF-8 support. If not, the use
639 of this option provokes an error. Details of how this option changes the
640 behaviour of PCRE are given in the
641 .\" HTML <a href="pcre.html#utf8support">
642 .\" </a>
643 section on UTF-8 support
644 .\"
645 in the main
646 .\" HREF
647 \fBpcre\fP
648 .\"
649 page.
650 .sp
651 PCRE_NO_UTF8_CHECK
652 .sp
653 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
654 automatically checked. There is a discussion about the
655 .\" HTML <a href="pcre.html#utf8strings">
656 .\" </a>
657 validity of UTF-8 strings
658 .\"
659 in the main
660 .\" HREF
661 \fBpcre\fP
662 .\"
663 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
664 returns an error. If you already know that your pattern is valid, and you want
665 to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
666 option. When it is set, the effect of passing an invalid UTF-8 string as a
667 pattern is undefined. It may cause your program to crash. Note that this option
668 can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
669 the UTF-8 validity checking of subject strings.
670 .
671 .
672 .SH "COMPILATION ERROR CODES"
673 .rs
674 .sp
675 The following table lists the error codes than may be returned by
676 \fBpcre_compile2()\fP, along with the error messages that may be returned by
677 both compiling functions. As PCRE has developed, some error codes have fallen
678 out of use. To avoid confusion, they have not been re-used.
679 .sp
680 0 no error
681 1 \e at end of pattern
682 2 \ec at end of pattern
683 3 unrecognized character follows \e
684 4 numbers out of order in {} quantifier
685 5 number too big in {} quantifier
686 6 missing terminating ] for character class
687 7 invalid escape sequence in character class
688 8 range out of order in character class
689 9 nothing to repeat
690 10 [this code is not in use]
691 11 internal error: unexpected repeat
692 12 unrecognized character after (? or (?-
693 13 POSIX named classes are supported only within a class
694 14 missing )
695 15 reference to non-existent subpattern
696 16 erroffset passed as NULL
697 17 unknown option bit(s) set
698 18 missing ) after comment
699 19 [this code is not in use]
700 20 regular expression is too large
701 21 failed to get memory
702 22 unmatched parentheses
703 23 internal error: code overflow
704 24 unrecognized character after (?<
705 25 lookbehind assertion is not fixed length
706 26 malformed number or name after (?(
707 27 conditional group contains more than two branches
708 28 assertion expected after (?(
709 29 (?R or (?[+-]digits must be followed by )
710 30 unknown POSIX class name
711 31 POSIX collating elements are not supported
712 32 this version of PCRE is not compiled with PCRE_UTF8 support
713 33 [this code is not in use]
714 34 character value in \ex{...} sequence is too large
715 35 invalid condition (?(0)
716 36 \eC not allowed in lookbehind assertion
717 37 PCRE does not support \eL, \el, \eN, \eU, or \eu
718 38 number after (?C is > 255
719 39 closing ) for (?C expected
720 40 recursive call could loop indefinitely
721 41 unrecognized character after (?P
722 42 syntax error in subpattern name (missing terminator)
723 43 two named subpatterns have the same name
724 44 invalid UTF-8 string
725 45 support for \eP, \ep, and \eX has not been compiled
726 46 malformed \eP or \ep sequence
727 47 unknown property name after \eP or \ep
728 48 subpattern name is too long (maximum 32 characters)
729 49 too many named subpatterns (maximum 10000)
730 50 [this code is not in use]
731 51 octal value is greater than \e377 (not in UTF-8 mode)
732 52 internal error: overran compiling workspace
733 53 internal error: previously-checked referenced subpattern not found
734 54 DEFINE group contains more than one branch
735 55 repeating a DEFINE group is not allowed
736 56 inconsistent NEWLINE options
737 57 \eg is not followed by a braced, angle-bracketed, or quoted
738 name/number or by a plain number
739 58 a numbered reference must not be zero
740 59 (*VERB) with an argument is not supported
741 60 (*VERB) not recognized
742 61 number is too big
743 62 subpattern name expected
744 63 digit expected after (?+
745 64 ] is an invalid data character in JavaScript compatibility mode
746 .sp
747 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
748 be used if the limits were changed when PCRE was built.
749 .
750 .
751 .SH "STUDYING A PATTERN"
752 .rs
753 .sp
754 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
755 .ti +5n
756 .B const char **\fIerrptr\fP);
757 .PP
758 If a compiled pattern is going to be used several times, it is worth spending
759 more time analyzing it in order to speed up the time taken for matching. The
760 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
761 argument. If studying the pattern produces additional information that will
762 help speed up matching, \fBpcre_study()\fP returns a pointer to a
763 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
764 results of the study.
765 .P
766 The returned value from \fBpcre_study()\fP can be passed directly to
767 \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
768 fields that can be set by the caller before the block is passed; these are
769 described
770 .\" HTML <a href="#extradata">
771 .\" </a>
772 below
773 .\"
774 in the section on matching a pattern.
775 .P
776 If studying the pattern does not produce any additional information
777 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
778 wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
779 own \fBpcre_extra\fP block.
780 .P
781 The second argument of \fBpcre_study()\fP contains option bits. At present, no
782 options are defined, and this argument should always be zero.
783 .P
784 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
785 studying succeeds (even if no data is returned), the variable it points to is
786 set to NULL. Otherwise it is set to point to a textual error message. This is a
787 static string that is part of the library. You must not try to free it. You
788 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
789 sure that it has run successfully.
790 .P
791 This is a typical call to \fBpcre_study\fP():
792 .sp
793 pcre_extra *pe;
794 pe = pcre_study(
795 re, /* result of pcre_compile() */
796 0, /* no options exist */
797 &error); /* set to NULL or points to a message */
798 .sp
799 At present, studying a pattern is useful only for non-anchored patterns that do
800 not have a single fixed starting character. A bitmap of possible starting
801 bytes is created.
802 .
803 .
804 .\" HTML <a name="localesupport"></a>
805 .SH "LOCALE SUPPORT"
806 .rs
807 .sp
808 PCRE handles caseless matching, and determines whether characters are letters,
809 digits, or whatever, by reference to a set of tables, indexed by character
810 value. When running in UTF-8 mode, this applies only to characters with codes
811 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
812 can be tested with \ep if PCRE is built with Unicode character property
813 support. The use of locales with Unicode is discouraged. If you are handling
814 characters with codes greater than 128, you should either use UTF-8 and
815 Unicode, or use locales, but not try to mix the two.
816 .P
817 PCRE contains an internal set of tables that are used when the final argument
818 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
819 Normally, the internal tables recognize only ASCII characters. However, when
820 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
821 default "C" locale of the local system, which may cause them to be different.
822 .P
823 The internal tables can always be overridden by tables supplied by the
824 application that calls PCRE. These may be created in a different locale from
825 the default. As more and more applications change to using Unicode, the need
826 for this locale support is expected to die away.
827 .P
828 External tables are built by calling the \fBpcre_maketables()\fP function,
829 which has no arguments, in the relevant locale. The result can then be passed
830 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
831 example, to build and use tables that are appropriate for the French locale
832 (where accented characters with values greater than 128 are treated as letters),
833 the following code could be used:
834 .sp
835 setlocale(LC_CTYPE, "fr_FR");
836 tables = pcre_maketables();
837 re = pcre_compile(..., tables);
838 .sp
839 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
840 are using Windows, the name for the French locale is "french".
841 .P
842 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
843 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
844 that the memory containing the tables remains available for as long as it is
845 needed.
846 .P
847 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
848 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
849 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
850 pattern, compilation, studying and matching all happen in the same locale, but
851 different patterns can be compiled in different locales.
852 .P
853 It is possible to pass a table pointer or NULL (indicating the use of the
854 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
855 this facility could be used to match a pattern in a different locale from the
856 one in which it was compiled. Passing table pointers at run time is discussed
857 below in the section on matching a pattern.
858 .
859 .
860 .SH "INFORMATION ABOUT A PATTERN"
861 .rs
862 .sp
863 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
864 .ti +5n
865 .B int \fIwhat\fP, void *\fIwhere\fP);
866 .PP
867 The \fBpcre_fullinfo()\fP function returns information about a compiled
868 pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
869 nevertheless retained for backwards compability (and is documented below).
870 .P
871 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
872 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
873 the pattern was not studied. The third argument specifies which piece of
874 information is required, and the fourth argument is a pointer to a variable
875 to receive the data. The yield of the function is zero for success, or one of
876 the following negative numbers:
877 .sp
878 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
879 the argument \fIwhere\fP was NULL
880 PCRE_ERROR_BADMAGIC the "magic number" was not found
881 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
882 .sp
883 The "magic number" is placed at the start of each compiled pattern as an simple
884 check against passing an arbitrary memory pointer. Here is a typical call of
885 \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
886 .sp
887 int rc;
888 size_t length;
889 rc = pcre_fullinfo(
890 re, /* result of pcre_compile() */
891 pe, /* result of pcre_study(), or NULL */
892 PCRE_INFO_SIZE, /* what is required */
893 &length); /* where to put the data */
894 .sp
895 The possible values for the third argument are defined in \fBpcre.h\fP, and are
896 as follows:
897 .sp
898 PCRE_INFO_BACKREFMAX
899 .sp
900 Return the number of the highest back reference in the pattern. The fourth
901 argument should point to an \fBint\fP variable. Zero is returned if there are
902 no back references.
903 .sp
904 PCRE_INFO_CAPTURECOUNT
905 .sp
906 Return the number of capturing subpatterns in the pattern. The fourth argument
907 should point to an \fBint\fP variable.
908 .sp
909 PCRE_INFO_DEFAULT_TABLES
910 .sp
911 Return a pointer to the internal default character tables within PCRE. The
912 fourth argument should point to an \fBunsigned char *\fP variable. This
913 information call is provided for internal use by the \fBpcre_study()\fP
914 function. External callers can cause PCRE to use its internal tables by passing
915 a NULL table pointer.
916 .sp
917 PCRE_INFO_FIRSTBYTE
918 .sp
919 Return information about the first byte of any matched string, for a
920 non-anchored pattern. The fourth argument should point to an \fBint\fP
921 variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
922 still recognized for backwards compatibility.)
923 .P
924 If there is a fixed first byte, for example, from a pattern such as
925 (cat|cow|coyote), its value is returned. Otherwise, if either
926 .sp
927 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
928 starts with "^", or
929 .sp
930 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
931 (if it were set, the pattern would be anchored),
932 .sp
933 -1 is returned, indicating that the pattern matches only at the start of a
934 subject string or after any newline within the string. Otherwise -2 is
935 returned. For anchored patterns, -2 is returned.
936 .sp
937 PCRE_INFO_FIRSTTABLE
938 .sp
939 If the pattern was studied, and this resulted in the construction of a 256-bit
940 table indicating a fixed set of bytes for the first byte in any matching
941 string, a pointer to the table is returned. Otherwise NULL is returned. The
942 fourth argument should point to an \fBunsigned char *\fP variable.
943 .sp
944 PCRE_INFO_HASCRORLF
945 .sp
946 Return 1 if the pattern contains any explicit matches for CR or LF characters,
947 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
948 explicit match is either a literal CR or LF character, or \er or \en.
949 .sp
950 PCRE_INFO_JCHANGED
951 .sp
952 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
953 0. The fourth argument should point to an \fBint\fP variable. (?J) and
954 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
955 .sp
956 PCRE_INFO_LASTLITERAL
957 .sp
958 Return the value of the rightmost literal byte that must exist in any matched
959 string, other than at its start, if such a byte has been recorded. The fourth
960 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
961 returned. For anchored patterns, a last literal byte is recorded only if it
962 follows something of variable length. For example, for the pattern
963 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
964 is -1.
965 .sp
966 PCRE_INFO_NAMECOUNT
967 PCRE_INFO_NAMEENTRYSIZE
968 PCRE_INFO_NAMETABLE
969 .sp
970 PCRE supports the use of named as well as numbered capturing parentheses. The
971 names are just an additional way of identifying the parentheses, which still
972 acquire numbers. Several convenience functions such as
973 \fBpcre_get_named_substring()\fP are provided for extracting captured
974 substrings by name. It is also possible to extract the data directly, by first
975 converting the name to a number in order to access the correct pointers in the
976 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
977 you need to use the name-to-number map, which is described by these three
978 values.
979 .P
980 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
981 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
982 entry; both of these return an \fBint\fP value. The entry size depends on the
983 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
984 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
985 are the number of the capturing parenthesis, most significant byte first. The
986 rest of the entry is the corresponding name, zero terminated. The names are in
987 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
988 their parentheses numbers. For example, consider the following pattern (assume
989 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
990 .sp
991 .\" JOIN
992 (?<date> (?<year>(\ed\ed)?\ed\ed) -
993 (?<month>\ed\ed) - (?<day>\ed\ed) )
994 .sp
995 There are four named subpatterns, so the table has four entries, and each entry
996 in the table is eight bytes long. The table is as follows, with non-printing
997 bytes shows in hexadecimal, and undefined bytes shown as ??:
998 .sp
999 00 01 d a t e 00 ??
1000 00 05 d a y 00 ?? ??
1001 00 04 m o n t h 00
1002 00 02 y e a r 00 ??
1003 .sp
1004 When writing code to extract data from named subpatterns using the
1005 name-to-number map, remember that the length of the entries is likely to be
1006 different for each compiled pattern.
1007 .sp
1008 PCRE_INFO_OKPARTIAL
1009 .sp
1010 Return 1 if the pattern can be used for partial matching, otherwise 0. The
1011 fourth argument should point to an \fBint\fP variable. From release 8.00, this
1012 always returns 1, because the restrictions that previously applied to partial
1013 matching have been lifted. The
1014 .\" HREF
1015 \fBpcrepartial\fP
1016 .\"
1017 documentation gives details of partial matching.
1018 .sp
1019 PCRE_INFO_OPTIONS
1020 .sp
1021 Return a copy of the options with which the pattern was compiled. The fourth
1022 argument should point to an \fBunsigned long int\fP variable. These option bits
1023 are those specified in the call to \fBpcre_compile()\fP, modified by any
1024 top-level option settings at the start of the pattern itself. In other words,
1025 they are the options that will be in force when matching starts. For example,
1026 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1027 result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1028 .P
1029 A pattern is automatically anchored by PCRE if all of its top-level
1030 alternatives begin with one of the following:
1031 .sp
1032 ^ unless PCRE_MULTILINE is set
1033 \eA always
1034 \eG always
1035 .\" JOIN
1036 .* if PCRE_DOTALL is set and there are no back
1037 references to the subpattern in which .* appears
1038 .sp
1039 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1040 \fBpcre_fullinfo()\fP.
1041 .sp
1042 PCRE_INFO_SIZE
1043 .sp
1044 Return the size of the compiled pattern, that is, the value that was passed as
1045 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1046 place the compiled data. The fourth argument should point to a \fBsize_t\fP
1047 variable.
1048 .sp
1049 PCRE_INFO_STUDYSIZE
1050 .sp
1051 Return the size of the data block pointed to by the \fIstudy_data\fP field in
1052 a \fBpcre_extra\fP block. That is, it is the value that was passed to
1053 \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1054 created by \fBpcre_study()\fP. The fourth argument should point to a
1055 \fBsize_t\fP variable.
1056 .
1057 .
1058 .SH "OBSOLETE INFO FUNCTION"
1059 .rs
1060 .sp
1061 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1062 .B *\fIfirstcharptr\fP);
1063 .PP
1064 The \fBpcre_info()\fP function is now obsolete because its interface is too
1065 restrictive to return all the available data about a compiled pattern. New
1066 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1067 \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1068 following negative numbers:
1069 .sp
1070 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1071 PCRE_ERROR_BADMAGIC the "magic number" was not found
1072 .sp
1073 If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1074 pattern was compiled is placed in the integer it points to (see
1075 PCRE_INFO_OPTIONS above).
1076 .P
1077 If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1078 it is used to pass back information about the first character of any matched
1079 string (see PCRE_INFO_FIRSTBYTE above).
1080 .
1081 .
1082 .SH "REFERENCE COUNTS"
1083 .rs
1084 .sp
1085 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1086 .PP
1087 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1088 data block that contains a compiled pattern. It is provided for the benefit of
1089 applications that operate in an object-oriented manner, where different parts
1090 of the application may be using the same compiled pattern, but you want to free
1091 the block when they are all done.
1092 .P
1093 When a pattern is compiled, the reference count field is initialized to zero.
1094 It is changed only by calling this function, whose action is to add the
1095 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1096 function is the new value. However, the value of the count is constrained to
1097 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1098 it is forced to the appropriate limit value.
1099 .P
1100 Except when it is zero, the reference count is not correctly preserved if a
1101 pattern is compiled on one host and then transferred to a host whose byte-order
1102 is different. (This seems a highly unlikely scenario.)
1103 .
1104 .
1105 .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1106 .rs
1107 .sp
1108 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1109 .ti +5n
1110 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1111 .ti +5n
1112 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1113 .P
1114 The function \fBpcre_exec()\fP is called to match a subject string against a
1115 compiled pattern, which is passed in the \fIcode\fP argument. If the
1116 pattern has been studied, the result of the study should be passed in the
1117 \fIextra\fP argument. This function is the main matching facility of the
1118 library, and it operates in a Perl-like manner. For specialist use there is
1119 also an alternative matching function, which is described
1120 .\" HTML <a href="#dfamatch">
1121 .\" </a>
1122 below
1123 .\"
1124 in the section about the \fBpcre_dfa_exec()\fP function.
1125 .P
1126 In most applications, the pattern will have been compiled (and optionally
1127 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1128 possible to save compiled patterns and study data, and then use them later
1129 in different processes, possibly even on different hosts. For a discussion
1130 about this, see the
1131 .\" HREF
1132 \fBpcreprecompile\fP
1133 .\"
1134 documentation.
1135 .P
1136 Here is an example of a simple call to \fBpcre_exec()\fP:
1137 .sp
1138 int rc;
1139 int ovector[30];
1140 rc = pcre_exec(
1141 re, /* result of pcre_compile() */
1142 NULL, /* we didn't study the pattern */
1143 "some string", /* the subject string */
1144 11, /* the length of the subject string */
1145 0, /* start at offset 0 in the subject */
1146 0, /* default options */
1147 ovector, /* vector of integers for substring information */
1148 30); /* number of elements (NOT size in bytes) */
1149 .
1150 .\" HTML <a name="extradata"></a>
1151 .SS "Extra data for \fBpcre_exec()\fR"
1152 .rs
1153 .sp
1154 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1155 data block. The \fBpcre_study()\fP function returns such a block (when it
1156 doesn't return NULL), but you can also create one for yourself, and pass
1157 additional information in it. The \fBpcre_extra\fP block contains the following
1158 fields (not necessarily in this order):
1159 .sp
1160 unsigned long int \fIflags\fP;
1161 void *\fIstudy_data\fP;
1162 unsigned long int \fImatch_limit\fP;
1163 unsigned long int \fImatch_limit_recursion\fP;
1164 void *\fIcallout_data\fP;
1165 const unsigned char *\fItables\fP;
1166 .sp
1167 The \fIflags\fP field is a bitmap that specifies which of the other fields
1168 are set. The flag bits are:
1169 .sp
1170 PCRE_EXTRA_STUDY_DATA
1171 PCRE_EXTRA_MATCH_LIMIT
1172 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1173 PCRE_EXTRA_CALLOUT_DATA
1174 PCRE_EXTRA_TABLES
1175 .sp
1176 Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1177 \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1178 the appropriate flag bit. You should not set this yourself, but you may add to
1179 the block by setting the other fields and their corresponding flag bits.
1180 .P
1181 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1182 vast amount of resources when running patterns that are not going to match,
1183 but which have a very large number of possibilities in their search trees. The
1184 classic example is the use of nested unlimited repeats.
1185 .P
1186 Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1187 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1188 number of times this function is called during a match, which has the effect of
1189 limiting the amount of backtracking that can take place. For patterns that are
1190 not anchored, the count restarts from zero for each position in the subject
1191 string.
1192 .P
1193 The default value for the limit can be set when PCRE is built; the default
1194 default is 10 million, which handles all but the most extreme cases. You can
1195 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1196 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1197 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1198 PCRE_ERROR_MATCHLIMIT.
1199 .P
1200 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1201 instead of limiting the total number of times that \fBmatch()\fP is called, it
1202 limits the depth of recursion. The recursion depth is a smaller number than the
1203 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1204 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1205 .P
1206 Limiting the recursion depth limits the amount of stack that can be used, or,
1207 when PCRE has been compiled to use memory on the heap instead of the stack, the
1208 amount of heap memory that can be used.
1209 .P
1210 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1211 built; the default default is the same value as the default for
1212 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1213 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1214 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1215 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1216 .P
1217 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1218 which is described in the
1219 .\" HREF
1220 \fBpcrecallout\fP
1221 .\"
1222 documentation.
1223 .P
1224 The \fItables\fP field is used to pass a character tables pointer to
1225 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1226 pattern. A non-NULL value is stored with the compiled pattern only if custom
1227 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1228 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1229 internal tables to be used. This facility is helpful when re-using patterns
1230 that have been saved after compiling with an external set of tables, because
1231 the external tables might be at a different address when \fBpcre_exec()\fP is
1232 called. See the
1233 .\" HREF
1234 \fBpcreprecompile\fP
1235 .\"
1236 documentation for a discussion of saving compiled patterns for later use.
1237 .
1238 .\" HTML <a name="execoptions"></a>
1239 .SS "Option bits for \fBpcre_exec()\fP"
1240 .rs
1241 .sp
1242 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1243 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1244 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,
1245 PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1246 .sp
1247 PCRE_ANCHORED
1248 .sp
1249 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1250 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1251 to be anchored by virtue of its contents, it cannot be made unachored at
1252 matching time.
1253 .sp
1254 PCRE_BSR_ANYCRLF
1255 PCRE_BSR_UNICODE
1256 .sp
1257 These options (which are mutually exclusive) control what the \eR escape
1258 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1259 match any Unicode newline sequence. These options override the choice that was
1260 made or defaulted when the pattern was compiled.
1261 .sp
1262 PCRE_NEWLINE_CR
1263 PCRE_NEWLINE_LF
1264 PCRE_NEWLINE_CRLF
1265 PCRE_NEWLINE_ANYCRLF
1266 PCRE_NEWLINE_ANY
1267 .sp
1268 These options override the newline definition that was chosen or defaulted when
1269 the pattern was compiled. For details, see the description of
1270 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1271 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1272 the way the match position is advanced after a match failure for an unanchored
1273 pattern.
1274 .P
1275 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1276 match attempt for an unanchored pattern fails when the current position is at a
1277 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1278 characters, the match position is advanced by two characters instead of one, in
1279 other words, to after the CRLF.
1280 .P
1281 The above rule is a compromise that makes the most common cases work as
1282 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1283 set), it does not match the string "\er\enA" because, after failing at the
1284 start, it skips both the CR and the LF before retrying. However, the pattern
1285 [\er\en]A does match that string, because it contains an explicit CR or LF
1286 reference, and so advances only by one character after the first failure.
1287 .P
1288 An explicit match for CR of LF is either a literal appearance of one of those
1289 characters, or one of the \er or \en escape sequences. Implicit matches such as
1290 [^X] do not count, nor does \es (which includes CR and LF in the characters
1291 that it matches).
1292 .P
1293 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1294 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1295 .sp
1296 PCRE_NOTBOL
1297 .sp
1298 This option specifies that first character of the subject string is not the
1299 beginning of a line, so the circumflex metacharacter should not match before
1300 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1301 never to match. This option affects only the behaviour of the circumflex
1302 metacharacter. It does not affect \eA.
1303 .sp
1304 PCRE_NOTEOL
1305 .sp
1306 This option specifies that the end of the subject string is not the end of a
1307 line, so the dollar metacharacter should not match it nor (except in multiline
1308 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1309 compile time) causes dollar never to match. This option affects only the
1310 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1311 .sp
1312 PCRE_NOTEMPTY
1313 .sp
1314 An empty string is not considered to be a valid match if this option is set. If
1315 there are alternatives in the pattern, they are tried. If all the alternatives
1316 match the empty string, the entire match fails. For example, if the pattern
1317 .sp
1318 a?b?
1319 .sp
1320 is applied to a string not beginning with "a" or "b", it matches the empty
1321 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1322 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1323 .P
1324 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1325 of a pattern match of the empty string within its \fBsplit()\fP function, and
1326 when using the /g modifier. It is possible to emulate Perl's behaviour after
1327 matching a null string by first trying the match again at the same offset with
1328 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1329 starting offset (see below) and trying an ordinary match again. There is some
1330 code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1331 .sp
1332 PCRE_NO_START_OPTIMIZE
1333 .sp
1334 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1335 a match, in order to speed up the process. For example, if it is known that a
1336 match must start with a specific character, it searches the subject for that
1337 character, and fails immediately if it cannot find it, without actually running
1338 the main matching function. When callouts are in use, these optimizations can
1339 cause them to be skipped. This option disables the "start-up" optimizations,
1340 causing performance to suffer, but ensuring that the callouts do occur.
1341 .sp
1342 PCRE_NO_UTF8_CHECK
1343 .sp
1344 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1345 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1346 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1347 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1348 strings in the
1349 .\" HTML <a href="pcre.html#utf8strings">
1350 .\" </a>
1351 section on UTF-8 support
1352 .\"
1353 in the main
1354 .\" HREF
1355 \fBpcre\fP
1356 .\"
1357 page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1358 the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1359 PCRE_ERROR_BADUTF8_OFFSET is returned.
1360 .P
1361 If you already know that your subject is valid, and you want to skip these
1362 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1363 calling \fBpcre_exec()\fP. You might want to do this for the second and
1364 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1365 all the matches in a single subject string. However, you should be sure that
1366 the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1367 PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1368 subject, or a value of \fIstartoffset\fP that does not point to the start of a
1369 UTF-8 character, is undefined. Your program may crash.
1370 .sp
1371 PCRE_PARTIAL
1372 .sp
1373 This option turns on the partial matching feature. If the subject string fails
1374 to match the pattern, but at some point during the matching process the end of
1375 the subject was reached (that is, the subject partially matches the pattern and
1376 the failure to match occurred only because there were not enough subject
1377 characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1378 PCRE_ERROR_NOMATCH. The portion of the string that provided the longest partial
1379 match is set as the first matching string. There is further discussion in the
1380 .\" HREF
1381 \fBpcrepartial\fP
1382 .\"
1383 documentation.
1384 .
1385 .SS "The string to be matched by \fBpcre_exec()\fP"
1386 .rs
1387 .sp
1388 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1389 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1390 in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1391 a UTF-8 character. Unlike the pattern string, the subject may contain binary
1392 zero bytes. When the starting offset is zero, the search for a match starts at
1393 the beginning of the subject, and this is by far the most common case.
1394 .P
1395 A non-zero starting offset is useful when searching for another match in the
1396 same subject by calling \fBpcre_exec()\fP again after a previous success.
1397 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1398 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1399 lookbehind. For example, consider the pattern
1400 .sp
1401 \eBiss\eB
1402 .sp
1403 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1404 the current position in the subject is not a word boundary.) When applied to
1405 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1406 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1407 subject, namely "issipi", it does not match, because \eB is always false at the
1408 start of the subject, which is deemed to be a word boundary. However, if
1409 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1410 set to 4, it finds the second occurrence of "iss" because it is able to look
1411 behind the starting point to discover that it is preceded by a letter.
1412 .P
1413 If a non-zero starting offset is passed when the pattern is anchored, one
1414 attempt to match at the given offset is made. This can only succeed if the
1415 pattern does not require the match to be at the start of the subject.
1416 .
1417 .SS "How \fBpcre_exec()\fP returns captured substrings"
1418 .rs
1419 .sp
1420 In general, a pattern matches a certain portion of the subject, and in
1421 addition, further substrings from the subject may be picked out by parts of the
1422 pattern. Following the usage in Jeffrey Friedl's book, this is called
1423 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1424 a fragment of a pattern that picks out a substring. PCRE supports several other
1425 kinds of parenthesized subpattern that do not cause substrings to be captured.
1426 .P
1427 Captured substrings are returned to the caller via a vector of integers whose
1428 address is passed in \fIovector\fP. The number of elements in the vector is
1429 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1430 argument is NOT the size of \fIovector\fP in bytes.
1431 .P
1432 The first two-thirds of the vector is used to pass back captured substrings,
1433 each substring using a pair of integers. The remaining third of the vector is
1434 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1435 and is not available for passing back information. The number passed in
1436 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1437 rounded down.
1438 .P
1439 When a match is successful, information about captured substrings is returned
1440 in pairs of integers, starting at the beginning of \fIovector\fP, and
1441 continuing up to two-thirds of its length at the most. The first element of
1442 each pair is set to the byte offset of the first character in a substring, and
1443 the second is set to the byte offset of the first character after the end of a
1444 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1445 mode. They are not character counts.
1446 .P
1447 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1448 portion of the subject string matched by the entire pattern. The next pair is
1449 used for the first capturing subpattern, and so on. The value returned by
1450 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1451 For example, if two substrings have been captured, the returned value is 3. If
1452 there are no capturing subpatterns, the return value from a successful match is
1453 1, indicating that just the first pair of offsets has been set.
1454 .P
1455 If a capturing subpattern is matched repeatedly, it is the last portion of the
1456 string that it matched that is returned.
1457 .P
1458 If the vector is too small to hold all the captured substring offsets, it is
1459 used as far as possible (up to two-thirds of its length), and the function
1460 returns a value of zero. If the substring offsets are not of interest,
1461 \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1462 \fIovecsize\fP as zero. However, if the pattern contains back references and
1463 the \fIovector\fP is not big enough to remember the related substrings, PCRE
1464 has to get additional memory for use during matching. Thus it is usually
1465 advisable to supply an \fIovector\fP.
1466 .P
1467 The \fBpcre_info()\fP function can be used to find out how many capturing
1468 subpatterns there are in a compiled pattern. The smallest size for
1469 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1470 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1471 .P
1472 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1473 the subject when subpattern \fIn\fP has not been used at all. For example, if
1474 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1475 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1476 happens, both values in the offset pairs corresponding to unused subpatterns
1477 are set to -1.
1478 .P
1479 Offset values that correspond to unused subpatterns at the end of the
1480 expression are also set to -1. For example, if the string "abc" is matched
1481 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1482 return from the function is 2, because the highest used capturing subpattern
1483 number is 1. However, you can refer to the offsets for the second and third
1484 capturing subpatterns if you wish (assuming the vector is large enough, of
1485 course).
1486 .P
1487 Some convenience functions are provided for extracting the captured substrings
1488 as separate strings. These are described below.
1489 .
1490 .\" HTML <a name="errorlist"></a>
1491 .SS "Error return values from \fBpcre_exec()\fP"
1492 .rs
1493 .sp
1494 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1495 defined in the header file:
1496 .sp
1497 PCRE_ERROR_NOMATCH (-1)
1498 .sp
1499 The subject string did not match the pattern.
1500 .sp
1501 PCRE_ERROR_NULL (-2)
1502 .sp
1503 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1504 NULL and \fIovecsize\fP was not zero.
1505 .sp
1506 PCRE_ERROR_BADOPTION (-3)
1507 .sp
1508 An unrecognized bit was set in the \fIoptions\fP argument.
1509 .sp
1510 PCRE_ERROR_BADMAGIC (-4)
1511 .sp
1512 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1513 the case when it is passed a junk pointer and to detect when a pattern that was
1514 compiled in an environment of one endianness is run in an environment with the
1515 other endianness. This is the error that PCRE gives when the magic number is
1516 not present.
1517 .sp
1518 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1519 .sp
1520 While running the pattern match, an unknown item was encountered in the
1521 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1522 of the compiled pattern.
1523 .sp
1524 PCRE_ERROR_NOMEMORY (-6)
1525 .sp
1526 If a pattern contains back references, but the \fIovector\fP that is passed to
1527 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1528 gets a block of memory at the start of matching to use for this purpose. If the
1529 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1530 automatically freed at the end of matching.
1531 .sp
1532 PCRE_ERROR_NOSUBSTRING (-7)
1533 .sp
1534 This error is used by the \fBpcre_copy_substring()\fP,
1535 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1536 below). It is never returned by \fBpcre_exec()\fP.
1537 .sp
1538 PCRE_ERROR_MATCHLIMIT (-8)
1539 .sp
1540 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1541 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1542 above.
1543 .sp
1544 PCRE_ERROR_CALLOUT (-9)
1545 .sp
1546 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1547 use by callout functions that want to yield a distinctive error code. See the
1548 .\" HREF
1549 \fBpcrecallout\fP
1550 .\"
1551 documentation for details.
1552 .sp
1553 PCRE_ERROR_BADUTF8 (-10)
1554 .sp
1555 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1556 .sp
1557 PCRE_ERROR_BADUTF8_OFFSET (-11)
1558 .sp
1559 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1560 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1561 .sp
1562 PCRE_ERROR_PARTIAL (-12)
1563 .sp
1564 The subject string did not match, but it did match partially. See the
1565 .\" HREF
1566 \fBpcrepartial\fP
1567 .\"
1568 documentation for details of partial matching.
1569 .sp
1570 PCRE_ERROR_BADPARTIAL (-13)
1571 .sp
1572 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1573 option was used with a compiled pattern containing items that were not
1574 supported for partial matching. From release 8.00 onwards, there are no
1575 restrictions on 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 exactly the same as for \fBpcre_exec()\fP, so their description is not repeated
1868 here.
1869 .sp
1870 PCRE_PARTIAL
1871 .sp
1872 This has the same general effect as it does for \fBpcre_exec()\fP, but the
1873 details are slightly different. When PCRE_PARTIAL is set for
1874 \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1875 PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1876 complete matches, but there is still at least one matching possibility. The
1877 portion of the string that provided the longest partial match is set as the
1878 first matching string.
1879 .sp
1880 PCRE_DFA_SHORTEST
1881 .sp
1882 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1883 soon as it has found one match. Because of the way the alternative algorithm
1884 works, this is necessarily the shortest possible match at the first possible
1885 matching point in the subject string.
1886 .sp
1887 PCRE_DFA_RESTART
1888 .sp
1889 When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1890 a partial match, it is possible to call it again, with additional subject
1891 characters, and have it continue with the same match. The PCRE_DFA_RESTART
1892 option requests this action; when it is set, the \fIworkspace\fP and
1893 \fIwscount\fP options must reference the same vector as before because data
1894 about the match so far is left in them after a partial match. There is more
1895 discussion of this facility in the
1896 .\" HREF
1897 \fBpcrepartial\fP
1898 .\"
1899 documentation.
1900 .
1901 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1902 .rs
1903 .sp
1904 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1905 substring in the subject. Note, however, that all the matches from one run of
1906 the function start at the same point in the subject. The shorter matches are
1907 all initial substrings of the longer matches. For example, if the pattern
1908 .sp
1909 <.*>
1910 .sp
1911 is matched against the string
1912 .sp
1913 This is <something> <something else> <something further> no more
1914 .sp
1915 the three matched strings are
1916 .sp
1917 <something>
1918 <something> <something else>
1919 <something> <something else> <something further>
1920 .sp
1921 On success, the yield of the function is a number greater than zero, which is
1922 the number of matched substrings. The substrings themselves are returned in
1923 \fIovector\fP. Each string uses two elements; the first is the offset to the
1924 start, and the second is the offset to the end. In fact, all the strings have
1925 the same start offset. (Space could have been saved by giving this only once,
1926 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1927 returns data, even though the meaning of the strings is different.)
1928 .P
1929 The strings are returned in reverse order of length; that is, the longest
1930 matching string is given first. If there were too many matches to fit into
1931 \fIovector\fP, the yield of the function is zero, and the vector is filled with
1932 the longest matches.
1933 .
1934 .SS "Error returns from \fBpcre_dfa_exec()\fP"
1935 .rs
1936 .sp
1937 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1938 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1939 described
1940 .\" HTML <a href="#errorlist">
1941 .\" </a>
1942 above.
1943 .\"
1944 There are in addition the following errors that are specific to
1945 \fBpcre_dfa_exec()\fP:
1946 .sp
1947 PCRE_ERROR_DFA_UITEM (-16)
1948 .sp
1949 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1950 that it does not support, for instance, the use of \eC or a back reference.
1951 .sp
1952 PCRE_ERROR_DFA_UCOND (-17)
1953 .sp
1954 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1955 uses a back reference for the condition, or a test for recursion in a specific
1956 group. These are not supported.
1957 .sp
1958 PCRE_ERROR_DFA_UMLIMIT (-18)
1959 .sp
1960 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1961 block that contains a setting of the \fImatch_limit\fP field. This is not
1962 supported (it is meaningless).
1963 .sp
1964 PCRE_ERROR_DFA_WSSIZE (-19)
1965 .sp
1966 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1967 \fIworkspace\fP vector.
1968 .sp
1969 PCRE_ERROR_DFA_RECURSE (-20)
1970 .sp
1971 When a recursive subpattern is processed, the matching function calls itself
1972 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1973 error is given if the output vector is not large enough. This should be
1974 extremely rare, as a vector of size 1000 is used.
1975 .
1976 .
1977 .SH "SEE ALSO"
1978 .rs
1979 .sp
1980 \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1981 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1982 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1983 .
1984 .
1985 .SH AUTHOR
1986 .rs
1987 .sp
1988 .nf
1989 Philip Hazel
1990 University Computing Service
1991 Cambridge CB2 3QH, England.
1992 .fi
1993 .
1994 .
1995 .SH REVISION
1996 .rs
1997 .sp
1998 .nf
1999 Last updated: 26 August 2009
2000 Copyright (c) 1997-2009 University of Cambridge.
2001 .fi

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