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1 nigel 79 .TH PCREAPI 3
2 nigel 63 .SH NAME
3     PCRE - Perl-compatible regular expressions
4 nigel 75 .SH "PCRE NATIVE API"
5 nigel 63 .rs
6     .sp
7     .B #include <pcre.h>
8     .PP
9     .SM
10     .br
11 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
12 nigel 63 .ti +5n
13 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
14 nigel 63 .ti +5n
15 nigel 75 .B const unsigned char *\fItableptr\fP);
16 nigel 63 .PP
17     .br
18 nigel 77 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19     .ti +5n
20     .B int *\fIerrorcodeptr\fP,
21     .ti +5n
22     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23     .ti +5n
24     .B const unsigned char *\fItableptr\fP);
25     .PP
26     .br
27 nigel 75 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
28 nigel 63 .ti +5n
29 nigel 75 .B const char **\fIerrptr\fP);
30 nigel 63 .PP
31     .br
32 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33 nigel 63 .ti +5n
34 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35 nigel 63 .ti +5n
36 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37 nigel 63 .PP
38     .br
39 nigel 77 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
40     .ti +5n
41     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
42     .ti +5n
43     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
44     .ti +5n
45     .B int *\fIworkspace\fP, int \fIwscount\fP);
46     .PP
47     .br
48 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
49 nigel 63 .ti +5n
50 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
51 nigel 63 .ti +5n
52 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
53 nigel 63 .ti +5n
54 nigel 75 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
55 nigel 63 .PP
56     .br
57 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
58 nigel 63 .ti +5n
59 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
60 nigel 63 .ti +5n
61 nigel 75 .B int \fIbuffersize\fP);
62 nigel 63 .PP
63     .br
64 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
65 nigel 63 .ti +5n
66 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
67 nigel 63 .ti +5n
68 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
69 nigel 63 .ti +5n
70 nigel 75 .B const char **\fIstringptr\fP);
71 nigel 63 .PP
72     .br
73 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
74 nigel 63 .ti +5n
75 nigel 75 .B const char *\fIname\fP);
76 nigel 63 .PP
77     .br
78 nigel 91 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
79     .ti +5n
80     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
81     .PP
82     .br
83 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
84 nigel 63 .ti +5n
85 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
86 nigel 63 .ti +5n
87 nigel 75 .B const char **\fIstringptr\fP);
88 nigel 63 .PP
89     .br
90 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
91 nigel 63 .ti +5n
92 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
93 nigel 63 .PP
94     .br
95 nigel 75 .B void pcre_free_substring(const char *\fIstringptr\fP);
96 nigel 63 .PP
97     .br
98 nigel 75 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
99 nigel 63 .PP
100     .br
101     .B const unsigned char *pcre_maketables(void);
102     .PP
103     .br
104 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
105 nigel 63 .ti +5n
106 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
107 nigel 63 .PP
108     .br
109 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
110     .B *\fIfirstcharptr\fP);
111 nigel 63 .PP
112     .br
113 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
114     .PP
115     .br
116 nigel 75 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
117 nigel 63 .PP
118     .br
119     .B char *pcre_version(void);
120     .PP
121     .br
122     .B void *(*pcre_malloc)(size_t);
123     .PP
124     .br
125     .B void (*pcre_free)(void *);
126     .PP
127     .br
128 nigel 73 .B void *(*pcre_stack_malloc)(size_t);
129     .PP
130     .br
131     .B void (*pcre_stack_free)(void *);
132     .PP
133     .br
134 nigel 63 .B int (*pcre_callout)(pcre_callout_block *);
135 nigel 75 .
136     .
137     .SH "PCRE API OVERVIEW"
138 nigel 63 .rs
139     .sp
140 nigel 93 PCRE has its own native API, which is described in this document. There are
141     also some wrapper functions that correspond to the POSIX regular expression
142 nigel 77 API. These are described in the
143 nigel 75 .\" HREF
144     \fBpcreposix\fP
145     .\"
146 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
147     wrapper is distributed with PCRE. It is documented in the
148     .\" HREF
149     \fBpcrecpp\fP
150     .\"
151     page.
152 nigel 75 .P
153 nigel 77 The native API C function prototypes are defined in the header file
154     \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
155     It can normally be accessed by adding \fB-lpcre\fP to the command for linking
156     an application that uses PCRE. The header file defines the macros PCRE_MAJOR
157     and PCRE_MINOR to contain the major and minor release numbers for the library.
158 nigel 75 Applications can use these to include support for different releases of PCRE.
159     .P
160 nigel 77 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
161     and \fBpcre_exec()\fP are used for compiling and matching regular expressions
162     in a Perl-compatible manner. A sample program that demonstrates the simplest
163     way of using them is provided in the file called \fIpcredemo.c\fP in the source
164     distribution. The
165 nigel 75 .\" HREF
166     \fBpcresample\fP
167     .\"
168     documentation describes how to run it.
169     .P
170 nigel 77 A second matching function, \fBpcre_dfa_exec()\fP, which is not
171     Perl-compatible, is also provided. This uses a different algorithm for the
172 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
173 nigel 93 point in the subject), and scans the subject just once. However, this algorithm
174     does not return captured substrings. A description of the two matching
175     algorithms and their advantages and disadvantages is given in the
176 nigel 77 .\" HREF
177     \fBpcrematching\fP
178     .\"
179     documentation.
180     .P
181 nigel 75 In addition to the main compiling and matching functions, there are convenience
182 nigel 77 functions for extracting captured substrings from a subject string that is
183     matched by \fBpcre_exec()\fP. They are:
184 nigel 75 .sp
185     \fBpcre_copy_substring()\fP
186     \fBpcre_copy_named_substring()\fP
187     \fBpcre_get_substring()\fP
188     \fBpcre_get_named_substring()\fP
189     \fBpcre_get_substring_list()\fP
190     \fBpcre_get_stringnumber()\fP
191 nigel 91 \fBpcre_get_stringtable_entries()\fP
192 nigel 75 .sp
193     \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
194 nigel 63 provided, to free the memory used for extracted strings.
195 nigel 75 .P
196     The function \fBpcre_maketables()\fP is used to build a set of character tables
197 nigel 77 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
198     or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
199     specialist use. Most commonly, no special tables are passed, in which case
200     internal tables that are generated when PCRE is built are used.
201 nigel 75 .P
202     The function \fBpcre_fullinfo()\fP is used to find out information about a
203     compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
204 nigel 63 some of the available information, but is retained for backwards compatibility.
205 nigel 75 The function \fBpcre_version()\fP returns a pointer to a string containing the
206 nigel 63 version of PCRE and its date of release.
207 nigel 75 .P
208 nigel 77 The function \fBpcre_refcount()\fP maintains a reference count in a data block
209     containing a compiled pattern. This is provided for the benefit of
210     object-oriented applications.
211     .P
212 nigel 75 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
213     the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
214 nigel 63 respectively. PCRE calls the memory management functions via these variables,
215     so a calling program can replace them if it wishes to intercept the calls. This
216     should be done before calling any PCRE functions.
217 nigel 75 .P
218     The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
219 nigel 73 indirections to memory management functions. These special functions are used
220     only when PCRE is compiled to use the heap for remembering data, instead of
221 nigel 91 recursive function calls, when running the \fBpcre_exec()\fP function. See the
222     .\" HREF
223     \fBpcrebuild\fP
224     .\"
225     documentation for details of how to do this. It is a non-standard way of
226     building PCRE, for use in environments that have limited stacks. Because of the
227     greater use of memory management, it runs more slowly. Separate functions are
228     provided so that special-purpose external code can be used for this case. When
229     used, these functions are always called in a stack-like manner (last obtained,
230     first freed), and always for memory blocks of the same size. There is a
231     discussion about PCRE's stack usage in the
232     .\" HREF
233     \fBpcrestack\fP
234     .\"
235     documentation.
236 nigel 75 .P
237     The global variable \fBpcre_callout\fP initially contains NULL. It can be set
238 nigel 63 by the caller to a "callout" function, which PCRE will then call at specified
239 nigel 75 points during a matching operation. Details are given in the
240     .\" HREF
241     \fBpcrecallout\fP
242     .\"
243 nigel 63 documentation.
244 nigel 75 .
245     .
246 nigel 91 .SH NEWLINES
247 nigel 93 .rs
248 nigel 91 .sp
249 nigel 93 PCRE supports four different conventions for indicating line breaks in
250     strings: a single CR (carriage return) character, a single LF (linefeed)
251     character, the two-character sequence CRLF, or any Unicode newline sequence.
252     The Unicode newline sequences are the three just mentioned, plus the single
253     characters VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line,
254     U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
255     .P
256     Each of the first three conventions is used by at least one operating system as
257     its standard newline sequence. When PCRE is built, a default can be specified.
258     The default default is LF, which is the Unix standard. When PCRE is run, the
259     default can be overridden, either when a pattern is compiled, or when it is
260     matched.
261     .P
262 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
263 nigel 93 pair of characters that indicate a line break". The choice of newline
264     convention affects the handling of the dot, circumflex, and dollar
265     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
266     recognized line ending sequence, the match position advancement for a
267     non-anchored pattern. The choice of newline convention does not affect the
268     interpretation of the \en or \er escape sequences.
269 nigel 91 .
270     .
271 nigel 63 .SH MULTITHREADING
272     .rs
273     .sp
274     The PCRE functions can be used in multi-threading applications, with the
275 nigel 75 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
276     \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
277     callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
278     .P
279 nigel 63 The compiled form of a regular expression is not altered during matching, so
280     the same compiled pattern can safely be used by several threads at once.
281 nigel 75 .
282     .
283     .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
284 nigel 63 .rs
285     .sp
286 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
287     time, possibly by a different program, and even on a host other than the one on
288     which it was compiled. Details are given in the
289     .\" HREF
290     \fBpcreprecompile\fP
291     .\"
292     documentation.
293     .
294     .
295     .SH "CHECKING BUILD-TIME OPTIONS"
296     .rs
297     .sp
298     .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
299 nigel 63 .PP
300 nigel 75 The function \fBpcre_config()\fP makes it possible for a PCRE client to
301 nigel 63 discover which optional features have been compiled into the PCRE library. The
302     .\" HREF
303 nigel 75 \fBpcrebuild\fP
304 nigel 63 .\"
305     documentation has more details about these optional features.
306 nigel 75 .P
307     The first argument for \fBpcre_config()\fP is an integer, specifying which
308 nigel 63 information is required; the second argument is a pointer to a variable into
309     which the information is placed. The following information is available:
310 nigel 75 .sp
311 nigel 63 PCRE_CONFIG_UTF8
312 nigel 75 .sp
313 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
314     otherwise it is set to zero.
315 nigel 75 .sp
316     PCRE_CONFIG_UNICODE_PROPERTIES
317     .sp
318     The output is an integer that is set to one if support for Unicode character
319     properties is available; otherwise it is set to zero.
320     .sp
321 nigel 63 PCRE_CONFIG_NEWLINE
322 nigel 75 .sp
323 nigel 91 The output is an integer whose value specifies the default character sequence
324 nigel 93 that is recognized as meaning "newline". The four values that are supported
325     are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY. The default should
326     normally be the standard sequence for your operating system.
327 nigel 75 .sp
328 nigel 63 PCRE_CONFIG_LINK_SIZE
329 nigel 75 .sp
330 nigel 63 The output is an integer that contains the number of bytes used for internal
331     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
332     allow larger regular expressions to be compiled, at the expense of slower
333     matching. The default value of 2 is sufficient for all but the most massive
334     patterns, since it allows the compiled pattern to be up to 64K in size.
335 nigel 75 .sp
336 nigel 63 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
337 nigel 75 .sp
338 nigel 63 The output is an integer that contains the threshold above which the POSIX
339 nigel 75 interface uses \fBmalloc()\fP for output vectors. Further details are given in
340     the
341     .\" HREF
342     \fBpcreposix\fP
343     .\"
344     documentation.
345     .sp
346 nigel 63 PCRE_CONFIG_MATCH_LIMIT
347 nigel 75 .sp
348 nigel 63 The output is an integer that gives the default limit for the number of
349 nigel 75 internal matching function calls in a \fBpcre_exec()\fP execution. Further
350     details are given with \fBpcre_exec()\fP below.
351     .sp
352 nigel 87 PCRE_CONFIG_MATCH_LIMIT_RECURSION
353     .sp
354     The output is an integer that gives the default limit for the depth of
355     recursion when calling the internal matching function in a \fBpcre_exec()\fP
356     execution. Further details are given with \fBpcre_exec()\fP below.
357     .sp
358 nigel 73 PCRE_CONFIG_STACKRECURSE
359 nigel 75 .sp
360 nigel 77 The output is an integer that is set to one if internal recursion when running
361     \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
362     to remember their state. This is the usual way that PCRE is compiled. The
363     output is zero if PCRE was compiled to use blocks of data on the heap instead
364     of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
365     \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
366     avoiding the use of the stack.
367 nigel 75 .
368     .
369     .SH "COMPILING A PATTERN"
370 nigel 63 .rs
371     .sp
372 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
373 nigel 63 .ti +5n
374 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
375 nigel 63 .ti +5n
376 nigel 75 .B const unsigned char *\fItableptr\fP);
377 nigel 77 .sp
378     .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
379     .ti +5n
380     .B int *\fIerrorcodeptr\fP,
381     .ti +5n
382     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
383     .ti +5n
384     .B const unsigned char *\fItableptr\fP);
385 nigel 75 .P
386 nigel 77 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
387     called to compile a pattern into an internal form. The only difference between
388     the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
389     \fIerrorcodeptr\fP, via which a numerical error code can be returned.
390 nigel 75 .P
391 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
392     \fIpattern\fP argument. A pointer to a single block of memory that is obtained
393     via \fBpcre_malloc\fP is returned. This contains the compiled code and related
394     data. The \fBpcre\fP type is defined for the returned block; this is a typedef
395     for a structure whose contents are not externally defined. It is up to the
396 nigel 91 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
397 nigel 77 .P
398 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
399 nigel 75 depend on memory location, the complete \fBpcre\fP data block is not
400     fully relocatable, because it may contain a copy of the \fItableptr\fP
401     argument, which is an address (see below).
402     .P
403 nigel 93 The \fIoptions\fP argument contains various bit settings that affect the
404 nigel 75 compilation. It should be zero if no options are required. The available
405     options are described below. Some of them, in particular, those that are
406     compatible with Perl, can also be set and unset from within the pattern (see
407     the detailed description in the
408     .\" HREF
409     \fBpcrepattern\fP
410     .\"
411     documentation). For these options, the contents of the \fIoptions\fP argument
412     specifies their initial settings at the start of compilation and execution. The
413 nigel 91 PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
414     matching as well as at compile time.
415 nigel 75 .P
416     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
417     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
418     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
419 nigel 87 error message. This is a static string that is part of the library. You must
420     not try to free it. The offset from the start of the pattern to the character
421     where the error was discovered is placed in the variable pointed to by
422 nigel 75 \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
423     .P
424 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
425     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
426     returned via this argument in the event of an error. This is in addition to the
427     textual error message. Error codes and messages are listed below.
428     .P
429 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
430     character tables that are built when PCRE is compiled, using the default C
431     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
432     call to \fBpcre_maketables()\fP. This value is stored with the compiled
433     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
434     passed to it. For more discussion, see the section on locale support below.
435     .P
436     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
437     .sp
438 nigel 63 pcre *re;
439     const char *error;
440     int erroffset;
441     re = pcre_compile(
442     "^A.*Z", /* the pattern */
443     0, /* default options */
444     &error, /* for error message */
445     &erroffset, /* for error offset */
446     NULL); /* use default character tables */
447 nigel 75 .sp
448     The following names for option bits are defined in the \fBpcre.h\fP header
449     file:
450     .sp
451 nigel 63 PCRE_ANCHORED
452 nigel 75 .sp
453 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
454 nigel 75 constrained to match only at the first matching point in the string that is
455 nigel 63 being searched (the "subject string"). This effect can also be achieved by
456     appropriate constructs in the pattern itself, which is the only way to do it in
457     Perl.
458 nigel 75 .sp
459     PCRE_AUTO_CALLOUT
460     .sp
461     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
462     all with number 255, before each pattern item. For discussion of the callout
463     facility, see the
464     .\" HREF
465     \fBpcrecallout\fP
466     .\"
467     documentation.
468     .sp
469 nigel 63 PCRE_CASELESS
470 nigel 75 .sp
471 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
472     letters. It is equivalent to Perl's /i option, and it can be changed within a
473 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
474     concept of case for characters whose values are less than 128, so caseless
475     matching is always possible. For characters with higher values, the concept of
476     case is supported if PCRE is compiled with Unicode property support, but not
477     otherwise. If you want to use caseless matching for characters 128 and above,
478     you must ensure that PCRE is compiled with Unicode property support as well as
479     with UTF-8 support.
480 nigel 75 .sp
481 nigel 63 PCRE_DOLLAR_ENDONLY
482 nigel 75 .sp
483 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
484     end of the subject string. Without this option, a dollar also matches
485 nigel 91 immediately before a newline at the end of the string (but not before any other
486     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
487     There is no equivalent to this option in Perl, and no way to set it within a
488     pattern.
489 nigel 75 .sp
490 nigel 63 PCRE_DOTALL
491 nigel 75 .sp
492 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
493 nigel 91 including those that indicate newline. Without it, a dot does not match when
494     the current position is at a newline. This option is equivalent to Perl's /s
495     option, and it can be changed within a pattern by a (?s) option setting. A
496 nigel 93 negative class such as [^a] always matches newline characters, independent of
497     the setting of this option.
498 nigel 75 .sp
499 nigel 91 PCRE_DUPNAMES
500     .sp
501     If this bit is set, names used to identify capturing subpatterns need not be
502     unique. This can be helpful for certain types of pattern when it is known that
503     only one instance of the named subpattern can ever be matched. There are more
504     details of named subpatterns below; see also the
505     .\" HREF
506     \fBpcrepattern\fP
507     .\"
508     documentation.
509     .sp
510 nigel 63 PCRE_EXTENDED
511 nigel 75 .sp
512 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
513     ignored except when escaped or inside a character class. Whitespace does not
514     include the VT character (code 11). In addition, characters between an
515 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
516     ignored. This is equivalent to Perl's /x option, and it can be changed within a
517     pattern by a (?x) option setting.
518 nigel 75 .P
519 nigel 63 This option makes it possible to include comments inside complicated patterns.
520     Note, however, that this applies only to data characters. Whitespace characters
521     may never appear within special character sequences in a pattern, for example
522     within the sequence (?( which introduces a conditional subpattern.
523 nigel 75 .sp
524 nigel 63 PCRE_EXTRA
525 nigel 75 .sp
526 nigel 63 This option was invented in order to turn on additional functionality of PCRE
527     that is incompatible with Perl, but it is currently of very little use. When
528     set, any backslash in a pattern that is followed by a letter that has no
529     special meaning causes an error, thus reserving these combinations for future
530     expansion. By default, as in Perl, a backslash followed by a letter with no
531 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
532     give a warning for this.) There are at present no other features controlled by
533     this option. It can also be set by a (?X) option setting within a pattern.
534 nigel 75 .sp
535 nigel 77 PCRE_FIRSTLINE
536     .sp
537     If this option is set, an unanchored pattern is required to match before or at
538 nigel 91 the first newline in the subject string, though the matched text may continue
539     over the newline.
540 nigel 77 .sp
541 nigel 63 PCRE_MULTILINE
542 nigel 75 .sp
543     By default, PCRE treats the subject string as consisting of a single line of
544     characters (even if it actually contains newlines). The "start of line"
545 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
546     line" metacharacter ($) matches only at the end of the string, or before a
547     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
548     Perl.
549 nigel 75 .P
550 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
551 nigel 91 match immediately following or immediately before internal newlines in the
552     subject string, respectively, as well as at the very start and end. This is
553     equivalent to Perl's /m option, and it can be changed within a pattern by a
554     (?m) option setting. If there are no newlines in a subject string, or no
555 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
556 nigel 75 .sp
557 nigel 91 PCRE_NEWLINE_CR
558     PCRE_NEWLINE_LF
559     PCRE_NEWLINE_CRLF
560 nigel 93 PCRE_NEWLINE_ANY
561 nigel 91 .sp
562     These options override the default newline definition that was chosen when PCRE
563     was built. Setting the first or the second specifies that a newline is
564 nigel 93 indicated by a single character (CR or LF, respectively). Setting
565     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
566     CRLF sequence. Setting PCRE_NEWLINE_ANY specifies that any Unicode newline
567     sequence should be recognized. The Unicode newline sequences are the three just
568     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
569     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
570     (paragraph separator, U+2029). The last two are recognized only in UTF-8 mode.
571 nigel 91 .P
572 nigel 93 The newline setting in the options word uses three bits that are treated
573     as a number, giving eight possibilities. Currently only five are used (default
574     plus the four values above). This means that if you set more than one newline
575     option, the combination may or may not be sensible. For example,
576     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
577     other combinations yield unused numbers and cause an error.
578     .P
579     The only time that a line break is specially recognized when compiling a
580     pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
581     class is encountered. This indicates a comment that lasts until after the next
582     line break sequence. In other circumstances, line break sequences are treated
583     as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
584     as whitespace characters and are therefore ignored.
585     .P
586     The newline option that is set at compile time becomes the default that is used
587     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
588 nigel 91 .sp
589 nigel 63 PCRE_NO_AUTO_CAPTURE
590 nigel 75 .sp
591 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
592     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
593     were followed by ?: but named parentheses can still be used for capturing (and
594     they acquire numbers in the usual way). There is no equivalent of this option
595     in Perl.
596 nigel 75 .sp
597 nigel 63 PCRE_UNGREEDY
598 nigel 75 .sp
599 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
600     greedy by default, but become greedy if followed by "?". It is not compatible
601     with Perl. It can also be set by a (?U) option setting within the pattern.
602 nigel 75 .sp
603 nigel 63 PCRE_UTF8
604 nigel 75 .sp
605 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
606     of UTF-8 characters instead of single-byte character strings. However, it is
607 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
608 nigel 63 of this option provokes an error. Details of how this option changes the
609     behaviour of PCRE are given in the
610     .\" HTML <a href="pcre.html#utf8support">
611     .\" </a>
612     section on UTF-8 support
613     .\"
614     in the main
615     .\" HREF
616 nigel 75 \fBpcre\fP
617 nigel 63 .\"
618     page.
619 nigel 75 .sp
620 nigel 71 PCRE_NO_UTF8_CHECK
621 nigel 75 .sp
622 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
623     automatically checked. If an invalid UTF-8 sequence of bytes is found,
624 nigel 75 \fBpcre_compile()\fP returns an error. If you already know that your pattern is
625 nigel 71 valid, and you want to skip this check for performance reasons, you can set the
626     PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
627     UTF-8 string as a pattern is undefined. It may cause your program to crash.
628 nigel 77 Note that this option can also be passed to \fBpcre_exec()\fP and
629     \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject
630     strings.
631 nigel 75 .
632     .
633 nigel 77 .SH "COMPILATION ERROR CODES"
634     .rs
635     .sp
636     The following table lists the error codes than may be returned by
637     \fBpcre_compile2()\fP, along with the error messages that may be returned by
638 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
639     out of use. To avoid confusion, they have not been re-used.
640 nigel 77 .sp
641     0 no error
642     1 \e at end of pattern
643     2 \ec at end of pattern
644     3 unrecognized character follows \e
645     4 numbers out of order in {} quantifier
646     5 number too big in {} quantifier
647     6 missing terminating ] for character class
648     7 invalid escape sequence in character class
649     8 range out of order in character class
650     9 nothing to repeat
651 nigel 93 10 [this code is not in use]
652 nigel 77 11 internal error: unexpected repeat
653     12 unrecognized character after (?
654     13 POSIX named classes are supported only within a class
655     14 missing )
656     15 reference to non-existent subpattern
657     16 erroffset passed as NULL
658     17 unknown option bit(s) set
659     18 missing ) after comment
660 nigel 93 19 [this code is not in use]
661 nigel 77 20 regular expression too large
662     21 failed to get memory
663     22 unmatched parentheses
664     23 internal error: code overflow
665     24 unrecognized character after (?<
666     25 lookbehind assertion is not fixed length
667 nigel 91 26 malformed number or name after (?(
668 nigel 77 27 conditional group contains more than two branches
669     28 assertion expected after (?(
670     29 (?R or (?digits must be followed by )
671     30 unknown POSIX class name
672     31 POSIX collating elements are not supported
673     32 this version of PCRE is not compiled with PCRE_UTF8 support
674 nigel 93 33 [this code is not in use]
675 nigel 77 34 character value in \ex{...} sequence is too large
676     35 invalid condition (?(0)
677     36 \eC not allowed in lookbehind assertion
678     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
679     38 number after (?C is > 255
680     39 closing ) for (?C expected
681     40 recursive call could loop indefinitely
682     41 unrecognized character after (?P
683 nigel 93 42 syntax error in subpattern name (missing terminator)
684 nigel 91 43 two named subpatterns have the same name
685 nigel 77 44 invalid UTF-8 string
686     45 support for \eP, \ep, and \eX has not been compiled
687     46 malformed \eP or \ep sequence
688     47 unknown property name after \eP or \ep
689 nigel 91 48 subpattern name is too long (maximum 32 characters)
690     49 too many named subpatterns (maximum 10,000)
691     50 repeated subpattern is too long
692     51 octal value is greater than \e377 (not in UTF-8 mode)
693 nigel 93 52 internal error: overran compiling workspace
694     53 internal error: previously-checked referenced subpattern not found
695     54 DEFINE group contains more than one branch
696     55 repeating a DEFINE group is not allowed
697     56 inconsistent NEWLINE options"
698 nigel 77 .
699     .
700 nigel 75 .SH "STUDYING A PATTERN"
701 nigel 63 .rs
702     .sp
703 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
704 nigel 63 .ti +5n
705 nigel 75 .B const char **\fIerrptr\fP);
706 nigel 63 .PP
707 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
708     more time analyzing it in order to speed up the time taken for matching. The
709     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
710     argument. If studying the pattern produces additional information that will
711     help speed up matching, \fBpcre_study()\fP returns a pointer to a
712     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
713     results of the study.
714     .P
715     The returned value from \fBpcre_study()\fP can be passed directly to
716     \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
717 nigel 63 fields that can be set by the caller before the block is passed; these are
718 nigel 75 described
719     .\" HTML <a href="#extradata">
720     .\" </a>
721     below
722     .\"
723     in the section on matching a pattern.
724     .P
725 nigel 77 If studying the pattern does not produce any additional information
726 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
727     wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
728     own \fBpcre_extra\fP block.
729     .P
730     The second argument of \fBpcre_study()\fP contains option bits. At present, no
731     options are defined, and this argument should always be zero.
732     .P
733     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
734 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
735 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
736     static string that is part of the library. You must not try to free it. You
737     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
738     sure that it has run successfully.
739 nigel 75 .P
740     This is a typical call to \fBpcre_study\fP():
741     .sp
742 nigel 63 pcre_extra *pe;
743     pe = pcre_study(
744     re, /* result of pcre_compile() */
745     0, /* no options exist */
746     &error); /* set to NULL or points to a message */
747 nigel 75 .sp
748 nigel 63 At present, studying a pattern is useful only for non-anchored patterns that do
749     not have a single fixed starting character. A bitmap of possible starting
750 nigel 75 bytes is created.
751     .
752     .
753 nigel 63 .\" HTML <a name="localesupport"></a>
754 nigel 75 .SH "LOCALE SUPPORT"
755 nigel 63 .rs
756     .sp
757 nigel 77 PCRE handles caseless matching, and determines whether characters are letters
758 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
759 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
760 nigel 75 less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
761     can be tested with \ep if PCRE is built with Unicode character property
762 nigel 87 support. The use of locales with Unicode is discouraged.
763 nigel 75 .P
764     An internal set of tables is created in the default C locale when PCRE is
765     built. This is used when the final argument of \fBpcre_compile()\fP is NULL,
766     and is sufficient for many applications. An alternative set of tables can,
767     however, be supplied. These may be created in a different locale from the
768     default. As more and more applications change to using Unicode, the need for
769     this locale support is expected to die away.
770     .P
771     External tables are built by calling the \fBpcre_maketables()\fP function,
772     which has no arguments, in the relevant locale. The result can then be passed
773     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
774     example, to build and use tables that are appropriate for the French locale
775     (where accented characters with values greater than 128 are treated as letters),
776     the following code could be used:
777     .sp
778     setlocale(LC_CTYPE, "fr_FR");
779 nigel 63 tables = pcre_maketables();
780     re = pcre_compile(..., tables);
781 nigel 75 .sp
782     When \fBpcre_maketables()\fP runs, the tables are built in memory that is
783     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
784     that the memory containing the tables remains available for as long as it is
785     needed.
786     .P
787     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
788     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
789     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
790     pattern, compilation, studying and matching all happen in the same locale, but
791     different patterns can be compiled in different locales.
792     .P
793     It is possible to pass a table pointer or NULL (indicating the use of the
794     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
795     this facility could be used to match a pattern in a different locale from the
796     one in which it was compiled. Passing table pointers at run time is discussed
797     below in the section on matching a pattern.
798     .
799     .
800     .SH "INFORMATION ABOUT A PATTERN"
801 nigel 63 .rs
802     .sp
803 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
804 nigel 63 .ti +5n
805 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
806 nigel 63 .PP
807 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
808     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
809 nigel 63 nevertheless retained for backwards compability (and is documented below).
810 nigel 75 .P
811     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
812     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
813 nigel 63 the pattern was not studied. The third argument specifies which piece of
814     information is required, and the fourth argument is a pointer to a variable
815     to receive the data. The yield of the function is zero for success, or one of
816     the following negative numbers:
817 nigel 75 .sp
818     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
819     the argument \fIwhere\fP was NULL
820 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
821 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
822     .sp
823     The "magic number" is placed at the start of each compiled pattern as an simple
824     check against passing an arbitrary memory pointer. Here is a typical call of
825     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
826     .sp
827 nigel 63 int rc;
828 nigel 91 size_t length;
829 nigel 63 rc = pcre_fullinfo(
830     re, /* result of pcre_compile() */
831     pe, /* result of pcre_study(), or NULL */
832     PCRE_INFO_SIZE, /* what is required */
833     &length); /* where to put the data */
834 nigel 75 .sp
835     The possible values for the third argument are defined in \fBpcre.h\fP, and are
836 nigel 63 as follows:
837 nigel 75 .sp
838 nigel 63 PCRE_INFO_BACKREFMAX
839 nigel 75 .sp
840 nigel 63 Return the number of the highest back reference in the pattern. The fourth
841 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
842 nigel 63 no back references.
843 nigel 75 .sp
844 nigel 63 PCRE_INFO_CAPTURECOUNT
845 nigel 75 .sp
846 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
847 nigel 75 should point to an \fBint\fP variable.
848     .sp
849 nigel 77 PCRE_INFO_DEFAULT_TABLES
850 nigel 75 .sp
851     Return a pointer to the internal default character tables within PCRE. The
852     fourth argument should point to an \fBunsigned char *\fP variable. This
853     information call is provided for internal use by the \fBpcre_study()\fP
854     function. External callers can cause PCRE to use its internal tables by passing
855     a NULL table pointer.
856     .sp
857 nigel 63 PCRE_INFO_FIRSTBYTE
858 nigel 75 .sp
859 nigel 63 Return information about the first byte of any matched string, for a
860 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
861     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
862     still recognized for backwards compatibility.)
863 nigel 75 .P
864     If there is a fixed first byte, for example, from a pattern such as
865 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
866 nigel 75 .sp
867 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
868     starts with "^", or
869 nigel 75 .sp
870 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
871     (if it were set, the pattern would be anchored),
872 nigel 75 .sp
873 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
874     subject string or after any newline within the string. Otherwise -2 is
875     returned. For anchored patterns, -2 is returned.
876 nigel 75 .sp
877 nigel 63 PCRE_INFO_FIRSTTABLE
878 nigel 75 .sp
879 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
880     table indicating a fixed set of bytes for the first byte in any matching
881     string, a pointer to the table is returned. Otherwise NULL is returned. The
882 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
883     .sp
884 nigel 63 PCRE_INFO_LASTLITERAL
885 nigel 75 .sp
886 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
887     string, other than at its start, if such a byte has been recorded. The fourth
888 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
889 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
890     follows something of variable length. For example, for the pattern
891 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
892 nigel 65 is -1.
893 nigel 75 .sp
894 nigel 63 PCRE_INFO_NAMECOUNT
895     PCRE_INFO_NAMEENTRYSIZE
896     PCRE_INFO_NAMETABLE
897 nigel 75 .sp
898 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
899     names are just an additional way of identifying the parentheses, which still
900 nigel 91 acquire numbers. Several convenience functions such as
901     \fBpcre_get_named_substring()\fP are provided for extracting captured
902     substrings by name. It is also possible to extract the data directly, by first
903     converting the name to a number in order to access the correct pointers in the
904     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
905     you need to use the name-to-number map, which is described by these three
906     values.
907 nigel 75 .P
908 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
909     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
910 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
911 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
912 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
913 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
914     rest of the entry is the corresponding name, zero terminated. The names are in
915 nigel 91 alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
916     their parentheses numbers. For example, consider the following pattern (assume
917 nigel 63 PCRE_EXTENDED is set, so white space - including newlines - is ignored):
918 nigel 75 .sp
919     .\" JOIN
920 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
921     (?<month>\ed\ed) - (?<day>\ed\ed) )
922 nigel 75 .sp
923 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
924     in the table is eight bytes long. The table is as follows, with non-printing
925 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
926     .sp
927 nigel 63 00 01 d a t e 00 ??
928     00 05 d a y 00 ?? ??
929     00 04 m o n t h 00
930     00 02 y e a r 00 ??
931 nigel 75 .sp
932     When writing code to extract data from named subpatterns using the
933 nigel 91 name-to-number map, remember that the length of the entries is likely to be
934 nigel 75 different for each compiled pattern.
935     .sp
936 nigel 63 PCRE_INFO_OPTIONS
937 nigel 75 .sp
938 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
939 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
940     are those specified in the call to \fBpcre_compile()\fP, modified by any
941 nigel 63 top-level option settings within the pattern itself.
942 nigel 75 .P
943 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
944     alternatives begin with one of the following:
945 nigel 75 .sp
946 nigel 63 ^ unless PCRE_MULTILINE is set
947 nigel 75 \eA always
948     \eG always
949     .\" JOIN
950 nigel 63 .* if PCRE_DOTALL is set and there are no back
951     references to the subpattern in which .* appears
952 nigel 75 .sp
953 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
954 nigel 75 \fBpcre_fullinfo()\fP.
955     .sp
956 nigel 63 PCRE_INFO_SIZE
957 nigel 75 .sp
958 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
959 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
960     place the compiled data. The fourth argument should point to a \fBsize_t\fP
961 nigel 63 variable.
962 nigel 75 .sp
963 nigel 63 PCRE_INFO_STUDYSIZE
964 nigel 75 .sp
965     Return the size of the data block pointed to by the \fIstudy_data\fP field in
966     a \fBpcre_extra\fP block. That is, it is the value that was passed to
967     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
968     created by \fBpcre_study()\fP. The fourth argument should point to a
969     \fBsize_t\fP variable.
970     .
971     .
972     .SH "OBSOLETE INFO FUNCTION"
973 nigel 63 .rs
974     .sp
975 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
976     .B *\fIfirstcharptr\fP);
977 nigel 63 .PP
978 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
979 nigel 63 restrictive to return all the available data about a compiled pattern. New
980 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
981     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
982 nigel 63 following negative numbers:
983 nigel 75 .sp
984     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
985 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
986 nigel 75 .sp
987     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
988 nigel 63 pattern was compiled is placed in the integer it points to (see
989     PCRE_INFO_OPTIONS above).
990 nigel 75 .P
991     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
992 nigel 63 it is used to pass back information about the first character of any matched
993     string (see PCRE_INFO_FIRSTBYTE above).
994 nigel 75 .
995     .
996 nigel 77 .SH "REFERENCE COUNTS"
997 nigel 63 .rs
998     .sp
999 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1000     .PP
1001     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1002     data block that contains a compiled pattern. It is provided for the benefit of
1003     applications that operate in an object-oriented manner, where different parts
1004     of the application may be using the same compiled pattern, but you want to free
1005     the block when they are all done.
1006     .P
1007     When a pattern is compiled, the reference count field is initialized to zero.
1008     It is changed only by calling this function, whose action is to add the
1009     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1010     function is the new value. However, the value of the count is constrained to
1011     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1012     it is forced to the appropriate limit value.
1013     .P
1014     Except when it is zero, the reference count is not correctly preserved if a
1015     pattern is compiled on one host and then transferred to a host whose byte-order
1016     is different. (This seems a highly unlikely scenario.)
1017     .
1018     .
1019     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1020     .rs
1021     .sp
1022 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1023 nigel 63 .ti +5n
1024 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1025 nigel 63 .ti +5n
1026 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1027     .P
1028     The function \fBpcre_exec()\fP is called to match a subject string against a
1029     compiled pattern, which is passed in the \fIcode\fP argument. If the
1030 nigel 63 pattern has been studied, the result of the study should be passed in the
1031 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1032     library, and it operates in a Perl-like manner. For specialist use there is
1033     also an alternative matching function, which is described
1034     .\" HTML <a href="#dfamatch">
1035     .\" </a>
1036     below
1037     .\"
1038     in the section about the \fBpcre_dfa_exec()\fP function.
1039 nigel 75 .P
1040     In most applications, the pattern will have been compiled (and optionally
1041     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1042     possible to save compiled patterns and study data, and then use them later
1043     in different processes, possibly even on different hosts. For a discussion
1044     about this, see the
1045     .\" HREF
1046     \fBpcreprecompile\fP
1047     .\"
1048     documentation.
1049     .P
1050     Here is an example of a simple call to \fBpcre_exec()\fP:
1051     .sp
1052 nigel 63 int rc;
1053     int ovector[30];
1054     rc = pcre_exec(
1055     re, /* result of pcre_compile() */
1056     NULL, /* we didn't study the pattern */
1057     "some string", /* the subject string */
1058     11, /* the length of the subject string */
1059     0, /* start at offset 0 in the subject */
1060     0, /* default options */
1061 nigel 75 ovector, /* vector of integers for substring information */
1062 nigel 77 30); /* number of elements (NOT size in bytes) */
1063 nigel 75 .
1064     .\" HTML <a name="extradata"></a>
1065     .SS "Extra data for \fBpcre_exec()\fR"
1066     .rs
1067     .sp
1068     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1069     data block. The \fBpcre_study()\fP function returns such a block (when it
1070 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1071 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1072     fields (not necessarily in this order):
1073 nigel 75 .sp
1074     unsigned long int \fIflags\fP;
1075     void *\fIstudy_data\fP;
1076     unsigned long int \fImatch_limit\fP;
1077 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1078 nigel 75 void *\fIcallout_data\fP;
1079     const unsigned char *\fItables\fP;
1080     .sp
1081     The \fIflags\fP field is a bitmap that specifies which of the other fields
1082 nigel 63 are set. The flag bits are:
1083 nigel 75 .sp
1084 nigel 63 PCRE_EXTRA_STUDY_DATA
1085     PCRE_EXTRA_MATCH_LIMIT
1086 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1087 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1088 nigel 75 PCRE_EXTRA_TABLES
1089     .sp
1090     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1091     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1092     the appropriate flag bit. You should not set this yourself, but you may add to
1093     the block by setting the other fields and their corresponding flag bits.
1094     .P
1095     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1096 nigel 63 vast amount of resources when running patterns that are not going to match,
1097     but which have a very large number of possibilities in their search trees. The
1098 nigel 75 classic example is the use of nested unlimited repeats.
1099     .P
1100     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1101 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1102     number of times this function is called during a match, which has the effect of
1103     limiting the amount of backtracking that can take place. For patterns that are
1104     not anchored, the count restarts from zero for each position in the subject
1105     string.
1106 nigel 75 .P
1107 nigel 87 The default value for the limit can be set when PCRE is built; the default
1108 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1109 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1110     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1111     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1112     PCRE_ERROR_MATCHLIMIT.
1113 nigel 75 .P
1114 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1115     instead of limiting the total number of times that \fBmatch()\fP is called, it
1116     limits the depth of recursion. The recursion depth is a smaller number than the
1117     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1118     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1119     .P
1120     Limiting the recursion depth limits the amount of stack that can be used, or,
1121     when PCRE has been compiled to use memory on the heap instead of the stack, the
1122     amount of heap memory that can be used.
1123     .P
1124     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1125     built; the default default is the same value as the default for
1126     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1127     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1128     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1129     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1130     .P
1131 nigel 75 The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1132     which is described in the
1133     .\" HREF
1134     \fBpcrecallout\fP
1135     .\"
1136     documentation.
1137     .P
1138     The \fItables\fP field is used to pass a character tables pointer to
1139     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1140     pattern. A non-NULL value is stored with the compiled pattern only if custom
1141     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1142     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1143     internal tables to be used. This facility is helpful when re-using patterns
1144     that have been saved after compiling with an external set of tables, because
1145     the external tables might be at a different address when \fBpcre_exec()\fP is
1146     called. See the
1147     .\" HREF
1148     \fBpcreprecompile\fP
1149     .\"
1150     documentation for a discussion of saving compiled patterns for later use.
1151     .
1152     .SS "Option bits for \fBpcre_exec()\fP"
1153     .rs
1154     .sp
1155     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1156 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1157     PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1158 nigel 75 .sp
1159     PCRE_ANCHORED
1160     .sp
1161     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1162     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1163     to be anchored by virtue of its contents, it cannot be made unachored at
1164     matching time.
1165     .sp
1166 nigel 91 PCRE_NEWLINE_CR
1167     PCRE_NEWLINE_LF
1168     PCRE_NEWLINE_CRLF
1169 nigel 93 PCRE_NEWLINE_ANY
1170 nigel 91 .sp
1171     These options override the newline definition that was chosen or defaulted when
1172 nigel 93 the pattern was compiled. For details, see the description of
1173     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1174     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1175     the way the match position is advanced after a match failure for an unanchored
1176     pattern. When PCRE_NEWLINE_CRLF or PCRE_NEWLINE_ANY is set, and a match attempt
1177     fails when the current position is at a CRLF sequence, the match position is
1178     advanced by two characters instead of one, in other words, to after the CRLF.
1179 nigel 91 .sp
1180 nigel 63 PCRE_NOTBOL
1181 nigel 75 .sp
1182     This option specifies that first character of the subject string is not the
1183     beginning of a line, so the circumflex metacharacter should not match before
1184     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1185     never to match. This option affects only the behaviour of the circumflex
1186     metacharacter. It does not affect \eA.
1187     .sp
1188 nigel 63 PCRE_NOTEOL
1189 nigel 75 .sp
1190     This option specifies that the end of the subject string is not the end of a
1191     line, so the dollar metacharacter should not match it nor (except in multiline
1192     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1193     compile time) causes dollar never to match. This option affects only the
1194     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1195     .sp
1196 nigel 63 PCRE_NOTEMPTY
1197 nigel 75 .sp
1198 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1199     there are alternatives in the pattern, they are tried. If all the alternatives
1200     match the empty string, the entire match fails. For example, if the pattern
1201 nigel 75 .sp
1202 nigel 63 a?b?
1203 nigel 75 .sp
1204 nigel 63 is applied to a string not beginning with "a" or "b", it matches the empty
1205     string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1206     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1207 nigel 75 .P
1208 nigel 63 Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1209 nigel 75 of a pattern match of the empty string within its \fBsplit()\fP function, and
1210 nigel 63 when using the /g modifier. It is possible to emulate Perl's behaviour after
1211     matching a null string by first trying the match again at the same offset with
1212 nigel 75 PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1213     starting offset (see below) and trying an ordinary match again. There is some
1214     code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1215     .sp
1216     PCRE_NO_UTF8_CHECK
1217     .sp
1218     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1219     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1220     The value of \fIstartoffset\fP is also checked to ensure that it points to the
1221     start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
1222     \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP
1223     contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1224     .P
1225     If you already know that your subject is valid, and you want to skip these
1226     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1227     calling \fBpcre_exec()\fP. You might want to do this for the second and
1228     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1229     all the matches in a single subject string. However, you should be sure that
1230     the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1231     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1232     subject, or a value of \fIstartoffset\fP that does not point to the start of a
1233     UTF-8 character, is undefined. Your program may crash.
1234     .sp
1235     PCRE_PARTIAL
1236     .sp
1237     This option turns on the partial matching feature. If the subject string fails
1238     to match the pattern, but at some point during the matching process the end of
1239     the subject was reached (that is, the subject partially matches the pattern and
1240     the failure to match occurred only because there were not enough subject
1241     characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1242     PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1243     may appear in the pattern. These are discussed in the
1244     .\" HREF
1245     \fBpcrepartial\fP
1246     .\"
1247     documentation.
1248     .
1249     .SS "The string to be matched by \fBpcre_exec()\fP"
1250     .rs
1251     .sp
1252     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1253     \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
1254     \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
1255     UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1256     bytes. When the starting offset is zero, the search for a match starts at the
1257     beginning of the subject, and this is by far the most common case.
1258     .P
1259 nigel 63 A non-zero starting offset is useful when searching for another match in the
1260 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1261     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1262 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1263     lookbehind. For example, consider the pattern
1264 nigel 75 .sp
1265     \eBiss\eB
1266     .sp
1267     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1268 nigel 63 the current position in the subject is not a word boundary.) When applied to
1269 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1270     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1271     subject, namely "issipi", it does not match, because \eB is always false at the
1272 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1273 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1274 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1275     behind the starting point to discover that it is preceded by a letter.
1276 nigel 75 .P
1277 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1278 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1279 nigel 63 pattern does not require the match to be at the start of the subject.
1280 nigel 75 .
1281     .SS "How \fBpcre_exec()\fP returns captured substrings"
1282     .rs
1283     .sp
1284 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1285     addition, further substrings from the subject may be picked out by parts of the
1286     pattern. Following the usage in Jeffrey Friedl's book, this is called
1287     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1288     a fragment of a pattern that picks out a substring. PCRE supports several other
1289     kinds of parenthesized subpattern that do not cause substrings to be captured.
1290 nigel 75 .P
1291 nigel 63 Captured substrings are returned to the caller via a vector of integer offsets
1292 nigel 75 whose address is passed in \fIovector\fP. The number of elements in the vector
1293     is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
1294     this argument is NOT the size of \fIovector\fP in bytes.
1295     .P
1296     The first two-thirds of the vector is used to pass back captured substrings,
1297     each substring using a pair of integers. The remaining third of the vector is
1298     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1299     and is not available for passing back information. The length passed in
1300     \fIovecsize\fP should always be a multiple of three. If it is not, it is
1301     rounded down.
1302     .P
1303     When a match is successful, information about captured substrings is returned
1304     in pairs of integers, starting at the beginning of \fIovector\fP, and
1305 nigel 63 continuing up to two-thirds of its length at the most. The first element of a
1306     pair is set to the offset of the first character in a substring, and the second
1307     is set to the offset of the first character after the end of a substring. The
1308 nigel 75 first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
1309 nigel 63 subject string matched by the entire pattern. The next pair is used for the
1310 nigel 75 first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
1311 nigel 91 is one more than the highest numbered pair that has been set. For example, if
1312     two substrings have been captured, the returned value is 3. If there are no
1313     capturing subpatterns, the return value from a successful match is 1,
1314     indicating that just the first pair of offsets has been set.
1315 nigel 75 .P
1316 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1317 nigel 75 string that it matched that is returned.
1318     .P
1319     If the vector is too small to hold all the captured substring offsets, it is
1320     used as far as possible (up to two-thirds of its length), and the function
1321     returns a value of zero. In particular, if the substring offsets are not of
1322     interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1323     \fIovecsize\fP as zero. However, if the pattern contains back references and
1324     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1325     has to get additional memory for use during matching. Thus it is usually
1326     advisable to supply an \fIovector\fP.
1327     .P
1328 nigel 91 The \fBpcre_info()\fP function can be used to find out how many capturing
1329 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1330 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1331     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1332 nigel 91 .P
1333     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1334     the subject when subpattern \fIn\fP has not been used at all. For example, if
1335     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1336     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1337     happens, both values in the offset pairs corresponding to unused subpatterns
1338     are set to -1.
1339     .P
1340     Offset values that correspond to unused subpatterns at the end of the
1341     expression are also set to -1. For example, if the string "abc" is matched
1342     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1343     return from the function is 2, because the highest used capturing subpattern
1344     number is 1. However, you can refer to the offsets for the second and third
1345     capturing subpatterns if you wish (assuming the vector is large enough, of
1346     course).
1347     .P
1348     Some convenience functions are provided for extracting the captured substrings
1349     as separate strings. These are described below.
1350 nigel 75 .
1351 nigel 77 .\" HTML <a name="errorlist"></a>
1352 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1353 nigel 75 .rs
1354     .sp
1355     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1356 nigel 63 defined in the header file:
1357 nigel 75 .sp
1358 nigel 63 PCRE_ERROR_NOMATCH (-1)
1359 nigel 75 .sp
1360 nigel 63 The subject string did not match the pattern.
1361 nigel 75 .sp
1362 nigel 63 PCRE_ERROR_NULL (-2)
1363 nigel 75 .sp
1364     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1365     NULL and \fIovecsize\fP was not zero.
1366     .sp
1367 nigel 63 PCRE_ERROR_BADOPTION (-3)
1368 nigel 75 .sp
1369     An unrecognized bit was set in the \fIoptions\fP argument.
1370     .sp
1371 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1372 nigel 75 .sp
1373 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1374 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1375     compiled in an environment of one endianness is run in an environment with the
1376     other endianness. This is the error that PCRE gives when the magic number is
1377     not present.
1378     .sp
1379 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1380 nigel 75 .sp
1381 nigel 63 While running the pattern match, an unknown item was encountered in the
1382     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1383     of the compiled pattern.
1384 nigel 75 .sp
1385 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1386 nigel 75 .sp
1387     If a pattern contains back references, but the \fIovector\fP that is passed to
1388     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1389 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1390 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1391     automatically freed at the end of matching.
1392     .sp
1393 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1394 nigel 75 .sp
1395     This error is used by the \fBpcre_copy_substring()\fP,
1396     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1397     below). It is never returned by \fBpcre_exec()\fP.
1398     .sp
1399 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1400 nigel 75 .sp
1401 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1402     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1403     above.
1404     .sp
1405 nigel 63 PCRE_ERROR_CALLOUT (-9)
1406 nigel 75 .sp
1407     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1408 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1409 nigel 75 .\" HREF
1410     \fBpcrecallout\fP
1411     .\"
1412     documentation for details.
1413     .sp
1414 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1415 nigel 75 .sp
1416 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1417 nigel 75 .sp
1418 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1419 nigel 75 .sp
1420 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1421 nigel 75 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1422     .sp
1423 nigel 77 PCRE_ERROR_PARTIAL (-12)
1424 nigel 75 .sp
1425     The subject string did not match, but it did match partially. See the
1426     .\" HREF
1427     \fBpcrepartial\fP
1428     .\"
1429     documentation for details of partial matching.
1430     .sp
1431 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1432 nigel 75 .sp
1433     The PCRE_PARTIAL option was used with a compiled pattern containing items that
1434     are not supported for partial matching. See the
1435     .\" HREF
1436     \fBpcrepartial\fP
1437     .\"
1438     documentation for details of partial matching.
1439     .sp
1440 nigel 77 PCRE_ERROR_INTERNAL (-14)
1441 nigel 75 .sp
1442     An unexpected internal error has occurred. This error could be caused by a bug
1443     in PCRE or by overwriting of the compiled pattern.
1444     .sp
1445 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1446 nigel 75 .sp
1447     This error is given if the value of the \fIovecsize\fP argument is negative.
1448 nigel 93 .sp
1449     PCRE_ERROR_RECURSIONLIMIT (-21)
1450     .sp
1451     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1452     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1453     description above.
1454     .sp
1455     PCRE_ERROR_NULLWSLIMIT (-22)
1456     .sp
1457     When a group that can match an empty substring is repeated with an unbounded
1458     upper limit, the subject position at the start of the group must be remembered,
1459     so that a test for an empty string can be made when the end of the group is
1460     reached. Some workspace is required for this; if it runs out, this error is
1461     given.
1462     .sp
1463     PCRE_ERROR_BADNEWLINE (-23)
1464     .sp
1465     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1466     .P
1467     Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.
1468 nigel 75 .
1469     .
1470     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1471 nigel 63 .rs
1472     .sp
1473 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1474 nigel 63 .ti +5n
1475 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1476 nigel 63 .ti +5n
1477 nigel 75 .B int \fIbuffersize\fP);
1478 nigel 63 .PP
1479     .br
1480 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1481 nigel 63 .ti +5n
1482 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1483 nigel 63 .ti +5n
1484 nigel 75 .B const char **\fIstringptr\fP);
1485 nigel 63 .PP
1486     .br
1487 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1488 nigel 63 .ti +5n
1489 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1490 nigel 63 .PP
1491     Captured substrings can be accessed directly by using the offsets returned by
1492 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1493     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1494     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1495 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1496     by number. The next section describes functions for extracting named
1497 nigel 91 substrings.
1498 nigel 75 .P
1499 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1500     further zero added on the end, but the result is not, of course, a C string.
1501     However, you can process such a string by referring to the length that is
1502     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1503     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1504     for handling strings containing binary zeros, because the end of the final
1505     string is not independently indicated.
1506     .P
1507 nigel 63 The first three arguments are the same for all three of these functions:
1508 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1509     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1510     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1511 nigel 63 captured by the match, including the substring that matched the entire regular
1512 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1513     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1514     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1515     number of elements in the vector divided by three.
1516     .P
1517     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1518     extract a single substring, whose number is given as \fIstringnumber\fP. A
1519     value of zero extracts the substring that matched the entire pattern, whereas
1520     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1521     the string is placed in \fIbuffer\fP, whose length is given by
1522     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1523     obtained via \fBpcre_malloc\fP, and its address is returned via
1524     \fIstringptr\fP. The yield of the function is the length of the string, not
1525 nigel 93 including the terminating zero, or one of these error codes:
1526 nigel 75 .sp
1527 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1528 nigel 75 .sp
1529     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1530     memory failed for \fBpcre_get_substring()\fP.
1531     .sp
1532 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1533 nigel 75 .sp
1534     There is no substring whose number is \fIstringnumber\fP.
1535     .P
1536     The \fBpcre_get_substring_list()\fP function extracts all available substrings
1537 nigel 63 and builds a list of pointers to them. All this is done in a single block of
1538 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1539     is returned via \fIlistptr\fP, which is also the start of the list of string
1540 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
1541 nigel 93 function is zero if all went well, or the error code
1542 nigel 75 .sp
1543 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1544 nigel 75 .sp
1545 nigel 63 if the attempt to get the memory block failed.
1546 nigel 75 .P
1547 nigel 63 When any of these functions encounter a substring that is unset, which can
1548 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
1549     subject, but subpattern \fIn\fP has not been used at all, they return an empty
1550 nigel 63 string. This can be distinguished from a genuine zero-length substring by
1551 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1552 nigel 63 substrings.
1553 nigel 75 .P
1554     The two convenience functions \fBpcre_free_substring()\fP and
1555     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1556     a previous call of \fBpcre_get_substring()\fP or
1557     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1558     the function pointed to by \fBpcre_free\fP, which of course could be called
1559 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
1560 nigel 91 linked via a special interface to another programming language that cannot use
1561 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
1562 nigel 63 provided.
1563 nigel 75 .
1564     .
1565     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1566 nigel 63 .rs
1567     .sp
1568 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1569 nigel 63 .ti +5n
1570 nigel 75 .B const char *\fIname\fP);
1571 nigel 63 .PP
1572     .br
1573 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1574 nigel 63 .ti +5n
1575 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1576     .ti +5n
1577     .B int \fIstringcount\fP, const char *\fIstringname\fP,
1578     .ti +5n
1579     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1580 nigel 63 .PP
1581     .br
1582 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1583 nigel 63 .ti +5n
1584 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1585 nigel 63 .ti +5n
1586 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1587 nigel 63 .ti +5n
1588 nigel 75 .B const char **\fIstringptr\fP);
1589 nigel 63 .PP
1590 nigel 75 To extract a substring by name, you first have to find associated number.
1591     For example, for this pattern
1592     .sp
1593 nigel 93 (a+)b(?<xxx>\ed+)...
1594 nigel 75 .sp
1595 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1596     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1597     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1598     pattern, and the second is the name. The yield of the function is the
1599 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1600     that name.
1601     .P
1602     Given the number, you can extract the substring directly, or use one of the
1603     functions described in the previous section. For convenience, there are also
1604     two functions that do the whole job.
1605     .P
1606 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1607     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1608 nigel 75 functions that extract by number. As these are described in the previous
1609     section, they are not re-described here. There are just two differences:
1610     .P
1611 nigel 63 First, instead of a substring number, a substring name is given. Second, there
1612     is an extra argument, given at the start, which is a pointer to the compiled
1613     pattern. This is needed in order to gain access to the name-to-number
1614     translation table.
1615 nigel 75 .P
1616     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1617     then call \fIpcre_copy_substring()\fP or \fIpcre_get_substring()\fP, as
1618 nigel 63 appropriate.
1619 nigel 77 .
1620     .
1621 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
1622     .rs
1623     .sp
1624     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1625     .ti +5n
1626     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1627     .PP
1628     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1629     are not required to be unique. Normally, patterns with duplicate names are such
1630     that in any one match, only one of the named subpatterns participates. An
1631     example is shown in the
1632     .\" HREF
1633     \fBpcrepattern\fP
1634     .\"
1635     documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP
1636     and \fBpcre_get_named_substring()\fP return the first substring corresponding
1637     to the given name that is set. If none are set, an empty string is returned.
1638     The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are
1639     associated with the name, but it is not defined which it is.
1640     .sp
1641     If you want to get full details of all captured substrings for a given name,
1642     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1643     argument is the compiled pattern, and the second is the name. The third and
1644     fourth are pointers to variables which are updated by the function. After it
1645     has run, they point to the first and last entries in the name-to-number table
1646     for the given name. The function itself returns the length of each entry, or
1647 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1648     described above in the section entitled \fIInformation about a pattern\fP.
1649     Given all the relevant entries for the name, you can extract each of their
1650     numbers, and hence the captured data, if any.
1651 nigel 91 .
1652     .
1653 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
1654     .rs
1655     .sp
1656     The traditional matching function uses a similar algorithm to Perl, which stops
1657     when it finds the first match, starting at a given point in the subject. If you
1658     want to find all possible matches, or the longest possible match, consider
1659     using the alternative matching function (see below) instead. If you cannot use
1660     the alternative function, but still need to find all possible matches, you
1661     can kludge it up by making use of the callout facility, which is described in
1662     the
1663     .\" HREF
1664     \fBpcrecallout\fP
1665     .\"
1666     documentation.
1667 nigel 75 .P
1668 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
1669     When your callout function is called, extract and save the current matched
1670     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1671     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1672     will yield PCRE_ERROR_NOMATCH.
1673     .
1674     .
1675     .\" HTML <a name="dfamatch"></a>
1676     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1677     .rs
1678     .sp
1679     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1680     .ti +5n
1681     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1682     .ti +5n
1683     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1684     .ti +5n
1685     .B int *\fIworkspace\fP, int \fIwscount\fP);
1686     .P
1687     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1688 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
1689     just once, and does not backtrack. This has different characteristics to the
1690     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1691     patterns are not supported. Nevertheless, there are times when this kind of
1692     matching can be useful. For a discussion of the two matching algorithms, see
1693     the
1694 nigel 77 .\" HREF
1695     \fBpcrematching\fP
1696     .\"
1697     documentation.
1698     .P
1699     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1700     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1701     different way, and this is described below. The other common arguments are used
1702     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1703     here.
1704     .P
1705     The two additional arguments provide workspace for the function. The workspace
1706     vector should contain at least 20 elements. It is used for keeping track of
1707     multiple paths through the pattern tree. More workspace will be needed for
1708 nigel 91 patterns and subjects where there are a lot of potential matches.
1709 nigel 77 .P
1710 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1711 nigel 77 .sp
1712     int rc;
1713     int ovector[10];
1714     int wspace[20];
1715 nigel 87 rc = pcre_dfa_exec(
1716 nigel 77 re, /* result of pcre_compile() */
1717     NULL, /* we didn't study the pattern */
1718     "some string", /* the subject string */
1719     11, /* the length of the subject string */
1720     0, /* start at offset 0 in the subject */
1721     0, /* default options */
1722     ovector, /* vector of integers for substring information */
1723     10, /* number of elements (NOT size in bytes) */
1724     wspace, /* working space vector */
1725     20); /* number of elements (NOT size in bytes) */
1726     .
1727     .SS "Option bits for \fBpcre_dfa_exec()\fP"
1728     .rs
1729     .sp
1730     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1731 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1732     PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
1733 nigel 77 PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1734     the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1735     .sp
1736     PCRE_PARTIAL
1737     .sp
1738     This has the same general effect as it does for \fBpcre_exec()\fP, but the
1739     details are slightly different. When PCRE_PARTIAL is set for
1740     \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1741     PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1742     complete matches, but there is still at least one matching possibility. The
1743     portion of the string that provided the partial match is set as the first
1744     matching string.
1745     .sp
1746     PCRE_DFA_SHORTEST
1747     .sp
1748     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1749 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
1750     works, this is necessarily the shortest possible match at the first possible
1751     matching point in the subject string.
1752 nigel 77 .sp
1753     PCRE_DFA_RESTART
1754     .sp
1755     When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1756     a partial match, it is possible to call it again, with additional subject
1757     characters, and have it continue with the same match. The PCRE_DFA_RESTART
1758     option requests this action; when it is set, the \fIworkspace\fP and
1759     \fIwscount\fP options must reference the same vector as before because data
1760     about the match so far is left in them after a partial match. There is more
1761     discussion of this facility in the
1762     .\" HREF
1763     \fBpcrepartial\fP
1764     .\"
1765     documentation.
1766     .
1767     .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1768     .rs
1769     .sp
1770     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1771     substring in the subject. Note, however, that all the matches from one run of
1772     the function start at the same point in the subject. The shorter matches are
1773     all initial substrings of the longer matches. For example, if the pattern
1774     .sp
1775     <.*>
1776     .sp
1777     is matched against the string
1778     .sp
1779     This is <something> <something else> <something further> no more
1780     .sp
1781     the three matched strings are
1782     .sp
1783     <something>
1784     <something> <something else>
1785     <something> <something else> <something further>
1786     .sp
1787     On success, the yield of the function is a number greater than zero, which is
1788     the number of matched substrings. The substrings themselves are returned in
1789     \fIovector\fP. Each string uses two elements; the first is the offset to the
1790 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
1791     the same start offset. (Space could have been saved by giving this only once,
1792     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1793     returns data, even though the meaning of the strings is different.)
1794 nigel 77 .P
1795     The strings are returned in reverse order of length; that is, the longest
1796     matching string is given first. If there were too many matches to fit into
1797     \fIovector\fP, the yield of the function is zero, and the vector is filled with
1798     the longest matches.
1799     .
1800     .SS "Error returns from \fBpcre_dfa_exec()\fP"
1801     .rs
1802     .sp
1803     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1804     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1805     described
1806     .\" HTML <a href="#errorlist">
1807     .\" </a>
1808     above.
1809     .\"
1810     There are in addition the following errors that are specific to
1811     \fBpcre_dfa_exec()\fP:
1812     .sp
1813     PCRE_ERROR_DFA_UITEM (-16)
1814     .sp
1815     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1816     that it does not support, for instance, the use of \eC or a back reference.
1817     .sp
1818     PCRE_ERROR_DFA_UCOND (-17)
1819     .sp
1820 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1821     uses a back reference for the condition, or a test for recursion in a specific
1822     group. These are not supported.
1823 nigel 77 .sp
1824     PCRE_ERROR_DFA_UMLIMIT (-18)
1825     .sp
1826     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1827     block that contains a setting of the \fImatch_limit\fP field. This is not
1828     supported (it is meaningless).
1829     .sp
1830     PCRE_ERROR_DFA_WSSIZE (-19)
1831     .sp
1832     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1833     \fIworkspace\fP vector.
1834     .sp
1835     PCRE_ERROR_DFA_RECURSE (-20)
1836     .sp
1837     When a recursive subpattern is processed, the matching function calls itself
1838     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1839     error is given if the output vector is not large enough. This should be
1840     extremely rare, as a vector of size 1000 is used.
1841 nigel 93 .
1842     .
1843     .SH "SEE ALSO"
1844     .rs
1845     .sp
1846     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1847     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1848     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1849 nigel 77 .P
1850 nigel 63 .in 0
1851 nigel 93 Last updated: 30 November 2006
1852 nigel 63 .br
1853 nigel 87 Copyright (c) 1997-2006 University of Cambridge.

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