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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 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
11 nigel 63 .ti +5n
12 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
13 nigel 63 .ti +5n
14 nigel 75 .B const unsigned char *\fItableptr\fP);
15 nigel 63 .PP
16 nigel 77 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
17     .ti +5n
18     .B int *\fIerrorcodeptr\fP,
19     .ti +5n
20     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
21     .ti +5n
22     .B const unsigned char *\fItableptr\fP);
23     .PP
24 nigel 75 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
25 nigel 63 .ti +5n
26 nigel 75 .B const char **\fIerrptr\fP);
27 nigel 63 .PP
28 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
29 nigel 63 .ti +5n
30 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
31 nigel 63 .ti +5n
32 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
33 nigel 63 .PP
34 nigel 77 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
35     .ti +5n
36     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
37     .ti +5n
38     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
39     .ti +5n
40     .B int *\fIworkspace\fP, int \fIwscount\fP);
41     .PP
42 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
43 nigel 63 .ti +5n
44 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
45 nigel 63 .ti +5n
46 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
47 nigel 63 .ti +5n
48 nigel 75 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
49 nigel 63 .PP
50 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
51 nigel 63 .ti +5n
52 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53 nigel 63 .ti +5n
54 nigel 75 .B int \fIbuffersize\fP);
55 nigel 63 .PP
56 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
57 nigel 63 .ti +5n
58 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
59 nigel 63 .ti +5n
60 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
61 nigel 63 .ti +5n
62 nigel 75 .B const char **\fIstringptr\fP);
63 nigel 63 .PP
64 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
65 nigel 63 .ti +5n
66 nigel 75 .B const char *\fIname\fP);
67 nigel 63 .PP
68 nigel 91 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
69     .ti +5n
70     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71     .PP
72 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
73 nigel 63 .ti +5n
74 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
75 nigel 63 .ti +5n
76 nigel 75 .B const char **\fIstringptr\fP);
77 nigel 63 .PP
78 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
79 nigel 63 .ti +5n
80 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
81 nigel 63 .PP
82 nigel 75 .B void pcre_free_substring(const char *\fIstringptr\fP);
83 nigel 63 .PP
84 nigel 75 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
85 nigel 63 .PP
86     .B const unsigned char *pcre_maketables(void);
87     .PP
88 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
89 nigel 63 .ti +5n
90 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
91 nigel 63 .PP
92 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
93     .B *\fIfirstcharptr\fP);
94 nigel 63 .PP
95 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
96     .PP
97 nigel 75 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
98 nigel 63 .PP
99     .B char *pcre_version(void);
100     .PP
101     .B void *(*pcre_malloc)(size_t);
102     .PP
103     .B void (*pcre_free)(void *);
104     .PP
105 nigel 73 .B void *(*pcre_stack_malloc)(size_t);
106     .PP
107     .B void (*pcre_stack_free)(void *);
108     .PP
109 nigel 63 .B int (*pcre_callout)(pcre_callout_block *);
110 nigel 75 .
111     .
112     .SH "PCRE API OVERVIEW"
113 nigel 63 .rs
114     .sp
115 nigel 93 PCRE has its own native API, which is described in this document. There are
116     also some wrapper functions that correspond to the POSIX regular expression
117 nigel 77 API. These are described in the
118 nigel 75 .\" HREF
119     \fBpcreposix\fP
120     .\"
121 nigel 77 documentation. Both of these APIs define a set of C function calls. A C++
122     wrapper is distributed with PCRE. It is documented in the
123     .\" HREF
124     \fBpcrecpp\fP
125     .\"
126     page.
127 nigel 75 .P
128 nigel 77 The native API C function prototypes are defined in the header file
129     \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
130     It can normally be accessed by adding \fB-lpcre\fP to the command for linking
131     an application that uses PCRE. The header file defines the macros PCRE_MAJOR
132     and PCRE_MINOR to contain the major and minor release numbers for the library.
133 nigel 75 Applications can use these to include support for different releases of PCRE.
134     .P
135 ph10 525 In a Windows environment, if you want to statically link an application program
136     against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137 ph10 526 including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138     \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139 ph10 525 \fB__declspec(dllimport)\fP, with unwanted results.
140     .P
141 nigel 77 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142     and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143     in a Perl-compatible manner. A sample program that demonstrates the simplest
144 ph10 429 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
145     source distribution. A listing of this program is given in the
146 nigel 75 .\" HREF
147 ph10 429 \fBpcredemo\fP
148     .\"
149     documentation, and the
150     .\" HREF
151 nigel 75 \fBpcresample\fP
152     .\"
153 ph10 312 documentation describes how to compile and run it.
154 nigel 75 .P
155 nigel 77 A second matching function, \fBpcre_dfa_exec()\fP, which is not
156     Perl-compatible, is also provided. This uses a different algorithm for the
157 nigel 91 matching. The alternative algorithm finds all possible matches (at a given
158 ph10 435 point in the subject), and scans the subject just once (unless there are
159     lookbehind assertions). However, this algorithm does not return captured
160     substrings. A description of the two matching algorithms and their advantages
161     and disadvantages is given in the
162 nigel 77 .\" HREF
163     \fBpcrematching\fP
164     .\"
165     documentation.
166     .P
167 nigel 75 In addition to the main compiling and matching functions, there are convenience
168 nigel 77 functions for extracting captured substrings from a subject string that is
169     matched by \fBpcre_exec()\fP. They are:
170 nigel 75 .sp
171     \fBpcre_copy_substring()\fP
172     \fBpcre_copy_named_substring()\fP
173     \fBpcre_get_substring()\fP
174     \fBpcre_get_named_substring()\fP
175     \fBpcre_get_substring_list()\fP
176     \fBpcre_get_stringnumber()\fP
177 nigel 91 \fBpcre_get_stringtable_entries()\fP
178 nigel 75 .sp
179     \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
180 nigel 63 provided, to free the memory used for extracted strings.
181 nigel 75 .P
182     The function \fBpcre_maketables()\fP is used to build a set of character tables
183 nigel 77 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
184     or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
185     specialist use. Most commonly, no special tables are passed, in which case
186     internal tables that are generated when PCRE is built are used.
187 nigel 75 .P
188     The function \fBpcre_fullinfo()\fP is used to find out information about a
189     compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
190 nigel 63 some of the available information, but is retained for backwards compatibility.
191 nigel 75 The function \fBpcre_version()\fP returns a pointer to a string containing the
192 nigel 63 version of PCRE and its date of release.
193 nigel 75 .P
194 nigel 77 The function \fBpcre_refcount()\fP maintains a reference count in a data block
195     containing a compiled pattern. This is provided for the benefit of
196     object-oriented applications.
197     .P
198 nigel 75 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
199     the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
200 nigel 63 respectively. PCRE calls the memory management functions via these variables,
201     so a calling program can replace them if it wishes to intercept the calls. This
202     should be done before calling any PCRE functions.
203 nigel 75 .P
204     The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
205 nigel 73 indirections to memory management functions. These special functions are used
206     only when PCRE is compiled to use the heap for remembering data, instead of
207 nigel 91 recursive function calls, when running the \fBpcre_exec()\fP function. See the
208     .\" HREF
209     \fBpcrebuild\fP
210     .\"
211     documentation for details of how to do this. It is a non-standard way of
212     building PCRE, for use in environments that have limited stacks. Because of the
213     greater use of memory management, it runs more slowly. Separate functions are
214     provided so that special-purpose external code can be used for this case. When
215     used, these functions are always called in a stack-like manner (last obtained,
216     first freed), and always for memory blocks of the same size. There is a
217     discussion about PCRE's stack usage in the
218     .\" HREF
219     \fBpcrestack\fP
220     .\"
221     documentation.
222 nigel 75 .P
223     The global variable \fBpcre_callout\fP initially contains NULL. It can be set
224 nigel 63 by the caller to a "callout" function, which PCRE will then call at specified
225 nigel 75 points during a matching operation. Details are given in the
226     .\" HREF
227     \fBpcrecallout\fP
228     .\"
229 nigel 63 documentation.
230 nigel 75 .
231     .
232 ph10 227 .\" HTML <a name="newlines"></a>
233 nigel 91 .SH NEWLINES
234 nigel 93 .rs
235 nigel 91 .sp
236 ph10 149 PCRE supports five different conventions for indicating line breaks in
237 nigel 93 strings: a single CR (carriage return) character, a single LF (linefeed)
238 ph10 149 character, the two-character sequence CRLF, any of the three preceding, or any
239     Unicode newline sequence. The Unicode newline sequences are the three just
240     mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
241     U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
242     (paragraph separator, U+2029).
243 nigel 93 .P
244     Each of the first three conventions is used by at least one operating system as
245     its standard newline sequence. When PCRE is built, a default can be specified.
246     The default default is LF, which is the Unix standard. When PCRE is run, the
247     default can be overridden, either when a pattern is compiled, or when it is
248     matched.
249     .P
250 ph10 227 At compile time, the newline convention can be specified by the \fIoptions\fP
251     argument of \fBpcre_compile()\fP, or it can be specified by special text at the
252     start of the pattern itself; this overrides any other settings. See the
253     .\" HREF
254     \fBpcrepattern\fP
255     .\"
256     page for details of the special character sequences.
257     .P
258 nigel 91 In the PCRE documentation the word "newline" is used to mean "the character or
259 nigel 93 pair of characters that indicate a line break". The choice of newline
260     convention affects the handling of the dot, circumflex, and dollar
261     metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
262     recognized line ending sequence, the match position advancement for a
263 ph10 226 non-anchored pattern. There is more detail about this in the
264     .\" HTML <a href="#execoptions">
265     .\" </a>
266     section on \fBpcre_exec()\fP options
267     .\"
268 ph10 231 below.
269     .P
270     The choice of newline convention does not affect the interpretation of
271     the \en or \er escape sequences, nor does it affect what \eR matches, which is
272     controlled in a similar way, but by separate options.
273 nigel 91 .
274     .
275 nigel 63 .SH MULTITHREADING
276     .rs
277     .sp
278     The PCRE functions can be used in multi-threading applications, with the
279 nigel 75 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
280     \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
281     callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
282     .P
283 nigel 63 The compiled form of a regular expression is not altered during matching, so
284     the same compiled pattern can safely be used by several threads at once.
285 nigel 75 .
286     .
287     .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
288 nigel 63 .rs
289     .sp
290 nigel 75 The compiled form of a regular expression can be saved and re-used at a later
291     time, possibly by a different program, and even on a host other than the one on
292     which it was compiled. Details are given in the
293     .\" HREF
294     \fBpcreprecompile\fP
295     .\"
296 ph10 155 documentation. However, compiling a regular expression with one version of PCRE
297     for use with a different version is not guaranteed to work and may cause
298     crashes.
299 nigel 75 .
300     .
301     .SH "CHECKING BUILD-TIME OPTIONS"
302     .rs
303     .sp
304     .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
305 nigel 63 .PP
306 nigel 75 The function \fBpcre_config()\fP makes it possible for a PCRE client to
307 nigel 63 discover which optional features have been compiled into the PCRE library. The
308     .\" HREF
309 nigel 75 \fBpcrebuild\fP
310 nigel 63 .\"
311     documentation has more details about these optional features.
312 nigel 75 .P
313     The first argument for \fBpcre_config()\fP is an integer, specifying which
314 nigel 63 information is required; the second argument is a pointer to a variable into
315     which the information is placed. The following information is available:
316 nigel 75 .sp
317 nigel 63 PCRE_CONFIG_UTF8
318 nigel 75 .sp
319 nigel 63 The output is an integer that is set to one if UTF-8 support is available;
320     otherwise it is set to zero.
321 nigel 75 .sp
322     PCRE_CONFIG_UNICODE_PROPERTIES
323     .sp
324     The output is an integer that is set to one if support for Unicode character
325     properties is available; otherwise it is set to zero.
326     .sp
327 nigel 63 PCRE_CONFIG_NEWLINE
328 nigel 75 .sp
329 nigel 91 The output is an integer whose value specifies the default character sequence
330 nigel 93 that is recognized as meaning "newline". The four values that are supported
331 ph10 392 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
332 ph10 391 Though they are derived from ASCII, the same values are returned in EBCDIC
333     environments. The default should normally correspond to the standard sequence
334     for your operating system.
335 nigel 75 .sp
336 ph10 231 PCRE_CONFIG_BSR
337     .sp
338     The output is an integer whose value indicates what character sequences the \eR
339     escape sequence matches by default. A value of 0 means that \eR matches any
340     Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
341     or CRLF. The default can be overridden when a pattern is compiled or matched.
342     .sp
343 nigel 63 PCRE_CONFIG_LINK_SIZE
344 nigel 75 .sp
345 nigel 63 The output is an integer that contains the number of bytes used for internal
346     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
347     allow larger regular expressions to be compiled, at the expense of slower
348     matching. The default value of 2 is sufficient for all but the most massive
349     patterns, since it allows the compiled pattern to be up to 64K in size.
350 nigel 75 .sp
351 nigel 63 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
352 nigel 75 .sp
353 nigel 63 The output is an integer that contains the threshold above which the POSIX
354 nigel 75 interface uses \fBmalloc()\fP for output vectors. Further details are given in
355     the
356     .\" HREF
357     \fBpcreposix\fP
358     .\"
359     documentation.
360     .sp
361 nigel 63 PCRE_CONFIG_MATCH_LIMIT
362 nigel 75 .sp
363 ph10 376 The output is a long integer that gives the default limit for the number of
364 nigel 75 internal matching function calls in a \fBpcre_exec()\fP execution. Further
365     details are given with \fBpcre_exec()\fP below.
366     .sp
367 nigel 87 PCRE_CONFIG_MATCH_LIMIT_RECURSION
368     .sp
369 ph10 376 The output is a long integer that gives the default limit for the depth of
370 nigel 87 recursion when calling the internal matching function in a \fBpcre_exec()\fP
371     execution. Further details are given with \fBpcre_exec()\fP below.
372     .sp
373 nigel 73 PCRE_CONFIG_STACKRECURSE
374 nigel 75 .sp
375 nigel 77 The output is an integer that is set to one if internal recursion when running
376     \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
377     to remember their state. This is the usual way that PCRE is compiled. The
378     output is zero if PCRE was compiled to use blocks of data on the heap instead
379     of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
380     \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
381     avoiding the use of the stack.
382 nigel 75 .
383     .
384     .SH "COMPILING A PATTERN"
385 nigel 63 .rs
386     .sp
387 nigel 75 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
388 nigel 63 .ti +5n
389 nigel 75 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
390 nigel 63 .ti +5n
391 nigel 75 .B const unsigned char *\fItableptr\fP);
392 nigel 77 .sp
393     .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
394     .ti +5n
395     .B int *\fIerrorcodeptr\fP,
396     .ti +5n
397     .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
398     .ti +5n
399     .B const unsigned char *\fItableptr\fP);
400 nigel 75 .P
401 nigel 77 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
402     called to compile a pattern into an internal form. The only difference between
403     the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
404 ph10 461 \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
405     too much repetition, we refer just to \fBpcre_compile()\fP below, but the
406 ph10 456 information applies equally to \fBpcre_compile2()\fP.
407 nigel 75 .P
408 nigel 77 The pattern is a C string terminated by a binary zero, and is passed in the
409     \fIpattern\fP argument. A pointer to a single block of memory that is obtained
410     via \fBpcre_malloc\fP is returned. This contains the compiled code and related
411     data. The \fBpcre\fP type is defined for the returned block; this is a typedef
412     for a structure whose contents are not externally defined. It is up to the
413 nigel 91 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
414 nigel 77 .P
415 nigel 63 Although the compiled code of a PCRE regex is relocatable, that is, it does not
416 nigel 75 depend on memory location, the complete \fBpcre\fP data block is not
417     fully relocatable, because it may contain a copy of the \fItableptr\fP
418     argument, which is an address (see below).
419     .P
420 nigel 93 The \fIoptions\fP argument contains various bit settings that affect the
421 nigel 75 compilation. It should be zero if no options are required. The available
422 ph10 412 options are described below. Some of them (in particular, those that are
423 ph10 456 compatible with Perl, but some others as well) can also be set and unset from
424 ph10 412 within the pattern (see the detailed description in the
425 nigel 75 .\" HREF
426     \fBpcrepattern\fP
427     .\"
428 ph10 412 documentation). For those options that can be different in different parts of
429 ph10 456 the pattern, the contents of the \fIoptions\fP argument specifies their
430 ph10 461 settings at the start of compilation and execution. The PCRE_ANCHORED,
431 ph10 456 PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
432     of matching as well as at compile time.
433 nigel 75 .P
434     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
435     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
436     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
437 nigel 87 error message. This is a static string that is part of the library. You must
438 ph10 454 not try to free it. The byte offset from the start of the pattern to the
439 ph10 456 character that was being processed when the error was discovered is placed in
440 ph10 454 the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
441     an immediate error is given. Some errors are not detected until checks are
442     carried out when the whole pattern has been scanned; in this case the offset is
443     set to the end of the pattern.
444 nigel 75 .P
445 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
446     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
447     returned via this argument in the event of an error. This is in addition to the
448     textual error message. Error codes and messages are listed below.
449     .P
450 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
451     character tables that are built when PCRE is compiled, using the default C
452     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
453     call to \fBpcre_maketables()\fP. This value is stored with the compiled
454     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
455     passed to it. For more discussion, see the section on locale support below.
456     .P
457     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
458     .sp
459 nigel 63 pcre *re;
460     const char *error;
461     int erroffset;
462     re = pcre_compile(
463     "^A.*Z", /* the pattern */
464     0, /* default options */
465     &error, /* for error message */
466     &erroffset, /* for error offset */
467     NULL); /* use default character tables */
468 nigel 75 .sp
469     The following names for option bits are defined in the \fBpcre.h\fP header
470     file:
471     .sp
472 nigel 63 PCRE_ANCHORED
473 nigel 75 .sp
474 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
475 nigel 75 constrained to match only at the first matching point in the string that is
476 nigel 63 being searched (the "subject string"). This effect can also be achieved by
477     appropriate constructs in the pattern itself, which is the only way to do it in
478     Perl.
479 nigel 75 .sp
480     PCRE_AUTO_CALLOUT
481     .sp
482     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
483     all with number 255, before each pattern item. For discussion of the callout
484     facility, see the
485     .\" HREF
486     \fBpcrecallout\fP
487     .\"
488     documentation.
489     .sp
490 ph10 231 PCRE_BSR_ANYCRLF
491     PCRE_BSR_UNICODE
492     .sp
493     These options (which are mutually exclusive) control what the \eR escape
494     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
495     match any Unicode newline sequence. The default is specified when PCRE is
496     built. It can be overridden from within the pattern, or by setting an option
497     when a compiled pattern is matched.
498     .sp
499 nigel 63 PCRE_CASELESS
500 nigel 75 .sp
501 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
502     letters. It is equivalent to Perl's /i option, and it can be changed within a
503 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
504     concept of case for characters whose values are less than 128, so caseless
505     matching is always possible. For characters with higher values, the concept of
506     case is supported if PCRE is compiled with Unicode property support, but not
507     otherwise. If you want to use caseless matching for characters 128 and above,
508     you must ensure that PCRE is compiled with Unicode property support as well as
509     with UTF-8 support.
510 nigel 75 .sp
511 nigel 63 PCRE_DOLLAR_ENDONLY
512 nigel 75 .sp
513 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
514     end of the subject string. Without this option, a dollar also matches
515 nigel 91 immediately before a newline at the end of the string (but not before any other
516     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
517     There is no equivalent to this option in Perl, and no way to set it within a
518     pattern.
519 nigel 75 .sp
520 nigel 63 PCRE_DOTALL
521 nigel 75 .sp
522 nigel 63 If this bit is set, a dot metacharater in the pattern matches all characters,
523 nigel 91 including those that indicate newline. Without it, a dot does not match when
524     the current position is at a newline. This option is equivalent to Perl's /s
525     option, and it can be changed within a pattern by a (?s) option setting. A
526 nigel 93 negative class such as [^a] always matches newline characters, independent of
527     the setting of this option.
528 nigel 75 .sp
529 nigel 91 PCRE_DUPNAMES
530     .sp
531     If this bit is set, names used to identify capturing subpatterns need not be
532     unique. This can be helpful for certain types of pattern when it is known that
533     only one instance of the named subpattern can ever be matched. There are more
534     details of named subpatterns below; see also the
535     .\" HREF
536     \fBpcrepattern\fP
537     .\"
538     documentation.
539     .sp
540 nigel 63 PCRE_EXTENDED
541 nigel 75 .sp
542 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
543     ignored except when escaped or inside a character class. Whitespace does not
544     include the VT character (code 11). In addition, characters between an
545 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
546     ignored. This is equivalent to Perl's /x option, and it can be changed within a
547     pattern by a (?x) option setting.
548 nigel 75 .P
549 nigel 63 This option makes it possible to include comments inside complicated patterns.
550     Note, however, that this applies only to data characters. Whitespace characters
551     may never appear within special character sequences in a pattern, for example
552     within the sequence (?( which introduces a conditional subpattern.
553 nigel 75 .sp
554 nigel 63 PCRE_EXTRA
555 nigel 75 .sp
556 nigel 63 This option was invented in order to turn on additional functionality of PCRE
557     that is incompatible with Perl, but it is currently of very little use. When
558     set, any backslash in a pattern that is followed by a letter that has no
559     special meaning causes an error, thus reserving these combinations for future
560     expansion. By default, as in Perl, a backslash followed by a letter with no
561 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
562 ph10 513 give an error for this, by running it with the -w option.) There are at present
563     no other features controlled by this option. It can also be set by a (?X)
564     option setting within a pattern.
565 nigel 75 .sp
566 nigel 77 PCRE_FIRSTLINE
567     .sp
568     If this option is set, an unanchored pattern is required to match before or at
569 nigel 91 the first newline in the subject string, though the matched text may continue
570     over the newline.
571 nigel 77 .sp
572 ph10 336 PCRE_JAVASCRIPT_COMPAT
573     .sp
574 ph10 345 If this option is set, PCRE's behaviour is changed in some ways so that it is
575 ph10 336 compatible with JavaScript rather than Perl. The changes are as follows:
576     .P
577     (1) A lone closing square bracket in a pattern causes a compile-time error,
578     because this is illegal in JavaScript (by default it is treated as a data
579     character). Thus, the pattern AB]CD becomes illegal when this option is set.
580     .P
581     (2) At run time, a back reference to an unset subpattern group matches an empty
582 ph10 345 string (by default this causes the current matching alternative to fail). A
583     pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
584     an "a" in the subject), whereas it fails by default, for Perl compatibility.
585 ph10 336 .sp
586 nigel 63 PCRE_MULTILINE
587 nigel 75 .sp
588     By default, PCRE treats the subject string as consisting of a single line of
589     characters (even if it actually contains newlines). The "start of line"
590 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
591     line" metacharacter ($) matches only at the end of the string, or before a
592     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
593     Perl.
594 nigel 75 .P
595 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
596 nigel 91 match immediately following or immediately before internal newlines in the
597     subject string, respectively, as well as at the very start and end. This is
598     equivalent to Perl's /m option, and it can be changed within a pattern by a
599     (?m) option setting. If there are no newlines in a subject string, or no
600 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
601 nigel 75 .sp
602 nigel 91 PCRE_NEWLINE_CR
603     PCRE_NEWLINE_LF
604     PCRE_NEWLINE_CRLF
605 ph10 150 PCRE_NEWLINE_ANYCRLF
606 nigel 93 PCRE_NEWLINE_ANY
607 nigel 91 .sp
608     These options override the default newline definition that was chosen when PCRE
609     was built. Setting the first or the second specifies that a newline is
610 nigel 93 indicated by a single character (CR or LF, respectively). Setting
611     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
612 ph10 149 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
613     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
614     that any Unicode newline sequence should be recognized. The Unicode newline
615     sequences are the three just mentioned, plus the single characters VT (vertical
616     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
617     separator, U+2028), and PS (paragraph separator, U+2029). The last two are
618     recognized only in UTF-8 mode.
619 nigel 91 .P
620 nigel 93 The newline setting in the options word uses three bits that are treated
621 ph10 149 as a number, giving eight possibilities. Currently only six are used (default
622     plus the five values above). This means that if you set more than one newline
623 nigel 93 option, the combination may or may not be sensible. For example,
624     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
625 ph10 149 other combinations may yield unused numbers and cause an error.
626 nigel 93 .P
627     The only time that a line break is specially recognized when compiling a
628     pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
629     class is encountered. This indicates a comment that lasts until after the next
630     line break sequence. In other circumstances, line break sequences are treated
631     as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
632     as whitespace characters and are therefore ignored.
633     .P
634     The newline option that is set at compile time becomes the default that is used
635     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
636 nigel 91 .sp
637 nigel 63 PCRE_NO_AUTO_CAPTURE
638 nigel 75 .sp
639 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
640     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
641     were followed by ?: but named parentheses can still be used for capturing (and
642     they acquire numbers in the usual way). There is no equivalent of this option
643     in Perl.
644 nigel 75 .sp
645 ph10 518 PCRE_UCP
646     .sp
647     This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
648     POSIX character classes. By default, only ASCII characters are recognized, but
649     if PCRE_UCP is set, Unicode properties are used instead to classify characters.
650     More details are given in the section on
651     .\" HTML <a href="pcre.html#genericchartypes">
652     .\" </a>
653     generic character types
654     .\"
655     in the
656     .\" HREF
657     \fBpcrepattern\fP
658     .\"
659     page. If you set PCRE_UCP, matching one of the items it affects takes much
660     longer. The option is available only if PCRE has been compiled with Unicode
661     property support.
662     .sp
663 nigel 63 PCRE_UNGREEDY
664 nigel 75 .sp
665 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
666     greedy by default, but become greedy if followed by "?". It is not compatible
667     with Perl. It can also be set by a (?U) option setting within the pattern.
668 nigel 75 .sp
669 nigel 63 PCRE_UTF8
670 nigel 75 .sp
671 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
672     of UTF-8 characters instead of single-byte character strings. However, it is
673 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
674 nigel 63 of this option provokes an error. Details of how this option changes the
675     behaviour of PCRE are given in the
676     .\" HTML <a href="pcre.html#utf8support">
677     .\" </a>
678     section on UTF-8 support
679     .\"
680     in the main
681     .\" HREF
682 nigel 75 \fBpcre\fP
683 nigel 63 .\"
684     page.
685 nigel 75 .sp
686 nigel 71 PCRE_NO_UTF8_CHECK
687 nigel 75 .sp
688 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
689 ph10 211 automatically checked. There is a discussion about the
690     .\" HTML <a href="pcre.html#utf8strings">
691     .\" </a>
692     validity of UTF-8 strings
693     .\"
694     in the main
695     .\" HREF
696     \fBpcre\fP
697     .\"
698     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
699     returns an error. If you already know that your pattern is valid, and you want
700     to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
701     option. When it is set, the effect of passing an invalid UTF-8 string as a
702     pattern is undefined. It may cause your program to crash. Note that this option
703     can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
704     the UTF-8 validity checking of subject strings.
705 nigel 75 .
706     .
707 nigel 77 .SH "COMPILATION ERROR CODES"
708     .rs
709     .sp
710     The following table lists the error codes than may be returned by
711     \fBpcre_compile2()\fP, along with the error messages that may be returned by
712 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
713     out of use. To avoid confusion, they have not been re-used.
714 nigel 77 .sp
715     0 no error
716     1 \e at end of pattern
717     2 \ec at end of pattern
718     3 unrecognized character follows \e
719     4 numbers out of order in {} quantifier
720     5 number too big in {} quantifier
721     6 missing terminating ] for character class
722     7 invalid escape sequence in character class
723     8 range out of order in character class
724     9 nothing to repeat
725 nigel 93 10 [this code is not in use]
726 nigel 77 11 internal error: unexpected repeat
727 ph10 290 12 unrecognized character after (? or (?-
728 nigel 77 13 POSIX named classes are supported only within a class
729     14 missing )
730     15 reference to non-existent subpattern
731     16 erroffset passed as NULL
732     17 unknown option bit(s) set
733     18 missing ) after comment
734 nigel 93 19 [this code is not in use]
735 ph10 290 20 regular expression is too large
736 nigel 77 21 failed to get memory
737     22 unmatched parentheses
738     23 internal error: code overflow
739     24 unrecognized character after (?<
740     25 lookbehind assertion is not fixed length
741 nigel 91 26 malformed number or name after (?(
742 nigel 77 27 conditional group contains more than two branches
743     28 assertion expected after (?(
744 ph10 181 29 (?R or (?[+-]digits must be followed by )
745 nigel 77 30 unknown POSIX class name
746     31 POSIX collating elements are not supported
747     32 this version of PCRE is not compiled with PCRE_UTF8 support
748 nigel 93 33 [this code is not in use]
749 nigel 77 34 character value in \ex{...} sequence is too large
750     35 invalid condition (?(0)
751     36 \eC not allowed in lookbehind assertion
752     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
753     38 number after (?C is > 255
754     39 closing ) for (?C expected
755     40 recursive call could loop indefinitely
756     41 unrecognized character after (?P
757 nigel 93 42 syntax error in subpattern name (missing terminator)
758 nigel 91 43 two named subpatterns have the same name
759 nigel 77 44 invalid UTF-8 string
760     45 support for \eP, \ep, and \eX has not been compiled
761     46 malformed \eP or \ep sequence
762     47 unknown property name after \eP or \ep
763 nigel 91 48 subpattern name is too long (maximum 32 characters)
764 ph10 290 49 too many named subpatterns (maximum 10000)
765 ph10 202 50 [this code is not in use]
766 nigel 91 51 octal value is greater than \e377 (not in UTF-8 mode)
767 nigel 93 52 internal error: overran compiling workspace
768     53 internal error: previously-checked referenced subpattern not found
769     54 DEFINE group contains more than one branch
770     55 repeating a DEFINE group is not allowed
771 ph10 231 56 inconsistent NEWLINE options
772 ph10 345 57 \eg is not followed by a braced, angle-bracketed, or quoted
773     name/number or by a plain number
774 ph10 336 58 a numbered reference must not be zero
775 ph10 510 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
776 ph10 290 60 (*VERB) not recognized
777     61 number is too big
778     62 subpattern name expected
779 ph10 292 63 digit expected after (?+
780 ph10 336 64 ] is an invalid data character in JavaScript compatibility mode
781 ph10 510 65 different names for subpatterns of the same number are not allowed
782     66 (*MARK) must have an argument
783 ph10 518 67 this version of PCRE is not compiled with PCRE_UCP support
784 ph10 290 .sp
785 ph10 292 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
786 ph10 290 be used if the limits were changed when PCRE was built.
787 nigel 77 .
788     .
789 nigel 75 .SH "STUDYING A PATTERN"
790 nigel 63 .rs
791     .sp
792 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
793 nigel 63 .ti +5n
794 nigel 75 .B const char **\fIerrptr\fP);
795 nigel 63 .PP
796 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
797     more time analyzing it in order to speed up the time taken for matching. The
798     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
799     argument. If studying the pattern produces additional information that will
800     help speed up matching, \fBpcre_study()\fP returns a pointer to a
801     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
802     results of the study.
803     .P
804     The returned value from \fBpcre_study()\fP can be passed directly to
805 ph10 455 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
806     also contains other fields that can be set by the caller before the block is
807     passed; these are described
808 nigel 75 .\" HTML <a href="#extradata">
809     .\" </a>
810     below
811     .\"
812     in the section on matching a pattern.
813     .P
814 ph10 455 If studying the pattern does not produce any useful information,
815 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
816 ph10 461 wants to pass any of the other fields to \fBpcre_exec()\fP or
817 ph10 455 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
818 nigel 75 .P
819     The second argument of \fBpcre_study()\fP contains option bits. At present, no
820     options are defined, and this argument should always be zero.
821     .P
822     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
823 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
824 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
825     static string that is part of the library. You must not try to free it. You
826     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
827     sure that it has run successfully.
828 nigel 75 .P
829     This is a typical call to \fBpcre_study\fP():
830     .sp
831 nigel 63 pcre_extra *pe;
832     pe = pcre_study(
833     re, /* result of pcre_compile() */
834     0, /* no options exist */
835     &error); /* set to NULL or points to a message */
836 nigel 75 .sp
837 ph10 455 Studying a pattern does two things: first, a lower bound for the length of
838 ph10 461 subject string that is needed to match the pattern is computed. This does not
839     mean that there are any strings of that length that match, but it does
840     guarantee that no shorter strings match. The value is used by
841     \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
842     match strings that are shorter than the lower bound. You can find out the value
843 ph10 455 in a calling program via the \fBpcre_fullinfo()\fP function.
844     .P
845     Studying a pattern is also useful for non-anchored patterns that do not have a
846     single fixed starting character. A bitmap of possible starting bytes is
847 ph10 461 created. This speeds up finding a position in the subject at which to start
848 ph10 455 matching.
849 nigel 75 .
850     .
851 nigel 63 .\" HTML <a name="localesupport"></a>
852 nigel 75 .SH "LOCALE SUPPORT"
853 nigel 63 .rs
854     .sp
855 ph10 139 PCRE handles caseless matching, and determines whether characters are letters,
856 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
857 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
858 ph10 518 less than 128. By default, higher-valued codes never match escapes such as \ew
859     or \ed, but they can be tested with \ep if PCRE is built with Unicode character
860     property support. Alternatively, the PCRE_UCP option can be set at compile
861     time; this causes \ew and friends to use Unicode property support instead of
862     built-in tables. The use of locales with Unicode is discouraged. If you are
863     handling characters with codes greater than 128, you should either use UTF-8
864     and Unicode, or use locales, but not try to mix the two.
865 nigel 75 .P
866 ph10 139 PCRE contains an internal set of tables that are used when the final argument
867     of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
868 ph10 142 Normally, the internal tables recognize only ASCII characters. However, when
869 ph10 139 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
870     default "C" locale of the local system, which may cause them to be different.
871 nigel 75 .P
872 ph10 139 The internal tables can always be overridden by tables supplied by the
873     application that calls PCRE. These may be created in a different locale from
874     the default. As more and more applications change to using Unicode, the need
875     for this locale support is expected to die away.
876     .P
877 nigel 75 External tables are built by calling the \fBpcre_maketables()\fP function,
878     which has no arguments, in the relevant locale. The result can then be passed
879     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
880     example, to build and use tables that are appropriate for the French locale
881     (where accented characters with values greater than 128 are treated as letters),
882     the following code could be used:
883     .sp
884     setlocale(LC_CTYPE, "fr_FR");
885 nigel 63 tables = pcre_maketables();
886     re = pcre_compile(..., tables);
887 nigel 75 .sp
888 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
889 ph10 139 are using Windows, the name for the French locale is "french".
890     .P
891 nigel 75 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
892     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
893     that the memory containing the tables remains available for as long as it is
894     needed.
895     .P
896     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
897     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
898     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
899     pattern, compilation, studying and matching all happen in the same locale, but
900     different patterns can be compiled in different locales.
901     .P
902     It is possible to pass a table pointer or NULL (indicating the use of the
903     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
904     this facility could be used to match a pattern in a different locale from the
905     one in which it was compiled. Passing table pointers at run time is discussed
906     below in the section on matching a pattern.
907     .
908     .
909     .SH "INFORMATION ABOUT A PATTERN"
910 nigel 63 .rs
911     .sp
912 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
913 nigel 63 .ti +5n
914 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
915 nigel 63 .PP
916 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
917     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
918 nigel 63 nevertheless retained for backwards compability (and is documented below).
919 nigel 75 .P
920     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
921     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
922 nigel 63 the pattern was not studied. The third argument specifies which piece of
923     information is required, and the fourth argument is a pointer to a variable
924     to receive the data. The yield of the function is zero for success, or one of
925     the following negative numbers:
926 nigel 75 .sp
927     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
928     the argument \fIwhere\fP was NULL
929 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
930 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
931     .sp
932     The "magic number" is placed at the start of each compiled pattern as an simple
933     check against passing an arbitrary memory pointer. Here is a typical call of
934     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
935     .sp
936 nigel 63 int rc;
937 nigel 91 size_t length;
938 nigel 63 rc = pcre_fullinfo(
939     re, /* result of pcre_compile() */
940     pe, /* result of pcre_study(), or NULL */
941     PCRE_INFO_SIZE, /* what is required */
942     &length); /* where to put the data */
943 nigel 75 .sp
944     The possible values for the third argument are defined in \fBpcre.h\fP, and are
945 nigel 63 as follows:
946 nigel 75 .sp
947 nigel 63 PCRE_INFO_BACKREFMAX
948 nigel 75 .sp
949 nigel 63 Return the number of the highest back reference in the pattern. The fourth
950 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
951 nigel 63 no back references.
952 nigel 75 .sp
953 nigel 63 PCRE_INFO_CAPTURECOUNT
954 nigel 75 .sp
955 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
956 nigel 75 should point to an \fBint\fP variable.
957     .sp
958 nigel 77 PCRE_INFO_DEFAULT_TABLES
959 nigel 75 .sp
960     Return a pointer to the internal default character tables within PCRE. The
961     fourth argument should point to an \fBunsigned char *\fP variable. This
962     information call is provided for internal use by the \fBpcre_study()\fP
963     function. External callers can cause PCRE to use its internal tables by passing
964     a NULL table pointer.
965     .sp
966 nigel 63 PCRE_INFO_FIRSTBYTE
967 nigel 75 .sp
968 nigel 63 Return information about the first byte of any matched string, for a
969 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
970     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
971     still recognized for backwards compatibility.)
972 nigel 75 .P
973     If there is a fixed first byte, for example, from a pattern such as
974 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
975 nigel 75 .sp
976 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
977     starts with "^", or
978 nigel 75 .sp
979 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
980     (if it were set, the pattern would be anchored),
981 nigel 75 .sp
982 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
983     subject string or after any newline within the string. Otherwise -2 is
984     returned. For anchored patterns, -2 is returned.
985 nigel 75 .sp
986 nigel 63 PCRE_INFO_FIRSTTABLE
987 nigel 75 .sp
988 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
989     table indicating a fixed set of bytes for the first byte in any matching
990     string, a pointer to the table is returned. Otherwise NULL is returned. The
991 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
992     .sp
993 ph10 226 PCRE_INFO_HASCRORLF
994     .sp
995 ph10 227 Return 1 if the pattern contains any explicit matches for CR or LF characters,
996 ph10 243 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
997 ph10 231 explicit match is either a literal CR or LF character, or \er or \en.
998 ph10 226 .sp
999 ph10 169 PCRE_INFO_JCHANGED
1000     .sp
1001 ph10 278 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1002     0. The fourth argument should point to an \fBint\fP variable. (?J) and
1003     (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1004 ph10 169 .sp
1005 nigel 63 PCRE_INFO_LASTLITERAL
1006 nigel 75 .sp
1007 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
1008     string, other than at its start, if such a byte has been recorded. The fourth
1009 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1010 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
1011     follows something of variable length. For example, for the pattern
1012 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1013 nigel 65 is -1.
1014 nigel 75 .sp
1015 ph10 455 PCRE_INFO_MINLENGTH
1016     .sp
1017     If the pattern was studied and a minimum length for matching subject strings
1018     was computed, its value is returned. Otherwise the returned value is -1. The
1019 ph10 456 value is a number of characters, not bytes (this may be relevant in UTF-8
1020 ph10 455 mode). The fourth argument should point to an \fBint\fP variable. A
1021     non-negative value is a lower bound to the length of any matching string. There
1022     may not be any strings of that length that do actually match, but every string
1023     that does match is at least that long.
1024     .sp
1025 nigel 63 PCRE_INFO_NAMECOUNT
1026     PCRE_INFO_NAMEENTRYSIZE
1027     PCRE_INFO_NAMETABLE
1028 nigel 75 .sp
1029 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
1030     names are just an additional way of identifying the parentheses, which still
1031 nigel 91 acquire numbers. Several convenience functions such as
1032     \fBpcre_get_named_substring()\fP are provided for extracting captured
1033     substrings by name. It is also possible to extract the data directly, by first
1034     converting the name to a number in order to access the correct pointers in the
1035     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1036     you need to use the name-to-number map, which is described by these three
1037     values.
1038 nigel 75 .P
1039 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1040     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1041 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
1042 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1043 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1044 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
1045 ph10 461 rest of the entry is the corresponding name, zero terminated.
1046 ph10 457 .P
1047     The names are in alphabetical order. Duplicate names may appear if (?| is used
1048     to create multiple groups with the same number, as described in the
1049     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1050     .\" </a>
1051     section on duplicate subpattern numbers
1052     .\"
1053     in the
1054     .\" HREF
1055     \fBpcrepattern\fP
1056     .\"
1057 ph10 461 page. Duplicate names for subpatterns with different numbers are permitted only
1058     if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1059     table in the order in which they were found in the pattern. In the absence of
1060     (?| this is the order of increasing number; when (?| is used this is not
1061 ph10 457 necessarily the case because later subpatterns may have lower numbers.
1062     .P
1063     As a simple example of the name/number table, consider the following pattern
1064     (assume PCRE_EXTENDED is set, so white space - including newlines - is
1065     ignored):
1066 nigel 75 .sp
1067     .\" JOIN
1068 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1069     (?<month>\ed\ed) - (?<day>\ed\ed) )
1070 nigel 75 .sp
1071 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
1072     in the table is eight bytes long. The table is as follows, with non-printing
1073 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
1074     .sp
1075 nigel 63 00 01 d a t e 00 ??
1076     00 05 d a y 00 ?? ??
1077     00 04 m o n t h 00
1078     00 02 y e a r 00 ??
1079 nigel 75 .sp
1080     When writing code to extract data from named subpatterns using the
1081 nigel 91 name-to-number map, remember that the length of the entries is likely to be
1082 nigel 75 different for each compiled pattern.
1083     .sp
1084 ph10 169 PCRE_INFO_OKPARTIAL
1085     .sp
1086 ph10 435 Return 1 if the pattern can be used for partial matching with
1087     \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1088     \fBint\fP variable. From release 8.00, this always returns 1, because the
1089     restrictions that previously applied to partial matching have been lifted. The
1090 ph10 169 .\" HREF
1091     \fBpcrepartial\fP
1092     .\"
1093 ph10 426 documentation gives details of partial matching.
1094 ph10 169 .sp
1095 nigel 63 PCRE_INFO_OPTIONS
1096 nigel 75 .sp
1097 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
1098 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
1099     are those specified in the call to \fBpcre_compile()\fP, modified by any
1100 ph10 196 top-level option settings at the start of the pattern itself. In other words,
1101     they are the options that will be in force when matching starts. For example,
1102     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1103     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1104 nigel 75 .P
1105 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
1106     alternatives begin with one of the following:
1107 nigel 75 .sp
1108 nigel 63 ^ unless PCRE_MULTILINE is set
1109 nigel 75 \eA always
1110     \eG always
1111     .\" JOIN
1112 nigel 63 .* if PCRE_DOTALL is set and there are no back
1113     references to the subpattern in which .* appears
1114 nigel 75 .sp
1115 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1116 nigel 75 \fBpcre_fullinfo()\fP.
1117     .sp
1118 nigel 63 PCRE_INFO_SIZE
1119 nigel 75 .sp
1120 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
1121 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1122     place the compiled data. The fourth argument should point to a \fBsize_t\fP
1123 nigel 63 variable.
1124 nigel 75 .sp
1125 nigel 63 PCRE_INFO_STUDYSIZE
1126 nigel 75 .sp
1127     Return the size of the data block pointed to by the \fIstudy_data\fP field in
1128     a \fBpcre_extra\fP block. That is, it is the value that was passed to
1129     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1130 ph10 455 created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1131     study data, zero is returned. The fourth argument should point to a
1132 nigel 75 \fBsize_t\fP variable.
1133     .
1134     .
1135     .SH "OBSOLETE INFO FUNCTION"
1136 nigel 63 .rs
1137     .sp
1138 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1139     .B *\fIfirstcharptr\fP);
1140 nigel 63 .PP
1141 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
1142 nigel 63 restrictive to return all the available data about a compiled pattern. New
1143 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1144     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1145 nigel 63 following negative numbers:
1146 nigel 75 .sp
1147     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1148 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
1149 nigel 75 .sp
1150     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1151 nigel 63 pattern was compiled is placed in the integer it points to (see
1152     PCRE_INFO_OPTIONS above).
1153 nigel 75 .P
1154     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1155 nigel 63 it is used to pass back information about the first character of any matched
1156     string (see PCRE_INFO_FIRSTBYTE above).
1157 nigel 75 .
1158     .
1159 nigel 77 .SH "REFERENCE COUNTS"
1160 nigel 63 .rs
1161     .sp
1162 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1163     .PP
1164     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1165     data block that contains a compiled pattern. It is provided for the benefit of
1166     applications that operate in an object-oriented manner, where different parts
1167     of the application may be using the same compiled pattern, but you want to free
1168     the block when they are all done.
1169     .P
1170     When a pattern is compiled, the reference count field is initialized to zero.
1171     It is changed only by calling this function, whose action is to add the
1172     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1173     function is the new value. However, the value of the count is constrained to
1174     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1175     it is forced to the appropriate limit value.
1176     .P
1177     Except when it is zero, the reference count is not correctly preserved if a
1178     pattern is compiled on one host and then transferred to a host whose byte-order
1179     is different. (This seems a highly unlikely scenario.)
1180     .
1181     .
1182     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1183     .rs
1184     .sp
1185 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1186 nigel 63 .ti +5n
1187 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1188 nigel 63 .ti +5n
1189 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1190     .P
1191     The function \fBpcre_exec()\fP is called to match a subject string against a
1192     compiled pattern, which is passed in the \fIcode\fP argument. If the
1193 ph10 455 pattern was studied, the result of the study should be passed in the
1194 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1195     library, and it operates in a Perl-like manner. For specialist use there is
1196     also an alternative matching function, which is described
1197     .\" HTML <a href="#dfamatch">
1198     .\" </a>
1199     below
1200     .\"
1201     in the section about the \fBpcre_dfa_exec()\fP function.
1202 nigel 75 .P
1203     In most applications, the pattern will have been compiled (and optionally
1204     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1205     possible to save compiled patterns and study data, and then use them later
1206     in different processes, possibly even on different hosts. For a discussion
1207     about this, see the
1208     .\" HREF
1209     \fBpcreprecompile\fP
1210     .\"
1211     documentation.
1212     .P
1213     Here is an example of a simple call to \fBpcre_exec()\fP:
1214     .sp
1215 nigel 63 int rc;
1216     int ovector[30];
1217     rc = pcre_exec(
1218     re, /* result of pcre_compile() */
1219     NULL, /* we didn't study the pattern */
1220     "some string", /* the subject string */
1221     11, /* the length of the subject string */
1222     0, /* start at offset 0 in the subject */
1223     0, /* default options */
1224 nigel 75 ovector, /* vector of integers for substring information */
1225 nigel 77 30); /* number of elements (NOT size in bytes) */
1226 nigel 75 .
1227     .\" HTML <a name="extradata"></a>
1228     .SS "Extra data for \fBpcre_exec()\fR"
1229     .rs
1230     .sp
1231     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1232     data block. The \fBpcre_study()\fP function returns such a block (when it
1233 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1234 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1235     fields (not necessarily in this order):
1236 nigel 75 .sp
1237     unsigned long int \fIflags\fP;
1238     void *\fIstudy_data\fP;
1239     unsigned long int \fImatch_limit\fP;
1240 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1241 nigel 75 void *\fIcallout_data\fP;
1242     const unsigned char *\fItables\fP;
1243 ph10 512 unsigned char **\fImark\fP;
1244 nigel 75 .sp
1245     The \fIflags\fP field is a bitmap that specifies which of the other fields
1246 nigel 63 are set. The flag bits are:
1247 nigel 75 .sp
1248 nigel 63 PCRE_EXTRA_STUDY_DATA
1249     PCRE_EXTRA_MATCH_LIMIT
1250 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1251 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1252 nigel 75 PCRE_EXTRA_TABLES
1253 ph10 512 PCRE_EXTRA_MARK
1254 nigel 75 .sp
1255     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1256     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1257     the appropriate flag bit. You should not set this yourself, but you may add to
1258     the block by setting the other fields and their corresponding flag bits.
1259     .P
1260     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1261 nigel 63 vast amount of resources when running patterns that are not going to match,
1262     but which have a very large number of possibilities in their search trees. The
1263 ph10 456 classic example is a pattern that uses nested unlimited repeats.
1264 nigel 75 .P
1265     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1266 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1267     number of times this function is called during a match, which has the effect of
1268     limiting the amount of backtracking that can take place. For patterns that are
1269     not anchored, the count restarts from zero for each position in the subject
1270     string.
1271 nigel 75 .P
1272 nigel 87 The default value for the limit can be set when PCRE is built; the default
1273 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1274 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1275     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1276     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1277     PCRE_ERROR_MATCHLIMIT.
1278 nigel 75 .P
1279 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1280     instead of limiting the total number of times that \fBmatch()\fP is called, it
1281     limits the depth of recursion. The recursion depth is a smaller number than the
1282     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1283     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1284     .P
1285     Limiting the recursion depth limits the amount of stack that can be used, or,
1286     when PCRE has been compiled to use memory on the heap instead of the stack, the
1287     amount of heap memory that can be used.
1288     .P
1289     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1290     built; the default default is the same value as the default for
1291     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1292     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1293     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1294     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1295     .P
1296 ph10 440 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1297     and is described in the
1298 nigel 75 .\" HREF
1299     \fBpcrecallout\fP
1300     .\"
1301     documentation.
1302     .P
1303     The \fItables\fP field is used to pass a character tables pointer to
1304     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1305     pattern. A non-NULL value is stored with the compiled pattern only if custom
1306     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1307     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1308     internal tables to be used. This facility is helpful when re-using patterns
1309     that have been saved after compiling with an external set of tables, because
1310     the external tables might be at a different address when \fBpcre_exec()\fP is
1311     called. See the
1312     .\" HREF
1313     \fBpcreprecompile\fP
1314     .\"
1315     documentation for a discussion of saving compiled patterns for later use.
1316 ph10 510 .P
1317     If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1318 ph10 512 be set to point to a \fBchar *\fP variable. If the pattern contains any
1319 ph10 510 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1320     a name to pass back, a pointer to the name string (zero terminated) is placed
1321     in the variable pointed to by the \fImark\fP field. The names are within the
1322     compiled pattern; if you wish to retain such a name you must copy it before
1323     freeing the memory of a compiled pattern. If there is no name to pass back, the
1324     variable pointed to by the \fImark\fP field set to NULL. For details of the
1325     backtracking control verbs, see the section entitled
1326     .\" HTML <a href="pcrepattern#backtrackcontrol">
1327     .\" </a>
1328     "Backtracking control"
1329     .\"
1330     in the
1331     .\" HREF
1332     \fBpcrepattern\fP
1333     .\"
1334     documentation.
1335 nigel 75 .
1336 ph10 510 .
1337 ph10 226 .\" HTML <a name="execoptions"></a>
1338 nigel 75 .SS "Option bits for \fBpcre_exec()\fP"
1339     .rs
1340     .sp
1341     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1342 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1343 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1344     PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1345     PCRE_PARTIAL_HARD.
1346 nigel 75 .sp
1347     PCRE_ANCHORED
1348     .sp
1349     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1350     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1351     to be anchored by virtue of its contents, it cannot be made unachored at
1352     matching time.
1353     .sp
1354 ph10 231 PCRE_BSR_ANYCRLF
1355     PCRE_BSR_UNICODE
1356     .sp
1357     These options (which are mutually exclusive) control what the \eR escape
1358     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1359     match any Unicode newline sequence. These options override the choice that was
1360     made or defaulted when the pattern was compiled.
1361     .sp
1362 nigel 91 PCRE_NEWLINE_CR
1363     PCRE_NEWLINE_LF
1364     PCRE_NEWLINE_CRLF
1365 ph10 150 PCRE_NEWLINE_ANYCRLF
1366 nigel 93 PCRE_NEWLINE_ANY
1367 nigel 91 .sp
1368     These options override the newline definition that was chosen or defaulted when
1369 nigel 93 the pattern was compiled. For details, see the description of
1370     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1371     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1372     the way the match position is advanced after a match failure for an unanchored
1373 ph10 227 pattern.
1374 ph10 225 .P
1375 ph10 226 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1376     match attempt for an unanchored pattern fails when the current position is at a
1377 ph10 230 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1378 ph10 226 characters, the match position is advanced by two characters instead of one, in
1379     other words, to after the CRLF.
1380     .P
1381 ph10 227 The above rule is a compromise that makes the most common cases work as
1382     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1383     set), it does not match the string "\er\enA" because, after failing at the
1384     start, it skips both the CR and the LF before retrying. However, the pattern
1385     [\er\en]A does match that string, because it contains an explicit CR or LF
1386 ph10 226 reference, and so advances only by one character after the first failure.
1387     .P
1388 ph10 231 An explicit match for CR of LF is either a literal appearance of one of those
1389     characters, or one of the \er or \en escape sequences. Implicit matches such as
1390 ph10 230 [^X] do not count, nor does \es (which includes CR and LF in the characters
1391     that it matches).
1392     .P
1393 ph10 226 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1394     valid newline sequence and explicit \er or \en escapes appear in the pattern.
1395 nigel 91 .sp
1396 nigel 63 PCRE_NOTBOL
1397 nigel 75 .sp
1398     This option specifies that first character of the subject string is not the
1399     beginning of a line, so the circumflex metacharacter should not match before
1400     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1401     never to match. This option affects only the behaviour of the circumflex
1402     metacharacter. It does not affect \eA.
1403     .sp
1404 nigel 63 PCRE_NOTEOL
1405 nigel 75 .sp
1406     This option specifies that the end of the subject string is not the end of a
1407     line, so the dollar metacharacter should not match it nor (except in multiline
1408     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1409     compile time) causes dollar never to match. This option affects only the
1410     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1411     .sp
1412 nigel 63 PCRE_NOTEMPTY
1413 nigel 75 .sp
1414 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1415     there are alternatives in the pattern, they are tried. If all the alternatives
1416     match the empty string, the entire match fails. For example, if the pattern
1417 nigel 75 .sp
1418 nigel 63 a?b?
1419 nigel 75 .sp
1420 ph10 442 is applied to a string not beginning with "a" or "b", it matches an empty
1421 nigel 63 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1422     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1423 ph10 442 .sp
1424     PCRE_NOTEMPTY_ATSTART
1425     .sp
1426 ph10 461 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1427 ph10 442 the start of the subject is permitted. If the pattern is anchored, such a match
1428     can occur only if the pattern contains \eK.
1429 nigel 75 .P
1430 ph10 442 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1431     does make a special case of a pattern match of the empty string within its
1432     \fBsplit()\fP function, and when using the /g modifier. It is possible to
1433     emulate Perl's behaviour after matching a null string by first trying the match
1434     again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1435     if that fails, by advancing the starting offset (see below) and trying an
1436     ordinary match again. There is some code that demonstrates how to do this in
1437     the
1438 ph10 429 .\" HREF
1439     \fBpcredemo\fP
1440     .\"
1441     sample program.
1442 nigel 75 .sp
1443 ph10 389 PCRE_NO_START_OPTIMIZE
1444     .sp
1445 ph10 392 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1446 ph10 389 a match, in order to speed up the process. For example, if it is known that a
1447     match must start with a specific character, it searches the subject for that
1448     character, and fails immediately if it cannot find it, without actually running
1449     the main matching function. When callouts are in use, these optimizations can
1450     cause them to be skipped. This option disables the "start-up" optimizations,
1451     causing performance to suffer, but ensuring that the callouts do occur.
1452     .sp
1453 nigel 75 PCRE_NO_UTF8_CHECK
1454     .sp
1455     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1456     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1457 ph10 211 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1458     start of a UTF-8 character. There is a discussion about the validity of UTF-8
1459     strings in the
1460     .\" HTML <a href="pcre.html#utf8strings">
1461     .\" </a>
1462     section on UTF-8 support
1463     .\"
1464     in the main
1465     .\" HREF
1466     \fBpcre\fP
1467     .\"
1468     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1469     the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1470 ph10 209 PCRE_ERROR_BADUTF8_OFFSET is returned.
1471 nigel 75 .P
1472     If you already know that your subject is valid, and you want to skip these
1473     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1474     calling \fBpcre_exec()\fP. You might want to do this for the second and
1475     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1476     all the matches in a single subject string. However, you should be sure that
1477     the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1478     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1479     subject, or a value of \fIstartoffset\fP that does not point to the start of a
1480     UTF-8 character, is undefined. Your program may crash.
1481     .sp
1482 ph10 461 PCRE_PARTIAL_HARD
1483 ph10 428 PCRE_PARTIAL_SOFT
1484 nigel 75 .sp
1485 ph10 428 These options turn on the partial matching feature. For backwards
1486     compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1487     occurs if the end of the subject string is reached successfully, but there are
1488     not enough subject characters to complete the match. If this happens when
1489     PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1490     PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1491     by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1492     returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1493 ph10 435 was inspected when the partial match was found is set as the first matching
1494     string. There is a more detailed discussion in the
1495 nigel 75 .\" HREF
1496     \fBpcrepartial\fP
1497     .\"
1498     documentation.
1499     .
1500     .SS "The string to be matched by \fBpcre_exec()\fP"
1501     .rs
1502     .sp
1503     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1504 ph10 368 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1505     in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1506     a UTF-8 character. Unlike the pattern string, the subject may contain binary
1507     zero bytes. When the starting offset is zero, the search for a match starts at
1508     the beginning of the subject, and this is by far the most common case.
1509 nigel 75 .P
1510 nigel 63 A non-zero starting offset is useful when searching for another match in the
1511 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1512     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1513 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1514     lookbehind. For example, consider the pattern
1515 nigel 75 .sp
1516     \eBiss\eB
1517     .sp
1518     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1519 nigel 63 the current position in the subject is not a word boundary.) When applied to
1520 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1521     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1522     subject, namely "issipi", it does not match, because \eB is always false at the
1523 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1524 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1525 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1526     behind the starting point to discover that it is preceded by a letter.
1527 nigel 75 .P
1528 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1529 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1530 nigel 63 pattern does not require the match to be at the start of the subject.
1531 nigel 75 .
1532     .SS "How \fBpcre_exec()\fP returns captured substrings"
1533     .rs
1534     .sp
1535 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1536     addition, further substrings from the subject may be picked out by parts of the
1537     pattern. Following the usage in Jeffrey Friedl's book, this is called
1538     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1539     a fragment of a pattern that picks out a substring. PCRE supports several other
1540     kinds of parenthesized subpattern that do not cause substrings to be captured.
1541 nigel 75 .P
1542 ph10 368 Captured substrings are returned to the caller via a vector of integers whose
1543     address is passed in \fIovector\fP. The number of elements in the vector is
1544     passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1545     argument is NOT the size of \fIovector\fP in bytes.
1546 nigel 75 .P
1547     The first two-thirds of the vector is used to pass back captured substrings,
1548     each substring using a pair of integers. The remaining third of the vector is
1549     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1550 ph10 368 and is not available for passing back information. The number passed in
1551 nigel 75 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1552     rounded down.
1553     .P
1554     When a match is successful, information about captured substrings is returned
1555     in pairs of integers, starting at the beginning of \fIovector\fP, and
1556 ph10 371 continuing up to two-thirds of its length at the most. The first element of
1557 ph10 368 each pair is set to the byte offset of the first character in a substring, and
1558     the second is set to the byte offset of the first character after the end of a
1559     substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1560     mode. They are not character counts.
1561 nigel 75 .P
1562 ph10 368 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1563     portion of the subject string matched by the entire pattern. The next pair is
1564     used for the first capturing subpattern, and so on. The value returned by
1565     \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1566     For example, if two substrings have been captured, the returned value is 3. If
1567     there are no capturing subpatterns, the return value from a successful match is
1568     1, indicating that just the first pair of offsets has been set.
1569     .P
1570 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1571 nigel 75 string that it matched that is returned.
1572     .P
1573     If the vector is too small to hold all the captured substring offsets, it is
1574     used as far as possible (up to two-thirds of its length), and the function
1575 ph10 368 returns a value of zero. If the substring offsets are not of interest,
1576     \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1577 nigel 75 \fIovecsize\fP as zero. However, if the pattern contains back references and
1578     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1579     has to get additional memory for use during matching. Thus it is usually
1580     advisable to supply an \fIovector\fP.
1581     .P
1582 ph10 456 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1583 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1584 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1585     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1586 nigel 91 .P
1587     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1588     the subject when subpattern \fIn\fP has not been used at all. For example, if
1589     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1590     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1591     happens, both values in the offset pairs corresponding to unused subpatterns
1592     are set to -1.
1593     .P
1594     Offset values that correspond to unused subpatterns at the end of the
1595     expression are also set to -1. For example, if the string "abc" is matched
1596     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1597     return from the function is 2, because the highest used capturing subpattern
1598     number is 1. However, you can refer to the offsets for the second and third
1599     capturing subpatterns if you wish (assuming the vector is large enough, of
1600     course).
1601     .P
1602     Some convenience functions are provided for extracting the captured substrings
1603     as separate strings. These are described below.
1604 nigel 75 .
1605 nigel 77 .\" HTML <a name="errorlist"></a>
1606 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1607 nigel 75 .rs
1608     .sp
1609     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1610 nigel 63 defined in the header file:
1611 nigel 75 .sp
1612 nigel 63 PCRE_ERROR_NOMATCH (-1)
1613 nigel 75 .sp
1614 nigel 63 The subject string did not match the pattern.
1615 nigel 75 .sp
1616 nigel 63 PCRE_ERROR_NULL (-2)
1617 nigel 75 .sp
1618     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1619     NULL and \fIovecsize\fP was not zero.
1620     .sp
1621 nigel 63 PCRE_ERROR_BADOPTION (-3)
1622 nigel 75 .sp
1623     An unrecognized bit was set in the \fIoptions\fP argument.
1624     .sp
1625 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1626 nigel 75 .sp
1627 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1628 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1629     compiled in an environment of one endianness is run in an environment with the
1630     other endianness. This is the error that PCRE gives when the magic number is
1631     not present.
1632     .sp
1633 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1634 nigel 75 .sp
1635 nigel 63 While running the pattern match, an unknown item was encountered in the
1636     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1637     of the compiled pattern.
1638 nigel 75 .sp
1639 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1640 nigel 75 .sp
1641     If a pattern contains back references, but the \fIovector\fP that is passed to
1642     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1643 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1644 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1645     automatically freed at the end of matching.
1646 ph10 531 .P
1647     This error is also given if \fBpcre_stack_malloc()\fP fails in
1648     \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1649     \fB--disable-stack-for-recursion\fP.
1650 nigel 75 .sp
1651 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1652 nigel 75 .sp
1653     This error is used by the \fBpcre_copy_substring()\fP,
1654     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1655     below). It is never returned by \fBpcre_exec()\fP.
1656     .sp
1657 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1658 nigel 75 .sp
1659 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1660     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1661     above.
1662     .sp
1663 nigel 63 PCRE_ERROR_CALLOUT (-9)
1664 nigel 75 .sp
1665     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1666 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1667 nigel 75 .\" HREF
1668     \fBpcrecallout\fP
1669     .\"
1670     documentation for details.
1671     .sp
1672 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1673 nigel 75 .sp
1674 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1675 nigel 75 .sp
1676 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1677 nigel 75 .sp
1678 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1679 nigel 75 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1680     .sp
1681 nigel 77 PCRE_ERROR_PARTIAL (-12)
1682 nigel 75 .sp
1683     The subject string did not match, but it did match partially. See the
1684     .\" HREF
1685     \fBpcrepartial\fP
1686     .\"
1687     documentation for details of partial matching.
1688     .sp
1689 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1690 nigel 75 .sp
1691 ph10 426 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1692     option was used with a compiled pattern containing items that were not
1693 ph10 461 supported for partial matching. From release 8.00 onwards, there are no
1694 ph10 426 restrictions on partial matching.
1695 nigel 75 .sp
1696 nigel 77 PCRE_ERROR_INTERNAL (-14)
1697 nigel 75 .sp
1698     An unexpected internal error has occurred. This error could be caused by a bug
1699     in PCRE or by overwriting of the compiled pattern.
1700     .sp
1701 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1702 nigel 75 .sp
1703     This error is given if the value of the \fIovecsize\fP argument is negative.
1704 nigel 93 .sp
1705     PCRE_ERROR_RECURSIONLIMIT (-21)
1706     .sp
1707     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1708     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1709     description above.
1710     .sp
1711     PCRE_ERROR_BADNEWLINE (-23)
1712     .sp
1713     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1714     .P
1715 ph10 197 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1716 nigel 75 .
1717     .
1718     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1719 nigel 63 .rs
1720     .sp
1721 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1722 nigel 63 .ti +5n
1723 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1724 nigel 63 .ti +5n
1725 nigel 75 .B int \fIbuffersize\fP);
1726 nigel 63 .PP
1727 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1728 nigel 63 .ti +5n
1729 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1730 nigel 63 .ti +5n
1731 nigel 75 .B const char **\fIstringptr\fP);
1732 nigel 63 .PP
1733 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1734 nigel 63 .ti +5n
1735 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1736 nigel 63 .PP
1737     Captured substrings can be accessed directly by using the offsets returned by
1738 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1739     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1740     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1741 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1742     by number. The next section describes functions for extracting named
1743 nigel 91 substrings.
1744 nigel 75 .P
1745 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1746     further zero added on the end, but the result is not, of course, a C string.
1747     However, you can process such a string by referring to the length that is
1748     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1749     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1750     for handling strings containing binary zeros, because the end of the final
1751     string is not independently indicated.
1752     .P
1753 nigel 63 The first three arguments are the same for all three of these functions:
1754 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1755     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1756     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1757 nigel 63 captured by the match, including the substring that matched the entire regular
1758 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1759     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1760     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1761     number of elements in the vector divided by three.
1762     .P
1763     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1764     extract a single substring, whose number is given as \fIstringnumber\fP. A
1765     value of zero extracts the substring that matched the entire pattern, whereas
1766     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1767     the string is placed in \fIbuffer\fP, whose length is given by
1768     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1769     obtained via \fBpcre_malloc\fP, and its address is returned via
1770     \fIstringptr\fP. The yield of the function is the length of the string, not
1771 nigel 93 including the terminating zero, or one of these error codes:
1772 nigel 75 .sp
1773 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1774 nigel 75 .sp
1775     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1776     memory failed for \fBpcre_get_substring()\fP.
1777     .sp
1778 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1779 nigel 75 .sp
1780     There is no substring whose number is \fIstringnumber\fP.
1781     .P
1782     The \fBpcre_get_substring_list()\fP function extracts all available substrings
1783 nigel 63 and builds a list of pointers to them. All this is done in a single block of
1784 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1785     is returned via \fIlistptr\fP, which is also the start of the list of string
1786 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
1787 nigel 93 function is zero if all went well, or the error code
1788 nigel 75 .sp
1789 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1790 nigel 75 .sp
1791 nigel 63 if the attempt to get the memory block failed.
1792 nigel 75 .P
1793 nigel 63 When any of these functions encounter a substring that is unset, which can
1794 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
1795     subject, but subpattern \fIn\fP has not been used at all, they return an empty
1796 nigel 63 string. This can be distinguished from a genuine zero-length substring by
1797 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1798 nigel 63 substrings.
1799 nigel 75 .P
1800     The two convenience functions \fBpcre_free_substring()\fP and
1801     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1802     a previous call of \fBpcre_get_substring()\fP or
1803     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1804     the function pointed to by \fBpcre_free\fP, which of course could be called
1805 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
1806 nigel 91 linked via a special interface to another programming language that cannot use
1807 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
1808 nigel 63 provided.
1809 nigel 75 .
1810     .
1811     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1812 nigel 63 .rs
1813     .sp
1814 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1815 nigel 63 .ti +5n
1816 nigel 75 .B const char *\fIname\fP);
1817 nigel 63 .PP
1818 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1819 nigel 63 .ti +5n
1820 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1821     .ti +5n
1822     .B int \fIstringcount\fP, const char *\fIstringname\fP,
1823     .ti +5n
1824     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1825 nigel 63 .PP
1826 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1827 nigel 63 .ti +5n
1828 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1829 nigel 63 .ti +5n
1830 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1831 nigel 63 .ti +5n
1832 nigel 75 .B const char **\fIstringptr\fP);
1833 nigel 63 .PP
1834 nigel 75 To extract a substring by name, you first have to find associated number.
1835     For example, for this pattern
1836     .sp
1837 nigel 93 (a+)b(?<xxx>\ed+)...
1838 nigel 75 .sp
1839 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1840     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1841     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1842     pattern, and the second is the name. The yield of the function is the
1843 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1844     that name.
1845     .P
1846     Given the number, you can extract the substring directly, or use one of the
1847     functions described in the previous section. For convenience, there are also
1848     two functions that do the whole job.
1849     .P
1850 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1851     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1852 nigel 75 functions that extract by number. As these are described in the previous
1853     section, they are not re-described here. There are just two differences:
1854     .P
1855 nigel 63 First, instead of a substring number, a substring name is given. Second, there
1856     is an extra argument, given at the start, which is a pointer to the compiled
1857     pattern. This is needed in order to gain access to the name-to-number
1858     translation table.
1859 nigel 75 .P
1860     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1861 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1862     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1863 ph10 128 the behaviour may not be what you want (see the next section).
1864 ph10 385 .P
1865 ph10 457 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1866     subpatterns with the same number, as described in the
1867     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1868     .\" </a>
1869     section on duplicate subpattern numbers
1870     .\"
1871     in the
1872     .\" HREF
1873     \fBpcrepattern\fP
1874     .\"
1875     page, you cannot use names to distinguish the different subpatterns, because
1876     names are not included in the compiled code. The matching process uses only
1877     numbers. For this reason, the use of different names for subpatterns of the
1878     same number causes an error at compile time.
1879 nigel 77 .
1880 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
1881     .rs
1882     .sp
1883     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1884     .ti +5n
1885     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1886     .PP
1887     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1888 ph10 457 are not required to be unique. (Duplicate names are always allowed for
1889     subpatterns with the same number, created by using the (?| feature. Indeed, if
1890     such subpatterns are named, they are required to use the same names.)
1891     .P
1892     Normally, patterns with duplicate names are such that in any one match, only
1893     one of the named subpatterns participates. An example is shown in the
1894 nigel 91 .\" HREF
1895     \fBpcrepattern\fP
1896     .\"
1897 ph10 208 documentation.
1898 ph10 203 .P
1899     When duplicates are present, \fBpcre_copy_named_substring()\fP and
1900     \fBpcre_get_named_substring()\fP return the first substring corresponding to
1901     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1902     returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1903     returns one of the numbers that are associated with the name, but it is not
1904     defined which it is.
1905     .P
1906 nigel 91 If you want to get full details of all captured substrings for a given name,
1907     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1908     argument is the compiled pattern, and the second is the name. The third and
1909     fourth are pointers to variables which are updated by the function. After it
1910     has run, they point to the first and last entries in the name-to-number table
1911     for the given name. The function itself returns the length of each entry, or
1912 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1913     described above in the section entitled \fIInformation about a pattern\fP.
1914     Given all the relevant entries for the name, you can extract each of their
1915     numbers, and hence the captured data, if any.
1916 nigel 91 .
1917     .
1918 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
1919     .rs
1920     .sp
1921     The traditional matching function uses a similar algorithm to Perl, which stops
1922     when it finds the first match, starting at a given point in the subject. If you
1923     want to find all possible matches, or the longest possible match, consider
1924     using the alternative matching function (see below) instead. If you cannot use
1925     the alternative function, but still need to find all possible matches, you
1926     can kludge it up by making use of the callout facility, which is described in
1927     the
1928     .\" HREF
1929     \fBpcrecallout\fP
1930     .\"
1931     documentation.
1932 nigel 75 .P
1933 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
1934     When your callout function is called, extract and save the current matched
1935     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1936     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1937     will yield PCRE_ERROR_NOMATCH.
1938     .
1939     .
1940     .\" HTML <a name="dfamatch"></a>
1941     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1942     .rs
1943     .sp
1944     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1945     .ti +5n
1946     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1947     .ti +5n
1948     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1949     .ti +5n
1950     .B int *\fIworkspace\fP, int \fIwscount\fP);
1951     .P
1952     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1953 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
1954     just once, and does not backtrack. This has different characteristics to the
1955     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1956     patterns are not supported. Nevertheless, there are times when this kind of
1957 ph10 461 matching can be useful. For a discussion of the two matching algorithms, and a
1958 ph10 435 list of features that \fBpcre_dfa_exec()\fP does not support, see the
1959 nigel 77 .\" HREF
1960     \fBpcrematching\fP
1961     .\"
1962     documentation.
1963     .P
1964     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1965     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1966     different way, and this is described below. The other common arguments are used
1967     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1968     here.
1969     .P
1970     The two additional arguments provide workspace for the function. The workspace
1971     vector should contain at least 20 elements. It is used for keeping track of
1972     multiple paths through the pattern tree. More workspace will be needed for
1973 nigel 91 patterns and subjects where there are a lot of potential matches.
1974 nigel 77 .P
1975 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1976 nigel 77 .sp
1977     int rc;
1978     int ovector[10];
1979     int wspace[20];
1980 nigel 87 rc = pcre_dfa_exec(
1981 nigel 77 re, /* result of pcre_compile() */
1982     NULL, /* we didn't study the pattern */
1983     "some string", /* the subject string */
1984     11, /* the length of the subject string */
1985     0, /* start at offset 0 in the subject */
1986     0, /* default options */
1987     ovector, /* vector of integers for substring information */
1988     10, /* number of elements (NOT size in bytes) */
1989     wspace, /* working space vector */
1990     20); /* number of elements (NOT size in bytes) */
1991     .
1992     .SS "Option bits for \fBpcre_dfa_exec()\fP"
1993     .rs
1994     .sp
1995     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1996 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1997 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1998     PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
1999     and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
2000     for \fBpcre_exec()\fP, so their description is not repeated here.
2001 nigel 77 .sp
2002 ph10 428 PCRE_PARTIAL_HARD
2003 ph10 461 PCRE_PARTIAL_SOFT
2004 nigel 77 .sp
2005 ph10 428 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2006     details are slightly different. When PCRE_PARTIAL_HARD is set for
2007     \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2008     is reached and there is still at least one matching possibility that requires
2009     additional characters. This happens even if some complete matches have also
2010     been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2011     is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2012     there have been no complete matches, but there is still at least one matching
2013 ph10 435 possibility. The portion of the string that was inspected when the longest
2014     partial match was found is set as the first matching string in both cases.
2015 nigel 77 .sp
2016     PCRE_DFA_SHORTEST
2017     .sp
2018     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2019 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
2020     works, this is necessarily the shortest possible match at the first possible
2021     matching point in the subject string.
2022 nigel 77 .sp
2023     PCRE_DFA_RESTART
2024     .sp
2025 ph10 428 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2026     again, with additional subject characters, and have it continue with the same
2027     match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2028     \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2029     before because data about the match so far is left in them after a partial
2030     match. There is more discussion of this facility in the
2031 nigel 77 .\" HREF
2032     \fBpcrepartial\fP
2033     .\"
2034     documentation.
2035     .
2036     .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2037     .rs
2038     .sp
2039     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2040     substring in the subject. Note, however, that all the matches from one run of
2041     the function start at the same point in the subject. The shorter matches are
2042     all initial substrings of the longer matches. For example, if the pattern
2043     .sp
2044     <.*>
2045     .sp
2046     is matched against the string
2047     .sp
2048     This is <something> <something else> <something further> no more
2049     .sp
2050     the three matched strings are
2051     .sp
2052     <something>
2053     <something> <something else>
2054     <something> <something else> <something further>
2055     .sp
2056     On success, the yield of the function is a number greater than zero, which is
2057     the number of matched substrings. The substrings themselves are returned in
2058     \fIovector\fP. Each string uses two elements; the first is the offset to the
2059 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
2060     the same start offset. (Space could have been saved by giving this only once,
2061     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2062     returns data, even though the meaning of the strings is different.)
2063 nigel 77 .P
2064     The strings are returned in reverse order of length; that is, the longest
2065     matching string is given first. If there were too many matches to fit into
2066     \fIovector\fP, the yield of the function is zero, and the vector is filled with
2067     the longest matches.
2068     .
2069     .SS "Error returns from \fBpcre_dfa_exec()\fP"
2070     .rs
2071     .sp
2072     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2073     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2074     described
2075     .\" HTML <a href="#errorlist">
2076     .\" </a>
2077     above.
2078     .\"
2079     There are in addition the following errors that are specific to
2080     \fBpcre_dfa_exec()\fP:
2081     .sp
2082     PCRE_ERROR_DFA_UITEM (-16)
2083     .sp
2084     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2085     that it does not support, for instance, the use of \eC or a back reference.
2086     .sp
2087     PCRE_ERROR_DFA_UCOND (-17)
2088     .sp
2089 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2090     uses a back reference for the condition, or a test for recursion in a specific
2091     group. These are not supported.
2092 nigel 77 .sp
2093     PCRE_ERROR_DFA_UMLIMIT (-18)
2094     .sp
2095     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2096     block that contains a setting of the \fImatch_limit\fP field. This is not
2097     supported (it is meaningless).
2098     .sp
2099     PCRE_ERROR_DFA_WSSIZE (-19)
2100     .sp
2101     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2102     \fIworkspace\fP vector.
2103     .sp
2104     PCRE_ERROR_DFA_RECURSE (-20)
2105     .sp
2106     When a recursive subpattern is processed, the matching function calls itself
2107     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2108     error is given if the output vector is not large enough. This should be
2109     extremely rare, as a vector of size 1000 is used.
2110 nigel 93 .
2111     .
2112     .SH "SEE ALSO"
2113     .rs
2114     .sp
2115     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2116     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2117     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2118 ph10 99 .
2119     .
2120     .SH AUTHOR
2121     .rs
2122     .sp
2123     .nf
2124     Philip Hazel
2125     University Computing Service
2126     Cambridge CB2 3QH, England.
2127     .fi
2128     .
2129     .
2130     .SH REVISION
2131     .rs
2132     .sp
2133     .nf
2134 ph10 531 Last updated: 01 June 2010
2135 ph10 510 Copyright (c) 1997-2010 University of Cambridge.
2136 ph10 99 .fi

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