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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 569 not try to free it. The offset from the start of the pattern to the byte that
439     was being processed when the error was discovered is placed in the variable
440     pointed to by \fIerroffset\fP, which must not be NULL. If it is, an immediate
441     error is given. Some errors are not detected until checks are carried out when
442     the whole pattern has been scanned; in this case the offset is set to the end
443 ph10 572 of the pattern.
444 nigel 75 .P
445 ph10 572 Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
446 ph10 569 point into the middle of a UTF-8 character (for example, when
447     PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
448     .P
449 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
450     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
451     returned via this argument in the event of an error. This is in addition to the
452     textual error message. Error codes and messages are listed below.
453     .P
454 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
455     character tables that are built when PCRE is compiled, using the default C
456     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
457     call to \fBpcre_maketables()\fP. This value is stored with the compiled
458     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
459     passed to it. For more discussion, see the section on locale support below.
460     .P
461     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
462     .sp
463 nigel 63 pcre *re;
464     const char *error;
465     int erroffset;
466     re = pcre_compile(
467     "^A.*Z", /* the pattern */
468     0, /* default options */
469     &error, /* for error message */
470     &erroffset, /* for error offset */
471     NULL); /* use default character tables */
472 nigel 75 .sp
473     The following names for option bits are defined in the \fBpcre.h\fP header
474     file:
475     .sp
476 nigel 63 PCRE_ANCHORED
477 nigel 75 .sp
478 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
479 nigel 75 constrained to match only at the first matching point in the string that is
480 nigel 63 being searched (the "subject string"). This effect can also be achieved by
481     appropriate constructs in the pattern itself, which is the only way to do it in
482     Perl.
483 nigel 75 .sp
484     PCRE_AUTO_CALLOUT
485     .sp
486     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
487     all with number 255, before each pattern item. For discussion of the callout
488     facility, see the
489     .\" HREF
490     \fBpcrecallout\fP
491     .\"
492     documentation.
493     .sp
494 ph10 231 PCRE_BSR_ANYCRLF
495     PCRE_BSR_UNICODE
496     .sp
497     These options (which are mutually exclusive) control what the \eR escape
498     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
499     match any Unicode newline sequence. The default is specified when PCRE is
500     built. It can be overridden from within the pattern, or by setting an option
501     when a compiled pattern is matched.
502     .sp
503 nigel 63 PCRE_CASELESS
504 nigel 75 .sp
505 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
506     letters. It is equivalent to Perl's /i option, and it can be changed within a
507 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
508     concept of case for characters whose values are less than 128, so caseless
509     matching is always possible. For characters with higher values, the concept of
510     case is supported if PCRE is compiled with Unicode property support, but not
511     otherwise. If you want to use caseless matching for characters 128 and above,
512     you must ensure that PCRE is compiled with Unicode property support as well as
513     with UTF-8 support.
514 nigel 75 .sp
515 nigel 63 PCRE_DOLLAR_ENDONLY
516 nigel 75 .sp
517 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
518     end of the subject string. Without this option, a dollar also matches
519 nigel 91 immediately before a newline at the end of the string (but not before any other
520     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
521     There is no equivalent to this option in Perl, and no way to set it within a
522     pattern.
523 nigel 75 .sp
524 nigel 63 PCRE_DOTALL
525 nigel 75 .sp
526 ph10 572 If this bit is set, a dot metacharacter in the pattern matches a character of
527     any value, including one that indicates a newline. However, it only ever
528     matches one character, even if newlines are coded as CRLF. Without this option,
529     a dot does not match when the current position is at a newline. This option is
530     equivalent to Perl's /s option, and it can be changed within a pattern by a
531     (?s) option setting. A negative class such as [^a] always matches newline
532     characters, independent of the setting of this option.
533 nigel 75 .sp
534 nigel 91 PCRE_DUPNAMES
535     .sp
536     If this bit is set, names used to identify capturing subpatterns need not be
537     unique. This can be helpful for certain types of pattern when it is known that
538     only one instance of the named subpattern can ever be matched. There are more
539     details of named subpatterns below; see also the
540     .\" HREF
541     \fBpcrepattern\fP
542     .\"
543     documentation.
544     .sp
545 nigel 63 PCRE_EXTENDED
546 nigel 75 .sp
547 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
548     ignored except when escaped or inside a character class. Whitespace does not
549     include the VT character (code 11). In addition, characters between an
550 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
551     ignored. This is equivalent to Perl's /x option, and it can be changed within a
552     pattern by a (?x) option setting.
553 nigel 75 .P
554 ph10 572 Which characters are interpreted as newlines
555     is controlled by the options passed to \fBpcre_compile()\fP or by a special
556     sequence at the start of the pattern, as described in the section entitled
557     .\" HTML <a href="pcrepattern.html#newlines">
558     .\" </a>
559     "Newline conventions"
560     .\"
561     in the \fBpcrepattern\fP documentation. Note that the end of this type of
562     comment is a literal newline sequence in the pattern; escape sequences that
563     happen to represent a newline do not count.
564     .P
565 nigel 63 This option makes it possible to include comments inside complicated patterns.
566     Note, however, that this applies only to data characters. Whitespace characters
567     may never appear within special character sequences in a pattern, for example
568 ph10 572 within the sequence (?( that introduces a conditional subpattern.
569 nigel 75 .sp
570 nigel 63 PCRE_EXTRA
571 nigel 75 .sp
572 nigel 63 This option was invented in order to turn on additional functionality of PCRE
573     that is incompatible with Perl, but it is currently of very little use. When
574     set, any backslash in a pattern that is followed by a letter that has no
575     special meaning causes an error, thus reserving these combinations for future
576     expansion. By default, as in Perl, a backslash followed by a letter with no
577 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
578 ph10 513 give an error for this, by running it with the -w option.) There are at present
579     no other features controlled by this option. It can also be set by a (?X)
580     option setting within a pattern.
581 nigel 75 .sp
582 nigel 77 PCRE_FIRSTLINE
583     .sp
584     If this option is set, an unanchored pattern is required to match before or at
585 nigel 91 the first newline in the subject string, though the matched text may continue
586     over the newline.
587 nigel 77 .sp
588 ph10 336 PCRE_JAVASCRIPT_COMPAT
589     .sp
590 ph10 345 If this option is set, PCRE's behaviour is changed in some ways so that it is
591 ph10 336 compatible with JavaScript rather than Perl. The changes are as follows:
592     .P
593     (1) A lone closing square bracket in a pattern causes a compile-time error,
594     because this is illegal in JavaScript (by default it is treated as a data
595     character). Thus, the pattern AB]CD becomes illegal when this option is set.
596     .P
597     (2) At run time, a back reference to an unset subpattern group matches an empty
598 ph10 345 string (by default this causes the current matching alternative to fail). A
599     pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
600     an "a" in the subject), whereas it fails by default, for Perl compatibility.
601 ph10 336 .sp
602 nigel 63 PCRE_MULTILINE
603 nigel 75 .sp
604     By default, PCRE treats the subject string as consisting of a single line of
605     characters (even if it actually contains newlines). The "start of line"
606 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
607     line" metacharacter ($) matches only at the end of the string, or before a
608     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
609     Perl.
610 nigel 75 .P
611 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
612 nigel 91 match immediately following or immediately before internal newlines in the
613     subject string, respectively, as well as at the very start and end. This is
614     equivalent to Perl's /m option, and it can be changed within a pattern by a
615     (?m) option setting. If there are no newlines in a subject string, or no
616 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
617 nigel 75 .sp
618 nigel 91 PCRE_NEWLINE_CR
619     PCRE_NEWLINE_LF
620     PCRE_NEWLINE_CRLF
621 ph10 150 PCRE_NEWLINE_ANYCRLF
622 nigel 93 PCRE_NEWLINE_ANY
623 nigel 91 .sp
624     These options override the default newline definition that was chosen when PCRE
625     was built. Setting the first or the second specifies that a newline is
626 nigel 93 indicated by a single character (CR or LF, respectively). Setting
627     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
628 ph10 149 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
629     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
630     that any Unicode newline sequence should be recognized. The Unicode newline
631     sequences are the three just mentioned, plus the single characters VT (vertical
632     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
633     separator, U+2028), and PS (paragraph separator, U+2029). The last two are
634     recognized only in UTF-8 mode.
635 nigel 91 .P
636 nigel 93 The newline setting in the options word uses three bits that are treated
637 ph10 149 as a number, giving eight possibilities. Currently only six are used (default
638     plus the five values above). This means that if you set more than one newline
639 nigel 93 option, the combination may or may not be sensible. For example,
640     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
641 ph10 149 other combinations may yield unused numbers and cause an error.
642 nigel 93 .P
643 ph10 572 The only time that a line break in a pattern is specially recognized when
644     compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
645     and so are ignored in this mode. Also, an unescaped # outside a character class
646     indicates a comment that lasts until after the next line break sequence. In
647     other circumstances, line break sequences in patterns are treated as literal
648     data.
649 nigel 93 .P
650     The newline option that is set at compile time becomes the default that is used
651     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
652 nigel 91 .sp
653 nigel 63 PCRE_NO_AUTO_CAPTURE
654 nigel 75 .sp
655 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
656     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
657     were followed by ?: but named parentheses can still be used for capturing (and
658     they acquire numbers in the usual way). There is no equivalent of this option
659     in Perl.
660 nigel 75 .sp
661 ph10 518 PCRE_UCP
662     .sp
663 ph10 572 This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
664     \ew, and some of the POSIX character classes. By default, only ASCII characters
665     are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
666     classify characters. More details are given in the section on
667 ph10 518 .\" HTML <a href="pcre.html#genericchartypes">
668     .\" </a>
669     generic character types
670     .\"
671     in the
672     .\" HREF
673     \fBpcrepattern\fP
674     .\"
675     page. If you set PCRE_UCP, matching one of the items it affects takes much
676     longer. The option is available only if PCRE has been compiled with Unicode
677     property support.
678     .sp
679 nigel 63 PCRE_UNGREEDY
680 nigel 75 .sp
681 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
682     greedy by default, but become greedy if followed by "?". It is not compatible
683     with Perl. It can also be set by a (?U) option setting within the pattern.
684 nigel 75 .sp
685 nigel 63 PCRE_UTF8
686 nigel 75 .sp
687 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
688     of UTF-8 characters instead of single-byte character strings. However, it is
689 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
690 nigel 63 of this option provokes an error. Details of how this option changes the
691     behaviour of PCRE are given in the
692     .\" HTML <a href="pcre.html#utf8support">
693     .\" </a>
694     section on UTF-8 support
695     .\"
696     in the main
697     .\" HREF
698 nigel 75 \fBpcre\fP
699 nigel 63 .\"
700     page.
701 nigel 75 .sp
702 nigel 71 PCRE_NO_UTF8_CHECK
703 nigel 75 .sp
704 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
705 ph10 211 automatically checked. There is a discussion about the
706     .\" HTML <a href="pcre.html#utf8strings">
707     .\" </a>
708     validity of UTF-8 strings
709     .\"
710     in the main
711     .\" HREF
712     \fBpcre\fP
713     .\"
714     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
715     returns an error. If you already know that your pattern is valid, and you want
716     to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
717     option. When it is set, the effect of passing an invalid UTF-8 string as a
718     pattern is undefined. It may cause your program to crash. Note that this option
719     can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
720     the UTF-8 validity checking of subject strings.
721 nigel 75 .
722     .
723 nigel 77 .SH "COMPILATION ERROR CODES"
724     .rs
725     .sp
726     The following table lists the error codes than may be returned by
727     \fBpcre_compile2()\fP, along with the error messages that may be returned by
728 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
729     out of use. To avoid confusion, they have not been re-used.
730 nigel 77 .sp
731     0 no error
732     1 \e at end of pattern
733     2 \ec at end of pattern
734     3 unrecognized character follows \e
735     4 numbers out of order in {} quantifier
736     5 number too big in {} quantifier
737     6 missing terminating ] for character class
738     7 invalid escape sequence in character class
739     8 range out of order in character class
740     9 nothing to repeat
741 nigel 93 10 [this code is not in use]
742 nigel 77 11 internal error: unexpected repeat
743 ph10 290 12 unrecognized character after (? or (?-
744 nigel 77 13 POSIX named classes are supported only within a class
745     14 missing )
746     15 reference to non-existent subpattern
747     16 erroffset passed as NULL
748     17 unknown option bit(s) set
749     18 missing ) after comment
750 nigel 93 19 [this code is not in use]
751 ph10 290 20 regular expression is too large
752 nigel 77 21 failed to get memory
753     22 unmatched parentheses
754     23 internal error: code overflow
755     24 unrecognized character after (?<
756     25 lookbehind assertion is not fixed length
757 nigel 91 26 malformed number or name after (?(
758 nigel 77 27 conditional group contains more than two branches
759     28 assertion expected after (?(
760 ph10 181 29 (?R or (?[+-]digits must be followed by )
761 nigel 77 30 unknown POSIX class name
762     31 POSIX collating elements are not supported
763     32 this version of PCRE is not compiled with PCRE_UTF8 support
764 nigel 93 33 [this code is not in use]
765 nigel 77 34 character value in \ex{...} sequence is too large
766     35 invalid condition (?(0)
767     36 \eC not allowed in lookbehind assertion
768     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
769     38 number after (?C is > 255
770     39 closing ) for (?C expected
771     40 recursive call could loop indefinitely
772     41 unrecognized character after (?P
773 nigel 93 42 syntax error in subpattern name (missing terminator)
774 nigel 91 43 two named subpatterns have the same name
775 nigel 77 44 invalid UTF-8 string
776     45 support for \eP, \ep, and \eX has not been compiled
777     46 malformed \eP or \ep sequence
778     47 unknown property name after \eP or \ep
779 nigel 91 48 subpattern name is too long (maximum 32 characters)
780 ph10 290 49 too many named subpatterns (maximum 10000)
781 ph10 202 50 [this code is not in use]
782 nigel 91 51 octal value is greater than \e377 (not in UTF-8 mode)
783 nigel 93 52 internal error: overran compiling workspace
784 ph10 548 53 internal error: previously-checked referenced subpattern
785 ph10 546 not found
786 nigel 93 54 DEFINE group contains more than one branch
787     55 repeating a DEFINE group is not allowed
788 ph10 231 56 inconsistent NEWLINE options
789 ph10 345 57 \eg is not followed by a braced, angle-bracketed, or quoted
790     name/number or by a plain number
791 ph10 336 58 a numbered reference must not be zero
792 ph10 510 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
793 ph10 290 60 (*VERB) not recognized
794     61 number is too big
795     62 subpattern name expected
796 ph10 292 63 digit expected after (?+
797 ph10 336 64 ] is an invalid data character in JavaScript compatibility mode
798 ph10 548 65 different names for subpatterns of the same number are
799 ph10 546 not allowed
800 ph10 510 66 (*MARK) must have an argument
801 ph10 518 67 this version of PCRE is not compiled with PCRE_UCP support
802 ph10 290 .sp
803 ph10 292 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
804 ph10 290 be used if the limits were changed when PCRE was built.
805 nigel 77 .
806     .
807 nigel 75 .SH "STUDYING A PATTERN"
808 nigel 63 .rs
809     .sp
810 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
811 nigel 63 .ti +5n
812 nigel 75 .B const char **\fIerrptr\fP);
813 nigel 63 .PP
814 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
815     more time analyzing it in order to speed up the time taken for matching. The
816     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
817     argument. If studying the pattern produces additional information that will
818     help speed up matching, \fBpcre_study()\fP returns a pointer to a
819     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
820     results of the study.
821     .P
822     The returned value from \fBpcre_study()\fP can be passed directly to
823 ph10 455 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
824     also contains other fields that can be set by the caller before the block is
825     passed; these are described
826 nigel 75 .\" HTML <a href="#extradata">
827     .\" </a>
828     below
829     .\"
830     in the section on matching a pattern.
831     .P
832 ph10 455 If studying the pattern does not produce any useful information,
833 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
834 ph10 461 wants to pass any of the other fields to \fBpcre_exec()\fP or
835 ph10 455 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
836 nigel 75 .P
837     The second argument of \fBpcre_study()\fP contains option bits. At present, no
838     options are defined, and this argument should always be zero.
839     .P
840     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
841 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
842 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
843     static string that is part of the library. You must not try to free it. You
844     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
845     sure that it has run successfully.
846 nigel 75 .P
847     This is a typical call to \fBpcre_study\fP():
848     .sp
849 nigel 63 pcre_extra *pe;
850     pe = pcre_study(
851     re, /* result of pcre_compile() */
852     0, /* no options exist */
853     &error); /* set to NULL or points to a message */
854 nigel 75 .sp
855 ph10 455 Studying a pattern does two things: first, a lower bound for the length of
856 ph10 461 subject string that is needed to match the pattern is computed. This does not
857     mean that there are any strings of that length that match, but it does
858     guarantee that no shorter strings match. The value is used by
859     \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
860     match strings that are shorter than the lower bound. You can find out the value
861 ph10 455 in a calling program via the \fBpcre_fullinfo()\fP function.
862     .P
863     Studying a pattern is also useful for non-anchored patterns that do not have a
864     single fixed starting character. A bitmap of possible starting bytes is
865 ph10 461 created. This speeds up finding a position in the subject at which to start
866 ph10 455 matching.
867 ph10 547 .P
868 ph10 548 The two optimizations just described can be disabled by setting the
869     PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
870     \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
871 ph10 572 callouts or (*MARK), and you want to make use of these facilities in cases
872     where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
873 ph10 547 .\" HTML <a href="#execoptions">
874     .\" </a>
875     below.
876     .\"
877 nigel 75 .
878     .
879 nigel 63 .\" HTML <a name="localesupport"></a>
880 nigel 75 .SH "LOCALE SUPPORT"
881 nigel 63 .rs
882     .sp
883 ph10 139 PCRE handles caseless matching, and determines whether characters are letters,
884 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
885 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
886 ph10 518 less than 128. By default, higher-valued codes never match escapes such as \ew
887     or \ed, but they can be tested with \ep if PCRE is built with Unicode character
888     property support. Alternatively, the PCRE_UCP option can be set at compile
889     time; this causes \ew and friends to use Unicode property support instead of
890     built-in tables. The use of locales with Unicode is discouraged. If you are
891     handling characters with codes greater than 128, you should either use UTF-8
892     and Unicode, or use locales, but not try to mix the two.
893 nigel 75 .P
894 ph10 139 PCRE contains an internal set of tables that are used when the final argument
895     of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
896 ph10 142 Normally, the internal tables recognize only ASCII characters. However, when
897 ph10 139 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
898     default "C" locale of the local system, which may cause them to be different.
899 nigel 75 .P
900 ph10 139 The internal tables can always be overridden by tables supplied by the
901     application that calls PCRE. These may be created in a different locale from
902     the default. As more and more applications change to using Unicode, the need
903     for this locale support is expected to die away.
904     .P
905 nigel 75 External tables are built by calling the \fBpcre_maketables()\fP function,
906     which has no arguments, in the relevant locale. The result can then be passed
907     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
908     example, to build and use tables that are appropriate for the French locale
909     (where accented characters with values greater than 128 are treated as letters),
910     the following code could be used:
911     .sp
912     setlocale(LC_CTYPE, "fr_FR");
913 nigel 63 tables = pcre_maketables();
914     re = pcre_compile(..., tables);
915 nigel 75 .sp
916 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
917 ph10 139 are using Windows, the name for the French locale is "french".
918     .P
919 nigel 75 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
920     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
921     that the memory containing the tables remains available for as long as it is
922     needed.
923     .P
924     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
925     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
926     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
927     pattern, compilation, studying and matching all happen in the same locale, but
928     different patterns can be compiled in different locales.
929     .P
930     It is possible to pass a table pointer or NULL (indicating the use of the
931     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
932     this facility could be used to match a pattern in a different locale from the
933     one in which it was compiled. Passing table pointers at run time is discussed
934     below in the section on matching a pattern.
935     .
936     .
937     .SH "INFORMATION ABOUT A PATTERN"
938 nigel 63 .rs
939     .sp
940 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
941 nigel 63 .ti +5n
942 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
943 nigel 63 .PP
944 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
945     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
946 nigel 63 nevertheless retained for backwards compability (and is documented below).
947 nigel 75 .P
948     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
949     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
950 nigel 63 the pattern was not studied. The third argument specifies which piece of
951     information is required, and the fourth argument is a pointer to a variable
952     to receive the data. The yield of the function is zero for success, or one of
953     the following negative numbers:
954 nigel 75 .sp
955     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
956     the argument \fIwhere\fP was NULL
957 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
958 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
959     .sp
960     The "magic number" is placed at the start of each compiled pattern as an simple
961     check against passing an arbitrary memory pointer. Here is a typical call of
962     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
963     .sp
964 nigel 63 int rc;
965 nigel 91 size_t length;
966 nigel 63 rc = pcre_fullinfo(
967     re, /* result of pcre_compile() */
968     pe, /* result of pcre_study(), or NULL */
969     PCRE_INFO_SIZE, /* what is required */
970     &length); /* where to put the data */
971 nigel 75 .sp
972     The possible values for the third argument are defined in \fBpcre.h\fP, and are
973 nigel 63 as follows:
974 nigel 75 .sp
975 nigel 63 PCRE_INFO_BACKREFMAX
976 nigel 75 .sp
977 nigel 63 Return the number of the highest back reference in the pattern. The fourth
978 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
979 nigel 63 no back references.
980 nigel 75 .sp
981 nigel 63 PCRE_INFO_CAPTURECOUNT
982 nigel 75 .sp
983 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
984 nigel 75 should point to an \fBint\fP variable.
985     .sp
986 nigel 77 PCRE_INFO_DEFAULT_TABLES
987 nigel 75 .sp
988     Return a pointer to the internal default character tables within PCRE. The
989     fourth argument should point to an \fBunsigned char *\fP variable. This
990     information call is provided for internal use by the \fBpcre_study()\fP
991     function. External callers can cause PCRE to use its internal tables by passing
992     a NULL table pointer.
993     .sp
994 nigel 63 PCRE_INFO_FIRSTBYTE
995 nigel 75 .sp
996 nigel 63 Return information about the first byte of any matched string, for a
997 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
998     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
999     still recognized for backwards compatibility.)
1000 nigel 75 .P
1001     If there is a fixed first byte, for example, from a pattern such as
1002 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
1003 nigel 75 .sp
1004 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1005     starts with "^", or
1006 nigel 75 .sp
1007 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1008     (if it were set, the pattern would be anchored),
1009 nigel 75 .sp
1010 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
1011     subject string or after any newline within the string. Otherwise -2 is
1012     returned. For anchored patterns, -2 is returned.
1013 nigel 75 .sp
1014 nigel 63 PCRE_INFO_FIRSTTABLE
1015 nigel 75 .sp
1016 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
1017     table indicating a fixed set of bytes for the first byte in any matching
1018     string, a pointer to the table is returned. Otherwise NULL is returned. The
1019 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
1020     .sp
1021 ph10 226 PCRE_INFO_HASCRORLF
1022     .sp
1023 ph10 227 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1024 ph10 243 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1025 ph10 231 explicit match is either a literal CR or LF character, or \er or \en.
1026 ph10 226 .sp
1027 ph10 169 PCRE_INFO_JCHANGED
1028     .sp
1029 ph10 278 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1030     0. The fourth argument should point to an \fBint\fP variable. (?J) and
1031     (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1032 ph10 169 .sp
1033 nigel 63 PCRE_INFO_LASTLITERAL
1034 nigel 75 .sp
1035 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
1036     string, other than at its start, if such a byte has been recorded. The fourth
1037 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1038 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
1039     follows something of variable length. For example, for the pattern
1040 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1041 nigel 65 is -1.
1042 nigel 75 .sp
1043 ph10 455 PCRE_INFO_MINLENGTH
1044     .sp
1045     If the pattern was studied and a minimum length for matching subject strings
1046     was computed, its value is returned. Otherwise the returned value is -1. The
1047 ph10 456 value is a number of characters, not bytes (this may be relevant in UTF-8
1048 ph10 455 mode). The fourth argument should point to an \fBint\fP variable. A
1049     non-negative value is a lower bound to the length of any matching string. There
1050     may not be any strings of that length that do actually match, but every string
1051     that does match is at least that long.
1052     .sp
1053 nigel 63 PCRE_INFO_NAMECOUNT
1054     PCRE_INFO_NAMEENTRYSIZE
1055     PCRE_INFO_NAMETABLE
1056 nigel 75 .sp
1057 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
1058     names are just an additional way of identifying the parentheses, which still
1059 nigel 91 acquire numbers. Several convenience functions such as
1060     \fBpcre_get_named_substring()\fP are provided for extracting captured
1061     substrings by name. It is also possible to extract the data directly, by first
1062     converting the name to a number in order to access the correct pointers in the
1063     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1064     you need to use the name-to-number map, which is described by these three
1065     values.
1066 nigel 75 .P
1067 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1068     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1069 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
1070 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1071 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1072 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
1073 ph10 461 rest of the entry is the corresponding name, zero terminated.
1074 ph10 457 .P
1075     The names are in alphabetical order. Duplicate names may appear if (?| is used
1076     to create multiple groups with the same number, as described in the
1077     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1078     .\" </a>
1079     section on duplicate subpattern numbers
1080     .\"
1081     in the
1082     .\" HREF
1083     \fBpcrepattern\fP
1084     .\"
1085 ph10 461 page. Duplicate names for subpatterns with different numbers are permitted only
1086     if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1087     table in the order in which they were found in the pattern. In the absence of
1088     (?| this is the order of increasing number; when (?| is used this is not
1089 ph10 457 necessarily the case because later subpatterns may have lower numbers.
1090     .P
1091     As a simple example of the name/number table, consider the following pattern
1092     (assume PCRE_EXTENDED is set, so white space - including newlines - is
1093     ignored):
1094 nigel 75 .sp
1095     .\" JOIN
1096 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1097     (?<month>\ed\ed) - (?<day>\ed\ed) )
1098 nigel 75 .sp
1099 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
1100     in the table is eight bytes long. The table is as follows, with non-printing
1101 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
1102     .sp
1103 nigel 63 00 01 d a t e 00 ??
1104     00 05 d a y 00 ?? ??
1105     00 04 m o n t h 00
1106     00 02 y e a r 00 ??
1107 nigel 75 .sp
1108     When writing code to extract data from named subpatterns using the
1109 nigel 91 name-to-number map, remember that the length of the entries is likely to be
1110 nigel 75 different for each compiled pattern.
1111     .sp
1112 ph10 169 PCRE_INFO_OKPARTIAL
1113     .sp
1114 ph10 435 Return 1 if the pattern can be used for partial matching with
1115     \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1116     \fBint\fP variable. From release 8.00, this always returns 1, because the
1117     restrictions that previously applied to partial matching have been lifted. The
1118 ph10 169 .\" HREF
1119     \fBpcrepartial\fP
1120     .\"
1121 ph10 426 documentation gives details of partial matching.
1122 ph10 169 .sp
1123 nigel 63 PCRE_INFO_OPTIONS
1124 nigel 75 .sp
1125 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
1126 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
1127     are those specified in the call to \fBpcre_compile()\fP, modified by any
1128 ph10 196 top-level option settings at the start of the pattern itself. In other words,
1129     they are the options that will be in force when matching starts. For example,
1130     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1131     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1132 nigel 75 .P
1133 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
1134     alternatives begin with one of the following:
1135 nigel 75 .sp
1136 nigel 63 ^ unless PCRE_MULTILINE is set
1137 nigel 75 \eA always
1138     \eG always
1139     .\" JOIN
1140 nigel 63 .* if PCRE_DOTALL is set and there are no back
1141     references to the subpattern in which .* appears
1142 nigel 75 .sp
1143 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1144 nigel 75 \fBpcre_fullinfo()\fP.
1145     .sp
1146 nigel 63 PCRE_INFO_SIZE
1147 nigel 75 .sp
1148 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
1149 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1150     place the compiled data. The fourth argument should point to a \fBsize_t\fP
1151 nigel 63 variable.
1152 nigel 75 .sp
1153 nigel 63 PCRE_INFO_STUDYSIZE
1154 nigel 75 .sp
1155     Return the size of the data block pointed to by the \fIstudy_data\fP field in
1156     a \fBpcre_extra\fP block. That is, it is the value that was passed to
1157     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1158 ph10 455 created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1159     study data, zero is returned. The fourth argument should point to a
1160 nigel 75 \fBsize_t\fP variable.
1161     .
1162     .
1163     .SH "OBSOLETE INFO FUNCTION"
1164 nigel 63 .rs
1165     .sp
1166 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1167     .B *\fIfirstcharptr\fP);
1168 nigel 63 .PP
1169 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
1170 nigel 63 restrictive to return all the available data about a compiled pattern. New
1171 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1172     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1173 nigel 63 following negative numbers:
1174 nigel 75 .sp
1175     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1176 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
1177 nigel 75 .sp
1178     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1179 nigel 63 pattern was compiled is placed in the integer it points to (see
1180     PCRE_INFO_OPTIONS above).
1181 nigel 75 .P
1182     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1183 nigel 63 it is used to pass back information about the first character of any matched
1184     string (see PCRE_INFO_FIRSTBYTE above).
1185 nigel 75 .
1186     .
1187 nigel 77 .SH "REFERENCE COUNTS"
1188 nigel 63 .rs
1189     .sp
1190 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1191     .PP
1192     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1193     data block that contains a compiled pattern. It is provided for the benefit of
1194     applications that operate in an object-oriented manner, where different parts
1195     of the application may be using the same compiled pattern, but you want to free
1196     the block when they are all done.
1197     .P
1198     When a pattern is compiled, the reference count field is initialized to zero.
1199     It is changed only by calling this function, whose action is to add the
1200     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1201     function is the new value. However, the value of the count is constrained to
1202     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1203     it is forced to the appropriate limit value.
1204     .P
1205     Except when it is zero, the reference count is not correctly preserved if a
1206     pattern is compiled on one host and then transferred to a host whose byte-order
1207     is different. (This seems a highly unlikely scenario.)
1208     .
1209     .
1210     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1211     .rs
1212     .sp
1213 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1214 nigel 63 .ti +5n
1215 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1216 nigel 63 .ti +5n
1217 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1218     .P
1219     The function \fBpcre_exec()\fP is called to match a subject string against a
1220     compiled pattern, which is passed in the \fIcode\fP argument. If the
1221 ph10 455 pattern was studied, the result of the study should be passed in the
1222 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1223     library, and it operates in a Perl-like manner. For specialist use there is
1224     also an alternative matching function, which is described
1225     .\" HTML <a href="#dfamatch">
1226     .\" </a>
1227     below
1228     .\"
1229     in the section about the \fBpcre_dfa_exec()\fP function.
1230 nigel 75 .P
1231     In most applications, the pattern will have been compiled (and optionally
1232     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1233     possible to save compiled patterns and study data, and then use them later
1234     in different processes, possibly even on different hosts. For a discussion
1235     about this, see the
1236     .\" HREF
1237     \fBpcreprecompile\fP
1238     .\"
1239     documentation.
1240     .P
1241     Here is an example of a simple call to \fBpcre_exec()\fP:
1242     .sp
1243 nigel 63 int rc;
1244     int ovector[30];
1245     rc = pcre_exec(
1246     re, /* result of pcre_compile() */
1247     NULL, /* we didn't study the pattern */
1248     "some string", /* the subject string */
1249     11, /* the length of the subject string */
1250     0, /* start at offset 0 in the subject */
1251     0, /* default options */
1252 nigel 75 ovector, /* vector of integers for substring information */
1253 nigel 77 30); /* number of elements (NOT size in bytes) */
1254 nigel 75 .
1255     .\" HTML <a name="extradata"></a>
1256     .SS "Extra data for \fBpcre_exec()\fR"
1257     .rs
1258     .sp
1259     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1260     data block. The \fBpcre_study()\fP function returns such a block (when it
1261 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1262 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1263     fields (not necessarily in this order):
1264 nigel 75 .sp
1265     unsigned long int \fIflags\fP;
1266     void *\fIstudy_data\fP;
1267     unsigned long int \fImatch_limit\fP;
1268 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1269 nigel 75 void *\fIcallout_data\fP;
1270     const unsigned char *\fItables\fP;
1271 ph10 512 unsigned char **\fImark\fP;
1272 nigel 75 .sp
1273     The \fIflags\fP field is a bitmap that specifies which of the other fields
1274 nigel 63 are set. The flag bits are:
1275 nigel 75 .sp
1276 nigel 63 PCRE_EXTRA_STUDY_DATA
1277     PCRE_EXTRA_MATCH_LIMIT
1278 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1279 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1280 nigel 75 PCRE_EXTRA_TABLES
1281 ph10 512 PCRE_EXTRA_MARK
1282 nigel 75 .sp
1283     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1284     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1285     the appropriate flag bit. You should not set this yourself, but you may add to
1286     the block by setting the other fields and their corresponding flag bits.
1287     .P
1288     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1289 nigel 63 vast amount of resources when running patterns that are not going to match,
1290     but which have a very large number of possibilities in their search trees. The
1291 ph10 456 classic example is a pattern that uses nested unlimited repeats.
1292 nigel 75 .P
1293     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1294 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1295     number of times this function is called during a match, which has the effect of
1296     limiting the amount of backtracking that can take place. For patterns that are
1297     not anchored, the count restarts from zero for each position in the subject
1298     string.
1299 nigel 75 .P
1300 nigel 87 The default value for the limit can be set when PCRE is built; the default
1301 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1302 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1303     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1304     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1305     PCRE_ERROR_MATCHLIMIT.
1306 nigel 75 .P
1307 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1308     instead of limiting the total number of times that \fBmatch()\fP is called, it
1309     limits the depth of recursion. The recursion depth is a smaller number than the
1310     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1311     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1312     .P
1313     Limiting the recursion depth limits the amount of stack that can be used, or,
1314     when PCRE has been compiled to use memory on the heap instead of the stack, the
1315     amount of heap memory that can be used.
1316     .P
1317     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1318     built; the default default is the same value as the default for
1319     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1320     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1321     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1322     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1323     .P
1324 ph10 440 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1325     and is described in the
1326 nigel 75 .\" HREF
1327     \fBpcrecallout\fP
1328     .\"
1329     documentation.
1330     .P
1331     The \fItables\fP field is used to pass a character tables pointer to
1332     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1333     pattern. A non-NULL value is stored with the compiled pattern only if custom
1334     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1335     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1336     internal tables to be used. This facility is helpful when re-using patterns
1337     that have been saved after compiling with an external set of tables, because
1338     the external tables might be at a different address when \fBpcre_exec()\fP is
1339     called. See the
1340     .\" HREF
1341     \fBpcreprecompile\fP
1342     .\"
1343     documentation for a discussion of saving compiled patterns for later use.
1344 ph10 510 .P
1345     If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1346 ph10 512 be set to point to a \fBchar *\fP variable. If the pattern contains any
1347 ph10 510 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1348     a name to pass back, a pointer to the name string (zero terminated) is placed
1349     in the variable pointed to by the \fImark\fP field. The names are within the
1350     compiled pattern; if you wish to retain such a name you must copy it before
1351     freeing the memory of a compiled pattern. If there is no name to pass back, the
1352     variable pointed to by the \fImark\fP field set to NULL. For details of the
1353     backtracking control verbs, see the section entitled
1354     .\" HTML <a href="pcrepattern#backtrackcontrol">
1355     .\" </a>
1356     "Backtracking control"
1357     .\"
1358     in the
1359     .\" HREF
1360     \fBpcrepattern\fP
1361     .\"
1362     documentation.
1363 nigel 75 .
1364 ph10 510 .
1365 ph10 226 .\" HTML <a name="execoptions"></a>
1366 nigel 75 .SS "Option bits for \fBpcre_exec()\fP"
1367     .rs
1368     .sp
1369     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1370 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1371 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1372     PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1373     PCRE_PARTIAL_HARD.
1374 nigel 75 .sp
1375     PCRE_ANCHORED
1376     .sp
1377     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1378     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1379     to be anchored by virtue of its contents, it cannot be made unachored at
1380     matching time.
1381     .sp
1382 ph10 231 PCRE_BSR_ANYCRLF
1383     PCRE_BSR_UNICODE
1384     .sp
1385     These options (which are mutually exclusive) control what the \eR escape
1386     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1387     match any Unicode newline sequence. These options override the choice that was
1388     made or defaulted when the pattern was compiled.
1389     .sp
1390 nigel 91 PCRE_NEWLINE_CR
1391     PCRE_NEWLINE_LF
1392     PCRE_NEWLINE_CRLF
1393 ph10 150 PCRE_NEWLINE_ANYCRLF
1394 nigel 93 PCRE_NEWLINE_ANY
1395 nigel 91 .sp
1396     These options override the newline definition that was chosen or defaulted when
1397 nigel 93 the pattern was compiled. For details, see the description of
1398     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1399     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1400     the way the match position is advanced after a match failure for an unanchored
1401 ph10 227 pattern.
1402 ph10 225 .P
1403 ph10 226 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1404     match attempt for an unanchored pattern fails when the current position is at a
1405 ph10 230 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1406 ph10 226 characters, the match position is advanced by two characters instead of one, in
1407     other words, to after the CRLF.
1408     .P
1409 ph10 227 The above rule is a compromise that makes the most common cases work as
1410     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1411     set), it does not match the string "\er\enA" because, after failing at the
1412     start, it skips both the CR and the LF before retrying. However, the pattern
1413     [\er\en]A does match that string, because it contains an explicit CR or LF
1414 ph10 226 reference, and so advances only by one character after the first failure.
1415     .P
1416 ph10 231 An explicit match for CR of LF is either a literal appearance of one of those
1417     characters, or one of the \er or \en escape sequences. Implicit matches such as
1418 ph10 230 [^X] do not count, nor does \es (which includes CR and LF in the characters
1419     that it matches).
1420     .P
1421 ph10 226 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1422     valid newline sequence and explicit \er or \en escapes appear in the pattern.
1423 nigel 91 .sp
1424 nigel 63 PCRE_NOTBOL
1425 nigel 75 .sp
1426     This option specifies that first character of the subject string is not the
1427     beginning of a line, so the circumflex metacharacter should not match before
1428     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1429     never to match. This option affects only the behaviour of the circumflex
1430     metacharacter. It does not affect \eA.
1431     .sp
1432 nigel 63 PCRE_NOTEOL
1433 nigel 75 .sp
1434     This option specifies that the end of the subject string is not the end of a
1435     line, so the dollar metacharacter should not match it nor (except in multiline
1436     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1437     compile time) causes dollar never to match. This option affects only the
1438     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1439     .sp
1440 nigel 63 PCRE_NOTEMPTY
1441 nigel 75 .sp
1442 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1443     there are alternatives in the pattern, they are tried. If all the alternatives
1444     match the empty string, the entire match fails. For example, if the pattern
1445 nigel 75 .sp
1446 nigel 63 a?b?
1447 nigel 75 .sp
1448 ph10 442 is applied to a string not beginning with "a" or "b", it matches an empty
1449 nigel 63 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1450     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1451 ph10 442 .sp
1452     PCRE_NOTEMPTY_ATSTART
1453     .sp
1454 ph10 461 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1455 ph10 442 the start of the subject is permitted. If the pattern is anchored, such a match
1456     can occur only if the pattern contains \eK.
1457 nigel 75 .P
1458 ph10 442 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1459     does make a special case of a pattern match of the empty string within its
1460     \fBsplit()\fP function, and when using the /g modifier. It is possible to
1461     emulate Perl's behaviour after matching a null string by first trying the match
1462     again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1463     if that fails, by advancing the starting offset (see below) and trying an
1464     ordinary match again. There is some code that demonstrates how to do this in
1465     the
1466 ph10 429 .\" HREF
1467     \fBpcredemo\fP
1468     .\"
1469 ph10 572 sample program. In the most general case, you have to check to see if the
1470     newline convention recognizes CRLF as a newline, and if so, and the current
1471 ph10 566 character is CR followed by LF, advance the starting offset by two characters
1472     instead of one.
1473 nigel 75 .sp
1474 ph10 389 PCRE_NO_START_OPTIMIZE
1475     .sp
1476 ph10 392 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1477 ph10 542 a match, in order to speed up the process. For example, if it is known that an
1478     unanchored match must start with a specific character, it searches the subject
1479     for that character, and fails immediately if it cannot find it, without
1480 ph10 545 actually running the main matching function. This means that a special item
1481 ph10 542 such as (*COMMIT) at the start of a pattern is not considered until after a
1482 ph10 548 suitable starting point for the match has been found. When callouts or (*MARK)
1483 ph10 546 items are in use, these "start-up" optimizations can cause them to be skipped
1484     if the pattern is never actually used. The start-up optimizations are in effect
1485     a pre-scan of the subject that takes place before the pattern is run.
1486     .P
1487     The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1488     causing performance to suffer, but ensuring that in cases where the result is
1489     "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1490     are considered at every possible starting position in the subject string.
1491     Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1492     Consider the pattern
1493 ph10 389 .sp
1494 ph10 546 (*COMMIT)ABC
1495     .sp
1496     When this is compiled, PCRE records the fact that a match must start with the
1497 ph10 548 character "A". Suppose the subject string is "DEFABC". The start-up
1498     optimization scans along the subject, finds "A" and runs the first match
1499 ph10 546 attempt from there. The (*COMMIT) item means that the pattern must match the
1500 ph10 548 current starting position, which in this case, it does. However, if the same
1501     match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1502     subject string does not happen. The first match attempt is run starting from
1503 ph10 546 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1504     the overall result is "no match". If the pattern is studied, more start-up
1505     optimizations may be used. For example, a minimum length for the subject may be
1506     recorded. Consider the pattern
1507     .sp
1508     (*MARK:A)(X|Y)
1509     .sp
1510 ph10 548 The minimum length for a match is one character. If the subject is "ABC", there
1511     will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1512     If the pattern is studied, the final attempt does not take place, because PCRE
1513     knows that the subject is too short, and so the (*MARK) is never encountered.
1514     In this case, studying the pattern does not affect the overall match result,
1515     which is still "no match", but it does affect the auxiliary information that is
1516 ph10 546 returned.
1517     .sp
1518 nigel 75 PCRE_NO_UTF8_CHECK
1519     .sp
1520     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1521     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1522 ph10 211 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1523     start of a UTF-8 character. There is a discussion about the validity of UTF-8
1524     strings in the
1525     .\" HTML <a href="pcre.html#utf8strings">
1526     .\" </a>
1527     section on UTF-8 support
1528     .\"
1529     in the main
1530     .\" HREF
1531     \fBpcre\fP
1532     .\"
1533     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1534 ph10 569 the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1535     a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. If
1536     \fIstartoffset\fP contains a value that does not point to the start of a UTF-8
1537     character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1538     returned.
1539 nigel 75 .P
1540     If you already know that your subject is valid, and you want to skip these
1541     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1542     calling \fBpcre_exec()\fP. You might want to do this for the second and
1543     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1544     all the matches in a single subject string. However, you should be sure that
1545 ph10 567 the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1546     end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1547     invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1548     undefined. Your program may crash.
1549 nigel 75 .sp
1550 ph10 461 PCRE_PARTIAL_HARD
1551 ph10 428 PCRE_PARTIAL_SOFT
1552 nigel 75 .sp
1553 ph10 428 These options turn on the partial matching feature. For backwards
1554     compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1555     occurs if the end of the subject string is reached successfully, but there are
1556     not enough subject characters to complete the match. If this happens when
1557 ph10 553 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1558     testing any remaining alternatives. Only if no complete match can be found is
1559     PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1560     PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1561     but only if no complete match can be found.
1562     .P
1563     If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1564     partial match is found, \fBpcre_exec()\fP immediately returns
1565     PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1566 ph10 572 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1567 ph10 553 important that an alternative complete match.
1568     .P
1569     In both cases, the portion of the string that was inspected when the partial
1570     match was found is set as the first matching string. There is a more detailed
1571     discussion of partial and multi-segment matching, with examples, in the
1572 nigel 75 .\" HREF
1573     \fBpcrepartial\fP
1574     .\"
1575     documentation.
1576     .
1577 ph10 567 .
1578 nigel 75 .SS "The string to be matched by \fBpcre_exec()\fP"
1579     .rs
1580     .sp
1581     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1582 ph10 368 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1583 ph10 572 in \fIstartoffset\fP. If this is negative or greater than the length of the
1584     subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1585     offset is zero, the search for a match starts at the beginning of the subject,
1586     and this is by far the most common case. In UTF-8 mode, the byte offset must
1587     point to the start of a UTF-8 character (or the end of the subject). Unlike the
1588     pattern string, the subject may contain binary zero bytes.
1589 nigel 75 .P
1590 nigel 63 A non-zero starting offset is useful when searching for another match in the
1591 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1592     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1593 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1594     lookbehind. For example, consider the pattern
1595 nigel 75 .sp
1596     \eBiss\eB
1597     .sp
1598     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1599 nigel 63 the current position in the subject is not a word boundary.) When applied to
1600 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1601     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1602     subject, namely "issipi", it does not match, because \eB is always false at the
1603 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1604 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1605 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1606     behind the starting point to discover that it is preceded by a letter.
1607 nigel 75 .P
1608 ph10 567 Finding all the matches in a subject is tricky when the pattern can match an
1609     empty string. It is possible to emulate Perl's /g behaviour by first trying the
1610     match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1611     PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1612     and trying an ordinary match again. There is some code that demonstrates how to
1613     do this in the
1614     .\" HREF
1615     \fBpcredemo\fP
1616     .\"
1617 ph10 572 sample program. In the most general case, you have to check to see if the
1618     newline convention recognizes CRLF as a newline, and if so, and the current
1619 ph10 567 character is CR followed by LF, advance the starting offset by two characters
1620     instead of one.
1621     .P
1622 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1623 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1624 nigel 63 pattern does not require the match to be at the start of the subject.
1625 nigel 75 .
1626 ph10 567 .
1627 nigel 75 .SS "How \fBpcre_exec()\fP returns captured substrings"
1628     .rs
1629     .sp
1630 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1631     addition, further substrings from the subject may be picked out by parts of the
1632     pattern. Following the usage in Jeffrey Friedl's book, this is called
1633     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1634     a fragment of a pattern that picks out a substring. PCRE supports several other
1635     kinds of parenthesized subpattern that do not cause substrings to be captured.
1636 nigel 75 .P
1637 ph10 368 Captured substrings are returned to the caller via a vector of integers whose
1638     address is passed in \fIovector\fP. The number of elements in the vector is
1639     passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1640     argument is NOT the size of \fIovector\fP in bytes.
1641 nigel 75 .P
1642     The first two-thirds of the vector is used to pass back captured substrings,
1643     each substring using a pair of integers. The remaining third of the vector is
1644     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1645 ph10 368 and is not available for passing back information. The number passed in
1646 nigel 75 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1647     rounded down.
1648     .P
1649     When a match is successful, information about captured substrings is returned
1650     in pairs of integers, starting at the beginning of \fIovector\fP, and
1651 ph10 371 continuing up to two-thirds of its length at the most. The first element of
1652 ph10 368 each pair is set to the byte offset of the first character in a substring, and
1653     the second is set to the byte offset of the first character after the end of a
1654     substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1655     mode. They are not character counts.
1656 nigel 75 .P
1657 ph10 368 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1658     portion of the subject string matched by the entire pattern. The next pair is
1659     used for the first capturing subpattern, and so on. The value returned by
1660     \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1661     For example, if two substrings have been captured, the returned value is 3. If
1662     there are no capturing subpatterns, the return value from a successful match is
1663     1, indicating that just the first pair of offsets has been set.
1664     .P
1665 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1666 nigel 75 string that it matched that is returned.
1667     .P
1668     If the vector is too small to hold all the captured substring offsets, it is
1669     used as far as possible (up to two-thirds of its length), and the function
1670 ph10 368 returns a value of zero. If the substring offsets are not of interest,
1671     \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1672 nigel 75 \fIovecsize\fP as zero. However, if the pattern contains back references and
1673     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1674     has to get additional memory for use during matching. Thus it is usually
1675     advisable to supply an \fIovector\fP.
1676     .P
1677 ph10 456 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1678 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1679 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1680     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1681 nigel 91 .P
1682     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1683     the subject when subpattern \fIn\fP has not been used at all. For example, if
1684     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1685     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1686     happens, both values in the offset pairs corresponding to unused subpatterns
1687     are set to -1.
1688     .P
1689     Offset values that correspond to unused subpatterns at the end of the
1690     expression are also set to -1. For example, if the string "abc" is matched
1691     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1692     return from the function is 2, because the highest used capturing subpattern
1693 ph10 568 number is 1, and the offsets for for the second and third capturing subpatterns
1694     (assuming the vector is large enough, of course) are set to -1.
1695 nigel 91 .P
1696 ph10 568 \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
1697     parentheses in the pattern are never changed. That is, if a pattern contains
1698     \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
1699     \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
1700     whatever values they previously had.
1701     .P
1702 nigel 91 Some convenience functions are provided for extracting the captured substrings
1703     as separate strings. These are described below.
1704 nigel 75 .
1705 nigel 77 .\" HTML <a name="errorlist"></a>
1706 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1707 nigel 75 .rs
1708     .sp
1709     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1710 nigel 63 defined in the header file:
1711 nigel 75 .sp
1712 nigel 63 PCRE_ERROR_NOMATCH (-1)
1713 nigel 75 .sp
1714 nigel 63 The subject string did not match the pattern.
1715 nigel 75 .sp
1716 nigel 63 PCRE_ERROR_NULL (-2)
1717 nigel 75 .sp
1718     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1719     NULL and \fIovecsize\fP was not zero.
1720     .sp
1721 nigel 63 PCRE_ERROR_BADOPTION (-3)
1722 nigel 75 .sp
1723     An unrecognized bit was set in the \fIoptions\fP argument.
1724     .sp
1725 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1726 nigel 75 .sp
1727 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1728 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1729     compiled in an environment of one endianness is run in an environment with the
1730     other endianness. This is the error that PCRE gives when the magic number is
1731     not present.
1732     .sp
1733 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1734 nigel 75 .sp
1735 nigel 63 While running the pattern match, an unknown item was encountered in the
1736     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1737     of the compiled pattern.
1738 nigel 75 .sp
1739 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1740 nigel 75 .sp
1741     If a pattern contains back references, but the \fIovector\fP that is passed to
1742     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1743 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1744 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1745     automatically freed at the end of matching.
1746 ph10 531 .P
1747 ph10 535 This error is also given if \fBpcre_stack_malloc()\fP fails in
1748 ph10 531 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1749     \fB--disable-stack-for-recursion\fP.
1750 nigel 75 .sp
1751 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1752 nigel 75 .sp
1753     This error is used by the \fBpcre_copy_substring()\fP,
1754     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1755     below). It is never returned by \fBpcre_exec()\fP.
1756     .sp
1757 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1758 nigel 75 .sp
1759 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1760     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1761     above.
1762     .sp
1763 nigel 63 PCRE_ERROR_CALLOUT (-9)
1764 nigel 75 .sp
1765     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1766 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1767 nigel 75 .\" HREF
1768     \fBpcrecallout\fP
1769     .\"
1770     documentation for details.
1771     .sp
1772 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1773 nigel 75 .sp
1774 nigel 71 A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1775 ph10 572 However, if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8
1776 ph10 569 character at the end of the subject, PCRE_ERROR_SHORTUTF8 is used instead.
1777 nigel 75 .sp
1778 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1779 nigel 75 .sp
1780 nigel 73 The UTF-8 byte sequence that was passed as a subject was valid, but the value
1781 ph10 572 of \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1782 ph10 569 end of the subject.
1783 nigel 75 .sp
1784 nigel 77 PCRE_ERROR_PARTIAL (-12)
1785 nigel 75 .sp
1786     The subject string did not match, but it did match partially. See the
1787     .\" HREF
1788     \fBpcrepartial\fP
1789     .\"
1790     documentation for details of partial matching.
1791     .sp
1792 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1793 nigel 75 .sp
1794 ph10 426 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1795     option was used with a compiled pattern containing items that were not
1796 ph10 461 supported for partial matching. From release 8.00 onwards, there are no
1797 ph10 426 restrictions on partial matching.
1798 nigel 75 .sp
1799 nigel 77 PCRE_ERROR_INTERNAL (-14)
1800 nigel 75 .sp
1801     An unexpected internal error has occurred. This error could be caused by a bug
1802     in PCRE or by overwriting of the compiled pattern.
1803     .sp
1804 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1805 nigel 75 .sp
1806     This error is given if the value of the \fIovecsize\fP argument is negative.
1807 nigel 93 .sp
1808     PCRE_ERROR_RECURSIONLIMIT (-21)
1809     .sp
1810     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1811     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1812     description above.
1813     .sp
1814     PCRE_ERROR_BADNEWLINE (-23)
1815     .sp
1816     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1817 ph10 567 .sp
1818     PCRE_ERROR_BADOFFSET (-24)
1819     .sp
1820 ph10 572 The value of \fIstartoffset\fP was negative or greater than the length of the
1821 ph10 567 subject, that is, the value in \fIlength\fP.
1822 ph10 569 .sp
1823     PCRE_ERROR_SHORTUTF8 (-25)
1824     .sp
1825 ph10 572 The subject string ended with an incomplete (truncated) UTF-8 character, and
1826     the PCRE_PARTIAL_HARD option was set. Without this option, PCRE_ERROR_BADUTF8
1827 ph10 569 is returned in this situation.
1828 nigel 93 .P
1829 ph10 197 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1830 nigel 75 .
1831     .
1832     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1833 nigel 63 .rs
1834     .sp
1835 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1836 nigel 63 .ti +5n
1837 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1838 nigel 63 .ti +5n
1839 nigel 75 .B int \fIbuffersize\fP);
1840 nigel 63 .PP
1841 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1842 nigel 63 .ti +5n
1843 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1844 nigel 63 .ti +5n
1845 nigel 75 .B const char **\fIstringptr\fP);
1846 nigel 63 .PP
1847 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1848 nigel 63 .ti +5n
1849 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1850 nigel 63 .PP
1851     Captured substrings can be accessed directly by using the offsets returned by
1852 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1853     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1854     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1855 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1856     by number. The next section describes functions for extracting named
1857 nigel 91 substrings.
1858 nigel 75 .P
1859 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1860     further zero added on the end, but the result is not, of course, a C string.
1861     However, you can process such a string by referring to the length that is
1862     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1863     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1864     for handling strings containing binary zeros, because the end of the final
1865     string is not independently indicated.
1866     .P
1867 nigel 63 The first three arguments are the same for all three of these functions:
1868 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1869     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1870     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1871 nigel 63 captured by the match, including the substring that matched the entire regular
1872 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1873     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1874     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1875     number of elements in the vector divided by three.
1876     .P
1877     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1878     extract a single substring, whose number is given as \fIstringnumber\fP. A
1879     value of zero extracts the substring that matched the entire pattern, whereas
1880     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1881     the string is placed in \fIbuffer\fP, whose length is given by
1882     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1883     obtained via \fBpcre_malloc\fP, and its address is returned via
1884     \fIstringptr\fP. The yield of the function is the length of the string, not
1885 nigel 93 including the terminating zero, or one of these error codes:
1886 nigel 75 .sp
1887 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1888 nigel 75 .sp
1889     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1890     memory failed for \fBpcre_get_substring()\fP.
1891     .sp
1892 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1893 nigel 75 .sp
1894     There is no substring whose number is \fIstringnumber\fP.
1895     .P
1896     The \fBpcre_get_substring_list()\fP function extracts all available substrings
1897 nigel 63 and builds a list of pointers to them. All this is done in a single block of
1898 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1899     is returned via \fIlistptr\fP, which is also the start of the list of string
1900 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
1901 nigel 93 function is zero if all went well, or the error code
1902 nigel 75 .sp
1903 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1904 nigel 75 .sp
1905 nigel 63 if the attempt to get the memory block failed.
1906 nigel 75 .P
1907 nigel 63 When any of these functions encounter a substring that is unset, which can
1908 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
1909     subject, but subpattern \fIn\fP has not been used at all, they return an empty
1910 nigel 63 string. This can be distinguished from a genuine zero-length substring by
1911 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1912 nigel 63 substrings.
1913 nigel 75 .P
1914     The two convenience functions \fBpcre_free_substring()\fP and
1915     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1916     a previous call of \fBpcre_get_substring()\fP or
1917     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1918     the function pointed to by \fBpcre_free\fP, which of course could be called
1919 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
1920 nigel 91 linked via a special interface to another programming language that cannot use
1921 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
1922 nigel 63 provided.
1923 nigel 75 .
1924     .
1925     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1926 nigel 63 .rs
1927     .sp
1928 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1929 nigel 63 .ti +5n
1930 nigel 75 .B const char *\fIname\fP);
1931 nigel 63 .PP
1932 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1933 nigel 63 .ti +5n
1934 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1935     .ti +5n
1936     .B int \fIstringcount\fP, const char *\fIstringname\fP,
1937     .ti +5n
1938     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1939 nigel 63 .PP
1940 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
1941 nigel 63 .ti +5n
1942 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
1943 nigel 63 .ti +5n
1944 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
1945 nigel 63 .ti +5n
1946 nigel 75 .B const char **\fIstringptr\fP);
1947 nigel 63 .PP
1948 nigel 75 To extract a substring by name, you first have to find associated number.
1949     For example, for this pattern
1950     .sp
1951 nigel 93 (a+)b(?<xxx>\ed+)...
1952 nigel 75 .sp
1953 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
1954     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1955     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1956     pattern, and the second is the name. The yield of the function is the
1957 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1958     that name.
1959     .P
1960     Given the number, you can extract the substring directly, or use one of the
1961     functions described in the previous section. For convenience, there are also
1962     two functions that do the whole job.
1963     .P
1964 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
1965     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1966 nigel 75 functions that extract by number. As these are described in the previous
1967     section, they are not re-described here. There are just two differences:
1968     .P
1969 nigel 63 First, instead of a substring number, a substring name is given. Second, there
1970     is an extra argument, given at the start, which is a pointer to the compiled
1971     pattern. This is needed in order to gain access to the name-to-number
1972     translation table.
1973 nigel 75 .P
1974     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1975 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1976     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1977 ph10 128 the behaviour may not be what you want (see the next section).
1978 ph10 385 .P
1979 ph10 457 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1980     subpatterns with the same number, as described in the
1981     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1982     .\" </a>
1983     section on duplicate subpattern numbers
1984     .\"
1985     in the
1986     .\" HREF
1987     \fBpcrepattern\fP
1988     .\"
1989     page, you cannot use names to distinguish the different subpatterns, because
1990     names are not included in the compiled code. The matching process uses only
1991     numbers. For this reason, the use of different names for subpatterns of the
1992     same number causes an error at compile time.
1993 nigel 77 .
1994 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
1995     .rs
1996     .sp
1997     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1998     .ti +5n
1999     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2000     .PP
2001     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2002 ph10 457 are not required to be unique. (Duplicate names are always allowed for
2003     subpatterns with the same number, created by using the (?| feature. Indeed, if
2004     such subpatterns are named, they are required to use the same names.)
2005     .P
2006     Normally, patterns with duplicate names are such that in any one match, only
2007     one of the named subpatterns participates. An example is shown in the
2008 nigel 91 .\" HREF
2009     \fBpcrepattern\fP
2010     .\"
2011 ph10 208 documentation.
2012 ph10 203 .P
2013     When duplicates are present, \fBpcre_copy_named_substring()\fP and
2014     \fBpcre_get_named_substring()\fP return the first substring corresponding to
2015     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2016     returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2017     returns one of the numbers that are associated with the name, but it is not
2018     defined which it is.
2019     .P
2020 nigel 91 If you want to get full details of all captured substrings for a given name,
2021     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2022     argument is the compiled pattern, and the second is the name. The third and
2023     fourth are pointers to variables which are updated by the function. After it
2024     has run, they point to the first and last entries in the name-to-number table
2025     for the given name. The function itself returns the length of each entry, or
2026 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2027     described above in the section entitled \fIInformation about a pattern\fP.
2028     Given all the relevant entries for the name, you can extract each of their
2029     numbers, and hence the captured data, if any.
2030 nigel 91 .
2031     .
2032 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
2033     .rs
2034     .sp
2035     The traditional matching function uses a similar algorithm to Perl, which stops
2036     when it finds the first match, starting at a given point in the subject. If you
2037     want to find all possible matches, or the longest possible match, consider
2038     using the alternative matching function (see below) instead. If you cannot use
2039     the alternative function, but still need to find all possible matches, you
2040     can kludge it up by making use of the callout facility, which is described in
2041     the
2042     .\" HREF
2043     \fBpcrecallout\fP
2044     .\"
2045     documentation.
2046 nigel 75 .P
2047 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
2048     When your callout function is called, extract and save the current matched
2049     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2050     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2051     will yield PCRE_ERROR_NOMATCH.
2052     .
2053     .
2054     .\" HTML <a name="dfamatch"></a>
2055     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2056     .rs
2057     .sp
2058     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2059     .ti +5n
2060     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2061     .ti +5n
2062     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2063     .ti +5n
2064     .B int *\fIworkspace\fP, int \fIwscount\fP);
2065     .P
2066     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2067 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
2068     just once, and does not backtrack. This has different characteristics to the
2069     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2070     patterns are not supported. Nevertheless, there are times when this kind of
2071 ph10 461 matching can be useful. For a discussion of the two matching algorithms, and a
2072 ph10 435 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2073 nigel 77 .\" HREF
2074     \fBpcrematching\fP
2075     .\"
2076     documentation.
2077     .P
2078     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2079     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2080     different way, and this is described below. The other common arguments are used
2081     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2082     here.
2083     .P
2084     The two additional arguments provide workspace for the function. The workspace
2085     vector should contain at least 20 elements. It is used for keeping track of
2086     multiple paths through the pattern tree. More workspace will be needed for
2087 nigel 91 patterns and subjects where there are a lot of potential matches.
2088 nigel 77 .P
2089 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2090 nigel 77 .sp
2091     int rc;
2092     int ovector[10];
2093     int wspace[20];
2094 nigel 87 rc = pcre_dfa_exec(
2095 nigel 77 re, /* result of pcre_compile() */
2096     NULL, /* we didn't study the pattern */
2097     "some string", /* the subject string */
2098     11, /* the length of the subject string */
2099     0, /* start at offset 0 in the subject */
2100     0, /* default options */
2101     ovector, /* vector of integers for substring information */
2102     10, /* number of elements (NOT size in bytes) */
2103     wspace, /* working space vector */
2104     20); /* number of elements (NOT size in bytes) */
2105     .
2106     .SS "Option bits for \fBpcre_dfa_exec()\fP"
2107     .rs
2108     .sp
2109     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2110 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2111 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2112 ph10 542 PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2113     PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2114     All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2115     so their description is not repeated here.
2116 nigel 77 .sp
2117 ph10 428 PCRE_PARTIAL_HARD
2118 ph10 461 PCRE_PARTIAL_SOFT
2119 nigel 77 .sp
2120 ph10 428 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2121     details are slightly different. When PCRE_PARTIAL_HARD is set for
2122     \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2123     is reached and there is still at least one matching possibility that requires
2124     additional characters. This happens even if some complete matches have also
2125     been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2126     is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2127     there have been no complete matches, but there is still at least one matching
2128 ph10 435 possibility. The portion of the string that was inspected when the longest
2129     partial match was found is set as the first matching string in both cases.
2130 ph10 553 There is a more detailed discussion of partial and multi-segment matching, with
2131     examples, in the
2132     .\" HREF
2133     \fBpcrepartial\fP
2134     .\"
2135     documentation.
2136 nigel 77 .sp
2137     PCRE_DFA_SHORTEST
2138     .sp
2139     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2140 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
2141     works, this is necessarily the shortest possible match at the first possible
2142     matching point in the subject string.
2143 nigel 77 .sp
2144     PCRE_DFA_RESTART
2145     .sp
2146 ph10 428 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2147     again, with additional subject characters, and have it continue with the same
2148     match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2149     \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2150     before because data about the match so far is left in them after a partial
2151     match. There is more discussion of this facility in the
2152 nigel 77 .\" HREF
2153     \fBpcrepartial\fP
2154     .\"
2155     documentation.
2156     .
2157     .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2158     .rs
2159     .sp
2160     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2161     substring in the subject. Note, however, that all the matches from one run of
2162     the function start at the same point in the subject. The shorter matches are
2163     all initial substrings of the longer matches. For example, if the pattern
2164     .sp
2165     <.*>
2166     .sp
2167     is matched against the string
2168     .sp
2169     This is <something> <something else> <something further> no more
2170     .sp
2171     the three matched strings are
2172     .sp
2173     <something>
2174     <something> <something else>
2175     <something> <something else> <something further>
2176     .sp
2177     On success, the yield of the function is a number greater than zero, which is
2178     the number of matched substrings. The substrings themselves are returned in
2179     \fIovector\fP. Each string uses two elements; the first is the offset to the
2180 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
2181     the same start offset. (Space could have been saved by giving this only once,
2182     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2183     returns data, even though the meaning of the strings is different.)
2184 nigel 77 .P
2185     The strings are returned in reverse order of length; that is, the longest
2186     matching string is given first. If there were too many matches to fit into
2187     \fIovector\fP, the yield of the function is zero, and the vector is filled with
2188     the longest matches.
2189     .
2190     .SS "Error returns from \fBpcre_dfa_exec()\fP"
2191     .rs
2192     .sp
2193     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2194     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2195     described
2196     .\" HTML <a href="#errorlist">
2197     .\" </a>
2198     above.
2199     .\"
2200     There are in addition the following errors that are specific to
2201     \fBpcre_dfa_exec()\fP:
2202     .sp
2203     PCRE_ERROR_DFA_UITEM (-16)
2204     .sp
2205     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2206     that it does not support, for instance, the use of \eC or a back reference.
2207     .sp
2208     PCRE_ERROR_DFA_UCOND (-17)
2209     .sp
2210 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2211     uses a back reference for the condition, or a test for recursion in a specific
2212     group. These are not supported.
2213 nigel 77 .sp
2214     PCRE_ERROR_DFA_UMLIMIT (-18)
2215     .sp
2216     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2217     block that contains a setting of the \fImatch_limit\fP field. This is not
2218     supported (it is meaningless).
2219     .sp
2220     PCRE_ERROR_DFA_WSSIZE (-19)
2221     .sp
2222     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2223     \fIworkspace\fP vector.
2224     .sp
2225     PCRE_ERROR_DFA_RECURSE (-20)
2226     .sp
2227     When a recursive subpattern is processed, the matching function calls itself
2228     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2229     error is given if the output vector is not large enough. This should be
2230     extremely rare, as a vector of size 1000 is used.
2231 nigel 93 .
2232     .
2233     .SH "SEE ALSO"
2234     .rs
2235     .sp
2236     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2237     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2238     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2239 ph10 99 .
2240     .
2241     .SH AUTHOR
2242     .rs
2243     .sp
2244     .nf
2245     Philip Hazel
2246     University Computing Service
2247     Cambridge CB2 3QH, England.
2248     .fi
2249     .
2250     .
2251     .SH REVISION
2252     .rs
2253     .sp
2254     .nf
2255 ph10 572 Last updated: 13 November 2010
2256 ph10 510 Copyright (c) 1997-2010 University of Cambridge.
2257 ph10 99 .fi

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