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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 576 PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
432     PCRE_NO_START_OPT options can be set at the time of matching as well as at
433     compile time.
434 nigel 75 .P
435     If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
436     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
437     NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
438 nigel 87 error message. This is a static string that is part of the library. You must
439 ph10 598 not try to free it. Normally, the offset from the start of the pattern to the
440     byte that was being processed when the error was discovered is placed in the
441     variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
442     immediate error is given). However, for an invalid UTF-8 string, the offset is
443     that of the first byte of the failing character. Also, some errors are not
444     detected until checks are carried out when the whole pattern has been scanned;
445     in these cases the offset passed back is the length of the pattern.
446 nigel 75 .P
447 ph10 572 Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
448 ph10 598 sometimes point into the middle of a UTF-8 character.
449 ph10 569 .P
450 nigel 77 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
451     \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
452     returned via this argument in the event of an error. This is in addition to the
453     textual error message. Error codes and messages are listed below.
454     .P
455 nigel 75 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
456     character tables that are built when PCRE is compiled, using the default C
457     locale. Otherwise, \fItableptr\fP must be an address that is the result of a
458     call to \fBpcre_maketables()\fP. This value is stored with the compiled
459     pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
460     passed to it. For more discussion, see the section on locale support below.
461     .P
462     This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
463     .sp
464 nigel 63 pcre *re;
465     const char *error;
466     int erroffset;
467     re = pcre_compile(
468     "^A.*Z", /* the pattern */
469     0, /* default options */
470     &error, /* for error message */
471     &erroffset, /* for error offset */
472     NULL); /* use default character tables */
473 nigel 75 .sp
474     The following names for option bits are defined in the \fBpcre.h\fP header
475     file:
476     .sp
477 nigel 63 PCRE_ANCHORED
478 nigel 75 .sp
479 nigel 63 If this bit is set, the pattern is forced to be "anchored", that is, it is
480 nigel 75 constrained to match only at the first matching point in the string that is
481 nigel 63 being searched (the "subject string"). This effect can also be achieved by
482     appropriate constructs in the pattern itself, which is the only way to do it in
483     Perl.
484 nigel 75 .sp
485     PCRE_AUTO_CALLOUT
486     .sp
487     If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
488     all with number 255, before each pattern item. For discussion of the callout
489     facility, see the
490     .\" HREF
491     \fBpcrecallout\fP
492     .\"
493     documentation.
494     .sp
495 ph10 231 PCRE_BSR_ANYCRLF
496     PCRE_BSR_UNICODE
497     .sp
498     These options (which are mutually exclusive) control what the \eR escape
499     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
500     match any Unicode newline sequence. The default is specified when PCRE is
501     built. It can be overridden from within the pattern, or by setting an option
502     when a compiled pattern is matched.
503     .sp
504 nigel 63 PCRE_CASELESS
505 nigel 75 .sp
506 nigel 63 If this bit is set, letters in the pattern match both upper and lower case
507     letters. It is equivalent to Perl's /i option, and it can be changed within a
508 nigel 77 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
509     concept of case for characters whose values are less than 128, so caseless
510     matching is always possible. For characters with higher values, the concept of
511     case is supported if PCRE is compiled with Unicode property support, but not
512     otherwise. If you want to use caseless matching for characters 128 and above,
513     you must ensure that PCRE is compiled with Unicode property support as well as
514     with UTF-8 support.
515 nigel 75 .sp
516 nigel 63 PCRE_DOLLAR_ENDONLY
517 nigel 75 .sp
518 nigel 63 If this bit is set, a dollar metacharacter in the pattern matches only at the
519     end of the subject string. Without this option, a dollar also matches
520 nigel 91 immediately before a newline at the end of the string (but not before any other
521     newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
522     There is no equivalent to this option in Perl, and no way to set it within a
523     pattern.
524 nigel 75 .sp
525 nigel 63 PCRE_DOTALL
526 nigel 75 .sp
527 ph10 572 If this bit is set, a dot metacharacter in the pattern matches a character of
528     any value, including one that indicates a newline. However, it only ever
529     matches one character, even if newlines are coded as CRLF. Without this option,
530     a dot does not match when the current position is at a newline. This option is
531     equivalent to Perl's /s option, and it can be changed within a pattern by a
532     (?s) option setting. A negative class such as [^a] always matches newline
533     characters, independent of the setting of this option.
534 nigel 75 .sp
535 nigel 91 PCRE_DUPNAMES
536     .sp
537     If this bit is set, names used to identify capturing subpatterns need not be
538     unique. This can be helpful for certain types of pattern when it is known that
539     only one instance of the named subpattern can ever be matched. There are more
540     details of named subpatterns below; see also the
541     .\" HREF
542     \fBpcrepattern\fP
543     .\"
544     documentation.
545     .sp
546 nigel 63 PCRE_EXTENDED
547 nigel 75 .sp
548 nigel 63 If this bit is set, whitespace data characters in the pattern are totally
549     ignored except when escaped or inside a character class. Whitespace does not
550     include the VT character (code 11). In addition, characters between an
551 nigel 91 unescaped # outside a character class and the next newline, inclusive, are also
552     ignored. This is equivalent to Perl's /x option, and it can be changed within a
553     pattern by a (?x) option setting.
554 nigel 75 .P
555 ph10 598 Which characters are interpreted as newlines is controlled by the options
556     passed to \fBpcre_compile()\fP or by a special sequence at the start of the
557     pattern, as described in the section entitled
558 ph10 572 .\" HTML <a href="pcrepattern.html#newlines">
559     .\" </a>
560     "Newline conventions"
561     .\"
562     in the \fBpcrepattern\fP documentation. Note that the end of this type of
563     comment is a literal newline sequence in the pattern; escape sequences that
564     happen to represent a newline do not count.
565     .P
566 nigel 63 This option makes it possible to include comments inside complicated patterns.
567     Note, however, that this applies only to data characters. Whitespace characters
568     may never appear within special character sequences in a pattern, for example
569 ph10 572 within the sequence (?( that introduces a conditional subpattern.
570 nigel 75 .sp
571 nigel 63 PCRE_EXTRA
572 nigel 75 .sp
573 nigel 63 This option was invented in order to turn on additional functionality of PCRE
574     that is incompatible with Perl, but it is currently of very little use. When
575     set, any backslash in a pattern that is followed by a letter that has no
576     special meaning causes an error, thus reserving these combinations for future
577     expansion. By default, as in Perl, a backslash followed by a letter with no
578 nigel 91 special meaning is treated as a literal. (Perl can, however, be persuaded to
579 ph10 513 give an error for this, by running it with the -w option.) There are at present
580     no other features controlled by this option. It can also be set by a (?X)
581     option setting within a pattern.
582 nigel 75 .sp
583 nigel 77 PCRE_FIRSTLINE
584     .sp
585     If this option is set, an unanchored pattern is required to match before or at
586 nigel 91 the first newline in the subject string, though the matched text may continue
587     over the newline.
588 nigel 77 .sp
589 ph10 336 PCRE_JAVASCRIPT_COMPAT
590     .sp
591 ph10 345 If this option is set, PCRE's behaviour is changed in some ways so that it is
592 ph10 336 compatible with JavaScript rather than Perl. The changes are as follows:
593     .P
594     (1) A lone closing square bracket in a pattern causes a compile-time error,
595     because this is illegal in JavaScript (by default it is treated as a data
596     character). Thus, the pattern AB]CD becomes illegal when this option is set.
597     .P
598     (2) At run time, a back reference to an unset subpattern group matches an empty
599 ph10 345 string (by default this causes the current matching alternative to fail). A
600     pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
601     an "a" in the subject), whereas it fails by default, for Perl compatibility.
602 ph10 336 .sp
603 nigel 63 PCRE_MULTILINE
604 nigel 75 .sp
605     By default, PCRE treats the subject string as consisting of a single line of
606     characters (even if it actually contains newlines). The "start of line"
607 nigel 63 metacharacter (^) matches only at the start of the string, while the "end of
608     line" metacharacter ($) matches only at the end of the string, or before a
609     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
610     Perl.
611 nigel 75 .P
612 nigel 63 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
613 nigel 91 match immediately following or immediately before internal newlines in the
614     subject string, respectively, as well as at the very start and end. This is
615     equivalent to Perl's /m option, and it can be changed within a pattern by a
616     (?m) option setting. If there are no newlines in a subject string, or no
617 nigel 63 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
618 nigel 75 .sp
619 nigel 91 PCRE_NEWLINE_CR
620     PCRE_NEWLINE_LF
621     PCRE_NEWLINE_CRLF
622 ph10 150 PCRE_NEWLINE_ANYCRLF
623 nigel 93 PCRE_NEWLINE_ANY
624 nigel 91 .sp
625     These options override the default newline definition that was chosen when PCRE
626     was built. Setting the first or the second specifies that a newline is
627 nigel 93 indicated by a single character (CR or LF, respectively). Setting
628     PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
629 ph10 149 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
630     preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
631     that any Unicode newline sequence should be recognized. The Unicode newline
632     sequences are the three just mentioned, plus the single characters VT (vertical
633     tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
634     separator, U+2028), and PS (paragraph separator, U+2029). The last two are
635     recognized only in UTF-8 mode.
636 nigel 91 .P
637 nigel 93 The newline setting in the options word uses three bits that are treated
638 ph10 149 as a number, giving eight possibilities. Currently only six are used (default
639     plus the five values above). This means that if you set more than one newline
640 nigel 93 option, the combination may or may not be sensible. For example,
641     PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
642 ph10 149 other combinations may yield unused numbers and cause an error.
643 nigel 93 .P
644 ph10 572 The only time that a line break in a pattern is specially recognized when
645     compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
646     and so are ignored in this mode. Also, an unescaped # outside a character class
647     indicates a comment that lasts until after the next line break sequence. In
648     other circumstances, line break sequences in patterns are treated as literal
649     data.
650 nigel 93 .P
651     The newline option that is set at compile time becomes the default that is used
652     for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
653 nigel 91 .sp
654 nigel 63 PCRE_NO_AUTO_CAPTURE
655 nigel 75 .sp
656 nigel 63 If this option is set, it disables the use of numbered capturing parentheses in
657     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
658     were followed by ?: but named parentheses can still be used for capturing (and
659     they acquire numbers in the usual way). There is no equivalent of this option
660     in Perl.
661 nigel 75 .sp
662 ph10 576 NO_START_OPTIMIZE
663     .sp
664     This is an option that acts at matching time; that is, it is really an option
665     for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
666     it is remembered with the compiled pattern and assumed at matching time. For
667     details see the discussion of PCRE_NO_START_OPTIMIZE
668     .\" HTML <a href="#execoptions">
669     .\" </a>
670     below.
671     .\"
672     .sp
673 ph10 518 PCRE_UCP
674     .sp
675 ph10 572 This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
676     \ew, and some of the POSIX character classes. By default, only ASCII characters
677     are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
678     classify characters. More details are given in the section on
679 ph10 518 .\" HTML <a href="pcre.html#genericchartypes">
680     .\" </a>
681     generic character types
682     .\"
683     in the
684     .\" HREF
685     \fBpcrepattern\fP
686     .\"
687     page. If you set PCRE_UCP, matching one of the items it affects takes much
688     longer. The option is available only if PCRE has been compiled with Unicode
689     property support.
690     .sp
691 nigel 63 PCRE_UNGREEDY
692 nigel 75 .sp
693 nigel 63 This option inverts the "greediness" of the quantifiers so that they are not
694     greedy by default, but become greedy if followed by "?". It is not compatible
695     with Perl. It can also be set by a (?U) option setting within the pattern.
696 nigel 75 .sp
697 nigel 63 PCRE_UTF8
698 nigel 75 .sp
699 nigel 63 This option causes PCRE to regard both the pattern and the subject as strings
700     of UTF-8 characters instead of single-byte character strings. However, it is
701 nigel 75 available only when PCRE is built to include UTF-8 support. If not, the use
702 nigel 63 of this option provokes an error. Details of how this option changes the
703     behaviour of PCRE are given in the
704     .\" HTML <a href="pcre.html#utf8support">
705     .\" </a>
706     section on UTF-8 support
707     .\"
708     in the main
709     .\" HREF
710 nigel 75 \fBpcre\fP
711 nigel 63 .\"
712     page.
713 nigel 75 .sp
714 nigel 71 PCRE_NO_UTF8_CHECK
715 nigel 75 .sp
716 nigel 71 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
717 ph10 211 automatically checked. There is a discussion about the
718     .\" HTML <a href="pcre.html#utf8strings">
719     .\" </a>
720     validity of UTF-8 strings
721     .\"
722     in the main
723     .\" HREF
724     \fBpcre\fP
725     .\"
726     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
727     returns an error. If you already know that your pattern is valid, and you want
728     to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
729     option. When it is set, the effect of passing an invalid UTF-8 string as a
730     pattern is undefined. It may cause your program to crash. Note that this option
731     can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
732     the UTF-8 validity checking of subject strings.
733 nigel 75 .
734     .
735 nigel 77 .SH "COMPILATION ERROR CODES"
736     .rs
737     .sp
738     The following table lists the error codes than may be returned by
739     \fBpcre_compile2()\fP, along with the error messages that may be returned by
740 nigel 93 both compiling functions. As PCRE has developed, some error codes have fallen
741     out of use. To avoid confusion, they have not been re-used.
742 nigel 77 .sp
743     0 no error
744     1 \e at end of pattern
745     2 \ec at end of pattern
746     3 unrecognized character follows \e
747     4 numbers out of order in {} quantifier
748     5 number too big in {} quantifier
749     6 missing terminating ] for character class
750     7 invalid escape sequence in character class
751     8 range out of order in character class
752     9 nothing to repeat
753 nigel 93 10 [this code is not in use]
754 nigel 77 11 internal error: unexpected repeat
755 ph10 290 12 unrecognized character after (? or (?-
756 nigel 77 13 POSIX named classes are supported only within a class
757     14 missing )
758     15 reference to non-existent subpattern
759     16 erroffset passed as NULL
760     17 unknown option bit(s) set
761     18 missing ) after comment
762 nigel 93 19 [this code is not in use]
763 ph10 290 20 regular expression is too large
764 nigel 77 21 failed to get memory
765     22 unmatched parentheses
766     23 internal error: code overflow
767     24 unrecognized character after (?<
768     25 lookbehind assertion is not fixed length
769 nigel 91 26 malformed number or name after (?(
770 nigel 77 27 conditional group contains more than two branches
771     28 assertion expected after (?(
772 ph10 181 29 (?R or (?[+-]digits must be followed by )
773 nigel 77 30 unknown POSIX class name
774     31 POSIX collating elements are not supported
775     32 this version of PCRE is not compiled with PCRE_UTF8 support
776 nigel 93 33 [this code is not in use]
777 nigel 77 34 character value in \ex{...} sequence is too large
778     35 invalid condition (?(0)
779     36 \eC not allowed in lookbehind assertion
780     37 PCRE does not support \eL, \el, \eN, \eU, or \eu
781     38 number after (?C is > 255
782     39 closing ) for (?C expected
783     40 recursive call could loop indefinitely
784     41 unrecognized character after (?P
785 nigel 93 42 syntax error in subpattern name (missing terminator)
786 nigel 91 43 two named subpatterns have the same name
787 nigel 77 44 invalid UTF-8 string
788     45 support for \eP, \ep, and \eX has not been compiled
789     46 malformed \eP or \ep sequence
790     47 unknown property name after \eP or \ep
791 nigel 91 48 subpattern name is too long (maximum 32 characters)
792 ph10 290 49 too many named subpatterns (maximum 10000)
793 ph10 202 50 [this code is not in use]
794 nigel 91 51 octal value is greater than \e377 (not in UTF-8 mode)
795 nigel 93 52 internal error: overran compiling workspace
796 ph10 548 53 internal error: previously-checked referenced subpattern
797 ph10 546 not found
798 nigel 93 54 DEFINE group contains more than one branch
799     55 repeating a DEFINE group is not allowed
800 ph10 231 56 inconsistent NEWLINE options
801 ph10 345 57 \eg is not followed by a braced, angle-bracketed, or quoted
802     name/number or by a plain number
803 ph10 336 58 a numbered reference must not be zero
804 ph10 510 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
805 ph10 290 60 (*VERB) not recognized
806     61 number is too big
807     62 subpattern name expected
808 ph10 292 63 digit expected after (?+
809 ph10 336 64 ] is an invalid data character in JavaScript compatibility mode
810 ph10 548 65 different names for subpatterns of the same number are
811 ph10 546 not allowed
812 ph10 510 66 (*MARK) must have an argument
813 ph10 518 67 this version of PCRE is not compiled with PCRE_UCP support
814 ph10 290 .sp
815 ph10 292 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
816 ph10 290 be used if the limits were changed when PCRE was built.
817 nigel 77 .
818     .
819 nigel 75 .SH "STUDYING A PATTERN"
820 nigel 63 .rs
821     .sp
822 nigel 77 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
823 nigel 63 .ti +5n
824 nigel 75 .B const char **\fIerrptr\fP);
825 nigel 63 .PP
826 nigel 75 If a compiled pattern is going to be used several times, it is worth spending
827     more time analyzing it in order to speed up the time taken for matching. The
828     function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
829     argument. If studying the pattern produces additional information that will
830     help speed up matching, \fBpcre_study()\fP returns a pointer to a
831     \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
832     results of the study.
833     .P
834     The returned value from \fBpcre_study()\fP can be passed directly to
835 ph10 455 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
836     also contains other fields that can be set by the caller before the block is
837     passed; these are described
838 nigel 75 .\" HTML <a href="#extradata">
839     .\" </a>
840     below
841     .\"
842     in the section on matching a pattern.
843     .P
844 ph10 455 If studying the pattern does not produce any useful information,
845 nigel 75 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
846 ph10 461 wants to pass any of the other fields to \fBpcre_exec()\fP or
847 ph10 455 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
848 nigel 75 .P
849     The second argument of \fBpcre_study()\fP contains option bits. At present, no
850     options are defined, and this argument should always be zero.
851     .P
852     The third argument for \fBpcre_study()\fP is a pointer for an error message. If
853 nigel 63 studying succeeds (even if no data is returned), the variable it points to is
854 nigel 87 set to NULL. Otherwise it is set to point to a textual error message. This is a
855     static string that is part of the library. You must not try to free it. You
856     should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
857     sure that it has run successfully.
858 nigel 75 .P
859     This is a typical call to \fBpcre_study\fP():
860     .sp
861 nigel 63 pcre_extra *pe;
862     pe = pcre_study(
863     re, /* result of pcre_compile() */
864     0, /* no options exist */
865     &error); /* set to NULL or points to a message */
866 nigel 75 .sp
867 ph10 455 Studying a pattern does two things: first, a lower bound for the length of
868 ph10 461 subject string that is needed to match the pattern is computed. This does not
869     mean that there are any strings of that length that match, but it does
870     guarantee that no shorter strings match. The value is used by
871     \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
872     match strings that are shorter than the lower bound. You can find out the value
873 ph10 455 in a calling program via the \fBpcre_fullinfo()\fP function.
874     .P
875     Studying a pattern is also useful for non-anchored patterns that do not have a
876     single fixed starting character. A bitmap of possible starting bytes is
877 ph10 461 created. This speeds up finding a position in the subject at which to start
878 ph10 455 matching.
879 ph10 547 .P
880 ph10 548 The two optimizations just described can be disabled by setting the
881     PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
882     \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
883 ph10 572 callouts or (*MARK), and you want to make use of these facilities in cases
884     where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
885 ph10 547 .\" HTML <a href="#execoptions">
886     .\" </a>
887     below.
888     .\"
889 nigel 75 .
890     .
891 nigel 63 .\" HTML <a name="localesupport"></a>
892 nigel 75 .SH "LOCALE SUPPORT"
893 nigel 63 .rs
894     .sp
895 ph10 139 PCRE handles caseless matching, and determines whether characters are letters,
896 nigel 75 digits, or whatever, by reference to a set of tables, indexed by character
897 nigel 77 value. When running in UTF-8 mode, this applies only to characters with codes
898 ph10 518 less than 128. By default, higher-valued codes never match escapes such as \ew
899     or \ed, but they can be tested with \ep if PCRE is built with Unicode character
900     property support. Alternatively, the PCRE_UCP option can be set at compile
901     time; this causes \ew and friends to use Unicode property support instead of
902     built-in tables. The use of locales with Unicode is discouraged. If you are
903     handling characters with codes greater than 128, you should either use UTF-8
904     and Unicode, or use locales, but not try to mix the two.
905 nigel 75 .P
906 ph10 139 PCRE contains an internal set of tables that are used when the final argument
907     of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
908 ph10 142 Normally, the internal tables recognize only ASCII characters. However, when
909 ph10 139 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
910     default "C" locale of the local system, which may cause them to be different.
911 nigel 75 .P
912 ph10 139 The internal tables can always be overridden by tables supplied by the
913     application that calls PCRE. These may be created in a different locale from
914     the default. As more and more applications change to using Unicode, the need
915     for this locale support is expected to die away.
916     .P
917 nigel 75 External tables are built by calling the \fBpcre_maketables()\fP function,
918     which has no arguments, in the relevant locale. The result can then be passed
919     to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
920     example, to build and use tables that are appropriate for the French locale
921     (where accented characters with values greater than 128 are treated as letters),
922     the following code could be used:
923     .sp
924     setlocale(LC_CTYPE, "fr_FR");
925 nigel 63 tables = pcre_maketables();
926     re = pcre_compile(..., tables);
927 nigel 75 .sp
928 ph10 142 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
929 ph10 139 are using Windows, the name for the French locale is "french".
930     .P
931 nigel 75 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
932     obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
933     that the memory containing the tables remains available for as long as it is
934     needed.
935     .P
936     The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
937     pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
938     and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
939     pattern, compilation, studying and matching all happen in the same locale, but
940     different patterns can be compiled in different locales.
941     .P
942     It is possible to pass a table pointer or NULL (indicating the use of the
943     internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
944     this facility could be used to match a pattern in a different locale from the
945     one in which it was compiled. Passing table pointers at run time is discussed
946     below in the section on matching a pattern.
947     .
948     .
949 ph10 598 .\" HTML <a name="infoaboutpattern"></a>
950 nigel 75 .SH "INFORMATION ABOUT A PATTERN"
951 nigel 63 .rs
952     .sp
953 nigel 75 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
954 nigel 63 .ti +5n
955 nigel 75 .B int \fIwhat\fP, void *\fIwhere\fP);
956 nigel 63 .PP
957 nigel 75 The \fBpcre_fullinfo()\fP function returns information about a compiled
958     pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
959 nigel 63 nevertheless retained for backwards compability (and is documented below).
960 nigel 75 .P
961     The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
962     pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
963 nigel 63 the pattern was not studied. The third argument specifies which piece of
964     information is required, and the fourth argument is a pointer to a variable
965     to receive the data. The yield of the function is zero for success, or one of
966     the following negative numbers:
967 nigel 75 .sp
968     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
969     the argument \fIwhere\fP was NULL
970 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
971 nigel 75 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
972     .sp
973     The "magic number" is placed at the start of each compiled pattern as an simple
974     check against passing an arbitrary memory pointer. Here is a typical call of
975     \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
976     .sp
977 nigel 63 int rc;
978 nigel 91 size_t length;
979 nigel 63 rc = pcre_fullinfo(
980     re, /* result of pcre_compile() */
981     pe, /* result of pcre_study(), or NULL */
982     PCRE_INFO_SIZE, /* what is required */
983     &length); /* where to put the data */
984 nigel 75 .sp
985     The possible values for the third argument are defined in \fBpcre.h\fP, and are
986 nigel 63 as follows:
987 nigel 75 .sp
988 nigel 63 PCRE_INFO_BACKREFMAX
989 nigel 75 .sp
990 nigel 63 Return the number of the highest back reference in the pattern. The fourth
991 nigel 75 argument should point to an \fBint\fP variable. Zero is returned if there are
992 nigel 63 no back references.
993 nigel 75 .sp
994 nigel 63 PCRE_INFO_CAPTURECOUNT
995 nigel 75 .sp
996 nigel 63 Return the number of capturing subpatterns in the pattern. The fourth argument
997 nigel 75 should point to an \fBint\fP variable.
998     .sp
999 nigel 77 PCRE_INFO_DEFAULT_TABLES
1000 nigel 75 .sp
1001     Return a pointer to the internal default character tables within PCRE. The
1002     fourth argument should point to an \fBunsigned char *\fP variable. This
1003     information call is provided for internal use by the \fBpcre_study()\fP
1004     function. External callers can cause PCRE to use its internal tables by passing
1005     a NULL table pointer.
1006     .sp
1007 nigel 63 PCRE_INFO_FIRSTBYTE
1008 nigel 75 .sp
1009 nigel 63 Return information about the first byte of any matched string, for a
1010 nigel 91 non-anchored pattern. The fourth argument should point to an \fBint\fP
1011     variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
1012     still recognized for backwards compatibility.)
1013 nigel 75 .P
1014     If there is a fixed first byte, for example, from a pattern such as
1015 nigel 93 (cat|cow|coyote), its value is returned. Otherwise, if either
1016 nigel 75 .sp
1017 nigel 63 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1018     starts with "^", or
1019 nigel 75 .sp
1020 nigel 63 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1021     (if it were set, the pattern would be anchored),
1022 nigel 75 .sp
1023 nigel 63 -1 is returned, indicating that the pattern matches only at the start of a
1024     subject string or after any newline within the string. Otherwise -2 is
1025     returned. For anchored patterns, -2 is returned.
1026 nigel 75 .sp
1027 nigel 63 PCRE_INFO_FIRSTTABLE
1028 nigel 75 .sp
1029 nigel 63 If the pattern was studied, and this resulted in the construction of a 256-bit
1030     table indicating a fixed set of bytes for the first byte in any matching
1031     string, a pointer to the table is returned. Otherwise NULL is returned. The
1032 nigel 75 fourth argument should point to an \fBunsigned char *\fP variable.
1033     .sp
1034 ph10 226 PCRE_INFO_HASCRORLF
1035     .sp
1036 ph10 227 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1037 ph10 243 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1038 ph10 231 explicit match is either a literal CR or LF character, or \er or \en.
1039 ph10 226 .sp
1040 ph10 169 PCRE_INFO_JCHANGED
1041     .sp
1042 ph10 278 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1043     0. The fourth argument should point to an \fBint\fP variable. (?J) and
1044     (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1045 ph10 169 .sp
1046 nigel 63 PCRE_INFO_LASTLITERAL
1047 nigel 75 .sp
1048 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
1049     string, other than at its start, if such a byte has been recorded. The fourth
1050 nigel 75 argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1051 nigel 65 returned. For anchored patterns, a last literal byte is recorded only if it
1052     follows something of variable length. For example, for the pattern
1053 nigel 75 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1054 nigel 65 is -1.
1055 nigel 75 .sp
1056 ph10 455 PCRE_INFO_MINLENGTH
1057     .sp
1058     If the pattern was studied and a minimum length for matching subject strings
1059     was computed, its value is returned. Otherwise the returned value is -1. The
1060 ph10 456 value is a number of characters, not bytes (this may be relevant in UTF-8
1061 ph10 455 mode). The fourth argument should point to an \fBint\fP variable. A
1062     non-negative value is a lower bound to the length of any matching string. There
1063     may not be any strings of that length that do actually match, but every string
1064     that does match is at least that long.
1065     .sp
1066 nigel 63 PCRE_INFO_NAMECOUNT
1067     PCRE_INFO_NAMEENTRYSIZE
1068     PCRE_INFO_NAMETABLE
1069 nigel 75 .sp
1070 nigel 63 PCRE supports the use of named as well as numbered capturing parentheses. The
1071     names are just an additional way of identifying the parentheses, which still
1072 nigel 91 acquire numbers. Several convenience functions such as
1073     \fBpcre_get_named_substring()\fP are provided for extracting captured
1074     substrings by name. It is also possible to extract the data directly, by first
1075     converting the name to a number in order to access the correct pointers in the
1076     output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1077     you need to use the name-to-number map, which is described by these three
1078     values.
1079 nigel 75 .P
1080 nigel 63 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1081     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1082 nigel 75 entry; both of these return an \fBint\fP value. The entry size depends on the
1083 nigel 63 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1084 nigel 75 entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1085 nigel 63 are the number of the capturing parenthesis, most significant byte first. The
1086 ph10 461 rest of the entry is the corresponding name, zero terminated.
1087 ph10 457 .P
1088     The names are in alphabetical order. Duplicate names may appear if (?| is used
1089     to create multiple groups with the same number, as described in the
1090     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1091     .\" </a>
1092     section on duplicate subpattern numbers
1093     .\"
1094     in the
1095     .\" HREF
1096     \fBpcrepattern\fP
1097     .\"
1098 ph10 461 page. Duplicate names for subpatterns with different numbers are permitted only
1099     if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1100     table in the order in which they were found in the pattern. In the absence of
1101     (?| this is the order of increasing number; when (?| is used this is not
1102 ph10 457 necessarily the case because later subpatterns may have lower numbers.
1103     .P
1104     As a simple example of the name/number table, consider the following pattern
1105     (assume PCRE_EXTENDED is set, so white space - including newlines - is
1106     ignored):
1107 nigel 75 .sp
1108     .\" JOIN
1109 nigel 93 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1110     (?<month>\ed\ed) - (?<day>\ed\ed) )
1111 nigel 75 .sp
1112 nigel 63 There are four named subpatterns, so the table has four entries, and each entry
1113     in the table is eight bytes long. The table is as follows, with non-printing
1114 nigel 75 bytes shows in hexadecimal, and undefined bytes shown as ??:
1115     .sp
1116 nigel 63 00 01 d a t e 00 ??
1117     00 05 d a y 00 ?? ??
1118     00 04 m o n t h 00
1119     00 02 y e a r 00 ??
1120 nigel 75 .sp
1121     When writing code to extract data from named subpatterns using the
1122 nigel 91 name-to-number map, remember that the length of the entries is likely to be
1123 nigel 75 different for each compiled pattern.
1124     .sp
1125 ph10 169 PCRE_INFO_OKPARTIAL
1126     .sp
1127 ph10 435 Return 1 if the pattern can be used for partial matching with
1128     \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1129     \fBint\fP variable. From release 8.00, this always returns 1, because the
1130     restrictions that previously applied to partial matching have been lifted. The
1131 ph10 169 .\" HREF
1132     \fBpcrepartial\fP
1133     .\"
1134 ph10 426 documentation gives details of partial matching.
1135 ph10 169 .sp
1136 nigel 63 PCRE_INFO_OPTIONS
1137 nigel 75 .sp
1138 nigel 63 Return a copy of the options with which the pattern was compiled. The fourth
1139 nigel 75 argument should point to an \fBunsigned long int\fP variable. These option bits
1140     are those specified in the call to \fBpcre_compile()\fP, modified by any
1141 ph10 196 top-level option settings at the start of the pattern itself. In other words,
1142     they are the options that will be in force when matching starts. For example,
1143     if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1144     result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1145 nigel 75 .P
1146 nigel 63 A pattern is automatically anchored by PCRE if all of its top-level
1147     alternatives begin with one of the following:
1148 nigel 75 .sp
1149 nigel 63 ^ unless PCRE_MULTILINE is set
1150 nigel 75 \eA always
1151     \eG always
1152     .\" JOIN
1153 nigel 63 .* if PCRE_DOTALL is set and there are no back
1154     references to the subpattern in which .* appears
1155 nigel 75 .sp
1156 nigel 63 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1157 nigel 75 \fBpcre_fullinfo()\fP.
1158     .sp
1159 nigel 63 PCRE_INFO_SIZE
1160 nigel 75 .sp
1161 nigel 63 Return the size of the compiled pattern, that is, the value that was passed as
1162 nigel 75 the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1163     place the compiled data. The fourth argument should point to a \fBsize_t\fP
1164 nigel 63 variable.
1165 nigel 75 .sp
1166 nigel 63 PCRE_INFO_STUDYSIZE
1167 nigel 75 .sp
1168     Return the size of the data block pointed to by the \fIstudy_data\fP field in
1169     a \fBpcre_extra\fP block. That is, it is the value that was passed to
1170     \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1171 ph10 455 created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1172     study data, zero is returned. The fourth argument should point to a
1173 nigel 75 \fBsize_t\fP variable.
1174     .
1175     .
1176     .SH "OBSOLETE INFO FUNCTION"
1177 nigel 63 .rs
1178     .sp
1179 nigel 75 .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1180     .B *\fIfirstcharptr\fP);
1181 nigel 63 .PP
1182 nigel 75 The \fBpcre_info()\fP function is now obsolete because its interface is too
1183 nigel 63 restrictive to return all the available data about a compiled pattern. New
1184 nigel 75 programs should use \fBpcre_fullinfo()\fP instead. The yield of
1185     \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1186 nigel 63 following negative numbers:
1187 nigel 75 .sp
1188     PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1189 nigel 63 PCRE_ERROR_BADMAGIC the "magic number" was not found
1190 nigel 75 .sp
1191     If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1192 nigel 63 pattern was compiled is placed in the integer it points to (see
1193     PCRE_INFO_OPTIONS above).
1194 nigel 75 .P
1195     If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1196 nigel 63 it is used to pass back information about the first character of any matched
1197     string (see PCRE_INFO_FIRSTBYTE above).
1198 nigel 75 .
1199     .
1200 nigel 77 .SH "REFERENCE COUNTS"
1201 nigel 63 .rs
1202     .sp
1203 nigel 77 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1204     .PP
1205     The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1206     data block that contains a compiled pattern. It is provided for the benefit of
1207     applications that operate in an object-oriented manner, where different parts
1208     of the application may be using the same compiled pattern, but you want to free
1209     the block when they are all done.
1210     .P
1211     When a pattern is compiled, the reference count field is initialized to zero.
1212     It is changed only by calling this function, whose action is to add the
1213     \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1214     function is the new value. However, the value of the count is constrained to
1215     lie between 0 and 65535, inclusive. If the new value is outside these limits,
1216     it is forced to the appropriate limit value.
1217     .P
1218     Except when it is zero, the reference count is not correctly preserved if a
1219     pattern is compiled on one host and then transferred to a host whose byte-order
1220     is different. (This seems a highly unlikely scenario.)
1221     .
1222     .
1223     .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1224     .rs
1225     .sp
1226 nigel 75 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1227 nigel 63 .ti +5n
1228 nigel 75 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1229 nigel 63 .ti +5n
1230 nigel 75 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1231     .P
1232     The function \fBpcre_exec()\fP is called to match a subject string against a
1233     compiled pattern, which is passed in the \fIcode\fP argument. If the
1234 ph10 455 pattern was studied, the result of the study should be passed in the
1235 nigel 77 \fIextra\fP argument. This function is the main matching facility of the
1236     library, and it operates in a Perl-like manner. For specialist use there is
1237     also an alternative matching function, which is described
1238     .\" HTML <a href="#dfamatch">
1239     .\" </a>
1240     below
1241     .\"
1242     in the section about the \fBpcre_dfa_exec()\fP function.
1243 nigel 75 .P
1244     In most applications, the pattern will have been compiled (and optionally
1245     studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1246     possible to save compiled patterns and study data, and then use them later
1247     in different processes, possibly even on different hosts. For a discussion
1248     about this, see the
1249     .\" HREF
1250     \fBpcreprecompile\fP
1251     .\"
1252     documentation.
1253     .P
1254     Here is an example of a simple call to \fBpcre_exec()\fP:
1255     .sp
1256 nigel 63 int rc;
1257     int ovector[30];
1258     rc = pcre_exec(
1259     re, /* result of pcre_compile() */
1260     NULL, /* we didn't study the pattern */
1261     "some string", /* the subject string */
1262     11, /* the length of the subject string */
1263     0, /* start at offset 0 in the subject */
1264     0, /* default options */
1265 nigel 75 ovector, /* vector of integers for substring information */
1266 nigel 77 30); /* number of elements (NOT size in bytes) */
1267 nigel 75 .
1268     .\" HTML <a name="extradata"></a>
1269     .SS "Extra data for \fBpcre_exec()\fR"
1270     .rs
1271     .sp
1272     If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1273     data block. The \fBpcre_study()\fP function returns such a block (when it
1274 nigel 63 doesn't return NULL), but you can also create one for yourself, and pass
1275 nigel 87 additional information in it. The \fBpcre_extra\fP block contains the following
1276     fields (not necessarily in this order):
1277 nigel 75 .sp
1278     unsigned long int \fIflags\fP;
1279     void *\fIstudy_data\fP;
1280     unsigned long int \fImatch_limit\fP;
1281 nigel 87 unsigned long int \fImatch_limit_recursion\fP;
1282 nigel 75 void *\fIcallout_data\fP;
1283     const unsigned char *\fItables\fP;
1284 ph10 512 unsigned char **\fImark\fP;
1285 nigel 75 .sp
1286     The \fIflags\fP field is a bitmap that specifies which of the other fields
1287 nigel 63 are set. The flag bits are:
1288 nigel 75 .sp
1289 nigel 63 PCRE_EXTRA_STUDY_DATA
1290     PCRE_EXTRA_MATCH_LIMIT
1291 nigel 87 PCRE_EXTRA_MATCH_LIMIT_RECURSION
1292 nigel 63 PCRE_EXTRA_CALLOUT_DATA
1293 nigel 75 PCRE_EXTRA_TABLES
1294 ph10 512 PCRE_EXTRA_MARK
1295 nigel 75 .sp
1296     Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1297     \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1298     the appropriate flag bit. You should not set this yourself, but you may add to
1299     the block by setting the other fields and their corresponding flag bits.
1300     .P
1301     The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1302 nigel 63 vast amount of resources when running patterns that are not going to match,
1303     but which have a very large number of possibilities in their search trees. The
1304 ph10 456 classic example is a pattern that uses nested unlimited repeats.
1305 nigel 75 .P
1306     Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1307 nigel 87 (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1308     number of times this function is called during a match, which has the effect of
1309     limiting the amount of backtracking that can take place. For patterns that are
1310     not anchored, the count restarts from zero for each position in the subject
1311     string.
1312 nigel 75 .P
1313 nigel 87 The default value for the limit can be set when PCRE is built; the default
1314 nigel 63 default is 10 million, which handles all but the most extreme cases. You can
1315 nigel 87 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1316     block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1317     the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1318     PCRE_ERROR_MATCHLIMIT.
1319 nigel 75 .P
1320 nigel 87 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1321     instead of limiting the total number of times that \fBmatch()\fP is called, it
1322     limits the depth of recursion. The recursion depth is a smaller number than the
1323     total number of calls, because not all calls to \fBmatch()\fP are recursive.
1324     This limit is of use only if it is set smaller than \fImatch_limit\fP.
1325     .P
1326     Limiting the recursion depth limits the amount of stack that can be used, or,
1327     when PCRE has been compiled to use memory on the heap instead of the stack, the
1328     amount of heap memory that can be used.
1329     .P
1330     The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1331     built; the default default is the same value as the default for
1332     \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1333     with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1334     PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1335     is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1336     .P
1337 ph10 440 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1338     and is described in the
1339 nigel 75 .\" HREF
1340     \fBpcrecallout\fP
1341     .\"
1342     documentation.
1343     .P
1344     The \fItables\fP field is used to pass a character tables pointer to
1345     \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1346     pattern. A non-NULL value is stored with the compiled pattern only if custom
1347     tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1348     If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1349     internal tables to be used. This facility is helpful when re-using patterns
1350     that have been saved after compiling with an external set of tables, because
1351     the external tables might be at a different address when \fBpcre_exec()\fP is
1352     called. See the
1353     .\" HREF
1354     \fBpcreprecompile\fP
1355     .\"
1356     documentation for a discussion of saving compiled patterns for later use.
1357 ph10 510 .P
1358     If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1359 ph10 512 be set to point to a \fBchar *\fP variable. If the pattern contains any
1360 ph10 510 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1361     a name to pass back, a pointer to the name string (zero terminated) is placed
1362     in the variable pointed to by the \fImark\fP field. The names are within the
1363     compiled pattern; if you wish to retain such a name you must copy it before
1364     freeing the memory of a compiled pattern. If there is no name to pass back, the
1365     variable pointed to by the \fImark\fP field set to NULL. For details of the
1366     backtracking control verbs, see the section entitled
1367     .\" HTML <a href="pcrepattern#backtrackcontrol">
1368     .\" </a>
1369     "Backtracking control"
1370     .\"
1371     in the
1372     .\" HREF
1373     \fBpcrepattern\fP
1374     .\"
1375     documentation.
1376 nigel 75 .
1377 ph10 510 .
1378 ph10 226 .\" HTML <a name="execoptions"></a>
1379 nigel 75 .SS "Option bits for \fBpcre_exec()\fP"
1380     .rs
1381     .sp
1382     The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1383 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1384 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1385     PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1386     PCRE_PARTIAL_HARD.
1387 nigel 75 .sp
1388     PCRE_ANCHORED
1389     .sp
1390     The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1391     matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1392     to be anchored by virtue of its contents, it cannot be made unachored at
1393     matching time.
1394     .sp
1395 ph10 231 PCRE_BSR_ANYCRLF
1396     PCRE_BSR_UNICODE
1397     .sp
1398     These options (which are mutually exclusive) control what the \eR escape
1399     sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1400     match any Unicode newline sequence. These options override the choice that was
1401     made or defaulted when the pattern was compiled.
1402     .sp
1403 nigel 91 PCRE_NEWLINE_CR
1404     PCRE_NEWLINE_LF
1405     PCRE_NEWLINE_CRLF
1406 ph10 150 PCRE_NEWLINE_ANYCRLF
1407 nigel 93 PCRE_NEWLINE_ANY
1408 nigel 91 .sp
1409     These options override the newline definition that was chosen or defaulted when
1410 nigel 93 the pattern was compiled. For details, see the description of
1411     \fBpcre_compile()\fP above. During matching, the newline choice affects the
1412     behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1413     the way the match position is advanced after a match failure for an unanchored
1414 ph10 227 pattern.
1415 ph10 225 .P
1416 ph10 226 When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1417     match attempt for an unanchored pattern fails when the current position is at a
1418 ph10 230 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1419 ph10 226 characters, the match position is advanced by two characters instead of one, in
1420     other words, to after the CRLF.
1421     .P
1422 ph10 227 The above rule is a compromise that makes the most common cases work as
1423     expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1424     set), it does not match the string "\er\enA" because, after failing at the
1425     start, it skips both the CR and the LF before retrying. However, the pattern
1426     [\er\en]A does match that string, because it contains an explicit CR or LF
1427 ph10 226 reference, and so advances only by one character after the first failure.
1428     .P
1429 ph10 231 An explicit match for CR of LF is either a literal appearance of one of those
1430     characters, or one of the \er or \en escape sequences. Implicit matches such as
1431 ph10 230 [^X] do not count, nor does \es (which includes CR and LF in the characters
1432     that it matches).
1433     .P
1434 ph10 226 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1435     valid newline sequence and explicit \er or \en escapes appear in the pattern.
1436 nigel 91 .sp
1437 nigel 63 PCRE_NOTBOL
1438 nigel 75 .sp
1439     This option specifies that first character of the subject string is not the
1440     beginning of a line, so the circumflex metacharacter should not match before
1441     it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1442     never to match. This option affects only the behaviour of the circumflex
1443     metacharacter. It does not affect \eA.
1444     .sp
1445 nigel 63 PCRE_NOTEOL
1446 nigel 75 .sp
1447     This option specifies that the end of the subject string is not the end of a
1448     line, so the dollar metacharacter should not match it nor (except in multiline
1449     mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1450     compile time) causes dollar never to match. This option affects only the
1451     behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1452     .sp
1453 nigel 63 PCRE_NOTEMPTY
1454 nigel 75 .sp
1455 nigel 63 An empty string is not considered to be a valid match if this option is set. If
1456     there are alternatives in the pattern, they are tried. If all the alternatives
1457     match the empty string, the entire match fails. For example, if the pattern
1458 nigel 75 .sp
1459 nigel 63 a?b?
1460 nigel 75 .sp
1461 ph10 442 is applied to a string not beginning with "a" or "b", it matches an empty
1462 nigel 63 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1463     valid, so PCRE searches further into the string for occurrences of "a" or "b".
1464 ph10 442 .sp
1465     PCRE_NOTEMPTY_ATSTART
1466     .sp
1467 ph10 461 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1468 ph10 442 the start of the subject is permitted. If the pattern is anchored, such a match
1469     can occur only if the pattern contains \eK.
1470 nigel 75 .P
1471 ph10 442 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1472     does make a special case of a pattern match of the empty string within its
1473     \fBsplit()\fP function, and when using the /g modifier. It is possible to
1474     emulate Perl's behaviour after matching a null string by first trying the match
1475     again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1476     if that fails, by advancing the starting offset (see below) and trying an
1477     ordinary match again. There is some code that demonstrates how to do this in
1478     the
1479 ph10 429 .\" HREF
1480     \fBpcredemo\fP
1481     .\"
1482 ph10 572 sample program. In the most general case, you have to check to see if the
1483     newline convention recognizes CRLF as a newline, and if so, and the current
1484 ph10 566 character is CR followed by LF, advance the starting offset by two characters
1485     instead of one.
1486 nigel 75 .sp
1487 ph10 389 PCRE_NO_START_OPTIMIZE
1488     .sp
1489 ph10 392 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1490 ph10 542 a match, in order to speed up the process. For example, if it is known that an
1491     unanchored match must start with a specific character, it searches the subject
1492     for that character, and fails immediately if it cannot find it, without
1493 ph10 545 actually running the main matching function. This means that a special item
1494 ph10 542 such as (*COMMIT) at the start of a pattern is not considered until after a
1495 ph10 548 suitable starting point for the match has been found. When callouts or (*MARK)
1496 ph10 546 items are in use, these "start-up" optimizations can cause them to be skipped
1497     if the pattern is never actually used. The start-up optimizations are in effect
1498     a pre-scan of the subject that takes place before the pattern is run.
1499     .P
1500     The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1501     causing performance to suffer, but ensuring that in cases where the result is
1502     "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1503 ph10 579 are considered at every possible starting position in the subject string. If
1504     PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1505 ph10 576 time.
1506     .P
1507 ph10 546 Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1508     Consider the pattern
1509 ph10 389 .sp
1510 ph10 546 (*COMMIT)ABC
1511     .sp
1512     When this is compiled, PCRE records the fact that a match must start with the
1513 ph10 548 character "A". Suppose the subject string is "DEFABC". The start-up
1514     optimization scans along the subject, finds "A" and runs the first match
1515 ph10 546 attempt from there. The (*COMMIT) item means that the pattern must match the
1516 ph10 548 current starting position, which in this case, it does. However, if the same
1517     match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1518     subject string does not happen. The first match attempt is run starting from
1519 ph10 546 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1520     the overall result is "no match". If the pattern is studied, more start-up
1521     optimizations may be used. For example, a minimum length for the subject may be
1522     recorded. Consider the pattern
1523     .sp
1524     (*MARK:A)(X|Y)
1525     .sp
1526 ph10 548 The minimum length for a match is one character. If the subject is "ABC", there
1527     will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1528     If the pattern is studied, the final attempt does not take place, because PCRE
1529     knows that the subject is too short, and so the (*MARK) is never encountered.
1530     In this case, studying the pattern does not affect the overall match result,
1531     which is still "no match", but it does affect the auxiliary information that is
1532 ph10 546 returned.
1533     .sp
1534 nigel 75 PCRE_NO_UTF8_CHECK
1535     .sp
1536     When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1537     string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1538 ph10 211 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1539     start of a UTF-8 character. There is a discussion about the validity of UTF-8
1540     strings in the
1541     .\" HTML <a href="pcre.html#utf8strings">
1542     .\" </a>
1543     section on UTF-8 support
1544     .\"
1545     in the main
1546     .\" HREF
1547     \fBpcre\fP
1548     .\"
1549     page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1550 ph10 569 the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
1551 ph10 654 a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
1552 ph10 598 both cases, information about the precise nature of the error may also be
1553     returned (see the descriptions of these errors in the section entitled \fIError
1554     return values from\fP \fBpcre_exec()\fP
1555     .\" HTML <a href="#errorlist">
1556     .\" </a>
1557     below).
1558     .\"
1559     If \fIstartoffset\fP contains a value that does not point to the start of a
1560     UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1561 ph10 569 returned.
1562 nigel 75 .P
1563     If you already know that your subject is valid, and you want to skip these
1564     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1565     calling \fBpcre_exec()\fP. You might want to do this for the second and
1566     subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1567     all the matches in a single subject string. However, you should be sure that
1568 ph10 567 the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1569     end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1570     invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1571     undefined. Your program may crash.
1572 nigel 75 .sp
1573 ph10 461 PCRE_PARTIAL_HARD
1574 ph10 428 PCRE_PARTIAL_SOFT
1575 nigel 75 .sp
1576 ph10 428 These options turn on the partial matching feature. For backwards
1577     compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1578     occurs if the end of the subject string is reached successfully, but there are
1579     not enough subject characters to complete the match. If this happens when
1580 ph10 553 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1581     testing any remaining alternatives. Only if no complete match can be found is
1582     PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1583     PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1584     but only if no complete match can be found.
1585     .P
1586     If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1587     partial match is found, \fBpcre_exec()\fP immediately returns
1588     PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1589 ph10 572 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1590 ph10 553 important that an alternative complete match.
1591     .P
1592     In both cases, the portion of the string that was inspected when the partial
1593     match was found is set as the first matching string. There is a more detailed
1594     discussion of partial and multi-segment matching, with examples, in the
1595 nigel 75 .\" HREF
1596     \fBpcrepartial\fP
1597     .\"
1598     documentation.
1599     .
1600 ph10 567 .
1601 nigel 75 .SS "The string to be matched by \fBpcre_exec()\fP"
1602     .rs
1603     .sp
1604     The subject string is passed to \fBpcre_exec()\fP as a pointer in
1605 ph10 368 \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1606 ph10 572 in \fIstartoffset\fP. If this is negative or greater than the length of the
1607     subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1608     offset is zero, the search for a match starts at the beginning of the subject,
1609     and this is by far the most common case. In UTF-8 mode, the byte offset must
1610     point to the start of a UTF-8 character (or the end of the subject). Unlike the
1611     pattern string, the subject may contain binary zero bytes.
1612 nigel 75 .P
1613 nigel 63 A non-zero starting offset is useful when searching for another match in the
1614 nigel 75 same subject by calling \fBpcre_exec()\fP again after a previous success.
1615     Setting \fIstartoffset\fP differs from just passing over a shortened string and
1616 nigel 63 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1617     lookbehind. For example, consider the pattern
1618 nigel 75 .sp
1619     \eBiss\eB
1620     .sp
1621     which finds occurrences of "iss" in the middle of words. (\eB matches only if
1622 nigel 63 the current position in the subject is not a word boundary.) When applied to
1623 nigel 75 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1624     occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1625     subject, namely "issipi", it does not match, because \eB is always false at the
1626 nigel 63 start of the subject, which is deemed to be a word boundary. However, if
1627 nigel 75 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1628 nigel 63 set to 4, it finds the second occurrence of "iss" because it is able to look
1629     behind the starting point to discover that it is preceded by a letter.
1630 nigel 75 .P
1631 ph10 567 Finding all the matches in a subject is tricky when the pattern can match an
1632     empty string. It is possible to emulate Perl's /g behaviour by first trying the
1633     match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1634     PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1635     and trying an ordinary match again. There is some code that demonstrates how to
1636     do this in the
1637     .\" HREF
1638     \fBpcredemo\fP
1639     .\"
1640 ph10 572 sample program. In the most general case, you have to check to see if the
1641     newline convention recognizes CRLF as a newline, and if so, and the current
1642 ph10 567 character is CR followed by LF, advance the starting offset by two characters
1643     instead of one.
1644     .P
1645 nigel 63 If a non-zero starting offset is passed when the pattern is anchored, one
1646 nigel 75 attempt to match at the given offset is made. This can only succeed if the
1647 nigel 63 pattern does not require the match to be at the start of the subject.
1648 nigel 75 .
1649 ph10 567 .
1650 nigel 75 .SS "How \fBpcre_exec()\fP returns captured substrings"
1651     .rs
1652     .sp
1653 nigel 63 In general, a pattern matches a certain portion of the subject, and in
1654     addition, further substrings from the subject may be picked out by parts of the
1655     pattern. Following the usage in Jeffrey Friedl's book, this is called
1656     "capturing" in what follows, and the phrase "capturing subpattern" is used for
1657     a fragment of a pattern that picks out a substring. PCRE supports several other
1658     kinds of parenthesized subpattern that do not cause substrings to be captured.
1659 nigel 75 .P
1660 ph10 368 Captured substrings are returned to the caller via a vector of integers whose
1661     address is passed in \fIovector\fP. The number of elements in the vector is
1662     passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1663     argument is NOT the size of \fIovector\fP in bytes.
1664 nigel 75 .P
1665     The first two-thirds of the vector is used to pass back captured substrings,
1666     each substring using a pair of integers. The remaining third of the vector is
1667     used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1668 ph10 368 and is not available for passing back information. The number passed in
1669 nigel 75 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1670     rounded down.
1671     .P
1672     When a match is successful, information about captured substrings is returned
1673     in pairs of integers, starting at the beginning of \fIovector\fP, and
1674 ph10 371 continuing up to two-thirds of its length at the most. The first element of
1675 ph10 368 each pair is set to the byte offset of the first character in a substring, and
1676     the second is set to the byte offset of the first character after the end of a
1677     substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1678     mode. They are not character counts.
1679 nigel 75 .P
1680 ph10 368 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1681     portion of the subject string matched by the entire pattern. The next pair is
1682     used for the first capturing subpattern, and so on. The value returned by
1683     \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1684     For example, if two substrings have been captured, the returned value is 3. If
1685     there are no capturing subpatterns, the return value from a successful match is
1686     1, indicating that just the first pair of offsets has been set.
1687     .P
1688 nigel 63 If a capturing subpattern is matched repeatedly, it is the last portion of the
1689 nigel 75 string that it matched that is returned.
1690     .P
1691     If the vector is too small to hold all the captured substring offsets, it is
1692     used as far as possible (up to two-thirds of its length), and the function
1693 ph10 368 returns a value of zero. If the substring offsets are not of interest,
1694     \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1695 nigel 75 \fIovecsize\fP as zero. However, if the pattern contains back references and
1696     the \fIovector\fP is not big enough to remember the related substrings, PCRE
1697     has to get additional memory for use during matching. Thus it is usually
1698     advisable to supply an \fIovector\fP.
1699     .P
1700 ph10 456 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1701 nigel 63 subpatterns there are in a compiled pattern. The smallest size for
1702 nigel 75 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1703     the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1704 nigel 91 .P
1705     It is possible for capturing subpattern number \fIn+1\fP to match some part of
1706     the subject when subpattern \fIn\fP has not been used at all. For example, if
1707     the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1708     function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1709     happens, both values in the offset pairs corresponding to unused subpatterns
1710     are set to -1.
1711     .P
1712     Offset values that correspond to unused subpatterns at the end of the
1713     expression are also set to -1. For example, if the string "abc" is matched
1714     against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1715     return from the function is 2, because the highest used capturing subpattern
1716 ph10 568 number is 1, and the offsets for for the second and third capturing subpatterns
1717     (assuming the vector is large enough, of course) are set to -1.
1718 nigel 91 .P
1719 ph10 568 \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
1720     parentheses in the pattern are never changed. That is, if a pattern contains
1721     \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
1722     \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
1723     whatever values they previously had.
1724     .P
1725 nigel 91 Some convenience functions are provided for extracting the captured substrings
1726     as separate strings. These are described below.
1727 nigel 75 .
1728 ph10 598 .
1729 nigel 77 .\" HTML <a name="errorlist"></a>
1730 nigel 91 .SS "Error return values from \fBpcre_exec()\fP"
1731 nigel 75 .rs
1732     .sp
1733     If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1734 nigel 63 defined in the header file:
1735 nigel 75 .sp
1736 nigel 63 PCRE_ERROR_NOMATCH (-1)
1737 nigel 75 .sp
1738 nigel 63 The subject string did not match the pattern.
1739 nigel 75 .sp
1740 nigel 63 PCRE_ERROR_NULL (-2)
1741 nigel 75 .sp
1742     Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1743     NULL and \fIovecsize\fP was not zero.
1744     .sp
1745 nigel 63 PCRE_ERROR_BADOPTION (-3)
1746 nigel 75 .sp
1747     An unrecognized bit was set in the \fIoptions\fP argument.
1748     .sp
1749 nigel 63 PCRE_ERROR_BADMAGIC (-4)
1750 nigel 75 .sp
1751 nigel 63 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1752 nigel 75 the case when it is passed a junk pointer and to detect when a pattern that was
1753     compiled in an environment of one endianness is run in an environment with the
1754     other endianness. This is the error that PCRE gives when the magic number is
1755     not present.
1756     .sp
1757 nigel 93 PCRE_ERROR_UNKNOWN_OPCODE (-5)
1758 nigel 75 .sp
1759 nigel 63 While running the pattern match, an unknown item was encountered in the
1760     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1761     of the compiled pattern.
1762 nigel 75 .sp
1763 nigel 63 PCRE_ERROR_NOMEMORY (-6)
1764 nigel 75 .sp
1765     If a pattern contains back references, but the \fIovector\fP that is passed to
1766     \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1767 nigel 63 gets a block of memory at the start of matching to use for this purpose. If the
1768 nigel 75 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1769     automatically freed at the end of matching.
1770 ph10 531 .P
1771 ph10 535 This error is also given if \fBpcre_stack_malloc()\fP fails in
1772 ph10 531 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1773     \fB--disable-stack-for-recursion\fP.
1774 nigel 75 .sp
1775 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
1776 nigel 75 .sp
1777     This error is used by the \fBpcre_copy_substring()\fP,
1778     \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1779     below). It is never returned by \fBpcre_exec()\fP.
1780     .sp
1781 nigel 63 PCRE_ERROR_MATCHLIMIT (-8)
1782 nigel 75 .sp
1783 nigel 87 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1784     \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1785     above.
1786     .sp
1787 nigel 63 PCRE_ERROR_CALLOUT (-9)
1788 nigel 75 .sp
1789     This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1790 nigel 63 use by callout functions that want to yield a distinctive error code. See the
1791 nigel 75 .\" HREF
1792     \fBpcrecallout\fP
1793     .\"
1794     documentation for details.
1795     .sp
1796 nigel 73 PCRE_ERROR_BADUTF8 (-10)
1797 nigel 75 .sp
1798 ph10 598 A string that contains an invalid UTF-8 byte sequence was passed as a subject,
1799     and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
1800     (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
1801     UTF-8 character is placed in the first element, and a reason code is placed in
1802     the second element. The reason codes are listed in the
1803     .\" HTML <a href="#badutf8reasons">
1804     .\" </a>
1805     following section.
1806     .\"
1807     For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
1808     truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
1809     PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
1810 nigel 75 .sp
1811 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
1812 nigel 75 .sp
1813 ph10 654 The UTF-8 byte sequence that was passed as a subject was checked and found to
1814 ph10 598 be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
1815     \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
1816 ph10 569 end of the subject.
1817 nigel 75 .sp
1818 nigel 77 PCRE_ERROR_PARTIAL (-12)
1819 nigel 75 .sp
1820     The subject string did not match, but it did match partially. See the
1821     .\" HREF
1822     \fBpcrepartial\fP
1823     .\"
1824     documentation for details of partial matching.
1825     .sp
1826 nigel 77 PCRE_ERROR_BADPARTIAL (-13)
1827 nigel 75 .sp
1828 ph10 426 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1829     option was used with a compiled pattern containing items that were not
1830 ph10 461 supported for partial matching. From release 8.00 onwards, there are no
1831 ph10 426 restrictions on partial matching.
1832 nigel 75 .sp
1833 nigel 77 PCRE_ERROR_INTERNAL (-14)
1834 nigel 75 .sp
1835     An unexpected internal error has occurred. This error could be caused by a bug
1836     in PCRE or by overwriting of the compiled pattern.
1837     .sp
1838 nigel 77 PCRE_ERROR_BADCOUNT (-15)
1839 nigel 75 .sp
1840     This error is given if the value of the \fIovecsize\fP argument is negative.
1841 nigel 93 .sp
1842     PCRE_ERROR_RECURSIONLIMIT (-21)
1843     .sp
1844     The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1845     field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1846     description above.
1847     .sp
1848     PCRE_ERROR_BADNEWLINE (-23)
1849     .sp
1850     An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1851 ph10 567 .sp
1852     PCRE_ERROR_BADOFFSET (-24)
1853     .sp
1854 ph10 572 The value of \fIstartoffset\fP was negative or greater than the length of the
1855 ph10 567 subject, that is, the value in \fIlength\fP.
1856 ph10 569 .sp
1857     PCRE_ERROR_SHORTUTF8 (-25)
1858     .sp
1859 ph10 598 This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
1860     ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
1861     Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
1862     fact sufficient to detect this case, but this special error code for
1863     PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
1864     retained for backwards compatibility.
1865 ph10 642 .sp
1866     PCRE_ERROR_RECURSELOOP (-26)
1867     .sp
1868 ph10 654 This error is returned when \fBpcre_exec()\fP detects a recursion loop within
1869     the pattern. Specifically, it means that either the whole pattern or a
1870     subpattern has been called recursively for the second time at the same position
1871 ph10 642 in the subject string. Some simple patterns that might do this are detected and
1872     faulted at compile time, but more complicated cases, in particular mutual
1873     recursions between two different subpatterns, cannot be detected until run
1874     time.
1875 nigel 93 .P
1876 ph10 197 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1877 nigel 75 .
1878     .
1879 ph10 598 .\" HTML <a name="badutf8reasons"></a>
1880     .SS "Reason codes for invalid UTF-8 strings"
1881     .rs
1882     .sp
1883 ph10 654 When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
1884     PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
1885     least 2, the offset of the start of the invalid UTF-8 character is placed in
1886     the first output vector element (\fIovector[0]\fP) and a reason code is placed
1887 ph10 598 in the second element (\fIovector[1]\fP). The reason codes are given names in
1888     the \fBpcre.h\fP header file:
1889     .sp
1890     PCRE_UTF8_ERR1
1891     PCRE_UTF8_ERR2
1892     PCRE_UTF8_ERR3
1893     PCRE_UTF8_ERR4
1894     PCRE_UTF8_ERR5
1895     .sp
1896 ph10 654 The string ends with a truncated UTF-8 character; the code specifies how many
1897 ph10 598 bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
1898     no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
1899 ph10 654 allows for up to 6 bytes, and this is checked first; hence the possibility of
1900 ph10 598 4 or 5 missing bytes.
1901     .sp
1902     PCRE_UTF8_ERR6
1903     PCRE_UTF8_ERR7
1904     PCRE_UTF8_ERR8
1905     PCRE_UTF8_ERR9
1906     PCRE_UTF8_ERR10
1907     .sp
1908 ph10 654 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
1909 ph10 598 character do not have the binary value 0b10 (that is, either the most
1910     significant bit is 0, or the next bit is 1).
1911 ph10 654 .sp
1912 ph10 598 PCRE_UTF8_ERR11
1913     PCRE_UTF8_ERR12
1914     .sp
1915 ph10 654 A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
1916     these code points are excluded by RFC 3629.
1917     .sp
1918 ph10 598 PCRE_UTF8_ERR13
1919     .sp
1920 ph10 654 A 4-byte character has a value greater than 0x10fff; these code points are
1921 ph10 598 excluded by RFC 3629.
1922 ph10 654 .sp
1923 ph10 598 PCRE_UTF8_ERR14
1924     .sp
1925     A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
1926 ph10 654 code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
1927 ph10 598 from UTF-8.
1928 ph10 654 .sp
1929 ph10 598 PCRE_UTF8_ERR15
1930     PCRE_UTF8_ERR16
1931     PCRE_UTF8_ERR17
1932     PCRE_UTF8_ERR18
1933     PCRE_UTF8_ERR19
1934     .sp
1935 ph10 654 A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
1936     value that can be represented by fewer bytes, which is invalid. For example,
1937 ph10 598 the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
1938     one byte.
1939     .sp
1940     PCRE_UTF8_ERR20
1941     .sp
1942 ph10 654 The two most significant bits of the first byte of a character have the binary
1943     value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
1944 ph10 598 byte can only validly occur as the second or subsequent byte of a multi-byte
1945     character.
1946     .sp
1947     PCRE_UTF8_ERR21
1948     .sp
1949     The first byte of a character has the value 0xfe or 0xff. These values can
1950     never occur in a valid UTF-8 string.
1951     .
1952     .
1953 nigel 75 .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1954 nigel 63 .rs
1955     .sp
1956 nigel 75 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1957 nigel 63 .ti +5n
1958 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1959 nigel 63 .ti +5n
1960 nigel 75 .B int \fIbuffersize\fP);
1961 nigel 63 .PP
1962 nigel 75 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1963 nigel 63 .ti +5n
1964 nigel 75 .B int \fIstringcount\fP, int \fIstringnumber\fP,
1965 nigel 63 .ti +5n
1966 nigel 75 .B const char **\fIstringptr\fP);
1967 nigel 63 .PP
1968 nigel 75 .B int pcre_get_substring_list(const char *\fIsubject\fP,
1969 nigel 63 .ti +5n
1970 nigel 75 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1971 nigel 63 .PP
1972     Captured substrings can be accessed directly by using the offsets returned by
1973 nigel 75 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1974     \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1975     \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1976 nigel 63 as new, separate, zero-terminated strings. These functions identify substrings
1977     by number. The next section describes functions for extracting named
1978 nigel 91 substrings.
1979 nigel 75 .P
1980 nigel 91 A substring that contains a binary zero is correctly extracted and has a
1981     further zero added on the end, but the result is not, of course, a C string.
1982     However, you can process such a string by referring to the length that is
1983     returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1984     Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1985     for handling strings containing binary zeros, because the end of the final
1986     string is not independently indicated.
1987     .P
1988 nigel 63 The first three arguments are the same for all three of these functions:
1989 nigel 75 \fIsubject\fP is the subject string that has just been successfully matched,
1990     \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1991     \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1992 nigel 63 captured by the match, including the substring that matched the entire regular
1993 nigel 75 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1994     than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1995     space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1996     number of elements in the vector divided by three.
1997     .P
1998     The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1999     extract a single substring, whose number is given as \fIstringnumber\fP. A
2000     value of zero extracts the substring that matched the entire pattern, whereas
2001     higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2002     the string is placed in \fIbuffer\fP, whose length is given by
2003     \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2004     obtained via \fBpcre_malloc\fP, and its address is returned via
2005     \fIstringptr\fP. The yield of the function is the length of the string, not
2006 nigel 93 including the terminating zero, or one of these error codes:
2007 nigel 75 .sp
2008 nigel 63 PCRE_ERROR_NOMEMORY (-6)
2009 nigel 75 .sp
2010     The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2011     memory failed for \fBpcre_get_substring()\fP.
2012     .sp
2013 nigel 63 PCRE_ERROR_NOSUBSTRING (-7)
2014 nigel 75 .sp
2015     There is no substring whose number is \fIstringnumber\fP.
2016     .P
2017     The \fBpcre_get_substring_list()\fP function extracts all available substrings
2018 nigel 63 and builds a list of pointers to them. All this is done in a single block of
2019 nigel 75 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2020     is returned via \fIlistptr\fP, which is also the start of the list of string
2021 nigel 63 pointers. The end of the list is marked by a NULL pointer. The yield of the
2022 nigel 93 function is zero if all went well, or the error code
2023 nigel 75 .sp
2024 nigel 63 PCRE_ERROR_NOMEMORY (-6)
2025 nigel 75 .sp
2026 nigel 63 if the attempt to get the memory block failed.
2027 nigel 75 .P
2028 nigel 63 When any of these functions encounter a substring that is unset, which can
2029 nigel 75 happen when capturing subpattern number \fIn+1\fP matches some part of the
2030     subject, but subpattern \fIn\fP has not been used at all, they return an empty
2031 nigel 63 string. This can be distinguished from a genuine zero-length substring by
2032 nigel 75 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2033 nigel 63 substrings.
2034 nigel 75 .P
2035     The two convenience functions \fBpcre_free_substring()\fP and
2036     \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2037     a previous call of \fBpcre_get_substring()\fP or
2038     \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2039     the function pointed to by \fBpcre_free\fP, which of course could be called
2040 nigel 63 directly from a C program. However, PCRE is used in some situations where it is
2041 nigel 91 linked via a special interface to another programming language that cannot use
2042 nigel 75 \fBpcre_free\fP directly; it is for these cases that the functions are
2043 nigel 63 provided.
2044 nigel 75 .
2045     .
2046     .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2047 nigel 63 .rs
2048     .sp
2049 nigel 75 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2050 nigel 63 .ti +5n
2051 nigel 75 .B const char *\fIname\fP);
2052 nigel 63 .PP
2053 nigel 75 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2054 nigel 63 .ti +5n
2055 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
2056     .ti +5n
2057     .B int \fIstringcount\fP, const char *\fIstringname\fP,
2058     .ti +5n
2059     .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2060 nigel 63 .PP
2061 nigel 75 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
2062 nigel 63 .ti +5n
2063 nigel 75 .B const char *\fIsubject\fP, int *\fIovector\fP,
2064 nigel 63 .ti +5n
2065 nigel 75 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2066 nigel 63 .ti +5n
2067 nigel 75 .B const char **\fIstringptr\fP);
2068 nigel 63 .PP
2069 nigel 75 To extract a substring by name, you first have to find associated number.
2070     For example, for this pattern
2071     .sp
2072 nigel 93 (a+)b(?<xxx>\ed+)...
2073 nigel 75 .sp
2074 nigel 91 the number of the subpattern called "xxx" is 2. If the name is known to be
2075     unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2076     calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2077     pattern, and the second is the name. The yield of the function is the
2078 nigel 75 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2079     that name.
2080     .P
2081     Given the number, you can extract the substring directly, or use one of the
2082     functions described in the previous section. For convenience, there are also
2083     two functions that do the whole job.
2084     .P
2085 nigel 91 Most of the arguments of \fBpcre_copy_named_substring()\fP and
2086     \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2087 nigel 75 functions that extract by number. As these are described in the previous
2088     section, they are not re-described here. There are just two differences:
2089     .P
2090 nigel 63 First, instead of a substring number, a substring name is given. Second, there
2091     is an extra argument, given at the start, which is a pointer to the compiled
2092     pattern. This is needed in order to gain access to the name-to-number
2093     translation table.
2094 nigel 75 .P
2095     These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2096 ph10 127 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2097     appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2098 ph10 128 the behaviour may not be what you want (see the next section).
2099 ph10 385 .P
2100 ph10 457 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2101     subpatterns with the same number, as described in the
2102     .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2103     .\" </a>
2104     section on duplicate subpattern numbers
2105     .\"
2106     in the
2107     .\" HREF
2108     \fBpcrepattern\fP
2109     .\"
2110     page, you cannot use names to distinguish the different subpatterns, because
2111     names are not included in the compiled code. The matching process uses only
2112     numbers. For this reason, the use of different names for subpatterns of the
2113     same number causes an error at compile time.
2114 nigel 77 .
2115 nigel 91 .SH "DUPLICATE SUBPATTERN NAMES"
2116     .rs
2117     .sp
2118     .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2119     .ti +5n
2120     .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2121     .PP
2122     When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2123 ph10 457 are not required to be unique. (Duplicate names are always allowed for
2124     subpatterns with the same number, created by using the (?| feature. Indeed, if
2125     such subpatterns are named, they are required to use the same names.)
2126     .P
2127     Normally, patterns with duplicate names are such that in any one match, only
2128     one of the named subpatterns participates. An example is shown in the
2129 nigel 91 .\" HREF
2130     \fBpcrepattern\fP
2131     .\"
2132 ph10 208 documentation.
2133 ph10 203 .P
2134     When duplicates are present, \fBpcre_copy_named_substring()\fP and
2135     \fBpcre_get_named_substring()\fP return the first substring corresponding to
2136     the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2137     returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2138     returns one of the numbers that are associated with the name, but it is not
2139     defined which it is.
2140     .P
2141 nigel 91 If you want to get full details of all captured substrings for a given name,
2142     you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2143     argument is the compiled pattern, and the second is the name. The third and
2144     fourth are pointers to variables which are updated by the function. After it
2145     has run, they point to the first and last entries in the name-to-number table
2146     for the given name. The function itself returns the length of each entry, or
2147 nigel 93 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2148 ph10 598 described above in the section entitled \fIInformation about a pattern\fP
2149     .\" HTML <a href="#infoaboutpattern">
2150     .\" </a>
2151     above.
2152     .\"
2153 nigel 93 Given all the relevant entries for the name, you can extract each of their
2154     numbers, and hence the captured data, if any.
2155 nigel 91 .
2156     .
2157 nigel 77 .SH "FINDING ALL POSSIBLE MATCHES"
2158     .rs
2159     .sp
2160     The traditional matching function uses a similar algorithm to Perl, which stops
2161     when it finds the first match, starting at a given point in the subject. If you
2162     want to find all possible matches, or the longest possible match, consider
2163     using the alternative matching function (see below) instead. If you cannot use
2164     the alternative function, but still need to find all possible matches, you
2165     can kludge it up by making use of the callout facility, which is described in
2166     the
2167     .\" HREF
2168     \fBpcrecallout\fP
2169     .\"
2170     documentation.
2171 nigel 75 .P
2172 nigel 77 What you have to do is to insert a callout right at the end of the pattern.
2173     When your callout function is called, extract and save the current matched
2174     substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2175     other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2176     will yield PCRE_ERROR_NOMATCH.
2177     .
2178     .
2179     .\" HTML <a name="dfamatch"></a>
2180     .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2181     .rs
2182     .sp
2183     .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2184     .ti +5n
2185     .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2186     .ti +5n
2187     .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2188     .ti +5n
2189     .B int *\fIworkspace\fP, int \fIwscount\fP);
2190     .P
2191     The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2192 nigel 93 a compiled pattern, using a matching algorithm that scans the subject string
2193     just once, and does not backtrack. This has different characteristics to the
2194     normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2195     patterns are not supported. Nevertheless, there are times when this kind of
2196 ph10 461 matching can be useful. For a discussion of the two matching algorithms, and a
2197 ph10 435 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2198 nigel 77 .\" HREF
2199     \fBpcrematching\fP
2200     .\"
2201     documentation.
2202     .P
2203     The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2204     \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2205     different way, and this is described below. The other common arguments are used
2206     in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2207     here.
2208     .P
2209     The two additional arguments provide workspace for the function. The workspace
2210     vector should contain at least 20 elements. It is used for keeping track of
2211     multiple paths through the pattern tree. More workspace will be needed for
2212 nigel 91 patterns and subjects where there are a lot of potential matches.
2213 nigel 77 .P
2214 nigel 87 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2215 nigel 77 .sp
2216     int rc;
2217     int ovector[10];
2218     int wspace[20];
2219 nigel 87 rc = pcre_dfa_exec(
2220 nigel 77 re, /* result of pcre_compile() */
2221     NULL, /* we didn't study the pattern */
2222     "some string", /* the subject string */
2223     11, /* the length of the subject string */
2224     0, /* start at offset 0 in the subject */
2225     0, /* default options */
2226     ovector, /* vector of integers for substring information */
2227     10, /* number of elements (NOT size in bytes) */
2228     wspace, /* working space vector */
2229     20); /* number of elements (NOT size in bytes) */
2230     .
2231     .SS "Option bits for \fBpcre_dfa_exec()\fP"
2232     .rs
2233     .sp
2234     The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2235 nigel 91 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2236 ph10 442 PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2237 ph10 542 PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2238     PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2239     All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2240     so their description is not repeated here.
2241 nigel 77 .sp
2242 ph10 428 PCRE_PARTIAL_HARD
2243 ph10 461 PCRE_PARTIAL_SOFT
2244 nigel 77 .sp
2245 ph10 428 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2246     details are slightly different. When PCRE_PARTIAL_HARD is set for
2247     \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2248     is reached and there is still at least one matching possibility that requires
2249     additional characters. This happens even if some complete matches have also
2250     been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2251     is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2252     there have been no complete matches, but there is still at least one matching
2253 ph10 435 possibility. The portion of the string that was inspected when the longest
2254     partial match was found is set as the first matching string in both cases.
2255 ph10 553 There is a more detailed discussion of partial and multi-segment matching, with
2256     examples, in the
2257     .\" HREF
2258     \fBpcrepartial\fP
2259     .\"
2260     documentation.
2261 nigel 77 .sp
2262     PCRE_DFA_SHORTEST
2263     .sp
2264     Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2265 nigel 93 soon as it has found one match. Because of the way the alternative algorithm
2266     works, this is necessarily the shortest possible match at the first possible
2267     matching point in the subject string.
2268 nigel 77 .sp
2269     PCRE_DFA_RESTART
2270     .sp
2271 ph10 428 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2272     again, with additional subject characters, and have it continue with the same
2273     match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2274     \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2275     before because data about the match so far is left in them after a partial
2276     match. There is more discussion of this facility in the
2277 nigel 77 .\" HREF
2278     \fBpcrepartial\fP
2279     .\"
2280     documentation.
2281     .
2282 ph10 598 .
2283 nigel 77 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2284     .rs
2285     .sp
2286     When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2287     substring in the subject. Note, however, that all the matches from one run of
2288     the function start at the same point in the subject. The shorter matches are
2289     all initial substrings of the longer matches. For example, if the pattern
2290     .sp
2291     <.*>
2292     .sp
2293     is matched against the string
2294     .sp
2295     This is <something> <something else> <something further> no more
2296     .sp
2297     the three matched strings are
2298     .sp
2299     <something>
2300     <something> <something else>
2301     <something> <something else> <something further>
2302     .sp
2303     On success, the yield of the function is a number greater than zero, which is
2304     the number of matched substrings. The substrings themselves are returned in
2305     \fIovector\fP. Each string uses two elements; the first is the offset to the
2306 nigel 93 start, and the second is the offset to the end. In fact, all the strings have
2307     the same start offset. (Space could have been saved by giving this only once,
2308     but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2309     returns data, even though the meaning of the strings is different.)
2310 nigel 77 .P
2311     The strings are returned in reverse order of length; that is, the longest
2312     matching string is given first. If there were too many matches to fit into
2313     \fIovector\fP, the yield of the function is zero, and the vector is filled with
2314     the longest matches.
2315     .
2316 ph10 598 .
2317 nigel 77 .SS "Error returns from \fBpcre_dfa_exec()\fP"
2318     .rs
2319     .sp
2320     The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2321     Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2322     described
2323     .\" HTML <a href="#errorlist">
2324     .\" </a>
2325     above.
2326     .\"
2327     There are in addition the following errors that are specific to
2328     \fBpcre_dfa_exec()\fP:
2329     .sp
2330     PCRE_ERROR_DFA_UITEM (-16)
2331     .sp
2332     This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2333     that it does not support, for instance, the use of \eC or a back reference.
2334     .sp
2335     PCRE_ERROR_DFA_UCOND (-17)
2336     .sp
2337 nigel 93 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2338     uses a back reference for the condition, or a test for recursion in a specific
2339     group. These are not supported.
2340 nigel 77 .sp
2341     PCRE_ERROR_DFA_UMLIMIT (-18)
2342     .sp
2343     This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2344     block that contains a setting of the \fImatch_limit\fP field. This is not
2345     supported (it is meaningless).
2346     .sp
2347     PCRE_ERROR_DFA_WSSIZE (-19)
2348     .sp
2349     This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2350     \fIworkspace\fP vector.
2351     .sp
2352     PCRE_ERROR_DFA_RECURSE (-20)
2353     .sp
2354     When a recursive subpattern is processed, the matching function calls itself
2355     recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2356     error is given if the output vector is not large enough. This should be
2357     extremely rare, as a vector of size 1000 is used.
2358 nigel 93 .
2359     .
2360     .SH "SEE ALSO"
2361     .rs
2362     .sp
2363     \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2364     \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2365     \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2366 ph10 99 .
2367     .
2368     .SH AUTHOR
2369     .rs
2370     .sp
2371     .nf
2372     Philip Hazel
2373     University Computing Service
2374     Cambridge CB2 3QH, England.
2375     .fi
2376     .
2377     .
2378     .SH REVISION
2379     .rs
2380     .sp
2381     .nf
2382 ph10 642 Last updated: 28 July 2011
2383 ph10 598 Copyright (c) 1997-2011 University of Cambridge.
2384 ph10 99 .fi

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