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Revision 230 - (hide annotations) (download)
Mon Sep 10 13:23:56 2007 UTC (7 years ago) by ph10
File size: 82595 byte(s)
(1) Move internal flags out of the options field, to make room.
(2) \r and \n must be explicit to trigger the special CRLF handline exception.
(3) (?J) at the start now sets JCHANGED as well as DUPNAMES.

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

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