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Allow fixed-length subroutine calls in lookbehinds.

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

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