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


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