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1 nigel 63 .TH PCRE 3
2     .SH NAME
3     PCRE - Perl-compatible regular expressions
5     .rs
6     .sp
7     .B #include <pcre.h>
8     .PP
9     .SM
10     .br
11     .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,
12     .ti +5n
13     .B const char **\fIerrptr\fR, int *\fIerroffset\fR,
14     .ti +5n
15     .B const unsigned char *\fItableptr\fR);
16     .PP
17     .br
18     .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,
19     .ti +5n
20     .B const char **\fIerrptr\fR);
21     .PP
22     .br
23     .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
24     .ti +5n
25     .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,
26     .ti +5n
27     .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);
28     .PP
29     .br
30     .B int pcre_copy_named_substring(const pcre *\fIcode\fR,
31     .ti +5n
32     .B const char *\fIsubject\fR, int *\fIovector\fR,
33     .ti +5n
34     .B int \fIstringcount\fR, const char *\fIstringname\fR,
35     .ti +5n
36     .B char *\fIbuffer\fR, int \fIbuffersize\fR);
37     .PP
38     .br
39     .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,
40     .ti +5n
41     .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,
42     .ti +5n
43     .B int \fIbuffersize\fR);
44     .PP
45     .br
46     .B int pcre_get_named_substring(const pcre *\fIcode\fR,
47     .ti +5n
48     .B const char *\fIsubject\fR, int *\fIovector\fR,
49     .ti +5n
50     .B int \fIstringcount\fR, const char *\fIstringname\fR,
51     .ti +5n
52     .B const char **\fIstringptr\fR);
53     .PP
54     .br
55     .B int pcre_get_stringnumber(const pcre *\fIcode\fR,
56     .ti +5n
57     .B const char *\fIname\fR);
58     .PP
59     .br
60     .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,
61     .ti +5n
62     .B int \fIstringcount\fR, int \fIstringnumber\fR,
63     .ti +5n
64     .B const char **\fIstringptr\fR);
65     .PP
66     .br
67     .B int pcre_get_substring_list(const char *\fIsubject\fR,
68     .ti +5n
69     .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"
70     .PP
71     .br
72     .B void pcre_free_substring(const char *\fIstringptr\fR);
73     .PP
74     .br
75     .B void pcre_free_substring_list(const char **\fIstringptr\fR);
76     .PP
77     .br
78     .B const unsigned char *pcre_maketables(void);
79     .PP
80     .br
81     .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
82     .ti +5n
83     .B int \fIwhat\fR, void *\fIwhere\fR);
84     .PP
85     .br
86     .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int
87     .B *\fIfirstcharptr\fR);
88     .PP
89     .br
90     .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);
91     .PP
92     .br
93     .B char *pcre_version(void);
94     .PP
95     .br
96     .B void *(*pcre_malloc)(size_t);
97     .PP
98     .br
99     .B void (*pcre_free)(void *);
100     .PP
101     .br
102 nigel 73 .B void *(*pcre_stack_malloc)(size_t);
103     .PP
104     .br
105     .B void (*pcre_stack_free)(void *);
106     .PP
107     .br
108 nigel 63 .B int (*pcre_callout)(pcre_callout_block *);
110     .SH PCRE API
111     .rs
112     .sp
113     PCRE has its own native API, which is described in this document. There is also
114     a set of wrapper functions that correspond to the POSIX regular expression API.
115     These are described in the \fBpcreposix\fR documentation.
117     The native API function prototypes are defined in the header file \fBpcre.h\fR,
118     and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be
119     accessed by adding \fB-lpcre\fR to the command for linking an application which
120     calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to
121     contain the major and minor release numbers for the library. Applications can
122     use these to include support for different releases.
124     The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR
125     are used for compiling and matching regular expressions. A sample program that
126     demonstrates the simplest way of using them is given in the file
127     \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.
129     There are convenience functions for extracting captured substrings from a
130     matched subject string. They are:
132     \fBpcre_copy_substring()\fR
133     \fBpcre_copy_named_substring()\fR
134     \fBpcre_get_substring()\fR
135     \fBpcre_get_named_substring()\fR
136     \fBpcre_get_substring_list()\fR
138     \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also
139     provided, to free the memory used for extracted strings.
141     The function \fBpcre_maketables()\fR is used (optionally) to build a set of
142     character tables in the current locale for passing to \fBpcre_compile()\fR.
144     The function \fBpcre_fullinfo()\fR is used to find out information about a
145     compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only
146     some of the available information, but is retained for backwards compatibility.
147     The function \fBpcre_version()\fR returns a pointer to a string containing the
148     version of PCRE and its date of release.
150     The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain
151     the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions
152     respectively. PCRE calls the memory management functions via these variables,
153     so a calling program can replace them if it wishes to intercept the calls. This
154     should be done before calling any PCRE functions.
156 nigel 73 The global variables \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are also
157     indirections to memory management functions. These special functions are used
158     only when PCRE is compiled to use the heap for remembering data, instead of
159     recursive function calls. This is a non-standard way of building PCRE, for use
160     in environments that have limited stacks. Because of the greater use of memory
161     management, it runs more slowly. Separate functions are provided so that
162     special-purpose external code can be used for this case. When used, these
163     functions are always called in a stack-like manner (last obtained, first
164     freed), and always for memory blocks of the same size.
166 nigel 63 The global variable \fBpcre_callout\fR initially contains NULL. It can be set
167     by the caller to a "callout" function, which PCRE will then call at specified
168     points during a matching operation. Details are given in the \fBpcrecallout\fR
169     documentation.
172     .rs
173     .sp
174     The PCRE functions can be used in multi-threading applications, with the
175 nigel 73 proviso that the memory management functions pointed to by \fBpcre_malloc\fR,
176     \fBpcre_free\fR, \fBpcre_stack_malloc\fR, and \fBpcre_stack_free\fR, and the
177     callout function pointed to by \fBpcre_callout\fR, are shared by all threads.
178 nigel 63
179     The compiled form of a regular expression is not altered during matching, so
180     the same compiled pattern can safely be used by several threads at once.
183     .rs
184     .sp
185     .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);
186     .PP
187     The function \fBpcre_config()\fR makes it possible for a PCRE client to
188     discover which optional features have been compiled into the PCRE library. The
189     .\" HREF
190     \fBpcrebuild\fR
191     .\"
192     documentation has more details about these optional features.
194     The first argument for \fBpcre_config()\fR is an integer, specifying which
195     information is required; the second argument is a pointer to a variable into
196     which the information is placed. The following information is available:
200     The output is an integer that is set to one if UTF-8 support is available;
201     otherwise it is set to zero.
205     The output is an integer that is set to the value of the code that is used for
206     the newline character. It is either linefeed (10) or carriage return (13), and
207     should normally be the standard character for your operating system.
211     The output is an integer that contains the number of bytes used for internal
212     linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
213     allow larger regular expressions to be compiled, at the expense of slower
214     matching. The default value of 2 is sufficient for all but the most massive
215     patterns, since it allows the compiled pattern to be up to 64K in size.
219     The output is an integer that contains the threshold above which the POSIX
220     interface uses \fBmalloc()\fR for output vectors. Further details are given in
221     the \fBpcreposix\fR documentation.
225     The output is an integer that gives the default limit for the number of
226     internal matching function calls in a \fBpcre_exec()\fR execution. Further
227     details are given with \fBpcre_exec()\fR below.
231     The output is an integer that is set to one if internal recursion is
232     implemented by recursive function calls that use the stack to remember their
233     state. This is the usual way that PCRE is compiled. The output is zero if PCRE
234     was compiled to use blocks of data on the heap instead of recursive function
235     calls. In this case, \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are
236     called to manage memory blocks on the heap, thus avoiding the use of the stack.
239     .rs
240     .sp
241     .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,
242     .ti +5n
243     .B const char **\fIerrptr\fR, int *\fIerroffset\fR,
244     .ti +5n
245     .B const unsigned char *\fItableptr\fR);
246     .PP
248     The function \fBpcre_compile()\fR is called to compile a pattern into an
249     internal form. The pattern is a C string terminated by a binary zero, and
250     is passed in the argument \fIpattern\fR. A pointer to a single block of memory
251     that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled
252     code and related data. The \fBpcre\fR type is defined for the returned block;
253     this is a typedef for a structure whose contents are not externally defined. It
254     is up to the caller to free the memory when it is no longer required.
256     Although the compiled code of a PCRE regex is relocatable, that is, it does not
257     depend on memory location, the complete \fBpcre\fR data block is not
258     fully relocatable, because it contains a copy of the \fItableptr\fR argument,
259     which is an address (see below).
261     The \fIoptions\fR argument contains independent bits that affect the
262     compilation. It should be zero if no options are required. Some of the options,
263     in particular, those that are compatible with Perl, can also be set and unset
264     from within the pattern (see the detailed description of regular expressions
265     in the \fBpcrepattern\fR documentation). For these options, the contents of the
266     \fIoptions\fR argument specifies their initial settings at the start of
267     compilation and execution. The PCRE_ANCHORED option can be set at the time of
268     matching as well as at compile time.
270     If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.
271     Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns
272     NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual
273     error message. The offset from the start of the pattern to the character where
274     the error was discovered is placed in the variable pointed to by
275     \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.
277     If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of
278     character tables which are built when it is compiled, using the default C
279     locale. Otherwise, \fItableptr\fR must be the result of a call to
280     \fBpcre_maketables()\fR. See the section on locale support below.
282     This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:
284     pcre *re;
285     const char *error;
286     int erroffset;
287     re = pcre_compile(
288     "^A.*Z", /* the pattern */
289     0, /* default options */
290     &error, /* for error message */
291     &erroffset, /* for error offset */
292     NULL); /* use default character tables */
294     The following option bits are defined:
298     If this bit is set, the pattern is forced to be "anchored", that is, it is
299     constrained to match only at the first matching point in the string which is
300     being searched (the "subject string"). This effect can also be achieved by
301     appropriate constructs in the pattern itself, which is the only way to do it in
302     Perl.
306     If this bit is set, letters in the pattern match both upper and lower case
307     letters. It is equivalent to Perl's /i option, and it can be changed within a
308     pattern by a (?i) option setting.
312     If this bit is set, a dollar metacharacter in the pattern matches only at the
313     end of the subject string. Without this option, a dollar also matches
314     immediately before the final character if it is a newline (but not before any
315     other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is
316     set. There is no equivalent to this option in Perl, and no way to set it within
317     a pattern.
321     If this bit is set, a dot metacharater in the pattern matches all characters,
322     including newlines. Without it, newlines are excluded. This option is
323     equivalent to Perl's /s option, and it can be changed within a pattern by a
324     (?s) option setting. A negative class such as [^a] always matches a newline
325     character, independent of the setting of this option.
329     If this bit is set, whitespace data characters in the pattern are totally
330     ignored except when escaped or inside a character class. Whitespace does not
331     include the VT character (code 11). In addition, characters between an
332     unescaped # outside a character class and the next newline character,
333     inclusive, are also ignored. This is equivalent to Perl's /x option, and it can
334     be changed within a pattern by a (?x) option setting.
336     This option makes it possible to include comments inside complicated patterns.
337     Note, however, that this applies only to data characters. Whitespace characters
338     may never appear within special character sequences in a pattern, for example
339     within the sequence (?( which introduces a conditional subpattern.
341     PCRE_EXTRA
343     This option was invented in order to turn on additional functionality of PCRE
344     that is incompatible with Perl, but it is currently of very little use. When
345     set, any backslash in a pattern that is followed by a letter that has no
346     special meaning causes an error, thus reserving these combinations for future
347     expansion. By default, as in Perl, a backslash followed by a letter with no
348     special meaning is treated as a literal. There are at present no other features
349     controlled by this option. It can also be set by a (?X) option setting within a
350     pattern.
354     By default, PCRE treats the subject string as consisting of a single "line" of
355     characters (even if it actually contains several newlines). The "start of line"
356     metacharacter (^) matches only at the start of the string, while the "end of
357     line" metacharacter ($) matches only at the end of the string, or before a
358     terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
359     Perl.
361     When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
362     match immediately following or immediately before any newline in the subject
363     string, respectively, as well as at the very start and end. This is equivalent
364     to Perl's /m option, and it can be changed within a pattern by a (?m) option
365     setting. If there are no "\\n" characters in a subject string, or no
366     occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
370     If this option is set, it disables the use of numbered capturing parentheses in
371     the pattern. Any opening parenthesis that is not followed by ? behaves as if it
372     were followed by ?: but named parentheses can still be used for capturing (and
373     they acquire numbers in the usual way). There is no equivalent of this option
374     in Perl.
378     This option inverts the "greediness" of the quantifiers so that they are not
379     greedy by default, but become greedy if followed by "?". It is not compatible
380     with Perl. It can also be set by a (?U) option setting within the pattern.
382     PCRE_UTF8
384     This option causes PCRE to regard both the pattern and the subject as strings
385     of UTF-8 characters instead of single-byte character strings. However, it is
386     available only if PCRE has been built to include UTF-8 support. If not, the use
387     of this option provokes an error. Details of how this option changes the
388     behaviour of PCRE are given in the
389     .\" HTML <a href="pcre.html#utf8support">
390     .\" </a>
391     section on UTF-8 support
392     .\"
393     in the main
394     .\" HREF
395     \fBpcre\fR
396     .\"
397     page.
399 nigel 71 PCRE_NO_UTF8_CHECK
401     When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
402     automatically checked. If an invalid UTF-8 sequence of bytes is found,
403     \fBpcre_compile()\fR returns an error. If you already know that your pattern is
404     valid, and you want to skip this check for performance reasons, you can set the
405     PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
406     UTF-8 string as a pattern is undefined. It may cause your program to crash.
407     Note that there is a similar option for suppressing the checking of subject
408     strings passed to \fBpcre_exec()\fR.
412     .rs
413     .sp
414     .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,
415     .ti +5n
416     .B const char **\fIerrptr\fR);
417     .PP
418     When a pattern is going to be used several times, it is worth spending more
419     time analyzing it in order to speed up the time taken for matching. The
420     function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first
421     argument. If studing the pattern produces additional information that will help
422     speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR
423     block, in which the \fIstudy_data\fR field points to the results of the study.
425     The returned value from a \fBpcre_study()\fR can be passed directly to
426     \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other
427     fields that can be set by the caller before the block is passed; these are
428     described below. If studying the pattern does not produce any additional
429     information, \fBpcre_study()\fR returns NULL. In that circumstance, if the
430     calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it
431     must set up its own \fBpcre_extra\fR block.
433     The second argument contains option bits. At present, no options are defined
434     for \fBpcre_study()\fR, and this argument should always be zero.
436     The third argument for \fBpcre_study()\fR is a pointer for an error message. If
437     studying succeeds (even if no data is returned), the variable it points to is
438     set to NULL. Otherwise it points to a textual error message. You should
439     therefore test the error pointer for NULL after calling \fBpcre_study()\fR, to
440     be sure that it has run successfully.
442     This is a typical call to \fBpcre_study\fR():
444     pcre_extra *pe;
445     pe = pcre_study(
446     re, /* result of pcre_compile() */
447     0, /* no options exist */
448     &error); /* set to NULL or points to a message */
450     At present, studying a pattern is useful only for non-anchored patterns that do
451     not have a single fixed starting character. A bitmap of possible starting
452     characters is created.
454     .\" HTML <a name="localesupport"></a>
456     .rs
457     .sp
458     PCRE handles caseless matching, and determines whether characters are letters,
459     digits, or whatever, by reference to a set of tables. When running in UTF-8
460     mode, this applies only to characters with codes less than 256. The library
461     contains a default set of tables that is created in the default C locale when
462     PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR
463     is NULL, and is sufficient for many applications.
465     An alternative set of tables can, however, be supplied. Such tables are built
466     by calling the \fBpcre_maketables()\fR function, which has no arguments, in the
467     relevant locale. The result can then be passed to \fBpcre_compile()\fR as often
468     as necessary. For example, to build and use tables that are appropriate for the
469     French locale (where accented characters with codes greater than 128 are
470     treated as letters), the following code could be used:
472     setlocale(LC_CTYPE, "fr");
473     tables = pcre_maketables();
474     re = pcre_compile(..., tables);
476     The tables are built in memory that is obtained via \fBpcre_malloc\fR. The
477     pointer that is passed to \fBpcre_compile\fR is saved with the compiled
478     pattern, and the same tables are used via this pointer by \fBpcre_study()\fR
479     and \fBpcre_exec()\fR. Thus, for any single pattern, compilation, studying and
480     matching all happen in the same locale, but different patterns can be compiled
481     in different locales. It is the caller's responsibility to ensure that the
482     memory containing the tables remains available for as long as it is needed.
485     .rs
486     .sp
487     .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
488     .ti +5n
489     .B int \fIwhat\fR, void *\fIwhere\fR);
490     .PP
491     The \fBpcre_fullinfo()\fR function returns information about a compiled
492     pattern. It replaces the obsolete \fBpcre_info()\fR function, which is
493     nevertheless retained for backwards compability (and is documented below).
495     The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled
496     pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if
497     the pattern was not studied. The third argument specifies which piece of
498     information is required, and the fourth argument is a pointer to a variable
499     to receive the data. The yield of the function is zero for success, or one of
500     the following negative numbers:
502     PCRE_ERROR_NULL the argument \fIcode\fR was NULL
503     the argument \fIwhere\fR was NULL
504     PCRE_ERROR_BADMAGIC the "magic number" was not found
505     PCRE_ERROR_BADOPTION the value of \fIwhat\fR was invalid
507     Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the
508     compiled pattern:
510     int rc;
511     unsigned long int length;
512     rc = pcre_fullinfo(
513     re, /* result of pcre_compile() */
514     pe, /* result of pcre_study(), or NULL */
515     PCRE_INFO_SIZE, /* what is required */
516     &length); /* where to put the data */
518     The possible values for the third argument are defined in \fBpcre.h\fR, and are
519     as follows:
523     Return the number of the highest back reference in the pattern. The fourth
524     argument should point to an \fBint\fR variable. Zero is returned if there are
525     no back references.
529     Return the number of capturing subpatterns in the pattern. The fourth argument
530     should point to an \fbint\fR variable.
534     Return information about the first byte of any matched string, for a
535     non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the
536     old name is still recognized for backwards compatibility.)
538     If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),
539     it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either
541     (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
542     starts with "^", or
544     (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
545     (if it were set, the pattern would be anchored),
547     -1 is returned, indicating that the pattern matches only at the start of a
548     subject string or after any newline within the string. Otherwise -2 is
549     returned. For anchored patterns, -2 is returned.
553     If the pattern was studied, and this resulted in the construction of a 256-bit
554     table indicating a fixed set of bytes for the first byte in any matching
555     string, a pointer to the table is returned. Otherwise NULL is returned. The
556     fourth argument should point to an \fBunsigned char *\fR variable.
560 nigel 65 Return the value of the rightmost literal byte that must exist in any matched
561     string, other than at its start, if such a byte has been recorded. The fourth
562     argument should point to an \fBint\fR variable. If there is no such byte, -1 is
563     returned. For anchored patterns, a last literal byte is recorded only if it
564     follows something of variable length. For example, for the pattern
565     /^a\\d+z\\d+/ the returned value is "z", but for /^a\\dz\\d/ the returned value
566     is -1.
567 nigel 63
572     PCRE supports the use of named as well as numbered capturing parentheses. The
573     names are just an additional way of identifying the parentheses, which still
574     acquire a number. A caller that wants to extract data from a named subpattern
575     must convert the name to a number in order to access the correct pointers in
576     the output vector (described with \fBpcre_exec()\fR below). In order to do
577     this, it must first use these three values to obtain the name-to-number mapping
578     table for the pattern.
580     The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
581     the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
582     entry; both of these return an \fBint\fR value. The entry size depends on the
583     length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
584     entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry
585     are the number of the capturing parenthesis, most significant byte first. The
586     rest of the entry is the corresponding name, zero terminated. The names are in
587     alphabetical order. For example, consider the following pattern (assume
588     PCRE_EXTENDED is set, so white space - including newlines - is ignored):
590     (?P<date> (?P<year>(\\d\\d)?\\d\\d) -
591     (?P<month>\\d\\d) - (?P<day>\\d\\d) )
593     There are four named subpatterns, so the table has four entries, and each entry
594     in the table is eight bytes long. The table is as follows, with non-printing
595     bytes shows in hex, and undefined bytes shown as ??:
597     00 01 d a t e 00 ??
598     00 05 d a y 00 ?? ??
599     00 04 m o n t h 00
600     00 02 y e a r 00 ??
602     When writing code to extract data from named subpatterns, remember that the
603     length of each entry may be different for each compiled pattern.
607     Return a copy of the options with which the pattern was compiled. The fourth
608     argument should point to an \fBunsigned long int\fR variable. These option bits
609     are those specified in the call to \fBpcre_compile()\fR, modified by any
610     top-level option settings within the pattern itself.
612     A pattern is automatically anchored by PCRE if all of its top-level
613     alternatives begin with one of the following:
615     ^ unless PCRE_MULTILINE is set
616     \\A always
617     \\G always
618     .* if PCRE_DOTALL is set and there are no back
619     references to the subpattern in which .* appears
621     For such patterns, the PCRE_ANCHORED bit is set in the options returned by
622     \fBpcre_fullinfo()\fR.
626     Return the size of the compiled pattern, that is, the value that was passed as
627     the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to
628     place the compiled data. The fourth argument should point to a \fBsize_t\fR
629     variable.
633     Returns the size of the data block pointed to by the \fIstudy_data\fR field in
634     a \fBpcre_extra\fR block. That is, it is the value that was passed to
635     \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data
636     created by \fBpcre_study()\fR. The fourth argument should point to a
637     \fBsize_t\fR variable.
640     .rs
641     .sp
642     .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int
643     .B *\fIfirstcharptr\fR);
644     .PP
645     The \fBpcre_info()\fR function is now obsolete because its interface is too
646     restrictive to return all the available data about a compiled pattern. New
647     programs should use \fBpcre_fullinfo()\fR instead. The yield of
648     \fBpcre_info()\fR is the number of capturing subpatterns, or one of the
649     following negative numbers:
651     PCRE_ERROR_NULL the argument \fIcode\fR was NULL
652     PCRE_ERROR_BADMAGIC the "magic number" was not found
654     If the \fIoptptr\fR argument is not NULL, a copy of the options with which the
655     pattern was compiled is placed in the integer it points to (see
656     PCRE_INFO_OPTIONS above).
658     If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,
659     it is used to pass back information about the first character of any matched
660     string (see PCRE_INFO_FIRSTBYTE above).
663     .rs
664     .sp
665     .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
666     .ti +5n
667     .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,
668     .ti +5n
669     .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);
670     .PP
671     The function \fBpcre_exec()\fR is called to match a subject string against a
672     pre-compiled pattern, which is passed in the \fIcode\fR argument. If the
673     pattern has been studied, the result of the study should be passed in the
674     \fIextra\fR argument.
676     Here is an example of a simple call to \fBpcre_exec()\fR:
678     int rc;
679     int ovector[30];
680     rc = pcre_exec(
681     re, /* result of pcre_compile() */
682     NULL, /* we didn't study the pattern */
683     "some string", /* the subject string */
684     11, /* the length of the subject string */
685     0, /* start at offset 0 in the subject */
686     0, /* default options */
687     ovector, /* vector for substring information */
688     30); /* number of elements in the vector */
690     If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR
691     data block. The \fBpcre_study()\fR function returns such a block (when it
692     doesn't return NULL), but you can also create one for yourself, and pass
693     additional information in it. The fields in the block are as follows:
695     unsigned long int \fIflags\fR;
696     void *\fIstudy_data\fR;
697     unsigned long int \fImatch_limit\fR;
698     void *\fIcallout_data\fR;
700     The \fIflags\fR field is a bitmap that specifies which of the other fields
701     are set. The flag bits are:
707     Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the
708     \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with
709     the appropriate flag bit. You should not set this yourself, but you can add to
710     the block by setting the other fields.
712     The \fImatch_limit\fR field provides a means of preventing PCRE from using up a
713     vast amount of resources when running patterns that are not going to match,
714     but which have a very large number of possibilities in their search trees. The
715     classic example is the use of nested unlimited repeats. Internally, PCRE uses a
716     function called \fBmatch()\fR which it calls repeatedly (sometimes
717     recursively). The limit is imposed on the number of times this function is
718     called during a match, which has the effect of limiting the amount of recursion
719     and backtracking that can take place. For patterns that are not anchored, the
720     count starts from zero for each position in the subject string.
722     The default limit for the library can be set when PCRE is built; the default
723     default is 10 million, which handles all but the most extreme cases. You can
724     reduce the default by suppling \fBpcre_exec()\fR with a \fRpcre_extra\fR block
725     in which \fImatch_limit\fR is set to a smaller value, and
726     PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fR field. If the limit is
727     exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.
729     The \fIpcre_callout\fR field is used in conjunction with the "callout" feature,
730     which is described in the \fBpcrecallout\fR documentation.
732     The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose
733     unused bits must be zero. This limits \fBpcre_exec()\fR to matching at the
734     first matching position. However, if a pattern was compiled with PCRE_ANCHORED,
735     or turned out to be anchored by virtue of its contents, it cannot be made
736     unachored at matching time.
738 nigel 71 When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8
739 nigel 73 string is automatically checked, and the value of \fIstartoffset\fR is also
740     checked to ensure that it points to the start of a UTF-8 character. If an
741     invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fR returns the error
742     PCRE_ERROR_BADUTF8. If \fIstartoffset\fR contains an invalid value,
743     PCRE_ERROR_BADUTF8_OFFSET is returned.
744 nigel 71
745 nigel 73 If you already know that your subject is valid, and you want to skip these
746     checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
747     calling \fBpcre_exec()\fR. You might want to do this for the second and
748     subsequent calls to \fBpcre_exec()\fR if you are making repeated calls to find
749     all the matches in a single subject string. However, you should be sure that
750     the value of \fIstartoffset\fR points to the start of a UTF-8 character. When
751     PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
752     subject, or a value of \fIstartoffset\fR that does not point to the start of a
753     UTF-8 character, is undefined. Your program may crash.
755 nigel 63 There are also three further options that can be set only at matching time:
759     The first character of the string is not the beginning of a line, so the
760     circumflex metacharacter should not match before it. Setting this without
761     PCRE_MULTILINE (at compile time) causes circumflex never to match.
765     The end of the string is not the end of a line, so the dollar metacharacter
766     should not match it nor (except in multiline mode) a newline immediately before
767     it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never
768     to match.
772     An empty string is not considered to be a valid match if this option is set. If
773     there are alternatives in the pattern, they are tried. If all the alternatives
774     match the empty string, the entire match fails. For example, if the pattern
776     a?b?
778     is applied to a string not beginning with "a" or "b", it matches the empty
779     string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
780     valid, so PCRE searches further into the string for occurrences of "a" or "b".
782     Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
783     of a pattern match of the empty string within its \fBsplit()\fR function, and
784     when using the /g modifier. It is possible to emulate Perl's behaviour after
785     matching a null string by first trying the match again at the same offset with
786     PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see
787     below) and trying an ordinary match again.
789     The subject string is passed to \fBpcre_exec()\fR as a pointer in
790 nigel 73 \fIsubject\fR, a length in \fIlength\fR, and a starting byte offset in
791 nigel 63 \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary
792     zero bytes. When the starting offset is zero, the search for a match starts at
793     the beginning of the subject, and this is by far the most common case.
795     If the pattern was compiled with the PCRE_UTF8 option, the subject must be a
796 nigel 73 sequence of bytes that is a valid UTF-8 string, and the starting offset must
797     point to the beginning of a UTF-8 character. If an invalid UTF-8 string or
798     offset is passed, an error (either PCRE_ERROR_BADUTF8 or
799     PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is
800     set, in which case PCRE's behaviour is not defined.
801 nigel 63
802     A non-zero starting offset is useful when searching for another match in the
803     same subject by calling \fBpcre_exec()\fR again after a previous success.
804     Setting \fIstartoffset\fR differs from just passing over a shortened string and
805     setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
806     lookbehind. For example, consider the pattern
808     \\Biss\\B
810     which finds occurrences of "iss" in the middle of words. (\\B matches only if
811     the current position in the subject is not a word boundary.) When applied to
812     the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first
813     occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the
814     subject, namely "issipi", it does not match, because \\B is always false at the
815     start of the subject, which is deemed to be a word boundary. However, if
816     \fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR
817     set to 4, it finds the second occurrence of "iss" because it is able to look
818     behind the starting point to discover that it is preceded by a letter.
820     If a non-zero starting offset is passed when the pattern is anchored, one
821     attempt to match at the given offset is tried. This can only succeed if the
822     pattern does not require the match to be at the start of the subject.
824     In general, a pattern matches a certain portion of the subject, and in
825     addition, further substrings from the subject may be picked out by parts of the
826     pattern. Following the usage in Jeffrey Friedl's book, this is called
827     "capturing" in what follows, and the phrase "capturing subpattern" is used for
828     a fragment of a pattern that picks out a substring. PCRE supports several other
829     kinds of parenthesized subpattern that do not cause substrings to be captured.
831     Captured substrings are returned to the caller via a vector of integer offsets
832     whose address is passed in \fIovector\fR. The number of elements in the vector
833     is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass
834     back captured substrings, each substring using a pair of integers. The
835     remaining third of the vector is used as workspace by \fBpcre_exec()\fR while
836     matching capturing subpatterns, and is not available for passing back
837     information. The length passed in \fIovecsize\fR should always be a multiple of
838     three. If it is not, it is rounded down.
840     When a match has been successful, information about captured substrings is
841     returned in pairs of integers, starting at the beginning of \fIovector\fR, and
842     continuing up to two-thirds of its length at the most. The first element of a
843     pair is set to the offset of the first character in a substring, and the second
844     is set to the offset of the first character after the end of a substring. The
845     first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the
846     subject string matched by the entire pattern. The next pair is used for the
847     first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR
848     is the number of pairs that have been set. If there are no capturing
849     subpatterns, the return value from a successful match is 1, indicating that
850     just the first pair of offsets has been set.
852     Some convenience functions are provided for extracting the captured substrings
853     as separate strings. These are described in the following section.
855     It is possible for an capturing subpattern number \fIn+1\fR to match some
856     part of the subject when subpattern \fIn\fR has not been used at all. For
857     example, if the string "abc" is matched against the pattern (a|(z))(bc)
858     subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset
859     values corresponding to the unused subpattern are set to -1.
861     If a capturing subpattern is matched repeatedly, it is the last portion of the
862     string that it matched that gets returned.
864     If the vector is too small to hold all the captured substrings, it is used as
865     far as possible (up to two-thirds of its length), and the function returns a
866     value of zero. In particular, if the substring offsets are not of interest,
867     \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and
868     \fIovecsize\fR as zero. However, if the pattern contains back references and
869     the \fIovector\fR isn't big enough to remember the related substrings, PCRE has
870     to get additional memory for use during matching. Thus it is usually advisable
871     to supply an \fIovector\fR.
873     Note that \fBpcre_info()\fR can be used to find out how many capturing
874     subpatterns there are in a compiled pattern. The smallest size for
875     \fIovector\fR that will allow for \fIn\fR captured substrings, in addition to
876     the offsets of the substring matched by the whole pattern, is (\fIn\fR+1)*3.
878     If \fBpcre_exec()\fR fails, it returns a negative number. The following are
879     defined in the header file:
883     The subject string did not match the pattern.
885     PCRE_ERROR_NULL (-2)
887     Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was
888     NULL and \fIovecsize\fR was not zero.
892     An unrecognized bit was set in the \fIoptions\fR argument.
896     PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
897     the case when it is passed a junk pointer. This is the error it gives when the
898     magic number isn't present.
902     While running the pattern match, an unknown item was encountered in the
903     compiled pattern. This error could be caused by a bug in PCRE or by overwriting
904     of the compiled pattern.
908     If a pattern contains back references, but the \fIovector\fR that is passed to
909     \fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE
910     gets a block of memory at the start of matching to use for this purpose. If the
911     call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at
912     the end of matching.
916     This error is used by the \fBpcre_copy_substring()\fR,
917     \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see
918     below). It is never returned by \fBpcre_exec()\fR.
922     The recursion and backtracking limit, as specified by the \fImatch_limit\fR
923     field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the
924     description above.
928     This error is never generated by \fBpcre_exec()\fR itself. It is provided for
929     use by callout functions that want to yield a distinctive error code. See the
930     \fBpcrecallout\fR documentation for details.
932 nigel 73 PCRE_ERROR_BADUTF8 (-10)
933 nigel 71
934     A string that contains an invalid UTF-8 byte sequence was passed as a subject.
936 nigel 73 PCRE_ERROR_BADUTF8_OFFSET (-11)
938     The UTF-8 byte sequence that was passed as a subject was valid, but the value
939     of \fIstartoffset\fR did not point to the beginning of a UTF-8 character.
942     .rs
943     .sp
944     .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,
945     .ti +5n
946     .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,
947     .ti +5n
948     .B int \fIbuffersize\fR);
949     .PP
950     .br
951     .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,
952     .ti +5n
953     .B int \fIstringcount\fR, int \fIstringnumber\fR,
954     .ti +5n
955     .B const char **\fIstringptr\fR);
956     .PP
957     .br
958     .B int pcre_get_substring_list(const char *\fIsubject\fR,
959     .ti +5n
960     .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"
961     .PP
962     Captured substrings can be accessed directly by using the offsets returned by
963     \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions
964     \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and
965     \fBpcre_get_substring_list()\fR are provided for extracting captured substrings
966     as new, separate, zero-terminated strings. These functions identify substrings
967     by number. The next section describes functions for extracting named
968     substrings. A substring that contains a binary zero is correctly extracted and
969     has a further zero added on the end, but the result is not, of course,
970     a C string.
972     The first three arguments are the same for all three of these functions:
973     \fIsubject\fR is the subject string which has just been successfully matched,
974     \fIovector\fR is a pointer to the vector of integer offsets that was passed to
975     \fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that were
976     captured by the match, including the substring that matched the entire regular
977     expression. This is the value returned by \fBpcre_exec\fR if it is greater than
978     zero. If \fBpcre_exec()\fR returned zero, indicating that it ran out of space
979     in \fIovector\fR, the value passed as \fIstringcount\fR should be the size of
980     the vector divided by three.
982     The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR
983     extract a single substring, whose number is given as \fIstringnumber\fR. A
984     value of zero extracts the substring that matched the entire pattern, while
985     higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,
986     the string is placed in \fIbuffer\fR, whose length is given by
987     \fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is
988     obtained via \fBpcre_malloc\fR, and its address is returned via
989     \fIstringptr\fR. The yield of the function is the length of the string, not
990     including the terminating zero, or one of
994     The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get
995     memory failed for \fBpcre_get_substring()\fR.
999     There is no substring whose number is \fIstringnumber\fR.
1001     The \fBpcre_get_substring_list()\fR function extracts all available substrings
1002     and builds a list of pointers to them. All this is done in a single block of
1003     memory which is obtained via \fBpcre_malloc\fR. The address of the memory block
1004     is returned via \fIlistptr\fR, which is also the start of the list of string
1005     pointers. The end of the list is marked by a NULL pointer. The yield of the
1006     function is zero if all went well, or
1010     if the attempt to get the memory block failed.
1012     When any of these functions encounter a substring that is unset, which can
1013     happen when capturing subpattern number \fIn+1\fR matches some part of the
1014     subject, but subpattern \fIn\fR has not been used at all, they return an empty
1015     string. This can be distinguished from a genuine zero-length substring by
1016     inspecting the appropriate offset in \fIovector\fR, which is negative for unset
1017     substrings.
1019     The two convenience functions \fBpcre_free_substring()\fR and
1020     \fBpcre_free_substring_list()\fR can be used to free the memory returned by
1021     a previous call of \fBpcre_get_substring()\fR or
1022     \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call
1023     the function pointed to by \fBpcre_free\fR, which of course could be called
1024     directly from a C program. However, PCRE is used in some situations where it is
1025     linked via a special interface to another programming language which cannot use
1026     \fBpcre_free\fR directly; it is for these cases that the functions are
1027     provided.
1030     .rs
1031     .sp
1032     .B int pcre_copy_named_substring(const pcre *\fIcode\fR,
1033     .ti +5n
1034     .B const char *\fIsubject\fR, int *\fIovector\fR,
1035     .ti +5n
1036     .B int \fIstringcount\fR, const char *\fIstringname\fR,
1037     .ti +5n
1038     .B char *\fIbuffer\fR, int \fIbuffersize\fR);
1039     .PP
1040     .br
1041     .B int pcre_get_stringnumber(const pcre *\fIcode\fR,
1042     .ti +5n
1043     .B const char *\fIname\fR);
1044     .PP
1045     .br
1046     .B int pcre_get_named_substring(const pcre *\fIcode\fR,
1047     .ti +5n
1048     .B const char *\fIsubject\fR, int *\fIovector\fR,
1049     .ti +5n
1050     .B int \fIstringcount\fR, const char *\fIstringname\fR,
1051     .ti +5n
1052     .B const char **\fIstringptr\fR);
1053     .PP
1054     To extract a substring by name, you first have to find associated number. This
1055     can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the
1056     compiled pattern, and the second is the name. For example, for this pattern
1058     ab(?<xxx>\\d+)...
1060     the number of the subpattern called "xxx" is 1. Given the number, you can then
1061     extract the substring directly, or use one of the functions described in the
1062     previous section. For convenience, there are also two functions that do the
1063     whole job.
1065     Most of the arguments of \fIpcre_copy_named_substring()\fR and
1066     \fIpcre_get_named_substring()\fR are the same as those for the functions that
1067     extract by number, and so are not re-described here. There are just two
1068     differences.
1070     First, instead of a substring number, a substring name is given. Second, there
1071     is an extra argument, given at the start, which is a pointer to the compiled
1072     pattern. This is needed in order to gain access to the name-to-number
1073     translation table.
1075     These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they
1076     then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as
1077     appropriate.
1079     .in 0
1080 nigel 73 Last updated: 09 December 2003
1081 nigel 63 .br
1082     Copyright (c) 1997-2003 University of Cambridge.

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