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revision 63 by nigel, Sat Feb 24 21:40:03 2007 UTC revision 567 by ph10, Sat Nov 6 17:10:00 2010 UTC
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1  .TH PCRE 3  .TH PCREAPI 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH SYNOPSIS OF PCRE API  .SH "PCRE NATIVE API"
5  .rs  .rs
6  .sp  .sp
7  .B #include <pcre.h>  .B #include <pcre.h>
8  .PP  .PP
9  .SM  .SM
10  .br  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
 .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  
11  .ti +5n  .ti +5n
12  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
13  .ti +5n  .ti +5n
14  .B const unsigned char *\fItableptr\fR);  .B const unsigned char *\fItableptr\fP);
15  .PP  .PP
16  .br  .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
 .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  
17  .ti +5n  .ti +5n
18  .B const char **\fIerrptr\fR);  .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    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
25    .ti +5n
26    .B const char **\fIerrptr\fP);
27  .PP  .PP
28  .br  .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
 .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  
29  .ti +5n  .ti +5n
30  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
31  .ti +5n  .ti +5n
32  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
33  .PP  .PP
34  .br  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
 .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  
35  .ti +5n  .ti +5n
36  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
37  .ti +5n  .ti +5n
38  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
39  .ti +5n  .ti +5n
40  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B int *\fIworkspace\fP, int \fIwscount\fP);
41  .PP  .PP
42  .br  .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
 .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
43  .ti +5n  .ti +5n
44  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
45  .ti +5n  .ti +5n
46  .B int \fIbuffersize\fR);  .B int \fIstringcount\fP, const char *\fIstringname\fP,
47    .ti +5n
48    .B char *\fIbuffer\fP, int \fIbuffersize\fP);
49  .PP  .PP
50  .br  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
51  .B int pcre_get_named_substring(const pcre *\fIcode\fR,  .ti +5n
52    .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53  .ti +5n  .ti +5n
54  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B int \fIbuffersize\fP);
55    .PP
56    .B int pcre_get_named_substring(const pcre *\fIcode\fP,
57  .ti +5n  .ti +5n
58  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
59  .ti +5n  .ti +5n
60  .B const char **\fIstringptr\fR);  .B int \fIstringcount\fP, const char *\fIstringname\fP,
61    .ti +5n
62    .B const char **\fIstringptr\fP);
63    .PP
64    .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
65    .ti +5n
66    .B const char *\fIname\fP);
67  .PP  .PP
68  .br  .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
69  .ti +5n  .ti +5n
70  .B const char *\fIname\fR);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71  .PP  .PP
72  .br  .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
73  .ti +5n  .ti +5n
74  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
75  .ti +5n  .ti +5n
76  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
77  .PP  .PP
78  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
79  .ti +5n  .ti +5n
80  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
81  .PP  .PP
82  .br  .B void pcre_free_substring(const char *\fIstringptr\fP);
 .B void pcre_free_substring(const char *\fIstringptr\fR);  
83  .PP  .PP
84  .br  .B void pcre_free_substring_list(const char **\fIstringptr\fP);
 .B void pcre_free_substring_list(const char **\fIstringptr\fR);  
85  .PP  .PP
 .br  
86  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
87  .PP  .PP
88  .br  .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
 .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  
89  .ti +5n  .ti +5n
90  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
91  .PP  .PP
92  .br  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
93  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B *\fIfirstcharptr\fP);
 .B *\fIfirstcharptr\fR);  
94  .PP  .PP
95  .br  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
96  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  .PP
97    .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
98  .PP  .PP
 .br  
99  .B char *pcre_version(void);  .B char *pcre_version(void);
100  .PP  .PP
 .br  
101  .B void *(*pcre_malloc)(size_t);  .B void *(*pcre_malloc)(size_t);
102  .PP  .PP
 .br  
103  .B void (*pcre_free)(void *);  .B void (*pcre_free)(void *);
104  .PP  .PP
105  .br  .B void *(*pcre_stack_malloc)(size_t);
106    .PP
107    .B void (*pcre_stack_free)(void *);
108    .PP
109  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
110    .
111  .SH PCRE API  .
112    .SH "PCRE API OVERVIEW"
113  .rs  .rs
114  .sp  .sp
115  PCRE has its own native API, which is described in this document. There is also  PCRE has its own native API, which is described in this document. There are
116  a set of wrapper functions that correspond to the POSIX regular expression API.  also some wrapper functions that correspond to the POSIX regular expression
117  These are described in the \fBpcreposix\fR documentation.  API. These are described in the
118    .\" HREF
119  The native API function prototypes are defined in the header file \fBpcre.h\fR,  \fBpcreposix\fP
120  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  .\"
121  accessed by adding \fB-lpcre\fR to the command for linking an application which  documentation. Both of these APIs define a set of C function calls. A C++
122  calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to  wrapper is distributed with PCRE. It is documented in the
123  contain the major and minor release numbers for the library. Applications can  .\" HREF
124  use these to include support for different releases.  \fBpcrecpp\fP
125    .\"
126  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  page.
127  are used for compiling and matching regular expressions. A sample program that  .P
128  demonstrates the simplest way of using them is given in the file  The native API C function prototypes are defined in the header file
129  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  \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  There are convenience functions for extracting captured substrings from a  an application that uses PCRE. The header file defines the macros PCRE_MAJOR
132  matched subject string. They are:  and PCRE_MINOR to contain the major and minor release numbers for the library.
133    Applications can use these to include support for different releases of PCRE.
134    \fBpcre_copy_substring()\fR  .P
135    \fBpcre_copy_named_substring()\fR  In a Windows environment, if you want to statically link an application program
136    \fBpcre_get_substring()\fR  against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
137    \fBpcre_get_named_substring()\fR  including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
138    \fBpcre_get_substring_list()\fR  \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
139    \fB__declspec(dllimport)\fP, with unwanted results.
140  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  .P
141    The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
142    and \fBpcre_exec()\fP are used for compiling and matching regular expressions
143    in a Perl-compatible manner. A sample program that demonstrates the simplest
144    way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
145    source distribution. A listing of this program is given in the
146    .\" HREF
147    \fBpcredemo\fP
148    .\"
149    documentation, and the
150    .\" HREF
151    \fBpcresample\fP
152    .\"
153    documentation describes how to compile and run it.
154    .P
155    A second matching function, \fBpcre_dfa_exec()\fP, which is not
156    Perl-compatible, is also provided. This uses a different algorithm for the
157    matching. The alternative algorithm finds all possible matches (at a given
158    point in the subject), and scans the subject just once (unless there are
159    lookbehind assertions). However, this algorithm does not return captured
160    substrings. A description of the two matching algorithms and their advantages
161    and disadvantages is given in the
162    .\" HREF
163    \fBpcrematching\fP
164    .\"
165    documentation.
166    .P
167    In addition to the main compiling and matching functions, there are convenience
168    functions for extracting captured substrings from a subject string that is
169    matched by \fBpcre_exec()\fP. They are:
170    .sp
171      \fBpcre_copy_substring()\fP
172      \fBpcre_copy_named_substring()\fP
173      \fBpcre_get_substring()\fP
174      \fBpcre_get_named_substring()\fP
175      \fBpcre_get_substring_list()\fP
176      \fBpcre_get_stringnumber()\fP
177      \fBpcre_get_stringtable_entries()\fP
178    .sp
179    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
180  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
181    .P
182  The function \fBpcre_maketables()\fR is used (optionally) to build a set of  The function \fBpcre_maketables()\fP is used to build a set of character tables
183  character tables in the current locale for passing to \fBpcre_compile()\fR.  in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
184    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
185  The function \fBpcre_fullinfo()\fR is used to find out information about a  specialist use. Most commonly, no special tables are passed, in which case
186  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
187    .P
188    The function \fBpcre_fullinfo()\fP is used to find out information about a
189    compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
190  some of the available information, but is retained for backwards compatibility.  some of the available information, but is retained for backwards compatibility.
191  The function \fBpcre_version()\fR returns a pointer to a string containing the  The function \fBpcre_version()\fP returns a pointer to a string containing the
192  version of PCRE and its date of release.  version of PCRE and its date of release.
193    .P
194  The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain  The function \fBpcre_refcount()\fP maintains a reference count in a data block
195  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  containing a compiled pattern. This is provided for the benefit of
196    object-oriented applications.
197    .P
198    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
199    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
200  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
201  so a calling program can replace them if it wishes to intercept the calls. This  so a calling program can replace them if it wishes to intercept the calls. This
202  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
203    .P
204  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
205    indirections to memory management functions. These special functions are used
206    only when PCRE is compiled to use the heap for remembering data, instead of
207    recursive function calls, when running the \fBpcre_exec()\fP function. See the
208    .\" HREF
209    \fBpcrebuild\fP
210    .\"
211    documentation for details of how to do this. It is a non-standard way of
212    building PCRE, for use in environments that have limited stacks. Because of the
213    greater use of memory management, it runs more slowly. Separate functions are
214    provided so that special-purpose external code can be used for this case. When
215    used, these functions are always called in a stack-like manner (last obtained,
216    first freed), and always for memory blocks of the same size. There is a
217    discussion about PCRE's stack usage in the
218    .\" HREF
219    \fBpcrestack\fP
220    .\"
221    documentation.
222    .P
223    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
224  by the caller to a "callout" function, which PCRE will then call at specified  by the caller to a "callout" function, which PCRE will then call at specified
225  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
226    .\" HREF
227    \fBpcrecallout\fP
228    .\"
229  documentation.  documentation.
230    .
231    .
232    .\" HTML <a name="newlines"></a>
233    .SH NEWLINES
234    .rs
235    .sp
236    PCRE supports five different conventions for indicating line breaks in
237    strings: a single CR (carriage return) character, a single LF (linefeed)
238    character, the two-character sequence CRLF, any of the three preceding, or any
239    Unicode newline sequence. The Unicode newline sequences are the three just
240    mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
241    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
242    (paragraph separator, U+2029).
243    .P
244    Each of the first three conventions is used by at least one operating system as
245    its standard newline sequence. When PCRE is built, a default can be specified.
246    The default default is LF, which is the Unix standard. When PCRE is run, the
247    default can be overridden, either when a pattern is compiled, or when it is
248    matched.
249    .P
250    At compile time, the newline convention can be specified by the \fIoptions\fP
251    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
252    start of the pattern itself; this overrides any other settings. See the
253    .\" HREF
254    \fBpcrepattern\fP
255    .\"
256    page for details of the special character sequences.
257    .P
258    In the PCRE documentation the word "newline" is used to mean "the character or
259    pair of characters that indicate a line break". The choice of newline
260    convention affects the handling of the dot, circumflex, and dollar
261    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
262    recognized line ending sequence, the match position advancement for a
263    non-anchored pattern. There is more detail about this in the
264    .\" HTML <a href="#execoptions">
265    .\" </a>
266    section on \fBpcre_exec()\fP options
267    .\"
268    below.
269    .P
270    The choice of newline convention does not affect the interpretation of
271    the \en or \er escape sequences, nor does it affect what \eR matches, which is
272    controlled in a similar way, but by separate options.
273    .
274    .
275  .SH MULTITHREADING  .SH MULTITHREADING
276  .rs  .rs
277  .sp  .sp
278  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
279  proviso that the memory management functions pointed to by \fBpcre_malloc\fR  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
280  and \fBpcre_free\fR, and the callout function pointed to by \fBpcre_callout\fR,  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
281  are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
282    .P
283  The compiled form of a regular expression is not altered during matching, so  The compiled form of a regular expression is not altered during matching, so
284  the same compiled pattern can safely be used by several threads at once.  the same compiled pattern can safely be used by several threads at once.
285    .
286  .SH CHECKING BUILD-TIME OPTIONS  .
287    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
288    .rs
289    .sp
290    The compiled form of a regular expression can be saved and re-used at a later
291    time, possibly by a different program, and even on a host other than the one on
292    which it was compiled. Details are given in the
293    .\" HREF
294    \fBpcreprecompile\fP
295    .\"
296    documentation. However, compiling a regular expression with one version of PCRE
297    for use with a different version is not guaranteed to work and may cause
298    crashes.
299    .
300    .
301    .SH "CHECKING BUILD-TIME OPTIONS"
302  .rs  .rs
303  .sp  .sp
304  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
305  .PP  .PP
306  The function \fBpcre_config()\fR makes it possible for a PCRE client to  The function \fBpcre_config()\fP makes it possible for a PCRE client to
307  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
308  .\" HREF  .\" HREF
309  \fBpcrebuild\fR  \fBpcrebuild\fP
310  .\"  .\"
311  documentation has more details about these optional features.  documentation has more details about these optional features.
312    .P
313  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
314  information is required; the second argument is a pointer to a variable into  information is required; the second argument is a pointer to a variable into
315  which the information is placed. The following information is available:  which the information is placed. The following information is available:
316    .sp
317    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
318    .sp
319  The output is an integer that is set to one if UTF-8 support is available;  The output is an integer that is set to one if UTF-8 support is available;
320  otherwise it is set to zero.  otherwise it is set to zero.
321    .sp
322      PCRE_CONFIG_UNICODE_PROPERTIES
323    .sp
324    The output is an integer that is set to one if support for Unicode character
325    properties is available; otherwise it is set to zero.
326    .sp
327    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
328    .sp
329  The output is an integer that is set to the value of the code that is used for  The output is an integer whose value specifies the default character sequence
330  the newline character. It is either linefeed (10) or carriage return (13), and  that is recognized as meaning "newline". The four values that are supported
331  should normally be the standard character for your operating system.  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
332    Though they are derived from ASCII, the same values are returned in EBCDIC
333    environments. The default should normally correspond to the standard sequence
334    for your operating system.
335    .sp
336      PCRE_CONFIG_BSR
337    .sp
338    The output is an integer whose value indicates what character sequences the \eR
339    escape sequence matches by default. A value of 0 means that \eR matches any
340    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
341    or CRLF. The default can be overridden when a pattern is compiled or matched.
342    .sp
343    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
344    .sp
345  The output is an integer that contains the number of bytes used for internal  The output is an integer that contains the number of bytes used for internal
346  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
347  allow larger regular expressions to be compiled, at the expense of slower  allow larger regular expressions to be compiled, at the expense of slower
348  matching. The default value of 2 is sufficient for all but the most massive  matching. The default value of 2 is sufficient for all but the most massive
349  patterns, since it allows the compiled pattern to be up to 64K in size.  patterns, since it allows the compiled pattern to be up to 64K in size.
350    .sp
351    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
352    .sp
353  The output is an integer that contains the threshold above which the POSIX  The output is an integer that contains the threshold above which the POSIX
354  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
355  the \fBpcreposix\fR documentation.  the
356    .\" HREF
357    \fBpcreposix\fP
358    .\"
359    documentation.
360    .sp
361    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
362    .sp
363  The output is an integer that gives the default limit for the number of  The output is a long integer that gives the default limit for the number of
364  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
365  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
366    .sp
367  .SH COMPILING A PATTERN    PCRE_CONFIG_MATCH_LIMIT_RECURSION
368  .rs  .sp
369  .sp  The output is a long integer that gives the default limit for the depth of
370  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  recursion when calling the internal matching function in a \fBpcre_exec()\fP
371  .ti +5n  execution. Further details are given with \fBpcre_exec()\fP below.
372  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .sp
373  .ti +5n    PCRE_CONFIG_STACKRECURSE
374  .B const unsigned char *\fItableptr\fR);  .sp
375  .PP  The output is an integer that is set to one if internal recursion when running
376    \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
377  The function \fBpcre_compile()\fR is called to compile a pattern into an  to remember their state. This is the usual way that PCRE is compiled. The
378  internal form. The pattern is a C string terminated by a binary zero, and  output is zero if PCRE was compiled to use blocks of data on the heap instead
379  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
380  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
381  code and related data. The \fBpcre\fR type is defined for the returned block;  avoiding the use of the stack.
382  this is a typedef for a structure whose contents are not externally defined. It  .
383  is up to the caller to free the memory when it is no longer required.  .
384    .SH "COMPILING A PATTERN"
385    .rs
386    .sp
387    .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
388    .ti +5n
389    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
390    .ti +5n
391    .B const unsigned char *\fItableptr\fP);
392    .sp
393    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
394    .ti +5n
395    .B int *\fIerrorcodeptr\fP,
396    .ti +5n
397    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
398    .ti +5n
399    .B const unsigned char *\fItableptr\fP);
400    .P
401    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
402    called to compile a pattern into an internal form. The only difference between
403    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
404    \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
405    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
406    information applies equally to \fBpcre_compile2()\fP.
407    .P
408    The pattern is a C string terminated by a binary zero, and is passed in the
409    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
410    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
411    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
412    for a structure whose contents are not externally defined. It is up to the
413    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
414    .P
415  Although the compiled code of a PCRE regex is relocatable, that is, it does not  Although the compiled code of a PCRE regex is relocatable, that is, it does not
416  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
417  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
418  which is an address (see below).  argument, which is an address (see below).
419    .P
420  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
421  compilation. It should be zero if no options are required. Some of the options,  compilation. It should be zero if no options are required. The available
422  in particular, those that are compatible with Perl, can also be set and unset  options are described below. Some of them (in particular, those that are
423  from within the pattern (see the detailed description of regular expressions  compatible with Perl, but some others as well) can also be set and unset from
424  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
425  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
426  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
427  matching as well as at compile time.  .\"
428    documentation). For those options that can be different in different parts of
429  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their
430  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED,
431  NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual  PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
432  error message. The offset from the start of the pattern to the character where  of matching as well as at compile time.
433  the error was discovered is placed in the variable pointed to by  .P
434  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
435    Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
436  If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
437  character tables which are built when it is compiled, using the default C  error message. This is a static string that is part of the library. You must
438  locale. Otherwise, \fItableptr\fR must be the result of a call to  not try to free it. The byte offset from the start of the pattern to the
439  \fBpcre_maketables()\fR. See the section on locale support below.  character that was being processed when the error was discovered is placed in
440    the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
441  This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:  an immediate error is given. Some errors are not detected until checks are
442    carried out when the whole pattern has been scanned; in this case the offset is
443    set to the end of the pattern.
444    .P
445    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
446    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
447    returned via this argument in the event of an error. This is in addition to the
448    textual error message. Error codes and messages are listed below.
449    .P
450    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
451    character tables that are built when PCRE is compiled, using the default C
452    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
453    call to \fBpcre_maketables()\fP. This value is stored with the compiled
454    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
455    passed to it. For more discussion, see the section on locale support below.
456    .P
457    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
458    .sp
459    pcre *re;    pcre *re;
460    const char *error;    const char *error;
461    int erroffset;    int erroffset;
# Line 265  This code fragment shows a typical strai Line 465  This code fragment shows a typical strai
465      &error,           /* for error message */      &error,           /* for error message */
466      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
467      NULL);            /* use default character tables */      NULL);            /* use default character tables */
468    .sp
469  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
470    file:
471    .sp
472    PCRE_ANCHORED    PCRE_ANCHORED
473    .sp
474  If this bit is set, the pattern is forced to be "anchored", that is, it is  If this bit is set, the pattern is forced to be "anchored", that is, it is
475  constrained to match only at the first matching point in the string which is  constrained to match only at the first matching point in the string that is
476  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
477  appropriate constructs in the pattern itself, which is the only way to do it in  appropriate constructs in the pattern itself, which is the only way to do it in
478  Perl.  Perl.
479    .sp
480      PCRE_AUTO_CALLOUT
481    .sp
482    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
483    all with number 255, before each pattern item. For discussion of the callout
484    facility, see the
485    .\" HREF
486    \fBpcrecallout\fP
487    .\"
488    documentation.
489    .sp
490      PCRE_BSR_ANYCRLF
491      PCRE_BSR_UNICODE
492    .sp
493    These options (which are mutually exclusive) control what the \eR escape
494    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
495    match any Unicode newline sequence. The default is specified when PCRE is
496    built. It can be overridden from within the pattern, or by setting an option
497    when a compiled pattern is matched.
498    .sp
499    PCRE_CASELESS    PCRE_CASELESS
500    .sp
501  If this bit is set, letters in the pattern match both upper and lower case  If this bit is set, letters in the pattern match both upper and lower case
502  letters. It is equivalent to Perl's /i option, and it can be changed within a  letters. It is equivalent to Perl's /i option, and it can be changed within a
503  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
504    concept of case for characters whose values are less than 128, so caseless
505    matching is always possible. For characters with higher values, the concept of
506    case is supported if PCRE is compiled with Unicode property support, but not
507    otherwise. If you want to use caseless matching for characters 128 and above,
508    you must ensure that PCRE is compiled with Unicode property support as well as
509    with UTF-8 support.
510    .sp
511    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
512    .sp
513  If this bit is set, a dollar metacharacter in the pattern matches only at the  If this bit is set, a dollar metacharacter in the pattern matches only at the
514  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
515  immediately before the final character if it is a newline (but not before any  immediately before a newline at the end of the string (but not before any other
516  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is  newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
517  set. There is no equivalent to this option in Perl, and no way to set it within  There is no equivalent to this option in Perl, and no way to set it within a
518  a pattern.  pattern.
519    .sp
520    PCRE_DOTALL    PCRE_DOTALL
521    .sp
522  If this bit is set, a dot metacharater in the pattern matches all characters,  If this bit is set, a dot metacharater in the pattern matches all characters,
523  including newlines. Without it, newlines are excluded. This option is  including those that indicate newline. Without it, a dot does not match when
524  equivalent to Perl's /s option, and it can be changed within a pattern by a  the current position is at a newline. This option is equivalent to Perl's /s
525  (?s) option setting. A negative class such as [^a] always matches a newline  option, and it can be changed within a pattern by a (?s) option setting. A
526  character, independent of the setting of this option.  negative class such as [^a] always matches newline characters, independent of
527    the setting of this option.
528    .sp
529      PCRE_DUPNAMES
530    .sp
531    If this bit is set, names used to identify capturing subpatterns need not be
532    unique. This can be helpful for certain types of pattern when it is known that
533    only one instance of the named subpattern can ever be matched. There are more
534    details of named subpatterns below; see also the
535    .\" HREF
536    \fBpcrepattern\fP
537    .\"
538    documentation.
539    .sp
540    PCRE_EXTENDED    PCRE_EXTENDED
541    .sp
542  If this bit is set, whitespace data characters in the pattern are totally  If this bit is set, whitespace data characters in the pattern are totally
543  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. Whitespace does not
544  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
545  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
546  inclusive, are also ignored. This is equivalent to Perl's /x option, and it can  ignored. This is equivalent to Perl's /x option, and it can be changed within a
547  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
548    .P
549  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
550  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
551  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
552  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( which introduces a conditional subpattern.
553    .sp
554    PCRE_EXTRA    PCRE_EXTRA
555    .sp
556  This option was invented in order to turn on additional functionality of PCRE  This option was invented in order to turn on additional functionality of PCRE
557  that is incompatible with Perl, but it is currently of very little use. When  that is incompatible with Perl, but it is currently of very little use. When
558  set, any backslash in a pattern that is followed by a letter that has no  set, any backslash in a pattern that is followed by a letter that has no
559  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
560  expansion. By default, as in Perl, a backslash followed by a letter with no  expansion. By default, as in Perl, a backslash followed by a letter with no
561  special meaning is treated as a literal. There are at present no other features  special meaning is treated as a literal. (Perl can, however, be persuaded to
562  controlled by this option. It can also be set by a (?X) option setting within a  give an error for this, by running it with the -w option.) There are at present
563  pattern.  no other features controlled by this option. It can also be set by a (?X)
564    option setting within a pattern.
565    .sp
566      PCRE_FIRSTLINE
567    .sp
568    If this option is set, an unanchored pattern is required to match before or at
569    the first newline in the subject string, though the matched text may continue
570    over the newline.
571    .sp
572      PCRE_JAVASCRIPT_COMPAT
573    .sp
574    If this option is set, PCRE's behaviour is changed in some ways so that it is
575    compatible with JavaScript rather than Perl. The changes are as follows:
576    .P
577    (1) A lone closing square bracket in a pattern causes a compile-time error,
578    because this is illegal in JavaScript (by default it is treated as a data
579    character). Thus, the pattern AB]CD becomes illegal when this option is set.
580    .P
581    (2) At run time, a back reference to an unset subpattern group matches an empty
582    string (by default this causes the current matching alternative to fail). A
583    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
584    an "a" in the subject), whereas it fails by default, for Perl compatibility.
585    .sp
586    PCRE_MULTILINE    PCRE_MULTILINE
587    .sp
588  By default, PCRE treats the subject string as consisting of a single "line" of  By default, PCRE treats the subject string as consisting of a single line of
589  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
590  metacharacter (^) matches only at the start of the string, while the "end of  metacharacter (^) matches only at the start of the string, while the "end of
591  line" metacharacter ($) matches only at the end of the string, or before a  line" metacharacter ($) matches only at the end of the string, or before a
592  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
593  Perl.  Perl.
594    .P
595  When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs  When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
596  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
597  string, respectively, as well as at the very start and end. This is equivalent  subject string, respectively, as well as at the very start and end. This is
598  to Perl's /m option, and it can be changed within a pattern by a (?m) option  equivalent to Perl's /m option, and it can be changed within a pattern by a
599  setting. If there are no "\\n" characters in a subject string, or no  (?m) option setting. If there are no newlines in a subject string, or no
600  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
601    .sp
602      PCRE_NEWLINE_CR
603      PCRE_NEWLINE_LF
604      PCRE_NEWLINE_CRLF
605      PCRE_NEWLINE_ANYCRLF
606      PCRE_NEWLINE_ANY
607    .sp
608    These options override the default newline definition that was chosen when PCRE
609    was built. Setting the first or the second specifies that a newline is
610    indicated by a single character (CR or LF, respectively). Setting
611    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
612    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
613    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
614    that any Unicode newline sequence should be recognized. The Unicode newline
615    sequences are the three just mentioned, plus the single characters VT (vertical
616    tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
617    separator, U+2028), and PS (paragraph separator, U+2029). The last two are
618    recognized only in UTF-8 mode.
619    .P
620    The newline setting in the options word uses three bits that are treated
621    as a number, giving eight possibilities. Currently only six are used (default
622    plus the five values above). This means that if you set more than one newline
623    option, the combination may or may not be sensible. For example,
624    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
625    other combinations may yield unused numbers and cause an error.
626    .P
627    The only time that a line break is specially recognized when compiling a
628    pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
629    class is encountered. This indicates a comment that lasts until after the next
630    line break sequence. In other circumstances, line break sequences are treated
631    as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
632    as whitespace characters and are therefore ignored.
633    .P
634    The newline option that is set at compile time becomes the default that is used
635    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
636    .sp
637    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
638    .sp
639  If this option is set, it disables the use of numbered capturing parentheses in  If this option is set, it disables the use of numbered capturing parentheses in
640  the pattern. Any opening parenthesis that is not followed by ? behaves as if it  the pattern. Any opening parenthesis that is not followed by ? behaves as if it
641  were followed by ?: but named parentheses can still be used for capturing (and  were followed by ?: but named parentheses can still be used for capturing (and
642  they acquire numbers in the usual way). There is no equivalent of this option  they acquire numbers in the usual way). There is no equivalent of this option
643  in Perl.  in Perl.
644    .sp
645      PCRE_UCP
646    .sp
647    This option changes the way PCRE processes \eb, \ed, \es, \ew, and some of the
648    POSIX character classes. By default, only ASCII characters are recognized, but
649    if PCRE_UCP is set, Unicode properties are used instead to classify characters.
650    More details are given in the section on
651    .\" HTML <a href="pcre.html#genericchartypes">
652    .\" </a>
653    generic character types
654    .\"
655    in the
656    .\" HREF
657    \fBpcrepattern\fP
658    .\"
659    page. If you set PCRE_UCP, matching one of the items it affects takes much
660    longer. The option is available only if PCRE has been compiled with Unicode
661    property support.
662    .sp
663    PCRE_UNGREEDY    PCRE_UNGREEDY
664    .sp
665  This option inverts the "greediness" of the quantifiers so that they are not  This option inverts the "greediness" of the quantifiers so that they are not
666  greedy by default, but become greedy if followed by "?". It is not compatible  greedy by default, but become greedy if followed by "?". It is not compatible
667  with Perl. It can also be set by a (?U) option setting within the pattern.  with Perl. It can also be set by a (?U) option setting within the pattern.
668    .sp
669    PCRE_UTF8    PCRE_UTF8
670    .sp
671  This option causes PCRE to regard both the pattern and the subject as strings  This option causes PCRE to regard both the pattern and the subject as strings
672  of UTF-8 characters instead of single-byte character strings. However, it is  of UTF-8 characters instead of single-byte character strings. However, it is
673  available only if PCRE has been built to include UTF-8 support. If not, the use  available only when PCRE is built to include UTF-8 support. If not, the use
674  of this option provokes an error. Details of how this option changes the  of this option provokes an error. Details of how this option changes the
675  behaviour of PCRE are given in the  behaviour of PCRE are given in the
676  .\" HTML <a href="pcre.html#utf8support">  .\" HTML <a href="pcre.html#utf8support">
# Line 367  section on UTF-8 support Line 679  section on UTF-8 support
679  .\"  .\"
680  in the main  in the main
681  .\" HREF  .\" HREF
682  \fBpcre\fR  \fBpcre\fP
683  .\"  .\"
684  page.  page.
685    .sp
686  .SH STUDYING A PATTERN    PCRE_NO_UTF8_CHECK
687    .sp
688    When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
689    automatically checked. There is a discussion about the
690    .\" HTML <a href="pcre.html#utf8strings">
691    .\" </a>
692    validity of UTF-8 strings
693    .\"
694    in the main
695    .\" HREF
696    \fBpcre\fP
697    .\"
698    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
699    returns an error. If you already know that your pattern is valid, and you want
700    to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
701    option. When it is set, the effect of passing an invalid UTF-8 string as a
702    pattern is undefined. It may cause your program to crash. Note that this option
703    can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
704    the UTF-8 validity checking of subject strings.
705    .
706    .
707    .SH "COMPILATION ERROR CODES"
708  .rs  .rs
709  .sp  .sp
710  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  The following table lists the error codes than may be returned by
711    \fBpcre_compile2()\fP, along with the error messages that may be returned by
712    both compiling functions. As PCRE has developed, some error codes have fallen
713    out of use. To avoid confusion, they have not been re-used.
714    .sp
715       0  no error
716       1  \e at end of pattern
717       2  \ec at end of pattern
718       3  unrecognized character follows \e
719       4  numbers out of order in {} quantifier
720       5  number too big in {} quantifier
721       6  missing terminating ] for character class
722       7  invalid escape sequence in character class
723       8  range out of order in character class
724       9  nothing to repeat
725      10  [this code is not in use]
726      11  internal error: unexpected repeat
727      12  unrecognized character after (? or (?-
728      13  POSIX named classes are supported only within a class
729      14  missing )
730      15  reference to non-existent subpattern
731      16  erroffset passed as NULL
732      17  unknown option bit(s) set
733      18  missing ) after comment
734      19  [this code is not in use]
735      20  regular expression is too large
736      21  failed to get memory
737      22  unmatched parentheses
738      23  internal error: code overflow
739      24  unrecognized character after (?<
740      25  lookbehind assertion is not fixed length
741      26  malformed number or name after (?(
742      27  conditional group contains more than two branches
743      28  assertion expected after (?(
744      29  (?R or (?[+-]digits must be followed by )
745      30  unknown POSIX class name
746      31  POSIX collating elements are not supported
747      32  this version of PCRE is not compiled with PCRE_UTF8 support
748      33  [this code is not in use]
749      34  character value in \ex{...} sequence is too large
750      35  invalid condition (?(0)
751      36  \eC not allowed in lookbehind assertion
752      37  PCRE does not support \eL, \el, \eN, \eU, or \eu
753      38  number after (?C is > 255
754      39  closing ) for (?C expected
755      40  recursive call could loop indefinitely
756      41  unrecognized character after (?P
757      42  syntax error in subpattern name (missing terminator)
758      43  two named subpatterns have the same name
759      44  invalid UTF-8 string
760      45  support for \eP, \ep, and \eX has not been compiled
761      46  malformed \eP or \ep sequence
762      47  unknown property name after \eP or \ep
763      48  subpattern name is too long (maximum 32 characters)
764      49  too many named subpatterns (maximum 10000)
765      50  [this code is not in use]
766      51  octal value is greater than \e377 (not in UTF-8 mode)
767      52  internal error: overran compiling workspace
768      53  internal error: previously-checked referenced subpattern
769            not found
770      54  DEFINE group contains more than one branch
771      55  repeating a DEFINE group is not allowed
772      56  inconsistent NEWLINE options
773      57  \eg is not followed by a braced, angle-bracketed, or quoted
774            name/number or by a plain number
775      58  a numbered reference must not be zero
776      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
777      60  (*VERB) not recognized
778      61  number is too big
779      62  subpattern name expected
780      63  digit expected after (?+
781      64  ] is an invalid data character in JavaScript compatibility mode
782      65  different names for subpatterns of the same number are
783            not allowed
784      66  (*MARK) must have an argument
785      67  this version of PCRE is not compiled with PCRE_UCP support
786    .sp
787    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
788    be used if the limits were changed when PCRE was built.
789    .
790    .
791    .SH "STUDYING A PATTERN"
792    .rs
793    .sp
794    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
795  .ti +5n  .ti +5n
796  .B const char **\fIerrptr\fR);  .B const char **\fIerrptr\fP);
797  .PP  .PP
798  When a pattern is going to be used several times, it is worth spending more  If a compiled pattern is going to be used several times, it is worth spending
799  time analyzing it in order to speed up the time taken for matching. The  more time analyzing it in order to speed up the time taken for matching. The
800  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
801  argument. If studing the pattern produces additional information that will help  argument. If studying the pattern produces additional information that will
802  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  help speed up matching, \fBpcre_study()\fP returns a pointer to a
803  block, in which the \fIstudy_data\fR field points to the results of the study.  \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
804    results of the study.
805  The returned value from a \fBpcre_study()\fR can be passed directly to  .P
806  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  The returned value from \fBpcre_study()\fP can be passed directly to
807  fields that can be set by the caller before the block is passed; these are  \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
808  described below. If studying the pattern does not produce any additional  also contains other fields that can be set by the caller before the block is
809  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the  passed; these are described
810  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it  .\" HTML <a href="#extradata">
811  must set up its own \fBpcre_extra\fR block.  .\" </a>
812    below
813  The second argument contains option bits. At present, no options are defined  .\"
814  for \fBpcre_study()\fR, and this argument should always be zero.  in the section on matching a pattern.
815    .P
816  The third argument for \fBpcre_study()\fR is a pointer for an error message. If  If studying the pattern does not produce any useful information,
817    \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
818    wants to pass any of the other fields to \fBpcre_exec()\fP or
819    \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
820    .P
821    The second argument of \fBpcre_study()\fP contains option bits. At present, no
822    options are defined, and this argument should always be zero.
823    .P
824    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
825  studying succeeds (even if no data is returned), the variable it points to is  studying succeeds (even if no data is returned), the variable it points to is
826  set to NULL. Otherwise it points to a textual error message. You should  set to NULL. Otherwise it is set to point to a textual error message. This is a
827  therefore test the error pointer for NULL after calling \fBpcre_study()\fR, to  static string that is part of the library. You must not try to free it. You
828  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
829    sure that it has run successfully.
830  This is a typical call to \fBpcre_study\fR():  .P
831    This is a typical call to \fBpcre_study\fP():
832    .sp
833    pcre_extra *pe;    pcre_extra *pe;
834    pe = pcre_study(    pe = pcre_study(
835      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
836      0,              /* no options exist */      0,              /* no options exist */
837      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
838    .sp
839  At present, studying a pattern is useful only for non-anchored patterns that do  Studying a pattern does two things: first, a lower bound for the length of
840  not have a single fixed starting character. A bitmap of possible starting  subject string that is needed to match the pattern is computed. This does not
841  characters is created.  mean that there are any strings of that length that match, but it does
842    guarantee that no shorter strings match. The value is used by
843    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
844    match strings that are shorter than the lower bound. You can find out the value
845    in a calling program via the \fBpcre_fullinfo()\fP function.
846    .P
847    Studying a pattern is also useful for non-anchored patterns that do not have a
848    single fixed starting character. A bitmap of possible starting bytes is
849    created. This speeds up finding a position in the subject at which to start
850    matching.
851    .P
852    The two optimizations just described can be disabled by setting the
853    PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
854    \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
855    callouts, or make use of (*MARK), and you make use of these in cases where
856    matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
857    .\" HTML <a href="#execoptions">
858    .\" </a>
859    below.
860    .\"
861    .
862    .
863  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
864  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
865  .rs  .rs
866  .sp  .sp
867  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
868  digits, or whatever, by reference to a set of tables. When running in UTF-8  digits, or whatever, by reference to a set of tables, indexed by character
869  mode, this applies only to characters with codes less than 256. The library  value. When running in UTF-8 mode, this applies only to characters with codes
870  contains a default set of tables that is created in the default C locale when  less than 128. By default, higher-valued codes never match escapes such as \ew
871  PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR  or \ed, but they can be tested with \ep if PCRE is built with Unicode character
872  is NULL, and is sufficient for many applications.  property support. Alternatively, the PCRE_UCP option can be set at compile
873    time; this causes \ew and friends to use Unicode property support instead of
874  An alternative set of tables can, however, be supplied. Such tables are built  built-in tables. The use of locales with Unicode is discouraged. If you are
875  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  handling characters with codes greater than 128, you should either use UTF-8
876  relevant locale. The result can then be passed to \fBpcre_compile()\fR as often  and Unicode, or use locales, but not try to mix the two.
877  as necessary. For example, to build and use tables that are appropriate for the  .P
878  French locale (where accented characters with codes greater than 128 are  PCRE contains an internal set of tables that are used when the final argument
879  treated as letters), the following code could be used:  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
880    Normally, the internal tables recognize only ASCII characters. However, when
881    setlocale(LC_CTYPE, "fr");  PCRE is built, it is possible to cause the internal tables to be rebuilt in the
882    default "C" locale of the local system, which may cause them to be different.
883    .P
884    The internal tables can always be overridden by tables supplied by the
885    application that calls PCRE. These may be created in a different locale from
886    the default. As more and more applications change to using Unicode, the need
887    for this locale support is expected to die away.
888    .P
889    External tables are built by calling the \fBpcre_maketables()\fP function,
890    which has no arguments, in the relevant locale. The result can then be passed
891    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
892    example, to build and use tables that are appropriate for the French locale
893    (where accented characters with values greater than 128 are treated as letters),
894    the following code could be used:
895    .sp
896      setlocale(LC_CTYPE, "fr_FR");
897    tables = pcre_maketables();    tables = pcre_maketables();
898    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
899    .sp
900  The tables are built in memory that is obtained via \fBpcre_malloc\fR. The  The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
901  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
902  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
903  and \fBpcre_exec()\fR. Thus, for any single pattern, compilation, studying and  When \fBpcre_maketables()\fP runs, the tables are built in memory that is
904  matching all happen in the same locale, but different patterns can be compiled  obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
905  in different locales. It is the caller's responsibility to ensure that the  that the memory containing the tables remains available for as long as it is
906  memory containing the tables remains available for as long as it is needed.  needed.
907    .P
908  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
909    pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
910    and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
911    pattern, compilation, studying and matching all happen in the same locale, but
912    different patterns can be compiled in different locales.
913    .P
914    It is possible to pass a table pointer or NULL (indicating the use of the
915    internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
916    this facility could be used to match a pattern in a different locale from the
917    one in which it was compiled. Passing table pointers at run time is discussed
918    below in the section on matching a pattern.
919    .
920    .
921    .SH "INFORMATION ABOUT A PATTERN"
922  .rs  .rs
923  .sp  .sp
924  .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
925  .ti +5n  .ti +5n
926  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
927  .PP  .PP
928  The \fBpcre_fullinfo()\fR function returns information about a compiled  The \fBpcre_fullinfo()\fP function returns information about a compiled
929  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
930  nevertheless retained for backwards compability (and is documented below).  nevertheless retained for backwards compability (and is documented below).
931    .P
932  The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled  The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
933  pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if  pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
934  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
935  information is required, and the fourth argument is a pointer to a variable  information is required, and the fourth argument is a pointer to a variable
936  to receive the data. The yield of the function is zero for success, or one of  to receive the data. The yield of the function is zero for success, or one of
937  the following negative numbers:  the following negative numbers:
938    .sp
939    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
940                          the argument \fIwhere\fR was NULL                          the argument \fIwhere\fP was NULL
941    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
942    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADOPTION  the value of \fIwhat\fP was invalid
943    .sp
944  Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the  The "magic number" is placed at the start of each compiled pattern as an simple
945  compiled pattern:  check against passing an arbitrary memory pointer. Here is a typical call of
946    \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
947    .sp
948    int rc;    int rc;
949    unsigned long int length;    size_t length;
950    rc = pcre_fullinfo(    rc = pcre_fullinfo(
951      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
952      pe,               /* result of pcre_study(), or NULL */      pe,               /* result of pcre_study(), or NULL */
953      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
954      &length);         /* where to put the data */      &length);         /* where to put the data */
955    .sp
956  The possible values for the third argument are defined in \fBpcre.h\fR, and are  The possible values for the third argument are defined in \fBpcre.h\fP, and are
957  as follows:  as follows:
958    .sp
959    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
960    .sp
961  Return the number of the highest back reference in the pattern. The fourth  Return the number of the highest back reference in the pattern. The fourth
962  argument should point to an \fBint\fR variable. Zero is returned if there are  argument should point to an \fBint\fP variable. Zero is returned if there are
963  no back references.  no back references.
964    .sp
965    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
966    .sp
967  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
968  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
969    .sp
970      PCRE_INFO_DEFAULT_TABLES
971    .sp
972    Return a pointer to the internal default character tables within PCRE. The
973    fourth argument should point to an \fBunsigned char *\fP variable. This
974    information call is provided for internal use by the \fBpcre_study()\fP
975    function. External callers can cause PCRE to use its internal tables by passing
976    a NULL table pointer.
977    .sp
978    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
979    .sp
980  Return information about the first byte of any matched string, for a  Return information about the first byte of any matched string, for a
981  non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the  non-anchored pattern. The fourth argument should point to an \fBint\fP
982  old name is still recognized for backwards compatibility.)  variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
983    still recognized for backwards compatibility.)
984  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
985  it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either  If there is a fixed first byte, for example, from a pattern such as
986    (cat|cow|coyote), its value is returned. Otherwise, if either
987    .sp
988  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
989  starts with "^", or  starts with "^", or
990    .sp
991  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
992  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
993    .sp
994  -1 is returned, indicating that the pattern matches only at the start of a  -1 is returned, indicating that the pattern matches only at the start of a
995  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
996  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
997    .sp
998    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
999    .sp
1000  If the pattern was studied, and this resulted in the construction of a 256-bit  If the pattern was studied, and this resulted in the construction of a 256-bit
1001  table indicating a fixed set of bytes for the first byte in any matching  table indicating a fixed set of bytes for the first byte in any matching
1002  string, a pointer to the table is returned. Otherwise NULL is returned. The  string, a pointer to the table is returned. Otherwise NULL is returned. The
1003  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1004    .sp
1005      PCRE_INFO_HASCRORLF
1006    .sp
1007    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1008    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1009    explicit match is either a literal CR or LF character, or \er or \en.
1010    .sp
1011      PCRE_INFO_JCHANGED
1012    .sp
1013    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1014    0. The fourth argument should point to an \fBint\fP variable. (?J) and
1015    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1016    .sp
1017    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1018    .sp
1019  For a non-anchored pattern, return the value of the rightmost literal byte  Return the value of the rightmost literal byte that must exist in any matched
1020  which must exist in any matched string, other than at its start. The fourth  string, other than at its start, if such a byte has been recorded. The fourth
1021  argument should point to an \fBint\fR variable. If there is no such byte, or if  argument should point to an \fBint\fP variable. If there is no such byte, -1 is
1022  the pattern is anchored, -1 is returned. For example, for the pattern  returned. For anchored patterns, a last literal byte is recorded only if it
1023  /a\\d+z\\d+/ the returned value is 'z'.  follows something of variable length. For example, for the pattern
1024    /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1025    is -1.
1026    .sp
1027      PCRE_INFO_MINLENGTH
1028    .sp
1029    If the pattern was studied and a minimum length for matching subject strings
1030    was computed, its value is returned. Otherwise the returned value is -1. The
1031    value is a number of characters, not bytes (this may be relevant in UTF-8
1032    mode). The fourth argument should point to an \fBint\fP variable. A
1033    non-negative value is a lower bound to the length of any matching string. There
1034    may not be any strings of that length that do actually match, but every string
1035    that does match is at least that long.
1036    .sp
1037    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1038    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1039    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
1040    .sp
1041  PCRE supports the use of named as well as numbered capturing parentheses. The  PCRE supports the use of named as well as numbered capturing parentheses. The
1042  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
1043  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
1044  must convert the name to a number in order to access the correct pointers in  \fBpcre_get_named_substring()\fP are provided for extracting captured
1045  the output vector (described with \fBpcre_exec()\fR below). In order to do  substrings by name. It is also possible to extract the data directly, by first
1046  this, it must first use these three values to obtain the name-to-number mapping  converting the name to a number in order to access the correct pointers in the
1047  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1048    you need to use the name-to-number map, which is described by these three
1049    values.
1050    .P
1051  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1052  the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each  the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1053  entry; both of these return an \fBint\fR value. The entry size depends on the  entry; both of these return an \fBint\fP value. The entry size depends on the
1054  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1055  entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1056  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1057  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1058  alphabetical order. For example, consider the following pattern (assume  .P
1059  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  The names are in alphabetical order. Duplicate names may appear if (?| is used
1060    to create multiple groups with the same number, as described in the
1061    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1062    (?P<month>\\d\\d) - (?P<day>\\d\\d) )  .\" </a>
1063    section on duplicate subpattern numbers
1064    .\"
1065    in the
1066    .\" HREF
1067    \fBpcrepattern\fP
1068    .\"
1069    page. Duplicate names for subpatterns with different numbers are permitted only
1070    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1071    table in the order in which they were found in the pattern. In the absence of
1072    (?| this is the order of increasing number; when (?| is used this is not
1073    necessarily the case because later subpatterns may have lower numbers.
1074    .P
1075    As a simple example of the name/number table, consider the following pattern
1076    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1077    ignored):
1078    .sp
1079    .\" JOIN
1080      (?<date> (?<year>(\ed\ed)?\ed\ed) -
1081      (?<month>\ed\ed) - (?<day>\ed\ed) )
1082    .sp
1083  There are four named subpatterns, so the table has four entries, and each entry  There are four named subpatterns, so the table has four entries, and each entry
1084  in the table is eight bytes long. The table is as follows, with non-printing  in the table is eight bytes long. The table is as follows, with non-printing
1085  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1086    .sp
1087    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1088    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1089    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1090    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1091    .sp
1092  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1093  length of each entry may be different for each compiled pattern.  name-to-number map, remember that the length of the entries is likely to be
1094    different for each compiled pattern.
1095    .sp
1096      PCRE_INFO_OKPARTIAL
1097    .sp
1098    Return 1 if the pattern can be used for partial matching with
1099    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1100    \fBint\fP variable. From release 8.00, this always returns 1, because the
1101    restrictions that previously applied to partial matching have been lifted. The
1102    .\" HREF
1103    \fBpcrepartial\fP
1104    .\"
1105    documentation gives details of partial matching.
1106    .sp
1107    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1108    .sp
1109  Return a copy of the options with which the pattern was compiled. The fourth  Return a copy of the options with which the pattern was compiled. The fourth
1110  argument should point to an \fBunsigned long int\fR variable. These option bits  argument should point to an \fBunsigned long int\fP variable. These option bits
1111  are those specified in the call to \fBpcre_compile()\fR, modified by any  are those specified in the call to \fBpcre_compile()\fP, modified by any
1112  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1113    they are the options that will be in force when matching starts. For example,
1114    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1115    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1116    .P
1117  A pattern is automatically anchored by PCRE if all of its top-level  A pattern is automatically anchored by PCRE if all of its top-level
1118  alternatives begin with one of the following:  alternatives begin with one of the following:
1119    .sp
1120    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1121    \\A    always    \eA    always
1122    \\G    always    \eG    always
1123    .\" JOIN
1124    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1125            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1126    .sp
1127  For such patterns, the PCRE_ANCHORED bit is set in the options returned by  For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1128  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1129    .sp
1130    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1131    .sp
1132  Return the size of the compiled pattern, that is, the value that was passed as  Return the size of the compiled pattern, that is, the value that was passed as
1133  the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to  the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
1134  place the compiled data. The fourth argument should point to a \fBsize_t\fR  place the compiled data. The fourth argument should point to a \fBsize_t\fP
1135  variable.  variable.
1136    .sp
1137    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1138    .sp
1139  Returns the size of the data block pointed to by the \fIstudy_data\fR field in  Return the size of the data block pointed to by the \fIstudy_data\fP field in
1140  a \fBpcre_extra\fR block. That is, it is the value that was passed to  a \fBpcre_extra\fP block. That is, it is the value that was passed to
1141  \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1142  created by \fBpcre_study()\fR. The fourth argument should point to a  created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1143  \fBsize_t\fR variable.  study data, zero is returned. The fourth argument should point to a
1144    \fBsize_t\fP variable.
1145  .SH OBSOLETE INFO FUNCTION  .
1146    .
1147    .SH "OBSOLETE INFO FUNCTION"
1148  .rs  .rs
1149  .sp  .sp
1150  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1151  .B *\fIfirstcharptr\fR);  .B *\fIfirstcharptr\fP);
1152  .PP  .PP
1153  The \fBpcre_info()\fR function is now obsolete because its interface is too  The \fBpcre_info()\fP function is now obsolete because its interface is too
1154  restrictive to return all the available data about a compiled pattern. New  restrictive to return all the available data about a compiled pattern. New
1155  programs should use \fBpcre_fullinfo()\fR instead. The yield of  programs should use \fBpcre_fullinfo()\fP instead. The yield of
1156  \fBpcre_info()\fR is the number of capturing subpatterns, or one of the  \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
1157  following negative numbers:  following negative numbers:
1158    .sp
1159    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
1160    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
1161    .sp
1162  If the \fIoptptr\fR argument is not NULL, a copy of the options with which the  If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
1163  pattern was compiled is placed in the integer it points to (see  pattern was compiled is placed in the integer it points to (see
1164  PCRE_INFO_OPTIONS above).  PCRE_INFO_OPTIONS above).
1165    .P
1166  If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,  If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
1167  it is used to pass back information about the first character of any matched  it is used to pass back information about the first character of any matched
1168  string (see PCRE_INFO_FIRSTBYTE above).  string (see PCRE_INFO_FIRSTBYTE above).
1169    .
1170  .SH MATCHING A PATTERN  .
1171    .SH "REFERENCE COUNTS"
1172    .rs
1173    .sp
1174    .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1175    .PP
1176    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1177    data block that contains a compiled pattern. It is provided for the benefit of
1178    applications that operate in an object-oriented manner, where different parts
1179    of the application may be using the same compiled pattern, but you want to free
1180    the block when they are all done.
1181    .P
1182    When a pattern is compiled, the reference count field is initialized to zero.
1183    It is changed only by calling this function, whose action is to add the
1184    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1185    function is the new value. However, the value of the count is constrained to
1186    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1187    it is forced to the appropriate limit value.
1188    .P
1189    Except when it is zero, the reference count is not correctly preserved if a
1190    pattern is compiled on one host and then transferred to a host whose byte-order
1191    is different. (This seems a highly unlikely scenario.)
1192    .
1193    .
1194    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1195  .rs  .rs
1196  .sp  .sp
1197  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1198  .ti +5n  .ti +5n
1199  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1200  .ti +5n  .ti +5n
1201  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1202  .PP  .P
1203  The function \fBpcre_exec()\fR is called to match a subject string against a  The function \fBpcre_exec()\fP is called to match a subject string against a
1204  pre-compiled pattern, which is passed in the \fIcode\fR argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1205  pattern has been studied, the result of the study should be passed in the  pattern was studied, the result of the study should be passed in the
1206  \fIextra\fR argument.  \fIextra\fP argument. This function is the main matching facility of the
1207    library, and it operates in a Perl-like manner. For specialist use there is
1208  Here is an example of a simple call to \fBpcre_exec()\fR:  also an alternative matching function, which is described
1209    .\" HTML <a href="#dfamatch">
1210    .\" </a>
1211    below
1212    .\"
1213    in the section about the \fBpcre_dfa_exec()\fP function.
1214    .P
1215    In most applications, the pattern will have been compiled (and optionally
1216    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1217    possible to save compiled patterns and study data, and then use them later
1218    in different processes, possibly even on different hosts. For a discussion
1219    about this, see the
1220    .\" HREF
1221    \fBpcreprecompile\fP
1222    .\"
1223    documentation.
1224    .P
1225    Here is an example of a simple call to \fBpcre_exec()\fP:
1226    .sp
1227    int rc;    int rc;
1228    int ovector[30];    int ovector[30];
1229    rc = pcre_exec(    rc = pcre_exec(
# Line 645  Here is an example of a simple call to \ Line 1233  Here is an example of a simple call to \
1233      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1234      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1235      0,              /* default options */      0,              /* default options */
1236      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1237      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1238    .
1239  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .\" HTML <a name="extradata"></a>
1240  data block. The \fBpcre_study()\fR function returns such a block (when it  .SS "Extra data for \fBpcre_exec()\fR"
1241    .rs
1242    .sp
1243    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1244    data block. The \fBpcre_study()\fP function returns such a block (when it
1245  doesn't return NULL), but you can also create one for yourself, and pass  doesn't return NULL), but you can also create one for yourself, and pass
1246  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1247    fields (not necessarily in this order):
1248    unsigned long int \fIflags\fR;  .sp
1249    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1250    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1251    void *\fIcallout_data\fR;    unsigned long int \fImatch_limit\fP;
1252      unsigned long int \fImatch_limit_recursion\fP;
1253  The \fIflags\fR field is a bitmap that specifies which of the other fields    void *\fIcallout_data\fP;
1254      const unsigned char *\fItables\fP;
1255      unsigned char **\fImark\fP;
1256    .sp
1257    The \fIflags\fP field is a bitmap that specifies which of the other fields
1258  are set. The flag bits are:  are set. The flag bits are:
1259    .sp
1260    PCRE_EXTRA_STUDY_DATA    PCRE_EXTRA_STUDY_DATA
1261    PCRE_EXTRA_MATCH_LIMIT    PCRE_EXTRA_MATCH_LIMIT
1262      PCRE_EXTRA_MATCH_LIMIT_RECURSION
1263    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1264      PCRE_EXTRA_TABLES
1265  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the    PCRE_EXTRA_MARK
1266  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with  .sp
1267  the appropriate flag bit. You should not set this yourself, but you can add to  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1268  the block by setting the other fields.  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1269    the appropriate flag bit. You should not set this yourself, but you may add to
1270  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  the block by setting the other fields and their corresponding flag bits.
1271    .P
1272    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1273  vast amount of resources when running patterns that are not going to match,  vast amount of resources when running patterns that are not going to match,
1274  but which have a very large number of possibilities in their search trees. The  but which have a very large number of possibilities in their search trees. The
1275  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is a pattern that uses nested unlimited repeats.
1276  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1277  recursively). The limit is imposed on the number of times this function is  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1278  called during a match, which has the effect of limiting the amount of recursion  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
1279  and backtracking that can take place. For patterns that are not anchored, the  number of times this function is called during a match, which has the effect of
1280  count starts from zero for each position in the subject string.  limiting the amount of backtracking that can take place. For patterns that are
1281    not anchored, the count restarts from zero for each position in the subject
1282  The default limit for the library can be set when PCRE is built; the default  string.
1283    .P
1284    The default value for the limit can be set when PCRE is built; the default
1285  default is 10 million, which handles all but the most extreme cases. You can  default is 10 million, which handles all but the most extreme cases. You can
1286  reduce the default by suppling \fBpcre_exec()\fR with a \fRpcre_extra\fR block  override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1287  in which \fImatch_limit\fR is set to a smaller value, and  block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1288  PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fR field. If the limit is  the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1289  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1290    .P
1291  The \fIpcre_callout\fR field is used in conjunction with the "callout" feature,  The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1292  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1293    limits the depth of recursion. The recursion depth is a smaller number than the
1294  The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose  total number of calls, because not all calls to \fBmatch()\fP are recursive.
1295  unused bits must be zero. This limits \fBpcre_exec()\fR to matching at the  This limit is of use only if it is set smaller than \fImatch_limit\fP.
1296  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1297  or turned out to be anchored by virtue of its contents, it cannot be made  Limiting the recursion depth limits the amount of stack that can be used, or,
1298  unachored at matching time.  when PCRE has been compiled to use memory on the heap instead of the stack, the
1299    amount of heap memory that can be used.
1300  There are also three further options that can be set only at matching time:  .P
1301    The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1302    built; the default default is the same value as the default for
1303    \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1304    with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1305    PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1306    is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1307    .P
1308    The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1309    and is described in the
1310    .\" HREF
1311    \fBpcrecallout\fP
1312    .\"
1313    documentation.
1314    .P
1315    The \fItables\fP field is used to pass a character tables pointer to
1316    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1317    pattern. A non-NULL value is stored with the compiled pattern only if custom
1318    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1319    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1320    internal tables to be used. This facility is helpful when re-using patterns
1321    that have been saved after compiling with an external set of tables, because
1322    the external tables might be at a different address when \fBpcre_exec()\fP is
1323    called. See the
1324    .\" HREF
1325    \fBpcreprecompile\fP
1326    .\"
1327    documentation for a discussion of saving compiled patterns for later use.
1328    .P
1329    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1330    be set to point to a \fBchar *\fP variable. If the pattern contains any
1331    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1332    a name to pass back, a pointer to the name string (zero terminated) is placed
1333    in the variable pointed to by the \fImark\fP field. The names are within the
1334    compiled pattern; if you wish to retain such a name you must copy it before
1335    freeing the memory of a compiled pattern. If there is no name to pass back, the
1336    variable pointed to by the \fImark\fP field set to NULL. For details of the
1337    backtracking control verbs, see the section entitled
1338    .\" HTML <a href="pcrepattern#backtrackcontrol">
1339    .\" </a>
1340    "Backtracking control"
1341    .\"
1342    in the
1343    .\" HREF
1344    \fBpcrepattern\fP
1345    .\"
1346    documentation.
1347    .
1348    .
1349    .\" HTML <a name="execoptions"></a>
1350    .SS "Option bits for \fBpcre_exec()\fP"
1351    .rs
1352    .sp
1353    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1354    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1355    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1356    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1357    PCRE_PARTIAL_HARD.
1358    .sp
1359      PCRE_ANCHORED
1360    .sp
1361    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1362    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1363    to be anchored by virtue of its contents, it cannot be made unachored at
1364    matching time.
1365    .sp
1366      PCRE_BSR_ANYCRLF
1367      PCRE_BSR_UNICODE
1368    .sp
1369    These options (which are mutually exclusive) control what the \eR escape
1370    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1371    match any Unicode newline sequence. These options override the choice that was
1372    made or defaulted when the pattern was compiled.
1373    .sp
1374      PCRE_NEWLINE_CR
1375      PCRE_NEWLINE_LF
1376      PCRE_NEWLINE_CRLF
1377      PCRE_NEWLINE_ANYCRLF
1378      PCRE_NEWLINE_ANY
1379    .sp
1380    These options override the newline definition that was chosen or defaulted when
1381    the pattern was compiled. For details, see the description of
1382    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1383    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1384    the way the match position is advanced after a match failure for an unanchored
1385    pattern.
1386    .P
1387    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1388    match attempt for an unanchored pattern fails when the current position is at a
1389    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1390    characters, the match position is advanced by two characters instead of one, in
1391    other words, to after the CRLF.
1392    .P
1393    The above rule is a compromise that makes the most common cases work as
1394    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1395    set), it does not match the string "\er\enA" because, after failing at the
1396    start, it skips both the CR and the LF before retrying. However, the pattern
1397    [\er\en]A does match that string, because it contains an explicit CR or LF
1398    reference, and so advances only by one character after the first failure.
1399    .P
1400    An explicit match for CR of LF is either a literal appearance of one of those
1401    characters, or one of the \er or \en escape sequences. Implicit matches such as
1402    [^X] do not count, nor does \es (which includes CR and LF in the characters
1403    that it matches).
1404    .P
1405    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1406    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1407    .sp
1408    PCRE_NOTBOL    PCRE_NOTBOL
1409    .sp
1410  The first character of the string is not the beginning of a line, so the  This option specifies that first character of the subject string is not the
1411  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1412  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1413    never to match. This option affects only the behaviour of the circumflex
1414    metacharacter. It does not affect \eA.
1415    .sp
1416    PCRE_NOTEOL    PCRE_NOTEOL
1417    .sp
1418  The end of the string is not the end of a line, so the dollar metacharacter  This option specifies that the end of the subject string is not the end of a
1419  should not match it nor (except in multiline mode) a newline immediately before  line, so the dollar metacharacter should not match it nor (except in multiline
1420  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1421  to match.  compile time) causes dollar never to match. This option affects only the
1422    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1423    .sp
1424    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1425    .sp
1426  An empty string is not considered to be a valid match if this option is set. If  An empty string is not considered to be a valid match if this option is set. If
1427  there are alternatives in the pattern, they are tried. If all the alternatives  there are alternatives in the pattern, they are tried. If all the alternatives
1428  match the empty string, the entire match fails. For example, if the pattern  match the empty string, the entire match fails. For example, if the pattern
1429    .sp
1430    a?b?    a?b?
1431    .sp
1432  is applied to a string not beginning with "a" or "b", it matches the empty  is applied to a string not beginning with "a" or "b", it matches an empty
1433  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1434  valid, so PCRE searches further into the string for occurrences of "a" or "b".  valid, so PCRE searches further into the string for occurrences of "a" or "b".
1435    .sp
1436  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1437  of a pattern match of the empty string within its \fBsplit()\fR function, and  .sp
1438  when using the /g modifier. It is possible to emulate Perl's behaviour after  This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1439  matching a null string by first trying the match again at the same offset with  the start of the subject is permitted. If the pattern is anchored, such a match
1440  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  can occur only if the pattern contains \eK.
1441  below) and trying an ordinary match again.  .P
1442    Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1443  The subject string is passed to \fBpcre_exec()\fR as a pointer in  does make a special case of a pattern match of the empty string within its
1444  \fIsubject\fR, a length in \fIlength\fR, and a starting offset in  \fBsplit()\fP function, and when using the /g modifier. It is possible to
1445  \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary  emulate Perl's behaviour after matching a null string by first trying the match
1446  zero bytes. When the starting offset is zero, the search for a match starts at  again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1447  the beginning of the subject, and this is by far the most common case.  if that fails, by advancing the starting offset (see below) and trying an
1448    ordinary match again. There is some code that demonstrates how to do this in
1449  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  the
1450  sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is  .\" HREF
1451  passed, PCRE's behaviour is not defined.  \fBpcredemo\fP
1452    .\"
1453    sample program. In the most general case, you have to check to see if the
1454    newline convention recognizes CRLF as a newline, and if so, and the current
1455    character is CR followed by LF, advance the starting offset by two characters
1456    instead of one.
1457    .sp
1458      PCRE_NO_START_OPTIMIZE
1459    .sp
1460    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1461    a match, in order to speed up the process. For example, if it is known that an
1462    unanchored match must start with a specific character, it searches the subject
1463    for that character, and fails immediately if it cannot find it, without
1464    actually running the main matching function. This means that a special item
1465    such as (*COMMIT) at the start of a pattern is not considered until after a
1466    suitable starting point for the match has been found. When callouts or (*MARK)
1467    items are in use, these "start-up" optimizations can cause them to be skipped
1468    if the pattern is never actually used. The start-up optimizations are in effect
1469    a pre-scan of the subject that takes place before the pattern is run.
1470    .P
1471    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1472    causing performance to suffer, but ensuring that in cases where the result is
1473    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1474    are considered at every possible starting position in the subject string.
1475    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1476    Consider the pattern
1477    .sp
1478      (*COMMIT)ABC
1479    .sp
1480    When this is compiled, PCRE records the fact that a match must start with the
1481    character "A". Suppose the subject string is "DEFABC". The start-up
1482    optimization scans along the subject, finds "A" and runs the first match
1483    attempt from there. The (*COMMIT) item means that the pattern must match the
1484    current starting position, which in this case, it does. However, if the same
1485    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1486    subject string does not happen. The first match attempt is run starting from
1487    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1488    the overall result is "no match". If the pattern is studied, more start-up
1489    optimizations may be used. For example, a minimum length for the subject may be
1490    recorded. Consider the pattern
1491    .sp
1492      (*MARK:A)(X|Y)
1493    .sp
1494    The minimum length for a match is one character. If the subject is "ABC", there
1495    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1496    If the pattern is studied, the final attempt does not take place, because PCRE
1497    knows that the subject is too short, and so the (*MARK) is never encountered.
1498    In this case, studying the pattern does not affect the overall match result,
1499    which is still "no match", but it does affect the auxiliary information that is
1500    returned.
1501    .sp
1502      PCRE_NO_UTF8_CHECK
1503    .sp
1504    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1505    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1506    The value of \fIstartoffset\fP is also checked to ensure that it points to the
1507    start of a UTF-8 character. There is a discussion about the validity of UTF-8
1508    strings in the
1509    .\" HTML <a href="pcre.html#utf8strings">
1510    .\" </a>
1511    section on UTF-8 support
1512    .\"
1513    in the main
1514    .\" HREF
1515    \fBpcre\fP
1516    .\"
1517    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1518    the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains a value that does
1519    not point to the start of a UTF-8 character (or to the end of the subject),
1520    PCRE_ERROR_BADUTF8_OFFSET is returned.
1521    .P
1522    If you already know that your subject is valid, and you want to skip these
1523    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1524    calling \fBpcre_exec()\fP. You might want to do this for the second and
1525    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1526    all the matches in a single subject string. However, you should be sure that
1527    the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
1528    end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1529    invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
1530    undefined. Your program may crash.
1531    .sp
1532      PCRE_PARTIAL_HARD
1533      PCRE_PARTIAL_SOFT
1534    .sp
1535    These options turn on the partial matching feature. For backwards
1536    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1537    occurs if the end of the subject string is reached successfully, but there are
1538    not enough subject characters to complete the match. If this happens when
1539    PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1540    testing any remaining alternatives. Only if no complete match can be found is
1541    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1542    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1543    but only if no complete match can be found.
1544    .P
1545    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1546    partial match is found, \fBpcre_exec()\fP immediately returns
1547    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1548    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1549    important that an alternative complete match.
1550    .P
1551    In both cases, the portion of the string that was inspected when the partial
1552    match was found is set as the first matching string. There is a more detailed
1553    discussion of partial and multi-segment matching, with examples, in the
1554    .\" HREF
1555    \fBpcrepartial\fP
1556    .\"
1557    documentation.
1558    .
1559    .
1560    .SS "The string to be matched by \fBpcre_exec()\fP"
1561    .rs
1562    .sp
1563    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1564    \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1565    in \fIstartoffset\fP. If this is negative or greater than the length of the
1566    subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET.
1567    .P
1568    In UTF-8 mode, the byte offset must point to the start of a UTF-8 character (or
1569    the end of the subject). Unlike the pattern string, the subject may contain
1570    binary zero bytes. When the starting offset is zero, the search for a match
1571    starts at the beginning of the subject, and this is by far the most common
1572    case.
1573    .P
1574  A non-zero starting offset is useful when searching for another match in the  A non-zero starting offset is useful when searching for another match in the
1575  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1576  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1577  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1578  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1579    .sp
1580    \\Biss\\B    \eBiss\eB
1581    .sp
1582  which finds occurrences of "iss" in the middle of words. (\\B matches only if  which finds occurrences of "iss" in the middle of words. (\eB matches only if
1583  the current position in the subject is not a word boundary.) When applied to  the current position in the subject is not a word boundary.) When applied to
1584  the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first  the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1585  occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the  occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1586  subject, namely "issipi", it does not match, because \\B is always false at the  subject, namely "issipi", it does not match, because \eB is always false at the
1587  start of the subject, which is deemed to be a word boundary. However, if  start of the subject, which is deemed to be a word boundary. However, if
1588  \fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR  \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1589  set to 4, it finds the second occurrence of "iss" because it is able to look  set to 4, it finds the second occurrence of "iss" because it is able to look
1590  behind the starting point to discover that it is preceded by a letter.  behind the starting point to discover that it is preceded by a letter.
1591    .P
1592    Finding all the matches in a subject is tricky when the pattern can match an
1593    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1594    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1595    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1596    and trying an ordinary match again. There is some code that demonstrates how to
1597    do this in the
1598    .\" HREF
1599    \fBpcredemo\fP
1600    .\"
1601    sample program. In the most general case, you have to check to see if the
1602    newline convention recognizes CRLF as a newline, and if so, and the current
1603    character is CR followed by LF, advance the starting offset by two characters
1604    instead of one.
1605    .P
1606  If a non-zero starting offset is passed when the pattern is anchored, one  If a non-zero starting offset is passed when the pattern is anchored, one
1607  attempt to match at the given offset is tried. This can only succeed if the  attempt to match at the given offset is made. This can only succeed if the
1608  pattern does not require the match to be at the start of the subject.  pattern does not require the match to be at the start of the subject.
1609    .
1610    .
1611    .SS "How \fBpcre_exec()\fP returns captured substrings"
1612    .rs
1613    .sp
1614  In general, a pattern matches a certain portion of the subject, and in  In general, a pattern matches a certain portion of the subject, and in
1615  addition, further substrings from the subject may be picked out by parts of the  addition, further substrings from the subject may be picked out by parts of the
1616  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1617  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1618  a fragment of a pattern that picks out a substring. PCRE supports several other  a fragment of a pattern that picks out a substring. PCRE supports several other
1619  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1620    .P
1621  Captured substrings are returned to the caller via a vector of integer offsets  Captured substrings are returned to the caller via a vector of integers whose
1622  whose address is passed in \fIovector\fR. The number of elements in the vector  address is passed in \fIovector\fP. The number of elements in the vector is
1623  is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass  passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1624  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1625  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1626  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1627  information. The length passed in \fIovecsize\fR should always be a multiple of  each substring using a pair of integers. The remaining third of the vector is
1628  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1629    and is not available for passing back information. The number passed in
1630  When a match has been successful, information about captured substrings is  \fIovecsize\fP should always be a multiple of three. If it is not, it is
1631  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
1632  continuing up to two-thirds of its length at the most. The first element of a  .P
1633  pair is set to the offset of the first character in a substring, and the second  When a match is successful, information about captured substrings is returned
1634  is set to the offset of the first character after the end of a substring. The  in pairs of integers, starting at the beginning of \fIovector\fP, and
1635  first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the  continuing up to two-thirds of its length at the most. The first element of
1636  subject string matched by the entire pattern. The next pair is used for the  each pair is set to the byte offset of the first character in a substring, and
1637  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR  the second is set to the byte offset of the first character after the end of a
1638  is the number of pairs that have been set. If there are no capturing  substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1639  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
1640  just the first pair of offsets has been set.  .P
1641    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1642  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
1643  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
1644    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1645  It is possible for an capturing subpattern number \fIn+1\fR to match some  For example, if two substrings have been captured, the returned value is 3. If
1646  part of the subject when subpattern \fIn\fR has not been used at all. For  there are no capturing subpatterns, the return value from a successful match is
1647  example, if the string "abc" is matched against the pattern (a|(z))(bc)  1, indicating that just the first pair of offsets has been set.
1648  subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset  .P
 values corresponding to the unused subpattern are set to -1.  
   
1649  If a capturing subpattern is matched repeatedly, it is the last portion of the  If a capturing subpattern is matched repeatedly, it is the last portion of the
1650  string that it matched that gets returned.  string that it matched that is returned.
1651    .P
1652  If the vector is too small to hold all the captured substrings, it is used as  If the vector is too small to hold all the captured substring offsets, it is
1653  far as possible (up to two-thirds of its length), and the function returns a  used as far as possible (up to two-thirds of its length), and the function
1654  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. If the substring offsets are not of interest,
1655  \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and  \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1656  \fIovecsize\fR as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1657  the \fIovector\fR isn't big enough to remember the related substrings, PCRE has  the \fIovector\fP is not big enough to remember the related substrings, PCRE
1658  to get additional memory for use during matching. Thus it is usually advisable  has to get additional memory for use during matching. Thus it is usually
1659  to supply an \fIovector\fR.  advisable to supply an \fIovector\fP.
1660    .P
1661  Note that \fBpcre_info()\fR can be used to find out how many capturing  The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1662  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1663  \fIovector\fR that will allow for \fIn\fR captured substrings, in addition to  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1664  the offsets of the substring matched by the whole pattern, is (\fIn\fR+1)*3.  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1665    .P
1666  If \fBpcre_exec()\fR fails, it returns a negative number. The following are  It is possible for capturing subpattern number \fIn+1\fP to match some part of
1667    the subject when subpattern \fIn\fP has not been used at all. For example, if
1668    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1669    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1670    happens, both values in the offset pairs corresponding to unused subpatterns
1671    are set to -1.
1672    .P
1673    Offset values that correspond to unused subpatterns at the end of the
1674    expression are also set to -1. For example, if the string "abc" is matched
1675    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1676    return from the function is 2, because the highest used capturing subpattern
1677    number is 1. However, you can refer to the offsets for the second and third
1678    capturing subpatterns if you wish (assuming the vector is large enough, of
1679    course).
1680    .P
1681    Some convenience functions are provided for extracting the captured substrings
1682    as separate strings. These are described below.
1683    .
1684    .\" HTML <a name="errorlist"></a>
1685    .SS "Error return values from \fBpcre_exec()\fP"
1686    .rs
1687    .sp
1688    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1689  defined in the header file:  defined in the header file:
1690    .sp
1691    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
1692    .sp
1693  The subject string did not match the pattern.  The subject string did not match the pattern.
1694    .sp
1695    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
1696    .sp
1697  Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was  Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1698  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
1699    .sp
1700    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
1701    .sp
1702  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
1703    .sp
1704    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
1705    .sp
1706  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1707  the case when it is passed a junk pointer. This is the error it gives when the  the case when it is passed a junk pointer and to detect when a pattern that was
1708  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
1709    other endianness. This is the error that PCRE gives when the magic number is
1710    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
1711    .sp
1712      PCRE_ERROR_UNKNOWN_OPCODE (-5)
1713    .sp
1714  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
1715  compiled pattern. This error could be caused by a bug in PCRE or by overwriting  compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1716  of the compiled pattern.  of the compiled pattern.
1717    .sp
1718    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1719    .sp
1720  If a pattern contains back references, but the \fIovector\fR that is passed to  If a pattern contains back references, but the \fIovector\fP that is passed to
1721  \fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE  \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1722  gets a block of memory at the start of matching to use for this purpose. If the  gets a block of memory at the start of matching to use for this purpose. If the
1723  call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at  call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1724  the end of matching.  automatically freed at the end of matching.
1725    .P
1726    This error is also given if \fBpcre_stack_malloc()\fP fails in
1727    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1728    \fB--disable-stack-for-recursion\fP.
1729    .sp
1730    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1731    .sp
1732  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
1733  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1734  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
1735    .sp
1736    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
1737    .sp
1738  The recursion and backtracking limit, as specified by the \fImatch_limit\fR  The backtracking limit, as specified by the \fImatch_limit\fP field in a
1739  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1740  description above.  above.
1741    .sp
1742    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
1743    .sp
1744  This error is never generated by \fBpcre_exec()\fR itself. It is provided for  This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1745  use by callout functions that want to yield a distinctive error code. See the  use by callout functions that want to yield a distinctive error code. See the
1746  \fBpcrecallout\fR documentation for details.  .\" HREF
1747    \fBpcrecallout\fP
1748  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  .\"
1749    documentation for details.
1750    .sp
1751      PCRE_ERROR_BADUTF8        (-10)
1752    .sp
1753    A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1754    .sp
1755      PCRE_ERROR_BADUTF8_OFFSET (-11)
1756    .sp
1757    The UTF-8 byte sequence that was passed as a subject was valid, but the value
1758    of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1759    .sp
1760      PCRE_ERROR_PARTIAL        (-12)
1761    .sp
1762    The subject string did not match, but it did match partially. See the
1763    .\" HREF
1764    \fBpcrepartial\fP
1765    .\"
1766    documentation for details of partial matching.
1767    .sp
1768      PCRE_ERROR_BADPARTIAL     (-13)
1769    .sp
1770    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1771    option was used with a compiled pattern containing items that were not
1772    supported for partial matching. From release 8.00 onwards, there are no
1773    restrictions on partial matching.
1774    .sp
1775      PCRE_ERROR_INTERNAL       (-14)
1776    .sp
1777    An unexpected internal error has occurred. This error could be caused by a bug
1778    in PCRE or by overwriting of the compiled pattern.
1779    .sp
1780      PCRE_ERROR_BADCOUNT       (-15)
1781    .sp
1782    This error is given if the value of the \fIovecsize\fP argument is negative.
1783    .sp
1784      PCRE_ERROR_RECURSIONLIMIT (-21)
1785    .sp
1786    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1787    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1788    description above.
1789    .sp
1790      PCRE_ERROR_BADNEWLINE     (-23)
1791    .sp
1792    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1793    .sp
1794      PCRE_ERROR_BADOFFSET      (-24)
1795    .sp
1796    The value of \fIstartoffset\fP was negative or greater than the length of the
1797    subject, that is, the value in \fIlength\fP.
1798    .P
1799    Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1800    .
1801    .
1802    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1803  .rs  .rs
1804  .sp  .sp
1805  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1806  .ti +5n  .ti +5n
1807  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1808  .ti +5n  .ti +5n
1809  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
1810  .PP  .PP
1811  .br  .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
1812  .ti +5n  .ti +5n
1813  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
1814  .ti +5n  .ti +5n
1815  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1816  .PP  .PP
1817  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
1818  .ti +5n  .ti +5n
1819  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1820  .PP  .PP
1821  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
1822  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1823  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1824  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1825  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
1826  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
1827  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
1828  has a further zero added on the end, but the result is not, of course,  .P
1829  a C string.  A substring that contains a binary zero is correctly extracted and has a
1830    further zero added on the end, but the result is not, of course, a C string.
1831    However, you can process such a string by referring to the length that is
1832    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1833    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1834    for handling strings containing binary zeros, because the end of the final
1835    string is not independently indicated.
1836    .P
1837  The first three arguments are the same for all three of these functions:  The first three arguments are the same for all three of these functions:
1838  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
1839  \fIovector\fR is a pointer to the vector of integer offsets that was passed to  \fIovector\fP is a pointer to the vector of integer offsets that was passed to
1840  \fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that were  \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
1841  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
1842  expression. This is the value returned by \fBpcre_exec\fR if it is greater than  expression. This is the value returned by \fBpcre_exec()\fP if it is greater
1843  zero. If \fBpcre_exec()\fR returned zero, indicating that it ran out of space  than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
1844  in \fIovector\fR, the value passed as \fIstringcount\fR should be the size of  space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
1845  the vector divided by three.  number of elements in the vector divided by three.
1846    .P
1847  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1848  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
1849  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
1850  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1851  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
1852  \fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is  \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
1853  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
1854  \fIstringptr\fR. The yield of the function is the length of the string, not  \fIstringptr\fP. The yield of the function is the length of the string, not
1855  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
1856    .sp
1857    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1858    .sp
1859  The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get  The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
1860  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
1861    .sp
1862    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1863    .sp
1864  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
1865    .P
1866  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
1867  and builds a list of pointers to them. All this is done in a single block of  and builds a list of pointers to them. All this is done in a single block of
1868  memory which is obtained via \fBpcre_malloc\fR. The address of the memory block  memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
1869  is returned via \fIlistptr\fR, which is also the start of the list of string  is returned via \fIlistptr\fP, which is also the start of the list of string
1870  pointers. The end of the list is marked by a NULL pointer. The yield of the  pointers. The end of the list is marked by a NULL pointer. The yield of the
1871  function is zero if all went well, or  function is zero if all went well, or the error code
1872    .sp
1873    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1874    .sp
1875  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
1876    .P
1877  When any of these functions encounter a substring that is unset, which can  When any of these functions encounter a substring that is unset, which can
1878  happen when capturing subpattern number \fIn+1\fR matches some part of the  happen when capturing subpattern number \fIn+1\fP matches some part of the
1879  subject, but subpattern \fIn\fR has not been used at all, they return an empty  subject, but subpattern \fIn\fP has not been used at all, they return an empty
1880  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
1881  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1882  substrings.  substrings.
1883    .P
1884  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
1885  \fBpcre_free_substring_list()\fR can be used to free the memory returned by  \fBpcre_free_substring_list()\fP can be used to free the memory returned by
1886  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
1887  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1888  the function pointed to by \fBpcre_free\fR, which of course could be called  the function pointed to by \fBpcre_free\fP, which of course could be called
1889  directly from a C program. However, PCRE is used in some situations where it is  directly from a C program. However, PCRE is used in some situations where it is
1890  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
1891  \fBpcre_free\fR directly; it is for these cases that the functions are  \fBpcre_free\fP directly; it is for these cases that the functions are
1892  provided.  provided.
1893    .
1894  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
1895    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1896  .rs  .rs
1897  .sp  .sp
1898  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1899  .ti +5n  .ti +5n
1900  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
1901    .PP
1902    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1903  .ti +5n  .ti +5n
1904  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1905  .ti +5n  .ti +5n
1906  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B int \fIstringcount\fP, const char *\fIstringname\fP,
 .PP  
 .br  
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
1907  .ti +5n  .ti +5n
1908  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1909  .PP  .PP
1910  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
1911  .ti +5n  .ti +5n
1912  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1913  .ti +5n  .ti +5n
1914  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
1915  .ti +5n  .ti +5n
1916  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1917  .PP  .PP
1918  To extract a substring by name, you first have to find associated number. This  To extract a substring by name, you first have to find associated number.
1919  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
1920  compiled pattern, and the second is the name. For example, for this pattern  .sp
1921      (a+)b(?<xxx>\ed+)...
1922    ab(?<xxx>\\d+)...  .sp
1923    the number of the subpattern called "xxx" is 2. If the name is known to be
1924  the number of the subpattern called "xxx" is 1. Given the number, you can then  unique (PCRE_DUPNAMES was not set), you can find the number from the name by
1925  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1926  previous section. For convenience, there are also two functions that do the  pattern, and the second is the name. The yield of the function is the
1927  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1928    that name.
1929  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
1930  \fIpcre_get_named_substring()\fR are the same as those for the functions that  Given the number, you can extract the substring directly, or use one of the
1931  extract by number, and so are not re-described here. There are just two  functions described in the previous section. For convenience, there are also
1932  differences.  two functions that do the whole job.
1933    .P
1934    Most of the arguments of \fBpcre_copy_named_substring()\fP and
1935    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1936    functions that extract by number. As these are described in the previous
1937    section, they are not re-described here. There are just two differences:
1938    .P
1939  First, instead of a substring number, a substring name is given. Second, there  First, instead of a substring number, a substring name is given. Second, there
1940  is an extra argument, given at the start, which is a pointer to the compiled  is an extra argument, given at the start, which is a pointer to the compiled
1941  pattern. This is needed in order to gain access to the name-to-number  pattern. This is needed in order to gain access to the name-to-number
1942  translation table.  translation table.
1943    .P
1944  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1945  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1946  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1947    the behaviour may not be what you want (see the next section).
1948  .in 0  .P
1949  Last updated: 03 February 2003  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1950  .br  subpatterns with the same number, as described in the
1951  Copyright (c) 1997-2003 University of Cambridge.  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1952    .\" </a>
1953    section on duplicate subpattern numbers
1954    .\"
1955    in the
1956    .\" HREF
1957    \fBpcrepattern\fP
1958    .\"
1959    page, you cannot use names to distinguish the different subpatterns, because
1960    names are not included in the compiled code. The matching process uses only
1961    numbers. For this reason, the use of different names for subpatterns of the
1962    same number causes an error at compile time.
1963    .
1964    .SH "DUPLICATE SUBPATTERN NAMES"
1965    .rs
1966    .sp
1967    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1968    .ti +5n
1969    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1970    .PP
1971    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1972    are not required to be unique. (Duplicate names are always allowed for
1973    subpatterns with the same number, created by using the (?| feature. Indeed, if
1974    such subpatterns are named, they are required to use the same names.)
1975    .P
1976    Normally, patterns with duplicate names are such that in any one match, only
1977    one of the named subpatterns participates. An example is shown in the
1978    .\" HREF
1979    \fBpcrepattern\fP
1980    .\"
1981    documentation.
1982    .P
1983    When duplicates are present, \fBpcre_copy_named_substring()\fP and
1984    \fBpcre_get_named_substring()\fP return the first substring corresponding to
1985    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1986    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1987    returns one of the numbers that are associated with the name, but it is not
1988    defined which it is.
1989    .P
1990    If you want to get full details of all captured substrings for a given name,
1991    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1992    argument is the compiled pattern, and the second is the name. The third and
1993    fourth are pointers to variables which are updated by the function. After it
1994    has run, they point to the first and last entries in the name-to-number table
1995    for the given name. The function itself returns the length of each entry, or
1996    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1997    described above in the section entitled \fIInformation about a pattern\fP.
1998    Given all the relevant entries for the name, you can extract each of their
1999    numbers, and hence the captured data, if any.
2000    .
2001    .
2002    .SH "FINDING ALL POSSIBLE MATCHES"
2003    .rs
2004    .sp
2005    The traditional matching function uses a similar algorithm to Perl, which stops
2006    when it finds the first match, starting at a given point in the subject. If you
2007    want to find all possible matches, or the longest possible match, consider
2008    using the alternative matching function (see below) instead. If you cannot use
2009    the alternative function, but still need to find all possible matches, you
2010    can kludge it up by making use of the callout facility, which is described in
2011    the
2012    .\" HREF
2013    \fBpcrecallout\fP
2014    .\"
2015    documentation.
2016    .P
2017    What you have to do is to insert a callout right at the end of the pattern.
2018    When your callout function is called, extract and save the current matched
2019    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2020    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2021    will yield PCRE_ERROR_NOMATCH.
2022    .
2023    .
2024    .\" HTML <a name="dfamatch"></a>
2025    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2026    .rs
2027    .sp
2028    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2029    .ti +5n
2030    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2031    .ti +5n
2032    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2033    .ti +5n
2034    .B int *\fIworkspace\fP, int \fIwscount\fP);
2035    .P
2036    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2037    a compiled pattern, using a matching algorithm that scans the subject string
2038    just once, and does not backtrack. This has different characteristics to the
2039    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2040    patterns are not supported. Nevertheless, there are times when this kind of
2041    matching can be useful. For a discussion of the two matching algorithms, and a
2042    list of features that \fBpcre_dfa_exec()\fP does not support, see the
2043    .\" HREF
2044    \fBpcrematching\fP
2045    .\"
2046    documentation.
2047    .P
2048    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2049    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2050    different way, and this is described below. The other common arguments are used
2051    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2052    here.
2053    .P
2054    The two additional arguments provide workspace for the function. The workspace
2055    vector should contain at least 20 elements. It is used for keeping track of
2056    multiple paths through the pattern tree. More workspace will be needed for
2057    patterns and subjects where there are a lot of potential matches.
2058    .P
2059    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2060    .sp
2061      int rc;
2062      int ovector[10];
2063      int wspace[20];
2064      rc = pcre_dfa_exec(
2065        re,             /* result of pcre_compile() */
2066        NULL,           /* we didn't study the pattern */
2067        "some string",  /* the subject string */
2068        11,             /* the length of the subject string */
2069        0,              /* start at offset 0 in the subject */
2070        0,              /* default options */
2071        ovector,        /* vector of integers for substring information */
2072        10,             /* number of elements (NOT size in bytes) */
2073        wspace,         /* working space vector */
2074        20);            /* number of elements (NOT size in bytes) */
2075    .
2076    .SS "Option bits for \fBpcre_dfa_exec()\fP"
2077    .rs
2078    .sp
2079    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2080    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2081    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2082    PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2083    PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2084    All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2085    so their description is not repeated here.
2086    .sp
2087      PCRE_PARTIAL_HARD
2088      PCRE_PARTIAL_SOFT
2089    .sp
2090    These have the same general effect as they do for \fBpcre_exec()\fP, but the
2091    details are slightly different. When PCRE_PARTIAL_HARD is set for
2092    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2093    is reached and there is still at least one matching possibility that requires
2094    additional characters. This happens even if some complete matches have also
2095    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2096    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2097    there have been no complete matches, but there is still at least one matching
2098    possibility. The portion of the string that was inspected when the longest
2099    partial match was found is set as the first matching string in both cases.
2100    There is a more detailed discussion of partial and multi-segment matching, with
2101    examples, in the
2102    .\" HREF
2103    \fBpcrepartial\fP
2104    .\"
2105    documentation.
2106    .sp
2107      PCRE_DFA_SHORTEST
2108    .sp
2109    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2110    soon as it has found one match. Because of the way the alternative algorithm
2111    works, this is necessarily the shortest possible match at the first possible
2112    matching point in the subject string.
2113    .sp
2114      PCRE_DFA_RESTART
2115    .sp
2116    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2117    again, with additional subject characters, and have it continue with the same
2118    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2119    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2120    before because data about the match so far is left in them after a partial
2121    match. There is more discussion of this facility in the
2122    .\" HREF
2123    \fBpcrepartial\fP
2124    .\"
2125    documentation.
2126    .
2127    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2128    .rs
2129    .sp
2130    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2131    substring in the subject. Note, however, that all the matches from one run of
2132    the function start at the same point in the subject. The shorter matches are
2133    all initial substrings of the longer matches. For example, if the pattern
2134    .sp
2135      <.*>
2136    .sp
2137    is matched against the string
2138    .sp
2139      This is <something> <something else> <something further> no more
2140    .sp
2141    the three matched strings are
2142    .sp
2143      <something>
2144      <something> <something else>
2145      <something> <something else> <something further>
2146    .sp
2147    On success, the yield of the function is a number greater than zero, which is
2148    the number of matched substrings. The substrings themselves are returned in
2149    \fIovector\fP. Each string uses two elements; the first is the offset to the
2150    start, and the second is the offset to the end. In fact, all the strings have
2151    the same start offset. (Space could have been saved by giving this only once,
2152    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2153    returns data, even though the meaning of the strings is different.)
2154    .P
2155    The strings are returned in reverse order of length; that is, the longest
2156    matching string is given first. If there were too many matches to fit into
2157    \fIovector\fP, the yield of the function is zero, and the vector is filled with
2158    the longest matches.
2159    .
2160    .SS "Error returns from \fBpcre_dfa_exec()\fP"
2161    .rs
2162    .sp
2163    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2164    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2165    described
2166    .\" HTML <a href="#errorlist">
2167    .\" </a>
2168    above.
2169    .\"
2170    There are in addition the following errors that are specific to
2171    \fBpcre_dfa_exec()\fP:
2172    .sp
2173      PCRE_ERROR_DFA_UITEM      (-16)
2174    .sp
2175    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2176    that it does not support, for instance, the use of \eC or a back reference.
2177    .sp
2178      PCRE_ERROR_DFA_UCOND      (-17)
2179    .sp
2180    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2181    uses a back reference for the condition, or a test for recursion in a specific
2182    group. These are not supported.
2183    .sp
2184      PCRE_ERROR_DFA_UMLIMIT    (-18)
2185    .sp
2186    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2187    block that contains a setting of the \fImatch_limit\fP field. This is not
2188    supported (it is meaningless).
2189    .sp
2190      PCRE_ERROR_DFA_WSSIZE     (-19)
2191    .sp
2192    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2193    \fIworkspace\fP vector.
2194    .sp
2195      PCRE_ERROR_DFA_RECURSE    (-20)
2196    .sp
2197    When a recursive subpattern is processed, the matching function calls itself
2198    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2199    error is given if the output vector is not large enough. This should be
2200    extremely rare, as a vector of size 1000 is used.
2201    .
2202    .
2203    .SH "SEE ALSO"
2204    .rs
2205    .sp
2206    \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2207    \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2208    \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2209    .
2210    .
2211    .SH AUTHOR
2212    .rs
2213    .sp
2214    .nf
2215    Philip Hazel
2216    University Computing Service
2217    Cambridge CB2 3QH, England.
2218    .fi
2219    .
2220    .
2221    .SH REVISION
2222    .rs
2223    .sp
2224    .nf
2225    Last updated: 06 November 2010
2226    Copyright (c) 1997-2010 University of Cambridge.
2227    .fi

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