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revision 73 by nigel, Sat Feb 24 21:40:30 2007 UTC revision 142 by ph10, Fri Mar 30 15:55:18 2007 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,
43  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .ti +5n
44    .B const char *\fIsubject\fP, int *\fIovector\fP,
45  .ti +5n  .ti +5n
46  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
47  .ti +5n  .ti +5n
48  .B int \fIbuffersize\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
49  .PP  .PP
50  .br  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
51  .ti +5n  .ti +5n
52  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53  .ti +5n  .ti +5n
54  .B int \fIstringcount\fR, const char *\fIstringname\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 const char **\fIstringptr\fR);  .B const char *\fIsubject\fP, int *\fIovector\fP,
59    .ti +5n
60    .B int \fIstringcount\fP, const char *\fIstringname\fP,
61    .ti +5n
62    .B const char **\fIstringptr\fP);
63  .PP  .PP
64  .br  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
65  .ti +5n  .ti +5n
66  .B const char *\fIname\fR);  .B const char *\fIname\fP);
67  .PP  .PP
68  .br  .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
69  .ti +5n  .ti +5n
70  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71    .PP
72    .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
73  .ti +5n  .ti +5n
74  .B const char **\fIstringptr\fR);  .B int \fIstringcount\fP, int \fIstringnumber\fP,
75    .ti +5n
76    .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
92    .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
93    .B *\fIfirstcharptr\fP);
94  .PP  .PP
95  .br  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
 .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  
 .B *\fIfirstcharptr\fR);  
96  .PP  .PP
97  .br  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
 .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  
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
 .br  
105  .B void *(*pcre_stack_malloc)(size_t);  .B void *(*pcre_stack_malloc)(size_t);
106  .PP  .PP
 .br  
107  .B void (*pcre_stack_free)(void *);  .B void (*pcre_stack_free)(void *);
108  .PP  .PP
 .br  
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  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
136    \fBpcre_get_substring()\fR  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
137    \fBpcre_get_named_substring()\fR  in a Perl-compatible manner. A sample program that demonstrates the simplest
138    \fBpcre_get_substring_list()\fR  way of using them is provided in the file called \fIpcredemo.c\fP in the source
139    distribution. The
140  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  .\" HREF
141    \fBpcresample\fP
142    .\"
143    documentation describes how to run it.
144    .P
145    A second matching function, \fBpcre_dfa_exec()\fP, which is not
146    Perl-compatible, is also provided. This uses a different algorithm for the
147    matching. The alternative algorithm finds all possible matches (at a given
148    point in the subject), and scans the subject just once. However, this algorithm
149    does not return captured substrings. A description of the two matching
150    algorithms and their advantages and disadvantages is given in the
151    .\" HREF
152    \fBpcrematching\fP
153    .\"
154    documentation.
155    .P
156    In addition to the main compiling and matching functions, there are convenience
157    functions for extracting captured substrings from a subject string that is
158    matched by \fBpcre_exec()\fP. They are:
159    .sp
160      \fBpcre_copy_substring()\fP
161      \fBpcre_copy_named_substring()\fP
162      \fBpcre_get_substring()\fP
163      \fBpcre_get_named_substring()\fP
164      \fBpcre_get_substring_list()\fP
165      \fBpcre_get_stringnumber()\fP
166      \fBpcre_get_stringtable_entries()\fP
167    .sp
168    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
169  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
170    .P
171  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
172  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,
173    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
174  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
175  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
176    .P
177    The function \fBpcre_fullinfo()\fP is used to find out information about a
178    compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
179  some of the available information, but is retained for backwards compatibility.  some of the available information, but is retained for backwards compatibility.
180  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
181  version of PCRE and its date of release.  version of PCRE and its date of release.
182    .P
183  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
184  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  containing a compiled pattern. This is provided for the benefit of
185    object-oriented applications.
186    .P
187    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
188    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
189  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
190  so a calling program can replace them if it wishes to intercept the calls. This  so a calling program can replace them if it wishes to intercept the calls. This
191  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
192    .P
193  The global variables \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are also  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
194  indirections to memory management functions. These special functions are used  indirections to memory management functions. These special functions are used
195  only when PCRE is compiled to use the heap for remembering data, instead of  only when PCRE is compiled to use the heap for remembering data, instead of
196  recursive function calls. This is a non-standard way of building PCRE, for use  recursive function calls, when running the \fBpcre_exec()\fP function. See the
197  in environments that have limited stacks. Because of the greater use of memory  .\" HREF
198  management, it runs more slowly. Separate functions are provided so that  \fBpcrebuild\fP
199  special-purpose external code can be used for this case. When used, these  .\"
200  functions are always called in a stack-like manner (last obtained, first  documentation for details of how to do this. It is a non-standard way of
201  freed), and always for memory blocks of the same size.  building PCRE, for use in environments that have limited stacks. Because of the
202    greater use of memory management, it runs more slowly. Separate functions are
203  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  provided so that special-purpose external code can be used for this case. When
204    used, these functions are always called in a stack-like manner (last obtained,
205    first freed), and always for memory blocks of the same size. There is a
206    discussion about PCRE's stack usage in the
207    .\" HREF
208    \fBpcrestack\fP
209    .\"
210    documentation.
211    .P
212    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
213  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
214  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
215    .\" HREF
216    \fBpcrecallout\fP
217    .\"
218  documentation.  documentation.
219    .
220    .
221    .SH NEWLINES
222    .rs
223    .sp
224    PCRE supports four different conventions for indicating line breaks in
225    strings: a single CR (carriage return) character, a single LF (linefeed)
226    character, the two-character sequence CRLF, or any Unicode newline sequence.
227    The Unicode newline sequences are the three just mentioned, plus the single
228    characters VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line,
229    U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
230    .P
231    Each of the first three conventions is used by at least one operating system as
232    its standard newline sequence. When PCRE is built, a default can be specified.
233    The default default is LF, which is the Unix standard. When PCRE is run, the
234    default can be overridden, either when a pattern is compiled, or when it is
235    matched.
236    .P
237    In the PCRE documentation the word "newline" is used to mean "the character or
238    pair of characters that indicate a line break". The choice of newline
239    convention affects the handling of the dot, circumflex, and dollar
240    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
241    recognized line ending sequence, the match position advancement for a
242    non-anchored pattern. The choice of newline convention does not affect the
243    interpretation of the \en or \er escape sequences.
244    .
245    .
246  .SH MULTITHREADING  .SH MULTITHREADING
247  .rs  .rs
248  .sp  .sp
249  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
250  proviso that the memory management functions pointed to by \fBpcre_malloc\fR,  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
251  \fBpcre_free\fR, \fBpcre_stack_malloc\fR, and \fBpcre_stack_free\fR, and the  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
252  callout function pointed to by \fBpcre_callout\fR, are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
253    .P
254  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
255  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.
256    .
257  .SH CHECKING BUILD-TIME OPTIONS  .
258    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
259  .rs  .rs
260  .sp  .sp
261  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  The compiled form of a regular expression can be saved and re-used at a later
262    time, possibly by a different program, and even on a host other than the one on
263    which it was compiled. Details are given in the
264    .\" HREF
265    \fBpcreprecompile\fP
266    .\"
267    documentation.
268    .
269    .
270    .SH "CHECKING BUILD-TIME OPTIONS"
271    .rs
272    .sp
273    .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
274  .PP  .PP
275  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
276  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
277  .\" HREF  .\" HREF
278  \fBpcrebuild\fR  \fBpcrebuild\fP
279  .\"  .\"
280  documentation has more details about these optional features.  documentation has more details about these optional features.
281    .P
282  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
283  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
284  which the information is placed. The following information is available:  which the information is placed. The following information is available:
285    .sp
286    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
287    .sp
288  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;
289  otherwise it is set to zero.  otherwise it is set to zero.
290    .sp
291      PCRE_CONFIG_UNICODE_PROPERTIES
292    .sp
293    The output is an integer that is set to one if support for Unicode character
294    properties is available; otherwise it is set to zero.
295    .sp
296    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
297    .sp
298  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
299  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
300  should normally be the standard character for your operating system.  are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY. The default should
301    normally be the standard sequence for your operating system.
302    .sp
303    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
304    .sp
305  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
306  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
307  allow larger regular expressions to be compiled, at the expense of slower  allow larger regular expressions to be compiled, at the expense of slower
308  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
309  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.
310    .sp
311    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
312    .sp
313  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
314  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
315  the \fBpcreposix\fR documentation.  the
316    .\" HREF
317    \fBpcreposix\fP
318    .\"
319    documentation.
320    .sp
321    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
322    .sp
323  The output is an integer that gives the default limit for the number of  The output is an integer that gives the default limit for the number of
324  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
325  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
326    .sp
327      PCRE_CONFIG_MATCH_LIMIT_RECURSION
328    .sp
329    The output is an integer that gives the default limit for the depth of
330    recursion when calling the internal matching function in a \fBpcre_exec()\fP
331    execution. Further details are given with \fBpcre_exec()\fP below.
332    .sp
333    PCRE_CONFIG_STACKRECURSE    PCRE_CONFIG_STACKRECURSE
334    .sp
335  The output is an integer that is set to one if internal recursion is  The output is an integer that is set to one if internal recursion when running
336  implemented by recursive function calls that use the stack to remember their  \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
337  state. This is the usual way that PCRE is compiled. The output is zero if PCRE  to remember their state. This is the usual way that PCRE is compiled. The
338  was compiled to use blocks of data on the heap instead of recursive function  output is zero if PCRE was compiled to use blocks of data on the heap instead
339  calls. In this case, \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
340  called to manage memory blocks on the heap, thus avoiding the use of the stack.  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
341    avoiding the use of the stack.
342  .SH COMPILING A PATTERN  .
343  .rs  .
344  .sp  .SH "COMPILING A PATTERN"
345  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  .rs
346  .ti +5n  .sp
347  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
348  .ti +5n  .ti +5n
349  .B const unsigned char *\fItableptr\fR);  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
350  .PP  .ti +5n
351    .B const unsigned char *\fItableptr\fP);
352  The function \fBpcre_compile()\fR is called to compile a pattern into an  .sp
353  internal form. The pattern is a C string terminated by a binary zero, and  .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
354  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  .ti +5n
355  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  .B int *\fIerrorcodeptr\fP,
356  code and related data. The \fBpcre\fR type is defined for the returned block;  .ti +5n
357  this is a typedef for a structure whose contents are not externally defined. It  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
358  is up to the caller to free the memory when it is no longer required.  .ti +5n
359    .B const unsigned char *\fItableptr\fP);
360    .P
361    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
362    called to compile a pattern into an internal form. The only difference between
363    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
364    \fIerrorcodeptr\fP, via which a numerical error code can be returned.
365    .P
366    The pattern is a C string terminated by a binary zero, and is passed in the
367    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
368    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
369    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
370    for a structure whose contents are not externally defined. It is up to the
371    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
372    .P
373  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
374  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
375  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
376  which is an address (see below).  argument, which is an address (see below).
377    .P
378  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
379  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
380  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
381  from within the pattern (see the detailed description of regular expressions  compatible with Perl, can also be set and unset from within the pattern (see
382  in the \fBpcrepattern\fR documentation). For these options, the contents of the  the detailed description in the
383  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
384  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
385    .\"
386    documentation). For these options, the contents of the \fIoptions\fP argument
387    specifies their initial settings at the start of compilation and execution. The
388    PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of
389  matching as well as at compile time.  matching as well as at compile time.
390    .P
391  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
392  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
393  NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
394  error message. The offset from the start of the pattern to the character where  error message. This is a static string that is part of the library. You must
395  the error was discovered is placed in the variable pointed to by  not try to free it. The offset from the start of the pattern to the character
396  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  where the error was discovered is placed in the variable pointed to by
397    \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
398  If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of  .P
399  character tables which are built when it is compiled, using the default C  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
400  locale. Otherwise, \fItableptr\fR must be the result of a call to  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
401  \fBpcre_maketables()\fR. See the section on locale support below.  returned via this argument in the event of an error. This is in addition to the
402    textual error message. Error codes and messages are listed below.
403  This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:  .P
404    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
405    character tables that are built when PCRE is compiled, using the default C
406    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
407    call to \fBpcre_maketables()\fP. This value is stored with the compiled
408    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
409    passed to it. For more discussion, see the section on locale support below.
410    .P
411    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
412    .sp
413    pcre *re;    pcre *re;
414    const char *error;    const char *error;
415    int erroffset;    int erroffset;
# Line 290  This code fragment shows a typical strai Line 419  This code fragment shows a typical strai
419      &error,           /* for error message */      &error,           /* for error message */
420      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
421      NULL);            /* use default character tables */      NULL);            /* use default character tables */
422    .sp
423  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
424    file:
425    .sp
426    PCRE_ANCHORED    PCRE_ANCHORED
427    .sp
428  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
429  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
430  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
431  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
432  Perl.  Perl.
433    .sp
434      PCRE_AUTO_CALLOUT
435    .sp
436    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
437    all with number 255, before each pattern item. For discussion of the callout
438    facility, see the
439    .\" HREF
440    \fBpcrecallout\fP
441    .\"
442    documentation.
443    .sp
444    PCRE_CASELESS    PCRE_CASELESS
445    .sp
446  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
447  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
448  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
449    concept of case for characters whose values are less than 128, so caseless
450    matching is always possible. For characters with higher values, the concept of
451    case is supported if PCRE is compiled with Unicode property support, but not
452    otherwise. If you want to use caseless matching for characters 128 and above,
453    you must ensure that PCRE is compiled with Unicode property support as well as
454    with UTF-8 support.
455    .sp
456    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
457    .sp
458  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
459  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
460  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
461  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.
462  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
463  a pattern.  pattern.
464    .sp
465    PCRE_DOTALL    PCRE_DOTALL
466    .sp
467  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,
468  including newlines. Without it, newlines are excluded. This option is  including those that indicate newline. Without it, a dot does not match when
469  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
470  (?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
471  character, independent of the setting of this option.  negative class such as [^a] always matches newline characters, independent of
472    the setting of this option.
473    .sp
474      PCRE_DUPNAMES
475    .sp
476    If this bit is set, names used to identify capturing subpatterns need not be
477    unique. This can be helpful for certain types of pattern when it is known that
478    only one instance of the named subpattern can ever be matched. There are more
479    details of named subpatterns below; see also the
480    .\" HREF
481    \fBpcrepattern\fP
482    .\"
483    documentation.
484    .sp
485    PCRE_EXTENDED    PCRE_EXTENDED
486    .sp
487  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
488  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. Whitespace does not
489  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
490  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
491  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
492  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
493    .P
494  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
495  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
496  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
497  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( which introduces a conditional subpattern.
498    .sp
499    PCRE_EXTRA    PCRE_EXTRA
500    .sp
501  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
502  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
503  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
504  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
505  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
506  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
507  controlled by this option. It can also be set by a (?X) option setting within a  give a warning for this.) There are at present no other features controlled by
508  pattern.  this option. It can also be set by a (?X) option setting within a pattern.
509    .sp
510      PCRE_FIRSTLINE
511    .sp
512    If this option is set, an unanchored pattern is required to match before or at
513    the first newline in the subject string, though the matched text may continue
514    over the newline.
515    .sp
516    PCRE_MULTILINE    PCRE_MULTILINE
517    .sp
518  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
519  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
520  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
521  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
522  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
523  Perl.  Perl.
524    .P
525  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
526  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
527  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
528  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
529  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
530  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
531    .sp
532      PCRE_NEWLINE_CR
533      PCRE_NEWLINE_LF
534      PCRE_NEWLINE_CRLF
535      PCRE_NEWLINE_ANY
536    .sp
537    These options override the default newline definition that was chosen when PCRE
538    was built. Setting the first or the second specifies that a newline is
539    indicated by a single character (CR or LF, respectively). Setting
540    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
541    CRLF sequence. Setting PCRE_NEWLINE_ANY specifies that any Unicode newline
542    sequence should be recognized. The Unicode newline sequences are the three just
543    mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
544    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
545    (paragraph separator, U+2029). The last two are recognized only in UTF-8 mode.
546    .P
547    The newline setting in the options word uses three bits that are treated
548    as a number, giving eight possibilities. Currently only five are used (default
549    plus the four values above). This means that if you set more than one newline
550    option, the combination may or may not be sensible. For example,
551    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
552    other combinations yield unused numbers and cause an error.
553    .P
554    The only time that a line break is specially recognized when compiling a
555    pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
556    class is encountered. This indicates a comment that lasts until after the next
557    line break sequence. In other circumstances, line break sequences are treated
558    as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
559    as whitespace characters and are therefore ignored.
560    .P
561    The newline option that is set at compile time becomes the default that is used
562    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
563    .sp
564    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
565    .sp
566  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
567  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
568  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
569  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
570  in Perl.  in Perl.
571    .sp
572    PCRE_UNGREEDY    PCRE_UNGREEDY
573    .sp
574  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
575  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
576  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.
577    .sp
578    PCRE_UTF8    PCRE_UTF8
579    .sp
580  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
581  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
582  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
583  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
584  behaviour of PCRE are given in the  behaviour of PCRE are given in the
585  .\" HTML <a href="pcre.html#utf8support">  .\" HTML <a href="pcre.html#utf8support">
# Line 392  section on UTF-8 support Line 588  section on UTF-8 support
588  .\"  .\"
589  in the main  in the main
590  .\" HREF  .\" HREF
591  \fBpcre\fR  \fBpcre\fP
592  .\"  .\"
593  page.  page.
594    .sp
595    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
596    .sp
597  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
598  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. If an invalid UTF-8 sequence of bytes is found,
599  \fBpcre_compile()\fR returns an error. If you already know that your pattern is  \fBpcre_compile()\fP returns an error. If you already know that your pattern is
600  valid, and you want to skip this check for performance reasons, you can set the  valid, and you want to skip this check for performance reasons, you can set the
601  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid
602  UTF-8 string as a pattern is undefined. It may cause your program to crash.  UTF-8 string as a pattern is undefined. It may cause your program to crash.
603  Note that there is a similar option for suppressing the checking of subject  Note that this option can also be passed to \fBpcre_exec()\fP and
604  strings passed to \fBpcre_exec()\fR.  \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject
605    strings.
606    .
607  .SH STUDYING A PATTERN  .
608  .rs  .SH "COMPILATION ERROR CODES"
609  .sp  .rs
610  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  .sp
611  .ti +5n  The following table lists the error codes than may be returned by
612  .B const char **\fIerrptr\fR);  \fBpcre_compile2()\fP, along with the error messages that may be returned by
613  .PP  both compiling functions. As PCRE has developed, some error codes have fallen
614  When a pattern is going to be used several times, it is worth spending more  out of use. To avoid confusion, they have not been re-used.
615  time analyzing it in order to speed up the time taken for matching. The  .sp
616  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first     0  no error
617  argument. If studing the pattern produces additional information that will help     1  \e at end of pattern
618  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR     2  \ec at end of pattern
619  block, in which the \fIstudy_data\fR field points to the results of the study.     3  unrecognized character follows \e
620       4  numbers out of order in {} quantifier
621  The returned value from a \fBpcre_study()\fR can be passed directly to     5  number too big in {} quantifier
622  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other     6  missing terminating ] for character class
623       7  invalid escape sequence in character class
624       8  range out of order in character class
625       9  nothing to repeat
626      10  [this code is not in use]
627      11  internal error: unexpected repeat
628      12  unrecognized character after (?
629      13  POSIX named classes are supported only within a class
630      14  missing )
631      15  reference to non-existent subpattern
632      16  erroffset passed as NULL
633      17  unknown option bit(s) set
634      18  missing ) after comment
635      19  [this code is not in use]
636      20  regular expression too large
637      21  failed to get memory
638      22  unmatched parentheses
639      23  internal error: code overflow
640      24  unrecognized character after (?<
641      25  lookbehind assertion is not fixed length
642      26  malformed number or name after (?(
643      27  conditional group contains more than two branches
644      28  assertion expected after (?(
645      29  (?R or (?digits must be followed by )
646      30  unknown POSIX class name
647      31  POSIX collating elements are not supported
648      32  this version of PCRE is not compiled with PCRE_UTF8 support
649      33  [this code is not in use]
650      34  character value in \ex{...} sequence is too large
651      35  invalid condition (?(0)
652      36  \eC not allowed in lookbehind assertion
653      37  PCRE does not support \eL, \el, \eN, \eU, or \eu
654      38  number after (?C is > 255
655      39  closing ) for (?C expected
656      40  recursive call could loop indefinitely
657      41  unrecognized character after (?P
658      42  syntax error in subpattern name (missing terminator)
659      43  two named subpatterns have the same name
660      44  invalid UTF-8 string
661      45  support for \eP, \ep, and \eX has not been compiled
662      46  malformed \eP or \ep sequence
663      47  unknown property name after \eP or \ep
664      48  subpattern name is too long (maximum 32 characters)
665      49  too many named subpatterns (maximum 10,000)
666      50  repeated subpattern is too long
667      51  octal value is greater than \e377 (not in UTF-8 mode)
668      52  internal error: overran compiling workspace
669      53  internal error: previously-checked referenced subpattern not found
670      54  DEFINE group contains more than one branch
671      55  repeating a DEFINE group is not allowed
672      56  inconsistent NEWLINE options"
673    .
674    .
675    .SH "STUDYING A PATTERN"
676    .rs
677    .sp
678    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
679    .ti +5n
680    .B const char **\fIerrptr\fP);
681    .PP
682    If a compiled pattern is going to be used several times, it is worth spending
683    more time analyzing it in order to speed up the time taken for matching. The
684    function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
685    argument. If studying the pattern produces additional information that will
686    help speed up matching, \fBpcre_study()\fP returns a pointer to a
687    \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
688    results of the study.
689    .P
690    The returned value from \fBpcre_study()\fP can be passed directly to
691    \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
692  fields that can be set by the caller before the block is passed; these are  fields that can be set by the caller before the block is passed; these are
693  described below. If studying the pattern does not produce any additional  described
694  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the  .\" HTML <a href="#extradata">
695  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it  .\" </a>
696  must set up its own \fBpcre_extra\fR block.  below
697    .\"
698  The second argument contains option bits. At present, no options are defined  in the section on matching a pattern.
699  for \fBpcre_study()\fR, and this argument should always be zero.  .P
700    If studying the pattern does not produce any additional information
701  The third argument for \fBpcre_study()\fR is a pointer for an error message. If  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
702    wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
703    own \fBpcre_extra\fP block.
704    .P
705    The second argument of \fBpcre_study()\fP contains option bits. At present, no
706    options are defined, and this argument should always be zero.
707    .P
708    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
709  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
710  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
711  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
712  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
713    sure that it has run successfully.
714  This is a typical call to \fBpcre_study\fR():  .P
715    This is a typical call to \fBpcre_study\fP():
716    .sp
717    pcre_extra *pe;    pcre_extra *pe;
718    pe = pcre_study(    pe = pcre_study(
719      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
720      0,              /* no options exist */      0,              /* no options exist */
721      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
722    .sp
723  At present, studying a pattern is useful only for non-anchored patterns that do  At present, studying a pattern is useful only for non-anchored patterns that do
724  not have a single fixed starting character. A bitmap of possible starting  not have a single fixed starting character. A bitmap of possible starting
725  characters is created.  bytes is created.
726    .
727    .
728  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
729  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
730  .rs  .rs
731  .sp  .sp
732  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
733  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
734  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
735  contains a default set of tables that is created in the default C locale when  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
736  PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR  can be tested with \ep if PCRE is built with Unicode character property
737  is NULL, and is sufficient for many applications.  support. The use of locales with Unicode is discouraged. If you are handling
738    characters with codes greater than 128, you should either use UTF-8 and
739  An alternative set of tables can, however, be supplied. Such tables are built  Unicode, or use locales, but not try to mix the two.
740  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  .P
741  relevant locale. The result can then be passed to \fBpcre_compile()\fR as often  PCRE contains an internal set of tables that are used when the final argument
742  as necessary. For example, to build and use tables that are appropriate for the  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
743  French locale (where accented characters with codes greater than 128 are  Normally, the internal tables recognize only ASCII characters. However, when
744  treated as letters), the following code could be used:  PCRE is built, it is possible to cause the internal tables to be rebuilt in the
745    default "C" locale of the local system, which may cause them to be different.
746    setlocale(LC_CTYPE, "fr");  .P
747    The internal tables can always be overridden by tables supplied by the
748    application that calls PCRE. These may be created in a different locale from
749    the default. As more and more applications change to using Unicode, the need
750    for this locale support is expected to die away.
751    .P
752    External tables are built by calling the \fBpcre_maketables()\fP function,
753    which has no arguments, in the relevant locale. The result can then be passed
754    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
755    example, to build and use tables that are appropriate for the French locale
756    (where accented characters with values greater than 128 are treated as letters),
757    the following code could be used:
758    .sp
759      setlocale(LC_CTYPE, "fr_FR");
760    tables = pcre_maketables();    tables = pcre_maketables();
761    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
762    .sp
763  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
764  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
765  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
766  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
767  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
768  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
769  memory containing the tables remains available for as long as it is needed.  needed.
770    .P
771  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
772    pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
773    and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
774    pattern, compilation, studying and matching all happen in the same locale, but
775    different patterns can be compiled in different locales.
776    .P
777    It is possible to pass a table pointer or NULL (indicating the use of the
778    internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
779    this facility could be used to match a pattern in a different locale from the
780    one in which it was compiled. Passing table pointers at run time is discussed
781    below in the section on matching a pattern.
782    .
783    .
784    .SH "INFORMATION ABOUT A PATTERN"
785  .rs  .rs
786  .sp  .sp
787  .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,"
788  .ti +5n  .ti +5n
789  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
790  .PP  .PP
791  The \fBpcre_fullinfo()\fR function returns information about a compiled  The \fBpcre_fullinfo()\fP function returns information about a compiled
792  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
793  nevertheless retained for backwards compability (and is documented below).  nevertheless retained for backwards compability (and is documented below).
794    .P
795  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
796  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
797  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
798  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
799  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
800  the following negative numbers:  the following negative numbers:
801    .sp
802    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
803                          the argument \fIwhere\fR was NULL                          the argument \fIwhere\fP was NULL
804    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
805    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADOPTION  the value of \fIwhat\fP was invalid
806    .sp
807  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
808  compiled pattern:  check against passing an arbitrary memory pointer. Here is a typical call of
809    \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
810    .sp
811    int rc;    int rc;
812    unsigned long int length;    size_t length;
813    rc = pcre_fullinfo(    rc = pcre_fullinfo(
814      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
815      pe,               /* result of pcre_study(), or NULL */      pe,               /* result of pcre_study(), or NULL */
816      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
817      &length);         /* where to put the data */      &length);         /* where to put the data */
818    .sp
819  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
820  as follows:  as follows:
821    .sp
822    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
823    .sp
824  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
825  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
826  no back references.  no back references.
827    .sp
828    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
829    .sp
830  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
831  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
832    .sp
833      PCRE_INFO_DEFAULT_TABLES
834    .sp
835    Return a pointer to the internal default character tables within PCRE. The
836    fourth argument should point to an \fBunsigned char *\fP variable. This
837    information call is provided for internal use by the \fBpcre_study()\fP
838    function. External callers can cause PCRE to use its internal tables by passing
839    a NULL table pointer.
840    .sp
841    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
842    .sp
843  Return information about the first byte of any matched string, for a  Return information about the first byte of any matched string, for a
844  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
845  old name is still recognized for backwards compatibility.)  variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
846    still recognized for backwards compatibility.)
847  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
848  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
849    (cat|cow|coyote), its value is returned. Otherwise, if either
850    .sp
851  (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
852  starts with "^", or  starts with "^", or
853    .sp
854  (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
855  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
856    .sp
857  -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
858  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
859  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
860    .sp
861    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
862    .sp
863  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
864  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
865  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
866  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
867    .sp
868    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
869    .sp
870  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal byte that must exist in any matched
871  string, other than at its start, if such a byte has been recorded. The fourth  string, other than at its start, if such a byte has been recorded. The fourth
872  argument should point to an \fBint\fR variable. If there is no such byte, -1 is  argument should point to an \fBint\fP variable. If there is no such byte, -1 is
873  returned. For anchored patterns, a last literal byte is recorded only if it  returned. For anchored patterns, a last literal byte is recorded only if it
874  follows something of variable length. For example, for the pattern  follows something of variable length. For example, for the pattern
875  /^a\\d+z\\d+/ the returned value is "z", but for /^a\\dz\\d/ the returned value  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
876  is -1.  is -1.
877    .sp
878    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
879    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
880    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
881    .sp
882  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
883  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
884  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
885  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
886  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
887  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
888  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
889    you need to use the name-to-number map, which is described by these three
890    values.
891    .P
892  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
893  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
894  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
895  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
896  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
897  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
898  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated. The names are in
899  alphabetical order. For example, consider the following pattern (assume  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
900    their parentheses numbers. For example, consider the following pattern (assume
901  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  PCRE_EXTENDED is set, so white space - including newlines - is ignored):
902    .sp
903    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  .\" JOIN
904    (?P<month>\\d\\d) - (?P<day>\\d\\d) )    (?<date> (?<year>(\ed\ed)?\ed\ed) -
905      (?<month>\ed\ed) - (?<day>\ed\ed) )
906    .sp
907  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
908  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
909  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
910    .sp
911    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
912    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
913    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
914    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
915    .sp
916  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
917  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
918    different for each compiled pattern.
919    .sp
920    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
921    .sp
922  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
923  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
924  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
925  top-level option settings within the pattern itself.  top-level option settings within the pattern itself.
926    .P
927  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
928  alternatives begin with one of the following:  alternatives begin with one of the following:
929    .sp
930    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
931    \\A    always    \eA    always
932    \\G    always    \eG    always
933    .\" JOIN
934    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
935            references to the subpattern in which .* appears            references to the subpattern in which .* appears
936    .sp
937  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
938  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
939    .sp
940    PCRE_INFO_SIZE    PCRE_INFO_SIZE
941    .sp
942  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
943  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
944  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
945  variable.  variable.
946    .sp
947    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
948    .sp
949  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
950  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
951  \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
952  created by \fBpcre_study()\fR. The fourth argument should point to a  created by \fBpcre_study()\fP. The fourth argument should point to a
953  \fBsize_t\fR variable.  \fBsize_t\fP variable.
954    .
955  .SH OBSOLETE INFO FUNCTION  .
956    .SH "OBSOLETE INFO FUNCTION"
957  .rs  .rs
958  .sp  .sp
959  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
960  .B *\fIfirstcharptr\fR);  .B *\fIfirstcharptr\fP);
961  .PP  .PP
962  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
963  restrictive to return all the available data about a compiled pattern. New  restrictive to return all the available data about a compiled pattern. New
964  programs should use \fBpcre_fullinfo()\fR instead. The yield of  programs should use \fBpcre_fullinfo()\fP instead. The yield of
965  \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
966  following negative numbers:  following negative numbers:
967    .sp
968    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
969    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
970    .sp
971  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
972  pattern was compiled is placed in the integer it points to (see  pattern was compiled is placed in the integer it points to (see
973  PCRE_INFO_OPTIONS above).  PCRE_INFO_OPTIONS above).
974    .P
975  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,
976  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
977  string (see PCRE_INFO_FIRSTBYTE above).  string (see PCRE_INFO_FIRSTBYTE above).
978    .
979  .SH MATCHING A PATTERN  .
980    .SH "REFERENCE COUNTS"
981  .rs  .rs
982  .sp  .sp
983  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
984    .PP
985    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
986    data block that contains a compiled pattern. It is provided for the benefit of
987    applications that operate in an object-oriented manner, where different parts
988    of the application may be using the same compiled pattern, but you want to free
989    the block when they are all done.
990    .P
991    When a pattern is compiled, the reference count field is initialized to zero.
992    It is changed only by calling this function, whose action is to add the
993    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
994    function is the new value. However, the value of the count is constrained to
995    lie between 0 and 65535, inclusive. If the new value is outside these limits,
996    it is forced to the appropriate limit value.
997    .P
998    Except when it is zero, the reference count is not correctly preserved if a
999    pattern is compiled on one host and then transferred to a host whose byte-order
1000    is different. (This seems a highly unlikely scenario.)
1001    .
1002    .
1003    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1004    .rs
1005    .sp
1006    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1007  .ti +5n  .ti +5n
1008  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1009  .ti +5n  .ti +5n
1010  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1011  .PP  .P
1012  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
1013  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
1014  pattern has been studied, the result of the study should be passed in the  pattern has been studied, the result of the study should be passed in the
1015  \fIextra\fR argument.  \fIextra\fP argument. This function is the main matching facility of the
1016    library, and it operates in a Perl-like manner. For specialist use there is
1017  Here is an example of a simple call to \fBpcre_exec()\fR:  also an alternative matching function, which is described
1018    .\" HTML <a href="#dfamatch">
1019    .\" </a>
1020    below
1021    .\"
1022    in the section about the \fBpcre_dfa_exec()\fP function.
1023    .P
1024    In most applications, the pattern will have been compiled (and optionally
1025    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1026    possible to save compiled patterns and study data, and then use them later
1027    in different processes, possibly even on different hosts. For a discussion
1028    about this, see the
1029    .\" HREF
1030    \fBpcreprecompile\fP
1031    .\"
1032    documentation.
1033    .P
1034    Here is an example of a simple call to \fBpcre_exec()\fP:
1035    .sp
1036    int rc;    int rc;
1037    int ovector[30];    int ovector[30];
1038    rc = pcre_exec(    rc = pcre_exec(
# Line 684  Here is an example of a simple call to \ Line 1042  Here is an example of a simple call to \
1042      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1043      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1044      0,              /* default options */      0,              /* default options */
1045      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1046      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1047    .
1048  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .\" HTML <a name="extradata"></a>
1049  data block. The \fBpcre_study()\fR function returns such a block (when it  .SS "Extra data for \fBpcre_exec()\fR"
1050    .rs
1051    .sp
1052    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1053    data block. The \fBpcre_study()\fP function returns such a block (when it
1054  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
1055  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1056    fields (not necessarily in this order):
1057    unsigned long int \fIflags\fR;  .sp
1058    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1059    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1060    void *\fIcallout_data\fR;    unsigned long int \fImatch_limit\fP;
1061      unsigned long int \fImatch_limit_recursion\fP;
1062  The \fIflags\fR field is a bitmap that specifies which of the other fields    void *\fIcallout_data\fP;
1063      const unsigned char *\fItables\fP;
1064    .sp
1065    The \fIflags\fP field is a bitmap that specifies which of the other fields
1066  are set. The flag bits are:  are set. The flag bits are:
1067    .sp
1068    PCRE_EXTRA_STUDY_DATA    PCRE_EXTRA_STUDY_DATA
1069    PCRE_EXTRA_MATCH_LIMIT    PCRE_EXTRA_MATCH_LIMIT
1070      PCRE_EXTRA_MATCH_LIMIT_RECURSION
1071    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1072      PCRE_EXTRA_TABLES
1073  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the  .sp
1074  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with  Other flag bits should be set to zero. The \fIstudy_data\fP field is set in the
1075  the appropriate flag bit. You should not set this yourself, but you can add to  \fBpcre_extra\fP block that is returned by \fBpcre_study()\fP, together with
1076  the block by setting the other fields.  the appropriate flag bit. You should not set this yourself, but you may add to
1077    the block by setting the other fields and their corresponding flag bits.
1078  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  .P
1079    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1080  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,
1081  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
1082  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is the use of nested unlimited repeats.
1083  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1084  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
1085  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
1086  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
1087  count starts from zero for each position in the subject string.  limiting the amount of backtracking that can take place. For patterns that are
1088    not anchored, the count restarts from zero for each position in the subject
1089  The default limit for the library can be set when PCRE is built; the default  string.
1090    .P
1091    The default value for the limit can be set when PCRE is built; the default
1092  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
1093  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
1094  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
1095  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
1096  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1097    .P
1098  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
1099  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1100    limits the depth of recursion. The recursion depth is a smaller number than the
1101  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.
1102  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.
1103  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1104  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,
1105  unachored at matching time.  when PCRE has been compiled to use memory on the heap instead of the stack, the
1106    amount of heap memory that can be used.
1107  When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8  .P
1108  string is automatically checked, and the value of \fIstartoffset\fR is also  The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1109  checked to ensure that it points to the start of a UTF-8 character. If an  built; the default default is the same value as the default for
1110  invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fR returns the error  \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1111  PCRE_ERROR_BADUTF8. If \fIstartoffset\fR contains an invalid value,  with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1112  PCRE_ERROR_BADUTF8_OFFSET is returned.  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1113    is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1114  If you already know that your subject is valid, and you want to skip these  .P
1115  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when  The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,
1116  calling \fBpcre_exec()\fR. You might want to do this for the second and  which is described in the
1117  subsequent calls to \fBpcre_exec()\fR if you are making repeated calls to find  .\" HREF
1118  all the matches in a single subject string. However, you should be sure that  \fBpcrecallout\fP
1119  the value of \fIstartoffset\fR points to the start of a UTF-8 character. When  .\"
1120  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a  documentation.
1121  subject, or a value of \fIstartoffset\fR that does not point to the start of a  .P
1122  UTF-8 character, is undefined. Your program may crash.  The \fItables\fP field is used to pass a character tables pointer to
1123    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1124  There are also three further options that can be set only at matching time:  pattern. A non-NULL value is stored with the compiled pattern only if custom
1125    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1126    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1127    internal tables to be used. This facility is helpful when re-using patterns
1128    that have been saved after compiling with an external set of tables, because
1129    the external tables might be at a different address when \fBpcre_exec()\fP is
1130    called. See the
1131    .\" HREF
1132    \fBpcreprecompile\fP
1133    .\"
1134    documentation for a discussion of saving compiled patterns for later use.
1135    .
1136    .SS "Option bits for \fBpcre_exec()\fP"
1137    .rs
1138    .sp
1139    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1140    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1141    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1142    .sp
1143      PCRE_ANCHORED
1144    .sp
1145    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1146    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1147    to be anchored by virtue of its contents, it cannot be made unachored at
1148    matching time.
1149    .sp
1150      PCRE_NEWLINE_CR
1151      PCRE_NEWLINE_LF
1152      PCRE_NEWLINE_CRLF
1153      PCRE_NEWLINE_ANY
1154    .sp
1155    These options override the newline definition that was chosen or defaulted when
1156    the pattern was compiled. For details, see the description of
1157    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1158    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1159    the way the match position is advanced after a match failure for an unanchored
1160    pattern. When PCRE_NEWLINE_CRLF or PCRE_NEWLINE_ANY is set, and a match attempt
1161    fails when the current position is at a CRLF sequence, the match position is
1162    advanced by two characters instead of one, in other words, to after the CRLF.
1163    .sp
1164    PCRE_NOTBOL    PCRE_NOTBOL
1165    .sp
1166  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
1167  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1168  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1169    never to match. This option affects only the behaviour of the circumflex
1170    metacharacter. It does not affect \eA.
1171    .sp
1172    PCRE_NOTEOL    PCRE_NOTEOL
1173    .sp
1174  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
1175  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
1176  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1177  to match.  compile time) causes dollar never to match. This option affects only the
1178    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1179    .sp
1180    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1181    .sp
1182  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
1183  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
1184  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
1185    .sp
1186    a?b?    a?b?
1187    .sp
1188  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 the empty
1189  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
1190  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".
1191    .P
1192  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
1193  of a pattern match of the empty string within its \fBsplit()\fR function, and  of a pattern match of the empty string within its \fBsplit()\fP function, and
1194  when using the /g modifier. It is possible to emulate Perl's behaviour after  when using the /g modifier. It is possible to emulate Perl's behaviour after
1195  matching a null string by first trying the match again at the same offset with  matching a null string by first trying the match again at the same offset with
1196  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the
1197  below) and trying an ordinary match again.  starting offset (see below) and trying an ordinary match again. There is some
1198    code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.
1199  The subject string is passed to \fBpcre_exec()\fR as a pointer in  .sp
1200  \fIsubject\fR, a length in \fIlength\fR, and a starting byte offset in    PCRE_NO_UTF8_CHECK
1201  \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary  .sp
1202  zero bytes. When the starting offset is zero, the search for a match starts at  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1203  the beginning of the subject, and this is by far the most common case.  string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1204    The value of \fIstartoffset\fP is also checked to ensure that it points to the
1205  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,
1206  sequence of bytes that is a valid UTF-8 string, and the starting offset must  \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP
1207  point to the beginning of a UTF-8 character. If an invalid UTF-8 string or  contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
1208  offset is passed, an error (either PCRE_ERROR_BADUTF8 or  .P
1209  PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is  If you already know that your subject is valid, and you want to skip these
1210  set, in which case PCRE's behaviour is not defined.  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1211    calling \fBpcre_exec()\fP. You might want to do this for the second and
1212    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1213    all the matches in a single subject string. However, you should be sure that
1214    the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1215    PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1216    subject, or a value of \fIstartoffset\fP that does not point to the start of a
1217    UTF-8 character, is undefined. Your program may crash.
1218    .sp
1219      PCRE_PARTIAL
1220    .sp
1221    This option turns on the partial matching feature. If the subject string fails
1222    to match the pattern, but at some point during the matching process the end of
1223    the subject was reached (that is, the subject partially matches the pattern and
1224    the failure to match occurred only because there were not enough subject
1225    characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of
1226    PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what
1227    may appear in the pattern. These are discussed in the
1228    .\" HREF
1229    \fBpcrepartial\fP
1230    .\"
1231    documentation.
1232    .
1233    .SS "The string to be matched by \fBpcre_exec()\fP"
1234    .rs
1235    .sp
1236    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1237    \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in
1238    \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a
1239    UTF-8 character. Unlike the pattern string, the subject may contain binary zero
1240    bytes. When the starting offset is zero, the search for a match starts at the
1241    beginning of the subject, and this is by far the most common case.
1242    .P
1243  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
1244  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1245  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1246  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
1247  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1248    .sp
1249    \\Biss\\B    \eBiss\eB
1250    .sp
1251  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
1252  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
1253  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
1254  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
1255  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
1256  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
1257  \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
1258  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
1259  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.
1260    .P
1261  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
1262  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
1263  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.
1264    .
1265    .SS "How \fBpcre_exec()\fP returns captured substrings"
1266    .rs
1267    .sp
1268  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
1269  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
1270  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1271  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1272  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
1273  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1274    .P
1275  Captured substrings are returned to the caller via a vector of integer offsets  Captured substrings are returned to the caller via a vector of integer offsets
1276  whose address is passed in \fIovector\fR. The number of elements in the vector  whose address is passed in \fIovector\fP. The number of elements in the vector
1277  is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass  is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:
1278  back captured substrings, each substring using a pair of integers. The  this argument is NOT the size of \fIovector\fP in bytes.
1279  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1280  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1281  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
1282  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1283    and is not available for passing back information. The length passed in
1284  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
1285  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
1286    .P
1287    When a match is successful, information about captured substrings is returned
1288    in pairs of integers, starting at the beginning of \fIovector\fP, and
1289  continuing up to two-thirds of its length at the most. The first element of a  continuing up to two-thirds of its length at the most. The first element of a
1290  pair is set to the offset of the first character in a substring, and the second  pair is set to the offset of the first character in a substring, and the second
1291  is set to the offset of the first character after the end of a substring. The  is set to the offset of the first character after the end of a substring. The
1292  first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the  first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the
1293  subject string matched by the entire pattern. The next pair is used for the  subject string matched by the entire pattern. The next pair is used for the
1294  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP
1295  is the number of pairs that have been set. If there are no capturing  is one more than the highest numbered pair that has been set. For example, if
1296  subpatterns, the return value from a successful match is 1, indicating that  two substrings have been captured, the returned value is 3. If there are no
1297  just the first pair of offsets has been set.  capturing subpatterns, the return value from a successful match is 1,
1298    indicating that just the first pair of offsets has been set.
1299  Some convenience functions are provided for extracting the captured substrings  .P
 as separate strings. These are described in the following section.  
   
 It is possible for an capturing subpattern number \fIn+1\fR to match some  
 part of the subject when subpattern \fIn\fR has not been used at all. For  
 example, if the string "abc" is matched against the pattern (a|(z))(bc)  
 subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset  
 values corresponding to the unused subpattern are set to -1.  
   
1300  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
1301  string that it matched that gets returned.  string that it matched that is returned.
1302    .P
1303  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
1304  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
1305  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. In particular, if the substring offsets are not of
1306  \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and  interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1307  \fIovecsize\fR as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1308  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
1309  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
1310  to supply an \fIovector\fR.  advisable to supply an \fIovector\fP.
1311    .P
1312  Note that \fBpcre_info()\fR can be used to find out how many capturing  The \fBpcre_info()\fP function can be used to find out how many capturing
1313  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1314  \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
1315  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.
1316    .P
1317  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
1318    the subject when subpattern \fIn\fP has not been used at all. For example, if
1319    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1320    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1321    happens, both values in the offset pairs corresponding to unused subpatterns
1322    are set to -1.
1323    .P
1324    Offset values that correspond to unused subpatterns at the end of the
1325    expression are also set to -1. For example, if the string "abc" is matched
1326    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1327    return from the function is 2, because the highest used capturing subpattern
1328    number is 1. However, you can refer to the offsets for the second and third
1329    capturing subpatterns if you wish (assuming the vector is large enough, of
1330    course).
1331    .P
1332    Some convenience functions are provided for extracting the captured substrings
1333    as separate strings. These are described below.
1334    .
1335    .\" HTML <a name="errorlist"></a>
1336    .SS "Error return values from \fBpcre_exec()\fP"
1337    .rs
1338    .sp
1339    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1340  defined in the header file:  defined in the header file:
1341    .sp
1342    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
1343    .sp
1344  The subject string did not match the pattern.  The subject string did not match the pattern.
1345    .sp
1346    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
1347    .sp
1348  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
1349  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
1350    .sp
1351    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
1352    .sp
1353  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
1354    .sp
1355    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
1356    .sp
1357  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
1358  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
1359  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
1360    other endianness. This is the error that PCRE gives when the magic number is
1361    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
1362    .sp
1363      PCRE_ERROR_UNKNOWN_OPCODE (-5)
1364    .sp
1365  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
1366  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
1367  of the compiled pattern.  of the compiled pattern.
1368    .sp
1369    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1370    .sp
1371  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
1372  \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
1373  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
1374  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
1375  the end of matching.  automatically freed at the end of matching.
1376    .sp
1377    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1378    .sp
1379  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
1380  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1381  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
1382    .sp
1383    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
1384    .sp
1385  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
1386  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1387  description above.  above.
1388    .sp
1389    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
1390    .sp
1391  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
1392  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
1393  \fBpcrecallout\fR documentation for details.  .\" HREF
1394    \fBpcrecallout\fP
1395    .\"
1396    documentation for details.
1397    .sp
1398    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
1399    .sp
1400  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1401    .sp
1402    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
1403    .sp
1404  The UTF-8 byte sequence that was passed as a subject was valid, but the value  The UTF-8 byte sequence that was passed as a subject was valid, but the value
1405  of \fIstartoffset\fR did not point to the beginning of a UTF-8 character.  of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1406    .sp
1407  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER    PCRE_ERROR_PARTIAL        (-12)
1408    .sp
1409    The subject string did not match, but it did match partially. See the
1410    .\" HREF
1411    \fBpcrepartial\fP
1412    .\"
1413    documentation for details of partial matching.
1414    .sp
1415      PCRE_ERROR_BADPARTIAL     (-13)
1416    .sp
1417    The PCRE_PARTIAL option was used with a compiled pattern containing items that
1418    are not supported for partial matching. See the
1419    .\" HREF
1420    \fBpcrepartial\fP
1421    .\"
1422    documentation for details of partial matching.
1423    .sp
1424      PCRE_ERROR_INTERNAL       (-14)
1425    .sp
1426    An unexpected internal error has occurred. This error could be caused by a bug
1427    in PCRE or by overwriting of the compiled pattern.
1428    .sp
1429      PCRE_ERROR_BADCOUNT       (-15)
1430    .sp
1431    This error is given if the value of the \fIovecsize\fP argument is negative.
1432    .sp
1433      PCRE_ERROR_RECURSIONLIMIT (-21)
1434    .sp
1435    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1436    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1437    description above.
1438    .sp
1439      PCRE_ERROR_NULLWSLIMIT    (-22)
1440    .sp
1441    When a group that can match an empty substring is repeated with an unbounded
1442    upper limit, the subject position at the start of the group must be remembered,
1443    so that a test for an empty string can be made when the end of the group is
1444    reached. Some workspace is required for this; if it runs out, this error is
1445    given.
1446    .sp
1447      PCRE_ERROR_BADNEWLINE     (-23)
1448    .sp
1449    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1450    .P
1451    Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.
1452    .
1453    .
1454    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1455  .rs  .rs
1456  .sp  .sp
1457  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1458  .ti +5n  .ti +5n
1459  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1460  .ti +5n  .ti +5n
1461  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
1462  .PP  .PP
1463  .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,  
1464  .ti +5n  .ti +5n
1465  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
1466  .ti +5n  .ti +5n
1467  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1468  .PP  .PP
1469  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
1470  .ti +5n  .ti +5n
1471  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1472  .PP  .PP
1473  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
1474  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1475  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1476  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1477  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
1478  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
1479  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
1480  has a further zero added on the end, but the result is not, of course,  .P
1481  a C string.  A substring that contains a binary zero is correctly extracted and has a
1482    further zero added on the end, but the result is not, of course, a C string.
1483    However, you can process such a string by referring to the length that is
1484    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1485    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1486    for handling strings containing binary zeros, because the end of the final
1487    string is not independently indicated.
1488    .P
1489  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:
1490  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
1491  \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
1492  \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
1493  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
1494  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
1495  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
1496  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
1497  the vector divided by three.  number of elements in the vector divided by three.
1498    .P
1499  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1500  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
1501  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
1502  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1503  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
1504  \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
1505  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
1506  \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
1507  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
1508    .sp
1509    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1510    .sp
1511  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
1512  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
1513    .sp
1514    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1515    .sp
1516  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
1517    .P
1518  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
1519  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
1520  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
1521  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
1522  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
1523  function is zero if all went well, or  function is zero if all went well, or the error code
1524    .sp
1525    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1526    .sp
1527  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
1528    .P
1529  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
1530  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
1531  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
1532  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
1533  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1534  substrings.  substrings.
1535    .P
1536  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
1537  \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
1538  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
1539  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1540  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
1541  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
1542  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
1543  \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
1544  provided.  provided.
1545    .
1546  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
1547    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1548  .rs  .rs
1549  .sp  .sp
1550  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1551  .ti +5n  .ti +5n
1552  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
1553    .PP
1554    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1555  .ti +5n  .ti +5n
1556  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1557  .ti +5n  .ti +5n
1558  .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,  
1559  .ti +5n  .ti +5n
1560  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1561  .PP  .PP
1562  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
1563  .ti +5n  .ti +5n
1564  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1565  .ti +5n  .ti +5n
1566  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
1567  .ti +5n  .ti +5n
1568  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1569  .PP  .PP
1570  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.
1571  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
1572  compiled pattern, and the second is the name. For example, for this pattern  .sp
1573      (a+)b(?<xxx>\ed+)...
1574    ab(?<xxx>\\d+)...  .sp
1575    the number of the subpattern called "xxx" is 2. If the name is known to be
1576  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
1577  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1578  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
1579  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1580    that name.
1581  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
1582  \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
1583  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
1584  differences.  two functions that do the whole job.
1585    .P
1586    Most of the arguments of \fBpcre_copy_named_substring()\fP and
1587    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1588    functions that extract by number. As these are described in the previous
1589    section, they are not re-described here. There are just two differences:
1590    .P
1591  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
1592  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
1593  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
1594  translation table.  translation table.
1595    .P
1596  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1597  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1598  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1599    the behaviour may not be what you want (see the next section).
1600  .in 0  .
1601  Last updated: 09 December 2003  .
1602  .br  .SH "DUPLICATE SUBPATTERN NAMES"
1603  Copyright (c) 1997-2003 University of Cambridge.  .rs
1604    .sp
1605    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1606    .ti +5n
1607    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1608    .PP
1609    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1610    are not required to be unique. Normally, patterns with duplicate names are such
1611    that in any one match, only one of the named subpatterns participates. An
1612    example is shown in the
1613    .\" HREF
1614    \fBpcrepattern\fP
1615    .\"
1616    documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP
1617    and \fBpcre_get_named_substring()\fP return the first substring corresponding
1618    to the given name that is set. If none are set, an empty string is returned.
1619    The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are
1620    associated with the name, but it is not defined which it is.
1621    .sp
1622    If you want to get full details of all captured substrings for a given name,
1623    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1624    argument is the compiled pattern, and the second is the name. The third and
1625    fourth are pointers to variables which are updated by the function. After it
1626    has run, they point to the first and last entries in the name-to-number table
1627    for the given name. The function itself returns the length of each entry, or
1628    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1629    described above in the section entitled \fIInformation about a pattern\fP.
1630    Given all the relevant entries for the name, you can extract each of their
1631    numbers, and hence the captured data, if any.
1632    .
1633    .
1634    .SH "FINDING ALL POSSIBLE MATCHES"
1635    .rs
1636    .sp
1637    The traditional matching function uses a similar algorithm to Perl, which stops
1638    when it finds the first match, starting at a given point in the subject. If you
1639    want to find all possible matches, or the longest possible match, consider
1640    using the alternative matching function (see below) instead. If you cannot use
1641    the alternative function, but still need to find all possible matches, you
1642    can kludge it up by making use of the callout facility, which is described in
1643    the
1644    .\" HREF
1645    \fBpcrecallout\fP
1646    .\"
1647    documentation.
1648    .P
1649    What you have to do is to insert a callout right at the end of the pattern.
1650    When your callout function is called, extract and save the current matched
1651    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1652    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1653    will yield PCRE_ERROR_NOMATCH.
1654    .
1655    .
1656    .\" HTML <a name="dfamatch"></a>
1657    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1658    .rs
1659    .sp
1660    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1661    .ti +5n
1662    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1663    .ti +5n
1664    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1665    .ti +5n
1666    .B int *\fIworkspace\fP, int \fIwscount\fP);
1667    .P
1668    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1669    a compiled pattern, using a matching algorithm that scans the subject string
1670    just once, and does not backtrack. This has different characteristics to the
1671    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1672    patterns are not supported. Nevertheless, there are times when this kind of
1673    matching can be useful. For a discussion of the two matching algorithms, see
1674    the
1675    .\" HREF
1676    \fBpcrematching\fP
1677    .\"
1678    documentation.
1679    .P
1680    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1681    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1682    different way, and this is described below. The other common arguments are used
1683    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1684    here.
1685    .P
1686    The two additional arguments provide workspace for the function. The workspace
1687    vector should contain at least 20 elements. It is used for keeping track of
1688    multiple paths through the pattern tree. More workspace will be needed for
1689    patterns and subjects where there are a lot of potential matches.
1690    .P
1691    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1692    .sp
1693      int rc;
1694      int ovector[10];
1695      int wspace[20];
1696      rc = pcre_dfa_exec(
1697        re,             /* result of pcre_compile() */
1698        NULL,           /* we didn't study the pattern */
1699        "some string",  /* the subject string */
1700        11,             /* the length of the subject string */
1701        0,              /* start at offset 0 in the subject */
1702        0,              /* default options */
1703        ovector,        /* vector of integers for substring information */
1704        10,             /* number of elements (NOT size in bytes) */
1705        wspace,         /* working space vector */
1706        20);            /* number of elements (NOT size in bytes) */
1707    .
1708    .SS "Option bits for \fBpcre_dfa_exec()\fP"
1709    .rs
1710    .sp
1711    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1712    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1713    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,
1714    PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are
1715    the same as for \fBpcre_exec()\fP, so their description is not repeated here.
1716    .sp
1717      PCRE_PARTIAL
1718    .sp
1719    This has the same general effect as it does for \fBpcre_exec()\fP, but the
1720    details are slightly different. When PCRE_PARTIAL is set for
1721    \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into
1722    PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no
1723    complete matches, but there is still at least one matching possibility. The
1724    portion of the string that provided the partial match is set as the first
1725    matching string.
1726    .sp
1727      PCRE_DFA_SHORTEST
1728    .sp
1729    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1730    soon as it has found one match. Because of the way the alternative algorithm
1731    works, this is necessarily the shortest possible match at the first possible
1732    matching point in the subject string.
1733    .sp
1734      PCRE_DFA_RESTART
1735    .sp
1736    When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns
1737    a partial match, it is possible to call it again, with additional subject
1738    characters, and have it continue with the same match. The PCRE_DFA_RESTART
1739    option requests this action; when it is set, the \fIworkspace\fP and
1740    \fIwscount\fP options must reference the same vector as before because data
1741    about the match so far is left in them after a partial match. There is more
1742    discussion of this facility in the
1743    .\" HREF
1744    \fBpcrepartial\fP
1745    .\"
1746    documentation.
1747    .
1748    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1749    .rs
1750    .sp
1751    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1752    substring in the subject. Note, however, that all the matches from one run of
1753    the function start at the same point in the subject. The shorter matches are
1754    all initial substrings of the longer matches. For example, if the pattern
1755    .sp
1756      <.*>
1757    .sp
1758    is matched against the string
1759    .sp
1760      This is <something> <something else> <something further> no more
1761    .sp
1762    the three matched strings are
1763    .sp
1764      <something>
1765      <something> <something else>
1766      <something> <something else> <something further>
1767    .sp
1768    On success, the yield of the function is a number greater than zero, which is
1769    the number of matched substrings. The substrings themselves are returned in
1770    \fIovector\fP. Each string uses two elements; the first is the offset to the
1771    start, and the second is the offset to the end. In fact, all the strings have
1772    the same start offset. (Space could have been saved by giving this only once,
1773    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1774    returns data, even though the meaning of the strings is different.)
1775    .P
1776    The strings are returned in reverse order of length; that is, the longest
1777    matching string is given first. If there were too many matches to fit into
1778    \fIovector\fP, the yield of the function is zero, and the vector is filled with
1779    the longest matches.
1780    .
1781    .SS "Error returns from \fBpcre_dfa_exec()\fP"
1782    .rs
1783    .sp
1784    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1785    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1786    described
1787    .\" HTML <a href="#errorlist">
1788    .\" </a>
1789    above.
1790    .\"
1791    There are in addition the following errors that are specific to
1792    \fBpcre_dfa_exec()\fP:
1793    .sp
1794      PCRE_ERROR_DFA_UITEM      (-16)
1795    .sp
1796    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1797    that it does not support, for instance, the use of \eC or a back reference.
1798    .sp
1799      PCRE_ERROR_DFA_UCOND      (-17)
1800    .sp
1801    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1802    uses a back reference for the condition, or a test for recursion in a specific
1803    group. These are not supported.
1804    .sp
1805      PCRE_ERROR_DFA_UMLIMIT    (-18)
1806    .sp
1807    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1808    block that contains a setting of the \fImatch_limit\fP field. This is not
1809    supported (it is meaningless).
1810    .sp
1811      PCRE_ERROR_DFA_WSSIZE     (-19)
1812    .sp
1813    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1814    \fIworkspace\fP vector.
1815    .sp
1816      PCRE_ERROR_DFA_RECURSE    (-20)
1817    .sp
1818    When a recursive subpattern is processed, the matching function calls itself
1819    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1820    error is given if the output vector is not large enough. This should be
1821    extremely rare, as a vector of size 1000 is used.
1822    .
1823    .
1824    .SH "SEE ALSO"
1825    .rs
1826    .sp
1827    \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1828    \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1829    \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1830    .
1831    .
1832    .SH AUTHOR
1833    .rs
1834    .sp
1835    .nf
1836    Philip Hazel
1837    University Computing Service
1838    Cambridge CB2 3QH, England.
1839    .fi
1840    .
1841    .
1842    .SH REVISION
1843    .rs
1844    .sp
1845    .nf
1846    Last updated: 06 March 2007
1847    Copyright (c) 1997-2007 University of Cambridge.
1848    .fi

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