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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
28    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
29    .ti +5n
30    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
31    .ti +5n
32    .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,"
35  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .ti +5n
36    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
37  .ti +5n  .ti +5n
38  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
39  .ti +5n  .ti +5n
40  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int *\fIworkspace\fP, int \fIwscount\fP);
41  .PP  .PP
42  .br  .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
 .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  
43  .ti +5n  .ti +5n
44  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
45  .ti +5n  .ti +5n
46  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
47  .ti +5n  .ti +5n
48  .B char *\fIbuffer\fR, 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_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
51  .ti +5n  .ti +5n
52  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
53  .ti +5n  .ti +5n
54  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
55  .PP  .PP
56  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
57  .B int pcre_get_named_substring(const pcre *\fIcode\fR,  .ti +5n
58    .B const char *\fIsubject\fP, int *\fIovector\fP,
59  .ti +5n  .ti +5n
60  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
61  .ti +5n  .ti +5n
62  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char **\fIstringptr\fP);
63    .PP
64    .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
65  .ti +5n  .ti +5n
66  .B const char **\fIstringptr\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_stringnumber(const pcre *\fIcode\fR,  
69  .ti +5n  .ti +5n
70  .B const char *\fIname\fR);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
71  .PP  .PP
72  .br  .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
 .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,  
73  .ti +5n  .ti +5n
74  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
75  .ti +5n  .ti +5n
76  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
77  .PP  .PP
78  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
79  .ti +5n  .ti +5n
80  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
81  .PP  .PP
82  .br  .B void pcre_free_substring(const char *\fIstringptr\fP);
 .B void pcre_free_substring(const char *\fIstringptr\fR);  
83  .PP  .PP
84  .br  .B void pcre_free_substring_list(const char **\fIstringptr\fP);
 .B void pcre_free_substring_list(const char **\fIstringptr\fR);  
85  .PP  .PP
 .br  
86  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
87  .PP  .PP
88  .br  .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
 .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  
89  .ti +5n  .ti +5n
90  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
91    .PP
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
105  .br  .B void *(*pcre_stack_malloc)(size_t);
106    .PP
107    .B void (*pcre_stack_free)(void *);
108    .PP
109  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
110    .
111  .SH PCRE API  .
112    .SH "PCRE API OVERVIEW"
113  .rs  .rs
114  .sp  .sp
115  PCRE has its own native API, which is described in this document. There is also  PCRE has its own native API, which is described in this document. There are
116  a set of wrapper functions that correspond to the POSIX regular expression API.  also some wrapper functions that correspond to the POSIX regular expression
117  These are described in the \fBpcreposix\fR documentation.  API. These are described in the
118    .\" HREF
119  The native API function prototypes are defined in the header file \fBpcre.h\fR,  \fBpcreposix\fP
120  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  .\"
121  accessed by adding \fB-lpcre\fR to the command for linking an application which  documentation. Both of these APIs define a set of C function calls. A C++
122  calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to  wrapper is distributed with PCRE. It is documented in the
123  contain the major and minor release numbers for the library. Applications can  .\" HREF
124  use these to include support for different releases.  \fBpcrecpp\fP
125    .\"
126  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  page.
127  are used for compiling and matching regular expressions. A sample program that  .P
128  demonstrates the simplest way of using them is given in the file  The native API C function prototypes are defined in the header file
129  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
130    It can normally be accessed by adding \fB-lpcre\fP to the command for linking
131  There are convenience functions for extracting captured substrings from a  an application that uses PCRE. The header file defines the macros PCRE_MAJOR
132  matched subject string. They are:  and PCRE_MINOR to contain the major and minor release numbers for the library.
133    Applications can use these to include support for different releases of PCRE.
134    \fBpcre_copy_substring()\fR  .P
135    \fBpcre_copy_named_substring()\fR  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 PCRE
139    source distribution. A listing of this program is given in the
140  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  .\" HREF
141    \fBpcredemo\fP
142    .\"
143    documentation, and the
144    .\" HREF
145    \fBpcresample\fP
146    .\"
147    documentation describes how to compile and run it.
148    .P
149    A second matching function, \fBpcre_dfa_exec()\fP, which is not
150    Perl-compatible, is also provided. This uses a different algorithm for the
151    matching. The alternative algorithm finds all possible matches (at a given
152    point in the subject), and scans the subject just once (unless there are
153    lookbehind assertions). However, this algorithm does not return captured
154    substrings. A description of the two matching algorithms and their advantages
155    and disadvantages is given in the
156    .\" HREF
157    \fBpcrematching\fP
158    .\"
159    documentation.
160    .P
161    In addition to the main compiling and matching functions, there are convenience
162    functions for extracting captured substrings from a subject string that is
163    matched by \fBpcre_exec()\fP. They are:
164    .sp
165      \fBpcre_copy_substring()\fP
166      \fBpcre_copy_named_substring()\fP
167      \fBpcre_get_substring()\fP
168      \fBpcre_get_named_substring()\fP
169      \fBpcre_get_substring_list()\fP
170      \fBpcre_get_stringnumber()\fP
171      \fBpcre_get_stringtable_entries()\fP
172    .sp
173    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
174  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
175    .P
176  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
177  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,
178    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
179  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
180  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
181    .P
182    The function \fBpcre_fullinfo()\fP is used to find out information about a
183    compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
184  some of the available information, but is retained for backwards compatibility.  some of the available information, but is retained for backwards compatibility.
185  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
186  version of PCRE and its date of release.  version of PCRE and its date of release.
187    .P
188  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
189  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  containing a compiled pattern. This is provided for the benefit of
190    object-oriented applications.
191    .P
192    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
193    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
194  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
195  so a calling program can replace them if it wishes to intercept the calls. This  so a calling program can replace them if it wishes to intercept the calls. This
196  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
197    .P
198  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
199    indirections to memory management functions. These special functions are used
200    only when PCRE is compiled to use the heap for remembering data, instead of
201    recursive function calls, when running the \fBpcre_exec()\fP function. See the
202    .\" HREF
203    \fBpcrebuild\fP
204    .\"
205    documentation for details of how to do this. It is a non-standard way of
206    building PCRE, for use in environments that have limited stacks. Because of the
207    greater use of memory management, it runs more slowly. Separate functions are
208    provided so that special-purpose external code can be used for this case. When
209    used, these functions are always called in a stack-like manner (last obtained,
210    first freed), and always for memory blocks of the same size. There is a
211    discussion about PCRE's stack usage in the
212    .\" HREF
213    \fBpcrestack\fP
214    .\"
215    documentation.
216    .P
217    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
218  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
219  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
220    .\" HREF
221    \fBpcrecallout\fP
222    .\"
223  documentation.  documentation.
224    .
225    .
226    .\" HTML <a name="newlines"></a>
227    .SH NEWLINES
228    .rs
229    .sp
230    PCRE supports five different conventions for indicating line breaks in
231    strings: a single CR (carriage return) character, a single LF (linefeed)
232    character, the two-character sequence CRLF, any of the three preceding, or any
233    Unicode newline sequence. The Unicode newline sequences are the three just
234    mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
235    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
236    (paragraph separator, U+2029).
237    .P
238    Each of the first three conventions is used by at least one operating system as
239    its standard newline sequence. When PCRE is built, a default can be specified.
240    The default default is LF, which is the Unix standard. When PCRE is run, the
241    default can be overridden, either when a pattern is compiled, or when it is
242    matched.
243    .P
244    At compile time, the newline convention can be specified by the \fIoptions\fP
245    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
246    start of the pattern itself; this overrides any other settings. See the
247    .\" HREF
248    \fBpcrepattern\fP
249    .\"
250    page for details of the special character sequences.
251    .P
252    In the PCRE documentation the word "newline" is used to mean "the character or
253    pair of characters that indicate a line break". The choice of newline
254    convention affects the handling of the dot, circumflex, and dollar
255    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
256    recognized line ending sequence, the match position advancement for a
257    non-anchored pattern. There is more detail about this in the
258    .\" HTML <a href="#execoptions">
259    .\" </a>
260    section on \fBpcre_exec()\fP options
261    .\"
262    below.
263    .P
264    The choice of newline convention does not affect the interpretation of
265    the \en or \er escape sequences, nor does it affect what \eR matches, which is
266    controlled in a similar way, but by separate options.
267    .
268    .
269  .SH MULTITHREADING  .SH MULTITHREADING
270  .rs  .rs
271  .sp  .sp
272  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
273  proviso that the memory management functions pointed to by \fBpcre_malloc\fR  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
274  and \fBpcre_free\fR, and the callout function pointed to by \fBpcre_callout\fR,  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
275  are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
276    .P
277  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
278  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.
279    .
280  .SH CHECKING BUILD-TIME OPTIONS  .
281    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
282  .rs  .rs
283  .sp  .sp
284  .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
285    time, possibly by a different program, and even on a host other than the one on
286    which it was compiled. Details are given in the
287    .\" HREF
288    \fBpcreprecompile\fP
289    .\"
290    documentation. However, compiling a regular expression with one version of PCRE
291    for use with a different version is not guaranteed to work and may cause
292    crashes.
293    .
294    .
295    .SH "CHECKING BUILD-TIME OPTIONS"
296    .rs
297    .sp
298    .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
299  .PP  .PP
300  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
301  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
302  .\" HREF  .\" HREF
303  \fBpcrebuild\fR  \fBpcrebuild\fP
304  .\"  .\"
305  documentation has more details about these optional features.  documentation has more details about these optional features.
306    .P
307  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
308  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
309  which the information is placed. The following information is available:  which the information is placed. The following information is available:
310    .sp
311    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
312    .sp
313  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;
314  otherwise it is set to zero.  otherwise it is set to zero.
315    .sp
316      PCRE_CONFIG_UNICODE_PROPERTIES
317    .sp
318    The output is an integer that is set to one if support for Unicode character
319    properties is available; otherwise it is set to zero.
320    .sp
321    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
322    .sp
323  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
324  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
325  should normally be the standard character for your operating system.  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
326    Though they are derived from ASCII, the same values are returned in EBCDIC
327    environments. The default should normally correspond to the standard sequence
328    for your operating system.
329    .sp
330      PCRE_CONFIG_BSR
331    .sp
332    The output is an integer whose value indicates what character sequences the \eR
333    escape sequence matches by default. A value of 0 means that \eR matches any
334    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
335    or CRLF. The default can be overridden when a pattern is compiled or matched.
336    .sp
337    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
338    .sp
339  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
340  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
341  allow larger regular expressions to be compiled, at the expense of slower  allow larger regular expressions to be compiled, at the expense of slower
342  matching. The default value of 2 is sufficient for all but the most massive  matching. The default value of 2 is sufficient for all but the most massive
343  patterns, since it allows the compiled pattern to be up to 64K in size.  patterns, since it allows the compiled pattern to be up to 64K in size.
344    .sp
345    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
346    .sp
347  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
348  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
349  the \fBpcreposix\fR documentation.  the
350    .\" HREF
351    \fBpcreposix\fP
352    .\"
353    documentation.
354    .sp
355    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
356    .sp
357  The output is an integer that gives the default limit for the number of  The output is a long integer that gives the default limit for the number of
358  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
359  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
360    .sp
361  .SH COMPILING A PATTERN    PCRE_CONFIG_MATCH_LIMIT_RECURSION
362  .rs  .sp
363  .sp  The output is a long integer that gives the default limit for the depth of
364  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  recursion when calling the internal matching function in a \fBpcre_exec()\fP
365  .ti +5n  execution. Further details are given with \fBpcre_exec()\fP below.
366  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .sp
367  .ti +5n    PCRE_CONFIG_STACKRECURSE
368  .B const unsigned char *\fItableptr\fR);  .sp
369  .PP  The output is an integer that is set to one if internal recursion when running
370    \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
371  The function \fBpcre_compile()\fR is called to compile a pattern into an  to remember their state. This is the usual way that PCRE is compiled. The
372  internal form. The pattern is a C string terminated by a binary zero, and  output is zero if PCRE was compiled to use blocks of data on the heap instead
373  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
374  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
375  code and related data. The \fBpcre\fR type is defined for the returned block;  avoiding the use of the stack.
376  this is a typedef for a structure whose contents are not externally defined. It  .
377  is up to the caller to free the memory when it is no longer required.  .
378    .SH "COMPILING A PATTERN"
379    .rs
380    .sp
381    .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
382    .ti +5n
383    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
384    .ti +5n
385    .B const unsigned char *\fItableptr\fP);
386    .sp
387    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
388    .ti +5n
389    .B int *\fIerrorcodeptr\fP,
390    .ti +5n
391    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
392    .ti +5n
393    .B const unsigned char *\fItableptr\fP);
394    .P
395    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
396    called to compile a pattern into an internal form. The only difference between
397    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
398    \fIerrorcodeptr\fP, via which a numerical error code can be returned.
399    .P
400    The pattern is a C string terminated by a binary zero, and is passed in the
401    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
402    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
403    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
404    for a structure whose contents are not externally defined. It is up to the
405    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
406    .P
407  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
408  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
409  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
410  which is an address (see below).  argument, which is an address (see below).
411    .P
412  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
413  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
414  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
415  from within the pattern (see the detailed description of regular expressions  compatible with Perl, but also some others) can also be set and unset from
416  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
417  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
418  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
419  matching as well as at compile time.  .\"
420    documentation). For those options that can be different in different parts of
421  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their initial
422  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED and
423  NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual  PCRE_NEWLINE_\fIxxx\fP options can be set at the time of matching as well as at
424  error message. The offset from the start of the pattern to the character where  compile time.
425  the error was discovered is placed in the variable pointed to by  .P
426  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
427    Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
428  If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
429  character tables which are built when it is compiled, using the default C  error message. This is a static string that is part of the library. You must
430  locale. Otherwise, \fItableptr\fR must be the result of a call to  not try to free it. The offset from the start of the pattern to the character
431  \fBpcre_maketables()\fR. See the section on locale support below.  where the error was discovered is placed in the variable pointed to by
432    \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.
433  This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:  .P
434    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
435    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
436    returned via this argument in the event of an error. This is in addition to the
437    textual error message. Error codes and messages are listed below.
438    .P
439    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
440    character tables that are built when PCRE is compiled, using the default C
441    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
442    call to \fBpcre_maketables()\fP. This value is stored with the compiled
443    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
444    passed to it. For more discussion, see the section on locale support below.
445    .P
446    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
447    .sp
448    pcre *re;    pcre *re;
449    const char *error;    const char *error;
450    int erroffset;    int erroffset;
# Line 265  This code fragment shows a typical strai Line 454  This code fragment shows a typical strai
454      &error,           /* for error message */      &error,           /* for error message */
455      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
456      NULL);            /* use default character tables */      NULL);            /* use default character tables */
457    .sp
458  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
459    file:
460    .sp
461    PCRE_ANCHORED    PCRE_ANCHORED
462    .sp
463  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
464  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
465  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
466  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
467  Perl.  Perl.
468    .sp
469      PCRE_AUTO_CALLOUT
470    .sp
471    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
472    all with number 255, before each pattern item. For discussion of the callout
473    facility, see the
474    .\" HREF
475    \fBpcrecallout\fP
476    .\"
477    documentation.
478    .sp
479      PCRE_BSR_ANYCRLF
480      PCRE_BSR_UNICODE
481    .sp
482    These options (which are mutually exclusive) control what the \eR escape
483    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
484    match any Unicode newline sequence. The default is specified when PCRE is
485    built. It can be overridden from within the pattern, or by setting an option
486    when a compiled pattern is matched.
487    .sp
488    PCRE_CASELESS    PCRE_CASELESS
489    .sp
490  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
491  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
492  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
493    concept of case for characters whose values are less than 128, so caseless
494    matching is always possible. For characters with higher values, the concept of
495    case is supported if PCRE is compiled with Unicode property support, but not
496    otherwise. If you want to use caseless matching for characters 128 and above,
497    you must ensure that PCRE is compiled with Unicode property support as well as
498    with UTF-8 support.
499    .sp
500    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
501    .sp
502  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
503  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
504  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
505  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.
506  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
507  a pattern.  pattern.
508    .sp
509    PCRE_DOTALL    PCRE_DOTALL
510    .sp
511  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,
512  including newlines. Without it, newlines are excluded. This option is  including those that indicate newline. Without it, a dot does not match when
513  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
514  (?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
515  character, independent of the setting of this option.  negative class such as [^a] always matches newline characters, independent of
516    the setting of this option.
517    .sp
518      PCRE_DUPNAMES
519    .sp
520    If this bit is set, names used to identify capturing subpatterns need not be
521    unique. This can be helpful for certain types of pattern when it is known that
522    only one instance of the named subpattern can ever be matched. There are more
523    details of named subpatterns below; see also the
524    .\" HREF
525    \fBpcrepattern\fP
526    .\"
527    documentation.
528    .sp
529    PCRE_EXTENDED    PCRE_EXTENDED
530    .sp
531  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
532  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. Whitespace does not
533  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
534  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
535  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
536  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
537    .P
538  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
539  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. Whitespace characters
540  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
541  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( which introduces a conditional subpattern.
542    .sp
543    PCRE_EXTRA    PCRE_EXTRA
544    .sp
545  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
546  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
547  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
548  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
549  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
550  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
551  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
552  pattern.  this option. It can also be set by a (?X) option setting within a pattern.
553    .sp
554      PCRE_FIRSTLINE
555    .sp
556    If this option is set, an unanchored pattern is required to match before or at
557    the first newline in the subject string, though the matched text may continue
558    over the newline.
559    .sp
560      PCRE_JAVASCRIPT_COMPAT
561    .sp
562    If this option is set, PCRE's behaviour is changed in some ways so that it is
563    compatible with JavaScript rather than Perl. The changes are as follows:
564    .P
565    (1) A lone closing square bracket in a pattern causes a compile-time error,
566    because this is illegal in JavaScript (by default it is treated as a data
567    character). Thus, the pattern AB]CD becomes illegal when this option is set.
568    .P
569    (2) At run time, a back reference to an unset subpattern group matches an empty
570    string (by default this causes the current matching alternative to fail). A
571    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
572    an "a" in the subject), whereas it fails by default, for Perl compatibility.
573    .sp
574    PCRE_MULTILINE    PCRE_MULTILINE
575    .sp
576  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
577  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
578  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
579  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
580  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
581  Perl.  Perl.
582    .P
583  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
584  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
585  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
586  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
587  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
588  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
589    .sp
590      PCRE_NEWLINE_CR
591      PCRE_NEWLINE_LF
592      PCRE_NEWLINE_CRLF
593      PCRE_NEWLINE_ANYCRLF
594      PCRE_NEWLINE_ANY
595    .sp
596    These options override the default newline definition that was chosen when PCRE
597    was built. Setting the first or the second specifies that a newline is
598    indicated by a single character (CR or LF, respectively). Setting
599    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
600    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
601    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
602    that any Unicode newline sequence should be recognized. The Unicode newline
603    sequences are the three just mentioned, plus the single characters VT (vertical
604    tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
605    separator, U+2028), and PS (paragraph separator, U+2029). The last two are
606    recognized only in UTF-8 mode.
607    .P
608    The newline setting in the options word uses three bits that are treated
609    as a number, giving eight possibilities. Currently only six are used (default
610    plus the five values above). This means that if you set more than one newline
611    option, the combination may or may not be sensible. For example,
612    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
613    other combinations may yield unused numbers and cause an error.
614    .P
615    The only time that a line break is specially recognized when compiling a
616    pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
617    class is encountered. This indicates a comment that lasts until after the next
618    line break sequence. In other circumstances, line break sequences are treated
619    as literal data, except that in PCRE_EXTENDED mode, both CR and LF are treated
620    as whitespace characters and are therefore ignored.
621    .P
622    The newline option that is set at compile time becomes the default that is used
623    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
624    .sp
625    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
626    .sp
627  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
628  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
629  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
630  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
631  in Perl.  in Perl.
632    .sp
633    PCRE_UNGREEDY    PCRE_UNGREEDY
634    .sp
635  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
636  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
637  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.
638    .sp
639    PCRE_UTF8    PCRE_UTF8
640    .sp
641  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
642  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
643  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
644  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
645  behaviour of PCRE are given in the  behaviour of PCRE are given in the
646  .\" HTML <a href="pcre.html#utf8support">  .\" HTML <a href="pcre.html#utf8support">
# Line 367  section on UTF-8 support Line 649  section on UTF-8 support
649  .\"  .\"
650  in the main  in the main
651  .\" HREF  .\" HREF
652  \fBpcre\fR  \fBpcre\fP
653  .\"  .\"
654  page.  page.
655    .sp
656  .SH STUDYING A PATTERN    PCRE_NO_UTF8_CHECK
657    .sp
658    When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
659    automatically checked. There is a discussion about the
660    .\" HTML <a href="pcre.html#utf8strings">
661    .\" </a>
662    validity of UTF-8 strings
663    .\"
664    in the main
665    .\" HREF
666    \fBpcre\fP
667    .\"
668    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
669    returns an error. If you already know that your pattern is valid, and you want
670    to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
671    option. When it is set, the effect of passing an invalid UTF-8 string as a
672    pattern is undefined. It may cause your program to crash. Note that this option
673    can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
674    the UTF-8 validity checking of subject strings.
675    .
676    .
677    .SH "COMPILATION ERROR CODES"
678    .rs
679    .sp
680    The following table lists the error codes than may be returned by
681    \fBpcre_compile2()\fP, along with the error messages that may be returned by
682    both compiling functions. As PCRE has developed, some error codes have fallen
683    out of use. To avoid confusion, they have not been re-used.
684    .sp
685       0  no error
686       1  \e at end of pattern
687       2  \ec at end of pattern
688       3  unrecognized character follows \e
689       4  numbers out of order in {} quantifier
690       5  number too big in {} quantifier
691       6  missing terminating ] for character class
692       7  invalid escape sequence in character class
693       8  range out of order in character class
694       9  nothing to repeat
695      10  [this code is not in use]
696      11  internal error: unexpected repeat
697      12  unrecognized character after (? or (?-
698      13  POSIX named classes are supported only within a class
699      14  missing )
700      15  reference to non-existent subpattern
701      16  erroffset passed as NULL
702      17  unknown option bit(s) set
703      18  missing ) after comment
704      19  [this code is not in use]
705      20  regular expression is too large
706      21  failed to get memory
707      22  unmatched parentheses
708      23  internal error: code overflow
709      24  unrecognized character after (?<
710      25  lookbehind assertion is not fixed length
711      26  malformed number or name after (?(
712      27  conditional group contains more than two branches
713      28  assertion expected after (?(
714      29  (?R or (?[+-]digits must be followed by )
715      30  unknown POSIX class name
716      31  POSIX collating elements are not supported
717      32  this version of PCRE is not compiled with PCRE_UTF8 support
718      33  [this code is not in use]
719      34  character value in \ex{...} sequence is too large
720      35  invalid condition (?(0)
721      36  \eC not allowed in lookbehind assertion
722      37  PCRE does not support \eL, \el, \eN, \eU, or \eu
723      38  number after (?C is > 255
724      39  closing ) for (?C expected
725      40  recursive call could loop indefinitely
726      41  unrecognized character after (?P
727      42  syntax error in subpattern name (missing terminator)
728      43  two named subpatterns have the same name
729      44  invalid UTF-8 string
730      45  support for \eP, \ep, and \eX has not been compiled
731      46  malformed \eP or \ep sequence
732      47  unknown property name after \eP or \ep
733      48  subpattern name is too long (maximum 32 characters)
734      49  too many named subpatterns (maximum 10000)
735      50  [this code is not in use]
736      51  octal value is greater than \e377 (not in UTF-8 mode)
737      52  internal error: overran compiling workspace
738      53  internal error: previously-checked referenced subpattern not found
739      54  DEFINE group contains more than one branch
740      55  repeating a DEFINE group is not allowed
741      56  inconsistent NEWLINE options
742      57  \eg is not followed by a braced, angle-bracketed, or quoted
743            name/number or by a plain number
744      58  a numbered reference must not be zero
745      59  (*VERB) with an argument is not supported
746      60  (*VERB) not recognized
747      61  number is too big
748      62  subpattern name expected
749      63  digit expected after (?+
750      64  ] is an invalid data character in JavaScript compatibility mode
751    .sp
752    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
753    be used if the limits were changed when PCRE was built.
754    .
755    .
756    .SH "STUDYING A PATTERN"
757  .rs  .rs
758  .sp  .sp
759  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
760  .ti +5n  .ti +5n
761  .B const char **\fIerrptr\fR);  .B const char **\fIerrptr\fP);
762  .PP  .PP
763  When a pattern is going to be used several times, it is worth spending more  If a compiled pattern is going to be used several times, it is worth spending
764  time analyzing it in order to speed up the time taken for matching. The  more time analyzing it in order to speed up the time taken for matching. The
765  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
766  argument. If studing the pattern produces additional information that will help  argument. If studying the pattern produces additional information that will
767  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  help speed up matching, \fBpcre_study()\fP returns a pointer to a
768  block, in which the \fIstudy_data\fR field points to the results of the study.  \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
769    results of the study.
770  The returned value from a \fBpcre_study()\fR can be passed directly to  .P
771  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  The returned value from \fBpcre_study()\fP can be passed directly to
772    \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other
773  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
774  described below. If studying the pattern does not produce any additional  described
775  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the  .\" HTML <a href="#extradata">
776  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it  .\" </a>
777  must set up its own \fBpcre_extra\fR block.  below
778    .\"
779  The second argument contains option bits. At present, no options are defined  in the section on matching a pattern.
780  for \fBpcre_study()\fR, and this argument should always be zero.  .P
781    If studying the pattern does not produce any additional information
782  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
783    wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its
784    own \fBpcre_extra\fP block.
785    .P
786    The second argument of \fBpcre_study()\fP contains option bits. At present, no
787    options are defined, and this argument should always be zero.
788    .P
789    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
790  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
791  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
792  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
793  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
794    sure that it has run successfully.
795  This is a typical call to \fBpcre_study\fR():  .P
796    This is a typical call to \fBpcre_study\fP():
797    .sp
798    pcre_extra *pe;    pcre_extra *pe;
799    pe = pcre_study(    pe = pcre_study(
800      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
801      0,              /* no options exist */      0,              /* no options exist */
802      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
803    .sp
804  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
805  not have a single fixed starting character. A bitmap of possible starting  not have a single fixed starting character. A bitmap of possible starting
806  characters is created.  bytes is created.
807    .
808    .
809  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
810  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
811  .rs  .rs
812  .sp  .sp
813  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
814  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
815  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
816  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
817  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
818  is NULL, and is sufficient for many applications.  support. The use of locales with Unicode is discouraged. If you are handling
819    characters with codes greater than 128, you should either use UTF-8 and
820  An alternative set of tables can, however, be supplied. Such tables are built  Unicode, or use locales, but not try to mix the two.
821  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  .P
822  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
823  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.
824  French locale (where accented characters with codes greater than 128 are  Normally, the internal tables recognize only ASCII characters. However, when
825  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
826    default "C" locale of the local system, which may cause them to be different.
827    setlocale(LC_CTYPE, "fr");  .P
828    The internal tables can always be overridden by tables supplied by the
829    application that calls PCRE. These may be created in a different locale from
830    the default. As more and more applications change to using Unicode, the need
831    for this locale support is expected to die away.
832    .P
833    External tables are built by calling the \fBpcre_maketables()\fP function,
834    which has no arguments, in the relevant locale. The result can then be passed
835    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
836    example, to build and use tables that are appropriate for the French locale
837    (where accented characters with values greater than 128 are treated as letters),
838    the following code could be used:
839    .sp
840      setlocale(LC_CTYPE, "fr_FR");
841    tables = pcre_maketables();    tables = pcre_maketables();
842    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
843    .sp
844  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
845  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
846  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
847  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
848  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
849  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
850  memory containing the tables remains available for as long as it is needed.  needed.
851    .P
852  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
853    pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
854    and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
855    pattern, compilation, studying and matching all happen in the same locale, but
856    different patterns can be compiled in different locales.
857    .P
858    It is possible to pass a table pointer or NULL (indicating the use of the
859    internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
860    this facility could be used to match a pattern in a different locale from the
861    one in which it was compiled. Passing table pointers at run time is discussed
862    below in the section on matching a pattern.
863    .
864    .
865    .SH "INFORMATION ABOUT A PATTERN"
866  .rs  .rs
867  .sp  .sp
868  .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,"
869  .ti +5n  .ti +5n
870  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
871  .PP  .PP
872  The \fBpcre_fullinfo()\fR function returns information about a compiled  The \fBpcre_fullinfo()\fP function returns information about a compiled
873  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
874  nevertheless retained for backwards compability (and is documented below).  nevertheless retained for backwards compability (and is documented below).
875    .P
876  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
877  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
878  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
879  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
880  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
881  the following negative numbers:  the following negative numbers:
882    .sp
883    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
884                          the argument \fIwhere\fR was NULL                          the argument \fIwhere\fP was NULL
885    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
886    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADOPTION  the value of \fIwhat\fP was invalid
887    .sp
888  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
889  compiled pattern:  check against passing an arbitrary memory pointer. Here is a typical call of
890    \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
891    .sp
892    int rc;    int rc;
893    unsigned long int length;    size_t length;
894    rc = pcre_fullinfo(    rc = pcre_fullinfo(
895      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
896      pe,               /* result of pcre_study(), or NULL */      pe,               /* result of pcre_study(), or NULL */
897      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
898      &length);         /* where to put the data */      &length);         /* where to put the data */
899    .sp
900  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
901  as follows:  as follows:
902    .sp
903    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
904    .sp
905  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
906  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
907  no back references.  no back references.
908    .sp
909    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
910    .sp
911  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
912  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
913    .sp
914      PCRE_INFO_DEFAULT_TABLES
915    .sp
916    Return a pointer to the internal default character tables within PCRE. The
917    fourth argument should point to an \fBunsigned char *\fP variable. This
918    information call is provided for internal use by the \fBpcre_study()\fP
919    function. External callers can cause PCRE to use its internal tables by passing
920    a NULL table pointer.
921    .sp
922    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
923    .sp
924  Return information about the first byte of any matched string, for a  Return information about the first byte of any matched string, for a
925  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
926  old name is still recognized for backwards compatibility.)  variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
927    still recognized for backwards compatibility.)
928  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
929  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
930    (cat|cow|coyote), its value is returned. Otherwise, if either
931    .sp
932  (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
933  starts with "^", or  starts with "^", or
934    .sp
935  (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
936  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
937    .sp
938  -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
939  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
940  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
941    .sp
942    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
943    .sp
944  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
945  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
946  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
947  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
948    .sp
949      PCRE_INFO_HASCRORLF
950    .sp
951    Return 1 if the pattern contains any explicit matches for CR or LF characters,
952    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
953    explicit match is either a literal CR or LF character, or \er or \en.
954    .sp
955      PCRE_INFO_JCHANGED
956    .sp
957    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
958    0. The fourth argument should point to an \fBint\fP variable. (?J) and
959    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
960    .sp
961    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
962    .sp
963  For a non-anchored pattern, return the value of the rightmost literal byte  Return the value of the rightmost literal byte that must exist in any matched
964  which must exist in any matched string, other than at its start. The fourth  string, other than at its start, if such a byte has been recorded. The fourth
965  argument should point to an \fBint\fR variable. If there is no such byte, or if  argument should point to an \fBint\fP variable. If there is no such byte, -1 is
966  the pattern is anchored, -1 is returned. For example, for the pattern  returned. For anchored patterns, a last literal byte is recorded only if it
967  /a\\d+z\\d+/ the returned value is 'z'.  follows something of variable length. For example, for the pattern
968    /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
969    is -1.
970    .sp
971    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
972    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
973    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
974    .sp
975  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
976  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
977  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
978  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
979  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
980  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
981  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
982    you need to use the name-to-number map, which is described by these three
983    values.
984    .P
985  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
986  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
987  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
988  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
989  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
990  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
991  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
992  alphabetical order. For example, consider the following pattern (assume  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of
993    their parentheses numbers. For example, consider the following pattern (assume
994  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  PCRE_EXTENDED is set, so white space - including newlines - is ignored):
995    .sp
996    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  .\" JOIN
997    (?P<month>\\d\\d) - (?P<day>\\d\\d) )    (?<date> (?<year>(\ed\ed)?\ed\ed) -
998      (?<month>\ed\ed) - (?<day>\ed\ed) )
999    .sp
1000  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
1001  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
1002  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1003    .sp
1004    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1005    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1006    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1007    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1008    .sp
1009  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1010  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
1011    different for each compiled pattern.
1012    .sp
1013      PCRE_INFO_OKPARTIAL
1014    .sp
1015    Return 1 if the pattern can be used for partial matching with
1016    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1017    \fBint\fP variable. From release 8.00, this always returns 1, because the
1018    restrictions that previously applied to partial matching have been lifted. The
1019    .\" HREF
1020    \fBpcrepartial\fP
1021    .\"
1022    documentation gives details of partial matching.
1023    .sp
1024    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1025    .sp
1026  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
1027  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
1028  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
1029  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1030    they are the options that will be in force when matching starts. For example,
1031    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1032    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1033    .P
1034  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
1035  alternatives begin with one of the following:  alternatives begin with one of the following:
1036    .sp
1037    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1038    \\A    always    \eA    always
1039    \\G    always    \eG    always
1040    .\" JOIN
1041    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1042            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1043    .sp
1044  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
1045  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1046    .sp
1047    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1048    .sp
1049  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
1050  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
1051  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
1052  variable.  variable.
1053    .sp
1054    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1055    .sp
1056  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
1057  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
1058  \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
1059  created by \fBpcre_study()\fR. The fourth argument should point to a  created by \fBpcre_study()\fP. The fourth argument should point to a
1060  \fBsize_t\fR variable.  \fBsize_t\fP variable.
1061    .
1062  .SH OBSOLETE INFO FUNCTION  .
1063    .SH "OBSOLETE INFO FUNCTION"
1064  .rs  .rs
1065  .sp  .sp
1066  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
1067  .B *\fIfirstcharptr\fR);  .B *\fIfirstcharptr\fP);
1068  .PP  .PP
1069  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
1070  restrictive to return all the available data about a compiled pattern. New  restrictive to return all the available data about a compiled pattern. New
1071  programs should use \fBpcre_fullinfo()\fR instead. The yield of  programs should use \fBpcre_fullinfo()\fP instead. The yield of
1072  \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
1073  following negative numbers:  following negative numbers:
1074    .sp
1075    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
1076    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC   the "magic number" was not found
1077    .sp
1078  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
1079  pattern was compiled is placed in the integer it points to (see  pattern was compiled is placed in the integer it points to (see
1080  PCRE_INFO_OPTIONS above).  PCRE_INFO_OPTIONS above).
1081    .P
1082  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,
1083  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
1084  string (see PCRE_INFO_FIRSTBYTE above).  string (see PCRE_INFO_FIRSTBYTE above).
1085    .
1086  .SH MATCHING A PATTERN  .
1087    .SH "REFERENCE COUNTS"
1088  .rs  .rs
1089  .sp  .sp
1090  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1091    .PP
1092    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1093    data block that contains a compiled pattern. It is provided for the benefit of
1094    applications that operate in an object-oriented manner, where different parts
1095    of the application may be using the same compiled pattern, but you want to free
1096    the block when they are all done.
1097    .P
1098    When a pattern is compiled, the reference count field is initialized to zero.
1099    It is changed only by calling this function, whose action is to add the
1100    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1101    function is the new value. However, the value of the count is constrained to
1102    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1103    it is forced to the appropriate limit value.
1104    .P
1105    Except when it is zero, the reference count is not correctly preserved if a
1106    pattern is compiled on one host and then transferred to a host whose byte-order
1107    is different. (This seems a highly unlikely scenario.)
1108    .
1109    .
1110    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1111    .rs
1112    .sp
1113    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1114  .ti +5n  .ti +5n
1115  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1116  .ti +5n  .ti +5n
1117  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1118  .PP  .P
1119  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
1120  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
1121  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
1122  \fIextra\fR argument.  \fIextra\fP argument. This function is the main matching facility of the
1123    library, and it operates in a Perl-like manner. For specialist use there is
1124  Here is an example of a simple call to \fBpcre_exec()\fR:  also an alternative matching function, which is described
1125    .\" HTML <a href="#dfamatch">
1126    .\" </a>
1127    below
1128    .\"
1129    in the section about the \fBpcre_dfa_exec()\fP function.
1130    .P
1131    In most applications, the pattern will have been compiled (and optionally
1132    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1133    possible to save compiled patterns and study data, and then use them later
1134    in different processes, possibly even on different hosts. For a discussion
1135    about this, see the
1136    .\" HREF
1137    \fBpcreprecompile\fP
1138    .\"
1139    documentation.
1140    .P
1141    Here is an example of a simple call to \fBpcre_exec()\fP:
1142    .sp
1143    int rc;    int rc;
1144    int ovector[30];    int ovector[30];
1145    rc = pcre_exec(    rc = pcre_exec(
# Line 645  Here is an example of a simple call to \ Line 1149  Here is an example of a simple call to \
1149      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1150      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1151      0,              /* default options */      0,              /* default options */
1152      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1153      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1154    .
1155  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .\" HTML <a name="extradata"></a>
1156  data block. The \fBpcre_study()\fR function returns such a block (when it  .SS "Extra data for \fBpcre_exec()\fR"
1157    .rs
1158    .sp
1159    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1160    data block. The \fBpcre_study()\fP function returns such a block (when it
1161  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
1162  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1163    fields (not necessarily in this order):
1164    unsigned long int \fIflags\fR;  .sp
1165    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1166    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1167    void *\fIcallout_data\fR;    unsigned long int \fImatch_limit\fP;
1168      unsigned long int \fImatch_limit_recursion\fP;
1169  The \fIflags\fR field is a bitmap that specifies which of the other fields    void *\fIcallout_data\fP;
1170      const unsigned char *\fItables\fP;
1171    .sp
1172    The \fIflags\fP field is a bitmap that specifies which of the other fields
1173  are set. The flag bits are:  are set. The flag bits are:
1174    .sp
1175    PCRE_EXTRA_STUDY_DATA    PCRE_EXTRA_STUDY_DATA
1176    PCRE_EXTRA_MATCH_LIMIT    PCRE_EXTRA_MATCH_LIMIT
1177      PCRE_EXTRA_MATCH_LIMIT_RECURSION
1178    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1179      PCRE_EXTRA_TABLES
1180  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the  .sp
1181  \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
1182  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
1183  the block by setting the other fields.  the appropriate flag bit. You should not set this yourself, but you may add to
1184    the block by setting the other fields and their corresponding flag bits.
1185  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  .P
1186    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1187  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,
1188  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
1189  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is the use of nested unlimited repeats.
1190  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1191  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
1192  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
1193  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
1194  count starts from zero for each position in the subject string.  limiting the amount of backtracking that can take place. For patterns that are
1195    not anchored, the count restarts from zero for each position in the subject
1196  The default limit for the library can be set when PCRE is built; the default  string.
1197    .P
1198    The default value for the limit can be set when PCRE is built; the default
1199  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
1200  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
1201  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
1202  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
1203  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1204    .P
1205  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
1206  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1207    limits the depth of recursion. The recursion depth is a smaller number than the
1208  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.
1209  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.
1210  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1211  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,
1212  unachored at matching time.  when PCRE has been compiled to use memory on the heap instead of the stack, the
1213    amount of heap memory that can be used.
1214  There are also three further options that can be set only at matching time:  .P
1215    The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1216    built; the default default is the same value as the default for
1217    \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1218    with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1219    PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1220    is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1221    .P
1222    The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1223    and is described in the
1224    .\" HREF
1225    \fBpcrecallout\fP
1226    .\"
1227    documentation.
1228    .P
1229    The \fItables\fP field is used to pass a character tables pointer to
1230    \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1231    pattern. A non-NULL value is stored with the compiled pattern only if custom
1232    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1233    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1234    internal tables to be used. This facility is helpful when re-using patterns
1235    that have been saved after compiling with an external set of tables, because
1236    the external tables might be at a different address when \fBpcre_exec()\fP is
1237    called. See the
1238    .\" HREF
1239    \fBpcreprecompile\fP
1240    .\"
1241    documentation for a discussion of saving compiled patterns for later use.
1242    .
1243    .\" HTML <a name="execoptions"></a>
1244    .SS "Option bits for \fBpcre_exec()\fP"
1245    .rs
1246    .sp
1247    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1248    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1249    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_START_OPTIMIZE,
1250    PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.
1251    .sp
1252      PCRE_ANCHORED
1253    .sp
1254    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1255    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1256    to be anchored by virtue of its contents, it cannot be made unachored at
1257    matching time.
1258    .sp
1259      PCRE_BSR_ANYCRLF
1260      PCRE_BSR_UNICODE
1261    .sp
1262    These options (which are mutually exclusive) control what the \eR escape
1263    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1264    match any Unicode newline sequence. These options override the choice that was
1265    made or defaulted when the pattern was compiled.
1266    .sp
1267      PCRE_NEWLINE_CR
1268      PCRE_NEWLINE_LF
1269      PCRE_NEWLINE_CRLF
1270      PCRE_NEWLINE_ANYCRLF
1271      PCRE_NEWLINE_ANY
1272    .sp
1273    These options override the newline definition that was chosen or defaulted when
1274    the pattern was compiled. For details, see the description of
1275    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1276    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1277    the way the match position is advanced after a match failure for an unanchored
1278    pattern.
1279    .P
1280    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1281    match attempt for an unanchored pattern fails when the current position is at a
1282    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1283    characters, the match position is advanced by two characters instead of one, in
1284    other words, to after the CRLF.
1285    .P
1286    The above rule is a compromise that makes the most common cases work as
1287    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1288    set), it does not match the string "\er\enA" because, after failing at the
1289    start, it skips both the CR and the LF before retrying. However, the pattern
1290    [\er\en]A does match that string, because it contains an explicit CR or LF
1291    reference, and so advances only by one character after the first failure.
1292    .P
1293    An explicit match for CR of LF is either a literal appearance of one of those
1294    characters, or one of the \er or \en escape sequences. Implicit matches such as
1295    [^X] do not count, nor does \es (which includes CR and LF in the characters
1296    that it matches).
1297    .P
1298    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1299    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1300    .sp
1301    PCRE_NOTBOL    PCRE_NOTBOL
1302    .sp
1303  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
1304  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1305  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1306    never to match. This option affects only the behaviour of the circumflex
1307    metacharacter. It does not affect \eA.
1308    .sp
1309    PCRE_NOTEOL    PCRE_NOTEOL
1310    .sp
1311  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
1312  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
1313  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1314  to match.  compile time) causes dollar never to match. This option affects only the
1315    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1316    .sp
1317    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1318    .sp
1319  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
1320  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
1321  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
1322    .sp
1323    a?b?    a?b?
1324    .sp
1325  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
1326  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
1327  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".
1328    .P
1329  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
1330  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
1331  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
1332  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
1333  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
1334  below) and trying an ordinary match again.  starting offset (see below) and trying an ordinary match again. There is some
1335    code that demonstrates how to do this in the
1336  The subject string is passed to \fBpcre_exec()\fR as a pointer in  .\" HREF
1337  \fIsubject\fR, a length in \fIlength\fR, and a starting offset in  \fBpcredemo\fP
1338  \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary  .\"
1339    sample program.
1340    .sp
1341      PCRE_NO_START_OPTIMIZE
1342    .sp
1343    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1344    a match, in order to speed up the process. For example, if it is known that a
1345    match must start with a specific character, it searches the subject for that
1346    character, and fails immediately if it cannot find it, without actually running
1347    the main matching function. When callouts are in use, these optimizations can
1348    cause them to be skipped. This option disables the "start-up" optimizations,
1349    causing performance to suffer, but ensuring that the callouts do occur.
1350    .sp
1351      PCRE_NO_UTF8_CHECK
1352    .sp
1353    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1354    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1355    The value of \fIstartoffset\fP is also checked to ensure that it points to the
1356    start of a UTF-8 character. There is a discussion about the validity of UTF-8
1357    strings in the
1358    .\" HTML <a href="pcre.html#utf8strings">
1359    .\" </a>
1360    section on UTF-8 support
1361    .\"
1362    in the main
1363    .\" HREF
1364    \fBpcre\fP
1365    .\"
1366    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1367    the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1368    PCRE_ERROR_BADUTF8_OFFSET is returned.
1369    .P
1370    If you already know that your subject is valid, and you want to skip these
1371    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1372    calling \fBpcre_exec()\fP. You might want to do this for the second and
1373    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1374    all the matches in a single subject string. However, you should be sure that
1375    the value of \fIstartoffset\fP points to the start of a UTF-8 character. When
1376    PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a
1377    subject, or a value of \fIstartoffset\fP that does not point to the start of a
1378    UTF-8 character, is undefined. Your program may crash.
1379    .sp
1380      PCRE_PARTIAL_HARD
1381      PCRE_PARTIAL_SOFT
1382    .sp
1383    These options turn on the partial matching feature. For backwards
1384    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1385    occurs if the end of the subject string is reached successfully, but there are
1386    not enough subject characters to complete the match. If this happens when
1387    PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1388    PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1389    by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1390    returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1391    was inspected when the partial match was found is set as the first matching
1392    string. There is a more detailed discussion in the
1393    .\" HREF
1394    \fBpcrepartial\fP
1395    .\"
1396    documentation.
1397    .
1398    .SS "The string to be matched by \fBpcre_exec()\fP"
1399    .rs
1400    .sp
1401    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1402    \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1403    in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1404    a UTF-8 character. Unlike the pattern string, the subject may contain binary
1405  zero bytes. When the starting offset is zero, the search for a match starts at  zero bytes. When the starting offset is zero, the search for a match starts at
1406  the beginning of the subject, and this is by far the most common case.  the beginning of the subject, and this is by far the most common case.
1407    .P
 If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  
 sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is  
 passed, PCRE's behaviour is not defined.  
   
1408  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
1409  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1410  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1411  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
1412  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1413    .sp
1414    \\Biss\\B    \eBiss\eB
1415    .sp
1416  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
1417  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
1418  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
1419  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
1420  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
1421  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
1422  \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
1423  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
1424  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.
1425    .P
1426  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
1427  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
1428  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.
1429    .
1430    .SS "How \fBpcre_exec()\fP returns captured substrings"
1431    .rs
1432    .sp
1433  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
1434  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
1435  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1436  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1437  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
1438  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1439    .P
1440  Captured substrings are returned to the caller via a vector of integer offsets  Captured substrings are returned to the caller via a vector of integers whose
1441  whose address is passed in \fIovector\fR. The number of elements in the vector  address is passed in \fIovector\fP. The number of elements in the vector is
1442  is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass  passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1443  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1444  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1445  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1446  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
1447  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1448    and is not available for passing back information. The number passed in
1449  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
1450  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
1451  continuing up to two-thirds of its length at the most. The first element of a  .P
1452  pair is set to the offset of the first character in a substring, and the second  When a match is successful, information about captured substrings is returned
1453  is set to the offset of the first character after the end of a substring. The  in pairs of integers, starting at the beginning of \fIovector\fP, and
1454  first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the  continuing up to two-thirds of its length at the most. The first element of
1455  subject string matched by the entire pattern. The next pair is used for the  each pair is set to the byte offset of the first character in a substring, and
1456  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR  the second is set to the byte offset of the first character after the end of a
1457  is the number of pairs that have been set. If there are no capturing  substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1458  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
1459  just the first pair of offsets has been set.  .P
1460    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1461  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
1462  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
1463    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1464  It is possible for an capturing subpattern number \fIn+1\fR to match some  For example, if two substrings have been captured, the returned value is 3. If
1465  part of the subject when subpattern \fIn\fR has not been used at all. For  there are no capturing subpatterns, the return value from a successful match is
1466  example, if the string "abc" is matched against the pattern (a|(z))(bc)  1, indicating that just the first pair of offsets has been set.
1467  subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset  .P
 values corresponding to the unused subpattern are set to -1.  
   
1468  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
1469  string that it matched that gets returned.  string that it matched that is returned.
1470    .P
1471  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
1472  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
1473  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. If the substring offsets are not of interest,
1474  \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and  \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1475  \fIovecsize\fR as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1476  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
1477  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
1478  to supply an \fIovector\fR.  advisable to supply an \fIovector\fP.
1479    .P
1480  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
1481  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1482  \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
1483  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.
1484    .P
1485  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
1486    the subject when subpattern \fIn\fP has not been used at all. For example, if
1487    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1488    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1489    happens, both values in the offset pairs corresponding to unused subpatterns
1490    are set to -1.
1491    .P
1492    Offset values that correspond to unused subpatterns at the end of the
1493    expression are also set to -1. For example, if the string "abc" is matched
1494    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1495    return from the function is 2, because the highest used capturing subpattern
1496    number is 1. However, you can refer to the offsets for the second and third
1497    capturing subpatterns if you wish (assuming the vector is large enough, of
1498    course).
1499    .P
1500    Some convenience functions are provided for extracting the captured substrings
1501    as separate strings. These are described below.
1502    .
1503    .\" HTML <a name="errorlist"></a>
1504    .SS "Error return values from \fBpcre_exec()\fP"
1505    .rs
1506    .sp
1507    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1508  defined in the header file:  defined in the header file:
1509    .sp
1510    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
1511    .sp
1512  The subject string did not match the pattern.  The subject string did not match the pattern.
1513    .sp
1514    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
1515    .sp
1516  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
1517  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
1518    .sp
1519    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
1520    .sp
1521  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
1522    .sp
1523    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
1524    .sp
1525  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
1526  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
1527  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
1528    other endianness. This is the error that PCRE gives when the magic number is
1529    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
1530    .sp
1531      PCRE_ERROR_UNKNOWN_OPCODE (-5)
1532    .sp
1533  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
1534  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
1535  of the compiled pattern.  of the compiled pattern.
1536    .sp
1537    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1538    .sp
1539  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
1540  \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
1541  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
1542  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
1543  the end of matching.  automatically freed at the end of matching.
1544    .sp
1545    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1546    .sp
1547  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
1548  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1549  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
1550    .sp
1551    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
1552    .sp
1553  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
1554  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1555  description above.  above.
1556    .sp
1557    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
1558    .sp
1559  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
1560  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
1561  \fBpcrecallout\fR documentation for details.  .\" HREF
1562    \fBpcrecallout\fP
1563  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  .\"
1564    documentation for details.
1565    .sp
1566      PCRE_ERROR_BADUTF8        (-10)
1567    .sp
1568    A string that contains an invalid UTF-8 byte sequence was passed as a subject.
1569    .sp
1570      PCRE_ERROR_BADUTF8_OFFSET (-11)
1571    .sp
1572    The UTF-8 byte sequence that was passed as a subject was valid, but the value
1573    of \fIstartoffset\fP did not point to the beginning of a UTF-8 character.
1574    .sp
1575      PCRE_ERROR_PARTIAL        (-12)
1576    .sp
1577    The subject string did not match, but it did match partially. See the
1578    .\" HREF
1579    \fBpcrepartial\fP
1580    .\"
1581    documentation for details of partial matching.
1582    .sp
1583      PCRE_ERROR_BADPARTIAL     (-13)
1584    .sp
1585    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1586    option was used with a compiled pattern containing items that were not
1587    supported for partial matching. From release 8.00 onwards, there are no
1588    restrictions on partial matching.
1589    .sp
1590      PCRE_ERROR_INTERNAL       (-14)
1591    .sp
1592    An unexpected internal error has occurred. This error could be caused by a bug
1593    in PCRE or by overwriting of the compiled pattern.
1594    .sp
1595      PCRE_ERROR_BADCOUNT       (-15)
1596    .sp
1597    This error is given if the value of the \fIovecsize\fP argument is negative.
1598    .sp
1599      PCRE_ERROR_RECURSIONLIMIT (-21)
1600    .sp
1601    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
1602    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1603    description above.
1604    .sp
1605      PCRE_ERROR_BADNEWLINE     (-23)
1606    .sp
1607    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1608    .P
1609    Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1610    .
1611    .
1612    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
1613  .rs  .rs
1614  .sp  .sp
1615  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
1616  .ti +5n  .ti +5n
1617  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
1618  .ti +5n  .ti +5n
1619  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
1620  .PP  .PP
1621  .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,  
1622  .ti +5n  .ti +5n
1623  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
1624  .ti +5n  .ti +5n
1625  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1626  .PP  .PP
1627  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
1628  .ti +5n  .ti +5n
1629  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
1630  .PP  .PP
1631  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
1632  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
1633  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
1634  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
1635  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
1636  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
1637  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
1638  has a further zero added on the end, but the result is not, of course,  .P
1639  a C string.  A substring that contains a binary zero is correctly extracted and has a
1640    further zero added on the end, but the result is not, of course, a C string.
1641    However, you can process such a string by referring to the length that is
1642    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
1643    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
1644    for handling strings containing binary zeros, because the end of the final
1645    string is not independently indicated.
1646    .P
1647  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:
1648  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
1649  \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
1650  \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
1651  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
1652  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
1653  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
1654  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
1655  the vector divided by three.  number of elements in the vector divided by three.
1656    .P
1657  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
1658  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
1659  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
1660  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
1661  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
1662  \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
1663  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
1664  \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
1665  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
1666    .sp
1667    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1668    .sp
1669  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
1670  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
1671    .sp
1672    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
1673    .sp
1674  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
1675    .P
1676  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
1677  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
1678  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
1679  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
1680  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
1681  function is zero if all went well, or  function is zero if all went well, or the error code
1682    .sp
1683    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
1684    .sp
1685  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
1686    .P
1687  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
1688  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
1689  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
1690  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
1691  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
1692  substrings.  substrings.
1693    .P
1694  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
1695  \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
1696  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
1697  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
1698  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
1699  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
1700  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
1701  \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
1702  provided.  provided.
1703    .
1704  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
1705    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
1706  .rs  .rs
1707  .sp  .sp
1708  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
1709  .ti +5n  .ti +5n
1710  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
1711    .PP
1712    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
1713  .ti +5n  .ti +5n
1714  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1715  .ti +5n  .ti +5n
1716  .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,  
1717  .ti +5n  .ti +5n
1718  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
1719  .PP  .PP
1720  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
1721  .ti +5n  .ti +5n
1722  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
1723  .ti +5n  .ti +5n
1724  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
1725  .ti +5n  .ti +5n
1726  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
1727  .PP  .PP
1728  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.
1729  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
1730  compiled pattern, and the second is the name. For example, for this pattern  .sp
1731      (a+)b(?<xxx>\ed+)...
1732    ab(?<xxx>\\d+)...  .sp
1733    the number of the subpattern called "xxx" is 2. If the name is known to be
1734  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
1735  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
1736  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
1737  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
1738    that name.
1739  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
1740  \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
1741  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
1742  differences.  two functions that do the whole job.
1743    .P
1744    Most of the arguments of \fBpcre_copy_named_substring()\fP and
1745    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
1746    functions that extract by number. As these are described in the previous
1747    section, they are not re-described here. There are just two differences:
1748    .P
1749  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
1750  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
1751  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
1752  translation table.  translation table.
1753    .P
1754  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1755  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1756  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1757    the behaviour may not be what you want (see the next section).
1758  .in 0  .P
1759  Last updated: 03 February 2003  \fBWarning:\fP If the pattern uses the "(?|" feature to set up multiple
1760  .br  subpatterns with the same number, you cannot use names to distinguish them,
1761  Copyright (c) 1997-2003 University of Cambridge.  because names are not included in the compiled code. The matching process uses
1762    only numbers.
1763    .
1764    .SH "DUPLICATE SUBPATTERN NAMES"
1765    .rs
1766    .sp
1767    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
1768    .ti +5n
1769    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1770    .PP
1771    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1772    are not required to be unique. Normally, patterns with duplicate names are such
1773    that in any one match, only one of the named subpatterns participates. An
1774    example is shown in the
1775    .\" HREF
1776    \fBpcrepattern\fP
1777    .\"
1778    documentation.
1779    .P
1780    When duplicates are present, \fBpcre_copy_named_substring()\fP and
1781    \fBpcre_get_named_substring()\fP return the first substring corresponding to
1782    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1783    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1784    returns one of the numbers that are associated with the name, but it is not
1785    defined which it is.
1786    .P
1787    If you want to get full details of all captured substrings for a given name,
1788    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1789    argument is the compiled pattern, and the second is the name. The third and
1790    fourth are pointers to variables which are updated by the function. After it
1791    has run, they point to the first and last entries in the name-to-number table
1792    for the given name. The function itself returns the length of each entry, or
1793    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
1794    described above in the section entitled \fIInformation about a pattern\fP.
1795    Given all the relevant entries for the name, you can extract each of their
1796    numbers, and hence the captured data, if any.
1797    .
1798    .
1799    .SH "FINDING ALL POSSIBLE MATCHES"
1800    .rs
1801    .sp
1802    The traditional matching function uses a similar algorithm to Perl, which stops
1803    when it finds the first match, starting at a given point in the subject. If you
1804    want to find all possible matches, or the longest possible match, consider
1805    using the alternative matching function (see below) instead. If you cannot use
1806    the alternative function, but still need to find all possible matches, you
1807    can kludge it up by making use of the callout facility, which is described in
1808    the
1809    .\" HREF
1810    \fBpcrecallout\fP
1811    .\"
1812    documentation.
1813    .P
1814    What you have to do is to insert a callout right at the end of the pattern.
1815    When your callout function is called, extract and save the current matched
1816    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
1817    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
1818    will yield PCRE_ERROR_NOMATCH.
1819    .
1820    .
1821    .\" HTML <a name="dfamatch"></a>
1822    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
1823    .rs
1824    .sp
1825    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1826    .ti +5n
1827    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1828    .ti +5n
1829    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
1830    .ti +5n
1831    .B int *\fIworkspace\fP, int \fIwscount\fP);
1832    .P
1833    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
1834    a compiled pattern, using a matching algorithm that scans the subject string
1835    just once, and does not backtrack. This has different characteristics to the
1836    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1837    patterns are not supported. Nevertheless, there are times when this kind of
1838    matching can be useful. For a discussion of the two matching algorithms, and a
1839    list of features that \fBpcre_dfa_exec()\fP does not support, see the
1840    .\" HREF
1841    \fBpcrematching\fP
1842    .\"
1843    documentation.
1844    .P
1845    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
1846    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
1847    different way, and this is described below. The other common arguments are used
1848    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
1849    here.
1850    .P
1851    The two additional arguments provide workspace for the function. The workspace
1852    vector should contain at least 20 elements. It is used for keeping track of
1853    multiple paths through the pattern tree. More workspace will be needed for
1854    patterns and subjects where there are a lot of potential matches.
1855    .P
1856    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
1857    .sp
1858      int rc;
1859      int ovector[10];
1860      int wspace[20];
1861      rc = pcre_dfa_exec(
1862        re,             /* result of pcre_compile() */
1863        NULL,           /* we didn't study the pattern */
1864        "some string",  /* the subject string */
1865        11,             /* the length of the subject string */
1866        0,              /* start at offset 0 in the subject */
1867        0,              /* default options */
1868        ovector,        /* vector of integers for substring information */
1869        10,             /* number of elements (NOT size in bytes) */
1870        wspace,         /* working space vector */
1871        20);            /* number of elements (NOT size in bytes) */
1872    .
1873    .SS "Option bits for \fBpcre_dfa_exec()\fP"
1874    .rs
1875    .sp
1876    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1877    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1878    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD,
1879    PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
1880    four of these are exactly the same as for \fBpcre_exec()\fP, so their
1881    description is not repeated here.
1882    .sp
1883      PCRE_PARTIAL_HARD
1884      PCRE_PARTIAL_SOFT
1885    .sp
1886    These have the same general effect as they do for \fBpcre_exec()\fP, but the
1887    details are slightly different. When PCRE_PARTIAL_HARD is set for
1888    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
1889    is reached and there is still at least one matching possibility that requires
1890    additional characters. This happens even if some complete matches have also
1891    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1892    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1893    there have been no complete matches, but there is still at least one matching
1894    possibility. The portion of the string that was inspected when the longest
1895    partial match was found is set as the first matching string in both cases.
1896    .sp
1897      PCRE_DFA_SHORTEST
1898    .sp
1899    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
1900    soon as it has found one match. Because of the way the alternative algorithm
1901    works, this is necessarily the shortest possible match at the first possible
1902    matching point in the subject string.
1903    .sp
1904      PCRE_DFA_RESTART
1905    .sp
1906    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
1907    again, with additional subject characters, and have it continue with the same
1908    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1909    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
1910    before because data about the match so far is left in them after a partial
1911    match. There is more discussion of this facility in the
1912    .\" HREF
1913    \fBpcrepartial\fP
1914    .\"
1915    documentation.
1916    .
1917    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
1918    .rs
1919    .sp
1920    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
1921    substring in the subject. Note, however, that all the matches from one run of
1922    the function start at the same point in the subject. The shorter matches are
1923    all initial substrings of the longer matches. For example, if the pattern
1924    .sp
1925      <.*>
1926    .sp
1927    is matched against the string
1928    .sp
1929      This is <something> <something else> <something further> no more
1930    .sp
1931    the three matched strings are
1932    .sp
1933      <something>
1934      <something> <something else>
1935      <something> <something else> <something further>
1936    .sp
1937    On success, the yield of the function is a number greater than zero, which is
1938    the number of matched substrings. The substrings themselves are returned in
1939    \fIovector\fP. Each string uses two elements; the first is the offset to the
1940    start, and the second is the offset to the end. In fact, all the strings have
1941    the same start offset. (Space could have been saved by giving this only once,
1942    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
1943    returns data, even though the meaning of the strings is different.)
1944    .P
1945    The strings are returned in reverse order of length; that is, the longest
1946    matching string is given first. If there were too many matches to fit into
1947    \fIovector\fP, the yield of the function is zero, and the vector is filled with
1948    the longest matches.
1949    .
1950    .SS "Error returns from \fBpcre_dfa_exec()\fP"
1951    .rs
1952    .sp
1953    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
1954    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
1955    described
1956    .\" HTML <a href="#errorlist">
1957    .\" </a>
1958    above.
1959    .\"
1960    There are in addition the following errors that are specific to
1961    \fBpcre_dfa_exec()\fP:
1962    .sp
1963      PCRE_ERROR_DFA_UITEM      (-16)
1964    .sp
1965    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
1966    that it does not support, for instance, the use of \eC or a back reference.
1967    .sp
1968      PCRE_ERROR_DFA_UCOND      (-17)
1969    .sp
1970    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
1971    uses a back reference for the condition, or a test for recursion in a specific
1972    group. These are not supported.
1973    .sp
1974      PCRE_ERROR_DFA_UMLIMIT    (-18)
1975    .sp
1976    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
1977    block that contains a setting of the \fImatch_limit\fP field. This is not
1978    supported (it is meaningless).
1979    .sp
1980      PCRE_ERROR_DFA_WSSIZE     (-19)
1981    .sp
1982    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
1983    \fIworkspace\fP vector.
1984    .sp
1985      PCRE_ERROR_DFA_RECURSE    (-20)
1986    .sp
1987    When a recursive subpattern is processed, the matching function calls itself
1988    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
1989    error is given if the output vector is not large enough. This should be
1990    extremely rare, as a vector of size 1000 is used.
1991    .
1992    .
1993    .SH "SEE ALSO"
1994    .rs
1995    .sp
1996    \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
1997    \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
1998    \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
1999    .
2000    .
2001    .SH AUTHOR
2002    .rs
2003    .sp
2004    .nf
2005    Philip Hazel
2006    University Computing Service
2007    Cambridge CB2 3QH, England.
2008    .fi
2009    .
2010    .
2011    .SH REVISION
2012    .rs
2013    .sp
2014    .nf
2015    Last updated: 09 September 2009
2016    Copyright (c) 1997-2009 University of Cambridge.
2017    .fi

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