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1  .TH PCRE 3  .TH PCREAPI 3 "29 October 2012" "PCRE 8.32"
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
 .SH SYNOPSIS OF PCRE API  
 .rs  
4  .sp  .sp
5  .B #include <pcre.h>  .B #include <pcre.h>
6  .PP  .
7    .
8    .SH "PCRE NATIVE API BASIC FUNCTIONS"
9    .rs
10    .sp
11  .SM  .SM
12  .br  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  .ti +5n
14    .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15    .ti +5n
16    .B const unsigned char *\fItableptr\fP);
17    .PP
18    .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19    .ti +5n
20    .B int *\fIerrorcodeptr\fP,
21  .ti +5n  .ti +5n
22  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23  .ti +5n  .ti +5n
24  .B const unsigned char *\fItableptr\fR);  .B const unsigned char *\fItableptr\fP);
25  .PP  .PP
26  .br  .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
 .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  
27  .ti +5n  .ti +5n
28  .B const char **\fIerrptr\fR);  .B const char **\fIerrptr\fP);
29  .PP  .PP
30  .br  .B void pcre_free_study(pcre_extra *\fIextra\fP);
31  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  .PP
32    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33  .ti +5n  .ti +5n
34  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35  .ti +5n  .ti +5n
36  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37  .PP  .PP
38  .br  .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .ti +5n
40    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41    .ti +5n
42    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43    .ti +5n
44    .B int *\fIworkspace\fP, int \fIwscount\fP);
45    .
46    .
47    .SH "PCRE NATIVE API STRING EXTRACTION FUNCTIONS"
48    .rs
49    .sp
50    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51  .ti +5n  .ti +5n
52  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
53  .ti +5n  .ti +5n
54  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
55  .ti +5n  .ti +5n
56  .B char *\fIbuffer\fR, int \fIbuffersize\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57  .PP  .PP
58  .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,  
59  .ti +5n  .ti +5n
60  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61  .ti +5n  .ti +5n
62  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
63  .PP  .PP
64  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
65  .ti +5n  .ti +5n
66  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
67  .ti +5n  .ti +5n
68  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
69    .ti +5n
70    .B const char **\fIstringptr\fP);
71    .PP
72    .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73  .ti +5n  .ti +5n
74  .B const char **\fIstringptr\fR);  .B const char *\fIname\fP);
75  .PP  .PP
76  .br  .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
 .B int pcre_get_stringnumber(const pcre *\fIcode\fR,  
77  .ti +5n  .ti +5n
78  .B const char *\fIname\fR);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79  .PP  .PP
80  .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,  
81  .ti +5n  .ti +5n
82  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
83  .ti +5n  .ti +5n
84  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
85  .PP  .PP
86  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
87  .ti +5n  .ti +5n
88  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89  .PP  .PP
90  .br  .B void pcre_free_substring(const char *\fIstringptr\fP);
 .B void pcre_free_substring(const char *\fIstringptr\fR);  
91  .PP  .PP
92  .br  .B void pcre_free_substring_list(const char **\fIstringptr\fP);
93  .B void pcre_free_substring_list(const char **\fIstringptr\fR);  .
94    .
95    .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
96    .rs
97    .sp
98    .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
99    .PP
100    .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
101    .PP
102    .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
103    .ti +5n
104    .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
105  .PP  .PP
 .br  
106  .B const unsigned char *pcre_maketables(void);  .B const unsigned char *pcre_maketables(void);
107  .PP  .PP
108  .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,"  
109  .ti +5n  .ti +5n
110  .B int \fIwhat\fR, void *\fIwhere\fR);  .B int \fIwhat\fP, void *\fIwhere\fP);
111  .PP  .PP
112  .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);  
113  .PP  .PP
114  .br  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
 .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  
115  .PP  .PP
116  .br  .B const char *pcre_version(void);
 .B char *pcre_version(void);  
117  .PP  .PP
118  .br  .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
119    .ti +5n
120    .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
121    .
122    .
123    .SH "PCRE NATIVE API INDIRECTED FUNCTIONS"
124    .rs
125    .sp
126  .B void *(*pcre_malloc)(size_t);  .B void *(*pcre_malloc)(size_t);
127  .PP  .PP
 .br  
128  .B void (*pcre_free)(void *);  .B void (*pcre_free)(void *);
129  .PP  .PP
 .br  
130  .B void *(*pcre_stack_malloc)(size_t);  .B void *(*pcre_stack_malloc)(size_t);
131  .PP  .PP
 .br  
132  .B void (*pcre_stack_free)(void *);  .B void (*pcre_stack_free)(void *);
133  .PP  .PP
 .br  
134  .B int (*pcre_callout)(pcre_callout_block *);  .B int (*pcre_callout)(pcre_callout_block *);
135    .
136  .SH PCRE API  .
137    .SH "PCRE 8-BIT, 16-BIT AND 32-BIT LIBRARIES"
138  .rs  .rs
139  .sp  .sp
140  PCRE has its own native API, which is described in this document. There is also  From release 8.30, PCRE can be compiled as a library for handling 16-bit
141  a set of wrapper functions that correspond to the POSIX regular expression API.  character strings as well as, or instead of, the original library that handles
142  These are described in the \fBpcreposix\fR documentation.  8-bit character strings. From release 8.32, PCRE can also be compiled as a
143    library for handling 32-bit character strings. To avoid too much complication,
144  The native API function prototypes are defined in the header file \fBpcre.h\fR,  this document describes the 8-bit versions of the functions, with only
145  and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be  occasional references to the 16-bit and 32-bit libraries.
146  accessed by adding \fB-lpcre\fR to the command for linking an application which  .P
147  calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to  The 16-bit and 32-bit functions operate in the same way as their 8-bit
148  contain the major and minor release numbers for the library. Applications can  counterparts; they just use different data types for their arguments and
149  use these to include support for different releases.  results, and their names start with \fBpcre16_\fP or \fBpcre32_\fP instead of
150    \fBpcre_\fP. For every option that has UTF8 in its name (for example,
151  The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR  PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced
152  are used for compiling and matching regular expressions. A sample program that  by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the
153  demonstrates the simplest way of using them is given in the file  16-bit and 32-bit option names define the same bit values.
154  \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.  .P
155    References to bytes and UTF-8 in this document should be read as references to
156  There are convenience functions for extracting captured substrings from a  16-bit data quantities and UTF-16 when using the 16-bit library, or 32-bit data
157  matched subject string. They are:  quantities and UTF-32 when using the 32-bit library, unless specified
158    otherwise. More details of the specific differences for the 16-bit and 32-bit
159    \fBpcre_copy_substring()\fR  libraries are given in the
160    \fBpcre_copy_named_substring()\fR  .\" HREF
161    \fBpcre_get_substring()\fR  \fBpcre16\fP
162    \fBpcre_get_named_substring()\fR  .\"
163    \fBpcre_get_substring_list()\fR  and
164    .\" HREF
165  \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also  \fBpcre32\fP
166    .\"
167    pages.
168    .
169    .
170    .SH "PCRE API OVERVIEW"
171    .rs
172    .sp
173    PCRE has its own native API, which is described in this document. There are
174    also some wrapper functions (for the 8-bit library only) that correspond to the
175    POSIX regular expression API, but they do not give access to all the
176    functionality. They are described in the
177    .\" HREF
178    \fBpcreposix\fP
179    .\"
180    documentation. Both of these APIs define a set of C function calls. A C++
181    wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
182    documented in the
183    .\" HREF
184    \fBpcrecpp\fP
185    .\"
186    page.
187    .P
188    The native API C function prototypes are defined in the header file
189    \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
190    \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
191    command for linking an application that uses PCRE. The header file defines the
192    macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
193    for the library. Applications can use these to include support for different
194    releases of PCRE.
195    .P
196    In a Windows environment, if you want to statically link an application program
197    against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
198    including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
199    \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
200    \fB__declspec(dllimport)\fP, with unwanted results.
201    .P
202    The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
203    and \fBpcre_exec()\fP are used for compiling and matching regular expressions
204    in a Perl-compatible manner. A sample program that demonstrates the simplest
205    way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
206    source distribution. A listing of this program is given in the
207    .\" HREF
208    \fBpcredemo\fP
209    .\"
210    documentation, and the
211    .\" HREF
212    \fBpcresample\fP
213    .\"
214    documentation describes how to compile and run it.
215    .P
216    Just-in-time compiler support is an optional feature of PCRE that can be built
217    in appropriate hardware environments. It greatly speeds up the matching
218    performance of many patterns. Simple programs can easily request that it be
219    used if available, by setting an option that is ignored when it is not
220    relevant. More complicated programs might need to make use of the functions
221    \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
222    \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
223    .P
224    From release 8.32 there is also a direct interface for JIT execution, which
225    gives improved performance. The JIT-specific functions are discussed in the
226    .\" HREF
227    \fBpcrejit\fP
228    .\"
229    documentation.
230    .P
231    A second matching function, \fBpcre_dfa_exec()\fP, which is not
232    Perl-compatible, is also provided. This uses a different algorithm for the
233    matching. The alternative algorithm finds all possible matches (at a given
234    point in the subject), and scans the subject just once (unless there are
235    lookbehind assertions). However, this algorithm does not return captured
236    substrings. A description of the two matching algorithms and their advantages
237    and disadvantages is given in the
238    .\" HREF
239    \fBpcrematching\fP
240    .\"
241    documentation.
242    .P
243    In addition to the main compiling and matching functions, there are convenience
244    functions for extracting captured substrings from a subject string that is
245    matched by \fBpcre_exec()\fP. They are:
246    .sp
247      \fBpcre_copy_substring()\fP
248      \fBpcre_copy_named_substring()\fP
249      \fBpcre_get_substring()\fP
250      \fBpcre_get_named_substring()\fP
251      \fBpcre_get_substring_list()\fP
252      \fBpcre_get_stringnumber()\fP
253      \fBpcre_get_stringtable_entries()\fP
254    .sp
255    \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
256  provided, to free the memory used for extracted strings.  provided, to free the memory used for extracted strings.
257    .P
258  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
259  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,
260    or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
261  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
262  compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only  internal tables that are generated when PCRE is built are used.
263  some of the available information, but is retained for backwards compatibility.  .P
264  The function \fBpcre_version()\fR returns a pointer to a string containing the  The function \fBpcre_fullinfo()\fP is used to find out information about a
265  version of PCRE and its date of release.  compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
266    string containing the version of PCRE and its date of release.
267  The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain  .P
268  the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions  The function \fBpcre_refcount()\fP maintains a reference count in a data block
269    containing a compiled pattern. This is provided for the benefit of
270    object-oriented applications.
271    .P
272    The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
273    the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
274  respectively. PCRE calls the memory management functions via these variables,  respectively. PCRE calls the memory management functions via these variables,
275  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
276  should be done before calling any PCRE functions.  should be done before calling any PCRE functions.
277    .P
278  The global variables \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are also  The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
279  indirections to memory management functions. These special functions are used  indirections to memory management functions. These special functions are used
280  only when PCRE is compiled to use the heap for remembering data, instead of  only when PCRE is compiled to use the heap for remembering data, instead of
281  recursive function calls. This is a non-standard way of building PCRE, for use  recursive function calls, when running the \fBpcre_exec()\fP function. See the
282  in environments that have limited stacks. Because of the greater use of memory  .\" HREF
283  management, it runs more slowly. Separate functions are provided so that  \fBpcrebuild\fP
284  special-purpose external code can be used for this case. When used, these  .\"
285  functions are always called in a stack-like manner (last obtained, first  documentation for details of how to do this. It is a non-standard way of
286  freed), and always for memory blocks of the same size.  building PCRE, for use in environments that have limited stacks. Because of the
287    greater use of memory management, it runs more slowly. Separate functions are
288  The global variable \fBpcre_callout\fR initially contains NULL. It can be set  provided so that special-purpose external code can be used for this case. When
289    used, these functions are always called in a stack-like manner (last obtained,
290    first freed), and always for memory blocks of the same size. There is a
291    discussion about PCRE's stack usage in the
292    .\" HREF
293    \fBpcrestack\fP
294    .\"
295    documentation.
296    .P
297    The global variable \fBpcre_callout\fP initially contains NULL. It can be set
298  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
299  points during a matching operation. Details are given in the \fBpcrecallout\fR  points during a matching operation. Details are given in the
300    .\" HREF
301    \fBpcrecallout\fP
302    .\"
303  documentation.  documentation.
304    .
305    .
306    .\" HTML <a name="newlines"></a>
307    .SH NEWLINES
308    .rs
309    .sp
310    PCRE supports five different conventions for indicating line breaks in
311    strings: a single CR (carriage return) character, a single LF (linefeed)
312    character, the two-character sequence CRLF, any of the three preceding, or any
313    Unicode newline sequence. The Unicode newline sequences are the three just
314    mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed,
315    U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
316    (paragraph separator, U+2029).
317    .P
318    Each of the first three conventions is used by at least one operating system as
319    its standard newline sequence. When PCRE is built, a default can be specified.
320    The default default is LF, which is the Unix standard. When PCRE is run, the
321    default can be overridden, either when a pattern is compiled, or when it is
322    matched.
323    .P
324    At compile time, the newline convention can be specified by the \fIoptions\fP
325    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
326    start of the pattern itself; this overrides any other settings. See the
327    .\" HREF
328    \fBpcrepattern\fP
329    .\"
330    page for details of the special character sequences.
331    .P
332    In the PCRE documentation the word "newline" is used to mean "the character or
333    pair of characters that indicate a line break". The choice of newline
334    convention affects the handling of the dot, circumflex, and dollar
335    metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
336    recognized line ending sequence, the match position advancement for a
337    non-anchored pattern. There is more detail about this in the
338    .\" HTML <a href="#execoptions">
339    .\" </a>
340    section on \fBpcre_exec()\fP options
341    .\"
342    below.
343    .P
344    The choice of newline convention does not affect the interpretation of
345    the \en or \er escape sequences, nor does it affect what \eR matches, which is
346    controlled in a similar way, but by separate options.
347    .
348    .
349  .SH MULTITHREADING  .SH MULTITHREADING
350  .rs  .rs
351  .sp  .sp
352  The PCRE functions can be used in multi-threading applications, with the  The PCRE functions can be used in multi-threading applications, with the
353  proviso that the memory management functions pointed to by \fBpcre_malloc\fR,  proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
354  \fBpcre_free\fR, \fBpcre_stack_malloc\fR, and \fBpcre_stack_free\fR, and the  \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
355  callout function pointed to by \fBpcre_callout\fR, are shared by all threads.  callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
356    .P
357  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
358  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.
359    .P
360  .SH CHECKING BUILD-TIME OPTIONS  If the just-in-time optimization feature is being used, it needs separate
361    memory stack areas for each thread. See the
362    .\" HREF
363    \fBpcrejit\fP
364    .\"
365    documentation for more details.
366    .
367    .
368    .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
369    .rs
370    .sp
371    The compiled form of a regular expression can be saved and re-used at a later
372    time, possibly by a different program, and even on a host other than the one on
373    which it was compiled. Details are given in the
374    .\" HREF
375    \fBpcreprecompile\fP
376    .\"
377    documentation, which includes a description of the
378    \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
379    expression with one version of PCRE for use with a different version is not
380    guaranteed to work and may cause crashes.
381    .
382    .
383    .SH "CHECKING BUILD-TIME OPTIONS"
384  .rs  .rs
385  .sp  .sp
386  .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);  .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
387  .PP  .PP
388  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
389  discover which optional features have been compiled into the PCRE library. The  discover which optional features have been compiled into the PCRE library. The
390  .\" HREF  .\" HREF
391  \fBpcrebuild\fR  \fBpcrebuild\fP
392  .\"  .\"
393  documentation has more details about these optional features.  documentation has more details about these optional features.
394    .P
395  The first argument for \fBpcre_config()\fR is an integer, specifying which  The first argument for \fBpcre_config()\fP is an integer, specifying which
396  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
397  which the information is placed. The following information is available:  which the information is placed. The returned value is zero on success, or the
398    negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
399    not recognized. The following information is available:
400    .sp
401    PCRE_CONFIG_UTF8    PCRE_CONFIG_UTF8
402    .sp
403  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;
404  otherwise it is set to zero.  otherwise it is set to zero. This value should normally be given to the 8-bit
405    version of this function, \fBpcre_config()\fP. If it is given to the 16-bit
406    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
407    .sp
408      PCRE_CONFIG_UTF16
409    .sp
410    The output is an integer that is set to one if UTF-16 support is available;
411    otherwise it is set to zero. This value should normally be given to the 16-bit
412    version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
413    or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION.
414    .sp
415      PCRE_CONFIG_UTF32
416    .sp
417    The output is an integer that is set to one if UTF-32 support is available;
418    otherwise it is set to zero. This value should normally be given to the 32-bit
419    version of this function, \fBpcre32_config()\fP. If it is given to the 8-bit
420    or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION.
421    .sp
422      PCRE_CONFIG_UNICODE_PROPERTIES
423    .sp
424    The output is an integer that is set to one if support for Unicode character
425    properties is available; otherwise it is set to zero.
426    .sp
427      PCRE_CONFIG_JIT
428    .sp
429    The output is an integer that is set to one if support for just-in-time
430    compiling is available; otherwise it is set to zero.
431    .sp
432      PCRE_CONFIG_JITTARGET
433    .sp
434    The output is a pointer to a zero-terminated "const char *" string. If JIT
435    support is available, the string contains the name of the architecture for
436    which the JIT compiler is configured, for example "x86 32bit (little endian +
437    unaligned)". If JIT support is not available, the result is NULL.
438    .sp
439    PCRE_CONFIG_NEWLINE    PCRE_CONFIG_NEWLINE
440    .sp
441  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
442  the newline character. It is either linefeed (10) or carriage return (13), and  that is recognized as meaning "newline". The values that are supported in
443  should normally be the standard character for your operating system.  ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for
444    ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the
445    same values. However, the value for LF is normally 21, though some EBCDIC
446    environments use 37. The corresponding values for CRLF are 3349 and 3365. The
447    default should normally correspond to the standard sequence for your operating
448    system.
449    .sp
450      PCRE_CONFIG_BSR
451    .sp
452    The output is an integer whose value indicates what character sequences the \eR
453    escape sequence matches by default. A value of 0 means that \eR matches any
454    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
455    or CRLF. The default can be overridden when a pattern is compiled or matched.
456    .sp
457    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
458    .sp
459  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
460  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values  linkage in compiled regular expressions. For the 8-bit library, the value can
461  allow larger regular expressions to be compiled, at the expense of slower  be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
462  matching. The default value of 2 is sufficient for all but the most massive  a number of bytes. For the 32-bit library, the value is either 2 or 4 and is
463  patterns, since it allows the compiled pattern to be up to 64K in size.  still a number of bytes. The default value of 2 is sufficient for all but the
464    most massive patterns, since it allows the compiled pattern to be up to 64K in
465    size. Larger values allow larger regular expressions to be compiled, at the
466    expense of slower matching.
467    .sp
468    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
469    .sp
470  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
471  interface uses \fBmalloc()\fR for output vectors. Further details are given in  interface uses \fBmalloc()\fP for output vectors. Further details are given in
472  the \fBpcreposix\fR documentation.  the
473    .\" HREF
474    \fBpcreposix\fP
475    .\"
476    documentation.
477    .sp
478    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
479    .sp
480  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
481  internal matching function calls in a \fBpcre_exec()\fR execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
482  details are given with \fBpcre_exec()\fR below.  details are given with \fBpcre_exec()\fP below.
483    .sp
484      PCRE_CONFIG_MATCH_LIMIT_RECURSION
485    .sp
486    The output is a long integer that gives the default limit for the depth of
487    recursion when calling the internal matching function in a \fBpcre_exec()\fP
488    execution. Further details are given with \fBpcre_exec()\fP below.
489    .sp
490    PCRE_CONFIG_STACKRECURSE    PCRE_CONFIG_STACKRECURSE
491    .sp
492  The output is an integer that is set to one if internal recursion is  The output is an integer that is set to one if internal recursion when running
493  implemented by recursive function calls that use the stack to remember their  \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
494  state. This is the usual way that PCRE is compiled. The output is zero if PCRE  to remember their state. This is the usual way that PCRE is compiled. The
495  was compiled to use blocks of data on the heap instead of recursive function  output is zero if PCRE was compiled to use blocks of data on the heap instead
496  calls. In this case, \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are  of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
497  called to manage memory blocks on the heap, thus avoiding the use of the stack.  \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
498    avoiding the use of the stack.
499  .SH COMPILING A PATTERN  .
500  .rs  .
501  .sp  .SH "COMPILING A PATTERN"
502  .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,  .rs
503  .ti +5n  .sp
504  .B const char **\fIerrptr\fR, int *\fIerroffset\fR,  .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
505  .ti +5n  .ti +5n
506  .B const unsigned char *\fItableptr\fR);  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
507  .PP  .ti +5n
508    .B const unsigned char *\fItableptr\fP);
509  The function \fBpcre_compile()\fR is called to compile a pattern into an  .sp
510  internal form. The pattern is a C string terminated by a binary zero, and  .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
511  is passed in the argument \fIpattern\fR. A pointer to a single block of memory  .ti +5n
512  that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled  .B int *\fIerrorcodeptr\fP,
513  code and related data. The \fBpcre\fR type is defined for the returned block;  .ti +5n
514  this is a typedef for a structure whose contents are not externally defined. It  .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
515  is up to the caller to free the memory when it is no longer required.  .ti +5n
516    .B const unsigned char *\fItableptr\fP);
517    .P
518    Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
519    called to compile a pattern into an internal form. The only difference between
520    the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
521    \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
522    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
523    information applies equally to \fBpcre_compile2()\fP.
524    .P
525    The pattern is a C string terminated by a binary zero, and is passed in the
526    \fIpattern\fP argument. A pointer to a single block of memory that is obtained
527    via \fBpcre_malloc\fP is returned. This contains the compiled code and related
528    data. The \fBpcre\fP type is defined for the returned block; this is a typedef
529    for a structure whose contents are not externally defined. It is up to the
530    caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
531    .P
532  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
533  depend on memory location, the complete \fBpcre\fR data block is not  depend on memory location, the complete \fBpcre\fP data block is not
534  fully relocatable, because it contains a copy of the \fItableptr\fR argument,  fully relocatable, because it may contain a copy of the \fItableptr\fP
535  which is an address (see below).  argument, which is an address (see below).
536    .P
537  The \fIoptions\fR argument contains independent bits that affect the  The \fIoptions\fP argument contains various bit settings that affect the
538  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
539  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
540  from within the pattern (see the detailed description of regular expressions  compatible with Perl, but some others as well) can also be set and unset from
541  in the \fBpcrepattern\fR documentation). For these options, the contents of the  within the pattern (see the detailed description in the
542  \fIoptions\fR argument specifies their initial settings at the start of  .\" HREF
543  compilation and execution. The PCRE_ANCHORED option can be set at the time of  \fBpcrepattern\fP
544  matching as well as at compile time.  .\"
545    documentation). For those options that can be different in different parts of
546  If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.  the pattern, the contents of the \fIoptions\fP argument specifies their
547  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns  settings at the start of compilation and execution. The PCRE_ANCHORED,
548  NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual  PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
549  error message. The offset from the start of the pattern to the character where  PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at
550  the error was discovered is placed in the variable pointed to by  compile time.
551  \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.  .P
552    If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
553  If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
554  character tables which are built when it is compiled, using the default C  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
555  locale. Otherwise, \fItableptr\fR must be the result of a call to  error message. This is a static string that is part of the library. You must
556  \fBpcre_maketables()\fR. See the section on locale support below.  not try to free it. Normally, the offset from the start of the pattern to the
557    byte that was being processed when the error was discovered is placed in the
558  This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:  variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
559    immediate error is given). However, for an invalid UTF-8 string, the offset is
560    that of the first byte of the failing character.
561    .P
562    Some errors are not detected until the whole pattern has been scanned; in these
563    cases, the offset passed back is the length of the pattern. Note that the
564    offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
565    into the middle of a UTF-8 character.
566    .P
567    If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
568    \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
569    returned via this argument in the event of an error. This is in addition to the
570    textual error message. Error codes and messages are listed below.
571    .P
572    If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
573    character tables that are built when PCRE is compiled, using the default C
574    locale. Otherwise, \fItableptr\fP must be an address that is the result of a
575    call to \fBpcre_maketables()\fP. This value is stored with the compiled
576    pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
577    passed to it. For more discussion, see the section on locale support below.
578    .P
579    This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
580    .sp
581    pcre *re;    pcre *re;
582    const char *error;    const char *error;
583    int erroffset;    int erroffset;
# Line 290  This code fragment shows a typical strai Line 587  This code fragment shows a typical strai
587      &error,           /* for error message */      &error,           /* for error message */
588      &erroffset,       /* for error offset */      &erroffset,       /* for error offset */
589      NULL);            /* use default character tables */      NULL);            /* use default character tables */
590    .sp
591  The following option bits are defined:  The following names for option bits are defined in the \fBpcre.h\fP header
592    file:
593    .sp
594    PCRE_ANCHORED    PCRE_ANCHORED
595    .sp
596  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
597  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
598  being searched (the "subject string"). This effect can also be achieved by  being searched (the "subject string"). This effect can also be achieved by
599  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
600  Perl.  Perl.
601    .sp
602      PCRE_AUTO_CALLOUT
603    .sp
604    If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
605    all with number 255, before each pattern item. For discussion of the callout
606    facility, see the
607    .\" HREF
608    \fBpcrecallout\fP
609    .\"
610    documentation.
611    .sp
612      PCRE_BSR_ANYCRLF
613      PCRE_BSR_UNICODE
614    .sp
615    These options (which are mutually exclusive) control what the \eR escape
616    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
617    match any Unicode newline sequence. The default is specified when PCRE is
618    built. It can be overridden from within the pattern, or by setting an option
619    when a compiled pattern is matched.
620    .sp
621    PCRE_CASELESS    PCRE_CASELESS
622    .sp
623  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
624  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
625  pattern by a (?i) option setting.  pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
626    concept of case for characters whose values are less than 128, so caseless
627    matching is always possible. For characters with higher values, the concept of
628    case is supported if PCRE is compiled with Unicode property support, but not
629    otherwise. If you want to use caseless matching for characters 128 and above,
630    you must ensure that PCRE is compiled with Unicode property support as well as
631    with UTF-8 support.
632    .sp
633    PCRE_DOLLAR_ENDONLY    PCRE_DOLLAR_ENDONLY
634    .sp
635  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
636  end of the subject string. Without this option, a dollar also matches  end of the subject string. Without this option, a dollar also matches
637  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
638  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.
639  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
640  a pattern.  pattern.
641    .sp
642    PCRE_DOTALL    PCRE_DOTALL
643    .sp
644  If this bit is set, a dot metacharater in the pattern matches all characters,  If this bit is set, a dot metacharacter in the pattern matches a character of
645  including newlines. Without it, newlines are excluded. This option is  any value, including one that indicates a newline. However, it only ever
646    matches one character, even if newlines are coded as CRLF. Without this option,
647    a dot does not match when the current position is at a newline. This option is
648  equivalent to Perl's /s option, and it can be changed within a pattern by a  equivalent to Perl's /s option, and it can be changed within a pattern by a
649  (?s) option setting. A negative class such as [^a] always matches a newline  (?s) option setting. A negative class such as [^a] always matches newline
650  character, independent of the setting of this option.  characters, independent of the setting of this option.
651    .sp
652      PCRE_DUPNAMES
653    .sp
654    If this bit is set, names used to identify capturing subpatterns need not be
655    unique. This can be helpful for certain types of pattern when it is known that
656    only one instance of the named subpattern can ever be matched. There are more
657    details of named subpatterns below; see also the
658    .\" HREF
659    \fBpcrepattern\fP
660    .\"
661    documentation.
662    .sp
663    PCRE_EXTENDED    PCRE_EXTENDED
664    .sp
665  If this bit is set, whitespace data characters in the pattern are totally  If this bit is set, white space data characters in the pattern are totally
666  ignored except when escaped or inside a character class. Whitespace does not  ignored except when escaped or inside a character class. White space does not
667  include the VT character (code 11). In addition, characters between an  include the VT character (code 11). In addition, characters between an
668  unescaped # outside a character class and the next newline character,  unescaped # outside a character class and the next newline, inclusive, are also
669  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
670  be changed within a pattern by a (?x) option setting.  pattern by a (?x) option setting.
671    .P
672    Which characters are interpreted as newlines is controlled by the options
673    passed to \fBpcre_compile()\fP or by a special sequence at the start of the
674    pattern, as described in the section entitled
675    .\" HTML <a href="pcrepattern.html#newlines">
676    .\" </a>
677    "Newline conventions"
678    .\"
679    in the \fBpcrepattern\fP documentation. Note that the end of this type of
680    comment is a literal newline sequence in the pattern; escape sequences that
681    happen to represent a newline do not count.
682    .P
683  This option makes it possible to include comments inside complicated patterns.  This option makes it possible to include comments inside complicated patterns.
684  Note, however, that this applies only to data characters. Whitespace characters  Note, however, that this applies only to data characters. White space characters
685  may never appear within special character sequences in a pattern, for example  may never appear within special character sequences in a pattern, for example
686  within the sequence (?( which introduces a conditional subpattern.  within the sequence (?( that introduces a conditional subpattern.
687    .sp
688    PCRE_EXTRA    PCRE_EXTRA
689    .sp
690  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
691  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
692  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
693  special meaning causes an error, thus reserving these combinations for future  special meaning causes an error, thus reserving these combinations for future
694  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
695  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
696  controlled by this option. It can also be set by a (?X) option setting within a  give an error for this, by running it with the -w option.) There are at present
697  pattern.  no other features controlled by this option. It can also be set by a (?X)
698    option setting within a pattern.
699    .sp
700      PCRE_FIRSTLINE
701    .sp
702    If this option is set, an unanchored pattern is required to match before or at
703    the first newline in the subject string, though the matched text may continue
704    over the newline.
705    .sp
706      PCRE_JAVASCRIPT_COMPAT
707    .sp
708    If this option is set, PCRE's behaviour is changed in some ways so that it is
709    compatible with JavaScript rather than Perl. The changes are as follows:
710    .P
711    (1) A lone closing square bracket in a pattern causes a compile-time error,
712    because this is illegal in JavaScript (by default it is treated as a data
713    character). Thus, the pattern AB]CD becomes illegal when this option is set.
714    .P
715    (2) At run time, a back reference to an unset subpattern group matches an empty
716    string (by default this causes the current matching alternative to fail). A
717    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
718    an "a" in the subject), whereas it fails by default, for Perl compatibility.
719    .P
720    (3) \eU matches an upper case "U" character; by default \eU causes a compile
721    time error (Perl uses \eU to upper case subsequent characters).
722    .P
723    (4) \eu matches a lower case "u" character unless it is followed by four
724    hexadecimal digits, in which case the hexadecimal number defines the code point
725    to match. By default, \eu causes a compile time error (Perl uses it to upper
726    case the following character).
727    .P
728    (5) \ex matches a lower case "x" character unless it is followed by two
729    hexadecimal digits, in which case the hexadecimal number defines the code point
730    to match. By default, as in Perl, a hexadecimal number is always expected after
731    \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
732    binary zero character followed by z).
733    .sp
734    PCRE_MULTILINE    PCRE_MULTILINE
735    .sp
736  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
737  characters (even if it actually contains several newlines). The "start of line"  characters (even if it actually contains newlines). The "start of line"
738  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
739  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
740  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
741  Perl.  Perl.
742    .P
743  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
744  match immediately following or immediately before any newline in the subject  match immediately following or immediately before internal newlines in the
745  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
746  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
747  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
748  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
749    .sp
750      PCRE_NEWLINE_CR
751      PCRE_NEWLINE_LF
752      PCRE_NEWLINE_CRLF
753      PCRE_NEWLINE_ANYCRLF
754      PCRE_NEWLINE_ANY
755    .sp
756    These options override the default newline definition that was chosen when PCRE
757    was built. Setting the first or the second specifies that a newline is
758    indicated by a single character (CR or LF, respectively). Setting
759    PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
760    CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
761    preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
762    that any Unicode newline sequence should be recognized.
763    .P
764    In an ASCII/Unicode environment, the Unicode newline sequences are the three
765    just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form
766    feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
767    (paragraph separator, U+2029). For the 8-bit library, the last two are
768    recognized only in UTF-8 mode.
769    .P
770    When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for
771    CR is 0x0d, the same as ASCII. However, the character code for LF is normally
772    0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is
773    not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all
774    less than 256. For more details, see the
775    .\" HREF
776    \fBpcrebuild\fP
777    .\"
778    documentation.
779    .P
780    The newline setting in the options word uses three bits that are treated
781    as a number, giving eight possibilities. Currently only six are used (default
782    plus the five values above). This means that if you set more than one newline
783    option, the combination may or may not be sensible. For example,
784    PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
785    other combinations may yield unused numbers and cause an error.
786    .P
787    The only time that a line break in a pattern is specially recognized when
788    compiling is when PCRE_EXTENDED is set. CR and LF are white space characters,
789    and so are ignored in this mode. Also, an unescaped # outside a character class
790    indicates a comment that lasts until after the next line break sequence. In
791    other circumstances, line break sequences in patterns are treated as literal
792    data.
793    .P
794    The newline option that is set at compile time becomes the default that is used
795    for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
796    .sp
797    PCRE_NO_AUTO_CAPTURE    PCRE_NO_AUTO_CAPTURE
798    .sp
799  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
800  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
801  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
802  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
803  in Perl.  in Perl.
804    .sp
805      NO_START_OPTIMIZE
806    .sp
807    This is an option that acts at matching time; that is, it is really an option
808    for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
809    it is remembered with the compiled pattern and assumed at matching time. For
810    details see the discussion of PCRE_NO_START_OPTIMIZE
811    .\" HTML <a href="#execoptions">
812    .\" </a>
813    below.
814    .\"
815    .sp
816      PCRE_UCP
817    .sp
818    This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
819    \ew, and some of the POSIX character classes. By default, only ASCII characters
820    are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
821    classify characters. More details are given in the section on
822    .\" HTML <a href="pcre.html#genericchartypes">
823    .\" </a>
824    generic character types
825    .\"
826    in the
827    .\" HREF
828    \fBpcrepattern\fP
829    .\"
830    page. If you set PCRE_UCP, matching one of the items it affects takes much
831    longer. The option is available only if PCRE has been compiled with Unicode
832    property support.
833    .sp
834    PCRE_UNGREEDY    PCRE_UNGREEDY
835    .sp
836  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
837  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
838  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.
839    .sp
840    PCRE_UTF8    PCRE_UTF8
841    .sp
842  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
843  of UTF-8 characters instead of single-byte character strings. However, it is  of UTF-8 characters instead of single-byte strings. However, it is available
844  available only if PCRE has been built to include UTF-8 support. If not, the use  only when PCRE is built to include UTF support. If not, the use of this option
845  of this option provokes an error. Details of how this option changes the  provokes an error. Details of how this option changes the behaviour of PCRE are
846  behaviour of PCRE are given in the  given in the
 .\" HTML <a href="pcre.html#utf8support">  
 .\" </a>  
 section on UTF-8 support  
 .\"  
 in the main  
847  .\" HREF  .\" HREF
848  \fBpcre\fR  \fBpcreunicode\fP
849  .\"  .\"
850  page.  page.
851    .sp
852    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
853    .sp
854  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is  When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
855  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
856  \fBpcre_compile()\fR returns an error. If you already know that your pattern is  .\" HTML <a href="pcreunicode.html#utf8strings">
857  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
858  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
859  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
860  Note that there is a similar option for suppressing the checking of subject  in the
861  strings passed to \fBpcre_exec()\fR.  .\" HREF
862    \fBpcreunicode\fP
863    .\"
864  .SH STUDYING A PATTERN  page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
865  .rs  error. If you already know that your pattern is valid, and you want to skip
866  .sp  this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
867  .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,  When it is set, the effect of passing an invalid UTF-8 string as a pattern is
868  .ti +5n  undefined. It may cause your program to crash. Note that this option can also
869  .B const char **\fIerrptr\fR);  be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
870  .PP  validity checking of subject strings only. If the same string is being matched
871  When a pattern is going to be used several times, it is worth spending more  many times, the option can be safely set for the second and subsequent
872  time analyzing it in order to speed up the time taken for matching. The  matchings to improve performance.
873  function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first  .
874  argument. If studing the pattern produces additional information that will help  .
875  speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR  .SH "COMPILATION ERROR CODES"
876  block, in which the \fIstudy_data\fR field points to the results of the study.  .rs
877    .sp
878  The returned value from a \fBpcre_study()\fR can be passed directly to  The following table lists the error codes than may be returned by
879  \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other  \fBpcre_compile2()\fP, along with the error messages that may be returned by
880  fields that can be set by the caller before the block is passed; these are  both compiling functions. Note that error messages are always 8-bit ASCII
881  described below. If studying the pattern does not produce any additional  strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes
882  information, \fBpcre_study()\fR returns NULL. In that circumstance, if the  have fallen out of use. To avoid confusion, they have not been re-used.
883  calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it  .sp
884  must set up its own \fBpcre_extra\fR block.     0  no error
885       1  \e at end of pattern
886  The second argument contains option bits. At present, no options are defined     2  \ec at end of pattern
887  for \fBpcre_study()\fR, and this argument should always be zero.     3  unrecognized character follows \e
888       4  numbers out of order in {} quantifier
889  The third argument for \fBpcre_study()\fR is a pointer for an error message. If     5  number too big in {} quantifier
890       6  missing terminating ] for character class
891       7  invalid escape sequence in character class
892       8  range out of order in character class
893       9  nothing to repeat
894      10  [this code is not in use]
895      11  internal error: unexpected repeat
896      12  unrecognized character after (? or (?-
897      13  POSIX named classes are supported only within a class
898      14  missing )
899      15  reference to non-existent subpattern
900      16  erroffset passed as NULL
901      17  unknown option bit(s) set
902      18  missing ) after comment
903      19  [this code is not in use]
904      20  regular expression is too large
905      21  failed to get memory
906      22  unmatched parentheses
907      23  internal error: code overflow
908      24  unrecognized character after (?<
909      25  lookbehind assertion is not fixed length
910      26  malformed number or name after (?(
911      27  conditional group contains more than two branches
912      28  assertion expected after (?(
913      29  (?R or (?[+-]digits must be followed by )
914      30  unknown POSIX class name
915      31  POSIX collating elements are not supported
916      32  this version of PCRE is compiled without UTF support
917      33  [this code is not in use]
918      34  character value in \ex{...} sequence is too large
919      35  invalid condition (?(0)
920      36  \eC not allowed in lookbehind assertion
921      37  PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
922      38  number after (?C is > 255
923      39  closing ) for (?C expected
924      40  recursive call could loop indefinitely
925      41  unrecognized character after (?P
926      42  syntax error in subpattern name (missing terminator)
927      43  two named subpatterns have the same name
928      44  invalid UTF-8 string (specifically UTF-8)
929      45  support for \eP, \ep, and \eX has not been compiled
930      46  malformed \eP or \ep sequence
931      47  unknown property name after \eP or \ep
932      48  subpattern name is too long (maximum 32 characters)
933      49  too many named subpatterns (maximum 10000)
934      50  [this code is not in use]
935      51  octal value is greater than \e377 in 8-bit non-UTF-8 mode
936      52  internal error: overran compiling workspace
937      53  internal error: previously-checked referenced subpattern
938            not found
939      54  DEFINE group contains more than one branch
940      55  repeating a DEFINE group is not allowed
941      56  inconsistent NEWLINE options
942      57  \eg is not followed by a braced, angle-bracketed, or quoted
943            name/number or by a plain number
944      58  a numbered reference must not be zero
945      59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
946      60  (*VERB) not recognized
947      61  number is too big
948      62  subpattern name expected
949      63  digit expected after (?+
950      64  ] is an invalid data character in JavaScript compatibility mode
951      65  different names for subpatterns of the same number are
952            not allowed
953      66  (*MARK) must have an argument
954      67  this version of PCRE is not compiled with Unicode property
955            support
956      68  \ec must be followed by an ASCII character
957      69  \ek is not followed by a braced, angle-bracketed, or quoted name
958      70  internal error: unknown opcode in find_fixedlength()
959      71  \eN is not supported in a class
960      72  too many forward references
961      73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
962      74  invalid UTF-16 string (specifically UTF-16)
963      75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
964      76  character value in \eu.... sequence is too large
965      77  invalid UTF-32 string (specifically UTF-32)
966    .sp
967    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
968    be used if the limits were changed when PCRE was built.
969    .
970    .
971    .\" HTML <a name="studyingapattern"></a>
972    .SH "STUDYING A PATTERN"
973    .rs
974    .sp
975    .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
976    .ti +5n
977    .B const char **\fIerrptr\fP);
978    .PP
979    If a compiled pattern is going to be used several times, it is worth spending
980    more time analyzing it in order to speed up the time taken for matching. The
981    function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
982    argument. If studying the pattern produces additional information that will
983    help speed up matching, \fBpcre_study()\fP returns a pointer to a
984    \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
985    results of the study.
986    .P
987    The returned value from \fBpcre_study()\fP can be passed directly to
988    \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
989    also contains other fields that can be set by the caller before the block is
990    passed; these are described
991    .\" HTML <a href="#extradata">
992    .\" </a>
993    below
994    .\"
995    in the section on matching a pattern.
996    .P
997    If studying the pattern does not produce any useful information,
998    \fBpcre_study()\fP returns NULL by default. In that circumstance, if the
999    calling program wants to pass any of the other fields to \fBpcre_exec()\fP or
1000    \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block. However,
1001    if \fBpcre_study()\fP is called with the PCRE_STUDY_EXTRA_NEEDED option, it
1002    returns a \fBpcre_extra\fP block even if studying did not find any additional
1003    information. It may still return NULL, however, if an error occurs in
1004    \fBpcre_study()\fP.
1005    .P
1006    The second argument of \fBpcre_study()\fP contains option bits. There are three
1007    further options in addition to PCRE_STUDY_EXTRA_NEEDED:
1008    .sp
1009      PCRE_STUDY_JIT_COMPILE
1010      PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
1011      PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
1012    .sp
1013    If any of these are set, and the just-in-time compiler is available, the
1014    pattern is further compiled into machine code that executes much faster than
1015    the \fBpcre_exec()\fP interpretive matching function. If the just-in-time
1016    compiler is not available, these options are ignored. All undefined bits in the
1017    \fIoptions\fP argument must be zero.
1018    .P
1019    JIT compilation is a heavyweight optimization. It can take some time for
1020    patterns to be analyzed, and for one-off matches and simple patterns the
1021    benefit of faster execution might be offset by a much slower study time.
1022    Not all patterns can be optimized by the JIT compiler. For those that cannot be
1023    handled, matching automatically falls back to the \fBpcre_exec()\fP
1024    interpreter. For more details, see the
1025    .\" HREF
1026    \fBpcrejit\fP
1027    .\"
1028    documentation.
1029    .P
1030    The third argument for \fBpcre_study()\fP is a pointer for an error message. If
1031  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
1032  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
1033  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
1034  be sure that it has run successfully.  should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
1035    sure that it has run successfully.
1036  This is a typical call to \fBpcre_study\fR():  .P
1037    When you are finished with a pattern, you can free the memory used for the
1038    pcre_extra *pe;  study data by calling \fBpcre_free_study()\fP. This function was added to the
1039    pe = pcre_study(  API for release 8.20. For earlier versions, the memory could be freed with
1040    \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
1041    where JIT optimization is not used, but it is advisable to change to the new
1042    function when convenient.
1043    .P
1044    This is a typical way in which \fBpcre_study\fP() is used (except that in a
1045    real application there should be tests for errors):
1046    .sp
1047      int rc;
1048      pcre *re;
1049      pcre_extra *sd;
1050      re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1051      sd = pcre_study(
1052      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
1053      0,              /* no options exist */      0,              /* no options */
1054      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
1055      rc = pcre_exec(   /* see below for details of pcre_exec() options */
1056  At present, studying a pattern is useful only for non-anchored patterns that do      re, sd, "subject", 7, 0, 0, ovector, 30);
1057  not have a single fixed starting character. A bitmap of possible starting    ...
1058  characters is created.    pcre_free_study(sd);
1059      pcre_free(re);
1060    .sp
1061    Studying a pattern does two things: first, a lower bound for the length of
1062    subject string that is needed to match the pattern is computed. This does not
1063    mean that there are any strings of that length that match, but it does
1064    guarantee that no shorter strings match. The value is used to avoid wasting
1065    time by trying to match strings that are shorter than the lower bound. You can
1066    find out the value in a calling program via the \fBpcre_fullinfo()\fP function.
1067    .P
1068    Studying a pattern is also useful for non-anchored patterns that do not have a
1069    single fixed starting character. A bitmap of possible starting bytes is
1070    created. This speeds up finding a position in the subject at which to start
1071    matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.
1072    In 32-bit mode, the bitmap is used for 32-bit values less than 256.)
1073    .P
1074    These two optimizations apply to both \fBpcre_exec()\fP and
1075    \fBpcre_dfa_exec()\fP, and the information is also used by the JIT compiler.
1076    The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option
1077    when calling \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP, but if this is done,
1078    JIT execution is also disabled. You might want to do this if your pattern
1079    contains callouts or (*MARK) and you want to make use of these facilities in
1080    cases where matching fails. See the discussion of PCRE_NO_START_OPTIMIZE
1081    .\" HTML <a href="#execoptions">
1082    .\" </a>
1083    below.
1084    .\"
1085    .
1086    .
1087  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
1088  .SH LOCALE SUPPORT  .SH "LOCALE SUPPORT"
1089  .rs  .rs
1090  .sp  .sp
1091  PCRE handles caseless matching, and determines whether characters are letters,  PCRE handles caseless matching, and determines whether characters are letters,
1092  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
1093  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
1094  contains a default set of tables that is created in the default C locale when  with codes less than 128. By default, higher-valued codes never match escapes
1095  PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR  such as \ew or \ed, but they can be tested with \ep if PCRE is built with
1096  is NULL, and is sufficient for many applications.  Unicode character property support. Alternatively, the PCRE_UCP option can be
1097    set at compile time; this causes \ew and friends to use Unicode property
1098  An alternative set of tables can, however, be supplied. Such tables are built  support instead of built-in tables. The use of locales with Unicode is
1099  by calling the \fBpcre_maketables()\fR function, which has no arguments, in the  discouraged. If you are handling characters with codes greater than 128, you
1100  relevant locale. The result can then be passed to \fBpcre_compile()\fR as often  should either use UTF-8 and Unicode, or use locales, but not try to mix the
1101  as necessary. For example, to build and use tables that are appropriate for the  two.
1102  French locale (where accented characters with codes greater than 128 are  .P
1103  treated as letters), the following code could be used:  PCRE contains an internal set of tables that are used when the final argument
1104    of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1105    setlocale(LC_CTYPE, "fr");  Normally, the internal tables recognize only ASCII characters. However, when
1106    PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1107    default "C" locale of the local system, which may cause them to be different.
1108    .P
1109    The internal tables can always be overridden by tables supplied by the
1110    application that calls PCRE. These may be created in a different locale from
1111    the default. As more and more applications change to using Unicode, the need
1112    for this locale support is expected to die away.
1113    .P
1114    External tables are built by calling the \fBpcre_maketables()\fP function,
1115    which has no arguments, in the relevant locale. The result can then be passed
1116    to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1117    example, to build and use tables that are appropriate for the French locale
1118    (where accented characters with values greater than 128 are treated as letters),
1119    the following code could be used:
1120    .sp
1121      setlocale(LC_CTYPE, "fr_FR");
1122    tables = pcre_maketables();    tables = pcre_maketables();
1123    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
1124    .sp
1125  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
1126  pointer that is passed to \fBpcre_compile\fR is saved with the compiled  are using Windows, the name for the French locale is "french".
1127  pattern, and the same tables are used via this pointer by \fBpcre_study()\fR  .P
1128  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
1129  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
1130  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
1131  memory containing the tables remains available for as long as it is needed.  needed.
1132    .P
1133  .SH INFORMATION ABOUT A PATTERN  The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1134  .rs  pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1135  .sp  and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1136  .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  pattern, compilation, studying and matching all happen in the same locale, but
1137  .ti +5n  different patterns can be compiled in different locales.
1138  .B int \fIwhat\fR, void *\fIwhere\fR);  .P
1139  .PP  It is possible to pass a table pointer or NULL (indicating the use of the
1140  The \fBpcre_fullinfo()\fR function returns information about a compiled  internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1141  pattern. It replaces the obsolete \fBpcre_info()\fR function, which is  this facility could be used to match a pattern in a different locale from the
1142  nevertheless retained for backwards compability (and is documented below).  one in which it was compiled. Passing table pointers at run time is discussed
1143    below in the section on matching a pattern.
1144  The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled  .
1145  pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if  .
1146    .\" HTML <a name="infoaboutpattern"></a>
1147    .SH "INFORMATION ABOUT A PATTERN"
1148    .rs
1149    .sp
1150    .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1151    .ti +5n
1152    .B int \fIwhat\fP, void *\fIwhere\fP);
1153    .PP
1154    The \fBpcre_fullinfo()\fP function returns information about a compiled
1155    pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1156    library at version 8.30, after more than 10 years of obsolescence.
1157    .P
1158    The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1159    pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1160  the pattern was not studied. The third argument specifies which piece of  the pattern was not studied. The third argument specifies which piece of
1161  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
1162  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
1163  the following negative numbers:  the following negative numbers:
1164    .sp
1165    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL    PCRE_ERROR_NULL           the argument \fIcode\fP was NULL
1166                          the argument \fIwhere\fR was NULL                              the argument \fIwhere\fP was NULL
1167    PCRE_ERROR_BADMAGIC   the "magic number" was not found    PCRE_ERROR_BADMAGIC       the "magic number" was not found
1168    PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid    PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
1169                                endianness
1170  Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the    PCRE_ERROR_BADOPTION      the value of \fIwhat\fP was invalid
1171  compiled pattern:  .sp
1172    The "magic number" is placed at the start of each compiled pattern as an simple
1173    check against passing an arbitrary memory pointer. The endianness error can
1174    occur if a compiled pattern is saved and reloaded on a different host. Here is
1175    a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1176    pattern:
1177    .sp
1178    int rc;    int rc;
1179    unsigned long int length;    size_t length;
1180    rc = pcre_fullinfo(    rc = pcre_fullinfo(
1181      re,               /* result of pcre_compile() */      re,               /* result of pcre_compile() */
1182      pe,               /* result of pcre_study(), or NULL */      sd,               /* result of pcre_study(), or NULL */
1183      PCRE_INFO_SIZE,   /* what is required */      PCRE_INFO_SIZE,   /* what is required */
1184      &length);         /* where to put the data */      &length);         /* where to put the data */
1185    .sp
1186  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
1187  as follows:  as follows:
1188    .sp
1189    PCRE_INFO_BACKREFMAX    PCRE_INFO_BACKREFMAX
1190    .sp
1191  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
1192  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
1193  no back references.  no back references.
1194    .sp
1195    PCRE_INFO_CAPTURECOUNT    PCRE_INFO_CAPTURECOUNT
1196    .sp
1197  Return the number of capturing subpatterns in the pattern. The fourth argument  Return the number of capturing subpatterns in the pattern. The fourth argument
1198  should point to an \fbint\fR variable.  should point to an \fBint\fP variable.
1199    .sp
1200      PCRE_INFO_DEFAULT_TABLES
1201    .sp
1202    Return a pointer to the internal default character tables within PCRE. The
1203    fourth argument should point to an \fBunsigned char *\fP variable. This
1204    information call is provided for internal use by the \fBpcre_study()\fP
1205    function. External callers can cause PCRE to use its internal tables by passing
1206    a NULL table pointer.
1207    .sp
1208    PCRE_INFO_FIRSTBYTE    PCRE_INFO_FIRSTBYTE
1209    .sp
1210  Return information about the first byte of any matched string, for a  Return information about the first data unit of any matched string, for a
1211  non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the  non-anchored pattern. (The name of this option refers to the 8-bit library,
1212  old name is still recognized for backwards compatibility.)  where data units are bytes.) The fourth argument should point to an \fBint\fP
1213    variable.
1214  If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),  .P
1215  it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either  If there is a fixed first value, for example, the letter "c" from a pattern
1216    such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1217    value is always less than 256. In the 16-bit library the value can be up to
1218    0xffff. In the 32-bit library the value can be up to 0x10ffff.
1219    .P
1220    If there is no fixed first value, and if either
1221    .sp
1222  (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
1223  starts with "^", or  starts with "^", or
1224    .sp
1225  (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
1226  (if it were set, the pattern would be anchored),  (if it were set, the pattern would be anchored),
1227    .sp
1228  -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
1229  subject string or after any newline within the string. Otherwise -2 is  subject string or after any newline within the string. Otherwise -2 is
1230  returned. For anchored patterns, -2 is returned.  returned. For anchored patterns, -2 is returned.
1231    .P
1232    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1233    to return the full 32-bit range of the character, this value is deprecated;
1234    instead the PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER values
1235    should be used.
1236    .sp
1237    PCRE_INFO_FIRSTTABLE    PCRE_INFO_FIRSTTABLE
1238    .sp
1239  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
1240  table indicating a fixed set of bytes for the first byte in any matching  table indicating a fixed set of values for the first data unit in any matching
1241  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
1242  fourth argument should point to an \fBunsigned char *\fR variable.  fourth argument should point to an \fBunsigned char *\fP variable.
1243    .sp
1244      PCRE_INFO_HASCRORLF
1245    .sp
1246    Return 1 if the pattern contains any explicit matches for CR or LF characters,
1247    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1248    explicit match is either a literal CR or LF character, or \er or \en.
1249    .sp
1250      PCRE_INFO_JCHANGED
1251    .sp
1252    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1253    0. The fourth argument should point to an \fBint\fP variable. (?J) and
1254    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1255    .sp
1256      PCRE_INFO_JIT
1257    .sp
1258    Return 1 if the pattern was studied with one of the JIT options, and
1259    just-in-time compiling was successful. The fourth argument should point to an
1260    \fBint\fP variable. A return value of 0 means that JIT support is not available
1261    in this version of PCRE, or that the pattern was not studied with a JIT option,
1262    or that the JIT compiler could not handle this particular pattern. See the
1263    .\" HREF
1264    \fBpcrejit\fP
1265    .\"
1266    documentation for details of what can and cannot be handled.
1267    .sp
1268      PCRE_INFO_JITSIZE
1269    .sp
1270    If the pattern was successfully studied with a JIT option, return the size of
1271    the JIT compiled code, otherwise return zero. The fourth argument should point
1272    to a \fBsize_t\fP variable.
1273    .sp
1274    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
1275    .sp
1276  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal data unit that must exist in any
1277  string, other than at its start, if such a byte has been recorded. The fourth  matched string, other than at its start, if such a value has been recorded. The
1278  argument should point to an \fBint\fR variable. If there is no such byte, -1 is  fourth argument should point to an \fBint\fP variable. If there is no such
1279  returned. For anchored patterns, a last literal byte is recorded only if it  value, -1 is returned. For anchored patterns, a last literal value is recorded
1280  follows something of variable length. For example, for the pattern  only if it follows something of variable length. For example, for the pattern
1281  /^a\\d+z\\d+/ the returned value is "z", but for /^a\\dz\\d/ the returned value  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1282  is -1.  is -1.
1283    .P
1284    Since for the 32-bit library using the non-UTF-32 mode, this function is unable
1285    to return the full 32-bit range of the character, this value is deprecated;
1286    instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should
1287    be used.
1288    .sp
1289      PCRE_INFO_MAXLOOKBEHIND
1290    .sp
1291    Return the number of characters (NB not bytes) in the longest lookbehind
1292    assertion in the pattern. Note that the simple assertions \eb and \eB require a
1293    one-character lookbehind. This information is useful when doing multi-segment
1294    matching using the partial matching facilities.
1295    .sp
1296      PCRE_INFO_MINLENGTH
1297    .sp
1298    If the pattern was studied and a minimum length for matching subject strings
1299    was computed, its value is returned. Otherwise the returned value is -1. The
1300    value is a number of characters, which in UTF-8 mode may be different from the
1301    number of bytes. The fourth argument should point to an \fBint\fP variable. A
1302    non-negative value is a lower bound to the length of any matching string. There
1303    may not be any strings of that length that do actually match, but every string
1304    that does match is at least that long.
1305    .sp
1306    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
1307    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
1308    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
1309    .sp
1310  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
1311  names are just an additional way of identifying the parentheses, which still  names are just an additional way of identifying the parentheses, which still
1312  acquire a number. A caller that wants to extract data from a named subpattern  acquire numbers. Several convenience functions such as
1313  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
1314  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
1315  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
1316  table for the pattern.  output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1317    you need to use the name-to-number map, which is described by these three
1318    values.
1319    .P
1320  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
1321  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
1322  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
1323  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
1324  entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry  entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
1325  are the number of the capturing parenthesis, most significant byte first. The  the first two bytes of each entry are the number of the capturing parenthesis,
1326  rest of the entry is the corresponding name, zero terminated. The names are in  most significant byte first. In the 16-bit library, the pointer points to
1327  alphabetical order. For example, consider the following pattern (assume  16-bit data units, the first of which contains the parenthesis number.
1328  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  In the 32-bit library, the pointer points to 32-bit data units, the first of
1329    which contains the parenthesis number. The rest
1330    (?P<date> (?P<year>(\\d\\d)?\\d\\d) -  of the entry is the corresponding name, zero terminated.
1331    (?P<month>\\d\\d) - (?P<day>\\d\\d) )  .P
1332    The names are in alphabetical order. Duplicate names may appear if (?| is used
1333    to create multiple groups with the same number, as described in the
1334    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1335    .\" </a>
1336    section on duplicate subpattern numbers
1337    .\"
1338    in the
1339    .\" HREF
1340    \fBpcrepattern\fP
1341    .\"
1342    page. Duplicate names for subpatterns with different numbers are permitted only
1343    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1344    table in the order in which they were found in the pattern. In the absence of
1345    (?| this is the order of increasing number; when (?| is used this is not
1346    necessarily the case because later subpatterns may have lower numbers.
1347    .P
1348    As a simple example of the name/number table, consider the following pattern
1349    after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1350    space - including newlines - is ignored):
1351    .sp
1352    .\" JOIN
1353      (?<date> (?<year>(\ed\ed)?\ed\ed) -
1354      (?<month>\ed\ed) - (?<day>\ed\ed) )
1355    .sp
1356  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
1357  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
1358  bytes shows in hex, and undefined bytes shown as ??:  bytes shows in hexadecimal, and undefined bytes shown as ??:
1359    .sp
1360    00 01 d  a  t  e  00 ??    00 01 d  a  t  e  00 ??
1361    00 05 d  a  y  00 ?? ??    00 05 d  a  y  00 ?? ??
1362    00 04 m  o  n  t  h  00    00 04 m  o  n  t  h  00
1363    00 02 y  e  a  r  00 ??    00 02 y  e  a  r  00 ??
1364    .sp
1365  When writing code to extract data from named subpatterns, remember that the  When writing code to extract data from named subpatterns using the
1366  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
1367    different for each compiled pattern.
1368    .sp
1369      PCRE_INFO_OKPARTIAL
1370    .sp
1371    Return 1 if the pattern can be used for partial matching with
1372    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1373    \fBint\fP variable. From release 8.00, this always returns 1, because the
1374    restrictions that previously applied to partial matching have been lifted. The
1375    .\" HREF
1376    \fBpcrepartial\fP
1377    .\"
1378    documentation gives details of partial matching.
1379    .sp
1380    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1381    .sp
1382  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
1383  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
1384  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
1385  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1386    they are the options that will be in force when matching starts. For example,
1387    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1388    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1389    .P
1390  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
1391  alternatives begin with one of the following:  alternatives begin with one of the following:
1392    .sp
1393    ^     unless PCRE_MULTILINE is set    ^     unless PCRE_MULTILINE is set
1394    \\A    always    \eA    always
1395    \\G    always    \eG    always
1396    .\" JOIN
1397    .*    if PCRE_DOTALL is set and there are no back    .*    if PCRE_DOTALL is set and there are no back
1398            references to the subpattern in which .* appears            references to the subpattern in which .* appears
1399    .sp
1400  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
1401  \fBpcre_fullinfo()\fR.  \fBpcre_fullinfo()\fP.
1402    .sp
1403    PCRE_INFO_SIZE    PCRE_INFO_SIZE
1404    .sp
1405  Return the size of the compiled pattern, that is, the value that was passed as  Return the size of the compiled pattern in bytes (for both libraries). The
1406  the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to  fourth argument should point to a \fBsize_t\fP variable. This value does not
1407  place the compiled data. The fourth argument should point to a \fBsize_t\fR  include the size of the \fBpcre\fP structure that is returned by
1408  variable.  \fBpcre_compile()\fP. The value that is passed as the argument to
1409    \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1410    place the compiled data is the value returned by this option plus the size of
1411    the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1412    does not alter the value returned by this option.
1413    .sp
1414    PCRE_INFO_STUDYSIZE    PCRE_INFO_STUDYSIZE
1415    .sp
1416  Returns the size of the data block pointed to by the \fIstudy_data\fR field in  Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1417  a \fBpcre_extra\fR block. That is, it is the value that was passed to  field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1418  \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data  study data, zero is returned. The fourth argument should point to a
1419  created by \fBpcre_study()\fR. The fourth argument should point to a  \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1420  \fBsize_t\fR variable.  to record information that will speed up matching (see the section entitled
1421    .\" HTML <a href="#studyingapattern">
1422  .SH OBSOLETE INFO FUNCTION  .\" </a>
1423  .rs  "Studying a pattern"
1424  .sp  .\"
1425  .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int  above). The format of the \fIstudy_data\fP block is private, but its length
1426  .B *\fIfirstcharptr\fR);  is made available via this option so that it can be saved and restored (see the
1427  .PP  .\" HREF
1428  The \fBpcre_info()\fR function is now obsolete because its interface is too  \fBpcreprecompile\fP
1429  restrictive to return all the available data about a compiled pattern. New  .\"
1430  programs should use \fBpcre_fullinfo()\fR instead. The yield of  documentation for details).
1431  \fBpcre_info()\fR is the number of capturing subpatterns, or one of the  .sp
1432  following negative numbers:    PCRE_INFO_FIRSTCHARACTERFLAGS
1433    .sp
1434    PCRE_ERROR_NULL       the argument \fIcode\fR was NULL  Return information about the first data unit of any matched string, for a
1435    PCRE_ERROR_BADMAGIC   the "magic number" was not found  non-anchored pattern. The fourth argument should point to an \fBint\fP
1436    variable.
1437  If the \fIoptptr\fR argument is not NULL, a copy of the options with which the  .P
1438  pattern was compiled is placed in the integer it points to (see  If there is a fixed first value, for example, the letter "c" from a pattern
1439  PCRE_INFO_OPTIONS above).  such as (cat|cow|coyote), 1 is returned, and the character value can be
1440    retrieved using PCRE_INFO_FIRSTCHARACTER.
1441  If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,  .P
1442  it is used to pass back information about the first character of any matched  If there is no fixed first value, and if either
1443  string (see PCRE_INFO_FIRSTBYTE above).  .sp
1444    (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1445  .SH MATCHING A PATTERN  starts with "^", or
1446  .rs  .sp
1447  .sp  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1448  .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"  (if it were set, the pattern would be anchored),
1449  .ti +5n  .sp
1450  .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,  2 is returned, indicating that the pattern matches only at the start of a
1451  .ti +5n  subject string or after any newline within the string. Otherwise 0 is
1452  .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);  returned. For anchored patterns, 0 is returned.
1453  .PP  .sp
1454  The function \fBpcre_exec()\fR is called to match a subject string against a    PCRE_INFO_FIRSTCHARACTER
1455  pre-compiled pattern, which is passed in the \fIcode\fR argument. If the  .sp
1456  pattern has been studied, the result of the study should be passed in the  Return the fixed first character value, if PCRE_INFO_FIRSTCHARACTERFLAGS
1457  \fIextra\fR argument.  returned 1; otherwise returns 0. The fourth argument should point to an
1458    \fBuint_t\fP variable.
1459  Here is an example of a simple call to \fBpcre_exec()\fR:  .P
1460    In the 8-bit library, the value is always less than 256. In the 16-bit library
1461    int rc;  the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value
1462    int ovector[30];  can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode.
1463    rc = pcre_exec(  .P
1464    If there is no fixed first value, and if either
1465    .sp
1466    (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1467    starts with "^", or
1468    .sp
1469    (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1470    (if it were set, the pattern would be anchored),
1471    .sp
1472    -1 is returned, indicating that the pattern matches only at the start of a
1473    subject string or after any newline within the string. Otherwise -2 is
1474    returned. For anchored patterns, -2 is returned.
1475    .sp
1476      PCRE_INFO_REQUIREDCHARFLAGS
1477    .sp
1478    Returns 1 if there is a rightmost literal data unit that must exist in any
1479    matched string, other than at its start. The fourth argument should  point to
1480    an \fBint\fP variable. If there is no such value, 0 is returned. If returning
1481    1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR.
1482    .P
1483    For anchored patterns, a last literal value is recorded only if it follows
1484    something of variable length. For example, for the pattern /^a\ed+z\ed+/ the
1485    returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for
1486    /^a\edz\ed/ the returned value is 0.
1487    .sp
1488      PCRE_INFO_REQUIREDCHAR
1489    .sp
1490    Return the value of the rightmost literal data unit that must exist in any
1491    matched string, other than at its start, if such a value has been recorded. The
1492    fourth argument should point to an \fBuint32_t\fP variable. If there is no such
1493    value, 0 is returned.
1494    .
1495    .
1496    .SH "REFERENCE COUNTS"
1497    .rs
1498    .sp
1499    .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1500    .PP
1501    The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1502    data block that contains a compiled pattern. It is provided for the benefit of
1503    applications that operate in an object-oriented manner, where different parts
1504    of the application may be using the same compiled pattern, but you want to free
1505    the block when they are all done.
1506    .P
1507    When a pattern is compiled, the reference count field is initialized to zero.
1508    It is changed only by calling this function, whose action is to add the
1509    \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1510    function is the new value. However, the value of the count is constrained to
1511    lie between 0 and 65535, inclusive. If the new value is outside these limits,
1512    it is forced to the appropriate limit value.
1513    .P
1514    Except when it is zero, the reference count is not correctly preserved if a
1515    pattern is compiled on one host and then transferred to a host whose byte-order
1516    is different. (This seems a highly unlikely scenario.)
1517    .
1518    .
1519    .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
1520    .rs
1521    .sp
1522    .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1523    .ti +5n
1524    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1525    .ti +5n
1526    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1527    .P
1528    The function \fBpcre_exec()\fP is called to match a subject string against a
1529    compiled pattern, which is passed in the \fIcode\fP argument. If the
1530    pattern was studied, the result of the study should be passed in the
1531    \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1532    and \fIextra\fP arguments as many times as you like, in order to match
1533    different subject strings with the same pattern.
1534    .P
1535    This function is the main matching facility of the library, and it operates in
1536    a Perl-like manner. For specialist use there is also an alternative matching
1537    function, which is described
1538    .\" HTML <a href="#dfamatch">
1539    .\" </a>
1540    below
1541    .\"
1542    in the section about the \fBpcre_dfa_exec()\fP function.
1543    .P
1544    In most applications, the pattern will have been compiled (and optionally
1545    studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1546    possible to save compiled patterns and study data, and then use them later
1547    in different processes, possibly even on different hosts. For a discussion
1548    about this, see the
1549    .\" HREF
1550    \fBpcreprecompile\fP
1551    .\"
1552    documentation.
1553    .P
1554    Here is an example of a simple call to \fBpcre_exec()\fP:
1555    .sp
1556      int rc;
1557      int ovector[30];
1558      rc = pcre_exec(
1559      re,             /* result of pcre_compile() */      re,             /* result of pcre_compile() */
1560      NULL,           /* we didn't study the pattern */      NULL,           /* we didn't study the pattern */
1561      "some string",  /* the subject string */      "some string",  /* the subject string */
1562      11,             /* the length of the subject string */      11,             /* the length of the subject string */
1563      0,              /* start at offset 0 in the subject */      0,              /* start at offset 0 in the subject */
1564      0,              /* default options */      0,              /* default options */
1565      ovector,        /* vector for substring information */      ovector,        /* vector of integers for substring information */
1566      30);            /* number of elements in the vector */      30);            /* number of elements (NOT size in bytes) */
1567    .
1568  If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR  .
1569  data block. The \fBpcre_study()\fR function returns such a block (when it  .\" HTML <a name="extradata"></a>
1570    .SS "Extra data for \fBpcre_exec()\fR"
1571    .rs
1572    .sp
1573    If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1574    data block. The \fBpcre_study()\fP function returns such a block (when it
1575  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
1576  additional information in it. The fields in the block are as follows:  additional information in it. The \fBpcre_extra\fP block contains the following
1577    fields (not necessarily in this order):
1578    unsigned long int \fIflags\fR;  .sp
1579    void *\fIstudy_data\fR;    unsigned long int \fIflags\fP;
1580    unsigned long int \fImatch_limit\fR;    void *\fIstudy_data\fP;
1581    void *\fIcallout_data\fR;    void *\fIexecutable_jit\fP;
1582      unsigned long int \fImatch_limit\fP;
1583  The \fIflags\fR field is a bitmap that specifies which of the other fields    unsigned long int \fImatch_limit_recursion\fP;
1584  are set. The flag bits are:    void *\fIcallout_data\fP;
1585      const unsigned char *\fItables\fP;
1586    PCRE_EXTRA_STUDY_DATA    unsigned char **\fImark\fP;
1587    PCRE_EXTRA_MATCH_LIMIT  .sp
1588    In the 16-bit version of this structure, the \fImark\fP field has type
1589    "PCRE_UCHAR16 **".
1590    .sp
1591    In the 32-bit version of this structure, the \fImark\fP field has type
1592    "PCRE_UCHAR32 **".
1593    .P
1594    The \fIflags\fP field is used to specify which of the other fields are set. The
1595    flag bits are:
1596    .sp
1597    PCRE_EXTRA_CALLOUT_DATA    PCRE_EXTRA_CALLOUT_DATA
1598      PCRE_EXTRA_EXECUTABLE_JIT
1599  Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the    PCRE_EXTRA_MARK
1600  \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with    PCRE_EXTRA_MATCH_LIMIT
1601  the appropriate flag bit. You should not set this yourself, but you can add to    PCRE_EXTRA_MATCH_LIMIT_RECURSION
1602  the block by setting the other fields.    PCRE_EXTRA_STUDY_DATA
1603      PCRE_EXTRA_TABLES
1604  The \fImatch_limit\fR field provides a means of preventing PCRE from using up a  .sp
1605    Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1606    the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1607    returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1608    should not set these yourself, but you may add to the block by setting other
1609    fields and their corresponding flag bits.
1610    .P
1611    The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1612  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,
1613  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
1614  classic example is the use of nested unlimited repeats. Internally, PCRE uses a  classic example is a pattern that uses nested unlimited repeats.
1615  function called \fBmatch()\fR which it calls repeatedly (sometimes  .P
1616  recursively). The limit is imposed on the number of times this function is  Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1617  called during a match, which has the effect of limiting the amount of recursion  calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1618  and backtracking that can take place. For patterns that are not anchored, the  imposed on the number of times this function is called during a match, which
1619  count starts from zero for each position in the subject string.  has the effect of limiting the amount of backtracking that can take place. For
1620    patterns that are not anchored, the count restarts from zero for each position
1621  The default limit for the library can be set when PCRE is built; the default  in the subject string.
1622    .P
1623    When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1624    with a JIT option, the way that the matching is executed is entirely different.
1625    However, there is still the possibility of runaway matching that goes on for a
1626    very long time, and so the \fImatch_limit\fP value is also used in this case
1627    (but in a different way) to limit how long the matching can continue.
1628    .P
1629    The default value for the limit can be set when PCRE is built; the default
1630  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
1631  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
1632  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
1633  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
1634  exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.  PCRE_ERROR_MATCHLIMIT.
1635    .P
1636  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
1637  which is described in the \fBpcrecallout\fR documentation.  instead of limiting the total number of times that \fBmatch()\fP is called, it
1638    limits the depth of recursion. The recursion depth is a smaller number than the
1639  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.
1640  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.
1641  first matching position. However, if a pattern was compiled with PCRE_ANCHORED,  .P
1642  or turned out to be anchored by virtue of its contents, it cannot be made  Limiting the recursion depth limits the amount of machine stack that can be
1643  unachored at matching time.  used, or, when PCRE has been compiled to use memory on the heap instead of the
1644    stack, the amount of heap memory that can be used. This limit is not relevant,
1645  When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8  and is ignored, when matching is done using JIT compiled code.
1646  string is automatically checked, and the value of \fIstartoffset\fR is also  .P
1647  checked to ensure that it points to the start of a UTF-8 character. If an  The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1648  invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fR returns the error  built; the default default is the same value as the default for
1649  PCRE_ERROR_BADUTF8. If \fIstartoffset\fR contains an invalid value,  \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1650  PCRE_ERROR_BADUTF8_OFFSET is returned.  with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1651    PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1652  If you already know that your subject is valid, and you want to skip these  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1653  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when  .P
1654  calling \fBpcre_exec()\fR. You might want to do this for the second and  The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1655  subsequent calls to \fBpcre_exec()\fR if you are making repeated calls to find  and is described in the
1656  all the matches in a single subject string. However, you should be sure that  .\" HREF
1657  the value of \fIstartoffset\fR points to the start of a UTF-8 character. When  \fBpcrecallout\fP
1658  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a  .\"
1659  subject, or a value of \fIstartoffset\fR that does not point to the start of a  documentation.
1660  UTF-8 character, is undefined. Your program may crash.  .P
1661    The \fItables\fP field is used to pass a character tables pointer to
1662  There are also three further options that can be set only at matching time:  \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1663    pattern. A non-NULL value is stored with the compiled pattern only if custom
1664    tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1665    If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1666    internal tables to be used. This facility is helpful when re-using patterns
1667    that have been saved after compiling with an external set of tables, because
1668    the external tables might be at a different address when \fBpcre_exec()\fP is
1669    called. See the
1670    .\" HREF
1671    \fBpcreprecompile\fP
1672    .\"
1673    documentation for a discussion of saving compiled patterns for later use.
1674    .P
1675    If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1676    be set to point to a suitable variable. If the pattern contains any
1677    backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1678    a name to pass back, a pointer to the name string (zero terminated) is placed
1679    in the variable pointed to by the \fImark\fP field. The names are within the
1680    compiled pattern; if you wish to retain such a name you must copy it before
1681    freeing the memory of a compiled pattern. If there is no name to pass back, the
1682    variable pointed to by the \fImark\fP field is set to NULL. For details of the
1683    backtracking control verbs, see the section entitled
1684    .\" HTML <a href="pcrepattern#backtrackcontrol">
1685    .\" </a>
1686    "Backtracking control"
1687    .\"
1688    in the
1689    .\" HREF
1690    \fBpcrepattern\fP
1691    .\"
1692    documentation.
1693    .
1694    .
1695    .\" HTML <a name="execoptions"></a>
1696    .SS "Option bits for \fBpcre_exec()\fP"
1697    .rs
1698    .sp
1699    The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1700    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1701    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1702    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and
1703    PCRE_PARTIAL_SOFT.
1704    .P
1705    If the pattern was successfully studied with one of the just-in-time (JIT)
1706    compile options, the only supported options for JIT execution are
1707    PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,
1708    PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an
1709    unsupported option is used, JIT execution is disabled and the normal
1710    interpretive code in \fBpcre_exec()\fP is run.
1711    .sp
1712      PCRE_ANCHORED
1713    .sp
1714    The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1715    matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1716    to be anchored by virtue of its contents, it cannot be made unachored at
1717    matching time.
1718    .sp
1719      PCRE_BSR_ANYCRLF
1720      PCRE_BSR_UNICODE
1721    .sp
1722    These options (which are mutually exclusive) control what the \eR escape
1723    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1724    match any Unicode newline sequence. These options override the choice that was
1725    made or defaulted when the pattern was compiled.
1726    .sp
1727      PCRE_NEWLINE_CR
1728      PCRE_NEWLINE_LF
1729      PCRE_NEWLINE_CRLF
1730      PCRE_NEWLINE_ANYCRLF
1731      PCRE_NEWLINE_ANY
1732    .sp
1733    These options override the newline definition that was chosen or defaulted when
1734    the pattern was compiled. For details, see the description of
1735    \fBpcre_compile()\fP above. During matching, the newline choice affects the
1736    behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1737    the way the match position is advanced after a match failure for an unanchored
1738    pattern.
1739    .P
1740    When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1741    match attempt for an unanchored pattern fails when the current position is at a
1742    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1743    characters, the match position is advanced by two characters instead of one, in
1744    other words, to after the CRLF.
1745    .P
1746    The above rule is a compromise that makes the most common cases work as
1747    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1748    set), it does not match the string "\er\enA" because, after failing at the
1749    start, it skips both the CR and the LF before retrying. However, the pattern
1750    [\er\en]A does match that string, because it contains an explicit CR or LF
1751    reference, and so advances only by one character after the first failure.
1752    .P
1753    An explicit match for CR of LF is either a literal appearance of one of those
1754    characters, or one of the \er or \en escape sequences. Implicit matches such as
1755    [^X] do not count, nor does \es (which includes CR and LF in the characters
1756    that it matches).
1757    .P
1758    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1759    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1760    .sp
1761    PCRE_NOTBOL    PCRE_NOTBOL
1762    .sp
1763  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
1764  circumflex metacharacter should not match before it. Setting this without  beginning of a line, so the circumflex metacharacter should not match before
1765  PCRE_MULTILINE (at compile time) causes circumflex never to match.  it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1766    never to match. This option affects only the behaviour of the circumflex
1767    metacharacter. It does not affect \eA.
1768    .sp
1769    PCRE_NOTEOL    PCRE_NOTEOL
1770    .sp
1771  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
1772  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
1773  it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never  mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1774  to match.  compile time) causes dollar never to match. This option affects only the
1775    behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1776    .sp
1777    PCRE_NOTEMPTY    PCRE_NOTEMPTY
1778    .sp
1779  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
1780  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
1781  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
1782    .sp
1783    a?b?    a?b?
1784    .sp
1785  is applied to a string not beginning with "a" or "b", it matches the empty  is applied to a string not beginning with "a" or "b", it matches an empty
1786  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
1787  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".
1788    .sp
1789  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1790  of a pattern match of the empty string within its \fBsplit()\fR function, and  .sp
1791  when using the /g modifier. It is possible to emulate Perl's behaviour after  This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1792  matching a null string by first trying the match again at the same offset with  the start of the subject is permitted. If the pattern is anchored, such a match
1793  PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see  can occur only if the pattern contains \eK.
1794  below) and trying an ordinary match again.  .P
1795    Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1796  The subject string is passed to \fBpcre_exec()\fR as a pointer in  does make a special case of a pattern match of the empty string within its
1797  \fIsubject\fR, a length in \fIlength\fR, and a starting byte offset in  \fBsplit()\fP function, and when using the /g modifier. It is possible to
1798  \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary  emulate Perl's behaviour after matching a null string by first trying the match
1799  zero bytes. When the starting offset is zero, the search for a match starts at  again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1800  the beginning of the subject, and this is by far the most common case.  if that fails, by advancing the starting offset (see below) and trying an
1801    ordinary match again. There is some code that demonstrates how to do this in
1802  If the pattern was compiled with the PCRE_UTF8 option, the subject must be a  the
1803  sequence of bytes that is a valid UTF-8 string, and the starting offset must  .\" HREF
1804  point to the beginning of a UTF-8 character. If an invalid UTF-8 string or  \fBpcredemo\fP
1805  offset is passed, an error (either PCRE_ERROR_BADUTF8 or  .\"
1806  PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is  sample program. In the most general case, you have to check to see if the
1807  set, in which case PCRE's behaviour is not defined.  newline convention recognizes CRLF as a newline, and if so, and the current
1808    character is CR followed by LF, advance the starting offset by two characters
1809    instead of one.
1810    .sp
1811      PCRE_NO_START_OPTIMIZE
1812    .sp
1813    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1814    a match, in order to speed up the process. For example, if it is known that an
1815    unanchored match must start with a specific character, it searches the subject
1816    for that character, and fails immediately if it cannot find it, without
1817    actually running the main matching function. This means that a special item
1818    such as (*COMMIT) at the start of a pattern is not considered until after a
1819    suitable starting point for the match has been found. When callouts or (*MARK)
1820    items are in use, these "start-up" optimizations can cause them to be skipped
1821    if the pattern is never actually used. The start-up optimizations are in effect
1822    a pre-scan of the subject that takes place before the pattern is run.
1823    .P
1824    The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1825    causing performance to suffer, but ensuring that in cases where the result is
1826    "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1827    are considered at every possible starting position in the subject string. If
1828    PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1829    time. The use of PCRE_NO_START_OPTIMIZE disables JIT execution; when it is set,
1830    matching is always done using interpretively.
1831    .P
1832    Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1833    Consider the pattern
1834    .sp
1835      (*COMMIT)ABC
1836    .sp
1837    When this is compiled, PCRE records the fact that a match must start with the
1838    character "A". Suppose the subject string is "DEFABC". The start-up
1839    optimization scans along the subject, finds "A" and runs the first match
1840    attempt from there. The (*COMMIT) item means that the pattern must match the
1841    current starting position, which in this case, it does. However, if the same
1842    match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1843    subject string does not happen. The first match attempt is run starting from
1844    "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1845    the overall result is "no match". If the pattern is studied, more start-up
1846    optimizations may be used. For example, a minimum length for the subject may be
1847    recorded. Consider the pattern
1848    .sp
1849      (*MARK:A)(X|Y)
1850    .sp
1851    The minimum length for a match is one character. If the subject is "ABC", there
1852    will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1853    If the pattern is studied, the final attempt does not take place, because PCRE
1854    knows that the subject is too short, and so the (*MARK) is never encountered.
1855    In this case, studying the pattern does not affect the overall match result,
1856    which is still "no match", but it does affect the auxiliary information that is
1857    returned.
1858    .sp
1859      PCRE_NO_UTF8_CHECK
1860    .sp
1861    When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1862    string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1863    The entire string is checked before any other processing takes place. The value
1864    of \fIstartoffset\fP is also checked to ensure that it points to the start of a
1865    UTF-8 character. There is a discussion about the
1866    .\" HTML <a href="pcreunicode.html#utf8strings">
1867    .\" </a>
1868    validity of UTF-8 strings
1869    .\"
1870    in the
1871    .\" HREF
1872    \fBpcreunicode\fP
1873    .\"
1874    page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1875    error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1876    truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1877    cases, information about the precise nature of the error may also be returned
1878    (see the descriptions of these errors in the section entitled \fIError return
1879    values from\fP \fBpcre_exec()\fP
1880    .\" HTML <a href="#errorlist">
1881    .\" </a>
1882    below).
1883    .\"
1884    If \fIstartoffset\fP contains a value that does not point to the start of a
1885    UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1886    returned.
1887    .P
1888    If you already know that your subject is valid, and you want to skip these
1889    checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1890    calling \fBpcre_exec()\fP. You might want to do this for the second and
1891    subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1892    all the matches in a single subject string. However, you should be sure that
1893    the value of \fIstartoffset\fP points to the start of a character (or the end
1894    of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1895    invalid string as a subject or an invalid value of \fIstartoffset\fP is
1896    undefined. Your program may crash.
1897    .sp
1898      PCRE_PARTIAL_HARD
1899      PCRE_PARTIAL_SOFT
1900    .sp
1901    These options turn on the partial matching feature. For backwards
1902    compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1903    occurs if the end of the subject string is reached successfully, but there are
1904    not enough subject characters to complete the match. If this happens when
1905    PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1906    testing any remaining alternatives. Only if no complete match can be found is
1907    PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1908    PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1909    but only if no complete match can be found.
1910    .P
1911    If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1912    partial match is found, \fBpcre_exec()\fP immediately returns
1913    PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1914    when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1915    important that an alternative complete match.
1916    .P
1917    In both cases, the portion of the string that was inspected when the partial
1918    match was found is set as the first matching string. There is a more detailed
1919    discussion of partial and multi-segment matching, with examples, in the
1920    .\" HREF
1921    \fBpcrepartial\fP
1922    .\"
1923    documentation.
1924    .
1925    .
1926    .SS "The string to be matched by \fBpcre_exec()\fP"
1927    .rs
1928    .sp
1929    The subject string is passed to \fBpcre_exec()\fP as a pointer in
1930    \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1931    in \fIstartoffset\fP. If this is negative or greater than the length of the
1932    subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1933    offset is zero, the search for a match starts at the beginning of the subject,
1934    and this is by far the most common case. In UTF-8 mode, the byte offset must
1935    point to the start of a UTF-8 character (or the end of the subject). Unlike the
1936    pattern string, the subject may contain binary zero bytes.
1937    .P
1938  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
1939  same subject by calling \fBpcre_exec()\fR again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
1940  Setting \fIstartoffset\fR differs from just passing over a shortened string and  Setting \fIstartoffset\fP differs from just passing over a shortened string and
1941  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
1942  lookbehind. For example, consider the pattern  lookbehind. For example, consider the pattern
1943    .sp
1944    \\Biss\\B    \eBiss\eB
1945    .sp
1946  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
1947  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
1948  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
1949  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
1950  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
1951  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
1952  \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
1953  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
1954  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.
1955    .P
1956    Finding all the matches in a subject is tricky when the pattern can match an
1957    empty string. It is possible to emulate Perl's /g behaviour by first trying the
1958    match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1959    PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1960    and trying an ordinary match again. There is some code that demonstrates how to
1961    do this in the
1962    .\" HREF
1963    \fBpcredemo\fP
1964    .\"
1965    sample program. In the most general case, you have to check to see if the
1966    newline convention recognizes CRLF as a newline, and if so, and the current
1967    character is CR followed by LF, advance the starting offset by two characters
1968    instead of one.
1969    .P
1970  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
1971  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
1972  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.
1973    .
1974    .
1975    .SS "How \fBpcre_exec()\fP returns captured substrings"
1976    .rs
1977    .sp
1978  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
1979  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
1980  pattern. Following the usage in Jeffrey Friedl's book, this is called  pattern. Following the usage in Jeffrey Friedl's book, this is called
1981  "capturing" in what follows, and the phrase "capturing subpattern" is used for  "capturing" in what follows, and the phrase "capturing subpattern" is used for
1982  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
1983  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1984    .P
1985  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
1986  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
1987  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
1988  back captured substrings, each substring using a pair of integers. The  argument is NOT the size of \fIovector\fP in bytes.
1989  remaining third of the vector is used as workspace by \fBpcre_exec()\fR while  .P
1990  matching capturing subpatterns, and is not available for passing back  The first two-thirds of the vector is used to pass back captured substrings,
1991  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
1992  three. If it is not, it is rounded down.  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1993    and is not available for passing back information. The number passed in
1994  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
1995  returned in pairs of integers, starting at the beginning of \fIovector\fR, and  rounded down.
1996  continuing up to two-thirds of its length at the most. The first element of a  .P
1997  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
1998  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
1999  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
2000  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
2001  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
2002  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
2003  subpatterns, the return value from a successful match is 1, indicating that  mode. They are not character counts.
2004  just the first pair of offsets has been set.  .P
2005    The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
2006  Some convenience functions are provided for extracting the captured substrings  portion of the subject string matched by the entire pattern. The next pair is
2007  as separate strings. These are described in the following section.  used for the first capturing subpattern, and so on. The value returned by
2008    \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
2009  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
2010  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
2011  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.
2012  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.  
   
2013  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
2014  string that it matched that gets returned.  string that it matched that is returned.
2015    .P
2016  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
2017  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
2018  value of zero. In particular, if the substring offsets are not of interest,  returns a value of zero. If neither the actual string matched nor any captured
2019  \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and  substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
2020  \fIovecsize\fR as zero. However, if the pattern contains back references and  passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
2021  the \fIovector\fR isn't big enough to remember the related substrings, PCRE has  back references and the \fIovector\fP is not big enough to remember the related
2022  to get additional memory for use during matching. Thus it is usually advisable  substrings, PCRE has to get additional memory for use during matching. Thus it
2023  to supply an \fIovector\fR.  is usually advisable to supply an \fIovector\fP of reasonable size.
2024    .P
2025  Note that \fBpcre_info()\fR can be used to find out how many capturing  There are some cases where zero is returned (indicating vector overflow) when
2026    in fact the vector is exactly the right size for the final match. For example,
2027    consider the pattern
2028    .sp
2029      (a)(?:(b)c|bd)
2030    .sp
2031    If a vector of 6 elements (allowing for only 1 captured substring) is given
2032    with subject string "abd", \fBpcre_exec()\fP will try to set the second
2033    captured string, thereby recording a vector overflow, before failing to match
2034    "c" and backing up to try the second alternative. The zero return, however,
2035    does correctly indicate that the maximum number of slots (namely 2) have been
2036    filled. In similar cases where there is temporary overflow, but the final
2037    number of used slots is actually less than the maximum, a non-zero value is
2038    returned.
2039    .P
2040    The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
2041  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
2042  \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
2043  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.
2044    .P
2045  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
2046    the subject when subpattern \fIn\fP has not been used at all. For example, if
2047    the string "abc" is matched against the pattern (a|(z))(bc) the return from the
2048    function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
2049    happens, both values in the offset pairs corresponding to unused subpatterns
2050    are set to -1.
2051    .P
2052    Offset values that correspond to unused subpatterns at the end of the
2053    expression are also set to -1. For example, if the string "abc" is matched
2054    against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
2055    return from the function is 2, because the highest used capturing subpattern
2056    number is 1, and the offsets for for the second and third capturing subpatterns
2057    (assuming the vector is large enough, of course) are set to -1.
2058    .P
2059    \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
2060    correspond to capturing parentheses in the pattern are never changed. That is,
2061    if a pattern contains \fIn\fP capturing parentheses, no more than
2062    \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
2063    elements (in the first two-thirds) retain whatever values they previously had.
2064    .P
2065    Some convenience functions are provided for extracting the captured substrings
2066    as separate strings. These are described below.
2067    .
2068    .
2069    .\" HTML <a name="errorlist"></a>
2070    .SS "Error return values from \fBpcre_exec()\fP"
2071    .rs
2072    .sp
2073    If \fBpcre_exec()\fP fails, it returns a negative number. The following are
2074  defined in the header file:  defined in the header file:
2075    .sp
2076    PCRE_ERROR_NOMATCH        (-1)    PCRE_ERROR_NOMATCH        (-1)
2077    .sp
2078  The subject string did not match the pattern.  The subject string did not match the pattern.
2079    .sp
2080    PCRE_ERROR_NULL           (-2)    PCRE_ERROR_NULL           (-2)
2081    .sp
2082  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
2083  NULL and \fIovecsize\fR was not zero.  NULL and \fIovecsize\fP was not zero.
2084    .sp
2085    PCRE_ERROR_BADOPTION      (-3)    PCRE_ERROR_BADOPTION      (-3)
2086    .sp
2087  An unrecognized bit was set in the \fIoptions\fR argument.  An unrecognized bit was set in the \fIoptions\fP argument.
2088    .sp
2089    PCRE_ERROR_BADMAGIC       (-4)    PCRE_ERROR_BADMAGIC       (-4)
2090    .sp
2091  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
2092  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
2093  magic number isn't present.  compiled in an environment of one endianness is run in an environment with the
2094    other endianness. This is the error that PCRE gives when the magic number is
2095    PCRE_ERROR_UNKNOWN_NODE   (-5)  not present.
2096    .sp
2097      PCRE_ERROR_UNKNOWN_OPCODE (-5)
2098    .sp
2099  While running the pattern match, an unknown item was encountered in the  While running the pattern match, an unknown item was encountered in the
2100  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
2101  of the compiled pattern.  of the compiled pattern.
2102    .sp
2103    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2104    .sp
2105  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
2106  \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
2107  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
2108  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
2109  the end of matching.  automatically freed at the end of matching.
2110    .P
2111    This error is also given if \fBpcre_stack_malloc()\fP fails in
2112    \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
2113    \fB--disable-stack-for-recursion\fP.
2114    .sp
2115    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2116    .sp
2117  This error is used by the \fBpcre_copy_substring()\fR,  This error is used by the \fBpcre_copy_substring()\fP,
2118  \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see  \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
2119  below). It is never returned by \fBpcre_exec()\fR.  below). It is never returned by \fBpcre_exec()\fP.
2120    .sp
2121    PCRE_ERROR_MATCHLIMIT     (-8)    PCRE_ERROR_MATCHLIMIT     (-8)
2122    .sp
2123  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
2124  field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the  \fBpcre_extra\fP structure (or defaulted) was reached. See the description
2125  description above.  above.
2126    .sp
2127    PCRE_ERROR_CALLOUT        (-9)    PCRE_ERROR_CALLOUT        (-9)
2128    .sp
2129  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
2130  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
2131  \fBpcrecallout\fR documentation for details.  .\" HREF
2132    \fBpcrecallout\fP
2133    .\"
2134    documentation for details.
2135    .sp
2136    PCRE_ERROR_BADUTF8        (-10)    PCRE_ERROR_BADUTF8        (-10)
2137    .sp
2138  A string that contains an invalid UTF-8 byte sequence was passed as a subject.  A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2139    and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2140    (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2141    UTF-8 character is placed in the first element, and a reason code is placed in
2142    the second element. The reason codes are listed in the
2143    .\" HTML <a href="#badutf8reasons">
2144    .\" </a>
2145    following section.
2146    .\"
2147    For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2148    truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2149    PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2150    .sp
2151    PCRE_ERROR_BADUTF8_OFFSET (-11)    PCRE_ERROR_BADUTF8_OFFSET (-11)
2152    .sp
2153  The UTF-8 byte sequence that was passed as a subject was valid, but the value  The UTF-8 byte sequence that was passed as a subject was checked and found to
2154  of \fIstartoffset\fR did not point to the beginning of a UTF-8 character.  be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2155    \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2156  .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  end of the subject.
2157    .sp
2158      PCRE_ERROR_PARTIAL        (-12)
2159    .sp
2160    The subject string did not match, but it did match partially. See the
2161    .\" HREF
2162    \fBpcrepartial\fP
2163    .\"
2164    documentation for details of partial matching.
2165    .sp
2166      PCRE_ERROR_BADPARTIAL     (-13)
2167    .sp
2168    This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2169    option was used with a compiled pattern containing items that were not
2170    supported for partial matching. From release 8.00 onwards, there are no
2171    restrictions on partial matching.
2172    .sp
2173      PCRE_ERROR_INTERNAL       (-14)
2174    .sp
2175    An unexpected internal error has occurred. This error could be caused by a bug
2176    in PCRE or by overwriting of the compiled pattern.
2177    .sp
2178      PCRE_ERROR_BADCOUNT       (-15)
2179    .sp
2180    This error is given if the value of the \fIovecsize\fP argument is negative.
2181    .sp
2182      PCRE_ERROR_RECURSIONLIMIT (-21)
2183    .sp
2184    The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2185    field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2186    description above.
2187    .sp
2188      PCRE_ERROR_BADNEWLINE     (-23)
2189    .sp
2190    An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2191    .sp
2192      PCRE_ERROR_BADOFFSET      (-24)
2193    .sp
2194    The value of \fIstartoffset\fP was negative or greater than the length of the
2195    subject, that is, the value in \fIlength\fP.
2196    .sp
2197      PCRE_ERROR_SHORTUTF8      (-25)
2198    .sp
2199    This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2200    ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2201    Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2202    fact sufficient to detect this case, but this special error code for
2203    PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2204    retained for backwards compatibility.
2205    .sp
2206      PCRE_ERROR_RECURSELOOP    (-26)
2207    .sp
2208    This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2209    the pattern. Specifically, it means that either the whole pattern or a
2210    subpattern has been called recursively for the second time at the same position
2211    in the subject string. Some simple patterns that might do this are detected and
2212    faulted at compile time, but more complicated cases, in particular mutual
2213    recursions between two different subpatterns, cannot be detected until run
2214    time.
2215    .sp
2216      PCRE_ERROR_JIT_STACKLIMIT (-27)
2217    .sp
2218    This error is returned when a pattern that was successfully studied using a
2219    JIT compile option is being matched, but the memory available for the
2220    just-in-time processing stack is not large enough. See the
2221    .\" HREF
2222    \fBpcrejit\fP
2223    .\"
2224    documentation for more details.
2225    .sp
2226      PCRE_ERROR_BADMODE        (-28)
2227    .sp
2228    This error is given if a pattern that was compiled by the 8-bit library is
2229    passed to a 16-bit or 32-bit library function, or vice versa.
2230    .sp
2231      PCRE_ERROR_BADENDIANNESS  (-29)
2232    .sp
2233    This error is given if a pattern that was compiled and saved is reloaded on a
2234    host with different endianness. The utility function
2235    \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2236    so that it runs on the new host.
2237    .sp
2238      PCRE_ERROR_BADLENGTH      (-32)
2239    .sp
2240    This error is given if \fBpcre_exec()\fP is called with a negative value for
2241    the \fIlength\fP argument.
2242    .P
2243    Error numbers -16 to -20, -22, 30, and -31 are not used by \fBpcre_exec()\fP.
2244    .
2245    .
2246    .\" HTML <a name="badutf8reasons"></a>
2247    .SS "Reason codes for invalid UTF-8 strings"
2248  .rs  .rs
2249  .sp  .sp
2250  .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,  This section applies only to the 8-bit library. The corresponding information
2251    for the 16-bit library is given in the
2252    .\" HREF
2253    \fBpcre16\fP
2254    .\"
2255    page. The corresponding information for the 32-bit library is given in the
2256    .\" HREF
2257    \fBpcre32\fP
2258    .\"
2259    page.
2260    .P
2261    When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2262    PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2263    least 2, the offset of the start of the invalid UTF-8 character is placed in
2264    the first output vector element (\fIovector[0]\fP) and a reason code is placed
2265    in the second element (\fIovector[1]\fP). The reason codes are given names in
2266    the \fBpcre.h\fP header file:
2267    .sp
2268      PCRE_UTF8_ERR1
2269      PCRE_UTF8_ERR2
2270      PCRE_UTF8_ERR3
2271      PCRE_UTF8_ERR4
2272      PCRE_UTF8_ERR5
2273    .sp
2274    The string ends with a truncated UTF-8 character; the code specifies how many
2275    bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2276    no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2277    allows for up to 6 bytes, and this is checked first; hence the possibility of
2278    4 or 5 missing bytes.
2279    .sp
2280      PCRE_UTF8_ERR6
2281      PCRE_UTF8_ERR7
2282      PCRE_UTF8_ERR8
2283      PCRE_UTF8_ERR9
2284      PCRE_UTF8_ERR10
2285    .sp
2286    The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2287    character do not have the binary value 0b10 (that is, either the most
2288    significant bit is 0, or the next bit is 1).
2289    .sp
2290      PCRE_UTF8_ERR11
2291      PCRE_UTF8_ERR12
2292    .sp
2293    A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2294    these code points are excluded by RFC 3629.
2295    .sp
2296      PCRE_UTF8_ERR13
2297    .sp
2298    A 4-byte character has a value greater than 0x10fff; these code points are
2299    excluded by RFC 3629.
2300    .sp
2301      PCRE_UTF8_ERR14
2302    .sp
2303    A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2304    code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2305    from UTF-8.
2306    .sp
2307      PCRE_UTF8_ERR15
2308      PCRE_UTF8_ERR16
2309      PCRE_UTF8_ERR17
2310      PCRE_UTF8_ERR18
2311      PCRE_UTF8_ERR19
2312    .sp
2313    A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2314    value that can be represented by fewer bytes, which is invalid. For example,
2315    the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2316    one byte.
2317    .sp
2318      PCRE_UTF8_ERR20
2319    .sp
2320    The two most significant bits of the first byte of a character have the binary
2321    value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2322    byte can only validly occur as the second or subsequent byte of a multi-byte
2323    character.
2324    .sp
2325      PCRE_UTF8_ERR21
2326    .sp
2327    The first byte of a character has the value 0xfe or 0xff. These values can
2328    never occur in a valid UTF-8 string.
2329    .sp
2330      PCRE_UTF8_ERR2
2331    .sp
2332    Non-character. These are the last two characters in each plane (0xfffe, 0xffff,
2333    0x1fffe, 0x1ffff .. 0x10fffe, 0x10ffff), and the characters 0xfdd0..0xfdef.
2334    .
2335    .
2336    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
2337    .rs
2338    .sp
2339    .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2340  .ti +5n  .ti +5n
2341  .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2342  .ti +5n  .ti +5n
2343  .B int \fIbuffersize\fR);  .B int \fIbuffersize\fP);
2344  .PP  .PP
2345  .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,  
2346  .ti +5n  .ti +5n
2347  .B int \fIstringcount\fR, int \fIstringnumber\fR,  .B int \fIstringcount\fP, int \fIstringnumber\fP,
2348  .ti +5n  .ti +5n
2349  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2350  .PP  .PP
2351  .br  .B int pcre_get_substring_list(const char *\fIsubject\fP,
 .B int pcre_get_substring_list(const char *\fIsubject\fR,  
2352  .ti +5n  .ti +5n
2353  .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"  .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2354  .PP  .PP
2355  Captured substrings can be accessed directly by using the offsets returned by  Captured substrings can be accessed directly by using the offsets returned by
2356  \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions  \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2357  \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and  \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2358  \fBpcre_get_substring_list()\fR are provided for extracting captured substrings  \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2359  as new, separate, zero-terminated strings. These functions identify substrings  as new, separate, zero-terminated strings. These functions identify substrings
2360  by number. The next section describes functions for extracting named  by number. The next section describes functions for extracting named
2361  substrings. A substring that contains a binary zero is correctly extracted and  substrings.
2362  has a further zero added on the end, but the result is not, of course,  .P
2363  a C string.  A substring that contains a binary zero is correctly extracted and has a
2364    further zero added on the end, but the result is not, of course, a C string.
2365    However, you can process such a string by referring to the length that is
2366    returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2367    Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2368    for handling strings containing binary zeros, because the end of the final
2369    string is not independently indicated.
2370    .P
2371  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:
2372  \fIsubject\fR is the subject string which has just been successfully matched,  \fIsubject\fP is the subject string that has just been successfully matched,
2373  \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
2374  \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
2375  captured by the match, including the substring that matched the entire regular  captured by the match, including the substring that matched the entire regular
2376  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
2377  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
2378  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
2379  the vector divided by three.  number of elements in the vector divided by three.
2380    .P
2381  The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR  The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2382  extract a single substring, whose number is given as \fIstringnumber\fR. A  extract a single substring, whose number is given as \fIstringnumber\fP. A
2383  value of zero extracts the substring that matched the entire pattern, while  value of zero extracts the substring that matched the entire pattern, whereas
2384  higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,  higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2385  the string is placed in \fIbuffer\fR, whose length is given by  the string is placed in \fIbuffer\fP, whose length is given by
2386  \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
2387  obtained via \fBpcre_malloc\fR, and its address is returned via  obtained via \fBpcre_malloc\fP, and its address is returned via
2388  \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
2389  including the terminating zero, or one of  including the terminating zero, or one of these error codes:
2390    .sp
2391    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2392    .sp
2393  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
2394  memory failed for \fBpcre_get_substring()\fR.  memory failed for \fBpcre_get_substring()\fP.
2395    .sp
2396    PCRE_ERROR_NOSUBSTRING    (-7)    PCRE_ERROR_NOSUBSTRING    (-7)
2397    .sp
2398  There is no substring whose number is \fIstringnumber\fR.  There is no substring whose number is \fIstringnumber\fP.
2399    .P
2400  The \fBpcre_get_substring_list()\fR function extracts all available substrings  The \fBpcre_get_substring_list()\fP function extracts all available substrings
2401  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
2402  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
2403  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
2404  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
2405  function is zero if all went well, or  function is zero if all went well, or the error code
2406    .sp
2407    PCRE_ERROR_NOMEMORY       (-6)    PCRE_ERROR_NOMEMORY       (-6)
2408    .sp
2409  if the attempt to get the memory block failed.  if the attempt to get the memory block failed.
2410    .P
2411  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
2412  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
2413  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
2414  string. This can be distinguished from a genuine zero-length substring by  string. This can be distinguished from a genuine zero-length substring by
2415  inspecting the appropriate offset in \fIovector\fR, which is negative for unset  inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2416  substrings.  substrings.
2417    .P
2418  The two convenience functions \fBpcre_free_substring()\fR and  The two convenience functions \fBpcre_free_substring()\fP and
2419  \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
2420  a previous call of \fBpcre_get_substring()\fR or  a previous call of \fBpcre_get_substring()\fP or
2421  \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call  \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2422  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
2423  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
2424  linked via a special interface to another programming language which cannot use  linked via a special interface to another programming language that cannot use
2425  \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
2426  provided.  provided.
2427    .
2428  .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME  .
2429    .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
2430  .rs  .rs
2431  .sp  .sp
2432  .B int pcre_copy_named_substring(const pcre *\fIcode\fR,  .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2433  .ti +5n  .ti +5n
2434  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIname\fP);
2435    .PP
2436    .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2437  .ti +5n  .ti +5n
2438  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2439  .ti +5n  .ti +5n
2440  .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,  
2441  .ti +5n  .ti +5n
2442  .B const char *\fIname\fR);  .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2443  .PP  .PP
2444  .br  .B int pcre_get_named_substring(const pcre *\fIcode\fP,
 .B int pcre_get_named_substring(const pcre *\fIcode\fR,  
2445  .ti +5n  .ti +5n
2446  .B const char *\fIsubject\fR, int *\fIovector\fR,  .B const char *\fIsubject\fP, int *\fIovector\fP,
2447  .ti +5n  .ti +5n
2448  .B int \fIstringcount\fR, const char *\fIstringname\fR,  .B int \fIstringcount\fP, const char *\fIstringname\fP,
2449  .ti +5n  .ti +5n
2450  .B const char **\fIstringptr\fR);  .B const char **\fIstringptr\fP);
2451  .PP  .PP
2452  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.
2453  can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the  For example, for this pattern
2454  compiled pattern, and the second is the name. For example, for this pattern  .sp
2455      (a+)b(?<xxx>\ed+)...
2456    ab(?<xxx>\\d+)...  .sp
2457    the number of the subpattern called "xxx" is 2. If the name is known to be
2458  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
2459  extract the substring directly, or use one of the functions described in the  calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2460  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
2461  whole job.  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2462    that name.
2463  Most of the arguments of \fIpcre_copy_named_substring()\fR and  .P
2464  \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
2465  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
2466  differences.  two functions that do the whole job.
2467    .P
2468    Most of the arguments of \fBpcre_copy_named_substring()\fP and
2469    \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2470    functions that extract by number. As these are described in the previous
2471    section, they are not re-described here. There are just two differences:
2472    .P
2473  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
2474  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
2475  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
2476  translation table.  translation table.
2477    .P
2478  These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2479  then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2480  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2481    the behaviour may not be what you want (see the next section).
2482  .in 0  .P
2483  Last updated: 09 December 2003  \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2484  .br  subpatterns with the same number, as described in the
2485  Copyright (c) 1997-2003 University of Cambridge.  .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2486    .\" </a>
2487    section on duplicate subpattern numbers
2488    .\"
2489    in the
2490    .\" HREF
2491    \fBpcrepattern\fP
2492    .\"
2493    page, you cannot use names to distinguish the different subpatterns, because
2494    names are not included in the compiled code. The matching process uses only
2495    numbers. For this reason, the use of different names for subpatterns of the
2496    same number causes an error at compile time.
2497    .
2498    .
2499    .SH "DUPLICATE SUBPATTERN NAMES"
2500    .rs
2501    .sp
2502    .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2503    .ti +5n
2504    .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2505    .PP
2506    When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2507    are not required to be unique. (Duplicate names are always allowed for
2508    subpatterns with the same number, created by using the (?| feature. Indeed, if
2509    such subpatterns are named, they are required to use the same names.)
2510    .P
2511    Normally, patterns with duplicate names are such that in any one match, only
2512    one of the named subpatterns participates. An example is shown in the
2513    .\" HREF
2514    \fBpcrepattern\fP
2515    .\"
2516    documentation.
2517    .P
2518    When duplicates are present, \fBpcre_copy_named_substring()\fP and
2519    \fBpcre_get_named_substring()\fP return the first substring corresponding to
2520    the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2521    returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2522    returns one of the numbers that are associated with the name, but it is not
2523    defined which it is.
2524    .P
2525    If you want to get full details of all captured substrings for a given name,
2526    you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2527    argument is the compiled pattern, and the second is the name. The third and
2528    fourth are pointers to variables which are updated by the function. After it
2529    has run, they point to the first and last entries in the name-to-number table
2530    for the given name. The function itself returns the length of each entry, or
2531    PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2532    described above in the section entitled \fIInformation about a pattern\fP
2533    .\" HTML <a href="#infoaboutpattern">
2534    .\" </a>
2535    above.
2536    .\"
2537    Given all the relevant entries for the name, you can extract each of their
2538    numbers, and hence the captured data, if any.
2539    .
2540    .
2541    .SH "FINDING ALL POSSIBLE MATCHES"
2542    .rs
2543    .sp
2544    The traditional matching function uses a similar algorithm to Perl, which stops
2545    when it finds the first match, starting at a given point in the subject. If you
2546    want to find all possible matches, or the longest possible match, consider
2547    using the alternative matching function (see below) instead. If you cannot use
2548    the alternative function, but still need to find all possible matches, you
2549    can kludge it up by making use of the callout facility, which is described in
2550    the
2551    .\" HREF
2552    \fBpcrecallout\fP
2553    .\"
2554    documentation.
2555    .P
2556    What you have to do is to insert a callout right at the end of the pattern.
2557    When your callout function is called, extract and save the current matched
2558    substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2559    other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2560    will yield PCRE_ERROR_NOMATCH.
2561    .
2562    .
2563    .SH "OBTAINING AN ESTIMATE OF STACK USAGE"
2564    .rs
2565    .sp
2566    Matching certain patterns using \fBpcre_exec()\fP can use a lot of process
2567    stack, which in certain environments can be rather limited in size. Some users
2568    find it helpful to have an estimate of the amount of stack that is used by
2569    \fBpcre_exec()\fP, to help them set recursion limits, as described in the
2570    .\" HREF
2571    \fBpcrestack\fP
2572    .\"
2573    documentation. The estimate that is output by \fBpcretest\fP when called with
2574    the \fB-m\fP and \fB-C\fP options is obtained by calling \fBpcre_exec\fP with
2575    the values NULL, NULL, NULL, -999, and -999 for its first five arguments.
2576    .P
2577    Normally, if its first argument is NULL, \fBpcre_exec()\fP immediately returns
2578    the negative error code PCRE_ERROR_NULL, but with this special combination of
2579    arguments, it returns instead a negative number whose absolute value is the
2580    approximate stack frame size in bytes. (A negative number is used so that it is
2581    clear that no match has happened.) The value is approximate because in some
2582    cases, recursive calls to \fBpcre_exec()\fP occur when there are one or two
2583    additional variables on the stack.
2584    .P
2585    If PCRE has been compiled to use the heap instead of the stack for recursion,
2586    the value returned is the size of each block that is obtained from the heap.
2587    .
2588    .
2589    .\" HTML <a name="dfamatch"></a>
2590    .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
2591    .rs
2592    .sp
2593    .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2594    .ti +5n
2595    .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2596    .ti +5n
2597    .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2598    .ti +5n
2599    .B int *\fIworkspace\fP, int \fIwscount\fP);
2600    .P
2601    The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2602    a compiled pattern, using a matching algorithm that scans the subject string
2603    just once, and does not backtrack. This has different characteristics to the
2604    normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2605    patterns are not supported. Nevertheless, there are times when this kind of
2606    matching can be useful. For a discussion of the two matching algorithms, and a
2607    list of features that \fBpcre_dfa_exec()\fP does not support, see the
2608    .\" HREF
2609    \fBpcrematching\fP
2610    .\"
2611    documentation.
2612    .P
2613    The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2614    \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2615    different way, and this is described below. The other common arguments are used
2616    in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2617    here.
2618    .P
2619    The two additional arguments provide workspace for the function. The workspace
2620    vector should contain at least 20 elements. It is used for keeping track of
2621    multiple paths through the pattern tree. More workspace will be needed for
2622    patterns and subjects where there are a lot of potential matches.
2623    .P
2624    Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2625    .sp
2626      int rc;
2627      int ovector[10];
2628      int wspace[20];
2629      rc = pcre_dfa_exec(
2630        re,             /* result of pcre_compile() */
2631        NULL,           /* we didn't study the pattern */
2632        "some string",  /* the subject string */
2633        11,             /* the length of the subject string */
2634        0,              /* start at offset 0 in the subject */
2635        0,              /* default options */
2636        ovector,        /* vector of integers for substring information */
2637        10,             /* number of elements (NOT size in bytes) */
2638        wspace,         /* working space vector */
2639        20);            /* number of elements (NOT size in bytes) */
2640    .
2641    .SS "Option bits for \fBpcre_dfa_exec()\fP"
2642    .rs
2643    .sp
2644    The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2645    zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2646    PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2647    PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
2648    PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
2649    All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2650    so their description is not repeated here.
2651    .sp
2652      PCRE_PARTIAL_HARD
2653      PCRE_PARTIAL_SOFT
2654    .sp
2655    These have the same general effect as they do for \fBpcre_exec()\fP, but the
2656    details are slightly different. When PCRE_PARTIAL_HARD is set for
2657    \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2658    is reached and there is still at least one matching possibility that requires
2659    additional characters. This happens even if some complete matches have also
2660    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2661    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2662    there have been no complete matches, but there is still at least one matching
2663    possibility. The portion of the string that was inspected when the longest
2664    partial match was found is set as the first matching string in both cases.
2665    There is a more detailed discussion of partial and multi-segment matching, with
2666    examples, in the
2667    .\" HREF
2668    \fBpcrepartial\fP
2669    .\"
2670    documentation.
2671    .sp
2672      PCRE_DFA_SHORTEST
2673    .sp
2674    Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2675    soon as it has found one match. Because of the way the alternative algorithm
2676    works, this is necessarily the shortest possible match at the first possible
2677    matching point in the subject string.
2678    .sp
2679      PCRE_DFA_RESTART
2680    .sp
2681    When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2682    again, with additional subject characters, and have it continue with the same
2683    match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2684    \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2685    before because data about the match so far is left in them after a partial
2686    match. There is more discussion of this facility in the
2687    .\" HREF
2688    \fBpcrepartial\fP
2689    .\"
2690    documentation.
2691    .
2692    .
2693    .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2694    .rs
2695    .sp
2696    When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2697    substring in the subject. Note, however, that all the matches from one run of
2698    the function start at the same point in the subject. The shorter matches are
2699    all initial substrings of the longer matches. For example, if the pattern
2700    .sp
2701      <.*>
2702    .sp
2703    is matched against the string
2704    .sp
2705      This is <something> <something else> <something further> no more
2706    .sp
2707    the three matched strings are
2708    .sp
2709      <something>
2710      <something> <something else>
2711      <something> <something else> <something further>
2712    .sp
2713    On success, the yield of the function is a number greater than zero, which is
2714    the number of matched substrings. The substrings themselves are returned in
2715    \fIovector\fP. Each string uses two elements; the first is the offset to the
2716    start, and the second is the offset to the end. In fact, all the strings have
2717    the same start offset. (Space could have been saved by giving this only once,
2718    but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2719    returns data, even though the meaning of the strings is different.)
2720    .P
2721    The strings are returned in reverse order of length; that is, the longest
2722    matching string is given first. If there were too many matches to fit into
2723    \fIovector\fP, the yield of the function is zero, and the vector is filled with
2724    the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2725    the entire \fIovector\fP for returning matched strings.
2726    .
2727    .
2728    .SS "Error returns from \fBpcre_dfa_exec()\fP"
2729    .rs
2730    .sp
2731    The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2732    Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2733    described
2734    .\" HTML <a href="#errorlist">
2735    .\" </a>
2736    above.
2737    .\"
2738    There are in addition the following errors that are specific to
2739    \fBpcre_dfa_exec()\fP:
2740    .sp
2741      PCRE_ERROR_DFA_UITEM      (-16)
2742    .sp
2743    This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2744    that it does not support, for instance, the use of \eC or a back reference.
2745    .sp
2746      PCRE_ERROR_DFA_UCOND      (-17)
2747    .sp
2748    This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2749    uses a back reference for the condition, or a test for recursion in a specific
2750    group. These are not supported.
2751    .sp
2752      PCRE_ERROR_DFA_UMLIMIT    (-18)
2753    .sp
2754    This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2755    block that contains a setting of the \fImatch_limit\fP or
2756    \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2757    meaningless for DFA matching).
2758    .sp
2759      PCRE_ERROR_DFA_WSSIZE     (-19)
2760    .sp
2761    This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2762    \fIworkspace\fP vector.
2763    .sp
2764      PCRE_ERROR_DFA_RECURSE    (-20)
2765    .sp
2766    When a recursive subpattern is processed, the matching function calls itself
2767    recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2768    error is given if the output vector is not large enough. This should be
2769    extremely rare, as a vector of size 1000 is used.
2770    .sp
2771      PCRE_ERROR_DFA_BADRESTART (-30)
2772    .sp
2773    When \fBpcre_dfa_exec()\fP is called with the \fBPCRE_DFA_RESTART\fP option,
2774    some plausibility checks are made on the contents of the workspace, which
2775    should contain data about the previous partial match. If any of these checks
2776    fail, this error is given.
2777    .
2778    .
2779    .SH "SEE ALSO"
2780    .rs
2781    .sp
2782    \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3),
2783    \fBpcrecpp(3)\fP(3), \fBpcrematching\fP(3), \fBpcrepartial\fP(3),
2784    \fBpcreposix\fP(3), \fBpcreprecompile\fP(3), \fBpcresample\fP(3),
2785    \fBpcrestack\fP(3).
2786    .
2787    .
2788    .SH AUTHOR
2789    .rs
2790    .sp
2791    .nf
2792    Philip Hazel
2793    University Computing Service
2794    Cambridge CB2 3QH, England.
2795    .fi
2796    .
2797    .
2798    .SH REVISION
2799    .rs
2800    .sp
2801    .nf
2802    Last updated: 29 October 2012
2803    Copyright (c) 1997-2012 University of Cambridge.
2804    .fi

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