/[pcre]/code/trunk/doc/pcreapi.3
ViewVC logotype

Diff of /code/trunk/doc/pcreapi.3

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 99 by ph10, Tue Mar 6 12:27:42 2007 UTC revision 461 by ph10, Mon Oct 5 10:59:35 2009 UTC
# Line 135  Applications can use these to include su Line 135  Applications can use these to include su
135  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,  The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
136  and \fBpcre_exec()\fP are used for compiling and matching regular expressions  and \fBpcre_exec()\fP are used for compiling and matching regular expressions
137  in a Perl-compatible manner. A sample program that demonstrates the simplest  in a Perl-compatible manner. A sample program that demonstrates the simplest
138  way of using them is provided in the file called \fIpcredemo.c\fP in the source  way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
139  distribution. The  source distribution. A listing of this program is given in the
140    .\" HREF
141    \fBpcredemo\fP
142    .\"
143    documentation, and the
144  .\" HREF  .\" HREF
145  \fBpcresample\fP  \fBpcresample\fP
146  .\"  .\"
147  documentation describes how to run it.  documentation describes how to compile and run it.
148  .P  .P
149  A second matching function, \fBpcre_dfa_exec()\fP, which is not  A second matching function, \fBpcre_dfa_exec()\fP, which is not
150  Perl-compatible, is also provided. This uses a different algorithm for the  Perl-compatible, is also provided. This uses a different algorithm for the
151  matching. The alternative algorithm finds all possible matches (at a given  matching. The alternative algorithm finds all possible matches (at a given
152  point in the subject), and scans the subject just once. However, this algorithm  point in the subject), and scans the subject just once (unless there are
153  does not return captured substrings. A description of the two matching  lookbehind assertions). However, this algorithm does not return captured
154  algorithms and their advantages and disadvantages is given in the  substrings. A description of the two matching algorithms and their advantages
155    and disadvantages is given in the
156  .\" HREF  .\" HREF
157  \fBpcrematching\fP  \fBpcrematching\fP
158  .\"  .\"
# Line 218  points during a matching operation. Deta Line 223  points during a matching operation. Deta
223  documentation.  documentation.
224  .  .
225  .  .
226    .\" HTML <a name="newlines"></a>
227  .SH NEWLINES  .SH NEWLINES
228  .rs  .rs
229  .sp  .sp
230  PCRE supports four different conventions for indicating line breaks in  PCRE supports five different conventions for indicating line breaks in
231  strings: a single CR (carriage return) character, a single LF (linefeed)  strings: a single CR (carriage return) character, a single LF (linefeed)
232  character, the two-character sequence CRLF, or any Unicode newline sequence.  character, the two-character sequence CRLF, any of the three preceding, or any
233  The Unicode newline sequences are the three just mentioned, plus the single  Unicode newline sequence. The Unicode newline sequences are the three just
234  characters VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line,  mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
235  U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).  U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
236    (paragraph separator, U+2029).
237  .P  .P
238  Each of the first three conventions is used by at least one operating system as  Each of the first three conventions is used by at least one operating system as
239  its standard newline sequence. When PCRE is built, a default can be specified.  its standard newline sequence. When PCRE is built, a default can be specified.
# Line 234  The default default is LF, which is the Line 241  The default default is LF, which is the
241  default can be overridden, either when a pattern is compiled, or when it is  default can be overridden, either when a pattern is compiled, or when it is
242  matched.  matched.
243  .P  .P
244    At compile time, the newline convention can be specified by the \fIoptions\fP
245    argument of \fBpcre_compile()\fP, or it can be specified by special text at the
246    start of the pattern itself; this overrides any other settings. See the
247    .\" HREF
248    \fBpcrepattern\fP
249    .\"
250    page for details of the special character sequences.
251    .P
252  In the PCRE documentation the word "newline" is used to mean "the character or  In the PCRE documentation the word "newline" is used to mean "the character or
253  pair of characters that indicate a line break". The choice of newline  pair of characters that indicate a line break". The choice of newline
254  convention affects the handling of the dot, circumflex, and dollar  convention affects the handling of the dot, circumflex, and dollar
255  metacharacters, the handling of #-comments in /x mode, and, when CRLF is a  metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
256  recognized line ending sequence, the match position advancement for a  recognized line ending sequence, the match position advancement for a
257  non-anchored pattern. The choice of newline convention does not affect the  non-anchored pattern. There is more detail about this in the
258  interpretation of the \en or \er escape sequences.  .\" HTML <a href="#execoptions">
259    .\" </a>
260    section on \fBpcre_exec()\fP options
261    .\"
262    below.
263    .P
264    The choice of newline convention does not affect the interpretation of
265    the \en or \er escape sequences, nor does it affect what \eR matches, which is
266    controlled in a similar way, but by separate options.
267  .  .
268  .  .
269  .SH MULTITHREADING  .SH MULTITHREADING
# Line 264  which it was compiled. Details are given Line 287  which it was compiled. Details are given
287  .\" HREF  .\" HREF
288  \fBpcreprecompile\fP  \fBpcreprecompile\fP
289  .\"  .\"
290  documentation.  documentation. However, compiling a regular expression with one version of PCRE
291    for use with a different version is not guaranteed to work and may cause
292    crashes.
293  .  .
294  .  .
295  .SH "CHECKING BUILD-TIME OPTIONS"  .SH "CHECKING BUILD-TIME OPTIONS"
# Line 297  properties is available; otherwise it is Line 322  properties is available; otherwise it is
322  .sp  .sp
323  The output is an integer whose value specifies the default character sequence  The output is an integer whose value specifies the default character sequence
324  that is recognized as meaning "newline". The four values that are supported  that is recognized as meaning "newline". The four values that are supported
325  are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY. The default should  are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
326  normally be the standard sequence for your operating system.  Though they are derived from ASCII, the same values are returned in EBCDIC
327    environments. The default should normally correspond to the standard sequence
328    for your operating system.
329    .sp
330      PCRE_CONFIG_BSR
331    .sp
332    The output is an integer whose value indicates what character sequences the \eR
333    escape sequence matches by default. A value of 0 means that \eR matches any
334    Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
335    or CRLF. The default can be overridden when a pattern is compiled or matched.
336  .sp  .sp
337    PCRE_CONFIG_LINK_SIZE    PCRE_CONFIG_LINK_SIZE
338  .sp  .sp
# Line 320  documentation. Line 354  documentation.
354  .sp  .sp
355    PCRE_CONFIG_MATCH_LIMIT    PCRE_CONFIG_MATCH_LIMIT
356  .sp  .sp
357  The output is an integer that gives the default limit for the number of  The output is a long integer that gives the default limit for the number of
358  internal matching function calls in a \fBpcre_exec()\fP execution. Further  internal matching function calls in a \fBpcre_exec()\fP execution. Further
359  details are given with \fBpcre_exec()\fP below.  details are given with \fBpcre_exec()\fP below.
360  .sp  .sp
361    PCRE_CONFIG_MATCH_LIMIT_RECURSION    PCRE_CONFIG_MATCH_LIMIT_RECURSION
362  .sp  .sp
363  The output is an integer that gives the default limit for the depth of  The output is a long integer that gives the default limit for the depth of
364  recursion when calling the internal matching function in a \fBpcre_exec()\fP  recursion when calling the internal matching function in a \fBpcre_exec()\fP
365  execution. Further details are given with \fBpcre_exec()\fP below.  execution. Further details are given with \fBpcre_exec()\fP below.
366  .sp  .sp
# Line 361  avoiding the use of the stack. Line 395  avoiding the use of the stack.
395  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be  Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
396  called to compile a pattern into an internal form. The only difference between  called to compile a pattern into an internal form. The only difference between
397  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,  the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
398  \fIerrorcodeptr\fP, via which a numerical error code can be returned.  \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
399    too much repetition, we refer just to \fBpcre_compile()\fP below, but the
400    information applies equally to \fBpcre_compile2()\fP.
401  .P  .P
402  The pattern is a C string terminated by a binary zero, and is passed in the  The pattern is a C string terminated by a binary zero, and is passed in the
403  \fIpattern\fP argument. A pointer to a single block of memory that is obtained  \fIpattern\fP argument. A pointer to a single block of memory that is obtained
# Line 377  argument, which is an address (see below Line 413  argument, which is an address (see below
413  .P  .P
414  The \fIoptions\fP argument contains various bit settings that affect the  The \fIoptions\fP argument contains various bit settings that affect the
415  compilation. It should be zero if no options are required. The available  compilation. It should be zero if no options are required. The available
416  options are described below. Some of them, in particular, those that are  options are described below. Some of them (in particular, those that are
417  compatible with Perl, can also be set and unset from within the pattern (see  compatible with Perl, but some others as well) can also be set and unset from
418  the detailed description in the  within the pattern (see the detailed description in the
419  .\" HREF  .\" HREF
420  \fBpcrepattern\fP  \fBpcrepattern\fP
421  .\"  .\"
422  documentation). For these options, the contents of the \fIoptions\fP argument  documentation). For those options that can be different in different parts of
423  specifies their initial settings at the start of compilation and execution. The  the pattern, the contents of the \fIoptions\fP argument specifies their
424  PCRE_ANCHORED and PCRE_NEWLINE_\fIxxx\fP options can be set at the time of  settings at the start of compilation and execution. The PCRE_ANCHORED,
425  matching as well as at compile time.  PCRE_BSR_\fIxxx\fP, and PCRE_NEWLINE_\fIxxx\fP options can be set at the time
426    of matching as well as at compile time.
427  .P  .P
428  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.  If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
429  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns  Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
430  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual  NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
431  error message. This is a static string that is part of the library. You must  error message. This is a static string that is part of the library. You must
432  not try to free it. The offset from the start of the pattern to the character  not try to free it. The byte offset from the start of the pattern to the
433  where the error was discovered is placed in the variable pointed to by  character that was being processed when the error was discovered is placed in
434  \fIerroffset\fP, which must not be NULL. If it is, an immediate error is given.  the variable pointed to by \fIerroffset\fP, which must not be NULL. If it is,
435    an immediate error is given. Some errors are not detected until checks are
436    carried out when the whole pattern has been scanned; in this case the offset is
437    set to the end of the pattern.
438  .P  .P
439  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the  If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
440  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is  \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
# Line 441  facility, see the Line 481  facility, see the
481  .\"  .\"
482  documentation.  documentation.
483  .sp  .sp
484      PCRE_BSR_ANYCRLF
485      PCRE_BSR_UNICODE
486    .sp
487    These options (which are mutually exclusive) control what the \eR escape
488    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
489    match any Unicode newline sequence. The default is specified when PCRE is
490    built. It can be overridden from within the pattern, or by setting an option
491    when a compiled pattern is matched.
492    .sp
493    PCRE_CASELESS    PCRE_CASELESS
494  .sp  .sp
495  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
# Line 513  If this option is set, an unanchored pat Line 562  If this option is set, an unanchored pat
562  the first newline in the subject string, though the matched text may continue  the first newline in the subject string, though the matched text may continue
563  over the newline.  over the newline.
564  .sp  .sp
565      PCRE_JAVASCRIPT_COMPAT
566    .sp
567    If this option is set, PCRE's behaviour is changed in some ways so that it is
568    compatible with JavaScript rather than Perl. The changes are as follows:
569    .P
570    (1) A lone closing square bracket in a pattern causes a compile-time error,
571    because this is illegal in JavaScript (by default it is treated as a data
572    character). Thus, the pattern AB]CD becomes illegal when this option is set.
573    .P
574    (2) At run time, a back reference to an unset subpattern group matches an empty
575    string (by default this causes the current matching alternative to fail). A
576    pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
577    an "a" in the subject), whereas it fails by default, for Perl compatibility.
578    .sp
579    PCRE_MULTILINE    PCRE_MULTILINE
580  .sp  .sp
581  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
# Line 532  occurrences of ^ or $ in a pattern, sett Line 595  occurrences of ^ or $ in a pattern, sett
595    PCRE_NEWLINE_CR    PCRE_NEWLINE_CR
596    PCRE_NEWLINE_LF    PCRE_NEWLINE_LF
597    PCRE_NEWLINE_CRLF    PCRE_NEWLINE_CRLF
598      PCRE_NEWLINE_ANYCRLF
599    PCRE_NEWLINE_ANY    PCRE_NEWLINE_ANY
600  .sp  .sp
601  These options override the default newline definition that was chosen when PCRE  These options override the default newline definition that was chosen when PCRE
602  was built. Setting the first or the second specifies that a newline is  was built. Setting the first or the second specifies that a newline is
603  indicated by a single character (CR or LF, respectively). Setting  indicated by a single character (CR or LF, respectively). Setting
604  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
605  CRLF sequence. Setting PCRE_NEWLINE_ANY specifies that any Unicode newline  CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
606  sequence should be recognized. The Unicode newline sequences are the three just  preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
607  mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,  that any Unicode newline sequence should be recognized. The Unicode newline
608  U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS  sequences are the three just mentioned, plus the single characters VT (vertical
609  (paragraph separator, U+2029). The last two are recognized only in UTF-8 mode.  tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
610    separator, U+2028), and PS (paragraph separator, U+2029). The last two are
611    recognized only in UTF-8 mode.
612  .P  .P
613  The newline setting in the options word uses three bits that are treated  The newline setting in the options word uses three bits that are treated
614  as a number, giving eight possibilities. Currently only five are used (default  as a number, giving eight possibilities. Currently only six are used (default
615  plus the four values above). This means that if you set more than one newline  plus the five values above). This means that if you set more than one newline
616  option, the combination may or may not be sensible. For example,  option, the combination may or may not be sensible. For example,
617  PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but  PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
618  other combinations yield unused numbers and cause an error.  other combinations may yield unused numbers and cause an error.
619  .P  .P
620  The only time that a line break is specially recognized when compiling a  The only time that a line break is specially recognized when compiling a
621  pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character  pattern is if PCRE_EXTENDED is set, and an unescaped # outside a character
# Line 595  page. Line 661  page.
661    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
662  .sp  .sp
663  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
664  automatically checked. If an invalid UTF-8 sequence of bytes is found,  automatically checked. There is a discussion about the
665  \fBpcre_compile()\fP returns an error. If you already know that your pattern is  .\" HTML <a href="pcre.html#utf8strings">
666  valid, and you want to skip this check for performance reasons, you can set the  .\" </a>
667  PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid  validity of UTF-8 strings
668  UTF-8 string as a pattern is undefined. It may cause your program to crash.  .\"
669  Note that this option can also be passed to \fBpcre_exec()\fP and  in the main
670  \fBpcre_dfa_exec()\fP, to suppress the UTF-8 validity checking of subject  .\" HREF
671  strings.  \fBpcre\fP
672    .\"
673    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
674    returns an error. If you already know that your pattern is valid, and you want
675    to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
676    option. When it is set, the effect of passing an invalid UTF-8 string as a
677    pattern is undefined. It may cause your program to crash. Note that this option
678    can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
679    the UTF-8 validity checking of subject strings.
680  .  .
681  .  .
682  .SH "COMPILATION ERROR CODES"  .SH "COMPILATION ERROR CODES"
# Line 625  out of use. To avoid confusion, they hav Line 699  out of use. To avoid confusion, they hav
699     9  nothing to repeat     9  nothing to repeat
700    10  [this code is not in use]    10  [this code is not in use]
701    11  internal error: unexpected repeat    11  internal error: unexpected repeat
702    12  unrecognized character after (?    12  unrecognized character after (? or (?-
703    13  POSIX named classes are supported only within a class    13  POSIX named classes are supported only within a class
704    14  missing )    14  missing )
705    15  reference to non-existent subpattern    15  reference to non-existent subpattern
# Line 633  out of use. To avoid confusion, they hav Line 707  out of use. To avoid confusion, they hav
707    17  unknown option bit(s) set    17  unknown option bit(s) set
708    18  missing ) after comment    18  missing ) after comment
709    19  [this code is not in use]    19  [this code is not in use]
710    20  regular expression too large    20  regular expression is too large
711    21  failed to get memory    21  failed to get memory
712    22  unmatched parentheses    22  unmatched parentheses
713    23  internal error: code overflow    23  internal error: code overflow
# Line 642  out of use. To avoid confusion, they hav Line 716  out of use. To avoid confusion, they hav
716    26  malformed number or name after (?(    26  malformed number or name after (?(
717    27  conditional group contains more than two branches    27  conditional group contains more than two branches
718    28  assertion expected after (?(    28  assertion expected after (?(
719    29  (?R or (?digits must be followed by )    29  (?R or (?[+-]digits must be followed by )
720    30  unknown POSIX class name    30  unknown POSIX class name
721    31  POSIX collating elements are not supported    31  POSIX collating elements are not supported
722    32  this version of PCRE is not compiled with PCRE_UTF8 support    32  this version of PCRE is not compiled with PCRE_UTF8 support
# Line 662  out of use. To avoid confusion, they hav Line 736  out of use. To avoid confusion, they hav
736    46  malformed \eP or \ep sequence    46  malformed \eP or \ep sequence
737    47  unknown property name after \eP or \ep    47  unknown property name after \eP or \ep
738    48  subpattern name is too long (maximum 32 characters)    48  subpattern name is too long (maximum 32 characters)
739    49  too many named subpatterns (maximum 10,000)    49  too many named subpatterns (maximum 10000)
740    50  repeated subpattern is too long    50  [this code is not in use]
741    51  octal value is greater than \e377 (not in UTF-8 mode)    51  octal value is greater than \e377 (not in UTF-8 mode)
742    52  internal error: overran compiling workspace    52  internal error: overran compiling workspace
743    53  internal error: previously-checked referenced subpattern not found    53  internal error: previously-checked referenced subpattern not found
744    54  DEFINE group contains more than one branch    54  DEFINE group contains more than one branch
745    55  repeating a DEFINE group is not allowed    55  repeating a DEFINE group is not allowed
746    56  inconsistent NEWLINE options"    56  inconsistent NEWLINE options
747      57  \eg is not followed by a braced, angle-bracketed, or quoted
748            name/number or by a plain number
749      58  a numbered reference must not be zero
750      59  (*VERB) with an argument is not supported
751      60  (*VERB) not recognized
752      61  number is too big
753      62  subpattern name expected
754      63  digit expected after (?+
755      64  ] is an invalid data character in JavaScript compatibility mode
756    .sp
757    The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
758    be used if the limits were changed when PCRE was built.
759  .  .
760  .  .
761  .SH "STUDYING A PATTERN"  .SH "STUDYING A PATTERN"
# Line 688  help speed up matching, \fBpcre_study()\ Line 774  help speed up matching, \fBpcre_study()\
774  results of the study.  results of the study.
775  .P  .P
776  The returned value from \fBpcre_study()\fP can be passed directly to  The returned value from \fBpcre_study()\fP can be passed directly to
777  \fBpcre_exec()\fP. However, a \fBpcre_extra\fP block also contains other  \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
778  fields that can be set by the caller before the block is passed; these are  also contains other fields that can be set by the caller before the block is
779  described  passed; these are described
780  .\" HTML <a href="#extradata">  .\" HTML <a href="#extradata">
781  .\" </a>  .\" </a>
782  below  below
783  .\"  .\"
784  in the section on matching a pattern.  in the section on matching a pattern.
785  .P  .P
786  If studying the pattern does not produce any additional information  If studying the pattern does not produce any useful information,
787  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program  \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
788  wants to pass any of the other fields to \fBpcre_exec()\fP, it must set up its  wants to pass any of the other fields to \fBpcre_exec()\fP or
789  own \fBpcre_extra\fP block.  \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
790  .P  .P
791  The second argument of \fBpcre_study()\fP contains option bits. At present, no  The second argument of \fBpcre_study()\fP contains option bits. At present, no
792  options are defined, and this argument should always be zero.  options are defined, and this argument should always be zero.
# Line 720  This is a typical call to \fBpcre_study\ Line 806  This is a typical call to \fBpcre_study\
806      0,              /* no options exist */      0,              /* no options exist */
807      &error);        /* set to NULL or points to a message */      &error);        /* set to NULL or points to a message */
808  .sp  .sp
809  At present, studying a pattern is useful only for non-anchored patterns that do  Studying a pattern does two things: first, a lower bound for the length of
810  not have a single fixed starting character. A bitmap of possible starting  subject string that is needed to match the pattern is computed. This does not
811  bytes is created.  mean that there are any strings of that length that match, but it does
812    guarantee that no shorter strings match. The value is used by
813    \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
814    match strings that are shorter than the lower bound. You can find out the value
815    in a calling program via the \fBpcre_fullinfo()\fP function.
816    .P
817    Studying a pattern is also useful for non-anchored patterns that do not have a
818    single fixed starting character. A bitmap of possible starting bytes is
819    created. This speeds up finding a position in the subject at which to start
820    matching.
821  .  .
822  .  .
823  .\" HTML <a name="localesupport"></a>  .\" HTML <a name="localesupport"></a>
824  .SH "LOCALE SUPPORT"  .SH "LOCALE SUPPORT"
825  .rs  .rs
826  .sp  .sp
827  PCRE handles caseless matching, and determines whether characters are letters  PCRE handles caseless matching, and determines whether characters are letters,
828  digits, or whatever, by reference to a set of tables, indexed by character  digits, or whatever, by reference to a set of tables, indexed by character
829  value. When running in UTF-8 mode, this applies only to characters with codes  value. When running in UTF-8 mode, this applies only to characters with codes
830  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but  less than 128. Higher-valued codes never match escapes such as \ew or \ed, but
831  can be tested with \ep if PCRE is built with Unicode character property  can be tested with \ep if PCRE is built with Unicode character property
832  support. The use of locales with Unicode is discouraged.  support. The use of locales with Unicode is discouraged. If you are handling
833  .P  characters with codes greater than 128, you should either use UTF-8 and
834  An internal set of tables is created in the default C locale when PCRE is  Unicode, or use locales, but not try to mix the two.
835  built. This is used when the final argument of \fBpcre_compile()\fP is NULL,  .P
836  and is sufficient for many applications. An alternative set of tables can,  PCRE contains an internal set of tables that are used when the final argument
837  however, be supplied. These may be created in a different locale from the  of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
838  default. As more and more applications change to using Unicode, the need for  Normally, the internal tables recognize only ASCII characters. However, when
839  this locale support is expected to die away.  PCRE is built, it is possible to cause the internal tables to be rebuilt in the
840    default "C" locale of the local system, which may cause them to be different.
841    .P
842    The internal tables can always be overridden by tables supplied by the
843    application that calls PCRE. These may be created in a different locale from
844    the default. As more and more applications change to using Unicode, the need
845    for this locale support is expected to die away.
846  .P  .P
847  External tables are built by calling the \fBpcre_maketables()\fP function,  External tables are built by calling the \fBpcre_maketables()\fP function,
848  which has no arguments, in the relevant locale. The result can then be passed  which has no arguments, in the relevant locale. The result can then be passed
# Line 754  the following code could be used: Line 855  the following code could be used:
855    tables = pcre_maketables();    tables = pcre_maketables();
856    re = pcre_compile(..., tables);    re = pcre_compile(..., tables);
857  .sp  .sp
858    The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
859    are using Windows, the name for the French locale is "french".
860    .P
861  When \fBpcre_maketables()\fP runs, the tables are built in memory that is  When \fBpcre_maketables()\fP runs, the tables are built in memory that is
862  obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure  obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
863  that the memory containing the tables remains available for as long as it is  that the memory containing the tables remains available for as long as it is
# Line 856  table indicating a fixed set of bytes fo Line 960  table indicating a fixed set of bytes fo
960  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
961  fourth argument should point to an \fBunsigned char *\fP variable.  fourth argument should point to an \fBunsigned char *\fP variable.
962  .sp  .sp
963      PCRE_INFO_HASCRORLF
964    .sp
965    Return 1 if the pattern contains any explicit matches for CR or LF characters,
966    otherwise 0. The fourth argument should point to an \fBint\fP variable. An
967    explicit match is either a literal CR or LF character, or \er or \en.
968    .sp
969      PCRE_INFO_JCHANGED
970    .sp
971    Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
972    0. The fourth argument should point to an \fBint\fP variable. (?J) and
973    (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
974    .sp
975    PCRE_INFO_LASTLITERAL    PCRE_INFO_LASTLITERAL
976  .sp  .sp
977  Return the value of the rightmost literal byte that must exist in any matched  Return the value of the rightmost literal byte that must exist in any matched
# Line 866  follows something of variable length. Fo Line 982  follows something of variable length. Fo
982  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value  /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
983  is -1.  is -1.
984  .sp  .sp
985      PCRE_INFO_MINLENGTH
986    .sp
987    If the pattern was studied and a minimum length for matching subject strings
988    was computed, its value is returned. Otherwise the returned value is -1. The
989    value is a number of characters, not bytes (this may be relevant in UTF-8
990    mode). The fourth argument should point to an \fBint\fP variable. A
991    non-negative value is a lower bound to the length of any matching string. There
992    may not be any strings of that length that do actually match, but every string
993    that does match is at least that long.
994    .sp
995    PCRE_INFO_NAMECOUNT    PCRE_INFO_NAMECOUNT
996    PCRE_INFO_NAMEENTRYSIZE    PCRE_INFO_NAMEENTRYSIZE
997    PCRE_INFO_NAMETABLE    PCRE_INFO_NAMETABLE
# Line 886  entry; both of these return an \fBint\fP Line 1012  entry; both of these return an \fBint\fP
1012  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
1013  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry  entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
1014  are the number of the capturing parenthesis, most significant byte first. The  are the number of the capturing parenthesis, most significant byte first. The
1015  rest of the entry is the corresponding name, zero terminated. The names are in  rest of the entry is the corresponding name, zero terminated.
1016  alphabetical order. When PCRE_DUPNAMES is set, duplicate names are in order of  .P
1017  their parentheses numbers. For example, consider the following pattern (assume  The names are in alphabetical order. Duplicate names may appear if (?| is used
1018  PCRE_EXTENDED is set, so white space - including newlines - is ignored):  to create multiple groups with the same number, as described in the
1019    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1020    .\" </a>
1021    section on duplicate subpattern numbers
1022    .\"
1023    in the
1024    .\" HREF
1025    \fBpcrepattern\fP
1026    .\"
1027    page. Duplicate names for subpatterns with different numbers are permitted only
1028    if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1029    table in the order in which they were found in the pattern. In the absence of
1030    (?| this is the order of increasing number; when (?| is used this is not
1031    necessarily the case because later subpatterns may have lower numbers.
1032    .P
1033    As a simple example of the name/number table, consider the following pattern
1034    (assume PCRE_EXTENDED is set, so white space - including newlines - is
1035    ignored):
1036  .sp  .sp
1037  .\" JOIN  .\" JOIN
1038    (?<date> (?<year>(\ed\ed)?\ed\ed) -    (?<date> (?<year>(\ed\ed)?\ed\ed) -
# Line 908  When writing code to extract data from n Line 1051  When writing code to extract data from n
1051  name-to-number map, remember that the length of the entries is likely to be  name-to-number map, remember that the length of the entries is likely to be
1052  different for each compiled pattern.  different for each compiled pattern.
1053  .sp  .sp
1054      PCRE_INFO_OKPARTIAL
1055    .sp
1056    Return 1 if the pattern can be used for partial matching with
1057    \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1058    \fBint\fP variable. From release 8.00, this always returns 1, because the
1059    restrictions that previously applied to partial matching have been lifted. The
1060    .\" HREF
1061    \fBpcrepartial\fP
1062    .\"
1063    documentation gives details of partial matching.
1064    .sp
1065    PCRE_INFO_OPTIONS    PCRE_INFO_OPTIONS
1066  .sp  .sp
1067  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
1068  argument should point to an \fBunsigned long int\fP variable. These option bits  argument should point to an \fBunsigned long int\fP variable. These option bits
1069  are those specified in the call to \fBpcre_compile()\fP, modified by any  are those specified in the call to \fBpcre_compile()\fP, modified by any
1070  top-level option settings within the pattern itself.  top-level option settings at the start of the pattern itself. In other words,
1071    they are the options that will be in force when matching starts. For example,
1072    if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1073    result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
1074  .P  .P
1075  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
1076  alternatives begin with one of the following:  alternatives begin with one of the following:
# Line 940  variable. Line 1097  variable.
1097  Return the size of the data block pointed to by the \fIstudy_data\fP field in  Return the size of the data block pointed to by the \fIstudy_data\fP field in
1098  a \fBpcre_extra\fP block. That is, it is the value that was passed to  a \fBpcre_extra\fP block. That is, it is the value that was passed to
1099  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data  \fBpcre_malloc()\fP when PCRE was getting memory into which to place the data
1100  created by \fBpcre_study()\fP. The fourth argument should point to a  created by \fBpcre_study()\fP. If \fBpcre_extra\fP is NULL, or there is no
1101    study data, zero is returned. The fourth argument should point to a
1102  \fBsize_t\fP variable.  \fBsize_t\fP variable.
1103  .  .
1104  .  .
# Line 1002  is different. (This seems a highly unlik Line 1160  is different. (This seems a highly unlik
1160  .P  .P
1161  The function \fBpcre_exec()\fP is called to match a subject string against a  The function \fBpcre_exec()\fP is called to match a subject string against a
1162  compiled pattern, which is passed in the \fIcode\fP argument. If the  compiled pattern, which is passed in the \fIcode\fP argument. If the
1163  pattern has been studied, the result of the study should be passed in the  pattern was studied, the result of the study should be passed in the
1164  \fIextra\fP argument. This function is the main matching facility of the  \fIextra\fP argument. This function is the main matching facility of the
1165  library, and it operates in a Perl-like manner. For specialist use there is  library, and it operates in a Perl-like manner. For specialist use there is
1166  also an alternative matching function, which is described  also an alternative matching function, which is described
# Line 1070  the block by setting the other fields an Line 1228  the block by setting the other fields an
1228  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a  The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1229  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,
1230  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
1231  classic example is the use of nested unlimited repeats.  classic example is a pattern that uses nested unlimited repeats.
1232  .P  .P
1233  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly  Internally, PCRE uses a function called \fBmatch()\fP which it calls repeatedly
1234  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the  (sometimes recursively). The limit set by \fImatch_limit\fP is imposed on the
# Line 1103  with a \fBpcre_extra\fP block in which \ Line 1261  with a \fBpcre_extra\fP block in which \
1261  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit  PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1262  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.  is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1263  .P  .P
1264  The \fIpcre_callout\fP field is used in conjunction with the "callout" feature,  The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1265  which is described in the  and is described in the
1266  .\" HREF  .\" HREF
1267  \fBpcrecallout\fP  \fBpcrecallout\fP
1268  .\"  .\"
# Line 1124  called. See the Line 1282  called. See the
1282  .\"  .\"
1283  documentation for a discussion of saving compiled patterns for later use.  documentation for a discussion of saving compiled patterns for later use.
1284  .  .
1285    .\" HTML <a name="execoptions"></a>
1286  .SS "Option bits for \fBpcre_exec()\fP"  .SS "Option bits for \fBpcre_exec()\fP"
1287  .rs  .rs
1288  .sp  .sp
1289  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1290  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1291  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1292    PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
1293    PCRE_PARTIAL_HARD.
1294  .sp  .sp
1295    PCRE_ANCHORED    PCRE_ANCHORED
1296  .sp  .sp
# Line 1138  matching position. If a pattern was comp Line 1299  matching position. If a pattern was comp
1299  to be anchored by virtue of its contents, it cannot be made unachored at  to be anchored by virtue of its contents, it cannot be made unachored at
1300  matching time.  matching time.
1301  .sp  .sp
1302      PCRE_BSR_ANYCRLF
1303      PCRE_BSR_UNICODE
1304    .sp
1305    These options (which are mutually exclusive) control what the \eR escape
1306    sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1307    match any Unicode newline sequence. These options override the choice that was
1308    made or defaulted when the pattern was compiled.
1309    .sp
1310    PCRE_NEWLINE_CR    PCRE_NEWLINE_CR
1311    PCRE_NEWLINE_LF    PCRE_NEWLINE_LF
1312    PCRE_NEWLINE_CRLF    PCRE_NEWLINE_CRLF
1313      PCRE_NEWLINE_ANYCRLF
1314    PCRE_NEWLINE_ANY    PCRE_NEWLINE_ANY
1315  .sp  .sp
1316  These options override the newline definition that was chosen or defaulted when  These options override the newline definition that was chosen or defaulted when
# Line 1148  the pattern was compiled. For details, s Line 1318  the pattern was compiled. For details, s
1318  \fBpcre_compile()\fP above. During matching, the newline choice affects the  \fBpcre_compile()\fP above. During matching, the newline choice affects the
1319  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter  behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1320  the way the match position is advanced after a match failure for an unanchored  the way the match position is advanced after a match failure for an unanchored
1321  pattern. When PCRE_NEWLINE_CRLF or PCRE_NEWLINE_ANY is set, and a match attempt  pattern.
1322  fails when the current position is at a CRLF sequence, the match position is  .P
1323  advanced by two characters instead of one, in other words, to after the CRLF.  When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
1324    match attempt for an unanchored pattern fails when the current position is at a
1325    CRLF sequence, and the pattern contains no explicit matches for CR or LF
1326    characters, the match position is advanced by two characters instead of one, in
1327    other words, to after the CRLF.
1328    .P
1329    The above rule is a compromise that makes the most common cases work as
1330    expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1331    set), it does not match the string "\er\enA" because, after failing at the
1332    start, it skips both the CR and the LF before retrying. However, the pattern
1333    [\er\en]A does match that string, because it contains an explicit CR or LF
1334    reference, and so advances only by one character after the first failure.
1335    .P
1336    An explicit match for CR of LF is either a literal appearance of one of those
1337    characters, or one of the \er or \en escape sequences. Implicit matches such as
1338    [^X] do not count, nor does \es (which includes CR and LF in the characters
1339    that it matches).
1340    .P
1341    Notwithstanding the above, anomalous effects may still occur when CRLF is a
1342    valid newline sequence and explicit \er or \en escapes appear in the pattern.
1343  .sp  .sp
1344    PCRE_NOTBOL    PCRE_NOTBOL
1345  .sp  .sp
# Line 1176  match the empty string, the entire match Line 1365  match the empty string, the entire match
1365  .sp  .sp
1366    a?b?    a?b?
1367  .sp  .sp
1368  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
1369  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
1370  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".
1371  .P  .sp
1372  Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case    PCRE_NOTEMPTY_ATSTART
1373  of a pattern match of the empty string within its \fBsplit()\fP function, and  .sp
1374  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
1375  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
1376  PCRE_NOTEMPTY and PCRE_ANCHORED, and then if that fails by advancing the  can occur only if the pattern contains \eK.
1377  starting offset (see below) and trying an ordinary match again. There is some  .P
1378  code that demonstrates how to do this in the \fIpcredemo.c\fP sample program.  Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1379    does make a special case of a pattern match of the empty string within its
1380    \fBsplit()\fP function, and when using the /g modifier. It is possible to
1381    emulate Perl's behaviour after matching a null string by first trying the match
1382    again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1383    if that fails, by advancing the starting offset (see below) and trying an
1384    ordinary match again. There is some code that demonstrates how to do this in
1385    the
1386    .\" HREF
1387    \fBpcredemo\fP
1388    .\"
1389    sample program.
1390    .sp
1391      PCRE_NO_START_OPTIMIZE
1392    .sp
1393    There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1394    a match, in order to speed up the process. For example, if it is known that a
1395    match must start with a specific character, it searches the subject for that
1396    character, and fails immediately if it cannot find it, without actually running
1397    the main matching function. When callouts are in use, these optimizations can
1398    cause them to be skipped. This option disables the "start-up" optimizations,
1399    causing performance to suffer, but ensuring that the callouts do occur.
1400  .sp  .sp
1401    PCRE_NO_UTF8_CHECK    PCRE_NO_UTF8_CHECK
1402  .sp  .sp
1403  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8  When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1404  string is automatically checked when \fBpcre_exec()\fP is subsequently called.  string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1405  The value of \fIstartoffset\fP is also checked to ensure that it points to the  The value of \fIstartoffset\fP is also checked to ensure that it points to the
1406  start of a UTF-8 character. If an invalid UTF-8 sequence of bytes is found,  start of a UTF-8 character. There is a discussion about the validity of UTF-8
1407  \fBpcre_exec()\fP returns the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP  strings in the
1408  contains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.  .\" HTML <a href="pcre.html#utf8strings">
1409    .\" </a>
1410    section on UTF-8 support
1411    .\"
1412    in the main
1413    .\" HREF
1414    \fBpcre\fP
1415    .\"
1416    page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
1417    the error PCRE_ERROR_BADUTF8. If \fIstartoffset\fP contains an invalid value,
1418    PCRE_ERROR_BADUTF8_OFFSET is returned.
1419  .P  .P
1420  If you already know that your subject is valid, and you want to skip these  If you already know that your subject is valid, and you want to skip these
1421  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when  checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
# Line 1207  PCRE_NO_UTF8_CHECK is set, the effect of Line 1427  PCRE_NO_UTF8_CHECK is set, the effect of
1427  subject, or a value of \fIstartoffset\fP that does not point to the start of a  subject, or a value of \fIstartoffset\fP that does not point to the start of a
1428  UTF-8 character, is undefined. Your program may crash.  UTF-8 character, is undefined. Your program may crash.
1429  .sp  .sp
1430    PCRE_PARTIAL    PCRE_PARTIAL_HARD
1431      PCRE_PARTIAL_SOFT
1432  .sp  .sp
1433  This option turns on the partial matching feature. If the subject string fails  These options turn on the partial matching feature. For backwards
1434  to match the pattern, but at some point during the matching process the end of  compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1435  the subject was reached (that is, the subject partially matches the pattern and  occurs if the end of the subject string is reached successfully, but there are
1436  the failure to match occurred only because there were not enough subject  not enough subject characters to complete the match. If this happens when
1437  characters), \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL instead of  PCRE_PARTIAL_HARD is set, \fBpcre_exec()\fP immediately returns
1438  PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is used, there are restrictions on what  PCRE_ERROR_PARTIAL. Otherwise, if PCRE_PARTIAL_SOFT is set, matching continues
1439  may appear in the pattern. These are discussed in the  by testing any other alternatives. Only if they all fail is PCRE_ERROR_PARTIAL
1440    returned (instead of PCRE_ERROR_NOMATCH). The portion of the string that
1441    was inspected when the partial match was found is set as the first matching
1442    string. There is a more detailed discussion in the
1443  .\" HREF  .\" HREF
1444  \fBpcrepartial\fP  \fBpcrepartial\fP
1445  .\"  .\"
# Line 1225  documentation. Line 1449  documentation.
1449  .rs  .rs
1450  .sp  .sp
1451  The subject string is passed to \fBpcre_exec()\fP as a pointer in  The subject string is passed to \fBpcre_exec()\fP as a pointer in
1452  \fIsubject\fP, a length in \fIlength\fP, and a starting byte offset in  \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
1453  \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of a  in \fIstartoffset\fP. In UTF-8 mode, the byte offset must point to the start of
1454  UTF-8 character. Unlike the pattern string, the subject may contain binary zero  a UTF-8 character. Unlike the pattern string, the subject may contain binary
1455  bytes. When the starting offset is zero, the search for a match starts at the  zero bytes. When the starting offset is zero, the search for a match starts at
1456  beginning of the subject, and this is by far the most common case.  the beginning of the subject, and this is by far the most common case.
1457  .P  .P
1458  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
1459  same subject by calling \fBpcre_exec()\fP again after a previous success.  same subject by calling \fBpcre_exec()\fP again after a previous success.
# Line 1263  pattern. Following the usage in Jeffrey Line 1487  pattern. Following the usage in Jeffrey
1487  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
1488  kinds of parenthesized subpattern that do not cause substrings to be captured.  kinds of parenthesized subpattern that do not cause substrings to be captured.
1489  .P  .P
1490  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
1491  whose address is passed in \fIovector\fP. The number of elements in the vector  address is passed in \fIovector\fP. The number of elements in the vector is
1492  is passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP:  passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1493  this argument is NOT the size of \fIovector\fP in bytes.  argument is NOT the size of \fIovector\fP in bytes.
1494  .P  .P
1495  The first two-thirds of the vector is used to pass back captured substrings,  The first two-thirds of the vector is used to pass back captured substrings,
1496  each substring using a pair of integers. The remaining third of the vector is  each substring using a pair of integers. The remaining third of the vector is
1497  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,  used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1498  and is not available for passing back information. The length passed in  and is not available for passing back information. The number passed in
1499  \fIovecsize\fP should always be a multiple of three. If it is not, it is  \fIovecsize\fP should always be a multiple of three. If it is not, it is
1500  rounded down.  rounded down.
1501  .P  .P
1502  When a match is successful, information about captured substrings is returned  When a match is successful, information about captured substrings is returned
1503  in pairs of integers, starting at the beginning of \fIovector\fP, and  in pairs of integers, starting at the beginning of \fIovector\fP, and
1504  continuing up to two-thirds of its length at the most. The first element of a  continuing up to two-thirds of its length at the most. The first element of
1505  pair is set to the offset of the first character in a substring, and the second  each pair is set to the byte offset of the first character in a substring, and
1506  is set to the offset of the first character after the end of a substring. The  the second is set to the byte offset of the first character after the end of a
1507  first pair, \fIovector[0]\fP and \fIovector[1]\fP, identify the portion of the  substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1508  subject string matched by the entire pattern. The next pair is used for the  mode. They are not character counts.
1509  first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fP  .P
1510  is one more than the highest numbered pair that has been set. For example, if  The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1511  two substrings have been captured, the returned value is 3. If there are no  portion of the subject string matched by the entire pattern. The next pair is
1512  capturing subpatterns, the return value from a successful match is 1,  used for the first capturing subpattern, and so on. The value returned by
1513  indicating that just the first pair of offsets has been set.  \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1514    For example, if two substrings have been captured, the returned value is 3. If
1515    there are no capturing subpatterns, the return value from a successful match is
1516    1, indicating that just the first pair of offsets has been set.
1517  .P  .P
1518  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
1519  string that it matched that is returned.  string that it matched that is returned.
1520  .P  .P
1521  If the vector is too small to hold all the captured substring offsets, it is  If the vector is too small to hold all the captured substring offsets, it is
1522  used as far as possible (up to two-thirds of its length), and the function  used as far as possible (up to two-thirds of its length), and the function
1523  returns a value of zero. In particular, if the substring offsets are not of  returns a value of zero. If the substring offsets are not of interest,
1524  interest, \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and  \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
1525  \fIovecsize\fP as zero. However, if the pattern contains back references and  \fIovecsize\fP as zero. However, if the pattern contains back references and
1526  the \fIovector\fP is not big enough to remember the related substrings, PCRE  the \fIovector\fP is not big enough to remember the related substrings, PCRE
1527  has to get additional memory for use during matching. Thus it is usually  has to get additional memory for use during matching. Thus it is usually
1528  advisable to supply an \fIovector\fP.  advisable to supply an \fIovector\fP.
1529  .P  .P
1530  The \fBpcre_info()\fP function can be used to find out how many capturing  The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1531  subpatterns there are in a compiled pattern. The smallest size for  subpatterns there are in a compiled pattern. The smallest size for
1532  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to  \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1533  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.  the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
# Line 1405  documentation for details of partial mat Line 1632  documentation for details of partial mat
1632  .sp  .sp
1633    PCRE_ERROR_BADPARTIAL     (-13)    PCRE_ERROR_BADPARTIAL     (-13)
1634  .sp  .sp
1635  The PCRE_PARTIAL option was used with a compiled pattern containing items that  This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
1636  are not supported for partial matching. See the  option was used with a compiled pattern containing items that were not
1637  .\" HREF  supported for partial matching. From release 8.00 onwards, there are no
1638  \fBpcrepartial\fP  restrictions on partial matching.
 .\"  
 documentation for details of partial matching.  
1639  .sp  .sp
1640    PCRE_ERROR_INTERNAL       (-14)    PCRE_ERROR_INTERNAL       (-14)
1641  .sp  .sp
# Line 1427  The internal recursion limit, as specifi Line 1652  The internal recursion limit, as specifi
1652  field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the  field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
1653  description above.  description above.
1654  .sp  .sp
   PCRE_ERROR_NULLWSLIMIT    (-22)  
 .sp  
 When a group that can match an empty substring is repeated with an unbounded  
 upper limit, the subject position at the start of the group must be remembered,  
 so that a test for an empty string can be made when the end of the group is  
 reached. Some workspace is required for this; if it runs out, this error is  
 given.  
 .sp  
1655    PCRE_ERROR_BADNEWLINE     (-23)    PCRE_ERROR_BADNEWLINE     (-23)
1656  .sp  .sp
1657  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.  An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
1658  .P  .P
1659  Error numbers -16 to -20 are not used by \fBpcre_exec()\fP.  Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
1660  .  .
1661  .  .
1662  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"  .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
# Line 1585  pattern. This is needed in order to gain Line 1802  pattern. This is needed in order to gain
1802  translation table.  translation table.
1803  .P  .P
1804  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they  These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
1805  then call \fIpcre_copy_substring()\fP or \fIpcre_get_substring()\fP, as  then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
1806  appropriate.  appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
1807  .  the behaviour may not be what you want (see the next section).
1808    .P
1809    \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
1810    subpatterns with the same number, as described in the
1811    .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1812    .\" </a>
1813    section on duplicate subpattern numbers
1814    .\"
1815    in the
1816    .\" HREF
1817    \fBpcrepattern\fP
1818    .\"
1819    page, you cannot use names to distinguish the different subpatterns, because
1820    names are not included in the compiled code. The matching process uses only
1821    numbers. For this reason, the use of different names for subpatterns of the
1822    same number causes an error at compile time.
1823  .  .
1824  .SH "DUPLICATE SUBPATTERN NAMES"  .SH "DUPLICATE SUBPATTERN NAMES"
1825  .rs  .rs
# Line 1597  appropriate. Line 1829  appropriate.
1829  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);  .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
1830  .PP  .PP
1831  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns  When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
1832  are not required to be unique. Normally, patterns with duplicate names are such  are not required to be unique. (Duplicate names are always allowed for
1833  that in any one match, only one of the named subpatterns participates. An  subpatterns with the same number, created by using the (?| feature. Indeed, if
1834  example is shown in the  such subpatterns are named, they are required to use the same names.)
1835    .P
1836    Normally, patterns with duplicate names are such that in any one match, only
1837    one of the named subpatterns participates. An example is shown in the
1838  .\" HREF  .\" HREF
1839  \fBpcrepattern\fP  \fBpcrepattern\fP
1840  .\"  .\"
1841  documentation. When duplicates are present, \fBpcre_copy_named_substring()\fP  documentation.
1842  and \fBpcre_get_named_substring()\fP return the first substring corresponding  .P
1843  to the given name that is set. If none are set, an empty string is returned.  When duplicates are present, \fBpcre_copy_named_substring()\fP and
1844  The \fBpcre_get_stringnumber()\fP function returns one of the numbers that are  \fBpcre_get_named_substring()\fP return the first substring corresponding to
1845  associated with the name, but it is not defined which it is.  the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
1846  .sp  returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
1847    returns one of the numbers that are associated with the name, but it is not
1848    defined which it is.
1849    .P
1850  If you want to get full details of all captured substrings for a given name,  If you want to get full details of all captured substrings for a given name,
1851  you must use the \fBpcre_get_stringtable_entries()\fP function. The first  you must use the \fBpcre_get_stringtable_entries()\fP function. The first
1852  argument is the compiled pattern, and the second is the name. The third and  argument is the compiled pattern, and the second is the name. The third and
# Line 1660  a compiled pattern, using a matching alg Line 1898  a compiled pattern, using a matching alg
1898  just once, and does not backtrack. This has different characteristics to the  just once, and does not backtrack. This has different characteristics to the
1899  normal algorithm, and is not compatible with Perl. Some of the features of PCRE  normal algorithm, and is not compatible with Perl. Some of the features of PCRE
1900  patterns are not supported. Nevertheless, there are times when this kind of  patterns are not supported. Nevertheless, there are times when this kind of
1901  matching can be useful. For a discussion of the two matching algorithms, see  matching can be useful. For a discussion of the two matching algorithms, and a
1902  the  list of features that \fBpcre_dfa_exec()\fP does not support, see the
1903  .\" HREF  .\" HREF
1904  \fBpcrematching\fP  \fBpcrematching\fP
1905  .\"  .\"
# Line 1700  Here is an example of a simple call to \ Line 1938  Here is an example of a simple call to \
1938  .sp  .sp
1939  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be  The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
1940  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,  zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1941  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
1942  PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last three of these are  PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST,
1943  the same as for \fBpcre_exec()\fP, so their description is not repeated here.  and PCRE_DFA_RESTART. All but the last four of these are exactly the same as
1944  .sp  for \fBpcre_exec()\fP, so their description is not repeated here.
1945    PCRE_PARTIAL  .sp
1946  .sp    PCRE_PARTIAL_HARD
1947  This has the same general effect as it does for \fBpcre_exec()\fP, but the    PCRE_PARTIAL_SOFT
1948  details are slightly different. When PCRE_PARTIAL is set for  .sp
1949  \fBpcre_dfa_exec()\fP, the return code PCRE_ERROR_NOMATCH is converted into  These have the same general effect as they do for \fBpcre_exec()\fP, but the
1950  PCRE_ERROR_PARTIAL if the end of the subject is reached, there have been no  details are slightly different. When PCRE_PARTIAL_HARD is set for
1951  complete matches, but there is still at least one matching possibility. The  \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
1952  portion of the string that provided the partial match is set as the first  is reached and there is still at least one matching possibility that requires
1953  matching string.  additional characters. This happens even if some complete matches have also
1954    been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
1955    is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
1956    there have been no complete matches, but there is still at least one matching
1957    possibility. The portion of the string that was inspected when the longest
1958    partial match was found is set as the first matching string in both cases.
1959  .sp  .sp
1960    PCRE_DFA_SHORTEST    PCRE_DFA_SHORTEST
1961  .sp  .sp
# Line 1723  matching point in the subject string. Line 1966  matching point in the subject string.
1966  .sp  .sp
1967    PCRE_DFA_RESTART    PCRE_DFA_RESTART
1968  .sp  .sp
1969  When \fBpcre_dfa_exec()\fP is called with the PCRE_PARTIAL option, and returns  When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
1970  a partial match, it is possible to call it again, with additional subject  again, with additional subject characters, and have it continue with the same
1971  characters, and have it continue with the same match. The PCRE_DFA_RESTART  match. The PCRE_DFA_RESTART option requests this action; when it is set, the
1972  option requests this action; when it is set, the \fIworkspace\fP and  \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
1973  \fIwscount\fP options must reference the same vector as before because data  before because data about the match so far is left in them after a partial
1974  about the match so far is left in them after a partial match. There is more  match. There is more discussion of this facility in the
 discussion of this facility in the  
1975  .\" HREF  .\" HREF
1976  \fBpcrepartial\fP  \fBpcrepartial\fP
1977  .\"  .\"
# Line 1833  Cambridge CB2 3QH, England. Line 2075  Cambridge CB2 3QH, England.
2075  .rs  .rs
2076  .sp  .sp
2077  .nf  .nf
2078  Last updated: 06 March 2007  Last updated: 03 October 2009
2079  Copyright (c) 1997-2007 University of Cambridge.  Copyright (c) 1997-2009 University of Cambridge.
2080  .fi  .fi

Legend:
Removed from v.99  
changed lines
  Added in v.461

  ViewVC Help
Powered by ViewVC 1.1.5